CA3114743C - Hot-rolled and annealed ferritic stainless steel sheet and method for producing the same - Google Patents
Hot-rolled and annealed ferritic stainless steel sheet and method for producing the same Download PDFInfo
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- CA3114743C CA3114743C CA3114743A CA3114743A CA3114743C CA 3114743 C CA3114743 C CA 3114743C CA 3114743 A CA3114743 A CA 3114743A CA 3114743 A CA3114743 A CA 3114743A CA 3114743 C CA3114743 C CA 3114743C
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 14
- 229910001220 stainless steel Inorganic materials 0.000 title claims description 34
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 106
- 239000010959 steel Substances 0.000 claims abstract description 106
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 32
- 229910052751 metal Inorganic materials 0.000 claims abstract description 25
- 239000002184 metal Substances 0.000 claims abstract description 25
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 8
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 8
- 238000000137 annealing Methods 0.000 claims description 41
- 238000005098 hot rolling Methods 0.000 claims description 30
- 229910052757 nitrogen Inorganic materials 0.000 claims description 14
- 229910052804 chromium Inorganic materials 0.000 claims description 12
- 229910052719 titanium Inorganic materials 0.000 claims description 11
- 239000000126 substance Substances 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 9
- 229910052758 niobium Inorganic materials 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- 229910052796 boron Inorganic materials 0.000 claims description 4
- 229910052791 calcium Inorganic materials 0.000 claims description 4
- 229910052749 magnesium Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 229910052726 zirconium Inorganic materials 0.000 claims description 4
- 238000004080 punching Methods 0.000 abstract description 49
- 230000007797 corrosion Effects 0.000 abstract description 35
- 238000005260 corrosion Methods 0.000 abstract description 35
- 238000005336 cracking Methods 0.000 abstract description 7
- 239000013078 crystal Substances 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 34
- 239000011651 chromium Substances 0.000 description 26
- 230000000694 effects Effects 0.000 description 23
- 239000010936 titanium Substances 0.000 description 23
- 238000000034 method Methods 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 12
- 229910001566 austenite Inorganic materials 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 11
- 230000006866 deterioration Effects 0.000 description 11
- 229910052761 rare earth metal Inorganic materials 0.000 description 11
- 229910000734 martensite Inorganic materials 0.000 description 10
- 238000001953 recrystallisation Methods 0.000 description 9
- 239000007789 gas Substances 0.000 description 8
- 150000002910 rare earth metals Chemical class 0.000 description 8
- 238000005096 rolling process Methods 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 206010070834 Sensitisation Diseases 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 125000004122 cyclic group Chemical class 0.000 description 5
- 238000007670 refining Methods 0.000 description 5
- 230000008313 sensitization Effects 0.000 description 5
- 239000007921 spray Substances 0.000 description 5
- 238000003466 welding Methods 0.000 description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 238000005507 spraying Methods 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000001887 electron backscatter diffraction Methods 0.000 description 2
- 229910001651 emery Inorganic materials 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000009736 wetting Methods 0.000 description 2
- 229910000760 Hardened steel Inorganic materials 0.000 description 1
- 229910004337 Ti-Ni Inorganic materials 0.000 description 1
- 229910011209 Ti—Ni Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- CXOWYMLTGOFURZ-UHFFFAOYSA-N azanylidynechromium Chemical compound [Cr]#N CXOWYMLTGOFURZ-UHFFFAOYSA-N 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- OXNIZHLAWKMVMX-UHFFFAOYSA-N picric acid Chemical compound OC1=C([N+]([O-])=O)C=C([N+]([O-])=O)C=C1[N+]([O-])=O OXNIZHLAWKMVMX-UHFFFAOYSA-N 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 238000011179 visual inspection Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/007—Heat treatment of ferrous alloys containing Co
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Steel (AREA)
- Manufacturing Of Steel Electrode Plates (AREA)
Abstract
The present invention provides: a ferrite stainless hot-rolled-and-annealed steel sheet that is excellent for punching, has substantial corrosion resistance, and makes it possible to achieve a prescribed dimensional precision without cracking when punched into a thick flange; and a production method for the ferrite stainless hot-rolled-and-annealed steel sheet. A ferrite stainless hot-rolled-and-annealed steel sheet that has a ferrite single phase structure that has a component composition that contains, by mass%, 0.001%0.020% of C, 0.05%1.00% of Si, 0.05%1.00% of Mn, no more than 0.04% of P, no more than 0.01% of S, 0.01%0.10% of Al, 10.0%20.0% of Cr, 0.50%2.00% of Ni, 0.10%0.40% of Ti, and 0.001%0.020% of N, the remainder being Fe and unavoidable impurities, the average crystal grain size of the metal structure of the ferrite single phase structure being 520 µm.
Description
DESCRIPTION
Title of Invention: HOT-ROLLED AND ANNEALED FERRITIC
STAINLESS STEEL SHEET AND METHOD FOR PRODUCING THE SAME
Technical Field [0001]
The present invention relates to a hot-rolled and annealed ferritic stainless steel sheet having excellent workability and being suitably used for flanges and so forth and to a method for producing the hot-rolled and annealed ferritic stainless steel sheet.
Background Art
Title of Invention: HOT-ROLLED AND ANNEALED FERRITIC
STAINLESS STEEL SHEET AND METHOD FOR PRODUCING THE SAME
Technical Field [0001]
The present invention relates to a hot-rolled and annealed ferritic stainless steel sheet having excellent workability and being suitably used for flanges and so forth and to a method for producing the hot-rolled and annealed ferritic stainless steel sheet.
Background Art
[0002]
In recent years, laws and regulations regarding exhaust gases from automobiles have been increasingly tightened in order to reduce the amount of emission of CO2, which is a greenhouse effect gas. An improvement in fuel economy is effective in reducing the amount of emission of CO2 in automotive exhaust gases. Thus, studies have been made of an increase in combustion temperature in engines.
In recent years, laws and regulations regarding exhaust gases from automobiles have been increasingly tightened in order to reduce the amount of emission of CO2, which is a greenhouse effect gas. An improvement in fuel economy is effective in reducing the amount of emission of CO2 in automotive exhaust gases. Thus, studies have been made of an increase in combustion temperature in engines.
[0003]
Exhaust gases generated by engines are released to the atmosphere through exhaust system components, such as exhaust gas recirculation (EGR) systems and mufflers. These components of automotive exhaust systems are fastened with flanges in order to prevent gas leakage. Flanges used for 2019500546W00-English specification Date Recue/Date Received 2021-03-29 exhaust system components need to have dimensional accuracy sufficient for fastening components.
Exhaust gases generated by engines are released to the atmosphere through exhaust system components, such as exhaust gas recirculation (EGR) systems and mufflers. These components of automotive exhaust systems are fastened with flanges in order to prevent gas leakage. Flanges used for 2019500546W00-English specification Date Recue/Date Received 2021-03-29 exhaust system components need to have dimensional accuracy sufficient for fastening components.
[0004]
Hitherto, such thick-wall flanges have been composed of plain carbon steel. In recent years, however, as a further improvement in the fuel economy of automobiles is required, combustion temperatures in engines and the temperatures of exhaust gases from engines have been further increased.
Thus, flanges are required to have higher high-temperature strength and corrosion resistance than before. From such a background, in recent years, stainless steel, which has higher high-temperature strength and corrosion resistance than plain carbon steel, in particular, a high-strength ferritic stainless steel sheet, which has a relatively low coefficient of thermal expansion and being less likely to generate thermal stress (for example, a thick sheet composed of ASTM A240/240M-S40975 (11 mass%Cr-Ti-Ni steel)) (for example, a sheet thickness of 5 mm or more), has been increasingly used.
Hitherto, such thick-wall flanges have been composed of plain carbon steel. In recent years, however, as a further improvement in the fuel economy of automobiles is required, combustion temperatures in engines and the temperatures of exhaust gases from engines have been further increased.
Thus, flanges are required to have higher high-temperature strength and corrosion resistance than before. From such a background, in recent years, stainless steel, which has higher high-temperature strength and corrosion resistance than plain carbon steel, in particular, a high-strength ferritic stainless steel sheet, which has a relatively low coefficient of thermal expansion and being less likely to generate thermal stress (for example, a thick sheet composed of ASTM A240/240M-S40975 (11 mass%Cr-Ti-Ni steel)) (for example, a sheet thickness of 5 mm or more), has been increasingly used.
[0005]
However, since flanges used in exhaust systems have thick walls (often 5 mm or more), there is a problem that cracking may occur during punching work in producing flanges to fail to appropriately produce flange components. A thick ferritic stainless steel sheet excellent in punching 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 workability is strongly demanded.
However, since flanges used in exhaust systems have thick walls (often 5 mm or more), there is a problem that cracking may occur during punching work in producing flanges to fail to appropriately produce flange components. A thick ferritic stainless steel sheet excellent in punching 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 workability is strongly demanded.
[0006]
In response to the demands of the market, for example, Patent Literature 1 discloses a hot-rolled ferritic stainless steel sheet containing, on a mass percent basis, C: 0.015% or less, Si: 0.01% to 0.4%, Mn: 0.01% to 0.8%, P:
0.04% or less, S: 0.01% or less, Cr: 14.0% to less than 18.0%, Ni: 0.05% to 1%, Nb: 0.3% to 0.6%, Ti: 0.05% or less, N: 0.020% or less, Al: 0.10% or less, and B: 0.0002% to 0.0020%, the balance being Fe and incidental impurities, the Nb, C, and N contents satisfying Nb/(C + N) 16, the CharPY
impact value being 10 J/cm2 or more at 0 C, the thickness of the sheet being 5.0 to 9.0 mm.
Citation List Patent Literature
In response to the demands of the market, for example, Patent Literature 1 discloses a hot-rolled ferritic stainless steel sheet containing, on a mass percent basis, C: 0.015% or less, Si: 0.01% to 0.4%, Mn: 0.01% to 0.8%, P:
0.04% or less, S: 0.01% or less, Cr: 14.0% to less than 18.0%, Ni: 0.05% to 1%, Nb: 0.3% to 0.6%, Ti: 0.05% or less, N: 0.020% or less, Al: 0.10% or less, and B: 0.0002% to 0.0020%, the balance being Fe and incidental impurities, the Nb, C, and N contents satisfying Nb/(C + N) 16, the CharPY
impact value being 10 J/cm2 or more at 0 C, the thickness of the sheet being 5.0 to 9.0 mm.
Citation List Patent Literature
[0007]
PTL 1: International Publication No. 2014/157576 Summary of Invention Technical Problem
PTL 1: International Publication No. 2014/157576 Summary of Invention Technical Problem
[0008]
The inventors produced experimentally a ferritic stainless steel sheet having a thickness of 10 mm and containing steel components in compliance with ASTM
A240/240M-540975 by a method disclosed in Patent Literature 1 and then produced flanges having holes with a diameter of 2019500546W00-English specification Date Recue/Date Received 2021-03-29 20 mm by punching work with a clearance of 10%. The results demonstrated that although no cracking occurred during the punching in any of the flanges, the circumference and/or center hole dimensions of each flange sometimes exceeded the tolerance of the component, which indicated that the steel sheet had not sufficient performance for the thick-wall flange.
The inventors produced experimentally a ferritic stainless steel sheet having a thickness of 10 mm and containing steel components in compliance with ASTM
A240/240M-540975 by a method disclosed in Patent Literature 1 and then produced flanges having holes with a diameter of 2019500546W00-English specification Date Recue/Date Received 2021-03-29 20 mm by punching work with a clearance of 10%. The results demonstrated that although no cracking occurred during the punching in any of the flanges, the circumference and/or center hole dimensions of each flange sometimes exceeded the tolerance of the component, which indicated that the steel sheet had not sufficient performance for the thick-wall flange.
[0009]
The present invention aims to solve the foregoing problems and provide a hot-rolled and annealed ferritic stainless steel sheet having sufficient corrosion resistance and excellent punching workability, a predetermined dimensional accuracy being obtained without cracking when the steel sheet is formed into a thick-wall flange by punching work, and a method for producing the hot-rolled and annealed ferritic stainless steel sheet.
Solution to Problem
The present invention aims to solve the foregoing problems and provide a hot-rolled and annealed ferritic stainless steel sheet having sufficient corrosion resistance and excellent punching workability, a predetermined dimensional accuracy being obtained without cracking when the steel sheet is formed into a thick-wall flange by punching work, and a method for producing the hot-rolled and annealed ferritic stainless steel sheet.
Solution to Problem
[0010]
The inventors have conducted detailed studies in order to solve the foregoing problems and have found that in order to obtain a predetermined dimensional accuracy without cracking during punching work, it is sufficient that the metal microstructure of a steel sheet is controlled to be a single ferrite phase microstructure having an average grain size of 5 to 20 Rm.
2019500546W00-English specification Date Recue/Date Received 2021-03-29
The inventors have conducted detailed studies in order to solve the foregoing problems and have found that in order to obtain a predetermined dimensional accuracy without cracking during punching work, it is sufficient that the metal microstructure of a steel sheet is controlled to be a single ferrite phase microstructure having an average grain size of 5 to 20 Rm.
2019500546W00-English specification Date Recue/Date Received 2021-03-29
[0011]
Additionally, the inventors have also found that the metal microstructure can be controlled to be a ferrite single phase having an average grain size of 5 to 20 pm by subjecting a ferritic stainless steel containing appropriate composition to hot rolling and subjecting the resulting hot-rolled steel sheet to hot-rolled steel sheet annealing under appropriate conditions that lead to a single ferrite phase, specifically, holding the hot-rolled steel sheet at 600 C or higher and lower than 750 C for 1 minute to 24 hours.
