A coil structure for plate magnetic pulse welding

Abstract

The present invention discloses a coil structure for plate magnetic pulse welding, comprising a multi-turn coaxial cable, an upper supporting plate, a lower supporting plate and a metal strip; the upper supporting plate and the lower supporting plate are used to clamp the multi-turn coaxial cable, and the metal strip is arranged on the upper supporting plate; the multi-turn coaxial cable comprises a core wire and a sheath wire; the metal strip is short-circuited with the sheath wire of the multi-turn coaxial cable, and the core wire and the sheath wire at the tail end of the multi-turn coaxial cable are short-circuited. The present invention short-circuits the sheath wire of the coaxial cable to a metal strip of a certain length, so that the loop current on the coaxial cable circulates through the metal strip of a certain length in sequence, in turns, and in order, and converges to generate a high peak pulse current that is several times the cross-sectional current of a single-turn coaxial cable, thereby improving the energy utilization rate of the coil and increasing the service life of the coil.

Description

Technical Field

[0001] The invention relates to the technical field of plate magnetic pulse welding, and in particular to a coil structure used for plate magnetic pulse welding. Background Art

[0002] The essence of sheet metal magnetic pulse welding (MPW) is solid-phase connection. It uses pulse current to generate a pulse magnetic field through a coil, and the electromagnetic force drives the flying plate. The flying plate collides with the substrate, and a jet is generated in the collision area to wash away the pollutants, oxide layer and a thin layer of metal on the surface of the plate to be connected, and under the action of impact pressure, a metallurgical joint is formed. Since the required discharge current cycle is short and the peak value is high during the sheet metal magnetic pulse welding process, the discharge circuit is required to have a sufficiently low impedance.

[0003] The plate magnetic pulse welding system mainly includes a capacitor bank 30, a welding coil 50, a flying plate 60 (connecting member) and a base plate 70 (connected member), etc. Figure 1 As shown, the alternating current of the external network is boosted by the transformer 10 and rectified by the rectifier 20 to charge the capacitor bank 30. When the capacitor bank 30 is charged to the preset voltage, the discharge switch 40 is closed, and a loop is formed between the capacitor and the welding coil 50, generating a pulse current. The electric energy stored in the capacitor bank 30 is discharged instantaneously through the welding coil 50, generating a changing magnetic field around the coil. The magnetic field interacts with the flying plate 60, and a secondary current opposite to the primary coil current is induced in the flying plate 60. The repulsive electromagnetic force between the two drives the flying plate to deform at a high rate, and accelerates the flying plate 60 to a speed VC of hundreds of meters per second within microseconds. The flying plate 60 collides with the substrate 70, and a jet is generated in the collision area to flush the pollutants, oxide layer and a thin layer of metal on the surface of the plate to be connected. As a result, the "clean" flying plate 60 and substrate 70 metals are exposed to each other, and a metallurgical joint is formed under the action of instantaneous impact pressure. The principle of the above process is as follows Figure 2 As shown, Figure 2 Among them, 80 is the weld and 90 is the collision point.

[0004] At present, in the process of plate magnetic pulse welding, there are three types of coil structures commonly used: I-shaped, U-shaped and E-shaped, such as Figure 3 As shown. Among them, the I-shaped single-turn coil is widely used due to its simple coil structure. These three coil structures are simple, but all have disadvantages such as low energy utilization and short coil service life. Summary of the invention

[0005] In order to improve the energy utilization rate of the coil and extend the service life of the coil, the present invention proposes a coil structure for plate magnetic pulse welding.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A coil structure for magnetic pulse welding of plates, comprising a multi-turn coaxial cable, an upper supporting plate, a lower supporting plate and a metal strip; the upper supporting plate and the lower supporting plate are used to clamp the multi-turn coaxial cable, and the metal strip is arranged on the upper supporting plate; the multi-turn coaxial cable comprises a core wire and a sheath wire; the metal strip is short-circuited with the sheath wire of the multi-turn coaxial cable, and the core wire and the sheath wire at the tail end of the multi-turn coaxial cable are short-circuited.

[0008] Optionally, the length of the metal strip is smaller than the length of each turn of the sheath wire.

[0009] Optionally, the cross-sectional area of ​​the metal strip is larger than the cross-sectional area of ​​each turn of the sheath wire.

[0010] Optionally, when the cross-sectional areas of the core wire and the sheath wire are constant, the smaller the ratio of the length of the metal strip to the length of each turn of the sheath wire is, the higher the peak current amplification factor on the metal strip is.

[0011] Optionally, the coil structure is directly used for magnetic pulse forming of a sheet material.

[0012] Optionally, the metal strip includes copper alloy, stainless steel and carbon steel.

