Magnesium alloy ring and method for producing the same

Abstract

The application provides a magnesium alloy ring piece and a preparation method thereof, and belongs to the technical field of magnesium alloys. The magnesium alloy ring piece is prepared by using a two-stage homogenization treatment process of low temperature first and high temperature later. Low temperature treatment can avoid overburning of low-melting-point phases formed in a non-equilibrium solidification process, and high temperature treatment can fully eliminate dendritic segregation in a cast ingot, thereby improving the plastic forming capacity of the cast ingot in a subsequent forging process. The first fire of multi-directional forging adopts a higher forging temperature, which can prevent cracking of plastic deformation of the ingot blank. In the multi-directional forging process, the ingot blank is fully deformed to reduce casting defects such as shrinkage holes, pores and porosity. The second fire reduces the forging temperature, which can prevent grain coarsening caused by excessively high temperature, and a homogeneous fine-grained forged blank is obtained, thereby improving the mechanical properties and heat resistance of the magnesium alloy ring piece.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy technology, specifically relating to a magnesium alloy ring-shaped component and its preparation method. Background Technology

[0002] VW93M magnesium alloy is an ultra-high strength, high-temperature resistant magnesium alloy that retains good mechanical properties at 250℃, while also possessing excellent hot working properties and creep resistance, making it a promising candidate for the aerospace industry. However, the fabrication of large-diameter VW93M magnesium alloy structural components faces numerous technical challenges: VW93M magnesium alloy has a high rare-earth content, which easily leads to defects such as segregation, hot cracking, and surface cold shuts during the fabrication of large-size ingots; magnesium alloys have few movable slip systems and poor plastic deformation capacity, making them prone to cracking during forging and ring rolling; and after plastic deformation, severe microstructural inhomogeneity and anisotropy easily occur, resulting in poor mechanical and heat resistance properties of the fabricated large-diameter magnesium alloy ring components. Therefore, how to fabricate high-strength, heat-resistant, large-diameter VW93M magnesium alloy ring components has become a pressing technical challenge in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a magnesium alloy ring-shaped component and its preparation method. The magnesium alloy ring-shaped component prepared by the method provided by this invention possesses high strength and heat resistance.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing a magnesium alloy ring-shaped component, comprising the following steps:

[0006] (1) The magnesium alloy ingot is subjected to a two-stage homogenization treatment to obtain a homogenized ingot blank; the two-stage homogenization treatment is to first hold at 350-380℃ for 3-5 hours, and then raise the temperature to 500-525℃ and hold for 18-24 hours.

[0007] (2) The homogenized billet obtained in step (1) is subjected to multi-directional forging to obtain a forging billet; the multi-directional forging includes a first fire forging and a second fire forging performed sequentially; the temperature of the first fire forging is 480-515℃; the temperature of the second fire forging is 10-20℃ lower than the temperature of the first fire forging.

[0008] (3) The forging blank obtained in step (2) is punched and expanded in sequence to obtain an expanded forging blank;

[0009] (4) The expanded forging blank obtained in step (3) is subjected to ring rolling to obtain an annular part;

[0010] (5) The ring-shaped part obtained in step (4) is subjected to aging treatment to obtain a magnesium alloy ring-shaped part.

[0011] Preferably, the first forging in step (2) includes forging the homogenized billet along the height of the billet, then alternating forging along two orthogonal directions perpendicular to the height of the billet, and then forging along the corner of the billet to obtain a cylindrical forging billet.

[0012] Preferably, the first forging has 1 pass and the deformation amount of the first forging is 40-60%; the alternating forging has 6-8 passes and the deformation amount of the alternating forging is 30-45%; the second forging has 8-12 passes and the deformation amount of the second forging is 25-40%.

[0013] Preferably, the second forging in step (2) includes forging the product obtained from the first forging along the height of the product obtained from the first forging in a third forging, and then performing rounding forging and upsetting in sequence.

[0014] Preferably, the third forging has 1 pass and the deformation amount of the third forging is 30-40%; the rounding forging has 8-12 passes and the deformation amount of the rounding forging is 5-20%; and the upsetting deformation amount is 15-25%.

[0015] Preferably, the forging speed of the hole expansion forging in step (3) is 200-300 mm / min.

[0016] Preferably, in step (4), the expanded forging billet is kept warm before ring rolling; the temperature of the warming is 460-530℃ and the warming time is 4-6h.

[0017] Preferably, in step (4), the rotational speed of the drive roller during ring rolling is 10-30 r / min, the linear feed speed of the core roller is 0.2-1.0 mm / s, and the tapered roller forges along the height of the expanded hole forging blank.