Additionally, the inventors have also found that the metal microstructure can be controlled to be a ferrite single phase having an average grain size of 5 to 20 pm by subjecting a ferritic stainless steel containing appropriate composition to hot rolling and subjecting the resulting hot-rolled steel sheet to hot-rolled steel sheet annealing under appropriate conditions that lead to a single ferrite phase, specifically, holding the hot-rolled steel sheet at 600 C or higher and lower than 750 C for 1 minute to 24 hours.
[0012]
These findings have led to the present invention.
The gist of the present invention is described below.
[1] A hot-rolled and annealed ferritic stainless steel sheet has a chemical composition containing, on a mass percent basis, C: 0.001% to 0.020%, Si: 0.05% to 1.00%, Mn: 0.05% to 1.00%, P: 0.04% or less, S: 0.01%
or less, Al: 0.01% to 0.10%, Cr: 10.0% to 20.0%, Ni:
0.50% to 2.00%, Ti: 0.10% to 0.40%, and N: 0.001% to 0.020%, the balance being Fe and incidental impurities;
and has a metal microstructure is a single ferrite phase microstructure having an average grain size of to 20 pm.
[1a] In an embodiment of [1], the hot-rolled and annealed ferritic stainless steel sheet has a chemical composition containing, on a mass percent basis: C:
0.001% to 0.020%, Si: 0.05% to 0.40%, Mn: 0.05% to 0.60%, P: 0.04% or less, S: 0.01% or less, Al: 0.01% to 0.10%, Cr: 11.2% to 20.0%, Ni: 0.50% to 0.86%, Ti:
0.10% to 0.40%, and N: 0.001% to 0.020%, the balance being Fe and incidental impurities.
Date Recue/Date Received 2022-06-08 - 5a -[2] The hot-rolled and annealed ferritic stainless steel sheet described in [1] further contains, on a mass percent basis, one or two or more selected from Cu: 0.01% to Date Recue/Date Received 2022-06-08 1.00%, Mo: 0.01% to 2.00%, W: 0.01% to 0.20%, and Co: 0.01%
to 0.20%.
[3] The hot-rolled and annealed ferritic stainless steel sheet described in [1] or [2] further contains, on a mass percent basis, one or two or more selected from V:
0.01% to 0.20%, Nb: 0.01% to 0.10%, Zr: 0.01% to 0.20%, REM:
0.001% to 0.100%, B: 0.0002% to 0.0025%, Mg: 0.0005% to 0.0030%, and Ca: 0.0003% to 0.0030%.
[4] A method for producing the hot-rolled and annealed ferritic stainless steel sheet described in any one of [1]
to [3] includes performing hot-rolled steel sheet annealing in which a hot-rolled steel sheet produced through a hot-rolling step is held at 600 C or higher and lower than 750 C
for 1 minute to 24 hours.
Advantageous Effects of Invention
These findings have led to the present invention.
The gist of the present invention is described below.
[1] A hot-rolled and annealed ferritic stainless steel sheet has a chemical composition containing, on a mass percent basis, C: 0.001% to 0.020%, Si: 0.05% to 1.00%, Mn: 0.05% to 1.00%, P: 0.04% or less, S: 0.01%
or less, Al: 0.01% to 0.10%, Cr: 10.0% to 20.0%, Ni:
0.50% to 2.00%, Ti: 0.10% to 0.40%, and N: 0.001% to 0.020%, the balance being Fe and incidental impurities;
and has a metal microstructure is a single ferrite phase microstructure having an average grain size of to 20 pm.
[1a] In an embodiment of [1], the hot-rolled and annealed ferritic stainless steel sheet has a chemical composition containing, on a mass percent basis: C:
0.001% to 0.020%, Si: 0.05% to 0.40%, Mn: 0.05% to 0.60%, P: 0.04% or less, S: 0.01% or less, Al: 0.01% to 0.10%, Cr: 11.2% to 20.0%, Ni: 0.50% to 0.86%, Ti:
0.10% to 0.40%, and N: 0.001% to 0.020%, the balance being Fe and incidental impurities.
Date Recue/Date Received 2022-06-08 - 5a -[2] The hot-rolled and annealed ferritic stainless steel sheet described in [1] further contains, on a mass percent basis, one or two or more selected from Cu: 0.01% to Date Recue/Date Received 2022-06-08 1.00%, Mo: 0.01% to 2.00%, W: 0.01% to 0.20%, and Co: 0.01%
to 0.20%.
[3] The hot-rolled and annealed ferritic stainless steel sheet described in [1] or [2] further contains, on a mass percent basis, one or two or more selected from V:
0.01% to 0.20%, Nb: 0.01% to 0.10%, Zr: 0.01% to 0.20%, REM:
0.001% to 0.100%, B: 0.0002% to 0.0025%, Mg: 0.0005% to 0.0030%, and Ca: 0.0003% to 0.0030%.
[4] A method for producing the hot-rolled and annealed ferritic stainless steel sheet described in any one of [1]
to [3] includes performing hot-rolled steel sheet annealing in which a hot-rolled steel sheet produced through a hot-rolling step is held at 600 C or higher and lower than 750 C
for 1 minute to 24 hours.
Advantageous Effects of Invention
[0013]
According to the present invention, a hot-rolled and annealed ferritic stainless steel sheet having sufficient corrosion resistance and excellent punching workability is provided.
According to the present invention, a hot-rolled and annealed ferritic stainless steel sheet having sufficient corrosion resistance and excellent punching workability is provided.
[0014]
The term "sufficient corrosion resistance" used in the present invention indicates that when a steel sheet obtained by subjecting surfaces thereof to abrasive finishing with 600-grit emery paper and then sealing end-face portions 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 thereof is subjected to five cycles of a cyclic salt-spray test specified in JIS H 8502 (one cycle of the test consisting of salt spraying (5% by mass NaCl, 35 C, spraying for 2 hours) -* drying (60 C, 4 hours, relative humidity:
40%) -* wetting (50 C, 2 hours, relative humidity: 95%)), the percentage of rusted area of the surfaces of the steel sheet (= rusted area/total area of steel sheet x 100[%]) is 25% or less.
The term "sufficient corrosion resistance" used in the present invention indicates that when a steel sheet obtained by subjecting surfaces thereof to abrasive finishing with 600-grit emery paper and then sealing end-face portions 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 thereof is subjected to five cycles of a cyclic salt-spray test specified in JIS H 8502 (one cycle of the test consisting of salt spraying (5% by mass NaCl, 35 C, spraying for 2 hours) -* drying (60 C, 4 hours, relative humidity:
40%) -* wetting (50 C, 2 hours, relative humidity: 95%)), the percentage of rusted area of the surfaces of the steel sheet (= rusted area/total area of steel sheet x 100[%]) is 25% or less.
[0015]
The punching workability is evaluated as follows:
Samples measuring 100 mm x 100 mm for testing are taken from a hot-rolled and annealed steel sheet. Five test specimens are produced by punching work with a crank press equipped with an upper die (punch) and a lower die (die) so as to form a hole having a diameter of 20 mm (tolerance: 0.1 mm) in the middle portion of each of the samples, the upper die having a cylindrical edge for punching, the lower die having a hole with a diameter of 20 mm or more. The punching work is performed by selecting the hole diameter of the lower die in accordance with the thickness of the test specimens in such a manner that the clearance between the upper die and the lower die is 10%. Here, the relationships among the clearance (C) [%], the hole diameter of the die (the inside diameter of the die) (Dd) [mm], the diameter of the punch (Dp) [mm], and the sheet thickness (t) [mm] are represented 2019500546W00-English specification Date Recue/Date Received 2021-03-29 by formula (1) below.
C = (Dd -Dp) + (2 x t) x 100 formula (1) The "excellent punching workability" in the present invention indicates that, with respect to the test specimens thus obtained, when the visual inspection of the appearance of each test specimen and the measurement of the diameter of the hole in the middle portion of the test specimen with a digital caliper are performed, no cracks are observed, and the hole diameter of each of the five test specimens after the punching work is in the range of 19.9 to 20.1 mm.
Description of Embodiments
The punching workability is evaluated as follows:
Samples measuring 100 mm x 100 mm for testing are taken from a hot-rolled and annealed steel sheet. Five test specimens are produced by punching work with a crank press equipped with an upper die (punch) and a lower die (die) so as to form a hole having a diameter of 20 mm (tolerance: 0.1 mm) in the middle portion of each of the samples, the upper die having a cylindrical edge for punching, the lower die having a hole with a diameter of 20 mm or more. The punching work is performed by selecting the hole diameter of the lower die in accordance with the thickness of the test specimens in such a manner that the clearance between the upper die and the lower die is 10%. Here, the relationships among the clearance (C) [%], the hole diameter of the die (the inside diameter of the die) (Dd) [mm], the diameter of the punch (Dp) [mm], and the sheet thickness (t) [mm] are represented 2019500546W00-English specification Date Recue/Date Received 2021-03-29 by formula (1) below.
C = (Dd -Dp) + (2 x t) x 100 formula (1) The "excellent punching workability" in the present invention indicates that, with respect to the test specimens thus obtained, when the visual inspection of the appearance of each test specimen and the measurement of the diameter of the hole in the middle portion of the test specimen with a digital caliper are performed, no cracks are observed, and the hole diameter of each of the five test specimens after the punching work is in the range of 19.9 to 20.1 mm.
Description of Embodiments
[0016]
Embodiments of the present invention will be described below.
Embodiments of the present invention will be described below.
[0017]
A hot-rolled and annealed ferritic stainless steel sheet of the present invention has a chemical composition containing, on a mass percent basis, C: 0.001% to 0.020%, Si: 0.05% to 1.00%, Mn: 0.05% to 1.00%, P: 0.04% or less, S:
0.01% or less, Al: 0.01% to 0.10%, Cr: 10.0% to 20.0%, Ni:
0.50% to 2.00%, Ti: 0.10% to 0.40%, and N: 0.001% to 0.020%, the balance being Fe and incidental impurities, in which a metal microstructure is a single ferrite phase microstructure having an average grain size of 5 to 20 Rm.
A hot-rolled and annealed ferritic stainless steel sheet of the present invention has a chemical composition containing, on a mass percent basis, C: 0.001% to 0.020%, Si: 0.05% to 1.00%, Mn: 0.05% to 1.00%, P: 0.04% or less, S:
0.01% or less, Al: 0.01% to 0.10%, Cr: 10.0% to 20.0%, Ni:
0.50% to 2.00%, Ti: 0.10% to 0.40%, and N: 0.001% to 0.020%, the balance being Fe and incidental impurities, in which a metal microstructure is a single ferrite phase microstructure having an average grain size of 5 to 20 Rm.
[0018]
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 The present invention will be described in detail below.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 The present invention will be described in detail below.
[0019]
The inventors have produced flanges having holes with a diameter of 20 mm by punching work with a clearance of 10%
using various ferritic stainless steel sheets having 10 mm in thick in conformity with ASTM A240/240M-S40975 (a chemical composition containing, on a mass percent basis, C
< 0.03%, Si 1.00%, Mn < 1.00%, P 0.040%, S 0.030%, Cr:
10.5% to 11.7%, Ni: 0.50% to 1.00%, N 0.03%, and Ti: 6 x (C + N) to 0.74%, the balance being Fe and incidental impurities). The results revealed that although no cracking occurred during the punching in any of the sheets, the circumference and/or center hole dimensions of each flange sometimes exceeded the tolerance of the component.
The inventors have produced flanges having holes with a diameter of 20 mm by punching work with a clearance of 10%
using various ferritic stainless steel sheets having 10 mm in thick in conformity with ASTM A240/240M-S40975 (a chemical composition containing, on a mass percent basis, C
< 0.03%, Si 1.00%, Mn < 1.00%, P 0.040%, S 0.030%, Cr:
10.5% to 11.7%, Ni: 0.50% to 1.00%, N 0.03%, and Ti: 6 x (C + N) to 0.74%, the balance being Fe and incidental impurities). The results revealed that although no cracking occurred during the punching in any of the sheets, the circumference and/or center hole dimensions of each flange sometimes exceeded the tolerance of the component.
[0020]
The inventors have studied in detail the reason why the levels of the dimensional accuracy in the punching work varied greatly, depending on the steel sheets, and have found that the dimensions of the component after the punching work tended to be smaller than the tolerance when the steel sheet subjected to the punching work had an average grain size of less than 5 WU and that the dimensions of the component after the punching work tended to be larger than the tolerance when the steel sheet had an average grain size of more than 20 m. The inventors have found out that 2019500546W00-English specification Date Recue/Date Received 2021-03-29 the reasons why sufficient dimensional accuracy is not stably obtained in the punching work are that an excessively small average grain size results in a small percentage of a sheared surface in the punching work due to an excessively hard steel sheet and that an excessively large average grain size results in the occurrence of large rollover or burrs in the punching work.
The inventors have studied in detail the reason why the levels of the dimensional accuracy in the punching work varied greatly, depending on the steel sheets, and have found that the dimensions of the component after the punching work tended to be smaller than the tolerance when the steel sheet subjected to the punching work had an average grain size of less than 5 WU and that the dimensions of the component after the punching work tended to be larger than the tolerance when the steel sheet had an average grain size of more than 20 m. The inventors have found out that 2019500546W00-English specification Date Recue/Date Received 2021-03-29 the reasons why sufficient dimensional accuracy is not stably obtained in the punching work are that an excessively small average grain size results in a small percentage of a sheared surface in the punching work due to an excessively hard steel sheet and that an excessively large average grain size results in the occurrence of large rollover or burrs in the punching work.
