Welding rod holder, dissimilar metal welding method, and manufacturing method for dissimilar metal joint

Abstract

To provide a welding rod holder which can hold a plurality of welding rods and individually deliver required amounts at any time when performing TIG welding, and which can be easily held and operated with one hand. [Solution] The holder body 2 is provided with a rod-shaped holder body 2 that can be held in one hand, a plurality of guide parts 3 that are provided on the holder body 2 and hold a plurality of welding rods W1, W2, W3 so that they can individually slide through the holder body 2, and individual operation rollers 4, 6, 8 and individual receiving rollers 5, 7, 9 that are arranged in a row in the longitudinal direction of the holder body 2 so that they can be rotated by hand and individually clamp the outer circumferential surfaces of the welding rods W1, W2, W3 held by the guide parts 3.

Description

[Technical Field]

[0001] The present invention relates to a welding rod holder that can be held in one hand, a dissimilar metal welding method for joining two members made of different types of metals by welding, and a method for manufacturing a dissimilar metal joint formed by joining two members made of different types of metals by welding. [Background technology]

[0002] Conventionally, among the above-mentioned welding rod holders, there is one that can hold only one welding rod and can supply the required amount of the welding rod at any time, as disclosed in Patent Document 1.

[0003] Furthermore, generally, when a member made of copper and a member made of stainless steel are simply welded, a brittle phase is generated at the joint surface, reducing the mechanical strength of the welded part. A conventional dissimilar metal welding method for avoiding this is disclosed in, for example, Patent Document 2, in which a dissimilar metal layer is formed on the surface of a first member to be joined, which is made of a first metal, and then a second metal layer is formed on the surface of this dissimilar metal layer, and then a second member to be joined, which is made of the second metal, is welded to this second metal layer, thereby joining the first member to be joined and the second member to be joined.

[0004] The dissimilar metal layer is formed by supplying a mixed filler metal containing a filler metal made of the first metal and particles made of a second metal having a melting point higher than that of the first metal to the surface of a first workpiece, and heating the mixed filler metal to a temperature equal to or higher than the melting point of the first metal and lower than the melting point of the second metal. In order to increase the joining strength between the first workpiece and the second workpiece, the formation of the dissimilar metal layer is repeated multiple times, and each time the ratio of the first metal to the second metal in the dissimilar metal layer is changed so that the ratio of the second metal gradually increases. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Utility Model Registration No. 3044697 [Patent Document 2] Japanese Patent Application Publication No. 2018-065144 Summary of the Invention [Problem to be solved by the invention]

[0006] However, this dissimilar metal welding method requires multiple arc passes to sequentially form multiple dissimilar metal layers, which is extremely time-consuming. Therefore, there is a demand for a dissimilar metal welding method that can complete welding with a single arc pass.

[0007] Furthermore, when dissimilar metal layers are repeatedly formed, the surface of the formed dissimilar metal layer cools and solidifies to a certain extent before the next dissimilar metal layer is formed on top of it. As a result, the dissimilar metal layers are not sufficiently interfused with each other, and boundary areas where the composition is slightly different from that of other areas are likely to occur. Since many of these overlap, this can cause an increase in the electrical resistance of the welded area.

[0008] It has been found that, in order to achieve high-quality welding of a first workpiece and a second workpiece made of dissimilar metals with a single arc travel, it is effective to use a TIG welding machine for welding, to generate molten pools that extend in a direction intersecting the welding progress direction within the expected melting amount regions of each of the first workpiece and the second workpiece during welding, while gradually extending the weld bead in the welding progress direction, and to prepare in advance a first welding rod made of a metal that has affinity for each of the first workpiece and the second workpiece, and a second welding rod made of the same metal as the first workpiece or a metal that has affinity for the first workpiece and that has affinity for the first welding rod, and to alternately use the first welding rod and the second welding rod during welding, and to extend the molten pools formed by melting the first welding rod and the second welding rod, respectively, in a direction intersecting the welding progress direction.

[0009] However, because conventional welding rod holders can only hold one welding rod, two welding rod holders are required to alternate between the first and second welding rods during welding, and it is extremely difficult to hold two welding rod holders in one hand and operate them quickly and accurately.

[0010] Furthermore, in order to alternately use the first welding rod and the second welding rod during welding, it is conceivable to hold the first welding rod and the second welding rod directly in one hand and operate them. In this case, even if two welding rods can be held in one hand, they cannot be fed out one by one from that hand, and therefore the first welding rod and the second welding rod cannot be fed stably, quickly, and accurately without hand shake.

