Large-size magnesium alloy multi-dimensional synergistic plastic forming process

Abstract

This invention discloses a multi-dimensional synergistic strong and plastic forming process for large-scale magnesium alloys, comprising the following steps: (1) homogenizing heat treatment and extrusion of magnesium alloy ingots, followed by heating the extruded billet to above the homogenization heat treatment temperature and holding it for 3-5 hours; (2) forging the extruded billet into a disc-shaped forging in one pass, and then squaring and rolling it to form a forging bar with a shaft diameter ratio of 2:1 to 3:1; (3) placing the forging bar between upper and lower dies and performing multi-pass forging using a rotary forging method, wherein the cross-sectional shape of the upper and lower dies is convex; (4) annealing the forged billet at high temperature; (5) forging the annealed billet in three directions and extruding it to form the final magnesium alloy component; (6) cooling the final magnesium alloy component to room temperature in four stages, then holding it in a liquid nitrogen environment for 5-10 hours, followed by heating it to room temperature and performing aging heat treatment. This invention can improve the preparation and processing capabilities of magnesium alloy forgings and realize their application in future new equipment.

Description

Technical Field

[0001] This invention relates to a multi-dimensional synergistic strong-plastic forming process for large-scale magnesium alloys, belonging to the field of magnesium alloy material forming technology. Background Technology

[0002] Magnesium alloys, as a novel lightweight material, have wide applications in the aerospace field. With the continuous research and development of new equipment and the upgrading of existing models, the demand for large-scale, high-performance magnesium alloy forgings is constantly increasing. Due to its unique hexagonal structure, magnesium alloys cannot be deformed at room temperature and must undergo plastic processing at high temperatures. However, the deformation processing window for magnesium alloys at high temperatures is extremely narrow, leading to significant challenges in process control, complex forging processes, and relatively low yields. Therefore, exploring suitable forging methods is crucial for improving the overall performance of magnesium alloys and meeting user needs.

[0003] Patent CN107034400A discloses a forging process to eliminate the anisotropy of large-size AQ80M magnesium alloy load-bearing components. It designs a forging processing method for AQ80M magnesium alloy, which adopts a method of first extruding and then forging after homogenization heat treatment. This forging method mainly emphasizes compression deformation along the Z, Y and X directions, combined with intermediate annealing, to finally realize the preparation of magnesium alloy forgings of specific specifications. It can be seen that the three-dimensional forging process plays an extremely important role in improving the performance of magnesium alloys.

[0004] Currently, magnesium alloy forging processes generally require larger-scale equipment, stricter deformation temperature conditions, and more frequent reheat treatments to achieve a more uniform microstructure. However, in practice, large-scale magnesium alloy forging equipment is scarce and often shared with aluminum alloys. This significantly limits process control and scheme adjustments during implementation, making it difficult to achieve ideal results. Furthermore, because the applications of magnesium alloys are far less mature and stable than those of aluminum alloys, existing forging processes are mostly in the exploratory stage, and in practice, the experience gained in preparing and processing aluminum alloys has relatively limited effectiveness when applied to magnesium alloy forgings. In conclusion, developing a magnesium alloy forging preparation and processing technology is both urgent and necessary.

[0005] Most existing magnesium alloy forging technologies share similar process characteristics, such as emphasizing remelting during forging, limiting cumulative deformation, and strictly controlling anvil temperature. While these are important for magnesium alloy forging, friction between the anvil and the magnesium alloy surface can easily lead to forging cracks, and the contact between the forging and the anvil during forging significantly reduces temperature. Therefore, developing an easy-to-operate forging process with low friction and minimal temperature drop is crucial for improving the manufacturing and processing level of magnesium alloy forgings. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-dimensional synergistic strong-plastic forming process for large-size magnesium alloys, so as to improve the preparation and processing capabilities of magnesium alloy forgings, realize the application of magnesium alloy preparation in future new equipment, and achieve the design goal of lightweighting.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A multi-dimensional synergistic strong-plastic forming process for large-scale magnesium alloys includes the following steps:

[0009] (1) The magnesium alloy ingot is subjected to homogenization heat treatment and extrusion, with the extrusion ratio controlled at 3~6. Then the extruded billet is heated to above the homogenization heat treatment temperature and held for 3~5 hours.

[0010] (2) Place the extruded billet on a heated anvil and forge it into a disc-shaped forging in one go. Then, roll the forging into a square shape to form a forging bar with a shaft diameter ratio of 2:1 to 3:1.

[0011] The square-rolling process here achieves a change in shape, with the original extrusion direction becoming the short direction (new radial direction) and the original radial direction becoming the long direction (new axial direction).

