CN107760996A - A kind of hot-rolled dual-phase steel and its processing method - Google Patents
A kind of hot-rolled dual-phase steel and its processing method Download PDFInfo
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- 229910000885 Dual-phase steel Inorganic materials 0.000 title claims abstract description 59
- 238000003672 processing method Methods 0.000 title claims abstract description 15
- 239000010959 steel Substances 0.000 claims abstract description 54
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 53
- 238000001816 cooling Methods 0.000 claims abstract description 47
- 238000005096 rolling process Methods 0.000 claims abstract description 24
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 21
- 230000008569 process Effects 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 14
- 238000005098 hot rolling Methods 0.000 claims abstract description 14
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 13
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 10
- 239000000126 substance Substances 0.000 claims abstract description 9
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 9
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 229910052742 iron Inorganic materials 0.000 claims abstract description 7
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 7
- 238000003723 Smelting Methods 0.000 claims abstract description 6
- 238000009749 continuous casting Methods 0.000 claims abstract description 5
- 229910000859 α-Fe Inorganic materials 0.000 claims description 17
- 229910000734 martensite Inorganic materials 0.000 claims description 16
- 229910045601 alloy Inorganic materials 0.000 claims description 8
- 239000000956 alloy Substances 0.000 claims description 8
- 230000009467 reduction Effects 0.000 claims description 7
- 238000012545 processing Methods 0.000 claims description 5
- 230000001133 acceleration Effects 0.000 claims description 4
- 239000000203 mixture Substances 0.000 abstract description 5
- 239000011651 chromium Substances 0.000 description 10
- 239000011572 manganese Substances 0.000 description 10
- 238000005204 segregation Methods 0.000 description 8
- 239000000243 solution Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 5
- 230000008859 change Effects 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000011574 phosphorus Substances 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000004886 process control Methods 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000032798 delamination Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000009489 vacuum treatment Methods 0.000 description 2
- 206010015150 Erythema Diseases 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 231100000321 erythema Toxicity 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- 230000007704 transition Effects 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- 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
-
- 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
-
- 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
-
- 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
-
- 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
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
-
- 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
-
- 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
Landscapes
- 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)
Abstract
The invention discloses a kind of hot-rolled dual-phase steel and its processing method, belong to technical field of steel rolling.According to mass percent, the chemical composition of the dual phase steel is：C：0.04%~0.08%, Si≤0.10%, Mn：1.40%~1.80%, P≤0.020%, S≤0.003%, Cr：0.60%~0.80%, Als：0.03%~0.10%, N≤0.005%, remaining is Fe and inevitable impurity.Its processing method includes molten iron pretreatment, smelting, continuous casting, heating, hot rolling, cooling, coiling process；Being finally obtained think gauge 600MPa levels has the dual phase steel of excellent cold formability energy, and has excellent comprehensive mechanical property and cold formability energy, disclosure satisfy that the automobile structures such as wheel spoke and needs the structural member demand of complicated cold forming.
Description
Technical Field
The invention relates to the technical field of steel rolling, in particular to hot-rolled dual-phase steel and a processing method thereof.
Background
With the development of industrial technology and the improvement of technological capability, particularly the development of the automobile industry, novel automobile structural materials represented by high-strength hot-rolled complex-phase steel are rapidly developed. The 600 MPa-level hot-rolled dual-phase steel is widely accepted in the market due to high strength, low yield ratio and excellent forming performance. At present, there is a trend to use dual phase steel for spokes and rims of wheels of large loaders, semitrailers and large buses, and some wheel manufacturers have started trial production. The rim and the spoke for the large wheel both need thick specifications, generally more than 8mm, and the original common hot-rolled dual-phase steel production technology is mainly used for manufacturing small wheels of passenger cars, and the production specifications are thinner, generally less than 6 mm. The hot-rolled dual-phase steel adopts two-stage control cooling, and after the thickness is increased, new requirements of the uniformity of the structure in the thickness direction and the specific gravity of a martensite structure on cooling conditions and cooling control are met. Meanwhile, the control requirement on segregation in steel is higher, and the original component system and processing technology for the wheels of the passenger cars cannot meet the requirement of thick dual-phase steel.
