A control method for improving wedge accuracy by rolling load redistribution in a hot rolling short flow

Abstract

The application provides a control method for improving wedge precision by rolling load redistribution in a short process hot rolling, comprising: adopting a constant pressure reduction mode to perform rolling mill load distribution; limiting F1 and F2 rack pressure reduction rates to fixed values, and calculating F3-F7 rack pressure reduction rates according to the fixed pressure reduction rates of F1 and F2 racks in a secondary control system; performing rolling load redistribution; after plate passing, the difference between actual rolling load of the last rack and set load is compared, when the deviation between actual rolling force and set rolling force reaches the minimum force difference effective proportion, part of the load is distributed to the front stage rack; and performing short stroke control of rolling mill guide plate opening; for F2-F7 racks, the head short stroke opening, the middle short stroke opening and the tail short stroke opening are set. The application solves the technical problem of low wedge precision in two-phase zone rolling in a short process hot rolling, improves the stability and continuity of two-phase zone rolling in the short process hot rolling, ensures the smooth production, and realizes the improvement of wedge precision in two-phase zone rolling in the short process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hot rolling strip manufacturing, and particularly relates to a control method for improving wedge precision by rolling load redistribution in a short process of hot rolling. BACKGROUND

[0002] Due to the process characteristics, the CSP production line (thin slab continuous casting and rolling production line) can obtain a more stable same-plate temperature difference compared to the conventional hot-rolled silicon steel, but due to the higher tapping temperature, the ferrite transformation (temperature is about 1020-960℃) exists in the rolling process in the finishing rolling process. In order to further improve the production line efficiency, the slab thickness at the inlet of the finishing rolling reaches 75mm, and the wedge precision is controlled to be 94.31% according to the previous process, and in order to ensure the same-plate difference precision of the secondary material, the wedge precision needs to be improved to more than 96%.

[0003] When the two-phase zone changes exist in the finishing rolling mill, the wedge control in the rolling process is a difficult point in the production process, and the wedge deviation on both sides of the strip will affect the rolling stability, and the hot-rolled secondary material has a high requirement for the wedge of the strip, and the poor wedge precision cannot meet the requirements of the secondary rolling in the later process, which will cause quality loss and stock generation. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a control method for improving wedge precision by rolling load redistribution in a short process of hot rolling, so as to solve the technical problem of low wedge precision in the two-phase zone rolling of the short process hot rolling, improve the stability and continuity of the two-phase zone rolling of the short process hot rolling, ensure the smooth production, and realize the improvement of the wedge precision in the two-phase zone rolling of the short process.

[0005] To achieve the above-mentioned purpose, the present application realizes the following technical scheme:

[0006] A control method for improving wedge precision by rolling load redistribution in a short process of hot rolling, comprising:

[0007] The rolling mill load distribution is carried out in a constant pressure reduction mode: the pressure reduction rates of F1 and F2 racks are limited to fixed values, and the secondary control system calculates the pressure reduction rates of F3-F7 racks according to the fixed pressure reduction rates of F1 and F2 racks;

[0008] Rolling load redistribution: after the plate is passed, the difference between the actual rolling load of the last rack and the set load is compared, and when the deviation between the actual rolling force and the set rolling force reaches the minimum force difference effective proportion, part of the load is distributed to the front racks;

[0009] Short stroke control of rolling mill guide pad opening: for F2-F7 racks, the head short stroke opening, the middle short stroke opening and the tail short stroke opening are set.

[0010] As a further optimization of the present application, the F1 stand reduction rate is 50%, the F2 stand reduction rate is 52%, the F3 stand reduction rate ranges from 45% to 52%, the F4 stand reduction rate ranges from 40% to 47%, the F5 stand reduction rate ranges from 26% to 38%, the F6 stand reduction rate ranges from 19% to 33%, and the F7 stand reduction rate ranges from 9% to 18%.

[0011] As a further optimization of the present application, the minimum effective proportion of force difference is 5% to 10%.

[0012] As a further optimization of the present application, the maximum distribution proportion of AGC action is 5% to 20%, which refers to the maximum distribution proportion with respect to the strip thickness.

[0013] As a further optimization of the present application, the maximum AGC action amount distributed to the F4 stand is 0.1 to 1.0 mm, the maximum AGC action amount distributed to the F5 stand is 0.1 to 0.6 mm, and the maximum AGC action amount distributed to the F6 stand is 0.1 to 0.6 mm.