[0013] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0014] In the present invention, the sheath wire of the coaxial cable is short-circuited to a metal strip of a certain length, so that the loop current on the coaxial cable circulates through the metal strip of a certain length in sequence, turn by turn, and generates a high peak pulse current that is several times the cross-sectional current of a single turn of the coaxial cable, thereby improving the energy utilization rate of the coil and increasing the service life of the coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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 labor.

[0016] Figure 1 It is a schematic diagram of a magnetic pulse welding system for dissimilar metal sheets;

[0017] Figure 2 It is a schematic diagram of the principle of magnetic pulse welding of dissimilar metal sheets;

[0018] Figure 3 Schematic diagram of the commonly used coil types for plate magnetic pulse welding, (a) I-shaped coil, (b) U-shaped coil, (c) E-shaped coil;

[0019] Figure 4 Simplified circuit diagram for a five-turn coaxial cable coil;

[0020] Figure 5 The discharge current curve of the 7-turn coaxial cable coil; (a) is the positive triaxial side view and (b) is the top view;

[0021] Figure 6 This is the discharge current curve of a 7-turn coaxial cable coil (peak current magnification is 5.3 times);

[0022] Figure 7 This is a schematic diagram of the tooling structure of a 7-turn coaxial cable coil;

[0023] Figure 8 This is the discharge current curve of a 2-turn parallel coaxial cable coil (peak current magnification is 3.8 times);

[0024] Fig. 9 The joint effect diagram of magnetic pulse welding; (a) is before connection, and (b) is after connection. DETAILED DESCRIPTION

[0025] 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.

[0026] In order to improve the energy utilization rate of the coil and extend the service life of the coil, the present invention proposes a coil structure for plate magnetic pulse welding.

[0027] 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.

[0028] like Figure 4-5 As shown, a coil structure for plate magnetic pulse welding includes a multi-turn coaxial cable, an upper support plate 101, a lower support plate 102 and a metal strip 103. The high-strength metal strip conductor mainly includes copper alloy, stainless steel, carbon steel, etc. The coil welding section is a part of the short-circuited copper strip. The metal strip 103 is arranged on the upper support plate 101; the multi-turn coaxial cable includes a core wire 104 and a sheath wire 105; the upper and lower clamping plates short-circuit the sheath wire 105 of the multi-turn coaxial cable to a certain length of the metal strip 103 ( Figure 5The core wire 104 and the sheath wire 105 at the tail end of the multi-turn coaxial cable are short-circuited, and the short-circuit position is 107. The current flows into the core wire 104 at the other end of the coaxial cable and flows out of the sheath wire 105. The loop current on the multi-turn coaxial cable circulates through the coil welding section (copper bar convergence section) in sequence, turn by turn, and converges to generate a high peak pulse current that is several times the cross-sectional current of the single-turn coaxial cable.

[0029] The coil structure of the present invention can be used for plate magnetic pulse welding as well as for plate magnetic pulse forming.

[0030] Through the invented special coil loop, the discharge current is circulated through a section of conductor in sequence, converging to generate high peak pulse current, thus improving the coil energy utilization rate. The simplified circuit diagram of the 5-turn coaxial cable coil is shown in the figure below. Figure 4 As shown, the peak current of the conductor segment is several times the peak current of the main circuit, and the theoretical current amplification factor is equal to the number of cycles. At the same time, except for the conductor segment for welding, the remaining circuits in the coil are connected by coaxial cables, so that the coil inductance value is maintained at a small value, and the period and peak current of the discharge current curve generated by the discharge circuit meet the conditions for magnetic pulse welding of the plate. Therefore, the present invention provides a coil structure for magnetic pulse welding of plate, which can amplify the pulse current through the discharge circuit to produce the effect of high peak pulse current under a given discharge energy.

[0031] Based on the above invention idea, by short-circuiting the sheath wire 105 of the coaxial cable to a certain length of metal strip 103 (belonging to the conductor segment for coil welding), the loop current on the coaxial cable circulates through the certain length of metal strip 103 in sequence, turn by turn, and generates a high peak pulse current that is several times the cross-sectional current of a single turn of the coaxial cable. The coil structure schematic diagram is shown in FIG. Figure 5 As shown. Since the current in the coaxial cable coil circulates through the short-circuited metal strip 103 in sequence, the peak current is not the superposition of the peak current on the single-turn coaxial cable, but is staggered and superimposed according to the formation of the loop; at the same time, the loop resistance of the coil of the invention increases, resulting in a certain degree of attenuation of the discharge current. Therefore, the peak current magnification on the metal strip 103 is less than the number of turns. The discharge current curve of the 7-turn coaxial cable coil (peak current magnification is 5.3 times) is shown as follows Figure 6 shown.

