Bimetal pipe electro-hydraulic composite forming device and forming method

Abstract

The invention discloses a bimetal tube electro-hydraulic composite forming device and method, and relates to the technical field of bimetal tube compositing, the forming device comprises an upper plug, a lower plug, an electrode and discharging equipment, and the top and the bottom of a bimetal tube are plugged through the upper plug and the lower plug respectively; electrodes are respectively arranged in the upper plug and the lower plug in a penetrating manner, a metal wire is connected between the two electrodes, the inner tube of the bimetal tube is filled with a liquid medium, and the end parts of the two electrodes and the metal wire are immersed in the liquid medium; and the other ends of the two electrodes are respectively connected with positive and negative electrodes of discharge equipment. The invention provides a bimetal tube electro-hydraulic composite process device and a process method, and provides an electro-hydraulic composite process material matching criterion, so that whether tube blanks made of two materials can be compounded through the process or not can be determined before an experiment, and the trial and error cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of bimetallic tube composite technology, and in particular to a bimetallic tube electro-hydraulic composite forming device and a forming method. Background Art

[0002] Bimetallic pipe is composed of two different metal pipes. The two pipe layers are closely combined through a certain composite technology. Bimetallic pipe has the best performance of two metal materials and gives full play to the excellent performance of the two pipes. It is not only high in strength, but also has good high temperature resistance and corrosion resistance. It can extend the service life of the pipe, save pipes, and reduce production costs. Therefore, bimetallic pipes are widely used in petrochemical, marine development, mechanical engineering, aerospace and other fields. Bimetallic pipes can be divided into lined composite pipes and outer coated composite pipes according to the relative position of the base pipe and the coating pipe. For lined composite pipes, it is currently mainly prepared by quasi-static composite processes such as hydraulics. However, for the composite of bimetallic pipes with thin inner linings, the pressure required for the hydraulic expansion process is relatively high, so the sealing conditions are required to be high, and internal high-voltage equipment is required, and the equipment cost is relatively high. Although the electromagnetic composite process does not require high-cost special equipment, it cannot be applied to the forming of bimetallic pipes with low conductivity materials as the coating pipe, and due to the limitations of coil size and strength, the life of the coil is difficult to support multiple stable discharges when forming small-diameter lined bimetallic composite pipes. The explosive composite process has potential safety hazards during forming, and cannot be mass-produced due to the limitations of its process principles. In addition, the inner surface quality of the formed bimetallic tube is poor and easily produces ablation marks.

[0003] Electrohydraulic expansion technology is an advanced connection technology based on the principle of electrohydraulic forming. Electrohydraulic forming technology is a forming and manufacturing process in which the electric energy stored in the discharge device is released instantly. The energy at the ends of the positive and negative electrodes explodes in the water to produce a strong shock wave. The liquid medium (usually water) is used as an energy transmission medium to drive the metal sheet or pipe to undergo plastic deformation. Controlling process parameters such as wire diameter, length, and discharge voltage can increase the impact load of the liquid and achieve forming connection. However, for high-rate composites, there is currently a lack of matching criteria for whether the metal tubes of the two materials can be composited. Summary of the invention

[0004] The purpose of the present invention is to provide a bimetallic tube electro-hydraulic composite forming device and forming method to solve the problems existing in the above-mentioned prior art. The device is suitable for the forming process of small-diameter bimetallic composite tubes with thin linings. The method is not limited by the electrical conductivity of the material on the basis of safety and energy saving. The formed bimetallic tube does not require secondary processing, and provides material matching criteria corresponding to the process.

[0005] To achieve the above-mentioned purpose, the present invention provides the following scheme: The present invention provides a bimetallic tube electro-hydraulic composite forming device, comprising an upper plug, a lower plug, electrodes and a discharge device, the top and bottom of the bimetallic tube are respectively sealed by the upper plug and the lower plug; electrodes are respectively passed through the upper plug and the lower plug, and a metal wire is connected between the two electrodes. The inner tube of the bimetallic tube is filled with a liquid medium, and the ends of the two electrodes and the metal wire are immersed in the liquid medium; the other ends of the two electrodes are respectively connected to the positive and negative poles of the discharge device.

