A method for preventing edge quality defects in hot rolled strip

Abstract

The application discloses a method for preventing quality defects of hot-rolled strip steel edges, and belongs to the technical field of hot-rolled strip steel quality control, and comprises the following steps: controlling the opening of side guides, adopting three-section independent control modes for the side guides before shearing and the side guides of a finishing mill respectively; detecting the wear degree of the side guides in real time or at fixed time intervals, replacing the side guide liners when the wear degree of the side guides exceeds a wear threshold; otherwise, the side guide liners are not replaced; detecting the oil cylinder pin shaft frame amount of the side guides in real time or at fixed time intervals, processing the oil cylinder pin shaft frame amount when the oil cylinder pin shaft frame amount exceeds a frame amount threshold; otherwise, the oil cylinder pin shaft frame amount is not processed; calibrating the center line of the side guides, and offsetting the center line of the side guides by X mm from the center line of a side guide frame according to the wear condition of the side guides; and the application solves the problem of strip edge quality defects caused by abnormal scratching of the strip edges and the side guides during the production of hot-rolled strip steel, and in particular, solves the problem of quality defects caused by the impact of strip head and tail side bending on the side guides.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hot strip quality control, and particularly relates to a method for preventing edge quality defects of hot strip. BACKGROUND

[0002] Hot continuous rolling is a continuous rolling process used to produce hot strip. This process includes heating the slab to a specific temperature, then processing it into strip of desired thickness and properties through a series of rolling steps such as rough rolling, finishing rolling, and finally cooling and coiling.

[0003] Currently, the production of hot strip in the hot continuous rolling process mainly involves the following steps: first, the slab is heated to a set temperature in a heating furnace; then the surface scale is removed by high-pressure water descaling; then rough rolling is performed to roll the slab into an intermediate blank; then finishing rolling is performed to roll the intermediate blank into the thickness of the finished strip; finally, it is cooled to a set temperature by a laminar flow cooling system and coiled into a coil on a coiler. During the finishing rolling process, side guide plate devices are used to control the position of the strip and prevent deviation.

[0004] However, it is found that during the production process, the edge of the strip is scratched due to abnormal scraping between the edge of the strip and the side guide plate; the side bending of the head and tail of the strip is a problem that is difficult to completely avoid. The side bending of the strip can be caused by various factors such as uneven deformation during hot rolling, equipment precision problems, initial slab state, stress distribution during rolling, and uneven temperature distribution, so there is an urgent need for a method that can effectively prevent the edge of the hot rolled strip from being scratched due to abnormal scraping with the side guide plate during the production process, thereby preventing edge quality defects, improving product quality and production efficiency. SUMMARY

[0005] The present application aims to provide a method for preventing edge quality defects of hot strip, to solve the technical problem of edge quality defects of hot strip caused by abnormal scraping between the edge of the strip and the finishing side guide plate due to side bending of the head and tail of the strip during the production process of hot strip as described in the background.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A method for preventing edge quality defects of hot strip, comprising:

[0008] Controlling the opening of the side guide plate, specifically including: using a three-segment independent control method for the pre-cut side guide plate and the finishing mill side guide plate respectively; to avoid the impact of the side bending of the head and tail of the strip on the side guide plate and reduce the probability of edge quality defects of the strip;

[0009] By detecting the wear degree of the side guide plate in real time or at a fixed time, when the wear degree of the side guide plate exceeds a wear threshold, the side guide plate lining is replaced; otherwise, the side guide plate lining is not replaced; so as to ensure the working precision of the side guide plate.

[0010] By detecting the oil cylinder pin shaft frame amount of the side guide plate in real time or at a fixed time, when the oil cylinder pin shaft frame amount of the side guide plate exceeds a frame amount threshold, the oil cylinder pin shaft frame amount is processed; otherwise, it is not processed; so as to improve the equipment precision and ensure the normal work of the side guide plate.

[0011] The center line of the side guide plate is calibrated, and according to the wear condition of the side guide plate, the center line of the side guide plate is offset to the transmission side or the operation side based on the center line of the archway; for compensating the deviation caused by wear, and ensuring the working precision.

