Manufacturing method for eliminating hard bending defect of head of hot rolled steel coil
By combining laminar flow cooling water spray and pinch roll gap correction with step mode and constant pressure control, the hard bending defect at the head of hot-rolled steel coils was solved, the yield and equipment life were improved, and the roundness of the inner ring was controlled.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-04
- Publication Date
- 2026-04-14
AI Technical Summary
The hard bend defect at the head of hot-rolled thick steel coils causes polygonal shapes or creases on the inner ring of the coil, affecting the yield and equipment life, and is difficult to control effectively.
The cooling length of the strip head is controlled by laminar flow cooling water spray response calibration method, the roll gap of the pinch rolls is corrected, and the winding method with step mode and constant pressure control is adopted to eliminate the hard bending defect at the head of hot rolled steel coil.
It effectively controls the out-of-roundness of the inner ring of steel coils, improves yield, reduces equipment impact, extends equipment service life, and solves user quality problems.
Smart Images
Figure CN121847597A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of strip rolling, and relates to a manufacturing method for eliminating the head hard bend defect of hot-rolled steel coils. Background Art
[0002] The phenomenon of "hard bend" at the head of hot-rolled thick-gauge steel coils is an industry problem. Generally, when thick-gauge strip steel is coiled at the head, the bending effect of the strip steel is poor, resulting in a polygon or fold mark on the inner circle of the steel coil. Generally, the defect is located in the inner 1-3 coils of the steel coil, and in severe cases, it can reach 5-6 coils. Moreover, as the plate thickness increases and the strength increases, the probability of the "hard bend" defect also increases. During the use process by users, especially for pipe production, this defect, firstly, affects the butt welding of steel pipes, and the "hard bend" position needs to be cut off or lifted by a special device; secondly, this position is flattened after pipe making, affecting the roundness of the entire steel pipe. Generally, pipe factories need to cut off the "hard bend" position in such cases, resulting in unnecessary waste, and at the same time reducing the成材率 (成材率 is not clear in the original text, assuming it should be "yield rate") and user satisfaction of users. Through on-site statistics, the average defect rate of "hard bend" in thick-gauge products is as high as 62%. Thirdly, when the steel coil is coiled at the inner circle with an excessive hard bend, due to poor roundness, it causes a large impact on the coiler equipment, not only affecting the service life of the equipment, but also leaving impact marks on the coiling rolls, which will cause periodic "indented marks" defects on the strip steel surface. Summary of the Invention
[0003] In order to solve the above problems, the technical solution adopted by the present invention is: a manufacturing method for eliminating the head hard bend defect of hot-rolled steel coils, including the following steps:
[0004] Adopt the laminar flow cooling water spray response calibration method to control the "dry head" cooling length of the hot-rolled strip steel to be coiled at the head; According to products with different thicknesses and widths, correct the pinch roll gap correction coefficient, and use the pinch rolls of the coiler after correction to coil the cooled strip steel at the head; The coiler coiling roll adopts a "stepping" mode. Based on the stepping timing tracking method, coil N circles for the part after the head has been coiled; When coiling the strip steel after N circles at M% of the set pressure, perform constant pressure control in real time, so that the coiling roll always holds the steel coil tightly with a small pressure during the coiling process of the steel coil, eliminating the head hard bend defect of the hot-rolled steel coil.
[0005] Furthermore: According to products with different thicknesses and widths, correct the pinch roll gap correction coefficient, and the specific requirements are as follows: When the width w ≤ 1800mm and the thickness is 12mm < H ≤ 16mm, the pinch roll gap correction value is: -0.4mm; When the width W > 1800mm and the thickness is 12mm < H ≤ 16mm, the pinch roll gap correction value is: -0.3mm; When the width w ≤ 1250 mm and the thickness is such that 16 mm < H ≤ 20 mm, the correction value of the pinch roll gap is: -0.6 mm; When the width 1250 mm < w ≤ 1800 mm and the thickness is such that 16 mm < H ≤ 20 mm, the correction value of the pinch roll gap is: -0.5 mm; When the width W > 1800 mm and the thickness is such that 16 mm < H ≤ 20 mm, the correction value of the pinch roll gap is: -0.3 mm; When the width w ≤ 1250 mm and the thickness is such that 20 mm < H ≤ 23 mm, the correction value of the pinch roll gap is: -0.7 mm; When the width 1250 mm < w ≤ 1500 mm and the thickness is such that 20 mm < H ≤ 23 mm, the correction value of the pinch roll gap is: -0.6 mm; When the width 1500 mm < w and the thickness is such that 20 mm < H ≤ 23 mm, the correction value of the pinch roll gap is: -0.5 mm; When the width w ≤ 1500 mm and the thickness is such that 23 mm < H ≤ 25.4 mm, the correction value of the pinch roll gap is: -0.7 mm; When the width 1500 mm < w ≤ 1800 mm and the thickness is such that 23 mm < H ≤ 25.4 mm, the correction value of the pinch roll gap is: -0.6 mm; When the width W > 1800 mm and the thickness is such that 23 mm < H ≤ 25.4 mm, the correction value of the pinch roll gap is: -0.5 mm.
