CN110760756B - Thick DP 680-grade hot-rolled dual-phase steel and preparation method thereof - Google Patents
Thick DP 680-grade hot-rolled dual-phase steel and preparation method thereof Download PDFInfo
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- 229910000885 Dual-phase steel Inorganic materials 0.000 title claims abstract description 45
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 238000005096 rolling process Methods 0.000 claims abstract description 67
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 59
- 239000010959 steel Substances 0.000 claims abstract description 59
- 238000001816 cooling Methods 0.000 claims abstract description 57
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000012535 impurity Substances 0.000 claims abstract description 12
- 239000000126 substance Substances 0.000 claims abstract description 12
- 239000000498 cooling water Substances 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 30
- 229910000859 α-Fe Inorganic materials 0.000 claims description 18
- 229910052742 iron Inorganic materials 0.000 claims description 15
- 229910000734 martensite Inorganic materials 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 7
- 229910052710 silicon Inorganic materials 0.000 description 11
- 239000010936 titanium Substances 0.000 description 11
- 229910052719 titanium Inorganic materials 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 7
- 229910052757 nitrogen Inorganic materials 0.000 description 7
- 229910052698 phosphorus Inorganic materials 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000000203 mixture Substances 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
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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
- 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
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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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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- 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
- C21D2211/008—Martensite
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Abstract
The invention relates to thick DP680 hot-rolled dual-phase steel and a preparation method thereof, wherein the steel comprises the following chemical components in percentage by weight: 0.045-0.08% of C, less than or equal to 0.04% of Si, 1.0-1.30% of Mn, 0.02-0.029% of Ti, 0.51-0.65% of Cr, less than or equal to 0.01% of P, less than or equal to 0.005% of S, 0.0015-0.0045% of N, 0.02-0.045% of Als, and the balance of Fe and unavoidable impurities. The preparation method comprises the following steps: heating a steel billet to 1220-1250 ℃, preserving heat for 2.0-2.5 h, and then rolling, wherein the initial rolling temperature of rough rolling is 1150-1200 ℃, the initial rolling temperature of finish rolling is 950-1000 ℃, and the final rolling temperature is 870-920 ℃; and carrying out water cooling-air cooling-water cooling three-stage cooling on the plate strip, wherein the coiling temperature is not lower than 400 ℃. The prepared steel plate has the tensile strength of 704-748 MPa, the yield strength of 418-446 MPa, the elongation of 28-33% and the yield ratio of 0.58-0.61, and can be used for producing steel plates with the thickness of 11-22 mm due to the addition of a certain amount of Cr element, so that the steel plate has the characteristics of high strength and low yield ratio and has good surface quality.
Description
The technical field is as follows:
the invention belongs to the technical fields of metallurgy and steel rolling, and particularly relates to thick DP680 hot-rolled dual-phase steel and a preparation method thereof.
Background art:
with the rapid development of national economy, the demand for heavy trucks is indispensable, especially in the aspects of transporting building materials, coal, steel and the like. The spoke for the heavy truck wheel needs a high-strength steel plate with good performance and a thicker specification (>10mm), so that the safety of the heavy truck can be effectively improved. The dual-phase steel has good comprehensive properties such as good strong plasticity, low yield ratio (Rp0.2/Rm), high initial work hardening rate and the like, so that the use requirement of the wheel spoke of the heavy truck can be met; meanwhile, the dual-phase steel is in the strength level, hot-rolled dual-phase steel produced and applied at home and abroad mainly takes DP540-DP600 as the main part, and the demand of higher-level DP steel is urgent. For example, heavy truck wheel spokes have a huge demand for DP680 grade hot-rolled dual-phase steel, and development and production of DP680 grade strength dual-phase steel are rarely reported.
