CN116377320A - Ultrahigh-strength steel with high strength and plastic product for cold rolling automobile and manufacturing method thereof - Google Patents
Ultrahigh-strength steel with high strength and plastic product for cold rolling automobile and manufacturing method thereof Download PDFInfo
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 33
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 title claims abstract description 18
- 238000005097 cold rolling Methods 0.000 title description 3
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 66
- 239000010959 steel Substances 0.000 claims abstract description 66
- 238000005096 rolling process Methods 0.000 claims abstract description 41
- 238000000137 annealing Methods 0.000 claims abstract description 27
- 238000009749 continuous casting Methods 0.000 claims abstract description 12
- 238000003723 Smelting Methods 0.000 claims abstract description 7
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000009628 steelmaking Methods 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 5
- 239000000126 substance Substances 0.000 claims abstract description 5
- 238000005554 pickling Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 22
- 229910001566 austenite Inorganic materials 0.000 claims description 18
- 230000008569 process Effects 0.000 claims description 14
- 229910000734 martensite Inorganic materials 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 5
- 230000032683 aging Effects 0.000 claims description 5
- 238000004321 preservation Methods 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 4
- 230000009467 reduction Effects 0.000 claims description 4
- 238000010583 slow cooling Methods 0.000 claims description 3
- 241001391944 Commicarpus scandens Species 0.000 claims description 2
- 238000004146 energy storage Methods 0.000 claims description 2
- 239000007789 gas Substances 0.000 claims description 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 2
- 239000001257 hydrogen Substances 0.000 claims description 2
- 230000006698 induction Effects 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 230000035882 stress Effects 0.000 claims description 2
- 238000005406 washing Methods 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 2
- 229910000859 α-Fe Inorganic materials 0.000 claims description 2
- 238000005452 bending Methods 0.000 abstract description 2
- 238000005336 cracking Methods 0.000 abstract description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 8
- 239000011572 manganese Substances 0.000 description 7
- 230000007547 defect Effects 0.000 description 5
- 229910052717 sulfur Inorganic materials 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 230000009931 harmful effect Effects 0.000 description 3
- 238000005098 hot rolling Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 238000005204 segregation Methods 0.000 description 3
- 230000000087 stabilizing effect Effects 0.000 description 3
- 229910000617 Mangalloy Inorganic materials 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 229910000576 Laminated steel Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000002788 crimping Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 238000003466 welding 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/30—Stress-relieving
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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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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- 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
- C21D8/0231—Warm rolling
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- 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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- C22C33/04—Making ferrous alloys by melting
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- 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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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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Abstract
The invention relates to a high-strength and high-ductility product ultra-high strength steel for a cold-rolled automobile and a manufacturing method thereof, wherein the chemical components comprise the following components in percentage by weight: 0.32 to 0.36 percent, si:1.2 to 1.5 percent of Mn:2.9 to 3.4 percent, P: less than or equal to 0.010 percent, S: less than or equal to 0.010%, al:0.02% -0.035%, ce:0.02% -0.04%, and the balance of Fe and unavoidable impurities. The invention has the advantages that: the production process of smelting in a steelmaking converter, continuous casting, hot continuous rolling, shielding annealing, pickling, rolling with temperature and continuous annealing can be completed on the existing production line without adding new production equipment; the produced steel coil (or steel plate) has high strength, high strength and high plastic product, and is bent 180 degrees without cracking under the condition of bending radius D=a.
Description
Technical Field
The invention relates to the field of steel production for automobiles, in particular to ultra-high-strength steel for a cold-rolled automobile with high strength and elongation and a manufacturing method thereof.
