A cold rolling production method of an ultra-thin steel strip for a battery accessory

Abstract

The present application belongs to the field of production and manufacture of cold-rolled precision strip steel, and relates to a cold-rolled production method of ultra-thin steel strip for battery accessories. The method comprises the following steps: raw material selection, selecting SPCC pickling coil with a thickness of 2.5-3.5 mm and a width of 300-850 mm, and the raw material has the following component mass percentage: C: 0.02-0.04%, Mn: 0.15-0.30%, Si≤0.03%, P≤0.015%, S≤0.010%, Alt≥0.025%, and the balance of Fe and trace impurities. The method comprises the following steps: primary cold rolling, primary degreasing, primary annealing, secondary rolling, secondary degreasing, secondary annealing and skin pass rolling. The finished steel strip prepared by the method has the following performances: hardness HV90-105, surface roughness Ra≤0.05 μm, elongation A≥32%, and thickness difference ±0.03 mm.

Description

Technical Field

[0001] This invention belongs to the field of cold-rolled precision strip steel production and relates to a cold-rolling production method for ultra-thin steel strips used in battery accessories. Background Technology

[0002] Lithium battery caps, conductive connectors, and battery brackets extensively use 0.12–0.30 mm SPCC cold-rolled steel strips. After the steel strips are stamped, they often need to be electroplated with nickel and copper for corrosion protection and conductivity.

[0003] The existing conventional SPCC steel strip production has the following defects:

[0004] 1) Incomplete removal of cold-rolled emulsion leaves tiny oil spots on the steel strip surface, which form carbon spots after annealing; after electroplating, the grains at the spots are abnormally large, resulting in microscopic roughness and black spots.

[0005] 2) The annealing process is not properly controlled, resulting in uneven grain size in the steel strip, wide hardness fluctuation range, and a large amount of metal powder (powder shedding) generated in the mold during the stamping process, which contaminates the mold and the product.

[0006] 3) The surface roughness of the leveling roller is too high, the surface Ra of the steel strip is greater than 0.15μm, the surface is microscopically uneven, and the color is dull after electroplating;

[0007] 4) The plasticity of materials R90 and N90 is unstable, making them prone to cracking during deep drawing, resulting in wavy and uneven risers.

[0008] Therefore, it is urgent to optimize the entire cold rolling production process to produce battery-specific ultra-thin steel strips with high surface cleanliness, stable mechanical properties, and compatibility with subsequent stamping and electroplating processes. Summary of the Invention

[0009] In view of the existing problems of oil residue, stamping powder shedding, cracking, riser waviness, rough electroplated surface and fluctuating mechanical properties of steel strip, the technical problem to be solved by the present invention is to provide a cold rolling production method for ultra-thin steel strip for battery accessories.

[0010] A cold-rolling production method for ultra-thin steel strips used in battery accessories includes the following steps:

[0011] S1. Raw material selection: Select SPCC pickled rolls with a thickness of 2.5-3.5mm and a width of 300mm-850mm. The raw material composition by mass percentage is: C: 0.02~0.04%, Mn: 0.15~0.30%, Si≤0.03%, P≤0.015%, S≤0.010%, Alt≥0.025%, with the balance being Fe and trace impurities.

[0012] S2. Single Cold Rolling: A six-roll reversible rolling mill is used. During the rolling process, the process lubricant is selected from rolling oil and water to form an emulsion with a weight concentration of 1.0-3.5%, and its stability coefficient is controlled at 0.85-0.95. The temperature of the emulsion is controlled at 45-60℃. The steel strip is rolled to 0.5-0.6mm in 3-5 passes. During the cold rolling process, the reduction rate of the first pass is controlled at 15%-35%, the reduction rate of the last pass is controlled at 8-20%, and the total reduction rate is controlled at 70-85%.

