A VW93M magnesium alloy inclined wall barrel forging and its preparation method and application

Abstract

The present invention provides a VW93M magnesium alloy oblique wall cylindrical forging, a preparation method and an application, and belongs to the technical field of magnesium alloy deformation processing. The present invention performs graded homogenization annealing on the VW93M magnesium alloy ingot, performs upsetting and blanking on the obtained homogenized ingot, performs upsetting treatment and rounding forging shaping on the obtained upsetting forging billet in sequence, performs die forging shaping on the obtained rounding forging billet, and then performs T5 heat treatment to obtain the VW93M magnesium alloy oblique wall cylindrical forging. The present invention is based on the high-strength and heat-resistant VW93M magnesium alloy, which has a lower density than aluminum alloy. The composite forming process of upsetting and blanking + rounding forging shaping + die forging is adopted to successfully prepare the VW93M magnesium alloy oblique wall cylindrical forging with excellent comprehensive mechanical properties, which is suitable for preparing missile cabins.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium alloy deformation processing, and in particular to a VW93M magnesium alloy inclined-wall cylindrical forging, a preparation method and an application thereof. Background Art

[0002] In order to reduce the resistance during flight, the missile shell is usually designed with a certain taper shape, so the missile mid-section compartment is usually required to be made into a sloping wall cylindrical component, and because it involves the connection between compartments, one end of the cabin must be designed with a large-sized end frame or flange ring structure for bolt connection. At present, this type of sloping wall cylindrical cabin cannot be made by ring rolling process, so the cabin is usually made of aluminum trusses and aluminum skin riveted, and the flange ring (end frame) is usually made by cutting aluminum plates. The two are usually connected by bolts. The missile cabin made by this method involves the use of a large number of aluminum and steel (titanium, aluminum) rivets (bolts), the assembly process is cumbersome, and the total mass of the cabin is large.

[0003] Magnesium alloy is the lightest metal structural material currently available in industry. Chinese patent CN117259635B discloses a method for preparing VW93M magnesium alloy medium and thick plates, which is specifically prepared by multiple high-speed multi-directional free forging. The VW93M magnesium alloy medium and thick plates have high strength and good plasticity. The shape of the forging has an important influence on the selection of the forming process, the formulation of the process route and the mechanical properties. How to prepare the inclined wall barrel forging with excellent comprehensive mechanical properties is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to provide a VW93M magnesium alloy inclined-wall cylindrical forging, a preparation method and an application thereof. The density of the VW93M magnesium alloy in the present invention is smaller than that of the aluminum alloy, and the VW93M magnesium alloy inclined-wall cylindrical forging has excellent comprehensive mechanical properties and is suitable for preparing a missile cabin.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a VW93M magnesium alloy inclined-wall cylindrical forging, comprising the following steps:

[0007] The VW93M magnesium alloy ingot is subjected to graded homogenization annealing to obtain a homogenized ingot;

[0008] The homogenized ingot is subjected to upsetting and drawing to obtain an upsetting and drawing forging billet; each upsetting and drawing includes sequentially performing upsetting treatment, drawing treatment and heat preservation treatment, the number of upsetting and drawing is 1-2 times, the pressing amount in the main deformation direction of the upsetting treatment in each upsetting and drawing is not less than 30%, and the forging speed of each upsetting and drawing is independently 1-10 mm / s;

[0009] The upsetting forging blank is subjected to upsetting treatment and rounding forging in sequence to obtain a rounding forging blank; the upsetting forging blank is subjected to upsetting treatment with a reduction amount of not less than 30% in the main deformation direction, and the forging speed is 1-10 mm / s; the rounding forging includes multiple rounding forging treatments performed in the radial direction, and the deformation amount of each rounding forging treatment does not exceed 8%;

[0010] The rounded forging blank is die-forged to obtain a formed forging; the die-forging speed is 0.1-6 mm / s;

[0011] The formed forging is subjected to T5 heat treatment to obtain the VW93M magnesium alloy inclined-wall cylindrical forging.

[0012] Preferably, the diameter of the VW93M magnesium alloy ingot is 400-550 mm; the graded homogenization annealing includes sequentially performing a first annealing and a second annealing; the temperature of the first annealing is 400-440° C., and the holding time is 5-8 h; the temperature of the second annealing is 500-540° C., and the holding time is 20-25 h.

[0013] Preferably, before the upsetting and drawing of the blank, the method further comprises: cutting the homogenized ingot to obtain a cast rod with a diameter of 400-500 mm and a length of 800-1250 mm.

[0014] Preferably, a first heat treatment is further performed between the cutting and upsetting of the blank, wherein the temperature of the first heat treatment is 420-530° C. and the holding time is 7-11 hours.

[0015] Preferably, each time the upsetting treatment in the upsetting and drawing process is performed, the upsetting treatment is performed once to a target height, and the drawing treatment is performed 8 to 12 times to a target height; each time the insulation treatment in the upsetting and drawing process is performed, the temperature is independently 420 to 500° C., and the insulation treatment time is independently 2 to 3 hours.

[0016] Preferably, the upsetting treatment of the forging blank is performed by forging to a target height in one time; and the number of the rounding forging treatment does not exceed 8 times.

[0017] Preferably, before the die forging, the process further includes: subjecting the rounded forging blank to a second heat treatment, wherein the temperature of the second heat treatment is 420-500° C., and the holding time is 7-11 hours.

[0018] Preferably, the temperature of the T5 heat treatment is 200-250° C., and the holding time is 14-24 hours.