[0021]
The inventors have conducted intensive studies on a method for producing a ferritic stainless steel sheet having a metal microstructure composed of a single ferrite phase having an average grain size of 5 to 20 pm from the viewpoints of steel composition, a hot-rolling process, and a hot-rolled steel sheet annealing process. The following method has been found to be effective: Steel composition, particularly Cr and Ni contents, are controlled to appropriate ranges. In a hot-rolling step, an austenite phase and a ferrite phase are formed, and then hot rolling is performed. Subsequently, the hot-rolled sheet is annealed in an appropriate temperature range in a single ferrite phase temperature region.
The inventors have conducted intensive studies on a method for producing a ferritic stainless steel sheet having a metal microstructure composed of a single ferrite phase having an average grain size of 5 to 20 pm from the viewpoints of steel composition, a hot-rolling process, and a hot-rolled steel sheet annealing process. The following method has been found to be effective: Steel composition, particularly Cr and Ni contents, are controlled to appropriate ranges. In a hot-rolling step, an austenite phase and a ferrite phase are formed, and then hot rolling is performed. Subsequently, the hot-rolled sheet is annealed in an appropriate temperature range in a single ferrite phase temperature region.
[0022]
A hot-rolled steel sheet annealing step is performed by performing holding the hot-rolled steel sheet in the appropriate temperature range in the single ferrite phase 2019500546W00-English specification Date Recue/Date Received 2021-03-29 temperature region, specifically at 600 C or higher and lower than 750 C for 1 minute to 24 hours. Regarding the ferrite phase and a martensite phase that have been present in the metal microstructure after the hot rolling, the hot-rolled steel sheet annealing brings recrystallization of the ferrite phase and transformation of the martensite phase into the ferrite phase, thereby providing a single ferrite-phase microstructure. An annealing temperature of the hot-rolled sheet of lower than 600 C results in insufficient recrystallization of the ferrite phase and insufficient transformation of the martensite phase into the ferrite phase, thereby easily forming punching cracks due to excessive hardening of the steel sheet. An annealing temperature of higher than 750 C results in excessively coarse grains having an average grain size of more than 20 m to easily cause large rollover and burrs during punching work, thereby failing to obtain a predetermined dimensional accuracy during the punching work. A holding time of less than 1 minute results in insufficient recrystallization of the ferrite phase and insufficient transformation of the martensite phase into the ferrite phase, thereby easily forming punching cracks due to excessive hardening of the steel sheet. A holding time of more than 24 hours results in excessively coarse grains having an average grain size of more than 20 m to easily cause large rollover and burrs 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 during punching work, thereby failing to obtain the predetermined dimensional accuracy during the punching work.
Accordingly, in the present invention, it is necessary to perform the hot-rolled steel sheet annealing in which holding is performed in a temperature range of 600 C or higher and lower than 750 C for 1 minute to 24 hours.
A hot-rolled steel sheet annealing step is performed by performing holding the hot-rolled steel sheet in the appropriate temperature range in the single ferrite phase 2019500546W00-English specification Date Recue/Date Received 2021-03-29 temperature region, specifically at 600 C or higher and lower than 750 C for 1 minute to 24 hours. Regarding the ferrite phase and a martensite phase that have been present in the metal microstructure after the hot rolling, the hot-rolled steel sheet annealing brings recrystallization of the ferrite phase and transformation of the martensite phase into the ferrite phase, thereby providing a single ferrite-phase microstructure. An annealing temperature of the hot-rolled sheet of lower than 600 C results in insufficient recrystallization of the ferrite phase and insufficient transformation of the martensite phase into the ferrite phase, thereby easily forming punching cracks due to excessive hardening of the steel sheet. An annealing temperature of higher than 750 C results in excessively coarse grains having an average grain size of more than 20 m to easily cause large rollover and burrs during punching work, thereby failing to obtain a predetermined dimensional accuracy during the punching work. A holding time of less than 1 minute results in insufficient recrystallization of the ferrite phase and insufficient transformation of the martensite phase into the ferrite phase, thereby easily forming punching cracks due to excessive hardening of the steel sheet. A holding time of more than 24 hours results in excessively coarse grains having an average grain size of more than 20 m to easily cause large rollover and burrs 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 during punching work, thereby failing to obtain the predetermined dimensional accuracy during the punching work.
Accordingly, in the present invention, it is necessary to perform the hot-rolled steel sheet annealing in which holding is performed in a temperature range of 600 C or higher and lower than 750 C for 1 minute to 24 hours.
[0023]
As described above, in the present invention, the metal microstructure is a single ferrite phase microstructure, and the single ferrite phase microstructure has an average grain size of 5 to 20 pm. The average grain size is preferably 7 pm or more, more preferably 10 pm or more. The average grain size is preferably 18 pm or less, more preferably 15 pm or less.
As described above, in the present invention, the metal microstructure is a single ferrite phase microstructure, and the single ferrite phase microstructure has an average grain size of 5 to 20 pm. The average grain size is preferably 7 pm or more, more preferably 10 pm or more. The average grain size is preferably 18 pm or less, more preferably 15 pm or less.
[0024]
The average grain size can be determined as follows: A
test piece for microstructure observation is taken from the middle portion of the sheet in the width direction. A
section thereof in the rolling direction is mirror-polished.
Then measurement and analysis are performed in the field of view including the entire thickness by a SEM/EBSD method.
Boundaries with a misorientation of 15 or more are defined as grain boundaries. The average grain size can be determined on the basis of an area method.
The average grain size can be determined as follows: A
test piece for microstructure observation is taken from the middle portion of the sheet in the width direction. A
section thereof in the rolling direction is mirror-polished.
Then measurement and analysis are performed in the field of view including the entire thickness by a SEM/EBSD method.
Boundaries with a misorientation of 15 or more are defined as grain boundaries. The average grain size can be determined on the basis of an area method.
[0025]
2019300546W00-English specification Date Recue/Date Received 2021-03-29 The thickness of the hot-rolled and annealed ferritic stainless steel sheet of the present invention is preferably, but not necessarily, 5.0 mm or more, more preferably 8.0 mm or more because the sheet thickness is desirably a sheet thickness that can be used for a thick-wall flange. The sheet thickness is preferably 15.0 mm or less, more preferably 13.0 mm or less.
2019300546W00-English specification Date Recue/Date Received 2021-03-29 The thickness of the hot-rolled and annealed ferritic stainless steel sheet of the present invention is preferably, but not necessarily, 5.0 mm or more, more preferably 8.0 mm or more because the sheet thickness is desirably a sheet thickness that can be used for a thick-wall flange. The sheet thickness is preferably 15.0 mm or less, more preferably 13.0 mm or less.
[0026]
The chemical composition of the hot-rolled and annealed ferritic stainless steel sheet of the present invention will be described below.
Hereinafter, the component contents are given in units of "%", which indicates "% by mass", unless otherwise specified.
The chemical composition of the hot-rolled and annealed ferritic stainless steel sheet of the present invention will be described below.
Hereinafter, the component contents are given in units of "%", which indicates "% by mass", unless otherwise specified.
[0027]
C: 0.001% to 0.020%
When C is contained in an amount of more than 0.020%, the workability and the corrosion resistance in a weld zone deteriorate markedly. A lower C content is more preferable from the viewpoints of the corrosion resistance and the workability. To obtain a C content of less than 0.001%, it takes long time to perform refining, which is not preferred in terms of production. Thus, the C content is in the range of 0.001% to 0.020%. The C content is preferably 0.003% or more, more preferably 0.004% or more. The C content is 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 preferably 0.015% or less, more preferably 0.012% or less.
C: 0.001% to 0.020%
When C is contained in an amount of more than 0.020%, the workability and the corrosion resistance in a weld zone deteriorate markedly. A lower C content is more preferable from the viewpoints of the corrosion resistance and the workability. To obtain a C content of less than 0.001%, it takes long time to perform refining, which is not preferred in terms of production. Thus, the C content is in the range of 0.001% to 0.020%. The C content is preferably 0.003% or more, more preferably 0.004% or more. The C content is 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 preferably 0.015% or less, more preferably 0.012% or less.
[0028]
Si: 0.05% to 1.00%
Si is an element that concentrates at an oxide layer formed during welding, is thus effective in improving the corrosion resistance in a weld zone, and is also effective as a deoxidizing element in the steelmaking process. These effects are obtained at a Si content of 0.05% or more and are enhanced as the Si content increases. However, a Si content of more than 1.00% results in an increase in rolling load and significant formation of scales in the hot-rolling step to induce the increases of surface defects and production costs and thus is not preferred. Accordingly, the Si content is 0.05% to 1.00%. The Si content is preferably 0.10% or more, more preferably 0.15% or more.
The Si content is preferably 0.60% or less, more preferably 0.40% or less.
Si: 0.05% to 1.00%
Si is an element that concentrates at an oxide layer formed during welding, is thus effective in improving the corrosion resistance in a weld zone, and is also effective as a deoxidizing element in the steelmaking process. These effects are obtained at a Si content of 0.05% or more and are enhanced as the Si content increases. However, a Si content of more than 1.00% results in an increase in rolling load and significant formation of scales in the hot-rolling step to induce the increases of surface defects and production costs and thus is not preferred. Accordingly, the Si content is 0.05% to 1.00%. The Si content is preferably 0.10% or more, more preferably 0.15% or more.
The Si content is preferably 0.60% or less, more preferably 0.40% or less.
[0029]
Mn: 0.05% to 1.00%
Mn is an austenite-forming element and effective in increasing the amount of austenite formed during heating before rolling in the hot-rolling step. Additionally, Mn acts as a deoxidizer. To obtain these effects, a Mn content of 0.05% or more is needed. However, a Mn content of more than 1.00% results in the promotion of the precipitation of 2019500546W00-English specification Date Recue/Date Received 2021-03-29 MnS acting as a starting point of corrosion to deteriorate the corrosion resistance. Accordingly, the Mn content is 0.05% to 1.00%. The Mn content is preferably 0.10% or more, more preferably 0.15% or more. The Mn content is preferably 0.60% or less, more preferably 0.30% or less.
Mn: 0.05% to 1.00%
Mn is an austenite-forming element and effective in increasing the amount of austenite formed during heating before rolling in the hot-rolling step. Additionally, Mn acts as a deoxidizer. To obtain these effects, a Mn content of 0.05% or more is needed. However, a Mn content of more than 1.00% results in the promotion of the precipitation of 2019500546W00-English specification Date Recue/Date Received 2021-03-29 MnS acting as a starting point of corrosion to deteriorate the corrosion resistance. Accordingly, the Mn content is 0.05% to 1.00%. The Mn content is preferably 0.10% or more, more preferably 0.15% or more. The Mn content is preferably 0.60% or less, more preferably 0.30% or less.
[0030]
P: 0.04% or Less P is an element that is unavoidably contained in steel and is also an element harmful to the corrosion resistance and workability; thus, the P content is preferably minimized.
In particular, a P content of more than 0.04% results in a significant deterioration in workability due to solution hardening. Accordingly, the P content is 0.04% or less. The P content is preferably 0.03% or less.
P: 0.04% or Less P is an element that is unavoidably contained in steel and is also an element harmful to the corrosion resistance and workability; thus, the P content is preferably minimized.
In particular, a P content of more than 0.04% results in a significant deterioration in workability due to solution hardening. Accordingly, the P content is 0.04% or less. The P content is preferably 0.03% or less.
[0031]
S: 0.01% or Less As with P, S is also an element that is unavoidably contained in steel and is also an element harmful to the corrosion resistance and workability; thus, the S content is preferably minimized. In particular, a S content of more than 0.01% results in a significant deterioration in corrosion resistance. Accordingly, the S content is 0.01%
or less. The S content is preferably 0.008% or less. The S
content is more preferably 0.003% or less.
S: 0.01% or Less As with P, S is also an element that is unavoidably contained in steel and is also an element harmful to the corrosion resistance and workability; thus, the S content is preferably minimized. In particular, a S content of more than 0.01% results in a significant deterioration in corrosion resistance. Accordingly, the S content is 0.01%
or less. The S content is preferably 0.008% or less. The S
content is more preferably 0.003% or less.
[0032]
2019500546W00-English specification Date Recue/Date Received 2021-03-29 Al: 0.01% to 0.10%
Al is an effective deoxidizer. Al has a higher affinity for nitrogen than Cr; thus, Al is effective in precipitating nitrogen in the form of aluminum nitride instead of chromium nitride to suppress sensitization when nitrogen enters a weld zone. These effects are obtained at an Al content of 0.01% or more. However, an Al content of more than 0.10%
results in the deterioration of the penetration characteristics during welding to deteriorate the welding workability and thus is not preferred. Accordingly, the Al content is in the range of 0.01% to 0.10%. The Al content is preferably 0.02% or more, more preferably 0.03% or more.
The Al content is preferably 0.06% or less, more preferably 0.04% or less.
2019500546W00-English specification Date Recue/Date Received 2021-03-29 Al: 0.01% to 0.10%
Al is an effective deoxidizer. Al has a higher affinity for nitrogen than Cr; thus, Al is effective in precipitating nitrogen in the form of aluminum nitride instead of chromium nitride to suppress sensitization when nitrogen enters a weld zone. These effects are obtained at an Al content of 0.01% or more. However, an Al content of more than 0.10%
results in the deterioration of the penetration characteristics during welding to deteriorate the welding workability and thus is not preferred. Accordingly, the Al content is in the range of 0.01% to 0.10%. The Al content is preferably 0.02% or more, more preferably 0.03% or more.
