A method for preventing strip breakage

Abstract

The application provides a method for preventing strip steel from being broken, wherein the method comprises the following steps: after a front strip steel and a rear strip steel are welded, the front strip steel and the rear strip steel are sequentially sent to a tension leveler to be tensioned and leveled, an acid pickling tank to be pickled, a cold continuous rolling mill to be rolled, and finally, a strip steel rolling is completed through a strip separating and cutting operation. The scheme provided by the application solves the problem that the specifications and yield strengths of the front strip steel and the rear strip steel span a large range in the existing cold rolling production process, and the welded seam area of the strip steel is prone to be broken and deviated in the dynamic change process of the specifications. The scheme provided by the application adjusts the production process parameters in the dynamic change process of the specifications of the strip steel, optimizes the mode of thickness control of the rolling mill, prevents the welded seam area of the strip steel from being broken and deviated in the dynamic change process of the specifications, greatly improves the efficiency and yield of the strip steel production, and effectively guarantees the quality of the products.

Description

Technical Field

[0001] This application relates to the field of steel rolling technology, and particularly to a method for preventing strip breakage. Background Technology

[0002] In modern cold rolling mill production, the production schedule and raw material inventory affect the large range of specifications and yield strength between the front and rear coils during the cold rolling process. This can cause strip breakage in the rolling mill, forcing the production line to stop, reducing the effective operating rate of the rolling mill, and resulting in scrap and damage to the rolls, which also affects product quality.

[0003] Therefore, how to prevent strip breakage and deviation accidents in the weld area during the dynamic change of strip specifications, improve the efficiency and yield of strip production, and ensure product quality are urgent technical problems to be solved. Summary of the Invention

[0004] The purpose of this application is to provide a method for preventing strip breakage. This application solves the problem in existing cold rolling production processes where the specifications and yield strength of the preceding and following strip coils vary greatly, causing strip breakage and deviation in the weld area during dynamic changes in specifications. The solution proposed in this application adjusts the production process parameters and optimizes the mill thickness control mode during dynamic changes in strip specifications, preventing strip breakage and deviation accidents in the weld area during dynamic changes in strip specifications. This greatly improves the efficiency and yield of strip production and effectively ensures product quality.

[0005] Specifically, this application adopts the following technical solution:

[0006] This application provides a method for preventing strip breakage, the method comprising: when the weld at the weld joint between the previous coil of strip and the next coil of strip passes through a tension leveler, controlling the set bending unit of the tension leveler to lift up, controlling the tension of the tension leveler to a first preset tension, and controlling the speed of the tension leveler to a first preset speed.

[0007] When the weld enters the first pickling section, the pickling speed of the strip is controlled to the second preset speed. When the weld exits the third pickling section, the pickling speed of the strip is controlled to increase to the third preset speed.

[0008] When the weld is rolled, it passes through the first stand to the fifth stand in sequence. If the yield strength of the previous coil of strip is greater than the yield strength of the next coil of strip, and when the weld reaches the mill inlet, the mill shearing and coiling mode is adjusted to the non-weld shearing mode. The rolling speed of each stand from the first stand to the fifth stand is controlled to the fourth preset speed. The tension between each stand from the first stand to the fourth stand is controlled to be reduced by 10% based on the actual tension.

[0009] After the weld reaches the second stand, the rolling force of the third stand is adjusted to the first preset rolling force, and the front tension of the third stand is adjusted to the third preset tension, and the front tension of the fourth stand is adjusted to the fourth preset tension.

[0010] After the weld reaches the third stand, the rolling force of the fourth stand is controlled to the second preset rolling force, and the front tension of the fourth stand is reduced by 5% to 10% based on the fourth preset tension.

[0011] After the weld reaches the fourth frame, the bending force of the working roll and the bending force of the intermediate roll of the fourth frame are increased by 10% to 15% based on the set bending force.

[0012] After the weld seam passes through the fifth stand and reaches the exit pinch roll, the rolling speed of each stand from the first stand to the fifth stand is controlled to the fifth preset speed, and the coiling and cutting operations are performed to complete the rolling of the strip steel.

[0013] In some embodiments of this application, based on the aforementioned scheme, before the weld at the weld joint between the preceding and following strip rolls passes through the straightening machine, the method further includes: cutting the tail end of the preceding strip roll and the head end of the following strip roll according to a preset length, and then welding the cut preceding and following strip rolls together.

[0014] In some embodiments of this application, based on the aforementioned scheme, after welding the sheared front coil and the sheared rear coil, the method further includes: when the width of the front coil is greater than the width of the rear coil, and the width difference between the front and rear coils is less than a preset width, the crescent is not removed; when the width of the front coil is less than the width of the rear coil, or the width difference between the front and rear coils is greater than or equal to a preset width, the crescent is removed, wherein the depth of the crescent is a preset depth.

