阅读说明：本技术 轨道车辆用复杂型铝合金零件快速超塑成形方法 (Rapid superplastic forming method for complex aluminum alloy parts for railway vehicles ) 是由 王春生 何广中 梁继业 于 2019-10-21 设计创作，主要内容包括：轨道车辆用复杂型铝合金零件快速超塑成形方法涉及铝合金薄壁零件热成形技术领域,该方法首先利用曲面形面的凸模,将板料压入凹模深度的70％～80％的位置,再在1～2分钟内对板料快速预成形；然后,先向模具内部反向充气,在2分钟内模具内部气压由0MPa增加到0.3MPa,对快速预成形后的板料进行超塑成形；再向模具内部正向充气,在12分钟内模具内部气压由0MPa增加到1.5MPa,并保持1.5MPa气压3分钟,进而完成铝合金零件的快速超塑成形。本发明利用具有形状的凸模对加热的板料进行热冲压预成形,然后再进行反向超塑气胀成形,优化板料壁厚分布,最后正向超塑气胀成形,从而将成形时间由1～3小时缩短到20分钟以内,显著提高生产效率,降低生产成本,并提高零件质量,降低操作难度。(A rapid superplastic forming method for complex aluminum alloy parts for rail vehicles relates to the technical field of thermal forming of aluminum alloy thin-wall parts, and comprises the steps of firstly pressing a plate into a position which is 70-80% of the depth of a female die by using a male die with a curved surface, and then performing rapid preforming on the plate within 1-2 minutes; then, reversely inflating the interior of the die, increasing the air pressure in the interior of the die from 0MPa to 0.3MPa within 2 minutes, and performing superplastic forming on the plate subjected to rapid preforming; and then, positively inflating the interior of the die, increasing the air pressure in the die from 0MPa to 1.5MPa within 12 minutes, and maintaining the air pressure at 1.5MPa for 3 minutes, thereby completing the rapid superplastic forming of the aluminum alloy part. According to the invention, the heated plate is subjected to hot stamping preforming by using the male die with the shape, then reverse superplastic gas bulging forming is carried out, the wall thickness distribution of the plate is optimized, and finally forward superplastic gas bulging forming is carried out, so that the forming time is shortened to be within 20 minutes from 1-3 hours, the production efficiency is obviously improved, the production cost is reduced, the part quality is improved, and the operation difficulty is reduced.)

1. The rapid superplastic forming method of the complex aluminum alloy part for the railway vehicle is characterized by comprising the following steps:

step one, manufacturing a die for a superplastic forming method, wherein the die comprises a male die (1) and a female die (2), the shape surface of the male die (1) is a bilaterally symmetrical curved surface, the height H1 of the male die (1) is 70% -80% of the depth H2 of the female die (2), one side of the male die (1) is provided with a male die air hole (1-1), and the male die (1) is provided with a sealing groove for ensuring that the interior of the die is sealed and airtight after the male die (1) is buckled with the female die (2) at the position of the male die (1) contacted with a plate material (3); the shape of the concave die (2) is matched with the shape of the aluminum alloy part to be formed along with the shape, and a concave die air hole (2-1) is formed at the bottom of the concave die (2);

step two, placing the die in the step one into a superplastic forming machine, placing the plate (3) on the female die (2), gradually buckling the male die (1) and the female die (2), and performing rapid preforming on the plate (3) within 1-2 minutes by a hot stamping method in the buckling process of the die until the male die (1) and the female die (2) are completely buckled;

step three, reversely inflating the interior of the die through the air holes (2-1) of the female die, and boosting the air pressure in the interior of the die from 0MPa to 0.3MPa at the boosting speed of 0.15MPa/min within 2 minutes, so as to perform superplastic forming on the plate (3) which is rapidly preformed in the step two;

and step four, positively inflating the interior of the die through the male die air holes (1-1), boosting the air pressure of the interior of the die from 0MPa to 1.5MPa at the boosting speed of 0.125MPa/min within 12 minutes, and then maintaining the air pressure of 1.5MPa for 3 minutes, thereby completing the rapid superplastic forming of the aluminum alloy part.

Technical Field

The invention relates to the technical field of hot forming of aluminum alloy thin-wall parts, in particular to a rapid superplastic forming method of a complex aluminum alloy part for a railway vehicle.