[0018] Preferably, the aging treatment temperature in step (5) is 200-225°C, and the aging treatment time is 15-36 hours.

[0019] The present invention also provides a magnesium alloy ring-shaped part prepared by the preparation method described in the above technical solution.

[0020] This invention provides a method for preparing a magnesium alloy ring-shaped component, comprising the following steps: subjecting a magnesium alloy ingot to a two-stage homogenization treatment to obtain a homogenized ingot blank; the two-stage homogenization treatment involves first holding the ingot at 350–380°C for 3–5 hours, then raising the temperature to 500–525°C and holding it for 18–24 hours; subjecting the homogenized ingot blank to multi-directional forging to obtain a forged blank; the multi-directional forging includes a first forging and a second forging performed sequentially; the temperature of the first forging is 480–515°C; the temperature of the second forging is 10–20°C lower than that of the first forging; subjecting the forged blank to punching and reaming forging sequentially to obtain a reamed forged blank; subjecting the reamed forged blank to ring rolling to obtain a ring-shaped component; and subjecting the ring-shaped component to aging treatment to obtain a magnesium alloy ring-shaped component. This invention employs a two-stage homogenization process, first at a low temperature and then at a high temperature. The low-temperature treatment avoids overburning of the low-melting-point phase formed during non-equilibrium solidification, while the high-temperature treatment effectively eliminates dendritic segregation in the ingot, improving the ingot's plastic forming ability in subsequent forging processes. The first forging in multi-directional forging uses a higher forging temperature to prevent plastic deformation cracking of the ingot. The multi-directional forging process allows the ingot to deform sufficiently, reducing casting defects such as shrinkage cavities, porosity, and looseness. The second forging lowers the forging temperature, preventing grain coarsening caused by excessively high temperatures and obtaining a homogeneous, fine-grained forging blank, thereby improving the mechanical properties and heat resistance of the magnesium alloy ring. Experimental results show that the room temperature mechanical properties of the magnesium alloy ring-shaped parts prepared by the method provided in this invention are as follows: tangential tensile strength 430–438 MPa, high-direction tensile strength 411–420 MPa; tangential yield strength 350–379 MPa, high-direction yield strength 303–310 MPa; tangential elongation after fracture 6.0–11.2%, high-direction elongation after fracture 6.2–10.3%; and mechanical properties at 250℃ are as follows: tangential tensile strength 302–310 MPa, high-direction tensile strength 267–276 MPa; tangential yield strength 249–258 MPa, high-direction yield strength 199–209 MPa; tangential elongation after fracture 11.8–14.3%, high-direction elongation after fracture 13.7–21.5%. Detailed Implementation

[0021] This invention provides a method for preparing a magnesium alloy ring-shaped component, comprising the following steps:

[0022] (1) The magnesium alloy ingot is subjected to a two-stage homogenization treatment to obtain a homogenized ingot blank; the two-stage homogenization treatment is to first hold at 350-380℃ for 3-5 hours, and then raise the temperature to 500-525℃ and hold for 18-24 hours.

[0023] (2) The homogenized billet obtained in step (1) is subjected to multi-directional forging to obtain a forging billet; the multi-directional forging includes a first fire forging and a second fire forging performed sequentially; the temperature of the first fire forging is 480-515℃; the temperature of the second fire forging is 10-20℃ lower than the temperature of the first fire forging.

[0024] (3) The forging blank obtained in step (2) is punched and expanded in sequence to obtain an expanded forging blank;

[0025] (4) The expanded forging blank obtained in step (3) is subjected to ring rolling to obtain an annular part;

[0026] (5) The ring-shaped part obtained in step (4) is subjected to aging treatment to obtain a magnesium alloy ring-shaped part.

[0027] This invention does not impose any special restrictions on the source of the raw materials; commercially available products familiar to those skilled in the art can be used.

[0028] This invention involves subjecting magnesium alloy ingots to a two-stage homogenization process to obtain homogenized ingot blanks.

[0029] In this invention, the magnesium alloy ingot is preferably a VW93M magnesium alloy ingot; the preferred chemical composition of the VW93M magnesium alloy ingot, by mass percentage, is: Gd 8.0–9.6%, Y 1.8–3.2%, Zr 0.3–0.7%, Er 0.02–0.3%, Ag 0.02–0.50%, and the balance Mg. This invention can further improve plasticity and strength by controlling the chemical composition content of the VW93M magnesium alloy ingot.

