Rolling mill and metal composite rolling method

Abstract

The invention discloses a rolling mill and a metal composite rolling method, and relates to the technical field of rolling mills for rolling and forming sections. The first rolling mill is used for rolling a composite metal blank; the composite metal blank comprises a double-layer metal blank which specifically comprises an inner-layer blank and an outer-layer blank; the inner-layer blank is arranged in the outer-layer blank and is made of different materials; the section of the inner-layer blank is in a central symmetry shape; the first rolling mill comprises a first rolling hole, and the first rolling hole is an asymmetric oval rolling hole; through the design of the asymmetric oval rolling holes, deformation is distributed more evenly, internal stress concentration is reduced, the size precision and surface quality of products are improved, and under the condition that the rolling hole alignment precision is reduced due to aging or improper maintenance of a rolling mill, the asymmetric oval rolling holes can still keep relatively stable rolling quality and low defective rate.

Description

Technical Field

[0001] The invention relates to the technical field of rolling mills for rolling profiled sections, and in particular to a rolling mill and a metal composite rolling method. Background Art

[0002] For a metal billet containing a first material and a second material, the metal billet of the first material is tubular, and the metal billet of the second material is solid. The first material and the second material are different. The metal billet of the second material is placed in the metal billet of the first material, and can be passed through a rolling mill to form a composite metal rod or wire. At present, the hole type of the rolling mill is an elliptical-circular hole type system. After such a rolling mill performs composite rolling on metal billets of different materials, the cross-section of the formed rod or wire is asymmetric, which affects the use of the composite metal rod or wire.

[0003] For example, a rolling mill and a metal composite rolling method in Chinese patent application number CN202111439098.7 are used to roll composite metal billets, the composite metal billets include inner layer billets and outer layer billets, the inner layer billets are arranged in the pipe column billet, and the rolling mill includes a plurality of first frames arranged in sequence according to the process, each first frame has an elliptical first rolling hole, and the long axes of the first rolling holes of two adjacent first frames are perpendicular to each other. The rolling mill can complete composite metal billets with various cross-sectional shapes and products of various target shapes on a continuous rolling production line, and can also make the cross-section center of the rolled bars or wires symmetrical, so as to minimize the deformation unevenness caused by the hole type.

[0004] However, the rolling holes with their long axes perpendicular to each other require that the long axis of the rolling holes of each first frame need to be precisely adjusted to be perpendicular to the adjacent frame, which places high requirements on equipment and maintenance costs. If deviations occur, deformation in a certain direction will gradually accumulate, making it difficult for the cross-section to be centrally symmetrical. In addition, the rolling holes with their long axes perpendicular to each other result in a large amount of deformation each time they are rolled, which places high requirements on the material properties of the composite metal billet and cannot be used on a large scale. Summary of the invention

[0005] The embodiments of the present application provide a rolling mill and a metal composite rolling method, thereby solving the problems of high cost and inability to apply on a large scale in the prior art, reducing production and maintenance costs, and having more application scenarios.

[0006] An embodiment of the present application provides a rolling mill, including a first rolling mill for rolling a composite metal billet; the composite metal billet includes a double-layer metal billet, specifically an inner layer billet and an outer layer billet; the inner layer billet is arranged in the outer layer billet, and the materials of the two are different; the cross-section of the inner layer billet is a centrally symmetrical shape; the first rolling mill contains a first rolling hole, and the first rolling hole is an asymmetric elliptical rolling hole.

[0007] Furthermore, the asymmetric elliptical rolled hole includes two semi-ellipses with the same major axis and different minor axes, wherein the minor axis lengths of the two semi-ellipses are L1 and L2, and L1=1.5L2.

[0008] Furthermore, of two adjacent first rolling holes, the latter first rolling hole is the former first rolling hole rotated 90° in the clockwise or counterclockwise direction, and the lengths of the major axis and minor axis of the first rolling hole of the latter first rolling mill are reduced by 6% relative to the lengths of the major axis and minor axis of the first rolling hole of the former first rolling mill, the length of the major axis of the first rolling hole of the first frame is 40-180mm, and the total length of the minor axis of the first rolling hole of the first frame is 30-150mm, and a roller gap is also provided in the major axis direction of the ellipse.

