Butt welding device of small-specification auxiliary electrode for vacuum consumable melting

Abstract

The butt welding device comprises a bottom crucible with an upward opening, an electric arc furnace body is arranged at the upper end of the bottom crucible in a sealing and covering mode, and a vacuumizing opening is formed in the circumferential face of the electric arc furnace body. An electrode rod capable of moving in the three-dimensional direction is arranged at the top of an inner cavity of the electric arc furnace body, a first butt welding auxiliary electrode is arranged in an inner cavity of the bottom crucible, the lower end of the electrode rod is connected with a second butt welding auxiliary electrode, and an expansion sleeve coaxial with the inner cavity of the bottom crucible is arranged at the upper end of the bottom crucible. An inner hole of the expansion sleeve is sequentially divided into a large-diameter section and a small-diameter section from top to bottom, the size of the small-diameter section is matched with the inner diameter of the first butt welding auxiliary electrode, and the upper end of the first butt welding auxiliary electrode extends into the large-diameter section. The expansion sleeve is used for constraining the molten pool, welding beading can be avoided, the welding quality is guaranteed, the expansion sleeve is used for conveniently mastering the welding opportunity and reducing the welding operation difficulty, and the expansion sleeve is suitable for general operation.

Description

Technical Field

[0001] The utility model relates to the technical field of metal material welding, in particular to a butt welding device for small-sized auxiliary electrodes used in vacuum consumable melting. Background Art

[0002] Titanium alloys have the advantages of high specific strength, good high-temperature performance, excellent corrosion resistance, etc., and are widely used in the fields of aviation, aerospace, medical treatment, shipbuilding, etc. In the industrial field, the most widely used melting method at present is vacuum consumable arc melting.

[0003] During the vacuum consumable melting process, the auxiliary electrode is one of the important tooling, which plays the roles of bearing weight, conducting electricity, and connecting the electrode rod and the consumable electrode. The quality of the auxiliary electrode directly affects the safety of melting, process stability, and product quality.

[0004] The auxiliary electrode is also one of the auxiliary materials with the largest consumption in the production process of titanium alloys. In industrial production, in order to reduce production costs and extend the service life of the auxiliary electrode, the butt welding method is often used to splice two or even more auxiliary electrodes with smaller lengths into an auxiliary electrode with a length meeting the requirements by welding, so as to achieve the purpose of recycling.

[0005] There are two common methods for butt welding of auxiliary electrodes in the prior art. One is to use a welding box to weld in a vacuum or inert gas atmosphere. However, this technology requires reprocessing the surface of the auxiliary electrode to be butt welded for easy assembly. After assembly, a welding torch is used for welding to increase the length for repeated use. The other method is to use a vacuum consumable arc furnace for in-furnace welding. This method does not require special treatment of the surface of the auxiliary electrode, but has certain requirements for the flatness of the welding surface, otherwise partial welding is likely to occur.

[0006] In the prior art, when using a welding box for welding, both the surface and the end face of the auxiliary electrode need to be processed, and the assembly gap generally cannot be greater than 3 mm, otherwise the weld seam is likely to crack and cannot be used. In addition, the weld seam girth welding technology used in welding boxes cannot ensure 100% full welding, and the cross-section of the butt welding of two auxiliary electrodes cannot be welded. Therefore, the biggest disadvantage of this technology is that the welding strength is relatively small. In actual production, because the auxiliary electrode plays the role of connecting the electrode rod and the ingot, the risk is very high.

[0007] When using in-furnace welding in a vacuum consumable arc furnace, in the existing conventional method, there is no restraint on the molten pool, and it is impossible to ensure that the molten pool is used for stable welding. Generally, the welding area accounts for about 70% or so, and the welding strength is relatively better.

[0008] However, when welding in a vacuum consumable arc furnace, since the molten metal is not restricted and cannot remain on the bonding surface, it overflows to form a weld bead. As a result, in actual production, the weld bead at the weld is relatively large, presenting the problem of being difficult to clean, which affects the welding quality.