[0012] (3) The forging bar is placed between the upper and lower dies and forged in multiple passes using a spiral forging method. The cross-sectional shape of the upper and lower dies is convex. The last forging is not on the same plane as the previous forging, and the forging trajectory is spiral in shape until the forging is completed.

[0013] (4) The forged billet is subjected to high-temperature annealing at a temperature of more than 95% of the homogenization heat treatment temperature and for a time of 0.5 to 3 hours.

[0014] (5) The annealed billet is forged in three directions to form a preform, which is then extruded to form the final magnesium alloy component;

[0015] (6) The final magnesium alloy component is cooled to room temperature in four stages, then kept in liquid nitrogen environment for 5~10 hours, then rapidly heated to room temperature and subjected to aging heat treatment to complete the preparation of the forging.

[0016] Preferably, in step (1), the magnesium alloy ingot has a diameter of 500~800mm and a height of 500~2000mm.

[0017] Preferably, in step (2), the temperature difference between the anvil and the magnesium alloy billet is 50~100℃, the forging speed is controlled at 15~30mm / s, and the deformation is controlled at 40~60%.

[0018] Preferably, in step (3), the upper and lower molds have the same structure and are symmetrically arranged on the upper and lower sides of the forging bar. The width of the top convex surface of the upper and lower molds is one-third of the overall width, and the height of the protruding part is consistent with the height of the bottom.

[0019] Preferably, in step (3), the forging pressure is 10-30% each time, the forging speed is 15-20 mm / s, and the forging bar is rotated 15-30° after each forging while advancing 4 / 5 of the convex width, thereby continuously rotating and advancing the forging.

[0020] Preferably, in step (5), the subsequent extrusion is forward extrusion, die forging, or reverse extrusion.

[0021] Preferably, in step (6), the four-stage cooling is air cooling, mist cooling, warm water cooling and ice water cooling in sequence.

[0022] The beneficial effects of this invention are:

[0023] According to the large-scale magnesium alloy multi-dimensional synergistic strong-plastic forming process of the present invention: 1. Using magnesium alloy after extrusion billet for subsequent forging is beneficial to the preparation of forgings and prevents cracking. 2. Using a convex die for multi-pass forging is beneficial to concentrate deformation at a single point, reducing the friction caused by the entire anvil directly contacting the forging and the temperature drop during contact with the anvil. 3. The spiral forging scheme of the present invention can reduce the risk of overall deformation, especially the problem of over-deformation of the microstructure caused by local material adapting to overall deformation during forging, thus reducing the risk of cracking. In addition, the deformation at the rear end during the deformation process can give the deformed material at the front end a certain time, which helps dislocation movement and promotes recrystallization or recovery, further reducing the risk of cracking. 4. Compared with other methods of direct multi-directional forging, the spiral forging scheme designed in the present invention increases the overall degree of deformation and more effectively achieves the uniformity of the microstructure. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the rotary forging process used in this invention. Detailed Implementation

[0025] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0026] In the following embodiments, the cracking rate of the obtained deformed components was tested. The testing method was as follows: based on the testing method of GB / T 6519-2024, the deformed components were tested and statistically analyzed. Taking one heat as the baseline, the proportion of cracked components among the number of target components that could be formed was regarded as the cracking rate. For example, for 1 ton of magnesium alloy melt as one heat, if bars with a diameter of 100 mm and a length of 2000 mm are prepared as unit components, assuming that 100 bars can be prepared, and after testing according to the national standard, it is found that 10 of them have cracks, then the cracking rate is 10%.

[0027] Example 1

[0028] A Mg-5Zn-1Mn (wt.%) (ZM51) ingot with a diameter of 500 mm and a height of 1500 mm was first subjected to homogenization heat treatment at 340℃ for 24 h followed by 370℃ for 12 h. The homogenized ingot was then extruded to form a billet at an extrusion ratio of 5 and an extrusion rate of 0.5 mm / s. The extruded magnesium alloy billet was subsequently heat-treated at 370℃ for 3 h.

[0029] The billet is removed and placed on a heated anvil to begin forging at 300°C. Asphalt is applied to both sides of the billet's cross-section and to lubricate the anvil, ensuring the forging speed is controlled at 20 mm / s. The billet is forged into a disc-shaped forging in one pass, with a deformation of 40%. The disc-shaped forging is then squared and rolled to form a forged bar with a shaft-to-diameter ratio of 3:1.

