A method for preparing an arc contact with a large head and a small cavity

Abstract

A method for preparing an arc contact with a large head and a small cavity includes the following steps: A copper-tungsten 80 alloy is obtained through integral sintering; W: 78%-82%, Cu: 18%-22%, with impurities <0.5%; a blank of QCr0.5 component one is obtained through extrusion molding; Cr: 0.4-1.1%, Cu: balance; the blank is then heat-treated with a solution aging temperature of 1010±10°C and an aging temperature of 450±10°C to achieve the required performance; the QCr0.5 component one is machined to obtain a pre-welded part, with the inner hole machined to the finished size, and a total length allowance of 1mm; the assembled welded part is placed in a vacuum welding chamber and a vacuum is applied to achieve a vacuum degree of 6×10⁻⁶. ‑2 Pa is used for welding. The advantages of this invention are: the inner cavity is directly machined to the finished size before welding, no further machining is required after welding, the process is simple, the production efficiency is high, the deformation is small, and the use of electron beam welding can ensure the welding penetration depth and reduce internal defects such as porosity.

Description

Technical Field

[0001] This invention relates to the field of high-voltage switches, and in particular to a method for preparing an arc contact with a large head and a small cavity. Background Technology

[0002] As one of the double-contact structures in sulfur hexafluoride circuit breakers, the arc contact generally adopts a self-operated contact finger structure. It relies on the elasticity of the moving arc contact finger flaps as a holding force to hold the stationary arc contact, thereby ensuring reliable electrical contact between the moving and stationary arc contacts. During operation, the arc contact is responsible for withstanding the electric arc generated during opening and closing currents.

[0003] When an arc contact is switched on or off, the electric arc generates high temperatures that erode the contact. Simultaneously, the increased temperature degrades the mechanical properties of the moving arc contact's finger segments, reducing yield strength, decreasing or even eliminating elastic deformation capacity, causing plastic deformation of the finger segments, and even leading to finger segment detachment. This can result in circuit breaker failure during opening and closing. Therefore, the arc contact is a crucial component of a circuit breaker, and its erosion resistance and mechanical strength directly affect the reliable opening and closing of the circuit breaker. The stability and high strength of the arc contact are of paramount importance to the lifespan and reliability of the circuit breaker.

[0004] Currently, the methods to integrate the two into a single unit include brazing, integral sintering, or friction welding. However, each of these three processes has its own drawbacks. Brazing, using silver-based brazing filler metal, often results in defects such as weld porosity and weld inclusions due to the inability to meet directional solidification conditions. The post-weld performance is only about 70% of the original material, with a weld bonding rate of only 75%, and this problem persists. Integral sintering or friction welding, due to the product's small head and large cavity structure, makes further processing impossible. Even if a processing method is found, the processing cost is too high, resulting in a large number of scraps and high manufacturing costs. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a new preparation method. This method involves directly machining the inner cavity of the pre-finished product before welding, eliminating the need for post-weld processing. The process is simple, highly efficient, and produces minimal local deformation. Combining this with electron beam welding ensures high welding quality, achieving a weld bonding rate of 98%. The welded product is free of defects such as porosity and weld inclusions.

[0006] This invention provides a method for preparing an arc contact with a large head and a small cavity, characterized in that: the specific steps of the method for preparing the arc contact with a large head and a small cavity are as follows:

[0007] Step 1: Obtain the copper-tungsten 80 alloy by integral sintering, with the following weight ratio of components: W: 78%-82%, Cu: 18%-22%, and impurities <0.5%.

[0008] Step 2: Obtain the blank of QCr0.5 component one by extrusion molding; Cr: 0.4-1.1%, Cu: balance. Heat treat the blank to achieve the performance requirements.

[0009] Step 3: The copper-tungsten 80 alloy is machined to obtain a pre-welded part, and the inner hole is machined to the finished size;

[0010] The QCr0.5 component is pre-welded by machining, with the inner hole machined to the finished size, and a total length allowance of 1mm; the surface roughness of the end face to be welded is 1.6.

[0011] Step 4: Use 280#400# sandpaper to grind the welding surface. After grinding, wipe it clean with alcohol to thoroughly remove the oil from the machined parts 1 and 2, which can prevent porosity caused by volatiles during welding.

[0012] Step 5: Assemble component 2 using tooling 1 and tooling 2. The clearance between tooling 1 and welding component 1 and welding component 2 is 0.2mm.