Disclosure of Invention
The invention aims to provide hot-rolled dual-phase steel and a processing method thereof, which can produce thick hot-rolled dual-phase steel and have excellent comprehensive mechanical property and cold forming property.
In order to achieve the aim, the invention provides hot-rolled dual-phase steel which comprises the following chemical components in percentage by mass: c: 0.04-0.08%, Si is less than or equal to 0.10%, Mn: 1.40-1.80%, P is less than or equal to 0.020%, S is less than or equal to 0.003%, Cr: 0.60% -0.80%, Als: 0.03-0.10 percent of the total weight of the alloy, less than or equal to 0.005 percent of N, and the balance of Fe and inevitable impurities.
Further, the internal microstructure of the dual phase steel is martensite + ferrite.
Further, the thickness of the dual-phase steel is 8.0-15.0 mm.
Further, the tensile strength of the dual-phase steel is more than or equal to 600MPa, and/or the yield strength of the dual-phase steel is more than or equal to 330 MPa.
Further, elongation A of the dual phase steel50≥26％。
The invention also provides a processing method of the hot-rolled dual-phase steel, which comprises the following steps: the process comprises the steps of molten iron pretreatment, smelting, continuous casting, heating, hot rolling, cooling and coiling; wherein,
the heating temperature is 1300-1400 ℃, and the total time is 200-360 min;
the initial rolling temperature of the hot rolling is more than or equal to 1290 ℃, the final rolling temperature is 790-850 ℃, and the steel rolling acceleration in the hot rolling process is controlled to be less than or equal to 0.005m/s2；
The cooling adopts two-section rapid cooling, the interval of the two-section cooling time is 9-12 s, the first-section cooling speed is 70-130 ℃/s, and the second-section cooling speed is more than or equal to 100 ℃/s.
Furthermore, the width reduction amount of the hot rolling plate blank is controlled to be less than or equal to 100mm in the hot rolling process.
Further, the coiling temperature is 150-300 ℃.
Further, the internal microstructure of the dual-phase steel obtained by the processing method is martensite + ferrite.
Furthermore, the thickness of the dual-phase steel plate is 8.0-15.0 mm, and/or the tensile strength is more than or equal to 600MPa, and/or the yield strength is more than or equal to 330 MPa.
One or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:
1. the hot-rolled dual-phase steel provided by the embodiment of the application adopts proper contents of carbon, manganese and chromium, improves the through-hardening coefficient of the steel, and ensures the formation of a final martensite + ferrite structure; the lower phosphorus content is adopted to prevent the delamination and the reduction of the forming performance caused by the segregation of central phosphorus; thereby ensuring the mechanical property and cold forming property of the final material and obtaining the thick 600MPa grade dual-phase steel with excellent cold forming property.
2. According to the processing method of the hot-rolled dual-phase steel, through the design of optimized alloy components, quasi-constant-speed rolling and two-section type rapid cooling are adopted in the production process, the phase change of martensite and ferrite in the steel is controlled, and the uniformity of the structure in the thickness direction is ensured, so that the mechanical property and the cold forming property of the material are finally ensured, and the requirements of automobile structural members such as wheel spokes and the like and structural members needing complex cold forming can be met.
Drawings
FIG. 1 is a metallographic structure photograph of a hot-rolled dual phase steel obtained in example 2 of the present application;
FIG. 2 is a photograph of the structure of the hot-rolled dual phase steel obtained in comparative example 2 of the present application.
Detailed Description
The embodiment of the application provides hot-rolled dual-phase steel and a processing method thereof, which can be used for producing thick hot-rolled dual-phase steel, have excellent comprehensive mechanical properties and cold forming properties, and can meet the requirements of automobile structural members such as wheel spokes and the like and structural members needing complex cold forming.
The technical solutions of the present application are described in detail below with reference to the drawings and specific embodiments, and it should be understood that the specific features in the embodiments and examples of the present application are described in detail in the technical solutions of the present application, but not limited to the technical solutions of the present application, and the technical features in the embodiments and examples of the present application may be combined with each other without conflict.
