A method of processing a cold rolled semi-hardened steel

Abstract

The application relates to a processing method of a cold-rolled semi-hardened steel, which comprises the following steps: respectively controlling the elongation of a strip steel to be a first set value, a second set value, a third set value and a fourth set value when the strip steel is pickled, phosphor-broken, leveled and tension-straightened; and controlling the roughness Ra and the peak density RPpc of the working roller of a leveler to be a set Ra value and a set RPpc value when the strip steel is leveled. The method improves the yield strength and the hardness of the strip steel by comprehensively adopting large-elongation control of the phosphor-breaking machine, the skin-pass machine and the tension-straightening machine, improves the work hardening of the strip steel, realizes semi-hardening form production of the strip steel, reduces the friction coefficient of the strip steel by controlling the roughness Ra and the peak density RPpc of the working roller of the leveler, increases the elongation of the leveler, and improves the strength and the hardness of the strip steel. The strip steel produced by the method is thinner and has higher strength, has a large deformation degree, can be applied to a slide rail material of an automobile structural part, and increases the safety of members.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cold-rolled steel processing, in particular to a processing method of cold-rolled semi-hardened steel. BACKGROUND

[0002] New energy vehicles have high requirements on the strength of seat slide rail materials in order to prevent the battery pack from moving upward during a collision process and affecting the position of vehicle members, so as to block the kinetic energy impact of the battery pack on the vehicle members to a certain extent.

[0003] Therefore, producing a slide rail material with thinner and higher strength automobile structural parts can have a greater degree of deformation, which can significantly improve the strength of the steel material and increase the safety of the members. SUMMARY

[0004] The present application provides a processing method of cold-rolled semi-hardened steel to solve the problem that the slide rail material of the existing automobile structural parts is not thin enough and the strength is not enough.

[0005] In a first aspect, the present application provides a processing method of cold-rolled semi-hardened steel, which comprises:

[0006] During pickling, phosphorus breaking, flattening and straightening of the strip steel, the elongation of the strip steel is controlled to be a first set value, a second set value, a third set value and a fourth set value, respectively.

[0007] During flattening of the strip steel, the work roll roughness Ra and the peak density RPpc of the flattening machine are controlled to be a set Ra value and a set RPpc value.

[0008] Further, the first set value is 8%-12%; and / or

[0009] The second set value is 2%-4%; and / or

[0010] The third set value is 5%-7%; and / or

[0011] The fourth set value is 0.5%-1.5%.

[0012] Further, the set Ra value is 0.4-0.6 μm; and the set RPpc value is 110-130 / cm 2 .

[0013] Further, the method further comprises:

[0014] During flattening of the strip steel, the center thickness of the strip steel is controlled to be 20-30 μm greater than the thickness of the strip steel at a distance of 40 mm from the edge of the strip steel.

[0015] Further, the process parameters of the phosphorus breaking include that the roughness Ra of the working roller of the phosphorus breaking machine is 0.8-1.2 μm, the insertion amount of the working roller of the phosphorus breaking machine is 25-35 mm, the unit tension of the phosphorus breaking machine is 90-110 MPa, and the speed of the phosphorus breaking machine is 180-220 m / min.

[0016] Further, the process parameters of the flattening include that the flattening rolling force is 5000-7000 kn, the inlet tension is 90-110 MPa, the outlet tension is 100-120 MPa, the initial setting value of the bending roller force is 650-750 Kn, and the process speed is 180-220 m / min.

[0017] Further, the process parameters of the straightening include that the roughness Ra of the working roller of the straightening machine is 0.7-0.9 μm, and the diameter of the working roller of the straightening machine is 70-90 mm.

[0018] Further, the chemical composition of the strip steel includes, in terms of mass fraction, C: 0.06%-0.1%, Mn: 0.35%-0.50%, P≤0.018%, S≤0.015%, Als≤0.08%, Cr≤0.08%, Cu≤0.0062%, N≤0.08%, and Si≤0.03%.

[0019] Further, the method further includes:

[0020] The strip steel is subjected to hot rolling and then coiling, and the coiling temperature of the tail of the strip steel is controlled to be higher than the coiling temperature of the head of the strip steel.

