An effective method for solving the problem of head and tail indentation in hot rolling coiling

Abstract

The present invention discloses an effective method for solving the problem of head and tail indentation in hot rolling coiling, which includes the following steps: calculating the strip head tracking by using the loading feedback signals of the cold metal detector, pinch rolls and coiling rolls, and performing a rhythmic and regular head pressure avoidance action according to the head tracking data. This avoidance action is different from the traditional pressure control and stepping control, but is a head pressure avoidance function realized by the rhythmic and regular change of the given value of the coiling roll pressing force in the full head pressure control mode; calculating the strip tail tracking by using the above-mentioned various feedback signals, and calculating the final pressing position of the coiling roll according to the estimated coiling thickness; controlling the coiling roll to press against the strip surface according to the strip tail tracking. The pressing process mainly maintains a high speed, but finally presses against the strip surface at a low speed to achieve light pressure and avoid generating indentation. The present invention solves the problem of indentation existing in hot rolling coiling by improving the control measures, and effectively eliminates the head indentation in hot rolling coiling.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical hot-rolled strip coiler control, and in particular to an effective method for solving the problem of indentation marks at the head and tail of a hot-rolled coiler. Background Art

[0002] The leading product of Baosteel Rare Earth Steel Plate Company's 2250mm hot-rolled products is high-quality rare earth hot-rolled coils. The slabs are sent to the slab warehouse of the hot rolling workshop by rollers and straddle cars. After heating, rolling, coiling, bundling, marking and weighing, the steel coils are transported to the hot rolling coil warehouse and the cold rolling raw material warehouse by the steel coil transportation system.

[0003] The main products are high-quality automobile steel, structural steel, pipeline steel, ship plate steel, etc., which give full play to the characteristics of large rolling capacity, complete equipment configuration and control measures of the rolling mill to produce high value-added hot-rolled dual-phase steel (DP), multi-phase steel (MP), phase transformation induced plasticity steel (TRIP), and high-strength pipeline steel (X100). The main features of the products are concentrated in high strength, high precision, high surface quality and thin specifications. The maximum tensile strength of the product is 1200N / mm 2 .

[0004] When coiling the tail, the tail pressing function of the auxiliary roll makes the tail of the strip roll tighter to prevent the tail from loosening. However, when the auxiliary roll presses the tail and contacts the steel coil, a pressure peak will be generated. Excessive pressure will not only damage the mechanical equipment, but also cause surface defects at the tail of the strip and produce indentations of the auxiliary roll.

[0005] Hot-rolled thin strip is also an important source of cold rolling mill materials. Customers of cold-rolled plates have continuously improved their requirements for the surface quality of the plates. The indentation of steel coils has been repeatedly raised as a major quality defect. At the same time, the indentation problem of thin hot-rolled strip steel has caused strip breakage accidents, large amounts of cutting losses, and low yield rates, which have had a huge impact on the cold rolling process and become a bottleneck problem restricting the company's production. After long-term use and debugging, the original constant pressure mode and step control mode cannot effectively solve the problem of head indentation of hot-rolled thin strips.

[0006] In recent years, many companies in the metallurgical steel rolling industry have made some major progress in tackling the indentation problem, but none of them have been able to completely solve the head and tail indentation problem.

[0007] Patent CN 103223420A discloses "A method and system for controlling the inner ring indentation of hot-rolled steel coils". A coiling temperature measuring device is set in front of the coiling unit. The primary computer is provided with a coiling torque setting unit, a coiling torque feedback unit, a delay setting unit and a delay timer. The coiling torque is calculated and set according to the coiling torque parameters of the strip steel, the pressurizing delay time of the coiling roll is set according to the slipping characteristic parameters of the strip steel, and the pressurizing delay timing is started when the set coiling torque is reached. When the delay ends, the coiling roll is opened to stop pressurizing, so as to minimize the pressure and time of the coiling roll in contact with the strip steel. The coiling torque parameters are preferably the width, thickness and thermal yield strength of the strip steel. The slipping characteristic parameters are preferably the width, coiling temperature and thickness of the strip steel. The disadvantage is that this solution shortens the pressurizing time of the coiling roll on the outer surface of the strip steel, weakens the pressing function of the coiling roll for assisting coiling, and at the same time does not consider the impact problem caused by inaccurate head tracking of the strip steel, and the analysis of the reasons for eliminating indentation is not deep enough, and the indentation cannot be eliminated fundamentally.

