A method for controlling thin gauge plate shape of a 3500mm plate mill

Abstract

The present application belongs to the technical field of steel rolling, and particularly relates to a method for controlling the shape of thin-gauge plates of a 3500mm plate mill. The method comprises the following steps: (1) form a coupling control interval table for automatic and manual leveling, and use the table to control the plate shape by means of automatic and manual leveling methods of RAC; (2) improve the plate rolling alignment and the stability of thin-gauge rolling by means of the control mode of alignment and stepped opening of each pass; (3) form a table of optimal tension values for each pass in the coiling stage, use the table to distribute the load of each pass in the coiling stage, correct the deviation of the head and tail of the coiling stage, and manually increase the tension value when the plate is tailing, with the tension value of the last pass being increased to 11N / mm 2 The present application can reduce the deviation of the tail after the tension loss of the limit thin steel plate during rolling, control the full-length camber, increase the rolling stability, improve the yield of the production line, and achieve the purpose of improving quality, reducing cost and increasing efficiency for the enterprise.

Description

Technical Field

[0001] This invention belongs to the field of steel rolling technology, and particularly relates to a method for controlling the shape of thin-gauge plates in a 3500mm rolling mill for medium and heavy plates. Background Technology

[0002] The hot roll mill uses a four-roll reversible mill for controlling the size and shape of steel plates. The front and rear coiling furnaces compensate for the temperature drop during the rolling process. That is, while the steel plate is being rolled by the reversible mill, it simultaneously enters the coiling furnaces on both sides of the hot roll mill for reheating, thus rolling thick slabs into thinner steel plates. However, thin and wide products have a large amount of warping and are difficult to shape control, often resulting in unplanned production line issues and frame scraping due to improper shape control.

[0003] Misalignment or poor shape of the steel plate at the beginning and end can easily lead to collisions between the plate head and the pusher, or even prevent the plate from entering the coiling furnace, causing operational malfunctions in the steel rolling process and ultimately interrupting production. This is a major reason for the poor stability of current hot-rolled coil mills. However, most current methods for adjusting plate shape rely on manual leveling by operators, which cannot promptly and accurately correct plate misalignment, thus forcing production stoppages. This significantly reduces the yield rate and mill utilization rate, and results in a substantial waste of additional human and material resources. Therefore, solving the plate shape control problem in hot-rolled coil mills has become an urgent issue for production line development.

[0004] The 3500mm medium-thick plate rolling mill is mainly used for rolling small batches of high-grade, thin-gauge medium-thick plates. Its main characteristic is the "flat rolling + coil rolling" rolling mode. In the early stages of rolling, when the plate thickness is relatively thick, a full longitudinal rolling mode is used. When the intermediate slab thickness is ≤25mm, the plate undergoes reversible rolling between the mill and the front and rear coiling furnaces. The front and rear coiling furnaces serve to keep the plate warm and reduce temperature drop. Compared to ordinary medium-thick plate rolling mills, it is more suitable for rolling thin-gauge, high-performance steel plates with narrow process windows. Its main rolling specifications are 3.5mm~50mm and widths of 1500mm~3250mm, offering unique advantages for rolling thin-gauge medium-thick plates. However, because the coil rolling process involves the plate's head and tail alternately remaining outside the coiling furnace, the head and tail temperatures are low, deformation resistance is high, the plate shape is poor, and deviation and tailing are severe, leading to reduced rolling stability. Summary of the Invention

[0005] The purpose of this invention is to provide a method for controlling the shape of thin-gauge plates in a 3500mm rolling mill for medium-thick plate furnace coils, so as to solve the problems existing in the prior art.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for controlling the shape of thin-gauge plates in a 3500mm rolling mill for medium-thick plate, comprising the following steps:

[0007] (1) Develop a coupled control interval table for automatic and manual leveling, and control the plate shape by means of automatic and manual leveling using RAC based on this table;

[0008] (2) Improve the stability of steel plate rolling centering and thin-gauge rolling by controlling the centering and stepped opening of each pass;

[0009] (3) Formulate the optimal tension value table for each pass in the rolling stage, and use it to distribute the load of each pass in the rolling stage. Correct the deviation at the beginning and end of the rolling stage, and manually increase the tension value when the steel plate is thrown off the end. The tension value of the last pass is increased to 11N / mm².