[0021] Further, the hot rolling and then coiling of the strip steel, and the control of the coiling temperature of the tail of the strip steel to be higher than the coiling temperature of the head of the strip steel include:

[0022] The strip steel is subjected to hot rolling and then coiling, and the coiling temperature of the strip steel is controlled to increase at a speed of 0.5 ℃ / m from a position 100 m away from the tail of the strip steel to a position 40 m away from the tail of the strip steel, and the coiling temperature of the strip steel is kept the same from the position 40 m away from the tail of the strip steel to the tail of the strip steel.

[0023] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages:

[0024] The embodiment of the present application provides a processing method of cold-rolled semi-hardened steel, which improves the yield strength and hardness of the strip steel by improving the work hardening of the strip steel through the comprehensive use of large elongation control in the phosphorus breaking machine, the finishing machine and the tension leveler, and realizes the production of the semi-hardened form of the strip steel; the friction coefficient of the strip steel is reduced, the elongation of the skin pass mill is increased, and the strength and hardness of the strip steel are improved by controlling the roughness Ra and peak density RPpc of the work roll of the skin pass mill. The strip steel produced by the method is thinner and has higher strength, has a large deformation degree, and can be applied to the slide rail material of automobile structural parts, thereby increasing the safety of members. BRIEF DESCRIPTION OF DRAWINGS

[0025] The drawings incorporated into the specification and constituting a part of the specification show embodiments consistent with the present application and, together with the specification, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, those drawings can also be obtained by those skilled in the art without creative labor under the premise of not departing from the principles of the present application.

[0027] Figure 1 A flowchart of a processing method of cold-rolled semi-hardened steel provided by the embodiment of the present application;

[0028] Figure 2 A three-dimensional surface topography of the cold-rolled semi-hardened steel obtained by the embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor under the premise of not departing from the principles of the present application belong to the scope of protection of the present application.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by the existing method.

[0031] In a first aspect, the embodiment of the present application provides a processing method of cold-rolled semi-hardened steel, as shown in the figure, the method comprises: Figure 1

[0032] During the pickling, phosphorus breaking, skin passing and tension leveling of the strip steel, the elongation of the strip steel is controlled to be a first set value, a second set value, a third set value and a fourth set value, respectively.​

[0033] During the strip flatting, the roughness Ra and the peak density RPpc of the working roll of the flatting mill are controlled to be the set Ra value and the set RPpc value.

[0034] The embodiment of the present application provides a processing method of cold-rolled semi-hardened steel, which improves the yield strength and hardness of the strip by improving the work hardening of the strip through the large elongation control of the phosphorus breaking machine, the skin pass mill and the tension leveler, and realizes the semi-hardened form production of the strip; the friction coefficient of the strip is reduced, the elongation of the flatting mill is increased, and the strength and hardness of the strip are improved by controlling the roughness Ra and the peak density RPpc of the working roll of the flatting mill. The strip produced by the method is thinner and has higher strength, has a large deformation degree, and can be applied to the slide rail material of automobile structural parts, and the safety of members is increased.

[0035] As an embodiment of the present application, the first set value is 8%-12%; and / or

[0036] the second set value is 2%-4%; and / or

[0037] the third set value is 5%-7%; and / or

[0038] the fourth set value is 0.5%-1.5%.

[0039] As an embodiment of the present application, the set Ra value is 0.4-0.6 μm; and the set RPpc value is 110-130 / cm 2 .

[0040] In the present application, the working roll with the roughness Ra and the peak density RPpc reduces the friction coefficient of the strip, increases the elongation of the flatting mill, and improves the strength and hardness of the steel.

[0041] As an embodiment of the present application, the method further comprises:

[0042] During the flatting of the strip, the center thickness of the strip is controlled to be 20-30 μm larger than the thickness of the strip at a distance of 40 mm from the edge of the strip.

[0043] As an embodiment of the present application, the process parameters of the phosphorus breaking include that the roughness Ra of the working roll of the phosphorus breaking machine is 0.8-1.2 μm, the insertion amount of the working roll of the phosphorus breaking machine is 25-35 mm, the unit tension of the phosphorus breaking machine is 90-110 MPa, and the speed of the phosphorus breaking machine is 180-220 m / min.

[0044] As an embodiment of the present application, the flattening process parameters include: flattening rolling force is 5000-7000 kn, inlet tension is 90-110 MPa, outlet tension is 100-120 MPa, bending roll force initial setting value is 650-750 Kn, and process speed is 180-220 m / min.