Background
The light weight and high strength of the automobile steel are the necessary trends of automobile safety, long service life, low cost, energy conservation and emission reduction. The first generation automobile steel (AHSS, IF, BH, DP, TRIP, martensitic steel and the like) cannot meet the increasing requirements of automobile safety collision coefficient and excellent formability of stamped parts on average 15-20 GPa percent of strong plastic product, and the second generation automobile steel (TWIP, austenitic stainless steel and the like) has excellent mechanical property strong plastic product which can reach 60GPa percent, but is difficult to be produced on a large scale due to overhigh material cost or process cost. The concept of third-generation automobile steel is then proposed, namely, the steel not only has good strength and plasticity, but also has alloy content far lower than that of second-generation automobile steel, thereby realizing multiple requirements of light weight, low cost and high safety. The method has the advantages that the content of residual austenite in steel is improved, the TRIP effect is generated in the austenite during deformation, the strength and the formability of the automobile steel plate are improved, in the ultrahigh-strength automobile steel, the high strength is provided by a large amount of martensite in a structure, the elongation is not high due to the insufficient content of the residual austenite, the Q & P annealing process is adopted to effectively improve the content of the residual austenite, and the redistribution of C element is completed in an aging section, so that the structure has high strength and good ductility. However, in the production process, the existence of O and S elements in the steel can lead to the reduction of the performance of the steel due to the aggregation of the O and S elements in the grain boundaries, so that a small amount of rare earth elements are added in the steel to combine with the O and S elements in the steel, the purification structure and the grain boundaries have better performance improvement, and the method for improving the strength of the steel by increasing the carbon content is much lower than the method for improving the strength of the steel by adding other alloy elements, but has the problem that the strength is too high to roll and the welding is difficult.
The publication number is CN112831721A, which discloses an additive manufacturing ultra-high-strength plastic-laminated steel material and a preparation method thereof, and has the defects that the additive manufacturing cost is high and the material is not suitable for mass production; the publication No. CN110055465A discloses a medium manganese ultra-high strength steel and a preparation method thereof, which have the defects that the cost is high due to the adoption of medium manganese components, and the medium manganese steel cannot be uniformly deformed due to the structure of the medium manganese steel, so that the production and the application are greatly limited; the publication number is CN114381655A, which discloses a high-strength plastic product cold-rolled QP steel and an annealing process and a manufacturing method thereof, and has the defects that the strength of a tensile product is not high; the publication No. CN109852887A is an ultra-high strength plastic product cold-rolled steel plate and a production method thereof, and has the defect that the tensile product strength is not high.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide the ultra-high strength steel for the cold-rolled automobile with high strength and elongation and the manufacturing method thereof, and the production process of optimizing the chemical component ratio, realizing the purification of steel, inhibiting the precipitation of carbide in tempered martensite by improving the carbon content and adding rare earth elements, and combining the production processes of steelmaking converter smelting, continuous casting, hot continuous rolling, covering annealing, acid cleaning, hot rolling and continuous annealing can be completed on the existing production line.
In order to achieve the above purpose, the present invention is realized by the following technical scheme:
ultra-high-strength steel for cold-rolled automobile with high strength and elongation products comprises the following chemical components in percentage by weight: 0.32 to 0.36 percent, si:1.2 to 1.5 percent of Mn:2.9 to 3.4 percent, P: less than or equal to 0.010 percent, S: less than or equal to 0.010%, al:0.02% -0.035%, ce:0.02% -0.04%, and the balance of Fe and unavoidable impurities.
The yield strength of the ultra-high strength steel for the cold-rolled automobile is more than or equal to 1089MPa, the tensile strength is more than 1470MPa, the elongation is more than 15%, the strength-plastic product is more than 23GPa, when the microstructure is austenite+martensite+ferrite, the austenite phase proportion is 10% -16%, the martensite phase proportion is 80% -88%, and when the microstructure is austenite+martensite, the austenite phase proportion is 9% -11%.
The main functions of the steel plate are as follows:
c: the element C is an austenite stabilizing element with the lowest cost and the best stabilizing effect in steel, and has good solid solution strengthening effect; too low a content of C element may decrease the strength of the steel and the stability of austenite; the content of C element is too high, carbide is easily precipitated at grain boundary, and the performance of steel is lowered, so that the content of C element is in the range of 0.32% -0.36%.
Mn: mn element is austenite stabilizing element in steel, and the content of Mn element is too low, which can lead to insufficient content of residual austenite after martensitic transformation of the steel plate and reduce the plasticity of the steel plate, so that the content of Mn element is 2.9-3.4%.
Si: si plays a role in deoxidizing mainly in steel, so that inclusions in the steel are reduced; the Si content is too low to play a deoxidizing role, and too high to reduce the surface quality of the steel sheet, so that the Si content is in the range of 1.2% to 1.5%.
P: the P element is a harmful element in steel, and the lower the content is, the better.