The Al content is preferably 0.06% or less, more preferably 0.04% or less.
[0033]
Cr: 10.0% to 20.0%
Cr is the most important element for ensuring the corrosion resistance of stainless steel. If the Cr content is less than 10.0%, the corrosion resistance in an automobile exhaust gas atmosphere cannot be ensured sufficiently. If the Cr content is more than 20.0%, an amount of an austenite phase formed in the hot-rolling step is insufficient even if a predetermined amount of Ni is contained; thus, the effect of reducing the size of grains in the metal microstructure in the hot-rolling step is not 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 sufficiently obtained to lead to an average grain size of more than 20 m after the hot-rolled steel sheet annealing, thereby failing to obtain the predetermined dimensional accuracy during the punching work. Accordingly, the Cr content is in the range of 10.0% to 20.0%. The Cr content is preferably in the range of 10.0% to 17.0%. The Cr content is more preferably 10.5% or more, even more preferably 11.2% or more. The Cr content is more preferably 12.0% or less, even more preferably 11.7% or less.
Cr: 10.0% to 20.0%
Cr is the most important element for ensuring the corrosion resistance of stainless steel. If the Cr content is less than 10.0%, the corrosion resistance in an automobile exhaust gas atmosphere cannot be ensured sufficiently. If the Cr content is more than 20.0%, an amount of an austenite phase formed in the hot-rolling step is insufficient even if a predetermined amount of Ni is contained; thus, the effect of reducing the size of grains in the metal microstructure in the hot-rolling step is not 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 sufficiently obtained to lead to an average grain size of more than 20 m after the hot-rolled steel sheet annealing, thereby failing to obtain the predetermined dimensional accuracy during the punching work. Accordingly, the Cr content is in the range of 10.0% to 20.0%. The Cr content is preferably in the range of 10.0% to 17.0%. The Cr content is more preferably 10.5% or more, even more preferably 11.2% or more. The Cr content is more preferably 12.0% or less, even more preferably 11.7% or less.
[0034]
Ni: 0.50% to 2.00%
Ni is an austenite-forming element and effective in increasing the amount of austenite formed during heating before rolling in the hot-rolling step. In the present invention, an austenite phase is formed during heating in the hot-rolling step by controlling the Cr and Ni contents to predetermined values. The formation of the austenite phase results in the grain refinement of the coarse-grained metal microstructure formed during casting. Additionally, the dynamic and/or static recrystallization of the austenite phase occurs in the hot rolling to lead to further grain refinement of the metal microstructure after the hot rolling, thereby contributing to the grain refinement of the metal microstructure after the hot-rolled steel sheet annealing.
These effects are obtained at a Ni content of 0.50% or more.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 A Ni content of more than 2.00% results in an excess of dissolved Ni. This is liable to cause the formation of punching cracks due to excessive hardening of the hot-rolled and annealed steel sheet. Accordingly, the Ni content is 0.50% to 2.00%. The Ni content is preferably 0.60% or more, more preferably 0.70% or more, even more preferably 0.75% or more. The Ni content is preferably 1.50% or less, more preferably 1.00% or less.
Ni: 0.50% to 2.00%
Ni is an austenite-forming element and effective in increasing the amount of austenite formed during heating before rolling in the hot-rolling step. In the present invention, an austenite phase is formed during heating in the hot-rolling step by controlling the Cr and Ni contents to predetermined values. The formation of the austenite phase results in the grain refinement of the coarse-grained metal microstructure formed during casting. Additionally, the dynamic and/or static recrystallization of the austenite phase occurs in the hot rolling to lead to further grain refinement of the metal microstructure after the hot rolling, thereby contributing to the grain refinement of the metal microstructure after the hot-rolled steel sheet annealing.
These effects are obtained at a Ni content of 0.50% or more.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 A Ni content of more than 2.00% results in an excess of dissolved Ni. This is liable to cause the formation of punching cracks due to excessive hardening of the hot-rolled and annealed steel sheet. Accordingly, the Ni content is 0.50% to 2.00%. The Ni content is preferably 0.60% or more, more preferably 0.70% or more, even more preferably 0.75% or more. The Ni content is preferably 1.50% or less, more preferably 1.00% or less.
[0035]
Ti: 0.10% to 0.40%
Ti preferentially combines with C and N and thus is effective in suppressing the precipitation of chromium carbonitride, reducing the recrystallization temperature, and suppressing a deterioration in corrosion resistance due to sensitization caused by the precipitation of chromium carbonitride. To obtain these effects, Ti needs to be contained in an amount of 0.10% or more. However, a Ti content of more than 0.40% results in the formation of coarse titanium carbonitride in a casting step to significantly deteriorate the toughness of the steel sheet and to cause surface defects and thus is not preferred in terms of production. Accordingly, the Ti content is 0.10%
to 0.40%. The Ti content is preferably 0.15% or more, more preferably 0.20% or more. The Ti content is preferably 0.35% or less. The Ti content is more preferably 0.30% or 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 less. Preferably, the Ti content is such that the Ti content satisfies the following formula Ti/(C + N) 8 (where, in the formula, Ti, C, and N are the amounts of the relevant elements contained (% by mass)) in view of the corrosion resistance in a weld zone.
Ti: 0.10% to 0.40%
Ti preferentially combines with C and N and thus is effective in suppressing the precipitation of chromium carbonitride, reducing the recrystallization temperature, and suppressing a deterioration in corrosion resistance due to sensitization caused by the precipitation of chromium carbonitride. To obtain these effects, Ti needs to be contained in an amount of 0.10% or more. However, a Ti content of more than 0.40% results in the formation of coarse titanium carbonitride in a casting step to significantly deteriorate the toughness of the steel sheet and to cause surface defects and thus is not preferred in terms of production. Accordingly, the Ti content is 0.10%
to 0.40%. The Ti content is preferably 0.15% or more, more preferably 0.20% or more. The Ti content is preferably 0.35% or less. The Ti content is more preferably 0.30% or 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 less. Preferably, the Ti content is such that the Ti content satisfies the following formula Ti/(C + N) 8 (where, in the formula, Ti, C, and N are the amounts of the relevant elements contained (% by mass)) in view of the corrosion resistance in a weld zone.
[0036]
N: 0.001% to 0.020%
At a N content of more than 0.020%, the workability and the corrosion resistance in a weld zone deteriorate markedly.
A lower N content is more preferable from the viewpoint of the corrosion resistance. It takes long time to perform refining to reduce the N content to less than 0.001%. Such refining leads to an increase in production cost and a deterioration in productivity, which is not preferred.
Accordingly, the N content is in the range of 0.001% to 0.020%. The N content is preferably 0.005% or more, more preferably 0.007% or more. The N content is preferably 0.015% or less. The N content is more preferably 0.012% or less.
N: 0.001% to 0.020%
At a N content of more than 0.020%, the workability and the corrosion resistance in a weld zone deteriorate markedly.
A lower N content is more preferable from the viewpoint of the corrosion resistance. It takes long time to perform refining to reduce the N content to less than 0.001%. Such refining leads to an increase in production cost and a deterioration in productivity, which is not preferred.
Accordingly, the N content is in the range of 0.001% to 0.020%. The N content is preferably 0.005% or more, more preferably 0.007% or more. The N content is preferably 0.015% or less. The N content is more preferably 0.012% or less.
[0037]
The present invention provides a ferritic stainless steel featured by containing the foregoing essential components and the balance being Fe and incidental impurities. If necessary, one or two or more selected from Cu, Mo, W, and Co, and/or one or two or more selected from V, 2019500546W00-English specification Date Recue/Date Received 2021-03-29 Nb, Zr, REM, B, Mg, and Ca may be further contained in ranges described below. The advantageous effects of the present invention are not impaired when the elements are contained in amounts of less than the lower limits. Thus, when the elements are contained in amounts of less than the lower limits, the elements are regarded as incidental impurities.
The present invention provides a ferritic stainless steel featured by containing the foregoing essential components and the balance being Fe and incidental impurities. If necessary, one or two or more selected from Cu, Mo, W, and Co, and/or one or two or more selected from V, 2019500546W00-English specification Date Recue/Date Received 2021-03-29 Nb, Zr, REM, B, Mg, and Ca may be further contained in ranges described below. The advantageous effects of the present invention are not impaired when the elements are contained in amounts of less than the lower limits. Thus, when the elements are contained in amounts of less than the lower limits, the elements are regarded as incidental impurities.
[0038]
Cu: 0.01% to 1.00%
Cu is an element particularly effective in improving the corrosion resistance of the base metal and a weld zone in an aqueous solution or when slightly acidic water droplets adhere thereto. The effect is obtained at a Cu content of 0.01% or more and is enhanced as the Cu content increases. However, a Cu content of more than 1.00% may result in a deterioration in hot workability to induce surface defects. Furthermore, a difficulty may lie in descaling after annealing. Accordingly, when Cu is contained, the Cu content is preferably in the range of 0.01% to 1.00%. The Cu content is more preferably 0.10% or more, even more preferably 0.30% or more. The Cu content is more preferably 0.60% or less, even more preferably 0.45% or less.
Cu: 0.01% to 1.00%
Cu is an element particularly effective in improving the corrosion resistance of the base metal and a weld zone in an aqueous solution or when slightly acidic water droplets adhere thereto. The effect is obtained at a Cu content of 0.01% or more and is enhanced as the Cu content increases. However, a Cu content of more than 1.00% may result in a deterioration in hot workability to induce surface defects. Furthermore, a difficulty may lie in descaling after annealing. Accordingly, when Cu is contained, the Cu content is preferably in the range of 0.01% to 1.00%. The Cu content is more preferably 0.10% or more, even more preferably 0.30% or more. The Cu content is more preferably 0.60% or less, even more preferably 0.45% or less.
[0039]
Mo: 0.01% to 2.00%
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 Mo is an element that markedly improves the corrosion resistance of stainless steel. The effect is obtained at a Mo content of 0.01% or more and is improved as the Mo content increases. However, a Mo content of more than 2.00%
may result in an increase in rolling load during hot rolling to deteriorate the productivity and an excessive increase in the strength of the steel sheet. Since Mo is an expensive element, a large amount of Mo contained results in an increase in production cost. Accordingly, when Mo is contained, the Mo content is preferably 0.01% to 2.00%. The Mo content is more preferably 0.10% or more, even more preferably 0.30% or more. The Mo content is more preferably 1.40% or less, even more preferably 0.90% or less.
Mo: 0.01% to 2.00%
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 Mo is an element that markedly improves the corrosion resistance of stainless steel. The effect is obtained at a Mo content of 0.01% or more and is improved as the Mo content increases. However, a Mo content of more than 2.00%
may result in an increase in rolling load during hot rolling to deteriorate the productivity and an excessive increase in the strength of the steel sheet. Since Mo is an expensive element, a large amount of Mo contained results in an increase in production cost. Accordingly, when Mo is contained, the Mo content is preferably 0.01% to 2.00%. The Mo content is more preferably 0.10% or more, even more preferably 0.30% or more. The Mo content is more preferably 1.40% or less, even more preferably 0.90% or less.
[0040]
W: 0.01% to 0.20%
As with Mo, W is effective in improving the corrosion resistance. The effect is obtained at a W content of 0.01%
or more. However, a W content of more than 0.20% may result in an increase in strength to lead to a deterioration in productivity due to, for example, an increase in rolling load. Accordingly, when W is contained, the W content is preferably in the range of 0.01% to 0.20%. The W content is more preferably 0.05% or more. The W content is more preferably 0.15% or less.
W: 0.01% to 0.20%
As with Mo, W is effective in improving the corrosion resistance. The effect is obtained at a W content of 0.01%
or more. However, a W content of more than 0.20% may result in an increase in strength to lead to a deterioration in productivity due to, for example, an increase in rolling load. Accordingly, when W is contained, the W content is preferably in the range of 0.01% to 0.20%. The W content is more preferably 0.05% or more. The W content is more preferably 0.15% or less.
[0041]
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 Co: 0.01% to 0.20%
Co is an element that improves the toughness. The effect is obtained when Co is contained in an amount of 0.01% or more. A Co content of more than 0.20% may result in a deterioration in workability. Accordingly, when Co is contained, the Co content is preferably in the range of 0.01% to 0.20%.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 Co: 0.01% to 0.20%
Co is an element that improves the toughness. The effect is obtained when Co is contained in an amount of 0.01% or more. A Co content of more than 0.20% may result in a deterioration in workability. Accordingly, when Co is contained, the Co content is preferably in the range of 0.01% to 0.20%.
[0042]
V: 0.01% to 0.20%
V combines with C and N in the form of carbonitride to suppress sensitization during welding, improving the corrosion resistance in the weld zone. The effect is obtained at a V content of 0.01% or more. A V content of more than 0.20% may result in significant deteriorations in workability and toughness. Accordingly, the V content is preferably 0.01% to 0.20%. The V content is more preferably 0.02% or more. The V content is more preferably 0.050% or less.
V: 0.01% to 0.20%
V combines with C and N in the form of carbonitride to suppress sensitization during welding, improving the corrosion resistance in the weld zone. The effect is obtained at a V content of 0.01% or more. A V content of more than 0.20% may result in significant deteriorations in workability and toughness. Accordingly, the V content is preferably 0.01% to 0.20%. The V content is more preferably 0.02% or more. The V content is more preferably 0.050% or less.