[0019] The present invention provides a VW93M magnesium alloy inclined-wall cylindrical forging prepared by the preparation method described in the above technical solution.

[0020] The present invention provides the use of the VW93M magnesium alloy inclined-wall cylindrical forging described in the above technical solution in the preparation of a missile cabin.

[0021] Beneficial effect: Based on the wide temperature range high-strength and toughness VW93M magnesium alloy, the present invention adopts the composite forming process of upsetting and drawing billet + rolling forging shaping + die forging forming to successfully prepare VW93M magnesium alloy inclined wall barrel forging. The density of VW93M magnesium alloy is smaller than that of aluminum alloy, and the VW93M magnesium alloy inclined wall barrel forging has excellent comprehensive mechanical properties and is suitable for preparing missile cabins. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a physical picture of a magnesium alloy ingot with a diameter of 460 mm obtained after semi-continuous casting in Example 1 of the present invention;

[0023] Figure 2 This is a physical picture of the rounded forging blank obtained after rounding forging in Example 1 of the present invention;

[0024] Figure 3 This is a physical picture of the VW93M magnesium alloy inclined-wall cylindrical forging prepared in Example 1 of the present invention;

[0025] Figure 4 This is a low-magnification metallographic structure characterization image of the VW93M magnesium alloy oblique-walled cylindrical forging prepared in Example 1;

[0026] Figure 5 This is a high-magnification electron backscatter diffraction (EBSD) characterization image of the VW93M magnesium alloy oblique-walled barrel-shaped forging prepared in Example 1;

[0027] Figure 6 This is the tensile fracture morphology of the VW93M magnesium alloy inclined-wall barrel forging prepared in Example 1. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a VW93M magnesium alloy inclined-wall cylindrical forging, comprising the following steps:

[0029] The VW93M magnesium alloy ingot is subjected to graded homogenization annealing to obtain a homogenized ingot;

[0030] The homogenized ingot is subjected to upsetting and drawing to obtain an upsetting and drawing forging billet; the upsetting and drawing is performed 1 to 2 times, each upsetting and drawing includes sequentially performing upsetting treatment, drawing treatment and heat preservation treatment, the pressing amount in the main deformation direction of the upsetting treatment in each upsetting and drawing is not less than 30%, and the forging speed of each upsetting and drawing is independently 1 to 10 mm / s;

[0031] The upsetting forging blank is subjected to upsetting treatment and rounding forging in sequence to obtain a rounding forging blank; the upsetting forging blank is subjected to upsetting treatment with a reduction amount of not less than 30% in the main deformation direction, and the forging speed is 1-10 mm / s; the rounding forging includes multiple rounding forging treatments performed in the radial direction, and the deformation amount of each rounding forging treatment does not exceed 8%;

[0032] The rounded forging blank is die-forged to obtain a formed forging; the die-forging speed is 0.1-6 mm / s;

[0033] The formed forging is subjected to T5 heat treatment to obtain a VW93M magnesium alloy inclined-wall cylindrical forging.

[0034] At present, in the relevant technology, the middle section of the missile compartment is usually required to be made into a sloping wall cylindrical component. A large amount of aluminum alloy is used when preparing the missile cabin, and a large number of steel (titanium, aluminum) rivets (bolts) are used. The assembly process is cumbersome and the total mass of the cabin is large. Compared with aluminum alloys, the comprehensive mechanical properties of Mg-Gd-Y-Zr alloys, such as high temperature mechanical properties and low temperature mechanical properties, are excellent, and the density is about 1 / 3 lower than that of aluminum alloys. Since the diameter and depth of the sloping wall cylindrical component are large, and the barrel wall has a certain taper, it is difficult to prepare the sloping wall cylindrical forgings by forging process, and the preparation of large-size free forging forging blanks of high-quality high rare earth magnesium alloys is also difficult. At present, there is no relevant research and successful cases on the preparation process of high-strength magnesium alloy sloping wall cylindrical forgings. Based on high-strength and heat-resistant VW93M magnesium alloy, the present invention adopts a composite forming process of upsetting and drawing the blank + rolling forging shaping + die forging forming, and successfully prepares VW93M magnesium alloy sloping wall cylindrical forgings with excellent comprehensive mechanical properties, which are suitable for preparing missile cabins. The method of the present invention is described in detail below.

[0035] The present invention performs graded homogenization annealing on a VW93M magnesium alloy ingot to obtain a homogenized ingot. As an embodiment of the present invention, the diameter (Φ) of the VW93M magnesium alloy ingot may be 400-550 mm, further may be 440-480 mm, specifically may be 440 mm, 450 mm, 460 mm, 470 mm or 480 mm; in terms of mass percentage, the composition of the VW93M magnesium alloy ingot may include: Gd 8.0-9.6%, Y 1.8-3.2%, Zr 0.3-0.7%, Ag 0.02-0.5%, Er 0.02-0.3%, and the rest is Mg and unavoidable impurities; further may include: Gd 8.8-9.2%, Y 2.0-2.6%, Zr 0.4-0.5%, Ag0.1-0.3%, Er 0.2-0.3%, and the rest is Mg and unavoidable impurities; specifically may include: Gd 8.98%, Y 2.33%, Zr0.44%, Ag 0.24%, Er 0.28%, and the rest are Mg and inevitable impurities. As an embodiment of the present invention, the VW93M magnesium alloy ingot can be prepared by a semi-continuous casting method. The present invention does not specifically limit the specific operating steps and conditions of the semi-continuous casting method, and the operating steps and conditions familiar to those skilled in the art can be adopted. In the embodiment of the present invention, the semi-continuous casting method can be used to prepare high-quality VW93M magnesium alloy ingots, which can reduce defects such as inclusions, pores, looseness, and center cracks. Controlling the number of defects can reduce its cracking tendency in the subsequent deformation process and improve the formability of the magnesium alloy in the subsequent forging and die forging deformation process.