S: the S element is a harmful element in steel, and the lower the content is, the better.
Al: the Al element is helpful for deoxidizing molten steel, and can inhibit the decomposition of residual austenite and the precipitation of carbide; the content of Al element is too high, which not only increases the production cost, but also causes the difficulty of continuous casting production, etc., so the content of Al element is controlled to be 0.02-0.035%.
Ce: has stronger deoxidizing and desulfurizing ability, can react with oxygen and sulfur to generate spherical rare earth oxide, improves the toughness and plasticity of steel, especially the transverse impact property, and improves the anisotropy of steel, thus the content of Ce element is 0.02-0.04%.
The alloy elements of excessive types are not added, the higher strength is achieved by improving the carbon content and regulating and controlling the structure in the steel, the strength of the steel is higher, cracks are easy to extend along inclusions and grain boundaries in the steel, the impurities and the segregation of the impurity elements at the grain boundaries occur in production, the plasticity and toughness of the steel are reduced, and the harm of nonmetallic inclusion to the steel is greatly reduced by adding the rare earth element Ce; the rare earth element Ce has obvious inhibition effect on coarsening of the crystal grains of the steel, and realizes fine grain strengthening effect; the rare earth element Ce has a certain solid solution amount in the steel, and the segregation of sulfur and phosphorus in the grain boundary can be inhibited by the segregation of the rare earth element Ce in the grain boundary, so that a compound with a higher melting point is formed with the impurities, and the harmful effects of the offset impurities are eliminated; by adding the rare earth element Ce, the strength-plastic product of the steel can be effectively improved.
A manufacturing method of ultra-high strength steel for cold rolling automobile with high strength and elongation product comprises the following steps: smelting in a steelmaking converter, continuous casting, hot continuous rolling, covering annealing, pickling, rolling at a temperature, and continuous annealing, wherein the control process comprises the following steps:
1) Smelting in a steelmaking converter: the temperature of the molten steel is 1500-1650 ℃;
2) Continuous casting: the casting temperature is 1350-1500 ℃;
3) Hot continuous rolling: the casting blank is fed into a furnace at 500-800 ℃, the heating temperature is 1100-1250 ℃, a rolling mill performs 7-9 times of rolling to a steel plate with the designed thickness specification, high-temperature rapid rolling is needed during rolling, the initial rolling temperature is 1050-1150 ℃, the final rolling temperature is over 900 ℃ (because the final rolling temperature is too low, hard phase tissues in the steel are caused, rolling is difficult), the rolling temperature is 700-750 ℃ high-temperature rolling, and the thickness of a hot rolled coil is 2.8-3.2 mm;
4) And (3) cover annealing: feeding the continuous casting blank into a furnace, wherein the temperature is 620-650 ℃ and the heat preservation is carried out for more than 5 hours, and the continuous casting blank is used for eliminating internal stress so as to facilitate subsequent rolling;
5) Acid washing: removing oxidized iron scales on the surface through acid liquor;
6) Rolling at a belt temperature: the steel coil is subjected to induction or water bath heating at 95-150 ℃ before rolling, the heat preservation time is more than 0.5-0.8 hour, the rolling can be performed through 3-6 times of rolling by a single-stand rolling mill, the total rolling reduction is more than 50%, enough cold deformation energy storage is ensured, and the thickness of the cold rolled coil is 1.26-1.6 mm;
7) Continuous annealing: heating at 10 ℃/s, annealing at 830-860 ℃ for 80-130 s, slow cooling to 690-710 ℃, fast cooling to 200-230 ℃, cooling at > 30 ℃/s, maintaining for 8-15 s, aging at 380-420 ℃ for 300-500 s, and cooling to room temperature, wherein nitrogen-hydrogen mixed gas is adopted in the furnace atmosphere to ensure the surface quality of the steel plate; the continuous annealing belt speed of the steel plate is 80m/min, v is more than or equal to 60m/min, the tension is too high and the weld is easy to break due to the too high speed, the annealing time is increased due to the too low belt speed, and the strength is reduced; the weight of a single coil of steel must be greater than 18t.