[0012] Preferably, the three-section independent control mode of the pre-cutting side guide plate is that: along the direction of the strip steel transmission, the opening of the first head side guide plate, the opening of the first middle side guide plate and the opening of the first tail side guide plate are independently set according to the requirements.

[0013] Preferably, the three-section independent control mode of the pre-cutting side guide plate specifically includes:

[0014] Head setting: before the strip steel enters the flying shear, the opening = the basic opening - X1;

[0015] Middle setting: after the strip steel is bitten by the finishing F1, the opening = the basic opening - X2;

[0016] Tail setting: before the strip steel tail is 2 meters away from the flying shear, the opening = the basic opening - X3;

[0017] Wherein: X1 < X2, X3 < X2.

[0018] Preferably, the gear and rack type transmission structure is used on both sides of the pre-cutting side guide plate, the gear and rack type transmission structures on both sides are controlled by the same oil cylinder, and the three-section position control setting range is ± 150 mm.

[0019] Preferably, the operation side of the finishing mill side guide plate is controlled by a first oil cylinder, and the transmission side of the finishing mill side guide plate is controlled by a second oil cylinder; the three-section control is set for the two sides respectively, and the setting range is ± 50 mm.

[0020] Preferably, the finishing equipment of the hot-rolled strip steel includes F1~Fn, n n finishing mills, n is a natural number greater than 1, each finishing mill adopts the three-section independent control mode, and along the direction of the strip steel transmission, the opening of the side guide plate of the lower finishing mill is smaller than the opening of the side guide plate of the upper finishing mill.

[0021] Preferably, for the finishing mill F i , i is a natural number from 1 to n; the opening of the side guide plate thereof is specifically:

[0022] Finish rolling mill F i Head setting: strip entering the finish rolling mill F i Before biting, opening = basic opening - Y i1

[0023] Finish rolling mill F i Middle setting: finish rolling mill F i After biting, opening = basic opening - Y i2

[0024] Finish rolling mill F i Tail setting: finish rolling mill F i After throwing, opening = basic opening - Y i3

[0025] Wherein: Y i1 < Y i2 , Y i3 < Y i2 .

[0026] Preferably, n = 7.

[0027] Preferably, the basic opening of the side guide plate = strip width + 80mm.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] The present application provides a method for preventing the edge quality defects of hot-rolled strip, which solves the problem of edge quality defects caused by the abnormal scratching of the strip edge and the side guide plate during the production of hot-rolled strip, especially the quality problem caused by the impact of the strip head and tail side bending on the side guide plate. The present application divides the control of the side guide plate into three sections, head, middle and tail, by setting a three-section position control system, and adopts differentiated opening setting, with larger opening at the head and tail, which effectively avoids the impact of the strip head and tail on the side guide plate, and prevents the scratching of the strip edge through precise opening control; through precise control of the side guide plate, the pre-cutting side guide plate adopts a gear and rack structure, the finish rolling mill side guide plate with a control range of ± 150mm is independently controlled by double oil cylinders, the control range is ± 50mm, and the racks from F1 to F7 are designed with decreasing opening, realizing precise control; the present application also sets strict equipment maintenance standards, controls the wear of the side guide plate within 5mm, controls the frame amount of the oil cylinder pin within 3mm, and flexibly adjusts the calibration center line (0-20mm offset) according to the wear condition, and regularly checks and maintains to ensure the accuracy of the equipment. Through the comprehensive application of the above technical means, the present application not only effectively solves the problem of strip edge quality defects and improves the product yield, but also reduces customer quality complaints, reduces economic losses of enterprises, improves production efficiency and product quality, and brings significant economic and social benefits to enterprises. BRIEF DESCRIPTION OF DRAWINGS

[0030] ​​​Fig. 1 Fig. 2 is a top view of the finishing mill in the preferred embodiment of the present application;

[0031] Fig. 2 Fig. 3 is a schematic view of the structure of the side guide of the finishing mill in the preferred embodiment of the present application;

[0032] Fig. 3 Fig. 4 is a schematic view of the three-section control of the side guide in the preferred embodiment of the present application.

[0033] Fig. 1 is a side guide. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative labor fall within the scope of the present application.

