A weldable lightweight long-life arc-starting electrode and welding method

Abstract

This invention provides a weldable, lightweight, long-life arc-initiating electrode and welding method, including an anode head, a cathode head, an anode column, and a cathode column. The anode head and cathode head are made of single or composite metal conductor materials resistant to arc erosion; the anode column and cathode column are also made of single or composite metal conductor materials. The current path is as follows: the arc igniter is connected to both ends of the track in the muzzle region of a high-speed electromagnetic propulsion device, powered by an external power source. Current flows through the track and armature path of the high-speed electromagnetic propulsion device. The armature, under electromagnetic force, accelerates and slides from the muzzle towards the muzzle. When the armature exits the muzzle, it disengages from the track. Simultaneously, the metal or plasma medium in the gap between the bypass electrodes of the arc igniter induces gap breakdown discharge, achieving arc initiation. This invention meets requirements for conductivity and high tensile strength.

Description

Technical Field

[0001] This invention belongs to the field of high-speed electromagnetic propulsion, specifically relating to a weldable lightweight long-life arc-starting electrode and welding method, which can conduct current levels of hundreds of kiloamperes or more. Background Technology

[0002] Conventional arc igniters often employ a large resistor connected in parallel at the muzzle to reduce the arc current by creating a circuit through the large resistor after the armature leaves the barrel. However, this parallel arc ignition structure consistently contributes to system energy loss during electromagnetic propulsion, thus reducing system efficiency. The muzzle arc igniter independently developed by the Institute of Electrical Engineering, Chinese Academy of Sciences, uses a parallel open-circuit gap electrode. When the armature moves within the barrel, it does not participate in system energy consumption. Upon exiting the barrel, the muzzle voltage jumps, exceeding the breakdown voltage threshold, causing an arc to ignite at the muzzle. The high-speed arc causes the gap between the arc igniter electrodes to break down and discharge, thus both igniting the arc, reducing the impact of muzzle arcing on the armature's flight attitude, and effectively protecting the muzzle material.

[0003] like Figure 1 As shown, the independently developed muzzle arc igniter includes a current-guiding anode 1a, a current-guiding cathode 1b, a bypass anode 2a, a bypass cathode 2b, a fastener 3a, and an insulating spacer 4a. The current-guiding anode 1a and the current-guiding cathode 1b are made of single or composite metallic good conductor materials and have a symmetrical structure. The bypass anode 2a and the bypass cathode 2b include an anode column, an anode head, a cathode column, and a cathode head, also made of single or composite metallic good conductor materials. The fastener 3a can be a standard bolt or nut, or it can be designed as a non-standard part according to the geometry of the arc igniter, or it can be connected to both ends of the armature / projectile of the electromagnetic rail launcher using a resin-based insulating fiber winding fastener device. It is powered by an external power source, and the current conducts through the track and armature path of the electromagnetic propulsion device. The armature, under electromagnetic force, accelerates and slides from the breech to the muzzle within the bore. When the armature exits the bore, it disengages from the track, and simultaneously, the gap between the bypass electrodes of the arc igniting device is induced by a metallic dielectric or plasma to break down and discharge, thus achieving the arc ignition effect.

