Multi-dimensional synergistic strong plastic forming process for large-sized magnesium alloy

Abstract

The invention discloses a large-size magnesium alloy multi-dimensional synergistic strong plastic forming process which comprises the following steps: (1) carrying out homogenizing heat treatment and extrusion on a magnesium alloy cast ingot, then heating an extruded blank to a temperature higher than the homogenizing heat treatment temperature, and keeping the temperature for 3-5 hours; (2) the extrusion blank is forged into a cake-shaped forge piece at a time, and then the cake-shaped forge piece is squared and rounded to form a forged rod with the shaft diameter ratio being 2: 1-3: 1; (3) the forging rod is placed between an upper die and a lower die and subjected to multi-pass forging in a screw-in type forging mode, and the sections of the upper die and the lower die are both in an inverted-T shape; (4) the forged blank is subjected to high-temperature annealing; and (5) the annealed blank is subjected to three-direction forging and extruded to form the final magnesium alloy component. And (6) the final magnesium alloy component is subjected to four-stage cooling to the room temperature and then kept for 5-10 h in the liquid nitrogen environment, then the temperature is increased to the room temperature, and aging heat treatment is conducted. The preparation and processing capacity of the magnesium alloy forge piece can be improved, and application to novel equipment in the future is achieved.

Description

Technical Field

[0001] The invention relates to a multi-dimensional coordinated strong plastic forming process for a large-size magnesium alloy, belonging to the technical field of magnesium alloy material forming. Background Art

[0002] As a new type of lightweight material, magnesium alloy has a wide range of 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-comprehensive performance magnesium alloy forgings continues to increase. Due to its unique hexagonal structural characteristics, magnesium alloys cannot be deformed at room temperature and must be plastically processed under high temperature conditions. However, the deformation processing window of magnesium alloys under high temperature conditions is extremely narrow, which makes process control more difficult, the forging preparation process becomes complicated, and the yield rate is at a relatively low level. It can be seen that exploring suitable forging methods is the key to improving the comprehensive performance of magnesium alloys and meeting user needs.

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

[0004] At present, magnesium alloy forging processes generally require larger-scale equipment, stricter deformation temperature conditions, and more remelting heat treatments to achieve a more uniform structure. However, in practice, large-scale magnesium alloy forging equipment is scarce and often shared with aluminum alloys, which makes process control and program adjustment have significant limitations in specific implementation, making it difficult to achieve an ideal state. In addition, since the application of magnesium alloys is far less mature and stable than that of aluminum alloys, the existing forging processes are mostly in the exploratory stage, and in actual operation, the experience of aluminum alloy preparation and processing is relatively limited when applied to the preparation of magnesium alloy forgings. In summary, the development of magnesium alloy forging preparation and processing technology is both urgent and necessary.

[0005] Most of the existing magnesium alloy forging processing technologies have similar process characteristics, such as emphasizing the remelting operation during forging, limiting the cumulative deformation during forging, and strictly controlling the anvil temperature during forging. These are important for magnesium alloy forging, but the friction between the anvil and the surface of the magnesium alloy is very likely to cause forging cracking, and the contact between the forging and the anvil during forging will cause a large drop in temperature. Therefore, the development of an easy-to-operate forging process with weak friction effect and small temperature drop is of vital significance to improving the preparation and processing level of magnesium alloy forgings. Summary of the invention

[0006] The purpose of the present invention is to provide a large-scale magnesium alloy multi-dimensional collaborative strength and plastic forming process 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 lightweight.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A large-scale magnesium alloy multi-dimensional synergistic strong plastic forming process comprises the following steps: (1) The magnesium alloy ingot is subjected to homogenization heat treatment and extrusion, and the extrusion ratio is controlled at 3-6. The extruded billet is then heated to a temperature above the homogenization heat treatment temperature and kept at this temperature for 3-5 hours; (2) The extruded billet is placed on a heated anvil and forged into a pancake-shaped forging at one time. Subsequently, the forging is squared and rounded to form a forged rod with an axis-to-diameter ratio of 2:1 to 3:1; The squaring and rounding here realizes the reversal of the shape, the original extrusion direction becomes the short direction (new radial direction), and the original radial direction becomes the long direction (new axial direction); (3) Place the forging rod between the upper and lower dies and perform multiple forgings by means of screw-in forging. The cross-sections of the upper and lower dies are both convex. The last forging is not in the same plane as the previous one, and the forging trajectory is in a spiral shape as a whole until the forging is completed. (4) The forged billet is subjected to high temperature annealing, the annealing temperature is more than 95% of the homogenization heat treatment temperature, and the annealing time is 0.5~3h; (5) The annealed billet is subjected to three-way forging to form a preformed billet, and 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 a liquid nitrogen environment for 5 to 10 hours, and then quickly heated to room temperature and subjected to aging heat treatment to complete the preparation of the forging.

