Welding device and method of welding

Abstract

To suppress contamination of outside air into a welding atmosphere from a wire nozzle for delivering a welding wire to improve shielding property of the welding atmosphere.SOLUTION: A welding device 1 for performing welding in an inert gas atmosphere includes: a welding torch 10; a wire feeding passage 30 through which a welding wire 21 to be delivered between the welding torch 10 and a base material 2 passes; and an inert gas supply passage 40 for supplying a gas including an inert gas as the main component into the wire feeding passage 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a welding apparatus and a welding method. [Background technology]

[0002] In recent years, there has been a demand for high efficiency and high quality in overlay welding while also taking into consideration environmental resistance. In terms of high efficiency, consumable electrode welding has been advantageous, but in terms of environmental resistance such as CO2 emissions, fumes, and slag disposal, and high quality such as beautiful bead appearance and low dilution rate, non-consumable electrode welding has been advantageous. In order to meet all of these requirements, the introduction of hot wire welding methods is progressing in non-consumable electrode welding methods such as TIG welding and plasma welding.

[0003] As a hot wire type welding method, Patent Documents 1 to 3 disclose a non-consumable electrode type welding device that performs welding by supplying a welding wire heated by electrical current to a molten pool. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 62-006907 [Patent Document 2] Japanese Patent Application Publication No. 62-026867 [Patent Document 3] JP-A-1-192477 Summary of the Invention [Problem to be solved by the invention]

[0005] When hot wire overlay welding is performed using an alloy containing a large amount of active metals such as titanium and magnesium as the base material or welding material, the mechanical properties of the alloy may be easily altered if the alloy comes into contact with air at a high temperature during welding. In addition, bubbles may be generated in the weld metal, causing porosity defects such as pits and blowholes. For this reason, an inert gas such as argon gas is supplied as a shielding gas around the molten pool formed at the tip of the welding torch, and welding is performed in an inert gas atmosphere.

[0006] On the other hand, in conventional welding devices, outside air is discharged together with the welding wire from the tip of the wire nozzle through which the welding wire is fed, and the outside air flows into the periphery of the molten pool, which is kept in an inert gas atmosphere by the shielding gas. That is, in conventional welding devices, the inflow of outside air into the periphery of the molten pool is detrimental from the viewpoint of improving the shielding properties of the welding atmosphere to obtain a high-quality bead.

[0007] The problem of improving the shielding properties of the welding atmosphere as described above is a problem common not only to hot wire overlay welding but also to welding methods in which welding is performed in an inert gas atmosphere while supplying a welding wire.

[0008] The present invention has been made in consideration of the above circumstances, and has an object to suppress the intrusion of outside air into a welding atmosphere from a wire nozzle that delivers a welding wire, and to improve the shielding properties of the welding atmosphere. [Means for solving the problem]

[0009] The present invention, which solves the above problems, is a welding device that performs welding in an inert gas atmosphere, and is characterized by comprising a welding torch, a wire feed path through which a welding wire passes to be fed between the welding torch and the base material, and an inert gas supply path that supplies a gas containing an inert gas as a main component into the wire feed path.

[0010] Another aspect of the present invention is a welding method for performing welding in an inert gas atmosphere, characterized in that when feeding the welding wire between a welding torch and a base material through a wire feed path through which the welding wire passes, a gas containing an inert gas as a main component is supplied into the wire feed path to perform the welding. Effect of the Invention

[0011] According to the present invention, it is possible to suppress the intrusion of outside air into the welding atmosphere from the wire nozzle that delivers the welding wire, thereby improving the shielding properties of the welding atmosphere. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a hot wire type plasma welding device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram for explaining the configuration of an apparatus around a welded portion. [Diagram 3] 4A to 4C are diagrams for explaining a schematic configuration of a wire feeding path. [Figure 4] 6 is a diagram for explaining a flow of an inert gas in a wire feeding path. FIG. [Diagram 5] FIG. 2 is a diagram for explaining a flow of an inert gas in a plasma welding apparatus. [Figure 6] 13 is a diagram showing an example of an arrangement of an inert gas supply path according to another embodiment; FIG. [Figure 7] 13A and 13B are diagrams illustrating an example of an arrangement of inert gas supply paths according to another embodiment. [Figure 8] 13A and 13B are diagrams illustrating an example of an arrangement of inert gas supply paths according to another embodiment. [Figure 9] FIG. 13 is a diagram showing a schematic configuration of a plasma welding device including a plurality of wire feed paths according to another embodiment. [Figure 10] FIG. 13 is a diagram showing an example of connection of a hot wire power supply according to another embodiment. [Figure 11] FIG. 13 is a diagram showing an example of connection of a hot wire power supply according to another embodiment. [Figure 12]FIG. 13 is a diagram showing a schematic configuration of a cold-wire type plasma welding device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are designated by the same reference numerals, and duplicated description will be omitted.