[0009] Furthermore, convex points are arranged on the semi-ellipse with a minor axis length of L1. The number of the convex points is an odd number. The convex points are spherical and the height is no more than one fifth of the minor axis of the semi-ellipse where the convex points are located.

[0010] Furthermore, the eccentricity of the ellipse of the first rolling mill also changes continuously, the minor axis of the semi-ellipse with convex points decreases uniformly, and the minor axis of the semi-ellipse without convex points increases uniformly;

[0011] Specifically: in the first rolling hole of the first first rolling mill, L1=1.5L2, and in the first rolling hole of the last first rolling mill, L2=1.5L1.

[0012] Furthermore, the spacing of the first rolling mill is divided into short spacing, normal spacing and long spacing. The normal spacing is 1.2 meters, the short spacing is 0.5 meters, and the long spacing is 2 meters.

[0013] Furthermore, the misalignment rate of the first rolling mill is 0%-15%, and the misalignment rate refers to the rough rolling slab before intermediate rolling. The symmetric center point of the cross section to the farthest point of the periphery is R, and the midpoint of the long axis of the first rolling mill of the nth stand is O. n , the midpoint of the long axis of the first rolling mill in the previous stand is marked as O n-1 , O n The points mapped on the rolled hole section and O n-1 The distance is recorded as O n-1 O n Specifically, O n-1 O n It is the distance between the center point of the cross section of the rough rolled billet and the midpoint of the long axis of the rolling hole when the rough rolled billet enters the next first rolling mill; n-1 O n The ratio to R is recorded as the misalignment rate.

[0014] Furthermore, the first rolling mill misalignment is specifically that two adjacent first rolling mills are misaligned in opposite directions; the misalignment direction refers to n-1 O n direction.

[0015] Furthermore, the offset direction of the second stand first rolling mill is in the short axis or long axis direction.

[0016] The metal composite rolling method of the rolling mill is specifically as follows:

[0017] S1. Obtaining a composite metal billet;

[0018] S2, rough rolling the asymmetric elliptical second rolling holes of the plurality of second stands of the composite metal billet to obtain a rough rolled billet; the rough rolling is performed in a rough rolling assembly, the rough rolling passes are 4-8 times, and the deformation rate of the rough rolling is 20-80%;

[0019] S3, sequentially passing the rough rolled billet through a plurality of asymmetric elliptical first rolling holes of the first stands for intermediate rolling to obtain an intermediate rolled billet, wherein the intermediate rolling passes are 8-20 times and the deformation rate of the intermediate rolling is 20-90%;

[0020] S4, finishing rolling the asymmetric elliptical third rolling holes of the plurality of third stands of the intermediate rolling billet to obtain an intermediate billet with symmetrically distributed cross sections of the inner and outer billets, the finishing rolling passes are 4-8 passes, and the deformation rate of the finishing rolling is 20-85%;

[0021] Among them, the rough rolling and the finish rolling are adaptively selected according to the shape of the composite metal billet.

[0022] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0023] First, the design of asymmetric elliptical rolling holes reduces internal stress concentration and improves the dimensional accuracy and surface quality of products. The design of asymmetric elliptical rolling holes allows different pressures and deformations to be applied to the material each time it is rolled, and the cross-sectional shape of the material is gradually adjusted to make it closer to the target shape. The deformation direction of each adjustment is different, but the difference in the deformation amount in each direction is very small after rolling multiple times of 4. Through multiple such adjustments, the cross-sectional asymmetry of the final product is reduced, and the performance of the composite metal billet is improved, the grain is refined, and the uniformity is improved. Since the asymmetric elliptical rolling holes will produce different deformation effects on the material each time it is rolled, the original anisotropy of the material is broken, so that it has more uniform performance in all directions, and the overall mechanical properties and reliability of the product are improved, especially in applications that need to withstand multi-directional stress. The design of asymmetric elliptical rolling holes allows composite metal billets of different materials, shapes and sizes to be adapted by simply adjusting the short axis length and rolling sequence. This enables the rolling mill to handle a wider range of input materials and produce a wider variety of finished products, thereby improving production efficiency and reducing costs.