[0008] Preferably, in step (1), the diameter of the magnesium alloy ingot is 500-800 mm and the height is 500-2000 mm.

[0009] Preferably, in step (2), the temperature difference between the anvil plate and the magnesium alloy billet is 50-100° C., the forging speed is controlled at 15-30 mm / s, and the deformation is controlled at 40-60%.

[0010] Preferably, in step (3), the upper and lower dies have the same structure and are symmetrically arranged on the upper and lower sides of the forging rod. The width of the top convex surface of the upper and lower dies is one third of the overall width, and the height of the protruding part is consistent with the height of the bottom.

[0011] Preferably, in step (3), the amount of downward pressure each time forging is 10-30%, the forging speed is 15-20 mm / s, and after each forging, the forging rod is rotated 15-30° and pushed forward 4 / 5 of the convex width, thereby continuously rotating and advancing the forging.

[0012] Preferably, in the step (5), the subsequent extrusion is forward extrusion, die forging or reverse extrusion.

[0013] Preferably, in step (6), the four levels of cooling are air cooling, mist cooling, warm water cooling and ice water cooling in sequence.

[0014] Beneficial effects of the present invention: According to the multi-dimensional synergistic strong plastic forming process of large-scale magnesium alloys of the present invention, 1. The magnesium alloy after extrusion blanking is selected for subsequent forging, which is beneficial to the preparation of forgings and prevents cracking. 2. The use of convex molds for multi-pass forging is beneficial to concentrate the deformation at one point, reducing the friction formed by the direct contact of the entire anvil plate with the forging and the temperature drop problem occurring during the contact with the anvil plate. 3. The use of the screw-in forging scheme of the present invention can reduce the overall deformation risk, especially the problem of excessive deformation of the structure caused by the local material in order to adapt to the overall deformation during the forging process, thereby reducing the risk of cracking. In addition, the deformation of the rear end during the deformation process can give the deformed material at the front end a certain amount of time, which is conducive to dislocation movement, and promotes recrystallization or recovery, further reducing the risk of cracking. 4. Compared with other methods of directly performing multi-directional forging, the screw-in forging scheme designed by the present invention increases the overall deformation degree and more advantageously achieves the uniformity of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the screw-forging process adopted in the present invention. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is described in detail below in conjunction with specific embodiments.

[0017] In the following embodiments, the cracking rate of the obtained deformed components is detected. The detection method is: based on the detection method of GB / T 6519-2024, the deformed components are detected and counted, and the proportion of the number of components with cracks in the number of target components that can be formed is regarded as the cracking rate, taking 1 heat as the benchmark. For example, for 1 ton of magnesium alloy melt as 1 heat, if a rod with a diameter of 100 mm and a length of 2000 mm is prepared as a unit component, assuming that 100 rods can be prepared, after using the national standard detection, it is found that 10 of them have cracks, then the cracking rate is 10%.

[0018] Example 1 The Mg-5Zn-1Mn (wt.%) (ZM51) ingot with a diameter of 500mm and a height of 1500mm was first subjected to homogenization heat treatment, and the heat treatment system was 340℃ 24h+370℃ 12h. The homogenized ingot was extruded and opened, with an extrusion ratio of 5 and an extrusion rate of 0.5mm / s. The extruded magnesium alloy billet was then heat treated at a heat treatment temperature of 370℃ and a heat treatment time of 3h.

[0019] The billet is taken out and placed on a heated anvil for forging. The anvil temperature is 300℃. Asphalt is applied to both sides of the cross section of the extruded billet and the anvil for lubrication to ensure that the forging speed is controlled at 20mm / s. The forging is completed in one go to form a pancake-shaped forging with a deformation of 40%. The pancake-shaped forging is squared and rounded to form a forged rod with an axis-diameter ratio of 3:1.