[0030] In one embodiment, the chemical composition of the magnesium alloy ingot can be 8.3-9.3% Gd, 2.1-2.7% Y, 0.35-0.6% Zr, 0.05-0.25% Er, 0.1-0.40% Ag, and the balance Mg; or it can be 8.5-9.0% Gd, 2.3-2.4% Y, 0.45-0.55% Zr, 0.15-0.20% Er, 0.2-0.35% Ag, and the balance Mg.

[0031] In this invention, the preferred mass ratio of Gd to Y is 3 ≤ Gd / Y ≤ 5. This invention achieves excellent rare earth precipitate morphology distribution by controlling the mass ratio of Gd to Y.

[0032] In this invention, the magnesium alloy ingot is preferably prepared using an electromagnetic semi-continuous casting method. This invention does not impose any particular limitation on the specific operation of the electromagnetic semi-continuous casting; any preparation method well-known to those skilled in the art can be used. The electromagnetic semi-continuous casting method used in this invention to prepare magnesium alloy ingots can reduce defects such as inclusions, porosity, looseness, and central cracks, thereby reducing its cracking tendency during subsequent deformation and improving the formability of the magnesium alloy during subsequent forging deformation.

[0033] In this invention, the diameter of the magnesium alloy ingot is preferably 450-730 mm; the length of the magnesium alloy ingot is preferably ≥2000 mm.

[0034] In this invention, the two-stage homogenization treatment involves first holding the material at 350–380°C for 3–5 hours, then raising the temperature to 500–525°C and holding it for 18–24 hours. This invention employs a two-stage homogenization process with a low-temperature followed by a high-temperature treatment. The low-temperature treatment avoids overheating of the low-melting-point phases formed during non-equilibrium solidification, while the high-temperature treatment effectively eliminates dendritic segregation in the ingot, improving its plasticity during subsequent forging. By limiting the process parameters of the two-stage homogenization treatment within the aforementioned range, the mechanical and heat resistance properties of the magnesium alloy ring-shaped parts can be further improved.

[0035] The present invention does not impose any special limitation on the heating rate; any operation familiar to those skilled in the art can be used.

[0036] In one implementation, the two-stage homogenization process can be to first keep the temperature at 360-370°C for 3.5-4.5 hours, and then raise the temperature to 505-520°C and keep it for 20-22 hours; or it can be to first keep the temperature at 365-370°C for 3.5-4 hours, and then raise the temperature to 510-515°C and keep it for 21-22 hours.

[0037] In this invention, the cooling method of the two-stage homogenization process is preferably furnace cooling and air cooling performed sequentially; the final temperature of the furnace cooling is preferably 200-350°C.

[0038] The present invention does not have any special limitations on the operation of the air cooling; air cooling to room temperature is sufficient.

[0039] After the two-stage homogenization process is completed, the product obtained by the two-stage homogenization process is preferably cut into blanks by a car body and a saw in sequence to obtain a homogenized ingot.

[0040] The present invention does not impose any special limitations on the operation of the car body and the sawing machine for cutting materials; any operation known to those skilled in the art can be used.

[0041] In this invention, the diameter of the homogenized billet is preferably 420-630 mm; the length of the homogenized billet is preferably 800-1300 mm.

[0042] After obtaining the homogenized ingot, the present invention performs multi-directional forging on the homogenized ingot to obtain a forged billet.

[0043] In this invention, the multi-directional forging includes a first forging and a second forging performed sequentially. The temperature of the first forging is 480–515°C, and the temperature of the second forging is 10–20°C lower than that of the first forging. In this invention, the first forging uses a higher forging temperature to prevent plastic deformation cracking of the ingot. The multi-directional forging process allows the ingot to deform sufficiently, reducing casting defects such as shrinkage cavities, porosity, and looseness. The second forging lowers the forging temperature, preventing grain coarsening caused by excessively high temperatures, resulting in a homogeneous, fine-grained forging blank, thereby improving the mechanical properties and heat resistance of the magnesium alloy ring.

[0044] In one embodiment, the temperature of the first forging can be 490-510°C or 495-505°C; the temperature of the second forging can be 10-15°C lower than the temperature of the first forging.

[0045] In this invention, the forging speed of the multi-directional forging is preferably 150–300 mm / min. As one embodiment, the forging speed of the multi-directional forging can be 180–200 mm / min.

[0046] In this invention, the equipment for the first forging is preferably preheated before the first forging; the preheating temperature is preferably 350–450°C. This invention does not have a specific limitation on the preheating time, as long as the equipment is preheated to the above range.