[0015] In some embodiments of this application, based on the aforementioned scheme, the first preset speed is 100m / min to 120m / min.

[0016] In some embodiments of this application, based on the foregoing scheme, the second preset speed is 80m / min to 100m / min.

[0017] In some embodiments of this application, based on the aforementioned scheme, the third preset speed is 120m / min to 150m / min.

[0018] In some embodiments of this application, based on the foregoing scheme, the fourth preset speed is 100m / min to 120m / min.

[0019] In some embodiments of this application, based on the foregoing scheme, the fifth preset speed is 80m / min to 100m / min.

[0020] In some embodiments of this application, based on the foregoing scheme, the method further includes:

[0021] If the yield strength of the previous strip is less than the yield strength of the next strip, when the weld reaches the mill inlet, the rolling speed of each stand from the first to the fifth stand is controlled to the sixth preset speed, and the tension between each stand from the first to the fourth stand is increased by 10% to 15% based on the actual tension.

[0022] After the weld reaches the first frame, the tension of the first frame is reduced by 10% to 15% based on the first actual tension;

[0023] After the weld reaches the second frame, the front tension of the first frame is adjusted to the first set tension, while the front tension of the second frame is reduced by 10% to 15% based on the second actual tension.

[0024] After the weld reaches the third frame, the front tension of the second frame is adjusted to the second set tension, while the front tension of the third frame is reduced by 10% to 15% based on the third actual tension.

[0025] After the weld reaches the fourth frame, the front tension of the third frame is adjusted to the third set tension, while the front tension of the fourth frame is reduced by 15% to 20% based on the fourth actual tension.

[0026] After the weld seam passes through the fifth stand and reaches the exit pinch roll, the front tension of the fourth stand is controlled to the fourth set tension, and the slitting and cutting operations are performed to complete the rolling of the strip.

[0027] In some embodiments of this application, based on the foregoing scheme, the sixth preset speed is 120m / min to 150m / min.

[0028] As can be seen from the above technical solution, this application has at least the following advantages and positive effects:

[0029] The proposed solution addresses the problem in existing cold-rolling production processes where the specifications and yield strength of the preceding and following strip coils vary significantly, leading to strip breakage and misalignment in the weld area during dynamic changes in strip specifications. The proposed solution adjusts production process parameters and optimizes mill thickness control during these dynamic changes, preventing strip breakage and misalignment in the weld area. This significantly improves strip production efficiency and yield, effectively ensuring product quality. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 A flowchart of a method for preventing strip breakage according to one embodiment of this application is shown;

[0032] Figure 2 A schematic diagram of the removal of the crescent-shaped part of the strip after welding is shown in one embodiment of this application. Detailed Implementation

[0033] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0034] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0035] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0036] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of these terms can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described.

[0037] In the production of cold-rolled strip steel, the front and rear coils of strip steel need to be welded together. The welded strip steel then sequentially passes through a tension leveler for tension leveling, a pickling section for pickling, a cold rolling mill for rolling, and finally is slit and cut off. Due to the large differences in specifications and yield strength between the front and rear coils during cold rolling, accidents such as strip breakage and misalignment may occur in the weld area during dynamic specification changes at the mill. This can force production line shutdowns, reduce mill efficiency, damage equipment such as rolls, significantly impact product quality, and increase resource waste.

[0038] In this application, a method for preventing strip breakage is proposed to address the above-mentioned problems. By adjusting the specified process parameters during the dynamic change of strip specifications, the thickness control mode of the rolling mill is optimized, which prevents strip breakage and deviation accidents caused by large spans between front and rear coil specifications. This improves the production efficiency and yield of strip, protects equipment such as rolls from damage, effectively controls product quality, and saves resources.

[0039] The implementation details of the technical solutions in the embodiments of this application are described in detail below:

[0040] Reference Figure 1 , Figure 1 This is a flowchart of a method for preventing strip breakage in one embodiment of this application.

[0041] According to a typical embodiment of this application, a method for preventing strip breakage is provided, the method comprising the following steps S1 to S7:

[0042] Step S1: When the weld at the joint between the previous coil of strip and the next coil of strip passes through the tension leveler, the set bending unit of the tension leveler is raised, the tension of the tension leveler is controlled to the first preset tension, and the speed of the tension leveler is controlled to the first preset speed.