[0035] As shown in Figs. 1-3

[0036] A method for preventing quality defects of the edge of hot-rolled strip steel,

[0037] In the main process of hot continuous rolling production, the slab is heated in a heating furnace, descaled by high-pressure water, rough-rolled, finished-rolled by a finishing mill, laminarly cooled, and coiled by a coiler. The specific process flow is as follows:

[0038] After the slab is heated to the set slab discharge temperature in the heating furnace, the slab is lifted by a tundish and placed on the discharge roller way of the heating furnace. The discharged slab is conveyed by the roller way to the high-pressure water descaling box, and the surface scale of the slab is removed by high-pressure water. Then, the slab is reversibly rolled by the rough rolling mill in five to seven passes to form an intermediate slab with a thickness of 30mm to 50mm. The intermediate slab after the rough rolling mill is sent to the finishing mill area by the roller way. Before entering the finishing mill, the intermediate slab is first cut by the flying shear to remove the head and tail of the intermediate slab. The flying shear is provided with a pre-cutting side guide, which plays a role of centering before the intermediate slab enters the finishing mill. After the head and tail are cut, the intermediate slab is sent to the finishing mill to remove the secondary scale by the high-pressure water descaling box, and then continuously rolled by the seven racks of the finishing mill. Before each rack of the finishing mill, there is a side guide 1, which is position-controlled and set with different opening values according to different widths of the strip steel. The side guide plays a role of correcting the deviation of the rolled piece during rolling. The intermediate slab is rolled into a finished strip steel by the finishing mill. The hot-rolled strip steel is cooled to the set coiling temperature by the laminar cooling system with an appropriate cooling system. The strip steel is sent to the coiler by the hot discharge roller way, and then sequentially passes through the coiling side guide 1, the pinch roll, the coiling assisting roll, and the winding drum to be coiled into a steel coil.

[0039] The reasons for the head and tail side bending of the hot-rolled strip steel include:

[0040] ​Uneven deformation in hot rolling process: In the process of hot continuous rolling, the strip steel is subjected to multiple passes of rolling. Uneven deformation may occur due to uneven temperature distribution, uneven rolling force, etc., resulting in head and tail side bending.

[0041] Equipment precision problem: Large deviation in control precision of side guide plate 1 leads to equipment precision decline, which may cause uneven deformation in the rolling process, and further cause head and tail side bending of the strip steel.

[0042] The slab coming out of the heating furnace may have some unevenness or bending in itself. This initial state may be amplified or retained in the subsequent rolling process.

[0043] In the continuous rolling process, the strip steel may develop complex internal stress distribution, especially in the head and tail parts. These stresses may cause the strip steel to bend sideways after leaving the rolling mill.

[0044] From the heating furnace to the various passes of rolling, the temperature distribution of the strip steel may not be uniform, especially the head and tail parts may have a temperature difference from the middle part. This may cause uneven shrinkage during cooling, causing side bending.

[0045] As can be seen from the above, the side bending of the head and tail of the strip steel is a difficult problem to completely avoid. Therefore, in order to control and reduce the negative effects of side bending, the present embodiment adopts various means for the side guide plate 1 to prevent the quality defects of the edge of the hot-rolled strip steel caused by abnormal scraping of the edge of the hot-rolled strip steel with the side guide plate 1.

[0046] Firstly, the abnormal scraping of the edge of the hot-rolled strip steel with the side guide plate 1 occurs mostly in the pre-cut side guide plate and the pre-finished side guide plate;

[0047] Since the opening degree of the side guide plate 1 remains fixed, when the head and tail of the strip steel bend sideways, the side guide plate 1 cannot effectively adapt to the actual position and shape of the strip steel. At this time, the side guide plate 1 cannot guide normally, the strip steel may run off, increasing the risk of abnormal contact with the side guide plate 1; even the head and tail of the side-bent strip steel may directly impact the side guide plate 1, not only causing damage to the edge of the strip steel, but also reducing the equipment precision of the side guide plate 1.

[0048] Therefore, the three-section independent control mode of the pre-cut side guide plate is: along the direction of strip steel transmission, the opening degree of the first head side guide plate, the opening degree of the first middle side guide plate, and the opening degree of the first tail side guide plate are independently set according to the requirements.