The term "and/or" herein is merely an association describing an associated object, meaning that three relationships may exist, e.g., a and/or B, may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
In order to achieve the above object, embodiments of the present application provide a hot-rolled dual-phase steel, which comprises the following chemical components by mass percent: c: 0.04-0.08%, Si is less than or equal to 0.10%, Mn: 1.40-1.80%, P is less than or equal to 0.020%, S is less than or equal to 0.003%, Cr: 0.60% -0.80%, Als: 0.03-0.10 percent of the total weight of the alloy, less than or equal to 0.005 percent of N, and the balance of Fe and inevitable impurities.
In this example, the internal microstructure of the dual phase steel was martensite + ferrite. The dual-phase structure of martensite + ferrite has the high strength of martensite and the high extensibility of ferrite concurrently for finally obtain high tensile strength, low yield strength and high extensibility, this kind of structure has high strain hardening effect simultaneously, through use processes such as punching press after, yield strength can promote by a wide margin, thereby guarantees the high performance of final work piece.
The hot-rolled dual-phase steel with the chemical components is formed by optimizing alloy elements and is based on the following principle:
the content range of the C element is controlled to be 0.04-0.08%, C is one of indispensable elements for improving the strength of steel in steel, but the over-high content of C can improve the hardenability of the steel, increase the martensite content in the cooling process, reduce the uniform elongation property and reduce the cold forming property of the steel.
The content of the Si element is controlled to be less than or equal to 0.10% in the embodiment of the application, because the Si is easy to form ferrous silicate and adhere to the surface of the steel plate to form quality defects such as surface erythema and the like.
According to the embodiment of the application, the content range of the Mn element is controlled to be 1.40-1.80%, the phase transition temperature of austenite converted into ferrite can be reduced, the hot working temperature area is enlarged, the realization of a two-phase structure process is facilitated, the hardenability of steel is improved, and the structure uniformity of a steel plate in the thickness direction is improved.
According to the embodiment of the application, the content of the P element is controlled to be less than or equal to 0.0020%, although the gamma phase region can be sealed by phosphorus, the two-phase control in the cooling process is facilitated, the P segregation is easily formed by high P, the central performance of the thick steel plate is reduced, and the final forming performance is influenced.
The embodiment of the application controls the content range of the Cr element to be 0.60-0.80%, the Cr is an element which closes a gamma phase region and infinitely expands α phase regions, and is beneficial to realizing two-phase control in the cooling process, and simultaneously the Cr can provide solid solution strengthening and improve the tensile strength of steel.
The content range of the Al element is controlled to be 0.03-0.10%, and the Al mainly plays a role in removing oxygen (O) in molten steel and has a micro-alloying effect of refining grains. The high Al content can increase Al oxide inclusions in molten steel, and the large size of inclusions can influence the pouring process, and more importantly can become an internal defect source of a steel plate, so that the cracking risk in the forming process is increased; the low-Si design is adopted, the deoxidation effect cannot be achieved when the Al content is too small, the yield in the smelting process of other elements is influenced, oxide inclusions in steel can be increased, and the final forming performance is influenced.
According to the embodiment of the application, N is controlled to be less than or equal to 0.005%, S is controlled to be less than or equal to 0.003%, N and S belong to harmful elements in converter steel, and the lower content is more favorable for obtaining high uniform extensibility.
According to the content, the quenching coefficient of the steel is improved by adopting proper contents of carbon, manganese and chromium in the components, and the formation of the final martensite + ferrite structure is ensured; the lower phosphorus content is adopted to prevent the delamination and the reduction of the forming performance caused by the segregation of central phosphorus; meanwhile, the contents of silicon, sulfur, aluminum and nitrogen are controlled, so that the mechanical property and the cold forming property of the final material are ensured, and by adopting the component design, the steel plate with the thickness of 8.0-15.0 mm and excellent cold forming property can be obtained. The tensile strength of the dual-phase steel is more than or equal to 600MPa, the yield strength is more than or equal to 330MPa, and the elongation percentage A50≥26％。
The embodiment of the application also provides a processing method of the hot-rolled dual-phase steel, which comprises the following steps: molten iron pretreatment → smelting → continuous casting → heating → hot rolling → cooling → coiling;
pretreating molten iron, and then carrying out converter smelting, deep desulfurization, vacuum treatment and continuous casting to obtain a plate blank; the chemical components by mass percent are as follows: c: 0.04-0.08%, Si is less than or equal to 0.10%, Mn: 1.40-1.80%, P is less than or equal to 0.020%, S is less than or equal to 0.003%, Cr: 0.60% -0.80%, Als: 0.03-0.10 percent of the total weight of the alloy, less than or equal to 0.005 percent of N, and the balance of Fe and inevitable impurities.
