A magnesium alloy conical cylinder and its preparation method and application

Abstract

The present invention provides a magnesium alloy conical cylinder and its preparation method and application, which belongs to the field of magnesium alloy technology. The preparation method of the magnesium alloy conical cylinder provided by the present invention comprises the following steps: annealing the magnesium alloy ingot to obtain the annealed ingot; multi-directional forging the annealed ingot to obtain a first ingot; bidirectional drawing forging the first ingot to obtain a second ingot; die forging the second ingot to obtain a conical cylinder; and T6 heat treatment of the conical cylinder to obtain a magnesium alloy conical cylinder. The present invention first anneals the magnesium alloy ingot to eliminate residual stress and avoid cracking of the ingot during the subsequent deformation process. Then, multi-directional forging, bidirectional drawing forging and die forging are used to solve the problem that large-sized magnesium alloy ingots are prone to cracking due to uneven deformation during the deformation process, effectively inhibit the growth of deformed grains during the heat preservation process, and refine the grain size.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnesium alloys, and in particular relates to a magnesium alloy conical cylinder and a preparation method and application thereof. Background Art

[0002] The conical tube is a key component on a missile. It has always been made of steel or aluminum alloy. However, in order to meet the requirements of weight reduction and improving fuel efficiency, designers are in urgent need of a lightweight material that can reduce the weight of the missile itself. VW93M magnesium alloy has attracted more and more attention due to its low density, excellent damping performance, high specific strength and specific stiffness. However, most magnesium alloys have a close-packed hexagonal structure with poor plastic deformation energy. When deformed, they easily form a strong deformation texture, which makes subsequent processing deformation difficult and uneven deformation of various parts, which in turn leads to processing cracking. Therefore, the large-scale magnesium alloy structural parts currently used are mainly cast magnesium alloys. Therefore, how to prepare a magnesium alloy conical tube with excellent mechanical properties has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0003] The purpose of the present invention is to provide a magnesium alloy conical cylinder and its preparation method and application. The magnesium alloy conical cylinder prepared by the preparation method provided by the present invention has excellent mechanical properties.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a magnesium alloy tapered cylinder, comprising the following steps:

[0006] (1) annealing the magnesium alloy ingot to obtain an annealed ingot;

[0007] (2) performing multi-directional forging on the annealed ingot obtained in step (1) to obtain a first ingot;

[0008] (3) performing bidirectional drawing forging on the first ingot obtained in step (2) to obtain a second ingot;

[0009] (4) forging the second ingot obtained in step (3) to obtain a tapered cylinder;

[0010] (5) The conical cylinder obtained in step (4) is subjected to T6 heat treatment to obtain a magnesium alloy conical cylinder.

[0011] Preferably, the multidirectional forging in step (2) includes the following steps:

[0012] 1) The annealed ingot is kept warm, and then forged along the X direction and / or Y direction of the annealed ingot with the height direction of the annealed ingot as the Z direction, and then rolling forged with the Z direction as the axis to obtain a billet;

[0013] 2) Repeat the operation of step 1) to obtain a first ingot.

[0014] Preferably, in step 1), the reduction speed for forging along the X direction and / or Y direction of the annealed ingot is 6-10 mm / s, and the single-pass reduction for forging along the X direction and / or Y direction of the annealed ingot is 20-40%.

[0015] Preferably, the number of rolling forging passes in step 1) is 3 to 6, and the deformation amount of a single rolling forging pass is 10 to 20%.

[0016] Preferably, the bidirectional drawing forging in step (3) includes the following steps:

[0017] ① The first ingot is kept warm, and then forged along the diameter direction of the first ingot to obtain an ingot blank;

[0018] ② Repeat step ① to obtain a second ingot.

[0019] Preferably, in step ①, the forging reduction speed is 3 to 6 mm / s, the forging reduction in a single pass is 5 to 20%, and the number of forging passes is 2 to 8.

[0020] Preferably, the die forging in step (4) includes primary die forging and secondary die forging performed sequentially.

[0021] Preferably, the forging speed of the primary die forging is 2-5 mm / s, and the deformation ratio of the primary die forging is 0.20-0.40; the forging speed of the secondary die forging is 2-5 mm / s, and the deformation ratio of the secondary die forging is 0.75-0.83.

[0022] The present invention also provides a magnesium alloy conical cylinder prepared by the preparation method described in the above technical solution.

[0023] The present invention also provides the application of the magnesium alloy conical tube described in the above technical solution in a missile.