[0036] As an embodiment of the present invention, the graded homogenization annealing may include sequentially performing a first annealing and a second annealing; the temperature of the first annealing may be 400-440°C, specifically 400°C, 410°C, 420°C, 430°C or 440°C, and the holding time may be 5-8h, specifically 5h, 6h, 7h or 8h; the temperature of the second annealing may be 500-540°C, specifically 500°C, 510°C, 520°C, 530°C or 540°C, and the holding time may be 20-25h, specifically 20h, 21h, 22h, 23h, 24h or 25h. In an embodiment of the present invention, the VW93M magnesium alloy ingot may be heated to the temperature of the first annealing with the furnace, and the first annealing may be performed by holding the temperature; then the temperature may be heated to the temperature of the second annealing, and the second annealing may be performed by holding the temperature, and finally air-cooled to room temperature. The purpose of adopting graded homogenization annealing in the embodiment of the present invention is to ensure that the large-sized ingot is heated steadily during the homogenization process, avoid cracking caused by sudden temperature changes, and make the organizational composition uniform, improve plasticity, and reduce deformation resistance.

[0037] After obtaining the homogenized ingot, the present invention performs upsetting and drawing of the homogenized ingot to obtain an upsetting and drawing forging billet. As an embodiment of the present invention, the process before upsetting and drawing may also include: cutting the homogenized ingot to obtain a cast rod with a diameter of 400-500 mm and a length of 800-1350 mm; the diameter of the cast rod may further be 400-430 mm, specifically 400 mm, 410 mm, 420 mm or 430 mm; the length may further be 900-1250 mm, specifically 900 mm, 950 mm, 1000 mm, 1050 mm, 1100 mm, 1150 mm, 1200 mm or 1250 mm. As an embodiment of the present invention, the process before cutting may also include sequentially performing mechanical car body and flaw detection. The present invention does not specifically limit the specific operating steps and conditions of the mechanical car body and flaw detection, and the operating steps and conditions familiar to those skilled in the art may be used.

[0038] As an embodiment of the present invention, a first heat treatment may be included between the cutting and the upsetting and drawing of the blank. The temperature of the first heat treatment may be 420-530°C, specifically 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C or 530°C; the insulation time may be 7-11h, specifically 7h, 8h, 9h, 10h or 11h.

[0039] In the present invention, the number of times of upsetting and drawing the blank can be 1 to 2 times, and each time the upsetting and drawing of the blank includes upsetting treatment, drawing treatment and heat preservation treatment in sequence. The pressing amount of the main deformation direction (i.e., axial direction) of the upsetting treatment in each upsetting and drawing of the blank is not less than 30%, for example, it can be 30 to 50%, specifically 30%, 35%, 40%, 45% or 50%; the forging speed of each upsetting and drawing of the blank is independently 1 to 10 mm / s, and can further be 1 to 5 mm / s, specifically 1 mm / s, 2 mm / s, 3 mm / s, 4 mm / s or 5 mm / s.

[0040] As an embodiment of the present invention, each time the upsetting treatment in the upsetting and drawing process can be a one-time forging to the target height; the drawing process can be a forging to the target height after 8 to 12 times, specifically 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, 11 times or 12 times, and the pressing amount of each forging during the drawing process can be 10 to 30%, specifically 10%, 15%, 20%, 25% or 30%. In the embodiment of the present invention, the upsetting process is forged to the target height once to ensure forgeability; the number of forging times during the drawing process is limited to the above range, in order to avoid insufficient deformation due to insufficient times, and to avoid cracking caused by excessive temperature reduction due to excessive forging times.

[0041] As an embodiment of the present invention, the temperature of the heat preservation treatment in each upsetting and drawing process can be independently 420-500°C, specifically 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C or 500°C; the time of the heat preservation treatment can be independently 2-3h, specifically 2h, 2.5h or 3h. In the embodiment of the present invention, the heat preservation treatment conditions are limited to the above range, which not only avoids the risk of overburning, but also ensures the good plastic deformation ability of the magnesium alloy; if the temperature is too high, there is a risk of overburning, and if the temperature is too low, it is easy to cause cracking.

[0042] As an embodiment of the present invention, the length of the upsetting and forging blank may be 400-700 mm, specifically 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm or 700 mm.

[0043] As an embodiment of the present invention, taking the number of times of upsetting and drawing to open the blank as 2 times as an example, specifically, the homogenized ingot is sequentially subjected to the first upsetting treatment, the first drawing treatment, the first insulation treatment, the second upsetting treatment, the second drawing treatment and the second insulation treatment; wherein the length of the forging blank after the first upsetting treatment can be 400-600 mm (specifically 400 mm, 450 mm, 500 mm, 550 mm or 600 mm, preferably 400 mm), and the length of the forging blank after the first drawing treatment can be 500-700 mm (specifically 500 mm, 550 mm, 600 mm, 650 mm or 700 mm). m, preferably 500mm), then the forging blank is heat-treated at 420~500℃ for 2~3h; after the forging blank is taken out of the furnace and subjected to the second upsetting treatment, the length of the forging blank can be 400~600mm (specifically 400mm, 450mm, 500mm, 550mm or 600mm, preferably 450mm), and the length of the forging blank after the second drawing treatment can be 500~700mm (specifically 500mm, 550mm, 600mm, 650mm or 700mm, preferably 500mm), then the forging blank is heat-treated at 420~500℃ for 2~3h to obtain an upsetting and drawing forging blank. The purpose of using multiple upsetting treatments and drawing treatments in the embodiment of the present invention is to forge to eliminate casting defects in the magnesium alloy, improve the alloy structure, ensure the plasticity of subsequent deformation and reduce the risk of cracking.