[0011] The present invention has been made in view of the above circumstances, and one of the objects of the present invention is to provide a welding rod holder that can hold a plurality of welding rods and individually pay out the required amount at any time when performing TIG welding, and that can be easily held and operated with one hand.

[0012] Another object of the present invention is to provide a dissimilar metal welding method that can weld a first workpiece and a second workpiece, each made of a different metal, in a single arc travel so as to obtain sufficient mechanical strength and durability.

[0013] It is still another object of the present invention to provide a method for manufacturing a dissimilar metal joined product, which is capable of producing a dissimilar metal joined product having sufficient mechanical strength and durability by joining a first workpiece and a second workpiece made of dissimilar metals by welding in a single arc travel.

[0014] A welding rod holder according to a first aspect of the present invention can be configured to include a rod-shaped holder body that can be held in one hand, a plurality of guide portions formed on the holder body so as to penetrate the holder body in the longitudinal direction, for individually slidably holding a plurality of welding rods, and a plurality of pairs of individual operating rollers and individual receiving rollers arranged in a row in the longitudinal direction of the holder body on the holder body so that the outer peripheries of the welding rods that have penetrated the plurality of guide portions can be individually clamped in pairs for each of the plurality of welding rods, and each can be rotated with the fingers of a hand.

[0015] With this configuration, multiple welding rods are held parallel to the longitudinal direction of the holder body, allowing for instantaneous switching between the currently used welding rod and another required welding rod. Furthermore, since multiple pairs of individual operation rollers and individual receiving rollers are aligned in a row along the longitudinal direction of the holder body, the girth dimensions of the holder body can be kept small even when multiple welding rods are held by a single welding rod holder. As a result, a welding rod holder can be provided that can hold multiple welding rods and individually pay out the required amount as needed during TIG welding, and is easy to hold and operate with one hand.

[0016] The welding rod holder according to the second aspect of the present invention can be configured so that the holder body includes the individual operation rollers and individual receiving rollers, as well as a common operation roller and a common receiving roller arranged in a line in the longitudinal direction of the holder body, so that the outer peripheries of the multiple welding rods can be clamped together and rotated with the fingers only when the multiple welding rods are simultaneously fed out.

[0017] With the above configuration, it is possible to provide a welding rod holder that can hold a plurality of welding rods and individually pay out the required amount at any time when performing TIG welding, as well as pay out the required amount of a plurality of welding rods all at once only when necessary.

[0018] The welding rod holder according to the third aspect of the present invention may be configured so that the outer diameter of at least one welding rod among the plurality of welding rods is different from the outer diameter of the other welding rods.

[0019] With the above-mentioned configuration, welding rods with different outer diameters can be held, which is convenient when welding dissimilar metals, for example, because it is possible to hold a welding rod with an appropriate outer diameter depending on the thermal conductivity of the welding base material and use that welding rod instead of other welding rods.

[0020] A dissimilar metal welding method according to a fourth aspect of the present invention is a dissimilar metal welding method for TIG welding a first workpiece to be joined and a second workpiece to be joined, which are made of dissimilar metals, wherein the thermal conductivity of the first workpiece to be joined is greater than the thermal conductivity of the second workpiece to be joined, and the dissimilar metal welding method includes a welding rod preparation step of preparing in advance a first welding rod made of a metal having an affinity for each of the first workpiece to be joined and the second workpiece to be joined, and a second welding rod made of a metal of the same type as the first workpiece to be joined or a metal having an affinity for the first workpiece to be joined and having an affinity for the first welding rod; a weld member preparation step in which a workpiece and the second workpiece are arranged side by side, a portion of the first workpiece that is inboard from the side edge of the second workpiece by a required width is set as a first planned melting region, and a portion of the second workpiece that is inboard from the side edge of the first workpiece by a required width is set as a second planned melting region; and a weld bead formation step in which a weld bead is formed by TIG welding that straddles the first planned melting region and the second planned melting region and extends along the boundary between the first workpiece and the second workpiece, In the weld bead forming process, an arc discharge is constantly generated between the TIG welding electrode and the base material, and the heating point on the base material by the arc discharge is moved in the width direction of the weld bead from a melting start point in the first planned melting region, which is set at a position further forward by a required distance from the tip of the weld bead being formed, to near the inner boundary of the second planned melting region, and the first welding rod is melted and added to the base material molten pool of the first workpiece and the base material molten pool of the second workpiece, which are generated by heating by the arc discharge, thereby forming the welds. an underlayment forming step of forming an underlayment extending in the width direction of the weld bead; and immediately after the underlayment forming step is completed, returning the heated point on the base material by the arc discharge to a melting start point set within the first intended melting region near the inner boundary of the first intended melting region and near the start end of the underlayment, and moving the heated point on the base material by the arc discharge onto the underlayment within the first intended melting region and moving it along the width direction of the weld bead on the underlayment to near the end of the underlayment.and an upper-bank formation step in which the second welding rod is melted and added to the molten base metal pool of the first workpiece and the molten base metal pool of the underbank portion, which are generated by heating due to the arc discharge, to form an upper-bank portion extending from near the inner boundary of the first intended melting region, over the underbank portion, to near the end of the underbank portion, by alternately repeating these steps to form the weld bead.