[0024] Second, the spherical convex points can evenly disperse the stress to the surrounding materials, reduce the stress concentration phenomenon, and thus improve the stability of the rolling process and product quality. The number of convex points is an odd number, forming a symmetrical stress distribution pattern during the rolling process, further reducing the risk of stress concentration; the presence of convex points will affect the heat conduction path and efficiency. During the rolling process, the metal billet will generate a lot of heat due to friction and plastic deformation, and the convex points will become "hot spots" for heat conduction, promoting uniform distribution of heat and improving temperature control during the rolling process; the convex points change the flow behavior of the metal billet during the rolling process; they act as "guides" to guide the material to flow in a specific direction, thereby improving the shape and dimensional accuracy of the rolled product;

[0025] Third, by making the minor axis of the ellipse with convex points gradually and evenly decrease, while the minor axis of the ellipse without convex points gradually and evenly increase, progressive deformation control is achieved during the rolling process, internal stress is reduced, and the fluidity and deformation uniformity of the metal are improved; progressive deformation makes the deformation of the metal during the rolling process more stable and uniform, avoiding problems such as stress concentration and cracks caused by rapid deformation. At the same time, the setting of the convex points further promotes the dispersion of stress and the flow of materials, and refines the metal structure; the eccentricity of the ellipse changes continuously during the rolling process, and this change further adjusts the flow direction and speed of the metal, thereby achieving precise control of the rolled product; the change in eccentricity changes the shape and size of the rolling hole, which in turn affects the deformation behavior and stress distribution of the metal during the rolling process. By reasonably adjusting the change law of eccentricity, the fluidity and deformation uniformity of the metal are optimized; the progressive deformation control and the change in the eccentricity of the ellipse work together to refine the metal structure and improve the mechanical properties such as strength and toughness of the material; the refinement of the metal structure increases the number of grain boundaries, thereby hindering the movement of dislocations and improving the strength and toughness of the material.

[0026] Fourth, by adjusting the mill spacing and dislocation rate, the deformation, dislocation density and recrystallization phenomenon during the rolling process are affected, thereby improving the microstructure and performance of the material; BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a metal composite material rolled by a rolling mill of the present invention;

[0028] Figure 2 A schematic diagram of a first rolling hole of a first rolling mill used in Embodiment 1 of the present invention;

[0029] Figure 3 A schematic diagram of a first rolling hole of a first rolling mill used in a second embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the first rolling hole of the first rolling mill used in Example 3 of the present invention. DETAILED DESCRIPTION

[0031] To facilitate the understanding of the present invention, the present application will be described more comprehensively below with reference to the relevant drawings; the drawings show preferred embodiments of the present invention, but the present invention can be implemented in many different forms and is not limited to the embodiments described herein; on the contrary, the purpose of providing these embodiments is to enable a more thorough and comprehensive understanding of the disclosed content of the present invention.

[0032] It should be noted that the terms “vertical”, “horizontal”, “up”, “down”, “left”, “right” and similar expressions used in this document are only for illustrative purposes and do not represent the only implementation method.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0034] Embodiment 1

[0035] The present application provides a rolling mill, comprising a first rolling mill for rolling a composite metal billet;

[0036] Among them, composite metal billets such as Figure 1 As shown, it includes a double-layer metal billet, specifically an inner layer billet and an outer layer billet; the inner layer billet is arranged inside the outer layer billet, and the materials of the two are different; the cross section of the inner layer billet is a centrally symmetrical shape, such as a square, a regular hexagon, a circle, etc.; the internal shape of the cross section of the outer layer billet should match the cross section shape of the inner layer billet, for example, if the cross section shape of the inner layer billet is circular, the internal shape of the cross section of the outer layer billet is also circular, and if the cross section shape of the inner layer billet is square, the cross section shape of the outer layer billet is also square;

