Method for controlling linear defects on edge surface of hot-rolled strip steel

Abstract

The invention discloses a control method for linear defects on the edge surface of hot-rolled strip steel, and belongs to the technical field of metallurgy. The method aims at solving the problem that in the rolling process of hot-rolled strip steel, various corner and near-corner narrow edge defects generated in the slab inheritance, heating, width reduction and thickness reduction are turned to the middle slab wide edge and become strip steel edge surface linear defects. According to the fixed-width machine hammer head with the middle protruding arc top face, a raw material plate blank is changed into a fixed-width middle blank with the narrow edge corresponding to the hammer head without the vertical plane protruding outer contour, the middle of the fixed-width middle blank is sunken, and the two corners of the fixed-width middle blank are in the shape similar to a swallow tail; for steel with serious corner defects, a vertical roller of an edging mechanism can be used in cooperation to bend the dovetail from the middle section and press the dovetail to the side edge of a rolled intermediate billet in the subsequent rolling process, and by changing the relative position relation of all points on the surface of the narrow edge and corner end points of the narrow edge in advance, overturning of the corner and the narrow edge part close to the corner of the raw material slab to the surface of the edge of the strip steel is restrained. And linear defects on the edge surface of the hot-rolled strip steel are eliminated or reduced.

Description

Technical Field

[0001] The present invention relates to the field of metallurgical technology, and more specifically, to a method for using a convex forging hammer head of a side-pressure width setting machine (hereinafter referred to as the width setting machine) to change a raw material slab into a width-setting intermediate slab with a narrow side corresponding to the raised outer contour of the hammer head's arc top and a concave middle, and two corners approximating a dovetail shape, while setting the width, so as to suppress the narrow side defects at the corners and near the corners of the raw material slab from turning into linear defects on the edge surface of the hot-rolled strip in the subsequent rolling process, and belongs to the technical field of hot rolling process. Background Art

[0002] The rolling of hot-rolled strip is unidirectional rolling along the length direction of the slab, and the shape of the narrow side of the slab has a great influence on the change of the edge morphology of the intermediate slab during the strip rolling process. Usually, because the flow of metal on the wide side surface of the billet to both sides is restricted by the huge friction between it and the roller surface, the narrow side of the plane or near the plane of the raw slab or forged fixed-width slab will gradually evolve from plane → drum-shaped surface → corner to strip edge surface → near-corner narrow side to edge surface during rolling, causing the inherited solidification defects at the corners and near-corners of the slab and the hot rolling process defects at the corners and near-corners of the slab during the heating, width setting and rolling of the slab to turn into continuous or intermittent linear defects on the edge surface of the strip, usually existing A single linear defect or multiple linear defect bands on the surface within the range of 10~30mm from the edge of the strip which is positively correlated with the amount of billet reduction, especially if the narrow side of the slab is bulging or the width is reduced too much to make the narrow side thicker, will aggravate the severity of the corner and narrow side of the intermediate billet turning over to the edge of the strip, further deteriorating the surface quality of the strip edge. The defects of the slab corners of crack-sensitive steel grades extending to the wide side can appear at a maximum of 50mm from the edge of the strip after turning over and extending longitudinally, which greatly affects the quality of the strip and reduces the yield rate of strip rolling.For this reason, metallurgical workers at both the hot rolling and continuous casting ends have tried to optimize the narrow edge shape of the slab after a lot of attempts to adjust the process parameters have not achieved good results. At the hot rolling end, since most modern strip steel rolling lines are equipped with step-by-step forging slab width setting machines designed to reduce the width specifications of the slab continuous casting billet, the narrow edge morphology of the slab can be changed accordingly by adjusting the outer contour of the working surface of the forging hammer head during the slab width setting process to control the flipping of various corner and near-corner narrow edge defects to the edge surface of the strip, such as Chinese patent application No. 2017114969828, 202310312256 5 and 2023104630254 respectively use a trapezoidal groove hammer to forge the four corners of the slab into a dog-bone-shaped cross-section with a convex middle plane of the narrow side, in order to reduce the corner defects in the rolling process by eliminating the inherent defects of the corners and increasing the corner temperature by pressing the parts; at the hot rolling end, there are also attempts to use a trapezoidal boss-shaped hammer to forge the middle part of the narrow side of the slab into a dog-bone-shaped cross-section with a concave middle plane of the narrow side to improve the edge quality of the strip. For example, a hot rolling production line uses two horizontal cross-sections with a height of 10mm, top edges of 155 and 170mm respectively, and a bottom edge and waist edge angle of 75° for the narrow side of a continuous casting slab with a thickness of 230mm. The convex hammer head with an isosceles trapezoidal cross section makes the narrow side of the slab into a dog-bone cross-section with a concave middle plane part during forging and setting the width, in order to partially reduce the turning of the narrow side near the corner to the edge surface of the strip to reduce the corner defects in the rolling process; at the continuous casting end, a large number of "chamfered crystallizer" technologies are used to change the right angle of the continuous casting billet into two large obtuse angles, eliminating and alleviating the various problems of the "right angle", and greatly improving the edge quality of the subsequent finished strip; still at the continuous casting end, there are many arc-shaped convex crystallizer narrow side copper plates that make the narrow side of the continuous casting billet a fully concave arc surface or a straight surface near the corner and a concave arc surface in the middle to reduce the continuous Related technologies for flipping the narrow edges of the corners and near-corners of the ingot to the edge surface of the plate and strip during rolling, such as Chinese patent applications No. 201520673254X, 2016107966888, 2022113292924, 202311001841X and 202410788229X, etc.; or at the continuous casting end, Chinese patent application No. 2017100790460 directly makes the narrow edge of the slab crystallizer into a protruding arc-shaped copper plate with a diameter of the slab thickness to cast a slab with an arc thickness without corners, so as to eliminate the corners that are prone to various solidification, heating and rolling defects.

[0003] Although various existing technologies have improved the linear defects on the edge of hot-rolled strip to a certain extent, the degree of improvement is far from ideal. The main problems are: 1) At the hot rolling end, (1) all existing technologies that attempt to use the fixed-width forging process to improve the problem of linear defects on the edge of the strip have a large proportion of vertical planes on the hammer head working surface, whether it is a trapezoidal groove or a trapezoidal boss. However, when the vertical plane is forged in the forward direction, the huge friction between the surfaces limits the rheology of the surface metal of the narrow edge of the slab, which makes the "dog bone" shape of the narrow edge area of ​​the fixed-width intermediate billet more severe, which is not conducive to reducing the linear defects on the surface. Specifically, (i) the local bulge on the wide edge near the narrow edge is relatively high, which will cause the problem of lateral folding during rolling; (ii) the total thickness of the billet near the narrow edge increases, and the roughness is not good. When rolling the slab, a greater friction force is generated between the upper and lower surfaces of the wide side near the narrow side and the rollers, which further restricts the flow of metal on the wide side surface at the corner of the slab along the middle part of the narrow side, and also increases the amount of metal that can flow freely laterally in the middle of the narrow side of the slab, which intensifies the degree of flipping of the slab corner and the narrow side near the corner to the edge surface of the strip; (2) The existing technology of using trapezoidal groove hammer heads, which has been tried more, has the effect of pushing the slab corner to and fixing it on the wide side surface of the intermediate slab, which not only makes the narrow side surface of the slab protrude outward from the end point of the side corner before rolling, but also may cause metal folding near the corner surface during the pushing process. The overlap is contrary to the purpose of suppressing the narrow surface of the corner and near-corner of the billet from turning over to the wide surface of the billet. This is also the principle problem that similar prior arts are basically ineffective or even have negative effects; (3) When the trapezoidal boss hammer head is used in the prior art, the height of the trapezoidal boss is too small to offset the rolling lateral bulging of the relatively much larger middle part of the narrow side. However, because its cross section is a vertical plane bent at a large angle, no matter how the relative length relationship between the bottom side, top side and bottom side of the trapezoid and the edge of the hammer head is adjusted, when the protruding height is further increased to increase the concave part in the middle of the narrow side surface of the billet to offset the lateral movement of the midpoint, a more serious fold in the middle of the side will occur. (4) In particular, the degree of dog-bone protrusions near the corners of the wide side of the fixed-width intermediate billet and the maximum thickness near the narrow side are aggravated with the increase of the width reduction of the slab. When the width reduction is large, the surface defects of the strip edge also increase exponentially accordingly, which greatly limits the performance of the width setting machine. The problems existing in the existing technology still limit the possible maximum width reduction of the slab, resulting in the width reduction of the width setting machine of most hot rolling production lines not exceeding half of the possible maximum width reduction capacity. The width specification of the slab is forced to increase by increasing the frequency of online width adjustment during the continuous casting process, which not only produces a large number of transition billets for width adjustment during continuous casting, but also limits the flexible production of strip rolling.

