Low-plasticity metal pipe-plate connecting method and device based on electromagnetic induction heating

Abstract

The invention belongs to the technical field of metal plate and pipe connection, and discloses a low-plasticity metal pipe-plate connection method and device based on electromagnetic induction heating. The method comprises the following steps that pipe blanks to be connected are inserted into a plate; the pipe blank is filled with solid particles; placing an upper coil on the upper side of the circular hole of the plate and placing a lower coil on the lower side; the upper coil and the lower coil correspond to a to-be-bulged area of the pipe blank; alternating current is introduced into the upper coil and the lower coil, and the to-be-bulged area of the pipe blank is heated; pressure is applied to the pressure applying end of the pipe blank, the solid particles are extruded, radial pressure is applied to the pipe blank, the temperature of a to-be-expanded area of the pipe blank is high, the pipe blank deforms preferentially after being extruded, the radial size of the expanded area of the pipe blank is continuously increased, and the pipe blank and the plate are locked. According to the low-plasticity metal pipe-plate connecting method adopting electromagnetic induction heating, the wall thickness distribution of the pipe blank is uniform in the plastic deformation period, the stress state is reasonable, and the connecting quality of the low-plasticity metal pipe-plate can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of plate-tube expansion connection, and in particular relates to a low-plasticity metal tube-plate connection method and device based on electromagnetic induction heating. Background Art

[0002] Plate-tube connection structures are widely used in aerospace, automobile, food, medicine and other fields, and their connection strength and quality are key indicators. However, different tube and plate materials have different mechanical properties such as plasticity and elastic modulus, and their expansion effects are also different. For example, low-plasticity tubes such as aluminum alloys and titanium alloys have uneven wall thickness during the expansion process, and even cracks and other defects may occur in severe cases. During use, stress concentration is easily caused, which reduces the service life of the tube and may cause tube rupture, causing safety problems such as leakage.

[0003] At present, the expansion process uses a tube expander to cause plastic deformation of the tube blank and elastic deformation of the plate hole, so as to tightly connect the tube blank and the plate, which has the advantages of high connection strength, low cost, and flexible operation. However, during the expansion process, the low-plasticity tube blank has limited plastic deformation capacity. When subjected to radial force applied by the tube expander or other expansion means, it is easy to exceed the limit deformation of the material and affect the connection quality. At the same time, for some bent tubes and plate expansion, the expansion points of traditional mechanical expansion are limited.

[0004] Therefore, it is urgent to develop new methods for low-plasticity metal tube-sheet connection. Summary of the invention

[0005] The purpose of the present invention is to provide a low-plasticity metal tube-plate connection method and device based on electromagnetic induction heating, so as to solve the problem that the expansion points of traditional mechanical expansion joints are limited and the ultimate deformation degree is difficult to control.

[0006] The present invention is achieved through the following technical solutions: A low-plasticity metal tube-plate connection method based on electromagnetic induction heating comprises the following steps: S1. inserting a tube blank to be connected into a plate; the tube blank is filled with solid particles; Place the upper coil on the upper side of the circular hole of the plate, and the lower coil on the lower side; The upper coil and the lower coil correspond to the tube blank to be expanded; S2, an alternating current is passed through the upper coil and the lower coil, and the tube blank to be expanded is heated; S3. Apply pressure to the pressure end of the tube billet, the solid particles are squeezed, and radial pressure is generated on the tube billet. The temperature of the tube billet in the expansion zone is high, and it is deformed first after being subjected to the extrusion force. The radial size of the expansion zone of the tube billet continues to increase and a lock is formed between the sheet and the sheet.

[0007] Further, in S1, a lower plug is installed at one end of the tube blank, solid particles are injected into the cavity of the tube blank, and a plunger is installed at the other end of the tube blank. Furthermore, in S2, the frequency, current intensity and power-on time of the alternating current flowing through the upper coil and the lower coil are determined by the tube blank material.