The slab is heated, two-stage heating is adopted in the embodiment, the heating temperature is controlled to be 1300-1400 ℃, preferably 1320-1380 ℃, and the total time is 200-360 min. By adopting high heating temperature and longer heating time, main elements in the steel billet can be fully dissolved in solid, elements such as C, Mn and P which are easy to segregate are diffused, the element segregation in the plate blank is prevented and reduced, and the final finished product is ensured not to have or only to have a band-shaped structure with a very low level by combining the control of the subsequent rolling process, so that the performance of the thickness center part of the thick steel plate is ensured, and the defects such as center layering and the like which have influence on the forming are prevented. The excessive heating temperature can cause the surface of the plate blank to be over-burnt to form surface net defects; the heating temperature is too low, so that element segregation cannot be prevented, the heating temperature is too low, the rolling speed needs to be increased in order to ensure the later rolling temperature control, the retention time of the air cooling temperature section in the middle of two-section cooling in the laminar cooling process is influenced, the phase change process of ferrite is influenced, and the final tissue composition and performance are further influenced.
Hot rolling the heated slab to obtain a hot rolled plate; in the embodiment, the initial rolling temperature of hot rolling is controlled to be more than or equal to 1290 ℃, the final rolling temperature is controlled to be 790-850 ℃, and the steel rolling acceleration in the hot rolling process is controlled to be less than or equal to 0.005m/s2. The finishing rolling temperature is selected to be 790-850 ℃, on one hand, more nucleation points can be formed after the austenite structure is fully deformed in a non-recrystallization area, on the other hand, a certain temperature gradient is ensured in the first section of laminar cooling, the supercooling degree of the deformed austenite structure after the first section of cooling is increased, and the ferrite phase transformation is promoted. In order to ensure the stability of the head, middle and tail temperature of the steel coil in the two-section cooling process and further ensure the stability of the whole-coil hole expanding performance, a 'short billet + quasi-constant speed rolling' mode is adopted. The short billet of 8.2-9.2 m is adopted for rolling, so that the temperature drop of the tail part of the steel coil can be ensured to be small in a quasi-constant speed rolling mode, and the performance reduction of the steel plate caused by overlarge temperature difference between the head and the tail can be avoided; and the acceleration of the rolled steel is less than or equal to 0.005m/s2The quasi-constant-speed rolling mode can ensure that the time of the strip steel is equal when the strip steel is cooled by laminar flow, so that the cooling effect is the same, the temperature hit rate is high, the head and tail temperatures are more uniform, and the stability is good.
Further, in order to improve the edge quality of the rolled steel plate, the width reduction amount of the hot rolled slab is required to be less than or equal to 100mm in the embodiment, because the excessive width reduction amount can cause excessive deformation energy of the rolled edge structure of the steel strip, lead to early phase transformation in the rolling process and cause the defect of the edge quality of the steel plate.
Cooling the hot rolled plate; in the embodiment, two-section rapid cooling is adopted for cooling, the interval of the two-section cooling time is 9-12 s, the first-section cooling speed is 70-130 ℃/s, and the second-section cooling speed is more than or equal to 100 ℃/s. Specifically, ultra-fast cooling equipment is adopted to enable the cooling speed of the first section of water cooling to reach 70-130 ℃/s, so that a large amount of deformation zones in the steel strip crystal grains after finish rolling are reserved, the number of nucleation positions in the phase change process is large, and the ferrite crystal grains after phase change are refined. Meanwhile, the first section of water cooling time can be shortened, enough air cooling time is reserved for the air cooling section, and the occurrence and proportion of ferrite phase change are ensured. And the second section of water cooling adopts encrypted cooling, and the cooling speed can also be higher than or equal to 100 ℃/s, so that the formation interval of pearlite and bainite can be avoided, and untransformed austenite is completely transformed into martensite.