[0014] As a further optimization of the present application, the F2 stand head short stroke opening is 60 to 90 mm, the middle short stroke opening is 40 to 60 mm, and the tail short stroke opening is 50 to 70 mm, the F3 stand head short stroke opening is 70 to 100 mm, the middle short stroke opening is 50 to 70 mm, and the tail short stroke opening is 60 to 80 mm, the F4 stand head short stroke opening is 60 to 90 mm, the middle short stroke opening is 40 to 60 mm, and the tail short stroke opening is 50 to 70 mm, the F5 stand head short stroke opening is 60 to 90 mm, the middle short stroke opening is 40 to 60 mm, and the tail short stroke opening is 50 to 70 mm, the F6 stand head short stroke opening is 55 to 85 mm, the middle short stroke opening is 30 to 55 mm, and the tail short stroke opening is 45 to 65 mm, and the F7 stand head short stroke opening is 55 to 85 mm, the middle short stroke opening is 30 to 55 mm, and the tail short stroke opening is 45 to 65 mm.

[0015] As a further optimization of the present application, the method is suitable for manufacturing products with a thickness of 1.2 mm to 3.0 mm.

[0016] As a further optimization of the present application, the products include electrical steel.

[0017] As a further optimization of the present application, the wedge precision of the strip during production is improved to more than 97%.

[0018] Compared with the prior art, the present application solves the problem of difficult control of the wedge precision of the hot rolling short process, solves the technical problem of easy deviation of the two-phase zone rolling of the electrical steel, realizes the purpose of large-scale production of the high wedge precision and high stability of the hot rolling short process strip steel, and has the following effects:

[0019] ① The method does not need to modify the equipment in the implementation process, and the existing equipment and control can be used.

[0020] ② The method is suitable for the rolling of the wedge-shaped precision required by the short process hot rolling finishing mill train, and solves the problem of low wedge precision of the two-phase zone rolling.

[0021] ③ The method is simple, easy to operate, and has strong practicability.

[0022] ④ In addition to the low wedge precision caused by the wedge difference of the slab, the problem of low wedge precision of the two-phase zone rolling is basically eliminated, the amount of waste products is reduced, and the thickness uniformity precision of the secondary material is improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a temperature-stress strain curve.

[0024] Figure 2 is a strip wedge schematic diagram. Figure 2 In the figure, X: strip distance from the edge position, including 25, 40, 50, 75, 100, … mm; Y: strip distance from the edge position, including 5, 10, 15, … mm; OS: strip operation side; DS: strip drive side; H: strip thickness; Hx1: strip thickness at x1; Hx2: strip thickness at x2; Hy1: strip thickness at y1; Hy2: strip thickness at y2. DETAILED DESCRIPTION

[0025] The specific embodiments are described below, and the advantages and various effects of the present application will be more clearly presented. Those skilled in the art should understand that these specific embodiments and examples are used to illustrate the present application, not to limit the present application.

[0026] In the entire specification, unless otherwise specifically stated, the terms used herein are understood as the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs, and if there is a conflict, the present specification takes precedence.

[0027] As Figure 1 is a phase change Z-shaped temperature-stress strain curve, as Figure 2 is a strip wedge schematic diagram.

[0028] The technical problem to be solved by the present application is that CSP rolling electrical steel is different from conventional hot rolling, and there is two-phase zone rolling, and there is a transformation from austenite to ferrite (the temperature is about 1020-960 DEG C) in the rolling process. In the two-phase zone rolling process, the rolling force changes greatly due to phase change, and the strip steel exists serious deviation in the finishing mill under the change of 60Mpa, so that the wedge shape changes greatly in the rolling mill, resulting in loss of wedge shape precision or sudden change of wedge shape.

[0029] To this end, the present application designs rolling control process parameters from three aspects of optimizing the load distribution strategy of the rolling mill under the constant reduction rate mode, the rolling load redistribution parameters, and the short stroke of the guide pad opening of the rolling mill. The specific technical solutions are as follows:

[0030] (1) Load distribution under constant reduction rate mode

[0031] The constant reduction rate mode is an important function of the secondary development of the rolling mill to improve quality control, specifically referring to limiting the reduction rate of F1\F2 rack to a fixed value, and the method of calculating the reduction rate of other racks after the fixed F1\F2 reduction rate by the secondary control system. Controlling the reduction rate of F3-F7 racks under the constant reduction rate mode is beneficial to improving the silicon steel wedge shape control ability, especially reducing the load of the two-phase zone rolling rack to facilitate wedge shape control. The mathematical model and algorithm involved in the calculation process of the secondary control system belong to the prior art, and the present application will not be described in detail. The specific control parameters are shown in Table 1:

[0032] Table 1 Reduction rate of each rack under constant reduction rate mode

[0033]

[0034] (2) Rolling load redistribution:

[0035] The rolling load redistribution (LDC) is to improve the stability in the rolling process, and dynamically adjusts the rolling load of the last rack in the rolling process to improve the plate shape control ability of the last rack. Its role is after the plate, by comparing the actual rolling load and the set load difference of the last rack, the load is distributed to the front rack, so that the actual rolling load of the last rack is controlled, thereby avoiding the deviation of the strip steel and improving the wedge shape precision.