[0043] In this application, after welding the previous coil of strip steel to the next coil of strip steel, it is also necessary to confirm whether the welding of the previous coil of strip steel to the next coil of strip steel is a case of large specification jump. If the yield strength of the previous coil of strip steel is greater than the yield strength of the next coil of strip steel, and the difference in yield strength between the previous coil of strip steel and the next coil of strip steel is greater than 150 MPa, the difference in raw material thickness between the previous coil of strip steel and the next coil of strip steel is greater than 0.5 mm, the thickness of the strip steel at the mill exit is: d2 > 1.35d1, where d2 is thick material and d1 is thin material, and the difference in finished product thickness between the previous coil of strip steel and the next coil of strip steel is greater than or equal to 0.5 mm, then the welding of the previous coil of strip steel to the next coil of strip steel is a case of large specification jump, and the weld is a weld with large specification jump.

[0044] If the yield strength of the preceding strip coil is less than the yield strength of the following strip coil, and the difference in yield strength between the preceding and following strip coils is less than or equal to 300 MPa, the difference in raw material thickness between the preceding and following strip coils is greater than 0.8 mm, the thickness of the strip at the mill exit is d2 ≤ 1.8d1, where d2 is for thicker material and d1 is for thinner material, and the difference in finished product thickness between the preceding and following strip coils is less than 0.8 mm, then the welding of the preceding and following strip coils is considered a case of large specification jump, and the weld is considered a weld with large specification jump.

[0045] In this application, when the weld seam at the junction of the preceding and following strip coils passes through a tension leveler, to ensure that the tension leveler's speed and tension allow for smooth passage of both coils and prevent strip breakage or deviation in the weld seam area, the tension leveler's set bending unit can be raised, and the tension and speed can be set to a first preset tension and a first preset speed. The set bending unit can be the tension leveler's third bending unit, which is raised and not used. The first preset tension can be obtained by reducing the tension leveler's current secondary set tension by 20% to 30%. By controlling the tension and speed of the tension leveler, strip breakage and deviation in the weld seam area at the junction of the preceding and following strip coils can be avoided due to excessive tension, stretching force, or excessive tension speed.

[0046] Step S2: When the weld enters the first pickling section, the pickling speed of the strip is controlled to the second preset speed. When the weld exits the third pickling section, the pickling speed of the strip is controlled to increase to the third preset speed.

[0047] In this application, after the preceding and following coils of strip steel are straightened, they also need to be pickled in a pickling tank to remove the iron oxide scale on the surface of the strip steel and obtain a cleaner strip steel surface. The pickling tank can be divided into three sections. When the weld enters the first pickling section, the pickling speed of the strip steel can be controlled at a second preset speed. When the weld exits the third pickling section, since the strip steel needs to be rinsed after pickling, in order to maintain the pickling efficiency of the strip steel, the pickling speed of the strip steel can be increased to a third preset speed to ensure that the preceding and following coils of strip steel pass smoothly through the pickling section for pickling.

[0048] Step S3: When the weld is rolled, it passes through the first stand to the fifth stand in sequence. If the yield strength of the previous coil of strip is greater than the yield strength of the next coil of strip, and when the weld reaches the mill inlet, the mill shearing and coiling mode is adjusted to the non-weld shearing mode. The rolling speed of each stand from the first stand to the fifth stand is controlled to the fourth preset speed. The tension between each stand from the first stand to the fourth stand is reduced by 10% based on the actual tension.

[0049] In this application, after the pickling and rinsing of the preceding and following coils of strip steel are completed, rolling operations can be performed on both coils. During rolling, the weld seam can sequentially pass through the first to fifth stands, which are cold continuous rolling mill stands. If the yield strength of the preceding coil of strip steel is greater than the yield strength of the following coil of strip steel (of the preceding coil), and when the weld seam reaches the mill inlet, the mill shearing and coiling mode can be adjusted to a non-weld seam shearing mode, using manual shearing. The rolling speed of each stand from the first to the fifth stand can be controlled to the fourth preset speed, and the tension between each stand from the first to the fourth stand can be reduced by 10% based on the actual tension. This avoids strip breakage and deviation accidents at the weld area of ​​the weld between the previous and the next coil of strip due to excessive rolling speed and excessive tension between the rolling mills.

[0050] Step S4: After the weld reaches the second stand, the rolling force of the third stand is adjusted to the first preset rolling force, and the front tension of the third stand is adjusted to the third preset tension, and the front tension of the fourth stand is adjusted to the fourth preset tension.