[0030] Using a robotic arm, the ZM51 forging bar is clamped, and then ingredients such as... are added to both ends of the anvil. Figure 1 The forging die shown is designed to be symmetrical, with the height of the protruding part of the die matching the height of the bottom. The ZM51 forging bar is placed between the upper and lower dies for forging. Each forging operation involves a 20% reduction in pressure and a forging speed of 20 mm / s. After each forging operation, a robotic arm rotates the forging bar 30° and simultaneously advances it forward by 4 / 5 of the convex width. This rotation and advancement is repeated continuously, ensuring that each subsequent forging operation is not on the same plane, and that the overall forging trajectory is a spiral shape, until the forging is complete.

[0031] The forged billet was placed in a heat treatment furnace for high-temperature annealing at 360℃ for 0.5 hours. Afterward, it was removed, stood upright, and pressed down along the extension direction of the forging bar with a deformation of 30%. Three-dimensional forging was then performed. When the pre-formed extruded billet shape was achieved, it was extruded at 350℃ with an extrusion ratio of 23, ultimately forming a magnesium alloy extruded bar. The extruded alloy underwent four-stage cooling: air cooling, mist cooling, warm water cooling, and ice water cooling. The ZM51 bar, cooled to room temperature, was then placed in a liquid nitrogen bath and held for 5 hours. It was then rapidly heated to room temperature. Finally, a two-stage aging heat treatment was performed: 90℃ for 32 hours + 175℃ for 14 hours. After the aging heat treatment, water cooling was performed to complete the preparation of the extruded ZM51 bar. Testing showed a crack rate of 0%.

[0032] Example 2

[0033] A Mg-7Gd-5Y-1Nd-0.5Zr (wt.%) (VW75) ingot with a diameter of 600 mm and a height of 1600 mm was first subjected to homogenization heat treatment at 520℃ for 20 h followed by 540℃ for 24 h. The homogenized ingot was then extruded to form a billet at an extrusion ratio of 3 and an extrusion rate of 0.5 mm / s. The extruded magnesium alloy billet was subsequently heat-treated at 540℃ for 3 h.

[0034] The billet is removed and placed on a heated anvil to begin forging at 480℃. Asphalt is applied to both sides of the billet's cross-section and to lubricate the anvil, ensuring the forging speed is controlled at 15mm / s. The billet is forged into a disc shape in one pass, with a deformation of 40%. The disc shape is then squared and rolled to form a forged bar with a shaft-to-diameter ratio of 2:1.

[0035] Using a robotic arm, the VW75 forging bar is clamped, and then granulation is added to both ends of the anvil. Figure 1 The forging die shown is designed to be symmetrical, with the height of the protruding part of the die matching the height of the bottom. A VW75 forging bar is placed between the upper and lower dies for forging. Each forging operation involves a 10% reduction in pressure at a forging speed of 15 mm / s. After each forging operation, a robotic arm rotates the forging bar 20° and simultaneously advances it forward by 4 / 5 of the convex width. This rotation and advancement is repeated continuously, ensuring that each subsequent forging operation is not on the same plane, and that the overall forging trajectory is a spiral shape, until the forging is complete.

[0036] The forged billet was placed in a heat treatment furnace for high-temperature annealing at 520℃ for 1 hour. Afterward, it was removed, stood upright, and pressed down along the extension direction of the forging bar with a deformation of 30%. Triaxial forging was then performed. When the pre-formed extruded billet was formed, it was extruded at 500℃ with an extrusion ratio of 8, ultimately forming a magnesium alloy extruded sheet. The extruded alloy underwent four-stage cooling: air cooling, mist cooling, warm water cooling, and ice water cooling. The VW75 sheet, cooled to room temperature, was then placed in a liquid nitrogen bath and held for 10 hours. Afterward, it was rapidly heated to room temperature. Finally, aging heat treatment was performed at 220℃ for 7 hours. Following aging, water cooling was applied to complete the preparation of the extruded VW75 sheet. Testing showed a crack rate of 0%.

[0037] Example 3

[0038] A Mg-7Y-1Nd-0.5Zr (wt.%) (WE71) ingot with a diameter of 500 mm and a height of 500 mm was first subjected to homogenization heat treatment at 450℃ for 24 hours. The homogenized ingot was then extruded to form a billet at an extrusion ratio of 6 and an extrusion rate of 0.5 mm / s. Subsequently, the extruded magnesium alloy billet underwent heat treatment at 450℃ for 3 hours.

[0039] The billet is removed and placed on a heated anvil to begin forging at 380℃. Asphalt is applied to both sides of the billet's cross-section and to lubricate the anvil, ensuring the forging speed is controlled at 25mm / s. The billet is forged into a disc shape in one pass, with a deformation of 50%. The disc shape is then squared and rolled to form a forged bar with a shaft-to-diameter ratio of 3:1.