[0036] Table 2 Rolling load redistribution parameter table

[0037]

[0038]

[0039] The maximum distribution ratio of the automatic gauge control (AGC) action in Table 2 refers to the maximum distribution ratio with respect to the strip thickness, for example, the strip thickness is 2.0 mm, and the maximum distribution ratio is 10%, that is, the maximum AGC action amount does not exceed 0.2 mm. The minimum effective ratio of the force difference refers to the deviation between the actual rolling force and the set rolling force reaching the set parameter value, and the LDC starts to take effect. The maximum AGC action amount distributed to the stands refers to the maximum AGC action amount distributed to each stand.

[0040] (3) Mill guide opening short stroke control:

[0041] The mill guide opening short stroke control is to improve the stability in the rolling process, so that the guide improves the centering of the strip entering the mill without damaging the strip edge quality, so that the strip will not produce uncontrolled deviation in the two-phase zone rolling process due to the large change of the rolling force.

[0042] Table 3 guide opening short stroke parameter table

[0043]

[0044] The role and mechanism of the main process in the application:

[0045] The application controls the load distribution in the constant reduction rate mode. When the two-phase zone rolling is performed in the constant reduction rate mode, there is a strength difference of 60 MPa in the two-phase zone rolling strip. In order to control the deviation stability of the strip in the strength difference interval and reduce the load of the phase change zone stand to improve the overall rolling stability, the wedge control precision is improved by reducing the deviation of the strip.

[0046] The application controls the rolling load redistribution parameters. After threading, the final stand will perform thickness feedback closed loop because the actual thickness of the strip fails to hit the target thickness, which will cause the deviation between the actual rolling force and the set rolling force. After the deviation, the strip shape control ability of the final stand will be weakened due to the excessive large or small rolling force, and the strip deviation phenomenon will occur, which will affect the wedge precision. The rolling load redistribution solves the problem of mismatching of the rolling force in the rolling process, improves the strip shape control ability of the final stand, and improves the wedge precision.

[0047] The application controls the guide opening short stroke. In order to improve the guide and guard effect of the guide on the strip before and after threading, reduce the deviation in the rolling process, ensure the centering of the strip entering the roll gap, and thus improve the wedge precision of the strip. However, the head and tail spread and guide nodulation need to be considered comprehensively, and the guide opening cannot be closed blindly.

[0048] The application will be further described in detail through specific embodiments:

[0049] The main components of the test steels of the following examples are as follows: C: 0.02-0.005%, Si≥1.56%, Mn: 0.75-0.82%, P≤0.004%, S≤0.005%, Als: 0.02-0.03%, and the balance being iron and unavoidable impurities. The thickness of the slab at the entry of the finishing rolling is 75 mm.

[0050] Example One:

[0051] ① Load distribution under constant reduction mode, as shown in Table 4.

[0052] Table 4

[0053]

[0054] ② Load redistribution during rolling, as shown in Table 5.

[0055] Table 5

[0056] Parameter Maximum allocation ratio of AGC action (%) 10％ Minimum effective ratio of force difference (%) 5％ Maximum allocated AGC action amount to F4 (mm) 0.6 Maximum allocated AGC action amount to F5 (mm) 0.4 Maximum allocated AGC action amount to F6 (mm) 0.4

[0057] ③ Short stroke parameters at the tail of the guide plate, as shown in Table 6.

[0058] Table 6

[0059]

[0060] Effect: The wedge precision of the strip during production is 98.65%.

[0061] Example Two:

[0062] ① Load distribution under constant reduction mode, as shown in Table 7.

[0063] Table 7

[0064]

[0065] ② Load redistribution during rolling, as shown in Table 8.

[0066] Table 8

[0067] Parameter Maximum allocation ratio of AGC action (%) 10％ Minimum effective ratio of force difference (%) 5％ Maximum allocated AGC action amount to F4 (mm) 0.8 Maximum allocated AGC action amount to F5 (mm) 0.5 Maximum allocated AGC action amount to F6 (mm) 0.5

[0068] ③ Short stroke parameters at the tail of the guide plate, as shown in Table 9.

[0069] Table 9

[0070]

[0071] Effect: The wedge precision of the strip during production is 98.29%. Example Three:

[0072] ① Load distribution under constant reduction mode, as shown in Table 10.

