CN115846496A - Coil induction heating air-bulging forming device and method for pipe fitting made of difficultly-deformed material - Google Patents

Abstract

The invention discloses a coil induction heating air-bulging forming device and a coil induction heating air-bulging forming method for a pipe fitting made of a difficult-to-deform material. The invention adopts an electromagnetic induction coil wound outside an internal bulging die, heats an original pipe fitting blank to a target bulging forming temperature in an induction heating mode, and arranges a left end composite structure and a right end composite structure on the left and right sides of the whole internal bulging die in a split manner, so as to expose a middle cavity of the external bulging die by separating the left end composite structure and the right end composite structure, and the middle cavity, the right end surface of the left end composite structure and the left end surface of the right end composite structure are meshed to form a complete die cavity; then injecting gas with preset pressure into the original pipe blank through the sealing heads sealed at the two ends of the original pipe blank, so that the original pipe blank is formed in an air expansion mode under the pressure provided by the gas until the original pipe blank is attached to the complete die cavity. The invention has simple structure and simple and convenient process, is convenient for the pipe fitting to carry out rapid hot gas expansion forming and improves the production efficiency.

Description

Coil induction heating air-bulging forming device and method for pipe fitting made of difficultly-deformed material

Technical Field

The invention belongs to the technical field of forming of pipe parts made of metal materials difficult to deform, and particularly relates to a forming device and a forming method for performing electromagnetic induction heating and air inflation on pipe parts made of the metal materials difficult to deform by using an electromagnetic induction heating principle.

Background

In the aerospace vehicle manufacturing industry and the automobile manufacturing industry, a pipe part is a part which is very wide in application and very important on the left and right, and has the characteristics of complex forming shape, various forming process methods, various used materials and the like. With the development of aerospace vehicles and automobile industries, people also put higher demands on the performance of pipe parts, and the pipe parts are required to have the characteristics of high temperature resistance, low density, high strength and the like. Materials such as titanium alloys, intermetallic compounds, and high-strength aluminum alloys have excellent properties such as low density and high specific strength, and members formed using these materials can be used for a long time in a high-temperature environment, for example: the common titanium alloy can be used at 400-600 ℃ for a long time, and the Ti2 AlNb-based intermetallic compound can be used at 600-750 ℃ for a long time. However, these materials have the disadvantages of poor plasticity, obvious rebound phenomenon, difficult deformation and the like, so that the forming difficulty of the pipe parts made of the materials difficult to deform is large. In addition, the microstructure of the raw material may be changed or damaged during the forming process, thereby deteriorating the usability of the formed pipe part. Therefore, it is required to develop a molding method capable of efficiently and inexpensively manufacturing a pipe part made of a hardly deformable material such as a titanium alloy.

A certain research results are available for a processing and forming device and a method for metal pipe parts difficult to deform.

Patent CN 201510191192.3 of Wangyun et al has stated an incremental temperature difference bulging device and bulging method of metal tubular product, the characteristics of this patent are that the structure includes bulging mould, electromagnetic induction heating mechanism and coil feed mechanism, at the in-process of heating bulging, the segmentation heats the part pipe and does not heat the mould, carry out the bulging to the tubular product of heating part, thereby realize the incremental temperature difference bulging of tubular product part, improve the formability of material, reduce the resilience of tubular product, solve the unstability of tubular product and the mesh of wrinkling the phenomenon. However, this patent requires a precise coil feeding mechanism, resulting in a complicated structure of the apparatus required for forming and high cost, and further, the patent employs an electromagnetic heating coil of a single turn, thereby having a problem of low heating efficiency.

Wang et al patent CN 201510050971.1 describes an electromagnetic induction heating bulging device and a forming method for a metal conductor pipe fitting, the invention is characterized in that a bulging die is positioned in an electromagnetic induction coil of an electromagnetic induction heating unit, only a pipe blank is heated without heating the die in forming, and thus, the air pressure bulging of the metal conductor pipe fitting in a high-temperature state is realized. However, in the invention, the electromagnetic induction coil is positioned outside the bulging die, so that the electromagnetic induction heating effect is poor, and meanwhile, a longer coil is needed, which causes the increase of the cost.