[0006] Furthermore: The corrected pinch roll gap of the coiler = actual plate thickness - pinch roll gap correction value.
[0007] Furthermore: The control valve response time of the laminar cooling water spraying device is calibrated using the laminar cooling water spraying response calibration method, specifically as follows: A timer is established, which starts timing when the button is pressed and stops timing when the button is released, and the time is displayed on the screen; After obtaining the data on the screen, the data value is recorded; When the valve is opened for the first time, the response time will be 3 to 5 times the normal level, so the response result of the first valve opening is not recorded, and recording starts from the second time; Each valve is continuously tested 3 to 5 times, After removing the obvious outliers from the results of multiple tests of a single valve, the average value is taken as the basis for modifying the single valve response time parameter.
[0008] Furthermore: The value range of N is 5 - 10.
[0009] Furthermore, the requirements for determining the step height of the winding machine's auxiliary winding roller are as follows: The step height of the auxiliary winding roller must be greater than the actual thickness of the plate being wound, and the step height = actual plate thickness × 1.5. The step height must refer to the pressure curve of the auxiliary winding roller during the stepping process, and the pressure curve of the auxiliary winding roller must not jump during the stepping process.
[0010] Furthermore: M takes the value 40%.
[0011] Furthermore, the cooling length of the "dry head" of the hot-rolled strip is 300mm-400mm.
[0012] This invention provides a manufacturing method for eliminating the hard bend defect at the head of hot-rolled steel coils. This method eliminates the hard bend phenomenon in the inner ring of hot-rolled thick steel coils, improving the yield rate for users and reducing the need for secondary processing and lifting operations after pipe making. Simultaneously, it reduces the impact of the strip head on the equipment during the coiling process of thick products, extending the equipment's service life.
[0013] Through the application of the above measures, the phenomenon of hard bending at the head of hot-rolled steel coils has been effectively controlled, with significant results. Actual statistics show an effectiveness rate exceeding 97%, essentially controlling the excessive roundness of the inner coil and resolving long-standing quality complaints from users. Simultaneously, the impact of the strip head on the winding rollers has decreased from 727KN to 269KN, a reduction of 62.9%, and the service life of the winding rollers has increased by 13%. Attached Figure Description
[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0015] Figure 1 This is a flowchart of the method described in this application; Figure 2 This is a schematic diagram of the "hard bend" phenomenon at the head of hot-rolled thick steel coils; Figure 3 This is a schematic diagram of the head winding of a hot-rolled thick steel coil, where (a) is before winding and (b) is after winding. Figure 4 This is a schematic diagram showing the effect of high-temperature sections of different lengths at the head of the strip on hard bending, where (a) is before cooling and (b) is after cooling; Figure 5 The diagram illustrates how the precise stepping function of the roller helps eliminate the hard bending phenomenon of the inner ring, where (a) is before stepping and (b) is after stepping. Detailed Implementation
[0016] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention may be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.
[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. The description of at least one exemplary embodiment below is actually only illustrative and in no way limits the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.
[0018] Figure 1 is a flowchart of the method of the present application; Figure 2 is a schematic diagram of the "hard bend" phenomenon at the head of a hot-rolled thick-gauge steel coil; A manufacturing method for eliminating the hard bend defect at the head of a hot-rolled steel coil includes the following steps: S1: Adopt the laminar flow cooling water spray response calibration method to control the "dry head" cooling length of the head of the hot-rolled strip to be coiled; S2: According to products with different thicknesses and widths, correct the pinch roll gap correction coefficient, and use the pinch rolls of the coiler after correction to coil the cooled head strip; S3: The coiler's coiling assistant roll adopts a "stepping" mode, and based on the stepping timing tracking method, coil N turns of the part after the head has been coiled; S4: When coiling the strip after N turns with M% of the set pressure, perform constant pressure control in real time, so that the coiling assistant roll always holds the steel coil tightly with a small pressure during the coiling process of the steel coil, eliminating the hard bend defect at the head of the hot-rolled steel coil.