[0051] In this application, after the weld seam passes through the first stand and reaches the second stand, the rolling force and tension of the first and second stands, under the thickness control mode of the rolling mill, have become the actual rolling force and tension of the subsequent strip coil. The rolling force of the third stand is adjusted to the first preset rolling force, and the front tension of the third stand is adjusted to the third preset tension. The front tension of the fourth stand is adjusted to the fourth preset tension. The first preset rolling force can be the median value between the actual value of the rolling force of the previous strip coil and the secondary set value of the rolling force of the subsequent strip coil. For example, if the actual value of the rolling force of the previous strip coil is 100 kN and the secondary set value of the rolling force of the subsequent strip coil is 98 kN, then the value of the first preset rolling force can be 99 kN. The third preset tension can be the value obtained by reducing the front tension of the third frame by 8% to 10% based on the existing actual front tension of the third frame, and the fourth preset tension can be the value obtained by reducing the front tension of the fourth frame by 8% to 10% based on the existing actual front tension of the fourth frame.

[0052] Step S5: After the weld reaches the third stand, control the rolling force of the fourth stand to the second preset rolling force, and at the same time control the front tension of the fourth stand to be reduced by 5% to 10% based on the fourth preset tension.

[0053] In this application, after the weld seam passes through the second stand and reaches the third stand, the rolling force and tension of the third stand, in thickness control mode, have become the actual rolling force and tension of the subsequent strip coil. When the weld seam reaches the third stand, the fifth stand exit thickness control feedback adjustment system can be shut down, while the fifth stand exit thickness gauge measurement data tracking is retained. After shutting down the fifth stand thickness feedback, the rolling force of the fourth stand can be controlled to a second preset rolling force. The second preset rolling force can be the median value between the actual value of the previous strip coil rolling force and the secondary set value of the subsequent strip coil rolling force. Simultaneously, the tension of the fourth stand can be reduced by 5% to 10% based on the fourth preset tension.

[0054] Step S6: After the weld seam passes through the third stand and reaches the fourth stand, the bending force of the working roll and the bending force of the intermediate roll of the fourth stand can be increased by 10% to 15% based on the set bending force. By rationally designing the bending force of the working roll and the bending force of the intermediate roll of the fourth stand, the shape control capability of the rolling mill can be improved, thereby reducing the generation of defects such as strip wavy shape and ensuring the quality of the strip.

[0055] Step S7: After the weld seam passes through the fifth stand and reaches the exit pinch roll, control the rolling speed of each stand from the first stand to the fifth stand to the fifth preset speed, and perform slitting and cutting operations to complete the rolling of the strip steel.

[0056] In this application, after the weld seam reaches the exit pinch rolls via the fifth stand, the fifth stand exit thickness control feedback adjustment system can be put into use. The actual strip shape between stands can be viewed using a monitoring screen, and the bending roll force of each stand can be adjusted according to the actual strip shape. After confirming that the strip shape has no obvious waviness, the rolling speed of each stand from the first to the fifth stand is controlled at the fifth preset speed. At this time, when the exit thickness fluctuation is observed to be around 10% and continuously decreasing, a shearing preparation operation is performed. The manual shearing preparation operation for non-weld seams lasts for 10 seconds. Within this preparation time, the actual exit thickness fluctuation can reach within 5% of the secondary set value, meeting the product quality requirements according to the technical specifications. At this time, shearing and coiling are performed. After shearing, the rolling mill resumes normal production speed.

[0057] In one embodiment of this application, before the weld at the weld joint between the preceding and following strip coils passes through the straightening machine, the method further includes: cutting the tail end of the preceding strip coil and the head end of the following strip coil according to a preset length, and then welding the cut preceding and following strip coils together.

[0058] In this application, before the weld at the junction of the preceding and following strip coils passes through the straightening machine, to ensure the strip's performance and excellent plate quality, a preset length is cut from the tail end of the preceding strip coil and a preset length is cut from the head end of the following strip coil. The cut preceding and following strip coils are then welded together. The preset length can be 5 meters or other preset lengths; this application does not impose any particular limitation and can adjust it according to actual needs.

[0059] In one embodiment of this application, after welding the sheared first coil of strip and the sheared second coil of strip, the method further includes:

[0060] When the width of the previous roll of strip is greater than the width of the next roll of strip, and the width difference between the previous roll and the next roll of strip is less than the preset width, the crescent shape is not removed.

[0061] When the width of the previous roll of strip is less than the width of the next roll of strip, or when the width difference between the previous roll and the next roll of strip is greater than or equal to a preset width, the crescent is cut off, and the depth of the crescent is a preset depth.

[0062] In this application, reference is made to Figure 2 After welding the sheared front coil and the sheared rear coil, it is necessary to determine whether the crescent-shaped portion needs to be removed based on the widths of the front and rear coils. The crescent-shaped portion is... Figure 2 The crescent-shaped portion shown has a depth of [missing information]. Figure 2 The distance to be cut in the width direction of the narrow strip steel shown. When the width of the preceding strip steel coil is greater than the width of the following strip steel coil, and the width difference between the preceding and following strip steel coils is less than a preset width, the crescent shape is not cut; when the width of the preceding strip steel coil is less than the width of the following strip steel coil, or the width difference between the preceding and following strip steel coils is greater than or equal to the preset width, the crescent shape is cut, and the depth of the crescent shape is a preset depth. The preset width can be 100mm, and the preset depth can be 10mm. This application does not impose any special restrictions on the preset width and preset depth, and they can be adjusted according to actual needs.