[0073] Table 10

[0074]

[0075] ii. Rolling load redistribution, as shown in Table 11.

[0076] Table 11

[0077]

[0078]

[0079] iii. Short stroke parameters at the tail of the guide plate, as shown in Table 12.

[0080] Table 12

[0081]

[0082] Effect: Wedge precision of the strip during production was 97.97%.

[0083] i. Load distribution under constant pressure rate mode, as shown in Table 13.

[0084] Table 13

[0085]

[0086] ii. Rolling load redistribution, as shown in Table 14.

[0087] Table 14

[0088] Parameter Maximum allocation ratio of AGC action (%) 10％ Minimum effective ratio of force difference (%) 5％ Maximum allocated AGC action amount to F4 (mm) 0.6 Maximum allocated AGC action amount to F5 (mm) 0.4 Maximum allocated AGC action amount to F6 (mm) 0.4

[0089] iii. Short stroke parameters at the tail of the guide plate, as shown in Table 15.

[0090] Table 15

[0091]

[0092]

[0093] Effect: Wedge precision of the strip during production was 100%.

[0094] The above detailed description of the embodiments of the present application is only some embodiments of the present application, and cannot be considered as limiting the scope of the present application. Any equivalent changes and improvements made according to the scope of the present application should still belong to the patent scope of the present application. Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application belong to the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A control method for improving wedge accuracy by rolling load redistribution in a hot rolling short flow, characterized by, The method comprises the following steps: The rolling mill load distribution is performed by using a constant voltage reduction mode: the reduction rates of the F1 and F2 stands are limited to fixed values, and the secondary control system calculates the reduction rates of the F3-F7 stands according to the fixed reduction rates of the F1 and F2 stands; The rolling load is redistributed: after the strip is passed, the difference between the actual rolling load of the last stand and the set load is compared, and when the deviation between the actual rolling force and the set rolling force reaches the minimum force difference effective proportion of 5%-10%, part of the load is distributed to the front stands; the maximum distribution proportion of AGC action is 5%-20%, which refers to the maximum distribution proportion relative to the strip thickness; the maximum AGC action amount distributed to the F4 stand is 0.1-1.0 mm, the maximum AGC action amount distributed to the F5 stand is 0.1-0.6 mm, and the maximum AGC action amount distributed to the F6 stand is 0.1-0.6 mm; The short stroke control of the rolling mill guide pad opening is performed: the head short stroke opening, the middle short stroke opening and the tail short stroke opening of the F2-F7 stands are set to improve the stability during rolling, so that the guide pad improves the centering of the strip entering the rolling mill without damaging the edge quality of the strip to suppress the deviation.

2. The control method of hot rolling short flow to improve wedge accuracy by rolling load redistribution according to claim 1, characterized in that: The reduction rate of the F1 stand is 50%, the reduction rate of the F2 stand is 52%, the reduction rate of the F3 stand ranges from 45% to 52%, the reduction rate of the F4 stand ranges from 40% to 47%, the reduction rate of the F5 stand ranges from 26% to 38%, the reduction rate of the F6 stand ranges from 19% to 33%, and the reduction rate of the F7 stand ranges from 9% to 18%.

3. The control method for improving wedge accuracy through rolling load redistribution in a hot rolling short-process according to claim 1, characterized in that: The head short stroke opening of the F2 stand is 60-90 mm, the middle short stroke opening is 40-60 mm, and the tail short stroke opening is 50-70 mm; the head short stroke opening of the F3 stand is 70-100 mm, the middle short stroke opening is 50-70 mm, and the tail short stroke opening is 60-80 mm; the head short stroke opening of the F4 stand is 60-90 mm, the middle short stroke opening is 40-60 mm, and the tail short stroke opening is 50-70 mm; the head short stroke opening of the F5 stand is 60-90 mm, the middle short stroke opening is 40-60 mm, and the tail short stroke opening is 50-70 mm; the head short stroke opening of the F6 stand is 55-85 mm, the middle short stroke opening is 30-55 mm, and the tail short stroke opening is 45-65 mm; and the head short stroke opening of the F7 stand is 55-85 mm, the middle short stroke opening is 30-55 mm, and the tail short stroke opening is 45-65 mm.

4. The method of claim 1, wherein the method is characterized by: The method is suitable for manufacturing products with a thickness of 1.2 mm-3.0 mm.

5. The control method of claim 4, wherein the wedge accuracy is improved by redistribution of the rolling load in a hot rolling short flow process, characterized by: The products include electrical steel.

6. The method of claim 1, wherein the method is characterized by: The wedge precision of the strip during production is improved to more than 97%.

Images