Strip steel and cold rolling method and application thereof

Abstract

The invention relates to the technical field of carbon steel cold rolling, in particular to strip steel and a cold rolling method and application thereof. The strip steel cold rolling method comprises the following steps that strip steel raw materials are subjected to the steps of medium wave rolling and double-side wave rolling, and the cold-rolled strip steel is obtained. According to the strip steel cold rolling method, medium wave rolling is combined with double-side wave rolling, and the technical problem of turtle back defects of cold-rolled medium carbon steel is effectively solved. The turtle back height of the strip steel obtained through the strip steel cold rolling method is 13 mm or below.

Description

Technical Field

[0001] The present application relates to the technical field of carbon steel cold rolling, and in particular to a strip steel and a cold rolling method and application thereof. Background Art

[0002] In the carbon steel production process, the steel strip is constantly deformed and hardened in one direction during cold rolling. The cold-hardened coil after rolling on an 18-roll mill usually has a quality defect of warping and turtleback. When the steel coil needs to be cut into steel plates and then processed into the required parts by laser cutting, if the steel plate has a turtleback warping defect, the steel plate or parts will collide with the laser head during processing, damaging the laser head; and the processed parts will also be unusable due to deformation. Especially for medium and high-strength steel strips, irreversible turtleback defects are prone to occur after cold rolling. In other words, the turtleback defects of medium and high-strength steel strips cannot be reduced or eliminated once they are rolled and formed.

[0003] At present, there are two main ways to improve the turtleback defect produced in strip steel: the first is to add additional straightening equipment or turtleback correction devices, but this will increase the cost of strip steel production; the second is to improve the turtleback defect produced in the strip steel during the hot rolling heating process, which is not suitable for medium and high strength strip steel rolling. Summary of the invention

[0004] In order to solve the above problems, the present application proposes a steel strip and a cold rolling method and application thereof, wherein the steel strip cold rolling method can not only effectively improve the technical problem of the turtle back defect of cold-rolled medium carbon steel, but also reduce the thickness difference between the edge and the center of the steel strip. The turtle back height of the steel strip rolled by the steel strip cold rolling method is less than 13 mm.

[0005] This application is implemented through the following technical solutions:

[0006] One of the purposes of the present application is to provide a strip cold rolling method, comprising the following steps:

[0007] The raw material of the steel strip is subjected to the steps of middle wave rolling and double-side wave rolling to obtain a cold-rolled steel strip;

[0008] Among them, the total number of rolling passes is 3 to 10, and the middle wave rolling passes account for 10% to 90%.

[0009] The strip cold rolling method provided in the present application adopts middle wave rolling combined with double side wave rolling to improve the warping (C warping) of the strip in the width direction.

[0010] In some possible implementations, in the wave rolling step, the reduction amount per pass is 10% to 30%. In this case, it can be ensured that the strip steel has a higher thickness control accuracy.

[0011] In some possible implementations, the middle wave rolling pass accounts for 10% to 50%. In this case, the thickness accuracy of the strip can be maintained and the rolling passes can be reserved for adjusting the plate shape.

[0012] In some possible implementations, the rolling temperature of the wave rolling is 50° C. to 200° C. In this case, the rolling heat can be effectively transferred.

[0013] In some possible implementations, in the double-side corrugated rolling step, the reduction in a single pass is 1% to 30%. In this case, the strip shape can be effectively regulated.

[0014] In some possible implementations, the rolling temperature of the double-side corrugation rolling is 50° C. to 200° C. In this case, the rolling heat can be effectively transferred.

[0015] In some possible implementations, the double-sided corrugated rolling has a strength of 1 IU to 20 IU. Within this strength range, the turtle back height can be effectively reduced to less than 10 mm.

[0016] In some possible implementations, the final reduction in the strip cold rolling method is 2% to 15%. In this case, the final reduction is a small reduction, and rolling with a small reduction can control the warping (L warping) of the strip in the length direction.

[0017] In some possible implementations, the strip cold rolling method further includes the steps of:

[0018] The strip steel after the middle wave rolling and the double side wave rolling is straightened.

[0019] In some possible implementations, the straightening step includes: applying a force on the steel strip in a direction opposite to the direction in which the steel strip is deformed during rolling, wherein the force is pressed into the steel strip to a depth of 10 mm to 80 mm.

[0020] In the above-mentioned strip straightening treatment, a force opposite to the strip deformation direction during rolling is applied to straighten the strip, thereby effectively improving the strip's turtleback warping problem. Combined with the small reduction in the last pass, the strip's turtleback warping problem is significantly improved.

[0021] In some possible implementations, the straightening process uses three-roller straightening, in which the three rollers are a rubber pressure roller, a plate roller, and a steering roller.