[0049] The two sides of the pre-cut side guide plate adopt gear and rack type transmission structure, and the gear and rack type transmission structures on both sides are controlled by the same oil cylinder. The three-section position control setting range is ±150mm.

[0050] The three-section independent control mode of the pre-cut side guide plate opening degree specifically includes:

[0051] Head setting: before the strip enters the flying shear, the opening = base opening - X1;

[0052] Middle setting: after the strip is bitten by the finishing mill F1, the opening = base opening - X2;

[0053] Tail setting: before the strip tail is 2 meters away from the flying shear, the opening = base opening - X3;

[0054] Wherein: X1 < X2, X3 < X2.

[0055] The finishing mill equipment of the hot-rolled strip includes F1-Fn. n There are n finishing mills, and n is a natural number greater than 1. Each finishing mill adopts a three-section independent control mode, and the opening of the side guide plate 1 of the lower side finishing mill is smaller than that of the upper side finishing mill along the strip transmission direction.

[0056] For the finishing mill F1, i i is a natural number from 1 to n; and the opening of the side guide plate 1 is specifically:

[0057] The head setting of the finishing mill F1, i before the strip enters the finishing mill F1, i , the opening = base opening - Y; i1

[0058] The middle setting of the finishing mill F1, i after the strip is bitten by the finishing mill F1, i , the opening = base opening - Y; i2

[0059] The tail setting of the finishing mill F1, i after the strip is thrown by the finishing mill F1, i , the opening = base opening - Y; i3

[0060] Wherein: Y i1 < Y i2 , Y i3 < Y i2 .

[0061] The first oil cylinder is used to control the operation side of the finishing mill side guide plate, the second oil cylinder is used to control the transmission side of the finishing mill side guide plate; the three-section control is set respectively for the two sides, and the setting range is ±50mm.

[0062] In this embodiment: n = 7,

[0063] The head opening of the side guide plate before the shearing = base opening - 10mm, the middle opening = base opening - 40mm, and the tail opening = base opening - 10mm;

[0064] ​​​The head side guide plate of the F1 rack head sets the head opening degree = basic opening degree - 20mm, the middle opening degree = basic opening degree - 40mm, and the tail opening degree = basic opening degree - 35mm.

[0065] The head side guide plate of the F2 rack head sets the head opening degree = basic opening degree - 20mm, the middle opening degree = basic opening degree - 35mm, and the tail opening degree = basic opening degree - 30mm.

[0066] The head side guide plate of the F3 rack head sets the head opening degree = basic opening degree - 20mm, the middle opening degree = basic opening degree - 35mm, and the tail opening degree = basic opening degree - 30mm.

[0067] The head side guide plate of the F4 rack head sets the head opening degree = basic opening degree - 20mm, the middle opening degree = basic opening degree - 35mm, and the tail opening degree = basic opening degree - 30mm.

[0068] The head side guide plate of the F5 rack head sets the head opening degree = basic opening degree - 20mm, the middle opening degree = basic opening degree - 35mm, and the tail opening degree = basic opening degree - 25mm.

[0069] The head side guide plate of the F6 rack head sets the head opening degree = basic opening degree - 20mm, the middle opening degree = basic opening degree - 30mm, and the tail opening degree = basic opening degree - 25mm.

[0070] The head side guide plate of the F7 rack head sets the head opening degree = basic opening degree - 20mm, the middle opening degree = basic opening degree - 25mm, and the tail opening degree = basic opening degree - 15mm.

[0071] In the embodiment, the width of the strip steel is 1500mm, and the basic opening degree of the side guide plate before shearing and the side guide plate of the finishing mill = strip steel width + 80mm = 1580mm.

[0072] In order to ensure the effect of the three-section control of the side guide plate 1, the equipment maintenance and precision control are further strengthened from the following three aspects in the embodiment:

[0073] The wear degree of the side guide plate 1 is detected in real time or at a fixed time, and when the wear degree of the side guide plate 1 exceeds the wear threshold, the side guide plate 1 lining plate is replaced; otherwise, the side guide plate 1 lining plate is not replaced; so as to ensure the working precision of the side guide plate 1.

