Crystallizer foot roller set for changing shape of narrow edge of continuous casting billet

Abstract

The utility model discloses a crystallizer foot roller set for changing the shape of a narrow edge of a continuous casting billet, and belongs to the technical field of metallurgy. The convex cambered surface foot roller group and the foot rollers thereof are used for extruding the narrow side plane of a plate blank at an outlet of a crystallizer into a concave cambered surface through one step or multiple steps on the premise of ensuring the quality improvement of a casting blank and the smooth operation of pouring operation, and the plate blank with the concave cambered surface can be formed by changing the relative position relation of each point of the narrow side of the plate blank and the corner end point of the plate blank. Excessive overturning of corner defects of the blank during rolling is inhibited, so that the edge defects of the surface of the steel plate are reduced, and bulging of narrow edges during high-pulling-speed pouring is avoided; meanwhile, aiming at the problems of short service period and the like caused by abrasion of a convex surface when the convex foot roller is used for supporting the narrow surface of the continuous casting billet to bulge in the prior art, the foot roller structure design and the outer diameter variable reference compensation auxiliary block are used for optimizing the alignment positioning method of the foot roller working surface; under the condition that larger friction force is generated through extrusion, the single-time service time and the number of times of the service period of the foot roller after one-time machining are increased, and the related use cost is correspondingly reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to a foot roller group of changing continuous casting blank narrow edge shape and the physical structure of foot roller, belong to metallurgy technical field. BACKGROUND

[0002] In the hot rolling process, especially the rolling of hot strip steel is unidirectional rolling along the length direction of slab, the shape of slab narrow edge has a huge impact on the edge profile of finished product. Generally, there are more genetic solidification defects in the corner and near-corner narrow edge region of slab, and more processing defects are generated during heating and blooming. During subsequent rolling, the edge of the slab plane or near-plane will gradually evolve from plane to drum surface to corner to the surface of the strip edge, and the near-corner narrow edge of the slab will also be turned over to the surface of the strip edge. The genetic and / or heating defects of the corner and near-corner narrow edge of the slab will be turned into continuous or intermittent linear defects on the surface of the steel plate edge. There is usually a single linear defect or multiple linear defect bands on the surface within a range of 10-40 mm from the edge of the steel plate, which is positively correlated with the reduction of the slab. Especially, the presence of more bulges in the corner and near-corner narrow edge of the slab will exacerbate the severity of the corner and near-corner narrow edge of the slab turning over to the surface of the strip edge, greatly affecting the quality of the surface of the edge of the steel plate and reducing the yield of the strip rolling. Therefore, metallurgists at both the hot rolling end and the continuous casting end have made efforts to optimize the shape of the narrow edge of the slab after a large number of attempts to adjust the process parameters, but the results are not satisfactory. For hot strip steel production lines equipped with forging and pressing width setting machines at the hot rolling end, some have achieved results by changing the shape of the working surface of the forging and pressing hammer head. For occasions where it is not possible to change the shape of the narrow edge of the slab at the hot rolling end, more methods are used at the continuous casting end as follows:(1) using an arc-shaped protruding mold narrow edge copper plate to make the initial solidification of the continuous casting slab narrow edge into a full concave arc surface or a near-corner straight surface and a middle concave arc surface to reduce the related technology of the corner and near-corner narrow edge of the continuous casting slab turning over to the surface of the steel plate edge during rolling, such as Chinese patent application numbers 201520673254X, 2016107966888, 2022113292924, 202311001841X, and 202410788229X, etc.(2) applying the "chamfered mold" technology to change each right angle of the continuous casting slab into two large obtuse angles, eliminating and reducing the various problems caused by the "right angle", and greatly improving the edge quality of the subsequent finished strip steel;(3) Chinese patent application number 2017100790460 directly makes the narrow edge of the slab mold into a convex arc-shaped thickness copper plate with a diameter of the thickness of the slab to cast a round arc thickness slab without corners, so as to eliminate the corners that are prone to produce various solidification, heating and rolling defects. The aforementioned methods all require corresponding changes in the shape and structure of the mold cavity, and the foot roller below the mold also needs to change the roller surface profile accordingly with the change in the shape of the narrow edge of the mold, but still only bears the supporting and guiding function.Although various prior arts have improved the surface linear defects of the hot-rolled strip steel to some extent, they also have some other negative effects, the main problems are: (1) for the narrow edge concave mold copper plate, the corner of the continuous casting billet will have relatively more defects due to its unfavorable solidification conditions, and these defects will also expand to the wide edge for the steel susceptible to cracks, and these defects cannot be reversed to the narrow edge during rolling, so the improvement effect of the surface linear defects of the strip steel edge is restricted; (2) for the narrow edge arc of the continuous casting billet, the arc-shaped mold copper plate on both sides of the narrow edge arc must be smoothly transitioned with the flat wide edge, so that very sharp corners appear on both sides of the narrow edge arc copper plate of the mold, if the slab width needs to be frequently adjusted during continuous casting, the very weak corners on both sides of the narrow edge arc copper plate will be worn out in a very short time to cause solidification protrusions and gap steel, not only causing surface defects of the continuous casting billet at the flat arc joint, but also causing the narrow edge copper plate of the mold to be damaged and causing pouring accidents; (3) for the large obtuse angle chamfer-shaped continuous casting billet, (i) because the large obtuse angle of the corner corresponds to the sharp corners on both sides of the narrow edge copper plate of the slot-shaped mold, when the slab width is frequently adjusted during continuous casting, the relatively thin and weak sharp corners on both sides of the narrow edge copper plate are relatively easy to be worn out, and solidification protrusions and gap steel will also occur, reducing the online continuous service life of the mold, (ii) there is an obtuse angle on the surface of the billet, although the probability of defects occurring at the obtuse angle is reduced and the degree is weakened, but if there are some serious angle defects, one side will reduce some defects and the other side will cause other defects.