[0009] Especially for small-sized auxiliary electrodes with a diameter less than 280 mm, when welding in a vacuum consumable arc furnace, as soon as the arc is established, the cross-sections of the two pairs of welding auxiliary electrodes begin to partially melt. Since the molten metal cannot remain on the bonding surface, it overflows to form a weld bead. At this time, there will be a small amount of adhesion during welding, while other parts are not melted and cannot be effectively adhered. Continuing to melt will result in a large weld bead or the area that melted first being burned out by the arc, forming a large notch, which will also lead to the problem of insufficient bonding surface. This requires grasping the welding timing. And during the process, the adjustment of current and voltage and the control of arc length are more complex, with extremely high operation difficulty and extremely low success rate, demanding very high operation ability from personnel and not being suitable for general operation by personnel.

[0010] Therefore, how to reduce the operation difficulty and ensure the butt welding quality when welding small-sized auxiliary electrodes using a vacuum consumable arc furnace is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Utility Model

[0011] The technical problem to be solved by the present utility model is to provide a butt welding device for small-sized auxiliary electrodes for vacuum consumable melting, which uses an expansion sleeve to restrict the molten pool, can avoid the formation of weld beads, ensure the welding quality, and is convenient to grasp the welding timing by using the expansion sleeve, reduce the welding operation difficulty, and is suitable for general operation.

[0012] In response to the above technical problem, the technical solution provided by the present utility model is a butt welding device for small-sized auxiliary electrodes for vacuum consumable melting, including a bottom crucible with an upward opening, the upper end of the bottom crucible is hermetically covered with an arc furnace body, a vacuum extraction port is arranged on the peripheral surface of the arc furnace body, an electrode rod that can move in three-dimensional directions is arranged at the top of the inner cavity of the arc furnace body, a first pair of welding auxiliary electrodes is arranged in the inner cavity of the bottom crucible, the lower end of the electrode rod is connected with a second pair of welding auxiliary electrodes, an expansion sleeve coaxial with its inner cavity is arranged at the upper end of the bottom crucible, the inner hole of the expansion sleeve is sequentially divided into a large-diameter section and a small-diameter section from top to bottom, the size of the small-diameter section is adapted to the inner diameter of the first pair of welding auxiliary electrodes, and the upper end of the first pair of welding auxiliary electrodes extends into the large-diameter section.

[0013] Further, the large-diameter section is a flared structure with an inner diameter gradually decreasing from top to bottom.

[0014] Further, the large-diameter section is a frustum structure with a larger upper part and a smaller lower part, and the generatrix of the frustum structure forms an angle of 45° with its axis.

[0015] Further, the material of the expansion sleeve is copper.

[0016] Further, the material of the expansion sleeve is T2 copper.

[0017] Further, there is a clearance fit between the first butt-welding auxiliary electrode and the small-diameter section of the expansion sleeve, and the clearance size is 0.4 mm to 0.6 mm.

[0018] Further, the flatness of the lower surface of the expansion sleeve is within the range of 0 mm to 0.1 mm, and the surface roughness Ra ≤ 3.2 μm.

[0019] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0020] (1) By providing an expansion sleeve, the inner hole of the expansion sleeve is divided into a large-diameter section and a small-diameter section from top to bottom. The size of the small-diameter section is adapted to the inner diameter of the bottom crucible, and the inner diameter of the bottom crucible is in turn adapted to the size of the first butt-welding auxiliary electrode. The upper end of the first butt-welding auxiliary electrode also extends into the large-diameter section. In this way, the upper part of the first butt-welding auxiliary electrode can be wrapped by the small-diameter section, and a reserved space is formed between the large-diameter section and the upper end of the first butt-welding auxiliary electrode.

[0021] During actual butt welding, the electrode rod is used to drive the second butt-welding auxiliary electrode to move to a position coaxial with the first butt-welding auxiliary electrode, and the inside of the electric arc furnace body is evacuated. One of the first butt-welding auxiliary electrode and the second butt-welding auxiliary electrode is connected to the positive electrode and the other is connected to the negative electrode of the power supply. The distance between the second butt-welding auxiliary electrode and the first butt-welding auxiliary electrode is adjusted by the electrode rod to quickly start an arc, and the opposite ends of the two butt-welding auxiliary electrodes to be welded are melted. Using the reserved space between the upper end of the first butt-welding auxiliary electrode and the large-diameter section of the expansion sleeve, the molten droplets formed by melting will fall and gather in the large-diameter section of the expansion sleeve. The molten pool is constrained by the expansion sleeve, so that the molten pool surrounds and wraps the outer periphery of the first butt-welding auxiliary electrode. When the molten pool in the expansion sleeve covers the upper end face of the first butt-welding auxiliary electrode, the welding timing is reached, and the electrode rod is lowered to complete the butt welding of the two butt-welding auxiliary electrodes.