Patent CN201610450190.6 discloses 780 MPa-grade hot-rolled high-hole-expansion dual-phase steel and a manufacturing method thereof, wherein silicon (Si) with the content of 0.8-1.8% is added during component design, and red iron scale is easily formed due to the high Si content, so that the surface quality of the steel plate is poor, and the use of the steel plate is restricted; patent CN201810340842.X discloses a 700 MPa-grade titanium-containing hot-rolled dual-phase steel plate and a manufacturing method thereof, wherein the content of added silicon (Si) in the component design is 0.80-1.20%, red iron scale is easy to form, the surface quality of the steel plate is poor, the use of the steel plate is restricted, meanwhile, the finish rolling temperature is 780-840 ℃, and the lower finish rolling temperature causes larger load of a rolling mill; the patent CN201710872795.9 discloses a hot-rolled dual-phase steel and a processing method thereof, wherein the finish rolling temperature is 790-850 ℃, the lower finish rolling temperature causes the load of a rolling mill to be larger, meanwhile, the coiling temperature is 150-300 ℃, and the lower coiling temperature causes the load of a coiling machine to be larger; patent CN201410414629.0 discloses a thick hot-rolled dual-phase steel plate and a manufacturing method thereof, wherein 0.20-0.50% of silicon (Si) is added in the component design, red iron scale is easily formed, the surface quality of the steel plate is poor, meanwhile, coiling is carried out at 150-300 ℃, and the coiling machine load is large due to the thick low-temperature coiling; patent CN201610866364.7 discloses a hot-rolled dual-phase steel with 600 MPa-level tensile strength and a manufacturing method thereof, wherein the strength level is 600MPa, the pursuit of a heavy truck for higher safety cannot be met, and the thickness specification of the hot-rolled dual-phase steel is 3.0-6.0 mm, and the requirement of a heavy truck spoke cannot be met. Patent CN201810578308.2 discloses a method for manufacturing a thin hot-rolled dual-phase steel plate, wherein the coiling temperature is 180-300 ℃, the coiling at low temperature causes large load of a coiling machine, the thickness of the produced hot-rolled plate is 0.75-1.4 mm, and the requirement of heavy truck spokes for thicker specification cannot be met.
The invention content is as follows:
the invention aims to overcome the defects in the prior art, provides thick DP680 hot-rolled dual-phase steel and a preparation method thereof, and solves the technical problems that the surface quality is influenced by low strength level and high silicon (Si) content and heavy trucks demand the hot-rolled dual-phase steel in thicker specifications. The high-temperature rolling and high-temperature coiling processes are realized, and a three-section cooling mode is adopted to obtain a two-phase structure.
In order to achieve the purpose, the invention adopts the following technical scheme:
the thick DP680 grade hot-rolled dual-phase steel comprises the following chemical components in percentage by weight: 0.045-0.08 percent of C, less than or equal to 0.04 percent of Si, 1.0-1.30 percent of Mn, 0.02-0.029 percent of Ti, 0.51-0.65 percent of Cr, less than or equal to 0.01 percent of P, less than or equal to 0.005 percent of S, 0.0015-0.0045 percent of N, 0.02-0.045 percent of Als, and the balance of iron and inevitable impurities.
The hot-rolled dual-phase steel plate is a ferrite and martensite dual-phase structure, wherein the volume fraction of ferrite is 71-85%, the volume fraction of martensite is 15-29%, and the average grain size of ferrite is 5.5-6.7 μm.
The thickness of the hot-rolled dual-phase steel plate is 11-22 mm, the tensile strength is 704-748 MPa, the yield strength is 418-446 MPa, the yield ratio is 0.58-0.61, and the elongation after fracture is 28% -33%.
A preparation method of thick DP680 hot-rolled dual-phase steel comprises the following steps:
(1) heating a steel billet to 1220-1250 ℃, and preserving heat for 2.0-2.5 h, wherein the steel billet comprises the following chemical components in percentage by weight: 0.045-0.08% of C, less than or equal to 0.04% of Si, 1.0-1.30% of Mn, 0.02-0.029% of Ti, 0.51-0.65% of Cr, less than or equal to 0.01% of P, less than or equal to 0.005% of S, 0.0015-0.0045% of N, 0.02-0.045% of Als, and the balance of iron and inevitable impurities;
(2) 4-5 passes of rolling are carried out on the heated billet, the initial rolling temperature of rough rolling is 1150-1200 ℃, the single-pass reduction rate of rough rolling is 36-50.7%, the initial rolling temperature of finish rolling is 950-1000 ℃, the single-pass reduction rate of finish rolling is 35.3-50%, and the final rolling temperature is 870-920 ℃, so that a plate strip is obtained;
(3) and cooling the plate strip to 400-500 ℃ at the cooling speed of 10-25 ℃/s, and coiling to obtain the thick DP680 grade hot-rolled dual-phase steel.
In the step (1), the thickness of the steel billet is 185-250 mm.
In the step (2), the thickness of the intermediate blank to be heated after rough rolling is 48-115 mm, and the thickness of the plate belt is 11-22 mm.
In the step (3), the strip is cooled by water cooling-air cooling-water cooling three-section cooling, which specifically comprises the following steps: (a) the plate strip is cooled to 610-640 ℃ by water with the cooling speed of 10-15 ℃/s; (b) cooling the strip steel subjected to water cooling in the step (a) in air for 15-20 s; (c) and (c) allowing the strip steel subjected to air cooling in the step (b) to enter laminar flow water at a cooling speed of 18-25 ℃/s, cooling to 400-500 ℃ and coiling to obtain thick DP680 hot-rolled dual-phase steel.