[0045] As an embodiment of the present application, the process parameters of the straightening include: roughness Ra of the work roll of the straightening machine is 0.7-0.9 μm, and diameter of the work roll of the straightening machine is 70-90 mm.

[0046] As an embodiment of the present application, the chemical composition of the strip steel includes, in mass fraction: C: 0.06%-0.1%, Mn: 0.35%-0.50%, P≤0.018%, S≤0.015%, Als≤0.08%, Cr≤0.08%, Cu≤0.0062%, N≤0.08%, and Si≤0.03%.

[0047] In the present application, alloy components are added to improve the strength and hardness while improving the toughness. C and Si elements are added to improve the strength of the steel, Mn element improves the strength and toughness of the strip steel, and Cu element improves the atmospheric corrosion resistance.

[0048] As an embodiment of the present application, the method further includes:

[0049] The strip steel is hot-rolled, and then coiled, and the coiling temperature of the tail of the strip steel is controlled to be higher than the coiling temperature of the head of the strip steel.

[0050] In the present application, during the hot rolling process, the tail section of the hot-rolled strip is exposed to the layer cooling and air for a time greater than the head, so that the temperature of the tail is about 20-30℃ lower than the temperature of the head, resulting in inconsistent performance of the head and tail of the hot-rolled coil, which further affects the cold-rolled and pickled strip steel, causing inconsistent hardness of the head and tail. The inconsistent performance of the head and tail easily leads to stamping cracking problem of the strip steel during the opening process in the automobile main engine factory. By using different coiling temperatures of the head and tail, the hardness of the head and tail can be made consistent.

[0051] As an embodiment of the present application, the hot-rolling and coiling of the strip steel, and controlling the coiling temperature of the tail of the strip steel to be higher than the coiling temperature of the head of the strip steel, includes:

[0052] The strip steel is hot-rolled, and then coiled, and the coiling temperature of the strip steel is increased at a speed of 0.5℃ / m from 100 m away from the tail to 40 m away from the tail, and the coiling temperature of the strip steel is kept the same from 40 m away from the tail to the tail.

[0053] In the present application, the hot rolling coiling temperature gradient control mainly increases the temperature compensation at the head and tail, balances the uniformity of the whole coil temperature, and further improves the performance uniformity.

[0054] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not used to limit the scope of the present application. The experimental methods in the following examples without specific conditions are generally determined according to the national standards. If there is no corresponding national standard, the general international standard, the conventional condition, or the condition suggested by the manufacturer is used.

[0055] Example 1

[0056] A processing method of a cold-rolled semi-hardened steel, specifically:

[0057] (1) Raw material selection: the composition of the strip steel is shown in Table 1;

[0058] (2) Pickling of the strip steel: the total elongation of the strip steel in the pickling line is controlled to be 10%;

[0059] (3) Phosphorus breaking of the strip steel: the roughness Ra of the working roll of the phosphorus breaking machine is 1 μm, the insertion amount of the working roll of the phosphorus breaking machine is 30 mm, the unit tension of the phosphorus breaking machine is 100 MPa, the elongation of the phosphorus breaking machine is set to be 3%, and the phosphorus breaking process speed is 200 m / min;

[0060] (4) Leveling of the strip steel: the C40 crown (the thickness of the strip steel at the center - the thickness of the strip steel at 40 mm away from the edge of the strip steel) of the incoming material of MCCR (hot rolling full continuous endless rolling) is controlled to be 25 μm; the constant rolling force mode is used, the lubrication of the leveling machine uses leveling liquid control, the concentration is 2%, and the injection flow rate is 30 L / min; the leveling roll uses a small diameter roll, the roll diameter is 400 mm, the roughness Ra is 0.5 μm, and the peak density Rpc is 120 / cm 2 ; the leveling rolling force is 6000 kn, the inlet tension is 100 MPa, the outlet tension is 110 MPa, the elongation of the strip steel is 6%, the initial setting value of the bending force is 700 Kn, and the process speed is 200 m / min;

[0061] (5) Tension leveling of the strip steel: the roughness Ra of the working roll of the tension leveling machine is 0.8 μm, the diameter of the working roll of the tension leveling machine is 80 mm; the insertion amount of the working roll of the tension leveling machine is 25 mm, the unit tension of the tension leveling machine is 100 MPa, the elongation of the tension leveling machine is set to be 1%, and the speed of the tension leveling machine is 200 m / min.