[0003] In the case of only having the supporting and guiding function to the flat surface of the narrow edge of the slab and inhibiting the bulging of the narrow surface of the cast slab, in order to obtain better supporting effect to the cast slab, there is also the prior art of using the convex roller surface foot roller to optimize the supporting capacity of the foot roller to the narrow edge, which can reduce the defects of the cast slab caused by the bulging of the narrow surface of the continuous casting slab, such as the middle protruding special-shaped whole foot roller disclosed in Chinese Patent No. 942456742 and Application No. 2013201081897, the middle part of the foot roller body is slightly protruding spindle-shaped or protruding platform working surface (the size unit of the disclosed figure in the application No. 2013201081897 is cm, which is wrong and should be mm, because the thickness of the thickest continuous casting slab in the industry is not more than 45 cm), the two side planes of the foot roller body are the reference surfaces for directly calibrating and aligning with the copper plate of the narrow edge of the crystallizer, but the middle supporting protrusion of such foot roller is fixed relative to the two side planes, and the two side planes are used as the reference surfaces for aligning the working surface of the foot roller with the surface of the copper plate of the narrow edge of the crystallizer (relative to the subsequent description in the specification, the corresponding pressing depth of the narrow edge plane of the continuous casting slab cannot be adjusted, and the initial s=s0=0 of the foot roller), and because the relative pressure is increased, the height of the spindle-shaped or platform working surface of the middle protrusion of the foot roller is reduced due to the additional friction with the surface of the continuous casting slab and the higher temperature, so the foot roller needs to be repaired after each service and then used again, the effective service life of the foot roller is low, and the related costs and expenses are increased; in addition, the development of high-efficiency continuous casting technology makes the casting speed of the continuous casting slab faster and faster, and the thickness of the slab for wide and thick plates is increasing due to the requirement of modern engineering for larger size, so the prior art of simply and locally supporting the narrow edge of the continuous casting slab with a few foot rollers cannot effectively inhibit the bulging of the narrow edge of the continuous casting slab, and it is difficult to extend and lengthen the crystallizer foot roller group.

[0004] In summary, it is still necessary to explore new methods for the surface defects of the hot-rolled steel plate edge to effectively control the bulging of the narrow edge of the continuous casting slab and inhibit the turning of the corner defects of the continuous casting slab to the surface of the steel plate in a simple and convenient manner with less additional negative effects, to systematically reduce the related costs and expenses, to improve the quality of the continuous casting slab, and to improve the edge surface quality of the steel plate (especially the steel strip). SUMMARY

[0005] 1. Problem to be solved

[0006] The purpose of the utility model is to change the flat surface of the narrow edge of the continuous casting slab into a concave arc surface in a high reliability, small negative effect, economic efficiency and simple and convenient manner without changing the initial solidification conditions of the corner of the continuous casting slab.