[0037] The first rolling mill Figure 2 As shown, it includes a plurality of first stands arranged in sequence according to the process, each first stand has an elliptical first rolling hole, and the first rolling hole of the first stand is an asymmetric elliptical first rolling hole, specifically, the ellipse of the first rolling hole includes two semi-ellipses with the same major axis and different minor axes, and the minor axis length is L1 and L2, L1=1.5L2, and of two adjacent first rolling holes, the latter first rolling hole is the former first rolling hole rotated 90° in the clockwise direction or counterclockwise direction, and the major axis and minor axis lengths of the first rolling hole of the latter first rolling mill are reduced by 6% relative to the major axis and minor axis lengths of the first rolling hole of the former first rolling mill, the major axis length of the first rolling hole of the first stand of the first rolling mill is 40-180mm, and the total minor axis length of the first rolling hole of the first stand is 30-150mm, and a roller gap is also provided in the major axis direction of the ellipse;

[0038] A metal composite rolling method is also provided, specifically:

[0039] S1. Obtaining a composite metal billet;

[0040] S2, rough rolling the asymmetric elliptical second rolling holes of the plurality of second stands of the composite metal billet to obtain a rough rolled billet; the rough rolling is performed in a rough rolling assembly, the rough rolling passes are 4-8 times, and the deformation rate of the rough rolling is 20-80%;

[0041] S3, sequentially passing the rough rolled billet through a plurality of asymmetric elliptical first rolling holes of the first stands for intermediate rolling to obtain an intermediate rolled billet, wherein the intermediate rolling passes are 8-20 times and the deformation rate of the intermediate rolling is 20-90%;

[0042] S4, finishing rolling the asymmetric elliptical third rolling holes of the plurality of third stands of the intermediate rolling billet to obtain an intermediate billet with symmetrically distributed cross sections of the inner and outer billets, the finishing rolling passes are 4-8 passes, and the deformation rate of the finishing rolling is 20-85%;

[0043] Among them, the rough rolling and the finish rolling are adaptively selected according to the shape of the composite metal billet;

[0044] For example, if the composite metal billet is in the shape of a round billet, the rough rolling is carried out using an elliptical-circular hole type system. If the composite metal billet is in the shape of a square billet or a rectangular billet, the rough rolling is carried out using a box type or a double-radius elliptical hole type. When the cross-section of the finished product is circular, the finishing rolling uses an elliptical-circular hole type; when the cross-section of the finished product is rectangular, the finishing rolling uses a square or rectangular hole type; when the cross-section of the finished product is a hexagonal cross-section, the finishing rolling uses a hexagonal hole type.

[0045] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0046] In the design of asymmetric elliptical rolling holes, due to the change in the length of the minor axis, the material will experience different deformation conditions at each rolling, which will distribute the deformation more evenly, reduce internal stress concentration, and improve the dimensional accuracy and surface quality of the product;

[0047] The design of the asymmetric elliptical rolling hole allows different pressures and deformations to be applied to the material each time the rolling is performed, and the cross-sectional shape of the material is gradually adjusted to make it closer to the target shape. The deformation direction of each adjustment is different, but the difference in the deformation amount in each direction is very small after rolling for multiples of 4 times. Through multiple such adjustments, the cross-sectional asymmetry of the final product is reduced, and the performance of the composite metal billet is improved, the grains are refined, and the uniformity is improved. Since the asymmetric elliptical rolling hole will produce different deformation effects on the material each time the rolling is performed, the original anisotropy of the material is broken, so that it has more uniform performance in all directions, and the overall mechanical properties and reliability of the product are improved, especially in applications that need to withstand multi-directional stress. The design of the asymmetric elliptical rolling hole allows the composite metal billets of different materials, shapes and sizes to be adapted by simply adjusting the short axis length and the rolling sequence; the rolling mill can handle a wider range of input materials and produce a wider variety of finished products, thereby improving production efficiency and reducing costs.