[0006] In one embodiment, both ends of the upper plug and the lower plug are connected by fastening bolts respectively.

[0007] In one embodiment, a liquid filling interface is provided on the upper plug, the liquid filling interface is communicated with the inner tube cavity of the bimetallic tube, and the liquid filling interface is used to fill the inner tube cavity of the bimetallic tube with liquid medium.

[0008] In one embodiment, the electrode comprises a positive electrode and a negative electrode, and the positive electrode and the negative electrode are respectively installed in a middle position of the upper plug and the lower plug through a threaded steel sleeve.

[0009] In one embodiment, an insulating sleeve is provided on the outer side of the electrode, and the upper outer side of the insulating sleeve is sealed and assembled inside the threaded steel sleeve.

[0010] In one embodiment, the insulating sleeve includes an insulating sleeve body and a protrusion, the protrusion is integrally formed in the middle part of the insulating sleeve body, the upper shoulder of the protrusion is arranged in contact with the inner wall of the threaded steel sleeve; the bottom of the protrusion is assembled in the opening of the upper plug or the lower plug, and a No. 1 sealing ring is arranged between the bottom of the protrusion and the upper plug or the lower plug.

[0011] In one embodiment, the electrode includes an integrated first connection end, an electrode body, and a second connection end, the first connection end is connected to a charging capacitor of a discharge device, the second connection end is connected to a metal wire, a shoulder is provided between the electrode body and the second connection end, and the shoulders of the electrode body and the second connection end are immersed in a liquid medium, and a No. 3 sealing ring is provided at the shoulders of the electrode body and the second connection end.

[0012] In one embodiment, a No. 2 sealing ring is provided between the top and bottom of the bimetallic tube and the upper plug; a No. 4 sealing ring is provided between the upper and lower ends of the inner tube of the bimetallic tube and the upper and lower plugs; the inner tube and outer tube of the bimetallic tube are assembled together through a gap ring.

[0013] In one embodiment, a vacuum joint is provided on the bottom side wall of the bimetallic tube, and the vacuum joint is connected to a vacuum device.

[0014] The present invention also provides a bimetallic tube electro-hydraulic composite forming method, which is applied to the above-mentioned bimetallic tube electro-hydraulic composite forming device, comprising:

[0015] Under the quasi-static material matching judgment condition, the material strain rate hardening parameter C is introduced, and the material matching criterion of the bimetallic tube electro-hydraulic composite needs to satisfy the following formula:

[0016]

[0017] Where: s ——yield strength of the outer tube under quasi-static conditions;

[0018] σ——Flow stress of the inner wall of the inner tube when the inner wall of the outer tube reaches the yield strength under quasi-static conditions;

[0019] Δ——gap between tubes;

[0020] d——outer diameter of inner tube;

[0021] E1——elastic modulus of outer tube;

[0022] E2——elastic modulus of inner tube;

[0023] C1——Outer tube strain rate strengthening parameter;

[0024] C2——Inner tube strain rate strengthening parameter;

[0025] ——The ratio of the strain rate when the inner and outer tubes are deformed to the strain rate under quasi-static conditions;

[0026] The electro-hydraulic composite forming process of bimetallic tube is as follows:

[0027] Step 1: Cut quasi-static tensile specimens and high-speed tensile specimens from the inner and outer tubes to be composited, and conduct quasi-static and high-speed tensile tests, record the yield strength of the material at different strain rates, and substitute Obtain the strain rate strengthening coefficient of the material; bring the obtained material performance parameters and tube blank geometric parameters into the formula of material matching criterion, and judge whether the criterion is valid at different strain rates according to the gap between tubes;

[0028] Step 2, simulating the composite process by finite element simulation software, changing the discharge parameters until the inner and outer tubes remain in contact after the shock wave ends, and recording the discharge parameters;

[0029] Step 3: Install the metal tube to be formed. First, place the No. 2 sealing ring in the groove of the gap ring, assemble the inner and outer tubes coaxially through the gap ring, place the No. 4 sealing ring in the groove of the plug, and fix the inner and outer tubes between the upper and lower plugs. Then tighten the fastening bolts to complete the installation of the metal tube.