[0008] Patent CN 105665452A discloses "A method for eliminating the head indentation of hot-rolled strip steel". Using load correction, when the head of the strip steel is in the first coil, the head tracking is corrected when passing through the pinch roll and three coiling rolls in sequence. The correction formula is S = V * t + Sx, where S is the head tracking distance, V is the strip steel speed, t is the running time, and Sx is the distance correction value, and Sx is 30, 35, 37, 40, 41 or 43. The disadvantage is that this compensation correction method does not consider that in actual production, the force value feedback signal sometimes fluctuates due to accidental impacts, resulting in incorrect correction tracking.

[0009] Patent CN 104874639A discloses "A dynamic control method for the roll gap of the coiling roll of a coiler". According to the steel grade, thickness and temperature of the strip steel, on the premise of ensuring no slipping accident, the coiling roll is kept at a relatively light set pressure, and the roll gap of the coiling roll is controlled to be dynamically opened synchronously with the increase of the coiling layer and the expansion of the coiler barrel, so that the inner ring arc indentation defect of all thickness hot-rolled steel coils is always kept at a relatively light level. The disadvantage is that the set value of the coiling roll jumping open completely depends on calling the static parameter table, without considering that in actual production, due to the influence of equipment accuracy, strip steel yield strength and material characteristics, there is a large deviation from the feedback, the control method is rigid, and there is no closed loop. Summary of the Invention

[0010] The purpose of the present invention is to provide an effective method for solving the head and tail indentation problems of hot-rolled coiling, and by improving the control measures, solve the indentation problem existing in hot-rolled coiling and effectively eliminate the head indentation of hot-rolled coiling.

[0011] To solve the above technical problems, the present invention adopts the following technical solutions:

[0012] An effective method for solving the problem of head and tail indentation in hot rolling coiling includes the following steps:

[0013] (1) According to the above technical background, using the loading feedback signals of the cold metal detector, pinch roll, and coiling roll, calculate the strip head tracking, and perform a rhythmic and regular head pressure avoidance action based on the head tracking data. This avoidance action is different from traditional pressure control and stepping control. Instead, in a full head pressure control mode, the given value of the coiling roll pressing force changes rhythmically and regularly to achieve the head pressure avoidance function.

[0014] (2) Using the above-mentioned various feedback signals, calculate the strip tail tracking, and calculate the final pressing position of the coiling roll according to the estimated coiling thickness; according to the strip tail tracking, control the coiling roll to press against the coiled surface. The main body of this pressing process maintains a high speed, but finally approaches the coiled surface at a low speed to achieve a light pressure and avoid generating indentations. The high speed and low speed mentioned here are relative concepts. Generally, the high speed during testing is above 150 mm / s, and the low speed generally refers to within 40 mm / s. In actual production, it is not completely restricted by this range. As long as the high and low speeds are separately controlled to achieve a light pressure of the coiling roll on the strip tail surface and effectively eliminate the indentations.

[0015] Further, the specific steps of step (1) include: when the strip head passes by, the cold metal detector is triggered by the detected temperature rise, and starts cumulative counting from the current position as the basic parameter for strip head tracking counting. The cumulative speed is the real-time speed of the strip, that is, TRKHEAD = 0 + a*V + compensation parameter combination; since the relative positions of the cold detector, pinch roll, and coiling roll are fixed measurement parameters, when the strip head passes through the pinch roll and coiling roll in sequence, the torque loading rise feedback signals detected by the drive systems of the pinch roll and coiling roll are used to further correct and calculate the strip head tracking. At the same time, the coiling roll performs a rhythmic and regular head pressure avoidance action according to the head tracking data.

[0016] Further, the specific steps of step (2) include: before the coiler finishes winding, the coiling roll remains open in the waiting position, with sufficient reserved space from the outer surface of the coil, in the range of 80 - 200 mm; using the above-mentioned various signals, referring to the head tracking calculation principle, calculate the strip tail tracking. When the tracking value reaches the preset value for holding the tail, execute the holding tail timing sequence, and the coiling roll presses tightly against the steel coil. And according to the estimated coiling diameter D of the steel coil of this model in the parameter table minus the diameter d of the mandrel at this time and then divided by 2, calculate the final estimated pressing roll gap of the coiling roll GAP pre = (D - d) / 2. Add the low speed setting length S to GAP pre to obtain the deceleration critical point GAP low speed; in the holding tail control, the coiling roll gradually presses against the coiled surface. The main body of this pressing process maintains a high speed. When the roll gap feedback reaches the deceleration critical point GAP low speed, it approaches the coiled surface at a low speed to achieve a light pressure and avoid generating indentations.