[0004] 2) At the continuous casting end, as the raw material of strip steel: First, the application effects of all existing technologies for improving the narrow edge morphology of continuous casting are completely destroyed when forging is performed under the existing slab width setting technology conditions; second, even without using a width setting machine and greatly increasing the slab width specifications, (1) for the narrow-edge concave continuous casting slab, due to its unfavorable solidification conditions, there are relatively more corner defects. For crack-sensitive steel types, these defects will also extend to the wide side. During rolling, these defects cannot be reversed to the narrow side, which restricts the improvement effect of linear defects on the edge surface of the strip steel; (2) for the narrow-edge arc continuous casting slab, because the arc narrow side of the arc crystallizer must smoothly transition with the straight wide side, very sharp edges appear on both sides of the arc copper plate of the narrow side of the crystallizer. Sharp corners. When the slab width is frequently adjusted during the continuous casting process without using a width setting machine, the very weak sharp corners on both sides of the narrow arc copper plate will be worn in a very short time, resulting in solidification protrusions and gaps that clamp steel. This will not only cause surface defects of the ingot at the junction of the flat arc surface, but may even damage the narrow copper plate of the crystallizer and cause casting accidents. (3) For chamfered ingots with large obtuse angles, because the large obtuse angles of the corners correspond to the sharp angles on both sides of the narrow copper plate of the trough crystallizer, when the slab width is frequently adjusted during the continuous casting process without using a width setting machine, the weaker sharp angles on both sides of the narrow copper plate are relatively easy to be worn, resulting in solidification protrusions and gaps that clamp steel, reducing the online continuous service life of the crystallizer.

[0005] In summary, it is still very necessary to explore new methods for linear defects on the edge of hot-rolled strip to effectively inhibit the flipping of the narrow edge of the slab corner and near the corner to the surface of the intermediate billet, control the width of the strip edge surface defect strip from the edge line, and possibly force the defects extending from the corner to the edge of the wide edge of the slab / intermediate billet to flip back to the side, so as to further improve the surface quality of the strip edge. Summary of the invention

[0006] 1. Problem to be solved The purpose of the present invention is to control the various corner and near-corner narrow edge defects inherited by the slab and / or generated during its heating, width setting and rolling processes to be flipped to the edge surface of the strip, thereby eliminating or reducing linear defects on the edge surface of the hot-rolled strip, while reducing the slab width specifications as much as possible and making full use of the width setting machine capacity to achieve a larger width reduction of the slab.

[0007] 2. Technical solution The technical solution adopted by the present invention is: 1) The working surface of the lateral forging hammer of the width setting machine is made into a triangle-like or bow-like shape with a cross section of an arc and an arc / straight line combination and a circular arc top convex shape without any vertical plane, so that the narrow side of the raw slab corresponds to the outer contour of the convex circular arc of the hammer head and is normally forged to become a fixed width intermediate billet with a concave middle part of the narrow side section and a dovetail-like corner. There is no vertical plane in the entire inner contour and the midpoint of the middle concave corresponds to the midpoint of the narrow side of the slab, and the end points of the dovetail tip correspond to the two corner end points of the narrow side of the slab. By changing the morphology of the narrow side of the raw slab, the relative position relationship between each point on the outer contour of the narrow side surface of the cross section and its corner end points is changed accordingly, and the metal flow state of each part during rolling is changed accordingly, so as to inhibit the turning of the narrow side part of the corner and the near-corner part of the continuous casting billet to the edge surface of the strip; 2) For steels that are sensitive to continuous casting cracks or have many corner defects during rolling, the vertical rolls of the edge rolling mechanism can be used in conjunction with the subsequent rolling to bend the dovetail tip angle from the middle section to the midline of the thickness of the narrow side of the intermediate billet and press it to the narrow side surface of the intermediate billet, further forcibly transferring the defects near the corners of the wide side of the billet to the edge of the strip; 3) Through the coordinated control of the width reduction of the width setting machine and the reduction of each pass of the roughing mill and the finishing mill, the same hammer head can achieve the control target of each point on the narrow side surface of any cross section of the fixed-width intermediate billet and the new intermediate billet generated by dovetail angle bending and pressing after rolling, while hitting the strip width target and under various conditions including the purpose of the strip.

[0008] The technical principles of the present invention that are significantly different from the prior art are as follows: 1) The relative position relationship between each point on the outer contour of the narrow side surface of the slab cross section and its two corner endpoints is optimized by designing the arc working surface of the hammer head, and the characteristics of the aforementioned points with metal rheology under positive pressure rolling are also adjusted accordingly. The essence of the flipping of the narrow surface of the corner and near-corner portion of the slab toward the wide side surface of the intermediate billet during the rolling process is that the end point position of the free flow of metal to the outside at each point on the narrow side surface of the slab (especially the middle section) is relatively far away from the end point position of the movement of the corresponding upper and lower corner end points to the outside due to the friction between the rollers; when the conventional flat working surface hammer is lateral forging, the narrow side surface of the slab cannot move up and down due to the friction between the hammer working surface, resulting in a bulge at the highest point on the wide side surface of the slab at a certain distance from the narrow side, that is, the so-called "dog bone" shape is formed. At this time, the corner end points and narrow sides of the slab are still thickened and "dog bone" shaped. The corner end points and narrow sides of the fixed width intermediate billet; Under the prior art, the slab and its fixed width intermediate billet still have serious flipping of the narrow surface of the corner and near-corner portion during the rolling process. The reasons are: (1) During positive pressure rolling, the friction between the support of the narrow side metal and the rollers at the edge of the wide side of the billet is very large, which limits the billet (1) The metal at the edge of the wide side (i.e., the corner of the slab / fixed width intermediate billet) moves toward the outer side; (2) The metal in the middle of the narrow side of the billet flows freely toward the outside due to the lack of external force restrictions, and the middle point of the narrow side surface thickness often has the largest flow distance; (3) As the billet is thinned and becomes a strip, the middle point or middle section of the original billet narrow side surface thickness becomes the side of the strip, and the part between it and the corner of the billet and the part between them flips to the surface near the side of the strip, forming a longitudinal strip of the strip edge after the corner and the narrow side near the corner of the billet are flipped; (4) Obviously, the thicker the billet, the greater the width reduction, the thinner the finished strip, and the greater the single-pass reduction of the billet, the wider the longitudinal strip of the strip edge after the corner and the narrow side near the corner of the billet are flipped; therefore, when the middle point of the slab narrow side thickness and the corresponding upper and lower corner end points are both at or close to the vertical line of the corresponding strip cross-section side, the slab corner will not flip to the strip edge surface.