At present, the common processing and forming method for the difficult-to-deform metal such as titanium alloy at home and abroad is to form after heating, and the processing and forming are carried out by heating a mould or heating raw materials by utilizing the characteristic that the plasticity of the heated material is improved to a certain extent. The traditional heating mode generally adopts a mode of heating by using a resistance wire or quartz, self generates heat after the resistance wire or the quartz is electrified, and then the heat is transferred to a workpiece to be processed through heat conduction, so that the effect of heating the workpiece is achieved. The traditional heating mode has low efficiency, 50% of energy is diffused into air, the electric energy loss is high, and meanwhile, the forming method has the defects of long heating time, difficulty in temperature control, high energy consumption, low production efficiency and the like, and is difficult to apply to large-scale production. Meanwhile, the heating equipment of the forming method is complex and expensive, and for materials which are difficult to deform, such as titanium alloy containing active metal elements, ti2 AlNb-based intermetallic compounds, high-strength aluminum alloy and the like, a cooling system, a vacuum device, a gas protection device and the like are needed, so that the potential safety hazard of the equipment is increased, and the environment is easily polluted. In addition, abnormal growth of crystal grains is likely to occur due to long-term heating, and the usability is lowered.

The metal part is heated by utilizing the principle of electromagnetic induction, the other mode is to heat the part by utilizing electric energy, alternating current with a certain degree is introduced into an electromagnetic induction coil to generate an alternating magnetic field, a monitoring part with magnetic conductivity is arranged in the magnetic field to cut alternating magnetic lines, so that alternating current (namely eddy current) is generated inside the metal part, the eddy current enables atoms inside the metal part to move randomly at a high speed, and the atoms collide and rub with each other to generate heat energy, thereby achieving the effect of heating the metal part. Compared with the traditional heating mode, the heating mode has higher energy conversion efficiency, avoids energy waste and greatly reduces the average preheating time; the production cost is reduced, the service life of the equipment is prolonged, and the parts can be fully and uniformly heated; because the electromagnetic induction heating equipment only heats the workpiece when in work and does not generate heat, the later maintenance cost can be reduced, the operation is reliable, the control is convenient, and the forming production is more green, energy-saving, safe and comfortable.

Disclosure of Invention

The invention aims to provide a coil induction heating ballooning forming device and a coil induction heating ballooning forming method for a pipe fitting made of a difficult-to-deform material. According to the electromagnetic effect, alternating current generated by an induction heating power supply generates an alternating magnetic field through an induction coil, and alternating current is generated inside a metal material arranged in the induction coil, so that heat energy is generated inside an object, and the metal is heated, so that the plastic deformation capacity of the metal material is improved, the flow stress of the material is reduced, and the metal material difficult to deform is easier to plastically form and process. The forming device described in the invention is a composite structure combining an electromagnetic induction heating device and an inflatable forming device, wherein the electromagnetic induction heating device is designed inside an inflatable forming die and is used as a part of a die cavity. The electromagnetic induction coil is divided into a left part and a right part and can move, when the coils of the left part and the right part are closed, the coils can be used as an electromagnetic induction device to heat a pipe fitting inside the die, and when the coils of the left part and the right part move to the leftmost end and the rightmost end to be meshed with the die, the coils can be supplemented to form a complete die cavity, so that the pipe can be subjected to gas expansion forming and attached to the die, and the pipe fitting with a certain section shape is obtained.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

a coil induction heating air-bulking forming device of a pipe fitting made of a difficult-to-deform material is used for heating air-bulking forming of an original pipe fitting blank and comprises an external air-bulking die, an internal air-bulking die arranged in the external air-bulking die, and a left sealing head and a right sealing head which are respectively sealed with the left end and the right end of the original pipe fitting blank; wherein:

the upper and lower split parts of the external bulging die are an upper external bulging die and a lower external bulging die, a middle die cavity is formed when the upper external bulging die and the lower external bulging die are assembled, and notches are formed in two sides of the middle die cavity;

the left and right split bodies of the internal bulging die are arranged into a left end composite structure and a right end composite structure; the shape of the inner cavity of the internal bulging die is matched with the shape of the outer wall of the original pipe fitting blank, and meanwhile, the axial length of the original pipe fitting blank is greater than that of the internal bulging die in a die closing state;

the left end composite structure comprises a left end inner bulging die arranged in a cylindrical shape and a left end electromagnetic induction coil wound on the outer wall of the left end inner bulging die; the right side of the left-end electromagnetic induction coil is provided with a copper ring a, and the left side of the left-end electromagnetic induction coil is connected with the anode of a power supply through a lead; the left end internal bulging die is capable of translating along a left side portion of the original tube blank;

the right end composite structure comprises a right end internal bulging die and a right end electromagnetic induction coil, wherein the right end internal bulging die is arranged in a cylindrical shape, and the right end electromagnetic induction coil is wound on the outer wall of the right end internal bulging die; the left side of the right electromagnetic induction coil is provided with a copper ring b, and the right side of the right electromagnetic induction coil is connected with the negative electrode of a power supply through a lead; the right end inner bulging die can translate along the right side part of the original pipe fitting blank;

when the upper external bulging die and the lower external bulging die are closed, the left end composite structure and the right end composite structure are translated oppositely until the copper rings a and b are contacted with each other, and the left end electromagnetic induction coil and the right end electromagnetic induction coil form a power-on loop with a power supply through wires; when the power supply of the power-on loop is switched on, an alternating magnetic field can be generated by the left end electromagnetic induction coil and the right end electromagnetic induction coil to heat an original pipe blank in the alternating magnetic field;

when the upper external bulging die and the lower external bulging die are closed, the left-end composite structure and the right-end composite structure are translated in an opposite mode until the copper ring a of the left-end composite structure and the copper ring b of the right-end composite structure are correspondingly meshed with notches on two sides of a middle die cavity of the external bulging die respectively, and a complete die cavity is formed.

Furthermore, the molded surfaces of the copper rings a and b, which are connected with the middle mold cavity of the external bulging mold, are both in a conical shape.

Furthermore, the external bulging die, the right-end internal bulging die and the left-end internal bulging die are all made of ceramic materials.

Further, the original tube blank is made of a titanium alloy, a Ti2 AlNb-based intermetallic compound, or a high strength aluminum alloy.

Further, the left end electromagnetic induction coil and the right end electromagnetic induction coil are made of copper bars.

The invention also aims to provide a coil induction heating ballooning forming method of a pipe fitting made of a difficultly-deformable material, which comprises the following steps of:

(1) Respectively and correspondingly embedding a left electromagnetic induction coil and a right electromagnetic induction coil outside the left-end internal bulging die and the right-end internal bulging die to correspondingly form a left-end composite structure and a right-end composite structure; respectively and correspondingly sleeving the combined left-end composite structure and right-end composite structure outside the left end and right end of the original pipe fitting blank, and finally respectively inserting the left-end sealing head and right-end sealing head into the left end and right end of the original pipe fitting blank;

(2) Placing the composite structure assembled in the step (1) in a die cavity formed by an upper external bulging die and a lower external bulging die, and combining the dies;

(3) Moving the left end composite structure and the right end composite structure to enable the circular rings at the end parts of the left end electromagnetic induction coil and the right end electromagnetic induction coil to be in contact, and at the moment, connecting the power supply, the circuit switch, the left end electromagnetic induction coil and the right end electromagnetic induction coil in series through a wire to form a power-on loop;