[0013] During cold rolling, the speed is controlled at 100-200 m / min for the first pass, and 400-700 m / min for subsequent passes. Thickness is controlled by flow rate per second, with a thickness tolerance of ±0.01 mm. The surface roughness of the rolls is Ra 0.25-0.35 μm. No vibration marks or grinding marks are allowed on the roll surface. The roll profile is determined based on the actual incoming material. The six-roll intermediate roll can move axially. The reversible cold rolling mill is equipped with ABB strip shape gauges at both the inlet and outlet, which can automatically adjust the strip shape. A high-pressure emulsion blowing device is used during the rolling process to reduce surface powder adhesion.

[0014] S3, One-time degreasing: Degreasing is performed using electrolytic degreasing method;

[0015] The mass concentration of the electrolytic degreasing solution should be controlled to be no more than 10 wt%, and the electrolysis current should be controlled between 3000-6000 A. To prevent sticking during bell-type annealing, the winding tension is generally 2.0-3.5 kg / mm. 2 Remove residual emulsion from the surface and dry with hot air.

[0016] S4. Single Annealing: Bright annealing adopts a strong circulation bell-type annealing furnace, and the annealing atmosphere adopts a mixed protective gas with a volume content of 75% H2 and 25% NH3.

[0017] During the annealing process, the heating rate is 8-10℃ / min during the heating stage, and protective gas is used to purge the steel strip from 380℃ to 500℃ to effectively remove oil stains from the surface. During the holding stage, the temperature is controlled at 600-660℃ and the holding time is controlled at 8-12 hours. The cooling stage adopts a staged cooling method, that is, first, the strip is naturally cooled to 520-540℃ with a heating hood, then air-cooled to 250-300℃, and finally water-cooled to 70-80℃ before being taken out of the furnace.

[0018] S5. Secondary rolling: Multi-pass reversible cold rolling, the steel strip is rolled to 0.13-0.18mm in 3-4 passes; during the cold rolling process, the reduction rate of the first pass is controlled at 15%-35%, the reduction rate of the last pass is controlled at 8-20%, and the total reduction rate is controlled at 60-80%.

[0019] During the secondary rolling process, the speed of the first pass is controlled at 100-200 m / min, and subsequent passes at 400-700 m / min. Thickness is controlled by a flow rate per second, with a thickness tolerance of ±0.01 mm. The surface roughness of the rolls is Ra 0.25-0.35 μm. No vibration marks or grinding marks are allowed on the roll surface. The cold rolling work roll profile is determined based on the actual incoming material. The six-roll intermediate roll can move axially. The reversible cold rolling mill is equipped with ABB strip shape gauges at both the inlet and outlet, which can automatically adjust the strip shape. A high-pressure emulsion blowing device is used during the rolling process to reduce surface powder adhesion.

[0020] S6. Secondary degreasing: Degreasing is performed using electrolytic degreasing method;

[0021] The concentration of the electrolytic degreasing solution should be controlled to be no more than 10 wt%, and the electrolysis current should be controlled between 3000-6000 A. To prevent sticking during annealing, the winding tension is generally 2.5-4.5 kg / mm. 2 Remove residual emulsion from the surface and dry with hot air.

[0022] S7. Secondary annealing: Bright annealing adopts a strong circulation bell-type annealing furnace, and the annealing atmosphere adopts a mixed protective gas with a volume content of 75% H2 and 25% NH3.

[0023] During the secondary annealing process, the heating rate is 8-10℃ / min during the heating stage, and protective gas is used for purging during the 380℃-500℃ stage to effectively remove oil contaminants from the steel strip surface. The holding temperature is controlled at 600-660℃ for 8-12 hours. The cooling stage employs a phased cooling method: first, natural cooling under a heating hood to 520-540℃, then air cooling to 250-300℃, and finally water cooling to 70-80℃ before exiting the furnace. After exiting the furnace, the steel strip exhibits a uniform recrystallized structure.

[0024] S8. Leveling Rolling: The working roll diameter is selected in the range of 300mm-340mm. Before use, the working roll is surface treated with electrochemical polishing technology and finely ground and polished with imported paper tape of 6-15μm. The roughness Ra≤0.05μm. The surface roughness of the leveled finished product is controlled below Ra≤0.05μm.