[0017] Furthermore, the coiling of the strip head adopts the pressure control mode of the coiling rolls until the calculated coiling turns reach the set turns for the opening of the coiling rolls, and then the three coiling rolls switch from pressure control back to position control.

[0018] Furthermore, according to the tracking data calculation, predict the timing when the strip head is about to arrive each time, and implement the avoidance action of the coiling rolls. This avoidance action does not switch to position control and still maintains pressure control. Only the set force value is changed, making the set force value during avoidance significantly smaller than the set force value during pressing, so as to achieve avoiding the impact of the strip head and thus eliminate the indentation.

[0019] Furthermore, the set force value of the coiling rolls during pressure avoidance adopts the method of calling parameters. The pressure settings during each pressing are X1, X2, X3, X4, X5... in sequence, and the pressure settings during each avoidance are Y1, Y2, Y3, Y4, Y5... in sequence, where X > Y; the set force value of the coiling rolls during pressure avoidance uses the set force value during pressing as X and the avoidance set force value as Y, and Y = αX, where 1 > α ≥ 0.

[0020] Furthermore, adopt the front correction method for pinch roll head tracking, that is, when the strip head passes through the pinch roll, the pinch roll triggers the loading signal through force value feedback; compare the accumulated tracking value SPR at this time with the size of the actual measured distance a from CMD to the pinch roll, and select the larger value; calculate the absolute value of the difference between SPR and a. If this absolute value is less than or equal to a certain protection range, correct the head tracking with the previously selected larger value, otherwise do not correct.

[0021] Furthermore, adopt the first turn tracking correction method for the coiling rolls. Taking the first coiling roll as an example, when the strip head reaches the first coiling roll, trigger the loading signal of the first coiling roll through force value feedback; compare the accumulated tracking value SWR1 at this time with the size of the actual measured distance b from CMD to the first coiling roll, and select the larger value; calculate the absolute value of the difference between SWR1 and b. If this absolute value is less than or equal to a certain protection range, correct the head tracking with the previously selected larger value, otherwise do not correct. The same applies to the second and third coiling rolls.

[0022] Furthermore, take the measure of gently pressing the tail to effectively control the indentation of the strip tail. That is, when the strip tail passes through the tracking trigger node, the coiling rolls start to approach the mandrel direction at high speed. Calculate the expected final coil radius R according to the strip tracking. Obtain the expected final gap Gap expected between the coiling rolls by subtracting the mandrel expansion radius r from R. When the actual feedback gap Gap actual - Gap expected ≤ the light pressing distance L, let the coiling rolls switch from high speed to low speed and continue to approach the mandrel direction. When the coiling rolls press against the strip surface and the feedback force value reaches the set threshold, the coiling rolls switch to the force control mode and the tail light pressing function ends;

[0023] Take the measure of gently pressing the tail to effectively control the indentation on the tail of the strip. That is, when the tail of the strip passes through the tracking trigger node, the coiling roll starts to approach the mandrel at high speed in the axial direction. Calculate the expected final coil radius R based on strip tracking. Obtain the expected final coiling roll gap Gap_estimated by subtracting the mandrel expansion radius r from R. When the actual feedback gap Gap_actual - Gap_estimated ≤ the light pressing distance L, let the coiling roll switch from high speed to low speed and continue to approach the mandrel in the axial direction. When the coiling roll presses against the strip surface and the feedback force value reaches the set threshold, the coiling roll switches to the force control mode and the tail light pressing function ends.

[0024] Furthermore, the main device used in this method is the hot rolling coiling machine control system, which includes a mandrel part, a pinch roll part, and a coiling roll part. Among them, the mandrel part is equipped with a position sensor for detecting the diameter, and the coiling roll part is equipped with a pressure sensor for detecting the load and a position sensor for detecting the position. The feedback values of the sensors are used for tracking calculation, and then the timing reference is calculated in real time through the tracking data to gradually carry out the coiling control. Its characteristic lies in adopting the measure of gently pressing the tail to effectively control the indentation on the tail of the strip.