[0010] Furthermore, in step (1), the method of automatic and manual leveling of RAC refers to adjusting the extension of HGC cylinder in an automatic and manual coupled manner according to the deviation of rolling force on both sides of the mill by the RAC control system. This makes the roll gap on the side with greater rolling force relatively smaller and the roll gap on the other side relatively larger, so as to keep the rolls parallel, eliminate the camber of the slab, and make the rolled plate straight. The normal adjustment value during automatic leveling is ±0.5mm, and the upper limit adjustment value is ±0.8mm.

[0011] Furthermore, in step (2), the centering control method for each pass is that the steel plate is centered and clamped with force before rolling in each pass of the flat rolling stage.

[0012] The step-by-step opening control method is to formulate a running clearance setting table between the pusher and the steel plate, and adjust the running clearance between each pusher and the steel plate based on this table. The opening degree of the pusher in the flat rolling stage is the slab width + 5mm, and the opening degree of each pass in the coil rolling stage is the slab width + 5~80mm.

[0013] Furthermore, during each centering pass, the clamping force of the pusher on the slab is 400KN, and the centerline deviation is ≤10mm.

[0014] Furthermore, the step-by-step opening control method also includes automatically opening the opening of the small pusher and the two large pushers after the last pass of the rolling mill to the maximum value.

[0015] Furthermore, in step (3), the method for correcting the deviation at the head and tail of the rolling stage is to increase or decrease the tension value according to the wave shape of the steel plate. For the waves on both sides of the steel plate, the actual tension value is increased, and for the waves in the middle, the actual tension value is decreased. The increase or decrease of the tension value each time is controlled within 0.1 N / mm².

[0016] The present invention has the following beneficial effects:

[0017] The system employs a combined automatic and manual leveling method, increasing the control of centering and stepped opening in each pass to improve steel plate alignment and enhance the accuracy of RAC automatic leveling, thereby improving the stability of thin-gauge rolling. During the steel ejection process in the coiler furnace, the tension value between the coiler furnace and the coil mill is increased to reduce tail-end deviation and overall camber control after steel plate de-tensioning, increasing rolling stability and production line yield, thus achieving the company's goals of quality improvement, cost reduction, and efficiency enhancement. Stable batch production of 6mm and below specifications has been achieved, with a significant improvement in the first-pass yield rate from 70% to 82%, and further improvements will be made based on actual production conditions. Currently, the monthly coil rolling ratio has increased from a maximum of 15% to 60%; the monthly stable rolling output of ≤7mm thin-gauge products has increased from an average of 5,000 tons per year to 35,000 tons, <10mm specifications have stabilized at 70,000 tons, and the annual output of <8mm specifications has reached 300,000 tons. Stable rolling of high-performance steel plates with narrow tolerance bands, including 4mm (0~0.2) and 5mm (0~0.2) luxury cruise ship steel, 5mm 9Ni steel, oil tank steel, wear-resistant L1 steel, and 4mm and 5mm Bess steel, has been achieved. The company has also successfully rolled products in extreme order specifications of 4*3000mm. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] Example 1:

[0020] A method for controlling the shape of thin-gauge plates in a 3500mm rolling mill for medium-thick plate hot rolling, characterized by comprising the following steps:

[0021] (1) Establish a coupled control interval table for automatic and manual leveling, and control the slab shape using the RAC automatic and manual leveling method based on this. The RAC automatic and manual leveling method refers to adjusting the extension of the HGC cylinder in an automatic and manual coupled manner according to the deviation of the rolling force on both sides of the mill, so that the roll gap on the side with greater rolling force becomes relatively smaller and the roll gap on the other side becomes relatively larger, in order to maintain the parallelism of the rolls, eliminate the camber of the slab, and make the rolled slab shape straight. The normal adjustment value during automatic leveling is ±0.5mm, that is, the adjustment range is -0.5~0.5mm in normal mode; the high limit adjustment value is ±0.8mm, that is, the adjustment range is -0.8~0.8mm in high limit mode. The coupled control interval table for automatic and manual leveling is shown in Table 1 and Table 2:

[0022] Table 1: Coupling Control Intervals for Automatic Leveling

[0023] <1000 2563 [1000~2000] 2876~3132 (2000~3000] 3207~3268 (3000~4000] 3132 (4000~5000] 3268 (5000~6000] 2876~3030 >6000 3348

[0024] Rolling force deviation is the deviation of rolling force between the drive side and the operating side of the mill, measured by a piezomagnetic pressure sensor on the top of the mill stand during the rolling process. The adjustment modulus of RAC is the rolling force difference in kN required for every 1mm adjustment. The RAC control system adjusts the modulus to a preset value or range based on the rolling force deviation on both sides of the mill, and then manually adjusts it further.

[0025] Table 2: Coupling Control Intervals for Manual Leveling

[0026] ≤1000 -0.4~0.4 (1000，2000) -0.3~0.3 [2000，3000) -0.2~0.2 [3000，4000) -0.1~0.1 [4000，5000) -0.1~0.1 [5000~6000] -0.06~0.06 >6000 -0.06~0.06

[0027] Table 2 records the manual leveling intervals corresponding to different rolling force deviation ranges. During manual leveling, the rolling force deviation on both sides of the mill is manually adjusted within a certain range. For example, when the rolling force difference is within the range of (1000, 2000), manual leveling is performed within the range of -0.3 to 0.3.

[0028] (2) Improve the rolling stability of thin gauges by controlling the centering and stepped opening of each pass.

[0029] The centering control method for each pass is as follows: before rolling, the steel plate is centered and clamped with force in each pass of the flat rolling stage. The clamping force of the pusher on the slab is 400kN, and the centerline deviation is ≤10mm. Centering in each pass is aimed at the shape control of the plate in the early stage of thin specification rolling, namely the flat rolling stage, to improve the rolling stability of thin specification coil rolling stage.

[0030] The step-by-step opening control method involves creating a table for setting the running clearance between the pusher and the steel plate, and adjusting the running clearance between each pusher and the steel plate based on this table. The specific adjustment parameters are shown in Table 3.

[0031] Table 3: Setting of running clearance between the pusher and the steel plate

[0032] Operating clearance value of the feed pusher of the front coiler furnace 5 80 Operating clearance value of the large pusher bed at the post-coiling furnace 5 80 The running clearance value of the small pusher bed before the rolling mill 5 5~50 Backlash value of small pusher after rolling mill 5 5~50

[0033] In the flat rolling stage, the opening degree of the pusher bed is the slab width + 5mm. In the coil rolling stage, the opening degree of each pass is the slab width + 5~80mm. In the last pass, the opening degree of the small pusher bed and the two large pusher beds after the mill are all automatically opened to the maximum value. This ensures that the steel plate is straight and without S-bends before coiling, which is beneficial for the shape control when coiling thin specifications.

[0034] For example, in the flat rolling stage, the slab width is 3000mm and the opening degree of the flat rolling pass is 3005mm. In the coil rolling stage, the slab width is 3000mm and the opening degree of the coil rolling pass is 3005~3080mm.

[0035] (3) Develop an optimal tension value table for each pass in the rolling stage, and use it to distribute the load for each pass in the rolling stage. Correct the deviation at the beginning and end of the rolling stage, and manually increase the tension value when the steel plate is discarded. The tension value of the last pass is increased to 11 N / mm². The method of correcting the deviation at the beginning and end of the rolling stage is to increase or decrease the tension value according to the waviness of the steel plate. Increase the actual tension value for waviness on both sides of the steel plate, and decrease the actual tension value for waviness in the middle. The increase or decrease of the tension value each time is controlled within 0.1 N / mm².

