Coil induction heating gas expansion forming device and forming method for pipe fittings of difficult-to-deform materials

Abstract

The present invention discloses a coil induction heating gas expansion forming device and a forming method for a tube fitting made of a difficult-to-deform material. The present invention uses an electromagnetic induction coil wound around an internal expansion die, heats the original tube fitting blank to the target gas expansion forming temperature by means of induction heating, and integrally divides the internal expansion die into a left composite structure and a right composite structure on the left and right. Furthermore, by separating the left composite structure and the right composite structure, the middle cavity of the external expansion die is exposed, and the middle cavity, the right end face of the left composite structure, and the left end face of the right composite structure are engaged to form a complete die cavity; then, through the sealing heads sealed at both ends of the original tube fitting blank, gas with a preset pressure is injected into the original tube fitting blank, so that the original tube fitting blank is gas-expanded and formed under the action of the pressure provided by the gas until it fits with the complete die cavity. The structure of the present invention is simple, the process is simple, it is convenient for the tube fitting to be quickly hot gas-expanded and formed, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of forming of tubular parts made of difficult-to-deform metal materials, and particularly relates to a forming device and a forming method for electromagnetic induction heating and gas bulging of tubular parts made of difficult-to-deform materials by using the principle of electromagnetic induction heating. Background Art

[0002] In the aerospace aircraft manufacturing industry and the automotive manufacturing industry, tubular parts are a kind of parts that are widely used and very important, and have the characteristics of complex forming shapes, diverse forming process methods, and a wide variety of materials used. With the development of aerospace aircraft and the automotive industry, people have put forward higher requirements for the performance of tubular parts, and require tubular parts to have characteristics such as high temperature resistance, low density, and high strength at the same time. Materials such as titanium alloys, intermetallic compounds, and high-strength aluminum alloys have excellent properties such as low density and high specific strength, and components formed using these materials can also be used for a long time in a relatively high-temperature environment. For example, common titanium alloys can be used for a long time at 400°C - 600°C, and Ti2AlNb-based intermetallic compounds can be used for a long time at 600°C - 750°C. However, these materials have disadvantages such as poor plastic properties, obvious springback phenomenon, and difficulty in deformation, resulting in great difficulty in forming tubular parts made of such difficult-to-deform materials. In addition, during the forming process, the microstructure of the raw material may change or be damaged, thereby deteriorating the service performance of the formed tubular parts. Therefore, there is an urgent need to develop a forming method that can manufacture tubular parts made of difficult-to-deform materials such as titanium alloys with high efficiency and low cost.

[0003] Regarding the processing and forming devices and methods for difficult-to-deform metal tubular parts, certain research results have been achieved.

[0004] The patent CN 201510191192.3 of Wang Yongjun et al. describes an incremental temperature difference bulging device and a bulging method for metal tubes. The characteristics of this patent are that the structure includes a bulging die, an electromagnetic induction heating mechanism, and a coil feeding mechanism. During the heating and bulging process, part of the tube blank is heated in segments without heating the die, and the heated part of the tube is bulged, so as to achieve the incremental temperature difference bulging of the tube part, improve the forming performance of the material, reduce the springback of the tube, and solve the problems of instability and wrinkling of the tube. However, because this patent requires an accurate coil feeding mechanism, the device structure required for forming is complex and costly. In addition, the electromagnetic heating coil used in this patent is a single turn, resulting in a problem of low heating efficiency.

[0005] The patent CN 201510050971.1 by Wang Wang et al. describes an electromagnetic induction heating and bulging device and forming method for metal conductor pipe fittings. The feature of this invention is that the bulging die is located inside the electromagnetic induction coil of the electromagnetic induction heating unit. During forming, only the pipe blank is heated and the die is not heated, thus realizing the gas pressure bulging of metal conductor pipe fittings at high temperature. However, in this invention, the electromagnetic induction coil is located outside the bulging die, resulting in poor electromagnetic induction heating effect. At the same time, a longer coil is required, increasing the cost.