[0047] In this invention, the equipment for the first forging is preferably an anvil with upper and lower flat anvils. This invention does not have a specific limitation on the type of the upper and lower flat anvils; any instruments and equipment well-known to those skilled in the art can be used. Preheating the upper and lower flat anvils before the first forging in this invention can prevent the magnesium alloy from cooling down at an extremely rapid rate, thus avoiding cracking.

[0048] In this invention, the first hot forging preferably includes forging the homogenized ingot along its height direction, then alternating forging along two orthogonal directions perpendicular to the height direction, and finally forging along the corner direction of the ingot to obtain a cylindrical forging blank. This invention, by limiting the steps of the first hot forging, enables the ingot to be forged into a cylindrical forging blank through reversal forging.

[0049] In this invention, the first forging preferably has 1 pass; the deformation amount of the first forging is preferably 40-60%; the alternating forging preferably has 6-8 passes; the deformation amount of the alternating forging passes is preferably 30-45%; the second forging preferably has 8-12 passes; the deformation amount of the second forging passes is preferably 25-40%. This invention limits the deformation amounts of the first forging, alternating forging, and second forging to the above ranges, enabling the billet to undergo sufficient deformation through multi-pass, high-deformation forging, thereby reducing casting defects such as shrinkage cavities, porosity, and looseness.

[0050] In one embodiment, the deformation amount of the first forging can be 45-55%, or even 50%; the number of passes of the alternating forging can be 7-8; the deformation amount of the alternating forging passes can be 35-40%; the number of passes of the second forging can be 9-11, or even 10; the deformation amount of the second forging passes can be 30-35%.

[0051] In this invention, the second fire forging preferably includes a third forging of the product obtained from the first fire forging along the height of the product obtained from the first fire forging, followed by rolling forging and upsetting in sequence.

[0052] In this invention, the third forging is preferably performed in one pass; the deformation amount of the third forging is preferably 30-40%; the rounding forging is preferably performed in 8-12 passes; the deformation amount of the rounding forging is preferably 5-20%; and the deformation amount of the upsetting is preferably 15-25%. By limiting the deformation amounts of the third forging, rounding forging, and upsetting to the above ranges, this invention enables the billet to undergo sufficient deformation through multi-pass forging with large deformation amounts, thereby reducing casting defects such as shrinkage cavities, porosity, and looseness.

[0053] In one embodiment, the deformation amount of the third forging can be 35-40%; the number of passes of the rounding forging can be 9-11, or even 10; the deformation amount per pass of the rounding forging can be 10-15%; and the deformation amount of the upsetting can be 20-22%.

[0054] In this invention, the diameter of the forging blank is preferably 750-950 mm; the height of the forging blank is preferably 250-450 mm.

[0055] After obtaining the forging blank, the present invention performs punching and reaming forging on the forging blank in sequence to obtain a reamed forging blank.

[0056] In this invention, the forging billet is preferably preheated before punching; the preheating temperature is preferably 460–500°C. This invention does not have a specific limitation on the preheating time; preheating to the above range is sufficient. Preheating the forging billet in this invention ensures the alloy's deformability.

[0057] In this invention, the punching position is preferably the center of the forging blank; the diameter of the circular hole obtained by punching is preferably 250-350 mm.

[0058] In this invention, the forging speed of the reaming forging is preferably 200-300 mm / min; the reaming forging is preferably performed on a stand. As one embodiment, the forging speed of the reaming forging can be 220-280 mm / min, or even 250-260 mm / min.

[0059] In this invention, when the temperature of the forging billet is below 390°C, it is preferable to heat the forging billet to 460-510°C and hold it for 0.5-1 hour; the number of forging passes for the hole expansion is preferably 1-2; and the diameter of the round hole of the product obtained by the hole expansion forging is preferably 700-1000 mm.

[0060] Before the ring rolling process, the present invention first uses a punching method to open a hole in the center of the forging billet, and then uses a frame-type hole enlargement method to enlarge the diameter of the circular hole and reduce the wall thickness of the ring. This process can avoid the large amount of material loss caused by the traditional hole turning method, and can also prevent defects such as end face concavity and folding when the circular billet with large wall thickness and small height-to-diameter ratio is directly ring rolled.

[0061] After obtaining the expanded hole forging blank, the present invention performs ring rolling to form the expanded hole forging blank to obtain a ring part.

[0062] In this invention, the expanded forging billet is preferably kept at a temperature of 460–530°C before ring rolling; the holding temperature is preferably 4–6 hours. This method of keeping the expanded forging billet at a temperature ensures the alloy's deformability.