(4) Turning off a circuit switch, wherein alternating current generated by a power supply generates an alternating magnetic field when passing through the left and right electromagnetic induction coils, so that the original pipe blank in the alternating magnetic field rapidly generates heat and the temperature rises until the temperature of the original pipe blank rises to a preset gas expansion temperature required by gas expansion forming;

(5) Disconnecting a circuit switch, separating the left-end composite structure and the right-end composite structure, moving the left-end composite structure leftwards until the left-end composite structure is meshed with a gap on the left side of a central die cavity formed when the upper external bulging die and the lower external bulging die are closed, moving the right-end composite structure rightwards until the right-end composite structure is meshed with a gap on the left side of the central die cavity formed when the upper external bulging die and the lower external bulging die are closed, and forming a complete die cavity by the right end face of the left-end composite structure and the left end face of the right-end composite structure and the central die cavities of the upper external bulging die and the lower external bulging die at the moment;

(6) Injecting gas into the original pipe fitting blank from the inner through holes of the left sealing head and the right sealing head to improve the inner pressure of the original pipe fitting blank, and rapidly expanding the original pipe fitting blank reaching the preset gas expansion temperature under the action of the gas pressure until a die cavity formed by a left end composite structure, an upper outer bulging die, a lower outer bulging die and a right end composite structure is attached;

(7) And loosening the upper external bulging die and the lower external bulging die, and taking down the left-end composite structure and the right-end composite structure to obtain the bulging-formed pipe fitting.

Further, in the step (1), the right end internal bulging die and the left end internal bulging die are made of ceramic materials.

Further, in step (1), the raw pipe blank is made of a titanium alloy, a Ti2 AlNb-based intermetallic compound, or a high strength aluminum alloy.

According to the technical scheme, compared with the prior art, the invention has the following advantages:

the forming device adopts the electromagnetic induction coil wound on the outer side of the internal bulging die, heats the original pipe blank arranged in the internal bulging die to a target bulging forming temperature in an induction heating mode, and integrally and separately sets the internal bulging die wound with the electromagnetic induction coil at the left part and the right part as two parts: the left end composite structure and the right end composite structure are separated, so that a middle cavity formed when the external bulging die is in a die assembly state is exposed, and the middle cavity, and a left end composite structure end face and a right end composite structure end face which are respectively meshed with two sides of the middle cavity form a complete die cavity; and then injecting gas with preset pressure into the original pipe fitting blank through sealing heads sealed at two ends of the original pipe fitting blank, so that the original pipe fitting blank which is inductively heated to the preset gas expansion forming temperature is subjected to gas expansion forming under the pressure action provided by the gas until the original pipe fitting blank is attached to the complete die cavity. Therefore, the forming device disclosed by the invention realizes induction heating preparation and gas bulging forming preparation of the original pipe fitting blank respectively and correspondingly through die assembly and separation of the left-end composite structure and the right-end composite structure, has the advantages of simple equipment structure and simple and convenient process, is convenient for the pipe fitting to carry out rapid hot gas bulging forming, and improves the production efficiency.

In addition, the invention also has the following advantages:

(1) By utilizing the electromagnetic induction principle, heat is generated in the metal material difficult to deform, the temperature of the pipe fitting to be processed is increased, the plastic forming capability of the metal material difficult to deform is improved, the flowing capability is reduced, and the problem that the metal material difficult to deform is difficult to perform plastic forming in the prior art is solved to a certain extent;

(2) The air-bulking forming die adopts non-metallic ceramic materials, so that only the pipe fitting is heated when the coil is electrified, the heating efficiency is improved, the heating time is shortened, the production period is reduced, and the loss of equipment in production and the maintenance cost are reduced because the coil and the die do not generate heat;

(3) The electromagnetic induction coil is provided with the plurality of rings, so that the heating efficiency is extremely high, and the electromagnetic induction coil is uniformly covered outside the pipe fitting, so that a uniform alternating magnetic field can be generated, heat can be uniformly generated inside the pipe fitting, a uniform high-temperature field can be generated, the distortion caused by heating temperature difference can be avoided, and the forming quality can be improved;

(4) The end part of the electromagnetic induction coil is a circular ring with a special shape, the circular ring can be used as an electrode to transfer current when in contact, the circular ring can be quickly separated after reaching the required temperature, the circular ring can be combined with a die to form a die cavity, the equipment structure is simple, the process is simple and convenient, the pipe fitting can be conveniently and quickly subjected to hot-air bulging forming, and the production efficiency is improved.