[0006] Currently, the common processing and forming methods for difficult-to-deform metals such as titanium alloys at home and abroad are forming after heating. Utilizing the characteristic that the plasticity of the material is improved to a certain extent after heating, processing and forming are carried out after heating the die or the raw material. The traditional heating methods generally use resistance wires or quartz for heating. After the resistance wires or quartz generate heat by themselves when electrified, the heat is transferred to the workpiece to be processed through heat conduction, thus achieving the effect of heating the workpiece. This traditional heating method has low efficiency, with 50% of the energy dissipated into the air, resulting in high power loss. At the same time, this forming method often has disadvantages such as long heating time, difficult temperature control, high energy consumption, and low production efficiency, making it difficult to be applied in large-scale production. Moreover, the heating equipment for this forming method is often complex and expensive. For difficult-to-deform materials such as titanium alloys containing active metal elements, Ti2AlNb-based intermetallic compounds, and high-strength aluminum alloys, cooling systems, vacuum, and gas protection devices are also required, which not only increase the potential safety hazards of the equipment but also easily pollute the environment. In addition, due to long-term heating, abnormal grain growth is likely to occur, reducing the service performance.

[0007] Heating metal parts using the principle of electromagnetic induction is another way to heat parts using electrical energy. By passing an alternating current of a certain degree through the electromagnetic induction coil, an alternating magnetic field is generated. The monitored parts with magnetic permeability are placed in the magnetic field to cut the alternating magnetic force lines, thereby generating an alternating current (i.e., eddy current) inside the metal parts. The eddy current makes the atoms inside the metal parts move at high speed and randomly, and the atoms collide and rub against each other to generate heat energy, thus achieving the effect of heating the metal parts. This heating method has a higher energy conversion efficiency compared to the traditional heating method, avoiding energy waste, significantly reducing the average preheating time; and reducing production costs, extending the service life of the equipment, and being able to heat the parts fully and evenly; since the electromagnetic induction heating equipment only heats the workpiece during operation and does not generate heat itself, it can reduce the later maintenance cost, and is reliable in operation, easy to control, making the forming production more green, energy-saving, safe, and comfortable. Summary of the Invention

[0008] The object of the present invention is to provide a coil induction heating and hydroforming device and a forming method for tubes made of difficult-to-deform materials. According to the electromagnetic effect, an alternating current generated by an induction heating power supply passes through an induction coil to generate an alternating magnetic field. An alternating current is generated inside the metal material placed therein, causing heat energy to be generated inside the object, thereby heating the metal to improve the plastic deformation ability of the metal material, reduce the flow stress of the material, and make some difficult-to-deform metal materials more easily subjected to plastic forming processing. The forming device described in the present invention is a composite structure combining an electromagnetic induction heating device and a hydroforming device. The electromagnetic induction heating device is designed inside the hydroforming die and serves as a part of the die cavity. The electromagnetic induction coil is divided into left and right parts and can be moved. When the coils of the left and right parts are closed, they can serve as an electromagnetic induction device to heat the tube inside the die. When the coils of the left and right parts are respectively moved to the leftmost and rightmost ends and engaged with the die, they can complement to form a complete die cavity, so that the tube can be hydroformed and conform to the die, obtaining a tube with a certain cross-sectional shape.

[0009] To achieve the above technical object, the present invention will adopt the following technical solutions:

[0010] A coil induction heating and hydroforming device for tubes made of difficult-to-deform materials, used for heating and hydroforming of the original tube blank, includes an external hydroforming die, an internal hydroforming die placed inside the external hydroforming die, and a left sealing head and a right sealing head respectively sealed to the left and right ends of the original tube blank; wherein:

[0011] The external hydroforming die is divided into an upper external hydroforming die and a lower external hydroforming die in an up-and-down split manner, and a middle die cavity is formed when the upper external hydroforming die and the lower external hydroforming die are closed. There are gaps on both sides of the middle die cavity;

[0012] The internal hydroforming die is divided into a left composite structure and a right composite structure in a left-and-right split manner; the inner cavity shape of the internal hydroforming die matches the outer wall shape of the original tube blank. At the same time, the axial length of the original tube blank is greater than the axial length of the internal hydroforming die in the closed die state;

[0013] The left composite structure includes a left-end internal hydroforming die arranged in a cylindrical shape and a left-end electromagnetic induction coil wound around the outer wall of the left-end internal hydroforming die; a copper ring a is arranged on the right side of the left-end electromagnetic induction coil, and the left side is connected to the positive pole of the power supply through a wire; the left-end internal hydroforming die can translate along the left part of the original tube blank;

[0014] The right - hand composite structure described above includes a right - hand internal hydroforming die arranged in a cylindrical shape and a right - hand electromagnetic induction coil wound around the outer wall of the right - hand internal hydroforming die; a copper ring b is arranged on the left side of the right - hand electromagnetic induction coil, and the right side is connected to the negative pole of the power supply through a wire; the right - hand internal hydroforming die can translate along the right - hand part of the original pipe blank.

