welding torch

Abstract

To provide a welding torch suitable for reduction in size and simplification in structure.SOLUTION: A welding torch A1 includes: an electrode 25 extending in an axial direction z; a first member 26 disposed outside the electrode 25; a nozzle 30 disposed outside the electrode 25; a locking member 33 fitted from outside across the first member 26 and the nozzle 30 to be locked on both of the first member 26 and the nozzle 30; and a centering member 34 disposed outside the electrode 25 and also inside the nozzle 30. The centering member 34 is fitted from outside to the electrode 25 in a concentric circular state, and the nozzle 30 is fitted from outside to the centering member 34 in a concentric circular state. The centering member 34 is inhibited from moving to the side z2 by contact between the end part on a z2 side and the end part on a z1 side of the first member 26, and inhibited from moving to the z1 side by contact between a centering member swollen part 342 and a nozzle primary part 301. The nozzle 30 is inhibited from moving to the z1 side by contact between a nozzle swollen part 302 and an intermediate step part 333.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a welding torch.

Background Art

[0002] In welding performed using a welding torch having a non-consumable electrode (TIG welding method or plasma welding method), usually, an arc is generated between an electrode (non-consumable electrode) formed of tungsten and a workpiece, and the workpiece is melted by the heat of the arc. In the TIG welding method, a shielding gas is flowed between a gas nozzle and the electrode. In the plasma welding method, in addition to the shielding gas, a plasma gas is flowed inside an insert tip disposed around the electrode, whereby the arc (plasma arc) is confined. As a result, a highly concentrated high-temperature plasma flow is generated, and welding is performed using the energy possessed by the plasma flow.

[0003] When welding a metal having a relatively low melting point (low melting metal) such as a galvanized steel sheet, zinc vapor and fumes are generated by the welding heat. When a metal such as fumes adheres to the electrode, the arc generated during welding becomes unstable. In the TIG welding method, usually, the tip of the electrode protrudes from the tip of the nozzle, and if the tip of the electrode is covered with a metal such as fumes, there is a risk of poor ignition at the start of welding. In the plasma welding method, usually, the tip of the electrode retreats from the tip of the insert tip surrounding the electrode. Further, a plasma gas is flowed inside the insert tip (around the electrode). Therefore, when welding a low melting metal such as a galvanized steel sheet, in the plasma welding method, a metal such as fumes is less likely to adhere to the electrode than in the TIG welding method. On the other hand, in the plasma welding method, a metal such as the above fumes may adhere to the tip of the insert tip, and when this happens, alloying occurs with the tip of the insert tip. Alloying of the tip of the insert tip may cause arc defects and welding defects.

[0004] Patent Document 1 discloses a configuration in which multiple side plasma gas ejection holes, consisting of small-diameter holes, are provided around the plasma gas ejection hole at the tip of the insert tip. By providing these additional side plasma gas ejection holes, the adhesion of fumes and other substances to the tip of the insert tip during welding is reduced. However, the structure described in Patent Document 1 results in a complex insert tip structure and leads to an enlargement of the tip of the insert tip (welding torch). Furthermore, if the axis of the insert tip, which is positioned with a gap around the electrode, is misaligned with the electrode's axis, the plasma gas ejected from the tip of the insert tip may become unevenly flowed, potentially leading to a decrease in welding quality. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-172644 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] This invention was conceived under these circumstances, and its main objective is to provide a welding torch suitable for simplifying its structure and miniaturizing it. [Means for solving the problem]

[0007] To solve the above problems, the present invention employs the following technical means.

[0008] The welding torch provided by the present invention comprises: a non-consumable electrode extending in the axial direction; a cylindrical first member disposed radially outside the non-consumable electrode; a cylindrical first nozzle disposed radially outside the non-consumable electrode and on one side in the axial direction relative to the first member; a cylindrical locking member fitted over a first portion on one side in the axial direction of the first member and a second portion on the other side in the axial direction of the first nozzle, and engaging with both the first member and the first nozzle; and a cylindrical electrode centering member disposed radially outside the non-consumable electrode and radially inside the second portion, wherein the electrode centering member is fitted concentrically with respect to the non-consumable electrode, and the electrode centering member includes a cylindrical centering member main portion and a centering member bulge portion that bulges radially outward from the centering member main portion, the second portion being the centering portion The second part is concentrically fitted to a portion located on one side in the axial direction of the material bulge, and the second part includes a cylindrical nozzle main part and a nozzle bulge that bulges radially outward from the other side in the axial direction of the nozzle main part, and the locking member includes a large-diameter cylindrical part fitted to the nozzle bulge, a small-diameter cylindrical part having a smaller inner diameter than the large-diameter cylindrical part and fitted to the nozzle main part, and an intermediate stepped part connected to both the large-diameter cylindrical part and the small-diameter cylindrical part, and the electrode centering member is prevented from moving to the other side in the axial direction by the other end in the axial direction abutting against the first part, the electrode centering member is prevented from moving to one side in the axial direction by the centering member bulge and the second part abutting against each other, and the first nozzle is prevented from moving to one side in the axial direction by the nozzle bulge and the intermediate stepped part abutting against each other.

[0009] In a preferred embodiment, the centering member bulge has a first contact surface located on one side in the axial direction, the second part has a second contact surface that contacts the first contact surface, and each of the first and second contact surfaces is inclined such that its radial dimension decreases as it moves toward one side in the axial direction.

[0010] In a preferred embodiment, the first part has a third contact surface located on one side in the axial direction, and the centering member bulge has a fourth contact surface located on the other side in the axial direction and in contact with the third contact surface, and each of the third and fourth contact surfaces is inclined such that its radial dimension increases toward one side in the axial direction.

[0011] In a preferred embodiment, the nozzle bulge portion has a fifth contact surface located on one side in the axial direction, the intermediate step portion has a sixth contact surface that contacts the fifth contact surface, and each of the fifth and sixth contact surfaces is inclined such that its radial dimension decreases as it moves toward one side in the axial direction.

[0012] In a preferred embodiment, the large-diameter cylindrical portion of the locking member and the first portion of the first member are connected by a screw.

[0013] In a preferred embodiment, the first nozzle is made of an insulating material.