[0063] In one embodiment of this application, the first preset speed can be 100m / min to 120m / min.

[0064] In one embodiment of this application, the second preset speed can be 80m / min to 100m / min.

[0065] In one embodiment of this application, the third preset speed can be 120m / min to 150m / min.

[0066] In one embodiment of this application, the fourth preset speed can be 100m / min to 120m / min.

[0067] In one embodiment of this application, the fifth preset speed can be 80m / min to 100m / min.

[0068] It should be noted that this application does not impose any special restrictions on the values ​​of the first preset speed, the second preset speed, the third preset speed, the fourth preset speed, and the fifth preset speed, and they can be adjusted according to actual needs.

[0069] In one embodiment of this application, the method further includes:

[0070] If the yield strength of the previous strip is less than the yield strength of the next strip, when the weld reaches the mill inlet, the rolling speed of each stand from the first to the fifth stand is controlled to the sixth preset speed, and the tension between each stand from the first to the fourth stand is increased by 10% to 15% based on the actual tension.

[0071] In this application, the preceding and following coils of strip steel are sequentially processed through welding, tension leveling, and pickling before being rolled. The rolling strategies of the preceding and following coils of strip steel, as well as the deviations in tension and rolling force between them, can be examined. If the yield strength of the preceding coil is less than that of the following coil, when the weld reaches the mill inlet, the rolling speed of each stand from the first to the fifth stand can be controlled to a sixth preset speed. The tension between each stand from the first to the fourth stand can be increased by 10% to 15% based on the existing actual tension, maintaining the normal operation of the thickness control mode for each stand.

[0072] In this application, after the weld reaches the first frame, the tension of the first frame has become the actual value of the subsequent coil of strip. Therefore, the tension of the first frame can be reduced by 10% to 15% based on the first actual tension. The first actual tension is the actual tension of the first frame at this point.

[0073] After the weld reaches the second stand, the front tension of the second stand has become the actual value of the next coil of strip. The front tension of the first stand is adjusted to the first set tension, while the front tension of the second stand is reduced by 10% to 15% based on the second actual tension. The first set tension is the set value of the front tension of the strip rolled by the first stand at this time, and the second actual tension is the actual front tension of the second stand at this time.

[0074] After the weld reaches the third stand, the front tension of the third stand has become the actual value of the next coil of strip. The front tension of the second stand is adjusted to the second set tension, while the front tension of the third stand is reduced by 10% to 15% based on the third actual tension. The second set tension is the set value of the front tension of the strip rolled by the second stand at this time, and the third actual tension is the actual front tension of the third stand at this time.

[0075] After the weld reaches the fourth stand, the front tension of the fourth stand has become the actual value of the next coil of strip. The front tension of the third stand is adjusted to the third set tension, while the front tension of the fourth stand is reduced by 15% to 20% based on the fourth actual tension. The third set tension is the set value of the front tension of the strip rolled in the third stand at this time, and the third actual tension is the actual front tension of the fourth stand at this time.

[0076] After the weld seam passes through the fifth stand and reaches the exit pinch roll, the tension of the fourth stand is controlled to the fourth set tension (the fourth set tension is the set value of the strip tension being rolled on the fourth stand at this time, i.e., restoring the tension of the fourth stand to the fourth set tension). At this time, the exit thickness fluctuation is observed. When the thickness fluctuation is around 10% and continues to decrease, a shearing preparation operation is performed. The manual shearing preparation operation for non-weld seams lasts for 10 seconds. Within this preparation time, the actual exit thickness fluctuation should be within 5% of the secondary set value. Meeting the product quality requirements according to the technical specifications, the coiling and cutting operations are then performed to complete the strip rolling. After shearing, the mill resumes normal production speed.

[0077] In one embodiment of this application, the sixth preset speed can be 120m / min to 150m / min. This application does not impose any special restrictions on the sixth preset speed, and it can be adjusted according to actual needs.

[0078] In this application, when performing the coiling and cutting operations, it should be noted that after the previous coil of strip steel is coiled with the next coil of strip steel, the coiled steel is sent to the offline inspection table. At the same time, the thickness curve of this coil is queried to check the actual thickness deviation length. After being sent to the offline inspection table, the thickness deviation part is cut off to complete the adjustment of this operation. Finally, the rolling mill resumes normal rolling.