[0025] Use low-concentration leveling emulsion, with a reduction rate of 3% and an operating speed of 50-100 m / min.

[0026] S9. Precision slitting: The battery parts are slitting into rolls according to the required width for stamping, and the finished products are inspected and put into storage.

[0027] The properties of the finished steel strip prepared by the method of this invention are as follows: hardness HV90~105; surface roughness Ra≤0.05μm; elongation A≥32%; thickness difference ±0.03mm.

[0028] The beneficial effects of the method of the present invention are as follows:

[0029] 1) The entire process involves multiple degreasing steps, which significantly eliminates residual emulsion on the steel strip surface and prevents oil spots and carbon black spots after annealing;

[0030] 2) The rolling and leveling roller system process and the leveling emulsion process result in a low surface roughness and bright finish on the finished steel strip, with a finished product Ra < 0.05μm, which reduces stamping friction and wear, and the plate surface is free of impurities and pits, resulting in an excellent appearance after stamping.

[0031] 3) Precision nitrogen-hydrogen annealing process results in uniform material structure, stable hardness range, and resistance to cracking during stretching and forming, as well as stable springback.

[0032] 4) Two-stage annealing ensures stable plasticity of R90 and N90, making it suitable for deep drawing and bending of battery accessories, and producing smooth and wave-free stamping risers;

[0033] 5) The rolling mill uses AGC to control thickness difference, resulting in smooth extension, good consistency in thickness difference, and small fluctuations, making it suitable for continuous high-speed stamping with progressive dies. Detailed Implementation

[0034] To address the problems of uneven steel strip performance, difficulty in controlling surface quality and thickness variation in existing technologies, this invention provides a relatively simple and low-cost method for producing cold-rolled steel strips for battery components, achieving uniform product performance and a good surface finish.

[0035] Example 1: This example uses SPHC hot-rolled pickled coil with a thickness of 3.0 mm and a width of 620 mm. The raw material composition by mass percentage is: 0.022% C, 0.010% Si, 0.16% Mn, 0.012% S, 0.015% P, 0.036% Alt, with the remainder being iron and unavoidable impurities. This steel grade has a coefficient of thermal expansion of 10⁻¹² × 10⁻⁶ / ℃ and an electrical conductivity of 35-40 × 1.163 W / m * ℃, meeting the requirements for subsequent processing.

[0036] The product undergoes a second cold rolling process on a high-precision six-roll reversible rolling mill, with a reduction of 80% in the first rolling and 65% in the second rolling. After electrolytic degreasing, it is held at 620±10℃ in a nitrogen-hydrogen protective furnace for 10 hours. After exiting the furnace, it is leveled with a smooth roll roughness of Ra0.03um. Then, it is slitting and shearing on a precision edge trimmer to obtain the finished product.

[0037] The specific process is as follows:

[0038] One-pass cold rolling: The rolling process is carried out on a six-roll reversible cold rolling mill. During rolling, the process lubricant is Shanghai Fuchs Oil Co., Ltd.'s 787 type rolling oil, known for its high stability. It is mixed with water to form a 2.4% (by weight) cold rolling emulsion with a stability coefficient controlled at 0.92. The temperature of the cold rolling emulsion is controlled at 55℃. The steel strip is rolled to 0.5mm in five passes. During cold rolling, the reduction rate is controlled at 30% for the first pass and 18% for the last pass, with a total reduction rate of 80%. The speed is controlled at 180m / min for the first pass and 600m / min for subsequent passes. Thickness is controlled using a flow rate per second, with a thickness tolerance controlled within ±0.005mm. The surface roughness of the rolls, Ra ≤ 0.25-0.35μm. No vibration marks or grinding marks are allowed on the roll surface. The roll shape of the cold rolling mill is determined according to the actual incoming material. The six-roll intermediate roll can move axially. The inlet and outlet of the reversible cold rolling mill are equipped with ABB shape gauges, which can automatically adjust the shape. The rolling process is equipped with a high-pressure emulsion blowing device to reduce surface powder adhesion.