[0008] Furthermore, the alternating current is a short-time high-frequency alternating current, and the specific parameters are: The AC frequency is 10kHz-1MHz, the current is 200A-500A, and the power-on time is 5s-20s.

[0009] Further, S2 is specifically as follows: after the alternating current is passed through the upper coil and the lower coil, an alternating magnetic field is generated. After the tube blank in the alternating magnetic field generates an induced electromotive force, an induced current is generated, which converts electrical energy into thermal energy, so that the temperature of the tube blank to be expanded is increased to a preset temperature.

[0010] Furthermore, the preset temperature is designed according to the material of the tube blank.

[0011] The present invention also discloses a low-plasticity metal tube-plate connection device based on electromagnetic induction heating for realizing the method, comprising an upper coil and a lower coil; When in use, the tube blank is inserted into the plate, the upper coil and the lower coil are sleeved on the outside of the tube blank, corresponding to the position of the area to be expanded, the upper coil is located on the upper surface of the plate, and the lower coil is located on the lower surface of the plate; one end of the tube blank is sealed by the lower plug, and a plunger is placed on the other end; the cavity formed by the tube blank, the plunger and the lower plug is filled with solid particles.

[0012] Furthermore, the upper coil and the lower coil are planar spiral coils.

[0013] Further, the solid particles are ceramic particles; When the product precision requirement is relatively low, the diameter of the solid particles is 1-5mm; when the product precision requirement is high, the diameter of the solid particles is 0.1-0.5mm.

[0014] Furthermore, the size of the lower coil and the upper coil is determined by the outer diameter of the tube, the thermal expansion coefficient of the material and the degree of pre-deformation; Sealing rings are respectively arranged between the tube blank and the plunger, and between the tube blank and the lower plug.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a low-plasticity metal tube-plate connection method based on electromagnetic induction heating. Solid particles are loaded into the tube blank, coils are placed above and below the plate, and alternating current is passed through the upper coil and the lower coil to generate an alternating magnetic field. The tube blank in the alternating magnetic field generates an induced electromotive force to generate an induced current, converting electrical energy into thermal energy, so that the temperature of the tube blank to be expanded is increased to a suitable temperature, and the plasticity is improved. Pressure is applied to one end of the tube blank to extrude the solid particles, and the solid particles generate radial pressure on the tube blank. The temperature of the tube blank to be expanded is high and the plasticity is good. After being subjected to the extrusion force, plastic deformation occurs before the low-temperature part. The outer diameter of the tube blank expansion zone continues to increase, and the plate and the tube blank are squeezed against each other to form a firm lock, completing the expansion process. Different from the traditional expansion process, a method for electromagnetic induction heating of the low-plasticity tube blank to be expanded is proposed to improve the plasticity of the tube blank to be expanded and optimize the stress state after forming. Solid particles are used as force transmission medium. Solid particles are less affected by the heat of the tube expansion zone during the expansion process. At the same time, compared with the traditional rigid mold, the stress state of the low-plasticity metal tube during the connection between the plate and the tube can be improved, and the connection quality between the plate and the tube can be effectively improved. The present invention solves the current problems of low-plasticity metal tube expansion deformation and limited expansion points, and can effectively improve the connection quality of low-plasticity metal tubes and plates. The expansion method using electromagnetic induction assisted heating can improve the plasticity of the tube to be expanded, promote the flow of tube material, make the wall thickness of the tube uniformly distributed during plastic deformation, and make the stress state reasonable, thereby increasing the service life of the connection.

[0016] The device disclosed in the present invention for realizing the method of connecting pipes and plates by utilizing plastic deformation of pipes has a simple structure, reasonable design, convenient installation, good compatibility with conventional equipment, and is suitable for mass production.

[0017] Furthermore, the force transmission medium is selected from ceramic particles, which are less affected by the alternating electric field and temperature during expansion. The particle size of ceramic particles is closely related to the molding quality. When the product precision requirement is relatively low, the particle diameter is generally 1-5mm. When the product precision requirement is high, the particle diameter is generally 0.1-0.5mm.