[0014] In a preferred embodiment, the system further includes a cylindrical second nozzle positioned radially outward from the first nozzle and the locking member. [Effects of the Invention]

[0015] In the welding torch according to the present invention, the first nozzle is arranged concentrically with respect to the non-consumable electrode via an electrode centering member. The locking member is fitted over a first portion on one axial side of the first member and a second portion on the other axial side of the first nozzle, and locks into both the first member and the first nozzle. With this configuration, some radial flexibility can be provided between the locking member and the first member or the first nozzle. Therefore, even if the non-consumable electrode is slightly bent due to manufacturing errors, for example, the first nozzle can be arranged concentrically with respect to the non-consumable electrode. If the first nozzle is misaligned, it is likely to cause uneven flow of gas between the non-consumable electrode and the first nozzle, but as described above, the structure equipped with the electrode centering member and the locking member ensures that the first nozzle is arranged concentrically with respect to the non-consumable electrode. This is suitable for improving welding quality.

[0016] Other features and advantages of the present invention will become more apparent from the detailed description below with reference to the accompanying drawings. [Brief explanation of the drawing]

[0017] [Figure 1] This is a front view showing an example of a welding torch according to the present invention. [Figure 2] Figure 1 is a plan view of the welding torch. [Figure 3] This is a cross-sectional view along line III-III in Figure 2. [Figure 4] This is a cross-sectional view along the line IV-IV in Figure 3. [Figure 5] This is an enlarged cross-sectional view along the VV line in Figure 3. [Figure 6] This is an enlarged cross-sectional view along the line VI-VI in Figure 3. [Figure 7] This is an enlarged cross-sectional view along the line VII-VII in Figure 3. [Figure 8] This is a magnified view of a portion of Figure 3. [Figure 9] This is a magnified view of a portion of Figure 3. [Figure 10]A cross-sectional view similar to FIG. 8 showing a modified example of the welding torch according to the present invention. [Figure 11] A cross-sectional view similar to FIG. 8 showing another modified example of the welding torch according to the present invention.

Embodiments for Carrying out the Invention

[0018] Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings. The terms "first", "second", etc. in the following description are merely used as labels and are not necessarily intended to assign an order to their objects.

[0019] FIGS. 1 to 9 show an example of the welding torch according to the present invention. The welding torch A1 of this embodiment includes a handle 1, a torch body 2, insulating rings 23, 24, a non-consumable electrode 25, a collet body 26, a collet 27, a collet pressing member 28, a cap 29, an inner nozzle 30, an outer nozzle 31, a nozzle holder 32, a locking member 33, an electrode centering member 34, a first gas pipe 41, a second gas pipe 42, a first cooling water pipe 43, and a second cooling water pipe 44. The welding torch A1 of this embodiment is configured to be held by an operator's hand to perform welding work. Also, although details will be described later, in the welding torch A1, two gas flow paths (a first gas flow path G1 and a second gas flow path G2) for flowing a predetermined welding gas are formed.

[0020] In the description of the welding torch A1, the vertical direction in the drawings in FIGS. 1 and 3 is an example of the "axial direction" of the present invention and is referred to as the "axial direction z". The direction orthogonal to the axial direction z in FIGS. 3 and 9 (the left-right direction in the drawings) is referred to as the "first direction x". Also, the lower side in the drawings in FIGS. 1 and 3 is an example of the "one side of the axial direction" of the present invention and is referred to as the "one side of the axial direction z1", and the upper side in the drawings is an example of the "other side of the axial direction" of the present invention and is referred to as the "other side of the axial direction z2".

[0021] The handle 1 is a part for an operator to hold by hand. As shown in FIG. 3, the handle 1 is a cylindrical member made of an insulating material.

[0022] The torch body 2 is cylindrical, with its end held by the handle 1. The torch body 2 includes a body body 20, a cylindrical member 21, and a cylindrical member 22. The body body 20 appropriately houses the components of the welding torch A1 inside. The body body 20 is made of an insulating material. The body body 20 has a first cylindrical portion 20A and a second cylindrical portion 20B.

[0023] The first cylindrical portion 20A extends along the axial direction z. The second cylindrical portion 20B is branched off from the first cylindrical portion 20A. The second cylindrical portion 20B extends in a direction intersecting the axial direction z (upper right direction in Figure 3). In the illustrated example, the angle between the direction in which the first cylindrical portion 20A extends (axial direction z) and the direction in which the second cylindrical portion 20B extends is approximately 65°. Note that the angle between the direction in which the first cylindrical portion 20A extends (axial direction z) and the direction in which the second cylindrical portion 20B extends is not particularly limited and may be, for example, a right angle (90°). The end of the second cylindrical portion 20B (upper right end in Figure 3) is held by the end of the handle 1. In the illustrated example, the end of the second cylindrical portion 20B and the end of the handle 1 are fixed to each other by a screw connection.

[0024] The cylindrical member 21 is positioned radially inward of the first cylindrical portion 20A. The cylindrical member 21 is a component that receives power from a power supply unit (not shown) and is made of a conductive material. Copper is an example of the conductive material that constitutes the cylindrical member 21. As shown in Figure 9, the cylindrical member 21 has a first gas inlet 211, a second gas inlet 212, a groove 213, a tapered surface 214, and a female threaded portion 215. The cylindrical member 22 is positioned radially outward of the cylindrical member 21. Details of the cylindrical members 21 and 22 will be described later.

[0025] The insulating rings 23 and 24 are cylindrical members made of insulating material. The insulating ring 23 is positioned adjacent to the first cylindrical portion 20A on the other side z2 in the axial direction. The insulating ring 24 is positioned adjacent to the second cylindrical portion 20B on one side z1 in the axial direction.

[0026] The non-consumable electrode 25 is a rod-shaped conductor extending along the axial direction z (the direction in which the axis CL extends). The non-consumable electrode 25 is made of, for example, tungsten. The non-consumable electrode 25 is connected to a power supply unit (not shown) via, for example, a conduit cable (not shown), and generates an arc between the electrode and the workpiece when an arc voltage is applied between the electrode and the workpiece.

[0027] The non-consumable electrode 25 has an electrode main portion 251 and an electrode tapered portion 252. The electrode main portion 251 is a part with a constant outer diameter and occupies most of the non-consumable electrode 25 excluding the tip. The electrode main portion 251 is a part that is formed in a substantially cylindrical shape so that the outer diameter is constant in the design, and may contain some manufacturing errors. The outer diameter of the electrode main portion 251 is not particularly limited, and in this embodiment, for example, it is about 1.6 to 4.0 mm. The electrode tapered portion 252 is connected to the electrode main portion 251 on the tip side (one side z1 in the axial direction) of the non-consumable electrode 25. The electrode tapered portion 252 has a diameter that decreases towards the tip side (one side z1 in the axial direction) of the non-consumable electrode 25 and is substantially conical in shape.