Compared with the prior art, the invention has the beneficial effects that:
the method has the advantages that the problems of difficult production of the ultra-high-strength steel can be solved by improving the carbon content and adding the rare earth element Ce, the steel is purified, the precipitation of carbide in tempered martensite is restrained through an annealing process of quenching and distribution, and the production process of smelting in a steelmaking converter, continuous casting, hot continuous rolling, shielding annealing, pickling, rolling with temperature and continuous annealing is matched, so that the production of the ultra-high-strength steel is finished on the existing production line without adding new production equipment; the produced steel coil (or steel plate) has high strength, high strength and high plastic product, and is bent 180 degrees without cracking under the condition of bending radius D=a.
Drawings
FIG. 1 shows a typical metallographic structure OM in the examples.
Fig. 2 is a typical metallographic structure SEM in the examples.
FIG. 3 is a typical engineering stress-strain curve for an example.
FIG. 4 is a residual austenite content test in the examples.
FIG. 5 is the results of example 1# cold roll.
Fig. 6 is a dynamic CCT curve of example 1 #.
Detailed Description
The present invention will be described in detail below with reference to the drawings of the specification, but it should be noted that the practice of the present invention is not limited to the following embodiments.
The specific components, process regimes and properties of the steel plates of the 10 examples are shown in tables 1-6.
TABLE 1 chemical composition (wt.%)
| Steel grade | C | Si | Mn | P | S | Al | Ce |
| A1 | 0.34 | 1.49 | 3 | 0.0087 | 0.0041 | 0.041 | 0.025 |
| A2 | 0.32 | 1.47 | 2.9 | 0.006 | 0.0038 | 0.035 | 0.018 |
| A3 | 0.35 | 1.5 | 3.03 | <0.005 | 0.0026 | 0.06 | 0.034 |
TABLE 2 Hot Rolling Process according to an embodiment of the invention
| Process number | Heating temperature/. Degree.C | Initial rolling temperature/DEGC | Finishing temperature/°c | Crimping temperature/°c |
| B1 | 1250 | 1105 | 901 | 643 |
| B2 | 1250 | 1123 | 929 | 645 |
| B3 | 1230 | 1136 | 909 | 633 |
Table 3 example hot rolling mechanical properties
| Steel grade | Process number | Rp 0.2 /MPa | Rm/MPa | A80/％ |
| A1 | B1 | 919 | 1206 | 8.5 |
| A2 | B2 | 899 | 1184 | 9.2 |
| A3 | B3 | 917 | 1218 | 8.3 |
TABLE 4 mechanical Properties after hot-rolled shields of examples
| Steel grade | Process number | Rp 0.2 /MPa | Rm/MPa | A80/％ |
| A1 | B1 | 853 | 1148 | 10.2 |
| A2 | B2 | 828 | 1117 | 10.8 |
| A3 | B3 | 867 | 1155 | 9.7 |
Table 5 example continuous annealing process
| Process number | Soaking temperature/. Degree.C | Slow cooling outlet temperature/°c | Quick cooling outlet temperature/°c | Aging temperature/. Degree.C |
| C1 | 850 | 700 | 220 | 380 |
| C2 | 850 | 690 | 220 | 380 |
| C3 | 850 | 700 | 220 | 400 |
| C4 | 840 | 690 | 200 | 400 |
| C5 | 830 | 705 | 230 | 420 |
| C6 | 860 | 710 | 220 | 380 |
Table 6 Cold Rolling continuous annealing Property of examples
| Example # | Steel grade | Process number | Process number | Rp0.2/MPa | Rm/MPa | A50/％ | Strong plastic product/GPa% |
| 1 | A1 | B1 | C1 | 1127 | 1509 | 15.3 | 23.1 |
| 2 | A1 | B1 | C2 | 1089 | 1476 | 16.3 | 24.1 |
| 3 | A1 | B1 | C3 | 1184 | 1493 | 16.5 | 24.6 |
| 4 | A1 | B1 | C4 | 1099 | 1489 | 15.8 | 23.5 |
| 5 | A1 | B1 | C5 | 1116 | 1475 | 16.4 | 24.2 |
| 6 | A1 | B1 | C6 | 1135 | 1522 | 15.2 | 23.1 |
| 7 | A2 | B2 | C3 | 1103 | 1477 | 15.6 | 23.0 |
| 8 | A3 | B3 | C1 | 1154 | 1512 | 15.3 | 23.1 |
| 9 | A3 | B3 | C2 | 1102 | 1534 | 15.9 | 24.4 |
| 10 | A3 | B3 | C3 | 1147 | 1508 | 16.1 | 24.3 |
Claims (6)
1. The ultra-high strength steel for the cold-rolled automobile with high strength and elongation product is characterized by comprising the following chemical components in percentage by weight: 0.32 to 0.36 percent, si:1.2 to 1.5 percent of Mn:2.9 to 3.4 percent, P: less than or equal to 0.010 percent, S: less than or equal to 0.010%, al:0.02% -0.035%, ce:0.02% -0.04%, and the balance of Fe and unavoidable impurities.
