CN113172143B - Method for improving wall thickness uniformity of superplastic air-inflated forming part by using variable surface - Google Patents

Abstract

The invention relates to a method for improving the wall thickness uniformity of superplastic inflatable parts by utilizing a variable profile, which specifically includes: a variable profile inflatable mold, a compression sealing device, a heating device and an air supply system; it is characterized by the following: The profile of the plastic expansion mold is composed of multiple ball-head cylinder devices with adjustable height. During the deformation process, controlling the axial displacement of the ball-head cylinder can dynamically adjust its profile shape. In ball-head cylinders and magnesium alloy plates, A material with good superplasticity and low price is used as an intermediary material; during the inflation molding process, the changes in the mold surface can be dynamically adjusted as needed to control the deformation sequence of each part of the alloy slab. When the slab and intermediary material When it is not in contact with the profile, it will undergo superplastic deformation under the action of air pressure. When the slab and the intermediary material are in contact with the profile, no superplastic deformation will occur due to friction; thus the slab is formed in steps, improving Improves the uniformity of wall thickness of superplastic alloy air-bulging parts.

Description

A method to improve the wall thickness uniformity of superplastic inflatable formed parts by using variable profiles

Technical field

0002. The present invention relates to the field of scientific research on metal materials, and specifically relates to a method for improving the wall thickness uniformity of superplastic inflatable formed parts by using variable profiles.

Background technique

0003. Superplastic forming is widely used in the aerospace field to form a variety of thin plate workpieces with complex shapes, light weight, and high structural strength. A simple superplastic forming process can produce workpieces with complex structures and nearly no machining allowance, and does not require welding or riveting, greatly reducing the number of processes and processing costs. When the material is in a superplastic state, its plastic deformation resistance decreases sharply, its plastic deformation ability increases significantly, and almost no strain hardening occurs, and it is approximately in a viscous flow state. Superplastic forming is a forming technology that places materials in a superplastic state. Compared with traditional processing technology, its advantages are very obvious.

0004. Superplastic bulging of metal sheets can be carried out by free bulging or in-mold bulging through medium pressure; this method is to first clamp the sheet on the mold, and use air pressure to blow the unclamped part of the sheet into the concave mold to form the parts. The shape is determined by the shape of the concave mold surface; the main forming process can be the free protrusion of the plate in the first stage and the process of the plate contacting the mold to complete forming in the second stage; this method can use a single concave mold to save mold design and manufacturing costs ; There is almost no wear on the mold during the forming process, so that the mold has a long service life; and it can be completely formed at one time, reducing the number of processing times and saving working time; Generally, this method is suitable for preparations with complex shapes, protruding surfaces or special shapes, and those that do not require uniformity. Thick-walled parts; if combined with diffusion bonding technology, multi-layer hollow structural parts can be prepared; during the inflation forming process of magnesium alloys, etc., the air pressure is generally controlled at 0.2-1.0MPa and the temperature is set at 573-723K; affects the superplastic gas The main factors that determine the quality of bulging products include the original grain size of the forming plate, the surface quality of the mold, anti-oxidation measures during the superplastic bulging process, the appropriate selection of the pressure curve, and the control accuracy of the forming temperature.

0005. Although the air bulging forming process has a series of advantages, the phenomenon of uneven thickness strain still exists in the actual processing process; during the bulging process, since the surrounding materials are compressed by the mold and do not participate in deformation, the increase in the part area is entirely caused by the material. At the same time, the uneven stress and strain fields cause a significant gap in the wall thickness of the final part. This problem is critical to whether the part can meet the design requirements and is a key issue that limits the application and development of this process.

Contents of the invention

0006. The purpose of the present invention is to provide a method for improving the uniformity of wall thickness of superplastic inflatable formed parts by using a variable profile, so as to solve the phenomenon of uneven wall thickness of sheet metal that occurs during the high-temperature inflatable forming of magnesium alloys, and further Improve the forming effect of this process.

0007. The technical solution adopted by the present invention to solve the above technical problems is: 0008. A method for improving the wall thickness uniformity of superplastic inflatable forming parts by using variable profiles, which is characterized in that: it includes an inflatable forming mold, a pressing Sealing device, heating device and air supply system; specifically including 1. Upper pad 2, insulation plate 3, upper heating plate 4, ventilation plate 5, workpiece 6, concave mold 7, superplastic mold pad 8, adjustable height The ball head cylinder 9, the heating rod 10, and the base; at the beginning of the inflation forming stage, the blank is not in contact with the profile surface, and the blank is in a free expansion state. The middle part of the blank is the thinnest, and the wall thickness near the edge is thicker. By adjusting the mold profile, so that the edge with thicker wall thickness continues to deform, and the middle part with thinner wall thickness is in contact with the mold surface and does not deform due to friction; because the increase in the surface area of the sheet during inflatable forming is achieved by reducing the thickness of the sheet , the edge part continues to deform, its surface area increases, and the thickness decreases, while the middle part does not deform or deforms later, and the thickness does not decrease or decreases less, thereby achieving controllable thickness distribution of the molded part; this technology uses adjustable overall wall thickness Distribution enables step-by-step changes in superplastic forming of materials.