[0018] Furthermore, sealing devices are provided between the lower plug and the tube blank, and between the plunger and the tube blank, to block leakage of the solid particle force transmission medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 for Figure 1 A partial structural cross-sectional view; Figure 3 It is a schematic diagram of the progressive expansion of a tube blank of the present invention; Figure 4 Schematic diagram of the mechanical locking structure of the tube blank and the plate to complete the connection; Figure 5 This is a schematic diagram of fixed-point expansion of bent pipe.

[0020] Among them, 1. plate; 2. tube blank; 3. lower plug; 4. lower coil; 5. upper coil; 6. solid particles; 7. plunger. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0022] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0023] It should be noted that the terms "comprises", "includes" or any other variants are intended to cover non-exclusive inclusion, so that a process, element, method, article or device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to the process, element, method, article or device. In addition, the terms "upper" and "lower" are based on the orientation and positional relationship of the devices or components shown in the drawings, and are only for the purpose of better describing the present invention, rather than requiring the devices, components or equipment shown to have this specific orientation, and therefore cannot be understood as limiting the present invention.

[0024] The features and performances of the present invention are further described in detail below in conjunction with the embodiments.

[0025] like Figure 1 and Figure 2 As shown, a set of specific devices for realizing the electromagnetic induction heating low-plasticity metal tube-plate connection method of the present invention is used as an example to explain the electromagnetic induction heating low-plasticity metal tube-plate connection method of the present invention in detail, which does not constitute a limitation of the present invention. The method of the present invention can be realized by using any existing device that can realize its step-by-step functions.

[0026] Example 1 The present invention discloses a low-plasticity metal tube-plate connecting device based on electromagnetic induction heating, comprising an upper coil 5 and a lower coil 4; when in use, a tube blank 2 is inserted into a plate 1 with a through hole, and the upper coil 5 and the lower coil 4 are sleeved on the outside of the tube blank 2, corresponding to the position of the area to be expanded, the upper coil 5 is located on the upper surface of the plate 1, and the lower coil 4 is located on the lower surface of the plate 1; one end of the tube blank 2 is sealed by a lower plug 3, and a plunger 7 is placed on the other end; the cavity formed by the tube blank 2, the plunger 7 and the lower plug 3 is filled with solid particles 6. In a preferred embodiment of the present invention, sealing rings are provided between the plunger 7 and the tube blank 2, and between the lower plug 3 and the tube blank 2.

[0027] The pipe blank 2 and the plate 1 to be connected are processed with a plunger 7, a lower plug 3, a lower coil 4 and an upper coil 5 according to the structure and size of the pipe blank 2 and the plate 1 to be connected.

[0028] The lower plug 3 is located at one end of the tube blank 2 and can withstand the pressure F2 and seal the tube blank 2.

[0029] Solid particles 6 are used as the force transmission medium, and ceramic particles are selected, which are less affected by the alternating electric field and temperature. The particle size of ceramic particles is closely related to the molding quality. When the product precision requirement is relatively low, the particle diameter is 1-5mm; when the product precision requirement is high, the particle diameter is 0.1-0.5mm.

[0030] The deformation of metal materials has its own suitable temperature range. For example, the commonly used aluminum alloy has better plasticity at 300℃-400℃. This temperature range can make the aluminum alloy more easily undergo plastic deformation and is suitable for expansion welding process.

[0031] According to the different materials of the tube 2, the temperature of the tube to be expanded can be changed by adjusting the number of coil turns, the intensity, frequency and power-on time of the current in the coil, so as to improve the forming performance of the low-plasticity tube. The alternating current is a short-time high-frequency alternating current, and the specific parameters are: the alternating current frequency is 10kHz-1MHz, the current size is 200A-500A, and the power-on time is 5s-20s.

[0032] The frequency of the current passing through the coil mainly depends on the size of the metal and the required heating depth. For heating thin tubes, high frequency (10kHz - 1MHz) is generally used to concentrate the heat.

