Method for improving surface quality of hot rolling vertical roll

Abstract

The present application relates to a kind of methods for improving the surface quality of hot rolling vertical roll, including the steps S1, the vertical roll is carried out after being scrapped and the surfacing of roll surface working layer;Step S2, the lower edge of vertical roll is extended 25~35mm;Step S3, the surface roughness of vertical roll lower bearing seat platform and the size tolerance of platform and roll lower shoulder surface cooperation are optimized.The present application can realize the working layer surfacing of scrapped roll reuse, and the cost reduction reaches more than 50%, while, the problem of serious granular defect of ordinary material vertical roll lower machine is solved, and the roll surface quality is significantly improved, so as to extend its in-machine service life, and improve the in-machine life of roll.

Description

Technical Field

[0001] This invention relates to the field of steel rolling technology, and in particular to a method for improving the surface quality of hot-rolled vertical rolls. Background Technology

[0002] In recent years, with changes in the structure of rolled products, product quality has become an increasingly prominent key factor on the 2300mm line. Especially against the backdrop of increased overall production of automotive sheet metal, the requirement to maintain stable quality throughout long rolling cycles presents a significant challenge to the application of vertical rolls. E1 and E2 vertical rolls are crucial production equipment on the roughing mill stand, affecting the edge quality and width control of the sheet metal on the production line, and are among the determining factors for rolling stability and quality.

[0003] The vertical rollers on the 2300mm line have always adhered to the material and specification standards designed by SMS. However, with the improvement of the product variety and quality of the production line, the original material of the vertical rollers can no longer meet the requirements. For example, the original graphite cast steel vertical rollers have developed granular defects after leaving the machine, vertical roller elevation issues, edge scratches, decreased bearing housing precision, aging lathe equipment, and limitations in the machining precision of the vertical rollers due to manual operation. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a method for improving the surface quality of hot rolling vertical rolls. This method enables the reuse of the working layer of scrap rolls through welding, resulting in a cost reduction of over 50%. Simultaneously, it solves the problem of severe particulate defects in ordinary material vertical rolls after they leave the mill, significantly improving the quality of the roll surface and thus extending its service life and improving the roll's on-machine lifespan.

[0005] The technical solution adopted in this invention is as follows: The present invention proposes a method for improving the surface quality of hot-rolled vertical rolls, the method comprising the following steps: Step S1: Perform overlay welding on the working layer of the scrapped vertical roll surface; Step S2: Extend the lower edge of the vertical roller by 25~35mm; Step S3: Optimize the surface roughness of the vertical roll lower bearing seat platform and the dimensional tolerance of the fit between the platform and the lower shoulder surface of the roll.

[0006] Furthermore, in step S1, the welding material for the working layer is Cr12.

[0007] Furthermore, in step S3, the dimensional tolerance of the platform and the lower shoulder surface of the roll is designed to be 5~15mm based on benchmarking and actual conditions.

[0008] Furthermore, in step S3, the surface roughness of the vertical roller lower bearing seat platform is Ra1.2~1.5μm.

[0009] Furthermore, the method also includes modifying the vertical roll processing lathe, that is, using ceramic inserts or PCBN superhard turning tools to turn the vertical rolls, so as to achieve turning and roll shape control of rolls with a hardness of 70~80HSD or above.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention can effectively reduce the procurement and maintenance costs of rolls. After upgrading the material of the existing rolls (the original graphite cast steel vertical rolls are scrapped and then re-welded with Cr12 material working layer), the procurement cost of vertical rolls is reduced by more than 50%, while the millimeter rolling volume of vertical rolls is increased by more than 30%, and the rolling turning and assembly costs are reduced.

[0011] 2. This invention modifies the lower edge of the vertical roll, extending it by 25-35mm to reduce centerline sinking during rolling, decrease strip edge defects, improve edge yield, and reduce defects such as black lines, edge scratches, and edge cracks. Through this modification, the edge yield is increased by approximately 1%, and the number of downgraded products due to edge defects is reduced by more than 30%.

[0012] 3. This invention can improve production line efficiency, reduce the number of roll changes, and extend the vertical roll rolling cycle. The roll change cycle for E1 vertical rolls can be extended from approximately 10 days to approximately 20 days, and the roll change cycle for E2 vertical rolls can be extended from approximately 15 days to approximately 20 days. This reduces roll change time by approximately 100 hours annually (65,000 tons), resulting in economic benefits of over 4.6 million yuan.

[0013] 4. Modify the machine tools to significantly improve the machining accuracy of vertical roller turning. Attached Figure Description

[0014] Figure 1 This is a schematic diagram comparing the surface morphology of the vertical roller after the material upgrade of the present invention. Detailed Implementation

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] It should be noted that in the description of this invention, the terms "upper", "lower", "top", "bottom", "one side", "the other side", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not mean that the device or element must have a specific orientation, or be constructed and operated in a specific orientation.

