A control method for ensuring roll shape by automatic levelling of pinch rolls

Abstract

This invention relates to a control method for automatically leveling the pinch roll to ensure the coil shape. The steps are as follows: pressing the pinch roll of the winding machine against the coil, recording the pressure on both sides of the pinch roll and the roll gap value, and writing them into two preset stiffness arrays; applying a preset pressure value G to one side of the pinch roll. 设 The corresponding roll gap value Gm is found based on the stiffness array of the same side. Based on the found roll gap value Gm and its corresponding stiffness array, the theoretical pressure value Fb on the other side of the pinch roll is determined. A safety limit is applied to the theoretical pressure value Fb to determine the final execution pressure value G on the other side. 执 The set pressure value G is applied to both sides of the pinch roller. 设 Execution pressure value G 执 This invention ensures that the roll gap value remains consistent on both sides under different pressures. It maintains consistent roll gaps on both sides, avoiding roll defects caused by pressure variations, significantly reducing roll rework rates, preventing losses during lifting due to misalignment, and minimizing quality losses.

Description

Technical Field

[0001] This patent application belongs to the field of hot-rolled strip steel production technology in the metallurgical industry, and more specifically, it relates to a control method for automatically leveling pinch rolls to ensure coil shape. Background Technology

[0002] A coiler is a coiling device for hot continuous rolling of strip and plate. It generally consists of a pressure head roll, pinch rolls, auxiliary coiling rolls, mandrel equipment, etc. The pinch rolls are located on the inlet side of the coiler and consist of two rolls of different diameters (lower pinch roll and upper pinch roll). They are mainly used to guide the strip head into the coiler and to establish and maintain tension in the strip after finishing rolling and strip throwing.

[0003] The lower pinch roll is fixed. The balancing and lifting of the upper pinch roll are achieved by hydraulic cylinders, each equipped with a position sensor and mounted separately on both sides of the pinch roll. The roll gap and pressure of the pinch roll are controlled by hydraulic servo valves. Each hydraulic cylinder, through pressure setting, can automatically balance the weight of the upper pinch roll drive shaft. The roll gap of the pinch roll is achieved by lifting the upper pinch roll. The roll gap of the pinch roll is preset according to the thickness of the strip. When the strip head enters the pinch roll, the pinch roll will switch from roll gap control to pressure control. The pressure setting can be based on the material specification table maintained manually.

[0004] Automatic control of pinch rolls includes: pinch roll gap control, pinch roll speed control, pressing roll control, and pinch roll cooling control.

[0005] The control steps for the pinch rollers are as follows:

[0006] When the coiler is selected to coil the next strip, the upper pinch roll descends from the standby position to the waiting position set by L2 (the secondary control system of the strip production line). At this time, the pinch roll adopts the position control method.

[0007] Once the strip enters the coiler and establishes tension with the mandrel, the pinch rolls switch from position control to pressure control. At this point, it is in front tension control mode, and the strip tension is mainly generated between the mandrel and the finishing mill.

[0008] After the first stand of the finishing mill (F1) discards the strip, the strip tension control method changes from front tension control to rear tension control. Regardless of whether it's front or rear tension control, the pinch rolls remain under pressure control, and the pinch roll pressure increases. The strip tension is primarily generated between the pinch rolls and the mandrel. If the first stand of the finishing mill has already discarded the strip before the coiler establishes tension, there is no front tension control; the strip tension control method directly changes to rear tension control.

[0009] As the strip continues to move forward, when the tail of the strip reaches a certain distance in front of the pinch roll (this distance can be adjusted according to the site conditions), the pinch roll switches to position control mode, and the position of the upper pinch roll remains stationary.

[0010] After the tail of the strip leaves the pinch roll, the pinch roll rises to the standby position, and the winding action ends.

[0011] In the above process, when the pinch roll is in the back tension control mode, the pressure on both sides of the pinch roll increases simultaneously and proportionally. Due to the difference in stiffness on both sides, the actual roll gap on both sides will be different, which will generate an axial pushing force on the strip steel, causing the strip tail boss to misalign, resulting in hanging damage and coil rework, which is unacceptable in the production process. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide a control method for automatic leveling of the pinch rollers to ensure the coil shape, which can avoid the occurrence of misalignment of the tail bosses of the strip, so as to ensure stable coiling of the strip, obtain a good coil shape, reduce hanging damage and coil rework, and solve the problems existing in the background art.

