Eight-pass hole-type continuous rolling copper clad aluminum rod process

Abstract

This invention relates to an eight-pass continuous rolling process for copper-clad aluminum bars, characterized by comprising rolling mills 1 to 8 arranged sequentially, with alternating horizontal and vertical rolling mills. The billet for the rolled product is a copper-clad aluminum cast billet, the cross-section of which is rectangular or circular. The process includes the following steps: 1) roughing rolling: using rolling mills 1 to 3 to obtain A1; 2) roughing rolling: using rolling mills 4 to 6 to obtain A2; 3) finishing rolling: using rolling mills 7 and 8 to obtain the final rolled product A3. The rolls of this invention can operate at high speed, eliminating the need to consider workpiece oscillation due to the good constraint effect of the workpiece within the pass. Furthermore, by increasing the reduction per pass, the number of rolling passes is reduced. Moreover, during the continuous rolling process from rolling mill 1 to rolling mill 8, the workpiece does not need to be flipped or reversed, achieving continuous rolling and greatly improving rolling efficiency.

Description

Technical Field

[0001] This invention relates to a process for continuous rolling of copper-clad aluminum bars using an eight-pass sub-pass type, belonging to the field of continuous rolling technology for copper-clad aluminum bars. Background Technology

[0002] Currently, there are several processes for preparing copper-aluminum composite materials: one is hydrostatic extrusion, which is basically a hot extrusion process. Copper tubes and aluminum rods are used as raw materials. The copper tubes are inserted into the aluminum rods, and copper-aluminum composite products of different specifications are pressed into the material under hydrostatic pressure through an extrusion die. Another method is to produce copper-aluminum composite rods using horizontal continuous casting direct composite forming technology, followed by a flat-vertical rolling process using a combination of flat and vertical rolls. The main advantages of this rolling method are: 1) The rolls are simple to process and do not require complex die shapes; 2) The flat and vertical rolls have a large adjustable range, and copper-aluminum composite rods of different specifications can be produced using a single set of equipment; 3) The rolling deformation is adjustable and can be adjusted according to the production process requirements, which can improve the pass rate and production efficiency.

[0003] Although this rolling method is simple and widely adopted, flat-roll vertical rolling has long suffered from the following problems: 1) Since copper-clad aluminum is a cladding material, applying shear stress to the sides of the copper-clad aluminum during flat-roll vertical rolling can easily cause the copper layer and aluminum core to delaminate, damaging the copper-aluminum interface. 2) The deformation uniformity is poor, and the cross-sectional shape of the rolled piece varies greatly in different passes, easily generating local stress. 3) Achieving a certain amount of deformation requires multiple passes of repeated processing, and the processing efficiency of each pass is relatively limited, resulting in low processing efficiency for flat-roll vertical rolling.

[0004] Patent CN103358099B discloses a die rolling process for copper-clad aluminum bars. The incoming material is a copper-clad aluminum composite consisting of a core aluminum and a copper cladding layer. The process includes the following steps: billet rolling; first pass flat-hole rolling; first pass vertical-hole rolling; second pass flat-hole rolling; second pass vertical-hole rolling; third pass flat-hole rolling; third pass vertical-hole rolling; fourth pass flat-hole rolling; fourth pass vertical-hole rolling; and fifth pass flat-hole rolling. This rolling process is suitable for processing square and rectangular billets. The rolling process uses nine die passes, achieving fully enclosed constraint rolling. Under the good constraint within the die, the rolled piece can deform simultaneously in both the width and thickness directions, achieving efficient area reduction. It also achieves width expansion by utilizing die constraints, controlling width expansion and solving the problem of cladding layer separation. The disadvantage is that all the passes from 1 to 9 are located on the rolls of a single rolling mill. After the first pass of roughing rolling is completed on pass 1 (D) to obtain billet A1, billet A1 needs to be rotated 90° and then rolled using pass 2 (E). After the first pass of vertical rolling is completed on pass 2 (E) to obtain billet A2, billet A2 needs to be rotated 90° and then rolled using pass 3 (F). Similarly, in the subsequent rolling processes, the billet needs to be rotated continuously to complete the process. Therefore, the rolling efficiency of copper-clad aluminum busbars is low. Summary of the Invention

[0005] The purpose of this invention is to provide a new technical solution to improve or solve the technical problems existing in the prior art as described above.