[0033] Furthermore, metal materials have their own suitable temperature range for deformation. For example, commonly used aluminum alloys have better plasticity at around 300°C-400°C. This temperature range can make aluminum alloys more susceptible to plastic deformation and is suitable for expansion welding processes.

[0034] The upper coil 5 and the lower coil 4 are planar spiral coils made of copper.

[0035] The present invention also discloses a low-plasticity metal tube-plate connection method using electromagnetic induction heating based on the above device, the specific steps of which are: S1, insert the tube blank 2 into the circular hole of the plate 1, and insert the upper coil 5 and the lower coil 4 into the tube blank 2 and correspond to the area to be expanded; solid particles 6 are injected into the cavity formed by the tube blank 2, the plunger 7 and the lower plug 3, such as Figure 2 shown.

[0036] S2, passing high-frequency alternating current through the upper coil 5 and the lower coil 4, so that the area to be expanded of the tube blank 2 is heated and heated.

[0037] S3, such as Figure 3 As shown in the figure, a pressure F1 is applied to the plunger 7 to squeeze the solid particles 6. The solid particles exert radial pressure on the tube 2. Since the temperature of the tube 2 to be expanded is high and the plasticity is good, the tube 2 is deformed first before other parts of the tube 2. The outer diameter of the tube 2 to be expanded is continuously increased, and a solid particle 6 is formed between the plate 1 and the tube 2. Figure 3 The strong lock shown in the figure finally obtains Figure 4 The tube-sheet connection structure shown.

[0038] The pressure F1 is determined by the yield strength of the tube blank 2 , and the lower plug 3 can maintain a good seal on the tube blank 2 under the action of the pressure F1 .

[0039] In a preferred embodiment of the present invention, the tube blank 2 is made of aluminum 6063, has a diameter of 20 mm, a wall thickness of 1 mm, and a length of 40 mm.

[0040] In a preferred embodiment of the present invention, the upper coil 5 and the lower coil 4 are circular planar spiral coils made of copper, with an inner diameter of 24 mm, an outer diameter of 27 mm, and 12 turns.

[0041] In a preferred embodiment of the present invention, the parameters of the current flowing through the upper coil 5 and the lower coil 4 are as follows: the current is 230A, the AC frequency is 30kHz, the power-on time is 5s, and the expected temperature of the tube blank 2 is 350°C.

[0042] In a preferred embodiment of the present invention, in S1, the outer wall of the tube blank 2 and the inner wall of the hole of the plate 1 have a clearance fit, the inner wall of the tube blank 2 and the outer wall of the plunger 7 have a clearance fit, and the inner wall of the tube blank 2 and the lower plug 3 have a clearance fit.

[0043] In a preferred embodiment of the present invention, the force transmission medium of the solid particles 6 is ceramic particles with a diameter of 0.5 mm.

[0044] In a preferred embodiment of the present invention, the lower plug 3 is fixed to the end of the tube blank 2 and can withstand an axial load greater than the pressure F1 and maintain a good sealing effect.

[0045] Example 2 Based on Example 1, the present invention discloses a low-plasticity metal tube-plate connection device based on electromagnetic induction heating, including an upper coil 5 and a lower coil 4; Figure 5 As shown, the tube blank 2 is a bent tube structure. When in use, the tube blank 2 is inserted into the plate 1 with a through hole, the upper coil 5 and the lower coil 4 are sleeved on the outside of the tube blank 2, corresponding to the position of the area to be expanded, the upper coil 5 is located on the upper surface of the plate 1, and the lower coil 4 is located on the lower surface of the plate 1; one end of the tube blank 2 is sealed by the lower plug 3, and the other end is placed with a plunger 7; the cavity formed by the tube blank 2, the plunger 7, and the lower plug 3 is filled with solid particles 6.