[0019] Steps S1 / S2 / S3 / S4 are executed in sequence; Furthermore: According to products with different thicknesses and widths, correct the pinch roll gap correction coefficient, and the specific requirements are as follows: When the width w ≤ 1800 mm and the thickness is 12 mm < H ≤ 16 mm, the pinch roll gap correction value is: -0.4 mm; When the width W > 1800 mm and the thickness is 12 mm < H ≤ 16 mm, the pinch roll gap correction value is: - ¬0.3 mm; When the width w ≤ 1250 mm and the thickness is 16 mm < H ≤ 20 mm, the pinch roll gap correction value is: -0.6 mm; When the width 1800mm < w ≤ 1250mm and the thickness 16mm < H ≤ 20mm, the correction value of the pinch roll gap is: -0.5mm; When the width W > 1800mm and the thickness 16mm < H ≤ 20mm, the correction value of the pinch roll gap is: -0.3mm; When the width w ≤ 1250mm and the thickness 20mm < H ≤ 23mm, the correction value of the pinch roll gap is: -0.7mm; When the width 1250mm < w ≤ 1500mm and the thickness 20mm < H ≤ 23mm, the correction value of the pinch roll gap is: -0.6mm; When the width 1500mm < w and the thickness 20mm < H ≤ 23mm, the correction value of the pinch roll gap is: -0.5mm; When the width w ≤ 1500mm and the thickness 23mm < H ≤ 25.4mm, the correction value of the pinch roll gap is: -0.7mm; When the width 1500mm < w ≤ 1800mm and the thickness 23mm < H ≤ 25.4mm, the correction value of the pinch roll gap is: -0.6mm; When the width W > 1800mm and the thickness 23mm < H ≤ 25.4mm, the correction value of the pinch roll gap is: -0.5mm.
[0020] Furthermore: The corrected pinch roll gap of the coiler = actual plate thickness - pinch roll gap correction value.
[0021] Furthermore: The control valve response time of the laminar cooling water spraying device is calibrated by using the laminar cooling water spraying response calibration method as follows: A timer is established, which starts timing when the button is pressed and stops timing when the button is released, and the time is displayed on the screen; After obtaining the data on the screen, the data value is recorded; When the valve is opened for the first time, the response time will be 3 to 5 times the normal level, so the response result of the first valve opening is not recorded and recording starts from the second time; Each valve is continuously tested 3 to 5 times, After removing the obvious outliers from the results of multiple tests of a single valve, the average value is submitted to the secondary level as the basis for modifying the single valve response time parameter.
[0022] Furthermore: The value range of N is 5 - 10.
[0023] Furthermore: The determination requirements for the step height of the coiler's wrapper roll are as follows: The step height of the auxiliary winding roller must be greater than the actual thickness of the plate being wound, and the step height = actual plate thickness × 1.5. The step height must refer to the pressure curve of the auxiliary winding roller during the stepping process, and the pressure curve of the auxiliary winding roller must not jump during the stepping process.
[0024] Furthermore: M takes the value 40%.
[0025] Furthermore: the step timing tracking method is as follows: The winding machine's step control uses a pre-winding inspection to track the starting point and the length tracked by the speed. By optimizing the control program, the original signal is transmitted directly via hardware, reducing the delay to 2 milliseconds and solving the delay problem.
[0026] Furthermore, the cooling length of the "dry head" of the hot-rolled strip is 300mm-400mm.
[0027] Figure 3 This is a schematic diagram of the head winding of a hot-rolled thick steel coil, where (a) is before winding and (b) is after winding. Figure 4 This is a schematic diagram showing the effect of high-temperature sections of different lengths at the head of the strip on hard bending, where (a) is before cooling and (b) is after cooling; Figure 5 The diagram illustrates how the precise stepping function of the roller helps eliminate the hard bending phenomenon of the inner ring, where (a) is before stepping and (b) is after stepping.
[0028] Example 1 A manufacturing method for eliminating hard bending defects at the head of hot-rolled steel coils includes the following steps: S1: The laminar flow cooling water spray response calibration method is adopted to control the cooling length of the "dry head" of the hot-rolled strip to be rolled; S2: The gap correction coefficient of the pinch roll is corrected according to the different thicknesses and widths of the products. The corrected pinch roll of the coiler is used to coil the cooled head strip. S3: The winding machine's auxiliary winding roller adopts a "stepping" mode, based on the stepping timing tracking method, to wind N turns of the part after the head has been wound; S4: When using a set pressure of M%, the strip is coiled after N turns, and constant pressure control is performed in real time to ensure that the auxiliary coiling roller holds the steel coil with low pressure throughout the coiling process, thus eliminating the hard bending defect at the head of the hot-rolled steel coil.