[0022] In some possible implementations, the rubber pressure roller, the plate-shaped roller and the steering roller are combined into a three-roll straightening device, in which the plate-shaped roller, the rubber pressure roller and the steering roller are sequentially distributed from the exit of the cold rolling mill. In this case, when the rolled strip passes through the plate-shaped roller and the steering roller, the pressure roller applies a force in the opposite direction of the strip deformation during rolling, thereby playing a reverse correction role on the turtleback condition.

[0023] In some possible implementations, the turtleback height of the steel strip obtained by the steel strip cold rolling method is less than 13 mm, preferably 6 mm to 13 mm; the thickness difference between the untrimmed steel strip edge at 30 mm and the center of the steel strip is less than 40 μm, preferably 25 μm to 40 μm.

[0024] The second object of the present application is to provide a steel strip, comprising iron and the following components by mass fraction:

[0025] 0.1%≤C≤1.5%, 0.1%≤Si≤0.50%, 0.1≤Mn≤1.4%, P≤0.03%, S≤0.03%, W (Cr+Ni+Mo) ≤2.0%, Al≤0.06%.

[0026] The strip steel provided in the present application is used as the strip steel raw material for the strip steel cold rolling method provided in the present application. The yield strength of the strip steel is above 500 MPa, and it is a medium-high strength steel grade that needs to improve the turtleback defect during the cold rolling process.

[0027] W (Cr+Ni+Mo) It refers to the mass fraction of the total content of Cr, Ni and Mo, among which the content of one or two metals can be infinitely close to 0 and cannot be included in the content.

[0028] In some possible implementations, the cold-rolled steel strip has a thickness of 0.3 mm to 10 mm and a width of 900 mm to 2250 mm.

[0029] In some possible implementations, the strip steel is composed of the following components in mass fractions: 0.1%≤C≤1.5%, 0.1%≤Si≤0.50%, 0.1≤Mn≤1.4%, P≤0.03%, S≤0.03%, W (Cr+Ni+Mo) ≤2.0%, Al≤0.06%, and the rest are Fe and unavoidable impurities.

[0030] In some possible implementations, the steel strip consists of the following components in mass fractions:

[0031] 0.41%≤C≤0.68%, 0.17%≤Si≤0.23%, 0.43≤Mn≤0.65%, 0.015%≤P≤0.02%, 0.0012%≤S≤0.02%, 0.25%≤Cr≤0.33%, 0.05%≤Ni≤0.18%, Al≤0.06%, and the rest are Fe and unavoidable impurities.

[0032] The third purpose of the present application is to provide a cold rolling method for strip steel for application in the field of carbon steel cold rolling technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0034] Figure 1 This is a schematic diagram of the cross-sectional structure of a turtleback defect in a steel strip after a steel strip cold rolling method in an embodiment of the present application.

[0035] Explanation of the accompanying drawings: 1-strip steel after cold rolling, 2-turtle back height, 3-edge C30 position, 4-strip steel center.

[0036] The purpose, features and advantages of this figure will be further described in conjunction with the embodiments with reference to the accompanying drawings. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0038] Obviously, the following descriptions are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in the field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0039] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter described in the claims.

[0040] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution, and all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0041] The term "pass ratio" is used when calculating a specific pass. If it is not an integer, it will be rounded up by 1. For example, if the total number of passes is 6 and the middle wave rolling pass accounts for 40%, the calculated rolling pass of the middle wave is 2.4, which is rounded up by 1, i.e. 3 passes.

[0042] Example 1

[0043] Embodiment 1 A strip steel is proposed, which is a 45Mn hot-rolled base plate, and is composed of the following components by mass fraction: 0.41% C, 0.23% Si, 0.65% Mn, 0.003% S, 0.015% P, 0.01% Al, 0.33% Cr, 0.05% Ni, and the rest is Fe and unavoidable impurities. The specification of the strip steel is 2.3 mm×2250 mm×full length.

[0044] Embodiment 1 also provides a cold rolling method of the steel strip of this embodiment, wherein the steel strip of this embodiment is pickled and then cold rolled, and the specific cold rolling steps include:

[0045] 1) Medium wave rolling is used for the 1st, 2nd and 3rd passes, and the reduction of each pass is 15%.

[0046] 2) Double-side wave rolling is used for the 4th, 5th and 6th passes, wherein the double-side wave rolling strength is 15IU, the single-pass reduction of the 4th and 5th passes is 15%, and the rolling reduction of the 6th pass is 5%.

[0047] 3) After double-sided corrugation rolling, straightening treatment is performed, that is, a force is applied to the strip in the opposite direction to the deformation direction of the strip during rolling, and the depth of the force pressed into the strip is 20 mm.