[0014] In this embodiment, a welding apparatus that performs welding in an inert gas atmosphere and improves the shielding performance of the welding atmosphere will be described by taking a hot wire type plasma welding apparatus that performs build-up welding as an example.

[0015] <Plasma welding equipment> Fig. 1 is a diagram showing a schematic configuration of a hot-wire type plasma welding device 1 according to the present embodiment. Fig. 2 is a diagram for explaining the configuration of the device around the welded portion. In both figures, some of the components of the device around the welded portion are shown in cross section.

[0016] The plasma welding apparatus 1 includes a welding torch 10, a wire feeder 20 that feeds a welding wire, and a wire feed path 30 for feeding the welding wire between the welding torch 10 and a base material 2 that is to be welded.

[0017] Welding torch 10 has a tungsten electrode 11 which is an example of a non-consumable electrode, a tip 12 surrounding the periphery of tungsten electrode 11 , and a shield cap 13 surrounding the periphery of tip 12 .

[0018] In the welding torch 10, a flow passage is formed between the tungsten electrode 11 and the inner peripheral surface of the tip 12, through which an inert gas such as argon gas is supplied as a pilot gas. In addition, a flow passage is formed between the outer peripheral surface of the tip 12 and the inner peripheral surface of the shield cap 13, through which an inert gas such as argon gas is supplied as a shield gas.

[0019] A shielding box 14, which is a container that is open at the bottom, is provided around the welding torch 10. The shielding box 14 is installed as necessary to make it easier to maintain an inert gas atmosphere in the vicinity of the welded part. The welding torch 10 is disposed on the top plate of the shielding box 14.

[0020] A plurality of shielding gas supply pipes 15 are connected to the top plate of the shielding box 14, supplying a shielding gas into the shielding box 14. An inert gas such as argon gas is used as the shielding gas. During overlay welding of the base material 2, the inert gas is supplied from the shielding gas supply pipes 15, making it easier to maintain the molten pool 3 and the bead 4 in the vicinity of the molten pool 3 in an inert gas atmosphere.

[0021] Wire feeder 20 has a wire spool 22 around which welding wire 21 is wound, a pair of feed rollers 23 that feed welding wire 21 fed from wire spool 22 toward welding torch 10, and a motor 24 that serves as a rotational drive source for feed rollers 23.

[0022] Wire feed path 30 is a feed path for feeding welding wire 21 fed from wire feeder 20 described above to the vicinity of the tip of welding torch 10, and is composed of a single component or a combination of multiple components. Wire feed path 30 according to this embodiment is composed of housing 31 through which welding wire 21 passes, conduit liner 32 as a first cylindrical body, and wire nozzle 33 as a second cylindrical body.

[0023] The housing 31 is provided in the middle of the wire feed path 30, and is disposed between the conduit liner 32 and the wire nozzle 33. A more detailed description of the housing 31 will be given later.

[0024] The conduit liner 32 is disposed between the wire feeder 20 and the housing 31, and one end of the conduit liner 32 is connected to the wire feeder 20 and the other end is connected to the housing 31. The welding wire 21 fed from the wire feeder 20 passes through the inside of the conduit liner 32 and is fed to the housing 31.

[0025] The wire nozzle 33 extends from the housing 31 to the vicinity of the tip of the welding torch 10. The welding wire 21 passing through the inside of the housing 31 passes through the inside of the wire nozzle 33 and reaches the molten pool 3 formed near the tip of the welding torch 10. In this embodiment, all parts of the wire nozzle 33 that come into contact with the welding wire 21 are made of an insulating material.