[0022] Constrained by the expansion sleeve, the molten pool can wrap the outer periphery and the upper end face of the first butt-welding auxiliary electrode, so that the molten droplets are retained on the bonding surface, ensuring 100% full welding, and avoiding the formation of welding beads. It also avoids the problems of large and difficult-to-clean welding beads and poor welding quality stability. At the same time, through the expansion sleeve, only an arc needs to be established to melt the metal, and by observing that the molten pool covers the upper end face of the first butt-welding auxiliary electrode, welding can be carried out, greatly reducing the operation difficulty and meeting general operations.

[0023] (2) The inner diameter of the large-diameter section has a flared structure with a larger upper part and a smaller lower part, which can avoid a large temperature difference between the lower part and the upper part of the molten pool, so that the molten droplets in the molten pool are always in a molten state, ensuring the welding quality.

[0024] (3) The expansion sleeve is made of copper. Copper is characterized by its high temperature resistance, good thermal conductivity, and fast heating and cooling. In this way, copper has good stability and will not react with the metal solution, resulting in the adhesion of metal droplets to the expansion sleeve or the deformation of the expansion sleeve. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the internal structure of the butt welding device in Embodiment 1 of the present utility model.

[0026] Figure 2 It is a front sectional view of the expansion sleeve in Embodiment 1 of the present utility model.

[0027] Figure 3 It is a top view of the expansion sleeve in Embodiment 1 of the present utility model.

[0028] In the figure: 1, bottom crucible; 11, crucible body; 12, connecting flange; 2, electric arc furnace body; 3, vacuum extraction port; 4, first butt welding auxiliary electrode; 5, second butt welding auxiliary electrode; 6, electrode rod; 7, expansion sleeve; 71, large diameter section; 72, small diameter section; 73, reserved space; 8, electric arc; S, air flow path. Detailed Embodiment

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application: Specific Embodiment 1:

[0031] Refer to Figure 1 , a butt welding device for small-sized auxiliary electrodes used in vacuum consumable melting of the present utility model (hereinafter referred to as the welding device) includes a bottom crucible 1 with an upward opening, and an electric arc furnace body 2 is hermetically covered on the upper end of the bottom crucible 1. Specifically, the bottom crucible 1 includes a crucible body 11 with an upward opening, and a connecting flange 12 is fixedly arranged at the upper end of the crucible body 11. The inner hole of the connecting flange 12 is adapted to the inner cavity of the crucible body 11, and the two are coaxially arranged. The electric arc furnace body 2 is fixedly covered on the connecting flange 12 with a downward opening, and the connection between the two is hermetically matched.

[0032] A vacuum extraction port 3 is arranged on the circumferential surface of the electric arc furnace body 2. An electrode rod 6 that can move in three-dimensional directions is arranged at the top of the inner cavity of the electric arc furnace body 2. Specifically, in this embodiment, the welding device further includes an electrode rod control system (not shown in the figure). There is a centering system and an X-Y fine adjustment device in the electrode rod control system, which can arbitrarily adjust the position of the electrode rod 6. Specifically, the electrode rod 6 and its electrode rod control system are the same as the corresponding mechanisms in the existing vacuum consumable arc furnace, which are conventional settings well-known to those skilled in the art and will not be elaborated here.

[0033] In this embodiment, asFigure 1 As shown, a first pair of welding auxiliary electrodes 4 are arranged in the inner cavity of the crucible body 11 of the bottom crucible 1. Specifically, the inner cavity size of the crucible body 11 is adapted to the size of the first pair of welding auxiliary electrodes 4. The first pair of welding auxiliary motors are coaxially installed in the inner cavity of the crucible body 11 and maintain their positions.