[0021] With this configuration, it is possible to weld a first workpiece and a second workpiece made of dissimilar metals in a single arc travel so as to obtain sufficient mechanical strength and durability, and the increase in electrical resistance in a direction intersecting the extension direction of the weld bead between the first workpiece and the second workpiece is suppressed compared to conventional methods.

[0022] A dissimilar metal welding method according to a fifth aspect of the present invention can be configured such that, in the under-buildup forming step, the welding current is increased when the under-buildup is formed in the first intended melting region and decreased when the under-buildup is formed in the second intended melting region, and that, in the upper-buildup forming step, the welding current is increased when the upper-buildup is formed in the first intended melting region and decreased when the upper-buildup is formed in the second intended melting region.

[0023] With this configuration, it is possible to prevent the temperature of the first workpiece to be joined from rising sufficiently in the first intended melting region, which would result in poor penetration of the second welding rod, and it is possible to prevent the temperature of the second workpiece to be joined from rising too much in the second intended melting region.

[0024] A dissimilar metal welding method according to a sixth aspect of the present invention can be configured such that, in the welding rod preparation step, the first welding rod and the second welding rod are attached to the welding rod holder according to any one of the first to third aspects of the present invention, and, in the weld bead formation step, the first welding rod and the second welding rod are selectively used by operating the welding rod holder during welding.

[0025] With the above-described configuration, TIG welding can be performed manually by holding the TIG welding torch and welding rod holder in each hand, which is convenient and does not require expensive automatic welding equipment.

[0026] A dissimilar metal welding method according to a seventh aspect of the present invention is a TIG welding method for welding a first workpiece to be joined and a second workpiece to be joined, which are made of dissimilar metals, the method comprising: a first welding rod made of a metal having an affinity for each of the first workpiece to be joined and the second workpiece to be joined; a second welding rod made of a metal of the same type as the first workpiece to be joined or a metal having an affinity for the first workpiece to be joined and having an affinity for the first welding rod; and a welding rod of the same type as the second welding rod but having an outer diameter larger than the outer diameter of the second welding rod. a welding rod preparation step in which a third welding rod made of the same metal as the first material to be welded is prepared in advance; a welded member preparation step in which the first material to be welded and the second material to be welded are arranged side by side, and a portion of the first material to be welded that is inward by a required width from the side edge of the first material to be welded that is inward by a required width from the side edge of the second material to be welded that is inward by a required width from the side edge of the second material to be welded that is inward by a required width from the side edge of the first material to be welded that is inward by a TIG welding step in which a weld bead that straddles the first and second intended melting regions and extends along the boundary between the first and second materials to be welded. and a weld bead forming step of forming a weld bead by generating an arc discharge between a TIG welding electrode and a base material from start to finish, and moving a heating point on the base material by the arc discharge in the width direction of the weld bead from a melting start point set at a position advanced a required distance from the tip of the weld bead being formed within the first planned melting region to near the inner boundary of the second planned melting region, and at the same time, inserting the first welding rod into a base material molten pool of the first workpiece and a base material molten pool of the second workpiece which are generated by heating by the arc discharge. an underlayment forming step in which an underlayment extending in the width direction of the weld bead is formed by melting and adding the arc discharge; and immediately after the underlayment forming step is completed, the heated point on the base material by the arc discharge is returned to a melting start point set within the first intended melting region near the inner boundary of the first intended melting region and near the start end of the underlayment, and moved on the first workpiece toward the underlayment; and further, the heated point on the base material by the arc discharge is moved onto the underlayment within the first intended melting region and moved on the underlayment in the width direction of the weld bead to near the end of the underlayment;The weld bead can be formed by alternately repeating the steps of: melting the second welding rod into the molten base metal pool of the first material to be joined and the molten base metal pool of the underlayment, which are generated by heating with the arc discharge, until the heated point on the base material by the arc discharge reaches a required distance before the boundary between the first material to be joined and the second material to be joined; and melting the third welding rod into the molten base metal pool of the underlayment, which forms an upper bank portion extending from near the rear boundary of the first intended melting area, over the underlayment, to near the end of the underlayment, when the heated point on the base material by the arc discharge reaches a required distance before the boundary between the first material to be joined and the second material to be joined.

