Aluminum alloy differential thick plate for automobiles and method for manufacturing the same

Abstract

An aluminum alloy differential thick plate for automobile and a preparation method thereof belong to the field of rolling technology. The aluminum alloy differential thick plate comprises the following components: Mg: 0.65-0.70%, Si: 0.70-0.85%, Mn: 0.08-0.13%, Cu: 0.09-0.12%, Ti: <0.02%, Zn: <0.01%, Cr: 0.01-0.03%, Fe: 0.15-0.21%, and the balance of Al. The preparation method comprises the following steps: using T4P state aluminum alloy equal-thickness plate as raw material, performing solid solution treatment after variable-thickness rolling, and then performing pre-aging treatment and natural aging treatment; performing pre-tensile strain treatment on the aluminum alloy differential thick plate after natural aging; and finally, heating and holding to simulate the paint baking hardening process. The differential thick plate prepared by the method has small mechanical property difference between the thin area and the thick area, high paint baking hardening capacity, and excellent comprehensive mechanical property, and can be used for manufacturing automobile lightweight parts. The technical route of obtaining the aluminum alloy differential thick plate by using variable-thickness rolling and heat treatment method has the advantages of high production efficiency, low production cost, and the like, and is easy to realize mass industrial production.

Description

Technical Field

[0001] This invention belongs to the field of rolling technology, and specifically relates to a differential thickness aluminum alloy plate for automobiles and its preparation method. Background Technology

[0002] Variable thickness rolling technology is another new material processing technology following laser welding. Compared with laser welding, the thin and thick areas of the differential thickness plate obtained by variable thickness rolling are continuously transitioned, which can achieve material saving and weight reduction while obtaining better formability and higher surface quality, playing a greater role in automotive lightweighting. Differential thickness plates have been applied in the manufacturing of lightweight automotive parts both domestically and internationally. There are many lightweight automotive parts that can be made from differential thickness plates, including B-pillars, anti-collision beams, and front longitudinal beams. Currently, low alloy steel differential thickness plates and hot-formed differential thickness plates are more commonly used.

[0003] The demand for lightweight vehicles has led to an increasing preference for aluminum alloys as a lightweight material in vehicle bodies. In new energy vehicles, aluminum alloys can effectively reduce vehicle weight, lower energy consumption, and improve power. Currently, the application of aluminum alloys in vehicle bodies and chassis is on the rise; compared to traditional steel bodies, lightweight aluminum alloy bodies offer more significant weight reduction. Combining variable thickness rolling technology with aluminum alloys will further advance the development of automotive lightweighting. Ideally, aluminum alloy differential thickness plate parts can reduce weight by at least 20-30% compared to parts of equal thickness, while achieving a material utilization rate exceeding 60%. These parts can be applied to vehicle chassis components, crossbeams, door components, seat components, and body components. Currently, aluminum alloy differential thickness plates are not yet in industrial production; therefore, the research and application of aluminum alloy differential thickness plates for automobiles represents a unique energy-saving and material-saving new technology with practical application value. Summary of the Invention

[0004] The purpose of this invention is to provide an aluminum alloy differential thickness plate for automobiles and its preparation method. Through variable thickness rolling, solution treatment, pre-aging treatment, natural aging treatment, pre-tensile strain and simulated paint hardening treatment, an aluminum alloy differential thickness plate with small differences in mechanical properties between the thin and thick areas, high paint hardening ability and excellent comprehensive mechanical properties is obtained.

[0005] The present invention discloses a method for preparing an aluminum alloy differential thickness plate for automobiles, comprising the following steps:

[0006] Step 1: Variable thickness rolling

[0007] The raw material is aluminum alloy sheet of equal thickness (T4P state) with a thickness of 3.0 mm. The raw material is rolled in a single pass with variable thickness on a four-roll cold rolling mill. By dynamically adjusting the roll gap in real time, the raw material is rolled into aluminum alloy differential thickness plate. The thickness of the thin zone and the thick zone of the aluminum alloy differential thickness plate are 1.0 mm and 2.0 mm, respectively, and there is a transition zone.

[0008] Step 2: Solution treatment

[0009] The aluminum alloy differential thickness plate is subjected to solution treatment to obtain a solution-treated aluminum alloy differential thickness plate.

[0010] Step 3: Pre-aging treatment

[0011] A solution-treated aluminum alloy differential thickness plate is subjected to pre-aging treatment to obtain a pre-aged aluminum alloy differential thickness plate.

[0012] Step 4: Natural Aging Processing

[0013] The pre-aged aluminum alloy differential thickness plate is subjected to natural aging, which is to be placed at room temperature for 30 days.

[0014] Step 5: Pre-stretching strain treatment

[0015] Aluminum alloy differential thickness plates after natural aging are subjected to pre-tensile strain treatment to obtain aluminum alloy differential thickness plates after pre-tensile strain treatment.