[0004] Because of the need to reduce the deflection of the muzzle of the high-speed electromagnetic propulsion device, there is a requirement for lightweight design; the muzzle is subjected to shock waves and transient electromagnetic forces, requiring strength; the muzzle area is subject to high-temperature fluid and plasma ablation, requiring temperature resistance; and the Joule heat generated by hundreds of kiloamperes to megaamperes of current is dissipated through the electric arc, also requiring conductivity. Therefore, the electrode material of the arc igniter needs to be lightweight, high-strength, and resistant to high-temperature electric arc ablation. Currently, integrated electrodes cannot simultaneously meet all these requirements. Therefore, high-melting-point, high-strength single metal or metal alloy materials are selected for the electrode head part that contacts the high-temperature electric arc, while high-strength, lightweight single metal or metal alloy materials are selected for the electrode post part. Furthermore, a reliable electrical connection must be achieved between the electrode head and the electrode post. Ordinary non-welding processes, such as bolt crimping, increase volume and weight and cannot achieve complete connection of the contact surface; fiber winding is also unsuitable for this structure; conventional lap welding is limited by the welding depth and cannot achieve complete welding of large-sized contact surfaces. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a weldable, lightweight, long-life arc-initiating electrode and its welding method. The arc-initiating electrode is a key flow-guiding component of the muzzle arc initiator in high-speed electromagnetic propulsion devices. It comprises at least four electrodes arranged symmetrically from left to right and top to bottom. Each electrode includes an electrode head and a bypass electrode post. To ensure the connection strength between the corresponding electrode head and electrode post, and the complete conduction of the pulsed high current within the electrode, the corresponding electrode head and electrode post are welded using a rotary friction welding process. This process ensures complete welding of the electrode head and electrode post welding surfaces. Rotary friction welding generates heat through relative rotational friction between the electrode head and electrode post, bringing the contact surface to a plastic state before applying pressure to achieve a solid-state connection, thus meeting requirements for conductivity and high tensile strength.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A weldable, lightweight, long-life arc-initiating electrode includes an anode head, a cathode head, an anode column, and a cathode column. The metal electrode head is made of a single or composite metal conductor that is resistant to arc erosion. Its cross-section at the weld point with the electrode column is circular or annular. The shape of the remaining parts can be designed according to the actual application. Its function is to divert the arc current between the armature and the track, achieving a long lifespan. The metal electrode column is also made of a single or composite metal conductor. Its cross-section at the weld point with the electrode head is circular or annular. The shape of the remaining parts can be designed according to the actual application. Its function is to conduct the residual current fed into the arc suppressor by the power supply, achieving lightweight design. The current path is as follows: the arc igniter is connected to both ends of the track in the muzzle region of a high-speed electromagnetic propulsion device, powered by an external power source. The current conducts through the track and armature path of the high-speed electromagnetic propulsion device. The armature, under electromagnetic force, accelerates and slides from the muzzle to the muzzle within the barrel. When the armature exits the barrel, it disengages from the track. Simultaneously, the metal or plasma medium in the bypass electrode gap of the arc igniter induces gap breakdown discharge, achieving arc initiation.

[0008] Furthermore, the rotary friction welding is a continuous rotary friction welding, with no holes or cracks at the welding interface, forming a fully sealed connection across the entire cross-section.

[0009] Furthermore, the anode head and cathode head are made of tungsten-copper alloy, and the anode column and cathode column are made of copper alloy or brass.

[0010] Furthermore, the outer diameter of the anode column and cathode column is equal to the outer diameter of the corresponding anode head and cathode head, or the outer diameter of the anode column and cathode column is slightly smaller than the outer diameter of the corresponding anode head and cathode head, forming a coaxial cylindrical structure.

[0011] Furthermore, the thickness of the anode head, cathode head, anode column, and cathode column is determined according to different diameters and weight requirements.

[0012] Furthermore, the coaxiality of the anode head and anode column, and the cathode head and cathode column after welding is no greater than 0.1 mm.

[0013] Furthermore, the length of the electrode gap is indirectly calculated based on the aperture and residual current, and is not greater than the aperture of the electromagnetic propulsion device. The outer diameter of the electrode is calculated based on the electromagnetic force it is subjected to.

[0014] This invention also provides a welding method for a weldable lightweight long-life arc-starting electrode, comprising the following steps:

[0015] Step 1. Clean the electrode head and electrode post;

[0016] Step 2. Place the electrode head and electrode post in the welding equipment and position them;

[0017] Step 3. Start the rotary friction welding equipment to rotate the electrode column while keeping the electrode head stationary;

[0018] Step 4. Continue to apply axial pressure to make the electrode head and electrode post come into close contact and undergo plastic deformation to form a weld.

[0019] Step 6. After welding is completed, the weld is cooled and solidified;

[0020] Step 7. After welding is completed, grind and clean the weld area that exceeds the original outer diameter to ensure that the surface dimensions are qualified.

[0021] Furthermore, in step 1, acetone is used for cleaning.

[0022] Furthermore, in step 3, the rotational speed of the electrode post is set to 3000 r / min and the axial pressure is 100 MPa; in step 4, the axial pressure is further applied to 200 MPa.