[0007] 2. Technical scheme

[0008] The technical scheme of the utility model is:

[0009] 1) Change the planar foot rollers in the existing crystallizer narrow side support and guide foot roller group to the central convex arc surface foot rollers. By using the arc-shaped convex working surface of the foot rollers, under the premise of ensuring that the relative deformation of the solidification interface of the narrow side of the continuous casting billet is less than the corresponding allowable critical strain value of the cast steel grade, the surface of the narrow side of the continuous casting billet leaving the crystallizer and entering the foot roller group is subjected to one step or multiple steps of extrusion by a pair of foot rollers, so that the flat surface of the narrow side of the continuous casting billet is plastically deformed into a narrow side concave arc surface with an arc midpoint target depth value.

[0010] 2) By increasing the diameter of the middle section of the existing foot roller convex arc surface and reducing the diameter of the reference body used for calibrating the relative position of the convex foot roller surface and the narrow side copper plate plane of the crystallizer, the maximum possible adjustment range of the extrusion insertion depth and / or the narrow side plane plane of the continuous casting billet can be obtained by using a set of reference compensation auxiliary blocks with selectable outer diameter or an adjustable outer diameter reference compensation auxiliary block. This allows the foot roller convex arc surface to be used directly for multiple service periods without processing after wear or oxidation during the previous service period.

[0011] The differences in principle and application features between this utility model and the prior art are as follows:

[0012] 1) The narrow, flat surface of the continuously cast billet is transformed into a concave arc surface through plastic deformation.

[0013] By utilizing the small thickness, good plasticity, and low strength of the billet shell at the crystallizer outlet, and using only the foot rolls with arc-shaped raised working surfaces to squeeze the conventional continuous casting billet leaving the crystallizer and entering the foot roll group, it is possible to easily and directly deform the narrow-side flat surface into a narrow-side concave arc surface with a target arc midpoint depth. This effectively controls the narrow-side bulging of the continuous casting billet and suppresses various defects in the subsequent rolling process, such as solidification inheritance at the corner of the billet, heating generation, and rolling defects, from turning onto the steel plate surface.

[0014] 2) It helps to better suppress the narrow edge bulging of the continuously cast billet and reduce the corresponding internal defects of the continuously cast billet.

[0015] When the foot roller of this utility model presses the narrow side of the continuous casting billet, (1) the concave arc surface formed after plastic deformation produces a good "arch bridge effect" on the static pressure of the liquid core of the continuous casting billet, which effectively suppresses the occurrence of narrow side bulging when the continuous casting billet leaves the foot roller group and continues to descend; (2) the simultaneous occurrence of the rigid corner billet shell deflection on both sides can also press the deviation angle internal crack on the wide side of the corner of the billet, which can improve the corner quality of the continuous casting billet and prevent the "deviation angle longitudinal crack" leakage that may occur during casting.

[0016] 3) The foot roller adopts an optimized combination of structure, materials, and processing technology, which greatly extends the number of times the foot roller has been used and its service life after a single processing.

[0017] Although the high-temperature solidified steel billet shell exhibits thinness, low strength, and good plasticity at the crystallizer exit, the friction between the working surface of the foot rollers that forcibly compress the billet shell and the billet surface in the method of this application is much greater than that of conventional support foot rollers, which merely suppress bulging of the billet shell (especially when the cold billet head passes through the foot roller group during initial casting and continuous casting). Consequently, the wear of the foot roller working surface is relatively severe. This application adopts the appendix to the specification. Figure 1 The foot roller morphology shown, the foot roller structure described in the claims, and the optimized foot roller materials and processing technology can be implemented in various forms, including an integral type with a wear-resistant layer welded onto the extrusion working surface, a two-piece combination type with a wear-resistant material extrusion ring and a roller body reference body nested together, or a three-piece combination type with a wear-resistant material middle section extrusion roller body and its two side reference roller bodies stacked together. This allows for: 1) on-site adjustment or restoration of the narrow edge surface indentation depth during the crystallizer preparation process before re-service after the foot roller working surface has been worn offline during service; 2) economical use of wear-resistant materials to reduce wear on the foot roller working surface; 3) multiple on-site adjustments to ensure the target indentation depth of the narrow edge surface after the foot roller working surface has been worn offline during service; 4) use wear-resistant materials that are not commonly used on narrow edge foot rollers to improve the wear resistance of the convex working surface; and 5) the use of corrosion-resistant materials (such as ferritic stainless steel) to make the reference body for calibrating and aligning the relative position of the foot roller surface and the narrow edge copper plate plane of the crystallizer permanently usable, thus providing the possibility of increasing the number of times the foot roller has been processed after one operation and extending its service life.