[0026] Next, the peripheral structure of the housing 31 will be described with reference mainly to Fig. 3. Fig. 3(a) is a side view of the periphery of the housing 31 as viewed from the wire feeder side, and Fig. 3(b) is a front view of the housing 31. Note that, to ensure visibility of the drawings and for ease of explanation, some of the components that may be illustrated with hidden lines in the housing 31 have been omitted from the illustration with hidden lines.

[0027] The housing 31 is composed of a main container 31a having a space 34 therein, and a cover 31b that covers the space 34 of the main container 31a. The main container 31a has an opening on the right side when the housing 31 is viewed from the wire feeder side as shown in Fig. 3(a), and the cover 31b is bolted to cover the opening on the right side of the main container 31a.

[0028] Between the main container 31a and the cover 31b, an O-ring 35 is provided as a sealant. When the O-ring 35 is provided, it is possible to prevent the atmosphere from flowing out from the space 34 of the main container 31a to the outside of the cover 31b, and it is possible to prevent the outside air from flowing into the housing 31 after the atmosphere inside the housing 31 is replaced, which will be described later.

[0029] Two guide rollers 36 are disposed at a distance from each other in a space 34 within the housing 31 to support the welding wire 21 passing through the housing 31 from below.

[0030] A power feed rod 37 is provided above the guide roller 36 as a power feeding electrode for feeding power to the welding wire 21. The power feed rod 37 is fixed to the housing 31 with its extension direction facing the vertical direction, and the lower end of the power feed rod 37 is constantly in contact with the welding wire 21 passing through the housing 31 by a spring (not shown).

[0031] 3(b), a relief hole 38 is formed in the cylindrical wire nozzle 33, penetrating from the inner peripheral surface to the outer peripheral surface. The relief hole 38 is located closer to the tip of the wire nozzle 33 (i.e., closer to the base material) than the connection point of an inert gas supply path 40, which will be described later, to the wire feed path 30. When such a relief hole 38 is provided, part of the gas supplied into the wire nozzle 33 can be released from the relief hole 38 to the outside of the wire nozzle 33.

[0032] (Inert gas supply line) 3(a), if the side where cover 31b is attached to main container 31a is referred to as the front side of main container 31a for the sake of convenience, an inert gas supply path 40 is connected to the back side of main container 31a. Inert gas supply path 40 is a flow path for supplying a gas mainly composed of an inert gas into the wire feed path.

[0033] 3(a), the inert gas supply path 40 is composed of a gas tube 41 connected to a gas supply source (not shown) such as a gas tank, and an elbow 42 to which the gas tube 41 is connected. One end of the elbow 42 is connected to the gas tube 41, and the other end of the elbow 42 is connected to the space 34 within the housing 31. By providing such an inert gas supply path 40, it is possible to supply a gas containing an inert gas as a main component into the housing 31.

[0034] The gas mainly composed of an inert gas is a gas having a composition in which the volume fraction of an inert gas such as helium gas, nitrogen gas, argon gas, etc. is 70% or more, and is different from air. The volume fraction of the inert gas is preferably 90% or more, and more preferably 99% or more.

[0035] Specific examples of the gas mainly composed of an inert gas include a mixed gas of argon gas and hydrogen gas, a mixed gas of argon gas and oxygen gas, etc. The gas mainly composed of an inert gas may be a gas with a volume fraction of the inert gas of 100%, or may be a mixed gas containing two or more kinds of inert gases, such as a mixed gas of argon gas and helium gas or a mixed gas of argon gas and nitrogen gas.

[0036] 1, the plasma welding device 1 is provided with a plasma welding power supply 50 as a first power supply for forming a plasma arc 5. The tungsten electrode 11 of the welding torch 10 and the base material 2 are electrically connected to the plasma welding power supply 50, and a plasma arc 5 is formed between the lower end of the tungsten electrode 11 and the surface of the base material 2 when electricity is applied.