[0048] In the design of asymmetric elliptical rolling holes, by gradually adjusting the minor axis length and rolling sequence, the material is gradually deformed to the target shape during multiple rolling processes, reducing the deformation amount of each rolling and lowering the requirements for the performance of the composite metal billet material. The reduction in material performance requirements allows more types of metal billets to be used in the rolling process, thereby expanding the production range and application areas, reducing raw material costs, and improving production efficiency.

[0049] The design of asymmetric elliptical rolling holes allows the flow and stress distribution of metal materials to be controlled by adjusting the ratio of the major and minor axes of the ellipse, as well as the rolling path and sequence during the rolling process. This flexibility allows the stress to be distributed as evenly as possible by adjusting the rolling parameters even when there are errors in the alignment of the rolling holes due to the aging of the rolling mill. The uniformity of stress distribution helps to reduce local stress concentration, thereby reducing the production of defective products such as material cracking and deformation caused by excessive stress. The design of asymmetric elliptical rolling holes itself has a certain fault tolerance. Due to the asymmetry of the elliptical shape, even if there is a certain alignment error between the rolling holes, the major and minor axis directions of the ellipse are adjusted to adapt to this error, so as not to cause serious stress concentration or material flow problems. When the alignment accuracy of the rolling holes decreases due to aging of the rolling mill or improper maintenance, the asymmetric elliptical rolling holes can still maintain relatively stable rolling quality and a low defective rate.

[0050] The asymmetric elliptical rolling hole design improves the stability and controllability of the rolling process through more uniform deformation distribution and smaller deformation, reduces failures and downtime during the rolling process, and improves production efficiency. Since the asymmetric elliptical rolling hole design has greater flexibility and adaptability, the rolling parameters and processes can be optimized according to specific material and finished product requirements. This helps to further improve product quality and production efficiency.

[0051] Embodiment 2

[0052] The above embodiment reduces deformation aggregation and improves the material properties of the composite metal billet by rolling the holes asymmetrically. In order to further increase the direction of deformation and reduce stress concentration, a convex point is set on the semi-ellipse with the short axis L1, and further improvements are made on the basis of the first embodiment.

[0053] like Figure 3 A convex point is also arranged on the semi-ellipse with the minor axis L1. The number of the convex points is an odd number. The convex points are spherical and the height is not greater than one fifth of the minor axis of the semi-ellipse where the convex points are located.

[0054] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0055] Spherical convex points can evenly disperse stress to the surrounding materials, reduce stress concentration, and thus improve the stability of the rolling process and product quality. The number of convex points is an odd number, forming a symmetrical stress distribution pattern during the rolling process, further reducing the risk of stress concentration. The presence of convex points will affect the heat conduction path and efficiency. During the rolling process, the metal billet will generate a lot of heat due to friction and plastic deformation, and the convex points will become "hot spots" for heat conduction, promoting uniform distribution of heat and improving temperature control during the rolling process. The convex points change the flow behavior of the metal billet during the rolling process. They act as "guides" to guide the material to flow in a specific direction, thereby improving the shape and dimensional accuracy of the rolled product.

[0056] The asymmetric ellipse design itself is used to adjust the shape and size of the rolled product. When used in combination with the convex points, it can more accurately control the material flow and shape change during the rolling process, thereby producing products that better meet the requirements. The asymmetric ellipse design can adapt to metal billets of different widths and thicknesses, while the convex points can further adjust the rolling parameters on this basis, thereby improving the adaptability and flexibility of the rolling mill. The combined use of asymmetric ellipses and convex points further optimizes the stress distribution, reduces defects such as deformation and cracks during the rolling process, and improves the quality and stability of the rolled products.

[0057] Embodiment 3

[0058] In the second embodiment, the stress is further dispersed and the uniformity of the blank is increased by designing the convex points. In order to control the deformation, refine the metal structure, and improve the mechanical properties such as the strength and toughness of the material, a variable rolling hole is designed, and further improved on the basis of the second embodiment.