[0018] Beneficial effects

[0019] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0020] 1) No modifications are required to the crystallizer. Only the working surface shape of the narrow-side foot roll in the crystallizer of conventional continuous casting technology needs to be changed. Its function is expanded from mainly supporting and guiding to mainly extruding and shaping while also supporting and guiding. This can suppress the flipping of the narrow-side metal at the corner and near corner of the raw slab to the edge surface of the strip, and effectively reduce / mitigate the number / degree of defects on the edge surface of the steel plate, especially various linear defects.

[0021] 2) Making the working surface of the foot roller into a convex shape corresponding to the narrow edge concave shape of the target billet is extremely simple and convenient compared to changing the copper plate surface of the crystallizer;

[0022] 3) It increases the number of times the foot roller can be used after one processing cycle and extends its service life, while reducing the related usage costs. Attached Figure Description

[0023] Figure 1This utility model discloses a schematic diagram of the shape and working condition of the foot roller in a crystallizer foot roller group used to change the shape of the narrow side of a continuously cast billet. In the figure: L is the length of the foot roller body, which is related to the thickness B of the narrow side of the continuously cast billet, usually L≈0.85B; l is the length of the convex arc surface part in the middle section of the foot roller, l≈2 / 3L; D is the diameter of the foot roller at the apex of the convex arc surface, which becomes D' after wear during service; d is the reference body diameter of the narrow side convex foot roller, used for calibration and alignment of the relative position of the convex foot roller surface and the copper plate plane of the narrow side of the crystallizer; h is the height of the convex arc surface of the foot roller corresponding to the extrusion depth of the narrow side of the continuously cast billet; δ is the thickness of the solidified billet shell of the narrow side; R is the radius of the convex arc surface of the foot roller, which is a perfect circle; s is a preset variable that changes with the wear and corrosion of the convex arc surface of the foot roller, corresponding to the adjustable / recoverable range of the extrusion depth of the plane / arc surface of the narrow side of the continuously cast billet and / or the number of times the foot roller can be used continuously after one processing, s=(D'-2h-d) / 2. Detailed Implementation

[0024] A set of mold foot rollers for changing the shape of the narrow edge of a continuously cast billet, characterized in that: 1) the set of mold foot rollers consists of multiple foot rollers, wherein the working surface of the foot rollers is a convex arc surface, used to extrude the straight surface of the narrow edge of the continuously cast billet below the mold outlet into a concave arc surface with the midpoint of the corresponding cross-section as the target indentation depth, in one or more steps, while ensuring that the relative deformation of the solidification interface of the narrow edge of the continuously cast billet is less than the corresponding allowable critical strain value of the cast steel grade; 2) the shape of the foot rollers is as shown in the attached figure. Figure 1 As shown in the figure: L is the length of the foot roller body; l is the length of the convex arc surface in the middle section of the foot roller, l≈2 / 3L; D is the diameter of the foot roller at the apex of the convex arc surface, which becomes D' after wear during service; d is the reference diameter of the narrow-side convex foot roller, used for calibration and alignment of the relative position of the convex foot roller surface and the narrow-side copper plate plane of the crystallizer; h is the height of the apex of the convex arc surface of the foot roller, corresponding to the pressing depth of the midpoint of the concave surface of the narrow side of the continuous casting billet; R is the radius of the convex arc surface of the foot roller, corresponding to the cross-sectional morphology of the concave surface of the narrow side of the continuous casting billet; s is a preset variable that changes with the wear and corrosion of the convex arc surface of the foot roller, corresponding to the adjustable stroke range of the foot roller, s=(D'-2h-d) / 2.

