CN112831722B - Ultrathin ultrahigh-strength austenitic stainless steel and production method thereof - Google Patents
Ultrathin ultrahigh-strength austenitic stainless steel and production method thereof Download PDFInfo
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- 229910000963 austenitic stainless steel Inorganic materials 0.000 title claims abstract description 19
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- 238000005096 rolling process Methods 0.000 claims abstract description 31
- 238000001816 cooling Methods 0.000 claims abstract description 24
- 238000005266 casting Methods 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 14
- 238000000137 annealing Methods 0.000 claims abstract description 12
- 238000005097 cold rolling Methods 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 6
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 3
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 3
- 229910000831 Steel Inorganic materials 0.000 claims description 34
- 239000010959 steel Substances 0.000 claims description 34
- 230000009467 reduction Effects 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 10
- 230000008569 process Effects 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 238000007664 blowing Methods 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 238000009749 continuous casting Methods 0.000 claims description 4
- 239000000498 cooling water Substances 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 238000006477 desulfuration reaction Methods 0.000 claims description 3
- 230000023556 desulfurization Effects 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- 238000007670 refining Methods 0.000 claims description 3
- 229910001220 stainless steel Inorganic materials 0.000 abstract description 20
- 239000010935 stainless steel Substances 0.000 abstract description 19
- 229910001566 austenite Inorganic materials 0.000 abstract description 10
- 239000000047 product Substances 0.000 description 11
- 230000007797 corrosion Effects 0.000 description 8
- 238000005260 corrosion Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 238000005728 strengthening Methods 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 229910000734 martensite Inorganic materials 0.000 description 6
- 239000006104 solid solution Substances 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
- 238000004321 preservation Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
- 238000010079 rubber tapping Methods 0.000 description 3
- 230000000087 stabilizing effect Effects 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- UFGZSIPAQKLCGR-UHFFFAOYSA-N chromium carbide Chemical compound [Cr]#C[Cr]C#[Cr] UFGZSIPAQKLCGR-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000005389 magnetism Effects 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910003470 tongbaite Inorganic materials 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 238000004134 energy conservation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- C21D6/00—Heat treatment of ferrous alloys
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- 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
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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Abstract
An ultra-thin ultra-high strength austenitic stainless steel comprises the following components in percentage by weight: c: 0.033 to 0.045%, Si: 0.29 to 0.44%, Mn: 1.0-1.38%, P: less than or equal to 0.012 percent, S: less than or equal to 0.005 percent, Cr: 17.3-18.9%, Ni: 7.74-8.52%, Nb: 0.04-0.09%, Mo: 0.05-0.50%, N: 0.02-0.50%, and the production method comprises the following steps: continuously casting into a blank; heating the thin slab; descaling by high-pressure water; rolling; laminar cooling; coiling; cold rolling; annealing at high temperature; and cooling to room temperature. The invention not only has a metallographic structure of full austenite, but also has a stainless steel plate with a thickness of 0.31-0.37 mm, a yield strength of 971-1049 MPa, a tensile strength of 1147-1203 MPa and an elongation of 15-23%.
Description
Technical Field
The invention relates to stainless steel and a production method thereof, in particular to ultra-thin ultra-high strength austenitic stainless steel and a production method thereof.
Background
The 300 series austenitic stainless steel accounts for more than 70 percent of the total production of the stainless steel in the world, and the steel has good corrosion resistance, no magnetism and high ductility and toughness. However, the yield strength is low, about 200-300 MPa. With the increasingly prominent problems of world resources, energy consumption, environmental protection requirements and the like, development requirements of energy conservation, consumption reduction and high efficiency are provided in the equipment manufacturing industry, and the light weight and long service life of various key structures become a general development trend. The strength of the austenitic stainless steel is improved, the thickness of the steel is reduced, the austenitic stainless steel is used for replacing a thick steel plate with low strength grade, the using amount of the steel can be greatly reduced, and the austenitic stainless steel is an important means for realizing resource saving. Therefore, the development of austenitic stainless steel with ultra-high strength is not only a requirement of market competition and industry development, but also an inevitable choice for gradually optimizing social environment. Thin gauge ultra-high strength austenitic stainless steels have received increasing attention in recent years as one of high performance steels.