[0046] The method is described in Example 1. Example 3 A low-plasticity metal tube-plate connection method based on electromagnetic induction heating comprises the following steps: Step 1, insert the tube blank 2 to be connected into the plate 1, the tube blank 2 is filled with solid particles 6, an upper coil 5 is placed on the upper side of the circular hole of the plate 1, and a lower coil 4 is placed on the lower side, and the upper coil 5 and the lower coil 4 correspond to the area to be expanded of the tube blank 2; A lower plug 3 is installed at one end of the tube blank 2, ceramic particles with a diameter of 0.1 mm are injected into the cavity of the tube blank 2, and a plunger 7 is installed at the other end of the tube blank 2; Step 2, an alternating current is passed through the upper coil 5 and the lower coil 4, the frequency of the alternating current passed through the upper coil 5 and the lower coil 4 is 500kHz, the current intensity is 500A, and the power-on time is 5s, so as to generate an alternating magnetic field, and an induced current is generated in the expansion area of ​​the tube blank 2 in the alternating magnetic field, and the electrical energy is converted into thermal energy, so that the temperature of the expansion area of ​​the tube blank 2 is increased to a preset temperature of 400°C, and the preset temperature is designed according to the material of the tube blank 2; Step 3, judging whether the temperature of the expansion zone of the tube blank 2 reaches the preset temperature of 400°C, if not, returning to step 2, if reached, executing step 4; Step 4: Apply a pressure of 120 MPa to the plunger 7 of the tube blank 2, the solid particles 6 are squeezed, and radial pressure is generated on the tube blank 2. The temperature in the expansion zone of the tube blank 2 is high and is subjected to the extrusion force, so deformation occurs first. The radial size of the expansion zone of the tube blank 2 continues to increase and forms a lock with the plate 1.

[0047] The upper coil 5 and the lower coil 4 are planar spiral coils, and the sizes of the upper coil 5 and the lower coil 4 are determined by the outer diameter of the tube blank 2 of 25 mm, the thermal expansion coefficient of the material and the pre-deformation degree of 25%.

[0048] Example 4 A low-plasticity metal tube-plate connection method based on electromagnetic induction heating comprises the following steps: Step 1, insert the tube blank 2 to be connected into the plate 1, the tube blank 2 is filled with solid particles 6, an upper coil 5 is placed on the upper side of the circular hole of the plate 1, and a lower coil 4 is placed on the lower side, and the upper coil 5 and the lower coil 4 correspond to the area to be expanded of the tube blank 2; A lower plug 3 is installed at one end of the tube blank 2 , ceramic particles are injected into the cavity of the tube blank 2 , and the diameter of the ceramic particles is 2 mm. A plunger 7 is installed at the other end of the tube blank 2 .

[0049] Step 2, an alternating current is passed through the upper coil 5 and the lower coil 4, the frequency of the alternating current passed through the upper coil 5 and the lower coil 4 is 200kHz, the current intensity is 200A, and the power-on time is 20s, so as to generate an alternating magnetic field, and an induced current is generated in the expansion area of ​​the tube blank 2 in the alternating magnetic field, and the electrical energy is converted into thermal energy, so that the temperature of the expansion area of ​​the tube blank 2 is increased to a preset temperature of 350°C, and the preset temperature is designed according to the material of the tube blank 2; Step 3, judging whether the temperature of the expansion zone of the tube blank 2 reaches the preset temperature of 350°C, if not, returning to step 2, if reached, executing step 4; Step 4: Apply a pressure of 110 MPa to the plunger 7 of the tube blank 2, the solid particles 6 are squeezed, and radial pressure is generated on the tube blank 2. The temperature in the expansion zone of the tube blank 2 is high and is subjected to the extrusion force, so deformation occurs first. The radial size of the expansion zone of the tube blank 2 continues to increase, and a lock is formed between the sheet 1.