Drawings

Fig. 1 is a schematic structural diagram of a coil induction heating ballooning forming device for a pipe made of a difficultly deformable material;

FIG. 2 is a schematic diagram of the first step in forming the inflatable forming apparatus of the present invention;

FIG. 3 is a schematic diagram of a third step in forming by the balloon forming apparatus of the present invention;

FIG. 4 is a schematic diagram of a fourth step in forming the inflatable forming apparatus of the present invention;

FIG. 5 is a schematic diagram of a sixth step in forming in the inflatable forming apparatus of the present invention;

figure 6 is a schematic cross-sectional view of the finished tube obtained after the complete completion of the forming step by the ballooning apparatus of the present invention;

in the figure: 1 is an upper external bulging die; 2, an original pipe fitting blank; 3 is a right-end electromagnetic induction coil; 4, a right-end internal bulging die; 5 is a right end sealing head; 6, a lower external bulging die; 7 is a left end sealing head; 8 is a left end internal bulging die; 9 is a left-end electromagnetic induction coil; 10 is a power supply; and 11 is a circuit switch.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention. The relative arrangement of the components and steps, expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as exemplary only and not as limiting. Thus, other examples of the exemplary embodiments may have different values.

For ease of description, spatially relative terms such as "over 8230 \ 8230;,"' over 8230;, \8230; upper surface "," above ", etc. may be used herein to describe the spatial relationship of one device or feature to another device or feature as shown in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary terms "at 8230; \8230; 'above" may include both orientations "at 8230; \8230;' above 8230; 'at 8230;' below 8230;" above ". The device may also be oriented in other different ways (rotated 90 degrees or at other orientations).

As shown in fig. 1 to 6, the coil induction heating and air-inflation forming device for a pipe fitting made of a difficult-to-deform material, which is disclosed by the invention, is used for heating and air-inflation forming of an original pipe fitting blank 2, and comprises external air-inflation dies 1 and 6, internal air-inflation dies 4 and 8 arranged in the external air-inflation dies, and a left sealing head 7 and a right sealing head 5 which are respectively sealed with the left end and the right end of the original pipe fitting blank 2; wherein:

the middle of the left end sealing head 7 and the right end sealing head 5 are provided with air inlets for injecting air into the inner tube of the original pipe fitting blank 2.

The external bulging dies 1 and 6 are divided into an upper external bulging die 1 and a lower external bulging die 6, a middle die cavity is formed when the upper external bulging die 1 and the lower external bulging die 6 are assembled, and notches are formed in two sides of the middle die cavity; the upper external bulging die 1 is made of ceramic material and carries the upper half of the central die cavity, and the lower external bulging die 6 is made of ceramic material and carries the lower half of the central die cavity.

The inner bulging dies 4 and 8 are arranged in a left-end composite structure and a right-end composite structure in a left-right split manner; the shape of the inner cavities of the internal bulging dies 4 and 8 is matched with the shape of the outer wall of the original pipe fitting blank 2, and meanwhile, the axial length of the original pipe fitting blank 2 is greater than that of the internal bulging dies in a die closing state; the original tube blank 2 is made of a non-deformable metal material, which may be selected from a titanium alloy, a Ti2 AlNb-based intermetallic compound or a high strength aluminum alloy.