Background

The locomotive light weight has important significance for improving the performance of the high-speed train. At present, the method generally adopted at home and abroad is material lightweight, namely, high-performance locomotives are all made of high-strength aluminum alloy materials. In order to further improve the performance of the locomotive, on the basis of material lightweight, the structure lightweight technology is gradually emphasized in recent years, namely, the use of connection technologies such as welding, screwing and riveting is greatly reduced through integral forming of aluminum alloy, and the weight is expected to be further reduced by 20-40%. The superplastic forming technology is a technology for forming an aluminum alloy integral part with a complex shape developed in recent years.

The aluminum alloy sheet is used for processing and manufacturing aluminum alloy vehicle body structural members for rail transit vehicles such as high-speed trains, subways, light rails and the like, such as various in-vehicle equipment such as door frames, window walls, inner and outer end walls, door column covers and the like, and other complex structural members. The important rail transit vehicle interior parts meet the comprehensive requirements of performance, precision and attractiveness, the shapes of a plurality of products are three-dimensional curved surfaces, so that high requirements on the manufacturing and assembling accuracy and surface quality of the interior parts are provided, and the cold forming deformation is limited, the resilience is large, and the requirements are difficult to meet. Therefore, the superplastic ballooning technique is the main manufacturing method.

The male die of the traditional superplastic gas bulging forming die is a plane, and only the female die is provided with a molded surface following the shape of a part to be processed. When superplastic gas bulging is carried out, a heated plate is pressed and attached to a female die through gas pressurization, no material is supplemented during forming, the final part shape is obtained completely by means of the bulging of the plate, and the phenomena that the plate deformation is large, the whole plate thickness is uneven, and a local plate is fractured due to the fact that the thickness is too thin easily occur in the forming process if the speed is too high. Therefore, in order to avoid the above phenomena, the air pressure must be slowly increased during the pressing process to ensure that the maximum elongation of the sheet is obtained, but since the male die is a plane, the space of the cavity of the whole die is large, and the amount of gas required for increasing the air pressure is large, which results in a long forming time.

Because the superplastic bulging forming needs to heat the die and the part to a higher temperature, the energy consumption is higher, and a part with a complex shape is formed, the inflation bulging needs dozens of minutes or even hours, and the process technology with low production efficiency and high cost is difficult to meet the requirement of mass production of the parts of the railway vehicle. Therefore, in order to meet the requirement of mass production of complex aluminum alloy parts of railway vehicles, a high-efficiency and low-cost forming process is needed to improve the superplastic forming production efficiency.

Disclosure of Invention

The invention provides a rapid superplastic forming method for complex aluminum alloy parts for railway vehicles, aiming at solving the technical problems of long forming time, easy occurrence of local fracture phenomenon and high cost in the existing superplastic forming process.

The technical scheme adopted by the invention for solving the technical problem is as follows:

the rapid superplastic forming method of the complex aluminum alloy part for the railway vehicle comprises the following steps:

step one, manufacturing a die for a superplastic forming method, wherein the die comprises a male die and a female die, the shape surface of the male die is a bilaterally symmetrical curved surface, the height H1 of the male die is 70% -80% of the depth H2 of the female die, one side of the male die is provided with a male die air hole, and the part of the male die, which is in contact with a plate material, is provided with a sealing groove for ensuring that the interior of the die is sealed and airtight after the male die is buckled with the female die; the shape of the concave die is matched with the shape of the aluminum alloy part to be formed along with the shape, and a concave die air hole is formed in the bottom of the concave die;

step two, placing the die in the step one into a superplastic forming machine, placing the plate on a female die, gradually buckling a male die and the female die, and performing rapid preforming on the plate within 1-2 minutes by a hot stamping method in the buckling process of the die until the male die and the female die are completely buckled;

step three, reversely inflating the interior of the die through the air holes of the female die, increasing the pressure in the interior of the die from 0MPa to 0.3MPa within 2 minutes according to the boosting speed of 0.15MPa/min, and further performing superplastic forming on the plate rapidly preformed in the step two;

and step four, positively inflating the interior of the die through the air holes of the male die, increasing the pressure of the interior of the die from 0MPa to 1.5MPa according to the boosting speed of 0.125MPa/min within 12 minutes, and then maintaining the pressure of 1.5MPa for 3 minutes, thereby completing the rapid superplastic forming of the aluminum alloy part.