[0013] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0014] A control method for automatically leveling the pinch rollers to ensure roll shape includes the following steps:

[0015] S1. Press the clamping rollers of the coiler against the rollers, record the pressure on both sides of the clamping rollers and the roller gap value, and write them into two set stiffness arrays.

[0016] S2, the pinch roller applies a set pressure value G on one side. 设 And calculate the corresponding roll gap value Gm based on the same-side stiffness array;

[0017] S3. Based on the calculated roll gap value Gm, and combined with the corresponding stiffness array on the other side, calculate the theoretical pressure value Fb on the other side of the pinch roll.

[0018] S4. Apply a safety limit to the calculated theoretical pressure value Fb to determine the final execution pressure value G on the other side. 执 ;

[0019] S5, set pressure values ​​G on both sides of the pinch roller. 设 Execution pressure value G 执 This ensures that the gap value between the two sides of the pinch roll remains consistent under different pressures.

[0020] Furthermore, in step S1, “pressing the pinch roll of the winding machine” means that the first-level PLC sets the pinch roll pressure, and within the range of working pressure, it gradually increases from 0 KN to the given pressure value. This pressure value covers the pressure used during normal production and is generally no more than 80% of the maximum allowable pressure of the pinch roll.

[0021] Furthermore, the primary PLC records the pressure and roll gap values ​​on both sides of the pinch roller at pressure intervals of 1KN to 5KN.

[0022] Furthermore, in step S2, the corresponding roll gap value Gm is calculated using the PLN function.

[0023] The PLN function is calculated as follows:

[0024]

[0025] in:

[0026] f(Z)——The roll gap value Gm that needs to be solved (corresponding to Gm);

[0027] X n-1 X n —The (n-1)th and nth pressure values ​​in the stiffness array;

[0028] Y n-1 Y n —The (n-1)th and nth roll gap values ​​in the stiffness array;

[0029] Z — The set pressure value to be executed. 设 (corresponding to G) 设 Its value satisfies the following condition: X n-1 <Z≤X n .

[0030] Furthermore, in step S3, the theoretical pressure value Fb on the other side of the pinch roller is calculated in reverse using the ILNL function.

[0031] The ILNL function is calculated as follows:

[0032]

[0033] in:

[0034] F(Z')——The theoretical pressure value Fb that needs to be solved (corresponding to Fb);

[0035] X n-1 X n —The (n-1)th and nth pressure values ​​in the stiffness array;

[0036] Y n-1 Y n —The (n-1)th and nth roll gap values ​​in the stiffness array;

[0037] Z' — The actual roll gap value Gm (corresponding to Gm), whose value satisfies the following condition: Y n-1 <Z'≤Y n .

[0038] Furthermore, in step S4, the theoretical pressure value Fb is safely limited using the LMT function; specifically, the theoretical pressure value Fb is limited to G. 设 If the value exceeds the range of (1±X%), then execute G. 设 * (1 ± X%), thus obtaining the final execution pressure value G on the other side. 执 ;

[0039] The LMT function is described below:

[0040]

[0041] in:

[0042] p(Fb) — The execution pressure value G that needs to be solved. 执 (corresponding to G) 执 );

[0043] Fb—Theoretical pressure value;

[0044] G 设 —Set pressure value for one side.

[0045] Furthermore, the value of X% ranges from 5% to 25%.

[0046] Due to the adoption of the above technical solution, the beneficial effects achieved by this invention are:

[0047] The clamping rolls of the coiler apply different pressures at different stages of strip coiling. Due to the different stiffness on both sides of the equipment, the actual roll gap changes differently on both sides when the same pressure is applied, which causes the strip to deviate and results in coil shape quality problems.

[0048] This invention enables the pinch rolls of the coiler to maintain the same roll gap conditions on both sides under different pressures, ensuring the alignment of the strip and eliminating the axial force on the strip when the pinch roll pressure changes. This results in stable strip winding, good coil shape, and reduced hanging damage and coil rework. Attached Figure Description

[0049] Figure 1 This is a stiffness curve of a pinch roll test in a steel plant in this invention.

[0050] Figure 2 For steel coils not produced using the method of this invention, there is a noticeable lateral boss on the outer ring;

[0051] Figure 3 The steel coil produced using the method of this invention has an outer ring boss that disappears and a good coil shape; Detailed Implementation

[0052] The present invention will be further described in detail below with reference to the embodiments.