[0079] The specific implementation of this application will be further illustrated by specific embodiments below, but the specific implementation of this application is not limited to the following embodiments.

[0080] Example 1:

[0081] The steel type and specifications of the previous and subsequent strip coils are shown in Table 1 below.

[0082]

[0083] Table 1

[0084] The yield strength difference between the previous and subsequent strip coils in Table 1 above is 208 MPa, the exit thickness difference is 0.53 mm, and d2 = 1.523d1, where d2 is the thicker material and d1 is the thinner material.

[0085] During the welding process between the preceding and following coils of strip steel, the tail end of the preceding coil and the head end of the following coil are sheared for a length of 5 meters. The sheared preceding and following coils are then welded together. The crescent-shaped portion is not removed after welding, and normal material feeding proceeds.

[0086] When the weld seam at the junction of the current and subsequent strip coils passes through the tension leveler, the No. 3 bending unit is lifted and not put into use. The tension of the tension leveler is reduced by 20% to 30% from the current secondary setting, and the speed of the tension leveler is adjusted to 105 m / min. After the weld seam passes through the tension leveler, the tension leveler returns to the two-bend-one-straighten mode, and the tension of the tension leveler is restored to the secondary setting tension of the current coil.

[0087] When the weld enters the first pickling section, in order to remove the iron oxide scale on the surface of the strip and obtain a cleaner strip surface, the pickling speed is adjusted to 100 m / min. When the weld exits the third pickling section, the pickling speed is adjusted to 145 m / min.

[0088] When the weld is rolled, it passes through the first stand to the fifth stand in sequence. If the yield strength of the previous coil of strip is greater than the yield strength of the next coil of strip, check the deviation values ​​of the rolling strategy, tension and rolling force of the previous coil of strip and the next coil of strip, as shown in Table 2 below.

[0089]

[0090] Table 2

[0091] When the weld reaches the mill inlet, the mill shearing and coiling mode is adjusted to non-weld shearing, and manual shearing is used. The rolling speed of each stand from the first to the fifth stand is adjusted to 105 m / min, and the tension between each stand from the first to the fourth stand is adjusted from 367 KN, 338 KN, 318 KN, and 303 KN to 330 KN, 300 KN, 285 KN, and 270 KN, respectively.

[0092] After the weld reaches the F2 stand, the rolling forces of the first and second stands in the thickness control mode have become the actual values ​​of the next coil of strip. The rolling force of the third stand is adjusted from 14.05MN to 11.3MN, and the front tension of the third stand is adjusted to 260KN, while the front tension of the fourth stand is adjusted to 245KN.

[0093] Once the weld reaches the third stand, shut down the fifth stand exit thickness control feedback adjustment system while retaining the thickness gauge measurement data tracking at the fifth stand exit. After shutting down the fifth stand thickness feedback, adjust the fourth stand rolling force from 12.41MN to 10.3MN, while simultaneously reducing the fourth stand front tension to 220KN.

[0094] When the weld reaches the fourth stand, the rolling force and tension of the fourth stand in the thickness control mode have changed to the actual values ​​of the next coil of strip, with a rolling force of 8.32MN and a tension of 181KN.

[0095] When the weld reaches the exit pinch roll, the fifth stand exit thickness control feedback adjustment system is put into use. The actual strip shape between stands is monitored using the monitoring screen, and the bending roll force of each stand is adjusted according to the actual strip shape. After the strip shape is no longer obviously wavy, the mill exit speed is adjusted to 85 m / min. At this time, when the exit thickness fluctuation is observed to be around 10% and continuously decreasing, the shearing preparation operation is performed. The manual shearing preparation operation for non-weld seams has a time limit of 10 seconds. If the actual exit thickness fluctuation within the preparation time reaches within 5% of the secondary set value, and meets the product quality requirements according to the technical specifications, shearing and coiling are then performed. After shearing, the mill resumes normal production speed.

[0096] After separating the previous and subsequent strip coils, the coiled steel is transferred to the offline inspection station. At the same time, the thickness curve of this coil is queried to check the actual thickness deviation length. The thickness fluctuation deviation is found to be 10M before the weld and 20M after the weld. After being transferred to the offline inspection station, the excess thickness portion is cut off, and the adjustment of the coiling and shearing operations is completed. The rolling mill resumes normal rolling.

[0097] Example 2:

[0098] The steel type and specifications of the previous and subsequent coils of strip are shown in Table 3 below.

[0099]

[0100] Table 3

[0101] The thickness difference between the raw material of the previous coil of strip and the next coil of strip in Table 1 above is 0.8 mm, the thickness difference at the exit is 1.19 mm, and d2 = 1.912d1, where d2 is the thick material and d1 is the thin material.