[0062] Example 2

[0063] A processing method of a cold-rolled semi-hardened steel, specifically:

[0064] (1) Raw material selection: the composition of the strip steel is shown in Table 1;

[0065] (2) Pickling of the strip steel: the total elongation of the strip steel in the pickling line is controlled to be 8%;

[0066] (3) Phosphorus breaking of the strip steel: the roughness Ra of the working roll of the phosphorus breaking mill is 0.8 μm, the insertion amount of the working roll of the phosphorus breaking mill is 25 mm, the unit tension of the phosphorus breaking mill is 90 MPa, the set elongation of the phosphorus breaking mill is 2%, and the phosphorus breaking process speed is 180 m / min;

[0067] (4) Leveling of the strip steel: the C40 convexity (the thickness of the center of the strip steel - the thickness of the strip steel at a distance of 40 mm from the edge of the strip steel) of the incoming material of the MCCR (hot rolling full continuous endless rolling) is controlled to be 20 μm; the constant rolling force mode is adopted, the lubrication of the leveling mill adopts the leveling liquid control, the concentration is 2%, and the injection flow is 30 L / min; the leveling mill roll adopts a small diameter roll, the roll diameter is 400 mm, the roughness Ra is 0.5 μm, and the peak density Rpc is 110 / cm 2 ; the leveling rolling force is 5000 kn, the inlet tension is 90 MPa, the outlet tension is 100 MPa, the elongation of the strip steel is 5%, the initial set value of the bending roll force is 650 Kn, and the process speed is 180 m / min;

[0068] (5) Tension leveling of the strip steel: the roughness Ra of the working roll of the tension leveling mill is 0.7 μm, and the diameter of the working roll of the tension leveling mill is 70 mm; the insertion amount of the working roll of the tension leveling mill is 20 mm, the unit tension of the tension leveling mill is 90 MPa, the set elongation of the tension leveling mill is 0.5%, and the speed of the tension leveling mill is 180 m / min.

[0069] Example 3

[0070] A processing method of a cold-rolled semi-hardened steel, in particular:

[0071] (1) Selection of raw materials: the composition of the strip steel is shown in Table 1;

[0072] (2) Pickling of the strip steel: the total elongation of the strip steel in the pickling line is controlled to be 12%;

[0073] (3) Phosphorus breaking of the strip steel: the roughness Ra of the working roll of the phosphorus breaking mill is 1.2 μm, the insertion amount of the working roll of the phosphorus breaking mill is 35 mm, the unit tension of the phosphorus breaking mill is 110 MPa, the set elongation of the phosphorus breaking mill is 4%, and the phosphorus breaking process speed is 220 m / min;

[0074] (4) Leveling of the strip steel: the C40 convexity (the thickness of the center of the strip steel - the thickness of the strip steel at a distance of 40 mm from the edge of the strip steel) of the incoming material of the MCCR (hot rolling full continuous endless rolling) is controlled to be 30 μm; the constant rolling force mode is adopted, the lubrication of the leveling mill adopts the leveling liquid control, the concentration is 2%, and the injection flow is 30 L / min; the leveling mill roll adopts a small diameter roll, the roll diameter is 400 mm, the roughness Ra is 0.6 μm, and the peak density Rpc is 130 / cm2 ; the flat rolling force is 7000 kn, the entry tension is 110 MPa, the exit tension is 120 MPa, the elongation of the strip steel is 7%, the initial setting value of the bending force is 750 Kn, and the process speed is 220 m / min;

[0075] (5) strip straightening: the roughness Ra of the work roll of the straightening machine is 0.9 μm, the diameter of the work roll of the straightening machine is 90 mm; the insertion amount of the work roll of the straightening machine is 30 mm, the unit tension of the straightening machine is 110 MPa, the set elongation of the straightening machine is 1.5%, and the speed of the straightening machine is 220 m / min.

