A rapid prototyping method for large-size thin-walled light alloy parts

Abstract

The application provides a rapid forming method for light alloy large-size thin-wall parts, which comprises the following steps: heating a male die and a female die of a forming mold, clamping a plate blank by using a clamping mechanism with an electric heating system, installing the clamping mechanism on a material transferring device, heating the plate blank to a target temperature during the transferring process of the plate blank, keeping the temperature constant, moving the plate blank to the top of the female die, and then controlling the male die to descend rapidly after the electric heating system is turned off, so that the plate blank is brought into the female die by the descending male die, until the male die descends to a first target position, and the formed part is taken out of the female die after the Nth time of pressing. The formed part is not affected by the temperature drop of the heating furnace and the transferring process, the forming efficiency is high, the surface quality of the formed part is good, and the deformation defects such as cracking and surface cracking which are prone to occur in conventional forging are avoided.

Description

Technical Field

[0001] This invention belongs to the field of light alloy plastic forming technology, specifically relating to a rapid forming method for large-size thin-walled light alloy parts. Background Technology

[0002] Compared to cast magnesium alloys, wrought magnesium / aluminum alloys have finer grains and eliminate casting defects, resulting in significantly improved overall mechanical properties. However, as close-packed hexagonal magnesium alloys, they have weak plastic deformation capabilities and are highly sensitive to deformation temperature, requiring hot forming. This involves heating the billet in a furnace, then placing it into a mold for forming. However, in multi-pass forming, the mechanical properties decrease with each heating, making it difficult to guarantee the final performance of the component. This is especially true for thin-walled magnesium alloy components, where the temperature drops sharply during the transfer from the holding furnace to the press, easily falling into the temperature range of deformation instability and often leading to deformation failure. Therefore, given the limitations of existing manufacturing processes in forming thin-walled magnesium alloy components, it is necessary to develop a rapid forming method for thin-walled magnesium alloy parts.

[0003] For large-sized thin-walled (wall thickness not greater than 12mm, and opening diameter not less than 260mm) lightweight alloy components with a hemispherical or near-hemispherical shell structure, springback occurs during plastic forming. In particular, the radial springback around the head area of ​​the component is relatively large. The larger the springback, the more difficult it is to guarantee the mechanical properties of the area. As a result, it is difficult to keep the tensile strength and elongation after fracture consistent in different parts of the entire component after forming. Summary of the Invention

[0004] At least in order to solve the technical problems mentioned in the background art, the present invention aims to provide a rapid prototyping method for large-size thin-walled parts made of light alloy.

[0005] The present invention adopts the following technical solution.

[0006] A rapid prototyping method for large-size thin-walled parts made of light alloys, comprising the following steps: Step 1: Based on the dimensions of the thin-walled part, cut the material from the sheet metal to obtain the slab blank; Step 2: Heat the punch and die of the forming mold until the temperature of the punch and die is 200℃-350℃ lower than the heating temperature of the slab. Step 3: The blank is clamped by a clamping mechanism with an electric heating system. The clamping mechanism is installed on the transfer equipment. During the transfer of the blank, the blank is heated to the target temperature and then kept at a constant temperature. Step 4: Move the slab directly above the die cavity, and control the punch to move downward within 10 seconds after turning off the electric heating system. Use the downward movement of the punch to bring the slab into the die cavity until the punch moves down to the first target position. Step 5: After the first stroke of the punch is completed, lift the punch, and then control the punch to press down for the Nth time, where N≥1 and is an integer. The amount of the Nth press down is 1%~3% of the product wall thickness, and hold the pressure for 20±3s. Step 6: Remove the molded part from the die cavity and trim it to obtain a thin-walled product.

[0007] In this invention, the thin-walled part is a hemispherical or near-hemispherical shell structure with a wall thickness of no more than 12 mm and an opening diameter of no less than 260 mm.

[0008] Furthermore, the cavity below the die has a constant volume receiving chamber filled with steel shot. A fluid medium inlet is provided in the middle of the bottom wall of the receiving chamber. The fluid medium inlet is connected to a high-pressure system that can supply a specified temperature. Several arrayed micropores are provided on the upper part of the side wall of the receiving chamber. The diameter of the micropores is smaller than the particle size of the steel shot.