[0006] The technical solution provided by this invention is as follows: A process for continuous rolling of copper-clad aluminum bars using eight passes includes rolling mills No. 1 to No. 8 arranged sequentially, with horizontal and vertical rolling mills alternating, and the pass shapes of the eight rolling mills alternating between elliptical and circular. The billet for the rolled product is a copper-clad aluminum cast billet, the cross-section of which is rectangular or circular. The process includes the following steps:

[0007] 1) Open rolling: Using rolling mills 1 to 3, the rolled piece passes through the passes on rolling mills 1 to 3 in sequence. The center lines of the passes on rolling mills 1 to 3 are on the same line to ensure that the rolled piece passes through straight. The total processing rate of open rolling is 45% to 55% and the total elongation is 1.35% to 1.50%, to obtain A1.

[0008] 2) Rough rolling: Using rolling mills No. 4 to No. 6, A1 is passed through the corresponding passes of rolling mills No. 4 to No. 6 in sequence. The center lines of the passes of rolling mills No. 4 to No. 6 are also on the same line. The total processing rate of rough rolling is 15% to 30% and the total elongation is 1.2% to 1.35%, to obtain A2.

[0009] 3) Finishing: Using mills 7 and 8, A2 is passed through the corresponding passes of mills 7 and 8 in sequence. The center lines of the passes of mills 7 and 8 are also on the same line. The total finishing rate is 12% to 15% and the total elongation ranges from 1.05% to 1.15%, to obtain the final rolled piece A3.

[0010] Furthermore, the absolute spread coefficient for each pass is 0.12 to 0.43.

[0011] Furthermore, the absolute spread factor for each pass is 0.22 to 0.38.

[0012] Furthermore, in the billet rolling stage, the first pass processing rate is 50% to 53%; the second pass processing rate is 38% to 40%; and the third pass processing rate is 35% to 37%.

[0013] Furthermore, in the roughing stage, the single-pass processing rate is 18% to 25%, and the single-pass elongation rate is 1.3% to 1.4%.

[0014] Furthermore, in the finishing rolling stage, the end face shrinkage rate per pass is 5% to 8%, and the processing rate per pass is about 10%.

[0015] Furthermore, rolling mills No. 1, No. 3, No. 5, and No. 7 employ flat rolling pass rolls, wherein the pass shape of the flat rolling pass rolls is elliptical or flat elliptical, and the ellipticity of the elliptical pass rolls is 0.4 to 0.9. Rolling mills No. 2, No. 4, No. 6, and No. 8 employ vertical rolling pass rolls, wherein the pass shape of the vertical rolling pass rolls is circular or near-circular.

[0016] Furthermore, when the cross-section of the copper-clad aluminum billet is rectangular, the width of the cross-section is 18mm to 32mm and the height is 20mm to 40mm.

[0017] Furthermore, the height-to-width ratio of the final rolled piece A3 is 0.9 to 1.8.

[0018] Furthermore, when the cross-section of the copper-clad aluminum billet is circular, the diameter of the cross-section is 20mm to 35mm.

[0019] The technical solution provided by this invention has the following advantages compared with the prior art:

[0020] 1) In the roll forming method, the bar is constrained in the roll, and its forming shape is precise and highly matched with the shape of the roll, so the cross-sectional shape and size of the bar can be precisely controlled;

[0021] 2) Due to the use of a die rolling method, the copper-clad aluminum is deformed evenly, thus achieving uniform deformation of the copper cladding layer and a uniform distribution of the copper layer in the finished rolled piece.