[0044] As an embodiment of the present invention, the upsetting and drawing of the blank can be specifically performed on a hydraulic press. Before the upsetting and drawing of the blank, the upper template and the lower template used can be preheated to 360-460°C, specifically 400°C.

[0045] After obtaining the upsetting forging blank, the present invention sequentially performs upsetting treatment and rounding forging shaping on the upsetting forging blank to obtain a rounding forging blank. In the present invention, the pressing amount in the main deformation direction of the upsetting forging blank is not less than 30%, for example, it can be 30~50%, specifically 30%, 35%, 40%, 45% or 50%; the forging speed is 1~10mm / s, further can be 1~5mm / s, specifically 1mm / s, 2mm / s, 3mm / s, 4mm / s or 5mm / s. As an embodiment of the present invention, the upsetting forging blank can be forged to the target height in one time. In the present invention, the rounding forging shaping includes multiple rounding forging treatments performed in the radial direction, and the deformation amount of each rounding forging treatment does not exceed 8%, for example, it can be 3~8%, specifically 3%, 4%, 5%, 6%, 7% or 8%. As an embodiment of the present invention, the number of times of the spherical forging treatment may not exceed 8 times, for example, may be 3 to 8 times, specifically 3 times, 4 times, 5 times, 6 times, 7 times or 8 times.

[0046] As an embodiment of the present invention, the rounded forging blank is in the shape of a round cake, and the end face diameter can be 700-850 mm, specifically 700 mm, 730 mm, 745 mm, 780 mm, 810 mm or 850 mm, preferably 745 mm; the maximum diameter can be 770-850 mm, specifically 770 mm, 800 mm, 820 mm or 850 mm, preferably 770 mm; the height can be 250-340 mm, specifically 250 mm, 280 mm, 300 mm, 330 mm, 332 mm or 340 mm, preferably 330-332 mm.

[0047] As an embodiment of the present invention, the upset forging blank is subjected to one upsetting treatment to obtain a cylindrical forging blank with a height of 350-450 mm (specifically 440-450 mm), and then the cylindrical surface is subjected to no more than 8 rounding forging treatments until there is no bulging at the waist (i.e., the forging direction covers the entire forging blank along the circumferential direction), and finally cooled in air to obtain a round cake-shaped forging blank (i.e., rounding forging blank). The purpose of performing multiple multi-directional small deformation rounding forging treatments in the radial direction in the embodiment of the present invention is to increase the deformation of the outer side of the cylindrical forging blank, so as to achieve the purpose of enhancing the uniformity of the structure, reducing the amount of subsequent cutting processing, and improving the material utilization rate.

[0048] In the embodiment of the present invention, the homogenized ingot is subjected to upsetting and blanking, and the upsetting and forging blank is subjected to upsetting treatment and rounding forging shaping in sequence, specifically, free forging blanking. By reasonably formulating the forging temperature (i.e., the temperature of the insulation treatment), forging speed, forging times and reduction amount, it is beneficial to maintain good plastic deformation ability while avoiding cracking of the magnesium alloy. The embodiments of the present invention have been verified by a large number of experiments, and the results show that a forging temperature of 420-500°C, a single pressing reduction of 30-50% (specifically 40%) for upsetting treatment, a single pressing reduction of 10-30% (specifically 15%) for drawing treatment, and multiple multi-directional small strain rolling forging treatments are performed to increase the uniformity of the billet structure and reduce the bulging amplitude of the forging waist to achieve the purpose of reducing the subsequent cutting amount and improving material utilization. This set of forging processes is combined with a forging speed of 1-10 mm / s (further 1-5 mm / s) to successfully forge a round cake-shaped forging billet with no cracks on the surface (i.e., a rounded forging billet).

[0049] After obtaining the rounded forging blank, the present invention performs die forging on the rounded forging blank to obtain a formed forging. As an embodiment of the present invention, the die forging may also include: performing a second heat treatment on the rounded forging blank, the temperature of the second heat treatment may be 420-500°C, specifically 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C or 500°C; the holding time may be 7-11h, specifically 7h, 8h, 9h, 10h or 11h. In the embodiment of the present invention, the conditions of the second heat treatment are limited to the above range, which not only avoids the risk of overburning, but also ensures the good plastic deformation ability of the magnesium alloy; if the temperature is too high, there is a risk of overburning, and if the temperature is too low, it is easy to cause cracking.

[0050] As an embodiment of the present invention, the second heat treatment may also include: turning the rounded forging blank into a cylindrical forging blank with a diameter of 720~820mm (specifically 750mm) and a height of 280~340mm (specifically 325mm), and performing flaw detection; then setting a double-sided chamfer of R20, and grinding a concave positioning recess with a depth of 5mm and a diameter of 100mm in the center of both sides of the circular forging blank. In the embodiment of the present invention, before die forging, the upper and lower surfaces of the circular forging blank are chamfered with a size of R20 to avoid the problem of cracking caused by local stress concentration in the forging blank during the die forging process; the concave positioning recesses on both sides of the circular forging blank are ground so that the forging blank can be placed in the center during the subsequent die forging to ensure that the metal material flows evenly in all directions along the circumference.