[0027] With the above configuration, a large amount of the second welding rod is required near the boundary between the first workpiece and the second workpiece in the upper buildup formation process. However, by using a third welding rod having a larger outer diameter than the second welding rod instead of the second welding rod, the upper buildup can be formed more efficiently than when the second welding rod is used.

[0028] A method for manufacturing a dissimilar metal joined product according to an eighth aspect of the present invention is a method for manufacturing a dissimilar metal joined product by TIG welding a first material to be joined and a second material to be joined, which are made of dissimilar metals, the thermal conductivity of the first material to be joined being higher than the thermal conductivity of the second material to be joined, and a first welding rod made of a metal having an affinity for each of the first material to be joined and the second material to be joined, and a second welding rod made of a metal of the same type as the first material to be joined or a metal having an affinity for the first material to be joined and having an affinity for the first welding rod are prepared in advance. a rod preparation step, a welded member preparation step in which the first material to be welded and the second material to be welded are arranged side by side, and a portion of the first material to be welded that is inboard a required width from the side edge of the first material to be welded on the side of the second material to be welded is set as a first planned melting region, and a portion of the second material to be welded that is inboard a required width from the side edge of the second material to be welded on the side of the first material to be welded is set as a second planned melting region, and a weld bead formation step in which a weld bead is formed by TIG welding that spans the first planned melting region and the second planned melting region and extends along the boundary between the first material to be welded and the second material to be welded. and in the weld bead forming step, an arc discharge is constantly generated between a TIG welding electrode and a base material, and a heating point on the base material by the arc discharge is moved in the width direction of the weld bead from a melting start point in the first planned melting region, which is set at a position further forward by a required distance from the tip of the weld bead being formed, to near the inner boundary of the second planned melting region, and the first welding rod is melted and added to a base material molten pool of the first workpiece and a base material molten pool of the second workpiece which are generated by heating by the arc discharge. an underlayment forming step of forming an underlayment extending in the width direction of the weld bead; and immediately after the underlayment forming step is completed, returning the heated point on the base material by the arc discharge to a melting start point set within the first intended melting region near the inner boundary of the first intended melting region and near the start end of the underlayment, and moving the heated point on the base material by the arc discharge onto the underlayment within the first intended melting region and moving it along the width direction of the weld bead on the underlayment to near the end of the underlayment,and an upper-bank formation step in which the second welding rod is melted and added to the molten base metal pool of the first workpiece and the molten base metal pool of the underbank portion, which are generated by heating due to the arc discharge, to form an upper-bank portion extending from near the inner boundary of the first intended melting region, over the underbank portion, to near the end of the underbank portion, by alternately repeating these steps to form the weld bead. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a front view of a welding rod holder according to a first embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. 2 is a cross-sectional view taken along the line AA in FIG. [Figure 5] FIG. 2 is a cross-sectional view taken along the arrow BB in FIG. [Figure 6] FIG. 10 is a bottom view showing the movable holding portion of the common receiving roller. [Figure 7] FIG. 10 is a cross-sectional view showing a state in which the common support roller presses the welding rod. [Figure 8] FIG. 1 is an explanatory diagram of TIG welding. [Figure 9] 1 is a flowchart of a dissimilar metal welding method according to a first embodiment of the present invention. [Figure 10] 10 is a flowchart showing a weld bead forming procedure in a weld bead forming step. [Figure 11] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 12] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 13] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 14] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 15] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 16]10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 17] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 18] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 19] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 20] 10A and 10B are explanatory diagrams of a welding operation in a weld bead forming process. [Figure 21] 3 is a photograph showing a cross section of a welded portion according to Example 1. [Figure 22] 10 is a photograph showing the appearance of the welded portion. [Figure 23] FIG. 10 is a plan view of a welding rod holder according to a second embodiment of the present invention. [Figure 24] 24 is a cross-sectional view taken along the line AA in FIG. 23. [Figure 25] FIG. 17 is an explanatory view of a welding operation in a weld bead forming step of a second embodiment, corresponding to FIG. 16 of the first embodiment. [Figure 26] FIG. 10 is a right side view of a welding rod holder according to a third embodiment of the present invention. [Figure 27] 27 is a cross-sectional view taken along the line FF in FIG. 26, showing the right tip portion of the welding rod holder. [Figure 28] FIG. 10 is a right side view showing a state in which a welding rod with a large outer diameter is held. [Figure 29] 24A and 24B are cross-sectional views of an individual operation roller and an individual receiving roller of a welding rod holder according to a third embodiment of the present invention. [Figure 30] FIG. 10 is a cross-sectional view showing a state in which a welding rod with a large outer diameter is held. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the descriptions in this specification and drawings are merely examples for embodying the technical concept of the present invention, and the present invention is not limited thereto. For example, the elements set forth in the claims are not limited to those described in the embodiments. In particular, descriptions of the dimensions, materials, shapes, arrangements, etc. of elements described in the embodiments do not limit the scope of the claims unless otherwise specified. Furthermore, each element constituting the present invention may be a single element formed by combining multiple elements, a single element divided into multiple elements, or multiple elements divided and reconfigured into multiple different elements. Furthermore, the function or processing of each element constituting the present invention may be realized by artificial intelligence to the extent possible. In the following description, the same names and symbols indicate the same or similar components, and detailed descriptions will be omitted as appropriate. Also, the size and positional relationship of components shown in the drawings may be exaggerated for clarity. (welding rod holder)