[0059] like Figure 4 ,During the rolling process, in addition to the continuous reduction of the overall ellipse, the eccentricity of the ellipse also changes continuously. The minor axis of the semi-ellipse with convex points gradually decreases evenly, while the minor axis of the semi-ellipse without convex points gradually increases evenly;

[0060] Specifically: in the first rolling hole of the first first rolling mill, L1=1.5L2, and in the first rolling hole of the last first rolling mill, L2=1.5L1.

[0061] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0062] By making the minor axis of the ellipse with convex points gradually and evenly decrease, while the minor axis of the ellipse without convex points gradually and evenly increase, progressive deformation control is achieved during the rolling process, internal stress is reduced, and the fluidity and deformation uniformity of the metal are improved; progressive deformation makes the deformation of the metal during the rolling process more stable and uniform, avoiding problems such as stress concentration and cracks caused by rapid deformation. At the same time, the setting of the convex points further promotes the dispersion of stress and the flow of materials, and refines the metal structure; the eccentricity of the ellipse changes continuously during the rolling process, and this change further adjusts the flow direction and speed of the metal, thereby achieving precise control of the rolled product; the change in eccentricity changes the shape and size of the rolling hole, thereby affecting the deformation behavior and stress distribution of the metal during the rolling process, and the fluidity and deformation uniformity of the metal are optimized by reasonably adjusting the change law of the eccentricity; the progressive deformation control and the change in the eccentricity of the ellipse work together to refine the metal structure and improve the mechanical properties of the material such as strength and toughness; the refinement of the metal structure increases the number of grain boundaries, thereby hindering the movement of dislocations and improving the strength and toughness of the material. At the same time, the refined structure also improves the processing performance and corrosion resistance of the material; by optimizing the fluidity and deformation uniformity of the metal, reducing internal stress and cracks and other problems, the quality and stability of the rolled products are significantly improved; the refined metal structure improves the mechanical properties of the material such as strength and toughness, making the rolled products have better performance and durability; the scheme is adjusted and optimized according to different metal materials and rolling requirements, enhancing the flexibility and adaptability of the rolling process;

[0063] By optimizing the fluidity and deformation uniformity of the metal, reducing surface defects and corrugations during the rolling process, the surface quality of the rolled products is improved, and failures and downtime during the rolling process are reduced, thereby improving production efficiency and reducing production costs.

[0064] Embodiment 4

[0065] Embodiment 3 adjusts the distance between L1 and L2 by gradually changing the eccentricity to improve the material strength. In order to increase the shear force, staggered rolling is performed, and further improvements are made on the basis of Embodiment 3.

[0066] Setting an adjustable first rolling mill spacing and staggering the first rolling mill;

[0067] Specifically: the default spacing of the first rolling mill without special settings is 1.2 meters, the spacing of the short-distance first rolling mill is 0.5 meters, and the spacing of the long-distance first rolling mill is 2 meters;

[0068] The first rolling mill misalignment is quantified as follows: the distance from the symmetrical center of the cross section to the farthest point on the periphery is R, and the midpoint of the long axis of the first rolling mill of the nth (n is greater than 1 and is a natural number) stand is O. n The midpoint of the long axis of the previous first rolling mill (i.e. the first rolling mill of the n-1th rolling mill) is marked as O n-1 , O n The points mapped on the rolled hole section and O n-1 The distance is recorded as O n-1 O n Specifically, O n-1 O n It is the distance between the center point of the cross section of the rough rolled billet and the midpoint of the long axis of the rolling hole when the rough rolled billet enters the next first rolling mill; n-1 O n The ratio of R is recorded as the dislocation rate, that is, dislocation rate = O n-1 O n / R×100%, misalignment rate 0%-15%;

[0069] Specifically, the first rolling mill misalignment is that the two adjacent first rolling mills are misaligned in opposite directions; the misalignment direction refers to n-1 O n direction;

[0070] In actual use, the offset direction of the second stand first rolling mill is in the short axis or long axis direction.