[0024] The present invention provides a method for preparing a magnesium alloy tapered tube, comprising the following steps: annealing a magnesium alloy ingot to obtain an annealed ingot; performing multi-directional forging on the annealed ingot to obtain a first ingot; performing bidirectional draw forging on the first ingot to obtain a second ingot; performing die forging on the second ingot to obtain a tapered tube; and performing T6 heat treatment on the tapered tube to obtain a magnesium alloy tapered tube. The present invention first anneals the magnesium alloy ingot to eliminate residual stress and prevent cracking during subsequent deformation. Subsequently, multi-directional forging, bidirectional draw forging, and die forging are used to address the problem of cracking in large magnesium alloy ingots due to uneven deformation during deformation. The method effectively inhibits the growth of deformed grains during the heat preservation process, significantly refining the grain size of the finished product. Experimental results show that the room temperature mechanical properties of the magnesium alloy conical cylinder prepared by the preparation method provided by the present invention are: yield strength 326~331MPa, tensile strength 418~425MPa, elongation 10~11%; 250℃ mechanical properties: yield strength 261~267MPa, tensile strength 351~363MPa, elongation 14~15%. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing a magnesium alloy tapered cylinder, comprising the following steps:

[0026] (1) annealing the magnesium alloy ingot to obtain an annealed ingot;

[0027] (2) performing multi-directional forging on the annealed ingot obtained in step (1) to obtain a first ingot;

[0028] (3) performing bidirectional drawing forging on the first ingot obtained in step (2) to obtain a second ingot;

[0029] (4) forging the second ingot obtained in step (3) to obtain a tapered cylinder;

[0030] (5) The conical cylinder obtained in step (4) is subjected to T6 heat treatment to obtain a magnesium alloy conical cylinder.

[0031] The present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0032] The present invention performs annealing treatment on the magnesium alloy ingot to obtain the annealed ingot.

[0033] In the present invention, the magnesium alloy ingot is preferably a VW93M magnesium alloy ingot; the chemical composition of the VW93M magnesium alloy ingot is preferably, by mass percentage, 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, more preferably Gd 8.3-9.3%, Y 2.1-2.7%, Zr 0.35-0.6%, Er 0.05-0.25%, Ag 0.1-0.40%, and the balance Mg, more preferably Gd 8.5-9.0%, Y 2.3-2.4%, Zr 0.45-0.55%, Er 0.15-0.20%, Ag 0.2-0.35%, and the balance Mg. The present invention can further improve the strength and heat resistance of the magnesium alloy by limiting the chemical component content of the VW93M magnesium alloy ingot to the above range.

[0034] In the present invention, the mass ratio of Gd to Y is preferably: 3 ≤ Gd / Y ≤ 5; the mass ratio of Ag to Er is preferably: 1 ≤ Ag / Er ≤ 3. By controlling the content ratio of Gd to Y and the mass ratio of Ag to Er, the present invention can obtain an excellent rare earth precipitate phase morphology distribution.

[0035] In the present invention, the magnesium alloy ingot is preferably produced using an electromagnetic semi-continuous casting method. The present invention does not specifically limit the specific operation of the electromagnetic semi-continuous casting method; the ingot can be produced using methods well known to those skilled in the art. The use of the electromagnetic semi-continuous casting method to produce the magnesium alloy ingot can reduce defects such as inclusions, porosity, porosity, and center cracks, thereby reducing the tendency to crack during subsequent deformation and improving the formability of the magnesium alloy during subsequent deformation.

[0036] In the present invention, the diameter of the magnesium alloy ingot is preferably 340-630 mm; the length of the magnesium alloy ingot is preferably ≥2000 mm.

[0037] In the present invention, the annealing treatment preferably includes stress relief annealing and homogenization treatment performed sequentially.

[0038] In the present invention, the holding temperature of the stress relief annealing is preferably 200-300°C; and the holding time of the stress relief annealing is preferably 10-15h. As an embodiment, the holding temperature of the stress relief annealing can be 250-280°C; and the holding time of the stress relief annealing can be 12-14h. The present invention performs stress relief annealing on magnesium alloy ingots to eliminate residual stress, avoid cracking of the ingots during subsequent deformation, and improve surface accuracy. It can not only avoid excessively long holding times, which lead to excessive grain growth and excessive precipitation, aggregation, and coarsening of the second phase, resulting in reduced strength, but also avoid excessively short holding times, which prevent the residual stress inside the alloy from being fully eliminated, thereby reducing the alloy's strength.

[0039] In the present invention, the holding temperature for the homogenization treatment is preferably 480-520°C, and the holding time for the homogenization treatment is preferably 18-24 hours. In one embodiment, the holding temperature for the homogenization treatment can be 490-500°C, and the holding time for the homogenization treatment can be 20-22 hours. In the present invention, limiting the homogenization process parameters to the above ranges can further improve the plasticity of the alloy.

[0040] The present invention has no particular limitation on the heating rates of the stress relief annealing and homogenization treatment, and any rate well known to those skilled in the art may be used.