[0028] The collet body 26, collet 27, and collet retaining member 28 cooperate with each other to hold the non-consumable electrode 25. The collet body 26, collet 27, and collet retaining member 28 are made of a conductive material. Copper is an example of the conductive material that makes up the collet body 26, collet 27, and collet retaining member 28.

[0029] The collet 27 surrounds the non-consumable electrode 25. The collet body 26 is positioned radially outward of the collet 27. The collet body 26 is also positioned radially inward of the cylindrical member 21. Although detailed illustrations are omitted, the collet body 26 is fixed to the cylindrical member 21, for example, by a screw connection.

[0030] The collet retaining member 28 is positioned on the other axial side z2 relative to the collet 27. Although detailed illustrations are omitted, the collet retaining member 28 has a threaded portion that is screwed into the cylindrical member 21. As shown in Figure 8, a female threaded portion 215 is formed at the upper end of the cylindrical member 21 (the end on the other axial side z2), and the threaded portion of the collet retaining member 28 is screwed into the female threaded portion 215. A cap 29 is provided on the other axial side z2 of the collet retaining member 28. By rotating this cap 29, the position of the collet retaining member 28 in the axial direction z relative to the collet body 26 can be adjusted. The end of the collet retaining member 28 on one axial side z1 abuts against the end of the collet 27 on the other axial side z2. When the collet retaining member 28 is moved to one axial side z1, the collet 27 is pressed against one axial side z1.

[0031] The collet 27 has multiple slits extending in the axial direction z at its tip end (one side z1 in the axial direction), and has multiple movable pieces 271 positioned between adjacent slits. As described above, when the collet retaining member 28 is moved to one side z1 in the axial direction, the collet 27 is pressed against that side z1. Then, the multiple movable pieces 271 at the tip of the collet 27 are pressed against the tip of the collet body 26, reducing its diameter, and the collet 27 holds the non-consumable electrode 25 between them. In this way, the non-consumable electrode 25 is held by the cooperation of the collet body 26, the collet 27, and the collet retaining member 28.

[0032] As shown in Figure 3, the inner nozzle 30 is positioned around the tip of the non-consumable electrode 25 (the end on one side z1 in the axial direction). The inner nozzle 30 is positioned on one side z1 in the axial direction relative to the collet body 26. The inner nozzle 30 is generally cylindrical and is positioned radially outward of the non-consumable electrode 25 (electrode main portion 251). In this embodiment, an electrode centering member 34 is interposed between the inner nozzle 30 and the non-consumable electrode 25.

[0033] As shown in Figure 8, the inner nozzle 30 includes a nozzle main portion 301, a nozzle bulge portion 302, and a tip-side cylindrical portion 303. The nozzle main portion 301 is located closer to the other axial side z2 and is substantially cylindrical. The nozzle bulge portion 302 bulges radially outward from the other axial side z2 of the nozzle main portion 301. The tip-side cylindrical portion 303 connects to and extends toward one axial side z1 of the nozzle main portion 301. The nozzle main portion 301 has a second contact surface 301a. The second contact surface 301a is a tapered surface that slopes so that its radial dimension decreases toward one axial side z1. The nozzle bulge portion 302 has a fifth contact surface 302a. The nozzle bulge portion 302 is a tapered surface that slopes so that its radial dimension decreases toward one axial side z1. The inner nozzle 30 in the above configuration is made of an insulating material. The constituent material of the inner nozzle 30 is not particularly limited and includes, for example, ceramic materials such as alumina and resin materials such as heat-resistant phenol. The inner nozzle 30 corresponds to an example of the "first nozzle" of the present invention.

[0034] As shown in Figure 8, the locking member 33 is fitted over both the collet body 26 and the inner nozzle 30. More specifically, the locking member 33 is fitted over one axial end z1 (first part) of the collet body 26 and the other axial end z2 (second part) of the inner nozzle 30.

[0035] The locking member 33 includes a large-diameter cylindrical portion 331, a small-diameter cylindrical portion 332, and an intermediate stepped portion 333. The large-diameter cylindrical portion 331 is located on the other side z2 in the axial direction and is fitted onto the nozzle bulge portion 302. The small-diameter cylindrical portion 332 has a smaller inner diameter than the large-diameter cylindrical portion 331. The small-diameter cylindrical portion 332 is located on one side z1 in the axial direction and is fitted onto the nozzle main portion 301. The intermediate stepped portion 333 is located in the center of the locking member 33 in the axial direction z and connects to both the large-diameter cylindrical portion 331 and the small-diameter cylindrical portion 332. The large-diameter cylindrical portion 331 has a female threaded portion 331a. The female threaded portion 331a is formed on the inner circumference of the large-diameter cylindrical portion 331. The intermediate stepped portion 333 has a sixth contact surface 333a. The sixth contact surface 333a is formed on the inner circumference of the intermediate step portion 333. The sixth contact surface 333a is a tapered surface that slopes such that its radial dimension decreases as it moves toward one side z1 in the axial direction. The sixth contact surface 333a is in contact with the fifth contact surface 302a of the nozzle bulge portion 302. In the illustrated example, the locking member 33 has a cap nut structure.

[0036] In this embodiment, as shown in Figures 3 and 8, the locking member 33 (large diameter cylindrical portion 331) and the end portion (first portion) of the collet body 26 on one axial side z1 are connected by a screw. For example, a male threaded portion 261a is formed on the outer circumference of the end portion of the collet body 26 on one axial side z1, and a female threaded portion 331a formed on the locking member 33 (large diameter cylindrical portion 331) is screwed into the male threaded portion 261a of the collet body 26. On the other hand, as shown in Figure 8, the small diameter cylindrical portion 332 on one axial side z1 of the locking member 33 is fitted onto the main nozzle portion 301, and the nozzle bulge portion 302 (fifth contact surface 302a) and the intermediate step portion 333 (sixth contact surface 333a) on the other axial side z2 of the inner nozzle 30 are in contact. As a result, the relative movement of the inner nozzle 30 and the locking member 33 in the axial direction z is restricted, and the movement of the inner nozzle 30 in one direction z1 in the axial direction is prevented. The collet body 26 with the above configuration corresponds to an example of the "first member" of the present invention.

[0037] As shown in Figure 8, the electrode centering member 34 is cylindrical and is positioned radially outside the non-consumable electrode 25 and radially inside the inner nozzle 30. The electrode centering member 34 includes a centering member main portion 341 and a centering member bulge portion 342. The centering member main portion 341 is generally cylindrical. A recess 301b is formed on the inner circumference of the nozzle main portion 301 in the inner nozzle 30, and the centering member main portion 341 is fitted into this recess 301b. The centering member bulge portion 342 bulges radially outward from the centering member main portion 341. In the illustrated example, the centering member bulge portion 342 bulges radially outward from the other axial side z2 of the centering member main portion 341.