[0009] According to the drum-shaped protrusion of the narrow side straight surface of the slab or the intermediate billet after width setting to both sides during the rolling process and its progress, the present invention performs a mirror flip in the opposite direction according to the protrusion amount and protrusion morphology, and combines the force and metal rheology of the concave narrow side of the mirror flipped concave narrow side during width setting and billet opening rolling, and uses a fixed width hammer with a convex cross-section similar to a round-end cone to forge a narrow side cross-section of the slab with a middle concave and a corner similar to a dovetail shape on the narrow side of the slab, and performs a cross-sectional view of each point on the outer contour of the narrow side cross-section of the billet, including the corresponding upper and lower corner endpoints. During rolling, the outward flow is offset / compensated in advance to achieve the target width of the strip, while making the middle point of the narrow side cross-sectional surface of the original width intermediate billet on the vertical line at the edge of the strip and the points on the outer contour gradually approach and finally basically coincide with the corner end point of the new intermediate billet formed after the dovetail angle bending and pressing into the narrow side during rolling. That is, relative to the vertical line at the edge of the strip, all points on the narrow side surface of the new intermediate billet cross-sectional surface after the dovetail angle bending have neither excessive protrusion to the outside nor excessive folding retained inside.The method of the present application adopts a hammer head with a triangular or bow-shaped working surface cross section and a round-end cone protrusion and no vertical plane in the outer contour. The differences between the width setting and rolling process and the prior art are as follows: (1) In the width setting process, (i) due to the high protrusion in the middle of the hammer head, more extrusion occurs in the middle area of ​​the narrow side of the billet during the width setting forging, and the forging pressure penetrates from the middle of the narrow side inward, so that the relative thickness of the middle part of the wide side of the billet increases, the local bulge height near the narrow side of the wide side surface is relatively reduced and extends to the middle of the wide side, and the stress of the surface area of ​​the narrow side near the corner is relatively relieved; (ii) the corner of the slab is relatively stable. The hammer working surface nearby has a certain inclination, so that the friction between the hammer working surface and the narrow side of the billet is reduced during fixed width forging. Under the premise of maintaining a large horizontal width reduction force, the metal on the narrow side surface will slide along the working surface to a certain extent. (iii) The round end cone protrusion and the hammer working surface with a certain inclination make the inner wall of the concave formed on the narrow side during fixed width forging produce upward and downward extrusion force, which is completely different from the various "dog bones" in the prior art, and will extrude the corners of the slab into a "dovetail" shape. (iv) For slabs of the same cross-sectional thickness, The greater / smaller the width reduction, the greater / smaller the thickness of the narrow side surface area of ​​the fixed-width intermediate billet after the width reduction. When the narrow side depression pressed by the hammer head of the present invention is used, it is also correspondingly deepened / shallowed, which can offset / compensate the lateral outward movement of the midpoint of the narrow side surface thickness of the intermediate billet during the rolling process under different width reductions; (2) During the rolling process, (i) due to the depression between the two "dovetail"-shaped acute angles of the narrow side, the friction between the two corners of the fixed-width intermediate billet and the roller surface is reduced due to the reduction of the lower support force when the fixed-width intermediate billet is rolled down, and the dovetail part can flow freely to the outside along with the metal in the middle part of the narrow side surface. (ii) The prefabricated depression in the middle area of ​​the narrow side makes each point on the narrow side surface of the fixed-width intermediate billet gradually approach its corresponding upper and lower corner endpoints during the rolling thinning process; (iii) The higher protrusion and inclined surface of the hammer head alleviate the local bulge on the wide side surface of the billet near the narrow side, eliminating the folding of the wide surface near the corner that may occur during rolling; (iv) Under the fully coordinated advance and real-time control of the above two aspects, the surface midpoint of the narrow side section of the slab and each point on the outer contour and its corresponding upper and lower corner endpoints are as close as possible to the side vertical line of the cross section of the finished strip.

[0010] 2) The surface quality of the strip edge is further optimized by bending the "dovetail" from the middle section to the midline of the thickness of the narrow side of the intermediate billet and pressing it to the midpoint of the narrow side of the intermediate billet The corner endpoint area of ​​the raw material slab is usually the point with the most defects in the corresponding finished strip steel. Various corner and near-corner narrow edge defects inherited from the slab and / or generated during its heating, width setting and rolling process will eventually appear on the edge surface of the strip steel. In particular, the corner cracks that are easy to be generated and extended to the wide edge surface at the corner of the continuous casting slab of crack-sensitive steel, the developed solidification grooves at the corner of ultra-low carbon steel, and the various corner defects that are easy to occur during heating and rolling of medium and high carbon steel slabs will seriously affect the edge surface quality of the strip steel. In other words, the effect of simply suppressing the corner endpoint of the slab / intermediate billet from turning over to the edge surface of the strip steel is not very ideal in theory, and it is also necessary to forcibly transfer various possible defects on the wide edge surface of the slab corner. In this regard, various existing technologies cannot even suppress the turning of the corner endpoint of the slab to the edge surface of the strip steel, let alone transfer various possible defects on the wide edge surface of the slab corner.

[0011] The present invention forges the narrow side of the raw slab into a fixed-width intermediate billet with upper and lower corners similar to dovetails at the narrow side section. The dovetail with the tip corresponding to the two corner endpoints of the narrow side of the slab can be conveniently bent from the middle section and pressed into the midpoint of the narrow side surface of the intermediate billet, and can further forcibly transfer various corner defects of the wide side surface of the raw slab / fixed-width intermediate billet to the edge of the strip steel to reduce the flipping to the edge surface of the strip steel. For low-alloy peritectic steel, medium-high carbon steel and ultra-low carbon steel with more corner defects on the wide side surface of the raw slab / fixed-width intermediate billet, a longer bending length can be applied in the rough rolling stage, and for steel types with fewer corner defects on the wide side surface, a shorter bending length can be applied. Even for steel types with few corner defects on the wide side surface, the tip of the dovetail should be slightly bent to avoid wear / scratches on the upper and lower roller surfaces caused by high-strength, low-temperature sharp corners that may flip up during edge rolling. Obviously, the bending of the narrow-corner dovetail tip of the intermediate billet toward the narrow side can moderately increase the temperature of the newly formed intermediate billet corner, which is beneficial to slow down the degree of dual-phase rolling with a large low-temperature phase ratio and avoid the original dovetail tip with more problems from flipping to the strip surface, which is more conducive to further reducing the surface defects of the strip edge. However, it should be noted that (1) the vertical roller cannot be used to roll or reduce the width of the intermediate billet before bending, and (2) the apparent roughness of the strip edge will appear after bending.