[0048] Example 2

[0049] Example 2 proposes a steel strip, which is a 65Mn annealed steel coil, and is composed of the following components in mass fractions:

[0050] 0.68% C, 0.17% Si, 0.43% Mn, 0.0012% S, 0.021% P, 0.05% Al, 0.25% Cr, 0.18% Ni, and the rest is Fe and unavoidable impurities. The specifications of the strip are 1.8mm×2250mm×full length.

[0051] Embodiment 2 also provides a cold rolling method for the strip steel of this embodiment, and the steps are basically the same as those of Embodiment 1, except that:

[0052] The middle wave rolling passes are the 1st, 2nd, 3rd, 4th and 5th passes; the double side wave rolling pass is the 6th pass, and the rolling reduction of the 6th pass is 8%.

[0053] Example 3

[0054] Example 3 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0055] Example 3 also proposes a cold rolling method for the strip steel of this embodiment, and the steps are basically the same as those of Example 1, except that the reduction in the 6th rolling pass is 2%.

[0056] Example 4

[0057] Example 4 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0058] Example 4 also proposes a cold rolling method for the strip steel of this embodiment, and the steps are basically the same as those of Example 1, except that the reduction in the 6th rolling pass is 8%.

[0059] Example 5

[0060] Example 5 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0061] Example 5 also proposes a cold rolling method for the strip steel of this embodiment, and the steps are basically the same as those of Example 1, except that the reduction in the 6th rolling pass is 12%.

[0062] Example 6

[0063] Example 6 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0064] Example 6 also proposes a cold rolling method for the strip steel of this embodiment, and the steps are basically the same as those of Example 1, except that the reduction in the sixth rolling pass is 15%.

[0065] Example 7

[0066] Example 7 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0067] Example 7 also proposes a cold rolling method for the steel strip of this embodiment, the steps of which are basically the same as those of Example 1, except that the depth of the force pressing into the steel strip is 10 mm.

[0068] Example 8

[0069] Example 8 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0070] Example 8 also proposes a cold rolling method for the steel strip of this embodiment, the steps of which are basically the same as those of Example 1, except that the depth of the force pressing into the steel strip is 40 mm.

[0071] Example 9

[0072] Example 9 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0073] Example 9 also proposes a cold rolling method for the steel strip of this embodiment, the steps of which are basically the same as those of Example 1, except that the depth of the force pressing into the steel strip is 58 mm.

[0074] Example 10

[0075] Example 10 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0076] Example 10 also proposes a cold rolling method for the steel strip of this embodiment, the steps of which are basically the same as those of Example 1, except that the depth of the force pressing into the steel strip is 72 mm.

[0077] Embodiment 11

[0078] Example 11 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0079] Example 11 also proposes a cold rolling method for the steel strip of this embodiment, the steps of which are basically the same as those of Example 1, except that the depth of the force pressing into the steel strip is 80 mm.

[0080] Example 12

[0081] Example 12 proposes a strip steel whose component content and specifications are the same as those of Example 1.

[0082] Example 12 also proposes a cold rolling method for the steel strip of this comparative example, and the steps are basically the same as those of Example 1, except that the steel strip is not straightened.

[0083] Comparative Example 1

[0084] Comparative Example 1 proposes a steel strip whose component content and specifications are the same as those of Example 1.

[0085] Comparative Example 1 also proposes a cold rolling method for the strip steel of this comparative example, and the steps are basically the same as those of Example 1, except that: the middle wave rolling passes are the 1st to 6th passes (i.e. not combined with double-side wave rolling), and the reduction amount of the 6th pass (the last pass) is 5%.

[0086] Comparative Example 2

[0087] Comparative Example 2 proposes a steel strip whose component content and specifications are the same as those of Example 1.

[0088] Comparative Example 2 also proposes a cold rolling method for the strip steel of this comparative example, and the steps are basically the same as those of Example 1, except that the reduction amount in the 6th pass (the last pass) is 50%.

[0089] Comparative Example 3

[0090] Comparative Example 3 proposes a steel strip whose component content and specifications are the same as those of Example 1.

[0091] Comparative Example 3 also proposes a cold rolling method for the steel strip of this comparative example, and the steps are basically the same as those of Example 1, except that the depth of the force pressed into the steel strip is 10 mm.

[0092] Comparative Example 4

[0093] Comparative Example 4 proposes a steel strip whose component content and specifications are the same as those of Example 1.

[0094] Comparative Example 4 also proposes a cold rolling method for the steel strip of this comparative example, and the steps are basically the same as those of Example 1, except that the depth of the force pressed into the steel strip is 100 mm.