[0031] A welding rod holder according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 6. The welding rod holder 1 includes a rod-shaped holder body 2 that can be held in one hand. As shown in FIGS. 3 and 4, the holder body 2 comprises a base 21, a side plate 22 fixed to the base 21, and a cover plate 23. The side plate 22 and the cover plate 23 are detachably fixed to the base 21 with machine screws (not shown). The base 21 has a recess 211 at its longitudinal center, and three guide members 3 are provided at both ends of the base 21 to individually slidably hold the welding rods W1, W2, and W3. The guide members 3 are through-holes whose central axes extend longitudinally through the base 21. The three guide members 3 can hold the three welding rods W1, W2, and W3 parallel to one another and pass through the holder body 2.

[0032] Three pairs of individual operation rollers 4, 6, and 8 and individual backing rollers 5, 7, and 9 are provided in a recess 211 in the middle of the base 21. The individual operation rollers 4, 6, and 8 and the individual backing rollers 5, 7, and 9 are rotatably attached at both ends to the base 21 and side plate 22 of the holder main body 2, and are arranged at required intervals in the longitudinal direction of the holder main body 2 so that the individual operation roller 4 and the individual backing roller 5 form a pair to clamp the welding rod W1, the individual operation roller 6 and the individual backing roller 7 form a pair to clamp the welding rod W2, and the individual operation roller 8 and the individual backing roller 9 form a pair to clamp the welding rod W3.

[0033] The individual operation rollers 4, 6, 8 have operation parts 41, 61, 81 on their outer circumferential surfaces, and parts of the operation parts 41, 61, 81 protrude from the holder body 2 through openings 231 formed in the cover plate 23 so that they can be turned with the fingers. In addition, a V-shaped groove is formed in the circumferential direction on the outer circumferential surfaces of the individual operation rollers 4, 6, 8 at a position facing the welding rod W1, W2 or W3 that it delivers.

[0034] The outer peripheries of the individual receiving rollers 5, 7, 9 and the common receiving roller 11 are made of rubber to increase the coefficient of friction and to provide elasticity.

[0035] To pay out welding rod W1 in the direction shown by arrow C in Fig. 1, the thumb of the hand holding holder body 2 is hooked on operating part 41 of individual operation roller 4, and individual operation roller 4 is rotated in the direction shown by arrow D in Fig. 1. Welding rods W2 and W3 can also be paid out in the same way as welding rod W1 by operating corresponding operating parts 61 and 81 to rotate individual operation rollers 6 and 8.

[0036] A set of common operation roller 10 and common backing roller 11 is disposed in a recess 211 in the middle of base 21 at a required distance from individual operation roller 4 and individual backing roller 5 in the longitudinal direction of holder body 2. Common operation roller 10 has an operating portion 101 on its outer circumferential surface, and a portion of operating portion 101 protrudes from holder body 2 through opening 231 so that it can be turned with the fingers of a hand. Only when three welding rods are simultaneously paid out, common operation roller 10 and common backing roller 11 form a pair so as to simultaneously clamp three welding rods W1, W2, and W3. To achieve this, this embodiment is provided with a movable holding portion 12 that holds common backing roller 11 so that it can move toward and away from the common operation roller.