[0015] When the upper external hydroforming die and the lower external hydroforming die are closed, the left - hand composite structure and the right - hand composite structure translate towards each other until, when closed, the copper ring a and the copper ring b touch each other, and the left - hand electromagnetic induction coil and the right - hand electromagnetic induction coil form an energized circuit with the power supply through a wire; when the energized circuit is connected to the power supply, an alternating magnetic field can be generated through the left - hand electromagnetic induction coil and the right - hand electromagnetic induction coil to heat the original pipe blank within the alternating magnetic field.

[0016] When the upper external hydroforming die and the lower external hydroforming die are closed, the left - hand composite structure and the right - hand composite structure translate away from each other until the copper ring a of the left - hand composite structure and the copper ring b of the right - hand composite structure are respectively meshed with the notch positions on both sides of the middle die cavity of the external hydroforming die to form a complete die cavity.

[0017] Furthermore, the profiled surfaces of the copper ring a and the copper ring b connected to the middle die cavity of the external hydroforming die are both arranged in a conical shape.

[0018] Furthermore, the external hydroforming die, the right - hand internal hydroforming die, and the left - hand internal hydroforming die are all made of ceramic materials.

[0019] Furthermore, the original pipe blank is made of titanium alloy, Ti2AlNb - based intermetallic compound, or high - strength aluminum alloy.

[0020] Furthermore, the left - hand electromagnetic induction coil and the right - hand electromagnetic induction coil are made of copper rods.

[0021] Another technical objective of the present invention is to provide a coil - induced heating gas - assisted forming method for pipes made of difficult - to - deform materials, including the following steps:

[0022] (1) Nest the left electromagnetic induction coil and the right electromagnetic induction coil respectively outside the left - hand internal hydroforming die and the right - hand internal hydroforming die to correspondingly form a left - hand composite structure and a right - hand composite structure; sleevethe combined left - hand composite structure and right - hand composite structure respectively outside the left - hand and right - hand ends of the original pipe blank, and finally insert the left - hand sealing head and the right - hand sealing head into the left - hand and right - hand ends of the original pipe blank respectively.

[0023] (2) Place the composite structure assembled in step (1) in the die cavity formed by the upper external hydroforming die and the lower external hydroforming die, and close the die.

[0024] (3) Move the left - end composite structure and the right - end composite structure so that the rings at the ends of the left - and right - end electromagnetic induction coils are in contact. At this time, the power supply, the circuit switch, the left - end electromagnetic induction coil, and the right - end electromagnetic induction coil are connected in series through wires to form a powered circuit;

[0025] (4) Close the circuit switch. The alternating current generated by the power supply generates an alternating magnetic field when passing through the left - and right - end electromagnetic induction coils, causing the original pipe blank located within the alternating magnetic field to rapidly generate heat by itself, increasing the temperature until the temperature of the original pipe blank rises to the preset gas - inflation temperature required for gas - inflation forming;

[0026] (5) Disconnect the circuit switch, separate the left - end composite structure and the right - end composite structure. The left - end composite structure moves to the left until it meshes with the notch on the left side of the central die cavity formed when the upper external bulging die and the lower external bulging die are closed, while the right - end composite structure moves to the right until it meshes with the notch on the left side of the central die cavity formed when the upper external bulging die and the lower external bulging die are closed. At this time, the right end face of the left - end composite structure and the left end face of the right - end composite structure, together with the central die cavity of the upper external bulging die and the lower external bulging die, form a complete die cavity;

[0027] (6) Inject gas into the original pipe blank through the internal through - holes of the left and right sealing heads to increase the internal pressure of the original pipe blank. Under the pressure of the gas, the original pipe blank at the preset gas - inflation temperature rapidly expands until it fits the die cavity formed by the left - end composite structure, the upper external bulging die, the lower external bulging die, and the right - end composite structure;

[0028] (7) Loosen the upper external bulging die and the lower external bulging die, and remove the left - end composite structure and the right - end composite structure, then the bulged and formed pipe is obtained.