[0016] Step 6: Simulated paint hardening treatment

[0017] Aluminum alloy differential thickness plates with pre-stretch strain treatment are subjected to simulated paint hardening treatment to obtain aluminum alloy differential thickness plates for automobiles.

[0018] Further, the raw materials mentioned in step 1, by mass percentage, include the following components: Mg: 0.65-0.70%, Si: 0.70-0.85%, Mn: 0.08-0.13%, Cu: 0.09-0.12%, Ti: ≤0.02%, Zn: ≤0.01%, Cr: 0.01-0.03%, Fe: 0.15-0.21%, with the balance being Al.

[0019] Furthermore, in step 1, the thickness difference ratio between the thin and thick regions of the aluminum alloy differential thickness plate is 1:2, and the transition zone curve is a straight-line dominant transition.

[0020] Furthermore, the solution temperature in step 2 is 530–550°C, and the solution time is 5–20 min.

[0021] Furthermore, the pre-aging temperature in step 3 is 110–130°C, and the pre-aging time is 5–15 min.

[0022] Furthermore, the strain of the pre-stretch strain treatment described in step 5 is 2%.

[0023] Furthermore, the simulated baking process described in step 6 involves heating and holding at 160–190°C for 25–35 minutes.

[0024] A type of aluminum alloy differential thickness plate for automobiles, prepared by the above method, has a tensile strength of 295MPa to 305MPa, a yield strength of 196MPa to 205MPa, an elongation after fracture of 26% to 30%, and a paint hardening value (BH value) of 96MPa to 106MPa.

[0025] The beneficial effects of this invention are:

[0026] The purpose of this invention is to prepare a differential thickness aluminum alloy plate for automobiles, wherein the tensile strength of the thin and thick sections is 295MPa-305MPa, the yield strength is 196MPa-205MPa, the elongation after fracture is 26%-30%, and the paint hardening value (BH value) of the thin and thick sections is 96MPa-106MPa. The differential thickness plate prepared by this invention exhibits small differences in mechanical properties between the thin and thick sections, high paint hardening ability, and excellent overall mechanical properties. It can be used as a raw material for manufacturing lightweight automotive parts, significantly reducing the structural weight of automotive components and achieving good energy conservation and emission reduction effects. The method of this invention utilizes variable thickness rolling and heat treatment to obtain differential thickness aluminum alloy plates, which has advantages such as high production efficiency, low production cost, and ease of large-scale industrial production. Attached Figure Description

[0027] Figure 1 The diagrams show two types of longitudinally variable thickness plates, where (a) is a schematic diagram of a laser-welded plate and (b) is a schematic diagram of a rolled differential thickness plate of the present invention.

[0028] Figure 2 The diagram shows the variable thickness rolling process in Embodiment 1 of the present invention and the prepared aluminum alloy differential thickness plate for automobiles; (a) Schematic diagram of variable thickness rolling; (b) Actual object of the differential thickness plate cut into square pieces;

[0029] Figure 3 The images show the engineering stress-strain curves obtained after mechanical property testing of the aluminum alloy differential thickness plate for automobiles prepared in Example 1 of the present invention, where (a) is the engineering stress-strain curve of the thin area (thickness 1.0 mm) and (b) is the engineering stress-strain curve of the thick area (thickness 2.0 mm). Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] To facilitate understanding of the present invention, several embodiments of the invention have been provided. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be more thorough and complete.

[0032] Figure 1 The diagrams show two types of longitudinally variable thickness plates, where (a) is a schematic diagram of a laser-welded plate and (b) is a schematic diagram of a rolled differential thickness plate according to the present invention.

[0033] Example 1

[0034] A method for preparing a differential thickness aluminum alloy plate for automobiles includes the following steps:

[0035] Step 1: Variable thickness rolling

[0036] The raw material is an aluminum alloy sheet of uniform thickness (T4P state) with the aforementioned chemical composition, and the mass percentages of its chemical elements are: Mg: 0.68%, Si: 0.75%, Mn: 0.11%, Cu: 0.11%, Ti: 0.02%, Zn: 0.01%, Cr: 0.03%, Fe: 0.15%, with the balance being Al, and a thickness of 3.0 mm. Single-pass variable thickness rolling is performed on a four-roll cold rolling mill. By dynamically adjusting the roll gap in real time, the raw material is rolled into an aluminum alloy sheet with varying thicknesses. The thicknesses of the thin and thick sections are 1.0 mm and 2.0 mm, respectively, with a thickness ratio of 1:2. The transition zone curve is a linear-dominated transition.

[0037] Step 2: Solution treatment

[0038] The aluminum alloy differential thickness plate obtained by variable thickness rolling was subjected to solution treatment at a temperature of 540℃ for 10 minutes.