[0032] In the coaxial cable coil, the formation of the loop is particularly critical. To ensure that the loop is carried out according to the design plan, it is necessary to ensure that the length of the metal strip 103 is less than the length of each turn of the coaxial cable sheath 105 or the cross-sectional area of ​​the metal strip 103 is greater than the cross-sectional area of ​​each turn of the coaxial cable coil sheath 105. The theoretical basis is that if the resistance of the metal strip 103 is less than the resistance of each turn of the coaxial cable coil sheath 105, the current will preferentially flow through the metal strip 103, and circulate and converge in turn to generate a large current, thereby realizing a multiple amplification of the discharge current peak.

[0033] Experimental studies have found that the peak current amplification factor β on the metal strip 103 is closely related to the length of the sheath wire 105 per turn of the coaxial cable coil lskin and the length of the metal strip 103 lcon. When the cross-sectional area of ​​the coaxial cable core and the sheath wire is certain, the smaller the ratio of the length of the metal strip 103 to the length of the sheath wire 105 per turn of the coaxial cable lcon / lskin, the higher the amplification efficiency β.

[0034] Amplification efficiency , where n a is the actual magnification, n t is the number of coil turns.

[0035] In addition, after numerical simulation and experimental research, it is concluded that the peak current amplification efficiency of the parallel coaxial cable coil is higher than that of the non-parallel coaxial cable coil. Parallel means that the core wires 104 of 2 or more turns of coaxial cable are connected in parallel, and the sheath wires 105 are connected in parallel to form the positive and negative electrodes connected to the equipment end, so that 2 or more turns of coaxial cable are connected in parallel to form a strand and pass through the copper bar segment at the same time. The discharge current curve of the 2-turn parallel coaxial cable coil with a total of 4 turns (peak current amplification factor is 3.8 times) is as follows Figure 8 Taking different types of coaxial cable coils as an example, the amplification efficiency of a 2-turn parallel coaxial cable coil with a total of 4 turns is 3.8 / 4=95%, the amplification efficiency of a 5-turn coaxial cable coil is 3.8 / 5=76%, and the amplification efficiency of a 7-turn coaxial cable coil is 5.3 / 7=76%.

[0036] The following combination Figure 5 and Figure 7 Specific implementation method:

[0037] (1) Design an n-turn coil and model it according to the initial parameters to determine the structure and size, such as Figure 5 shown.

[0038] (2) Based on numerical simulation software, simulation is performed to determine the inductance, resistance value, discharge current curve and peak value (amplification factor) of the coaxial cable coil.

[0039] (3) Iteratively optimize the coil structure and dimensions based on the numerical simulation results to determine the number of turns, height, and length of the coaxial cable, and design the tooling of the coaxial cable coil, such as Figure 7 As shown, the tooling consists of a coaxial cable coil 110, a support cylinder 111, a workbench 112, a left support plate 113, a right support plate 114, a limit bar 115, and a limit block 116. The support cylinder 111 and the left and right support plates are used to fix and limit the coaxial cable coil 110; the limit bar 115 is used to clamp the two sides of the coil to prevent the coil from being forced to move when working; the workbench 112 is used to provide a placement space for the parts to be connected (flying plate 60 and base plate 70); the limit block 116 is used to adjust the overlap gap between the flying plate 60 and the base plate 70.

[0040] (4) Determine the length of the coaxial cable and wind it into a spiral coil according to the design plan.

[0041] (5) Determine the short-circuit position of the sheathed wire 105 in the coaxial cable coil and the length of the stripped wire 105, and then use a customized copper block to short-circuit each turn of the sheathed wire 105 to the middle copper bar section (i.e., the current gathering section or welding section).

[0042] (6) Process the tail end of the coaxial cable coil and short-circuit the core wire 104 and the sheath wire 105 of the coaxial cable.

[0043] (7) Process the head position of the coaxial cable coil and use the core wire 104 and the sheath wire 105 of the coaxial cable as the positive and negative poles of the coil so as to connect to the interface of the electromagnetic forming equipment to form a loop.

[0044] (8) Assemble the coil, and then use the Rogowski coil to measure the discharge current curve of the single turn of the coaxial cable coil and the copper bar convergence section, i.e., the coil welding section (see Figure 5 )’s discharge current curve to determine the actual amplification factor and efficiency of the pulse current. Example

[0045] Coil-based magnetic pulse welding is implemented for AA1060 aluminum plate-DP600 steel plate. Among them, the connected plate is DP600 steel plate with a thickness of 1mm. The connecting plate is AA1060 aluminum plate with thicknesses of 0.5mm, 1.0mm, 1.5mm and 2.0mm respectively. The in-plane dimensions of both are 40mm×80mm. The thickness of the axial limit block is 2mm, that is, the axial gap between the connecting plate and the connected plate in the connection area is 2mm, and the width spacing of the limit block is 15mm. When a single limit block is used, the thickness of the limit block is 2mm, and the limit block is 10mm away from the free end of the flying plate.