[0012] 3) Under the condition of the target width of the strip, the strategy for optimizing the final positional relationship between each point on the outer contour of the narrow side surface of the raw slab cross section and its upper and lower corner endpoints at the edge of the finished strip is combined with its purpose. Hot-rolled strip products have various specifications and a wide range of uses, and the quality requirements for the edges and the subsequent processing of the edges are also different. For example, most thin plate products have strict requirements on edge surface defects, and straight shearing is used for trimming; thinner structural steels pay more attention to the internal quality of the strip, and in order to use materials reasonably, they often use a small amount of straight trimming on the edge of the strip, and even directly perform a single-sided welding groove on the edge of the strip; thicker structural steels also pay more attention to the internal quality of the strip, and often do not trim or perform a double-sided bevel welding on the edge of the strip after a small amount of trimming. Therefore, under the condition of ensuring the surface quality of the strip edge, combined with the use of the strip, when controlling the width of the slab and the rolling of the intermediate slab, the final position relationship between the middle point of the surface thickness of the narrow side of the cross section of the raw material slab, which is representative and easy to use as an indicator, and the end points of its upper and lower corners on the edge of the finished strip can further support the use of the strip by subsequent users.

[0013] The distribution of the three points of the middle point of the narrow side surface thickness of the raw material slab and its upper and lower corner endpoints on the edge of the finished strip and the edge surface quality are in four states: (1) The middle point of the narrow side surface thickness of the slab is located at the edge of the strip, and the two corner endpoints are at the edge or near the edge surface. In this case, the internal defects of the edge will be relatively few (in this case, H can be selected to be a relatively small value); (2) The middle point of the narrow side surface thickness and the two corner endpoints of the slab are both located at the edge of the strip. In this case, the relative relationship of the internal / surface defects of the edge depends on the type of steel; (3) The two corner endpoints of the slab edge are at the edge or the two corner endpoints are at the edge and close to the edge respectively, and the middle point of the narrow side surface thickness is located in the middle of the strip near the edge. In this case, the surface defects of the strip edge will be relatively few (in this case, H can be selected to be a relatively large value); (4) One corner endpoint of the slab edge is at the edge and the other corner endpoint is at the edge surface far away from the edge. In this case, the strip edge with the corner endpoint on the edge surface will have relatively more surface defects. The distribution difference of the two corner endpoints should be reduced by adjusting the alignment of the fixed width hammer.

[0014] In summary, in order to further achieve better strip material utilization when users use it, based on the principle of controlling the midpoint of the narrow side surface thickness of the raw slab and its upper and lower corner endpoints to the vertical line of the side of the finished strip cross section, the strategy for controlling its deviation is as follows: (1) For thin plate products, the third state mentioned above should be followed; (2) For thick-gauge strip products, especially products with double-sided groove treatment for welding, the first state mentioned above should be followed; (3) For thinner-gauge structural steel products, the second state mentioned above should be followed.

[0015] 4) Through the coordinated control of the width reduction of the width setting mill and the reduction of each pass of the roughing mill and the finishing mill, the edge quality of the strip can be better controlled under various conditions using the same width setting hammer.

[0016] During the service life of a forging hammer, only the same pair of hammers can be used to produce fixed-width intermediate billets for raw slabs of different widths of various specific steel grades and specific specifications of strip steel under different width reduction conditions, and (1) during rolling, the free flow of the midpoint of the narrow side surface to the outside is related to the amount of reduction, billet temperature and high-temperature physical properties of the steel grade. The thicker the billet, the greater the one-time reduction and the higher the billet temperature, the more the midpoint of the narrow side surface moves to the outside, and vice versa. (2) during rolling, the flow of the upper and lower dovetail corner endpoints on the narrow side surface of the billet to the outside is also related to the amount of reduction, billet temperature and high-temperature physical properties of the steel grade when the narrow side morphology is determined. (3) The fixed-width forging ability of the fixed-width machine to change the cross-sectional size of the slab is relatively single. Therefore, it is very It is necessary to establish a system control model to achieve that the midpoint of the narrow side surface of the raw slab and its corresponding upper and lower corner endpoints are located on the vertical line of the side of the cross-section of the target width and the specific purpose of the finished strip and are reasonably distributed, so as to calculate and determine: (1) the target value of the reduction amount of each pass of the roughing mill and each stand of the finishing mill and their coordinated control real-time adjustment value when using the same size of fixed-width intermediate billets to produce strips of various specifications and purposes within the corresponding range, or when using fixed-width intermediate billets of different widths and thicknesses within the corresponding range to produce strips of the same specifications and purposes; (2) the corresponding target width value of the fixed-width intermediate billet of the fixed-width mill under the conditions of using different steel grades and raw slabs of different widths to produce strips of various target thicknesses and purposes, and taking into account the wear of the outer profile of the hammer head during service life and the predicted rolling temperature.

[0017] 5) Principles and strategies for strip width control In the past, when hot-rolling production lines without width setting machines only used edge rolling mechanisms to reduce and set the width, the edge rolling and width reduction of the edge rolling machine vertical rollers also caused more surface defects on the edge of the strip, especially in the case of large width reduction and the later service period of the vertical rollers; modern hot-rolling production lines equipped with forging and width setting machines are usually equipped with multiple sets of edge rolling mechanisms, which provides the possibility of further improving the quality of the strip edge. In order to minimize the surface defects on the edge of the strip, the width setting machine should play the role of the width setting machine as much as possible in controlling the width of the strip, and avoid or limit the large amount of edge rolling width reduction in the edge rolling mechanism as much as possible. Especially in the case of the application of the method of the present invention, the edge rolling mechanism has new functional requirements such as quantitative bending dovetail, and it is even more necessary to use the edge rolling mechanism (including side guides) to assist in achieving the goal of controlling the surface defects on the edge of the strip. By fully considering (1) the purpose of the strip, (2) the type of steel, target thickness and target width, (3) the thickness and width of the raw slab, (4) the outer contour parameters of the forging hammer working surface, (5) the slab side pressure during the fixed-width forging process and the final fixed-width intermediate billet width, and (6) the real-time dynamic control of the coordinated control model of the intermediate billet thickness before each stand during the roughing and finishing rolling process, the intermediate billet temperature before the stand and its distribution, and the reduction amount of the previous pass, it is possible to enhance the system control capability of the width setting machine and each rolling mill over the strip width on the basis of the existing technology and reduce the negative impact of implementing edge width reduction.