[0029] Further, in step (1), both the right - end internal bulging die and the left - end internal bulging die are made of ceramic materials.

[0030] Further, in step (1), the original pipe blank is made of titanium alloy, Ti2AlNb - based intermetallic compound, or high - strength aluminum alloy.

[0031] According to the above - mentioned technical solution, compared with the prior art, the present invention has the following advantages:

[0032] The forming device described in the present invention uses an electromagnetic induction coil wound around the outside of an internal bulging die. By means of induction heating, the original pipe fitting blank placed inside the internal bulging die is heated to the target gas bulging forming temperature. The internal bulging die with the electromagnetic induction coil wound around its outside is integrally divided into two parts, a left - end composite structure and a right - end composite structure, from left to right. Furthermore, by separating the left - end composite structure and the right - end composite structure, the middle cavity formed when the external bulging die is in the closed - die state can be exposed. The middle cavity, the end face of the left - end composite structure and the end face of the right - end composite structure that are respectively engaged with both sides of the middle cavity form a complete die cavity. Then, through the sealing heads sealed at both ends of the original pipe fitting blank, gas with a preset pressure is injected into the original pipe fitting blank, so that the original pipe fitting blank heated by induction to the preset gas bulging forming temperature bulges and forms under the action of the pressure provided by the gas until it fits the complete die cavity. It can be seen from this that the forming device described in the present invention realizes the induction heating preparation and gas bulging forming preparation of the original pipe fitting blank respectively through the closing and separation of the left - end composite structure and the right - end composite structure. The equipment structure is simple, the process is convenient, which is convenient for the pipe fitting to quickly carry out hot gas bulging forming, and improves the production efficiency.

[0033] In addition, the present invention also has the following advantages:

[0034] (1) Utilizing the principle of electromagnetic induction, heat is generated in the difficult - to - deform metal material, increasing the temperature of the pipe fitting to be processed, improving the plastic forming ability of the difficult - to - deform metal material, and reducing its flowability. To a certain extent, it solves the problem that the difficult - to - deform metal material is difficult to be plastically processed and formed in the prior art;

[0035] (2) The gas bulging die in the present invention uses a non - metal ceramic material. Therefore, when the coil is energized, only the pipe fitting is heated, improving the heating efficiency, shortening the heating time, reducing the production cycle. And because the coil and the die itself do not generate heat, the loss of the equipment during production is reduced, and the maintenance cost is reduced;

[0036] (3) The electromagnetic induction coil in the present invention has multiple loops, so it has extremely high heating efficiency. And because the electromagnetic induction coil evenly covers the outside of the pipe fitting, a uniform alternating magnetic field can be generated, enabling the pipe fitting to generate heat evenly inside, generating a uniform high - temperature temperature field, thus avoiding distortion caused by the heating temperature difference and improving the forming quality;

[0037] (4) The end of the electromagnetic induction coil in the present invention is a ring with a special shape, which can be used as an electrode to transfer current when in contact. After reaching the required temperature, it can be quickly separated, and it can be combined with the die to form a die cavity. The equipment structure is simple, the process is convenient, which is convenient for the pipe fitting to quickly carry out hot gas bulging forming, and improves the production efficiency. Brief Description of the Drawings

[0038] Figure 1 It is a schematic structural diagram of a coil induction heating and hydroforming device for a difficult-to-deform material pipe fitting according to the present invention;

[0039] Figure 2 It is a schematic diagram of the first step of the hydroforming when the hydroforming device according to the present invention is performing forming;

[0040] Figure 3 It is a schematic diagram of the third step of the hydroforming when the hydroforming device according to the present invention is performing forming;

[0041] Figure 4 It is a schematic diagram of the fourth step of the hydroforming when the hydroforming device according to the present invention is performing forming;

[0042] Figure 5 It is a schematic diagram of the sixth step of the hydroforming when the hydroforming device according to the present invention is performing forming;

[0043] Figure 6 It is a schematic cross-sectional view of the finished pipe fitting obtained after all the forming steps of the hydroforming device according to the present invention;