At present, the most of the produced ultrahigh-strength stainless steel is only in a martensite structure, the produced ultrahigh-strength stainless steel correspondingly has magnetism and relatively poor ductility, toughness and corrosion resistance, and the comprehensive performance of the product becomes poor along with the improvement of the strength.
Chinese patent publication No. CN106011681A discloses a method for improving the mechanical properties of 316LN austenitic stainless steel. In the document, the cold rolling-annealing treatment is introduced to 316LN austenitic stainless steel, the rolling reduction is 30-90%, and then the temperature is kept for 1-1000s at 700-1000 ℃ to prepare the ultrafine grain austenitic stainless steel with the thickness of 3-4 mm. The yield strength of the stainless steel prepared by the method is 450-600MPa, and the elongation is more than 50%. The yield strength of the austenitic stainless steel prepared by the process can be improved to 600MPa through fine grain strengthening, and the austenitic stainless steel with the yield strength more than 900MPa is difficult to obtain.
Disclosure of Invention
The invention aims to solve the defects that most of ultrahigh-strength stainless steel in the prior art is only in a martensite structure and has relatively poor ductility, toughness and corrosion resistance, and provides the all-austenite stainless steel with the thickness of 0.31-0.37 mm, the yield strength of 971-1049 MPa, the tensile strength of 1147-1203 MPa and the elongation of 15-23% and the production method thereof.
The measures for realizing the aim are as follows:
an ultra-thin ultra-high strength austenitic stainless steel comprises the following components by weight percent: c: 0.033-0.045%, Si: 0.29 to 0.44%, Mn: 1.0-1.38%, P: less than or equal to 0.012%, S: less than or equal to 0.005 percent, Cr: 17.3-18.9%, Ni: 7.74-8.52%, Nb: 0.04-0.09%, Mo: 0.05-0.50%, N: 0.02-0.50%, and the balance of Fe and inevitable impurities.
Preferably: the Mn content is 1.1-1.32% by weight.
Preferably: the weight percentage content of Ni is 7.61-8.36%.
A method for producing ultra-thin ultra-high strength austenitic stainless steel comprises the following steps:
1) continuously casting the mixture into a blank after molten iron desulfurization, converter blowing, argon blowing and refining, wherein the blank drawing speed is controlled to be 4.7-5.3 m/min during continuous casting, and the thickness of the casting blank is controlled to be 58-67 mm;
2) heating the thin slab, controlling the discharging temperature to be 1237-1263 ℃, and controlling the heating time of the casting blank to be 84-96 min;
3) descaling a casting blank by adopting high-pressure water, wherein the pressure of the high-pressure water is controlled to be 28-33 MPa;
4) rolling by adopting seven racks, wherein the thickness of the rolled steel plate is 2.5-2.7 mm: during the process: controlling the initial rolling temperature to be 1171-1192 ℃, the rolling reduction of an F1 machine frame to be 61-65%, the rolling reduction of an F2 machine frame to be 52-57%, and the rolling reduction of the rest machine frames to be 8-37%, cooling the strip steel under the pressure of 25-30 MPa after the strip steel is taken out of an F2 machine frame, and controlling the outlet temperature of the F7 machine frame to be 857-882 ℃;
5) carrying out laminar cooling, and cooling to the coiling temperature at the cooling speed of 65-71 ℃/s;
6) coiling, controlling the coiling temperature to be 441-479 ℃, and cooling to room temperature after coiling;
7) performing cold rolling of not less than 4 times, wherein the rolling reduction rate of each time is controlled to be 47-53%, and the thickness of the cold rolled sheet after cold rolling is 0.31-0.37 mm;
8) carrying out high-temperature annealing at 849-1204 ℃, and preserving heat at the temperature for 23-150 s;
9) cooling the mixture to room temperature at a cooling rate of 17-33 ℃/s.
Preferably: the high-temperature annealing temperature is 1177-1187 ℃.