[0063] In one embodiment, the heat preservation temperature can be 470–520°C or 480–495°C; the heat preservation time can be 4–5 hours.

[0064] In this invention, the equipment for ring rolling is preferably preheated before the ring rolling process; the preheating temperature is preferably 200–350°C. This invention does not have a specific limitation on the preheating time, as long as it is within the above range.

[0065] In this invention, the equipment for ring rolling is preferably a drive roll, a core roll, a clamping roll, and upper and lower tapered rolls. This invention does not impose any special limitations on the equipment for ring rolling; any instruments and equipment well-known to those skilled in the art can be used.

[0066] In this invention, the rotational speed of the drive roller during ring rolling is preferably 10-30 r / min; the linear feed speed of the core roller during ring rolling is preferably 0.2-1.0 mm / s; the tapered roller forges along the height of the expanded hole forging blank during ring rolling; the forging reduction is preferably 2-10 mm; and the ring rolling is preferably a single-pass forming process.

[0067] After the ring rolling is completed, the present invention preferably air-cools the product obtained by the ring rolling to room temperature to obtain a ring-shaped part.

[0068] The present invention does not have any special limitations on the operation of air cooling to room temperature, and any operation known to those skilled in the art can be used.

[0069] This invention enables efficient one-pass forming of large-diameter annular parts by controlling the billet opening temperature (holding temperature), roll temperature, drive roll speed, core roll feed speed, and tapered roll reduction during ring rolling. Furthermore, a large number of dislocation arrays are formed in the annular parts, providing nucleation sites for the precipitation of strengthening phases during subsequent aging heat treatment, thereby improving the strength of the annular parts.

[0070] In this invention, the outer diameter of the annular component is preferably 1750-3700 mm; the wall thickness of the annular component is preferably 50-100 mm; and the height of the annular component is preferably 250-450 mm.

[0071] After obtaining the ring-shaped part, the present invention performs an aging treatment on the ring-shaped part to obtain a magnesium alloy ring-shaped part.

[0072] In this invention, the holding temperature for the aging treatment is preferably 200–225°C; the holding time for the aging treatment is preferably 15–36 hours. As one embodiment, the holding temperature for the aging treatment can be 205–220°C, or 210–215°C; the holding time for the aging treatment can be 16–32 hours, or 20–24 hours. By limiting the process parameters of the aging treatment within the above ranges, this invention effectively eliminates internal stress concentration and inhomogeneity, which is beneficial for grain refinement and the uniform distribution of the second phase, thereby improving the mechanical properties of the alloy.

[0073] In this invention, the outer diameter of the magnesium alloy ring is preferably 1750-3700 mm; the wall thickness of the magnesium alloy ring is preferably 50-100 mm; and the height of the ring is preferably 250-450 mm.

[0074] This invention addresses the demand for large-diameter, lightweight, and high-strength ring components in aerospace equipment. Through electromagnetic semi-continuous casting, multi-directional forging, punching, hole-expanding forging, ring rolling, and aging treatment, large-diameter, high-strength, and heat-resistant magnesium alloy ring components with an outer diameter of 1750–3700 mm are produced. This invention is of great significance for promoting the lightweight upgrading of my country's new generation of equipment.

[0075] The aluminum alloy ring-shaped part prepared by the method provided by this invention has a room temperature tangential tensile strength ≥420MPa, yield strength ≥340MPa, and elongation ≥6%. At 250℃, the tangential tensile strength ≥300MPa, yield strength ≥240MPa, and elongation ≥10%. The product prepared by this invention has the characteristics of large size, no cracks, good surface quality, high room temperature strength, and excellent heat resistance. It can provide large-size lightweight high-strength magnesium alloy shells for aerospace vehicles.

[0076] The present invention also provides a magnesium alloy ring-shaped part prepared by the preparation method described in the above technical solution.

[0077] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0078] Example 1

[0079] The preparation method of the magnesium alloy ring-shaped part is as follows:

[0080] (1) A magnesium alloy ingot with a diameter of 450 mm and a length of 3010 mm was prepared by electromagnetic semi-continuous casting. Then, it was held at 370℃ for 4 h and then held at 515℃ for 20 h for a two-stage homogenization heat treatment. Then, it was first furnace cooled to 200℃ and then air cooled to room temperature. Then, it was cut by turning and sawing to obtain a homogenized ingot with a diameter of 420 mm and a length of 1240 mm. The mass percentage composition of the magnesium alloy ingot is: Gd 8.7%, Y 2.1%, Zr 0.35%, Er 0.22%, Ag 0.20% and the balance Mg.