[0074] The oil cylinder pin shaft frame amount of the side guide plate 1 is detected in real time or at a fixed time, and when the oil cylinder pin shaft frame amount of the side guide plate 1 exceeds the frame amount threshold, the oil cylinder pin shaft frame amount is processed; otherwise, it is not processed; so as to improve the equipment precision and ensure the normal work of the side guide plate 1.

[0075] The center line of the side guide plate 1 is calibrated, and according to the wear condition of the side guide plate 1, the center line of the side guide plate 1 is offset to the transmission side or the operation side based on the center line of the housing; in specific production, according to the corresponding relationship between the wear condition of the side guide plate 1 and the offset, the rolling center line is offset to the side with more serious wear by 0-20 mm based on the center line of the housing.

[0076] The above description is only a preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preventing edge quality defects in hot-rolled strip steel, characterized in that, include: The opening of the control side guide plate (1) specifically includes: using three independent control methods for the shear front side guide plate and the finishing mill side guide plate respectively; The wear degree of the side guide plate (1) is detected in real time or at regular intervals. When the wear degree of the side guide plate (1) exceeds the wear threshold, the side guide plate liner is replaced; otherwise, the side guide plate liner is not replaced. The cylinder pin frame size of the side guide plate (1) is detected in real time or at regular intervals. When the cylinder pin frame size of the side guide plate (1) exceeds the frame size threshold, the cylinder pin frame size is processed; otherwise, no processing is performed. The centerline of the calibrated side guide plate (1) is offset towards the transmission side or the operation side, based on the wear condition of the side guide plate (1) and the centerline of the archway. The three-section independent control method of the front guide plate is as follows: along the direction of strip steel transmission, the opening of the No. 1 head side guide plate, the opening of the No. 1 middle side guide plate, and the opening of the No. 1 tail side guide plate are set independently according to the requirements. The three-segment independent control method for the opening of the shear front guide plate specifically includes: Head setting: Before the strip enters the flying shear, the opening is equal to the base opening minus 1; Middle setting: After the F1 steel bites, the opening degree = basic opening degree - x2; Tail setting: When the strip tail is 2 meters away from the flying shear, the opening = basic opening - x3; Where: X1 <X2,X3<X 2； Finishing equipment for hot-rolled strip steel includes F1 to F1. n There are a total of n finishing mills, where n is a natural number greater than 1. Each finishing mill adopts a three-segment independent control mode, and along the strip conveying direction, the opening of the side guide plate (1) of the lower finishing mill is smaller than the opening of the side guide plate (1) of the upper finishing mill. For finishing mill F i , where i is a natural number from 1 to n; the opening degree of its side guide plate (1) is specifically as follows: Finishing mill F i Head setting: Strip enters finishing mill F i Before, opening degree = basic opening degree - Y i1 ; Finishing mill F i The middle setting: finishing mill F i After the steel is engaged, the opening angle = basic opening angle - Y i2 ; Finishing mill F i Tail setting: Finishing mill F i After steel is poured, the opening angle = foundation opening angle - Y i3 ; Where: Y i1 <Y i2 Y i3 <Y i2 ; The basic opening of the side guide plate (1) = strip width + 80mm; It also includes controlling the wear of the control side guide plate to within 5mm and the cylinder pin frame displacement to within 3mm.

2. The method for preventing edge quality defects in hot-rolled strip steel according to claim 1, characterized in that: The front guide plate of the shear adopts a gear and rack transmission structure on both sides. The gear and rack transmission structure on both sides is controlled by the same hydraulic cylinder, and the three-stage position control setting range is ±150mm.

3. The method for preventing edge quality defects in hot-rolled strip steel according to claim 1, characterized in that: The No. 1 hydraulic cylinder controls the operating side of the finishing mill side guide plate, and the No. 2 hydraulic cylinder controls the transmission side of the finishing mill side guide plate; the three-stage control is set separately for both sides, with a setting range of ±50mm.

4. The method for preventing edge quality defects in hot-rolled strip steel according to claim 1, characterized in that: n=7。

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