[0095] In order to verify the advancement of the cold rolling method for steel strip provided in the embodiment of the present application, the schematic diagram of the cross section of the steel strip after cold rolling is as follows: Figure 1 As shown, the turtleback height (the turtleback height refers to: the horizontal distance between the position 3 30 mm (C30) from the edge and the center 4 of the strip) of the cold rolling method provided in the embodiment and the comparative example 1, and the thickness difference between the position 3 30 mm (C30) from the edge and the center 4 of the strip after cold rolling without trimming the strip are measured and calculated, and the measurement and calculation results are shown in Table 1 below.

[0096] Table 1

[0097]

[0098]

[0099] From Table 1 above, at least the following conclusions can be drawn:

[0100] ① In the strip cold rolling method of the embodiment of the present application, after the strip is subjected to middle wave rolling, double-side wave rolling and correction treatment, the turtle back defect is significantly improved, and the thickness difference between the edge C30 position and the center is small.

[0101] ② In the cold rolling method of the steel strip in the embodiment of the present application, the metal flow in the width direction of the steel strip during the cold rolling process is more uniform, and the warping of the steel strip in the length direction due to the deformation and work hardening caused by reciprocating rolling is effectively reduced. Thus, the turtle back warping defect at the outlet of the high-strength carbon steel in the cold rolling is effectively reduced, and the yield rate is improved.

[0102] ③ In the strip cold rolling method of the embodiment of the present application, a smaller final reduction can reduce the warping (L warping) in the length direction of the strip.

[0103] ④ In the strip cold rolling method of the embodiment of the present application, the middle wave rolling passes are 3 times (i.e., accounting for 50%), the double-side wave rolling passes are 3 times, and when the force is pressed into the strip to a depth of 20 mm, the turtle back is significantly improved; at the same time, the thickness difference between the edge C30 position and the center is the smallest.

[0104] ⑤ From the data of Example 12, it can be seen that even without straightening treatment, the turtleback height and thickness difference of the strip after cold rolling are only 12 mm and 26 μm, which indicates that the middle wave and double-side wave rolling modes in the strip cold rolling method of the embodiment of the present application can effectively reduce the turtleback height and thickness difference of the strip.

[0105] ⑥ It can be seen from the data of Example 1 and Comparative Examples 3 to 4 that when the depth of the force pressed into the strip is between 10mm and 80mm, the turtleback height and thickness difference of the strip obtained after cold rolling are within a reasonable range. Too shallow a depth will result in too high a turtleback height, and too deep a depth will increase the thickness difference between the edge C30 position and the center.

[0106] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for cold rolling a steel strip, characterized in that: The steps include: The raw material of the steel strip is subjected to the steps of middle wave rolling and double-side wave rolling to obtain a cold-rolled steel strip; Among them, the total number of rolling passes is 3 to 10, and the middle wave rolling passes account for 10% to 90%.

2. The strip cold rolling method according to claim 1, characterized in that: The middle wave rolling passes account for 10% to 50%.

3. The strip cold rolling method according to claim 1 or 2, characterized in that: In the middle wave rolling step, the reduction amount of a single pass is 10% to 30%; And / or, the rolling temperature of the wave rolling is 50°C to 200°C.

4. The strip cold rolling method according to claim 1 or 2, characterized in that: In the double-side wave rolling step, the reduction amount per single pass is 10% to 30%; And / or, the rolling temperature of the double-side corrugation rolling is 50° C. to 200° C.; And / or, the strength of the double-sided corrugation rolling is 1IU to 20IU.

5. The strip cold rolling method according to claim 4, characterized in that: In the strip cold rolling method, the final reduction is 2% to 15%.

6. The strip cold rolling method according to claim 5, characterized in that: The strip cold rolling method further comprises the steps of: The strip steel after the middle wave rolling and the double side wave rolling is straightened.

7. The strip cold rolling method according to claim 6, characterized in that: The straightening treatment step includes: applying a force on the steel strip in a direction opposite to the deformation direction of the steel strip during rolling, wherein the force is pressed into the steel strip to a depth of 10 mm to 80 mm.

8. A steel strip used in the steel strip cold rolling method according to any one of claims 1 to 7, comprising iron, characterized in that: It also includes the following mass fraction components: 0.1%≤C≤1.5%、0.1%≤Si≤0.50%、0.1≤Mn≤1.4%、P≤0.02%、S≤0.02%、W (Cr+Ni+Mo) ≤2.0%、Al≤0.06%。 9. The steel strip according to claim 8, characterized in that The strip steel has a thickness of 0.3 mm to 10 mm and a width of 900 mm to 2250 mm.

10. Application of the cold rolling method for steel strip according to any one of claims 1 to 7 in the technical field of carbon steel cold rolling.

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