[0041] After the annealing treatment is completed, the present invention preferably sequentially cools, machine-peels, and blanks the product obtained by the annealing treatment to obtain an annealed ingot.

[0042] In the present invention, the cooling is preferably air cooling. The present invention has no particular limitation on the operation of the air cooling, and air cooling to room temperature can be performed using an operation well known to those skilled in the art.

[0043] The present invention has no special limitation on the machining peeling and blanking operations, and operations well known to those skilled in the art may be used.

[0044] In the present invention, the shape of the annealed ingot is preferably cylindrical.

[0045] After obtaining the annealed ingot, the present invention performs multi-directional forging on the annealed ingot to obtain a first ingot.

[0046] In the present invention, the multidirectional forging preferably includes the following steps:

[0047] 1) The annealed ingot is kept warm, and then forged along the X direction and / or Y direction of the annealed ingot with the height direction of the annealed ingot as the Z direction, and then rolling forged with the Z direction as the axis to obtain a billet;

[0048] 2) Repeating step 1) to obtain a first ingot. The present invention maintains the magnesium alloy within a suitable processing temperature range by repeating the heat preservation and forging process, avoids the billet temperature from being too low, and ensures production continuity and high efficiency.

[0049] The present invention preferably keeps the annealed ingot warm, then forges it along the X and / or Y directions with its height as the Z direction, and then rolls it around the Z direction to obtain a billet.

[0050] In the present invention, the holding temperature is preferably 450-520°C and the holding time is preferably 10-20 hours. Limiting the holding process parameters within the above ranges avoids the risk of overburning due to excessively high holding temperatures while ensuring the alloy's deformability.

[0051] In the present invention, the forging equipment is preferably preheated before forging, and the preheating temperature is preferably 200-350° C. The present invention has no particular limitation on the preheating time, as long as the equipment is preheated to within the above range.

[0052] In the present invention, the forging equipment preferably comprises upper and lower flat anvils. The present invention does not specifically limit the type of the upper and lower flat anvils; any equipment familiar to those skilled in the art can be used. Preheating the upper and lower flat anvils prior to forging can prevent the magnesium alloy billet from cooling too rapidly and causing cracking.

[0053] In the present invention, the reduction speed during forging along the X and / or Y directions of the annealed ingot is preferably 6 to 10 mm / s; the reduction per pass during forging along the X and / or Y directions of the annealed ingot is preferably 20 to 40%; and the number of passes during forging along the X and / or Y directions of the annealed ingot is preferably 2 to 5. The present invention enables forging along the X and / or Y directions of the annealed ingot to press a cylindrical ingot into a hexahedron. Limiting the forging process parameters within the aforementioned ranges can further improve the mechanical properties and heat resistance of the magnesium alloy.

[0054] As an embodiment, the reduction speed of forging along the X direction and / or Y direction of the annealed ingot can be 7 to 8 mm / s; the single-pass reduction of forging along the X direction and / or Y direction of the annealed ingot can be 25 to 35%, or even 30%; the number of passes of forging along the X direction and / or Y direction of the annealed ingot can be 2 to 4.

[0055] In the present invention, the number of roll forging passes is preferably 3 to 6, and the deformation per roll forging pass is preferably 10 to 20%. As an embodiment, the number of roll forging passes can be 4 to 5, and the deformation per roll forging pass can be 15 to 20%. In the present invention, the roll forging can compress the edges and corners of the ingot, pressing hexahedrons into 12 to 18hedrons. The present invention limits the roll forging process parameters within the above ranges to further improve the mechanical properties and heat resistance of the magnesium alloy.

[0056] After obtaining the billet, the present invention preferably repeats the aforementioned heat preservation and forging operations to obtain a first ingot.

[0057] In the present invention, the number of repetitions is preferably 1 to 2 times.

[0058] In the present invention, the diameter of the first ingot is preferably 400-500 mm; the height of the first ingot is preferably 600-800 mm.

[0059] After obtaining the first ingot, the present invention performs bidirectional drawing forging on the first ingot to obtain the second ingot.

[0060] In the present invention, the bidirectional drawing forging preferably includes the following steps:

[0061] ① The first ingot is kept warm, and then forged along the diameter direction of the first ingot to obtain an ingot blank;

[0062] ② Repeat step ① to obtain a second ingot.

[0063] In the present invention, the first ingot is preferably kept warm, and then forged along the diameter direction of the first ingot to obtain an ingot blank.

[0064] In the present invention, the holding temperature is preferably 430-500°C and the holding time is preferably 8-18 hours. Limiting the holding process parameters within the above ranges avoids the risk of overheating due to excessively high holding temperatures while ensuring the alloy's deformability.