[0040] Using a robotic arm, the WE71 forging bar is clamped, and then ingredients such as... are added to both ends of the anvil. Figure 1 The forging die shown is designed to be symmetrical, with the height of the protruding part of the die matching the height of the bottom. The WE71 forging bar is placed between the upper and lower dies for forging. Each forging operation involves a 20% reduction in pressure and a forging speed of 20 mm / s. After each forging operation, a robotic arm rotates the forging bar 30° and simultaneously advances it forward by 4 / 5 of the convex width. This rotation and advancement is repeated continuously, ensuring that each subsequent forging operation is not on the same plane, and that the overall forging trajectory is a spiral shape, until the forging is complete.

[0041] The forged billet was placed in a heat treatment furnace for high-temperature annealing at 480℃ for 2 hours. Afterward, it was removed, stood upright, and pressed down along the extension direction of the forging bar with a deformation of 40%. Triaxial forging was then performed. When the pre-formed reverse-extruded billet was formed, it was reverse-extruded at 460℃, ultimately forming a WE71 alloy reverse-extruded barrel. The WE71 reverse-extruded barrel underwent four-stage cooling: air cooling, mist cooling, warm water cooling, and ice water cooling. The WE71 reverse-extruded barrel, cooled to room temperature, was then placed in a liquid nitrogen bath and held for 5 hours. It was then removed and rapidly heated to room temperature. Finally, aging heat treatment was performed at 200℃ for 46 hours. After aging heat treatment, water cooling was performed to complete the preparation of the WE71 reverse-extruded barrel. Testing showed a crack rate of 0%.

[0042] Example 4

[0043] Select Mg-8Gd-4Y-1.5Zn-0.5Zr (wt.%) with a diameter of 800mm and a height of 1000mm.

[0044] The (VW84B) ingot first undergoes homogenization heat treatment at 500℃ for 48 hours. The homogenized ingot is then extruded to form a billet at an extrusion ratio of 5 and an extrusion rate of 0.5 mm / s. Subsequently, the extruded magnesium alloy billet undergoes heat treatment at 500℃ for 5 hours.

[0045] The billet is removed and placed on a heated anvil to begin forging at 420°C. Asphalt is applied to both sides of the billet's cross-section and to lubricate the anvil, ensuring the forging speed is controlled at 20 mm / s. The billet is forged into a disc shape in one pass, with a deformation of 45%. The disc shape is then squared and rolled to form a forged bar with a shaft-to-diameter ratio of 3:1.

[0046] Using a robotic arm, the VW84B forging bar is clamped, and then additional materials are added to both ends of the anvil. Figure 1 The forging die shown is designed to be symmetrical, with the height of the protruding part of the die matching the height of the bottom. A VW84B forging bar is placed between the upper and lower dies for forging. Each forging operation involves a 30% reduction in pressure and a forging speed of 15 mm / s. After each forging operation, a robotic arm rotates the forging bar 30° and simultaneously advances it forward by 4 / 5 of the convex width. This rotation and advancement is repeated continuously, ensuring that each subsequent forging operation is not on the same plane, and that the overall forging trajectory is a spiral shape, until the forging is complete.

[0047] The forged billet was placed in a heat treatment furnace for high-temperature annealing at 500℃ for 3 hours. Afterward, it was removed, stood upright, and pressed down along the extension direction of the forging bar with a deformation of 30%. Three-dimensional forging was then performed. Once the pre-formed die-forged billet shape was achieved, it was die-forged at 460℃ to form a VW84B alloy die-forged part. The VW84B alloy underwent four-stage cooling: air cooling, mist cooling, warm water cooling, and ice water cooling. The forged part, cooled to room temperature, was then placed in a liquid nitrogen bath and held for 5 hours. It was then removed and rapidly heated to room temperature. Finally, aging heat treatment was performed at 200℃ for 72 hours. After aging heat treatment, water cooling was performed to complete the preparation of the VW84B alloy die-forged part. Testing showed a crack rate of 0%.

[0048] Example 5

[0049] A Mg-9Y-1MM-1Zn-0.6Zr(wt.%) (WE91B) ingot with a diameter of 800mm and a height of 2000mm was first subjected to homogenization heat treatment at 520℃ for 48 hours. The homogenized ingot was then extruded to form a billet at an extrusion ratio of 6 and an extrusion rate of 0.5mm / s. Subsequently, the extruded magnesium alloy billet underwent heat treatment at 520℃ for 4 hours.