[0025] Furthermore, when the tail of the strip passes through the tracking trigger node, the coiling roll starts to approach the mandrel at high speed in the axial direction. Calculate the expected final coil radius R based on strip tracking. Obtain the expected final coiling roll gap Gap_estimated by subtracting the mandrel expansion radius r from R. When the actual feedback gap Gap_actual - Gap_estimated ≤ the light pressing distance L, let the coiling roll switch from high speed to low speed and continue to approach the mandrel in the axial direction; when the coiling roll presses against the strip surface and the feedback force value reaches the set threshold, the coiling roll switches to the force control mode and the tail light pressing function ends.

[0026] Compared with the prior art, the beneficial technical effects of the present invention are:

[0027] For the coiling control system of hot-rolled strip using the effective method of the present invention to solve the problem of head and tail indentation in hot rolling coiling, before implementation, the head and tail indentation of the raw material was relatively severe, the indentation depth was relatively deep, and there was an obvious tactile sensation. The average proportion of head and tail cutting losses at the entrance of pickling and cold rolling in March and April was 1.32%. In May, research on head and tail indentation was carried out. After the measures were implemented, the indentation was significantly improved. The pickling and cold rolling section tried to shorten the head and tail shearing length of the test coil. The proportion of head and tail cutting losses at the entrance of pickling and cold rolling in May was 1.15%. On June 17th, after further optimizing the measures for research on head and tail indentation, they were solidified in the first-level program. The pickling and cold rolling section continued to reduce the head and tail shearing amount at the entrance. The proportion of head and tail cutting losses at the entrance of pickling and cold rolling in June decreased to 1.09%. See Figure 7 as shown in Fig. 7b. Description of the Drawings

[0028] The present invention will be further described below in conjunction with the description of the drawings.

[0029] Figure 1 It is the uncoiling diagram of the head indentation of the thin strip;

[0030] Figure 2 Uncoiling diagram of the indentation at the head of the thin strip

[0031] Figure 3 Flow chart of the avoidance control for the head of the first coiling roll

[0032] Figure 4 Schematic diagram of head coiling

[0033] Figure 5 Head pressure control curve diagram for Scheme 1

[0034] Figure 6 Head pressure control curve diagram for Scheme 2

[0035] Figure 7 Uncoiling diagram after the indentation at the head of the thin strip is eliminated

[0036] Figure 8 Flow chart of the forward correction for head tracking Specific implementation manner

[0037] The present invention will be further described below in conjunction with specific embodiments.

[0038] An effective method for solving the problem of head and tail indentation in hot rolling coiling includes:

[0039] 1. Head tracking calculation of the strip

[0040] 1.1 Head tracking signals: Before the head of the strip leaves the finishing mill and is about to enter the coiling mill, it first passes through the hot metal detector (HMD), triggering the preparation signal PHMD; then it passes through the cold metal detector (CMD), triggering the start signal PCMD for head tracking calculation; the head of the strip passes through the pinch roll, and the pinch roll triggers the loading signal PPR through force value feedback; the head of the strip passes through the first coiling roll (WR1) for the first time, and the first coiling roll triggers the loading signal PWR1 through force value feedback; the head of the strip passes through the second coiling roll (WR2) for the first time, and the second coiling roll triggers the loading signal PWR2 through force value feedback; the head of the strip passes through the third coiling roll (WR3) for the first time, and the third coiling roll triggers the loading signal PWR3 through force value feedback. See Figure 1 as shown.

[0041] 1.2 Head tracking calculation: After the preparation signal PHMD and the start signal PCMD are triggered successively, the head tracking calculation starts to accumulate from 0. When PPR is triggered, the head tracking signal can be corrected for the first time. When PWR1 is triggered, the head tracking signal can be corrected for the second time. When PWR2 is triggered, the head tracking signal can be corrected for the third time. When PWR3 is triggered, the head tracking signal can be corrected for the fourth time.