[0071] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0072] Short spacing reduces internal stress, improves material fluidity and deformation uniformity, and is suitable for thin or soft materials with high dimensional accuracy requirements. Long spacing can increase the shear deformation of the material, help refine the grains, and improve the mechanical properties of the material. It is suitable for the rolling of thick or hard materials. Standard spacing is suitable for most metal billets of medium thickness and medium strength, and can provide good material fluidity and deformation uniformity. The higher the misalignment rate, the greater the shear deformation of the material, which refines the grains and improves the mechanical properties of the material. When the misalignment rate is low, the material fluidity and deformation uniformity can be maintained, and it is suitable for most conventional rolling scenarios.

[0073] The offset rolling itself changes the stress distribution during the rolling process, making the deformation of the metal billet more uniform. Combined with the convex points, it further enhances the effect of stress dispersion and homogenization, and reduces the risk of internal stress and cracks. The convex points act as "guides" to guide the material to flow in a specific direction, thereby improving the shape and size accuracy of the rolled products. The eccentricity of the ellipse changes continuously during the rolling process. This change further adjusts the flow direction and speed of the metal. By reasonably adjusting the change law of the eccentricity, the shape and size of the rolled products can be accurately controlled. The combination of offset rolling and eccentricity changes can achieve all-round and precise control of the rolled products to meet higher precision requirements. The progressive deformation control and the change of the ellipse eccentricity work together to refine the metal structure, improve the mechanical properties of the material such as strength and toughness, and make the rolled products have better comprehensive performance. By optimizing the fluidity and deformation uniformity of the metal, internal stress and cracks are reduced, and the reliability and durability of the rolled products are significantly improved.

[0074] By adjusting the mill spacing and dislocation ratio, the deformation, dislocation density and recrystallization phenomenon during rolling are affected, thereby improving the microstructure and performance of the material;

[0075] For example, when the metal billet has medium thickness and strength, a moderate mill spacing (1.2 meters) combined with a moderate misalignment rate (10%) can provide good material fluidity and deformation uniformity, which is suitable for most conventional rolling scenarios; for thinner or lower-strength metal billets, a shorter mill spacing (0.5 meters) combined with a lower misalignment rate (5% or lower) can reduce internal stress, improve material fluidity and deformation uniformity, and thus obtain products with higher dimensional accuracy. For thicker or higher-strength metal billets, a longer mill spacing (2 meters) combined with a higher misalignment rate (15%) can increase the shear deformation of the material, help refine the grains, and improve the mechanical properties of the material.

[0076] In order to more specifically illustrate the technical solution of the present application, a specific experiment is used to illustrate the technical solution used in Example 1 to Example 4. The specific experimental grouping is shown in Table 1, where the silver content of 316L stainless steel is 0.05%:

[0077]

[0078]

[0079] Table 1

[0080] According to the above experimental grouping experiment, the cross-sectional shape of the composite metal billet used is a round billet, which is composed of a cylindrical inner billet and an annular outer billet, and the inner billet is inserted into the outer billet; the size of the center billet is Φ75mm, and the size of the annular billet is Φ150mm; the above composite metal square billet is subjected to 8 passes of rough rolling on a round hole type frame to obtain a rough rolling billet with a size of Φ90mm; the rough rolling billet is subjected to 12 passes of intermediate rolling on a frame with an asymmetric elliptical hole to obtain an intermediate rolling billet with a size of Φ45mm; the intermediate rolling billet is subjected to 8 passes of finish rolling on a frame with a round hole to obtain a 20MnSi bar with a center size of Φ14mm and an outer size of Φ25mm. The parameters of the obtained products are shown in Table 2;

[0081]

[0082]

[0083] Table 2

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A rolling mill, characterized in that: It includes a first rolling mill for rolling a composite metal billet; the composite metal billet includes a double-layer metal billet, specifically an inner layer billet and an outer layer billet; the inner layer billet is arranged in the outer layer billet, and the materials of the two are different; the cross-section of the inner layer billet is a centrally symmetrical shape; the first rolling mill contains a first rolling hole, and the first rolling hole is an asymmetric elliptical rolling hole.