The invention has the beneficial effects that: according to the method, before superplastic forming, a heated plate is subjected to hot stamping preforming by using a male die with a certain shape, more plates enter a cavity of a concave die, the preforming speed can be high, then reverse superplastic gas-bulging forming is performed in situ, the wall thickness distribution of the plates is optimized, and finally forward superplastic gas-bulging forming is performed, so that the forming time is shortened to be within 20 minutes from the original 1-3 hours, the production efficiency is obviously improved, the production cost is reduced, the part quality is improved, and the operation difficulty is reduced.

Drawings

FIG. 1 is a schematic structural diagram of a matching relationship between a die and a plate used in the rapid superplastic forming method of complex aluminum alloy parts for railway vehicles.

FIG. 2 is a schematic diagram of a preforming process in the rapid superplastic forming method of the complex aluminum alloy part for the railway vehicle.

FIG. 3 is a schematic diagram of a reverse superplastic ballooning forming process in the rapid superplastic forming method of the complex aluminum alloy part for the railway vehicle.

FIG. 4 is a schematic diagram of a positive superplastic ballooning forming process in the rapid superplastic forming method of the complex aluminum alloy part for the railway vehicle.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

As shown in fig. 1 to 4, the method for rapid superplastic forming of a complex aluminum alloy part for a railway vehicle of the present invention comprises the steps of:

step one, manufacturing a die for a superplastic forming method, wherein the die comprises a male die 1 and a female die 2, the shape surface of the male die 1 is a bilaterally symmetrical curved surface, the height H1 of the male die 1 is 70% -80% of the depth H2 of the female die 2, one side of the male die 1 is provided with a male die air hole 1-1, and the part of the male die 1, which is contacted with a plate 3, is provided with a sealing groove for ensuring that the interior of the die is sealed and airtight after the male die 1 and the female die 2 are buckled; the shape of the concave die 2 is matched with the shape of the aluminum alloy part to be formed along with the shape, and a concave die air hole 2-1 is formed at the bottom of the concave die 2;

step two, placing the die in the step one into a superplastic forming machine, placing the sheet material 3 on the female die 2, gradually buckling the male die 1 and the female die 2, and performing rapid preforming on the sheet material 3 within 1-2 minutes by a hot stamping method in the buckling process of the die until the male die 1 and the female die 2 are completely buckled; when the die is completely buckled, the sheet 3 can be pressed into 70-80% of the depth position in the female die 2, so that the internal space of a die cavity of the die is greatly reduced, the inflation quantity required during inflation is also greatly reduced, and the time required in the inflation process is saved.

Step three, reversely inflating the interior of the die through the air holes 2-1 of the female die, increasing the pressure in the interior of the die from 0MPa to 0.3MPa according to the boosting speed of 0.15MPa/min within 2 minutes, and further performing reverse superplastic forming on the plate 3 which is rapidly preformed in the step two, so that the plate 3 is attached to the male die 1, and the wall thickness of the plate 3 is uniformly distributed;

and step four, positively inflating the interior of the die through the male die air holes 1-1, increasing the pressure of the interior of the die from 0MPa to 1.5MPa at a boosting speed of 0.125MPa/min within 12 minutes, and then maintaining the pressure of 1.5MPa for 3 minutes, thereby completing the rapid superplastic forming of the aluminum alloy part.

The domestic aluminum alloy locomotive door frame part of the urban rail vehicle is characterized by a complex curved surface, a side wall reaching 80mm high, complete verticality and no inclination. The forming difficulty of the parts is as follows: the upper door frame is 700mm long and 500mm wide, the thickness of the door frame skin is 4mm, the shape of parts is complex, and a complex curved surface exists at the handle of the door frame, so that the forming is difficult; the upper surface of the door frame part is a complex curved surface, the height difference of each area is less than or equal to 2mm, and the traditional process has large resilience and quite large forming difficulty; the depth of a cavity of a door frame part is 80mm, the wall surface of the side wall of the door frame has zero inclination, the traditional stamping forming cannot realize the zero-degree draft inclination and the product with the depth at all, and the flange part of the door frame is a straight edge and is easier to wrinkle than a circular flange edge.

The rapid superplastic forming method for the complex aluminum alloy part for the railway vehicle can be used for participating the deformation of the bottom area of the door frame which is easy to attach a die and not easy to flow through the early pre-stretching forming and the back forward and reverse superplastic ballooning forming, so that the material is supplemented for the side wall area which is easy to thin, the small wall thickness reduction rate and the uniform wall thickness distribution of the side wall position are ensured, and the complex molded surface product with zero draft and deep cavity which cannot be realized by a stamping process can be formed.