[0046] The DP600 steel plate and AA1060 aluminum plate were both polished with sandpaper to remove rust until a new metal surface appeared. Then, the surface was cleaned with high-purity (ethanol mass fraction 99.7%) industrial alcohol to remove impurities and then blown dry. To ensure the surface quality of the samples, the prepared samples were connected within 30 minutes.

[0047] The rated voltage of the magnetic pulse welding device is 20kV, the capacitance is 100μF, the adjustable voltage range is 3~20kV, and the maximum discharge energy is 20kJ.

[0048] Based on the above experimental conditions, under the discharge voltage of 11kV, the connection joint of DP600-AA1060 (δ=0.5mm) was obtained; under the discharge voltage of 12kV, the connection joint of DP600-AA1060 (δ=1.0mm) was obtained; under the discharge voltage of 12kV, the connection joint of DP600-AA1060 (δ=1.5mm) was obtained; under the discharge voltage of 14kV, the connection joint of DP600-AA1060 (δ=2.0mm) was obtained. The connection effect diagram of the joint is shown in the figure. Fig. 9 shown.

[0049] In summary, under the condition that the maximum discharge energy does not exceed 9.8 kJ, the connection of AA1060 aluminum plates and DP600 steel plates with thicknesses of 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm was achieved. Example

[0050] Coil-based magnetic pulse welding is used for AA6101 high-strength aluminum alloy plate and DP600 steel plate. The plate to be connected is DP600 steel plate with a thickness of 1mm. The connecting plate is AA6101 high-strength aluminum alloy plate with a thickness of 0.8mm. The in-plane dimensions of both are 40mm×80mm. The thickness of the limit block used is 2mm, and the distance between the limit blocks is 15mm.

[0051] DP600 steel plate and AA6101 high-strength aluminum alloy plate are polished with sandpaper to remove rust until a new metal surface appears. Then use high-purity (ethanol mass fraction 99.7%) industrial alcohol to clean the surface, remove impurities, and then blow dry. To ensure the surface quality of the sample, the prepared sample must be connected within 30 minutes.

[0052] The rated voltage of the magnetic pulse welding device is 20kV, the capacitance is 100μF, the adjustable voltage range is 3~20kV, and the maximum discharge energy is 20kJ.

[0053] Based on the above experimental conditions, under the condition of discharge voltage 15kV, the connection joint of AA6101-DP600 was obtained. The connection effect diagram of the joint is shown in the figure. Fig. 9 That is, under the condition that the maximum discharge energy does not exceed 11.3kJ, the connection between the AA6101 high-strength aluminum alloy plate and the DP600 steel plate is achieved, further verifying the feasibility of the coil and the effective improvement of the coil energy utilization rate.

[0054] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0055] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea 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 coil structure for plate magnetic pulse welding, characterized in that: It comprises a multi-turn coaxial cable, an upper supporting plate, a lower supporting plate and a metal strip; the upper supporting plate and the lower supporting plate are used to clamp the multi-turn coaxial cable, and the metal strip is arranged on the upper supporting plate; the multi-turn coaxial cable comprises a core wire and a sheath wire; the metal strip is short-circuited with the sheath wire of the multi-turn coaxial cable, and the core wire and the sheath wire at the tail end of the multi-turn coaxial cable are short-circuited; the length of the metal strip is less than the length of each turn of the sheath wire of the coaxial cable or the cross-sectional area of ​​the metal strip is greater than the cross-sectional area of ​​each turn of the sheath wire of the coaxial cable coil; The tooling part of the coaxial cable coil is composed of a coaxial cable coil, a supporting cylinder, a workbench, a left supporting plate, a right supporting plate, a limiting strip and a limiting block; wherein the supporting cylinder, the left supporting plate and the right supporting plate are used to fix and limit the coaxial cable coil; the limiting strip is used to clamp both sides of the coil; the workbench is used to provide a placement space for the parts to be connected, and the parts to be connected include a flying plate and a base plate; the limiting block is used to adjust the overlapping gap between the flying plate and the base plate.

2. The coil structure for plate magnetic pulse welding according to claim 1, characterized in that: When the cross-sectional areas of the core wire and the sheath wire are constant, the smaller the ratio of the length of the metal strip to the length of each turn of the sheath wire is, the higher the peak current amplification factor on the metal strip is.

3. The coil structure for plate magnetic pulse welding according to claim 1, characterized in that: The coil structure is directly used for magnetic pulse forming of sheet materials.

4. The coil structure for plate magnetic pulse welding according to claim 1, characterized in that: The metal strips include copper alloys, stainless steel and carbon steel.

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