[0029] There is a significant correlation between the length of the "dry head" and the location of defects. When the high-temperature section of the strip extends to the second coil, the pressure from the coiling rollers during winding will cause a noticeable "hard bend" at the junction of the first and second coils. Therefore, shortening the high-temperature length of the strip head to less than one coil (coil diameter × 3.14 = 762 × 3.14 = 2392 mm) will result in greater yield strength in the low-temperature strip, helping to offset the pressure applied by the coiling rollers and avoiding hard bend defects. The strip head adopts a "dry head" mode and is controlled within 1.5 meters (the transition section is approximately 1-2 meters). Through field tests, the "dry head" mode helps to form a good bending effect at the head, but an excessively long high-temperature section at the strip head can lead to "hard bend" defects at the strip head position of each layer after the coiling rollers apply pressure. Therefore, controlling the dry head of the strip to 1-1.5 meters is more suitable.
[0030] Furthermore, based on products of different thicknesses and widths, the pinch roll gap correction coefficient is adjusted. The process of using the adjusted coiler pinch rolls to coil the cooled head strip is as follows: The main function of the pinch rolls in a coiler is to bend and guide the strip head, forming an easy-to-coil shape. Generally, the pinch roll gap is designed to be equal to the actual strip thickness minus 0.2mm. This improves the strip head bending effect without altering the mechanical structure. To improve the bending degree of the strip head during coiling, while ensuring equipment safety, the standby pinch roll gap is reduced to achieve a greater bending effect. However, in actual production, special attention must be paid to the pinch roll current to prevent overcurrent protection shutdown and coiler "steel jamming." Through testing, the pinch roll gap correction coefficient is selected from 0.3-0.7mm depending on the product thickness and width; details are shown in the table below.
[0031] Without altering the machinery, the bending effect of the strip head can be increased by changing the gap between the pinch rolls. Appropriately lowering the pinch roll gap enhances the bending effect, allowing the strip head to form an easily coiled shape and preventing coiling jams that can occur after the strip head shortens and its strength increases.
[0032] Furthermore, the winding machine's auxiliary winding roller adopts a "stepping" mode. Based on the stepping timing tracking method, the process of winding N turns after the head has already been wound is as follows: When winding thick plates, the working mode of the auxiliary winding rollers is changed from "stepping" + high pressure control of auxiliary winding rollers #2 and #3 to full "stepping" + low pressure "full pressure" winding mode to prevent loose winding, ensure good coil shape, and effectively avoid the "hard bend" defect at the head. After the strip head enters the coiler, the auxiliary winding rollers wind in the "stepping" mode for 5-10 turns (the number of stepping turns is selected according to the thickness and strength of the finished product). After the "stepping" action is completed, the auxiliary winding rollers tighten the steel coil with 40% of the set pressure. Constant pressure control is performed in real time through pressure sensors in the hydraulic cylinders controlling the gaps of the three auxiliary winding rollers to ensure that the auxiliary winding rollers always tighten the steel coil with low pressure during the winding process, ensuring that the tightness of each turn of the steel coil is appropriate.
[0033] The coiler's auxiliary winding rollers have precise "stepping" to prevent the strip head from colliding with the auxiliary winding rollers during winding, thus aggravating the "hard bend" defect at the head.
[0034] Precise control of the winding machine's auxiliary winding roller "stepping" function. Optimizing the parameters affecting the winding machine's auxiliary winding roller "stepping" function includes: Step height: The step height of the winding roller should be greater than the actual thickness of the plate being wound. Currently, the step height is calculated as the actual plate thickness × 1.5. Whether the step height is appropriate should be determined by referring to the pressure curve of the winding roller during the stepping process. It is required that the pressure curve of the winding roller does not jump during the stepping process.
[0035] Step timing tracking method: The current method for winding machine step control uses a cold check at the front of the winding machine to track the starting point and the speed tracking length. However, this method suffers from a 100-millisecond lag between the tracking and the cold check signal, causing inaccurate step control. By optimizing the control program and transmitting the original signal directly via hardware, the delay is reduced to 2 milliseconds, thus resolving the latency issue.
