A stamping process for high-strength aluminum alloy plates

Abstract

The present invention provides a stamping process for high-strength aluminum alloy plates, comprising the following steps: S1: melting and casting aluminum alloy to form aluminum alloy bars; S2: extruding the aluminum alloy bars into 6111 aluminum alloy plates; S3: performing solution treatment on the aluminum alloy plates; S4: stamping the aluminum alloy plates in the T4 state after solution treatment, including ① drawing; ② trimming and punching; ③ flanging and shaping; ④ punching the first through hole; ⑤ punching the second through hole; S5: performing artificial aging heat treatment on the workpiece to strengthen it to the T6 state; S6: achieving interference fit between the bolts and the workpiece. The present invention performs stamping in the T4 state after solution treatment, greatly improving the forming performance of aluminum alloy plates, avoiding the influence of age hardening on the forming performance of aluminum plates, and avoiding the cracking phenomenon during stamping in the T6 state, thereby obtaining the required high-strength and high-performance aluminum alloy components. It can use extruded aluminum plates instead of rolled aluminum plates to reduce costs and can be widely applied to automotive parts.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy sheet stamping parts, and particularly relates to a stamping forming process for high-strength aluminum alloy sheets. Background Art

[0002] In order to meet the development requirements of automotive lightweighting, more and more lightweight materials are being applied to automobiles. Aluminum alloy sheets have the characteristics of low density, light weight, easy processing and forming, corrosion resistance, age hardening, etc., and have become the first choice for major automobile factories to replace steel sheets to reduce vehicle weight. Due to the different materials of aluminum alloy sheets and steel sheets, there are significant differences in the mechanical properties between aluminum alloy sheets used for vehicle bodies and steel sheets. Therefore, the numerical simulation theory and process design experience or standards of traditional steel sheet stamping forming cannot be directly applied to the stamping process design of aluminum alloy body parts. Moreover, due to the age hardening phenomenon of aluminum sheets, their material parameters will change with the increase of storage time, resulting in unstable part quality after stamping forming.

[0003] Process Difficulties and Common Defects of Aluminum Alloy Sheet Stampings:

[0004] (1) Poor formability: Due to its face-centered cubic crystal structure, the plastic deformation ability of aluminum alloy is quite different from that of steel, so the stamping forming process of steel cannot be directly applied.

[0005] (2) Severe wrinkling tendency: Compared with steel sheets, the window between wrinkling and cracking of aluminum alloy sheets is narrower, and the wrinkling tendency is severe.

[0006] (3) Large springback, difficult to control part accuracy. The elastic modulus of aluminum alloy sheets is only one-third of that of steel sheets, and parts are more likely to spring back.

[0007] (4) Poor hemming property, easy to crack and produce "orange peel" defects.

[0008] (5) Strong adhesion of the surface oxide layer of the sheet, affecting the service life of the die. The surface oxide layer of the aluminum alloy sheet has a large friction with the die surface during the sheet drawing process, is easy to peel off and stick to the die surface, causing die damage.

[0009] (6) Large burrs after trimming and serious chip accumulation, affecting the part surface and increasing the die maintenance cost due to burrs.

[0010] Therefore, how to solve the problems that occur in the application of the above-mentioned aluminum alloy sheets on automobile bodies is of great significance for realizing automotive lightweighting. Summary of the Invention

[0011] Aiming at the problems existing in the prior art, the present invention provides a stamping forming process for high-strength aluminum alloy sheets to solve at least one of the above technical problems.

[0012] The technical solution of the present invention is: a stamping forming process for a high-strength aluminum alloy plate, which is used to process a workpiece, wherein the workpiece is a rectangular plate with flanges on three sides, first through holes are respectively provided on the four corners of the rectangular plate, a rectangular sink is provided in the middle of the rectangular plate, and the angle between the bottom surface of the sink and the rectangular plate is an acute angle, three second through holes are provided on the bottom surface of the sink, and bolts are respectively provided in the three second through holes, and the end of the bolt away from the head is a three-section stepped shaft, which is a press-fit section, a smooth axis section, and a threaded section in sequence, the press-fit section is a large end, the threaded section is a small end, the press-fit section is connected to the head of the bolt, and the head of the bolt is located in the sink. The stamping forming process comprises the following steps:

[0013] Step S1: melting and casting aluminum alloy to produce aluminum alloy aluminum rods;

[0014] Step S2: extruding the aluminum alloy rod into a 6111 aluminum alloy plate;

[0015] Step S3: performing solution treatment on the aluminum alloy plate;

[0016] Step S4: stamping the aluminum alloy sheet in the T4 state after solid solution:

[0017] The stamping process includes the following steps: ① drawing; ② trimming and punching; ③ flanging and shaping; ④ punching the first through hole; ⑤ punching the second through hole;

[0018] Step S5: The workpiece is subjected to artificial aging heat treatment to strengthen to T6 state;

[0019] Step S6: Interference fit between the bolt and the workpiece:

[0020] The threaded sections of the bolts pass through the corresponding second through holes respectively, and a 200T punch press is used to punch the bolts into the second through holes so that the crimping sections of the bolts are interference fit with the workpiece and the heads of the bolts are in contact with the bottom surface of the sinker.