[0025] Further, the h is associated with the thickness B of the narrow edge of the continuous casting billet, and the value is: 1) when three-step extrusion is used for the first three pairs of foot rollers, the corresponding possible value ranges of the first, second and third pairs of foot rollers h at the outlet of the crystallizer are h1=(1 / 36~1 / 28)B, h2=h1+(1 / 85~1 / 50)B and h3=h2+(1 / 130~1 / 70)B, and the specific values of the various parameters of the subsequent foot rollers are the same as those of the third pair of foot rollers, 2) when two-step extrusion is used for the first two pairs of foot rollers, the corresponding possible value ranges of the first and second pairs of foot rollers h at the outlet of the crystallizer are h1=(1 / 36~1 / 28)B and h2=h1+(1 / 85~1 / 50)B, and the specific values of the various parameters of the subsequent foot rollers are the same as those of the second pair of foot rollers, 3) when one-step extrusion is used for the first pair of foot rollers, the corresponding possible value range of the first pair of foot rollers h at the outlet of the crystallizer is h1=(1 / 36~1 / 28)B, and the specific values of the various parameters of the subsequent foot rollers are the same as those of the first pair of foot rollers; the R is associated with the thickness B of the narrow edge of the continuous casting billet, the solidification shell thickness δ and the critical strain value of the steel grade, and the calculated value of the convex arc surface radius of the foot roller corresponding to the relative deformation of the solidification interface arc length before and after the aforementioned pressing depth h is not greater than the critical strain of the corresponding steel grade, and the corresponding R1~h1 / R2~h2 / R3~h3, R1~h1 / R2~h2 and R1~h1 for the three pairs, two pairs and one pair of foot rollers are extruded, respectively; the initial design value s0 of the s is not less than 5.0 mm.

[0026] Further, the foot roller is a whole type, a two-piece combined type of an extruded ring and a roller body reference body nested, or a three-piece combined type of a middle extruded roller body and two reference roller bodies stacked on both sides thereof.

[0027] The application of the present application is further described below in combination with the embodiments:

[0028] Example 1

[0029] Basic conditions: continuous casting slab, thickness 250 mm, mainly high-grade steel, critical strain range of cast steel 0.35~0.50%, continuous casting billet casting speed 1.2-1.6 m / min; rolling medium plate thickness range 5.5~40.0 mm; original crystallizer plane foot roller outer diameter 120 mm; there are four pairs of foot rollers in the foot roller group.

[0030] Embodiment: according to the calculation of the casting speed 1.2 m / min, the average shell thickness of the continuous casting billet in the crystallizer outlet foot roller group area is 21 mm, and the narrow edge solidification interface chord length is 208 mm; as Figure 1The working surface of the shown circular-arc convex profile, wherein B = 250 mm, L = 210 mm, and l = 145 mm; according to the most stringent value of the critical strain value of the cast steel 0.35%, the maximum possible indentation depth of the narrow edge surface cross-sectional midpoint is 13.0 mm (7.5 mm + 3.5 mm + 2.0 mm), which requires three steps of extrusion using three foot rollers; the design is according to the indentation depth of 12.0 mm, the h value and the corresponding R calculation value of each step of extrusion foot roller are respectively: h1 = 7.0 mm (B / 35), R1 = 810 mm, h2 = h1 + 3.0 mm (B / 83) = 10.0 mm, R2 = 570 mm, h3 = h4 = h2 + 2.0 mm (B / 125) = 12.0 mm, R3 = R4 = 477 mm; the corresponding D1 = 138 mm, D2 = 144 mm, D3 = D4 = 148 mm, d1 = d2 = d3 = d4 = 110.0 mm at the top of the first to fourth pair of foot roller convex circular arcs; there is s 01 = s 02 = s 03 = s 04 = 7.0 mm; the new foot roller uses a set of magnetic reference compensation auxiliary blocks with an inner diameter of 110.0 mm and an outer diameter of 112.0-125.0 mm, which changes by 0.5 mm each time, and the reference compensation auxiliary block with an outer diameter of 124.0 mm is used to cooperate with the plug gauge to calibrate and align the relative position of the foot roller working surface and the narrow edge copper plate plane of the crystallizer.

[0031] Example 2

[0032] Basic conditions: same as example 1.