[0039] Step 3: Pre-aging treatment

[0040] The aluminum alloy differential thickness plate after solution treatment was subjected to pre-aging treatment. The pre-aging temperature range was 120℃ and the pre-aging time was 10min.

[0041] Step 4: Natural Aging Processing

[0042] The aluminum alloy differential thickness plate after pre-aging treatment is subjected to natural aging, which involves placing it at room temperature for 30 days.

[0043] Step 5: Pre-stretching strain treatment

[0044] The aluminum alloy differential thickness plate after natural aging is subjected to a 2% pre-tensile strain treatment.

[0045] Step 6: Simulated paint hardening treatment

[0046] The aluminum alloy differential thickness plate after pre-stretch strain treatment was heated at 180℃ and held for 30 minutes to simulate paint hardening treatment.

[0047] Figure 2 This embodiment shows a schematic diagram of variable thickness rolling and the prepared aluminum alloy differential thickness plate for automobiles; (a) Schematic diagram of variable thickness rolling; (b) Actual square piece cut from the differential thickness plate;

[0048] The mechanical properties of the aluminum alloy differential thickness plate for automobiles prepared in this embodiment were tested. Figure 3 The mechanical property test results of the aluminum alloy differential thickness plate for automobiles prepared in this embodiment are shown in the engineering stress-strain curves. (a) is the engineering stress-strain curve of the thin area (thickness 1.0 mm), and (b) is the engineering stress-strain curve of the thick area (thickness 2.0 mm). The tensile strengths of the thin and thick areas were measured to be 302 MPa and 300 MPa, respectively; the yield strengths were 197 MPa and 204 MPa, respectively; the elongation after fracture was 27.6% and 29.4%, respectively; and the paint hardening values ​​(BH values) of the thin and thick areas were 97 MPa and 106 MPa, respectively.

[0049] Example 2

[0050] A method for preparing a differential thickness aluminum alloy plate for automobiles includes the following steps:

[0051] Step 1: Variable thickness rolling

[0052] The raw material is an aluminum alloy sheet of uniform thickness (T4P state) with the aforementioned chemical composition, and its mass percentages of chemical elements are: Mg: 0.69%, Si: 0.73%, Mn: 0.10%, Cu: 0.11%, Ti: 0.02%, Zn: 0.01%, Cr: 0.03%, Fe: 0.15%, with the balance being Al, and a thickness of 3.0 mm. Single-pass variable thickness rolling is performed on a four-roll cold rolling mill. By dynamically adjusting the roll gap in real time, the raw material is rolled into an aluminum alloy sheet with varying thicknesses. The thicknesses of the thin and thick sections are 1.0 mm and 2.0 mm, respectively, with a thickness difference ratio of 1:2. The transition zone curve is a linear-dominated transition.

[0053] Step 2: Solution treatment

[0054] The aluminum alloy differential thickness plate obtained by variable thickness rolling was subjected to solution treatment at a temperature of 540℃ for 10 minutes.

[0055] Step 3: Pre-aging treatment

[0056] The aluminum alloy differential thickness plate after solution treatment was subjected to pre-aging treatment. The pre-aging temperature range was 120℃ and the pre-aging time was 15min.

[0057] Step 4: Natural Aging Processing

[0058] The aluminum alloy differential thickness plate after pre-aging treatment is subjected to natural aging, which involves placing it at room temperature for 30 days.

[0059] Step 5: Pre-stretching strain treatment

[0060] The aluminum alloy differential thickness plate after natural aging is subjected to a 2% pre-tensile strain treatment.

[0061] Step 6: Simulated paint hardening treatment

[0062] The aluminum alloy differential thickness plate after pre-stretch strain treatment was heated at 180℃ and held for 30 minutes to simulate paint hardening treatment.

[0063] The mechanical properties of the aluminum alloy differential thickness plate for automobiles prepared in this embodiment were tested. The tensile strengths of the thin and thick regions were measured to be 295 MPa and 296 MPa, respectively; the yield strengths were 201 MPa and 198 MPa, respectively; the elongation after fracture was 26.2% and 29.6%, respectively; and the paint hardening values ​​(BH values) of the thin and thick regions were 100 MPa and 96 MPa, respectively.

[0064] Example 3

[0065] A method for preparing a differential thickness aluminum alloy plate for automobiles includes the following steps:

[0066] Step 1: Variable thickness rolling

[0067] The raw material is an aluminum alloy sheet of uniform thickness (T4P state) with the aforementioned chemical composition, and the mass percentages of its chemical elements are: Mg: 0.68%, Si: 0.75%, Mn: 0.11%, Cu: 0.11%, Ti: 0.02%, Zn: 0.01%, Cr: 0.03%, Fe: 0.15%, with the balance being Al, and a thickness of 3.0 mm. Single-pass variable thickness rolling is performed on a four-roll cold rolling mill. By dynamically adjusting the roll gap in real time, the raw material is rolled into an aluminum alloy sheet with varying thicknesses. The thicknesses of the thin and thick sections are 1.0 mm and 2.0 mm, respectively, with a thickness ratio of 1:2. The transition zone curve is a linear-dominated transition.