[0042] 2. Forward correction for head tracking

[0043] 1.1 Pinch Roll (PR) Tracking Forward Correction: Before the strip head leaves the finishing mill and is about to enter the coiler, it first passes through the Hot Metal Detector (HMD) to trigger the preparation signal; then it passes through the Cold Metal Detector (CMD) to trigger the head tracking calculation; when the strip head passes through the pinch roll, the pinch roll triggers the loading signal through force value feedback; compare the accumulated tracking value SPR at this time with the actually measured distance a from the CMD to the pinch roll, and select the larger value; calculate the absolute value of the difference between SPR and a. If this absolute value is less than or equal to a certain protection range, correct the head tracking with the larger value selected previously, otherwise do not correct.

[0044] 1.2 First Turn Tracking Forward Correction of Wrapping Roll (WR): Taking the No. 1 wrapping roll as an example, when the strip head first reaches the No. 1 wrapping roll, it triggers the No. 1 wrapping roll loading signal through force value feedback; compare the accumulated tracking value SWR1 at this time with the actually measured distance b from the CMD to the No. 1 wrapping roll, and select the larger value; calculate the absolute value of the difference between SWR1 and b. If this absolute value is less than or equal to a certain protection range, correct the head tracking with the larger value selected previously, otherwise do not correct. The same applies to the No. 2 and No. 3 wrapping rolls. See Figure 8 as shown.

[0045] The design principle of this correction is based on the fact that technicians believe that there is always a slightly lagging phenomenon in some strip tracking calculations, so it is necessary to correct the head tracking forward.

[0046] 3. Wrapping Roll Pressure Control

[0047] According to the head tracking calculation, PPR plus delay, and PWR1 parallel trigger, switch the No. 1 wrapping roll from position control to pressure control; according to the head tracking calculation and PWR2 parallel trigger, switch the No. 2 wrapping roll from position control to pressure control; according to the head tracking calculation and PWR3 parallel trigger, switch the No. 3 wrapping roll from position control to pressure control. The pressure control mode of the three wrapping rolls will be maintained until the coiling turns (obtained from the head tracking calculation) reach the opening set turns of the wrapping roll, and the three wrapping rolls are switched back from pressure control to position control. See Figure 4 as shown.

[0048] According to the tracking data calculation, predict the timing when the leading end is about to arrive each time and implement the wrapping roll avoidance action. This avoidance action is different from the traditional stepping control jump action, that is, it does not switch to position control and still maintains pressure control, only changing the set force value so that the set force value during avoidance is significantly less than the set force value during pressing to achieve avoiding the impact of the leading end and thus eliminating the indentation. See Figure 3 as shown.

[0049] There are various ways to give this set force value:

[0050] 2.1 You can use the method of calling parameter table 1 (X>Y). The parameter table can be further divided and refined according to the thickness, temperature, steel type, etc. of the strip; see Table 1, Figure 5 shown.

[0051] Table 1

[0052]

[0053] 2.2 The pressure setting value is X, and the avoidance setting value is Y, Y = αX, where 1>α≧0. Figure 6 shown.

[0054] 4. Strip tail tracking calculation

[0055] Before the tail of the strip leaves the finishing mill and enters the coiler, it first passes through the hot metal detector (HMD). Based on the distance parameters preset in the system and the speed of the lower feed roller or core axis at this time, the real-time tracking of the tail of the strip can be calculated.

[0056] 5. Light pressure control at the tail of the auxiliary roll

[0057] When the tail of the strip passes the tracking trigger node, the auxiliary roll begins to approach the mandrel at high speed. The estimated final coil radius R is calculated based on the strip tracking, and the estimated final auxiliary roll gap Gap is obtained by subtracting the mandrel expansion radius r from R. When the feedback roll gap actual - Gap estimated ≦ light pressure distance L, the auxiliary roll switches from high speed to low speed and continues to approach the mandrel. The auxiliary roll presses against the surface of the strip. When the feedback force value reaches the set threshold, the auxiliary roll switches to force control mode, and the tail light pressure function ends.

[0058] 6. Example Analysis

[0059] During the coiling process of hot-rolled strip, when the tail of the strip is coiled, the tail pressing function of the auxiliary winding roller makes the tail of the strip roll tighter to prevent the tail from loosening. However, a pressure peak will be generated when the auxiliary winding roller contacts the steel coil at the moment of pressing the tail. Excessive pressure will not only cause damage to mechanical equipment, but also cause surface defects at the tail of the strip and produce tail indentations. When coiling the head of a thin-gauge strip, a constant pressure mode is usually used. When the head of the strip passes through the auxiliary winding roller, an impact will occur, leaving an indentation on the outer layer of the strip. If a force control / position control alternating step control mode is used, loose coiling is likely to occur, leading to a steel pile accident. The indentation problem at the head and tail of the hot-rolled strip has caused strip breakage accidents, large amounts of cutting losses, and low yield rates, all of which have had a huge impact on the cold rolling process and have become a bottleneck problem restricting production. See Figure 2 As shown in a.2b.