[0050] The upper coil 5 and the lower coil 4 are planar spiral coils, and the sizes of the upper coil 5 and the lower coil 4 are determined by the outer diameter of the tube blank 2 of 22 mm, the thermal expansion coefficient of the material and the pre-deformation degree of 22%.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A low-plasticity metal tube-plate connection method based on electromagnetic induction heating, characterized in that: The following steps are involved: S1, inserting a tube blank (2) to be connected into a plate (1); the tube blank (2) is filled with solid particles (6); An upper coil (5) is placed on the upper side of the circular hole of the plate (1), and a lower coil (4) is placed on the lower side; The upper coil (5) and the lower coil (4) correspond to the area to be expanded of the tube blank (2); S2, passing an alternating current through the upper coil (5) and the lower coil (4), causing the expansion zone of the tube blank (2) to heat up; S3, applying pressure to the pressure-applying end of the tube blank (2), the solid particles (6) are squeezed, and radial pressure is generated on the tube blank (2). The temperature of the tube blank (2) in the expansion zone is high, and it is deformed first after being subjected to the extrusion force. The radial size of the expansion zone of the tube blank (2) is continuously increased, and a lock is formed between the tube blank (2) and the plate (1).

2. A low-plasticity metal tube-sheet connection method based on electromagnetic induction heating according to claim 1, characterized in that: In S1, a lower plug (3) is installed at one end of the tube blank (2), solid particles (6) are injected into the cavity of the tube blank (2), and a plunger (7) is installed at the other end of the tube blank (2).

3. The low-plasticity metal tube-sheet connection method based on electromagnetic induction heating according to claim 1, characterized in that: In S2, the frequency, current intensity and power-on time of the alternating current flowing through the upper coil (5) and the lower coil (4) are determined by the material of the tube blank (2).

4. A low-plasticity metal tube-sheet connection method based on electromagnetic induction heating according to claim 3, characterized in that: Alternating current is a short-term high-frequency alternating current, and its specific parameters are: The AC frequency is 10kHz-1MHz, the current is 200A-500A, and the power-on time is 5s-20s.

5. The low-plasticity metal tube-sheet connection method based on electromagnetic induction heating according to claim 1, characterized in that: S2 is specifically as follows: after an alternating current is passed through the upper coil (5) and the lower coil (4), an alternating magnetic field is generated. After the tube blank (2) in the alternating magnetic field generates an induced electromotive force, an induced current is generated, and the electrical energy is converted into thermal energy, so that the temperature of the tube blank (2) to be expanded is increased to a preset temperature.

6. The low-plasticity metal tube-sheet connection method based on electromagnetic induction heating according to claim 1, characterized in that: The preset temperature is designed according to the material of the tube blank (2).

7. A low-plasticity metal tube-sheet connection device based on electromagnetic induction heating for implementing the method described in any one of claims 1 to 6, characterized in that: It comprises an upper coil (5) and a lower coil (4); When in use, the tube blank (2) is inserted into the plate (1), the upper coil (5) and the lower coil (4) are sleeved on the outside of the tube blank (2) and correspond to the position of the area to be expanded, the upper coil (5) is located on the upper surface of the plate (1), and the lower coil (4) is located on the lower surface of the plate (1); one end of the tube blank (2) is sealed by the lower plug (3), and the other end is placed with a plunger (7); the cavity formed by the tube blank (2), the plunger (7) and the lower plug (3) is filled with solid particles (6).

8. The low-plasticity metal tube-sheet connection device based on electromagnetic induction heating according to claim 6, characterized in that: The upper coil (5) and the lower coil (4) are planar spiral coils.

9. The low-plasticity metal tube-sheet connection device based on electromagnetic induction heating according to claim 6, characterized in that: The solid particles (6) are ceramic particles; When the product precision requirement is relatively low, the diameter of the solid particles (6) is 1-5 mm; when the product precision requirement is high, the diameter of the solid particles (6) is 0.1-0.5 mm.

10. The low-plasticity metal tube-sheet connection device based on electromagnetic induction heating according to claim 6, characterized in that: The sizes of the lower coil (4) and the upper coil (5) are determined by the outer diameter of the tube blank (2), the thermal expansion coefficient of the material and the degree of pre-deformation; Sealing rings are respectively provided between the tube blank (2) and the plunger (7), and between the tube blank (2) and the lower plug (3).

Images