[0038] The centering member bulge 342 has a first contact surface 342a and a fourth contact surface 342b. The first contact surface 342a and the fourth contact surface 342b are formed on the outer circumference of the centering member bulge 342. The first contact surface 342a is located on one side z1 in the axial direction and is a tapered surface that slopes so that its radial dimension decreases as it approaches one side z1 in the axial direction. The first contact surface 342a is in contact with the second contact surface 301a of the nozzle main part 301. The fourth contact surface 342b is located on the other side z2 in the axial direction and is a tapered surface that slopes so that its radial dimension increases as it approaches one side z1 in the axial direction. A third contact surface 262a is formed on the end (first part) of the collet body 26 on one side z1 in the axial direction. The third contact surface 262a is a tapered surface that is inclined such that its radial dimension increases as it approaches one side z1 in the axial direction, and it connects to the edge of the collet body 26 on one side z1 in the axial direction. The fourth contact surface 342b is in contact with this third contact surface 262a.

[0039] The inner diameter of the electrode centering member 34 (centering member main portion 341) is slightly larger than the outer diameter of the non-consumable electrode 25 (electrode main portion 251). As a result, the electrode centering member 34 is concentrically fitted onto the non-consumable electrode 25. Also, the inner diameter of the nozzle main portion 301 (recess 301b) of the inner nozzle 30 is slightly larger than the outer diameter of the centering member main portion 341. As a result, the inner nozzle 30 is concentrically fitted onto the electrode centering member 34 (centering member main portion 341). Therefore, the inner nozzle 30 is arranged concentrically with respect to the non-consumable electrode 25 via the electrode centering member 34.

[0040] In the illustrated mounting structure of the inner nozzle 30, locking member 33, and electrode centering member 34, the centering member bulge portion 342 (first contact surface 342a) of the electrode centering member 34 and the nozzle main portion 301 (second portion, second contact surface 301a) of the inner nozzle 30 are in contact. As a result, relative movement of the electrode centering member 34 and the inner nozzle 30 in the axial direction z is restricted, and movement of the electrode centering member 34 to one side z1 in the axial direction is prevented. In addition, the centering member bulge portion 342 (fourth contact surface 342b) of the electrode centering member 34 and the end portion (first portion, third contact surface 262a) on one side z1 in the axial direction of the collet body 26 are in contact. As a result, relative movement of the electrode centering member 34 and the collet body 26 in the axial direction z is restricted, and movement of the electrode centering member 34 to the other side z2 in the axial direction is prevented.

[0041] As shown in Figure 7, a plurality of grooves 341a are formed on the inner circumference of the electrode centering member 34 (main part of the centering member 341). These grooves 341a are provided at regular intervals in the circumferential direction of the electrode centering member 34. A gap is formed between the non-consumable electrode 25 and the portion where the grooves 341a are formed, and this gap constitutes the first gas flow path G1, which will be described later.

[0042] As shown in Figure 8, in this embodiment, the tip of the non-consumable electrode 25 coincides with the tip of the inner nozzle 30 in the axial direction z, or slightly protrudes from the tip of the inner nozzle 30 to one side z1 in the axial direction. The protrusion length P1 of the tip of the non-consumable electrode 25 protruding from the tip of the inner nozzle 30 to one side z1 in the axial direction is, for example, in the range of 0 to 2 mm.

[0043] The nozzle holder 32 is cylindrical in shape. The nozzle holder 32 is integrally connected to the outer circumference of the intermediate portion in the axial direction z of the collet body 26 by means of, for example, brazing.

[0044] As shown in Figures 3 and 8, the outer nozzle 31 is positioned radially outward of the inner nozzle 30. The outer nozzle 31 is positioned on one axial side z1 relative to the first cylindrical portion 20A, and an insulating ring 24 is interposed between the outer nozzle 31 and the first cylindrical portion 20A. In the illustrated example, the outer nozzle 31 is generally cylindrical, with the tip side (one axial side z1) having a smaller diameter compared to other parts. In this embodiment, the outer nozzle 31 is positioned concentrically with respect to the non-consumable electrode 25 and the inner nozzle 30. The outer nozzle 31 is attached, for example, to the outer circumference of the nozzle holder 32 by screw connection. Note that the outer nozzle 31 corresponds to an example of the "second nozzle" of the present invention.

[0045] As shown in Figure 8, in this embodiment, the tip of the inner nozzle 30 protrudes from the tip of the outer nozzle 31 in one axial direction z1. The protrusion length P2 of the tip of the inner nozzle 30 protruding from the tip of the outer nozzle 31 in one axial direction z1 is, for example, in the range of 0 to 5 mm.

[0046] As shown in Figures 3 to 9, in this embodiment, the welding torch A1 is formed with a first gas channel G1, a second gas channel G2, and a cooling water channel W.

[0047] In this embodiment, the welding gas supplied to the welding torch A1 includes two types of inert gases with different gas supply characteristics, such as gas type and flow rate. For the sake of explanation, these two types of inert gases will be appropriately referred to as "first inert gas" and "second inert gas."

[0048] The first gas flow path G1 is a flow path for the first inert gas. In Figures 3 and 8, the flow of the first inert gas is indicated by the dashed arrow. The first gas flow path G1 is formed between the collet 27 and the collet body 26, between the non-consumable electrode 25 (electrode main part 251) and the collet 27, between the non-consumable electrode 25 (electrode main part 251) and the collet body 26, between the non-consumable electrode 25 (electrode main part 251) and the electrode centering member 34 (centering member main part 341), and between the non-consumable electrode 25 (electrode main part 251) and the inner nozzle 30 (tip side cylindrical part 303).

[0049] In this embodiment, as shown in Figures 3 and 9, the torch body 2 (cylindrical member 21) is provided with a first gas inlet 211 for introducing a first inert gas. The first gas inlet 211 is connected to a first gas flow path G1. When the first inert gas is introduced from the first gas inlet 211, the first inert gas flows in the first gas flow path G1 from the other axial side z2 to the one axial side z1, passes between the non-consumable electrode 25 (electrode main part 251) and the inner nozzle 30, and is ejected from the opening 305 at the tip of the inner nozzle 30.

