A method and device for flattening a copper-steel solid self-lubricating bimetallic plate

Abstract

The application discloses a copper-steel solid self-lubricating bimetal plate flattening method and device, which comprises the following steps: S1, feeding the copper-steel bimetal self-lubricating plate to be flattened into a flattening machine for pre-flattening treatment, adjusting the distance between the upper and lower rollers of the flattening machine, so that the flatness of the plate in the length direction reaches the predetermined requirement after the plate passes through the flattening machine; S2, placing the pre-flattened plate on the workbench of a press, starting the press, and applying pressure to the plate to make the plate bend along the width direction towards the side where the copper layer is located. The application has the advantages of simple structure, and the pre-flattened plate is placed on the workbench of the press for pressure application, so that the plate bends along the width direction towards the side where the copper layer is located, a compressive stress opposite to the direction of residual tensile stress is actively applied on the copper alloy layer by using the process of elastic deformation and then plastic deformation of the plate, and the compressive stress and the residual tensile stress are offset after being superimposed on the alloy layer, so that the stress source causing the plate to rebound after flattening is eliminated.

Description

Technical Field

[0001] This invention relates to the field of metal sheet preparation technology, specifically a method and apparatus for leveling copper-steel solid self-lubricating bimetallic sheets. Background Technology

[0002] Copper-steel bimetallic composites, possessing both the excellent friction-reducing and wear-resistant properties of copper alloys and the high strength of steel, are widely used in the manufacture of self-lubricating bearings, sliding components, and other mechanical parts. In existing technologies, ordinary copper-steel bimetallic sheets, after sintering and rolling, can achieve good flatness through leveling using a conventional roller leveling machine. For example, for copper-steel bimetallic sheets containing no or low levels of solid lubricants, the flatness after leveling can typically reach within 0.15 mm, meeting the needs of general industrial applications.

[0003] However, with the continuous development of self-lubricating technology, copper-steel bimetallic self-lubricating sheets containing high-content solid self-lubricating materials have gradually become a research hotspot in the industry. These sheets have a high proportion of solid lubricants such as graphite added to the copper alloy layer, giving them excellent self-lubricating properties and high-temperature resistance. However, copper-steel bimetallic sheets containing high-graphite content face significant technical challenges in the leveling process. Specifically, for copper-steel bimetallic sheets containing high-graphite content with a total wall thickness of less than 3.0 mm and a copper layer thickness of about 1.0 mm, the flatness after leveling is often above 0.5 mm, far exceeding the 0.15 mm of ordinary copper-steel bimetallic sheets. Furthermore, the flatness worsens as the sheet width increases, and the copper layer bends outward along the length of the sheet after leveling, severely affecting the dimensional accuracy and performance of the product.

[0004] Studies have shown that the cause of the above problems is that graphite has an extremely low coefficient of thermal expansion, about 1 / 10 to 1 / 20 that of copper. During the sintering and cooling process, graphite particles hardly participate in the shrinkage, while the copper matrix and steel backing both undergo significant cooling and shrinkage. The severe mismatch in the coefficients of thermal expansion between the two leads to a large residual tensile stress inside the copper alloy layer. At the same time, the brittle graphite particles cannot effectively release stress through plastic deformation mechanisms such as dislocation slip like copper crystals, causing a large amount of residual stress to accumulate in the copper alloy layer. When the plate enters the leveling machine for roller leveling, the repeated bending action of the leveling machine will induce the concentrated release of the accumulated residual stress, causing the plate to rebound violently after leveling. The degree of rebound is unevenly distributed along the width direction, ultimately manifesting as a warped shape in which the copper layer bends outward.

[0005] To address the aforementioned residual stress problem, the conventional technical approach in this field is to employ stress-relief annealing. However, for copper-steel bimetallic sheets containing high graphite content, although stress-relief annealing can eliminate residual stress to some extent, the high annealing temperature and long holding time result in a significant decrease in the Brinell hardness of the copper alloy layer after annealing, leading to a substantial reduction in the wear resistance of the copper alloy layer. Simultaneously, after the residual stress accumulated inside the copper alloy layer is released during the annealing process, the copper alloy layer undergoes significant volume expansion, resulting in an increase in the sheet wall thickness and severely affecting the dimensional accuracy of the sheet. Therefore, a leveling method and apparatus for copper-steel solid self-lubricating bimetallic sheets is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for leveling copper-steel solid self-lubricating bimetallic plates, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for leveling copper-steel solid self-lubricating bimetallic plates, comprising the following steps: S1. The copper-steel bimetallic self-lubricating sheet to be leveled is fed into the leveling machine for pre-leveling treatment. The gap between the upper and lower rollers of the leveling machine is adjusted so that the flatness of the sheet in the length direction reaches the predetermined requirements after passing through the leveling machine. S2. Place the pre-leveled plate on the worktable of the press, start the press, apply pressure to the plate, and bend the plate along its width toward the side where the copper layer is located. The plate first undergoes elastic deformation, and then turns into plastic deformation, forming a pre-bent shape in the width direction of the plate. This pre-bent shape has a preset downward pressure. S3. Remove the pressure applied by the press and send the bent sheet back into the leveling machine for final leveling to obtain a copper-steel bimetallic self-lubricating sheet with the required flatness.