[0036] Table 4 shows the optimal tension values ​​for each thickness layer during the rolling stage.

[0037] Table 4: Optimal Tension Values ​​for Each Pass in the Rolling Stage

[0038] (14~20] 5~7 (10~14] 6~8 (8~10] 7.5~9 (6.5~8] 9~10 [3.5~6.5] 11

[0039] As shown in Table 4, the load of each pass is distributed according to the principle of equal convexity.

[0040] The tension control principle is as follows: The secondary CTES tension model calculates the tension setpoint for the coiling furnace hub, with separate tension setpoints for the hubs before and after the machine. The primary controller performs tension control, calculating the torque applied to the hub motor to generate appropriate tension on the strip. The secondary controller sends the tension setpoint and the steel plate bending stress to the primary controller, which then converts the tension setpoint and tension loss into a torque setpoint and sends it to the coiling furnace drive system. Tension loss includes steel plate bending loss, acceleration / deceleration loss, and friction loss. Because tension has a corrective effect, when the strip is about to be ejected from the coiling furnace at the tail end, the operator manually increases the steel plate tension value to balance the tension difference between the drive side and the operating side, thus preventing tail-end deviation.

[0041] Example 2:

[0042] Taking rolled steel grade AH36 with specifications of 6mm*3100mm as an example:

[0043] Billet specifications: thickness*width*length 150mm*3100mm*4310mm. The rolling process is 6 passes for flat rolling and 5 passes for coil rolling (6+5 rolling mode), totaling 11 passes, to produce a finished steel plate with dimensions of 6.1mm*3100mm*106mm. The thickness of the upper coil is fixed at 21~22mm. The load is distributed across each pass according to the principle of proportional crown, as shown in Table 5 below.

[0044] Table 5: Load Allocation Table for Each Track

[0045] Export thickness (mm) 120 91 66 47 31 21 15 11 8.5 7 6

[0046] For the first to third passes, the RAC module value is set to 2876~3132kn / mm, and the RAC motion amplitude range is set to the "high limit" mode, i.e. ±0.8mm; the manual leveling value is in the range of -0.4~0.4mm, and the "pass centering function" is activated; the centering gap value of each of the four pushers is set to 5mm for each pass.

[0047] For passes 4 to 6, the RAC module value is set to 2876~3132kn / mm, the manual leveling value is in the range of -0.2~0.2mm, and the RAC action amplitude range is selected in the "high limit" mode, i.e. ±0.8mm; when the "pass centering function" is put into use, the gap value of the two small pushers in passes 4 to 6 is set to 5mm, and the running gap value of the two large pushers is 5mm.

[0048] For the 7th and 8th passes, the RAC modulus values ​​are set to 3207 and 3268 kN / mm respectively, and the RAC action amplitude range is set to the "high limit" mode, i.e., ±0.8mm; the manual leveling value is in the range of -0.1~0.1mm, and the "pass centering function" is disabled; the running clearance value of the two small pushers in the 7th and 8th passes is set to 5mm; the running clearance value of the two large pushers is 80mm. When throwing steel at the tail, the unit tension is manually increased to 5~7N / mm in the 7th pass and to 6~8N / mm in the 8th pass.

[0049] For the 9th pass, the RAC modulus value is set to 3132 kN / mm, and the RAC action amplitude range is selected as "normal" mode, i.e., ±0.5mm; the manual leveling value is in the range of -0.1~0.1mm, and the "pass centering function" is disabled. The pusher bed running gap value is set as follows: 5mm for the small pusher bed in front of the mill and 10mm for the small pusher bed behind the mill; the running gap value of the two large pushers remains unchanged at 80mm, and the tail unit tension value is manually increased to 7.5~9N / mm² when throwing steel.