Compared with the prior art, the thick DP680 hot-rolled dual-phase steel and the preparation method thereof have the following beneficial effects:
(1) the invention adopts the design idea of low Si or even nearly no Si (Si is less than or equal to 0.04%) in the component design, reduces red iron scale on the surface of the steel plate and ensures the surface quality of the steel plate;
(2) the finish rolling temperature is 870-920 ℃, the finish rolling temperature is increased, and the load of a rolling mill is favorably reduced;
(3) the invention adds a certain content of Cr element (0.51-0.65 percent of Cr) in the composition design, so that the coiling temperature reaches 400-500 ℃, the surface quality of the strip steel is improved, and the equipment loss of a coiling machine is reduced.
(4) The invention realizes the preparation of thicker steel plates, has the thickness of 11-22 mm, and can meet the requirements of wheel spokes of heavy trucks.
Description of the drawings:
FIG. 1 is a drawing curve of thick gauge DP680 hot rolled dual phase steel prepared in example 2 of the present invention;
FIG. 2 is a metallographic microstructure (a structure photograph after etching with 4% nitric acid alcohol) of 1/4 in the thickness direction of a thick DP680 hot-rolled dual phase steel sheet prepared in example 3 according to the present invention.
The specific implementation mode is as follows:
the present invention will be described in further detail with reference to examples.
Example 1
The thick DP680 hot-rolled dual phase steel sheet of this example had a chemical composition of, in weight percent, 0.05% C, 0.04% Si, 1.0% Mn, 0.02% Ti, 0.51% Cr, 0.01% P, 0.005% S, 0.0015% N, 0.02% Als, and the balance iron and unavoidable impurities.
A preparation method of thick DP680 hot-rolled dual-phase steel with the thickness of 11mm comprises the following process steps:
(1) heating a steel billet with the thickness of 240mm to 1220 ℃, and preserving heat for 2.0h, wherein the steel billet comprises the following chemical components in percentage by weight: 0.05% of C, 0.04% of Si, 1.0% of Mn, 0.02% of Ti, 0.51% of Cr, 0.01% of P, 0.005% of S, 0.0015% of N, 0.02% of Als, and the balance of iron and inevitable impurities;
(2) rolling the heated billet in 5 passes, wherein the initial rolling temperature of rough rolling is 1150 ℃, the thickness of the intermediate billet after rough rolling to be warmed is 69mm, the initial rolling temperature of finish rolling is 950 ℃, the final rolling temperature is 870 ℃, and the reduction pass distribution is 240mm → 140mm → 69mm → 35mm → 18mm → 11mm, so as to obtain a steel plate with the thickness of 11 mm;
(3) carrying out water cooling-air cooling-water cooling three-stage cooling on the plate strip, (a) rolling the strip steel by a finishing mill set, and cooling the strip steel to 610 ℃ by water with the cooling speed of 10 ℃/s; (b) cooling the strip steel subjected to water cooling in the step (a) in air for 15 s; (c) and (c) allowing the strip steel subjected to air cooling in the step (b) to enter laminar flow water, cooling at the cooling speed of 25 ℃/s to 400 ℃ and coiling.
The thick DP680 grade hot-rolled dual-phase steel structure with the thickness of 11mm is a ferrite and martensite dual-phase structure, wherein the volume fraction of ferrite is 85 percent, the volume fraction of martensite is 15 percent, and the average grain size of ferrite is 5.5 mu m. The tensile strength is 704MPa, the yield strength is 418MPa, the yield ratio is 0.59, and the elongation after fracture is 33%.
Example 2
The thick DP680 grade hot rolled dual phase steel plate of this example has a chemical composition of, by weight, 0.06% C, 0.025% Si, 1.3% Mn, 0.023% Ti, 0.65% Cr, 0.002% P, 0.004% S, 0.0019% N, 0.045% Als, and the balance iron and unavoidable impurities.