[0037] The plasma welding apparatus 1 is also provided with a hot wire power supply 51 as a second power supply for electrically heating the welding wire 21. After wire feeding begins, the power feed rod 37 and the base material 2 come into contact with the welding wire 21 and the base material 2, the molten pool 3, or the plasma arc 5, thereby electrically connecting the power feed rod 37 and the base material 2 to the hot wire power supply 51, and when electricity is applied, the region from the tip of the welding wire 21 to the vicinity of the lower end of the power feed rod 37 is heated by resistance heating.

[0038] The above has described the schematic configuration of the plasma welding apparatus 1 according to this embodiment. In this plasma welding apparatus 1, before start of overlay welding of the base material 2, a gas mainly composed of an inert gas, for example, argon gas, is supplied into the housing 31 from the inert gas supply passage 40 shown in Fig. 3(a) .

[0039] Here, the flow of argon gas supplied into wire feed path 30 will be described with reference to Fig. 4. Fig. 4 is a schematic diagram showing a cross section of wire feed path 30, and the straight arrow in the figure indicates argon gas released from wire feed path 30.

[0040] The inside of the housing 31 is an air atmosphere before argon gas is supplied into the housing 31 from the inert gas supply path, but when argon gas is supplied into the housing 31, the housing 31 is filled with argon gas. As a result, the air inside the housing 31 is discharged from the housing 31 into the inside of the conduit liner 32 or the inside of the wire nozzle 33.

[0041] Thereafter, as argon gas continues to be supplied into the housing 31, the space 34 within the housing 31, the inside of the conduit liner 32 communicating with the space 34, and the inside of the wire nozzle 33 are replaced with an argon gas atmosphere. That is, as argon gas is supplied into the housing 31, the inside of the wire feed path 30 is replaced with an argon gas atmosphere. As a result, the welding wire 21 is fed out from the tip of the wire nozzle 33 and argon gas is released.

[0042] That is, according to the plasma welding device 1 of this embodiment, argon gas is released from the tip of the wire nozzle 33 during overlay welding of the base metal 2 as shown in Fig. 5, thereby preventing outside air from being mixed into the welding atmosphere around the tip of the welding torch 10. This improves the shielding properties of the welding atmosphere, and prevents deterioration of the mechanical properties of the weld metal and the occurrence of porosity defects caused by contact of air with the base metal in a high temperature state during welding.

[0043] If the flow rate of the argon gas supplied into the housing 31 is excessively high, the flow rate of the argon gas discharged from the tip of the wire nozzle 33 also increases. This high-speed gas flow acts to disturb the arc flow of the plasma arc 5, leading to instability of the plasma arc 5. As a result, the build-up bead 4 also becomes non-uniform, and the build-up bead is not normal, which may adversely affect the welding quality. If the flow rate of the argon gas into the housing 31 is kept low to avoid such problems, it will take time to replace the atmosphere inside the housing 31.

[0044] On the other hand, in the plasma welding apparatus 1 according to the present embodiment, the relief hole 38 is provided in the wire nozzle 33, so that a portion of the argon gas flowing inside the wire nozzle 33 is released into the shield box 14 from the relief hole 38. This makes it possible to reduce the discharge speed of the argon gas discharged from the tip of the wire nozzle 33.

[0045] In other words, even if the flow rate of argon gas into the housing 31 is increased, some of the argon gas can be released from the relief hole 38, thereby suppressing the discharge speed of the argon gas from the tip of the wire nozzle 33. In other words, when the relief hole 38 is provided, the flow rate of argon gas can be increased to shorten the time it takes to exhaust air from the housing 31, and the discharge speed of argon gas from the tip of the wire nozzle 33 can be kept appropriate to suppress disturbance of the plasma arc 5.

[0046] The welding performed by the plasma welding apparatus 1 is not limited to overlay welding, and may be other types of welding such as butt welding, lap welding, and fillet welding. The welding position and the shape of the groove are also not particularly limited. On the other hand, the plasma welding apparatus 1 according to the present embodiment is preferably applied to overlay welding.