[0053] A control method for automatically leveling the pinch rollers to ensure roll shape includes the following steps:

[0054] S1. Press the clamping rollers of the coiler against the rollers, record the pressure on both sides of the clamping rollers and the roller gap value, and write them into two set stiffness arrays.

[0055] S2, the pinch roller applies a set pressure value G on one side. 设 And calculate the corresponding roll gap value Gm based on the same-side stiffness array;

[0056] S3. Based on the calculated roll gap value Gm, and combined with the corresponding stiffness array on the other side, calculate the theoretical pressure value Fb on the other side of the pinch roll.

[0057] S4. Apply a safety limit to the calculated theoretical pressure value Fb to determine the final execution pressure value G on the other side. 执 ;

[0058] S5, set pressure values ​​G on both sides of the pinch roller. 设 Execution pressure value G 执 This ensures that the gap value between the two sides of the pinch roll remains consistent under different pressures.

[0059] In step S1, “pressing the pinch roll of the winding machine” means that the first-level PLC sets the pinch roll pressure, and within the range of working pressure, it gradually increases from 0 KN to the given pressure value. This pressure covers the pressure used during normal production and is generally no more than 80% of the maximum allowable pressure of the pinch roll.

[0060] The primary PLC records the pressure and roll gap values ​​on both sides of the pinch roller at intervals of 1KN to 5KN, for example, at intervals of 5KN and 8KN pressure.

[0061] In step S2, the corresponding roll gap value Gm is calculated using the PLN function.

[0062] The PLN function is calculated as follows:

[0063]

[0064] in:

[0065] f(Z)——The roll gap value Gm that needs to be solved (corresponding to Gm);

[0066] X n-1 X n —The (n-1)th and nth pressure values ​​in the stiffness array;

[0067] Yn-1 Y n —The (n-1)th and nth roll gap values ​​in the stiffness array;

[0068] Z — The set pressure value to be executed. 设 (corresponding to G) 设 Its value satisfies the following condition: X n-1 <Z≤X n .

[0069] In step S3, the theoretical pressure value Fb on the other side of the pinch roller is calculated in reverse using the ILNL function.

[0070] The ILNL function is calculated as follows:

[0071]

[0072] in:

[0073] F(Z')——The theoretical pressure value Fb that needs to be solved (corresponding to Fb);

[0074] X n-1 X n —The (n-1)th and nth pressure values ​​in the stiffness array;

[0075] Y n-1 Y n —The (n-1)th and nth roll gap values ​​in the stiffness array;

[0076] Z' — The actual roll gap value Gm (corresponding to Gm), whose value satisfies the following condition: Y n-1 <Z'≤Y n .

[0077] In step S4, the theoretical pressure value Fb is safely limited using the LMT function; specifically, the theoretical pressure value Fb is limited to G. 设 If the value exceeds the range of (1±X%), then execute G. 设 * (1 ± X%), thus obtaining the final execution pressure value G on the other side. 执 .

[0078] The LMT function is described below:

[0079]

[0080] in:

[0081] p(Fb) — The execution pressure value G that needs to be solved. 执 (corresponding to G) 执 );

[0082] Fb—Theoretical pressure value;

[0083] G 设 —Set pressure value for one side.

[0084] The value of x% ranges from 5% to 25%, for example, 5%, 10%, 15%, 20%, and 25%.

[0085] The present invention will be further illustrated by the following examples.

[0086] The table below shows the stiffness test data of the pinch roll of the No. 2 coiler in a certain factory. The example is that the pressure roll gap values ​​on both sides A and B of the coiler are recorded with a pressure interval of 5KN.

[0087] In practice, the first-level PLC program automatically records the pressure values ​​and position sensor data on both sides A and B every 5KN, and writes them into two set stiffness arrays for storage.

[0088]

[0089] For a more intuitive description, the stiffness curve is drawn manually as follows: Figure 1 As shown.

[0090] In actual production, the strip thickness is 3.5mm, the width is 1230mm, and the steel grade is QStE550TM. The pressure value G on one side of the pinch roll is set. 设 The pressure is 40 kN, and the set pressure value G is executed on side A (operating side). 设 40KN, the first-level PLC uses the PLN function to find the roller gap value Gm=-0.297mm in the stiffness curve of side A.

