A method for improving the shoulder defect of thin strip steel

Abstract

The present invention belongs to the technical field of thin strip continuous casting, and relates to a method for improving the plate shape shoulder defect of thin strip steel. The present invention controls the ratio of manganese element to silicon element in the continuous casting molten steel, regulates the composition of the deposited film on the surface of the crystallization roller during the continuous casting process, and improves the stability of the heat transfer of the crystallization roller. By controlling the temperature of the crystallization roller during the continuous casting process, the stability of the surface morphology of the crystallization roller during the continuous casting process is improved. At the same time, the plate shape of the continuously cast thin strip steel is monitored in real time to determine the plate shape shoulder value. Through the control equation of the torque and speed of the roller brush, the torque and speed of the roller brush during the continuous casting process are quickly responded and adjusted to achieve the purpose of controlling the plate shape shoulder. The method of the present invention achieves the purpose of controlling the plate shape shoulder of thin strip steel, improves the plate shape quality of the continuously cast thin strip steel, avoids the hot rolling rolling wave shape, solves the problem of ribs in one quarter of the steel coil, and improves the surface quality of the steel coil and the product qualification rate.

Description

Technical Field

[0001] The invention belongs to the technical field of thin strip continuous casting, relates to a plate shape control technology of thin strip steel produced by thin strip continuous casting, and more specifically to a method for improving the plate shape shoulder defect of thin strip steel. Background Art

[0002] The thin strip continuous casting process is to pass the molten steel through the flow distribution system and enter a pair of crystallization rollers rotating in opposite directions, and the thin strip steel is output as the crystallization rollers rotate. Subsequently, the thin strip steel is hot-rolled in one or two passes to become an ultra-thin strip steel product.

[0003] The shape of the thin strip steel after the molten steel passes through the crystallization roller has an extremely important influence on the subsequent hot rolling and the surface quality of the final hot-rolled steel coil. The thin strip steel has defects such as partial thickness, which directly affects the hot rolling, and it is very easy to have a wave shape during the rolling process. In more serious cases, it will be crushed, which seriously affects the normal continuous production process and the quality of the final product. Severe wave shape and thickness will also cause rib defects on the surface of the steel coil after the thin strip steel is coiled, which directly affects the product quality and qualified rate.

[0004] The existing shape control of thin strip steel is concentrated in the hot rolling process and in the aspect of convexity control. Chinese patent document 201810565018.4 provides a double-taper working roll and its roll shape design method, which flexibly designs the double-taper roll shape to control the shape of the edge of the hot-rolled strip during the hot rolling production process. Chinese patent document 201510995998.8 provides a shape control method and system for hot-rolled strip steel, which can effectively control the single-side wave and deviation defects of the hot-rolled strip steel and realize the shape control of the hot-rolled strip steel products. Chinese patent document 200910103109.7 provides a method and equipment for shape and precision control of hot-rolled strip steel, which adjusts the metal deformation capacity through the temperature distribution in the width direction to achieve ideal shape control, and realizes the control of the export shape through the arrangement of the mist cooling device. However, as mentioned above, the above control methods are mostly focused on convexity control.

[0005] At present, the existing technology cannot directly solve the plate quality of thin strip steel directly discharged from the crystallization roller during the continuous casting of molten steel thin strip. More specifically, there is no specific solution for the plate shoulder defect of thin strip steel (i.e., the problem of ribs in about one quarter of the steel coil).

[0006] It can be seen that a method is still needed to effectively improve the plate shoulder defect that occurs during the casting process of thin strip steel produced by thin strip continuous casting. Summary of the invention

[0007] The purpose of the present invention is to provide a production control method to effectively improve the shoulder defect of thin strip steel. In general, the method of the present invention effectively improves the shoulder defect of thin strip steel by controlling the ratio of manganese (Mn) content to silicon (Si) content in molten steel, the temperature of the crystallization roller, and quickly adjusting the torque and speed of the roller brush according to the shoulder value in real time, thereby improving the shoulder defect of thin strip steel and the shape quality of thin strip steel and the surface quality of steel coil.

[0008] The purpose of the present invention is specifically achieved through the following technical solutions:

[0009] According to one aspect of the present invention, a method for improving the shoulder defect of thin strip steel is proposed, the method comprising the following steps:

[0010] 1) Thin strip continuous casting:

[0011] After steelmaking in an electric furnace or converter, molten steel with qualified composition is obtained, and the ratio of Mn element content to Si element content in the molten steel is controlled between 3.1 and 3.9. The molten steel passes through a pair of crystallization rollers rotating in opposite directions and is continuously cast into a thin strip steel with a thickness of 1.4 to 2.8 mm.