The left end composite structure comprises a left end internal bulging die 8 which is arranged in a cylindrical shape and a left end electromagnetic induction coil 9 which is wound on the outer wall of the left end internal bulging die 8; the right side of the left electromagnetic induction coil 9 is provided with a copper ring a, and the left side is connected with the anode of a power supply 10 through a lead; the left end internal bulging die 8 is able to translate along the left side portion of the original tube blank 2; the left-end internal bulging die 8 is made of a ceramic material, and the right end portion of the left-end internal bulging die 8 is provided with an inclined surface. The left end electromagnetic induction coil 9 is formed by copper bar coiling, and the right-hand member portion of left end electromagnetic induction coil 9 is connected with the copper ring an of special shape, and in the drawing, the profile that copper ring a and middle part die cavity link up is the taper setting, and simultaneously, the outside bulging die inner wall outside copper ring a and the middle part die cavity has sliding connection face a.

The right end composite structure comprises a right end internal bulging die 4 and a right end electromagnetic induction coil 3, wherein the right end internal bulging die 4 is arranged in a cylindrical shape, and the right end electromagnetic induction coil is wound on the outer wall 4 of the right end internal bulging die; the left side of the right electromagnetic induction coil 3 is provided with a copper ring b, and the right side is connected with the negative electrode of a power supply 10 through a lead; the right end internal bulging die 4 is capable of translating along the right side portion of the original tube blank 2; the right-end internal bulging die 4 is made of a ceramic material, and the left end of the right-end internal bulging die 4 is provided with an inclined plane. The right-hand side electromagnetic induction coil 3 is formed by copper bar coiling, and the left end connection of right-hand side electromagnetic induction coil 3 has the copper ring b of special shape, and in the attached drawing, the profile that copper ring b and middle part die cavity link up is the taper setting, and simultaneously, copper ring b has sliding connection face b with the outside bulging die inner wall outside the middle part die cavity.

When the upper external bulging die 1 and the lower external bulging die 6 are closed, the left end composite structure and the right end composite structure are translated oppositely until the copper rings a and b are contacted with each other, and the left end electromagnetic induction coil 9 and the right end electromagnetic induction coil 3 form a power-on loop with the power supply 10 through wires; a circuit switch 11 is connected in series in the power-on loop, when a power supply 10 is switched on by closing the circuit switch 11, the left end electromagnetic induction coil 9 and the right end electromagnetic induction coil 3 generate an alternating magnetic field to heat the original pipe blank 2 in the alternating magnetic field; the power source 10 can generate an alternating current to a certain extent to inductively heat the original pipe blank 2 placed therebetween to a preset bulging temperature through the left end electromagnetic induction coil 9 and the right end electromagnetic induction coil 3.

When the upper external bulging die 1 and the lower external bulging die 6 are closed, the left-end composite structure and the right-end composite structure are translated in an opposite mode until the copper ring a of the left-end composite structure and the copper ring b of the right-end composite structure are correspondingly meshed with notches on two sides of a middle die cavity of the external bulging die respectively, and a complete die cavity is formed.

According to the inflatable forming device, the invention provides an inflatable forming method, which mainly comprises the following steps:

(1) As shown in fig. 2, a left electromagnetic induction coil 9 and a right electromagnetic induction coil 3 are respectively nested outside a left end internal bulging die 8 and a right end internal bulging die 4, composite structures are respectively sleeved outside the left end and the right end of an original pipe fitting blank 2, a left end sealing head 7 and a right end sealing head 5 are respectively inserted into the left end and the right end of the pipe fitting 2 to play a role of sealing the inside of the pipe fitting, and the composite structures formed by the above components are placed in die cavities of an upper external bulging die 1 and a lower external bulging die 6 and are subjected to die assembly;

(2) As shown in fig. 3, the left-end composite structure formed by the left-end electromagnetic induction coil 9 and the left-end internal bulging mold 8 and the right-end composite structure formed by the right-end electromagnetic induction coil 3 and the right-end internal bulging mold 4 are moved to make the rings at the ends of the left and right electromagnetic induction coils 9 and 3 contact with each other, so that the power supply 10, the circuit switch 11, the left-end electromagnetic induction coil 9 and the right-end electromagnetic induction coil 3 form a power-on loop;