[0081] (2) The homogenized billet obtained in step (1) is heated to 505°C, and the upper and lower anvils are preheated to 380°C. Then, the first multi-directional forging is carried out on a 3000t forging machine at a forging speed of 200mm / min. The first pass is forged along the height direction of the billet by 50%. Then, it is forged alternately along two orthogonal directions perpendicular to the height direction of the billet for a total of 6 passes, with a reduction of 35% per pass. Then, it is forged along the corner direction of the billet for 10 passes, with a reduction of 30% per pass. The billet is then forged into a cylindrical forging billet by reversing the direction. The temperature of the second forging is reduced to 490°C. The first pass is forged along the height direction of the cylindrical forging billet by 35%. Then, it is forged into a round forging billet with a deformation of 15% per pass for 8 passes. Finally, it is upset by 20% to form a circular forging billet with a diameter of 780mm and a height of 360mm.

[0082] (3) Heat the circular forging billet obtained in step (2) to 490°C, then punch a hole with a Φ320mm punch, and then transfer it to the frame. At a forging speed of 250mm / min, the inner diameter is expanded to 700mm in one pass to obtain an expanded forging billet.

[0083] (4) Heat the expanded hole forging blank obtained in step (3) to 500°C and keep it at that temperature for 4 hours. Preheat the active roller, core roller, clamping roller and upper and lower conical rollers to 300°C. Set the speed of the active roller to 16 r / min, set the linear feed speed of the core roller to 0.3 mm / s, apply a 3 mm reduction along the height of the conical roller, prepare it in one heat, and air cool it to room temperature to obtain an annular part with an outer diameter of 1785 mm, a wall thickness of 80 mm and a height of 360 mm.

[0084] (5) The ring-shaped part obtained in step (4) is aged at 220°C for 16 hours to obtain a magnesium alloy ring-shaped part.

[0085] Example 2

[0086] The preparation method of the magnesium alloy ring-shaped part is as follows:

[0087] (1) A magnesium alloy ingot with a diameter of 450 mm and a length of 2950 mm was prepared by electromagnetic semi-continuous casting. Then, it was held at 370℃ for 4 h and then held at 515℃ for 20 h for a two-stage homogenization heat treatment. After that, it was furnace cooled to 220℃ and then air cooled to room temperature. Then, it was cut by turning and sawing to obtain a homogenized ingot with a diameter of 420 mm and a length of 1300 mm. The mass percentage composition of the magnesium alloy ingot is: Gd 9.1%, Y 2.2%, Zr 0.38%, Er 0.21%, Ag 0.25% and the balance Mg.

[0088] (2) The homogenized billet obtained in step (1) is heated to 505°C, and the upper and lower anvils are preheated to 400°C. Then, the first multi-directional forging is carried out on a 3000t forging machine at a forging speed of 200mm / min. The first pass is forged along the height direction of the billet by 60%. Then, it is forged alternately along two orthogonal directions perpendicular to the height direction of the billet for a total of 6 passes, with a reduction of 40% per pass. Then, it is forged along the corner direction of the billet for 12 passes, with a reduction of 30% per pass. The billet is then forged into a cylindrical forging billet by reversing the direction. The temperature of the second forging is reduced to 495°C. The first pass is forged along the height direction of the cylindrical forging billet by 40%. Then, it is forged into a round forging billet with a deformation of 15% per pass for 10 passes. Finally, it is upset by 25% to form a circular forging billet with a diameter of 920mm and a height of 265mm.

[0089] (3) Heat the circular forging billet obtained in step (2) to 495°C, then punch a hole with a Φ320mm punch, then transfer it to the frame, and expand the inner diameter to 850mm in one pass at a forging speed of 200mm / min to obtain an expanded forging billet.

[0090] (4) Heat the expanded hole forging blank obtained in step (3) to 505℃ and keep it at that temperature for 4 hours. Preheat the active roller, core roller, clamping roller and upper and lower conical rollers to 340℃. Set the speed of the active roller to 15r / min, set the linear feed speed of the core roller to 0.35mm / s, apply a 4mm reduction along the height of the conical roller, prepare it in one heat, and air cool it to room temperature to obtain an annular part with an outer diameter of 3070mm, a wall thickness of 54mm and a height of 280mm.

[0091] (5) The ring-shaped part obtained in step (4) is aged at 220°C for 16 hours to obtain a magnesium alloy ring-shaped part.