[0030] Step 4: Assemble the electrodes, connect the metal wires between the electrodes, pass the connected electrodes through the middle of the tube, place the No. 3 sealing ring between the insulating sleeve and the electrode, place the No. 1 sealing ring between the insulating sleeve and the plug, insert the insulating sleeve from the tail of the electrode, then install the threaded steel sleeve and the nut on the electrode to complete the assembly and fixation of the electrode;

[0031] Step 5, open the liquid supply device to fill a certain amount of liquid into the liquid storage chamber of the inner tube;

[0032] Step 6: Turn on the vacuum pumping device so that the gap between the inner and outer tubes reaches a set vacuum state;

[0033] Step 7: Check the connection status of the discharge circuit. If the circuit is in the on state, the charge and discharge operation can be performed.

[0034] Step 8: Close the charging switch of the high-energy pulse discharge device, and the high-voltage power supply charges the charging capacitor through the high-voltage rectifier bridge and the current limiting resistor. After reaching the preset voltage, the charging switch is disconnected, and the discharge trigger switch is opened to connect the auxiliary discharge gap to start discharging the metal wire;

[0035] Step 9: After the discharge is completed, open the liquid reflux interface to recover the waste liquid;

[0036] Step 10, remove the formed bimetallic tube to complete the forming work;

[0037] Step 11, cut a ring sample, put it into a shear strength testing device, use a universal testing machine to apply gradually increasing pressure to the upper punch until the inner and outer tubes are sheared, record the maximum pressure value and the ratio of the contact area between the inner and outer tubes of the bimetallic tube, so as to obtain the shear strength of the bimetallic tube.

[0038] Compared with the prior art, the present invention has achieved the following beneficial technical effects:

[0039] The bimetallic tube electro-hydraulic composite forming device and forming method of the present invention comprises an upper plug, a lower plug, electrodes and a discharge device. The top and bottom of the bimetallic tube are respectively sealed by the upper plug and the lower plug; the upper plug and the lower plug are respectively provided with electrodes, a metal wire is connected between the two electrodes, the inner tube of the bimetallic tube is filled with a liquid medium, the ends of the two electrodes and the metal wire are immersed in the liquid medium; the other ends of the two electrodes are respectively connected to the positive and negative electrodes of the discharge device. The present invention proposes a bimetallic tube electro-hydraulic composite process device and process method, and proposes a material matching criterion for the electro-hydraulic composite process, so as to confirm whether the tube blanks of the two materials can be composited through this process before the experiment, thereby reducing the trial and error cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 It is a structural composition diagram of the bimetallic tube electro-hydraulic composite forming device;

[0042] Figure 2 It is the uniaxial tensile curve of the inner tube at different strain rates;

[0043] Figure 3 It is the uniaxial tensile curve of the outer tube at different strain rates;

[0044] Figure 4 This is a schematic diagram of a bimetallic tube shear strength test device;

[0045] Figure 5 It is the uniaxial tensile curve of 304 stainless steel at different strain rates;

[0046] Figure 6 It is the uniaxial tensile curve of Q345 steel at different strain rates;

[0047] Among them, 1. upper plug; 2. fastening bolt; 3. lower plug; 4. electrode; 5. insulating sleeve; 6. threaded steel sleeve; 7. No. 1 sealing ring; 8. liquid filling interface; 9. No. 2 sealing ring; 10. inner tube; 11. metal wire; 12. outer tube; 13. No. 3 sealing ring; 14. vacuum joint; 15. No. 4 sealing ring; 16. gap ring; 17. charging capacitor; 18. discharge gap. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The purpose of the present invention is to provide a bimetallic tube electro-hydraulic composite forming device and forming method to solve the problems existing in the above-mentioned prior art. The device is suitable for the forming process of small-diameter bimetallic composite tubes with thin linings. The method is not limited by the electrical conductivity of the material on the basis of safety and energy saving. The formed bimetallic tube does not require secondary processing, and provides material matching criteria corresponding to the process.