[0009] Preferably, the micropores are located 20-40 mm below the connection between the cavity wall and the die.

[0010] Preferably, the thin-walled part is made of AZ80 magnesium alloy, with an opening diameter of Φ300mm and a main body wall thickness of 10mm.

[0011] Preferably, the slab heating temperature is controlled at 150°C, the target temperature for mold heating is controlled at 360°C, and the specified temperature for the fluid medium is controlled at 145°C.

[0012] Beneficial effects: The method of this invention for preparing large-size thin-walled lightweight alloy parts is unaffected by temperature drops during the heating furnace and transfer process; the forming efficiency is high, several times higher than that of traditional methods using ordinary heating furnaces; the surface quality of the formed parts is good, avoiding deformation defects such as cracking and surface tearing that are prone to occur in conventional forging. This invention combines hot deformation and cold forming during the forming process, which can effectively prevent deformation after forming and significantly improve the performance of the formed parts; the equipment involved in this invention is simple, the process operation is convenient, and the implementation cost is low, which is conducive to realizing continuous large-scale industrial production. This invention is particularly suitable for preparing large-size thin-walled lightweight alloy components with hemispherical or near-hemispherical shell structures, ensuring that the tensile strength and elongation after fracture are basically consistent in different parts of the entire component. Attached Figure Description

[0013] Figure 1 This is a partial schematic diagram of the die in the embodiment; Figure 2 This is a partial schematic diagram of the sampling area during testing. Detailed Implementation

[0014] The technical solutions 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. Example

[0015] Combination Figure 1 As shown, a rapid prototyping method for large-size thin-walled parts of light alloys is used to prepare magnesium alloy thin-walled components (specifically AZ80 magnesium alloy, with an opening diameter of Φ300mm and a main body wall thickness of 10mm) with a hemispherical shell structure. The steps include: Step 1: Based on the dimensions of the thin-walled part, cut the sheet material (cutting diameter Φ295mm) to obtain the slab blank; Step 2: Heat the punch and die 3 of the forming mold until the temperature of the punch is controlled at 150°C and the temperature of the die 3 is controlled at 150°C. In this embodiment, a heating element 7 is provided on the upper part of the die 3, and a receiving chamber with a constant volume is provided below the die 3. The receiving chamber is filled with steel shot 2. The die 3 is located inside the cavity and above the steel shot 2 for slab forming (the workpiece in the forming process is shown as number 6). A fluid medium inlet 1 is provided in the middle of the bottom wall of the receiving chamber. The fluid medium inlet 1 is connected to a high-pressure system that can supply a specified temperature. A plurality of micropores 5 are arranged in an array on the upper part of the side wall of the receiving chamber. The diameter of the micropores 5 is smaller than the particle size of the steel shot 2. The particle size of the steel shot 2 is 2~3mm, and the diameter of the micropores 5 is 0.8~1.5mm. The micropores 5 are located 20~40mm below the connection between the cylindrical wall of the receiving chamber and the die 3. Step 3: The slab is clamped by a clamping mechanism with an electric heating system. The clamping mechanism is installed on the transfer equipment. During the transfer of the slab, the slab is heated to the target temperature (360°C) and then kept at a constant temperature. Step 4: Move the blank to the top of the die 3, and control the punch to move downward within 10 seconds after turning off the electric heating system. Use the downward movement of the punch to bring the blank into the die 3 until the punch moves down to the first target position. Then, the high-pressure system is turned on to supply hot air at a temperature of 145°C and a pressure of 0.6 MPa into the containment chamber. The hot air enters from the fluid medium inlet 1 and flows out from the micropore 5. Step 5: After the first stroke of the punch is completed, lift the punch and then control the punch to press down a second time. The second pressing amount is 2.5% of the product wall thickness, and hold the pressure for 20 seconds. Step 6: Remove the molded part from the cavity 3 and trim it to obtain a thin-walled component with a hemispherical shell structure. Example