[0065] In the present invention, the forging equipment is preferably preheated before forging, and the preheating temperature is preferably 200-300° C. The present invention has no particular limitation on the preheating time, as long as the equipment is preheated to within the above range.

[0066] In the present invention, the forging equipment preferably comprises upper and lower flat anvils. The present invention does not specifically limit the type of the upper and lower flat anvils; any equipment familiar to those skilled in the art can be used. Preheating the upper and lower flat anvils prior to forging can prevent the magnesium alloy billet from cooling too rapidly and causing cracking.

[0067] In the present invention, the forging reduction speed is preferably 3-6 mm / s; the forging reduction per pass is preferably 5-20%; and the number of forging passes is preferably 2-8. As an embodiment, the forging reduction speed can be 4-5 mm / s; the forging reduction per pass can be 10-15%; and the number of forging passes can be 5-6. The present invention limits the forging process parameters within the above ranges to further improve the mechanical properties and heat resistance of the magnesium alloy, avoiding excessively fast reduction speeds, which may lead to uneven material deformation during forging, and excessively slow reduction speeds, which may result in the material being exposed to high temperatures for too long, leading to grain growth. It also avoids excessively low reduction per pass, which may make it difficult to eliminate structural heterogeneity within the material, and excessively high reduction per pass, which may result in excessive stress and cracks within the material.

[0068] After obtaining the ingot, the present invention preferably repeats the aforementioned heat preservation and forging operations to obtain a second ingot.

[0069] In the present invention, the number of repetitions is preferably 2 to 4. As an embodiment, the number of repetitions can be 3.

[0070] In the present invention, the diameter of the second ingot is preferably 250-350 mm; the height of the second ingot is preferably 1000-1400 mm.

[0071] After obtaining the second ingot, the present invention performs die forging on the second ingot to obtain a tapered cylinder.

[0072] In the present invention, the second ingot is preferably processed and kept warm in sequence before the die forging.

[0073] In the present invention, the processing is preferably to process one end of the second ingot into a conical surface and the center of the other end into a groove. The present invention processes both ends of the second ingot to ensure centering and avoid eccentricity during die forging.

[0074] The present invention has no special limitation on the sizes of the conical surface and the groove, and they can be adjusted according to actual needs.

[0075] As an embodiment, the height of the cone surface may be ≥60 mm, and the angle of the cone surface may be 8°; the depth of the groove may be ≥10 mm, and the radius of the groove may be 40 to 80 mm.

[0076] In the present invention, the holding temperature is preferably 400-480°C and the holding time is preferably 6-10 hours. Limiting the holding process parameters within the above ranges avoids the risk of overheating due to excessively high holding temperatures while ensuring the alloy's deformability.

[0077] In the present invention, the die forging is preferably heat-insulated before die forging; the heat-insulating temperature is preferably 350-450°C; and the heat-insulating time is preferably 5-15 hours. Heat-insulating the die forging can prevent the magnesium alloy from cracking during die forging.

[0078] In the present invention, the die forging preferably includes primary die forging and secondary die forging performed sequentially.

[0079] In the present invention, the tapered surface of the second ingot is preferably facing downward during the primary die forging; and the upper flat die is preferably used for die forging during the primary die forging.

[0080] In the present invention, the forging speed of the single die forging is preferably 2-5 mm / s; the deformation ratio of the single die forging is preferably 0.20-0.40; and the reduction of the single die forging is preferably 200-400 mm. As an embodiment, the forging speed of the single die forging can be 3-4 mm / s; the deformation ratio of the single die forging can be 0.25-0.35, or even 0.30; and the reduction of the single die forging can be 250-300 mm. By limiting the forging speed of the single die forging to the above range, the present invention can ensure uniform deformation of the billet, prevent cracking and structural inhomogeneity, and optimize the properties of the alloy after deformation.

[0081] In the present invention, the height of the product obtained by the one-time die forging is preferably 800 to 1200 mm.

[0082] In the present invention, the product obtained by the primary die forging is preferably held at a temperature of 400-480°C before the secondary die forging, and the holding time is preferably 4-8 hours. In one embodiment, the holding temperature can be 420-460°C, or even 450°C, and the holding time can be 5-6 hours. Limiting the holding process parameters to the aforementioned ranges avoids the risk of overheating due to excessively high holding temperatures while ensuring the alloy's deformability.

[0083] In the present invention, the die forging die is preferably kept warm before the secondary die forging; the temperature of the heat preservation is preferably 350-450°C; and the heat preservation time is preferably 5-15 hours. Insulating the die forging die can prevent the magnesium alloy from cracking during die forging.

[0084] In the present invention, during the secondary die forging, the conical surface of the product obtained by the primary die forging is preferably facing downward; and during the secondary die forging, an upper conical die is preferably used for die forging.