[0018] 6) Changes in the concept of “width reduction” during slab width setting Due to the higher arc bulge in the middle part of the hammer head, when the corner end point of the narrow side of the slab just touches the working surface of the hammer head but there is no pressure during the width determination, the corner end point of the narrow side surface of the slab has not been compressed at all (that is, the maximum width of the slab has not been compressed), but the midpoint of the corresponding thickness has already been deeply pressed into a depression corresponding to the arc surface of the hammer head bulge. At this moment, if the further width reduction is stopped, the width of the finished strip rolled by the vertical roller will be smaller than the width of the finished strip of the same thickness rolled by the same vertical roller with a straight narrow side surface of the same width. In other words, the mass of the slab that has been forged by the protruding hammer head but has not been widened at its maximum width is less than the mass of the "same width" slab that has not been forged. Therefore, the concept of slab width reduction originally defined under the conditions of the vertical working surface hammer head corresponding to the width of the strip is very necessary to be adjusted. The present invention: (1) defines the difference between the average value of the width of the upper and lower surfaces of the raw material slab and the average value of the upper and lower wide side surfaces of the fixed-width intermediate slab as the slab width reduction, and the single-side width reduction is half of the slab width reduction; (2) In order to facilitate the calculation of the control model, the concept of "negative" width reduction is introduced at the same time, that is, the width reduction / single-side width reduction when the working surface of the arc-convex hammer head is in a state where it just contacts the narrow side surface of the slab and the corner end point has not been compressed at all (at this moment, the top surface of the arc-convex hammer head has been deeply pressed into the midpoint of the thickness of the corresponding narrow side, but the original slab width has not changed at all) is ±0mm, that is, if the distance between the vertical tangent line of the convex arc of the hammer head and the symmetrical point on the surface of the root area of ​​the hammer head is exactly the distance at the thickness of the slab is h (see the attached manual). Figure 1 , when B, H, R and b are determined, h is also a certain value), then the width reduction / single-sided width reduction at the moment when the top surface of the hammer head protrusion just contacts the midpoint of the width of the narrow side surface of the slab at the beginning of the operation are -2h / -h respectively; (3) Let y be the single-sided width reduction, x be the distance that the top point of the hammer head protrusion moves toward the center of the slab after contacting the narrow side surface of the slab during forging, then the corresponding slab width reduction is 2y, y=xh. Obviously, in order to obtain a certain effect of suppressing the flipping of the corners and the near-corner surfaces of the narrow side of the slab to the wide side, the single-sided width reduction y must be at least greater than -h, and it is best that y is greater than 0.

[0019] 7) Temperature drop problem at the tip of dovetail angle of fixed width intermediate billet Compared with various prior arts, the working surface of the forging hammer head of the present invention corresponding to the forging corner area of ​​the narrow side of the slab is changed from the vertical flat surface of 0° in the prior art to an inclined surface with an angle of 15~5° with the vertical line, so that the angle of the narrow side cross section of the fixed width intermediate billet is changed from a right angle to an acute angle of 75~85°. Although it helps to reduce the flipping of the slab corner to the strip surface, it is not conducive to the heat preservation of the corner, and there will be additional defects related to the edge of the strip caused by low-temperature corners such as dual-phase rolling, low plasticity zone rolling, etc., but these defects are also concentrated on the strip. The edge of the edge has little impact on steel quality and is easier to be removed during the subsequent trimming of the strip; choosing the lesser of two evils, compared with the surface defects of the strip edge with much greater negative impact, tolerating the partially controllable strip edge problems caused by a moderate reduction in corner temperature, which is also the fundamental difference of this method compared with the prior art in basic strategy; bending and pressing the dovetail from the middle section to the narrow side of the intermediate billet in the rough rolling stage helps to control the actual corner temperature of the intermediate billet during subsequent rolling passes, especially for intermediate raw materials for cold rolling with subsequent trimming or products with cleaned / chamfered edges.

[0020] 8) The actual depth of the concave depression on the narrow side of the slab during rolling of the fixed width intermediate slab Due to the small amount of slippage of the corner endpoints of the slab along the working surface of the hammer during the fixed-width forging process, the distance between the upper and lower dovetail corner endpoints on the same side of the fixed-width intermediate billet will be larger than other parts; when the first rough rolling starts to be pressed down, the four corners of the upper and lower surfaces of the intermediate billet will be flattened first, so that the depth of the depression between the midpoint of the line connecting the two dovetail corner endpoints on the same side to the midpoint of the narrow side surface increases, which is greater than the corresponding depth of the depression on the narrow side of the fixed-width intermediate billet.

[0021] 9) The life of the hammer head with arc-shaped raised working surface The high arc bulge in the middle of the forging hammer head will increase the thermal vibration strength and mechanical stress level of the hammer head surface material in this area, thus affecting its service performance. Therefore, the arc radius of the middle bulge should be increased as much as possible if allowed, and the straight lines / arcs on both sides of the arc should be tangent to the arc to extend the service life of the hammer head in one processing as much as possible.

[0022] 10) Regarding the auxiliary straight line segment L' of a circular arc-shaped convex profiled working surface in claim 2 related to H, R and α First, under the determined basic conditions (that is, when the hammer height and slab thickness are constant), in order to take into account the sufficient horizontal component force required for slab widening, avoid excessive bulging of the wide surface near the narrow side, and form a suitable dovetail, the angle α of the straight segment of the hammer L relative to the horizontal line is limited to 75~85°. Further calculation and verification optimization should be performed during implementation to determine the specific value, and its endpoints are the highest / lowest point of the hammer working surface and the upper / lower corner endpoints of the slab that are half the corresponding thickness b / 2 and symmetrical; secondly, according to the horizontal lateral movement law of the midpoint of the narrow side surface of the billet during rolling and each point, the midpoint position H of the raised arc in the middle part of the hammer cross section is selected to be a specific optimized value between b / 7~b / 4, and the specific optimized value of the raised arc radius R of about b / 5 (between b / 6~b / 4) is reasonably selected. value; furthermore, (1) when L and R are exactly tangent, L' is not required; (2) when the L ray does not intersect with R, α and / or H are appropriately adjusted to make L and R tangent, and L' is not required; (3) when the L ray intersects with R, (i) if α and / or H can be appropriately adjusted to make L and R tangent, L' is not required; (ii) if α and / or R can be appropriately adjusted to make L and R tangent, L' is not required; (iii) if the above adjustments cannot be made, add appropriate upper and lower auxiliary straight line segments L', whose angle β with the horizontal line is limited to the largest possible value between 60 and 75°, and whose endpoints are the tangent point with R and the upper / lower endpoints at half the slab thickness b / 2 of the corresponding L, respectively; obviously, in order to minimize the surface defects of the strip edge, L' is required in most cases to form a more reasonable hammer head morphology.

[0023] 11) The arc convexity in the middle of the forging hammer head is shaped in sections to alleviate the temperature drop in the corners during the width setting process According to the relationship between the moving step length of the slab and the effective working length of the hammer head during the width determination process, the hammer head can be segmented into two or more cross-sectional shapes along the horizontal direction, so that the narrow side morphology of the slab has an original vertical plane that gradually transitions to the final target cross-sectional morphology in steps. In particular, the forward forging can maintain the right angle of the slab or press the right angle into two large obtuse angles, which can not only reduce the temperature drop at the corner of the intermediate billet during the width determination process, but also is beneficial to the vertical centering or positioning of the concave morphology on the final cross-section of the intermediate billet with fixed width, and can also relatively improve the service life of the hammer head.