[0047] In overlay welding, it is advantageous to reduce the welding speed compared to welding multiple base materials from the viewpoint of securing the amount of excess metal and suppressing the occurrence of defects. However, if the welding speed is reduced, it takes time for the molten pool to completely solidify, and the area of ​​the molten pool also becomes wide. Therefore, in overlay welding, high shielding is required to maintain the welding atmosphere until the wide molten pool completely solidifies. For this reason, the plasma welding device 1 capable of improving the shielding of the welding atmosphere is useful for application to overlay welding.

[0048] Furthermore, when hot-wire welding is performed in which the welding wire 21 is heated, it takes longer for the solidification of the molten pool to be completed than in cold-wire welding. For this reason, high shielding is required to maintain the welding atmosphere as described above, and therefore the plasma welding apparatus 1 is usefully applied to hot-wire welding.

[0049] Furthermore, when an alloy containing a large amount of active metals such as titanium or magnesium is used as the base material or welding material, the molten pool in a high temperature state comes into contact with the outside air and reacts with the components contained in the outside air, which is likely to cause defects. For this reason, high shielding is required to maintain the welding atmosphere as described above, so the plasma welding device 1 is useful when applied to the welding of active metals.

[0050] Furthermore, copper parts are usually used in the wire feed path 30, and if air is present in the wire nozzle 33 during hot-wire welding, the heated welding wire 21 accelerates oxidation of the copper parts, making the copper parts more likely to wear out. On the other hand, in the plasma welding apparatus 1 according to the present embodiment, the heated welding wire 21 passes through the wire feed path in a state in which the atmosphere in the wire feed path is replaced with a gas mainly composed of an inert gas, so that oxidation wear of the copper parts constituting the wire nozzle 33 can be suppressed.

[0051] From the above viewpoints, the plasma welding apparatus 1 according to the present embodiment is particularly useful for application to hot wire type overlay welding of base metals or welding materials containing active metals. In addition to base metals containing active metals, the plasma welding apparatus 1 is also useful for application to welding of high-quality materials for use in harsh environments such as nuclear power-related parts and cryogenic steel, medical use, or food, for which air should not be mixed into the weld metal.

[0052] <Other embodiments> Next, the plasma welding apparatus 1 according to other embodiments will be described in order.

[0053] 6, the connection position of elbow 42 to housing 31 may be, for example, the bottom side of housing 31. In other words, the connection position of inert gas supply path 40 to wire feed path 30 is not particularly limited.

[0054] 7 and 8, for example, the inert gas supply line 40 may be connected to the conduit liner 32 instead of the housing 31. In the example shown in Fig. 7, the inert gas supply line 40 is connected to the middle of the conduit liner 32, and in the example shown in Fig. 8, the inert gas supply line 40 is connected to the connection portion between the wire feeder 20 and the conduit liner 32.

[0055] As shown in Fig. 9, a plurality of feeding paths may be provided for the welding wire 21. In the example shown in Fig. 9, two wire feeding paths 30a, 30b are provided, and a first hot wire power supply 51 is installed to supply power to a power feed rod 37a for one wire feeding path 30a, and a second hot wire power supply 52 is installed to supply power to a power feed rod 37b for the other wire feeding path 30b.

[0056] In the above example, the hot wire power supply 51 is connected to the power feed rod 37 and the base material 2. However, as shown in FIG. 10, the hot wire power supply 51 may be connected to the wire nozzle 33 and the power feed rod 37. In this case, the current-carrying part of the wire nozzle 33 is made of a conductive material such as copper, and the part in contact with the welding wire 21 other than the current-carrying part is made of an insulating material. Since the current-carrying part of the wire nozzle 33 generates heat, if air is present in the wire nozzle 33, the parts constituting the current-carrying part are easily oxidized and worn out. In addition, if the current-carrying part is made of copper, spark discharge caused by an oxide film may cause wire buckling and clogging due to welding between the welding wire 21 and the current-carrying part. If such wire buckling and clogging occurs, problems such as damage to the components of the wire nozzle 33 and temporary stoppage of production due to maintenance to eliminate buckling may occur. However, according to the plasma welding device 1 in which the inside of the wire nozzle 33 is replaced with a gas mainly composed of an inert gas, it is possible to suppress the wear and damage of parts and the decrease in productivity caused by such oxidation.