[0092] Example 3

[0093] The preparation method of the magnesium alloy ring-shaped part is as follows:

[0094] (1) A magnesium alloy ingot with a diameter of 730 mm and a length of 2000 mm was prepared by electromagnetic semi-continuous casting. Then, it was held at 380℃ for 4 h and then held at 515℃ for 24 h for a two-stage homogenization heat treatment. Then, it was first furnace cooled to 200℃ and then air cooled to room temperature. Then, it was cut by turning and sawing to obtain a homogenized ingot with a diameter of 630 mm and a length of 830 mm. The mass percentage composition of the magnesium alloy ingot is: Gd 9.2%, Y 2.3%, Zr 0.40%, Er 0.26%, Ag 0.28% and the balance Mg.

[0095] (2) The homogenized billet obtained in step (1) is heated to 500°C, and the upper and lower anvils are preheated to 400°C. Then, the first multi-directional forging is carried out on a 3000t forging machine at a forging speed of 180mm / min. The first pass is forged along the height direction of the billet by 40%, and then forged alternately along two orthogonal directions perpendicular to the height direction of the billet for a total of 6 passes, with a reduction of 30% per pass. Then, forging is carried out along the corner direction of the billet for 12 passes, with a reduction of 30% per pass. The billet is then forged into a cylindrical forging billet by reversing the direction. The temperature of the second forging is reduced to 490°C. The first pass is forged along the height direction of the cylindrical forging billet by 30%, and then forged into a rounded forging billet with a deformation of 15% per pass for 12 passes. Finally, it is upset by 25% to form a circular forging billet with a diameter of 950mm and a height of 360mm.

[0096] (3) Heat the circular forging billet obtained in step (2) to 500°C, then punch a hole with a Φ320mm punch, then transfer it to the frame, and expand the inner diameter to 1000mm in one pass at a forging speed of 300mm / min to obtain an expanded forging billet.

[0097] (4) Heat the expanded hole forging blank obtained in step (3) to 495°C and keep it at that temperature for 5 hours. Preheat the active roller, core roller, clamping roller and upper and lower conical rollers to 350°C. Set the speed of the active roller to 18 r / min, set the linear feed speed of the core roller to 0.4 mm / s, apply a 3 mm reduction along the height of the conical roller, prepare it in one heat, and air cool it to room temperature to obtain an annular part with an outer diameter of 3655 mm, a wall thickness of 65 mm and a height of 340 mm.

[0098] (5) The ring-shaped part obtained in step (4) is aged at 220°C for 18 hours to obtain a magnesium alloy ring-shaped part.

[0099] Comparative Example 1

[0100] The preparation method of the magnesium alloy ring-shaped part is as follows:

[0101] (1) A magnesium alloy ingot with a diameter of 450 mm and a length of 2950 mm was prepared by electromagnetic semi-continuous casting. Then, it was held at 380℃ for 4 h and then held at 520℃ for 20 h for a two-stage homogenization heat treatment. Then, it was first furnace cooled to 250℃ and then air cooled to room temperature. Then, it was cut by turning and sawing to obtain a homogenized ingot with a diameter of 425 mm and a length of 1300 mm. The mass percentage composition of the magnesium alloy ingot is: Gd 8.7%, Y 2.0%, Zr 0.31%, Er 0.25%, Ag 0.21% and the balance Mg.

[0102] (2) The homogenized billet obtained in step (1) is heated to 505°C, and the upper and lower anvils are preheated to 380°C. Then, the first multi-directional forging is carried out on a 3000t forging machine at a forging speed of 200mm / min. The first pass is forged along the height direction of the billet by 50%. Then, it is forged alternately along two orthogonal directions perpendicular to the height direction of the billet for a total of 6 passes, with a reduction of 25% per pass. Then, it is forged along the corner direction of the billet for 10 passes, with a reduction of 20% per pass. The billet is then forged into a cylindrical forging billet by reversing the direction. The temperature of the second forging is reduced to 500°C. The first pass is forged along the height direction of the cylindrical forging billet by 30%. Then, it is forged into a round forging billet with a deformation of 20% per pass for 12 passes. Finally, it is upset by 25% to form a circular forging billet with a diameter of 890mm and a height of 290mm.

[0103] (3) A Φ260mm circular hole is machined in the center of the circular forging blank obtained in step (2) using a lathe. After heating to 500℃ and holding for 8 hours, it is ring rolled on a ring rolling mill. The rolling mill roll temperature is heated to 250℃, the speed of the drive roll is set to 25r / min, and the linear feed speed of the core roll is set to 0.4mm / s. The inner hole of the magnesium alloy forging blank is rolled to 480mm in the first heat. After being held at 500℃ for 8 hours in the furnace, the inner hole is rolled to 980mm in the second heat. At this time, the end face of the ring part shows obvious bulging. After the end face is machined to be flat, it is placed in the furnace and held at 500℃ for 8 hours. The ring part with an outer diameter of 1765mm, a wall thickness of 90mm, and a height of 305mm is prepared by ring rolling in the third heat.