[0012] 2) Measure the maximum edge thickness:

[0013] The maximum thickness of the area between the edge A and B of the thin strip is determined by an online thickness gauge as H. c , and record the position coordinate of the maximum thickness from the edge as C, where the value of the edge A position is 5 to 100 mm from the edge, and the value of the edge B position is 150 to 450 mm from the edge;

[0014] 3) Calculate y at position C c value:

[0015] According to the full width thickness of the thin strip measured by the online thickness gauge, the quadratic flatness curve y=ax is fitted. 2 +bx+c, and calculate y at position C c value;

[0016] 4) Determine the flatness shrug value of thin strip steel:

[0017] The maximum thickness H measured by step 2) c The y at position C calculated in step 3) c The difference between the values ​​determines the plate shrug value S c for:

[0018] S c =H c -y c ,

[0019] 5) Adjust the roller brush torque and speed:

[0020] When the board shrug value S c When it is greater than the threshold value P, the following steps are used for adjustment:

[0021] Adjust the roller brush torque N0 to N, where: N = N0*(1+α*S c );

[0022] Adjust the roller brush speed S0 to S, where: S = S0*(1+β*S c );

[0023] Among them, the value range of P is 0~100μm, where:

[0024] N is the roller brush torque after adjustment, N0 is the roller brush torque before adjustment, α is the roller brush torque adjustment parameter, and the value of α is 0.002~0.01;

[0025] S is the roller brush speed after adjustment, S0 is the roller brush speed before adjustment, β is the roller brush speed adjustment parameter, and the value of β is 0.003~0.02.

[0026] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, the method further comprises: during the thin strip continuous casting process of step 1), controlling the temperature range of the crystallization roller to be between 300 and 490°C.

[0027] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, in the thin strip continuous casting process of step 1), the molten steel is low carbon steel, high carbon steel, low alloy steel or high alloy steel.

[0028] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, the width of the thin strip steel is between 500 and 2100 mm.

[0029] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, the position of the edge A is 10 to 60 mm.

[0030] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, the position of the edge B is 200 to 430 mm.

[0031] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, in step 5), the value range of P is 0 to 80 μm.

[0032] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, in step 5), the value range of P is 0 to 50 μm.

[0033] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, the roller brush torque is controlled between 310 and 430 lbf·in.

[0034] According to the method for improving the shoulder defect of thin strip steel of the present invention, preferably, the roller brush speed is controlled between 210 and 440 rpm.

[0035] Beneficial technical effects

[0036] Compared with the prior art, the technical concept and corresponding technical solution of the present invention can at least achieve the following beneficial technical effects:

[0037] The technical solution of the present invention fully considers the plate shape shrug defect of thin strip steel in the production process, and controls the cast plate shape of thin strip steel in the continuous casting process for the first time. In particular, it involves the process control of the roller brush in the continuous casting process of thin strip steel.

[0038] The technical solution of the present invention controls the manganese content and silicon content in the molten steel and controls their ratio, thereby controlling the composition of the oxide film on the surface of the crystallization roller and the interface heat transfer between the surface of the crystallization roller and the surface of the continuous casting thin strip steel, thereby controlling the surface morphology of the crystallization roller to control the plate shape profile during the continuous casting process.

[0039] In addition, the technical solution of the present invention uses a thickness measuring instrument to check the shape of the thin strip steel plate in real time, determine the shoulder value of the plate profile, and through the control equation, quickly adjust the rotation speed and torque of the roller brush, and control and quickly adjust the thickness of the oxide film on the surface of the crystallization roller in real time, thereby adjusting the surface morphology of the crystallization roller in real time, effectively solving the shoulder defect of the thin strip steel plate shape.

[0040] To sum up, the technical solution of the present invention improves the plate shape quality of continuously cast thin strip steel by controlling the plate shape contour of thin strip steel continuous casting, avoids the hot rolling wave shape, solves the shoulder defect of thin strip steel plate shape, and improves the surface quality of steel coils and product qualification rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments are briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0042] Figure 1 It is a schematic diagram of a thin strip steel plate-shaped shrug in the prior art.