[0102] During the welding process between the preceding and following coils of strip steel, the tail end of the preceding coil and the head end of the following coil are sheared for a length of 5 meters. The sheared preceding and following coils are then welded together. The crescent-shaped portion is not removed after welding, and normal material feeding proceeds.

[0103] When the weld seam at the junction of the current and subsequent strip coils passes through the tension leveler, the No. 3 bending unit is lifted and not put into use. The tension of the tension leveler is reduced by 20% to 30% from the current secondary setting, and the speed of the tension leveler is adjusted to 110 m / min. After the weld seam passes through the tension leveler, the tension leveler returns to the two-bend-one-straighten mode, and the tension of the tension leveler is restored to the secondary setting tension of the current coil.

[0104] When the weld enters the first pickling section, in order to remove the iron oxide scale on the surface of the strip and obtain a cleaner strip surface, the pickling speed is adjusted to 90 m / min. When the weld exits the third pickling section, the pickling speed is adjusted to 120 m / min.

[0105] When the weld is rolled, it passes through the first stand to the fifth stand in sequence. If the yield strength of the previous coil of strip is greater than the yield strength of the next coil of strip, check the deviation values ​​of the rolling strategy, tension and rolling force of the previous coil of strip and the next coil of strip, as shown in Table 4 below.

[0106]

[0107] Table 4

[0108] When the weld reaches the mill inlet, the mill shearing and coiling mode is adjusted to non-weld shearing, and manual shearing is used. The rolling speed of each stand from the first to the fifth stand is adjusted to 100 m / min, and the tension between each stand from the first to the fourth stand is adjusted from 430 KN, 350 KN, 273 KN, and 227 KN to 475 KN, 390 KN, 300 KN, and 255 KN, respectively.

[0109] After the weld reaches the first frame, the tension in front of the first frame has become the actual value of the next coil of strip, 514 kN. At this point, the tension in front of the first frame is adjusted to 460 kN.

[0110] After the weld reaches the second stand, the rolling force of the second stand in the thickness control mode has become the actual value of the next coil of strip, 501KN. At this time, the tension of the first stand is restored to the secondary setting value of the current coil, 514KN, and the tension of the second stand is simultaneously adjusted to 450KN.

[0111] When the weld reaches the third frame, the tension in front of the third frame has become the actual value of the next coil of strip, 455KN. At this time, the tension in front of the second frame is restored to the secondary setting value of 501KN for the current coil, and the tension in front of the third frame is simultaneously adjusted to 405KN.

[0112] When the weld reaches the fourth frame, the tension in front of the fourth frame has become the actual value of the next coil of strip, 426KN. At this time, the tension in front of the third frame is restored to the secondary setting value of 455KN for the current coil, and the tension in front of the fourth frame is simultaneously adjusted to 350KN.

[0113] When the weld reaches the exit pinch roll, the tension at the F4 stand is restored to the secondary setting of 426 kN for the current coil. The exit thickness fluctuation is then observed. When the thickness fluctuation is around 10% and continues to decrease, a shearing preparation operation is performed. The manual shearing preparation operation for non-weld seams takes 10 seconds. Within this preparation time, the actual exit thickness fluctuation should be within 5% of the secondary setting, meeting the product quality requirements according to the technical specifications. At this point, shearing and coil splitting are performed. After shearing, the mill resumes normal production speed.

[0114] After separating the previous and subsequent strip coils, the coils are transported to an offline inspection station. At the same time, the thickness curve of the coil is checked to see if the actual thickness deviation is more than 5 meters before the weld and 15 meters after the weld. After being placed on the offline inspection station, the excess thickness is cut off, and the adjustment of the coiling and shearing operations is completed. The rolling mill then resumes normal rolling.

[0115] As can be seen from the above technical solution, this application has at least the following advantages and positive effects:

[0116] Firstly, the solution proposed in this application can solve the problem that in the existing cold rolling production process, the large difference in specifications and yield strength between the previous and subsequent coils of strip steel makes it easy for strip breakage and deviation to occur in the weld area during the dynamic changes in specifications. The solution proposed in this application adjusts the production process parameters during the dynamic changes in strip steel specifications and optimizes the mill thickness control mode, preventing strip breakage and deviation accidents in the weld area during the dynamic changes in specifications, greatly improving the efficiency and yield of strip steel production, and effectively ensuring product quality.

[0117] Secondly, by adopting the solution proposed in this application, the tail end of the previous coil of strip steel and the head end of the next coil of strip steel are cut according to a preset length, and the cut-cut front coil of strip steel and the cut-cut rear coil of strip steel are welded together, which can ensure the performance of the strip steel and the high quality of the plate shape.