[0039] One-step degreasing: Electrolytic degreasing is used, with the concentration of the degreasing solution controlled at 2.8 wt% and the electrolysis current controlled at 5000 A. To prevent adhesion during annealing, the winding tension is generally 3.0 kg / mm. 2 Remove residual emulsion from the surface and dry with hot air at a temperature above 110℃.

[0040] Single-stage recrystallization annealing: A strong-circulation bell-type annealing furnace was used. The annealing atmosphere consisted of a mixed protective gas with a volume content of 75% H2 and 25% NH3. The heating rate was 10℃ / min. A large volume of reducing gas (75% H2 and 25% NH3) was purged at 400℃ to effectively remove oil contaminants from the steel strip surface. The annealing heating temperature was controlled at 620±10℃, and the annealing holding time was controlled at 10 hours. A staged cooling method was used: first, natural cooling under the heating hood to 520℃, then air cooling to 250℃, and finally water cooling to 70℃ before exiting the furnace. After exiting the furnace, the steel strip achieved a uniform recrystallized structure.

[0041] Secondary cold rolling: Performed on a six-roll reversible cold rolling mill. During the rolling process, the process lubricant is Shanghai Fuchs Oil Co., Ltd.'s 787 type rolling oil, known for its high stability. It is mixed with water to form a 2.4% (by weight) cold rolling emulsion with a stability coefficient controlled at 0.92. The temperature of the cold rolling emulsion is controlled at 45-60℃. The steel strip is rolled to 0.13mm in four passes. During cold rolling, the reduction rate in the first pass is controlled at 15%-35%, and the reduction rate in the last pass is controlled at 20%, with a total reduction rate controlled at 65%. The speed in the first pass is controlled at 150m / min, and subsequent passes at 400m / min. Thickness is controlled using a flow rate per second, with a thickness tolerance controlled within ±0.005mm. The surface roughness of the rolls, Ra ≤ 0.25-0.35μm, is required. No vibration marks or grinding marks are permitted on the roll surface. The roll shape of the cold rolling mill is determined according to the actual incoming material. The six-roll intermediate roll can move axially. The inlet and outlet of the reversible cold rolling mill are equipped with ABB shape gauges, which can automatically adjust the shape. The rolling process is equipped with a high-pressure emulsion blowing device to reduce surface powder adhesion.

[0042] Secondary degreasing: Electrolytic degreasing is used, with the concentration of the degreasing solution controlled at 2.8 wt% and the electrolysis current controlled at 5000 A. To prevent adhesion during annealing, the winding tension is generally 3.5 kg / mm. 2 Remove residual emulsion from the surface and dry with hot air at a temperature above 110℃.

[0043] Secondary recrystallization annealing: A strong-circulation bell-type annealing furnace was used. The annealing atmosphere consisted of a mixed protective gas with a volume content of 75% H2 and 25% NH3. The heating rate was initially 10℃ / min, followed by purging with a large volume of reducing gas (75% H2 and 25% NH3) at 400℃ to effectively remove oil contaminants from the steel strip surface. The annealing heating temperature was controlled at 620±10℃, and the annealing holding time was controlled at 10 hours. A staged cooling method was used: first, natural cooling under the heating hood to 520℃, then air cooling to 250℃, and finally water cooling to 70℃ before exiting the furnace. After exiting the furnace, the steel strip achieved a uniform recrystallized structure.

[0044] Leveling: The work roll diameter is 320mm. Before use, the work roll undergoes surface treatment using electrochemical polishing technology and is then finely ground and polished using imported 10μm paper tape, achieving a roughness Ra≤0.05μm. The reduction rate is 3%, thickness difference is controlled at ±0.003mm, operating speed is 80m / min, and oil is applied at 200mg / m² on both the top and bottom surfaces. The leveling emulsion uses a high-precision filtration system to prevent solid particles from transferring to the steel strip surface.