[0024] 12) The relationship between the horizontal center line of the hammer head protrusion and the middle line of the slab narrow side thickness When rolling is completed, it is very important to ensure that the upper and lower corner endpoints of the narrow side of the raw slab or the upper and lower dovetail angle endpoints of the narrow side of the fixed width intermediate billet are on the same vertical line of the strip edge or with very small deviation, so as to simultaneously control the upper and lower surface defects of the strip edge. This deviation is often closely related to the relative position relationship between the upper and lower dovetail angle endpoints after the fixed width, that is, the relationship between the horizontal center line of the hammer head protrusion and the middle line of the thickness of the narrow side of the slab. During the width setting process, the raw slab is bulged on the wide side surface near the narrow side and the lower dovetail angle appears, which causes a slight change in the relationship between the horizontal center line of the hammer head and the center line of the slab thickness at each forging when starting and ending the fixed width forging. Also, due to the systematic differences that may occur in the horizontal outward movement of the dovetail angle endpoints of the upper and lower surfaces of the fixed width intermediate billet during the subsequent rolling process, it is necessary to adjust the distance between the horizontal center line of the hammer head bulge and the middle line of the slab narrow side thickness or the relative position relationship between the upper and lower dovetail angle endpoints after width setting while adjusting the elevation of the conveying roller surface in the fixed width area accordingly so that the upper and lower dovetail angle endpoints of the narrow side of the fixed width intermediate billet can be better achieved by adjusting the distance between the horizontal center line of the hammer head bulge and the middle line of the slab narrow side thickness or the relative position relationship between the upper and lower dovetail angle endpoints after width setting. Based on the above goals, in some cases it is very likely that the upper and lower dovetail angle positions of the fixed width intermediate billet forged with a centerline symmetrical hammer are not completely symmetrical relative to the center line of the narrow side thickness of the forging intermediate billet. Beneficial Effects

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1) It inhibits the turning of the narrow metal at the corners and near the corners of the raw slab to the edge surface of the strip, and effectively reduces the number and degree of surface defects at the edge of the strip, especially various linear defects; 2) It fully utilizes the width reduction capability of the width setting machine, expands the coverage of the raw material slab width specifications for the strip steel, improves the flexibility of production organization, and also helps to reduce the specifications of the raw material slab; 3) Reduce / mitigate the number / degree of surface defects on the edge of the strip and improve the yield rate of the hot rolling process; 4) The difference between the thickness of the narrow side area and the thickness of the middle part of the fixed-width intermediate billet is reduced, and the head and tail cutting of each rolling intermediate billet is correspondingly reduced.

[0026] 5) Reduce the amount of trimming during subsequent processing of the strip. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1A schematic diagram of a convex cross-section of a width-fixing machine side pressure hammer in a method for controlling linear defects on the edge of a hot-rolled strip according to the present invention, in which: B is the height (or thickness) value of the hammer, b is the thickness value of the slab, the top height of the convex part H=b / 7~b / 4, the radius of the convex arc R≈b / 5 (between b / 6~b / 4), the angle α between the straight line segment L and the horizontal line is 75~85°, h is the distance between the symmetrical points on the surface of the root area of ​​the hammer convexity during forging, which is exactly the distance between the slab thickness and the apex of the hammer convexity, and the angles between the auxiliary straight line segment L' and the horizontal line satisfy β<α and β>60° in relation to the aforementioned H, R, b and α; Figure 2 A method for controlling linear defects on the edge of a hot-rolled steel strip according to the present invention is a cross-sectional diagram and a comparative diagram of the evolution of the narrow edge of a raw material slab and a fixed-width intermediate billet during the rolling process into a steel strip in the prior art. Taking a cold-rolled base material hot-rolled steel strip with a high requirement for the surface quality of the steel strip as an example, the evolution of the outer contour morphology of the narrow edge of each billet during the processing of the steel strip and the change in the relationship between the end point of the slab corner and the midpoint of the thickness of the narrow edge of the slab are compared. In the figure: 1 and 1' are the same raw material slabs; 2 is the fixed-width intermediate billet of the present invention, and 2' is the fixed-width intermediate billet of the prior art. Intermediate billets; 3-1, 3-2 and 3-3 are respectively the intermediate billet of the first rough rolling process of the present invention, the intermediate billet whose dovetail is bent from its middle section to the midline of the thickness of the narrow side of the intermediate billet and the intermediate billet after the bent dovetail is pressed to the narrow side, 3' is the rough rolling intermediate billet of the prior art; 4 is the finishing intermediate billet of the present invention, 4' is the finishing intermediate billet of the prior art; 5 is the finished strip of the present invention, 5' is the finished strip of the prior art; c is the end point of the corner of the slab, m is the midpoint of the thickness of the narrow side of the slab, and d is the schematic distance between the original point c and the point m of the slab at the edge of the finished strip. DETAILED DESCRIPTION

[0028] A method for controlling linear defects on the edge surface of a hot-rolled strip according to the present invention is specifically as follows: First, the working surface of the lateral forging hammer of the width setting machine is made into a triangle-like or bow-like shape with a cross section of an arc and an arc / straight line combination and a convex arc top without any vertical plane, so that the narrow side of the raw material slab corresponds to the outer contour of the convex arc of the hammer head and is forged into a fixed width intermediate billet with a concave middle part of the narrow side section and a dovetail-like corner, and the tip of the dovetail corresponds to the two corner end points of the narrow side of the slab; Secondly, in the subsequent rolling process, the dovetail is bent from its middle section toward the midline of the thickness of the narrow side of the intermediate billet and pressed toward the narrow side surface of the intermediate billet, and the bending length of the dovetail is 0-15 mm.

[0029] Furthermore, through the coordinated control of the width reduction amount of the width-fixing mill and the reduction amount of each pass of the roughing mill and the finishing mill, the same hammer head can, under the premise of hitting the strip width target and under various conditions including the purpose of the strip, achieve that all points on the narrow side surface of any cross-section of the fixed-width intermediate billet and all points on the narrow side surface of any cross-section of the new intermediate billet produced after dovetail angle bending and pressing are located at or close to the vertical line of the side of the corresponding strip cross-section after rolling is completed.

[0030] Further, a cross section of the hammer head protrusion profile is as follows Figure 1 As shown, B is the height of the hammer head, b is the thickness of the slab, the top height of the raised part H=b / 7~b / 4 (within the thickness range of 180~250mm for billet / 2.0~25mm for strip, a smaller value is taken for thinner slabs and thicker strips, and a larger value is taken for thicker slabs and thinner strips), the radius of the raised arc R≈b / 5*(b / 6~b / 4), the angle between the straight line segment L and the horizontal line α=75~85°, and the angle between the auxiliary straight line segment L' related to the aforementioned H, R and / or α and the horizontal line simultaneously satisfies β<α and β>60°.

[0031] Furthermore, the horizontal length of a cross-sectional protrusion of the hammer head protrusion profile can be: (1) running through the entire length of the hammer head; or (2) set at the rear section of the hammer head, and after one or more steps of transition, its effective length is not less than 1.2 times the feed stroke of the slab in a fixed-width forging cycle.

[0032] Furthermore, the bending of the dovetail from its middle section toward the midline of the thickness of the narrow side of the intermediate billet and pressing toward the midpoint of the narrow side of the intermediate billet are achieved by two waist surfaces of a vertical roller with a wide trapezoidal groove roller surface of a set of edge rolling mechanisms, and the pressing toward the midpoint of the narrow side of the intermediate billet is achieved by a flat surface / arc surface of vertical rollers of another set of edge rolling mechanisms / guide mechanisms in the same group or in succession for performing the bending; the bending length of the dovetail is optimized to be 3~12mm.

[0033] Furthermore, the coordinated control of the width reduction amount of the width-fixing mill and the reduction amount of each initial rolling pass of each stand and each finishing mill is a real-time dynamic control through a system model; the various conditions are inputs to the aforementioned dynamic control model, including: 1) the purpose of the strip, 2) the type of steel, target thickness and target width, 3) the thickness and width of the raw slab, 4) the outer contour parameters of the working surface of the forging hammer head, 5) the side pressure of the slab during the fixed-width forging process and the final fixed-width intermediate billet width, 6) the thickness of the intermediate billet before each stand during the rough and finishing rolling process, the temperature of the intermediate billet before the stand and its distribution, and the reduction amount of the previous pass; the control target that all points on the narrow side surface of any cross section of the fixed-width intermediate billet and all points on the narrow side surface of any cross section of the new intermediate billet generated after dovetail angle bending and pressing are located at or close to the vertical line of the side edge of the corresponding strip cross section after rolling is completed is that all points on the outer contour of the narrow side surface are no more than 8 mm away from the vertical line of the side edge of the corresponding strip cross section.