[0043] Figure 2 Schematic diagram of the thin strip steel plate shape according to Example 1 of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one of ordinary skill in the art to which the present invention belongs.

[0046] The following are embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments that can be obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] Figure 1 It is a schematic diagram of a thin strip steel plate-shaped shoulder in the prior art, Figure 2 Schematic diagram of the thin strip steel plate according to an embodiment of the present invention. The present invention is further described below through specific embodiments 1-3:

[0048] Example 1

[0049] The molten steel with qualified composition is obtained through electric furnace or converter steelmaking. The ratio of Mn element content to Si element content in the molten steel is 3.2. The molten steel passes through a pair of crystallization rollers rotating in opposite directions and is continuously cast into thin strip steel with a thickness of 1.97mm and a width of 1320mm. The temperature of the crystallization rollers is controlled at 325℃ during the continuous casting process.

[0050] The plate profile of the thin strip is measured by a thickness gauge, and the maximum thickness within 10mm to 200mm of the edge is determined to be 1.990mm, and the highest point is determined to be 65mm from the edge.

[0051] The thickness and shape profile of thin strip steel is fitted by quadratic equation, and the quadratic curve equation is:

[0052] y=2.035x 2 +2.6x+1.9, and the fitting thickness of the fitting curve at 65mm is calculated to be 1.920mm, and the shrug value is 73.96μm. Among them, the shrug control parameter P is 50.

[0053] The roller brush monitoring sensor detects that the roller torque is 312 lbf·in, the roller brush speed is 223 rpm, the torque adjustment parameter is 0.0037, the speed adjustment parameter is 0.0112, and N=N0*(1+α*S c) quickly adjust the roller brush torque to 326 lbf·in, by S=S0*(1+β*S c ) The roller brush speed was quickly adjusted to 253 rpm. The thin strip steel produced had no shoulder defects and the subsequent hot rolling was stable. After coiling, there was no quarter rib defect on the surface of the steel coil. The plate shape schematic diagram of Example 1 is referenced Figure 2 shown.

[0054] Example 2

[0055] The molten steel with qualified composition is obtained through electric furnace or converter steelmaking. The ratio of Mn element content to Si element content in the molten steel is 3.5. The molten steel passes through a pair of crystallization rollers rotating in opposite directions and is continuously cast into thin strip steel with a thickness of 1.94mm and a width of 1680mm. The temperature of the crystallization rollers is controlled at 370℃ during the continuous casting process.

[0056] The plate profile of the thin strip is measured by a thickness gauge, and it is determined that the maximum thickness within 60mm to 430mm of the edge is 1.928mm, and the highest point is determined to be 129mm from the edge.

[0057] The thickness and shape profile of thin strip steel is fitted by quadratic equation, and the quadratic curve equation is:

[0058] y=2.001x 2 +3.217x+1.824, and the fitting thickness of the fitting curve at 129mm is calculated to be 1.86mm, and the shrug value is 65.83μm. Among them, the shrug control parameter P is 60.

[0059] The roller brush monitoring sensor detects that the roller torque is 287 lbf·in, the roller brush speed is 246 rpm, the torque adjustment parameter is 0.0092, the speed adjustment parameter is 0.0074, and N=N0*(1+α*S c ) quickly adjust the roller brush torque to 361 lbf·in, by S=S0*(1+β*S c ) The roller brush speed was quickly adjusted to 297rpm, and the thin strip steel produced had no shoulder defects, and the subsequent hot rolling was stable. After coiling, there was no quarter rib defect on the surface of the steel coil.

[0060] Example 3

[0061] The molten steel with qualified composition is obtained through electric furnace or converter steelmaking. The ratio of Mn element content to Si element content in the molten steel is 3.8. The molten steel passes through a pair of crystallization rollers rotating in opposite directions and is continuously cast into thin strip steel with a thickness of 2.04mm and a width of 1500mm. The temperature of the crystallization rollers is controlled at 436℃ during the continuous casting process.

[0062] The plate profile of the thin strip is measured by a thickness gauge, and the maximum thickness within 50mm to 300mm of the edge is determined to be 2.038mm, and the highest point is determined to be 76mm from the edge.

[0063] The thickness and shape profile of thin strip steel is fitted by quadratic equation, and the quadratic curve equation is:

[0064] y=-1.928*10 -7 x 2 +2.876*10 -4 x+1.939, and the fitting thickness of the fitting curve at 76 mm is calculated to be 1.96 mm, and the shrug value is 78.26 μm. Among them, the shrug control parameter P is 75.