[0045] Slitting: The steel strip is slitted on a slitting machine. To ensure that the camber of the steel strip is ≤1.5mm / m, a wooden strip pressing method is used during the slitting process. The thickness of the wooden strip is uniform, and the size and specifications of the separating plates and isolation rings on the slitting line are consistent. Each steel strip is slitted on a single line. This yields a narrow strip finished product with a width tolerance of ±0.05mm.

[0046] The main technical indicators of the products obtained using the above process are obtained by testing with a hardness tester, micrometer, vernier caliper, and roughness tester:

[0047] Hardness: HV99;

[0048] Thickness: 0.13±0.003mm;

[0049] Width: 32±0.05mm;

[0050] Surface roughness Ra: 0.045um.

[0051] Example 2: This example uses SPHC hot-rolled pickled coil with a thickness of 3.0 mm and a width of 620 mm. The raw material composition by mass percentage is: 0.021% C, 0.011% Si, 0.15% Mn, 0.011% S, 0.014% P, 0.035% Alt, with the remainder being iron and unavoidable impurities. The coefficient of thermal expansion of this steel is 10⁻¹² × 10⁻⁶ / ℃, and the electrical conductivity is 35-40 × 1.163 W / m * ℃, meeting the requirements for subsequent processing.

[0052] The product undergoes a second cold rolling process on a high-precision six-roll reversible mill, with a reduction of 73% in the first rolling and 67% in the second rolling. After electrolytic degreasing, it is held at 630℃ for 10 hours in a nitrogen-hydrogen protective furnace. After exiting the furnace, it is leveled with a smooth roll roughness of Ra0.032um. Then, it is slitting and shearing on a precision edge trimmer to obtain the finished product.

[0053] The specific process is as follows:

[0054] One-pass cold rolling: The rolling process is carried out on a six-roll reversible cold rolling mill. During rolling, the process lubricant is Shanghai Fuchs Oil Co., Ltd.'s 787 type rolling oil, known for its high stability. It is mixed with water to form a 2.4% (by weight) cold rolling emulsion with a stability coefficient controlled at 0.92. The temperature of the cold rolling emulsion is controlled at 55℃. The steel strip is rolled to 0.6mm in five passes. During cold rolling, the reduction rate is controlled at 30% for the first pass and 15% for the last pass, with a total reduction rate of 73%. The speed is controlled at 150m / min for the first pass and 600m / min for subsequent passes. Thickness is controlled using a flow rate per second, with a thickness tolerance controlled within ±0.005mm. The surface roughness of the rolls, Ra ≤ 0.25-0.35μm. No vibration marks or grinding marks are allowed on the roll surface. The roll shape of the cold rolling mill is determined according to the actual incoming material. The six-roll intermediate roll can move axially. The inlet and outlet of the reversible cold rolling mill are equipped with ABB shape gauges, which can automatically adjust the shape. The rolling process is equipped with a high-pressure emulsion blowing device to reduce surface powder adhesion.

[0055] One-step degreasing: Mechanical and electrolytic degreasing methods are used. The concentration of the electrolytic degreasing solution is controlled at 2.4%, and the electrolysis current is controlled at 5000A. To prevent adhesion during annealing, the winding tension is generally 3.0 kg / mm. 2 Remove residual emulsion from the surface and dry with hot air at a temperature above 110℃.

[0056] Single-stage recrystallization annealing: A strong-circulation bell-type annealing furnace was used. The annealing atmosphere consisted of a mixed protective gas with a volume content of 75% H2 and 25% NH3. The heating rate was 10℃ / min. At the 400℃ stage, a large volume of reducing gas (75% H2 and 25% NH3) was purged to effectively remove oil contaminants from the steel strip surface. The annealing heating temperature was controlled at 630±10℃, and the annealing holding time was controlled at 10 hours. A staged cooling method was used: first, slow cooling under the heating hood to 520℃, then air cooling to 250℃, and finally water cooling to 70℃ before exiting the furnace. After exiting the furnace, the steel strip achieved a uniform recrystallized structure.

