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CN-117225974-B - Special-shaped thin-wall pipe fitting thermoforming device and method with additional air pressure assistance

CN117225974BCN 117225974 BCN117225974 BCN 117225974BCN-117225974-B

Abstract

The invention discloses a special-shaped thin-wall pipe fitting thermoforming device and method assisted by additional air pressure, which belong to the technical field of metal component forming and manufacturing, wherein electric plasticity and a good microstructure are obtained by utilizing resistance heating of a metal pipe fitting, forming performance is improved by controlling heating speed and temperature, air pressure loading speed and pressure intensity in the pipe fitting can be controlled in a pipe fitting forming stage, the cooperative effect of titanium alloy thermoforming strain hardening and strain rate hardening is realized, pipe fitting wall thickness uniformity is effectively improved, a mold is subjected to partition temperature control in a mold quenching stage, quenching cooling speed of a formed pipe fitting is controlled, gradient tissues are obtained according to performance requirements of different deformation areas of the component, the formed pipe fitting is subjected to stress relaxation under the action of temperature and pressure, additional tensile stress is generated by internal pressure, the horizontal cylinder is axially loaded to exert prestress, the stress relaxation is promoted to form under the combined action of deformation and high temperature, residual stress is reduced, rebound is reduced, and the strength and dimensional precision of the formed pipe fitting are improved.

Inventors

  • ZHENG KAILUN
  • LI DECHONG
  • Bao Zhennan
  • YUAN SHIJIAN

Assignees

  • 大连理工大学

Dates

Publication Date
20260512
Application Date
20230926

Claims (8)

  1. 1. The special-shaped thin-wall pipe fitting thermoforming device with the additional air pressure assistance is characterized by comprising a partition temperature control die, a self-resistance heating system, an air pressure control system and an axial force and displacement control system; the partition temperature control die is divided into an upper die and a lower die, a water cooling plate and a heat insulation plate are fixed at the position of the movable slide block through bolts between the upper die and the movable slide block, and the lower die, the heat insulation plate and the water cooling plate are fixedly arranged at a lower platform of a die assembly press; The partition temperature control die further comprises a forming die and a temperature control heating element, wherein a through hole is formed in the forming die, the temperature control heating element is arranged in the through hole and connected with an external temperature control box, and a thermocouple is further arranged in the forming die; the self-resistance heating system comprises a high-frequency switching power supply, a wire and copper electrodes, wherein the copper electrodes are arranged at two ends of a closed tube blank and used for clamping a part to be formed, and the copper electrodes are electrically connected with the high-frequency switching power supply through the wire; the forming air pressure control system comprises a high-pressure air source and an air pressure control cabinet, wherein the input end of the air pressure control cabinet is connected with the high-pressure air source, and an air passage is arranged between the output end of the air pressure control cabinet and the sealing head of the closed tube blank; The axial force and displacement control system comprises a horizontal cylinder and a force sensor, wherein the force sensor is arranged at the output end of the horizontal cylinder and is fixedly connected with the horizontal cylinder; The device also comprises a closed tube blank and a die closing press; A sealing plate is welded at one end of the closed tube blank, a sealing head is welded at the other end of the closed tube blank, one side of the sealing plate is provided with the axial force and displacement control system, one side of the sealing head is provided with the air pressure control system, the partition temperature control dies are symmetrically arranged at the upper side and the lower side of the closed tube blank respectively, and the partition temperature control dies are connected with the die closing press; The die assembly press comprises a servo oil cylinder and a movable slide block, wherein the servo oil cylinder is connected with the movable slide block; The molding method of the device comprises the following steps: step one, connecting a temperature control heating element through a temperature control box, controlling the temperature of a forming die to be T 1 , and keeping the temperature of each point in the die uniform through heat preservation; Step two, rapidly heating the metal pipe to a forming temperature T 2 at a heating rate H by utilizing a self-resistance heating system to obtain a microstructure with good plasticity; step three, after the metal pipe is heated to the target temperature, a slide block at the die assembly press machine drives the upper die to rapidly carry out die assembly and pressure maintaining, and the forming air pressure control system is regulated to carry out pressurization on the metal pipe at a pressurizing rate Inflating, pressurizing to the gas pressure p, synchronously performing metal pipe forming and in-mold quenching, synchronously axially displacing a horizontal cylinder, applying stress to a sealing plate, and regulating and controlling the internal stress state of the formed pipe; Fourthly, maintaining the forming grouting at a constant die temperature T 1 and a gas pressure p for 30min through die temperature control and air pressure control, enabling stress relaxation to occur on the forming pipe fitting at a constant temperature and a constant pressure, and applying additional tensile stress on the sealing plate under the action of high pressure in the pipe; And step five, unloading internal air pressure and axial stress of a horizontal cylinder in the closed tube blank, removing the copper electrode, opening a die to obtain a piece, cutting a sealing plate and a sealing head of the closed tube blank, and cutting the allowance to finish the forming and manufacturing of the metal special-shaped thin-wall tube.
  2. 2. The device for hot forming a special-shaped thin-wall pipe fitting with additional air pressure assistance according to claim 1, wherein the closed pipe blank is one of an alpha-type titanium alloy, a near alpha-type titanium alloy, an alpha+beta-type titanium alloy, an iron-based superalloy, a cobalt-based superalloy and a nickel-based superalloy.
  3. 3. The hot forming device for the special-shaped thin-wall pipe fitting with the additional air pressure assistance according to claim 1, wherein the processing material of the forming die is one of low carbon steel and H 13 、Ni 7 N, and asbestos is wound on the outer portion of the forming die.
  4. 4. The device for thermoforming an additional air-pressure assisted special-shaped thin-wall pipe fitting according to claim 1, wherein the cooling channels in the water cooling plate are flowing normal-temperature water cooling channels and are arranged in a straight-through or random mode.
  5. 5. The device for thermoforming an additional air pressure assisted thin-walled tube according to claim 1, wherein in the first step, the forming mold adopts a partition temperature control mode, and the temperature control interval T 1 is 0-700 ℃.
  6. 6. The device for hot forming an additional air pressure assisted special-shaped thin-wall pipe according to claim 1, wherein in the second step, the metal pipe is made of titanium alloy or high-temperature alloy, the forming temperature T 2 is 700-1000 ℃, and the heating rate H is 1-100 ℃.
  7. 7. The device for hot forming of a profiled thin-walled tube with additional air pressure assistance according to claim 1, wherein in the third step, the pressure range of the die assembly press is 50-1000 t.
  8. 8. The apparatus for hot forming a thin-walled tube of a profile with additional air pressure assist according to claim 7, wherein in the third step, the high-pressure gas introduced into the closed tube blank is one of air, nitrogen or argon, wherein the pressurizing rate is The pressure p of the gas is 0.05-5 MPa/s and 0.1-20 MPa.