[0008] As a further aspect of the present invention: in step S1, after the plate is pre-leveled, the copper layer in its width direction is bent outward.

[0009] As a further aspect of the present invention: in step S2, when the plate is placed on the workbench, its copper layer faces upward and its steel back faces downward.

[0010] As a further aspect of the present invention: in step S2, in the pre-bending state, the flatness of the middle bending portion in the width direction of the plate is controlled to be 1-2 mm.

[0011] As a further aspect of the present invention: in step S2, the amount of downward pressure is determined based on the width and thickness of the plate.

[0012] A leveling device for copper-steel bimetallic self-lubricating plates, comprising: Workbench; Two support rods are spaced apart on the worktable. The two support rods are used to support the plate together, and a clearance space is formed between the two support rods to allow the plate to bend and deform downward. Several locating pins are disposed on the worktable and distributed on the outer side of the pad rod, for abutting against the edge of the plate to define the placement position of the plate on the pad rod; and The upper pressure head is connected to the drive end of the press. The upper pressure head is located above the pad rod and is used to move downward under the drive of the press and apply pressure to the plate along the length of the plate, so that the plate undergoes plastic deformation between the two pad rods.

[0013] As a further aspect of the present invention: at least one slide groove is provided on the workbench along the width direction, and one of the pad rods slides in cooperation with the slide groove. The pad rod can be adjusted along the length direction of the slide groove to adapt to plates of different widths.

[0014] As a further aspect of the present invention: the pad rod is a cylindrical structure, and a protective layer is provided on the surface of the pad rod, the hardness of the protective layer being lower than the hardness of the plate.

[0015] As a further aspect of the present invention: the surface of the upper pressure head that comes into contact with the plate is an arc-shaped pressure surface.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention applies pressure to a pre-leveled sheet metal plate on a press, causing the plate to bend along its width toward the side containing the copper layer. By utilizing the process of elastic deformation followed by plastic deformation of the plate, a compressive stress opposite to the residual tensile stress is actively applied to the copper alloy layer. The two stresses superimpose on the alloy layer and cancel each other out, eliminating the stress source that causes the plate to rebound after leveling. This solves the problem of the copper layer bending outward and poor flatness of copper-steel bimetallic plates with high graphite content after leveling. Furthermore, it can be implemented with only a conventional leveling machine and press, without the need for additional complex equipment. The process is simple and suitable for batch leveling of copper-steel bimetallic self-lubricating plates with high graphite content, relatively soft copper layer, total wall thickness below 3.0 mm, and copper layer thickness of about 1.0 mm. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the leveling method of the present invention; Figure 2 This is a schematic diagram of the leveling device of the present invention; Figure 3 This is a schematic diagram of the plate material after ordinary leveling according to the present invention; In the diagram: 1. Workbench; 11. Slide groove; 2. Pad rod; 3. Locating pin; 4. Upper pressure head. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1 In this embodiment of the invention, a method for leveling a copper-steel solid self-lubricating bimetallic sheet includes the following steps: S1. The copper-steel bimetallic self-lubricating sheet to be leveled is fed into the leveling machine for pre-leveling treatment. The gap between the upper and lower rollers of the leveling machine is adjusted so that the flatness of the sheet in the length direction reaches the predetermined requirements after passing through the leveling machine. Specifically, before the copper-steel bimetallic self-lubricating sheet to be leveled is put into the leveling machine for pre-leveling, the sintered sheet is rolled to the required wall thickness and then fed into the leveling machine after the gap between the upper and lower rollers is adjusted. After the sheet passes through the leveling machine, the flatness in the length direction of the sheet is good and can meet the predetermined requirements, but the copper layer in the width direction is bent outward and does not meet the predetermined requirements.