[0085] In the present invention, the forging speed of the secondary die forging is preferably 2-5 mm / s; the deformation ratio of the secondary die forging is preferably 0.75-0.83; and the reduction of the secondary die forging is preferably 600-1000 mm. As an embodiment, the forging speed of the secondary die forging can be 3-4 mm / s; the deformation ratio of the secondary die forging can be 0.78-0.80; and the reduction of the secondary die forging can be 600-800 mm. By limiting the forging speed of the secondary die forging to the above range, the present invention ensures uniform deformation of the billet, prevents cracking and structural inhomogeneity, and optimizes the properties of the alloy after deformation.

[0086] In the present invention, the height of the conical cylinder is preferably 1000-1200 mm; the top diameter of the conical cylinder is preferably 200-250 mm; the bottom outer diameter of the conical cylinder is preferably 500-600 mm; the cone barrel depth of the conical cylinder is preferably 800-1000 mm; and the wall thickness of the conical cylinder is preferably 80-100 mm.

[0087] After obtaining the conical cylinder, the present invention performs T6 heat treatment on the conical cylinder to obtain a magnesium alloy conical cylinder.

[0088] In the present invention, the T6 heat treatment preferably includes solution treatment and aging treatment performed in sequence. The present invention adopts T6 heat treatment to make the comprehensive mechanical properties of the tapered tube more excellent.

[0089] In the present invention, the holding temperature of the solution treatment is preferably 380-450°C; and the holding time of the solution treatment is preferably 30-120 minutes. As an embodiment, the holding temperature of the solution treatment can be 400-420°C, and the holding time of the solution treatment can be 60-100 minutes. Limiting the process parameters of the solution treatment within the above ranges can effectively eliminate internal stress concentration and unevenness, promote grain refinement and uniform distribution of the secondary phase, and thus improve the mechanical properties of the alloy.

[0090] After the solution treatment is completed, the present invention preferably water quenches the product obtained by the solution treatment; the water quenching temperature is preferably 60-70° C. The present invention water quenches after the solution treatment to prevent surface cracking.

[0091] In the present invention, the holding temperature of the aging treatment is preferably 200-250°C, and the holding time of the aging treatment is preferably 12-40 hours. As an embodiment, the holding temperature of the aging treatment can be 220-240°C, and the holding time of the aging treatment can be 16-20 hours. Limiting the aging treatment process parameters within the above ranges can effectively eliminate internal stress concentration and unevenness, promote grain refinement and uniform distribution of the secondary phase, and thus improve the mechanical properties of the alloy.

[0092] After the T6 heat treatment is completed, the present invention preferably cools the product obtained by the T6 heat treatment to obtain a magnesium alloy conical cylinder.

[0093] In the present invention, the cooling is preferably air cooling. The present invention has no particular limitation on the operation of the air cooling, and air cooling to room temperature can be performed using an operation well known to those skilled in the art.

[0094] To meet the practical needs of large-scale magnesium alloy conical parts for missiles in the aerospace field, this invention, based on VW93M alloy, employs a process combining multi-directional forging, bidirectional drawing, and die forging to design a first-of-its-kind forming process for VW93M magnesium alloy conical barrel die forgings. This process produces magnesium alloy conical parts with a top diameter of 200-250 mm, a bottom outer diameter of 500-600 mm, a height of 1000-1200 mm, a wall thickness of 80-100 mm, and a barrel depth of 800-1000 mm. This process is of great significance for promoting the widespread application of magnesium alloys in the aerospace field.

[0095] The present invention adopts the method of first performing the first die forging with a flat anvil and then performing the second die forging with a cone head during die forging, and after bidirectional drawing, a cone surface is processed at one end of the ingot, and a central groove at the other end is used for positioning the lower cone die and the cone head for die forging, which effectively solves the problem of instability that is easy to occur during the deformation of large-size variable-section magnesium alloy ingots with a height-to-diameter ratio greater than 3, avoids the problem of eccentricity that is easy to occur during the deformation of the cone cylinder, and further ensures uniform deformation of the cone cylinder in the wall thickness direction.

[0096] The room temperature mechanical properties of the magnesium alloy conical cylinder prepared by the preparation method provided by the present invention are: tensile strength ≥415MPa, yield strength ≥325MPa, and elongation ≥10%; the mechanical properties at 250°C are: tensile strength ≥350MPa, yield strength ≥260MPa, and elongation ≥14.0%.

[0097] The magnesium alloy conical cylinder prepared by the present invention has the characteristics of large size, no cracks, ultra-high room temperature strength and excellent heat resistance, and can provide qualified magnesium alloy conical cylinder parts for fields such as aerospace.

[0098] The present invention also provides a magnesium alloy conical cylinder prepared by the preparation method described in the above technical solution.