[0016] Combination Figure 1 As shown, a rapid prototyping method for large-size thin-walled parts of light alloys is used to prepare magnesium alloy thin-walled components (specifically AZ80 magnesium alloy, with an opening diameter of Φ320mm and a main body wall thickness of 11mm) with a hemispherical shell structure. The steps include: Step 1: Based on the dimensions of the thin-walled part, cut the sheet material (cutting diameter Φ315mm) to obtain the slab blank; Step 2: Heat the punch and die 3 of the forming mold until the temperature of the punch is controlled at 152°C and the temperature of the die 3 is controlled at 152°C. In this embodiment, the cavity below the die 3 has a constant-volume receiving chamber filled with steel shot 2. A fluid medium inlet 1 is provided in the middle of the bottom wall of the receiving chamber, and the fluid medium inlet 1 is connected to a high-pressure system capable of supplying a specified temperature. Several arrayed micropores 5 are provided on the upper part of the side wall of the receiving chamber. The diameter of the micropores 5 is smaller than the particle size of the steel shot 2, which is 2~3mm, and the diameter of the micropores 5 is 0.8~1.5mm. The micropores 5 are located 20~40mm below the connection between the cavity wall and the die 3. Step 3: The blank is clamped by a clamping mechanism with an electric heating system. The clamping mechanism is installed on the transfer equipment. During the transfer of the blank, the blank is heated to the target temperature (363℃) and then kept at a constant temperature. Step 4: Move the blank to the top of the die 3, and control the punch to move downward within 10 seconds after turning off the electric heating system. Use the downward movement of the punch to bring the blank into the die 3 until the punch moves down to the first target position. Then, the high-pressure system is turned on to supply hot air at a temperature of 147°C and a pressure of 0.6 MPa into the containment chamber. The hot air enters from the fluid medium inlet 1 and flows out from the micropore 5. Step 5: After the first stroke of the punch is completed, lift the punch and then control the punch to press down a second time. The second pressing amount is 1.5% of the product wall thickness, and hold the pressure for 20 seconds. After the second stroke of the punch is completed, lift the punch and then control the punch to press down a third time. The third pressing amount is 2% of the product wall thickness, and hold the pressure for 20 seconds. Step 6: Remove the molded part from the cavity 3 and trim it to obtain a thin-walled component with a hemispherical shell structure.

[0017] Comparative Example: A rapid prototyping method for large-size thin-walled parts of light alloys, used to prepare magnesium alloy thin-walled components with a hemispherical shell structure (specifically, AZ80 magnesium alloy, with an opening diameter of Φ320mm and a main body wall thickness of 11mm), the steps include: blanking a sheet metal (blank diameter of Φ315mm) according to the product dimensions of the thin-walled part, to obtain a blank; heating the punch and die 3 of the forming mold until the temperature of the punch is controlled at 152℃ and the temperature of the die 3 is controlled at 152℃; clamping the blank using a clamping mechanism with an electric heating system, the clamping mechanism being installed on a transfer device, and the blank being transferred during the transfer process. After heating the billet to the target temperature (363℃), maintain the temperature. Move the billet directly above the die 3, and within 10 seconds after turning off the electric heating system, control the punch to descend, using the downward movement of the punch to bring the billet into the die 3 until the punch reaches the first target position. After the first stroke of the punch is completed, lift the punch, and then control the punch to press down a second time, with the second pressing amount being 1.5% of the product wall thickness, and hold the pressure for 20 seconds. After the second stroke of the punch is completed, lift the punch, and then control the punch to press down a third time, with the third pressing amount being 2% of the product wall thickness, and hold the pressure for 20 seconds. Remove the formed part from the die 3, and after trimming, obtain a thin-walled component with a hemispherical shell structure. The main difference between this and Example 2 is that a hard mold is used instead of the steel shot in Example 2, and the high-pressure fluid is omitted.

[0018] Combination Figure 1 As shown, after the workpiece 6 is pressed down for the Nth time and the punch is lifted, the workpiece 6 will spring back. After springing back, a cavity 4 of varying thickness will appear between the workpiece 6 and the steel shot 2. During the time between the punch being lifted and the next pressing down of the workpiece 6, the heat dissipated by the workpiece 6 will accumulate in the cavity 4 due to the existence of this specific cavity 4. Without temperature field interference, the temperature field on the surface of the workpiece 6 will be disordered and have poor uniformity, resulting in poor forming performance after the next extrusion. However, with the solution of the present invention, the consistency of the temperature field on the surface of the workpiece 6 can be ensured with almost no impact on the cavity morphology, and the forming performance of the workpiece after the next extrusion can be significantly optimized.