[0022] 3) Low energy consumption and high output in rolling: The rolls can run at high speed, and there is no need to consider the oscillation of the rolled piece because the rolled piece has a good constraint effect in the roll pass. At the same time, by increasing the reduction per pass, the number of rolling passes is reduced. Moreover, in the continuous rolling process from No. 1 to No. 8, the rolled piece does not need to be flipped and reversed. The rolled piece enters from No. 1 and exits directly from No. 8 and is rolled into the required finished product specifications, realizing continuous rolling and greatly improving rolling efficiency.

[0023] 4) Multiple roll patterns can be processed on the rolls of each rolling mill. The 1 to 8 rolling mills set up in sequence can be used to roll various specifications of workpieces, thus improving the utilization rate of the rolls;

[0024] 5) Improve yield: The rolling process is closed in the die throughout the rolling process. Except for the free deformation of the burrs at the beginning and end of the rolling, there is almost no scrap material generated at other locations. Attached Figure Description

[0025] Figure 1 The image shows a front view of rolling mills 1 to 8 of this invention.

[0026] Figure 2 This is a top view of rolling mills 1 to 8 of the present invention;

[0027] Figure 3 This is a schematic diagram of the roll profile structure corresponding to the rolls of mills 1 to 8 of the present invention;

[0028] Figure 4 This is a scanned image of the copper-aluminum interface. Detailed Implementation

[0029] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0030] like Figures 1-3 As shown, a process for continuous rolling of copper-clad aluminum bars using eight passes includes rolling mills No. 1 to No. 8 arranged sequentially. The eight rolling mills are arranged alternately as horizontal and vertical mills, and the pass shapes of the eight rolling mills are arranged alternately as elliptical and circular. The billet for the rolled product is a copper-clad aluminum cast billet, and the cross-section of the copper-clad aluminum cast billet is rectangular or circular. The process includes the following steps:

[0031] 1) Opening rolling: Using rolling mills 1 to 3, the rolled piece passes through the passes on rolling mills 1 to 3 in sequence. The center lines of the passes on rolling mills 1 to 3 are on the same line to ensure that the rolled piece passes through straight. The total processing rate of the opening rolling is 45% to 55%, and the total elongation is 1.35% to 1.50%. This elongation range realizes the maximum elongation deformation of the material, which is beneficial to the bonding between copper and aluminum in the material. A1 is obtained after these three passes of rolling.

[0032] 2) Rough rolling: Using rolling mills No. 4 to No. 6, A1 is passed through the corresponding passes of rolling mills No. 4 to No. 6 in sequence. The center lines of the passes of rolling mills No. 4 to No. 6 are also on the same line. The total processing rate of rough rolling is 15% to 30% and the total elongation is 1.2% to 1.35%. This elongation range realizes the further extension and deformation of the material, which is conducive to the coordinated deformation between copper and aluminum in the material. The rough rolling process realizes the deformation of the material to the specifications close to the finished product, and A2 is obtained.

[0033] 3) Finishing: Using mills 7 and 8, A2 is passed through the corresponding passes of mills 7 and 8 in sequence. The center lines of the passes of mills 7 and 8 are also on the same line. The total processing rate of finishing is 12% to 15%, and the total elongation ranges from 1.05% to 1.15%. As the material begins to work harden after multiple passes, this small adjustment of elongation achieves the elongation deformation of the material to the finished product, which is beneficial to the bonding between copper and aluminum in the material. Finishing can precisely control the size and shape before the finished product, and produce the final rolled piece A3.

[0034] like Figure 3 As shown, mills 1, 3, 5, and 7 use flat rolling pass rolls, with the pass shape being elliptical or flat-elliptical, and the ellipticity of the elliptical pass being 0.4–0.9. Mills 2, 4, 6, and 8 use vertical rolling pass rolls, with the pass shape being circular or near-circular. The flat rolling pass rolls have a horizontal axis and include a horizontally arranged upper roll and lower roll, which close to form a flat rolling pass. The vertical rolling pass rolls have a vertical axis and include a pair of vertically arranged vertical rolls, which close to form a vertical rolling pass.