[0033] On-site situation: after the fourth service period of the crystallizer is over, the top indentation depth recovery adjustment of one of the first pair of foot rollers: 1) the distance between the foot roller convex arc surface vertex and the corresponding foot roller reference body is 9.2 mm (about 4.8 mm of wear) and there is no eccentric wear, the average wear per service period is 1.20 mm; it is confirmed that the wear of the convex arc surface is relatively uniform, the circular arc radius is about 800 mm, which basically meets the requirements, and slight grinding is not required for machining; 2) it is determined that the distance between the foot roller reference body and the narrow edge copper plate of the crystallizer at the target value of the narrow edge plane extrusion indentation depth of the continuously cast slab is 7.0 mm, 3) the reference compensation auxiliary block with an appropriate outer diameter is selected as the reference compensation auxiliary block with an outer diameter of 114.0 mm, 4) the reference compensation auxiliary block is placed on the reference body at both ends of the foot roller and cooperates with the plug gauge with a thickness of 0.15, 0.20, and 0.25 mm, the gap between the outer arc surface of the reference compensation auxiliary block and the conventional calibration straight ruler closely attached to the narrow edge of the crystallizer is measured by the plug gauge, and the position of the foot roller shaft is adjusted to implement calibration and alignment, 5) the calibration and alignment of the foot roller surface and the copper plate surface of the crystallizer is completed and the foot roller is fixed, 6) the status of the foot roller is recorded and it is predicted that it can be served again once after the service period is over.

[0034] Example 3

[0035] Basic conditions: The critical strain of all cast steel grades in the next service period is 0.50%. For cold-rolled base material with thin specifications, it is necessary and possible to increase the pressing depth of the narrow face of the continuous casting billet by 1.2mm. The rest is the same as in Example 2.

[0036] On-site situation: After the crystallizer completed its fifth service life and was taken offline, the insertion depth of one of the first pair of foot rollers was restored and adjusted: The distance between the apex of the convex arc surface of the foot roller and the corresponding foot roller reference body was measured to be 7.8mm (approximately 6.2mm of wear) and there was no uneven wear. The average wear per service period was 1.24mm; it was confirmed that the wear of the convex arc surface was relatively uniform, with an arc radius of approximately 800mm, which basically met the requirements. Slight grinding was required without machining; 2) The total pressing amount that needs to be increased by 1.2mm is distributed as follows: 0.7mm, 0.3mm and 0.2mm are added to the first, second and third pairs of rollers, respectively. Therefore, the narrow-side plane extrusion and insertion of the continuous casting billet is determined as the first pair of foot rollers. The depth target value is increased from 7.0 to 7.7 mm. Under this target value, the distance between the foot roller reference body and the narrow copper plate of the crystallizer is 0.1 mm. 3) Since the s value is too small, there is no need to use the reference compensation auxiliary block. 4) Calculate and select feeler gauge thicknesses of 0.05, 0.10, and 0.15 mm. Measure the gap between the arc surface of the reference body and the conventional calibration ruler that is close to the narrow surface of the crystallizer by using the feeler gauge and adjust the position of the foot roller shaft to perform calibration and alignment. 5) Complete the calibration and alignment of the foot roller surface and the copper plate surface of the crystallizer and fix the foot roller. 6) Record the condition of the foot roller and make a prediction that it cannot be used again after the service life expires. It is recommended to directly transfer it to machining for repair after service.

[0037] The present application is described in detail in the specification combined 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 application defined by the appended claims. The detailed description and the accompanying drawings are merely intended to illustrate the content disclosed in the specification, for those skilled in the art to understand and read, and should only be considered as illustrative, not as a limiting condition for the implementation of the present application, so it does not have technical significance, any associated modification and adjustment, without affecting the effect and purpose of the present application, should still fall within the scope of the technical content disclosed by the present application. At the same time, the terms such as "up", "down", "left", "right", "middle" and the like in the specification are only for the convenience of clear description, and are not used to limit the scope of implementation, the change or adjustment of the relative relationship, without substantial changes in technical content, is also considered as the scope of implementation of the present application. In addition, the background art is intended to explain the status and significance of the present technology, and is not intended to limit the present application or the application field of the present application. More specifically, although the exemplary embodiments of the present application have been described herein, the present application is not limited to these embodiments, but includes any and all embodiments that can be recognized by those skilled in the art based on the foregoing detailed description. The limitations in the claims can be widely interpreted according to 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 should be considered as non-exclusive. Any steps listed in any method or process claim can be performed in any order and is not limited to the order presented in the claim. Therefore, the scope of the present application should only be determined by the appended claims and their legal equivalents, not by the description and examples given above.