Mechanism and action of each element and main process in the invention
C: in stainless steel, the solid solution strengthening and austenite stabilizing functions are mainly performed, and the content of the austenite needs to be accurately controlled. If the carbon content in the stainless steel is too low, the steel will be too soft and the strength will be too low. The carbon content is higher, so that a chromium carbide precipitated phase is easily generated, and the corrosion resistance of the stainless steel is reduced. The carbon content is therefore between 0.033 and 0.045%.
Si: si in steel is a deoxidizing element, and simultaneously, Si also plays a role in solid solution strengthening, the solid solution Si can inhibit the formation of a chromium carbide precipitation phase, and the content of Si is kept to be more than 0.29%; however, Si content more than 0.44% causes deterioration of plasticity of stainless steel, and thus it is most preferable to control it to 0.29-0.44%.
Mn: is an important solid solution strengthening element in steel, and can improve the strength of the steel; mn element can also reduce the martensite transformation temperature of the steel, and the steel can obtain an austenite phase structure at room temperature by combining the combined action of austenite stabilizing elements such as Ni and the like, so that the minimum Mn content is 1.1%; however, excessive increase of Mn content is likely to cause slab center segregation during continuous casting, and the usability of the material is reduced, so that the optimum Mn content range is 1.1-1.38%, and preferably 1.1-1.32% by weight.
P: is an impurity element in steel, is easy to be segregated in grain boundaries and influences the toughness of products, so the lower the content of the impurity element, the better the product. According to the actual control level, the control should be below 0.012%.
S: is an impurity element in steel, is easy to generate segregation at a crystal boundary, reduces the toughness of steel, and is fully removed during steel making, and the value of the impurity element is ensured to be lower than 0.005 percent.
Cr: is an essential element for maintaining the corrosion resistance and the high-temperature oxidation resistance of the stainless steel, and the optimal value of the Cr content in the embodiment of the invention is 17.3-18.9% in order to obtain the optimal corrosion resistance effect in the steel and comprehensively consider the cost.
Ni: the addition of Ni element in steel can play the role of solid solution strengthening and austenite stability improvement, and the combination of Ni and Mn element can reduce the martensite transformation point in steel to below room temperature. Therefore, the Ni content should be more than 7.7%, and because Ni is a precious metal, the reasonable addition range of Ni content is 7.74-8.52%, and the weight percentage content is preferably 7.61-8.36% in view of production cost.
Nb: is a strong carbide and nitride forming element, and the carbide and nitride precipitation can play a role in strengthening and improve the strength of the steel. However, the too high content of Nb tends to obtain coarse precipitates, so that the plasticity and corrosion resistance of the steel are significantly reduced, and therefore the Nb content in the examples of the present invention is controlled to 0.04 to 0.09%.
Mo: the Mo element can make a passive film on the surface of the stainless steel more compact and effectively improve the corrosion resistance of the stainless steel, so the Mo content is more than 0.05 percent, and the Mo content is designed to be less than 0.50 percent in consideration of production cost because the Mo is a noble metal.
N: the nitrogen element in the stainless steel has excellent solid solution strengthening effect and is also an element for stabilizing an austenite phase region, and can replace the noble metal of Ni in the stainless steel. The nitrogen element has limited solubility in steel and is difficult to be added in large quantity, so the content of the nitrogen element is controlled between 0.02 and 0.50 percent.