[0043]
Nb: 0.01% to 0.10%
Nb is effective in increasing the 0.2% proof stress by refining grains and precipitating in the form of a fine carbonitride. These effects are obtained at a Nb content of 0.01% or more. Nb is also effective in increasing the recrystallization temperature. At a Nb content of more than 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 0.10%, an excessively high annealing temperature is required for sufficient recrystallization in the hot-rolled steel sheet annealing; thus, a single ferrite phase microstructure having an average grain size of 5 to 20 pm after the hot-rolled steel sheet annealing, which is a requirement for the present invention, is not obtained, in some cases.
Accordingly, when Nb is contained, the Nb content is preferably in the range of 0.01% to 0.10%. The Nb content is more preferably 0.01% to 0.05%.
Nb: 0.01% to 0.10%
Nb is effective in increasing the 0.2% proof stress by refining grains and precipitating in the form of a fine carbonitride. These effects are obtained at a Nb content of 0.01% or more. Nb is also effective in increasing the recrystallization temperature. At a Nb content of more than 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 0.10%, an excessively high annealing temperature is required for sufficient recrystallization in the hot-rolled steel sheet annealing; thus, a single ferrite phase microstructure having an average grain size of 5 to 20 pm after the hot-rolled steel sheet annealing, which is a requirement for the present invention, is not obtained, in some cases.
Accordingly, when Nb is contained, the Nb content is preferably in the range of 0.01% to 0.10%. The Nb content is more preferably 0.01% to 0.05%.
[0044]
Zr: 0.01% to 0.20%
Zr combines with C and N and is effective in suppressing sensitization. The effect is obtained at a Zr content of 0.01% or more. A Zr content of more than 0.20%
may result in a significant deterioration in workability.
Accordingly, when Zr is contained, the Zr content is preferably in the range of 0.01% to 0.20%. The Zr content is more preferably in the range of 0.01% to 0.10%.
Zr: 0.01% to 0.20%
Zr combines with C and N and is effective in suppressing sensitization. The effect is obtained at a Zr content of 0.01% or more. A Zr content of more than 0.20%
may result in a significant deterioration in workability.
Accordingly, when Zr is contained, the Zr content is preferably in the range of 0.01% to 0.20%. The Zr content is more preferably in the range of 0.01% to 0.10%.
[0045]
REMs: 0.001% to 0.100%
Rare earth metals (REMs) are effective in improving oxidation resistance and suppress the formation of an oxide film in a weld zone (temper color due to welding) to suppress the formation of a Cr-depleted region immediately below the oxide film. The effect is obtained when REMs are 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 contained in amounts of 0.001% or more. When REMs are contained in amounts of more than 0.100%, the hot workability may deteriorate. Accordingly, when REMs are contained, REMs are preferably contained in the range of 0.001% to 0.100%. REMs are more preferably contained in the range of 0.001% to 0.050%.
REMs: 0.001% to 0.100%
Rare earth metals (REMs) are effective in improving oxidation resistance and suppress the formation of an oxide film in a weld zone (temper color due to welding) to suppress the formation of a Cr-depleted region immediately below the oxide film. The effect is obtained when REMs are 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 contained in amounts of 0.001% or more. When REMs are contained in amounts of more than 0.100%, the hot workability may deteriorate. Accordingly, when REMs are contained, REMs are preferably contained in the range of 0.001% to 0.100%. REMs are more preferably contained in the range of 0.001% to 0.050%.
[0046]
B: 0.0002% to 0.0025%
B is an element effective in improving resistance to secondary work embrittlement after deep drawing. The effect is obtained at a B content of 0.0002% or more. A B content of more than 0.0025% may result in deteriorations in workability and toughness. Accordingly, when B is contained, the B content is preferably in the range of 0.0002% to 0.0025%. The B content is more preferably 0.0003% or more.
The B content is more preferably 0.0006% or less.
B: 0.0002% to 0.0025%
B is an element effective in improving resistance to secondary work embrittlement after deep drawing. The effect is obtained at a B content of 0.0002% or more. A B content of more than 0.0025% may result in deteriorations in workability and toughness. Accordingly, when B is contained, the B content is preferably in the range of 0.0002% to 0.0025%. The B content is more preferably 0.0003% or more.
The B content is more preferably 0.0006% or less.
[0047]
Mg: 0.0005% to 0.0030%
Mg is an element effective in improving the fraction of equiaxed crystals in a slab to improve the workability and the toughness. Regarding Ti-containing steel as in the present invention, the coarsening of titanium carbonitride deteriorates the toughness. Mg is also effective in suppressing the coarsening of titanium carbonitride. These effects are obtained at a Mg content of 0.0005% or more. A
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 Mg content of 0.0030% may deteriorate the surface properties of steel. Accordingly, when Mg is contained, the Mg content is preferably in the range of 0.0005% to 0.0030%. The Mg content is more preferably 0.0010% or more. The Mg content is more preferably 0.0020% or less.
Mg: 0.0005% to 0.0030%
Mg is an element effective in improving the fraction of equiaxed crystals in a slab to improve the workability and the toughness. Regarding Ti-containing steel as in the present invention, the coarsening of titanium carbonitride deteriorates the toughness. Mg is also effective in suppressing the coarsening of titanium carbonitride. These effects are obtained at a Mg content of 0.0005% or more. A
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 Mg content of 0.0030% may deteriorate the surface properties of steel. Accordingly, when Mg is contained, the Mg content is preferably in the range of 0.0005% to 0.0030%. The Mg content is more preferably 0.0010% or more. The Mg content is more preferably 0.0020% or less.
[0048]
Ca: 0.0003% to 0.0030%
Ca is an element effective in preventing nozzle clogging due to the crystallization of Ti-based inclusions, which tends to occur during continuous casting. The effect is obtained at a Ca content of 0.0003% or more. However, a Ca content of more than 0.0030% may result in the formation of CaS to deteriorate the corrosion resistance. Accordingly, when Ca is contained, the Ca content is preferably in the range of 0.0003% to 0.0030%. The Ca content is more preferably 0.0005% or more. The Ca content is more preferably 0.0015% or less, even more preferably 0.0010% or less.
Ca: 0.0003% to 0.0030%
Ca is an element effective in preventing nozzle clogging due to the crystallization of Ti-based inclusions, which tends to occur during continuous casting. The effect is obtained at a Ca content of 0.0003% or more. However, a Ca content of more than 0.0030% may result in the formation of CaS to deteriorate the corrosion resistance. Accordingly, when Ca is contained, the Ca content is preferably in the range of 0.0003% to 0.0030%. The Ca content is more preferably 0.0005% or more. The Ca content is more preferably 0.0015% or less, even more preferably 0.0010% or less.
[0049]
A method for producing a hot-rolled and annealed ferritic stainless steel sheet of the present invention will be described below.
A method for producing a hot-rolled and annealed ferritic stainless steel sheet of the present invention will be described below.
[0050]
A hot-rolled and annealed ferritic stainless steel sheet of the present invention is produced by subjecting a 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 steel slab having the foregoing chemical composition to the usual hot rolling process to produce a hot-rolled steel sheet and then subjecting the resulting hot-rolled steel sheet to hot-rolled steel sheet annealing in which holding is performed at 600 C or higher and lower than 750 C for 1 minute to 24 hours.
A hot-rolled and annealed ferritic stainless steel sheet of the present invention is produced by subjecting a 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 steel slab having the foregoing chemical composition to the usual hot rolling process to produce a hot-rolled steel sheet and then subjecting the resulting hot-rolled steel sheet to hot-rolled steel sheet annealing in which holding is performed at 600 C or higher and lower than 750 C for 1 minute to 24 hours.
[0051]
First, a molten steel having the foregoing chemical composition is produced by a known method using, for example, a converter, an electric furnace, or a vacuum melting furnace and is formed into a steel (slab) by a continuous casting process or an ingot casting-slabbing process.
First, a molten steel having the foregoing chemical composition is produced by a known method using, for example, a converter, an electric furnace, or a vacuum melting furnace and is formed into a steel (slab) by a continuous casting process or an ingot casting-slabbing process.
[0052]
The slab is heated at 1,050 C to 1,250 C for 1 to 24 hours and then subjected to hot rolling. Alternatively, the as-cast slab is directly subjected to hot rolling before the temperature of the slab after casting is decreased to a temperature bellow the foregoing temperature range. In the present invention, the technique and conditions of the hot rolling are not particularly limited. When a coiling process is performed at an excessively low temperature, the hot-rolled steel sheet may be significantly hardened to make it difficult to perform the operation of the subsequent process. Thus, the coiling process is preferably performed at 550 C or higher.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29
The slab is heated at 1,050 C to 1,250 C for 1 to 24 hours and then subjected to hot rolling. Alternatively, the as-cast slab is directly subjected to hot rolling before the temperature of the slab after casting is decreased to a temperature bellow the foregoing temperature range. In the present invention, the technique and conditions of the hot rolling are not particularly limited. When a coiling process is performed at an excessively low temperature, the hot-rolled steel sheet may be significantly hardened to make it difficult to perform the operation of the subsequent process. Thus, the coiling process is preferably performed at 550 C or higher.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29
[0053]
Hot-Rolled Steel Sheet Annealing: Holding at 600 C or Higher and Lower Than 750 C for I Minute to 24 Hours In the present invention, after the completion of the hot-rolling step, the hot-rolled steel sheet annealing is performed. In the hot-rolled steel sheet annealing, a rolled deformed microstructure formed in the hot-rolling step is recrystallized without excessively coarsening the metal microstructure, and a martensite phase formed in the hot-rolling step is transformed into a ferrite phase. To obtain the effect, the hot-rolled steel sheet annealing needs to be performed at 600 C or higher and lower than 750 C. At an annealing temperature of lower than 600 C, insufficient recrystallization results in fine recovered grains from the hot-rolled deformed microstructure. The metal microstructure is excessively refined to fail to obtain the predetermined dimensional accuracy during punching work. Additionally, a deformed microstructure and a martensite phase remain in the metal microstructure after the hot-rolled steel sheet annealing. This may lead to the formation of punching cracks due to excessive hardening of the steel sheet even if the average grain size is within a predetermined range. An annealing temperature of 750 C or higher results in excessively coarse grains having an average grain size of more than 20 m, thereby failing to 2019500546W00-English specification Date Recue/Date Received 2021-03-29 obtain the predetermined dimensional accuracy during punching work. At a holding time of less than 1 minute, a deformed microstructure and a martensite phase remain in the metal microstructure after the hot-rolled steel sheet annealing. This easily leads to the formation of punching cracks due to excessive hardening of the steel sheet even if the average grain size is within a predetermined range. A
holding time of more than 24 hours results in excessively coarse grains having an average grain size of more than 20 m, thereby failing to obtain the predetermined dimensional accuracy during punching work. Accordingly, the hot-rolled steel sheet annealing is performed by performing holding in a temperature range of 600 C or higher and lower than 750 C
for 1 minute to 24 hours. The temperature of the hot-rolled steel sheet annealing is preferably 600 C or higher, more preferably 640 C or higher. The temperature of the hot-rolled steel sheet annealing is preferably 700 C or lower.
The holding time is preferably 1 hour or more, more preferably 6 hours or more. The holding time is preferably 20 hours or less, more preferably 12 hours or less. There is no particular limitation on the process of annealing the hot-rolled steel sheet, i.e., the hot-rolled steel sheet annealing process. Any one of box annealing (batch annealing) and continuous annealing may be employed.
Hot-Rolled Steel Sheet Annealing: Holding at 600 C or Higher and Lower Than 750 C for I Minute to 24 Hours In the present invention, after the completion of the hot-rolling step, the hot-rolled steel sheet annealing is performed. In the hot-rolled steel sheet annealing, a rolled deformed microstructure formed in the hot-rolling step is recrystallized without excessively coarsening the metal microstructure, and a martensite phase formed in the hot-rolling step is transformed into a ferrite phase. To obtain the effect, the hot-rolled steel sheet annealing needs to be performed at 600 C or higher and lower than 750 C. At an annealing temperature of lower than 600 C, insufficient recrystallization results in fine recovered grains from the hot-rolled deformed microstructure. The metal microstructure is excessively refined to fail to obtain the predetermined dimensional accuracy during punching work. Additionally, a deformed microstructure and a martensite phase remain in the metal microstructure after the hot-rolled steel sheet annealing. This may lead to the formation of punching cracks due to excessive hardening of the steel sheet even if the average grain size is within a predetermined range. An annealing temperature of 750 C or higher results in excessively coarse grains having an average grain size of more than 20 m, thereby failing to 2019500546W00-English specification Date Recue/Date Received 2021-03-29 obtain the predetermined dimensional accuracy during punching work. At a holding time of less than 1 minute, a deformed microstructure and a martensite phase remain in the metal microstructure after the hot-rolled steel sheet annealing. This easily leads to the formation of punching cracks due to excessive hardening of the steel sheet even if the average grain size is within a predetermined range. A
holding time of more than 24 hours results in excessively coarse grains having an average grain size of more than 20 m, thereby failing to obtain the predetermined dimensional accuracy during punching work. Accordingly, the hot-rolled steel sheet annealing is performed by performing holding in a temperature range of 600 C or higher and lower than 750 C
for 1 minute to 24 hours. The temperature of the hot-rolled steel sheet annealing is preferably 600 C or higher, more preferably 640 C or higher. The temperature of the hot-rolled steel sheet annealing is preferably 700 C or lower.