[0057] Furthermore, as shown in FIG. 11, even when a plurality of wire feed paths 30 are provided, hot wire power sources 51 and 52 may be connected to the wire nozzle 33 and the power feed rod 37.

[0058] The plasma welding apparatus 1 may be a cold wire welding apparatus instead of a hot wire welding apparatus. Fig. 12 shows an example of a cold wire plasma welding apparatus 1, in which an inert gas supply path 40 is connected to a wire nozzle 33 of a wire feed path 30.

[0059] In the above description, plasma welding using a non-consumable electrode is exemplified, but the welding method is not particularly limited and may be TIG welding, laser welding, or electron beam welding using a non-consumable electrode. In addition, the welding method may be, for example, MAG welding, MIG welding, submerged arc welding, electroslag welding, or electrogas welding.

[0060] In a non-consumable electrode welding device, wire feed path 30 is provided outside welding torch 10, whereas in a consumable electrode welding device, wire feed path 30 is provided inside welding torch 10. Even in this case, by supplying a gas mainly composed of an inert gas into the wire feed path, it is possible to prevent outside air from mixing into the welding atmosphere formed by the shielding gas flowing outside the wire feed path.

[0061] Although the embodiment of the present invention has been described above, the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention.

[0062] For example, the components of the above-described embodiments may be combined in any desired manner. Any combination will naturally provide the functions and advantages of each of the components in the combination, and will also provide other functions and advantages that will be apparent to those skilled in the art from the description of this specification.

[0063] In addition, the effects described in this specification are merely explanatory or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to a person skilled in the art from the description of this specification in addition to or in place of the above effects. [Industrial Applicability]

[0064] The present invention can be applied to a hot wire type plasma welding device. [Explanation of symbols]

[0065] 1. Plasma welding equipment 2 Base material 3. Molten Pool 4 Beads 5. Plasma Arc 10. Welding Torch 11 Tungsten electrodes 12 Chips 13 Shield Cap 14 Shielding box 15 Shielding gas supply pipe 20 Wire feeder 21 Welding Wire 22 Wire spool 23 Feeding roller 24 Motor 30 Wire feed path 31 Case 31a Main container 31b Cover 32 Conduit Liner 33 Wire nozzle 34 Space 35 O-ring 36 Guide roller 37 Power supply rod 38 Relief hole 40 Inert gas supply line 41 Gas tube 42 Elbow 50 Plasma welding power source 51 Hot Wire Power Supply 52 Hot Wire Power Supply

Claims

1. A welding device for performing welding in an inert gas atmosphere, A welding torch, a wire feed path through which a welding wire passes between the welding torch and a base metal; a gas supply passage for supplying a gas mainly composed of an inert gas into the wire feed passage,

2. the welding torch having a non-consumable electrode; The welding device according to claim 1 , wherein the wire feed path is disposed outside the welding torch.

3. The welding device according to claim 2 , further comprising a power electrode for heating the welding wire passing through the wire feed path.

4. a housing in which the power supply electrode is attached is provided on the wire feed path, 4. The welding device according to claim 3, wherein the inert gas supply line is connected to the housing.

5. a relief hole for releasing a portion of the gas to the outside of the wire feed path is formed in the wire feed path; The welding device according to any one of claims 1 to 4, characterized in that the relief hole is located closer to the base material than a connection point of the inert gas supply passage to the wire feed passage.

6. A welding method for performing welding in an inert gas atmosphere, comprising: A welding method characterized in that, when feeding the welding wire between a welding torch and a base metal through a wire feed path through which the welding wire passes, a gas mainly composed of an inert gas is supplied into the wire feed path to perform the welding.

7. the welding torch having a non-consumable electrode; The welding method according to claim 6, wherein the wire feed path is disposed outside the welding torch.

8. The welding method according to claim 7, further comprising the step of supplying power to the welding wire passing through the wire feed path to heat the welding wire and perform the welding.

9. a power supply electrode for supplying power to the welding wire is attached to a housing provided in the wire feed path; The welding method according to claim 8, wherein the gas is supplied into the housing.

10. The welding method according to any one of claims 6 to 9, characterized in that a portion of the gas flowing within the wire feed path is released to the outside of the wire feed path on the base metal side of the supply point of the gas to the wire feed path.

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