[0017] The present invention proposes a method for improving the surface quality of hot-rolled vertical rolls, comprising the following steps: Step S1: Re-weld the working layer of the scrapped vertical roll with a new material. The welding material is Cr12. This can realize the recycling of the vertical roll material, ensuring 100% safety of the roll in the machine, reducing the overall cost by more than 50%, and eliminating the granular defects on the roll surface.

[0018] Step S2: Extend the lower edge of the vertical roll by 25~35mm, preferably 30mm; this configuration design can effectively reduce the problem of centerline sinking during the rolling process, thereby reducing the generation of strip edge defects.

[0019] Step S3: Optimize the surface roughness of the vertical roll lower bearing seat platform and the dimensional tolerance of the platform and the lower shoulder surface of the roll; wherein, the optimized dimensional tolerance of the platform and the lower shoulder surface of the roll is designed to be 5~15mm based on benchmarking and actual conditions; the optimized surface roughness of the vertical roll lower bearing seat platform is set to Ra1.2~1.5μm.

[0020] Turning high-grade vertical rollers is a challenge. Currently, most machines use hand-operated lathes, which not only have low control precision but are also only suitable for turning low-hardness vertical rollers with a hardness of less than 50HSd. Furthermore, the roller profile cannot be controlled, and other roller surfaces cannot be turned.

[0021] Therefore, this invention modifies the vertical roll machining lathe by using ceramic inserts or PCBN superhard turning tools to machine the vertical rolls, thereby achieving the machining and roll shape control of rolls with a hardness of 70~80HSD or higher, thus improving the accuracy and quality of vertical roll surface machining.

[0022] The working principle of this invention is as follows: The material of the vertical rolls was optimized. The original graphite cast steel vertical rolls had poor high-temperature red hardness, rapid surface wear (easily causing steel to stick), surface oxidation, micro-polishing, and a continuously decreasing high-temperature friction coefficient. Longitudinal (rolling direction) shear resistance was low, and lateral compressive stress could not drag the corner metal into the slab; the corner metal flowed freely outward laterally, resulting in strong flattening and widening, plus shallow dog-bone deformation. Subsurface oxidation, microcracks, and the chilled hardened layer at the slab edges all turned onto the strip surface, producing black lines, peeling, serrated edges, and excessive cutting damage. After welding the vertical rolls, a new working layer was welded: the weld layer is a multi-element alloy metallurgical bonding layer with dispersed hard carbides in the matrix, exhibiting significantly higher high-temperature (900-1150℃) red hardness and high-temperature tempering resistance than ordinary cast steel vertical rolls. It has the following characteristics: 1) The roller surface maintains a stable micro-uneven morphology for a long time, and will not be polished at high temperature or wear out quickly; 2) The steady-state high temperature friction coefficient is 30% to 60% higher than that of ordinary vertical rollers, and the longitudinal friction of the contact arc is greatly improved; 3) The roller surface is free of steel sticking, local particles or pitting grooves, and the roller surface friction is uniform, and there is no problem of local friction loss.

[0023] From a mechanical fit perspective, the original vertical roll and rolling elevation fit has shifted downwards due to wear and tear on equipment such as the roller conveyor. During the rolling process, the strip head and tail are prone to scraping, affecting the quality of the strip edges. Therefore, the lower edge of the vertical roll is moved downwards to reduce such interference.

[0024] In vertical roll machining, due to the limitations of manual operation, it is impossible to machine arcs during vertical roll machining; only edge transitions are possible. During the rolling process, the edges of the slab are unconstrained, resulting in the metal turning outwards after extrusion, causing flattening and widening, and leading to upward floating of edge defects in the product. Achieving an end-machined arc transition utilizes the arc surface to wrap around the upper and lower edges of the slab, increasing the vertical binding force and locking the metal at the edges outwards. Simultaneously, it allows the compressive stress to be evenly distributed along the slab thickness, allowing deformation to penetrate deeper into the matrix, reducing dog-bone deformation, thus suppressing flattening and widening, eliminating black lines and peeling at the edges, and eliminating stress concentration at the corners, reducing edge cracks.

[0025] Matters not covered in this invention are common knowledge.

[0026] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for improving the surface quality of hot-rolled vertical rolls, characterized in that, The method includes the following steps: Step S1: Perform overlay welding on the working layer of the scrapped vertical roll surface; Step S2: Extend the lower edge of the vertical roller by 25~35mm; Step S3: Optimize the surface roughness of the vertical roll lower bearing seat platform and the dimensional tolerance of the fit between the platform and the lower shoulder surface of the roll; In step S1, the welding material for the working layer is Cr12; In step S3, the dimensional tolerance of the platform and the lower shoulder of the roll is designed to be 5~15mm based on benchmarking and actual conditions.

2. The method for improving the surface quality of hot-rolled vertical rolls according to claim 1, characterized in that: In step S3, the surface roughness of the vertical roller lower bearing seat platform is Ra1.2~1.5μm.

3. The method for improving the surface quality of hot-rolled vertical rolls according to claim 1, characterized in that: The method also includes modifying the vertical roll processing lathe, that is, using ceramic inserts or PCBN superhard turning tools to turn the vertical roll, so as to achieve turning and roll shape control of rolls with a hardness of 70~80HSD or above.

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