The holding time is preferably 1 hour or more, more preferably 6 hours or more. The holding time is preferably 20 hours or less, more preferably 12 hours or less. There is no particular limitation on the process of annealing the hot-rolled steel sheet, i.e., the hot-rolled steel sheet annealing process. Any one of box annealing (batch annealing) and continuous annealing may be employed.
[0054]
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 The resulting hot-rolled and annealed steel sheet may be subjected to descaling treatment using, for example, shot blasting or pickling, as needed. To improve surface properties, for example, grinding or polishing may be performed. The hot-rolled and annealed steel sheet according to the present invention may then be subjected to cold rolling and cold-rolled steel sheet annealing.
EXAMPLES
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 The resulting hot-rolled and annealed steel sheet may be subjected to descaling treatment using, for example, shot blasting or pickling, as needed. To improve surface properties, for example, grinding or polishing may be performed. The hot-rolled and annealed steel sheet according to the present invention may then be subjected to cold rolling and cold-rolled steel sheet annealing.
EXAMPLES
[0055]
The present invention will be described in detail below by examples.
The present invention will be described in detail below by examples.
[0056]
Molten stainless steels having chemical compositions given in Table 1 were produced with a 100 kg vacuum melting furnace. Steel ingots of those molten steels were heated at 1,100 C for 1 hour, hot-rolled to the thicknesses given in Table 2 (see "Thickness after completion of hot rolling" in Table 2), and subjected to simulated coiling treatment in which the steel sheets were held at 650 C for 1 hour and then furnace-cooled, thereby producing hot-rolled steel sheets. Subsequently, the hot-rolled steel sheets were subjected to hot-rolled steel sheet annealing in which the steel sheets were held at the temperatures given in Table 2 (see "Hot-rolled steel sheet annealing temperature" in Table 2) for 8 hours and then slowly cooled, thereby producing 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 hot-rolled and annealed steel sheets.
The thicknesses of the resulting hot-rolled and annealed steel sheets were the same as the respective thicknesses after the completion of the hot rolling.
The hot-rolled and annealed steel sheets thus obtained were evaluated as described below.
Molten stainless steels having chemical compositions given in Table 1 were produced with a 100 kg vacuum melting furnace. Steel ingots of those molten steels were heated at 1,100 C for 1 hour, hot-rolled to the thicknesses given in Table 2 (see "Thickness after completion of hot rolling" in Table 2), and subjected to simulated coiling treatment in which the steel sheets were held at 650 C for 1 hour and then furnace-cooled, thereby producing hot-rolled steel sheets. Subsequently, the hot-rolled steel sheets were subjected to hot-rolled steel sheet annealing in which the steel sheets were held at the temperatures given in Table 2 (see "Hot-rolled steel sheet annealing temperature" in Table 2) for 8 hours and then slowly cooled, thereby producing 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 hot-rolled and annealed steel sheets.
The thicknesses of the resulting hot-rolled and annealed steel sheets were the same as the respective thicknesses after the completion of the hot rolling.
The hot-rolled and annealed steel sheets thus obtained were evaluated as described below.
[0057]
(1) Evaluation of Metal Microstructure Test pieces for microstructure observation were taken from the middle portions of the sheets in the width direction. A section of each test piece in the rolling direction was mirror-polished. Then measurement and analysis were performed in the field of view including the entire thickness by a SEM/EBSD method. Boundaries with a misorientation of 15 or more were defined as grain boundaries. The average grain size was determined on the basis of an area method. A steel sheet having an average grain size of 5 lam or more and 20 WU or less is within the scope of the present invention. A steel sheet having an average grain size of less than 5 WU or more than 20 m is outside the scope of the present invention and underlined in Table 2.
(1) Evaluation of Metal Microstructure Test pieces for microstructure observation were taken from the middle portions of the sheets in the width direction. A section of each test piece in the rolling direction was mirror-polished. Then measurement and analysis were performed in the field of view including the entire thickness by a SEM/EBSD method. Boundaries with a misorientation of 15 or more were defined as grain boundaries. The average grain size was determined on the basis of an area method. A steel sheet having an average grain size of 5 lam or more and 20 WU or less is within the scope of the present invention. A steel sheet having an average grain size of less than 5 WU or more than 20 m is outside the scope of the present invention and underlined in Table 2.
[0058]
Similarly, test pieces for microstructure observation were taken from the middle portions of the sheets in the 2019500546W00-English specification Date Recue/Date Received 2021-03-29 width direction. A section of each test piece in the rolling direction was mirror-polished. The section was etched for observation with an aqueous solution of picric acid and hydrochloric acid to expose a metal microstructure.
The metal microstructure was observed with an optical microscope at a magnification of x500. Whether the metal microstructure of each steel sheet was a single ferrite phase microstructure was determined by distinguishing a ferrite phase from a martensite phase on the basis of the morphology of the metal microstructure. Specifically, a region in which a uniform and flat morphology was observed in a grain and a relatively bright tone was observed was regarded as a ferrite phase. A region in which surface morphology unique to the martensite phase, such as subboundaries and block boundaries, was observed in a grain and which exhibited a darker tone than the ferrite phase was regarded as a martensite phase. In the table, F indicates that the metal microstructure was a single ferrite phase microstructure.
Similarly, test pieces for microstructure observation were taken from the middle portions of the sheets in the 2019500546W00-English specification Date Recue/Date Received 2021-03-29 width direction. A section of each test piece in the rolling direction was mirror-polished. The section was etched for observation with an aqueous solution of picric acid and hydrochloric acid to expose a metal microstructure.
The metal microstructure was observed with an optical microscope at a magnification of x500. Whether the metal microstructure of each steel sheet was a single ferrite phase microstructure was determined by distinguishing a ferrite phase from a martensite phase on the basis of the morphology of the metal microstructure. Specifically, a region in which a uniform and flat morphology was observed in a grain and a relatively bright tone was observed was regarded as a ferrite phase. A region in which surface morphology unique to the martensite phase, such as subboundaries and block boundaries, was observed in a grain and which exhibited a darker tone than the ferrite phase was regarded as a martensite phase. In the table, F indicates that the metal microstructure was a single ferrite phase microstructure.
[0059]
(2) Evaluation of Corrosion Resistance Test pieces measuring 60 x 100 mm were taken from the hot-rolled and annealed steel sheets. Surfaces of each of the test pieces were subjected to abrasive finishing with 600-grit emery paper. Then end-face portions of each test 2019500546W00-English specification Date Recue/Date Received 2021-03-29 piece were sealed. The test pieces were subjected to a cyclic salt-spray test specified in JIS H 8502. One cycle of the cyclic salt-spray test consisted of salt spraying ( 5% by mass NaCl, 35 C, spraying for 2 hours) -* drying (60 C, 4 hours, relative humidity: 40%) -* wetting (50 C, 2 hours, relative humidity: 95%). The cyclic salt-spray test was performed five cycles. After the cyclic salt-spray test was performed five cycles, the surfaces of each test piece were photographed. The rusted area of the surfaces of the test piece was measured by image analysis. The percentage of rusted area ((rusted area of test piece/total area of test piece) x 100 [%]) was calculated with respect to the total area of the test piece. A percentage of rusted area of 10%
or less, which indicated that the steel sheet had outstanding corrosion resistance, was rated as "acceptable"
(D). A percentage of rusted area of more than 10% and 25%
or less was rated as "acceptable" (D). A percentage of rusted area of more than 25% was rated as "unacceptable" (x).
(2) Evaluation of Corrosion Resistance Test pieces measuring 60 x 100 mm were taken from the hot-rolled and annealed steel sheets. Surfaces of each of the test pieces were subjected to abrasive finishing with 600-grit emery paper. Then end-face portions of each test 2019500546W00-English specification Date Recue/Date Received 2021-03-29 piece were sealed. The test pieces were subjected to a cyclic salt-spray test specified in JIS H 8502. One cycle of the cyclic salt-spray test consisted of salt spraying ( 5% by mass NaCl, 35 C, spraying for 2 hours) -* drying (60 C, 4 hours, relative humidity: 40%) -* wetting (50 C, 2 hours, relative humidity: 95%). The cyclic salt-spray test was performed five cycles. After the cyclic salt-spray test was performed five cycles, the surfaces of each test piece were photographed. The rusted area of the surfaces of the test piece was measured by image analysis. The percentage of rusted area ((rusted area of test piece/total area of test piece) x 100 [%]) was calculated with respect to the total area of the test piece. A percentage of rusted area of 10%
or less, which indicated that the steel sheet had outstanding corrosion resistance, was rated as "acceptable"
(D). A percentage of rusted area of more than 10% and 25%
or less was rated as "acceptable" (D). A percentage of rusted area of more than 25% was rated as "unacceptable" (x).
[0060]
(3) Evaluation of Punching Work Samples measuring 100 mm x 100 mm for testing were taken from the hot-rolled and annealed steel sheets. Five test specimens were produced by punching work with a crank press equipped with an upper die (punch) and a lower die (die) so as to form a hole having a diameter of 20 mm 2019500546W00-English specification Date Recue/Date Received 2021-03-29 (tolerance: 0.1 mm) in the middle portion of each of the samples, the upper die having a cylindrical edge for punching and a diameter of 20 mm, the lower die having a hole appropriately selected in such a manner that the clearance between the upper die and the lower die was 10%.
The relationships among the clearance (C) [%], the hole diameter of the die (the inside diameter of the die) (Dd) [mm], the diameter of the punch (Dp) [mm], and the sheet thickness (t) [mm] are represented by formula (1) below.
C = (Dd -Dp) + (2 x t) x 100 formula (1) With respect to the test specimens thus obtained, the appearance of each test specimen was visually inspected, and the diameter of the hole in the middle portion of the test specimen was measured with a digital caliper. The case where no cracks were observed and where the hole diameter of each of the five test specimens after the punching work was in the range of 19.9 to 20.1 mm was rated as "acceptable"
(D). The case where any one of them was cracked or had a hole diameter of less than 19.9 mm or more than 20.1 mm was rated as "unacceptable" (x).
(3) Evaluation of Punching Work Samples measuring 100 mm x 100 mm for testing were taken from the hot-rolled and annealed steel sheets. Five test specimens were produced by punching work with a crank press equipped with an upper die (punch) and a lower die (die) so as to form a hole having a diameter of 20 mm 2019500546W00-English specification Date Recue/Date Received 2021-03-29 (tolerance: 0.1 mm) in the middle portion of each of the samples, the upper die having a cylindrical edge for punching and a diameter of 20 mm, the lower die having a hole appropriately selected in such a manner that the clearance between the upper die and the lower die was 10%.
The relationships among the clearance (C) [%], the hole diameter of the die (the inside diameter of the die) (Dd) [mm], the diameter of the punch (Dp) [mm], and the sheet thickness (t) [mm] are represented by formula (1) below.
C = (Dd -Dp) + (2 x t) x 100 formula (1) With respect to the test specimens thus obtained, the appearance of each test specimen was visually inspected, and the diameter of the hole in the middle portion of the test specimen was measured with a digital caliper. The case where no cracks were observed and where the hole diameter of each of the five test specimens after the punching work was in the range of 19.9 to 20.1 mm was rated as "acceptable"
(D). The case where any one of them was cracked or had a hole diameter of less than 19.9 mm or more than 20.1 mm was rated as "unacceptable" (x).
[0061]
Table 2 presents the test results together with hot-rolled steel sheet annealing conditions.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29
Table 2 presents the test results together with hot-rolled steel sheet annealing conditions.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29
[0062]
[Table 1]
Steel Chemical composition (% by mass) Remarks symbol C Si Mn P S Al Cr Ni Ti N Others Al 0.008 0.24 0.34 0.03 0.004 0.05 10.3 0.83 0.23 0.008 Example A2 0.006 0.24 0.30 0.02 0.004 0.04 15.7 0.85 0.25 0.007 Example A3 0.008 0.23 0.29 0.02 0.003 0.03 19.7 0.88 0.23 0.007 Example A4 0.007 0.27 0.27 0.03 0.004 0.06 11.5 0.86 0.25 0.008 Example A5 0.009 0.07 0.29 0.03 0.005 0.05 11.5 0.84 0.24 0.006 Example A6 0.008 0.11 0.30 0.04 0.004 0.03 11.3 0.82 0.26 0.009 Example A7 0.006 0.15 0.28 0.02 0.003 0.03 11.4 0.84 0.25 0.005 Example A8 0.008 0.58 0.32 0.03 0.004 0.04 11.6 0.81 0.25 0.008 Example A9 0.008 0.26 0.06 0.03 0.004 0.04 11.6 0.81 0.23 0.006 Example A10 0.007 0.23 0.10 0.03 0.003 0.03 11.4 0.83 0.21 0.009 Example All 0.008 0.24 0.17 0.04 0.005 0.03 11.6 0.85 0.20 0.010 Example Al2 0.006 0.27 0.97 0.02 0.003 0.06 11.6 0.90 0.22 0.006 Example A13 0.008 0.23 0.26 0.03 0.004 0.04 11.6 0.52 0.25 0.007 Example A14 0.007 0.26 0.27 0.03 0.003 0.06 11.7 0.98 0.24 0.008 Example A15 0.010 0.23 0.25 0.04 0.003 0.05 11.5 1.97 0.21 0.010 Example A16 0.008 0.28 0.25 0.02 0.004 0.04 10.2 0.51 0.24 0.007 Example A17 0.006 0.23 0.34 0.03 0.004 0.04 11.8 0.97 0.24 0.008 Example A18 0.009 0.25 0.35 0.03 0.005 0.01 19.6 1.98 0.23 0.011 Example A19 0.007 0.27 0.33 0.02 0.004 0.04 11.4 0.50 0.24 0.008 Cu: 0.34, B:
0.0011 Example A20 0.008 0.24 0.31 0.03 0.004 0.04 11.5 0.99 0.26 0.007 Mo: 0.51, Nb: 0.08 Example A21 0.007 0.28 0.28 0.02 0.004 0.03 11.6 0.83 0.26 0.007 Cu: 0.46 Example A22 0.009 0.23 0.35 0.03 0.004 0.06 11.6 0.88 0.23 0.008 Mo: 1.22 Example A23 0.007 0.26 0.27 0.02 0.004 0.06 11.7 0.78 0.22 0.009 W: 0.11 Example A24 0.008 0.25 0.31 0.03 0.003 0.04 11.6 0.88 0.23 0.007 Co: 0.15 Example A25 0.007 0.26 0.34 0.02 0.004 0.04 11.5 0.86 0.25 0.006 V: 0.12 Example A26 0.009 0.27 0.35 0.02 0.005 0.04 11.6 0.78 0.24 0.008 V: 0.05, Nb: 0.09 Example A27 0.008 0.25 0.26 0.03 0.005 0.05 11.5 0.86 0.24 0.007 Zr: 0.10 Example A28 0.008 0.24 0.34 0.03 0.004 0.04 11.6 0.86 0.25 0.009 REM: 0.008 Example A29 0.007 0.27 0.29 0.03 0.005 0.06 11.5 0.83 0.25 0.008 B: 0.0014 Example A30 0.006 0.27 0.32 0.03 0.004 0.04 11.5 0.80 0.23 0.006 Mg: 0.0007, Ca:
0.0005 Example B1 0.008 0.27 0.28 0.03 0.003 0.03 11.5 0.21 0.23 0.008 Comparative example B2 0.008 0.25 0.28 0.03 0.005 0.04 11.4 2.08 0.26 0.008 Comparative example B3 0.009 0.28 0.26 0.03 0.003 0.05 9.4 0.79 0.22 0.007 Comparative example B4 0.006 0.28 0.33 0.03 0.003 0.03 20.8 0.81 0.24 0.009 Comparative example B5 0.006 0.25 0.28 0.03 0.004 0.05 11.6 0.86 0.07 0.009 Comparative example The balance other than the component composition described above is Fe and incidental impurities.