0009. The air inflation mold is divided into a concave mold, a superplastic mold backing plate and a plurality of height-adjustable ball head cylinders. Since the superplastic air inflation forming pressure is small, the concave mold, superplastic mold backing plate and ball head are The requirements for the cylinder are not high, as long as it has a certain strength, hardness, anti-oxidation and non-flammability at the superplastic temperature. The superplastic backing plate deforms with the slab, and there are pits on the surface of the bottom ball head cylinder. The backing plate is added to prevent the plate from being deformed. The blank is in direct contact with the bottom ball-head cylinder, which can ensure the smooth surface of the slab; the compression sealing device includes an upper pad plate and a ventilation plate, and the pressure is supplied by the press. The working pressure of the equipment presses the heated slab through the pressing plate and the die. Tight, causing plastic deformation of the slab that softens in the hot state, thereby achieving compression and sealing; the heating device includes heating rods in the upper and lower heating plates, and a heat insulation plate is added to the outer part in contact with the pad; air supply The system is a ventilation panel with a hollow structure and a ventilation hole in the center.

0010. There is a ventilation hole in the center of the upper part of this superplastic inflation forming device, which is the blowing hole during the superplastic inflation forming process; there is a heat insulation plate interval between the upper heating plate and the upper backing plate, and a heating rod is placed in the hole to directly Plastic alloy sheet heating. After heating to an appropriate temperature, air bulging begins. Since the sheet material does not contact the mold cavity, free bulging occurs first. The middle part of the blank is the thinnest, and the wall thickness near the edge is thicker. After deformation for a period of time, adjust the mold. The height of the ball head cylinder at different positions on the profile allows the middle part to continue to contact the profile, and the edge part to break away from the profile, so that the edge part continues to deform and continue to thin; after the edge part is thinned to a certain extent, the central part of the ball The head cylinder height adjustment device descends and breaks away from the middle part of the blank, deforming the middle part of the blank, thereby making the processed sheet more uniform.

0011. Compared with the existing technology, the present invention has the following beneficial effects: 0012.1. By dynamically adjusting the mold surface, the deformation sequence of the blank can be controlled as needed to achieve uniform deformation of the entire body. Thus, the wall thickness can be controlled.

0013.2. By distributing multiple height-adjustable ball-head cylinders at the bottom, the deformation of the plate can be realized in any shape. Controlling the undulation of the ball-head cylinder can control the deformation sequence of the plate in stages, making the overall wall thickness more precise and controllable.

0014.3. Using a cheap material with good superplastic properties as a backing plate on the ball-head cylinder with an adjustable bottom height can avoid contact between the blank and the ball-head cylinder, greatly improve the surface quality of the part, and facilitate demolding. 0015.4. This method has low processing cost, flexible mold, strong adaptability, and good uniformity effect of finished products, which is conducive to improving production efficiency and saving production costs.

Description of drawings

0016. Figure 1 is a schematic diagram of a method for improving the wall thickness uniformity of superplastic inflatable parts using variable profiles; a multi-point processing magnesium alloy superplastic concave die inflatable forming device specifically includes 1. an upper backing plate 2 , heat insulation plate 3, upper heating plate 4, ventilation plate 5, workpiece 6, concave mold 7, superplastic mold backing plate 8, height-adjustable ball head cylinder 9, heating rod 10, base; among them, the inflatable forming mold is divided into It is a height adjustment device for the mold frame, superplastic mold backing plate and ball head cylinder. The height of the ball head cylinder is controlled by the bottom thread; due to the low pressure of superplastic inflatable forming, there are requirements for the concave mold, superplastic mold backing plate and ball head cylinder. Not high, as long as it has a certain strength, hardness, anti-oxidation and non-flammability at overspeeding temperatures; the compression sealing device includes an upper pad and a ventilation plate, the pressure is supplied by the press, and the working pressure of the equipment is controlled by the pressure plate and the die. The heated slab is compressed, causing the slab that becomes soft in the hot state to undergo plastic deformation, thereby achieving compression and sealing; the heating device includes heaters in the upper and lower heating plates, and the outer part is in contact with the upper pad Add a heat insulation board; the air supply system is a ventilation board with a hollow structure and a ventilation hole in the center.