(3) As shown in fig. 4, the circuit switch 11 is turned off, so that the power supply 10, the circuit switch 11, the left electromagnetic induction coil 9 and the right electromagnetic induction coil 3 form a power-on loop, the alternating current generated by the power supply 10 generates an alternating magnetic field when passing through the left and right electromagnetic induction coils 9 and 3, so that the pipe 2 in the magnetic field rapidly generates heat and the temperature rises until the temperature of the pipe rises to the temperature required for the bulging forming, and then the circuit switch 11 is turned off, so that the left composite structure formed by the left electromagnetic induction coil 9 and the left inner bulging mold 8 and the right composite structure formed by the right electromagnetic induction coil 3 and the right inner bulging mold 4 move left and right respectively and are attached to the inner mold cavities of the upper outer bulging mold 1 and the lower outer bulging mold 6, so as to form a complete mold cavity with a required shape;

(4) As shown in fig. 5, gas is injected into the pipe 2 from the inner through holes of the left and right sealing heads 7 and 5 to increase the inner pressure, and the pipe 2 rapidly expands under the action of high-pressure gas until a die cavity formed by the left end electromagnetic induction coil 9, the left end inner bulging die 8, the right end electromagnetic induction coil 3, the right end inner bulging die 4, the upper outer bulging die 1 and the lower outer bulging die 6 is attached;

(5) As shown in fig. 6, the upper external bulging die 1 and the lower external bulging die 6 are loosened, and the left-end electromagnetic induction coil 9, the left-end internal bulging die 8, the right-end electromagnetic induction coil 3 and the right-end internal bulging die 4 are removed from the pipe fitting 2, so that the formed pipe fitting made of the metal material difficult to deform and having a certain cross-sectional shape is obtained.

Claims (6)

1. A coil induction heating air-bulking forming device of a pipe fitting made of a difficult-to-deform material is used for heating air-bulking forming of an original pipe fitting blank and is characterized by comprising an external bulging die, an internal bulging die arranged in the external bulging die, and a left sealing head and a right sealing head which are correspondingly sealed with the left end and the right end of the original pipe fitting blank respectively; wherein:

the upper external bulging die and the lower external bulging die are arranged in a split manner from top to bottom, a middle die cavity is formed when the upper external bulging die and the lower external bulging die are assembled, and notches are formed in two sides of the middle die cavity;

the inner bulging die and the left and right split bodies are arranged into a left end composite structure and a right end composite structure; the shape of the inner cavity of the internal bulging die sum is matched with the shape of the outer wall of the original pipe fitting blank, and meanwhile, the axial length of the original pipe fitting blank is greater than that of the internal bulging die sum in a die closing state;

the left end composite structure comprises a cylindrical bulging die arranged in the left end and a left end electromagnetic induction coil wound on the outer wall of the left end internal bulging die; the right side of the left end electromagnetic induction coil is provided with a copper ring a, and the left side of the left end electromagnetic induction coil is connected with the anode of a power supply through a lead; the left-end internal bulging die can translate along the left part of the axis of the original pipe blank;

the right end composite structure comprises a right end internal bulging die and a right end electromagnetic induction coil, wherein the right end internal bulging die is arranged in a cylindrical shape, and the right end electromagnetic induction coil is wound on the outer wall of the right end internal bulging die; the left side of the right electromagnetic induction coil is provided with a copper ring b, and the right side of the right electromagnetic induction coil is connected with the negative electrode of a power supply through a lead; the right-end internal bulging die can translate along the right part of the axis of the original pipe blank;

when the upper external bulging die and the lower external bulging die are closed, the left end composite structure and the right end composite structure are translated oppositely until the copper rings a and b are contacted when the dies are closed, and the left end electromagnetic induction coil and the right end electromagnetic induction coil form a power-on closed loop with a power supply through wires; when the power supply 10 is switched on by the power-on circuit, an alternating magnetic field can be generated by the left end electromagnetic induction coil and the right end electromagnetic induction coil, and the original pipe blank in the alternating magnetic field is heated;

when the upper external bulging die and the lower external bulging die are closed, the left-end composite structure and the right-end composite structure are translated in an opposite mode until the copper ring a of the left-end composite structure and the copper ring b of the right-end composite structure are correspondingly meshed with notches on two sides of a middle die cavity of the external bulging die respectively, and a complete die cavity is formed.