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] like Figure 1-Figure 6 As shown, the present invention provides a bimetallic tube electro-hydraulic composite forming device, comprising an upper plug 1, a lower plug 3, an electrode 4 and a discharge device, the top and the bottom of the bimetallic tube are respectively blocked by the upper plug 1 and the lower plug 3; the upper plug 1 and the lower plug 3 are respectively penetrated with electrodes 4, a metal wire 11 is connected between the two electrodes 4, the inner tube 10 of the bimetallic tube is filled with a liquid medium, the ends of the two electrodes 4 and the metal wire 11 are immersed in the liquid medium; the other ends of the two electrodes 4 are respectively connected to the positive and negative poles of the discharge device.

[0052] In one embodiment, both ends of the upper plug 1 and the lower plug 3 are connected by fastening bolts 2 respectively.

[0053] In one embodiment, a liquid filling interface 8 is provided on the upper plug 1, and the liquid filling interface 8 is connected to the cavity of the inner tube 10 of the bimetallic tube. The liquid filling interface 8 is used to fill the cavity of the inner tube 10 of the bimetallic tube with liquid medium.

[0054] In one embodiment, the electrode 4 includes a positive electrode and a negative electrode, and the positive electrode and the negative electrode are respectively installed in the middle position of the upper plug 1 and the lower plug 3 through the threaded steel sleeve 6.

[0055] In one embodiment, an insulating sleeve 5 is provided on the outer side of the electrode 4 , and the upper outer side of the insulating sleeve 5 is sealed and assembled inside the threaded steel sleeve 6 .

[0056] In one of the embodiments, the insulating sleeve 5 includes an insulating sleeve main body and a protrusion, the protrusion is integrally formed in the middle part of the insulating sleeve main body, and the upper shoulder of the protrusion is arranged in contact with the inner wall of the threaded steel sleeve 6; the bottom of the protrusion is assembled in the opening of the upper plug 1 or the lower plug 3, and a No. 1 sealing ring 7 is arranged between the bottom of the protrusion and the upper plug 1 or the lower plug 3.

[0057] In one embodiment, the electrode 4 includes an integrated first connection end, an electrode body and a second connection end, the first connection end is connected to the charging capacitor 17 of the discharge device, the second connection end is connected to the metal wire 11, a shoulder is arranged between the electrode body and the second connection end, and the shoulder of the electrode body and the second connection end is immersed in the liquid medium, and a No. 3 sealing ring 13 is arranged at the shoulder of the electrode body and the second connection end.

[0058] In one of the embodiments, a No. 2 sealing ring 9 is provided between the top and bottom of the bimetallic tube and the upper plug 1; a No. 4 sealing ring 15 is provided between the upper and lower ends of the inner tube 10 of the bimetallic tube and the upper and lower plugs; the inner tube 10 and the outer tube 12 of the bimetallic tube are assembled together through a gap ring 16.

[0059] In one embodiment, a vacuum joint 14 is provided on the bottom side wall of the bimetallic tube, and the vacuum joint 14 is connected to a vacuum device.

[0060] The technical problem to be solved by the present invention is to propose a forming process suitable for small-diameter thin-lined bimetallic composite pipes. The method is not limited by the electrical conductivity of the material on the basis of safety and energy saving, and the formed bimetallic pipe does not require secondary processing, and provides corresponding material matching criteria for the process.

[0061] In order to solve the above technical problems, the present invention proposes to apply electrohydraulic forming technology to the field of bimetallic tube composite, and drive the inner tube 10 and the outer tube 12 to collide at high speed through the shock wave generated by the discharge of the underwater metal wire 11 to achieve the inner and outer tube composite, and proposes the material matching criterion of this method.