[0050] The second gas flow path G2 is a flow path for the second inert gas. In Figures 3 and 8, the flow of the second inert gas is indicated by dotted arrows. The second gas flow path G2 is formed between the collet body 26 and the cylindrical member 21, between the collet body 26 and the insulating ring 24, between the nozzle holder 32, the locking member 33 and the outer nozzle 31, and between the inner nozzle 30 and the outer nozzle 31, respectively.

[0051] In this embodiment, as shown in Figures 3 and 9, the torch body 2 (cylindrical member 21) is provided with a second gas inlet 212 for introducing a second inert gas. The second gas inlet 212 is connected to a second gas flow path G2. When the second inert gas is introduced from the second gas inlet 212, the second inert gas flows in the second gas flow path G2 from the other side z2 in the axial direction to the one side z1 in the axial direction, passes between the inner nozzle 30 and the outer nozzle 31, and is ejected from the opening 315 at the tip of the outer nozzle 31.

[0052] The cooling water channel W is a channel for the flow of cooling water. As shown in Figure 4, the cooling water channel W is formed along the circumferential direction of the non-consumable electrode 25. The cooling water channel W is mainly formed between the cylindrical member 21 and the cylindrical member 22.

[0053] Referring to Figure 9, the first gas inlet 211, second gas inlet 212, groove 213, tapered surface 214, and female thread portion 215 of the cylindrical member 21 will be described. As shown in Figure 9, the first gas inlet 211 is located on the other side z2 in the axial direction relative to the second gas inlet 212. The first gas inlet 211 is inclined with respect to the first direction x. The first gas inlet 211 is inclined so that as it approaches the non-consumable electrode 25 in the first direction x, it is located on one side z1 in the axial direction.

[0054] The second gas inlet 212 is inclined with respect to the first direction x. The second gas inlet 212 is inclined so that as it approaches the non-consumable electrode 25 in the first direction x, it is positioned on one side z1 in the axial direction. The first cylindrical portion 20A, located radially outward of the cylindrical member 21, is positioned to straddle the first gas inlet 211 and the second gas inlet 212 in the axial direction z.

[0055] The tapered surface 214 is located at the open end of the second gas inlet 212. The tapered surface 214 is inclined so as it approaches the non-consumable electrode 25, it is located on the other side z2 in the axial direction. In the cross-section shown in Figure 9, the angle between the tapered surface 214 and the second gas inlet 212 is approximately a right angle.

[0056] The groove 213 is a portion of the outer circumferential surface of the cylindrical member 21 that is recessed radially inward. The cylindrical member 22 is generally cylindrical and is positioned radially outside the cylindrical member 21. The cylindrical member 22 blocks the groove 213 from the radially outside. As shown in Figures 4 and 9, in this embodiment, the cooling water flow path W is formed by the space between the groove 213 and the cylindrical member 22 that blocks it. Also, in this embodiment, as shown in Figure 9, the cooling water flow path W is located between the first gas inlet 211 and the cylindrical member 22 in the axial direction z.

[0057] As shown in Figure 9, the female threaded portion 215 is adjacent to the first gas inlet 211 on the other axial side z2. The threaded portion of the collet retaining member 28 is screwed into this female threaded portion 215, as described above.

[0058] As shown in Figures 3 and 9, the first gas pipe 41 and the second gas pipe 42 pass through the inside of the second cylindrical section 20B. The first gas pipe 41 is a pipe that carries the first gas flow path G1 and is connected to the first gas inlet 211 of the cylindrical member 21. The second gas pipe 42 is a pipe that carries the second gas flow path G2 and is connected to the second gas inlet 212 of the cylindrical member 21. The second cylindrical section 20B has a constricted shape in which the portion closer to the first cylindrical section 20A has a smaller diameter than the portion closer to the handle 1. In the illustrated example, the first gas pipe 41 and the second gas pipe 42 are bent appropriately in accordance with this constricted shape of the second cylindrical section 20B. The end of the first gas pipe 41 that is connected to the first gas inlet 211 extends along the first direction x.

[0059] As shown in Figure 4, the first cooling water pipe 43 and the second cooling water pipe 44 are inserted inside the second cylindrical section 20B. In the illustrated example, the first cooling water pipe 43 is a pipe for supplying cooling water to the cooling water flow path W described above. The second cooling water pipe 44 is a pipe for sending the cooling water that has flowed through the cooling water flow path W to the outside. The end of the first cooling water pipe 43 on the first cylindrical section 20A side is connected to one end of the cooling water flow path W. The end of the second cooling water pipe 44 on the first cylindrical section 20A side is connected to the other end of the cooling water flow path W. As a result, as shown in Figure 4, the cooling water flows in the order of the first cooling water pipe 43, the cooling water flow path W, and the second cooling water pipe 44. In Figure 4, the flow of cooling water is represented by solid arrows.

[0060] The types of gases supplied to the welding torch A1, namely the first inert gas and the second inert gas, are not particularly limited and include, for example, at least one selected from argon (Ar) gas and helium (He) gas. The flow rates of the first and second inert gases supplied to the welding torch A1 are individually adjusted as appropriate depending on the welding conditions, etc.

[0061] As shown in Figure 8, the gap between the non-consumable electrode 25 (electrode main portion 251) and the inner nozzle 30 (tip side cylindrical portion 303) in the first gas flow path G1 is smaller than the gap between the inner nozzle 30 (tip side cylindrical portion 303) and the outer nozzle 31 in the second gas flow path G2. The minimum gap L1 between the non-consumable electrode 25 (electrode main portion 251) and the inner nozzle 30 (tip side cylindrical portion 303) in the first gas flow path G1 is, for example, about 0.4 to 1.8 mm. The minimum gap L2 between the inner nozzle 30 (tip side cylindrical portion 303) and the outer nozzle 31 in the second gas flow path G2 is, for example, about 1 to 4 mm. Regarding the ratio of the minimum gap L1 to the minimum gap L2, the minimum gap L1 is, for example, 0.2 to 0.5 times the minimum gap L2, and preferably 0.2 to 0.3 times the minimum gap L2.

[0062] Next, the operation of this embodiment will be described.

[0063] The welding torch A1 of this embodiment comprises a non-consumable electrode 25 extending in the axial direction z, a collet body 26 (first member), an inner nozzle 30 (first nozzle), a locking member 33, and an electrode centering member 34. The electrode centering member 34 is concentrically fitted onto the non-consumable electrode 25. The inner nozzle 30 (main nozzle portion 301) is concentrically fitted onto the electrode centering member 34 (main centering member portion 341). As a result, the inner nozzle 30 is positioned concentrically with respect to the non-consumable electrode 25 via the electrode centering member 34. The locking member 33 is fitted across the end portion (first part) of the collet body 26 (first member) on one side z1 in the axial direction and the end portion (second part) of the inner nozzle 30 on the other side z2 in the axial direction, and locks onto both the collet body 26 and the inner nozzle 30. With this configuration, some radial flexibility can be provided between the locking member 33 and the collet body 26 or inner nozzle 30. Therefore, even if the non-consumable electrode 25 is slightly bent due to manufacturing errors or the like, the inner nozzle 30 can be positioned concentrically with respect to the non-consumable electrode 25.