[0034] At the lower end of the electrode rod 6, a second pair of welding auxiliary electrodes 5 are assembled and connected through a pneumatic chuck (not shown in the figure) of the electrode rod 6. The electrode rod control system can drive the second pair of welding auxiliary electrodes 5 at the lower end of the electrode rod 6 to move and be coaxially centered with the first pair of welding auxiliary electrodes 4, and the distance between the first pair of welding auxiliary electrodes 4 and the second pair of welding auxiliary electrodes 5 can be adjusted to complete operations such as arc starting and butt welding.

[0035] In this embodiment, as Figure 1 shown, an expansion sleeve 7 is provided at the upper end of the connecting flange 12 of the bottom crucible 1, and the inner hole of the expansion sleeve 7 is coaxially arranged with the inner cavity of the bottom crucible 1. Specifically, the inner hole of the expansion sleeve 7 is divided into a large-diameter section 71 and a small-diameter section 72 from top to bottom, and the size of the small-diameter section 72 is adapted to the inner diameter of the first pair of welding auxiliary electrodes 4. When the first pair of welding auxiliary electrodes 4 are assembled into the inner cavity of the bottom crucible 1, the upper end of the first pair of welding auxiliary electrodes 4 extends into the large-diameter section 71.

[0036] By providing the expansion sleeve 7, the inner hole of the expansion sleeve 7 is divided into a large-diameter section 71 and a small-diameter section 72 from top to bottom. The size of the small-diameter section 72 is adapted to the inner diameter of the first pair of welding auxiliary electrodes 4, and the upper end of the first pair of welding auxiliary electrodes 4 also extends into the large-diameter section 71. In this way, the upper part of the first pair of welding auxiliary electrodes 4 can be wrapped by the small-diameter section 72, and a reserved space 73 is formed between the large-diameter section 71 and the upper end of the first pair of welding auxiliary electrodes 4.

[0037] During actual butt welding, the electrode rod 6 is used to drive the second pair of welding auxiliary electrodes 5 to move to a position coaxial with the first pair of welding auxiliary electrodes 4, and the inside of the arc furnace body 2 is evacuated. One of the first pair of welding auxiliary electrodes 4 and the second pair of welding auxiliary electrodes 5 is connected to the positive pole of the power supply, and the other is connected to the negative pole of the power supply.

[0038] The distance between the second pair of welding auxiliary electrodes 5 and the first pair of welding auxiliary electrodes 4 is adjusted by using the electrode rod 6 to quickly start an arc, and the opposite ends of the two welding auxiliary electrodes to be butt-welded are melted. By using the reserved space 73 between the upper end of the first pair of welding auxiliary electrodes 4 and the large-diameter section 71 of the expansion sleeve 7, the molten droplets formed by melting will fall and gather in the reserved space 73. Then, the molten pool is constrained by the expansion sleeve 7, so that the molten pool surrounds and wraps the outer circumference of the first pair of welding auxiliary electrodes 4. When the molten pool in the expansion sleeve 7 covers the upper end face of the first pair of welding auxiliary electrodes 4, the welding timing is reached, and the electrode rod 6 is lowered to complete the butt welding of the two pairs of welding auxiliary electrodes.

[0039] In this way, by expanding the restraint of the expansion sleeve 7, the molten pool can wrap the outer periphery and the upper end surface of the first pair of welding auxiliary electrodes 4, so that the molten droplets are retained on the bonding surface, ensuring 100% full welding, and avoiding the formation of welding beads, and avoiding the problems of large and difficult-to-clean welding beads and poor welding quality stability. At the same time, with the expansion sleeve 7, only an arc 8 needs to be established to melt the metal. By observing that the molten pool covers the upper end surface of the first pair of welding auxiliary electrodes 4, welding can be carried out, greatly reducing the operation difficulty and meeting general operations.