2. A rolling mill according to claim 1, characterized in that: The asymmetric elliptical rolled hole includes two semi-ellipses with the same major axis and different minor axes, wherein the minor axis lengths of the two semi-ellipses are L1 and L2, and L1=1.5L2.

3. A rolling mill as claimed in claim 2, characterized in that: Of two adjacent first rolling holes, the latter first rolling hole is the former first rolling hole rotated 90° in the clockwise or counterclockwise direction, and the major axis and minor axis lengths of the first rolling hole of the latter first rolling mill are reduced by 6% relative to the major axis and minor axis lengths of the first rolling hole of the former first rolling mill, the major axis length of the first rolling hole of the first frame is 40-180mm, and the total minor axis length of the first rolling hole of the first frame is 30-150mm, and a roller gap is also provided in the major axis direction of the ellipse.

4. A rolling mill according to claim 1, characterized in that: A convex point is also arranged on the semi-ellipse with a minor axis length of L1. The number of the convex points is an odd number. The convex points are spherical and the height is no greater than one fifth of the minor axis of the semi-ellipse where the convex points are located.

5. A rolling mill as claimed in claim 4, characterized in that: The eccentricity of the ellipse of the first rolling mill also changes continuously, the minor axis of the semi-ellipse with convex points decreases uniformly, and the minor axis of the semi-ellipse without convex points increases uniformly; Specifically: in the first rolling hole of the first first rolling mill, L1=1.5L2, and in the first rolling hole of the last first rolling mill, L2=1.5L1.

6. A rolling mill as claimed in claim 5, characterized in that: The spacing of the first rolling mill is divided into short spacing, normal spacing and long spacing. The normal spacing is 1.2 meters, the short spacing is 0.5 meters, and the long spacing is 2 meters.

7. A rolling mill according to claim 1, characterized in that: The misalignment rate of the first rolling mill is 0%-15%. The misalignment rate refers to the rough rolling slab before intermediate rolling. The farthest point from the symmetrical center of the cross section to the periphery is R, and the midpoint of the long axis of the first rolling mill of the nth stand is O. n , the midpoint of the long axis of the first rolling mill in the previous stand is marked as O n-1 , O n The points mapped on the rolled hole section and O n-1 The distance is recorded as O n-1 O n Specifically, O n-1 O n It is the distance between the center point of the cross section of the rough rolled billet and the midpoint of the long axis of the rolling hole when the rough rolled billet enters the next first rolling mill; n-1 O n The ratio to R is recorded as the misalignment rate.

8. A rolling mill according to claim 7, characterized in that: Specifically, the first rolling mill misalignment is that the two adjacent first rolling mills are misaligned in opposite directions; the misalignment direction refers to n-1 O n direction.

9. A rolling mill according to claim 8, characterized in that: The offset direction of the first rolling mill in the second stand is in the direction of the short axis or the long axis.

10. A metal composite rolling method of a rolling mill according to any one of claims 1 to 9, characterized in that: Specifically: S1. Obtaining a composite metal billet; S2, rough rolling the asymmetric elliptical second rolling holes of the plurality of second stands of the composite metal billet to obtain a rough rolled billet; the rough rolling is performed in a rough rolling assembly, the rough rolling passes are 4-8 times, and the deformation rate of the rough rolling is 20-80%; S3, sequentially passing the rough rolled billet through a plurality of asymmetric elliptical first rolling holes of the first stands for intermediate rolling to obtain an intermediate rolled billet, wherein the intermediate rolling passes are 8-20 times and the deformation rate of the intermediate rolling is 20-90%; S4, finishing rolling the asymmetric elliptical third rolling holes of the plurality of third stands of the intermediate rolling billet to obtain an intermediate billet with symmetrically distributed cross sections of the inner and outer billets, the finishing rolling passes are 4-8 passes, and the deformation rate of the finishing rolling is 20-85%; Among them, the rough rolling and the finish rolling are adaptively selected according to the shape of the composite metal billet.

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