[0020] Use the robot to pick up the ZM51 forging rod, and then add the following Figure 1 The forging die shown ensures that the die is symmetrical from top to bottom, and the height of the protruding part of the die is consistent with the bottom height. The ZM51 forging rod is placed between the upper and lower dies for forging, with a downward pressure of 20% each time and a forging speed of 20mm / s. After each forging, the forging rod is rotated 30° by a manipulator and pushed forward 4 / 5 of the convex width at the same time, so as to continuously rotate and push the forging, and the latter forging is ensured not to be in the same plane as the previous forging, and the forging trajectory is in a spiral shape as a whole until the forging is completed.

[0021] The forged billet is placed in a heat treatment furnace for high-temperature annealing. The annealing temperature is 360°C and the annealing time is 0.5h. Then it is taken out, and then the billet is erected and pressed down along the extension direction of the forged rod. The downward deformation is 30%. Three-way forging is performed. When the shape of the extruded preformed billet is formed, the billet is extruded. The extrusion temperature is 350°C and the extrusion ratio is 23, and finally a magnesium alloy extruded bar is formed. The extruded alloy is cooled in four stages, namely air cooling, mist cooling, warm water cooling and ice water cooling. After that, the ZM51 bar cooled to room temperature is placed in a liquid nitrogen tank, kept warm in a liquid nitrogen environment for 5h, and then taken out and quickly heated to room temperature. Finally, a two-stage aging heat treatment is performed. The heat treatment system is: 90°C 32h+175°C 14h. After the aging heat treatment is completed, water cooling is performed to complete the preparation of the extruded ZM51 bar. After testing, the cracking rate of the component is 0.

[0022] Example 2 The 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, and the heat treatment system was 520℃ 20h+540℃ 24h. The homogenized ingot was extruded and opened, with an extrusion ratio of 3 and an extrusion rate of 0.5mm / s. The extruded magnesium alloy billet was then heat treated at a heat treatment temperature of 540℃ and a heat treatment time of 3h.

[0023] The billet is taken out and placed on a heated anvil for forging. The anvil temperature is 480℃. Asphalt is applied to both sides of the cross section of the extruded billet and the anvil for lubrication to ensure that the forging speed is controlled at 15mm / s. The forging is completed in one go to form a pancake-shaped forging with a deformation of 40%. The pancake-shaped forging is squared and rounded to form a forged rod with an axis-diameter ratio of 2:1.

[0024] Use the robot to pick up the VW75 forging rod, and then add the following Figure 1 The forging die shown in the figure ensures that the die is symmetrical from top to bottom, and the height of the protruding part of the die is consistent with the height of the bottom. The VW75 forging rod is placed between the upper and lower dies for forging, with a downward pressure of 10% each time and a forging speed of 15mm / s. After each forging, the forging rod is rotated 20° by a manipulator and pushed forward 4 / 5 of the convex width at the same time, so as to continuously rotate and push the forging, and the latter forging is ensured not to be in the same plane as the previous forging, and the forging trajectory is in a spiral shape as a whole until the forging is completed.

[0025] The forged billet is placed in a heat treatment furnace for high-temperature annealing. The annealing temperature is 520°C and the annealing time is 1h. Then it is taken out, and then the billet is erected and pressed down along the extension direction of the forging rod. The downward deformation is 30%. Three-way forging is performed. When the shape of the extruded preformed billet is formed, the billet is extruded at a temperature of 500°C and an extrusion ratio of 8, and finally a magnesium alloy extruded sheet is formed. The extruded alloy is cooled in four stages, namely air cooling, mist cooling, warm water cooling and ice water cooling. After that, the VW75 sheet cooled to room temperature is placed in a liquid nitrogen tank, kept warm in a liquid nitrogen environment for 10h, and then taken out and quickly heated to room temperature. Finally, aging heat treatment is performed. The heat treatment system is: 220°C 7h. After the aging heat treatment is completed, water cooling is performed to complete the preparation of the extruded VW75 sheet. After testing, the cracking rate of the component is 0.

[0026] Example 3 The 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 ° C for 24 h. The homogenized ingot was extruded and opened with an extrusion ratio of 6 and an extrusion rate of 0.5 mm / s. The extruded magnesium alloy billet was then heat treated at a temperature of 450 ° C for 3 h.