Underlined values are outside the scope of the present invention.
[Table 1]
Steel Chemical composition (% by mass) Remarks symbol C Si Mn P S Al Cr Ni Ti N Others Al 0.008 0.24 0.34 0.03 0.004 0.05 10.3 0.83 0.23 0.008 Example A2 0.006 0.24 0.30 0.02 0.004 0.04 15.7 0.85 0.25 0.007 Example A3 0.008 0.23 0.29 0.02 0.003 0.03 19.7 0.88 0.23 0.007 Example A4 0.007 0.27 0.27 0.03 0.004 0.06 11.5 0.86 0.25 0.008 Example A5 0.009 0.07 0.29 0.03 0.005 0.05 11.5 0.84 0.24 0.006 Example A6 0.008 0.11 0.30 0.04 0.004 0.03 11.3 0.82 0.26 0.009 Example A7 0.006 0.15 0.28 0.02 0.003 0.03 11.4 0.84 0.25 0.005 Example A8 0.008 0.58 0.32 0.03 0.004 0.04 11.6 0.81 0.25 0.008 Example A9 0.008 0.26 0.06 0.03 0.004 0.04 11.6 0.81 0.23 0.006 Example A10 0.007 0.23 0.10 0.03 0.003 0.03 11.4 0.83 0.21 0.009 Example All 0.008 0.24 0.17 0.04 0.005 0.03 11.6 0.85 0.20 0.010 Example Al2 0.006 0.27 0.97 0.02 0.003 0.06 11.6 0.90 0.22 0.006 Example A13 0.008 0.23 0.26 0.03 0.004 0.04 11.6 0.52 0.25 0.007 Example A14 0.007 0.26 0.27 0.03 0.003 0.06 11.7 0.98 0.24 0.008 Example A15 0.010 0.23 0.25 0.04 0.003 0.05 11.5 1.97 0.21 0.010 Example A16 0.008 0.28 0.25 0.02 0.004 0.04 10.2 0.51 0.24 0.007 Example A17 0.006 0.23 0.34 0.03 0.004 0.04 11.8 0.97 0.24 0.008 Example A18 0.009 0.25 0.35 0.03 0.005 0.01 19.6 1.98 0.23 0.011 Example A19 0.007 0.27 0.33 0.02 0.004 0.04 11.4 0.50 0.24 0.008 Cu: 0.34, B:
0.0011 Example A20 0.008 0.24 0.31 0.03 0.004 0.04 11.5 0.99 0.26 0.007 Mo: 0.51, Nb: 0.08 Example A21 0.007 0.28 0.28 0.02 0.004 0.03 11.6 0.83 0.26 0.007 Cu: 0.46 Example A22 0.009 0.23 0.35 0.03 0.004 0.06 11.6 0.88 0.23 0.008 Mo: 1.22 Example A23 0.007 0.26 0.27 0.02 0.004 0.06 11.7 0.78 0.22 0.009 W: 0.11 Example A24 0.008 0.25 0.31 0.03 0.003 0.04 11.6 0.88 0.23 0.007 Co: 0.15 Example A25 0.007 0.26 0.34 0.02 0.004 0.04 11.5 0.86 0.25 0.006 V: 0.12 Example A26 0.009 0.27 0.35 0.02 0.005 0.04 11.6 0.78 0.24 0.008 V: 0.05, Nb: 0.09 Example A27 0.008 0.25 0.26 0.03 0.005 0.05 11.5 0.86 0.24 0.007 Zr: 0.10 Example A28 0.008 0.24 0.34 0.03 0.004 0.04 11.6 0.86 0.25 0.009 REM: 0.008 Example A29 0.007 0.27 0.29 0.03 0.005 0.06 11.5 0.83 0.25 0.008 B: 0.0014 Example A30 0.006 0.27 0.32 0.03 0.004 0.04 11.5 0.80 0.23 0.006 Mg: 0.0007, Ca:
0.0005 Example B1 0.008 0.27 0.28 0.03 0.003 0.03 11.5 0.21 0.23 0.008 Comparative example B2 0.008 0.25 0.28 0.03 0.005 0.04 11.4 2.08 0.26 0.008 Comparative example B3 0.009 0.28 0.26 0.03 0.003 0.05 9.4 0.79 0.22 0.007 Comparative example B4 0.006 0.28 0.33 0.03 0.003 0.03 20.8 0.81 0.24 0.009 Comparative example B5 0.006 0.25 0.28 0.03 0.004 0.05 11.6 0.86 0.07 0.009 Comparative example The balance other than the component composition described above is Fe and incidental impurities.
Underlined values are outside the scope of the present invention.
[0063]
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 [Table 2]
Hot-rolled steel Thickness after Metal Average Steel sheet annealing = Punching Corrosion No. symbol (*) size Remarks completion of microstructure grain temperature workability resistance hot rolling [mm] [Iirn]
[ C]
1 Al 10.1 652 F 11 0 0 Example 2 A2 9.9 653 F 16 0 0 Example 3 A3 10.2 655 F 19 0 0 Example 4 A4 9.8 651 F 12 0 0 Example A5 10.0 651 F 9 0 0 Example 6 A6 9.9 653 F 11 0 0 Example 7 A7 10.2 652 F 12 0 0 Example 8 A8 10.2 649 F 17 0 0 Example 9 A9 9.9 653 F 16 0 0 Example A10 9.9 654 F 10 0 0 Example 11 All 9.9 650 F 18 0 0 Example 12 Al2 9.8 647 F 8 0 0 Example 13 A13 10.3 655 F 5 0 0 Example 14 A14 10.0 646 F 19 0 0 Example A15 10.0 653 F 8 0 0 Example 16 A16 10.1 655 F 18 0 0 Example 17 A17 9.8 646 F 17 0 0 Example 18 A18 10.0 653 F 9 0 0 Example 19 A19 9.9 650 F 11 0 0 Example A20 9.8 652 F 10 0 0 Example 21 A21 9.8 645 F 13 0 0 Example 22 A22 9.9 652 F 12 0 0 Example 23 A23 10.1 646 F 13 0 0 Example 24 A24 9.8 652 F 14 0 0 Example A25 10.0 647 F 13 0 0 Example 26 A26 10.1 649 F 12 0 0 Example 27 A27 9.9 653 F 9 0 0 Example 28 A28 10.0 645 F 11 0 0 Example 29 A29 10.2 648 F 10 0 0 Example A30 10.2 655 F 12 0 0 Example 31 Al 5.2 652 F 10 0 0 Example 32 Al 8.1 650 F 12 0 0 Example 33 Al 13.0 645 F 16 0 0 Example 34 Al 14.7 647 F 18 0 0 Example A13 10.0 602 F 8 0 0 Example 36 A13 9.9 747 F 17 0 0 Example 37 B1 9.8 749 F 34 x 0 Comparative example 38 B2 9.8 652 F 8 x 0 Comparative example 39 B3 10.1 650 F 11 0 x Comparative example B4 9.8 651 F 26 x 0 Comparative example 41 B5 10.1 646 F 16 0 x Comparative example 43 A26 10.0 803 F 28 x 0 Comparative example 44 A14 9.9 806 F 34 x 0 Comparative example - Underlined values are outside the scope of the present invention.
*) F: ferrite phase 2019S00546W00-English specification Date Recue/Date Received 2021-03-29
2019S00546W00-English specification Date Recue/Date Received 2021-03-29 [Table 2]
Hot-rolled steel Thickness after Metal Average Steel sheet annealing = Punching Corrosion No. symbol (*) size Remarks completion of microstructure grain temperature workability resistance hot rolling [mm] [Iirn]
[ C]
1 Al 10.1 652 F 11 0 0 Example 2 A2 9.9 653 F 16 0 0 Example 3 A3 10.2 655 F 19 0 0 Example 4 A4 9.8 651 F 12 0 0 Example A5 10.0 651 F 9 0 0 Example 6 A6 9.9 653 F 11 0 0 Example 7 A7 10.2 652 F 12 0 0 Example 8 A8 10.2 649 F 17 0 0 Example 9 A9 9.9 653 F 16 0 0 Example A10 9.9 654 F 10 0 0 Example 11 All 9.9 650 F 18 0 0 Example 12 Al2 9.8 647 F 8 0 0 Example 13 A13 10.3 655 F 5 0 0 Example 14 A14 10.0 646 F 19 0 0 Example A15 10.0 653 F 8 0 0 Example 16 A16 10.1 655 F 18 0 0 Example 17 A17 9.8 646 F 17 0 0 Example 18 A18 10.0 653 F 9 0 0 Example 19 A19 9.9 650 F 11 0 0 Example A20 9.8 652 F 10 0 0 Example 21 A21 9.8 645 F 13 0 0 Example 22 A22 9.9 652 F 12 0 0 Example 23 A23 10.1 646 F 13 0 0 Example 24 A24 9.8 652 F 14 0 0 Example A25 10.0 647 F 13 0 0 Example 26 A26 10.1 649 F 12 0 0 Example 27 A27 9.9 653 F 9 0 0 Example 28 A28 10.0 645 F 11 0 0 Example 29 A29 10.2 648 F 10 0 0 Example A30 10.2 655 F 12 0 0 Example 31 Al 5.2 652 F 10 0 0 Example 32 Al 8.1 650 F 12 0 0 Example 33 Al 13.0 645 F 16 0 0 Example 34 Al 14.7 647 F 18 0 0 Example A13 10.0 602 F 8 0 0 Example 36 A13 9.9 747 F 17 0 0 Example 37 B1 9.8 749 F 34 x 0 Comparative example 38 B2 9.8 652 F 8 x 0 Comparative example 39 B3 10.1 650 F 11 0 x Comparative example B4 9.8 651 F 26 x 0 Comparative example 41 B5 10.1 646 F 16 0 x Comparative example 43 A26 10.0 803 F 28 x 0 Comparative example 44 A14 9.9 806 F 34 x 0 Comparative example - Underlined values are outside the scope of the present invention.
*) F: ferrite phase 2019S00546W00-English specification Date Recue/Date Received 2021-03-29
[0064]
In Nos. 1 to 36 in which the steel compositions and the hot-rolled steel sheet annealing conditions were within the scope of the present invention, the predetermined punching workability was obtained because, in addition to the formation of an austenite phase during heating in the hot-rolling step, recrystallization occurred by the predetermined hot-rolled steel sheet annealing without excessive coarsening of grains to obtain the predetermined average grain size. The evaluation results of the corrosion resistance of the resulting hot-rolled and annealed sheets revealed that each sheet had a percentage of rusted area of 25% or less and had sufficient corrosion resistance.
In Nos. 1 to 36 in which the steel compositions and the hot-rolled steel sheet annealing conditions were within the scope of the present invention, the predetermined punching workability was obtained because, in addition to the formation of an austenite phase during heating in the hot-rolling step, recrystallization occurred by the predetermined hot-rolled steel sheet annealing without excessive coarsening of grains to obtain the predetermined average grain size. The evaluation results of the corrosion resistance of the resulting hot-rolled and annealed sheets revealed that each sheet had a percentage of rusted area of 25% or less and had sufficient corrosion resistance.
[0065]
In particular, in each of No. 19 using Cu-containing steel A19, No. 21 using Cu-containing steel A21, No. 20 using Mo-containing steel A20, and No. 22 using Mo-containing steel A22, the percentage of rusted area was 10%
or less, and better corrosion resistance was provided.