[0062] In order to realize the composite of the two metal tubes, it is necessary to satisfy the requirement that the rebound amount of the outer tube 12 after unloading is greater than that of the inner tube 10, that is, When the material is deformed at a high rate, the stress will increase compared to the quasi-static condition, such as Figure 2 and Figure 3 As shown in the figure, the material matching criterion of hydraulic expansion under quasi-static conditions is not applicable. At the same time, the impact hydraulic strength generated by the electric explosion of the metal wire 11 is difficult to predict by formula. Therefore, in order to make a preliminary judgment on the material matching before the experiment, the strain rate strengthening parameter C of the material is introduced under the quasi-static material matching judgment condition, and the material is regarded as an ideal line-strengthened elastic-plastic material. The material matching of the bimetallic tube electro-hydraulic composite needs to satisfy the following formula:

[0063]

[0064] Where: s ——yield strength of the outer tube under quasi-static conditions;

[0065] σ——Flow stress of the inner wall of the inner tube when the inner wall of the outer tube reaches the yield strength under quasi-static conditions;

[0066] Δ——gap between tubes;

[0067] d——outer diameter of inner tube;

[0068] E1——elastic modulus of outer tube;

[0069] E2——elastic modulus of inner tube;

[0070] C1——Outer tube strain rate strengthening parameter;

[0071] C2——Inner tube strain rate strengthening parameter;

[0072] ——The ratio of the strain rate during deformation of the inner and outer tubes to the strain rate under quasi-static conditions.

[0073] The composite process of bimetallic tube is as follows:

[0074] Step 1: Cut quasi-static tensile specimens and high-speed tensile specimens from the inner and outer tubes to be composited, and conduct quasi-static and high-speed tensile tests, record the yield strength of the material at different strain rates, and substitute The strain rate strengthening coefficient of the material is obtained. The obtained material performance parameters and the geometric parameters of the tube blank are brought into the material matching criterion, and the inter-tube gap is used to determine whether the criterion is valid at different strain rates.

[0075] Step 2: Use finite element simulation software to simulate the composite process, change the discharge parameters until the inner and outer tubes remain in contact after the shock wave ends, and record the discharge parameters.

[0076] Step 3: Install the metal tube to be formed. First, place the No. 2 sealing ring 9 in the groove of the gap ring 16, assemble the inner and outer tubes coaxially with a certain gap through the gap ring 16, place the No. 4 sealing ring 15 in the groove of the plug, and fix the inner and outer tubes between the upper and lower plugs, then tighten the fastening bolts 2 to complete the installation of the metal tube.

[0077] Step 4, assemble the electrode 4. A metal wire 11 of a certain length is connected between the electrodes 4, and the connected electrode 4 passes through the middle of the tube blank, and the No. 3 sealing ring 13 is placed between the insulating sleeve 5 and the electrode 4, and the No. 1 sealing ring 7 is placed between the insulating sleeve 5 and the plug, and the insulating sleeve 5 is inserted from the tail of the electrode 4, and then the threaded cylinder sleeve and the nut on the electrode 4 are installed to complete the assembly and fixation of the electrode 4.

[0078] Step 5, opening the liquid supply device to fill a certain amount of liquid into the liquid storage chamber;

[0079] Step 6: Turn on the vacuum equipment to make the gap between the inner and outer tubes reach a certain vacuum state.

[0080] Step 7: Check the connection status of the discharge circuit. If the circuit is in the "on" state, the charging and discharging operations can be performed.

[0081] Step 8, close the charging switch of the high-energy pulse discharge device, the high-voltage power supply charges the charging capacitor 17 through the high-voltage rectifier bridge and the current limiting resistor, and disconnects the charging switch after reaching the preset voltage, opens the discharge trigger switch to connect the auxiliary discharge gap 18, and starts to discharge the metal wire 11;

[0082] Step 9: After the discharge is completed, open the liquid reflux interface to recover the waste liquid;

[0083] Step 10: Remove the formed bimetallic tube to complete the forming work.