[0013] Tooling 1 is explained. Its main function is to support component 1 and component 2, and it is a welding auxiliary locking bottom. The annular groove at the weld joint in tooling 1 is used to receive the welding beam. Its bolt holes are used for positioning. This tooling has a three-part structure, which facilitates the loading and unloading of this type of result that is large at the top and small at the bottom. The tooling can be reused. Tooling 2 is used to fix component 2 and tooling 1.

[0014] Step 6: Place the assembled welding parts into the vacuum welding chamber and evacuate the vacuum chamber to a level of 6×10-2 Pa for welding. When welding with electron beam, the finishing position of the circumferential welding is 5-8° higher than the starting position. High vacuum welding and a 5-8° circumferential finishing position effectively reduce welding porosity and improve the quality of the weld formation, eliminating the need for a second weld modification.

[0015] Welding speed: 4-6.5mm / s, welding time: 12.5-15.5s, focusing: 425-449mA, welding beam current: 78-88mA; accelerating voltage: 85kV, scanning: X10mA, Y5mA, frequency: 30Hz.

[0016] The advantages of focusing downwards are that it facilitates weld formation, resulting in a weld surface without depressions and eliminating the need for weld modification. High-vacuum welding also benefits weld formation.

[0017] Of course, the welding depth and welding parameters differ for different products. This should not be seen as a limitation on the range.

[0018] Step 7: After welding is completed, keep the area in the welding chamber warm;

[0019] Step 8: After welding, leave the welder in the welding chamber for 5 minutes before removing it. This prevents the high temperature from dropping rapidly after welding, allowing the temperature to decrease gradually and better ensuring post-weld performance. It also reduces the heat-affected zone.

[0020] Step 9: Perform dye penetrant testing on the weld after welding;

[0021] Step 10: Perform subsequent petal opening processing.

[0022] Advantages of this invention:

[0023] The inner cavity is directly machined to the finished size before welding, and no further machining is required after welding. The process is simple, the production efficiency is high, and the deformation is small. Electron beam welding can ensure the weld penetration depth and reduce internal defects such as porosity. Attached Figure Description

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0025] Figure 1 This is a schematic diagram of the cross-sectional structure of an arc contact with a large head and a small cavity according to the present invention;

[0026] Figure 2 This is a first-view structural schematic diagram of the clamp provided by the present invention;

[0027] Figure 3 A cross-sectional view of tooling 1 provided by the present invention;

[0028] Figure 4 A first-view view of the tooling 1 provided by the present invention;

[0029] Figure 5 A cross-sectional view of tooling 2 provided by the present invention; Detailed Implementation

[0030] Example 1

[0031] A method for preparing an arc contact with a large head and a small cavity, characterized in that: the specific steps of the method for preparing the arc contact with a large head and a small cavity are as follows:

[0032] Step 1: Obtain the copper-tungsten 80 alloy by integral sintering, with the following weight ratio of components: W: 78%-82%, Cu: 18%-22%, and impurities <0.5%.

[0033] Step 2: Obtain the blank of QCr0.5 component one by extrusion molding; Cr: 0.4-1.1%, Cu: balance. Heat treat the blank to achieve the performance requirements.

[0034] Step 3: The copper-tungsten 80 alloy is machined to obtain a pre-welded part, and the inner hole is machined to the finished size;

[0035] The QCr0.5 component is pre-welded by machining, with the inner hole machined to the finished size, and a total length allowance of 1mm; the surface roughness of the end face to be welded is 1.6.

[0036] Step 4: Use 280#400# sandpaper to grind the welding surface. After grinding, wipe it clean with alcohol to thoroughly remove the oil from the machined parts 1 and 2, which can prevent porosity caused by volatiles during welding.

[0037] Step 5: Assemble component 2 using tooling 1 and tooling 2. The clearance between tooling 1 and welding component 1 and welding component 2 is 0.2mm.

[0038] Tooling 1 is explained. Its main function is to support component 1 and component 2, and it is a welding auxiliary locking bottom. The annular groove at the weld joint in tooling 1 is used to receive the welding beam. Its bolt holes are used for positioning. This tooling has a three-part structure, which facilitates the loading and unloading of this type of result that is large at the top and small at the bottom. The tooling can be reused. Tooling 2 is used to fix component 2 and tooling 1.