In particular, in each of No. 19 using Cu-containing steel A19, No. 21 using Cu-containing steel A21, No. 20 using Mo-containing steel A20, and No. 22 using Mo-containing steel A22, the percentage of rusted area was 10%
or less, and better corrosion resistance was provided.
[0066]
In each of No. 3 using steel A3 having a high Cr content of 19.7% and No. 18 using steel A18 having a high Cr content of 19.6%, a strong passivation film was formed on the surfaces of the steel sheet; thus, the percentage of rusted area was 10% or less, and better corrosion resistance 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 was provided.
In each of No. 3 using steel A3 having a high Cr content of 19.7% and No. 18 using steel A18 having a high Cr content of 19.6%, a strong passivation film was formed on the surfaces of the steel sheet; thus, the percentage of rusted area was 10% or less, and better corrosion resistance 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 was provided.
[0067]
In No. 37 using steel Bl having a Ni content of less than that in the scope of the present invention, almost no austenite phase was formed during heating in the hot-rolling step to fail to obtain the effect of refining the metal microstructure. Thus, the average grain size was more than the scope of the present invention to fail to obtain the predetermined punching workability.
In No. 37 using steel Bl having a Ni content of less than that in the scope of the present invention, almost no austenite phase was formed during heating in the hot-rolling step to fail to obtain the effect of refining the metal microstructure. Thus, the average grain size was more than the scope of the present invention to fail to obtain the predetermined punching workability.
[0068]
In No. 38 using steel B2 having a Ni content of more than that in the scope of the present invention, although the predetermined average grain size was obtained, the excessive amount of dissolved Ni resulted in the excessively hardened steel sheet to cause cracking during punching work, thereby failing to process the steel sheet into a predetermined shape.
In No. 38 using steel B2 having a Ni content of more than that in the scope of the present invention, although the predetermined average grain size was obtained, the excessive amount of dissolved Ni resulted in the excessively hardened steel sheet to cause cracking during punching work, thereby failing to process the steel sheet into a predetermined shape.
[0069]
In No. 39 using steel B3 having a Cr content of less than that in the scope of the present invention, the predetermined corrosion resistance was not be obtained due to the insufficient Cr content.
In No. 39 using steel B3 having a Cr content of less than that in the scope of the present invention, the predetermined corrosion resistance was not be obtained due to the insufficient Cr content.
[0070]
In No. 40 using steel B4 having a Cr content of more than that in the scope of the present invention, the 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 excessive Cr content resulted in the decrease of the austenite phase formed during heating in the hot-rolling step, even though the predetermined amount of Ni was contained. Thus, the effect of grain refinement due to the formation of the austenite phase in the hot-rolling step was not sufficiently obtained. Thereby, the predetermined average grain size was not obtained, failing to obtain the predetermined punching workability.
In No. 40 using steel B4 having a Cr content of more than that in the scope of the present invention, the 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 excessive Cr content resulted in the decrease of the austenite phase formed during heating in the hot-rolling step, even though the predetermined amount of Ni was contained. Thus, the effect of grain refinement due to the formation of the austenite phase in the hot-rolling step was not sufficiently obtained. Thereby, the predetermined average grain size was not obtained, failing to obtain the predetermined punching workability.
[0071]
In No. 41 using steel B5 having a Ti content of less than that in the scope of the present invention, a large amount of chromium carbonitride was precipitated during the hot-rolled steel sheet annealing to cause sensitization, thereby failing to obtain the predetermined corrosion resistance.
In No. 41 using steel B5 having a Ti content of less than that in the scope of the present invention, a large amount of chromium carbonitride was precipitated during the hot-rolled steel sheet annealing to cause sensitization, thereby failing to obtain the predetermined corrosion resistance.
[0072]
In No. 43 in which the hot-rolled steel sheet annealing temperature was higher than that in the scope of the present invention, recrystallized grains formed coarsened significantly to fail to provide the predetermined average grain size, thereby failing to obtain the predetermined punching workability.
In No. 43 in which the hot-rolled steel sheet annealing temperature was higher than that in the scope of the present invention, recrystallized grains formed coarsened significantly to fail to provide the predetermined average grain size, thereby failing to obtain the predetermined punching workability.
[0073]
No. 44 is an example in which steel A14 containing the predetermined steel composition was annealed at 806 C, which 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 is higher than that in the scope of the present invention, to increase the average grain size to 34 m, which is more than that in the scope of the present invention. Although the predetermined steel composition was contained, the excessively coarse grains resulted in significant rollover and burrs during the punching work, thereby failing to obtain the predetermined punching workability.
Industrial Applicability
No. 44 is an example in which steel A14 containing the predetermined steel composition was annealed at 806 C, which 2019S00546W00-English specification Date Recue/Date Received 2021-03-29 is higher than that in the scope of the present invention, to increase the average grain size to 34 m, which is more than that in the scope of the present invention. Although the predetermined steel composition was contained, the excessively coarse grains resulted in significant rollover and burrs during the punching work, thereby failing to obtain the predetermined punching workability.
Industrial Applicability
[0074]
The hot-rolled and annealed ferritic stainless steel sheet according to the present invention is particularly suitable for applications that require high workability and corrosion resistance, for example, flanges having burring portions.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29
The hot-rolled and annealed ferritic stainless steel sheet according to the present invention is particularly suitable for applications that require high workability and corrosion resistance, for example, flanges having burring portions.
2019S00546W00-English specification Date Recue/Date Received 2021-03-29
Claims (4)
1. A hot-rolled and annealed ferritic stainless steel sheet having a chemical composition containing, on a mass percent basis:
C: 0.001% to 0.020%, Si: 0.05% to 0.40%, Mn: 0.05% to 0.60%, P: 0.04% or less, S: 0.01% or less, Al: 0.01% to 0.10%, Cr: 11.2% to 20.0%, Ni: 0.50% to 0.86%, Ti: 0.10% to 0.40%, and N: 0.001% to 0.020%, the balance being Fe and incidental impurities; and having a metal microstructure which is a single ferrite phase microstructure having an average grain size of 5 to 20 m.
C: 0.001% to 0.020%, Si: 0.05% to 0.40%, Mn: 0.05% to 0.60%, P: 0.04% or less, S: 0.01% or less, Al: 0.01% to 0.10%, Cr: 11.2% to 20.0%, Ni: 0.50% to 0.86%, Ti: 0.10% to 0.40%, and N: 0.001% to 0.020%, the balance being Fe and incidental impurities; and having a metal microstructure which is a single ferrite phase microstructure having an average grain size of 5 to 20 m.
2. The hot-rolled and annealed ferritic stainless steel sheet according to Claim 1, further containing, on a mass percent basis, one or two or more selected from:
Cu: 0.01% to 1.00%, Mo: 0.01% to 2.00%, W: 0.01% to 0.20%, and Co: 0.01% to 0.20%.
Date Recue/Date Received 2022-06-08
Cu: 0.01% to 1.00%, Mo: 0.01% to 2.00%, W: 0.01% to 0.20%, and Co: 0.01% to 0.20%.
Date Recue/Date Received 2022-06-08
3. The hot-rolled and annealed ferritic stainless steel sheet according to Claim 1 or 2, further containing, on a mass percent basis, one or two or more selected from:
V: 0.01% to 0.20%, Nb: 0.01% to 0.10%, Zr: 0.01% to 0.20%, REM: 0.001% to 0.100%, B: 0.0002% to 0.0025%, Mg: 0.0005% to 0.0030%, and Ca: 0.0003% to 0.0030%.
V: 0.01% to 0.20%, Nb: 0.01% to 0.10%, Zr: 0.01% to 0.20%, REM: 0.001% to 0.100%, B: 0.0002% to 0.0025%, Mg: 0.0005% to 0.0030%, and Ca: 0.0003% to 0.0030%.
4. A method for producing the hot-rolled and annealed ferritic stainless steel sheet according to any one of Claims 1 to 3, comprising:
performing hot-rolled steel sheet annealing in which a hot-rolled steel sheet produced through a hot-rolling step is held at 600 C
or higher and lower than 750 C for 1 minute to 24 hours.
Date Recue/Date Received 2022-06-08
performing hot-rolled steel sheet annealing in which a hot-rolled steel sheet produced through a hot-rolling step is held at 600 C
or higher and lower than 750 C for 1 minute to 24 hours.
Date Recue/Date Received 2022-06-08
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2018200479 | 2018-10-25 | ||
| JP2018-200479 | 2018-10-25 | ||
| PCT/JP2019/037430 WO2020084987A1 (en) | 2018-10-25 | 2019-09-25 | Ferrite stainless hot-rolled-and-annealed steel sheet and production method for same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA3114743A1 CA3114743A1 (en) | 2020-04-30 |
| CA3114743C true CA3114743C (en) | 2023-03-07 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA3114743A Active CA3114743C (en) | 2018-10-25 | 2019-09-25 | Hot-rolled and annealed ferritic stainless steel sheet and method for producing the same |
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| Country | Link |
|---|---|
| US (1) | US20210363604A1 (en) |
| JP (1) | JP7038799B2 (en) |
| KR (2) | KR20230142630A (en) |
| CN (1) | CN112888802A (en) |
| CA (1) | CA3114743C (en) |
| MX (1) | MX2021004713A (en) |
| TW (1) | TWI718712B (en) |
| WO (1) | WO2020084987A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3231174B2 (en) * | 1993-10-18 | 2001-11-19 | 新日本製鐵株式会社 | Hot-rolled high-strength steel sheet with good drawability and method for producing the same |
| JP2003213376A (en) * | 2002-01-15 | 2003-07-30 | Nisshin Steel Co Ltd | Ferritic stainless steel sheet having excellent secondary hole enlargementability and production method therefor |
| JP3886933B2 (en) * | 2003-06-04 | 2007-02-28 | 日新製鋼株式会社 | Ferritic stainless steel sheet excellent in press formability and secondary workability and manufacturing method thereof |
| JP4749888B2 (en) * | 2006-02-22 | 2011-08-17 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel sheet excellent in formability with less rough processing and manufacturing method thereof |
| JP5225620B2 (en) * | 2006-07-04 | 2013-07-03 | 新日鐵住金ステンレス株式会社 | Low chromium-containing stainless steel excellent in corrosion resistance of heat-affected zone multiple times and its manufacturing method |
| JP5045050B2 (en) * | 2006-10-05 | 2012-10-10 | Ｊｆｅスチール株式会社 | Ferritic stainless hot rolled steel sheet for cold rolling and method for producing the same |
| JP5196807B2 (en) * | 2007-02-26 | 2013-05-15 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel sheet excellent in formability with low roughness of processing surface and method for producing the same |
| CN102041452A (en) * | 2009-10-23 | 2011-05-04 | 宝山钢铁股份有限公司 | Medium chromium ferrite stainless steel and making method thereof |
| EP2980251B1 (en) | 2013-03-27 | 2017-12-13 | Nippon Steel & Sumikin Stainless Steel Corporation | Hot-rolled ferritic stainless-steel plate, process for producing same, and steel strip |
| JP6791646B2 (en) * | 2015-03-30 | 2020-11-25 | 日鉄ステンレス株式会社 | Stainless steel sheet with excellent toughness and its manufacturing method |
| ES2831841T3 (en) * | 2016-10-17 | 2021-06-09 | Jfe Steel Corp | Annealed hot rolled ferritic stainless steel sheet and method of producing the same |
| JP6765287B2 (en) * | 2016-11-17 | 2020-10-07 | 日鉄ステンレス株式会社 | Ferritic stainless steel, its manufacturing method, and fuel cell components |
| JP6432720B1 (en) * | 2017-04-27 | 2018-12-05 | Ｊｆｅスチール株式会社 | Ferritic stainless steel hot rolled annealed steel sheet and method for producing the same |
| EP3623489A4 (en) * | 2017-09-29 | 2020-07-08 | JFE Steel Corporation | Annealed hot-rolled ferritic stainless steel sheet and method for producing same |
| CN111295458A (en) * | 2017-10-30 | 2020-06-16 | 杰富意钢铁株式会社 | Ferritic stainless steel sheet and method for producing same |
-
2019
- 2019-09-25 MX MX2021004713A patent/MX2021004713A/en unknown
- 2019-09-25 CA CA3114743A patent/CA3114743C/en active Active
- 2019-09-25 JP JP2020506852A patent/JP7038799B2/en active Active
- 2019-09-25 CN CN201980069792.9A patent/CN112888802A/en active Pending
- 2019-09-25 KR KR1020237031897A patent/KR20230142630A/en not_active Application Discontinuation
- 2019-09-25 US US17/286,657 patent/US20210363604A1/en active Pending
- 2019-09-25 WO PCT/JP2019/037430 patent/WO2020084987A1/en active Application Filing
- 2019-09-25 KR KR1020217011576A patent/KR20210064281A/en not_active IP Right Cessation
- 2019-10-17 TW TW108137507A patent/TWI718712B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| JP7038799B2 (en) | 2022-03-18 |
| CN112888802A (en) | 2021-06-01 |
| KR20230142630A (en) | 2023-10-11 |
| US20210363604A1 (en) | 2021-11-25 |
| JPWO2020084987A1 (en) | 2021-02-15 |
| MX2021004713A (en) | 2021-06-04 |
| TWI718712B (en) | 2021-02-11 |
| TW202020182A (en) | 2020-06-01 |
| WO2020084987A1 (en) | 2020-04-30 |
| KR20210064281A (en) | 2021-06-02 |
| CA3114743A1 (en) | 2020-04-30 |
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