[0040] Preferably, in this embodiment, the large-diameter section 71 is a flared structure with an inner diameter gradually decreasing from top to bottom. Specifically, the large-diameter section 71 is a frustum structure with a larger top and a smaller bottom, and the generatrix of the frustum structure forms an angle of 45° with its axis. Such a setting can avoid a large temperature difference between the lower part and the upper part of the molten pool during welding start-up, ensure that the molten droplets in the molten pool are always in a molten state, and improve the subsequent welding quality. Of course, in other embodiments, when meeting the actual use requirements, the generatrix of the large-diameter section 71 can be not a straight line but an outwardly expanding arc-shaped line, and the large-diameter section 71 as a whole is in a bowl-shaped structure. In other embodiments, when meeting the actual use requirements, the large-diameter section 71 can also be designed with an equal diameter from top to bottom.

[0041] Preferably, the material of the expansion sleeve 7 is copper. Specifically, in this embodiment, T2 copper is used. The characteristics of copper are that it can withstand high temperatures, has good heat conduction performance, and heats and cools quickly. In this way, during welding, using the good stability of copper can avoid the reaction between the expansion sleeve 7 and the metal solution, resulting in the adhesion of metal droplets to the expansion sleeve 7 or the deformation of the expansion sleeve 7.

[0042] Preferably, in this embodiment, there is a clearance fit between the first pair of welding auxiliary electrodes 4 and the small-diameter section 72 of the expansion sleeve 7, and the clearance size is 0.5 mm. Of course, in other embodiments, the clearance between the first pair of welding auxiliary electrodes 4 and the small-diameter section 72 of the expansion sleeve 7 can also be 0.4 mm, 0.6 mm, etc. On the one hand, this facilitates the assembly of the first pair of welding auxiliary electrodes 4 and uses the small-diameter section 72 for guiding and limiting. On the other hand, it can avoid the leakage of the molten pool melt due to too large a clearance and ensure the butt welding quality.

[0043] In this embodiment, preferably, the flatness of the lower surface of the expansion sleeve 7 is in the range of 0 mm to 0.1 mm, and the surface roughness Ra ≤ 3.2 μm. This can ensure good contact between the lower surface of the expansion sleeve 7 and the upper end surface of the connecting flange 12, facilitating heat conduction.

[0044] In this embodiment, the specific structure of the expansion sleeve 7 is as Figure 2 、 3 shown. The axial length of the small-diameter section 72 is less than the axial length of the large-diameter section 71, ensuring sufficient reserved space 73 and reducing the distance between the molten pool and the bottom crucible 1, facilitating heat transfer.

[0045] Specifically, in this embodiment, the auxiliary electrode for butt welding is a small-sized auxiliary electrode, and its diameter ranges from 100 mm to 280 mm. In this embodiment, the outer diameter of the expansion sleeve 7 is 310 mm, the inner diameter of the upper end face of the expansion sleeve 7 is 300 mm, the height of the expansion sleeve 7 is 100 mm, and the axial length of the small-diameter section 72 of the expansion sleeve 7 is 10 mm, so as to obtain the specific structural parameters of the expansion sleeve 7 in this embodiment. Of course, in other embodiments, the size design of the expansion sleeve 7 can be specifically adjusted according to actual needs, and no limitation is made here.

[0046] In this embodiment, two symmetrical observation ports (not shown in the figure) are opened at the upper end of the electric arc furnace body 2, and cameras are installed on the observation ports, so that the melting condition of the materials in the furnace can be observed at any time.

[0047] The usage steps of this application are as follows:

[0048] (1) Install the first auxiliary electrode for butt welding 4 into the inner cavity of the bottom crucible 1.

[0049] (2) Adjust the height so that the upper end of the first auxiliary electrode for butt welding 4 protrudes 30 mm ± 5 mm above the upper end face of the bottom crucible 1; ensure that the upper end of the subsequent first auxiliary electrode for butt welding 4 extends into the large-diameter section 71 of the expansion sleeve 7.

[0050] (3) Assemble the expansion sleeve 7 on the first auxiliary electrode for butt welding 4, and adjust the position so that the expansion sleeve 7 is horizontally fitted and coaxially arranged with the end face of the connecting flange 12, and a reserved space 73 is formed between the large-diameter section 71 of the expansion sleeve 7 and the first auxiliary electrode for butt welding.

[0051] (4) Assemble the second auxiliary electrode for butt welding 5 on the pneumatic chuck of the electrode rod 6.