[0021] The present invention adopts 6111 extruded aluminum plate and then performs stamping forming process in T4 state. Compared with the conventional cold-rolled aluminum plate used for stamping, the forming performance of the aluminum alloy plate is greatly improved, and the influence of aging hardening on the forming performance of the aluminum plate is avoided. After forming, artificial aging heat treatment is performed to strengthen it to T6 state, and the required high-strength performance parts can be obtained. The performance of the aluminum plate reaches tensile strength Rm ≥ 330MPa, yield strength Rp0.2 ≥ 280MPa, elongation A 50 ≥14%; Through the above steps, high-strength and low-cost stamped aluminum alloy parts can be obtained, which can replace rolled aluminum plates with extruded aluminum plates to reduce costs and can be widely used in automotive parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a stamping diagram of a high-strength aluminum alloy plate of the present invention.

[0023] Figure 2 This is the front view after stamping the bolt of the present invention.

[0024] Figure 3 This is the back view after stamping the bolt of the present invention.

[0025] Figure 4 This is a schematic diagram of a typical binary phase diagram with solubility changes in the second embodiment of the present invention. Detailed implementation manners

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] Refer to Figures 1-4 , the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the implementation conditions of the present invention. Therefore, they do not have any technical essence. Any modification of the structure, change of the ratio relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that the technical content disclosed by the present invention can cover. At the same time, the terms such as "upper", "lower", "left", "right", "middle", and "one" used in this specification are only for the convenience of clear narration and are not used to limit the scope of implementation of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope that the present invention can implement.

[0028] Example 1. A workpiece of a high-strength aluminum alloy plate, refer to Figures 1-3 , the workpiece is a rectangular plate with flanges on three sides. First through holes are respectively arranged at the four corners of the rectangular plate. A rectangular counterbore is arranged in the middle of the rectangular plate. The included angle between the bottom surface of the counterbore and the rectangular plate is an acute angle. Three second through holes are arranged on the bottom surface of the counterbore. Bolts are respectively arranged in the three second through holes. One end of the bolt far from the head is a three-stage stepped shaft, which is successively a crimping section, a smooth shaft section, and a threaded section. The crimping section is the large end, and the threaded section is the small end. The crimping section is connected to the head of the bolt, and the head of the bolt is located in the counterbore.

[0029] Example 2. On the basis of Example 1, a stamping and forming process for a high-strength aluminum alloy plate includes the following steps:

[0030] Step S1: Melting and casting aluminum alloy to make an aluminum alloy rod;

[0031] Step S2: Extruding the aluminum alloy rod into a 6111 aluminum alloy plate. The extrusion process parameters of the aluminum alloy rod are: the temperature of the aluminum rod is 410 - 430 °C, the extrusion speed is 2.8 - 3.2 mm / s, the outlet temperature is 500 - 520 °C, and water cooling is used;

[0032] Step S3: The aluminum alloy plate is solution-treated.

[0033] Solution treatment refers to heating the alloy to a constant temperature in the high-temperature single-phase region, keeping it for a certain time to fully dissolve the excess phase into the solid solution, and then rapidly cooling to obtain a supersaturated solid solution. It is generally a preparatory heat treatment, and its role is to prepare the best conditions for subsequent processing or heat treatment. Solution treatment is to dissolve carbides, γ phases, etc. in the matrix to obtain a uniform supersaturated solid solution, which is convenient for re-precipitating fine-grained and uniformly distributed carbide and γ strengthening phases during aging. At the same time, it eliminates the stress generated by hot and cold processing and causes the alloy to recrystallize. Secondly, solution treatment is to obtain an appropriate grain size to ensure the high-temperature creep resistance of the alloy.