[0084] Step 11, cut a ring sample, put it into a shear strength testing device, use a universal testing machine to apply gradually increasing pressure to the upper punch until the inner and outer tubes are sheared, record the maximum pressure value and the ratio of the contact area between the inner and outer tubes of the bimetallic tube, so as to obtain the shear strength of the bimetallic tube.

[0085] The working principle of the above-mentioned bimetallic tube electro-hydraulic composite process method is as follows:

[0086] The electrohydraulic forming machine instantly releases the electric energy stored in the capacitor to generate a strong pulse current. When the current passes through the metal wire 11 between the positive and negative electrodes, it heats up and vaporizes it, and finally breaks it down and causes an electric explosion. Due to the incompressibility of the liquid medium, the electric explosion generates a strong shock wave. The shock wave is transmitted to the inner tube 10 through the liquid medium and drives the inner tube 10 to undergo high-speed plastic expansion and collide with the inner wall of the outer tube 12. Subsequently, the inner and outer tubes expand at the same time. After the shock wave ends (or the speed of the inner tube 10 drops to 0), the inner and outer tubes rebound at the same time. Due to the difference in the elasticity of the inner and outer tubes, residual contact force is generated at the contact interface of the inner and outer tubes, thereby realizing the compounding of the bimetallic tube.

[0087] The purpose of the present invention is to provide an economical, safe and practical method for small diameter lined thin wall bimetallic tubes. Compared with the existing bimetallic tube composite method, the electro-hydraulic composite method proposed in the present invention has the following beneficial effects:

[0088] 1. Compared with the hydraulic bulging composite process, it does not require large hydraulic equipment, only one discharge device and corresponding tooling are needed to complete the forming, and the cost is lower;

[0089] 2. Compared with the electromagnetic composite process, the electro-hydraulic expansion process is not limited by the conductivity of the material and can be used to prepare bimetallic tubes with a variety of matching materials. For small-diameter bimetallic tubes, the electromagnetic composite process has high requirements on the strength of the coil and it is difficult to achieve multiple stable forming, while the electro-hydraulic expansion process does not have this problem;

[0090] 3. Compared with the explosive composite process, the electro-hydraulic expansion process is safer, the inner surface quality of the prepared bimetallic tube is better, the deformation of the tube is controlled by voltage, the discharge energy is easy to accurately control, and the experimental results are highly stable.

[0091] Embodiment 1

[0092] Outer tube 12 material: 345 seamless steel pipe, length 100mm, outer diameter 62mm, wall thickness 5.6mm, strain rate strengthening parameter 0.07, yield strength 380MPa, elastic modulus 210GPa; inner tube 10 material: 304 stainless steel seamless pipe, length 90mm, outer diameter 50, wall thickness 1mm, yield strength 255MPa, strain rate strengthening parameter 0.0855, elastic modulus 194GPa. Processing requirements: Complete the composite of 304 stainless steel seamless pipe and 345 seamless steel pipe lining. When the pipe fitting is formed by hydraulic bulging and other methods, the tooling hydraulic sealing requirements are high. At the same time, the electromagnetic composite method cannot be used due to the limitation of material conductivity. After calculation, it meets the matching criteria of electro-hydraulic composite materials.

[0093] The method for forming a metal pipe of an energetic material using the electric pulse provided by the present invention:

[0094] Step 1: Cut quasi-static tensile specimens and high-speed tensile specimens from stainless steel tube billets and Q345 steel tube billets, and perform 0.002s -1 , 2500s -1 , 4500s -1 The tensile test under strain rate can obtain the stress-strain curve, such as Figure 5 and Figure 6 As shown, the yield strength of 304 stainless steel at three strain rates is 255MPa, 516MPa and 544MPa, respectively, and the yield strength of Q345 steel at three strain rates is 381MPa, 618MPa and 651MPa, respectively. The strain rate hardening parameter of 304 stainless steel is 0.086, and the strain rate hardening parameter of Q345 steel is 0.046. The gap between the tubes to be composited is 0.2mm. According to experience, the strain rate is less than 2000s -1 , after calculation, the criterion always holds true under this strain rate condition.