[0099] The present invention also provides the application of the magnesium alloy conical tube described in the above technical solution in a missile.

[0100] The present invention has no special limitation on the application operation of the magnesium alloy conical tube in the missile, and the application operation well known to those skilled in the art can be adopted.

[0101] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0102] Example 1

[0103] The preparation method of the magnesium alloy conical cylinder comprises the following steps:

[0104] (1) A magnesium alloy ingot with a diameter of 410 mm and a length of 3000 mm was prepared by an electromagnetic semi-continuous casting method, followed by stress relief annealing at 250° C. for 12 h, followed by homogenization at 500° C. for 20 h, followed by air cooling to room temperature, and then machining, peeling, and blanking to obtain an annealed ingot; wherein the magnesium alloy ingot has the following mass percentage composition: Mg-9.07Gd-2.18Y-0.33Zr-0.21Ag-0.23Er;

[0105] (2) The annealed ingot was kept at 510°C for 11 hours, and the upper and lower anvils were preheated to 350°C. Then, on a 3000-ton vertical hydraulic press, the annealed ingot was subjected to two forging passes along the X direction of the annealed ingot at a speed of 6 mm / s and a pass reduction of 40% with the height of the annealed ingot as the Z direction. Then, the annealed ingot was subjected to two forging passes along the Y direction of the annealed ingot at a speed of 6 mm / s and a pass reduction of 40% to press the cylinder into a hexahedron. Then, the hexahedron was rolled forged six times with the Z direction as the axis to press the hexahedron into a dodecahedron to obtain a blank; wherein, the deformation of a single pass of the rolling forging was 20%;

[0106] (3) Repeat step (2) twice to obtain a cylindrical first ingot with a diameter of 500 mm and a height of 620 mm;

[0107] (4) The first ingot obtained in step (3) is kept at 500° C. for 8 hours, the upper and lower flat anvils are preheated to 300° C., and forged along the diameter direction of the first ingot on a vertical hydraulic press to obtain an ingot blank; wherein the forging speed is 4 mm / s, the single-pass reduction is 5%, and the number of passes is 6;

[0108] (5) Repeat step (4) 4 times to obtain a second cylindrical ingot with a diameter of 300 mm and a height of 1300 mm;

[0109] (6) One end of the second ingot obtained in step (5) is processed into a 60mm high and 8° conical surface, and the center of the other end is processed into a 10mm deep groove with an R of 80mm. Then, the ingot is kept at 480°C for 10 hours, and the mold is kept at 450°C for 15 hours. Subsequently, the conical surface of the second ingot is turned downward in a 12,500-ton hydraulic press, and a flat die is used for die forging. The forging speed is 3mm / s, the pressing amount is 300mm, and the deformation ratio is 0.4. A conical magnesium alloy ingot with a diameter of 1000mm was prepared; the ingot was then kept at 480°C for 5 hours, the mold was kept at 450°C for 5 hours, and the ingot was placed with the cone side facing downward in a 12,500-ton hydraulic press. The ingot was then subjected to secondary die forging using the upper cone die at a forging speed of 3mm / s, a reduction of 600mm, and a deformation ratio of 0.83, resulting in a conical barrel with a top diameter of 250mm, a bottom outer diameter of 530mm, a height of 1000mm, a wall thickness of 86mm, and a barrel depth of 800mm.

[0110] (7) The conical tube obtained in step (6) is subjected to solution treatment at a temperature of 420° C. for 120 min, then quenched in hot water at 70° C., and then subjected to aging treatment at a temperature of 220° C. for 16 h, and air-cooled to room temperature to obtain a magnesium alloy conical tube.

[0111] The magnesium alloy conical cylinder prepared in Example 1 was subjected to performance testing according to the test standard GBT 16865-2013 Specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products. The test results were as follows: room temperature mechanical properties: tensile strength 419 MPa, yield strength 328 MPa, elongation 10%; 250°C mechanical properties: tensile strength 351 MPa, yield strength 262 MPa, elongation 15.0%.

[0112] Example 2

[0113] The preparation method of the magnesium alloy conical cylinder comprises the following steps:

[0114] (1) A magnesium alloy ingot with a diameter of 420 mm and a length of 3000 mm was prepared by an electromagnetic semi-continuous casting method, followed by stress relief annealing at 250° C. for 12 h, followed by homogenization at 500° C. for 20 h, followed by air cooling to room temperature, and then machining, peeling, and blanking to obtain an annealed ingot; wherein the magnesium alloy ingot has the following mass percentage composition: Mg-8.95Gd-2.76Y-0.40Zr-0.21Ag-0.14Er;

[0115] (2) The annealed ingot was kept at 510°C for 12 hours, and the upper and lower anvils were preheated to 350°C. Then, the ingot was forged in two passes along the X direction of the annealed ingot at a speed of 8 mm / s and a pass reduction of 30% on a 3000-ton vertical hydraulic press, with the height of the ingot as the Z direction. Then, the ingot was forged in two passes along the Y direction of the annealed ingot at a speed of 6 mm / s and a pass reduction of 40% to press the cylinder into a hexahedron. Then, the hexahedron was rolled forged in four passes with the Z direction as the axis to press the hexahedron into a dodecahedron to obtain a blank. The deformation of the rolling forging in a single pass was 15%.