After cooling, coiling the hot rolled plate to obtain a hot rolled plate coil; the coiling temperature is 150-300 ℃. The coiling temperature is 150-300 ℃, and on the basis of ensuring to obtain martensite, on one hand, residual heat of the steel coil is utilized to evaporate the cooling residual water of the steel coil to prevent the corrosion of the scale, on the other hand, the impact on equipment is reduced, and the smooth coiling process is ensured.
Further, the hot rolled coil is cut into steel sheets by a flat slitting.
According to the content, the hot-rolled dual-phase steel processing method provided by the application controls the content of elements which are easy to generate segregation, such as P, Mn and the like, by optimizing the chemical composition of the alloy, controls the phase transformation of martensite and ferrite in the steel by adopting a proper cooling strategy in the production process, and ensures the uniformity of the structure in the thickness direction, thereby finally ensuring the mechanical property and the cold forming property of the material. The method can be used for producing the steel plate with the thickness of 8.0-15.0 mm, and the dual-phase steel produced according to the embodiment has the following properties: the tensile strength is more than or equal to 600MPa, the yield strength is more than or equal to 330MPa, the elongation is more than or equal to 26%, the mechanical property fluctuation of the head, the middle and the tail is within 30MPa, and the surface quality meets the requirements of automobile structural parts and complex cold-formed structural parts with high surface quality requirements such as wheel spokes.
The present application is described in more detail by way of examples below. These examples are merely illustrative of the best mode of carrying out the invention and do not limit the scope of the invention in any way.
Carrying out top-bottom combined blowing on an 80-ton converter, adopting a molten iron deep desulphurization technology to ensure that S in molten iron is less than or equal to 0.002 percent, and carrying out vacuum treatment on the molten steel after argon blowing to ensure that the steel contains the following chemical components: c: 0.04-0.08%, Si is less than or equal to 0.10%, Mn: 1.40-1.80%, P is less than or equal to 0.020%, S is less than or equal to 0.003%, Cr: 0.60% -0.80%, Als: 0.03-0.10 percent of the total weight of the alloy, less than or equal to 0.005 percent of N, and the balance of Fe and inevitable impurities.
The chemical composition of the hot rolled dual phase steel of the examples of the present application is shown in table 1.
TABLE 1 examples Complex phase Steel compositions (mass% with the balance Fe and unavoidable impurities)
| C | Si | Mn | P | S | Cr | Als | N | |
| Example 1 | 0.055 | 0.05 | 1.55 | 0.015 | 0.002 | 0.60 | 0.044 | 0.003 |
| Example 2 | 0.055 | 0.05 | 1.55 | 0.015 | 0.002 | 0.60 | 0.044 | 0.003 |
| Example 3 | 0.064 | 0.07 | 1.65 | 0.013 | 0.001 | 0.75 | 0.053 | 0.003 |
| Example 4 | 0.064 | 0.07 | 1.65 | 0.013 | 0.001 | 0.75 | 0.053 | 0.003 |
| Example 5 | 0.080 | 0.08 | 1.47 | 0.014 | 0.001 | 0.80 | 0.10 | 0.004 |
| Example 6 | 0.040 | 0.06 | 1.80 | 0.016 | 0.002 | 0.72 | 0.030 | 0.004 |
| Example 7 | 0.055 | 0.07 | 1.40 | 0.015 | 0.001 | 0.68 | 0.068 | 0.003 |
| Comparative example 1 | 0.067 | 0.20 | 1.30 | 0.014 | 0.003 | 0.74 | 0.039 | 0.003 |
| Comparative example 2 | 0.084 | 0.09 | 1.65 | 0.045 | 0.002 | 0.72 | 0.047 | 0.004 |
The molten steel with different components shown in the table 1 is cast into panel breaking blank belts with the size of 210mm multiplied by 1000-1550 mm, and the panel breaking blank belts are cut into slabs with the length of 8.2-9.2 m according to fixed length. And then heating the plate blank, rolling the plate blank on a hot continuous rolling unit, and coiling the rolled steel strip into a hot rolled steel coil after laminar two-stage quick cooling.