2. The coil induction heating ballooning forming device for the pipe fitting made of the difficultly-deformable material as claimed in claim 1, wherein molded surfaces of the copper rings a and b, which are connected with a middle die cavity of the external bulging die, are arranged in a conical shape.

3. The coil induction heating physiosis forming device for the pipe fitting made of the difficultly-deformed material as claimed in claim 1, wherein the outer bulging die, the right-end inner bulging die and the left-end inner bulging die are made of ceramic materials.

4. The coil induction heating ballooning apparatus for a pipe of an undeformable material as claimed in claim 1, wherein the original pipe blank is made of a titanium alloy, ti2 AlNb-based intermetallic compound, or high strength aluminum alloy.

5. The coil induction heating ballooning forming device for the pipe fitting made of the difficultly-deformable material as claimed in claim 1, wherein the left-end electromagnetic induction coil and the right-end electromagnetic induction coil are made of copper bars.

6. A coil induction heating ballooning forming method for a pipe fitting made of a difficult-to-deform material is characterized by comprising the following steps of:

(1) Respectively and correspondingly embedding a left electromagnetic induction coil and a right electromagnetic induction coil outside the left-end internal bulging die and the right-end internal bulging die to correspondingly form a left-end composite structure and a right-end composite structure; respectively and correspondingly sleeving the combined left-end composite structure and right-end composite structure outside the left end and the right end of the original pipe fitting blank, and finally respectively inserting the left-end sealing head and the right-end sealing head into the left end and the right end of the original pipe fitting blank;

(2) Placing the composite structure assembled in the step (1) in a die cavity formed by an upper external bulging die and a lower external bulging die, and combining the dies;

(3) Moving the left end composite structure and the right end composite structure to enable the circular rings at the end parts of the left end electromagnetic induction coil and the right end electromagnetic induction coil to be in contact, and at the moment, forming a power-on closed loop by the power supply, the circuit switch, the left end electromagnetic induction coil and the right end electromagnetic induction coil through wires;

(4) Turning off a circuit switch, wherein alternating current generated by a power supply generates an alternating magnetic field when passing through the left and right electromagnetic induction coils, so that the original pipe blank in the alternating magnetic field rapidly generates heat and the temperature rises until the temperature of the original pipe blank rises to a preset gas expansion temperature required by gas expansion forming;

(5) Disconnecting a circuit switch, separating the left-end composite structure and the right-end composite structure, moving the left-end composite structure leftwards until the left-end composite structure is attached to a gap on the left side of a central die cavity formed when the upper external bulging die and the lower external bulging die are combined, moving the right-end composite structure rightwards until the right-end composite structure is attached to a gap on the left side of the central die cavity formed when the upper external bulging die and the lower external bulging die are combined, and forming a complete die cavity by the right end face of the left-end composite structure and the left end face of the right-end composite structure and the central die cavities of the upper external bulging die and the lower external bulging die at the moment;

(6) Injecting gas into the original pipe fitting blank from the inner through holes of the left sealing head and the right sealing head to improve the inner pressure of the original pipe fitting blank, and rapidly expanding the original pipe fitting blank reaching a preset gas expansion temperature under the action of the gas pressure until the original pipe fitting blank is attached to a die cavity formed by a left-end composite structure, an upper outer bulging die, a lower outer bulging die and a right-end composite structure;

(7) And (4) loosening the upper external bulging die and the lower external bulging die, and taking down the left-end composite structure and the right-end composite structure to obtain the bulging formed pipe fitting.

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