Description

Special-shaped thin-wall pipe fitting thermoforming device and method with additional air pressure assistance Technical Field The invention relates to the technical field of metal member forming and manufacturing, in particular to a special-shaped thin-wall pipe fitting thermoforming device and method with additional air pressure assistance. Background The special-shaped thin-wall metal pipe fittings made of titanium alloy and high-temperature alloy are key components in the field of aerospace high-end equipment, such as an aeroengine air inlet channel, a high-thrust rocket engine jet and the like. For different application fields, the common raw materials are mostly titanium alloy, heat-resistant high-strength steel, high-temperature alloy and the like. The materials have high deformation resistance at room temperature, small limiting expansion rate, low elastic modulus of parts, large rebound and poor dimensional accuracy of formed shapes, so that the traditional cold forming methods such as inner high-pressure forming and the like are difficult to manufacture the complex special-shaped shapes, and the forming temperature is required to be increased to improve the forming performance and accuracy. The conventional forming method at present mainly comprises splice welding forming, superplastic forming, hot air expansion forming and the like. The welding forming is to form an annular half shell by stamping a metal sheet, and weld the edge after correcting the edge. The method has the advantages that the resilience of the stamping part is large, the dimensional accuracy is low, the welding seam and the heat affected zone are easy to deform unevenly, the welding difficulty is high, the microstructure evolution at the welding seam is complex, compared with the base material with serious performance weakening, the microstructure is further stabilized by subsequent heat treatment, and the welding residual stress is eliminated. Compared with integral forming, the strength coefficient of the formed member is low, the structural performance and the dimensional accuracy are difficult to control accurately, and the requirements of high-end equipment on high reliability and integral development of the member are difficult to meet. The superplastic forming technology utilizes the high elongation rate of the metal material obtained under the specific temperature and strain rate conditions to realize the integral forming of the pipe component with the complex section. However, the superplastic forming has high forming temperature and slow deformation rate, the formed pipe fitting is easy to generate obvious uneven wall thickness and weakened performance, and is limited to fine-grain materials and equipment sizes, the manufacturing cost is high, the production period is long, and the large-scale production requirement of the components in the aerospace field is difficult to meet. The hot gas expansion forming process is to flush high pressure gas into the high temperature closed pipe blank, and the pipe blank is expanded and deformed fast with the inner pressure to form the required special thin wall pipe. However, the internal stress state in the pipe forming process is complex, obvious rebound easily occurs after cooling, and the process is further improved, so that the dimensional accuracy of the formed pipe is improved. In summary, the existing forming method has the problems of low production efficiency, low forming precision, weak component performance and the like, and cannot meet the forming requirements of thin-wall complex special-shaped pipe fittings in the aerospace field. Therefore, aiming at the manufacturing difficulty of coupling the forming precision of the complex special-shaped pipe fitting and the performance of the component, a new generation of integrated forming technology with shape control and controllability is urgently required, meanwhile, the precision, the strength and the production efficiency of the formed component are ensured, and the bottleneck problem of precision forming of the thin-wall complex special-shaped pipe fitting is solved. Disclosure of Invention The invention aims to provide a special-shaped thin-wall pipe fitting thermoforming device and method assisted by additional air pressure, which solve the defects in the prior art, integrate thermoforming, heat treatment and thermal correction processes, realize the shape control integrated forming of a metal thin-wall pipe fitting, and greatly improve the production efficiency on the premise of ensuring the performance and the dimensional accuracy of parts. In order to achieve the aim, the invention provides an additional air pressure auxiliary special-shaped thin-wall pipe fitting thermoforming device which comprises a partition temperature control die, a self-resistance heating system, an air pressure control system and an axial force and displacement control system; the partition temperature control die is divided into an upper d