The process control and hot-rolled dual-phase steel properties of the examples of the present application are shown in table 2.
TABLE 2 examples Process control and Hot Rolling Dual phase Steel Properties
As can be seen from Table 2, the dual phase steels obtained in examples 1 to 7 all satisfied the yield strength RP0.2Not less than 330MPa, tensile strength RmMore than or equal to 600MPa and elongation rate A50Not less than 26 percent. FIG. 1 is a drawing of this applicationReferring to the metallographic structure of the hot-rolled dual phase steel obtained in example 2, it can be seen from FIG. 1 that: the structure of the strip steel is martensite + ferrite, and the strip steel has excellent uniformity. The yield strength and the tensile strength of the dual-phase steel obtained in the comparative example 1 are lower, the dual-phase steel obtained in the comparative example 2 meets the requirements on mechanical properties, but the manufactured steel plate has broken lines at the center of the thickness of the steel plate after being sheared, and as shown in figure 2, the dual-phase steel obtained in the comparative example 2 cannot meet the requirements on cold stamping and forming due to P segregation after analysis.
The above results show that the hot-rolled dual-phase steel with the thick specification tensile strength of 600MPa and excellent cold forming performance can be obtained by adopting the component design and the process control in the embodiment of the application.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (10)
1. The hot-rolled dual-phase steel is characterized by comprising the following chemical components in percentage by mass: c: 0.04-0.08%, Si is less than or equal to 0.10%, Mn: 1.40-1.80%, P is less than or equal to 0.020%, S is less than or equal to 0.003%, Cr: 0.60% -0.80%, Als: 0.03-0.10 percent of the total weight of the alloy, less than or equal to 0.005 percent of N, and the balance of Fe and inevitable impurities.
2. A hot rolled dual phase steel as claimed in claim 1, characterized in that the internal microstructure of the dual phase steel is martensite + ferrite.
3. A hot rolled dual phase steel as claimed in claim 1 or 2, wherein the dual phase steel has a thickness of 8.0 to 15.0 mm.
4. Hot rolled dual phase steel according to claim 3, characterised in that the dual phase steel has a tensile strength of 600MPa or more and/or a yield strength of 330MPa or more.
5. Hot rolled dual phase steel according to claim 3, characterised in that said dual phase steel has an elongation A50≥26％。
6. A method of processing hot rolled dual phase steel according to any one of claims 1 to 5, characterized in that the method of processing comprises: the process comprises the steps of molten iron pretreatment, smelting, continuous casting, heating, hot rolling, cooling and coiling; wherein,
the heating temperature is 1300-1400 ℃, and the total time is 200-360 min;
the initial rolling temperature of the hot rolling is more than or equal to 1290 ℃, the final rolling temperature is 790-850 ℃, and the steel rolling acceleration in the hot rolling process is controlled to be less than or equal to 0.005m/s2；
The cooling adopts two-section rapid cooling, the interval of the two-section cooling time is 9-12 s, the first-section cooling speed is 70-130 ℃/s, and the second-section cooling speed is more than or equal to 100 ℃/s.
7. The processing method of hot rolled dual phase steel as claimed in claim 6, wherein the hot rolling process controls the width reduction of the hot rolled slab to 100mm or less.
8. The method of processing hot-rolled dual-phase steel as claimed in claim 6, wherein the coiling temperature is 150 to 300 ℃.
9. A hot-rolled dual-phase steel processing method as claimed in any one of claims 6 to 8, characterized in that the dual-phase steel obtained by said processing method has an internal microstructure of martensite + ferrite.
10. The method of processing hot-rolled dual-phase steel according to claim 9, wherein the dual-phase steel sheet has a thickness of 8.0 to 15.0mm, and/or a tensile strength of not less than 600MPa, and/or a yield strength of not less than 330 MPa.
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Application publication date: 20180306 |