[0044] In the figure: 1 is the upper external bulging die; 2 is the original pipe fitting blank; 3 is the right-end electromagnetic induction coil; 4 is the right-end internal bulging die; 5 is the right-end sealing head; 6 is the lower external bulging die; 7 is the left-end sealing head; 8 is the left-end internal bulging die; 9 is the left-end electromagnetic induction coil; 10 is the power supply; 11 is the circuit switch. Detailed implementation manners

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. Unless otherwise specifically stated, the relative arrangements, expressions, and numerical values of the components and steps described in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the said technologies, methods, and devices should be regarded as a part of the authorization specification. In all the examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0046] For ease of description, spatial relative terms, such as "above", "over", "on the upper surface", "upper", etc., may be used herein to describe the spatial positional relationship of one device or feature to other devices or features as shown in the figures. It should be understood that the spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, the device described as "above" or "over" other devices or structures will then be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations).

[0047] As Figures 1 to 6 shown, the coil induction heating gas expansion forming device for the difficult-to-deform material pipe fitting of the present invention is used for the heating gas expansion forming of the original pipe fitting blank 2, and includes external expansion molds 1 and 6, internal expansion molds 4 and 8 placed inside the external expansion molds, and a left sealing head 7 and a right sealing head 5 respectively hermetically connected to the left and right ends of the original pipe fitting blank 2; wherein:

[0048] Both the left end sealing head 7 and the right sealing head 5 are provided with air inlet holes in the middle for injecting gas into the inner pipe of the original pipe fitting blank 2.

[0049] The external expansion molds 1 and 6 are divided into an upper external expansion mold 1 and a lower external expansion mold 6 in an upper and lower split manner, and a middle mold cavity is formed when the upper external expansion mold 1 and the lower external expansion mold 6 are closed, and notches are provided on both sides of the middle mold cavity; the upper external expansion mold 1 is made of ceramic material and has the upper half of the middle mold cavity, and the lower external expansion mold 6 is made of ceramic material and has the lower half of the middle mold cavity.

[0050] The internal expansion molds 4 and 8 are divided into a left end composite structure and a right end composite structure in a left and right split manner; the inner cavity shapes of the internal expansion molds 4 and 8 match the outer wall shape of the original pipe fitting blank 2, and at the same time, the axial length of the original pipe fitting blank 2 is greater than the axial length of the internal expansion mold in the closed mold state; the original pipe fitting blank 2 is made of a difficult-to-deform metal material, and can be selected from titanium alloy, Ti2AlNb-based intermetallic compound or high-strength aluminum alloy.

[0051] The left-end composite structure described above includes a left-end internal bulging die 8 arranged in a cylindrical shape and a left-end electromagnetic induction coil 9 wound around the outer wall of the left-end internal bulging die 8. A copper ring a is arranged on the right side of the left-end electromagnetic induction coil 9, and the left side is connected to the positive pole of a power supply 10 through a wire. The left-end internal bulging die 8 can translate along the left part of the original pipe blank 2. The left-end internal bulging die 8 is made of ceramic material, and the right end of the left-end internal bulging die 8 has an inclined surface. The left-end electromagnetic induction coil 9 is wound by copper rods, and a copper ring a with a special shape is connected to the right end of the left-end electromagnetic induction coil 9. In the attached drawing, the profile surface where the copper ring a is connected to the middle die cavity is arranged in a conical shape. At the same time, the copper ring a has a sliding connection surface a with the inner wall of the external bulging die outside the middle die cavity.

[0052] The right-end composite structure described above includes a right-end internal bulging die 4 arranged in a cylindrical shape and a right-end electromagnetic induction coil 3 wound around the outer wall of the right-end internal bulging die 4. A copper ring b is arranged on the left side of the right-end electromagnetic induction coil 3, and the right side is connected to the negative pole of the power supply 10 through a wire. The right-end internal bulging die 4 can translate along the right part of the original pipe blank 2. The right-end internal bulging die 4 is made of ceramic material, and the left end of the right-end internal bulging die 4 has an inclined surface. The right-end electromagnetic induction coil 3 is wound by copper rods, and a copper ring b with a special shape is connected to the left end of the right-end electromagnetic induction coil 3. In the attached drawing, the profile surface where the copper ring b is connected to the middle die cavity is arranged in a conical shape. At the same time, the copper ring b has a sliding connection surface b with the inner wall of the external bulging die outside the middle die cavity.

