A method for improving mechanical properties of aluminum alloy sheet by ultra-low temperature rolling with coarse boundary liner and application thereof

Abstract

A method for improving mechanical properties of aluminum alloy sheet by using rough boundary lining ultra-low temperature rolling and application. The present application belongs to the field of metal forming processing technology. The forming process of the present application is to clamp the aluminum alloy sheet with two hard alloy lining plates whose edges are treated by increasing surface roughness, so that the sheet and the lining plate are subjected to ultra-low temperature treatment and rolling together. The method of the present application can not only increase the single pass reduction and improve the rolling efficiency during the whole sheet forming process, but also hinder the transverse expansion tendency of the sheet during rolling, reduce the generation of edge cracks, and more effectively refine the grain size. The method of the present application is simple in process and easy to realize, which is conducive to improving the rolling effect and can be used for large-scale industrial production of aluminum alloy sheet.

Description

Technical Field

[0001] This invention belongs to the field of metal forming and processing technology, specifically relating to a method and application of improving the mechanical properties of aluminum alloy sheets by using a rough boundary liner for ultra-low temperature rolling. Background Technology

[0002] Weight reduction is a major development trend in manufacturing fields such as automobiles, ships, and aerospace. Replacing steel with lightweight materials is an effective method for weight reduction. Aluminum alloys, due to their low density, high yield, low cost, and good mechanical properties and machinability, have already played a significant role in replacing traditional steel mechanical parts. However, with the development of modern industry, ordinary aluminum alloys are increasingly unable to meet higher performance requirements. Many large plastic deformation methods have been invented, such as equal channel angle extrusion (ECAP), high pressure torsion (HPT), and friction stir (FSP), to prepare fine-grained or ultrafine-grained aluminum alloys and obtain higher performance. However, these technologies cannot be used to prepare large-size ultrafine-grained sheets.

[0003] Currently, the vast majority of manufacturers still use rolling methods to produce industrial aluminum alloy sheets. Traditional aluminum alloy rolling technology typically employs multi-pass rolling with small single-pass reductions, which is beneficial for obtaining uniform deformation, uniform grain structure, and strong texture, but cannot be used to produce high-ductility thin sheets. Conversely, single-pass rolling with large reductions leads to uneven deformation. Moreover, due to the very large shear forces in the rolling direction (RD), aluminum alloy sheets are very prone to cracking, significantly reducing the sheet yield. Therefore, this rolling technology is difficult to use in industrial production. Summary of the Invention

[0004] To overcome the above-mentioned technical defects, the present invention provides a method and application for improving the mechanical properties of aluminum alloy sheets by using a rough boundary liner for ultra-low temperature rolling.

[0005] One objective of this invention is to provide a method for improving the mechanical properties of aluminum alloy sheets by using a rough boundary liner for ultra-low temperature rolling, the method comprising the following steps:

[0006] S1: The aluminum alloy sheet to be processed is clamped and fixed between two hard alloy backing plates. The surface of the backing plate in contact with the aluminum alloy sheet is roughened at the edges, and the aluminum alloy sheet is kept within the range of the rough edges to obtain a template.

[0007] S2: Place the sample in liquid nitrogen for deep cooling, remove it and immediately roll it, controlling the single-pass reduction to 30%. When rolling multiple passes, repeatedly place it in liquid nitrogen for deep cooling between passes, and then proceed to the next pass after cooling. After final rolling, allow the plate temperature to return to room temperature.

[0008] Preferably, the aluminum alloy sheet and the hard alloy liner in S1 are first ground to a roughness Ra≤3.2 before use, and then cleaned with acetone solution.

[0009] Preferably, the edge mentioned in S1 refers to the opposite side in the length direction of the liner.

[0010] More preferably, the width of the rough edge on one side is 10-20% of the width of the liner, and ≥5mm.

[0011] Preferably, the aluminum alloy sheet in S1 is a wrought aluminum alloy, more preferably a 6-series aluminum alloy.