[0076] Example 4

[0077] A processing method of a cold-rolled semi-hardened steel, specifically:

[0078] (1) raw material selection: the composition of the strip steel is shown in Table 1;

[0079] (2) pickling of the strip steel: the total elongation of the strip steel in the pickling line is controlled to be 10%;

[0080] (3) phosphor breaking of the strip steel: the roughness Ra of the work roll of the phosphor breaking machine is 0.9 μm, the insertion amount of the work roll of the phosphor breaking machine is 28 mm, the unit tension of the phosphor breaking machine is 95 MPa, the set elongation of the phosphor breaking machine is 3%, and the process speed of the phosphor breaking machine is 200 m / min;

[0081] (4) flattening of the strip steel: the C40 crown (the thickness of the strip steel at the center - the thickness of the strip steel at a distance of 40 mm from the edge of the strip steel) of the incoming material of the MCCR (hot rolling full continuous endless rolling) is controlled to be 23 μm; the constant rolling force mode is adopted, the lubrication of the flattening machine adopts the flattening liquid control, the concentration is 2%, and the injection flow is 30 L / min; the flattening roll adopts a small diameter roll, the diameter of the roll is 400 mm, the roughness Ra is 0.5 μm, and the peak density Rpc is 120 / cm 2 ; the flat rolling force is 5500 kn, the entry tension is 95 MPa, the exit tension is 105 MPa, the elongation of the strip steel is 6%, the initial setting value of the bending force is 680 Kn, and the process speed is 190 m / min;

[0082] (5) strip straightening: the roughness Ra of the work roll of the straightening machine is 0.8 μm, the diameter of the work roll of the straightening machine is 80 mm; the insertion amount of the work roll of the straightening machine is 25 mm, the unit tension of the straightening machine is 95 MPa, the set elongation of the straightening machine is 1%, and the speed of the straightening machine is 190 m / min.

[0083] Example 5

[0084] A processing method of a cold-rolled semi-hardened steel, specifically:

[0085] (1) raw material selection: the composition of the strip steel is shown in Table 1;

[0086] (2) Pickling of the strip: the total elongation of the strip in the pickling line is controlled to be 10%;

[0087] (3) Phosphorus breaking of the strip: the roughness Ra of the work roll of the phosphorus breaking mill is 0.9 μm, the insertion amount of the work roll of the phosphorus breaking mill is 32 mm, the unit tension of the phosphorus breaking mill is 105 MPa, the elongation of the phosphorus breaking mill is set to be 3%, and the process speed of the phosphorus breaking mill is 210 m / min;

[0088] (4) Skin passing of the strip: the C40 crown (the thickness of the center of the strip - the thickness of the strip at 40 mm from the edge of the strip) of the incoming material of MCCR (hot rolling full continuous endless rolling) is controlled to be 28 μm; the constant rolling force mode is used, the lubrication of the skin pass mill is controlled by using the skin pass liquid, the concentration is 2%, and the injection flow rate is 30 L / min; the small diameter roll is used for the roll of the skin pass mill, the diameter of the roll is 400 mm, the roughness Ra is 0.5 μm, and the peak density Rpc is 120 / cm 2 ; the skin pass rolling force is 6500 kn, the inlet tension is 105 MPa, the outlet tension is 115 MPa, the elongation of the strip is 6%, the initial set value of the bending force is 720 Kn, and the process speed is 210 m / min;

[0089] (5) Tension leveling of the strip: the roughness Ra of the work roll of the tension leveling mill is 0.8 μm, and the diameter of the work roll of the tension leveling mill is 80 mm; the insertion amount of the work roll of the tension leveling mill is 25 mm, the unit tension of the tension leveling mill is 105 MPa, the elongation of the tension leveling mill is set to be 1%, and the speed of the tension leveling mill is 210 m / min.

[0090] Table 1: Composition of the strip of the examples (in mass fraction)

[0091] Element C / ％ Si / % Mn / % P / ％ S / ％ Als / % Cr / ％ Cu / % N / ％ Example 1 0.08 0.02 0.40 0.012 0.01 0.05 0.06 0.0042 0.05 Example 2 0.06 0 0.35 0.008 0.012 0.06 0.07 0.0043 0.06 Example 3 0.1 0.03 0.50 0.018 0.015 0.08 0.08 0.0062 0.08 Example 4 0.07 0.03 0.45 0.013 0.011 0.06 0.06 0.0051 0.06 Example 5 0.08 0.01 0.42 0.015 0.013 0.07 0.07 0.0048 0.07

[0092] Comparative Examples 1 to 5

[0093] The composition of the strip is shown in Table 2, which is actually the same as that of Example 1.