0017. Figure 2 is a process flow of a multi-point processing superplastic alloy die inflation forming device and method.

Detailed ways

0018. The present invention provides a method for improving the wall thickness uniformity of superplastic inflatable formed parts by using variable profiles. The specific implementation is as follows: 0019.1. Select a suitable superplastic alloy slab and cut the plate to the appropriate size. In order to prevent local excessive thinning and cracking of the formed parts, the thickness of the slab should not be too small;

0020.2. Preheat the mold and slab. The mold temperature is set according to the superplastic temperature of the alloy sheet, and then the slab coated with lubricant is placed in the mold, tightly sealed and heated to the superplastic temperature;

0021.3. The air bulging forming stage begins. The first is free bulging. At this time, the gas pressure is small and the bulging is slow;

0022.4. Since the bottom end of the sheet has the largest deformation and the thinnest wall thickness at this time, the height adjustment cylinder of the variable profile die at the edge drops, and the cylinder in the middle rises; the middle of the sheet begins to fit with the bottom mold profile , the edge of the plate continues to form;

0023.5. After the air inflates and deforms to the appropriate position, the middle part separates from the bottom mold surface and continues to deform;

0024.6. In the final stage of forming, in order to fully fit the slab and the mold surface, greater pressure should be applied and maintained for a period of time. The amount of deformation at this stage is not large;

0025.7. After processing is completed, take out the processed parts.

Claims (2)

1. A method for improving the wall thickness uniformity of superplastic inflatable formed parts by using variable profiles, which is characterized by: including an inflatable forming mold, a compression sealing device, a heating device and an air supply system; Specifically, it includes upper pad, heat insulation plate, upper heating plate, ventilation plate, workpiece, concave mold, superplastic mold pad, height-adjustable ball-head cylinder, heating rod, and base; In the initial stage of air bulging forming, the slab is not in contact with the mold surface, and the slab is in a free expansion state. The middle part of the slab is the thinnest, and the wall thickness near the edge is thicker. By adjusting the mold surface, the thicker wall part can be made. The edge continues to deform, and the middle part with a thin wall thickness is in contact with the mold surface, and no longer deforms due to friction; since the increase in the surface area of the slab during inflatable forming is achieved by reducing the thickness of the slab, the edge part continues to deform. , its surface area increases, the thickness decreases, and the middle part is deformed, with no or less thickness reduction, thereby achieving controllable thickness distribution of the formed part; using the adjustable overall wall thickness distribution to achieve step-by-step changes in slab superplastic forming ; Among them, the inflatable forming mold is divided into a mold frame, a superplastic mold pad and a height-adjustable ball-head cylinder. The height of the ball-head cylinder is controlled by the bottom thread; due to the small pressure of superplastic inflatable molding, it is suitable for concave molds and superplastic molds. The requirements for the mold backing plate and the ball-head cylinder are not high, as long as they have a certain strength, hardness, oxidation resistance and non-flammability at the superplastic temperature. The superplastic mold backing plate deforms with the slab, and there are pits on the surface of the bottom ball-head cylinder. , add a superplastic mold backing plate to prevent direct contact between the slab and the bottom ball head cylinder to ensure a smooth surface of the slab; the compression sealing device is to balance the gas pressure and compress the metal slab, including the upper backing plate and ventilation plate, pressure Supplied by the press, the working pressure of the equipment compresses the heated slab through the pressing plate and the die, causing the slab that softens in the hot state to plastically deform, thereby achieving compression and sealing; the heating device includes an upper heating plate and a The heating rod is in the die, and a heat insulation board is added to the outer part in contact with the upper pad; the air supply system is a ventilation plate with a hollow structure and a ventilation hole in the center; There is a vent hole in the center of the vent plate, which is a blow hole during the superplastic inflation forming process; there is a heat insulation plate interval between the upper heating plate and the upper backing plate, and a heating rod is placed in the hole to directly heat the superplastic alloy slab; heating After reaching the appropriate temperature, air bulging begins. Since the slab is not in contact with the mold cavity, free bulging occurs first. The middle part of the slab is the thinnest, and the wall thickness near the edge is thicker. After deformation for a period of time, adjust the mold. The height of the ball head cylinder at different positions on the profile keeps the middle part in contact with the profile, and the edge part breaks away from the profile, so that the edge part continues to deform and continue to thin; after the edge part is thinned to a certain extent, the height of the central part The adjustable ball head cylinder descends and breaks away from the middle part of the slab, deforming the middle part of the slab, thereby making the processed slab more uniform. 2. A method for improving the wall thickness uniformity of superplastic inflatable formed parts by utilizing variable profiles according to claim 1, the specific steps are as follows: (1) Select a suitable superplastic alloy slab and cut the slab to the appropriate size. In order to prevent the formed part from being excessively thinned and causing cracks, the thickness of the slab should not be too small; (2) Preheat the mold and slab. The mold temperature is set according to the superplastic temperature of the alloy slab. Then the slab coated with lubricant is placed in the mold, pressed, sealed and heated to the superplastic temperature; (3) The air bulging forming stage begins, with free bulging first. At this time, the gas pressure is small and the bulging is slow; (4) Since the bottom end of the slab has the largest deformation and the thinnest wall thickness at this time, the height adjustment cylinder of the variable profile die at the edge descends, and the cylinder in the middle rises; the center of the slab begins to be in contact with the bottom mold profile The fit no longer deforms, while the edge of the slab continues to form; (5) After the air inflates and deforms to the appropriate position, the middle part separates from the bottom mold surface and continues to deform; (6) In the final stage of forming, in order to fully fit the slab and the mold surface, greater pressure should be applied and maintained for a period of time. The amount of deformation at this stage is not large; (7) After processing, take out the processed parts.