[0020] S2. Place the pre-leveled plate on the worktable 1 of the press, start the press, apply pressure to the plate, and bend the plate along its width toward the side where the copper layer is located. The plate first undergoes elastic deformation, and then turns into plastic deformation, forming a pre-bent shape in the width direction of the plate. This pre-bent shape has a preset downward pressure. Specifically, after leveling in step S1, the plate is placed on the pad 2. At this time, the copper layer of the plate on the workbench 1 faces upward and the steel back faces downward. Then, the plate is pushed so that one side of the plate edge abuts against the surface of the positioning pin 3 to limit the placement position of the plate on the pad 2. The press is started and the upper pressure head 4 is controlled to move downward to apply pressure to the plate on the pad 2. The amount of downward pressure is determined according to the width and thickness of the plate. During the pressure process, the plate first undergoes elastic deformation and then plastic deformation, so that the width direction of the plate forms a pre-bent shape. The flatness of the middle bending part in the width direction of the plate in the pre-bent shape is controlled to be 1-2 mm.

[0021] In the initial stage of pressing down by the upper pressure head 4, the plate undergoes elastic bending deformation. At this time, the stress inside the plate does not exceed the yield strength of the material. If the external force is removed, the plate completely returns to its original shape. At the same time, the active compressive stress applied by the upper pressure head 4 begins to superimpose with the original residual tensile stress in the copper alloy layer, and the net stress inside the copper alloy layer gradually decreases. When the pressure of the upper pressure head 4 continues to increase to exceed the yield strength of the plate, the plate begins to undergo plastic deformation, and irreversible crystal plane slip occurs inside the copper matrix, forming permanent bending deformation. At this time, the active compressive stress establishes a permanent compressive stress field in the copper alloy layer through plastic deformation. This permanent compressive stress field superimposes with the original residual tensile stress in the plate and cancels each other out in the alloy layer, thereby eliminating the stress source that causes the plate to rebound after leveling.

[0022] S3. Remove the pressure applied by the press and send the bent sheet back into the leveling machine for final leveling to obtain a copper-steel bimetallic self-lubricating sheet with the required flatness.

[0023] Specifically, after the pressure is applied, the press controls the upper pressure head 4 to move upward, so that the upper pressure head 4 is out of contact with the plate. Then the plate is taken out from the pad rod 2, and the bent plate is sent back to the leveling machine for final leveling. The feeding direction of the plate during leveling is consistent with the feeding direction during pre-leveling in step S1 to prevent bending deformation in opposite directions at both ends of the plate. After the plate passes through the leveling machine, a copper-steel bimetallic solid self-lubricating plate with flatness in both length and width directions that meets the requirements for use can be obtained. It should be noted that the leveling machine is existing technology and will not be described in detail here.

[0024] Through the coordinated efforts of the above three steps, high-precision leveling of bimetallic self-lubricating plates containing high-graphite copper-steel content was achieved.

[0025] Table 1 uses a sheet material with a width of 220mm, a length of 450mm, a wall thickness of 2.5mm, and a copper layer thickness of 1.0mm as an example:

[0026] Table 2. Reference relationship between copper layer pressing amount and plate width and wall thickness

[0027] Please see Figure 2-3 A leveling device for copper-steel bimetallic self-lubricating plates, comprising: Workbench 1; Two support rods 2 are spaced apart on the workbench 1. The two support rods 2 are used to support the plate together, and the two support rods 2 form a clearance space for the plate to bend and deform downward. Several locating pins 3 are disposed on the workbench 1 and distributed on the outer side of the support rod 2, used to abut against the edge of the plate to define the placement position of the plate on the support rod 2; and The upper pressure head 4 is connected to the drive end of the press. The upper pressure head 4 is located above the pad rod 2 and is used to move downward under the drive of the press and apply pressure to the plate along the length of the plate, so that the plate undergoes plastic deformation between the two pad rods 2.