[0037] As shown in Figure 5, in the movable holding part 12, the common receiving roller 11 is rotatably supported at both ends by a movable support 121, one end of a leaf spring 122 is fixed to the bottom of the base 21, the other end of the leaf spring 122 is fixed, and a pressed body 123 is placed on the underside of the leaf spring 122, and an accommodating hole 124 is formed in the axial direction of the common receiving roller 11 in the base 21 and side plate 22 of the holder main body 2, and a through hole 125 is formed in the bottom of the base 21, and the movable support 121 and common receiving roller 11 are accommodated in the accommodating hole 124, and a protrusion 126 formed on the bottom surface of the movable support 121 is inserted into the through hole 125, and the protrusion 126 is connected to the leaf spring 122 and the pressed body 123 with a small screw 127. When no pressing force is being applied to the pressed body 123 toward the common operation roller 10, the common backing roller 11 is slightly separated from the welding rods W1, W2, and W3 as shown in FIG. 3. When a pressing force is being applied to the pressed body 123 toward the common operation roller 10, the leaf spring 122 bends and the movable support 121 approaches the welding rods W1, W2, and W3, causing the common backing roller 11 to come into contact with and press the welding rods W1, W2, and W3 as shown in FIG. 7.

[0038] 1, the thumb of the hand holding the holder body 2 is hooked on the operating portion 101 of the common operating roller 10, and the common operating roller 10 is rotated in the direction shown by the arrow D in Fig. 1, and a pressing force is applied to the pressed body 123 with, for example, the index finger of the hand holding the holder body 2. By using the common operating roller 10 and the common receiving roller 11, when the protruding lengths of the welding rods W1, W2, and W3 from the tip of the welding rod holder 1 become short, the welding rods W1, W2, and W3 can be paid out simultaneously to protrude by the required length, thereby preventing a delay in the supply of the welding rods during welding and resulting in poor welding.

[0039] If necessary, the common operation roller 10 and the common backing roller 11 may be arranged on the holder body 2, for example, in place of the individual operation roller 8 and the individual backing roller 9. Furthermore, the number of welding rods that can be attached to the welding rod holder 1 is not limited to three, and may be two or four. (Dissimilar metal welding method)

[0040] A dissimilar metal welding method according to one embodiment of the present invention will be described with reference to Figures 8 to 20. Figure 8 is an explanatory diagram of TIG welding, Figure 9 is a flowchart of the dissimilar metal welding method, Figure 10 is a flowchart showing the weld bead formation procedure in the weld bead formation step shown in Figure 9, and Figures 11 to 20 are explanatory diagrams of the welding operation in the weld bead formation step. In Figures 11 to 20, (A) is a plan view of the welded portion of the first workpiece M1 and the second workpiece M2, and (B) is a cross-sectional view taken along the arrow EE in (A), both of which are enlarged schematic views of the welded portion. The first workpiece M1 and the second workpiece M2 shown in Figure 8 are side views of the first workpiece M1 and the second workpiece M2 shown in (B) of Figures 11 to 20, viewed from the right. 8 and 11 to 20(A), the dashed dotted line extending from the tip of electrode 14 virtually indicates the center line of the arc discharge between electrode 14 and the base material (first material to be joined M1, second material to be joined M2, etc.), and the tip of this dashed dotted line indicates the heating point of the base material by the arc discharge, and the base material is heated and melted from this heating point. The arrows in Fig. 8 and Fig. 11(A) indicate the direction in which the weld bead WB extends (welding progress direction).

[0041] In FIG. 8, the welding rod holder 1 is the same as that shown in FIGS. 1 to 7 and is used to join a first workpiece M1 and a second workpiece M2, each made of dissimilar metals, by TIG welding. When performing TIG welding, the welding rod holder 1 is held in one hand and a TIG welding torch 13 is held in the other. The torch 13 has a tungsten electrode 14 at its tip. During welding, it receives power from a TIG welding machine (not shown) to generate an arc discharge between the electrode 14 and the base metal, and can also emit inert gas from its tip to isolate the electrode, the base metal, and the molten part of the welding rod from the atmosphere. The torch 13 can be operated with one hand to change the orientation and position of the electrode 14 relative to the base metal, thereby changing the heating point of the base metal due to the arc discharge. The heating point of the base metal due to the arc discharge approximately coincides with the position of the base metal facing the tip of the electrode 14. The torch 13 also has a selector switch (not shown), and by operating this selector switch with the fingers, the magnitude of the arc current during welding can be changed according to the respective thermal conductivities of the first workpiece M1 and the second workpiece M2.

[0042] The dissimilar metal welding method according to the first embodiment of the present invention is a method of TIG welding a first workpiece M1 and a second workpiece M2 made of dissimilar metals, and includes a welding rod preparation step ST1, a workpiece preparation step ST2, and a weld bead formation step ST3, as shown in Fig. 9. By carrying out the dissimilar metal welding method shown in Fig. 9, a dissimilar metal welded product is produced in which the first workpiece M1 and the second workpiece M2 are joined by TIG welding. Note that in Fig. 9, the workpiece preparation step ST2 is carried out after the welding rod preparation step ST1, but in the present invention, either the welding rod preparation step ST1 or the workpiece preparation step ST2 may be carried out first, or they may be carried out simultaneously.