[0116] (3) Repeat step (2) twice to obtain a cylindrical first ingot with a diameter of 500 mm and a height of 610 mm;

[0117] (4) The first ingot obtained in step (3) is kept at 500° C. for 8 hours, the upper and lower flat anvils are preheated to 250° C., and forged along the diameter direction of the first ingot on a vertical hydraulic press to obtain an ingot blank; wherein the forging speed is 5 mm / s, the single-pass reduction is 5%, and the number of passes is 6;

[0118] (5) Repeat step (4) 4 times to obtain a second cylindrical ingot with a diameter of 290 mm and a height of 1320 mm;

[0119] (6) One end of the second ingot obtained in step (5) is processed into a 60mm high and 8° conical surface, and the center of the other end is processed into a 10mm deep groove with an R of 80mm. Then, the ingot is kept at 480°C for 11 hours, and the mold is kept at 450°C for 15 hours. Subsequently, the conical surface of the second ingot is turned downward in a 12,500-ton hydraulic press, and a die forging is performed with an upper flat die. The forging speed is 4mm / s, the pressing amount is 300mm, and the deformation ratio is 0.2, so as to obtain a high A conical magnesium alloy ingot with a diameter of 1000mm was prepared; the ingot was then kept at 480°C for 4 hours, the mold was kept at 450°C for 5 hours, and the ingot was placed with the cone side facing downward in a 12,500-ton hydraulic press. The ingot was then subjected to secondary die forging using the upper cone die at a forging speed of 4mm / s, a reduction of 600mm, and a deformation ratio of 0.75, resulting in a conical barrel with a top diameter of 250mm, a bottom outer diameter of 540mm, a height of 1000mm, a wall thickness of 90mm, and a barrel depth of 800mm.

[0120] (7) The conical tube obtained in step (6) is subjected to solution treatment at a temperature of 420° C. for 120 min, then quenched in hot water at 70° C., and then subjected to aging treatment at a temperature of 220° C. for 16 h, and air-cooled to room temperature to obtain a magnesium alloy conical tube.

[0121] The magnesium alloy conical cylinder prepared in Example 2 was subjected to performance testing according to the test standard GBT 16865-2013 Specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products. The test results were as follows: room temperature mechanical properties: tensile strength 418 MPa, yield strength 326 MPa, elongation 10%; 250°C mechanical properties: tensile strength 363 MPa, yield strength 267 MPa, elongation 14.0%.

[0122] Example 3

[0123] The preparation method of the magnesium alloy conical cylinder comprises the following steps:

[0124] (1) A magnesium alloy ingot with a diameter of 410 mm and a length of 3000 mm was prepared by an electromagnetic semi-continuous casting method, followed by stress relief annealing at 250° C. for 12 h, followed by homogenization at 500° C. for 20 h, followed by air cooling to room temperature, and then machining, peeling, and blanking to obtain an annealed ingot; wherein the magnesium alloy ingot has the following mass percentage composition: Mg-8.85Gd-2.66Y-0.40Zr-0.20Ag-0.15Er;

[0125] (2) The annealed ingot was kept at 510°C for 12 hours, and the upper and lower anvils were preheated to 350°C. Then, the ingot was forged in two passes along the X direction of the annealed ingot at a speed of 10 mm / s and a pass reduction of 30% on a 3000-ton vertical hydraulic press, with the height of the annealed ingot as the Z direction. Then, the ingot was forged in two passes along the Y direction of the annealed ingot at a speed of 10 mm / s and a pass reduction of 40% to press the cylinder into a hexahedron. Then, the hexahedron was rolled forged in four passes with the Z direction as the axis to press the hexahedron into a dodecahedron to obtain a blank; wherein the deformation of a single pass of the rolling forging was 10%;

[0126] (3) Repeat step (2) twice to obtain a cylindrical first ingot with a diameter of 500 mm and a height of 610 mm;

[0127] (4) The first ingot obtained in step (3) is kept at 500° C. for 8 hours, the upper and lower flat anvils are preheated to 250° C., and forged along the diameter direction of the first ingot on a vertical hydraulic press to obtain an ingot blank; wherein the forging speed is 5 mm / s, the single-pass reduction is 20%, and the number of passes is 8;