[0028] Specifically, the workbench 1 is installed on the press, providing a mounting base for the pad rods 2 and the positioning pins 3. The upper surface of the workbench 1 is a plane. Two pad rods 2 are parallel to each other and spaced apart. The space between the two pad rods 2 forms a clearance space for the sheet metal to bend downwards. The pad rods 2 are cylindrical structures, and their surfaces are covered with a protective layer. The hardness of the protective layer is lower than that of the sheet metal to prevent scratches on the back of the sheet metal during deformation and sliding. The pad rods 2 closer to the inner side of the press are fixedly installed on the workbench 1, while the pad rods 2 closer to the operating side are slidably connected to the workbench 1. At least one groove 11 is provided on the workbench 1 along its width direction. One of the pad rods 2 slides into the groove 11. The pad rod 2 can be adjusted along the length of the groove 11 to accommodate sheets of different widths. After the pad rod 2 is adjusted, it can be locked in place by a locking device. The locking mechanism will not interfere with the placement of the plate during the locking process. The structure of the locking mechanism is not limited. In this embodiment, preferably, the locking mechanism is a bolt. The upper surfaces of the two pads 2 together form a support surface for supporting the plate. There are several positioning pins 3, which are fixedly set on the worktable 1 and distributed on the outside of the pads 2. The upper end of the positioning pin 3 is higher than the upper surface of the pad 2. The positioning pin 3 is used to abut against the edge of the plate to limit the placement position of the plate on the pad 2. The upper pressure head 4 is set on the drive end of the press. The upper pressure head 4 is located above the pad 2. The upper pressure head 4 extends along the length direction of the plate. Its upper end is fixedly connected to the drive end of the press through the mold handle. The lower end forms a pressing surface. After the press is started, the upper pressure head 4 is driven to move downward. The pressing surface of the upper pressure head 4 contacts the upper surface of the plate along the length direction of the plate and applies pressure. The surface of the upper pressure head 4 that contacts the plate is an arc-shaped pressing surface.

[0029] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0030] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A method for leveling copper-steel solid self-lubricating bimetallic plates, characterized in that, Includes the following steps: S1. The copper-steel bimetallic self-lubricating sheet to be leveled is fed into the leveling machine for pre-leveling treatment. The gap between the upper and lower rollers of the leveling machine is adjusted so that the flatness of the sheet in the length direction reaches the predetermined requirements after passing through the leveling machine. S2. Place the pre-leveled plate on the worktable of the press, start the press, apply pressure to the plate, and bend the plate along its width toward the side where the copper layer is located. The plate first undergoes elastic deformation, and then turns into plastic deformation, forming a pre-bent shape in the width direction of the plate. This pre-bent shape has a preset downward pressure. S3. Remove the pressure applied by the press and send the bent sheet back into the leveling machine for final leveling to obtain a copper-steel bimetallic self-lubricating sheet with the required flatness.

2. The leveling method for copper-steel bimetallic self-lubricating plates according to claim 1, characterized in that, In step S1, after the plate is pre-leveled, the copper layer in its width direction is bent outward.

3. The leveling method for copper-steel bimetallic self-lubricating plates according to claim 1, characterized in that, In step S2, when the plate is placed on the workbench, its copper layer faces upward and its steel back faces downward.

4. The leveling method for copper-steel bimetallic self-lubricating plates according to claim 1, characterized in that, In step S2, the flatness of the bent portion in the width direction of the sheet metal is controlled to be 1-2 mm.

5. The leveling method for copper-steel bimetallic self-lubricating plates according to claim 1, characterized in that, In step S2, the amount of downward pressure is determined based on the width and thickness of the plate.

6. A leveling device for a copper-steel bimetallic self-lubricating sheet for implementing the method of claim 1, characterized in that, include: Workbench; Two support rods are spaced apart on the worktable. The two support rods are used to support the plate together, and a clearance space is formed between the two support rods to allow the plate to bend and deform downward. Several locating pins are disposed on the worktable and distributed on the outer side of the pad rod, for abutting against the edge of the plate to define the placement position of the plate on the pad rod; and The upper pressure head is connected to the drive end of the press. The upper pressure head is located above the pad rod and is used to move downward under the drive of the press and apply pressure to the plate along the length of the plate, so that the plate undergoes plastic deformation between the two pad rods.

7. The leveling device for copper-steel bimetallic self-lubricating plates according to claim 6, characterized in that, At least one slide groove is provided on the workbench along the width direction, and one of the pad rods slides in the slide groove. The pad rod can be adjusted along the length direction of the slide groove to adapt to plates of different widths.

8. The leveling device for copper-steel bimetallic self-lubricating plates according to claim 6, characterized in that, The pad rod has a cylindrical structure and a protective layer on its surface. The hardness of the protective layer is lower than that of the plate.

9. The leveling device for copper-steel bimetallic self-lubricating plates according to claim 6, characterized in that, The surface of the upper pressure head that comes into contact with the plate is an arc-shaped pressure surface.

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