[0053] 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 translate towards each other until the copper ring a and the copper ring b touch when closed. The left-end electromagnetic induction coil 9 and the right-end electromagnetic induction coil 3 form a closed circuit with the power supply 10 through wires. A circuit switch 11 is connected in series in the closed circuit. When the power supply 10 is turned 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 supply 10 can generate a certain degree of alternating current to inductively heat the original pipe blank 2 placed between the left-end electromagnetic induction coil 9 and the right-end electromagnetic induction coil 3 to a preset bulging temperature.

[0054] 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 translate away from each other until the copper ring a of the left-end composite structure and the copper ring b of the right-end composite structure are respectively meshed with the notch positions on both sides of the middle die cavity of the external bulging die to form a complete die cavity.

[0055] According to the above-mentioned air bulging forming device, the present invention provides an air bulging forming method, which mainly includes the following steps:

[0056] (1) As shown in Figure 2 , the left electromagnetic induction coil 9 and the right electromagnetic induction coil 3 are respectively nested outside the left - end internal bulging die 8 and the right - end internal bulging die 4. The composite structure is respectively sleeved outside the left end and the right end of the original pipe blank 2. The left - end sealing head 7 and the right - end sealing head 5 are respectively inserted into the left end and the right end of the pipe 2 to seal the inside of the pipe. The composite structure composed of the above components is placed in the mold cavities of the upper external bulging die 1 and the lower external bulging die 6, and the mold is closed;

[0057] (2) As shown in Figure 3 , move the left - end composite structure composed of the left - end electromagnetic induction coil 9 and the left - end internal bulging die 8 and the right - end composite structure composed of the right - end electromagnetic induction coil 3 and the right - end internal bulging die 4, so that the rings at the ends of the left and right electromagnetic induction coils 9 and 3 are in contact. Make 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 closed circuit;

[0058] (3) As shown in Figure 4 , close the circuit switch 11, 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 closed circuit. 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, causing the pipe 2 located in the magnetic field to quickly generate heat by itself, and the temperature rises until the temperature of the pipe rises to the temperature required for air - bulging forming. Then, disconnect the circuit switch 11, and move the left - end composite structure composed of the left - end electromagnetic induction coil 9 and the left - end internal bulging die 8 and the right - end composite structure composed of the right - end electromagnetic induction coil 3 and the right - end internal bulging die 4 to the left and right respectively, and fit them with the internal mold cavities of the upper external bulging die 1 and the lower external bulging die 6 to form a complete mold cavity with the required shape;

[0059] (4) As shown in Figure 5 , inject gas into the pipe 2 through the internal through - holes of the left and right sealing heads 7 and 5 to increase the internal pressure. Under the action of the high - pressure gas, the pipe 2 expands rapidly until it fits the mold cavity composed of the left - end electromagnetic induction coil 9, the left - end internal bulging die 8, the right - end electromagnetic induction coil 3, the right - end internal bulging die 4, the upper external bulging die 1 and the lower external bulging die 6;

[0060] (5) As shown in Figure 6 , loosen the upper external bulging die 1 and the lower external bulging die 6, and remove 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 from the pipe 2, then a formed pipe made of a difficult - to - deform metal material with a certain cross - sectional shape is obtained.