The tapping temperature is controlled to be 1237-1263 ℃, the heating time of the casting blank is controlled to be 84-96 min, because if the tapping temperature is lower than 1237 ℃, the heating time is lower than 84min, alloy elements are difficult to fully dissolve, the temperature of the plate blank is low, the soaking property is poor, the subsequent rolling is difficult, if the tapping temperature is too high, the heating time is too long, the surface of the casting blank generates thicker iron oxide scales, the subsequent process is difficult to remove, and the surface quality of the finished product is reduced. The invention controls the initial rolling temperature to be 1171-1192 ℃, the rolling reduction of an F1 machine frame to be 61-65%, the rolling reduction of an F2 machine frame to be 52-57%, and the rolling reduction of the rest machine frames to be 8-37%, and after the strip steel is discharged from the F2 machine frame, the strip steel is cooled under the pressure of cooling water of 25-30 MPa, and the outlet temperature of the F7 machine frame is controlled to be 857-882 ℃, because the subsequent tissue uniformity is difficult to ensure if the initial rolling temperature is too low, the rolling reduction of the F1 and the F2 machine frames is small, the equipment is easy to damage if the rolling reduction of the F1 and the F2 machine frames is too high, and in addition, the initial rolling temperature cannot be too high due to the limitation of the heating temperature; the too large reduction ratio of the F3-F7 frames can cause the strip shape to be difficult to control, and the too small reduction ratio of the F3-F7 frames can not obtain the required hot rolling outlet thickness. If the pressure of the cooling water is too low, the iron sheet on the surface of the rolled steel plate is difficult to remove completely, and the pressure of the cooling water is too high, so that the capacity of equipment is exceeded, the equipment is damaged, and the service life of the equipment is shortened; if the outlet temperature of the F7 stand is too low, mixed crystals can be caused, and the outlet temperature of the F7 stand is too high, so that the product structure crystal grains are coarse, the outlet thickness is too small, the product structure crystal grains are difficult to obtain due to the limitation of rolling capacity, the outlet thickness is too large, and the ultrathin finished products are difficult to obtain in the subsequent process.
The coiling temperature is controlled to be 441-479 ℃ in the invention, because if the coiling temperature is lower or higher than the range, the hot rolled structure with proper performance is difficult to obtain.
The rolling reduction rate of each pass is controlled to be 47-53%, because if the rolling reduction rate of each pass is too small, a cold-rolled plate consisting of a large amount of deformed martensite is difficult to obtain, and the subsequent annealing is difficult to obtain the austenitic stainless steel with ultrafine grains; if the reduction rate of each pass is too large and the equipment is easily damaged, and the deformed martensite generated in the cold-rolled sheet is unevenly distributed, the austenitic stainless steel compounded by ultrafine grains and coarse grains is easily formed by subsequent annealing.
The annealing temperature is 849-1204 ℃, and the heat preservation is carried out for 23-150 s at the temperature, because if the heating temperature is too low or the heat preservation time is too short, and the cooling speed is too high, the full austenite structure is difficult to be obtained by inverse transformation; if the heating temperature is too high or the heat preservation time is too long, and the cooling speed is too slow, all austenite crystal grains obtained by inverse phase transformation are easily and rapidly coarsened. This is disadvantageous in that a steel sheet having a structure of ultrafine fully austenitic grains is obtained.
Compared with the prior art, the invention has the advantages that the metallographic structure is fully austenitic, the thickness of the stainless steel plate is 0.31-0.37 mm, the yield strength is 971-1049 MPa, the tensile strength is 1147-1203 MPa, and the elongation is 15-23%.
Drawings
FIG. 1 is a topographical view of a stainless steel according to the present invention.
Detailed Description
The invention is further described below with reference to specific examples:
table 1 shows the control list of the main parameters of the processes of the examples and comparative examples of the present invention;
table 2 is a table of mechanical property testing conditions of each example and comparative example of the present invention.
The preparation method comprises the following steps:
1) continuously casting the mixture into a blank after molten iron desulfurization, converter blowing, argon blowing and refining, wherein the blank drawing speed is controlled to be 4.7-5.3 m/min during continuous casting, and the thickness of the casting blank is controlled to be 58-67 mm;
2) heating the thin slab, controlling the discharging temperature to be 1237-1263 ℃, and controlling the heating time of the casting blank to be 84-96 min;
3) descaling a casting blank by adopting high-pressure water, wherein the pressure of the high-pressure water is controlled to be 28-33 MPa;
4) rolling by adopting seven racks, wherein the thickness of the rolled steel plate is 2.5-2.7 mm: during the process: controlling the initial rolling temperature to be 1171-1192 ℃, the rolling reduction of an F1 machine frame to be 61-65%, the rolling reduction of an F2 machine frame to be 52-57%, and the rolling reduction of the rest machine frames to be 8-37%, cooling the strip steel under the pressure of 25-30 MPa after the strip steel is taken out of an F2 machine frame, and controlling the outlet temperature of the F7 machine frame to be 857-882 ℃;
5) carrying out laminar cooling, and cooling to the coiling temperature at the cooling speed of 65-71 ℃/s;
6) coiling, wherein the coiling temperature is controlled at 441-479 ℃;
7) performing cold rolling of not less than 4 times, wherein the rolling reduction rate of each time is controlled to be 47-53%, and the thickness of the cold rolled sheet after cold rolling is 0.31-0.37 mm;
8) annealing is carried out, the annealing temperature is 849-1204 ℃, and heat preservation is carried out at the temperature for 23-150 s;
preferably, the rolling reduction rate of each pass is controlled to be 47-51%;
preferably, the annealing temperature is controlled to be 910-1097 ℃, and the annealing time is 31-110 s.