2. The ultra-high-strength steel for cold-rolled automobile according to claim 1, wherein the yield strength of the ultra-high-strength steel for cold-rolled automobile is equal to or more than 1089MPa, the tensile strength is greater than 1470MPa, the elongation is greater than 15%, the strength-plastic product is greater than 23GPa%, the phase ratio of austenite is 10% to 16% when the microstructure is austenite+martensite+ferrite, the phase ratio of martensite is 80% to 88%, and the phase ratio of austenite is 9% to 11% when the microstructure is austenite+martensite.
3. The method for manufacturing the ultra-high-strength steel for the cold-rolled automobile with the product of high strength and elongation according to claim 1 or 2, wherein the manufacturing method is as follows: smelting in a steelmaking converter, continuous casting, hot continuous rolling, covering annealing, pickling, rolling at a temperature, and continuous annealing, wherein the control process comprises the following steps:
1) Smelting in a steelmaking converter: the temperature of the molten steel is 1500-1650 ℃;
2) Continuous casting: the casting temperature is 1350-1500 ℃;
3) Hot continuous rolling: the casting blank is fed into a furnace at 500-800 ℃, the heating temperature is 1100-1250 ℃, a rolling mill performs 7-9 times of rolling to a steel plate with designed thickness specification, high-temperature rapid rolling is required during rolling, the initial rolling temperature is 1050-1150 ℃, the final rolling temperature is above 900 ℃, and the curling temperature is 700-750 ℃ high-temperature curling;
4) And (3) cover annealing: feeding the continuous casting blank into a furnace, wherein the temperature is 620-650 ℃ and the heat preservation is carried out for more than 5 hours, and the continuous casting blank is used for eliminating internal stress so as to facilitate subsequent rolling;
5) Acid washing: removing oxidized iron scales on the surface through acid liquor;
6) Rolling at a belt temperature: the steel coil is subjected to induction or water bath heating at 95-150 ℃ before rolling, the heat preservation time is more than 0.5-0.8 hour, the steel coil can be rolled by 3-6 times of rolling by a single-stand rolling mill, the total rolling reduction is more than 50%, and enough cold deformation energy storage is ensured;
7) Continuous annealing: the heating rate is 10 ℃/s, the annealing temperature is 830-860 ℃, the annealing time is 80-130 s, the slow cooling temperature is 690-710 ℃, the fast cooling temperature is 200-230 ℃, the cooling rate is more than 30 ℃/s, the heat preservation time is 8-15 s, the aging temperature is 380-420 ℃, the aging time is 300-500 s, and the cooling to room temperature is performed.
4. The method for manufacturing ultra-high-strength steel for cold-rolled automobile with high strength and elongation according to claim 3, wherein the thickness of the hot rolled coil of the hot tie is 2.8-3.2 mm.
5. The method for manufacturing ultra-high-strength steel for cold-rolled automobile with high-strength and elongation product according to claim 3, wherein the thickness of the cold-rolled coil rolled at the temperature is 1.26-1.6 mm.
6. The method for manufacturing the ultra-high-strength steel for the cold-rolled automobile with high strength and elongation products according to claim 3, wherein in the continuous annealing, the atmosphere in the furnace adopts nitrogen-hydrogen mixed gas, so that the surface quality of the steel plate is ensured; the continuous annealing belt speed of the steel plate is 80m/min, v is more than or equal to 60m/min, the tension is too high and the weld is easy to break due to the too high speed, the annealing time is increased due to the too low belt speed, and the strength is reduced; the weight of a single coil of steel must be greater than 18t.
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