[0043] In the welding rod preparation step ST1, a first welding rod W1 made of a metal that has an affinity for each of the first workpiece M1 and the second workpiece M2, and a second welding rod W2 made of the same type of metal as the first welding rod W1 but that has an affinity for the first welding rod W1, are prepared. The first welding rod W1 and the second welding rod W2 are attached to a welding rod holder 1. The second welding rod W2 may be made of a metal that has an affinity for the first workpiece M1 and also has an affinity for the first welding rod W1.

[0044] In the workpiece preparation step ST2, as shown in FIG. 11(A), a first workpiece M1 and a second workpiece M2 are placed side by side. The thermal conductivity of the first workpiece M1 is assumed to be greater than that of the second workpiece M2. A first planned melting region A1 is defined as a region inward a required width from the side edge of the first workpiece M1 facing the second workpiece M2, and a second planned melting region A2 is defined as a region inward a required width from the side edge of the second workpiece M2 facing the first workpiece M1. In this embodiment, a K-shaped groove G is formed in advance at the side edge of the first workpiece M1 facing the second workpiece M2.

[0045] In the weld bead forming step ST3 shown in Figure 10, a weld bead WB for joining the first workpiece M1 and the second workpiece M2 is formed by TIG welding by alternately repeating an underlayment forming step ST31 and an upper lay portion forming step ST32. This weld bead WB straddles the first planned melting region A1 and the second planned melting region A2 and extends along the boundary Lb between the first workpiece M1 and the second workpiece M2. Furthermore, an arc discharge is constantly generated between the TIG welding electrode 14 and the base metal from the start of weld bead WB formation to the end of weld bead WB formation. Furthermore, in the underlayment forming step ST31 and the upper lay portion forming step ST32, a selector switch on the torch 13 is operated to increase the arc current when the torch 13 is in the first planned melting region and to decrease the arc current when the torch 13 is in the second planned melting region.

[0046] In this embodiment, as shown in FIG. 10, at the start of welding, the first underlayment forming step ST30 is performed, followed by the underlayment forming step ST31, which is then followed by the upper buildup forming step ST32, and thereafter the underlayment forming step ST31 and the upper buildup forming step ST32 are performed alternately and repeatedly, but depending on the situation, the upper buildup forming step ST32 may be performed following the first underlayment forming step ST30.

[0047] 11(A), at the start of welding, the torch 13 is operated so that the heated point on the base metal by the arc discharge is at the welding start point P01 in the first intended melting area A1, and the first workpiece M1 is locally melted around the welding start point P01 to form a base metal molten pool WP10. At this time, the first workpiece M1 to be joined has a high thermal conductivity, so heat easily escapes and the temperature of the heated point does not easily rise even when the base metal is heated by the arc discharge, so the arc current is set large so that the base metal can be melted efficiently.

[0048] When a molten base metal pool WP10 is generated at the welding start point P01, the supply of the first welding rod W1 to the molten base metal pool WP10 begins. The first welding rod W1 at the start of supply is shown by a two-dot chain line in Figure 12.

[0049] Furthermore, once a molten pool WP10 is generated at the welding start point P01, the heating point on the base metal due to the arc discharge is moved from the welding start point P01 to the welding end point P02 in the width direction of the weld bead WB, i.e., in a direction intersecting the extension direction of the weld bead WB. Note that the width direction of the weld bead WB is not limited to a direction that intersects the extension direction of the weld bead WB exactly at right angles.

[0050] While the heating point of the base metal is moving due to the arc discharge, the base metal is continuously melted to form a molten pool, and the first welding rod W1 is supplied to the molten pool. The first welding rod W1 is supplied while being moved in accordance with the movement of the heating point of the base metal due to the arc discharge. During supply, the first welding rod W1 moves from the position indicated by the two-dot chain line near the welding start point P01 in Figure 12(A) to the position indicated by the solid line near the welding end point P02.

[0051] When the heating point of the base material due to the arc discharge during movement comes near the boundary Lb between the first workpiece M1 and the second workpiece M2, the arc current is reduced to prevent the base material molten pool of the second workpiece M2 from melting too much.