[0012] Preferably, the length and width of the cemented carbide liner in S1 are both greater than those of the aluminum alloy sheet to be processed.

[0013] More preferably, the thickness H1 of the cemented carbide liner is 0.5 mm.

[0014] Preferably, the hardness of the cemented carbide liner in S1 is lower than the surface hardness of the roll.

[0015] Preferably, deep cooling is performed in S2 for 15-30 minutes.

[0016] The second objective of this invention is to provide an aluminum alloy sheet obtained by the above method.

[0017] The third objective of this invention is to provide an application of the above-mentioned method in the large-scale industrial production of aluminum alloy sheets.

[0018] The significant advantages of this invention compared to existing technologies are:

[0019] This invention provides a low-cost rolling method for large-scale industrial production of aluminum alloys with large reduction, and its specific advantages are as follows.

[0020] (1) The method of the present invention increases the single-pass rolling reduction, optimizes the rolling process of large reduction of sheet metal, realizes the rolling of large reduction of aluminum alloy sheet metal in a single pass, improves the forming efficiency of sheet metal, and has a simple process, is easy to implement, has high efficiency, and produces excellent finished product performance.

[0021] (2) During the rolling process, the liner can reduce the shear force along the rolling direction (RD) and convert the shear stress along the rolling direction (RD) into compressive stress in the contact surface normal direction (ND), which solves the edge cracking problem that occurs during the rolling process, effectively improves the single-pass reduction rate, and improves the rolling efficiency.

[0022] ​(3) The rough edges of the liner plate in the transverse direction increase the sliding friction between the plate and the liner plate, which hinders the transverse flow of the plate during the rolling process and increases the hydrostatic pressure of the plate. This greatly reduces the occurrence of edge cracks during the rolling process and achieves a better fine grain strengthening effect.

[0023] (4) During cryogenic rolling, the plate is directly exposed to the air and in direct contact with the rolls, which causes the plate temperature to rise rapidly during the rolling process. The liner can play a role in heat preservation, which helps to improve the rolling effect in the cryogenic environment and ensure the forming performance of the plate. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the principle of the method for efficient rolling of aluminum alloy sheets based on rough boundary liners according to the present invention.

[0025] Figure 2 Schematic diagram of a rough boundary liner;

[0026] Figure 3 This is a process flow diagram of the present invention;

[0027] In the diagram, 1-upper roll, 2-upper liner, 3-aluminum alloy sheet, 4-lower liner, 5-lower roll. Detailed Implementation

[0028] Combination Figures 1-3 The present invention utilizes a method for improving the mechanical properties of aluminum alloy sheets by ultra-low temperature rolling with a rough boundary liner, which is carried out according to the following steps:

[0029] (1) First, prepare aluminum alloy sheet 3, upper liner 2, and lower liner 4. The upper liner 2 and lower liner 4 are both made of 65Mn spring steel. The aluminum alloy sheet is a wrought aluminum alloy, preferably a 6-series aluminum alloy. The length and width of the hard alloy liner are both greater than the aluminum alloy sheet to be processed, and the thickness H1 of the hard alloy liner meets the requirement of 0.5mm.

[0030] Subsequently, the upper liner 2 and the lower liner 4 are pressed tightly against the aluminum alloy sheet 3. Figure 2 As shown in Figure A), the upper and lower surfaces of the aluminum alloy plate 3 are ground to a roughness Ra≤3.2, and the lining plate and aluminum alloy plate are cleaned with acetone solution.

[0031] Next, the two opposite edges along the length of the surfaces (surface A) where the upper and lower liner plates 2 and 4 are in close contact with the aluminum alloy sheet 3 are roughened. The width of each roughened edge is 10-20% of the liner width and ≥5mm, making the surface roughness of the treated surface much greater than that of the untreated surface (e.g., ...). Figure 2 (as shown); ​

[0032] Finally, the aluminum alloy sheet 3 is clamped and fixed between the upper liner 2 and the lower liner 4, ensuring that the aluminum alloy sheet 3 is within the range of the rough edge, thus obtaining the template.