[0057] Secondary cold rolling: Performed on a six-roll reversible cold rolling mill. During the rolling process, the process lubricant is Shanghai Fuchs Oil Co., Ltd.'s 787 type rolling oil, known for its high stability. It is mixed with water to form a 2.4% (by weight) cold rolling emulsion with a stability coefficient controlled at 0.92. The temperature of the cold rolling emulsion is controlled at 55℃. The steel strip is rolled to 0.14mm in 3-4 passes. During cold rolling, the reduction rate is controlled at 30% for the first pass and 17% for the last pass, with a total reduction rate of 77%. The speed is controlled at 150m / min for the first pass and 600m / min for subsequent passes. Thickness is controlled using a flow rate per second, with a thickness tolerance controlled within ±0.005mm. The roll surface roughness Ra ≤ 0.25-0.35μm. No vibration marks or grinding marks are allowed on the roll surface. The roll shape of the cold rolling mill is determined according to the actual incoming material. The six-roll intermediate roll can move axially. The inlet and outlet of the reversible cold rolling mill are equipped with ABB shape gauges, which can automatically adjust the shape. The rolling process is equipped with a high-pressure emulsion blowing device to reduce surface powder adhesion.

[0058] Secondary degreasing: Electrolytic degreasing is used, with the concentration of the degreasing solution controlled at 2.8 wt% and the electrolysis current controlled at 5000 A. To prevent adhesion during annealing, the winding tension is generally 3.5 kg / mm. 2 Remove residual emulsion from the surface, and dry with hot air at a temperature above 110℃.

[0059] Secondary recrystallization annealing: A strong-circulation bell-type annealing furnace was used. The annealing atmosphere consisted of a mixed protective gas with a volume content of 75% H2 and 25% NH3. The heating rate was initially 10℃ / min, followed by purging with a large volume of reducing gas (75% H2 and 25% NH3) at 400℃ to effectively remove oil contaminants from the steel strip surface. The annealing heating temperature was controlled at 630±10℃, and the annealing holding time was controlled at 10 hours. A staged cooling method was used: first, slow cooling under the heating hood to 520℃, then air cooling to 250℃, and finally water cooling to 70℃ before exiting the furnace. After exiting the furnace, the steel strip achieved a uniform recrystallized structure.

[0060] Leveling: The work roll diameter is selected within the range of 320mm. Before use, the work roll undergoes surface treatment using electrochemical polishing technology, followed by fine grinding and polishing with 10μm imported paper tape, achieving a roughness Ra≤0.05μm. The reduction rate is 3%, thickness difference is controlled within ±0.003mm, operating speed is 80m / min, and oil is applied at 200mg / m² on both the top and bottom surfaces. 2 The emulsion is smoothed using a high-precision filtration system to prevent solid particles from transferring to the steel belt surface.

[0061] Slitting: The steel strip is slitted on a slitting machine. To ensure that the camber of the steel strip is ≤1.5mm / m, a wooden strip pressing method is used during the slitting process. The thickness of the wooden strip is uniform, and the size and specifications of the separating plates and isolation rings on the slitting line are consistent. Each steel strip is slitted on a single line. This yields a narrow strip finished product with a width tolerance of ±0.05mm.

[0062] The main technical indicators of the products obtained using the above process are obtained by testing with a hardness tester, micrometer, vernier caliper, and roughness tester:

[0063] Hardness: HV102;

[0064] Thickness: 0.18±0.03mm;

[0065] Width: 32±0.05mm;

[0066] Surface roughness Ra: 0.047um.

