CN-121988651-A - Pulse current direct heating tube blank pushing and bending forming device and method

CN121988651ACN 121988651 ACN121988651 ACN 121988651ACN-121988651-A

Abstract

The invention discloses a pulse current direct heating tube blank push bending forming device and a pulse current direct heating tube blank push bending forming method, which belong to the technical field of tube blank push bending forming treatment and comprise a die combined backing plate, a first block die, a second block die, a third block die, a push head, a core rod, a pulse power supply and an infrared thermal imager, wherein the pulse power supply is connected with a negative electrode and a positive electrode, the positive electrode is connected with the push head, the negative electrode is connected with the core rod, a heat-resistant filler is filled in a tube blank, the push head pushes the tube blank to move in a cavity and bend and form along the cavity, the tube blank is contacted with the core rod under the push of the push head, and the infrared thermal imager detects the temperature of the tube blank and the first block die in real time. The invention directly heats the tube blank by pulse current and cools the inner side of the bending cavity of the die by circulating cooling water, thereby realizing the differential temperature control of the push bending die and further improving the material performance of the inner side and the outer side of the tube blank in the forming process.

Inventors

ZHANG FENGWEI
XIE JUN
XU XUEFENG
WANG HEYANG
QIU HAOYI
Wan Chenge
YUAN ZHENGANG
LIANG JIAYI

Assignees

南昌航空大学

Dates

Publication Date: 20260508
Application Date: 20260325

Claims (10)

1. The pulse current direct heating tube blank pushing and bending forming device is characterized by comprising a die combined base plate, a first block die, a second block die, a third block die, a push head, a core rod, a pulse power supply and an infrared thermal imager, wherein the first block die, the second block die and the third block die are connected to the die combined base plate, an insulating sheet is arranged between the first block die and the second block die, another insulating sheet is arranged between the second block die and the third block die, and a cavity is formed between the two insulating sheets; The pulse power supply is connected with a negative electrode and a positive electrode, the positive electrode is connected with a push head, the negative electrode is connected with a core rod, the tube blank is filled with heat-resistant filler, the push head pushes the tube blank to move in a cavity and bend and form along the cavity, the tube blank is also contacted with the core rod under the pushing of the push head, and the infrared thermal imager detects the temperature of the tube blank and the first block mold in real time.
2. The pulse current direct heating tube blank pushing and bending forming device according to claim 1, wherein the first block mold is provided with a cooling groove for cooling the temperature of the first block mold, the cooling groove is arranged along the extending direction of the cavity, and a cooling medium is arranged in the cooling groove.
3. The pulse current direct heating tube blank pushing and bending forming device according to claim 2, wherein the outer parts of the negative electrode and the positive electrode are provided with insulating sleeves, so that the exposed part of the negative electrode is only contacted with the core rod, and the exposed part of the positive electrode is only contacted with the push head.
4. The pulse current direct heating tube blank pushing and bending forming device according to claim 3, wherein an insulating sheet is arranged at the bottom of the die combined base plate, and the die combined base plate is insulated from a machine tool through the insulating sheet.
5. The pulse current direct heating tube blank pushing and bending forming device is characterized in that insulating sheets are arranged on the chassis of the push head and the chassis of the core rod, the push head and the core rod are insulated from a hydraulic cylinder through the insulating sheets, and insulating paint is smeared on the contact surface of the second block mold and the tube blank.
6. The pulse current direct heating tube blank pushing and bending forming device according to claim 5, wherein when the tube blank is contacted with the core rod under the pushing action of the pushing head, the current after the pulse power supply is electrified flows out from the positive electrode, sequentially passes through the pushing head, the tube blank and the core rod and flows in from the negative electrode.
7. The pulse current direct heating tube blank pushing and bending forming device according to claim 1, wherein the first blocking die, the second blocking die and the third blocking die are respectively connected with a die combined base plate through positioning pins.
8. A pulse current direct heating tube billet push bending forming device according to claim 1, wherein the die cavity comprises an input section, a bending section and an output section, the tube billet being drivable through the input section into the bending section and then to the output section.
9. A method for forming a push-bend tube blank forming apparatus by direct heating with a pulse current according to any one of the claims 1 to 8, characterized by comprising the steps of, The method comprises the steps of firstly, blanking and chamfering a tube blank, namely accurately blanking the tube blank with the length L by adopting a blanking mode with two-end compensation, calculating the blanking total length of the tube blank according to a formula I, cutting the front end of the tube blank with the length L by 45-60 degrees of slope angle, cutting the rear end of the tube blank by 45-60 degrees of slope angle, reserving an end face with the length H at the rear end of the tube blank, providing enough acting force area for a pushing head by the end face, preventing the pushing force from being eccentric and affecting the pushing and bending forming quality, and finally deburring the two ends of the tube blank and cleaning the tube blank; Filling a plurality of heat-resistant fillers from the pushed end of the tube blank to the inside, wherein each heat-resistant filler is a cylindrical block, and the diameter of each heat-resistant filler is smaller than the inner diameter of the tube blank by 2mm, so that the tube blank is convenient to take out after being bent and formed; Coating a lubricant on the tube blank, after coating, drawing an alignment center line on the outer side of the tube blank, and placing the tube blank into a bending cavity to enable the center line to be flush with a die closing line of a die, wherein the lubricant is high-temperature-resistant lubricating grease; The method comprises the steps of connecting an anode electrode with a push head, connecting a cathode electrode with a core rod, putting a tube blank filled with a small amount of heat-resistant filler into a cavity of a push bending die, pushing the push head against the rear end of the tube blank, moving the tube blank filled with the filler forward along the curved cavity at a constant speed under the action of push head pushing force, stopping moving the tube blank when the tube blank contacts with the core rod, adjusting current density, duty ratio and current frequency parameters, then starting a pulse power supply, directly heating the tube blank to a target temperature and keeping the temperature stable, simultaneously injecting cooling water into a cooling groove formed in a first blocking die, taking away heat of the first blocking die by circulating the cooling water which is at room temperature, and observing the temperature of the tube blank and the first blocking die in real time by an infrared thermal imager; Turning off a pulse power supply when the infrared thermal imager observes that the bending cavity of the tube blank and the first block mold reaches the target temperature, and moving the tube blank filled with the filler forwards at a uniform speed along the bending cavity under the action of pushing force of the pushing head to gradually finish pushing and bending forming of the tube with small bending radius; And step six, after the push bending forming is finished, removing the lubricant on the surface of the pipe blank part and the internal heat-resistant filler, and finally obtaining the formed pipe with small bending radius.
10. The method for forming a pulse current directly heated tube blank push-bending forming device according to claim 9, wherein the formula I is, , Wherein: Indicating the total length of the blank, Indicating the relative radius of curvature of the sheet, Representing the arc of a formed tube the lengths of the straight sections at the two sides, Indicating the machining allowance.