[0095] Step 2, simulating the composite process by finite element simulation software, the capacitance of the pulse current device is 200μF, and the relevant parameters of the metal wire 11 are as follows: the diameter of the metal aluminum wire is 0.5mm, and the length is 20mm. The simulation found that when the discharge voltage is 8kV, the inner and outer tubes always remain in contact during the unloading process.

[0096] Step 3: install the metal tube to be formed, assemble the electrode 4, fill the liquid and evacuate the space between the tubes, and perform the discharge operation after the inspection is completed.

[0097] Step 4: Remove the formed bimetallic tube, cut the ring sample and use the following method: Figure 4 The method shown measures the shear strength between the inner and outer tubes, and the shear strength is 0.6 MPa.

[0098] According to the standard CJ / T 192-2017, for lined stainless steel composite pipes not larger than DN250, the inter-tube bonding strength between the base pipe and the composite pipe should not be less than 0.3MPa. Therefore, the stainless steel pipe made by electro-hydraulic composite can meet the demand.

[0099] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure mark in the claims should not be regarded as limiting the claims involved.

[0100] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A bimetallic tube electro-hydraulic composite forming device, characterized in that: It comprises an upper plug, a lower plug, electrodes and a discharge device. The top and bottom of the bimetallic tube are respectively sealed by the upper plug and the lower plug; electrodes are respectively passed through the upper plug and the lower plug, and a metal wire is connected between the two electrodes. The inner tube of the bimetallic tube is filled with a liquid medium, and the ends of the two electrodes and the metal wire are immersed in the liquid medium; the other ends of the two electrodes are respectively connected to the positive and negative poles of the discharge device.

2. The bimetallic tube electro-hydraulic composite forming device according to claim 1, characterized in that: The two ends of the upper plug and the lower plug are connected by fastening bolts respectively.

3. The bimetallic tube electro-hydraulic composite forming device according to claim 1, characterized in that: The upper plug is provided with a liquid filling interface, the liquid filling interface is communicated with the inner tube cavity of the bimetallic tube, and the liquid filling interface is used to fill the inner tube cavity of the bimetallic tube with liquid medium.

4. The bimetallic tube electro-hydraulic composite forming device according to claim 1, characterized in that: The electrodes include a positive electrode and a negative electrode, and the positive electrode and the negative electrode are respectively installed in the middle position of the upper plug and the lower plug through a threaded steel sleeve.

5. The bimetallic tube electro-hydraulic composite forming device according to claim 1, characterized in that: An insulating sleeve is arranged on the outer side of the electrode, and the upper outer side of the insulating sleeve is sealed and assembled inside the threaded steel sleeve.

6. The bimetallic tube electro-hydraulic composite forming device according to claim 5, characterized in that: The insulating sleeve includes an insulating sleeve body and a raised portion, wherein the raised portion is integrally formed in the middle of the insulating sleeve body, and the upper shoulder of the raised portion is arranged in contact with the inner wall of the threaded steel sleeve; the bottom of the raised portion is assembled in the opening of the upper plug or the lower plug, and a No. 1 sealing ring is arranged between the bottom of the raised portion and the upper plug or the lower plug.

7. The bimetallic tube electro-hydraulic composite forming device according to claim 1, characterized in that: The electrode includes an integrated first connection end, an electrode body and a second connection end, the first connection end is connected to a charging capacitor of a discharge device, the second connection end is connected to a metal wire, a shoulder is provided between the electrode body and the second connection end, and the shoulder of the electrode body and the second connection end is immersed in a liquid medium, and a No. 3 sealing ring is provided at the shoulder of the electrode body and the second connection end.