[0027] The billet is taken out and placed on a heated anvil for forging. The anvil temperature is 380℃. Asphalt is applied to both sides of the cross section of the extruded billet and the anvil for lubrication to ensure that the forging speed is controlled at 25mm / s. The forging is completed in one go to form a pancake-shaped forging with a deformation of 50%. The pancake-shaped forging is squared and rounded to form a forged rod with an axis-diameter ratio of 3:1.

[0028] Use the robot to pick up the WE71 forging rod, and then add the following Figure 1 The forging die shown ensures that the die is symmetrical from top to bottom, and the height of the protruding part of the die is consistent with the bottom height. The WE71 forging rod is placed between the upper and lower dies for forging, with a downward pressure of 20% each time and a forging speed of 20mm / s. After each forging, the forging rod is rotated 30° by a manipulator and pushed forward 4 / 5 of the convex width at the same time, so as to continuously rotate and push the forging. The last forging is ensured not to be in the same plane as the previous forging, and the forging trajectory is in a spiral shape as a whole until the forging is completed.

[0029] The forged billet is placed in a heat treatment furnace for high-temperature annealing. The annealing temperature is selected to be 480℃, and the annealing time is 2h. Then it is taken out, and then the billet is erected and pressed down along the extension direction of the forging rod. The downward deformation is 40%. Three-way forging is performed. When the shape of the reverse extrusion preformed billet is formed, the billet is reverse extruded. The reverse extrusion temperature is 460℃, and finally a WE71 alloy reverse extrusion barrel is formed. The WE71 reverse extrusion barrel is cooled in four stages, namely air cooling, mist cooling, warm water cooling and ice water cooling. After that, the WE71 reverse extrusion barrel cooled to room temperature is placed in a liquid nitrogen tank, kept warm in a liquid nitrogen environment for 5h, and then taken out and quickly heated to room temperature. Finally, aging heat treatment is performed. The heat treatment system is: 200℃ 46h. After the aging heat treatment is completed, water cooling is performed to complete the preparation of the WE71 reverse extrusion barrel. After testing, the cracking rate of the component is 0.

[0030] Example 4 Select Mg-8Gd-4Y-1.5Zn-0.5Zr (wt.%) with a diameter of 800 mm and a height of 1000 mm. The (VW84B) ingot was first subjected to homogenization heat treatment at 500°C for 48h. The homogenized ingot was extruded and opened at an extrusion ratio of 5 and an extrusion rate of 0.5mm / s. The extruded magnesium alloy billet was then heat treated at 500°C for 5h.

[0031] The billet is taken out and placed on a heated anvil for forging. The anvil temperature is 420℃. Asphalt is applied to both sides of the cross section of the extruded billet and the anvil for lubrication to ensure that the forging speed is controlled at 20mm / s. The forging is completed in one go to form a pancake-shaped forging with a deformation of 45%. The pancake-shaped forging is squared and rounded to form a forged rod with an axis-diameter ratio of 3:1.

[0032] Use the robot to pick up the VW84B forging rod, and then add the following Figure 1 The forging die shown ensures that the die is symmetrical from top to bottom, and the height of the protruding part of the die is consistent with the bottom height. The VW84B forging rod is placed between the upper and lower dies for forging, with a downward pressure of 30% each time and a forging speed of 15mm / s. After each forging, the forging rod is rotated 30° by a manipulator and pushed forward 4 / 5 of the convex width at the same time, so as to continuously rotate and push the forging, and the latter forging is ensured not to be in the same plane as the previous forging, and the forging trajectory is in a spiral shape as a whole until the forging is completed.

[0033] The forged billet is placed in a heat treatment furnace for high-temperature annealing. The annealing temperature is 500℃ and the annealing time is 3h. Then it is taken out, and then the billet is erected and pressed down along the extension direction of the forging rod. The downward deformation is 30%. Three-way forging is performed. When the shape of the die forging prefabricated billet is formed, the billet is die forged at a die forging temperature of 460℃, and finally a VW84B alloy die forging is formed. The VW84B alloy is cooled in four stages, namely air cooling, mist cooling, warm water cooling and ice water cooling. After that, the die forging cooled to room temperature is placed in a liquid nitrogen tank, kept warm in a liquid nitrogen environment for 5h, and then taken out and quickly heated to room temperature. Finally, aging heat treatment is performed. The heat treatment system is: 200℃ 72h. After the aging heat treatment is completed, water cooling is performed to complete the preparation of the VW84B alloy die forging. After testing, the cracking rate of the component is 0.