[0064] If the inner nozzle 30 becomes misaligned with respect to the non-consumable electrode 25, a flow deviation occurs in the first inert gas (plasma gas) ejected from the opening 305 at the tip of the inner nozzle 30. The minimum gap L1 between the non-consumable electrode 25 (electrode main portion 251) and the inner nozzle 30 (tip side cylindrical portion 303) that constitute the first gas flow path G1 is narrow, and if the inner nozzle 30 becomes misaligned, it is likely to cause a flow deviation of the first inert gas (plasma gas). However, as described above, the structure equipped with the electrode centering member 34 and the locking member 33 ensures that the inner nozzle 30 is positioned concentrically with respect to the non-consumable electrode 25. This is suitable for improving welding quality.

[0065] Furthermore, since the inner nozzle 30 is arranged concentrically on the radially outer side of the non-consumable electrode 25, the gas (first inert gas) flowing through the first gas channel G1 between the non-consumable electrode 25 and the inner nozzle 30 becomes a nearly uniform and relatively high-speed airflow around the non-consumable electrode 25 and is ejected from the opening 305 at the tip of the inner nozzle 30. As a result, even when welding workpieces made of low-molten metal such as galvanized steel sheets, the high-speed airflow of the first inert gas flowing around the non-consumable electrode 25 blows away fumes and other contaminants generated during welding. Therefore, it is possible to prevent fumes and other contaminants from adhering to the tip of the non-consumable electrode 25 or the tip of the inner nozzle 30.

[0066] The locking member 33 and the end (first part) on one side z1 in the axial direction of the collet body 26 are connected by a screw. With this configuration, a reasonable amount of dimensional flexibility can be provided between the locking member 33 and the collet body 26 with a relatively simple structure. In addition, when replacing the inner nozzle 30, the inner nozzle 30 can be easily removed by loosening the female threaded portion 331a of the locking member 33, resulting in excellent workability for replacing the inner nozzle 30.

[0067] In the mounting structure of the inner nozzle 30, locking member 33, and electrode centering member 34, the end of the electrode centering member 34 on the other axial side z2 (centering member bulge 342) abuts against the end of the collet body 26 on one axial side z1 (first part). This prevents the electrode centering member 34 from moving to the other axial side z2. Furthermore, the centering member bulge 342 of the electrode centering member 34 abuts against the nozzle main part 301 (second part) of the inner nozzle 30. This prevents the electrode centering member 34 from moving to the one axial side z1. Also, the nozzle bulge 302 on the other axial side z2 of the inner nozzle 30 abuts against the intermediate step part 333 of the locking member 33. This prevents the inner nozzle 30 from moving to the one axial side z1. With this configuration, when the female thread portion 331a of the locking member 33 (large diameter cylindrical portion 331) and the male thread portion 261a of the collet body 26 are tightened, the portion of the inner nozzle 30 on the other side z2 in the axial direction (part of the main nozzle portion 301 and the nozzle bulge portion 302) is firmly held in place by compressive forces acting from both sides in the axial direction z by the centering member bulge portion 342 of the electrode centering member 34 and the intermediate step portion 333 of the locking member 33.

[0068] In this embodiment, the centering member bulge 342 of the electrode centering member 34 has a first contact surface 342a located on one side z1 in the axial direction. The nozzle main portion 301 of the inner nozzle 30 has a second contact surface 301a that contacts the first contact surface 342a. Each of the first contact surface 342a and the second contact surface 301a is inclined such that its radial dimension decreases as it moves toward one side z1 in the axial direction. With this configuration, the centering accuracy of the inner nozzle 30 relative to the electrode centering member 34 can be improved.

[0069] In this embodiment, the end portion (first part) of the collet body 26 on one side z1 in the axial direction has a third contact surface 262a. The centering member bulge 342 of the electrode centering member 34 has a fourth contact surface 342b located on the other side z2 in the axial direction. The fourth contact surface 342b is in contact with the third contact surface 262a, and both the third contact surface 262a and the fourth contact surface 342b are inclined such that their radial dimensions increase towards the one side z1 in the axial direction. With this configuration, the centering accuracy of the electrode centering member 34 with respect to the non-consumable electrode 25 can be improved.

[0070] In this embodiment, the nozzle bulge portion 302 of the inner nozzle 30 has a fifth contact surface 302a located on one side z1 in the axial direction. The intermediate step portion 333 of the locking member 33 has a sixth contact surface 333a that contacts the fifth contact surface 302a. Each of the fifth contact surface 302a and the sixth contact surface 333a is inclined such that its radial dimension decreases as it moves toward one side z1 in the axial direction. With this configuration, the alignment accuracy of the inner nozzle 30 with respect to the electrode alignment member 34 can be further improved.

[0071] The inner nozzle 30 is made of an insulating material. The insulating material has a compressive strength higher than its tensile strength. In this embodiment, as described above, the female thread portion 331a of the locking member 33 (large diameter cylindrical portion 331) and the male thread portion 261a of the collet body 26 are tightened together. As a result, the portion of the inner nozzle 30 on the other side z2 in the axial direction (part of the main nozzle portion 301 and the nozzle bulge portion 302) is firmly held in place by compressive forces acting from both sides in the axial direction z by the electrode centering member 34 (centering member bulge portion 342) and the locking member 33 (intermediate step portion 333). Such a configuration is preferable for increasing the durability of the inner nozzle 30.

[0072] In this embodiment, the outer nozzle 31 is positioned radially outward of the inner nozzle 30, and a second gas flow path G2 is formed between the inner nozzle 30 and the outer nozzle 31. With this configuration, during welding, the first inert gas flowing through the first gas flow path G1 and ejected from the tip of the inner nozzle 30 functions as a plasma gas, and the second inert gas flowing through the second gas flow path G2 and ejected from the tip of the outer nozzle 31 functions as a shielding gas. As a result, the arc generated between the workpiece and the tip of the non-consumable electrode 25 is narrowed, and welding can be performed efficiently using a high-energy-density arc (plasma arc).