[0038] It should be understood that the term "and / or" used herein is a description of the association relationship of the associated objects, which is defined to represent that there can be three relationships, for example, a and / or b can represent: a exists alone, a and b exist together, and b exists alone; The character " / " in this paper is defined to represent the "or" relationship of the associated objects before and after.

Claims

1. A set of crystallizer foot rollers for changing the narrow edge shape of a continuously cast billet, characterized in that: 1) The crystallizer foot roll assembly consists of multiple foot rolls, wherein the working surface of the foot rolls is a convex arc surface. This is used to extrude the straight surface of the narrow side of the continuously cast billet below the crystallizer outlet into a concave arc surface with the midpoint of the corresponding cross-section as the target indentation depth, under the premise that the relative deformation of the solidification interface of the narrow side of the continuously cast billet is less than the corresponding allowable critical strain value of the cast steel grade. 2) The geometric elements of the foot roll structure are: the length of the foot roll body (L); the length of the convex arc surface portion in the middle section of the foot roll (l), l≈2 / 3L; the top of the convex arc surface... The diameter (D) of the foot roller at the point of service wears out to become D'; the reference diameter (d) of the narrow-sided convex foot roller is used for calibration and alignment of the relative position of the convex foot roller surface and the narrow-sided copper plate plane of the crystallizer; the height (h) of the apex of the convex arc surface of the foot roller corresponds to the pressing depth at the midpoint of the concave surface of the narrow side of the continuous casting billet; the radius (R) of the convex arc surface of the circular foot roller corresponds to the cross-sectional morphology of the concave surface of the narrow side of the continuous casting billet; the preset variable (s) that changes with the wear and corrosion of the convex arc surface of the foot roller corresponds to the adjustable stroke range of the foot roller, s=(D'-2h-d) / 2.

2. A set of crystallizer foot rollers for changing the narrow edge shape of a continuously cast billet according to claim 1, characterized in that: The height (h) of the convex arc surface of the foot roll is related to the narrow side thickness B of the continuously cast billet, and its value is as follows: 1) When using the first three pairs of foot rolls for three-step extrusion, the possible values ​​of h for the first, second, and third pairs of foot rolls at the crystallizer outlet are h1 = (1 / 36~1 / 28)B, h2 = h1 + (1 / 85~1 / 50)B, and h3 = h2 + (1 / 130~1 / 70)B, respectively. The various parameters of the subsequent foot rolls are the same as the specific values ​​of the third pair of foot rolls. 2) When using the first two pairs of foot rolls for two-step extrusion, the possible values ​​of h for the first and second pairs of foot rolls at the crystallizer outlet are h1 = (1 / 36~1 / 28)B and h2 = h1 + (1 / 85~1 / 50)B, respectively. The various parameters of the subsequent foot rolls are the same as the specific values ​​of the second pair of foot rolls. Similarly, 3) When only the first pair of foot rollers is used for one-step extrusion, the possible range of h values ​​for the first pair of foot rollers at the crystallizer outlet is h1 = (1 / 36 ~ 1 / 28)B, and the various parameters of the subsequent foot rollers are the same as the specific values ​​of the first pair of foot rollers; the radius (R) of the convex arc surface of the circular foot roller is related to the narrow side thickness B of the continuous casting billet, the solidified billet shell thickness δ, and the critical strain value of the steel grade, and is the calculated value of the convex arc surface radius of the foot roller corresponding to the aforementioned extrusion depth h, where the relative deformation of the solidification interface arc length before and after extrusion is not greater than the critical strain of the corresponding steel grade. For the aforementioned three pairs, two pairs, and one pair of foot rollers, the corresponding values ​​are R1 ~ h1 / R2 ~ h2 / R3 ~ h3, R1 ~ h1 / R2 ~ h2, and R1 ~ h1; the initial design value s0 of s is not less than 5.0 mm.

3. A set of crystallizer foot rollers for changing the narrow edge shape of a continuously cast billet according to claim 1, characterized in that: The foot roller can be a single piece, a two-piece combination of a nested extrusion ring and a roller body reference body, or a three-piece combination of a mid-section extrusion roller body and two side reference roller bodies stacked together.

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