[0034] For most non-ferrous metal alloys, the purpose of solution treatment is to obtain a supersaturated solid solution to prepare the microstructure for subsequent aging treatment. Refer to Figure 4 , the room-temperature equilibrium microstructure of the C1 alloy with the composition at point n is the α + β two-phase structure, where α is the matrix solid solution and β is the second phase. After heating the C1 alloy to Tq and holding it for a sufficient time, the β phase will dissolve into the matrix to obtain a single-phase α solid solution. If the alloy is rapidly cooled from the Tq temperature to room temperature, since the diffusion and redistribution of alloying element atoms are too late to occur, the β phase cannot nucleate and grow, and the β phase cannot precipitate from the α phase. At this time, the room-temperature microstructure of the alloy is a single-phase supersaturated α solid solution with the composition at point n (the equilibrium composition of the α phase at room temperature is the composition at point b). This supersaturated solid solution is metastable thermodynamically. At an appropriate temperature, the supersaturated solid solution will undergo precipitation, thereby strengthening the alloy. The microstructure after solution treatment is not necessarily a single-phase supersaturated solid solution. For example, the C2 alloy in the figure contains the β phase at any temperature below the eutectic temperature. When heated to Tq, the microstructure of alloy C2 is the α phase and the β phase with the composition at point m. If quenched from Tq, its room-temperature microstructure contains a supersaturated α phase and a part of the β phase in addition.

[0035] Step S4: The aluminum alloy plate in the T4 state after solution treatment is stamped into shape:

[0036] The aluminum alloy plate in the T4 state after solution treatment completes the stamping process within 4 hours. The stamping into shape includes the following steps:

[0037] ① Drawing (DR), using a 400T hydraulic press to draw the shape of the aluminum alloy plate;

[0038] ② Trimming and punching (TR + PI), using a 200T punching machine for trimming and preliminary punching;

[0039] ③Flanging and shaping (FL+RST): Use a 400T hydraulic press to perform flanging and overall contour shaping on three sides of the aluminum alloy plate. The flanging directions of the three sides are consistent with the direction of the bottom surface of the sunken platform, and the fourth unflanged side is parallel to the short side of the rectangular sunken platform.

[0040] ④Punching of the first through holes (PI): Use a 200T punching press to punch the first through holes at the four corners of the main plane of the workpiece.

[0041] ⑤Punching of the second through holes (PI): Use a 200T punching press to punch the second through holes on the bottom surface of the sunken platform. The three second through holes are respectively distributed at the three vertices of an isosceles triangle.

[0042] Step S5: The workpiece is subjected to artificial aging heat treatment to be strengthened to the T6 state.

[0043] Step S6: Interference fit of the bolts and the workpiece: The threaded sections of the bolts respectively pass through the corresponding second through holes, and a 200T punching press is used to press the bolts into the second through holes, so that the crimping sections of the bolts are in interference fit with the workpiece, and the heads of the bolts are in contact with the bottom surface of the sunken platform. The present invention adopts a stamping forming process of 6111 extruded aluminum plate after solution treatment in the T4 state. Compared with the cold-rolled aluminum plate conventionally used for stamping, the formability of the aluminum alloy plate is greatly improved, and the influence of age hardening on the formability of the aluminum plate is avoided. After forming, artificial aging heat treatment is carried out to be strengthened to the T6 state, and parts with the required high strength performance can be obtained. The performance of the aluminum plate reaches tensile strength Rm≥330MPa, yield strength Rp0.2≥280MPa, and elongation A 50 ≥14%; High-strength and low-cost stamping aluminum alloy parts can be obtained through the above steps, and the cost can be reduced by using extruded aluminum plate instead of rolled aluminum plate, and it can be widely applied to automobile parts.

[0044] Example 3: On the basis of Example 2, in step S1, aluminum ingots, magnesium ingots, aluminum-silicon master alloy, manganese agent, chromium agent, and aluminum-50 copper master alloy are added to a 30T aluminum melting furnace; the molten aluminum obtained by melting includes the following components in mass percentage: 0.762% Si, 0.127% Fe, 0.095% Cu, 0.582% Mg, 0.464% Mn, 0.013% Zn, 0.021% Ti, 0.081% Cr, and the balance is Al.

[0045] Example 4: On the basis of Example 2, in step S2, the process parameters of the aluminum alloy aluminum rod extrusion are: the temperature of the aluminum rod is 420°C, the extrusion speed is 3mm / s, and the outlet temperature is 520°C.

[0046] Example 5: On the basis of Example 2, in step S3, the parameters for solution treatment of the aluminum alloy plate are as follows: the solution temperature is 490 ± 5 °C, the solution time is 30 minutes, and rapid water cooling is used. The present invention performs solution treatment on the extruded aluminum alloy plate, avoiding the influence of aluminum alloy age hardening on the forming performance of the aluminum plate.

[0047] Example 6: On the basis of Example 2, in step S5, the workpiece is artificially aged and heat treated to the T6 state, with an aging temperature of 180 ± 5 °C and a holding time of 6 hours. The present invention obtains the T6 state workpiece by natural cooling after furnace discharge, avoiding the cracking phenomenon during stamping in the T6 state. The tensile strength Rm of the stamped aluminum alloy workpiece is ≥ 330 MPa, the yield strength Rp0.2 is ≥ 280 MPa, and the elongation A 50 ≥ 14%.