[0051] As an embodiment of the present invention, the die used for the die forging includes an upper die and a lower die; the upper die is a truncated cone punch with a 5° draft angle, the bottom height of the lower die (die) ≤ 100mm (i.e. 0~100mm) is a straight-wall cavity, and the bottom height of the lower die (die) > 100mm is an inclined-wall cavity with a 0.5° draft angle; before the die forging, the upper die and the lower die can be preheated to 380~480℃ (specifically 400℃) and kept warm for 15h. In the embodiment of the present invention, the bottom of the die is designed as a straight-wall cavity so that the forging blank can be placed in the center during the subsequent die forging to ensure that the metal material flows uniformly in all directions along the circumference; preheating the upper die and the lower die to the above temperature range can not only make up for the temperature loss of the forging during the forging process, but also have a better insulation effect on the forging to ensure the deformation ability of the magnesium alloy, and to a certain extent improve the production efficiency.

[0052] In the present invention, the die forging molding speed (the downward speed of the upper die) is 0.1-6 mm / s, specifically 0.1 mm / s, 0.2 mm / s, 0.3 mm / s, 0.4 mm / s, 0.6 mm / s, 0.8 mm / s, 1 mm / s, 2 mm / s, 3 mm / s, 4 mm / s, 5 mm / s or 6 mm / s. The present invention adopts die forging molding, and ensures the performance consistency of each product by adopting a program-controlled die pressing speed, ensures the precise product shape and size, and provides guarantee for mass production. As an embodiment of the present invention, during die forging, the mold is pressed to close (the upper mold body can be pressed to a pressure of 35-40 mm before stopping forging), and a cylindrical component with an inclined wall with a bottom is obtained, the height of which is 700-800 mm, the outer diameter of the bottom is 720-760 mm, the outer diameter of the ring is 820-860 mm, the wall thickness is 50-90 mm, and the bottom thickness is 30-50 mm; the cylindrical component with an inclined wall is demolded and quenched in water to obtain a formed forging. As an embodiment of the present invention, during die forging, when the upper mold is pressed to a predetermined pressure, it should be ensured that the metal material does not overflow from the die mouth, resulting in a large area of ​​direct contact between the metal material and the air, so as to reduce the temperature drop of the ring part of the forging and improve the performance consistency of various parts of the forging. As an embodiment of the present invention, the total transfer time for quenching and cooling the inclined-wall cylindrical component in water after demolding can be less than 300 seconds, wherein the total time from the inclined-wall cylindrical component contacting the water surface to being completely immersed in water can be 15 to 20 seconds.

[0053] The die-pressing deformation of large-sized magnesium alloys easily generates a large amount of deformation heat, resulting in overburning of the forging blank; and due to the friction of the extrusion barrel and uneven deformation on the surface, surface cracks are prone to occur. In the embodiment of the present invention, the die forging temperature and die forging speed are reasonably formulated to facilitate the smooth die forging, and the concave positioning nest is designed in the die forging stage, which is conducive to the uniform flow of the metal material in the circumferential direction. The embodiments of the present invention have been verified by a large number of experiments, and the results show that a die-pressing temperature of 420~500℃ (i.e., the temperature of the second heat treatment) and a die-pressing speed of 0.1~6mm / s can successfully forge a forged part with no surface cracks.

[0054] After obtaining the formed forging, the present invention performs T5 heat treatment on the formed forging to obtain a VW93M magnesium alloy inclined wall barrel forging. As an embodiment of the present invention, the temperature of the T5 heat treatment can be 200-250°C, specifically 200°C, 210°C, 220°C, 230°C, 240°C or 250°C; the insulation time can be 14-24h, specifically 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h; after the insulation is completed, it can be taken out of the furnace and air-cooled. In the embodiment of the present invention, by performing T5 heat treatment on the formed forging under the above conditions, precipitation strengthening is formed in the alloy matrix, so that it has excellent comprehensive mechanical properties.

[0055] The invention is based on high-strength and heat-resistant VW93M magnesium alloy, and adopts a composite forming process of upsetting and drawing blank + rolling forging shaping + die forging forming, and successfully prepares a wide temperature range high-strength and tough magnesium alloy inclined wall barrel forging blank for missile cabin with no surface cracks, uniform microstructure and performance, internal metallurgical quality ultrasonic flaw detection reaching Class A standard, and excellent comprehensive mechanical properties. The blank can be used to replace other materials with large-sized inclined wall barrel-shaped complex components with longitudinal reinforcement ribs on the barrel wall, bottom plate, and end frames or flange rings on both ends of the barrel wall, thereby solving the problem that the inclined wall barrel-shaped complex structure blank is difficult to form; at the same time, the die forging and extrusion integrated forming process of the invention eliminates the bolt connection between the cabin facade and the cabin bottom end frame (flange ring) in the traditional missile cabin structure, thereby fundamentally improving the structural reliability, avoiding the risk of failure of bolted connectors under overload conditions at the connection part, and avoiding the risk of electrochemical corrosion caused by the connection of dissimilar metal materials, which is beneficial to the long-term storage and service of the missile cabin in harsh environments. For missile weapons, the use of magnesium alloy materials in the entire cabin helps to reduce weight, improve fuel efficiency, and enhance guidance accuracy, and has important application value.