[0065] The roller brush monitoring sensor detects that the roller torque is 327 lbf·in, the roller brush speed is 343 rpm, the torque adjustment parameter is 0.0058, the speed adjustment parameter is 0.0049, and N=N0*(1+α*S c ) quickly adjust the roller brush torque to 427 lbf·in, by S=S0*(1+β*S c ) The roller brush speed was quickly adjusted to 432rpm, and the thin strip steel produced had no shoulder defects, and the subsequent hot rolling was stable. After coiling, there was no quarter rib defect on the surface of the steel coil.

[0066] The above description is only a specific implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for improving the shoulder defect of thin strip steel, characterized in that: The method comprises the following steps: 1) Thin strip continuous casting: After steelmaking in an electric furnace or converter, molten steel with qualified composition is obtained, and the ratio of Mn element content to Si element content in the molten steel is controlled between 3.1 and 3.

9. The molten steel passes through a pair of crystallization rollers rotating in opposite directions and is continuously cast into a thin strip steel with a thickness of 1.4 to 2.8 mm. 2) Measure the maximum edge thickness: The maximum thickness of the area between point A and point B on the edge of the thin strip is determined by an online thickness measuring instrument as H. c , and record the position coordinate of the maximum thickness from the edge as C, wherein the vertical distance between point A and the width edge of the thin strip steel is 5 to 100 mm, and the vertical distance between point B and the width edge of the thin strip steel is 150 to 450 mm; 3) Calculate y at position C c value: According to the full width thickness of the thin strip measured by the online thickness gauge, the quadratic flatness curve y=ax is fitted. 2 +bx+c, and calculate y at position C c Value, where x is the vertical distance from the width edge of the thin strip, y is the thickness of the thin strip at point x obtained by fitting, and a, b, and c are the coefficients of the fitting quadratic curve; 4) Determine the flatness shrug value of thin strip steel: The maximum thickness H measured by step 2) c The y at position C calculated in step 3) c The difference between the values ​​determines the plate shrug value S c for: S c =H c -y c , 5) Adjust the roller brush torque and speed: When the board shrug value S c When it is greater than the threshold value P, the following steps are used for adjustment: Adjust the roller brush torque N0 to N, Where: N = N0*(1+α*S c ); Adjust the roller brush speed S0 to S, where: S = S0*(1+β*S c ); Among them, the value range of P is 0~100μm, where: N is the roller brush torque after adjustment, N0 is the roller brush torque before adjustment, α is the roller brush torque adjustment parameter, and the value of α is 0.002~0.01; S is the roller brush speed after adjustment, S0 is the roller brush speed before adjustment, β is the roller brush speed adjustment parameter, and the value of β is 0.003~0.

02.

2. The method for improving the shoulder defect of thin strip steel according to claim 1, characterized in that: The method further comprises: During the thin strip continuous casting process of step 1), the temperature range of the crystallization roller is controlled between 300 and 490°C.

3. The method for improving the shoulder defect of thin strip steel according to claim 1, characterized in that: In the thin strip continuous casting process of step 1), the molten steel is low carbon steel, high carbon steel, low alloy steel or high alloy steel.

4. The method for improving the shoulder defect of thin strip steel according to claim 1, characterized in that: The width of the thin strip steel is between 500 and 2100 mm.

5. The method for improving the shoulder defect of thin strip steel according to claim 1, characterized in that: The vertical distance between the point A and the width edge of the thin strip steel is 10 to 60 mm.

6. The method for improving the shoulder defect of thin strip steel according to claim 1, characterized in that: The vertical distance between the point B and the width edge of the thin strip steel is 200 to 430 mm.

7. The method for improving the shoulder defect of thin strip steel according to claim 1, characterized in that: In step 5), the value range of P is 0 to 80 μm.

8. The method for improving the shoulder defect of thin strip steel according to claim 7, characterized in that: In step 5), the value range of P is 0 to 50 μm.

9. The method for improving the shoulder defect of thin strip steel according to any one of claims 1 to 8, characterized in that: The roller brush torque is controlled between 310 and 430 lbf·in.

10. The method for improving the shoulder defect of thin strip steel according to any one of claims 1 to 8, characterized in that: The roller brush speed is controlled between 210 and 440 rpm.

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