[0128] (5) Repeat step (4) 4 times to obtain a second cylindrical ingot with a diameter of 290 mm and a height of 1320 mm;

[0129] (6) One end of the second ingot obtained in step (5) is processed into a 60mm high and 8° conical surface, and the center of the other end is processed into a 10mm deep groove with an R of 80mm. Then, the ingot is kept at 480°C for 11 hours, and the mold is kept at 450°C for 15 hours. Subsequently, the conical surface of the second ingot is turned downward in a 12,500-ton hydraulic press, and a die forging is performed with an upper flat die. The forging speed is 4mm / s, the pressing amount is 300mm, and the deformation ratio is 0.2, so as to obtain a high A conical magnesium alloy ingot with a diameter of 1000mm was prepared; the ingot was then kept at 480°C for 4 hours, the mold was kept at 450°C for 5 hours, and the ingot was placed with the cone side facing downward in a 12,500-ton hydraulic press. The ingot was then subjected to secondary die forging using the upper cone die at a forging speed of 4mm / s, a reduction of 600mm, and a deformation ratio of 0.75, resulting in a conical barrel with a top diameter of 250mm, a bottom outer diameter of 540mm, a height of 1000mm, a wall thickness of 90mm, and a barrel depth of 800mm.

[0130] (7) The conical tube obtained in step (6) is subjected to solution treatment at a temperature of 420° C. for 120 min, then quenched in hot water at 70° C., and then subjected to aging treatment at a temperature of 220° C. for 16 h, and air-cooled to room temperature to obtain a magnesium alloy conical tube.

[0131] The magnesium alloy conical cylinder prepared in Example 3 was subjected to performance testing according to the test standard GBT 16865-2013 Specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products. The test results were as follows: room temperature mechanical properties: tensile strength 425 MPa, yield strength 331 MPa, elongation 11%; 250°C mechanical properties: tensile strength 360 MPa, yield strength 261 MPa, elongation 14.0%.

[0132] It can be seen from the above examples that the magnesium alloy conical cylinder prepared by the preparation method provided by the present invention has excellent mechanical properties.

[0133] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a magnesium alloy tapered cylinder, comprising the following steps: (1) annealing the magnesium alloy ingot to obtain an annealed ingot; (2) performing multi-directional forging on the annealed ingot obtained in step (1) to obtain a first ingot; (3) performing bidirectional drawing forging on the first ingot obtained in step (2) to obtain a second ingot; (4) forging the second ingot obtained in step (3) to obtain a tapered cylinder; (5) subjecting the conical cylinder obtained in step (4) to T6 heat treatment to obtain a magnesium alloy conical cylinder; The multidirectional forging in step (2) is as follows: 1) keeping the annealed ingot warm, then forging the ingot along the X direction and / or Y direction with the height of the ingot as the Z direction, and then rolling forging the ingot with the Z direction as the axis to obtain a billet; the holding temperature is 450-520° C. and the holding time is 10-20 hours; 2) Repeating step 1) to obtain a first ingot; The second ingot is processed and kept warm in sequence before die forging; the processing is to process one end of the second ingot into a tapered surface and the center of the other end into a groove; The die forging in step (4) consists of a primary die forging and a secondary die forging performed sequentially; During the one-time die forging, the conical surface of the second ingot faces downward; during the one-time die forging, an upper flat die is used for die forging; During the secondary die forging, the conical surface of the product obtained by the primary die forging faces downward; during the secondary die forging, an upper conical die is used for die forging.

2. The preparation method according to claim 1, characterized in that In the step 1), the reduction speed of forging along the X direction and / or Y direction of the annealed ingot is 6-10 mm / s, and the reduction of a single pass of forging along the X direction and / or Y direction of the annealed ingot is 20-40%.

3. The preparation method according to claim 1, characterized in that The number of rolling forging passes in step 1) is 3 to 6, and the deformation amount of a single rolling forging pass is 10 to 20%.

4. The preparation method according to claim 1, characterized in that The bidirectional drawing forging in step (3) comprises the following steps: ① The first ingot is kept warm, and then forged along the diameter direction of the first ingot to obtain an ingot blank; ② Repeat step ① to obtain a second ingot.

5. The preparation method according to claim 4, characterized in that In the step ①, the forging reduction speed is 3-6 mm / s, the forging reduction in a single pass is 5-20%, and the number of forging passes is 2-8.

6. The preparation method according to claim 1, characterized in that The forging speed of the primary die forging is 2-5 mm / s, and the deformation ratio of the primary die forging is 0.20-0.40; the forging speed of the secondary die forging is 2-5 mm / s, and the deformation ratio of the secondary die forging is 0.75-0.

83.

7. The magnesium alloy tapered cylinder prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the magnesium alloy conical tube according to claim 7 in missiles.