[0052] (5) Adjust the electrode rod 6 to make the second auxiliary electrode for butt welding 5 and the first auxiliary electrode for butt welding 4 coaxial, and then seal the electric arc furnace body 2.

[0053] (6) Through the vacuum pumping port 3, evacuate the inside of the electric arc furnace body 2 according to the gas flow route S, the pre-vacuum is less than 5 Pa, perform leak detection, ensure that the leak rate is less than 1 Pa / min, the first auxiliary electrode for butt welding 4 and the second auxiliary electrode for butt welding 5 are respectively connected to the positive and negative poles of the power supply, set the welding parameters to start the arc, and use the arc 8 between the two to melt the metal for welding. The current range is controlled at 2.5 KA to 5.0 KA, and the voltage range is 24.0 V to 26.5 V.

[0054] (7) The melted metal falls and accumulates in the large-diameter section 71 of the expansion sleeve 7, and since the inner cavity of the large-diameter section 71 is a frustum structure, the shape of the molten pool formed by the molten droplets is also a frustum structure that is large at the top and small at the bottom and hollow, surrounding the outer periphery of the first auxiliary electrode for butt welding 4, and the expansion sleeve 7 is used to confine the molten pool.

[0055] (8) When the molten pool in the expansion sleeve 7 is filled with the cross-section of the first butt-welding auxiliary electrode 4, the electrode rod 6 is pressed down to the bottom to complete the welding, and then it is cooled and taken out of the furnace.

[0056] In this way, the butt-welding operation is completed. The overall operation is simple. It only needs to observe whether the molten pool covers the cross-section of the first butt-welding auxiliary electrode 4 to judge whether the butt-welding timing is reached. The operation difficulty is low, and it is suitable for general operation by personnel. Moreover, the molten pool is restricted by the expansion sleeve 7 to avoid the formation of welding beads, ensuring the welding quality.

[0057] The above is only a preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

[0058] In the description of the embodiments of the present application, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is usually placed during use. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to the present application. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0059] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and it does not mean that the structure must be completely horizontal, but it can be slightly inclined.

Claims

1. A butt welding device for small auxiliary electrodes for vacuum consumable melting, characterized in that: It includes a bottom crucible with an upward opening, an upper sealing cover of the bottom crucible is provided with an arc furnace body, a circumferential surface of the arc furnace body is provided with a vacuum port, an inner cavity top of the arc furnace body is provided with an electrode rod movable in three dimensions, the inner cavity of the bottom crucible is provided with a first pair of welding auxiliary electrodes, the lower end of the electrode rod is connected to a second pair of welding auxiliary electrodes, the upper end of the bottom crucible is provided with an expansion sleeve coaxial with the inner cavity, the inner hole of the expansion sleeve is divided into a large diameter section and a small diameter section from top to bottom, the size of the small diameter section is adapted to the inner diameter of the first pair of welding auxiliary electrodes, and the upper end of the first pair of welding auxiliary electrodes extends into the large diameter section.

2. The butt welding device of small-sized auxiliary electrode for vacuum consumable melting according to claim 1 is characterized in that: The large diameter section is a flared structure with an inner diameter gradually decreasing from top to bottom.

3. The butt welding device of small-sized auxiliary electrode for vacuum consumable melting according to claim 2 is characterized in that: The large diameter section is a frustum structure that is larger at the top and smaller at the bottom, and the angle between the generatrix of the frustum structure and its axis is 45°.

4. The butt welding device of small-sized auxiliary electrode for vacuum consumable melting according to claim 1 is characterized in that: The expansion sleeve is made of copper.

5. The butt welding device of small-sized auxiliary electrode for vacuum consumable melting according to claim 4 is characterized in that: The expansion sleeve is made of T2 copper.

6. The butt welding device of small-sized auxiliary electrode for vacuum consumable melting according to claim 1 is characterized in that: The first pair of welding auxiliary electrodes and the small diameter section of the expansion sleeve have a clearance fit, and the clearance size is 0.4 mm to 0.6 mm.

7. The butt welding device of small-sized auxiliary electrode for vacuum consumable melting according to claim 1 is characterized in that: The flatness of the lower surface of the expansion sleeve is in the range of 0 mm to 0.1 mm, and the surface roughness Ra is ≤ 3.2 μm.

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