[0023] Beneficial effects:

[0024] 1. Synergistic effect: Rotary friction welding, through solid metallurgical bonding (non-fusion welding), avoids defects caused by melting point differences and achieves atomic-level sealed connection between high-density electrode heads (tungsten copper) and lightweight electrode posts (beryllium copper or chromium copper and other copper alloys), while simultaneously satisfying the requirements of lightweight and long service life.

[0025] 2. In terms of feature dimensions, a collaborative structure is constructed with the "welding interface" as the core. The anode head and the anode column form a defect-free metallurgical transition layer through rotary friction welding. The grain size of the transition layer is ≤50μm (refining the grain to improve strength), the interface resistance is ≤5μΩ (reducing Joule heat), and the thickness of the transition layer is 10%~30% of the diameter of the electrode column (optimizing stress distribution).

[0026] 3. Achieving material synergy: Tungsten copper alloy (high melting point) and other copper alloys such as beryllium copper or chromium copper (high conductivity) form a gradient structure through dynamic recrystallization via friction welding, avoiding cracking caused by mismatch in thermal expansion coefficients.

[0027] Achieving geometric synergy: The welding surface is designed as a circular structure, which increases the contact area and eliminates edge incomplete penetration defects by utilizing the radial plastic flow of rotary friction welding.

[0028] The upsetting pressure of the rotary friction welding is ≥50MPa (to allow the copper column to fully plastically deform and fill the micro-pits of the tungsten head), the rotation speed is ≥2000rpm (to ensure that the interface temperature reaches the recrystallization temperature of copper but is lower than the melting point of tungsten), and the interface shear strength after welding is ≥200MPa.

[0029] 4. This invention exhibits synergistic effects: At the microscopic level, high rotation speed and high pressure dynamically soften the copper column, embedding it into microgrooves on the tungsten head surface, forming a dual reinforcement of mechanical interlocking and metallurgical bonding. At the macroscopic level, welding residual stress is released through the thin-walled design (thickness range) of the electrode column, preventing brittle fracture of the tungsten-copper head. Rotary friction welding makes the tungsten-copper-copper alloy interface properties approach those of a monolithic tungsten-copper electrode, but because the copper alloy occupies a larger volume and its density is almost halved, the weight is significantly reduced, and the lifespan meets the requirements of electromagnetic propulsion, thus achieving a synergistic effect. Attached Figure Description

[0030] Figure 1 A schematic diagram of an existing muzzle arc initiator;

[0031] Figure 2 This is a schematic diagram of the current path of a weldable lightweight long-life arc-starting electrode according to the present invention.

[0032] Figure 3 This is a schematic diagram of a weldable lightweight long-life arc-starting electrode according to Example 1;

[0033] Figure 4 This is a schematic diagram of a weldable lightweight long-life arc-starting electrode according to Example 2;

[0034] Figure 5 Tensile test curves of tungsten copper and beryllium copper weld surfaces after welding;

[0035] Figure 6 This is a schematic diagram of the current path before and after the armature leaves the barrel.

[0036] The attached figures are labeled as follows: current-conducting anode 1a, current-conducting cathode 1b, bypass anode 2a, bypass cathode 2b, fastener 3a, insulating spacer 4a, anode head 1, cathode head 2, anode column 3, and cathode column 4. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] The present invention provides a weldable, lightweight, long-life arc-starting electrode comprising an anode head 1, a cathode head 2, an anode column 3, and a cathode column 4. The anode head 1 and cathode head 2 are electrode heads, and the anode column 3 and cathode column 4 are electrode columns.

[0039] The electrode head is made of a single or composite metal conductor that is resistant to arc erosion, such as tungsten-copper alloy. The cross-section of the electrode head where it is welded to the electrode post is a circular or annular structure. The shape of the remaining parts can be designed according to the actual application. Its function is to divert the arc current between the armature and the rail and achieve a long life.

[0040] The electrode post is made of a single or composite metal good conductor material. The cross-section of the part where it is welded to the electrode head is a circular or annular structure. The shape of the rest of the structure can be designed according to the actual application. Its function is to conduct the residual current fed into the arc suppressor by the power supply and to achieve lightweighting.