[0056] The present invention provides a VW93M magnesium alloy inclined wall cylindrical forging prepared by the preparation method described in the above technical solution. As an embodiment of the present invention, the dimensions of the VW93M magnesium alloy inclined wall cylindrical forging can be: height of 700-800mm (specifically 730-736mm), bottom outer diameter of 720-760mm (specifically 740-750mm), bezel outer diameter of 820-860mm (specifically 830-840mm), wall thickness of 50-90mm (specifically 55-65mm), bottom thickness of 30-50mm (specifically 35-40mm).

[0057] As an embodiment of the present invention, the VW93M magnesium alloy inclined wall cylindrical forging has excellent comprehensive mechanical properties:

[0058] -55℃ axial yield strength ≥350MPa (specifically 366MPa), tensile strength ≥440MPa (specifically 466MPa), elongation ≥9% (specifically 10.1%); -55℃ tangential yield strength ≥320MPa (specifically 337MPa), tensile strength ≥430MPa (specifically 441MPa), elongation ≥9% (specifically 11.4%); -55℃ radial yield strength ≥240MPa (specifically 253MPa), tensile strength ≥370MPa (specifically 405MPa), elongation ≥7% (specifically 7.5%);

[0059] Room temperature axial yield strength ≥240MPa (specifically 256~261MPa), tensile strength ≥380MPa (specifically 404~410MPa), elongation ≥8% (specifically 8.2~11.9%); room temperature tangential yield strength ≥240MPa (specifically 243~265MPa), tensile strength ≥370MPa (specifically 381~403MPa), elongation ≥8% (specifically 9.0~11.9%); room temperature radial yield strength ≥200MPa (specifically 215~234MPa), tensile strength ≥340MPa (specifically 355~375MPa), elongation ≥5% (specifically 7.0~8.1%);

[0060] The axial yield strength at a high temperature of 200°C is ≥220MPa (specifically 241~251MPa), the tensile strength is ≥350MPa (specifically 352~359MPa), and the elongation is ≥10% (specifically 11.3~14.1%); the tangential yield strength at a high temperature of 200°C is ≥220MPa (specifically 228~248MPa), the tensile strength is ≥330MPa (specifically 340~352MPa), and the elongation is ≥10% (specifically 10.8~13.1%); the radial yield strength at a high temperature of 200°C is ≥200MPa (specifically 208~230MPa), the tensile strength is ≥300MPa (specifically 319~343MPa), and the elongation is ≥10% (specifically 10.5~12.3%).

[0061] The present invention provides the application of the VW93M magnesium alloy oblique wall cylindrical forgings described in the above technical solution in the preparation of missile cabins. The present invention adopts a magnesium alloy based on the Mg-Gd-Y-Zr alloy, and the VW93M magnesium alloy oblique wall cylindrical forgings prepared by forging and extrusion integrated molding technology can be used as a missile cabin blank, and a missile cabin structure with skin, reinforcement and flange ring (end frame) can be manufactured by machining in the later stage. On the one hand, the application of lightweight metal material magnesium alloy greatly reduces the weight of the cabin; on the other hand, this integrated molding process eliminates the mechanical connection between the truss and the side wall skin of the cabin cylinder, and the truss and the flange ring (end frame) at the bottom of the cabin cylinder, improves the structural reliability, and avoids the risk of electrochemical corrosion between dissimilar metal materials, which is conducive to the long-term storage and service of the missile cabin in harsh environments. The present invention does not specifically limit the specific application method of the VW93M magnesium alloy oblique wall cylindrical forgings, and the method well known to those skilled in the art can be used.

[0062] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part 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 creative work are within the scope of protection of the present invention.

[0063] Example 1

[0064] The composition of the magnesium alloy in this embodiment is Mg-8.98Gd-2.33Y-0.44Zr-0.24Ag-0.28Er, that is, by mass percentage, it includes Gd 8.98%, Y 2.33%, Zr 0.44%, Ag 0.24%, Er 0.28%, and the rest is Mg and unavoidable impurities; the method for preparing an inclined-wall cylindrical forging using the magnesium alloy with the above composition includes the following steps:

[0065] (1) According to the composition of the magnesium alloy, a magnesium alloy ingot with a diameter of 460 mm (such as Figure 1 shown);

[0066] (2) heating the magnesium alloy ingot to 400° C. and keeping the temperature for 5 h, then heating the magnesium alloy ingot to 510° C. and keeping the temperature for 20 h, and air cooling the ingot to room temperature to obtain a homogenized ingot;

[0067] (3) subjecting the homogenized ingot to mechanical lathing, flaw detection and cutting in sequence to obtain a cast rod having a diameter of 420 mm and a length of 1250 mm;

[0068] (4) The cast rod is heated to 500°C and kept at this temperature for 7 hours, and the cast rod after being kept at this temperature is placed on a hydraulic press (the upper and lower free forging mold plates used are preheated to 400°C) for two times of upsetting and drawing to obtain an upsetting and drawing forging billet; wherein the first upsetting and drawing billet is specifically performed in sequence: one upsetting treatment (one-time forging to a target height, specifically 400 mm), one drawing treatment (five times forging to a target height, specifically 500 mm), and keeping at 480°C for 7 hours. 2h; the second upsetting and drawing process is to carry out one upsetting treatment (one-time forging to the target height, specifically 450mm), one drawing treatment (five forgings to the target height, specifically 500mm), and keep warm at 470℃ for 2.5h; and the forging speed of each upsetting and drawing treatment is 3mm / s, the reduction amount in the main deformation direction (i.e. the axial direction of the cast rod) of each upsetting treatment is 40%, and the reduction amount of each drawing treatment is 15%;