[0091] The ILNL function can be used to reverse-engineer the theoretical pressure value Fb = 30.99 KN corresponding to the roll gap of Gm = -0.297 mm in the stiffness curve on side B.

[0092] To ensure operational safety, the theoretical pressure value Fb is limited using the LMT function, restricting the fluctuation range of the B-side operational calculation to a set pressure value G. 设 Within 20% of the limit, 30.99KN exceeds 20% of 40KN. Therefore, the actual pressure setpoint for side B is determined based on the 20% limit: Fb = 40 * (1 - 20%) = 32KN, which is the actual execution pressure value G on side B (drive side). 执 It has a strength of 32 kN.

[0093] Before this function was implemented, both sides A and B were subjected to a 40KN pressing force, causing misalignment of the protrusions at the tail of the steel coil, such as... Figure 2 As shown, you can see that there are many lines formed by the staggered layers of protrusions at the end of the steel coil.

[0094] After implementing this function, the pressure on side A is 40KN and the pressure on side B is 32KN, ensuring consistency on both sides of the pinch roll gap. The coil shape is significantly improved, the tail boss disappears, and the coil tail is smooth. This avoids the misalignment of the tail boss in the strip, resulting in stable strip winding, good coil shape, and reduced hanging damage and coil rework. Figure 3 As shown.

[0095] It can be seen that by applying the control method of the present invention, the roll gaps on both sides A and B can always be kept consistent, avoiding roll defects caused by pressure changes, significantly reducing the roll rework rate, avoiding losses during the hoisting process due to misalignment, and reducing quality loss.

Claims

1. A control method for automatically leveling pinch rollers to ensure roll shape, characterized in that... Includes the following steps: S1. Press the clamping rollers of the coiler against the rollers, record the pressure on both sides of the clamping rollers and the roller gap value, and write them into two set stiffness arrays. S2, the pinch roller applies a set pressure value G on one side. 设 And calculate the corresponding roll gap value Gm based on the same-side stiffness array; S3. Based on the calculated roll gap value Gm, and combined with the corresponding stiffness array on the other side, calculate the theoretical pressure value Fb on the other side of the pinch roll. S4. Apply a safety limit to the calculated theoretical pressure value Fb to determine the final execution pressure value G on the other side. 执 ; S5, set pressure values ​​G on both sides of the pinch roller. 设 Execution pressure value G 执 This ensures that the gap value between the two sides of the pinch roll remains consistent under different pressures.

2. The control method for automatically leveling the pinch rollers to ensure roll shape according to claim 1, characterized in that: In step S1, "pressing the pinch roller of the winding machine" means that the first-level PLC sets the pinch roller pressure, and within the range of working pressure, it gradually increases from 0 KN to a given pressure value that is no more than 80% of the maximum allowable pressure of the pinch roller.

3. The control method for automatically leveling the pinch rollers to ensure roll shape according to claim 2, characterized in that: The primary PLC records the pressure and roll gap values ​​on both sides of the pinch roller at intervals of 1KN to 5KN.

4. The control method for automatically leveling the pinch rollers to ensure roll shape according to claim 1, characterized in that: In step S3, the theoretical pressure value Fb on the other side of the pinch roller is calculated in reverse using the ILNL function. The ILNL function is calculated as follows: ， in: F(Z') – The theoretical pressure value Fb that needs to be solved; X n-1 X n —The (n-1)th and nth pressure values ​​in the stiffness array; Y n-1 Y n —The (n-1)th and nth roll gap values ​​in the stiffness array; Z'—The actual roll gap value Gm, which satisfies the following condition: Y n-1 <Z'≤Y n .

5. A control method for automatically leveling the pinch rollers to ensure roll shape according to any one of claims 1-4, characterized in that: In step S4, the theoretical pressure value Fb is safely limited using the LMT function; specifically, the theoretical pressure value Fb is limited to G. 设 If the value exceeds the range of (1±X%), then execute G. 设 * (1 ± X%), thus obtaining the final execution pressure value G on the other side. 执 ; The LMT function is described below: ， in: p(Fb) — The execution pressure value G that needs to be solved. 执 ; Fb—Theoretical pressure value; G 设 —Set pressure value for one side.

6. The control method for automatically leveling the pinch rollers to ensure roll shape according to claim 5, characterized in that: The value of x% ranges from 5% to 25%.

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