[0019] The performance of the thin-walled components prepared in the examples and comparative examples was tested, combined with... Figure 2As shown, each sampling area is 40cm long and 8cm wide. The results show that: in Example 1, the room temperature tensile strength of part A on the thin-walled component is 365MPa with an elongation after fracture of 11.0%; the room temperature tensile strength of part B is 367MPa with an elongation after fracture of 11.0%; and the room temperature tensile strength of part C is 366.5MPa with an elongation after fracture of 11.5%. In Example 2, the room temperature tensile strength of part A on the thin-walled component is 368MPa with an elongation after fracture of 11. The room temperature tensile strength of part B is 367.5 MPa and the elongation after fracture is 11.0%, while the room temperature tensile strength of part C is 367.5 MPa and the elongation after fracture is 11.5%. In the comparative example, the room temperature tensile strength of part A of the thin-walled component is 354 MPa and the elongation after fracture is 9%, the room temperature tensile strength of part B is 359.5 MPa and the elongation after fracture is 10.5%, and the room temperature tensile strength of part C is 362.5 MPa and the elongation after fracture is 11%.

[0020] The present invention provides a method for preparing large-size thin-walled lightweight alloy parts, where the formed parts are unaffected by temperature drops during the heating furnace and transfer process. It boasts high forming efficiency, several times higher than traditional methods using ordinary heating furnaces. The formed parts exhibit excellent surface quality, avoiding deformation defects such as cracking and surface tearing common in conventional forging. This invention combines hot deformation and cold forming during the forming process, effectively preventing post-forming deformation and significantly improving the performance of the formed parts. The equipment involved is simple, the process is easy to operate, and the implementation cost is low, facilitating continuous large-scale industrial production. This invention is particularly suitable for preparing large-size thin-walled lightweight alloy components with hemispherical or near-hemispherical shell structures, ensuring consistent tensile strength and elongation at fracture across different parts of the entire component.

Claims

1. A rapid prototyping method for large-size thin-walled parts made of light alloy, characterized in that the steps include... include: Step 1: Based on the dimensions of the thin-walled part, cut the material from the sheet metal to obtain the slab blank; Step 2: Heat the punch and die of the forming mold until the temperature of the punch and die is 200℃-350℃ lower than the heating temperature of the slab. Step 3: The blank is clamped by a clamping mechanism with an electric heating system. The clamping mechanism is installed on the transfer equipment. During the transfer of the blank, the blank is heated to the target temperature and then kept at a constant temperature. Step 4: Move the slab directly above the die cavity, and control the punch to move downward within 10 seconds after turning off the electric heating system. Use the downward movement of the punch to bring the slab into the die cavity until the punch moves down to the first target position. Step 5: After the first stroke of the punch is completed, lift the punch, and then control the punch to press down for the Nth time, where N≥1 and is an integer. The amount of the Nth press down is 1%~3% of the product wall thickness, and hold the pressure for 20±3s. Step 6: Remove the molded part from the die cavity and trim it to obtain a thin-walled product; The cavity below the die has a constant volume chamber filled with steel shot. A fluid medium inlet is provided in the middle of the bottom wall of the cavity. The fluid medium inlet is connected to a high-pressure system that can supply a specified temperature. Several arrayed micropores are provided on the upper side wall of the cavity. The diameter of the micropores is smaller than the diameter of the steel shot particles.

2. The rapid prototyping method according to claim 1, characterized in that: The thin-walled component has a hemispherical or near-hemispherical shell structure with a wall thickness of no more than 12 mm and an opening diameter of no less than 260 mm.

3. The rapid prototyping method according to claim 2, characterized in that: The micropores are located 20-40 mm below the connection between the cavity wall and the die.

4. The rapid prototyping method according to any one of claims 1-3, characterized in that: The thin-walled component is made of AZ80 magnesium alloy, with an opening diameter of Φ300mm and a main body wall thickness of 10mm.

5. The rapid prototyping method according to claim 4, characterized in that: The slab heating temperature is controlled at 150℃, the target temperature for mold heating is controlled at 360℃, and the specified temperature for the fluid medium is controlled at 145℃.

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