[0069] The upset forging blank is subjected to one upsetting treatment and one rounding forging shaping in sequence, and the forging speed of the upsetting treatment is 3 mm / s, and the pressing amount in the main deformation direction (i.e., the axial direction of the cast rod) is 40%; wherein the upsetting treatment is forged to a target height (specifically, 450 mm) in one time, and the rounding forging shaping includes four rounding forging treatments (the deformation amount of each rounding forging treatment does not exceed 8%), and the rounding forging treatment is used to prevent the waist of the forging blank from bulging (i.e., the forging direction covers the circumferential direction of the entire forging blank), and finally cooled in air to obtain a round cake-shaped forging blank with an end face diameter of 745 mm, a maximum diameter of 770 mm, and a height of 330 mm (i.e., a rounding forging blank, such as Figure 2 shown);

[0070] (5) The rounded forging blank is turned into a cylindrical forging blank with a diameter of 750 mm and a height of 325 mm, and then flaw detection is performed; then a double-sided chamfer R20 (radius R20) is set, and a concave positioning recess with a depth of 5 mm and a diameter of 100 mm is ground on the center of both sides of the forging blank. The obtained forging blank is heated to 480°C and kept warm for 10 hours, and then die forged. The die used for the die forging includes an upper die and a lower die. The upper die is a truncated cone punch with a draft angle of 5°, and the bottom height of the lower die (die) is ≤100 mm (i.e., 0~100 mm). The straight-wall cavity, the bottom height of the lower die (die)> 100mm part is an inclined-wall cavity with a demoulding angle of 0.5°, the upper die and the lower die are preheated to 400°C before use and kept warm for 15 hours; during the die forging, the upper die has a downward speed of 1mm / s, and is pressed to close the die (forging is stopped when the upper die body is pressed to a pressure loss of 40mm), and a cylindrical component with an inclined wall with a bottom is obtained, the height of which is 730mm, the outer diameter of the bottom is 740mm, the outer diameter of the ring is 830mm, the wall thickness is 55mm, and the bottom thickness is 40mm, and then demolded and quenched in water to obtain a formed forging;

[0071] (6) The formed forging is subjected to T5 heat treatment, specifically, the formed forging is heated to 230° C. and kept at this temperature for 22 hours, and then taken out of the furnace and air-cooled after the end of the heat preservation, to obtain a VW93M magnesium alloy inclined-wall cylindrical forging (such as Figure 3 as shown).

[0072] Example 2

[0073] (1) Prepare a cast rod with a diameter of 420 mm and a length of 900 mm according to the method of Example 1;

[0074] (2) The cast rod is heated to 500°C and kept at this temperature for 7 hours, and the cast rod after being kept at this temperature is placed on a hydraulic press (the upper and lower free forging mold plates used are preheated to 400°C) for two times of upsetting and drawing to obtain an upsetting and drawing forging billet; wherein the first upsetting and drawing billet is specifically performed in sequence: one upsetting treatment (one-time forging to a target height, specifically 400 mm), one drawing treatment (forging to a target height, specifically 500 mm, after five times of forging), and keeping at 480°C for 7 hours. 2h; the second upsetting and drawing process is to carry out one upsetting treatment (one-time forging to the target height, specifically 450mm), one drawing treatment (five forgings to the target height, specifically 500mm), and keep warm at 470℃ for 2.5h; and the forging speed of each upsetting and drawing treatment is 3mm / s, the reduction amount in the main deformation direction (i.e. the axial direction of the cast rod) of each upsetting treatment is 40%, and the reduction amount of each drawing treatment is 15%;

[0075] The upset forging blank is subjected to one upsetting treatment and one rounding forging shaping in sequence, and the forging speed of the upsetting treatment is 3 mm / s, and the pressing amount in the main deformation direction (i.e., the axial direction of the cast rod) is 40%; wherein the upsetting treatment is forged to a target height (specifically, 450 mm) in one time, and the rounding forging shaping includes four rounding forging treatments (the deformation amount of each rounding forging treatment does not exceed 8%), and the rounding forging treatment is used to prevent the waist of the forging blank from bulging (i.e., the forging direction covers the circumferential direction of the entire forging blank), and finally cooled in air to obtain a round cake-shaped forging blank (i.e., the rounding forging blank) with an end face diameter of 745 mm, a maximum diameter of 770 mm, and a height of 332 mm;

[0076] (3) The rounded forging blank is turned into a round pancake-shaped forging blank with a diameter of 750 mm and a height of 325 mm, and then flaw detection is performed; then a double-sided chamfer R20 (radius R20) is set, and a concave positioning recess with a depth of 5 mm and a diameter of 100 mm is ground on the center of both sides of the forging blank. The obtained forging blank is heated to 480°C and kept warm for 10 hours, and then die forged. The die used for the die forging includes an upper die and a lower die. The upper die is a truncated cone punch with a draft angle of 5°, and the bottom height of the lower die (die) is ≤100 mm (i.e., 0~100 mm). The straight-wall cavity, the bottom height of the lower die (die)> 100mm part is an inclined-wall cavity with a demoulding angle of 0.5°, the upper die and the lower die are preheated to 400°C before use and kept warm for 15 hours; during the die forging, the upper die has a downward speed of 2mm / s, and is pressed to close the die (forging is stopped when the upper die body is pressed to a lack of pressure of 35mm), and a cylindrical component with an inclined wall with a bottom is obtained, the height of which is 736mm, the outer diameter of the bottom is 740mm, the outer diameter of the ring is 830mm, the wall thickness is 55mm, and the bottom thickness is 35mm, and then demolding is carried out and quenching and cooling is carried out in water to obtain a formed forging;

[0077] (4) The formed forging is subjected to T5 heat treatment, specifically, the formed forging is heated to 230° C. and kept at this temperature for 22 hours, and then taken out of the furnace and air-cooled after the end of the heat preservation, thereby obtaining a VW93M magnesium alloy inclined-wall cylindrical forging.