[0050] For the 10th pass, the RAC modulus value is set to 3030 kN / mm, and the RAC action amplitude range is set to "normal" mode, i.e., ±0.5 mm. The manual leveling value is in the range of -0.06~0.06 mm, and the "pass centering function" is disabled. The pusher bed running gap value is set to 10 mm for the small pusher bed in front of the mill and 20 mm for the small pusher bed behind the mill. The "pinch roll tail correction" function is activated. When throwing steel, the tail unit tension value is manually increased to 9~10 N / mm², and the bending roll force value is manually reduced to between 1000~1300 kN to avoid the occurrence of mid-waves and prevent tail deviation.

[0051] The 11th pass is the last pass, also known as the finishing pass. Based on the rolling force deviation range, the RAC modulus value is set to 2876~3030 kN / mm, and the RAC action amplitude range is set to "normal" mode, i.e., ±0.5mm. The manual leveling value is in the range of -0.06~0.06mm, and the "pass centering function" is disabled. Pusher bed running clearance value: the running clearance value of the small pusher bed in front of the mill is set to 20mm. The small pusher bed and the two large pusher beds behind the mill are all automatically opened to the maximum value of 3500mm. When throwing the steel, manually increase the unit tension value at the tail to 11N / mm², and manually reduce the bending roll force value to between 500~1000kN to avoid the occurrence of central waves and prevent tail deviation.

[0052] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the inventive concept should fall within the protection scope of the present invention.

[0053] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for controlling the shape of thin-gauge plates in a 3500mm rolling mill for medium-thick plate, characterized in that, Includes the following steps: (1) Develop a coupled control interval table for automatic and manual leveling, and control the plate shape by means of automatic and manual leveling using RAC based on this table; (2) Improve the stability of steel plate rolling centering and thin-gauge rolling by controlling the centering and stepped opening of each pass; (3) Develop an optimal tension value table for each pass in the rolling stage, and use it to distribute the load for each pass in the rolling stage. Correct the deviation at the beginning and end of the rolling stage, and manually increase the tension value when the steel plate is discarded. The tension value of the last pass is increased to 11 N / mm. 2 ; The automatic and manual leveling method of RAC mentioned in step (1) refers to adjusting the extension of the HGC cylinder in an automatic and manual coupled manner according to the deviation of the rolling force on both sides of the mill by the RAC control system. This makes the roll gap on the side with greater rolling force relatively smaller and the roll gap on the other side relatively larger, so as to keep the rolls parallel, eliminate the camber of the slab, and make the rolled plate straight. The normal adjustment value during automatic leveling is ±0.5mm, and the upper limit adjustment value is ±0.8mm. The centering control method for each pass in step (2) is that the steel plate is centered and clamped with force before rolling in each pass of the flat rolling stage. The step-by-step opening control method is to formulate a running clearance setting table between the pusher and the steel plate, and adjust the running clearance between each pusher and the steel plate based on this table. The opening degree of the pusher in the flat rolling stage is the slab width + 5mm, and the opening degree of each pass in the coil rolling stage is the slab width + 5~80mm.

2. The method for controlling the shape of thin-gauge plates in a 3500mm rolling mill for medium-thick plate according to claim 1, characterized in that, During each centering pass, the clamping force of the pusher on the slab is 400KN, and the centerline deviation is ≤10mm.

3. The method for controlling the shape of thin-gauge plates in a 3500mm rolling mill for medium-thick plate according to claim 1, characterized in that, The step-by-step opening control method also includes automatically opening the opening of the small pusher and the two large pushers after the last pass of the rolling mill to the maximum value.

4. The method for controlling the shape of thin-gauge plates in a 3500mm rolling mill for medium-thick plate according to claim 1, characterized in that, The method for correcting the head and tail of the rolling stage in step (3) is to increase or decrease the tension value according to the wave shape of the steel plate. For the waves on both sides of the steel plate, the actual tension value is increased, and for the waves in the middle, the actual tension value is decreased. The increase or decrease of the tension value each time is controlled within 0.1 N / mm².