[0039] Step 6: Place the assembled welding parts into the vacuum welding chamber and evacuate the vacuum chamber to a level of 6×10-2 Pa for welding. When welding with electron beam, the finishing position of the circumferential welding is 5-8° higher than the starting position. High vacuum welding and a 5-8° circumferential finishing position effectively reduce welding porosity and improve the quality of the weld formation, eliminating the need for a second weld modification.

[0040] Welding speed: 4 mm / s, welding time: 12.5 s, focusing: 425 mA, welding beam current: 78 mA; accelerating voltage: 85 kV, scanning: X10 mA, Y5 mA, frequency: 30 Hz.

[0041] The advantages of focusing downwards are that it facilitates weld formation, resulting in a weld surface without depressions and eliminating the need for weld modification. High-vacuum welding also benefits weld formation.

[0042] Of course, the welding depth and welding parameters differ for different products. This should not be seen as a limitation on the range.

[0043] Step 7: After welding is completed, keep the area in the welding chamber warm;

[0044] Step 8: After welding, leave the welder in the welding chamber for 5 minutes before removing it. This prevents the high temperature from dropping rapidly after welding, allowing the temperature to decrease gradually and better ensuring post-weld performance. It also reduces the heat-affected zone.

[0045] Step 9: Perform dye penetrant testing on the weld after welding;

[0046] Step 10: Perform subsequent petal opening processing.

[0047] Example 2

[0048] The difference from Example 1 is as follows:

[0049] Welding speed: 5mm / s, welding time: 13.5s, focusing: 430mA, welding beam current: 82mA; accelerating voltage: 85kV, scanning: X10mA, Y5mA, frequency: 30Hz.

[0050] Example 3

[0051] The difference from Examples 1 and 2 is as follows:

[0052] Welding speed: 6.5 mm / s, welding time: 15.5 s, focusing: 449 mA, welding beam current: 88 mA; accelerating voltage: 85 kV, scanning: X10 mA, Y5 mA, frequency: 30 Hz.

[0053] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an arc contact with a large head and a small cavity, characterized in that: The head large cavity small arc contact manufacturing method comprises the following steps: Step one: obtain copper tungsten 80 alloy by bulk sintering; W: 78%-82%, Cu: 18%-22%, impurities <0.5%; Step two: obtain QCr0.5 component one blank by extrusion molding; Cr: 0.4-1.1%, Cu: balance, heat treat the blank, solid solution aging temperature: 1010±10°, aging temperature: 450±10°, reach the use performance, meet GB / T 8320-2017 standard; Step three: the copper tungsten 80 alloy is obtained by machining to obtain a pre-welding part, and the hole is processed to the finished product size; QCr0.5 component one is obtained by machining to obtain a pre-welding part, and the hole is processed to the finished product size, and the total length allowance is 1mm; the welding end surface roughness is 1.6; Step four: polish the welding surface with 280#400# sandpaper, and then wipe it clean with alcohol; Step five: assemble component two with tooling one (1) and tooling two (2), and the gap between tooling one (1) and the welding component one and the welding component two is 0.1mm; Tooling one (1) is described, which serves as a support for component one and component two and is an auxiliary support for welding, and the ring groove opposite the welding position in tooling one (1) can absorb the residual energy of electron beam welding; The bolt hole is used for positioning, and the tooling is a three-piece structure, which facilitates the assembly and disassembly of parts of this structure, and the tooling can be reused, and tooling two (2) is used to fix component two and tooling one (1); Step six: the assembled welding parts are put into the vacuum welding chamber to be vacuumized, so that the vacuum degree in the welding chamber reaches 6x10 - 2 The welding is performed on the PA; the arc starting area, the lap area and the arc receiving area of the electron beam welding are 8°; Step seven: after welding, keep the welding chamber for 5 minutes to prevent surface oxidation; Step eight: take out the part; Step nine: after welding, perform dye penetrant testing on the weld; Step ten: perform subsequent processing.

2. A method of manufacturing a head large cavity small arc contact according to claim 1, characterized in that: The welding parameters of step six are as follows: welding speed: 4-6.5mm / s, welding time: 12.5-15.5s, focusing: 425-449mA, welding beam current: 78-88mA; accelerating voltage: 85kV, scanning: X10mA, Y5mA, frequency: 30Hz.

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