A preparation method of thick DP680 hot-rolled dual-phase steel with the thickness of 13mm comprises the following process steps:
(1) heating a steel billet with the thickness of 220mm to 1250 ℃, and preserving heat for 2.3h, wherein the steel billet comprises the following chemical components in percentage by weight: 0.06% C, 0.025% Si, 1.3% Mn, 0.023% Ti, 0.65% Cr, 0.002% P, 0.004% S, 0.0019% N, 0.045% Als, the balance being iron and unavoidable impurities;
(2) rolling the heated billet in 5 passes, wherein the initial rolling temperature of rough rolling is 1200 ℃, the thickness of the intermediate billet after rough rolling is 72mm, the initial rolling temperature of finish rolling is 970 ℃, the final rolling temperature is 920 ℃, and the reduction pass distribution is 220mm → 140mm → 72mm → 36mm → 21mm → 13mm, so as to obtain a steel plate with the thickness of 13 mm;
(3) carrying out water cooling-air cooling-water cooling three-stage cooling on the plate strip, (a) rolling the strip steel by a finishing mill set, and cooling the strip steel to 640 ℃ by water with the cooling speed of 15 ℃/s; (b) cooling the strip steel subjected to water cooling in the step (a) in the air for 20 s; (c) and (c) allowing the strip steel subjected to air cooling in the step (b) to enter laminar flow water, cooling at the cooling speed of 18 ℃/s to 440 ℃, and coiling.
The thick DP680 grade hot-rolled dual-phase steel structure with the thickness of 13mm is a ferrite and martensite dual-phase structure, wherein the volume fraction of ferrite is 80%, the volume fraction of martensite is 20%, and the average grain size of ferrite is 5.9 μm. The tensile strength is 726MPa, the yield strength is 423MPa, the yield ratio is 0.58, the elongation after fracture is 31%, and the tensile curve of the thick DP680 grade hot-rolled dual-phase steel is shown in figure 1.
Example 3
The thick DP680 grade hot rolled dual phase steel plate of this example has a chemical composition of, in weight percent, 0.045% C, 0.016% Si, 1.23% Mn, 0.027% Ti, 0.6% Cr, 0.01% P, 0.005% S, 0.0023% N, 0.02% Als, and the balance iron and unavoidable impurities.
A preparation method of thick DP680 hot-rolled dual-phase steel with the thickness of 18mm comprises the following process steps:
(1) heating a steel billet with the thickness of 250mm to 1235 ℃, and preserving heat for 2.0h, wherein the steel billet comprises the following chemical components in percentage by weight: 0.045% of C, 0.016% of Si, 1.23% of Mn, 0.027% of Ti, 0.6% of Cr, 0.01% of P, 0.005% of S, 0.0023% of N, 0.02% of Als, and the balance of iron and inevitable impurities;
(2) rolling the heated steel billet for 5 passes, wherein the initial rolling temperature of rough rolling is 1180 ℃, the thickness of the intermediate billet after rough rolling is 48mm, the initial rolling temperature of finish rolling is 1000 ℃, the final rolling temperature is 900 ℃, and the reduction pass distribution is 250mm → 160mm → 85mm → 48mm → 29mm → 18mm, so as to obtain a steel plate with the thickness of 18 mm;
(3) carrying out water cooling-air cooling-water cooling three-stage cooling on the plate strip, (a) rolling the strip steel by a finishing mill group, and cooling the strip steel to 625 ℃ by water with the cooling speed of 14 ℃/s; (b) cooling the strip steel subjected to water cooling in the step (a) in air for 17 s; (c) and (c) allowing the strip steel subjected to air cooling in the step (b) to enter laminar flow water at a cooling speed of 20 ℃/s, and cooling to 465 ℃ for coiling.
The thick DP680 grade hot-rolled dual-phase steel structure with the thickness of 18mm is a ferrite and martensite dual-phase structure, wherein the volume fraction of ferrite is 74%, the volume fraction of martensite is 26%, and the average grain size of ferrite is 6.2 μm. The tensile strength is 723MPa, the yield strength is 439MPa, the yield ratio is 0.61, the elongation after fracture is 29%, and the metallographic microstructure (a microstructure photograph after 4% nitric acid alcohol corrosion) of the thick DP680 grade hot rolled dual phase steel plate at 1/4 in the thickness direction is shown in FIG. 2.
Example 4
The thick DP680 grade hot rolled dual phase steel sheet of this example had a chemical composition of, by weight, 0.08% C, 0.012% Si, 1.25% Mn, 0.029% Ti, 0.63% Cr, 0.005% P, 0.002% S, 0.0045% N, 0.023% Als, and the balance iron and unavoidable impurities.