[0035] The absolute spread factor for each pass is 0.12 to 0.43. Preferably, the absolute spread factor for each pass is 0.22 to 0.38.

[0036] In the initial rolling stage, the first pass has a processing rate of 50%–53%, and the billet is rolled into an elliptical cross-section on mill No. 1. The second pass has a processing rate of 38%–40%, and the ellipse is rolled into an approximately circular shape on mill No. 2. The third pass has a processing rate of 35%–37%, and the approximately circular bar is rolled into an approximately elliptical shape on mill No. 3. In the roughing stage, the processing rate per pass is 18%–25%, and the elongation per pass is 1.3%–1.4%. The material achieves a uniform copper layer distribution through gentle deformation. In the finishing stage, the processing amount is the smallest compared to the previous stages. The end face shrinkage rate per pass is about 5%–8%, and the processing rate per pass is about 10%. The material shape reaches the preset size through slight deformation. The roll surface is required to be polished, and the rolled material is smooth and flat.

[0037] When the cross-section of the copper-clad aluminum billet is rectangular, the width of the cross-section is 18mm to 32mm, the height is 20mm to 40mm, and the ratio of the height to the width of the final rolled piece A3 is 0.9 to 1.8.

[0038] When the cross-section of the copper-clad aluminum billet is circular, the diameter of the cross-section is 20mm to 35mm.

[0039] For example, a copper-clad aluminum billet with an incoming material size of 32mm x 40mm is rolled into a copper-clad aluminum composite round bar with a product size of φ12mm using the eight-pass continuous rolling process proposed in this invention. The copper layer is made of T2 grade copper, and the aluminum core is made of 1070 grade aluminum core. The copper volume ratio of the copper-clad aluminum is 25%. The rolling parameters of the eight-pass continuous rolling are shown in the table below:

[0040]

[0041]

[0042] The above flat rolling roll arrangement is a horizontal arrangement, with the upper and lower rolls closing to form a flat rolling pass. The vertical rolling roll arrangement is a vertical arrangement, with a pair of vertical rolls closing to form a vertical rolling pass.

[0043] Among them, the 1V, 3V, 5V and 7V passes of the unit are elliptical flat rolling passes with elliptical ovals of 0.62, 0.7, 0.85 and 0.89 respectively. The vertical passes of the unit, 2H, 4H, 6H and 8H, are circular or near-circular passes.

[0044] The ratio of the absolute width spread coefficient for the first to third passes is 0.15 to 0.43, with the absolute width spread coefficient preferably being 0.22 to 0.38. The absolute width spread coefficient is the ratio of the absolute width spread to the absolute reduction, where the width spread refers to the change in the width of the rolled piece, and the reduction refers to the decrease in the height of the rolled piece after rolling.

[0045] The first, second, and third passes are for billet rolling. The first pass has the largest processing volume, rolling the incoming material into an elliptical cross-sectional shape. The second pass has a relatively smaller processing volume, rolling the ellipse into an approximately circular shape. The third pass then rolls the circular bar into an approximately elliptical shape.

[0046] The fourth, fifth, and sixth passes are the roughing stage, where the amount of material processed is reduced compared to the billet stage. The elongation rate of these three passes is controlled at approximately 1.2%, and the material achieves a uniform copper layer distribution through gentle deformation.

[0047] The seventh and eighth passes are the finishing rolling stage, with the smallest processing volume compared to the first two stages. The end face shrinkage rate changes by about 5% to 8%, and the processing rate per pass is 12%. Through slight deformation, the material shape reaches the preset size. The roll surface is required to be polished, and the rolled material is smooth and flat.