[0034] Example 5 The Mg-9Y-1MM-1Zn-0.6Zr (wt.%) (WE91B) ingot with a diameter of 800 mm and a height of 2000 mm was first subjected to homogenization heat treatment at 520°C for 48 hours. The homogenized ingot was extruded and opened with an extrusion ratio of 6 and an extrusion rate of 0.5 mm / s. The extruded magnesium alloy billet was then heat treated at a temperature of 520°C for 4 hours.

[0035] The billet is taken out and placed on a heated anvil for forging. The anvil temperature is 460℃. Asphalt is applied to both sides of the cross section of the extruded billet and the anvil for lubrication to ensure that the forging speed is controlled at 30mm / s. The forging is completed in one go to form a pancake-shaped forging with a deformation of 60%. The pancake-shaped forging is squared and rounded to form a forged rod with an axis-diameter ratio of 5:2.

[0036] Use the robot to pick up the WE91B forging rod, and then add the following Figure 1 The forging die shown ensures that the die is symmetrical from top to bottom, and the height of the protruding part of the die is consistent with the bottom height. The WE91B forging rod is placed between the upper and lower dies for forging, with a downward pressure of 10% each time and a forging speed of 20mm / s. After each forging, the forging rod is rotated 25° by a manipulator and pushed forward 4 / 5 of the convex width at the same time, so as to continuously rotate and push the forging, and the latter forging is ensured not to be in the same plane as the previous forging, and the forging trajectory is in a spiral shape as a whole until the forging is completed.

[0037] The forged billet is placed in a heat treatment furnace for high-temperature annealing. The annealing temperature is 500℃ and the annealing time is 3h. Then it is taken out, and then the billet is erected and pressed down along the extension direction of the forging rod. The downward deformation is 30%. Three-way forging is performed. When the shape of the extruded preformed billet is formed, the billet is extruded. The extrusion temperature is 510℃ and the extrusion ratio is 23, and finally a magnesium alloy extruded bar is formed. The extruded alloy is cooled in four stages, namely air cooling, mist cooling, warm water cooling and ice water cooling. After that, the WE91B bar cooled to room temperature is placed in a liquid nitrogen tank, kept warm in a liquid nitrogen environment for 5h, and then taken out and quickly heated to room temperature. Finally, aging heat treatment is performed. The heat treatment system is: 200℃ 84h. After the aging heat treatment is completed, water cooling is performed to complete the preparation of the extruded WE91B bar. After testing, the cracking rate of the component is 0.

Claims

1. A large-scale magnesium alloy multi-dimensional synergistic strong plastic forming process, characterized in that: The steps include: (1) The magnesium alloy ingot is subjected to homogenization heat treatment and extrusion, and the extrusion ratio is controlled at 3-6. The extruded billet is then heated to a temperature above the homogenization heat treatment temperature and kept at this temperature for 3-5 hours; (2) The extruded billet is placed on a heated anvil and forged into a pancake-shaped forging at one time. Subsequently, the forging is squared and rounded to form a forged rod with an axis-to-diameter ratio of 2:1 to 3:1; (3) Place the forging rod between the upper and lower dies and perform multiple forgings by means of screw-in forging. The cross-sections of the upper and lower dies are both convex. The last forging is not in the same plane as the previous one, and the forging trajectory is in a spiral shape as a whole until the forging is completed. (4) The forged billet is subjected to high temperature annealing, the annealing temperature is more than 95% of the homogenization heat treatment temperature, and the annealing time is 0.5~3h; (5) The annealed billet is subjected to three-way forging to form a preformed billet, and 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 a liquid nitrogen environment for 5 to 10 hours, and then quickly 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 plastic forming process according to claim 1 is characterized in that: In the step (1), the diameter of the magnesium alloy ingot is 500-800 mm and the height is 500-2000 mm.

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

4. The large-scale magnesium alloy multi-dimensional synergistic strong plastic forming process according to claim 1 is 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 rod. 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.

5. The large-scale magnesium alloy multi-dimensional synergistic strong plastic forming process according to claim 1 or 4, characterized in that: In the step (3), the amount of downward pressure each time forging is 10-30%, the forging speed is 15-20 mm / s, and after each forging, the forging rod is rotated 15-30° and pushed forward 4 / 5 of the convex width, thereby continuously rotating and advancing the forging.

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

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

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