[0060] This invention was implemented on the 2250mm hot rolling production line of Baosteel Group Rare Earth Steel Plate Company in May 2022.

[0061] Before implementation, the indentation degree at the head and tail of the raw material was relatively heavy, the indentation depth was relatively deep, and there was an obvious tactile sensation. The average proportion of head and tail cutting losses at the entrance of the pickling and cold rolling process in March and April was 1.32%. In May, efforts were made to tackle the problem of head and tail indentation. After the implementation of the measures, the indentation was significantly improved. The pickling and cold rolling process tried to shorten the cutting length of the head and tail of the test coil. The proportion of head and tail cutting losses at the entrance of the pickling and cold rolling process in May was 1.15%. On June 17, after further optimization, the measures to tackle the problem of head and tail indentation were solidified in the first-level program. The pickling and cold rolling process continued to reduce the head and tail shearing amount at the entrance. The proportion of head and tail cutting losses at the entrance of the pickling and cold rolling process in June was reduced to 1.09%. See Figure 7 as shown in Fig. 7b.

[0062] Calculated based on the hot-rolled raw material price of 3,800 yuan / ton, the scrap steel price of 2,700 yuan / ton, and the average monthly output of the pickling and cold rolling process of 158,000 tons:

[0063] (Proportion of original cutting losses - Proportion of current cutting losses) * Average monthly output * (Raw material price - Scrap steel price) = (1.32% - 1.09%) * 158,000 * (3,800 - 2,700) ≈ 399,700 yuan.

[0064] Approximately 399,700 yuan of economic losses were recovered in June.

[0065] 399,700 * 12 ≈ 4,797,000 yuan.

[0066] Approximately 4,797,000 yuan of economic losses were recovered in one year.

[0067] The embodiments described above are only used to describe the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. An effective method for solving the problem of head and tail indentation in hot rolling coiling, characterized in that: It includes the following steps: (1) Utilize the loading feedback signals of the cold metal detector, pinch roll, and coiling roll to calculate the strip head tracking, and perform a rhythmic and regular head pressure avoidance action based on the head tracking data. This avoidance action is different from traditional pressure control and stepping control. Instead, it is a rhythmic and regular change in the given value of the coiling roll pressing force under the full head pressure control mode to achieve the head pressure avoidance function; (2) Utilize the above-mentioned various feedback signals to calculate the strip tail tracking, and calculate the final pressing position of the coiling roll according to the estimated coiling thickness; control the coiling roll to press against the strip surface according to the strip tail tracking. The main body of this pressing process maintains a high speed, but finally approaches the strip surface at a low speed to achieve light pressing and avoid generating indentations; The specific content of step (1) includes: When the strip head passes by, the cold metal detector is triggered by the detected temperature rise, and starts to accumulate from zero from the current position as the basic parameter for strip head tracking counting. The accumulation speed is the real-time speed of the strip, that is, TRKHEAD = 0 + a * V + compensation parameter combination; Since the relative positions of the cold detector, pinch roll, and coiling roll are fixed measurement parameters, when the strip head passes through the pinch roll and coiling roll in sequence, the torque loading rise feedback signals detected by the drive systems of the pinch roll and coiling roll are used to further correct and calculate the strip head tracking. At the same time, the coiling roll performs a rhythmic and regular head pressure avoidance action according to the head tracking data; The specific content of step (2) includes: Before the coiler finishes winding, the coiling roll remains open at the waiting position, with sufficient reserved space from the outer surface of the coil, in the range of 80 - 200 mm; Utilize the above-mentioned various signals, refer to the head tracking calculation principle, calculate the strip tail tracking. When the tracking value reaches the preset value for tail holding, execute the tail holding timing sequence. The coiling roll presses tightly against the steel coil, and calculate the final expected pressing roll gap GAP pre = (D - d) / 2 by subtracting the diameter d of the mandrel from the estimated coiling diameter D of this type of steel coil in the parameter table and then dividing by 2. Add the low-speed setting length S to GAP pre to obtain the deceleration critical point GAP low; In the tail holding control, the coiling roll gradually presses against the strip surface. The main body of this pressing process maintains a high speed. When the roll gap feedback reaches the deceleration critical point GAP low, it approaches the strip surface at a low speed to achieve light pressing and avoid generating indentations.