[0048] Scanning electron microscopy (SEM) analysis was performed on the copper-aluminum interface of the finished rolled product, and energy dispersive spectroscopy (EDS) analysis was conducted at the interface. The interface scanning image is shown below. Figure 4 As shown, EDS analysis reveals a good transition layer between copper and aluminum. The gradual transition between copper and aluminum begins at the 12μm position and is completed at the 32μm position. The composition changes continuously and uniformly. This bonding state belongs to the category of metallurgical bonding, which is different from other mechanical bonding of copper and aluminum.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for eight-pass continuous rolling of copper-clad aluminum bars, characterized in that, The process includes rolling mills 1 through 8 arranged sequentially, with horizontal and vertical mills alternating. The billet is a 32mm x 40mm copper-clad aluminum casting, rolled into a φ12mm copper-clad aluminum composite round bar. The copper layer is made of T2 grade copper, and the aluminum core is made of 1070 grade aluminum. The copper volume ratio of the copper-clad aluminum is 25%. The cross-section of the copper-clad aluminum casting is rectangular or circular. The process includes the following steps: 1) Opening rolling: Using rolling mills No. 1 to No. 3, the workpiece passes through the passes on rolling mills No. 1 to No. 3 in sequence. The center lines of the passes on rolling mills No. 1 to No. 3 are on the same line to ensure that the workpiece passes through straight. The total processing rate of opening rolling is 45% to 55% and the total elongation is 1.35% to 1.50%, to obtain A1. 2) Rough rolling: Using rolling mills No. 4 to No. 6, A1 is passed through the corresponding passes of rolling mills No. 4 to No. 6 in sequence. The center lines of the passes of rolling mills No. 4 to No. 6 are also on the same line. The total processing rate of rough rolling is 15% to 30% and the total elongation is 1.2% to 1.35% to obtain A2. 3) Finishing: Using rolling mills 7 and 8, A2 is passed through the corresponding passes on rolling mills 7 and 8 in sequence. The center lines of the passes on rolling mills 7 and 8 are also on the same line. The total finishing rate is 12% to 15% and the total elongation is 1.05% to 1.15%, to obtain the final rolled piece A3. The rolled piece enters from the No. 1 rolling mill and exits directly from the No. 8 rolling mill, where it is rolled into the required finished product specifications. The absolute spread coefficient for each pass is 0.22 to 0.38; Mills 1, 3, 5, and 7 employ flat rolling pass rolls, wherein the pass shape of the flat rolling pass rolls is elliptical or flat elliptical, and the ellipticity of the elliptical pass rolls is 0.4 to 0.

9. Mills 2, 4, 6, and 8 employ vertical rolling pass rolls, wherein the pass shape of the vertical rolling pass rolls is circular or near-circular. The axis of the flat rolling pass rolls is horizontally arranged, and each flat rolling pass roll includes a horizontally arranged upper roll and a lower roll, which close to form a flat rolling pass. The axis of the vertical rolling pass rolls is vertically arranged, and each vertical rolling pass roll includes a pair of vertically arranged vertical rolls, which close to form a vertical rolling pass.

2. The process for eight-pass continuous rolling of copper-clad aluminum bars according to claim 1, characterized in that, During the initial rolling stage, the first pass has a processing rate of 50%–53%; the second pass has a processing rate of 38%–40%; and the third pass has a processing rate of 35%–37%.

3. The process for eight-pass continuous rolling of copper-clad aluminum bars according to claim 2, characterized in that, During the roughing stage, the single-pass processing rate is 18% to 25%, and the single-pass elongation rate is 1.3% to 1.4%.

4. The process for eight-pass continuous rolling of copper-clad aluminum bars according to claim 3, characterized in that, During the finishing rolling stage, the end face shrinkage rate per pass is 5% to 8%, and the machining rate per pass is 10% to 12%.

5. The process for eight-pass continuous rolling of copper-clad aluminum bars according to claim 1, characterized in that, When the cross-section of the copper-clad aluminum billet is rectangular, the width of the cross-section is 18mm to 32mm and the height is 20mm to 40mm.

6. The process for eight-pass continuous rolling of copper-clad aluminum bars according to claim 1, characterized in that, The final height-to-width ratio of the rolled piece A3 is 0.9 to 1.

8.

7. The process for eight-pass continuous rolling of copper-clad aluminum bars according to claim 1, characterized in that, When the cross-section of the copper-clad aluminum billet is circular, the diameter of the cross-section is 20mm to 35mm.

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