Claims

1. A coil induction heating and hydroforming device for hard-to-deform material pipe fittings, used for the heating and hydroforming of the original pipe fitting blanks, characterized in that, It includes an external bulging die, an internal bulging die placed inside the external bulging die, and a left sealing head and a right sealing head respectively sealed to the left and right ends of the original pipe blank; where: The external bulging die is divided into an upper external bulging die and a lower external bulging die in the up and down direction. When the upper external bulging die and the lower external bulging die are closed, a middle die cavity is formed, and notches are provided on both sides of the middle die cavity; The internal bulging die is divided into a left-end composite structure and a right-end composite structure in the left and right direction; the inner cavity shape of the internal bulging die matches the outer wall shape of the original pipe blank. At the same time, the axial length of the original pipe blank is greater than the axial length of the internal bulging die in the closed die state; The left-end composite structure includes a left-end internal bulging die arranged in a cylindrical shape and a left-end electromagnetic induction coil wound around the outer wall of the left-end internal bulging die; a copper ring a is arranged on the right side of the left-end electromagnetic induction coil, and the left side is connected to the positive pole of the power supply through a wire; the left-end internal bulging die can translate along the left part of the axis of the original pipe blank; the surface of the copper ring a connecting with the middle die cavity of the external bulging die is arranged in a conical shape; The right-end composite structure includes a right-end internal bulging die arranged in a cylindrical shape and a right-end electromagnetic induction coil wound around the outer wall of the right-end internal bulging die; a copper ring b is arranged on the left side of the right-end electromagnetic induction coil, and the right side is connected to the negative pole of the power supply through a wire; the right-end internal bulging die can translate along the right part of the axis of the original pipe blank; the surface of the copper ring b connecting with the middle die cavity of the external bulging die is arranged in a conical shape; 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 translate towards each other until they are closed, and at this time, the copper ring a and the copper ring b are in contact. The left-end electromagnetic induction coil and the right-end electromagnetic induction coil form a closed energized circuit with the power supply through wires; when the energized circuit is connected to the power supply, an alternating magnetic field can be generated through the left-end electromagnetic induction coil and the right-end electromagnetic induction coil to heat the 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 translate away from each other until the copper ring a of the left-end composite structure and the copper ring b of the right-end composite structure are respectively meshed with the positions of the notches on both sides of the middle die cavity of the external bulging die to form a complete die cavity.

2. The coil induction heating and hydroforming device for hard-to-deform material pipe fittings according to claim 1, characterized in that, The external bulging die, the right-end internal bulging die, and the left-end internal bulging die are all made of ceramic materials.

3. The coil induction heating and hydroforming device for hard-to-deform material pipe fittings according to claim 1, characterized in that, The original pipe blank is made of titanium alloy, Ti2AlNb-based intermetallic compound, or high-strength aluminum alloy.

4. The coil induction heating and hydroforming device for hard-to-deform material pipe fittings according to claim 1, characterized in that, The left-end electromagnetic induction coil and the right-end electromagnetic induction coil are made of copper rods.

5. A forming method of the coil induction heating and hydroforming device for hard-to-deform material pipe fittings according to claim 1, characterized in that, It includes the following steps: (1) Nest the left electromagnetic induction coil and the right electromagnetic induction coil respectively 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; sleeved the combined left-end composite structure and right-end composite structure respectively outside the left end and the right end of the original pipe blank, and finally insert the left sealing head and the right sealing head into the left end and the right end of the original pipe blank respectively; (2) Place the composite structure assembled in step (1) in the mold cavity formed by the upper external bulging die and the lower external bulging die, and close the mold. (3) Move the left-end composite structure and the right-end composite structure so that the rings at the ends of the left and right electromagnetic induction coils are in contact. At this time, the power supply, the circuit switch, the left-end electromagnetic induction coil, and the right-end electromagnetic induction coil form a closed energized loop through the wire. (4) Close the circuit switch. The alternating current generated by the power supply generates an alternating magnetic field when passing through the left and right electromagnetic induction coils, causing the original pipe blank located in the alternating magnetic field to rapidly generate heat by itself, increasing the temperature until the temperature of the original pipe blank rises to the preset gas bulging temperature required for gas bulging forming. (5) Disconnect the circuit switch, separate the left-end composite structure and the right-end composite structure. The left-end composite structure moves to the left until it engages with the notch on the left side of the central mold cavity formed when the upper external bulging die and the lower external bulging die are closed, while the right-end composite structure moves to the right until it engages with the notch on the left side of the central mold cavity formed when the upper external bulging die and the lower external bulging die are closed. At this time, the right end face of the left-end composite structure and the left end face of the right-end composite structure and the central mold cavity of the upper external bulging die and the lower external bulging die form a complete mold cavity. (6) Inject gas into the original pipe blank through the internal through holes of the left and right sealing heads to increase the internal pressure of the original pipe blank. Under the pressure of the gas, the original pipe blank at the preset gas bulging temperature rapidly expands until it fits into the mold cavity formed by the left-end composite structure, the upper external bulging die, the lower external bulging die, and the right-end composite structure. (7) Loosen the upper external bulging die and the lower external bulging die, and remove the left-end composite structure and the right-end composite structure to obtain the pipe formed by bulging.

Images