[0041] like Figure 2 , Figure 6 As shown, the current path of the welded lightweight long-life arc-initiating electrode is as follows: the arc igniter is connected in parallel to both ends of the track in the bore region of the high-speed electromagnetic propulsion device and is powered by an external power source. The current is connected in series with the anode and cathode of the high-speed electromagnetic propulsion device and the anode and cathode of the arc igniter. The current conducts the track and armature path of the high-speed electromagnetic propulsion device. The armature is accelerated and slides from the bore tail to the bore mouth under the electromagnetic force. When the armature leaves the bore, it separates from the track. At the same time, the metal or plasma medium in the gap of the bypass electrode of the arc igniter induces the gap breakdown discharge, thereby realizing the arc ignition effect.

[0042] Example 1:

[0043] like Figure 3 As shown, the anode head 1 and cathode head 2 are both made of tungsten, with an outer diameter of 50 mm and a thickness of 20 mm. The anode post 3 and cathode post 4 are both made of copper, with an outer diameter of 50 mm and a thickness of 80 mm. The electrode gap is 10 mm long. A current source is connected to the high-speed electromagnetic propulsion device, using a 60 Hz and 1 mA AC current source, applied to the anode and cathode of the arc igniter. Compared with integrated arc ignition electrodes, this structure features high strength, lightweight, and long life; compared with other welded arc ignition electrodes, it features high strength and high current throughput. The electrode posts and electrode heads are cylindrical with a uniform cross-section and a circular structure.

[0044] Figure 3 In this assembly, the tracks are arranged vertically, but are not shown as they are obscured by the upper and lower flow-guiding electrode plates of the arc igniter. The left and right muzzle supports are placed on the lower tracks, and the upper track is placed on the muzzle supports, forming the inner bore assembly. The outer casing of the device is fitted over the inner bore assembly, which can be achieved through fiber winding or bolt pre-tightening. The upper and lower flow-guiding electrode plates of the arc igniter are connected to the upper and lower tracks, respectively.

[0045] Example 2:

[0046] like Figure 4As shown, the anode head 1 and cathode head 2 are both made of tungsten, with an outer diameter of 70 mm and a thickness of 20 mm. The anode column 3 and cathode column 4 are both made of copper, with an outer diameter of 50 mm and a thickness of 80 mm. The electrode gap is 10 mm long. A current source is connected to the high-speed electromagnetic propulsion device, using a 60 Hz and 1 mA AC current source, applied to the anode and cathode of the arc igniter. Compared with integrated arc ignition electrodes, this structure features high strength, lightweight, and long life; compared with other welded arc ignition electrodes, it features high strength and high current throughput. The electrode columns and electrode heads adopt a non-uniform cross-section columnar form with a circular cross-section, and the outer diameter of the electrode column is smaller than that of the electrode head.

[0047] Figure 4 In this assembly, the tracks are arranged vertically, but are not shown as they are obscured by the upper and lower flow-guiding electrode plates of the arc igniter. The left and right muzzle supports are placed on the lower tracks, and the upper track is placed on the muzzle supports, forming the inner bore assembly. The outer casing of the device is fitted over the inner bore assembly, which can be achieved through fiber winding or bolt pre-tightening. The upper and lower flow-guiding electrode plates of the arc igniter are connected to the upper and lower tracks, respectively.

[0048] This invention also provides a welding method for a weldable lightweight long-life arc-starting electrode, comprising:

[0049] The electrode post material has a lower melting point and softening temperature than the metal electrode tip material. The high-speed relative rotation between the two generates frictional heat, causing the electrode post material to melt first and then form a permanent seal under pressure. This allows for the smaller, lighter design of the denser electrode tip material, meeting requirements for lightweight construction and long lifespan. The specific steps include:

[0050] Step 1. Clean the electrode head and electrode column with acetone.

[0051] Step 2. Place the electrode head and electrode post in the welding equipment and position them.

[0052] Step 3. Start the rotary friction welding equipment, allowing the electrode post to rotate while keeping the electrode head stationary. Set the rotation speed of the electrode post to 3000 r / min and the axial pressure to 100 MPa.

[0053] Step 4. Continue to apply axial pressure to 200 MPa to make the electrode head and electrode post come into close contact and undergo plastic deformation to form a weld.