[0073] Furthermore, the tip of the non-consumable electrode 25 coincides with the tip of the inner nozzle 30 in the axial direction z, or slightly protrudes from the tip of the inner nozzle 30 to one side z1 in the axial direction. The protrusion length P1 of the tip of the non-consumable electrode 25 protruding from the tip of the inner nozzle 30 to one side z1 in the axial direction is in the range of 0 to 2 mm. With this tip position of the non-consumable electrode 25, the gap between the non-consumable electrode 25 and the inner nozzle 30 is kept approximately constant narrow in the range from the middle to near the tip in the axial direction z of the inner nozzle 30. Therefore, the first inert gas of the high-speed airflow flowing around the non-consumable electrode 25 is ejected from the opening 305 at the tip of the inner nozzle 30 with almost no decrease in flow velocity. This is advantageous in preventing the adhesion of fumes, etc., to the tip of the non-consumable electrode 25 and the tip of the inner nozzle 30. Moreover, the above-mentioned effects can be achieved by devising the shape and arrangement of the inner nozzle 30, making it possible to simplify the structure of the welding torch A1 and miniaturize the tip of the welding torch A1.

[0074] In welding torch A1, the minimum gap L1 between the non-consumable electrode 25 (main electrode portion 251) and the inner nozzle 30 (tip-side cylindrical portion 303) in the first gas flow path G1 is smaller than the minimum gap L2 between the inner nozzle 30 (tip-side cylindrical portion 303) and the outer nozzle 31 in the second gas flow path G2. With this configuration, it is possible to efficiently increase the flow velocity of the first inert gas flowing between the non-consumable electrode 25 and the inner nozzle 30. Therefore, the adhesion of fumes and the like to the tip of the non-consumable electrode 25 and the tip of the inner nozzle 30 is appropriately prevented, and the arc (plasma arc) generated between the workpiece and the non-consumable electrode 25 is tightened, and the concentration of the arc is further increased.

[0075] Figure 10 shows a modified example of the welding torch according to the present invention. In the welding torch A11 shown in Figure 10, the configuration of the collet body 26, inner nozzle 30, locking member 33, and electrode centering member 34 differs from that of the welding torch A1 of the above embodiment.

[0076] In welding torch A11, the third contact surface 262a of the above embodiment is not formed on the end of the collet body 26 on one side z1 in the axial direction. The fourth contact surface 342b is not formed on the centering member bulge 342 of the electrode centering member 34. The annular flat end surface of the electrode centering member 34 (centering member main part 341 and centering member bulge 342) facing the other side z2 in the axial direction is in contact with the annular flat end surface of the collet body 26 facing one side z1 in the axial direction. Furthermore, the fifth contact surface 302a of the above embodiment is not formed on the nozzle bulge 302 of the inner nozzle 30. The sixth contact surface 333a is not formed on the intermediate step portion 333 of the locking member 33. Furthermore, the annular flat end surface of the nozzle bulge portion 302 facing one side z1 in the axial direction and the annular flat end surface of the intermediate step portion 333 facing the other side z2 in the axial direction are in contact.

[0077] In this modified welding torch A11, similar to the welding torch A1 of the above embodiment, the inner nozzle 30 is arranged concentrically with respect to the non-consumable electrode 25 via the electrode centering member 34. The locking member 33 is fitted over the end (first part) on one axial side z1 of the collet body 26 (first member) and the end (second part) on the other axial side z2 of the inner nozzle 30, and locks to both the collet body 26 and the inner nozzle 30. With this configuration, some radial flexibility can be provided between the locking member 33 and the collet body 26 or the inner nozzle 30. Therefore, even if the non-consumable electrode 25 is slightly bent due to manufacturing errors, the inner nozzle 30 can be arranged concentrically with respect to the non-consumable electrode 25.

[0078] If the inner nozzle 30 becomes misaligned with respect to the non-consumable electrode 25, a flow deviation occurs in the first inert gas (plasma gas) ejected from the opening 305 at the tip of the inner nozzle 30. The minimum gap L1 between the non-consumable electrode 25 (electrode main portion 251) and the inner nozzle 30 (tip side cylindrical portion 303) that constitute the first gas flow path G1 is narrow, and if the inner nozzle 30 becomes misaligned, it is likely to cause a flow deviation of the first inert gas (plasma gas). However, as described above, the structure equipped with the electrode centering member 34 and the locking member 33 ensures that the inner nozzle 30 is positioned concentrically with respect to the non-consumable electrode 25. This is suitable for improving welding quality.

[0079] In welding torch A11, the end of the electrode centering member 34 on the other axial side z2 (centering member main portion 341 and centering member bulge portion 342) abuts against the end of the collet body 26 on one axial side z1 (first portion). This prevents the electrode centering member 34 from moving to the other axial side z2. Also, the centering member bulge portion 342 of the electrode centering member 34 abuts against the nozzle main portion 301 (second portion) of the inner nozzle 30. This prevents the electrode centering member 34 from moving to the one axial side z1. Furthermore, the nozzle bulge portion 302 on the other axial side z2 of the inner nozzle 30 abuts against the intermediate step portion 333 of the locking member 33. This prevents the inner nozzle 30 from moving to the one axial side z1. With this configuration, when the female thread portion 331a of the locking member 33 (large diameter cylindrical portion 331) and the male thread portion 261a of the collet body 26 are tightened, the portion of the inner nozzle 30 on the other side z2 in the axial direction (part of the main nozzle portion 301 and the nozzle bulge portion 302) is firmly held in place by compressive forces acting from both sides in the axial direction z by the centering member bulge portion 342 of the electrode centering member 34 and the intermediate step portion 333 of the locking member 33.

[0080] In welding torch A11, the centering member bulge 342 of the electrode centering member 34 has a first contact surface 342a located on one side z1 in the axial direction. The nozzle main part 301 of the inner nozzle 30 has a second contact surface 301a that contacts the first contact surface 342a. Each of the first contact surface 342a and the second contact surface 301a is inclined such that its radial dimension decreases as it moves toward one side z1 in the axial direction. With this configuration, the centering accuracy of the inner nozzle 30 relative to the electrode centering member 34 can be improved. In addition, welding torch A11 has the same effects as welding torch A1 of the above embodiment within the same range of configuration as welding torch A1 of the above embodiment.

[0081] Figure 11 shows another modified example of the welding torch according to the present invention. In the welding torch A12 shown in Figure 11, the configuration of the inner nozzle 30 and the electrode centering member 34 differs from that of the modified welding torch A11 shown in Figure 10.