[0033] (2) First, place the sample in liquid nitrogen for deep cooling for 15-30 minutes, and then immediately roll it after taking it out, controlling the single-pass reduction to be 30%.

[0034] Then, the aluminum alloy sheet 3 after one rolling pass is fixed again with the upper liner 2 and the lower liner 4, and then placed in liquid nitrogen for deep cooling for 15-30 minutes. After taking it out, the next rolling pass is immediately carried out until the expected reduction is achieved. The sheet temperature is then allowed to return to room temperature.

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0037] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0038] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0039] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0040] Example 1:

[0041] Combination Figures 1-3 The method for efficient rolling of aluminum alloy sheets based on rough boundary liners in this embodiment is carried out according to the following steps:

[0042] (1) First, prepare an annealed 6061 aluminum alloy plate 3 with a size of 5mm×30mm×40mm. The upper liner plate 2 and the lower liner plate 4 are both made of 65Mn spring steel with a size of 1mm×50mm×250mm.

[0043] Subsequently, the upper liner 2 and the lower liner 4 are pressed tightly against the aluminum alloy sheet 3. Figure 2 As shown in Figure A), the upper and lower surfaces of the aluminum alloy sheet 3 are polished with 180-grit sandpaper, and the lining plate and aluminum alloy sheet are cleaned with acetone solution.

[0044] Next, the two opposite edges along the length of the surfaces (surface A) where the upper and lower lining plates 2 and 4 are in close contact with the aluminum alloy sheet 3 are roughened using a knurling technique with a module m = 0.2. The roughened edge is 10mm wide on each side. Figure 2 (as shown);

[0045] Finally, the aluminum alloy sheet 3 is clamped and fixed between the upper liner 2 and the lower liner 4, ensuring that the aluminum alloy sheet 3 is within the range of the rough edge, thus obtaining the template.

[0046] (2) Place the sample in liquid nitrogen for deep cooling for 20 minutes, take it out and roll it immediately, and control the single-pass reduction to be 30%;

[0047] Then, the aluminum alloy sheet 3 after one rolling pass is fixed again with the upper liner 2 and the lower liner 4, and then placed in liquid nitrogen for deep cooling for 20 minutes. After taking it out, the next rolling pass is immediately carried out. The single pass reduction is 30%, and a total of 3 passes are rolled to the total design reduction of 90%. After rolling, the sheet temperature is allowed to return to room temperature.

[0048] The measured total reduction was 85%. Compared with room temperature rolling, the present invention requires significantly fewer rolling passes and a larger reduction per pass. The total reduction of 85% is achieved in just 3 passes, and no cracks appear on the edge of the plate after rolling.

[0049] For aluminum alloy sheets that have been restored to room temperature after final rolling, tensile tests were conducted on 6061 aluminum alloy tensile specimens in accordance with the relevant provisions of the national standard GB / T 228.1-2010 Metallic Materials - Tensile Testing at Room Temperature.

[0050] Tensile results show that the tensile strength of annealed 6061 aluminum alloy sheet rolled at room temperature is 220 MPa, while the tensile strength of the sample in this experiment is 252 MPa, representing an increase of about 30 MPa and a significant enhancement in mechanical properties.

[0051] Example 2:

[0052] Combination Figures 1-3 The method for efficient rolling of aluminum alloy sheets based on rough boundary liners in this embodiment is carried out according to the following steps:

[0053] (1) First, prepare a T6 state 6061 aluminum alloy plate 3 with a size of 5mm×30mm×40mm. The upper liner plate 2 and the lower liner plate 4 are both made of 65Mn spring steel with a size of 1mm×50mm×250mm.

[0054] Subsequently, the upper liner 2 and the lower liner 4 are pressed tightly against the aluminum alloy sheet 3. Figure 2 As shown in Figure A), the upper and lower surfaces of the aluminum alloy sheet 3 are polished with 180-grit sandpaper, and the lining plate and aluminum alloy sheet are cleaned with acetone solution.