Description

Pulse current direct heating tube blank pushing and bending forming device and method Technical Field The invention relates to the technical field of pipe pushing and bending forming treatment, in particular to a device and a method for directly heating a pipe blank by pulse current. Background The push-bending forming of the pipe blank is one of the core processes of plastic processing of metal pipes, and the principle is that axial thrust is applied by a pushing mechanism to enable the pipe blank to be subjected to plastic deformation along a preset die cavity, so that the pipe fitting with the required bending angle and the required external dimension is obtained. In the field of aerospace, a tube blank push bending forming technology faces a particularly serious challenge, the requirements on the forming quality of tube blanks for high-end equipment manufacturing in aerospace are increasingly severe, the tube blanks are required to have accurate dimensional accuracy and uniform wall thickness distribution, and higher requirements on forming efficiency, energy consumption control and complex working condition suitability are also provided, and particularly, the forming requirements on high-performance material tube blanks such as thin-wall tubes with small bending radius (the relative bending radius is less than or equal to 1) and high-temperature alloys are increasingly urgent. The conventional tube blank push-bending forming technology has difficulty in meeting the above requirements, and the core bottleneck is concentrated on the irrational heating mode. At present, heating modes adopted in the tube blank pushing and bending forming process mainly comprise medium/high frequency induction heating, flame heating, reverberatory furnace heating, heating rod indirect heating and the like. In order to improve the forming quality of the tube blank with small bending radius, a differential temperature push bending forming technology appears in the prior art, the outside of a heating rod heating die cavity and the inside of a cooling water tank cooling cavity are used for improving the plastic flow characteristics of different parts of the tube blank by utilizing the temperature difference. However, the technology is still essentially to indirectly heat the tube blank through a heating die, has the problems of low heating response speed, large heat loss, low heating efficiency and the like, and generally needs more than 60 minutes to heat the die to a preset temperature, and the contact area of the heating rod and the die is too high in temperature, and the rest area is low in temperature, so that obvious temperature gradient is formed, the rapid and uniform heating of the bent part of the tube blank can not be realized, the forming defect of the thin-wall tube with the small bending radius can not be solved, meanwhile, the problem of high energy consumption is not effectively relieved, and the production requirements of high efficiency and energy conservation can not be met. In recent years, the electric pulse heating technology has been tried to be applied to the field of metal plastic working because of advantages of high heating speed, high energy utilization rate, good temperature controllability and the like. However, in the prior art, electric pulses are mostly acted on a die, the tube blank is indirectly heated through heat transfer of the die, direct heating of pulse current to the tube blank is not realized, the defects of heat transfer loss, insufficient temperature control precision and the like still exist, the defects of the traditional heating mode cannot be fundamentally overcome, the suitability of a heating system and a push bending forming mechanism is poor, cooperative control of heating and push bending forming is difficult to realize, the severe requirements on heating speed, temperature uniformity and forming precision in the push bending forming process of the tube blank cannot be met, and the method is especially not suitable for push bending forming of high-performance material tube blanks (such as high-temperature alloy). The high-performance material has poor plasticity at normal temperature, needs rapid and uniform local heating to improve the plastic flow characteristic, cannot meet the core requirement in the traditional heating mode and the traditional electric pulse indirect heating mode, and severely limits the application expansion of the push-bending forming process in the field of manufacturing high-end pipe fittings. In summary, the existing tube blank push-bending forming technology has the defects of low heating efficiency, uneven temperature distribution, large heat loss, high energy consumption and the like, and does not meet the green aviation development requirement, and the heating rod has uneven heating temperature distribution, high temperature in the area directly contacted with the heating rod and lower temperature in the other areas, so that the temperature gra