[0118] Third, adopting the solution proposed in this application can reduce damage to equipment such as rolling mills, reduce the amount of scrapped equipment and strip steel, and greatly save money and resources.

[0119] Fourth, adopting the proposed solution will improve production efficiency, especially contributing significantly to the improvement of product quality, better maintaining the production line, ensuring the output of high-quality products, establishing a company image that prioritizes quality, and enhancing market competitiveness.

[0120] Although this application has been described with reference to several typical embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Since this application can be embodied in many forms without departing from the spirit or substance of the application, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A method for preventing steel strip breakage, characterized in that, The method includes: When the weld at the joint between the previous coil of strip and the next coil of strip passes through the tension leveler, the set bending unit of the tension leveler is raised, the tension of the tension leveler is controlled to the first preset tension, and the speed of the tension leveler is controlled to the first preset speed. When the weld enters the first pickling section, the pickling speed of the strip is controlled to the second preset speed. When the weld exits the third pickling section, the pickling speed of the strip is controlled to increase to the third preset speed. When the weld is rolled, it passes through the first stand to the fifth stand in sequence. If the yield strength of the previous coil of strip is greater than the yield strength of the next coil of strip, and when the weld reaches the mill inlet, the mill shearing and coiling mode is adjusted to the non-weld shearing mode. The rolling speed of each stand from the first stand to the fifth stand is controlled to the fourth preset speed. The tension between each stand from the first stand to the fourth stand is controlled to be reduced by 10% based on the actual tension. After the weld reaches the second stand, the rolling force of the third stand is adjusted to the first preset rolling force, and the front tension of the third stand is adjusted to the third preset tension, and the front tension of the fourth stand is adjusted to the fourth preset tension. After the weld reaches the third stand, the rolling force of the fourth stand is controlled to the second preset rolling force, and the front tension of the fourth stand is reduced by 5% to 10% based on the fourth preset tension. After the weld reaches the fourth frame, the bending force of the working roll and the bending force of the intermediate roll of the fourth frame are increased by 10% to 15% based on the set bending force. After the weld seam passes through the fifth stand and reaches the exit pinch roll, the rolling speed of each stand from the first stand to the fifth stand is controlled to the fifth preset speed, and the coiling and cutting operations are performed to complete the rolling of the strip steel.

2. The method according to claim 1, characterized in that, Before the weld at the junction of the preceding and following strip coils passes through the tension leveler, the method further includes: According to a preset length, the tail end of the previous coil of strip and the head end of the next coil of strip are cut, and the cut-out front coil of strip and the cut-out rear coil of strip are welded together.

3. The method according to claim 2, characterized in that, After welding the sheared first coil of strip and the sheared second coil of strip, the method further includes: When the width of the previous roll of strip is greater than the width of the next roll of strip, and the width difference between the previous roll and the next roll of strip is less than the preset width, the crescent is not removed. When the width of the previous roll of strip is less than the width of the next roll of strip, or when the width difference between the previous roll and the next roll of strip is greater than or equal to a preset width, the crescent is cut off, and the depth of the crescent is a preset depth.

4. The method according to claim 1, characterized in that, The first preset speed is 100m / min to 120m / min.

5. The method according to claim 1, characterized in that, The second preset speed is 80m / min to 100m / min.

6. The method according to claim 1, characterized in that, The third preset speed is 120m / min to 150m / min.

7. The method according to claim 1, characterized in that, The fourth preset speed is 100m / min to 120m / min.

8. The method according to claim 1, characterized in that, The fifth preset speed is 80m / min to 100m / min.

9. The method according to claim 1, characterized in that, The method further includes: If the yield strength of the previous strip is less than the yield strength of the next strip, when the weld reaches the mill inlet, the rolling speed of each stand from the first to the fifth stand is controlled to the sixth preset speed, and the tension between each stand from the first to the fourth stand is increased by 10% to 15% based on the actual tension. After the weld reaches the first frame, the tension of the first frame is reduced by 10% to 15% based on the first actual tension; After the weld reaches the second frame, the front tension of the first frame is adjusted to the first set tension, while the front tension of the second frame is reduced by 10% to 15% based on the second actual tension. After the weld reaches the third frame, the front tension of the second frame is adjusted to the second set tension, while the front tension of the third frame is reduced by 10% to 15% based on the third actual tension. After the weld reaches the fourth frame, the front tension of the third frame is adjusted to the third set tension, while the front tension of the fourth frame is reduced by 15% to 20% based on the fourth actual tension. After the weld seam passes through the fifth stand and reaches the exit pinch roll, the front tension of the fourth stand is controlled to the fourth set tension, and the slitting and cutting operations are performed to complete the rolling of the strip.

10. The method according to claim 9, characterized in that, The sixth preset speed is 120m / min to 150m / min.

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