[0054] Step 6. After welding is completed, the weld is cooled and cured.

[0055] Step 7. After welding is completed, grind and clean the weld area that exceeds the original outer diameter to ensure that the surface dimensions are qualified.

[0056] Example 3:

[0057] Tensile performance tests were performed on the friction welding electrode sample. The electrode has an outer diameter of 20 mm and an inner diameter of 14 mm. Calculations showed it needed to withstand a tensile force of over 40 kN. The tensile tests confirmed that the welding strength of the friction welding electrode met the design requirements. Figure 5 As shown, the main coordinate unit is kN, corresponding to the lower segment of the polyline, and the secondary coordinate unit is mm, corresponding to the upper segment of the polyline. Figure 5 The tensile test curves of the tungsten copper and beryllium copper welded surfaces are shown. After the tungsten copper electrode head and beryllium copper electrode post are welded using rotary friction welding, a tensile testing machine is used to apply a tensile force of about 40kN or more, and five tensile tests are performed continuously within 2 minutes to detect the tensile force and elongation. After the tensile test, the welded surface is considered qualified if there are no cracks or fractures.

[0058] After 100 tests, the friction welding electrode lost approximately 68g of mass; the integrated copper alloy electrode failed after only one test; the integrated tungsten electrode was not adopted due to its excessive weight, which did not meet the requirements for lightweighting; and the bolted tungsten-copper electrode was not adopted because its structural form did not meet the requirements for borehole operation.

Claims

1. A welded lightweight long-life arc striking electrode, characterized by, The electrode comprises an anode head, a cathode head, an anode column and a cathode column; the anode head and the anode column and the cathode head and the cathode column are respectively welded on a circular or circular ring welding surface by rotary friction welding to form solid metallurgical bonding; the anode head and the cathode head are arc-ablation-resistant metal conductors; the anode column and the cathode column are metal good conductors and have a melting point lower than that of the corresponding electrode head; the electrode is connected to both ends of a bore track of a high-speed electromagnetic propulsion device, and when the armature exits the bore, the electrode gap is induced to break down and discharge. The anode head and the cathode head are made of tungsten-copper alloy, and the anode column and the cathode column are made of copper alloy or brass.

2. The welded lightweight long-life arc striking electrode according to claim 1, characterized by The rotary friction welding is continuous rotary friction welding, and the welding interface is free of holes and cracks, forming a full-section sealed connection.

3. The welded long-life arc striking electrode according to claim 1, wherein The outer diameter of the anode column and the cathode column is equal to or slightly smaller than the outer diameter of the corresponding anode head and cathode head, forming a coaxial cylindrical structure.

4. The welded long-life arc striking electrode according to claim 1, wherein The thickness of the anode head and the cathode head and the thickness of the anode column and the cathode column are determined according to the caliber and weight requirements.

5. The welded lightweight long-life arc striking electrode according to claim 1, wherein The post-weld coaxiality of the anode head and the anode column and the cathode head and the cathode column is not greater than 0.1 mm.

6. The welded long-life arc striking electrode according to claim 1, wherein The length of the electrode gap is indirectly calculated according to the caliber and residual current, and is not greater than the caliber of the electromagnetic propulsion device, and the outer diameter of the electrode is calculated according to the electromagnetic force received.

7. The welding method of the welded lightweight long-life arc striking electrode according to any one of claims 1 to 6, characterized by, The method comprises the following steps: Step 1. Clean the electrode head and the electrode column; Step 2. Place the electrode head and the electrode column in the welding equipment and position them; Step 3. Start the rotary friction welding equipment, rotate the electrode column, and keep the electrode head stationary; Step 4. Continue to apply axial pressure to make the electrode head and the electrode column tightly contact and plastically deform to form a weld; Step 6. After welding is completed, cool and solidify the weld; Step 7. After welding is completed, polish and clean the dimensions of the welded part that exceed the original outer diameter to ensure that the surface dimensions are qualified.

8. The welding method of claim 7, wherein, In step 1, acetone is used for cleaning.

9. The welding method of claim 7, wherein, In step 3, the rotation speed of the electrode column is set to 3000 r / min, and the axial pressure is 100 MPa; in step 4, the axial pressure is continuously applied to 200 MPa.

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