[0050] The billet is removed and placed on a heated anvil to begin forging at 460℃. Asphalt is applied to both sides of the billet's cross-section and to lubricate the anvil, ensuring the forging speed is controlled at 30mm / s. The billet is forged into a disc-shaped forging in one pass, with a deformation of 60%. The disc-shaped forging is then squared and rolled to form a forged bar with a shaft-to-diameter ratio of 5:2.

[0051] Using a robotic arm, the WE91B forging bar is clamped, and then ingredients such as... are added to both ends of the anvil. Figure 1 The forging die shown is designed to be symmetrical, with the height of the protruding part of the die matching the height of the bottom. The WE91B forging bar is placed between the upper and lower dies for forging. Each forging operation involves a 10% downward pressure at a forging speed of 20 mm / s. After each forging operation, a robotic arm rotates the forging bar 25° and simultaneously advances it forward by 4 / 5 of the convex width. This rotation and advancement is repeated continuously, ensuring that each subsequent forging operation is not on the same plane, and that the overall forging trajectory is a spiral shape, until the forging is complete.

[0052] The forged billet was placed in a heat treatment furnace for high-temperature annealing at 500℃ for 3 hours. Afterward, it was removed, stood upright, and pressed down along the extension direction of the forged bar with a deformation of 30%. Three-dimensional forging was then performed. When the pre-formed extruded billet shape was achieved, it was extruded at 510℃ with an extrusion ratio of 23, ultimately forming a magnesium alloy extruded bar. The extruded alloy underwent four-stage cooling: air cooling, mist cooling, warm water cooling, and ice water cooling. The WE91B bar, cooled to room temperature, was then placed in a liquid nitrogen bath and held for 5 hours. It was then rapidly heated to room temperature. Finally, aging heat treatment was performed at 200℃ for 84 hours, followed by water cooling to complete the preparation of the extruded WE91B bar. Testing showed a crack rate of 0%.

Claims

1. A multi-dimensional synergistic strong-plastic forming process for large-size magnesium alloys, characterized in that, Includes the following steps: (1) The magnesium alloy ingot is subjected to homogenization heat treatment and extrusion, with the extrusion ratio controlled at 3~6. Then the extruded billet is heated to above the homogenization heat treatment temperature and held for 3~5 hours. (2) Place the extruded billet on a heated anvil and forge it into a disc-shaped forging in one go. Then, roll the forging into a square shape to form a forging bar with a shaft diameter ratio of 2:1 to 3:

1. (3) The forging bar is placed between the upper and lower dies and forged in multiple passes using a spiral forging method. The cross-sectional shape of the upper and lower dies is convex. The width of the top convex surface of the upper and lower dies is one-third of the overall width. The pressure of each forging is 10~30%, and the forging speed is 15~20mm / s. After each forging, the forging bar is rotated 15~30° and simultaneously advanced 4 / 5 of the convex surface width. The forging is continuously rotated and advanced in this way. The subsequent forging is not on the same plane as the previous forging, and the forging trajectory is in the shape of a spiral until the forging is completed. (4) The forged billet is subjected to high-temperature annealing at a temperature of more than 95% of the homogenization heat treatment temperature and for a time of 0.5 to 3 hours. (5) The annealed billet is forged in three directions to form a preform, which is then extruded to form the final magnesium alloy component; (6) The final magnesium alloy component is cooled to room temperature in four stages, then kept in liquid nitrogen environment for 5~10 hours, then rapidly heated to room temperature and subjected to aging heat treatment to complete the preparation of the forging.

2. The large-scale magnesium alloy multi-dimensional synergistic strong and plastic forming process according to claim 1, characterized in that, In step (1), the diameter of the magnesium alloy ingot is 500~800mm and the height is 500~2000mm.

3. The large-scale magnesium alloy multi-dimensional synergistic strong and plastic forming process according to claim 1, characterized in that, In step (2), the temperature difference between the anvil and the magnesium alloy billet is 50~100℃, the forging speed is controlled at 15~30mm / s, and the deformation is controlled at 40~60%.

4. The large-scale magnesium alloy multi-dimensional synergistic strong and plastic forming process according to claim 1, characterized in that, In step (3), the upper and lower molds have the same structure and are symmetrically arranged on the upper and lower sides of the forging bar. The height of the top protrusion of the upper and lower molds is the same as the height of the bottom.

5. The large-scale magnesium alloy multi-dimensional synergistic strong and plastic forming process according to claim 1, characterized in that, In step (5), the subsequent extrusion is forward extrusion, die forging, or reverse extrusion.

6. The large-scale magnesium alloy multi-dimensional synergistic strong and plastic forming process according to claim 1, characterized in that, In step (6), the four-stage cooling is air cooling, mist cooling, warm water cooling and ice water cooling in sequence.

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