Claims

1. A cold-rolling production method for ultra-thin steel strips used in battery accessories, characterized in that, It includes the following steps: S1. Raw material selection: Select SPCC pickled rolls with a thickness of 2.5-3.5mm and a width of 300mm-850mm. The raw material composition by mass percentage is: C: 0.02~0.04%, Mn: 0.15~0.30%, Si≤0.03%, P≤0.015%, S≤0.010%, Alt≥0.025%, with the balance being Fe and trace impurities. S2. Single-pass cold rolling: A six-roll reversible rolling mill is used. During the rolling process, the process lubricant is a mixture of rolling oil and water to form an emulsion with a weight concentration of 1.0-3.5%, and its stability coefficient is controlled at 0.85-0.

95. The emulsion temperature is controlled at 45-60℃. The steel strip is rolled to 0.5-0.6mm in 3-5 passes. During the cold rolling process, the reduction rate of the first pass is controlled at 15%-35%, the reduction rate of the last pass is controlled at 8-20%, and the total reduction rate is controlled at 70-85%. S3, One-time degreasing: Degreasing is performed using electrolytic degreasing method; S4. Single Annealing: Bright annealing adopts a strong circulation bell-type annealing furnace, and the annealing atmosphere adopts a mixed protective gas with a volume content of 75% H2 and 25% NH3. S5. Secondary rolling: Multi-pass reversible cold rolling, the steel strip is rolled to 0.13-0.18mm in 3-4 passes; during the cold rolling process, the reduction rate of the first pass is controlled at 15%-35%, the reduction rate of the last pass is controlled at 8-20%, and the total reduction rate is controlled at 60-80%. S6. Secondary degreasing: Degreasing is performed using electrolytic degreasing method; S7. Secondary annealing: Bright annealing adopts a strong circulation bell-type annealing furnace, and the annealing atmosphere adopts a mixed protective gas with a volume content of 75% H2 and 25% NH3. S8. Leveling Rolling: The working roll diameter is selected in the range of 300mm-340mm. Before use, the working roll is surface treated with electrochemical polishing technology and finely ground and polished with imported paper tape of 6-15μm. The roughness Ra≤0.05μm. The surface roughness of the leveled finished product is controlled below Ra≤0.05μm. S9. Precision slitting: The battery parts are slitting into rolls according to the required width for stamping, and the finished products are inspected and put into storage.

2. The cold rolling production method according to claim 1, characterized in that, in one cold rolling process, the speed of the first pass is controlled at 100-200 m / min, and the speed of each subsequent pass is controlled at 400-700 m / min, the thickness is controlled by the second flow rate, the thickness tolerance is controlled within ±0.01 mm, and the surface roughness of the rolls is Ra0.25-0.35 μm.

3. The cold rolling production method according to claim 1, characterized in that, during the first annealing process, the heating rate during the heating stage is 8-10℃ / min, and protective gas is purged during the 380℃-500℃ stage to effectively remove oil stains from the surface of the steel strip; the temperature during the holding stage is controlled at 600-660℃, and the holding time is controlled at 8-12 hours; the cooling stage adopts staged cooling, that is, first naturally cooling to 520-540℃ with a heating hood, then air cooling to 250-300℃, and finally water cooling to 70-80℃ before exiting the furnace.

4. The cold rolling production method according to claim 1, characterized in that, during the secondary rolling process, the speed of the first pass is controlled at 100-200 m / min, and the speed of each subsequent pass is controlled at 400-700 m / min, the thickness is controlled by the flow rate per second, the thickness tolerance is controlled within ±0.01 mm, and the surface roughness of the rolls is Ra0.25-0.35 μm.

5. The cold rolling production method according to claim 1, characterized in that, during the secondary annealing process, the heating rate during the heating stage is 8-10℃ / min, and protective gas is purged during the 380℃-500℃ stage to effectively remove oil stains from the surface of the steel strip; the temperature during the heat preservation stage is controlled at 600-660℃, and the heat preservation time is controlled at 8-12 hours; the cooling stage adopts staged cooling, that is, first naturally cooling to 520-540℃ with a heating hood, then air cooling to 250-300℃, and finally water cooling to 70-80℃ before exiting the furnace.