[0048] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A stamping process for a high-strength aluminum alloy plate, used for machining workpieces, characterized in that: The workpiece is a rectangular plate with flanges on three sides. First through holes are respectively arranged at the four corners of the rectangular plate. A rectangular counterbore is arranged in the middle of the rectangular plate. The included angle between the bottom surface of the counterbore and the rectangular plate is an acute angle. Three second through holes are arranged on the bottom surface of the counterbore. Bolts are respectively arranged in the three second through holes. One end of the bolt far from the head is a three-stage stepped shaft, which is successively a crimping section, a smooth shaft section, and a threaded section. The crimping section is the large end and the threaded section is the small end. The crimping section is connected to the head of the bolt. The head of the bolt is located in the counterbore. The stamping process includes the following steps: Step S1: Melt and cast aluminum alloy to make an aluminum alloy rod; Step S2: Extrude the aluminum alloy rod into an aluminum alloy plate; Step S3: Perform solution treatment on the aluminum alloy plate; Step S4: Stamp the solution-treated aluminum alloy plate in the T4 state: The stamping includes the following steps: ① Drawing; ② Trimming and punching; ③ Flanging and shaping; ④ Punching the first through holes; ⑤ Punching the second through holes; Using 6111 extruded aluminum plate to perform stamping process in the T4 state after solution treatment. Compared with the cold-rolled aluminum plate commonly used in stamping, the formability of the aluminum alloy plate is greatly improved, and the influence of age hardening on the formability of the aluminum plate is avoided; Step S5: Perform artificial aging heat treatment on the workpiece to strengthen it to the T6 state; After forming, perform artificial aging heat treatment again to strengthen it to the T6 state, and components with the required high strength performance can be obtained; Step S6: The bolts are in interference fit with the workpiece: The threaded sections of the bolts respectively pass through the corresponding second through holes. Use a 200T punching machine to punch the bolts into the second through holes, so that the crimping sections of the bolts are in interference fit with the workpiece, and the heads of the bolts are in contact with the bottom surface of the counterbore.

2. The stamping process of a high-strength aluminum alloy plate according to claim 1, characterized in that: In step S1, the molten aluminum alloy liquid includes the following components by mass percentage: 0.762% Si, 0.127% Fe, 0.095% Cu, 0.582% Mg, 0.464% Mn, 0.013% Zn, 0.021% Ti, 0.081% Cr, and the balance is Al.

3. The stamping process of a high-strength aluminum alloy plate according to claim 1, characterized in that: In step S2, the process parameters of the aluminum alloy rod extrusion are: the temperature of the aluminum rod is 410 - 430 °C, the extrusion speed is 2.8 - 3.2 mm / s, the outlet temperature is 500 - 520 °C, and water cooling is used.

4. The stamping process of a high-strength aluminum alloy plate according to claim 1, characterized in that: In step S3, the parameters for the solution treatment of the aluminum alloy plate are: the solution temperature is 490 ± 5 °C, the solution time is 30 minutes, and rapid water cooling is used.

5. The stamping process of a high-strength aluminum alloy plate according to claim 1, characterized in that: In step S4, complete the stamping process on the solution-treated aluminum alloy plate in the T4 state within 4 hours; The drawing in the stamping is to perform profile drawing on the aluminum alloy plate using a 400T hydraulic press.

6. The stamping process of a high-strength aluminum alloy plate according to claim 5, characterized in that: The trimming and punching in the stamping is to perform trimming and preliminary punching using a 200T punching machine.

7. The stamping process of a high-strength aluminum alloy plate according to claim 6, characterized in that: The flanging and shaping in the stamping is to perform flanging and overall contour shaping on three sides of the aluminum alloy plate using a 400T oil press. The flanging directions of the three sides are the same as the direction where the bottom surface of the counterbore is located, and the fourth side without flanging is parallel to the short side of the rectangular counterbore.

8. The stamping process of a high-strength aluminum alloy plate according to claim 7, characterized in that: The punching of the first through holes in the stamping is to punch the first through holes at the four corners of the main plane of the workpiece using a 200T punching machine.

9. The stamping process of a high-strength aluminum alloy plate according to claim 8, characterized in that: The second through-hole punching of the stamping is to punch the second through-hole on the bottom surface of the sunken platform by using a 200T punching press, and the three second through-holes are respectively distributed at the three vertices of an isosceles triangle.

10. A stamping process for a high-strength aluminum alloy plate according to claim 1, characterized in that: In step S5, the workpiece is strengthened to the T6 state by artificial aging heat treatment, the aging temperature is 180±5°C, and the heat preservation time is 6 hours.

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