[0034] The application of the present invention is further described below in conjunction with the implementation scheme. Example 1

[0035] Basic conditions: 2250 hot rolling mill; width setting mill hammer height 350mm, single-side hammer effective maximum working stroke 175mm; slab thickness 230mm; CQ / DQ grade thin strip with thickness δ=2.3mm, strip width 1600mm; slab width 1950mm, single-side width reduction 175mm.

[0036] Implementation plan: Figure 1 The cross section of the raised outer contour of the hammer head is shown, where B=350mm, b=230mm, H=b / 4≈58mm, R≈b / 5=46mm, α≈75°, β≈60°, running through the entire length of the hammer head; the bending length of the dovetail is 0 (no corner bending); the rough rolling and the previous pass of finishing rolling use relatively uniform reduction, and the last two passes of rough rolling use edge concave arc vertical rollers, and the width reduction each time is not more than 5mm.

[0037] Results achieved: The proportion of strip coils with edge defects was reduced from 1.87% in the past with the same steel grade, specification and half width reduction to 0.17%; the distribution bandwidth of linear defects on the edge surface was reduced from about 20mm from the edge in similar cases in the past to less than 8mm; the midpoint of the narrow edge surface of the original slab in the strip edge section was about 5mm away from the strip edge formed by the corner end point of the slab; the strip width target was hit. Example 2

[0038] Basic conditions: 2250 hot rolling mill; width setting machine hammer height 350mm, single-side hammer effective maximum working stroke 175mm; slab thickness 230mm; Q235 grade ordinary strip steel with thickness δ=5mm, strip width 1800mm; slab width 1950mm, single-side width reduction 70mm.

[0039] Implementation plan: Figure 1 The cross section of the raised outer contour of the hammer head is shown, where B=350mm, b=230mm, H=b / 4≈58mm, R≈b / 5=46mm, α≈75°, β≈60°, which runs through the entire length of the hammer head; the bending length of the dovetail is 3mm; a large reduction is used in the first two passes of rough rolling, and a relatively uniform reduction is used in the subsequent passes; after the first pass of rough rolling, a wide-mouthed trapezoidal groove vertical roller is used to bend the dovetail angle at 45° according to a length of 3mm and then an inner concave arc vertical roller is used to roll the edge according to the target width reduction of 2mm.

[0040] Results achieved: The proportion of strip coils with edge defects was reduced from 2.12% in the past with the same steel grade, specification and half width reduction to 0.29%; the distribution bandwidth of linear defects on the edge surface was reduced from about 20mm from the edge in similar cases in the past to less than 10mm; the end point of the narrow edge corner of the new intermediate billet produced by the dovetail angle bending of the fixed-width intermediate billet at the edge of the strip was about 6mm away from the strip edge formed by the midpoint of the narrow edge surface of the original slab; the strip width target was met. Example 3

[0041] Basic conditions: 2250 hot rolling mill; width setting mill hammer height 350mm, single-side hammer effective maximum working stroke 175mm; slab thickness 230mm; niobium-containing crack-sensitive peritectic steel with thickness δ=20mm, strip target width 1800mm; slab width 2050mm, single-side width reduction 125mm.

[0042] Implementation plan: Figure 1 The cross-section of the raised outer contour of the effective working area of ​​the rear section of the hammer head is shown, where B=350mm, b=230mm, H=b / 5=46mm, R=b / 5=46mm, α=80°, β≈66°, and the working surface of the front section of the hammer head is a vertical plane; relatively large pressure is used in each pass of rough rolling and finishing rolling. After the first pass of rough rolling, a wide-mouthed trapezoidal groove vertical roller is used to be bent at a dovetail angle of 45° at a length of 15mm and then an inner concave arc vertical roller is used to roll the edge according to the target width reduction of 3mm.

[0043] Results achieved: The proportion of strip coils with edge defects was reduced from 5.2% in the past with the same steel grade, specification and half width reduction to 0.83%, and the distribution bandwidth of linear defects on the edge surface was reduced from about 30mm from the edge in similar cases to less than 10mm; the end point of the narrow edge corner of the new intermediate billet produced by the dovetail angle bending of the fixed-width intermediate billet at the edge section of the strip was about 8mm away from the strip edge formed by the midpoint of the narrow edge surface of the original slab, but the strip edge was rough due to excessive dovetail angle bending, affecting the appearance; the strip width target was met. Example 4

[0044] Basic conditions: 1580 hot rolling mill; width setting mill hammer height 350mm, single-side hammer effective maximum working stroke 175mm; slab thickness 230mm; W470H grade electrical steel strip with thickness δ=2.3mm, strip width 1250mm; slab width 1450mm, single-side width reduction 90mm.

[0045] like Figure 1The cross-section of the raised outer contour of the effective working area of ​​the rear section of the hammer head is shown, where B=350mm, b=230mm, H=b / 4≈58mm, R≈b / 5=40mm, α=75°, β≈65°, and the working surface of the front section of the hammer head is a vertical plane; each pass of rough rolling and finish rolling adopts a relatively balanced proportion of reduction. After the first pass of rough rolling, a wide-mouth trapezoidal groove vertical roller is used for edge rolling to bend the dovetail angle at 45° according to a length of 12mm and then an inner plane vertical roller is used for edge rolling according to the target width reduction of 3mm.

[0046] Results achieved: The proportion of strip coils with edge defects was reduced from 11.9% in the past with the same steel grade, specification and half width reduction to 1.07%; the distribution bandwidth of linear defects on the edge surface was reduced from about 30mm from the edge in similar cases to less than 10mm; the end point of the narrow edge corner of the new intermediate billet produced by the dovetail angle bending of the fixed-width intermediate billet at the edge of the strip was about 5mm away from the strip edge formed by the midpoint of the narrow edge surface of the original slab; the strip width target was met. Example 5

[0047] Basic conditions: 1580 hot rolling mill; width setting mill hammer height 350mm, single-side hammer effective maximum working stroke 175mm; slab thickness 230mm; SAPH400-P phosphorus-containing weathering steel strip with thickness δ=3.0mm, strip width 1250mm; slab width 1411mm, single-side width reduction 80mm.

[0048] like Figure 1 The cross-section of the raised outer contour of the effective working area of ​​the rear section of the hammer head is shown, where B=350mm, b=230mm, H=b / 4≈58mm, R≈b / 5=40mm, α=75°, β≈65°, and the working surface of the front section of the hammer head is a vertical plane; each pass of rough rolling and finish rolling adopts a relatively balanced proportion of reduction. After the first pass of rough rolling, a wide-mouth trapezoidal groove vertical roller is used for edge rolling to bend the dovetail angle at 45° according to a length of 10mm and then an inner plane vertical roller is used for edge rolling according to the target width reduction of 3mm.