[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A manufacturing method for eliminating hard bending defects at the head of hot-rolled steel coils, characterized in that: It includes the following steps: Adopt the laminar flow cooling water spraying response calibration method to control the dry head cooling length of the head of the deconvolved hot-rolled strip; According to products with different thicknesses and widths, correct the pinch roll gap correction coefficient, and use the corrected pinch roll of the coiler to coil the cooled strip at the head; The coiler's wrapper roll adopts a stepping mode, and based on the stepping time sequence tracking method, coil the strip for N turns after the head has been coiled; When coiling the strip after N turns with M% of the set pressure, perform constant pressure control in real time, so that the wrapper roll always holds the steel coil tightly with a small pressure during the coiling process of the steel coil, eliminating the hard bend defect at the head of the hot-rolled steel coil.
2. The manufacturing method for eliminating the hard bending defect at the head of hot-rolled steel coil according to claim 1, characterized in that: According to products with different thicknesses and widths, correct the pinch roll gap correction coefficient, and the specific requirements are as follows: When the width w ≤ 1800mm and the thickness is 12mm < H ≤ 16mm, the pinch roll gap correction value is: -0.4mm; When the width W > 1800mm and the thickness is 12mm < H ≤ 16mm, the pinch roll gap correction value is: -0.3mm; When the width w ≤ 1250mm and the thickness is 16mm < H ≤ 20mm, the pinch roll gap correction value is: -0.6mm; When the width 1800mm < w ≤ 1250mm and the thickness is 16mm < H ≤ 20mm, the pinch roll gap correction value is: -0.5mm; When the width W > 1800mm and the thickness is 16mm < H ≤ 20mm, the pinch roll gap correction value is: -0.3mm; When the width w ≤ 1250mm and the thickness is 20mm < H ≤ 23mm, the pinch roll gap correction value is: -0.7mm; When the width 1250mm < w ≤ 1500mm and the thickness is 20mm < H ≤ 23mm, the pinch roll gap correction value is: -0.6mm; When the width 1500mm < w and the thickness is 20mm < H ≤ 23mm, the pinch roll gap correction value is: -0.5mm; When the width w ≤ 1500mm and the thickness is 23mm < H ≤ 25.4mm, the pinch roll gap correction value is: -0.7mm; When the width 1500mm < w ≤ 1800mm and the thickness is 23mm < H ≤ 25.4mm, the pinch roll gap correction value is: -0.6mm; When the width W > 1800mm and the thickness is 23mm < H ≤ 25.4mm, the pinch roll gap correction value is: -0.5mm.
3. The manufacturing method for eliminating the hard bending defect at the head of hot-rolled steel coil according to claim 1, characterized in that: The gap of the corrected pinch roll of the coiler = actual plate thickness - pinch roll gap correction value.
4. The manufacturing method for eliminating the hard bending defect at the head of hot-rolled steel coil according to claim 1, characterized in that: Calibrate the response time of the control valve of the laminar flow cooling water spraying device by adopting the laminar flow cooling water spraying response calibration method, specifically as follows: Establish a timer, start timing when the button is pressed, stop timing when the button is disconnected, and display the time on the screen; After obtaining the data on the screen, record the data value; When the valve is opened for the first time, the response time will be 3 to 5 times the normal level, so the response result of the first valve opening is not recorded, and recording starts from the second time; Each valve is continuously tested 3 to 5 times. After removing obvious outliers from multiple tests of a single valve, the average value is taken as the basis for modifying the response time parameter of the single valve.
5. The manufacturing method for eliminating the hard bending defect at the head of hot-rolled steel coil according to claim 1, characterized in that: The value of N is in the range of 5-10.
6. The manufacturing method for eliminating the hard bending defect at the head of hot-rolled steel coil according to claim 1, characterized in that: The requirements for determining the step height of the winding machine's auxiliary winding roller are as follows: The step height of the auxiliary winding roller must be greater than the actual thickness of the plate being wound, and the step height = actual plate thickness × 1.
5. The step height must refer to the pressure curve of the auxiliary winding roller during the stepping process, and the pressure curve of the auxiliary winding roller must not jump during the stepping process.
7. The manufacturing method for eliminating the hard bending defect at the head of hot-rolled steel coil according to claim 1, characterized in that: M is set to 40%.
8. The manufacturing method for eliminating the hard bending defect at the head of hot-rolled steel coil according to claim 1, characterized in that: The head-end dry cooling length of the hot-rolled strip is 300mm-400mm.