[0068] Step 2: Solution treatment

[0069] The aluminum alloy differential thickness plate obtained by variable thickness rolling was subjected to solution treatment at a temperature of 540℃ for 15 minutes.

[0070] Step 3: Pre-aging treatment

[0071] The aluminum alloy differential thickness plate after solution treatment was subjected to pre-aging treatment. The pre-aging temperature range was 120℃ and the pre-aging time was 10min.

[0072] Step 4: Natural Aging Processing

[0073] The aluminum alloy differential thickness plate after pre-aging treatment is subjected to natural aging, which involves placing it at room temperature for 30 days.

[0074] Step 5: Pre-stretching strain treatment

[0075] The aluminum alloy differential thickness plate after natural aging is subjected to a 2% pre-tensile strain treatment.

[0076] Step 6: Simulated paint hardening treatment

[0077] The aluminum alloy differential thickness plate after pre-stretch strain treatment was heated at 180℃ and held for 30 minutes to simulate paint hardening treatment.

[0078] The mechanical properties of the aluminum alloy differential thickness plate for automobiles prepared in this embodiment were tested. The tensile strength of the thin and thick regions were measured to be 303 MPa and 295 MPa, respectively; the yield strength was 197 MPa and 201 MPa, respectively; the elongation after fracture was 26.8% and 27.8%, respectively; and the paint hardening value (BH value) of the thin and thick regions was 97 MPa and 102 MPa, respectively.

Claims

1. A method for producing an aluminum alloy differential thick plate for an automobile, characterized by, Includes the following steps: Step 1: Variable thickness rolling The raw material is an aluminum alloy sheet of equal thickness, in T4P state, with a thickness of 3.0 mm. The raw material is subjected to single-pass variable thickness rolling on a four-roll cold rolling mill. By dynamically adjusting the roll gap in real time, the raw material is rolled into an aluminum alloy differential thickness plate. The thickness of the thin and thick areas of the aluminum alloy differential thickness plate is 1.0 mm and 2.0 mm, respectively, and it has a transition zone. The raw materials, by mass percentage, include the following components: Mg: 0.65~0.70%, Si: 0.70~0.85%, Mn: 0.08~0.13%, Cu: 0.09~0.12%, Ti: ≤0.02%, Zn: ≤0.01%, Cr: 0.01~0.03%, Fe: 0.15~0.21%, with the balance being Al; The thickness difference ratio between the thin and thick sections of the aluminum alloy differential thickness plate is 1:2, and the transition zone curve is a straight-line dominant transition. Step 2: Solution treatment The aluminum alloy differential thickness plate is subjected to solution treatment to obtain a solution-treated aluminum alloy differential thickness plate. Step 3: Pre-aging treatment The aluminum alloy differential thickness plate after solution treatment is subjected to pre-aging treatment at a temperature of 110~130℃ for 5~15min to obtain the pre-aged aluminum alloy differential thickness plate. Step 4: Natural Aging Processing The aluminum alloy differential thickness plate after pre-aging treatment is subjected to natural aging, which is to be placed at room temperature for 30 days. Step 5: Pre-stretching strain treatment Aluminum alloy differential thickness plates after natural aging are subjected to pre-tensile strain treatment to obtain aluminum alloy differential thickness plates after pre-tensile strain treatment. Step 6: Simulated paint hardening treatment Aluminum alloy differential thickness plates with pre-stretch strain treatment are subjected to simulated paint hardening treatment to obtain aluminum alloy differential thickness plates for automobiles.

2. The method for preparing differential thickness aluminum alloy plates for automobiles according to claim 1, characterized in that, Step 2: The solution temperature is 530~550℃, and the solution time is 5~20min.

3. The method for preparing differential thickness aluminum alloy plates for automobiles according to claim 1, characterized in that, The strain of the pre-stretch strain treatment described in step 5 is 2%.

4. The method for preparing differential thickness aluminum alloy plates for automobiles according to claim 1, characterized in that, Step 6 simulates the baking paint process by heating at 160~190℃ and holding for 25~35 minutes.

5. An aluminum alloy differential thickness plate for automobiles, prepared by any one of claims 1-4, wherein the aluminum alloy differential thickness plate for automobiles has a tensile strength of 295MPa~305MPa, a yield strength of 196MPa~205MPa, an elongation after fracture of 26%~30%, and a paint hardening value (BH value) of 96MPa~106MPa.

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