[0082] In welding torch A12, the centering member bulge 342 of the electrode centering member 34 does not have a first contact surface 342a. Also, the nozzle main portion 301 of the inner nozzle 30 does not have a second contact surface 301a. The annular flat end surface of the centering member bulge 342 facing one side z1 in the axial direction is in contact with the annular flat end surface of the nozzle main portion 301 facing the other side z2 in the axial direction.

[0083] In this modified welding torch A12, similar to the welding torch A1 of the above embodiment, the inner nozzle 30 is arranged concentrically with respect to the non-consumable electrode 25 via the electrode centering member 34. The locking member 33 is fitted over the end (first part) on one axial side z1 of the collet body 26 (first member) and the end (second part) on the other axial side z2 of the inner nozzle 30, and locks to both the collet body 26 and the inner nozzle 30. With this configuration, some radial flexibility can be provided between the locking member 33 and the collet body 26 or the inner nozzle 30. Therefore, even if the non-consumable electrode 25 is slightly bent due to manufacturing errors, the inner nozzle 30 can be arranged concentrically with respect to the non-consumable electrode 25.

[0084] If the inner nozzle 30 becomes misaligned with respect to the non-consumable electrode 25, a flow deviation occurs in the first inert gas (plasma gas) ejected from the opening 305 at the tip of the inner nozzle 30. The minimum gap L1 between the non-consumable electrode 25 (electrode main portion 251) and the inner nozzle 30 (tip side cylindrical portion 303) that constitute the first gas flow path G1 is narrow, and if the inner nozzle 30 becomes misaligned, it is likely to cause a flow deviation of the first inert gas (plasma gas). However, as described above, the structure equipped with the electrode centering member 34 and the locking member 33 ensures that the inner nozzle 30 is positioned concentrically with respect to the non-consumable electrode 25. This is suitable for improving welding quality.

[0085] In welding torch A12, the end of the electrode centering member 34 on the other axial side z2 (centering member main portion 341 and centering member bulge portion 342) abuts against the end of the collet body 26 on one axial side z1 (first portion). This prevents the electrode centering member 34 from moving to the other axial side z2. Also, the centering member bulge portion 342 of the electrode centering member 34 abuts against the nozzle main portion 301 (second portion) of the inner nozzle 30. This prevents the electrode centering member 34 from moving to the one axial side z1. Furthermore, the nozzle bulge portion 302 on the other axial side z2 of the inner nozzle 30 abuts against the intermediate step portion 333 of the locking member 33. This prevents the inner nozzle 30 from moving to the one axial side z1. With this configuration, when the female thread portion 331a of the locking member 33 (large diameter cylindrical portion 331) and the male thread portion 261a of the collet body 26 are tightened, the portion of the inner nozzle 30 on the other side z2 in the axial direction (part of the main nozzle portion 301 and the nozzle bulge portion 302) is firmly held in place by compressive force acting from both sides in the axial direction z by the centering member bulge portion 342 of the electrode centering member 34 and the intermediate step portion 333 of the locking member 33. In addition, within the scope of the same configuration as the welding torch A1 of the above embodiment, the welding torch A12 provides the same effects and advantages as the welding torch A1 of the above embodiment.

[0086] Although embodiments of the present invention have been described above, the scope of the present invention is not limited to the embodiments described above, and any modifications within the scope of the matters described in each claim are all included within the scope of the present invention.

[0087] In the above embodiment, the locking member 33 was locked to the end of the collet body 26 on one side z1 in the axial direction by screwing the female thread portion 331a of the locking member 33 (large diameter cylindrical portion 331) with the male thread portion 261a of the collet body 26, but the configuration is not limited to this. For example, the locking member 33 may be locked to the end of the collet body 26 on one side z1 in the axial direction by press-fitting the end of the collet body 26 on one side z1. [Explanation of Symbols]

[0088] A1, A11, A12: Welding torch, 25: Non-consumable electrode, 26: Collet body (first component), 30: Inner nozzle (first nozzle), 301: Nozzle main part, 301a: Second contact surface, 302: Nozzle bulge, 31: Outer nozzle (second nozzle), 33: Locking member, 331: Large diameter cylindrical part, 332: Small diameter cylindrical part, 333: Intermediate step part, 34: Electrode centering member, 341: Centering member main part, 342: Centering member bulge, 342a: First contact surface, z: Axial direction, z1: ​​One side in the axial direction, z2: Other side in the axial direction

Claims

1. A non-consumable electrode extending in the axial direction, A cylindrical first member positioned radially outward of the non-consumable electrode, A cylindrical first nozzle is positioned radially outward of the non-consumable electrode and on one side in the axial direction relative to the first member, A cylindrical locking member is fitted over the first portion on one side in the axial direction of the first member and the second portion on the other side in the axial direction of the first nozzle, and locks onto both the first member and the first nozzle. The device comprises a cylindrical electrode centering member positioned radially outward of the non-consumable electrode and radially inward of the second part, The electrode centering member is fitted concentrically to the non-consumable electrode. The electrode centering member includes a cylindrical main centering member portion and a centering member bulge portion that bulges radially outward from the main centering member portion. The second part is fitted concentrically to the portion of the main part of the centering member that is located on one side in the axial direction from the bulging part of the centering member. The second part includes a cylindrical nozzle main portion and a nozzle bulge portion that bulges radially outward from the other side of the nozzle main portion in the axial direction, The locking member includes a large-diameter cylindrical portion fitted onto the nozzle bulge, a small-diameter cylindrical portion having a smaller inner diameter than the large-diameter cylindrical portion and fitted onto the main part of the nozzle, and an intermediate stepped portion connected to both the large-diameter cylindrical portion and the small-diameter cylindrical portion. The electrode centering member is prevented from moving to the other side in the axial direction by the other end of the electrode centering member contacting the first part. The electrode centering member is prevented from moving to one side in the axial direction by the contact between the centering member bulge and the second part. A welding torch in which the first nozzle is prevented from moving to one side in the axial direction by the contact between the nozzle bulge and the intermediate step.

2. The bulging portion of the centering member has a first contact surface located on one side in the axial direction, The second part has a second contact surface that contacts the first contact surface, The welding torch according to claim 1, wherein each of the first contact surface and the second contact surface is inclined such that the radial dimension decreases as it is directed toward one side in the axial direction.

3. The welding torch according to claim 1 or 2, wherein the large-diameter cylindrical portion of the locking member and the first portion of the first member are connected by a screw.

4. The welding torch according to claim 3, wherein the first nozzle is made of an insulating material.

5. The welding torch according to claim 4, further comprising a cylindrical second nozzle positioned radially outward from the first nozzle and the locking member.

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