9) Cooling the mixture to room temperature at a cooling rate of 17-33 ℃/s.
TABLE 1 tabulation (wt%) of values of elements of examples of the invention and comparative examples
TABLE 2 list of values of main parameters of the processes of the examples and comparative examples of the present invention
TABLE 2 Table of mechanical property test conditions of examples and comparative examples of the present invention
As can be seen from table 3, the products with unchanged contents of various components obtained after the molten steel is smelted in the embodiment of the present invention are subjected to a series of rolling heat treatments, and the products in embodiments 1 to 6 of the present invention have good performances in terms of yield strength and tensile strength compared with comparative examples 1 and 2 with changed chemical components, and particularly, the yield strength, tensile strength, and the like are obviously higher than those of the comparative examples. The product obtained in the embodiments 1-6 of the invention has yield strength of 971-1049 MPa, tensile strength of 1147-1203 MPa, elongation of 15-23% and finished product thickness of 0.31-0.37 mm.
The embodiments of the present invention are merely preferred examples, and are not intended to limit the scope of the claims.
Claims (1)
1. An ultra-thin ultra-high strength austenitic stainless steel comprises the following components by weight percent: c: 0.033 to 0.045%, Si: 0.29 to 0.44%, Mn: 1.0-1.38%, P: less than or equal to 0.012%, S: less than or equal to 0.005 percent, Cr: 17.3-18.9%, Ni: 7.74-8.52%, Nb: 0.04-0.09%, Mo: 0.05-0.06%, N: 0.02% or N: 0.33-0.50%, and the balance of Fe and inevitable impurities;
the production method comprises the following steps:
1) continuously casting the mixture into a blank after molten iron desulfurization, converter blowing, argon blowing and refining, wherein the blank drawing speed is controlled to be 4.7-5.3 m/min during continuous casting, and the thickness of the casting blank is controlled to be 58-67 mm;
2) heating a casting blank, controlling the discharging temperature to be 1237-1263 ℃, and controlling the heating time of the casting blank to be 84-96 min;
3) descaling a casting blank by adopting high-pressure water, wherein the pressure of the high-pressure water is controlled to be 28-30 MPa;
4) rolling by adopting seven racks, wherein the thickness of the rolled steel plate is 2.5-2.7 mm: during the process:
the initial rolling temperature is controlled to be 1171-1192 ℃, the reduction rate of an F1 machine frame is controlled to be 61-65%, and an F2 machine
The reduction rate of the frame is 52-54%, the reduction rate of the rest frames is 8-37%, and after the steel strip is discharged from the F2 frame,
cooling the strip steel under the pressure of 25-30 MPa of cooling water, and controlling the temperature of an outlet of an F7 rack
At 857-882 ℃;
5) carrying out laminar cooling, and cooling to the coiling temperature at the cooling speed of 65-71 ℃/s;
6) coiling, controlling the coiling temperature to be 441-479 ℃, and cooling to room temperature after coiling;
7) performing cold rolling of not less than 4 times, wherein the rolling reduction rate of each time is controlled to be 47-53%, and the thickness of the cold rolled sheet after cold rolling is 0.31-0.37 mm;
8) carrying out high-temperature annealing at 1009-1204 ℃, and preserving heat at the temperature for 110-150 s;
9) cooling the mixture to room temperature at a cooling rate of 17-33 ℃/s.
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