[0078] Test Example 1

[0079] The VW93M magnesium alloy inclined-wall cylindrical forging prepared in Example 1 was characterized as follows:

[0080] Figure 4 This is a low-magnification metallographic structure characterization diagram of the VW93M magnesium alloy oblique-walled barrel-shaped forging prepared in Example 1. The results show that the alloy structure of the VW93M magnesium alloy oblique-walled barrel-shaped forging is consistent, without obvious coarse precipitates or inclusions.

[0081] Figure 5The high-magnification electron backscatter diffraction (EBSD) characterization diagram of the VW93M magnesium alloy inclined-wall cylindrical forging prepared in Example 1, where (a) is a contrast diagram and (b) is an IPF diagram; the results show that the alloy of the VW93M magnesium alloy inclined-wall cylindrical forging is fully recrystallized and has a uniform structure.

[0082] Figure 6 This is a tensile fracture morphology of the VW93M magnesium alloy oblique-walled cylindrical forging prepared in Example 1 (a tensile specimen was taken along the axial direction of the forging). The results show that there are no obvious non-metallic inclusions in the VW93M magnesium alloy oblique-walled cylindrical forging.

[0083] Test Example 2

[0084] The mechanical properties of the VW93M magnesium alloy inclined wall cylindrical forgings prepared in Example 1 and Example 2 were tested according to GB / T228-2002, and the results are shown in Tables 1 to 3. As can be seen from Tables 1 to 3, the VW93M magnesium alloy inclined wall cylindrical forgings prepared in the present invention have excellent mechanical properties.

[0085] Table 1 Mechanical properties of VW93M magnesium alloy inclined wall barrel forgings in Examples 1 and 2 (room temperature)

[0086]

[0087] Table 2 Mechanical properties of VW93M magnesium alloy inclined wall barrel forgings in Examples 1 and 2 (200°C)

[0088]

[0089] Table 3 Mechanical properties of VW93M magnesium alloy inclined wall barrel forgings in Example 1 (-55℃)

[0090]

[0091] 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a VW93M magnesium alloy inclined-wall cylindrical forging, comprising the following steps: The VW93M magnesium alloy ingot is subjected to graded homogenization annealing to obtain a homogenized ingot; The homogenized ingot is subjected to upsetting and drawing to obtain an upsetting and drawing forging billet; the upsetting and drawing is performed 1 to 2 times, each time the upsetting and drawing includes sequentially performing upsetting treatment, drawing treatment and heat preservation treatment, the pressing amount in the main deformation direction of the upsetting treatment in each upsetting and drawing is not less than 30%, and the forging speed of each upsetting and drawing is independently 1 to 10 mm / s; the upsetting treatment in each upsetting and drawing is forged once to a target height, and the drawing treatment is forged 8 to 12 times to a target height; the temperature of the heat preservation treatment in each upsetting and drawing is independently 420 to 500° C., and the heat preservation time is independently 2 to 3 hours; The upsetting forging blank is subjected to upsetting treatment and rounding forging in sequence to obtain a rounding forging blank; the upsetting forging blank is subjected to upsetting treatment with a reduction amount in the main deformation direction of not less than 30%, and a forging speed of 1-10 mm / s; the rounding forging includes multiple rounding forging treatments performed in the radial direction, and the deformation amount of each rounding forging treatment does not exceed 8%; the upsetting treatment of the upsetting forging blank is a one-time forging to a target height; the number of rounding forging treatments does not exceed 8 times; The rounded forging blank is die-forged to obtain a formed forging; the die-forging speed is 0.1-6 mm / s; The formed forging is subjected to T5 heat treatment to obtain the VW93M magnesium alloy inclined-wall cylindrical forging.

2. The preparation method according to claim 1, characterized in that: The diameter of the VW93M magnesium alloy ingot is 400-550 mm; the graded homogenization annealing includes sequentially performing a first annealing and a second annealing; the temperature of the first annealing is 400-440° C., and the holding time is 5-8 h; the temperature of the second annealing is 500-540° C., and the holding time is 20-25 h.

3. The preparation method according to claim 2, characterized in that: Before the upsetting and drawing of the blank, the method further includes: cutting the homogenized ingot to obtain a cast rod with a diameter of 400-500 mm and a length of 800-1250 mm.

4. The preparation method according to claim 3, characterized in that: The first heat treatment is also included between the cutting and upsetting of the blank, wherein the temperature of the first heat treatment is 420-530° C. and the insulation time is 7-11 hours.

5. The preparation method according to claim 1, characterized in that: Before the die forging, the method further includes: subjecting the rounded forging blank to a second heat treatment, wherein the temperature of the second heat treatment is 420-500° C. and the holding time is 7-11 hours.

6. The preparation method according to claim 1, characterized in that: The temperature of the T5 heat treatment is 200-250° C., and the insulation time is 14-24 hours.

7. A VW93M magnesium alloy inclined-wall cylindrical forging prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the VW93M magnesium alloy inclined-wall cylindrical forging described in claim 7 in the preparation of missile cabins.

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