[0104] Compared to the embodiments, Comparative Example 1 uses turning to machine the inner hole of the forging billet. Since the material loss during turning is much greater than that during punching and reaming when machining the same size inner hole, to prevent insufficient forging billet material after turning the hole too large, only a Φ260mm inner hole can be machined. This results in an excessively thick forging billet wall, making it impossible to ring roll to the target size in a single pass, and easily leading to end-face pit defects. Ultimately, the required ring part was produced through three passes of ring rolling and end-face machining between the second and third passes. Compared to the embodiments, Comparative Example 1 has a longer process flow and higher cost. Furthermore, the multiple reheating processes result in relatively coarse magnesium alloy grains and reduced strength.

[0105] Mechanical properties of the magnesium alloy ring parts prepared in Examples 1-3 and Comparative Example 1 were tested. The room temperature test standard was GB / T 228.1-2010; the high temperature test standard was GB / T 228.2-2015. Table 1 shows the mechanical property data of the VW93M magnesium alloy ring parts prepared in Examples 1-3 and Comparative Example 1.

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[0108] As can be seen from Table 1, the magnesium alloy ring parts prepared by this invention have excellent mechanical properties and heat resistance.

[0109] As can be seen from the above embodiments, the magnesium alloy ring parts prepared by the preparation method provided by the present invention have excellent mechanical properties and heat resistance.

[0110] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a magnesium alloy ring-shaped component, comprising the following steps: (1) The magnesium alloy ingot is subjected to a two-stage homogenization treatment to obtain a homogenized ingot blank; the two-stage homogenization treatment is to first hold at 350~380℃ for 3~5h, and then raise the temperature to 500~525℃ and hold for 18~24h. (2) The homogenized billet obtained in step (1) is subjected to multi-directional forging to obtain a forging billet; the multi-directional forging includes a first fire forging and a second fire forging performed sequentially; the temperature of the first fire forging is 480~515℃; the temperature of the second fire forging is 10~20℃ lower than the temperature of the first fire forging. (3) The forging blank obtained in step (2) is punched and expanded in sequence to obtain an expanded forging blank; (4) The expanded forging blank obtained in step (3) is subjected to ring rolling to obtain an annular part; (5) The ring-shaped part obtained in step (4) is subjected to aging treatment to obtain a magnesium alloy ring-shaped part; In step (1), the magnesium alloy ingot is a VW93M magnesium alloy ingot; the chemical composition of the VW93M magnesium alloy ingot, by mass percentage, is Gd 8.0~9.6%, Y 1.8~3.2%, Zr 0.3~0.7%, Er 0.02~0.3%, Ag 0.02~0.50% and balance Mg; The first forging in step (2) includes forging the homogenized billet along the height of the billet, then alternating forging along two orthogonal directions perpendicular to the height of the billet, and then forging along the corner of the billet to obtain a cylindrical forging billet. The first forging process consists of 1 pass, with a deformation rate of 40-60%; the alternating forging process consists of 6-8 passes, with a deformation rate of 30-45%; the second forging process consists of 8-12 passes, with a deformation rate of 25-40%. The second forging in step (2) includes forging the product obtained from the first forging along the height of the product obtained from the first forging, and then performing rounding forging and upsetting in sequence. The third forging process has 1 pass and a deformation of 30%; the rounding forging process has 8 to 12 passes and a deformation of 5 to 20%; the upsetting process has a deformation of 15 to 25%.

2. The preparation method according to claim 1, characterized in that, The forging speed for hole expansion forging in step (3) is 200~300mm / min.

3. The preparation method according to claim 1, characterized in that, In step (4), the expanded forging billet is kept warm before ring rolling; the temperature of the warming is 460~530℃ and the warming time is 4~6h.

4. The preparation method according to claim 1, characterized in that, In step (4), the rotational speed of the drive roller during ring rolling is 10~30 r / min, the linear feed speed of the core roller is 0.2~1.0 mm / s, and the tapered roller forges along the height of the expanded hole forging blank.

5. The preparation method according to claim 1, characterized in that, The aging treatment temperature in step (5) is 200~225℃, and the aging treatment time is 15~36h.

6. The magnesium alloy ring-shaped part prepared by the preparation method according to any one of claims 1 to 5.

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