8. The bimetallic tube electro-hydraulic composite forming device according to claim 1, characterized in that: No. 2 sealing rings are arranged between the top and bottom of the bimetallic tube and the upper plug; No. 4 sealing rings are arranged between the upper and lower ends of the inner tube of the bimetallic tube and the upper and lower plugs; the inner tube and outer tube of the bimetallic tube are assembled together through a gap ring.

9. The bimetallic tube electro-hydraulic composite forming device according to claim 1, characterized in that: A vacuum joint is provided on the bottom side wall of the bimetallic tube, and the vacuum joint is connected to the vacuum equipment.

10. A bimetallic tube electro-hydraulic composite forming method, applied to the bimetallic tube electro-hydraulic composite forming device according to any one of claims 1 to 9, characterized in that: include: Under the quasi-static material matching judgment condition, the material strain rate strengthening parameter C is introduced, and the material matching criterion of the bimetallic tube electro-hydraulic composite must satisfy the following formula: Where: s ——yield strength of the outer tube under quasi-static conditions; σ——Flow stress of the inner wall of the inner tube when the inner wall of the outer tube reaches the yield strength under quasi-static conditions; Δ——gap between tubes; d——outer diameter of inner tube; E1——elastic modulus of outer tube; E2——elastic modulus of inner tube; C1——Outer tube strain rate strengthening parameter; C2——Inner tube strain rate strengthening parameter; ——The ratio of the strain rate when the inner and outer tubes are deformed to the strain rate under quasi-static conditions; The electro-hydraulic composite forming process of bimetallic tube is as follows: Step 1: Cut quasi-static tensile specimens and high-speed tensile specimens from the inner and outer tubes to be composited, and conduct quasi-static and high-speed tensile tests, record the yield strength of the material at different strain rates, and substitute Obtain the strain rate strengthening coefficient of the material; bring the obtained material performance parameters and tube blank geometric parameters into the formula of material matching criterion, and judge whether the criterion is valid at different strain rates according to the gap between tubes; Step 2, simulating the composite process by finite element simulation software, changing the discharge parameters until the inner and outer tubes remain in contact after the shock wave ends, and recording the discharge parameters; Step 3: Install the metal tube to be formed. First, place the No. 2 sealing ring in the groove of the gap ring, assemble the inner and outer tubes coaxially through the gap ring, place the No. 4 sealing ring in the groove of the plug, and fix the inner and outer tubes between the upper and lower plugs. Then tighten the fastening bolts to complete the installation of the metal tube. Step 4: Assemble the electrodes, connect the metal wires between the electrodes, pass the connected electrodes through the middle of the tube, place the No. 3 sealing ring between the insulating sleeve and the electrode, place the No. 1 sealing ring between the insulating sleeve and the plug, insert the insulating sleeve from the tail of the electrode, then install the threaded steel sleeve and the nut on the electrode to complete the assembly and fixation of the electrode; Step 5, open the liquid supply device to fill a certain amount of liquid into the liquid storage chamber of the inner tube; Step 6: Turn on the vacuum pumping device so that the gap between the inner and outer tubes reaches a set vacuum state; Step 7: Check the connection status of the discharge circuit. If the circuit is in the on state, the charge and discharge operation can be performed. Step 8: Close the charging switch of the high-energy pulse discharge device, and the high-voltage power supply charges the charging capacitor through the high-voltage rectifier bridge and the current limiting resistor. After reaching the preset voltage, the charging switch is disconnected, and the discharge trigger switch is opened to connect the auxiliary discharge gap to start discharging the metal wire; Step 9: After the discharge is completed, open the liquid reflux interface to recover the waste liquid; Step 10, remove the formed bimetallic tube to complete the forming work; Step 11, cut a ring sample, put it into a shear strength testing device, use a universal testing machine to apply gradually increasing pressure to the upper punch until the inner and outer tubes are sheared, record the maximum pressure value and the ratio of the contact area between the inner and outer tubes of the bimetallic tube, so as to obtain the shear strength of the bimetallic tube.

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