A preparation method of thick DP680 hot-rolled dual-phase steel with the thickness of 22mm comprises the following process steps:
(1) heating a 185mm thick steel billet to 1240 ℃, and preserving heat for 2.5h, wherein the chemical components in percentage by weight are as follows: 0.08% C, 0.012% Si, 1.25% Mn, 0.029% Ti, 0.63% Cr, 0.005% P, 0.002% S, 0.0045% N, 0.023% Als, the balance being iron and unavoidable impurities;
(2) 4-pass rolling is carried out on the heated billet, the initial rolling temperature of rough rolling is 1175 ℃, the thickness of the intermediate billet after rough rolling is 115mm, the initial rolling temperature of finish rolling is 990 ℃, the final rolling temperature is 885 ℃, and the reduction pass distribution is 185mm → 115mm → 60mm → 34mm → 22mm, so as to obtain a steel plate with the thickness of 22 mm;
(3) carrying out water cooling-air cooling-water cooling three-stage cooling on the plate strip, (a) rolling the strip steel by a finishing mill group, and cooling the strip steel to 618 ℃ by water with the cooling speed of 15 ℃/s; (b) cooling the strip steel subjected to water cooling in the step (a) in the air for 19 s; (c) and (c) allowing the strip steel subjected to air cooling in the step (b) to enter laminar flow water, cooling at the cooling speed of 25 ℃/s to 500 ℃ and coiling.
The thick DP680 grade hot-rolled dual-phase steel structure with the thickness of 22mm is a ferrite and martensite dual-phase structure, wherein the volume fraction of ferrite is 71 percent, the volume fraction of martensite is 29 percent, and the average grain size of ferrite is 6.7 mu m. The tensile strength is 748MPa, the yield strength is 446MPa, the yield ratio is 0.60, and the elongation after fracture is 28%.
Claims (1)
1. A preparation method of a thick DP680 hot-rolled dual-phase steel plate is characterized by comprising the following steps:
(1) heating a steel billet with the thickness of 200-250 mm to 1220-1250 ℃, and preserving heat for 2.0-2.3 h, wherein the steel billet comprises the following chemical components in percentage by weight: 0.045-0.06% of C, less than or equal to 0.04% of Si, 1.0-1.30% of Mn, 0.02-0.027% of Ti, 0.51-0.65% of Cr, less than or equal to 0.01% of P, less than or equal to 0.005% of S, 0.0015-0.0023% of N, 0.02-0.045% of Als, and the balance of iron and inevitable impurities;
(2) carrying out 5-pass rolling on the heated steel billet, wherein the initial rolling temperature of rough rolling is 1150-1200 ℃, the single-pass reduction rate of rough rolling is 36% -50.7%, the thickness of the intermediate billet after rough rolling is 48-72 mm, the initial rolling temperature of finish rolling is 950-1000 ℃, the single-pass reduction rate of finish rolling is 35.3% -50%, and the final rolling temperature is 870-920 ℃, so as to obtain a steel plate with the thickness of 11-18 mm;
(3) the steel plate is cooled by adopting a water cooling-air cooling-water cooling three-section mode, and the method specifically comprises the following steps: (a) cooling the steel plate to 610-640 ℃ by water with the cooling speed of 10-15 ℃/s; (b) cooling the steel plate subjected to water cooling in the step (a) in air for 15-20 s; (c) allowing the steel plate subjected to air cooling in the step (b) to enter laminar flow water, cooling to 400-465 ℃ at the cooling speed of 18-25 ℃/s, and coiling to obtain a thick DP680 grade hot-rolled dual-phase steel plate, wherein the hot-rolled dual-phase steel plate is a ferrite and martensite dual-phase structure, the volume fraction of ferrite is 74-85%, the volume fraction of martensite is 15-26%, and the average grain size of ferrite is 5.5-6.2 mu m; the hot-rolled dual-phase steel plate has the tensile strength of 704-726 MPa, the yield strength of 418-439 MPa, the yield ratio of 0.58-0.61 and the elongation after fracture of 29-33%.
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| CN201911180955.9A CN110760756B (en) | 2019-11-27 | 2019-11-27 | Thick DP 680-grade hot-rolled dual-phase steel and preparation method thereof |
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| EP2489748B1 (en) * | 2011-02-18 | 2017-12-13 | ThyssenKrupp Steel Europe AG | Hot-rolled steel surface product produced from a complex phase steel and method for the manufacture |
| CN102321845A (en) * | 2011-09-21 | 2012-01-18 | 首钢总公司 | A kind of high-strength hot-rolled dual-phase steel and method of manufacture thereof |
| JP5821861B2 (en) * | 2013-01-23 | 2015-11-24 | 新日鐵住金株式会社 | High-strength hot-rolled steel sheet with excellent appearance and excellent balance between elongation and hole expansibility and method for producing the same |
| CN108411207B (en) * | 2018-04-11 | 2020-01-07 | 东北大学 | Thin-specification hot-rolled dual-phase steel with tensile strength of 600MPa and manufacturing method thereof |
| CN108277441B (en) * | 2018-04-11 | 2019-12-03 | 东北大学 | A kind of 600MPa grade Ti micro-alloying hot rolling biphase plate and preparation method thereof |
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