[0049] Results achieved: The proportion of strip coils with edge defects was reduced from 11.9% in the past with the same steel grade, specification and half width reduction to 1.07%; the distribution bandwidth of linear defects on the edge surface was reduced from about 25mm from the edge in similar cases to less than 10mm; the end point of the narrow edge corner of the new intermediate billet produced by the dovetail angle bending of the fixed-width intermediate billet at the edge of the strip was about 6mm away from the strip edge formed by the midpoint of the narrow edge surface of the original slab; the strip width target was met. Example 6

[0050] Basic conditions: 2250 hot rolling mill; width setting machine hammer height 350mm, single-side hammer effective maximum working stroke 175mm; slab thickness 230mm; Q355 ordinary low alloy steel with thickness δ=25mm, strip target width 1600mm; slab width 1850mm, single-side width reduction 125mm.

[0051] Implementation plan: Figure 1 The cross-section of the raised outer contour of the effective working area of ​​the rear section of the hammer head is shown, where B=350mm, b=230mm, H=b / 7≈35mm, R=b / 5=46mm, α=85°, β≈74°, and the working surface of the front section of the hammer head is a vertical plane; relatively large pressure is used in each pass of rough rolling and finishing rolling. After the first pass of rough rolling, a wide-mouthed trapezoidal groove vertical roller is used to bend the dovetail angle at 45° according to a length of 3mm and then the edge is rolled with an inner concave arc vertical roller according to the target width reduction of 2mm.

[0052] Results achieved: The proportion of strip coils with edge defects was reduced from 1.1% in the past with the same steel grade, specification and half width reduction to 0.22%; the distribution bandwidth of linear defects on the edge surface was reduced from about 20mm from the edge in similar cases to less than 8mm; the end point of the narrow edge corner of the new intermediate billet produced by the dovetail angle bending of the fixed-width intermediate billet at the edge of the strip was about 8mm away from the strip edge formed by the midpoint of the narrow edge surface of the original slab; the strip width target was met.

[0053] This specification describes the present invention in detail in conjunction with specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the present invention defined by the attached claims. The detailed description and drawings are only used to match the contents disclosed in the specification, so that people familiar with this technology can understand and read, and should only be considered as illustrative, not to limit the limiting conditions that the present invention can implement, so it has no technical substantive significance, and any associated modifications and adjustments, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that the technical content disclosed by the present invention can cover. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and so on quoted in this specification are also only for the convenience of narration, rather than for limiting the scope that can be implemented, and the changes or adjustments of their relative relationships, without substantially changing the technical content, should also be regarded as the scope that the present invention can implement. In addition, the background technology is intended to illustrate the current status and significance of the research and development of this technology, and is not intended to limit the application field of the present invention or this application and the present invention. More specifically, although exemplary embodiments of the present invention have been described herein, the present invention is not limited to these embodiments, but includes any and all embodiments that are recognizable by those skilled in the art based on the foregoing detailed description, such as combinations between the various embodiments, adaptive changes and / or replacements. The limitations in the claims may be interpreted broadly based on the language used in the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of the application, which examples should be considered non-exclusive. Any steps listed in any method or process claim may be performed in any order and are not limited to the order presented in the claim. Therefore, the scope of the present invention should be determined solely by the attached claims and their legal equivalents, rather than by the description and examples given above.

[0054] It should be understood that the term "and / or" used in this article is a description of the association relationship of associated objects, and is defined to indicate that three relationships may exist. For example, a and / or b can represent: a exists alone, a and b exist at the same time, and b exists alone. The character " / " in this article is defined to indicate an "or" relationship between the previously associated objects.

Claims

1. A method for controlling linear defects on the edge surface of a hot-rolled strip, characterized in that: 1) The working surface of the lateral forging hammer of the width setting machine is made into a triangle-like or bow-like shape with a cross section of an arc and an arc / straight line combination and a convex shape of the arc top without any vertical plane, so that the narrow side of the raw material slab corresponds to the outer contour of the convex arc of the hammer head and is normally forged to become a fixed width intermediate billet with a concave middle part of the narrow side section and a dovetail-like corner, and the tip of the dovetail corresponds to the two corner end points of the narrow side of the slab; 2) In the subsequent rolling process, the dovetail is bent from its middle section toward the center line of the thickness of the narrow side of the intermediate billet and pressed toward the narrow side surface of the intermediate billet, and the bending length of the dovetail is 0 to 15 mm. 3) Through the coordinated control of the width reduction of the width setting machine and the reduction of each pass of the roughing mill and the finishing mill, the same hammer head can achieve the goal of hitting the strip width target and under various conditions including the purpose of the strip, so that all points on the narrow side surface of any cross-section of the fixed-width intermediate billet and all points on the narrow side surface of any cross-section of the new intermediate billet generated after dovetail angle bending and pressing are located at or close to the vertical line of the side of the corresponding strip cross-section after rolling is completed.

2. The method for controlling linear defects on the edge surface of a hot-rolled strip according to claim 1, characterized in that: A cross section of the raised outer contour of the hammer head is shown in Figure 1 of the specification, wherein B is the height of the hammer head, b is the thickness of the slab, the top height of the raised part H=b / 7~b / 4, the radius of the raised arc R≈b / 5, the angle between the straight line segment L and the horizontal line α=75~85°, and the angle between the auxiliary straight line segment L' and the horizontal line related to the aforementioned H, R, b and α simultaneously satisfies β<α and β>60°.

3. The method for controlling linear defects on the edge surface of a hot-rolled strip according to claim 2, characterized in that: The horizontal length of a cross-sectional protrusion of the hammer head protrusion outer contour can be: 1) running through the entire length of the hammer head; or 2) set at the rear section of the hammer head, and after one or more steps of transition, its effective length is not less than 1.2 times the feed stroke of the slab in a fixed width forging cycle.

4. The method for controlling linear defects on the edge surface of a hot-rolled strip according to claim 1, characterized in that: The bending of the dovetail from its middle section toward the midline of the thickness of the narrow side of the intermediate billet and pressing toward the narrow side surface of the intermediate billet is achieved by two waist surfaces of a vertical roller with a wide trapezoidal groove roller surface of a group of edge rolling mechanisms, and pressing toward the narrow side surface of the intermediate billet is achieved by the plane / arc surface connection of the vertical rollers of the same group or another group of edge rolling mechanisms / guide mechanisms that implement the bending; the bending length of the dovetail is optimized to be 3 to 12 mm.

5. The method for controlling linear defects on the edge surface of a hot-rolled strip according to claim 1, characterized in that: The coordinated control of the width reduction amount of the width-fixing mill and the reduction amount of each initial rolling pass of each stand and each finishing mill is a real-time dynamic control through a system model; the various conditions are the inputs of the aforementioned dynamic control model, including: 1) the purpose of the strip steel, 2) the type of steel, target thickness and target width, 3) the thickness and width of the raw material slab, 4) the outer profile parameters of the working surface of the forging hammer head, 5) the side pressure of the slab in the fixed-width forging process and the final fixed-width intermediate billet width, 6) the thickness of the intermediate billet before each stand in the rough and finishing rolling processes, the temperature of the intermediate billet before the stand and its distribution and the reduction amount of the previous pass.

6. The method for controlling linear defects on the edge surface of a hot-rolled strip according to claim 1, characterized in that: All points on the narrow side surface of any cross section of the fixed width intermediate billet and all points on the narrow side surface of any cross section of the new intermediate billet produced after dovetail angle bending and pressing are located at or close to the perpendicular line of the side edge of the corresponding strip cross section after rolling is completed. The control target is that all points on the outer contour of the narrow side surface are no more than 8 mm away from the perpendicular line of the side edge of the corresponding strip cross section.

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