[0094] Table 2: Composition of the strip of the comparative examples (in mass fraction)

[0095] Element C / ％ Si / % Mn / % P / ％ S / ％ Als / % Cr / ％ Cu / % N / ％ Comparative Example 1 0.04 0.01 0.2 0.006 0.005 0.025 0.03 0.0021 0.025 Comparative Example 2 0.03 0 0.175 0.004 0.006 0.03 0.035 0.00215 0.03 Comparative Example 3 0.05 0.015 0.25 0.009 0.0075 0.04 0.04 0.0031 0.04 Comparative Example 4 0.035 0.015 0.225 0.0065 0.0055 0.03 0.03 0.00255 0.03 Comparative Example 5 0.04 0.005 0.21 0.0075 0.0065 0.035 0.035 0.0024 0.035

[0096] Table 3: Comparison of the strength and plasticity indexes of the cold-rolled half-hardened steel of the examples and the comparative examples

[0097]

[0098]

[0099] Various embodiments of the application can exist in a variety of forms; it should be understood that the description of the embodiments as being in a specific form is merely for convenience and brevity and should not be construed to limit the scope of the application; therefore, the description of a specific form should be considered to have specifically disclosed all possible sub-forms and individual numbers within the range. For example, it should be considered that the description of a range from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0100] In this document, the positional words such as "upper" and "lower" are specifically the directions of the drawing surface in the drawings, unless otherwise stated. In addition, in the description of the specification, the terms "include", "contain", and the like mean "include but are not limited to". In this document, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the cases where A exists alone, A and B exist together, and B exists alone. Where A and B can be singular or plural. In this document, "one or more" means one or more, and "multiple" means two or more. "At least one", "at least one of the following", or the like means any combination of the items, including single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0101] The above description is only a specific embodiment of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application should not be limited to the embodiments shown herein, but should be consistent with the widest scope of the principles and novel features applied herein.

Claims

1. A method of processing a cold-rolled semi-hardened steel, characterized in that, The method comprises: Controlling the elongation of the strip steel to be a first set value, a second set value, a third set value and a fourth set value respectively during pickling, phosphorus breaking, skin passing and tension leveling of the strip steel; Controlling the roughness Ra and peak density RPpc of the work roll of the skin pass mill to be a set Ra value and a set RPpc value during skin passing of the strip steel; The first set value is 8%-12%; The second set value is 2%-4%; The third set value is 5%-7%; The fourth set value is 0.5%-1.5%; The set Ra value is 0.4-0.6 μm; the set RPpc value is 110-130 / cm 2 .

2. The method of claim 1, wherein, The method further comprises: Controlling the center thickness of the strip steel to be 20-30μm larger than the thickness of the strip steel at a distance of 40mm from the edge of the strip steel during skin passing of the strip steel.

3. The method of claim 1, wherein, The process parameters of the phosphorus breaking include: the roughness Ra of the work roll of the phosphorus breaking mill is 0.8-1.2μm, the insertion amount of the work roll of the phosphorus breaking mill is 25-35mm, the unit tension of the phosphorus breaking mill is 90-110MPa, and the speed of the phosphorus breaking mill is 180-220m / min.

4. The method of claim 1, wherein, The process parameters of the skin passing include: the skin pass rolling force is 5000-7000kn, the inlet tension is 90-110MPa, the outlet tension is 100-120MPa, the initial set value of the bending force is 650-750Kn, and the process speed is 180-220m / min.

5. The method of claim 1, wherein, The process parameters of the tension leveling include: the roughness Ra of the work roll of the tension leveling mill is 0.7-0.9μm, and the diameter of the work roll of the tension leveling mill is 70-90mm.

6. The method of claim 1, wherein, The chemical composition of the strip steel includes: C: 0.06%-0.1%, Mn: 0.35%-0.50%, P≤0.018%, S≤0.015%, Als≤0.08%, Cr≤0.08%, Cu≤0.0062%, N≤0.08%, and Si≤0.03% by mass fraction.

7. The method of claim 1, wherein, The method further comprises: Hot rolling the strip steel, then coiling, and controlling the coiling temperature of the tail of the strip steel to be higher than the coiling temperature of the head of the strip steel.

8. The method of claim 7, wherein, The hot rolling of the strip steel, then coiling, and controlling the coiling temperature of the tail of the strip steel to be higher than the coiling temperature of the head of the strip steel, comprises: Hot rolling the strip steel, then coiling, and controlling the coiling temperature of the strip steel to increase at a speed of 0.5℃ / m from a distance of 100m from the tail to a distance of 40m from the tail, and the coiling temperature of the strip steel remains the same from the distance of 40m from the tail to the tail.

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