[0055] Next, the two opposite edges along the length of the surfaces (surface A) where the upper and lower lining plates 2 and 4 are in close contact with the aluminum alloy sheet 3 are roughened using a knurling technique with a module m = 0.2. The roughened edge is 10mm wide on each side (e.g., ...). Figure 2 (as shown);

[0056] Finally, the aluminum alloy sheet 3 is clamped and fixed between the upper liner 2 and the lower liner 4, ensuring that the aluminum alloy sheet 3 is within the range of the rough edge, thus obtaining the template.

[0057] (2) Place the sample in liquid nitrogen for deep cooling for 20 minutes, take it out and roll it immediately, and control the single-pass reduction to be 30%;

[0058] Then, the aluminum alloy sheet 3 after one rolling pass is fixed again with the upper liner 2 and the lower liner 4, and then placed in liquid nitrogen for deep cooling for 20 minutes. After taking it out, the next rolling pass is immediately carried out. The single pass reduction is 30%, and a total of 3 passes are rolled to the total design reduction of 90%. After rolling, the sheet temperature is allowed to return to room temperature.

[0059] The measured total reduction was 85%. Compared with room temperature rolling, the present invention requires significantly fewer rolling passes and a larger reduction per pass. The total reduction of 85% is achieved in just 3 passes, and no cracks appear on the edge of the plate after rolling.

[0060] For aluminum alloy sheets that have been restored to room temperature after final rolling, tensile tests were conducted on 6061 aluminum alloy tensile specimens in accordance with the relevant provisions of the national standard GB / T 228.1-2010 Metallic Materials - Tensile Testing at Room Temperature.

[0061] Tensile results show that the tensile strength of 6061 aluminum alloy sheet in T6 state under room temperature rolling is 365 MPa, while the tensile strength of the sample in this experiment is 393 MPa, which is about 30 MPa higher than the tensile strength, indicating an improvement in mechanical properties.

[0062] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for improving the mechanical properties of aluminum alloy sheets by using a rough boundary liner and ultra-low temperature rolling, characterized in that, It includes the following processes: S1: Clamp and fix the aluminum alloy sheet to be processed between two cemented carbide liners, roughen the surface of the liner in contact with the aluminum alloy sheet at the edges, and ensure that the aluminum alloy sheet is within the range of the rough edges to obtain a sample; S2: Deep-cool the sample in liquid nitrogen, immediately perform rolling after taking it out, control the reduction per pass to be 30%, during multi-pass rolling, repeatedly deep-cool it in liquid nitrogen between passes, and perform the next pass of rolling after cooling, and let the temperature of the sheet recover to room temperature in a room-temperature environment after final rolling.

2. The method according to claim 1, characterized in that, Before use, the aluminum alloy sheet and the cemented carbide liner in S1 are polished to a roughness Ra ≤ 3.2 and then cleaned with an acetone solution.

3. The method according to claim 1, characterized in that, The edge mentioned in S1 refers to the opposite sides in the length direction of the liner.

4. The method according to claim 3, characterized in that, The unilateral width of the rough edge is 10 - 20% of the width of the liner and ≥ 5 mm.

5. The method according to claim 1, characterized in that, The aluminum alloy sheet in S1 is a wrought aluminum alloy.

6. The method according to claim 1, characterized in that, In S1, the length and width of the cemented carbide liner are both larger than the aluminum alloy sheet to be processed, the thickness H1 of the cemented carbide liner satisfies 0.5 mm < H1 < 2 mm, the thickness H2 of the aluminum alloy sheet to be processed satisfies 3 mm < H2 < 15 mm, and H1 < H2.

7. The method according to claim 1, characterized in that, In S1, the hardness of the cemented carbide liner is lower than the surface hardness of the roll.

8. The method according to claim 1, characterized in that, In S2, deep-cool for 15 - 30 min.

9. An aluminum alloy sheet obtained by the method according to any one of claims 1 - 8.

10. Application of the method according to any one of claims 1 - 8 in large-scale industrial production of aluminum alloy sheets.

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