2. The effective method for solving the problem of head and tail indentation in hot rolling coiling according to claim 1, characterized in that: For the strip head coiling, the coiling roll pressure control mode is adopted until the coiling calculation number of turns reaches the coiling roll opening set number of turns, and the three coiling rolls switch back from pressure control to position control.

3. The effective method for solving the problem of head and tail indentation in hot rolling coiling according to claim 1, characterized in that: According to the tracking data calculation, predict the timing when each strip head is about to arrive, and implement the coiling roll avoidance action; This avoidance action does not switch to position control, but still maintains pressure control. Only the set force value is changed, making the set force value during avoidance significantly smaller than the set force value during pressing to achieve avoiding the impact of the strip head and thus eliminating indentations.

4. The effective method for solving the problem of head and tail indentation in hot rolling coiling according to claim 1, characterized in that: When setting the force value of the coiling roll during pressure avoidance, the method of calling parameters is adopted. Each time when pressing, the pressure settings are X1, X2, X3, X4, X5... in sequence. Each time when avoiding, the pressure settings are Y1, Y2, Y3, Y4, Y5... in sequence, where X > Y. When the coiling roll presses during pressure avoidance, the set force value is X, and when avoiding, the set force value is Y, and Y = αX, where 1 > α ≥ 0.

5. The effective method for solving the problem of head and tail indentation in hot rolling coiling according to claim 1, characterized in that: Adopt the head tracking and forward correction method of the pinch roll, that is, when the head of the strip steel passes through the pinch roll, the pinch roll triggers the loading signal through force value feedback; compare the size of the accumulated tracking value SPR at this time with the distance a from the actually measured CMD to the pinch roll, and select the larger value; calculate the absolute value of the difference between SPR and a. If this absolute value is less than or equal to a certain protection range, correct the head tracking with the larger value selected previously, otherwise do not correct.

6. The effective method for solving the problem of head and tail indentation in hot rolling coiling according to claim 1, characterized in that: Adopt the first-turn tracking correction method of the coiling roll. Taking the first coiling roll as an example, when the head of the strip steel reaches the first coiling roll, the first coiling roll loading signal is triggered through force value feedback; compare the size of the accumulated tracking value SWR1 at this time with the distance b from the actually measured CMD to the first coiling roll, and select the larger value; calculate the absolute value of the difference between SWR1 and b. If this absolute value is less than or equal to a certain protection range, correct the head tracking with the larger value selected previously, otherwise do not correct; The same applies to the second and third coiling rolls.

7. The effective method for solving the problem of head and tail indentation in hot rolling coiling according to claim 1, characterized in that: Adopt the tail light pressing measure to effectively control the indentation of the strip steel tail, that is, when the tail of the strip steel passes through the tracking trigger node, the coiling roll starts to approach the mandrel direction at high speed; calculate the expected final coil radius R according to the strip steel tracking. Subtract the mandrel expansion radius r from R to obtain the expected final coiling roll gap Gap expected. When the feedback gap Gap actual - Gap expected ≤ the light pressing distance L, let the coiling roll switch from high speed to low speed and continue to approach the mandrel direction; the coiling roll presses against the strip steel surface. After the feedback force value reaches the set threshold, the coiling roll switches to the force control mode, and the tail light pressing function ends.

8. The effective method for solving the problem of head and tail indentation in hot rolling coiling according to claim 1, characterized in that: The main device adopted by this method is the hot rolling coiling machine control system, including the mandrel part, the pinch roll part, and the coiling roll part. Among them, the mandrel part is equipped with a position sensor for detecting the diameter, and the coiling roll part is equipped with a pressure sensor for detecting the load and a position sensor for detecting the position. The feedback values of the sensors are used for tracking calculation, and then the timing reference is calculated in real time through the tracking data to gradually carry out the coiling control. Its characteristic lies in adopting the tail light pressing measure to effectively control the indentation of the strip steel tail.

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