[0052] When the heating point of the base material by the arc discharge is within the first planned melting area A1, the first workpiece M1 becomes the base material, and the base material melts to form a base material molten pool WP10. Then, by supplying the first welding rod W1 to this base material molten pool WP10 and melting it, a molten pool of alloy is formed in which the first workpiece M1 and the first welding rod W1 are mixed together.

[0053] Furthermore, when the heated point of the base material due to the moving arc discharge enters the second intended melting region A2, the second workpiece M2 becomes the base material, melts, and forms a base material molten pool of the second workpiece M2. Then, by supplying the first welding rod W1 to this base material molten pool of the second workpiece M2 and melting it, a molten pool of an alloy in which the second workpiece M2 and the first welding rod W1 are mixed is formed. An underlayment portion WP1 is then formed, where the molten pool of the alloy in which the first workpiece M1 and the first welding rod W1 are mixed together with the molten pool of the alloy in which the second workpiece M2 and the first welding rod W1 are mixed together. In the portion of this underlayment portion WP1 near the boundary Lb between the first workpiece M1 and the second workpiece M2, the first workpiece M1 and the second workpiece M2 are mixed and bonded with the first welding rod W1. The lower part of the underlayer WP1 on the first workpiece M1 side has a higher proportion of the components of the first workpiece M1, and the upper part has a higher proportion of the components of the first welding rod W1; the lower part of the underlayer WP1 on the second workpiece M2 side has a higher proportion of the components of the second workpiece M2, and the upper part has a higher proportion of the components of the first welding rod W1.

[0054] 12(A) , the electrode 14 moves to a position opposite the end point P02, as shown by the solid line, and the underlayment portion WP1 is formed, and the supply of the first welding rod W1 is stopped. This ends the first underlayment portion forming step ST30, and immediately thereafter, the next underlayment portion forming step ST31 begins.

[0055] In the underlayment forming process ST31, first, the electrode 14 is moved so that the heating point of the base material by the arc discharge moves from the end point P02 shown in Figure 12(A) to the melting start point P11 shown in Figure 13(A); at this point, the front edge of the underlayment WP1 becomes the tip WBf of the weld bead, and the melting start point P11 is set at a position where there is no gap between the tip WBf of the weld bead and the underlayment WP1 to be formed this time within the first intended melting region A1, and where the melting start point P11 is a required distance forward from the previous welding start point P01; and since the previous underlayment WP1 is also heated again and melted partially or entirely in the underlayment WP1 formed this time, the first intended melting region A1 contains not only the first material to be joined M1 but also the components of the underlayment WP1 formed last time. Similarly, the second intended melting region A2 contains not only the second material to be joined M2 but also the components of the underlayment WP1 formed last time, which is different from the initial underlayment forming process ST30.

[0056] 14, the electrode 14 moves to a position opposite the end point P12, and when the underside deposition portion WP1 is formed, the supply of the first welding rod W1 is stopped. This ends the underside deposition portion forming step ST31, and immediately thereafter, the upper side deposition portion forming step ST32 begins.

[0057] In the upper buildup forming step ST32, first, the electrode 14 is moved so that the heating point of the base metal by the arc discharge moves from the end point P12 shown in Fig. 14(A) to the melting start point P21 shown in Fig. 15(A). The tip of the second welding rod W2 is also moved to the vicinity of the melting start point P21 so that the second welding rod W2 can be supplied to the base metal molten pool WP21. When the electrode 14 is positioned opposite the melting start point P21 as shown in Fig. 15, the first workpiece M1 is melted locally around the melting start point P21, thereby forming the base metal molten pool WP21. At this time, the arc current is increased.

[0058] When a molten base metal pool WP21 is formed at the melting start point P21, the supply of the second welding rod W2 to the molten base metal pool WP21 begins. The second welding rod W2 at the start of supply is shown by the two-dot chain line in Figure 16.

[0059] Furthermore, when a base metal molten pool WP21 is formed at the melting start point P21, the electrode 14 is moved so that the heating point on the base metal by the arc discharge moves from the melting start point P21, over the first workpiece M1, over the underlay portion WP1, and to the end point P22 in the width direction of the weld bead WB. While the heating point on the base metal by the arc discharge is moving, the base metal is continuously melted to form a base metal molten pool, and the second welding rod W2 is supplied to the formed base metal molten pool. This supply of the second welding rod W2 is performed by moving the second welding rod W2 in accordance with the movement of the heating point on the base metal by the arc discharge. During supply, the second welding rod W2 moves from the position indicated by the two-dot chain line near the melting start point P21 in FIG. 16(A) to the position indicated by the solid line near the end point P22.

[0060] When the heating point of the base material due to the arc discharge comes near the boundary Lb between the first workpiece M1 and the second workpiece M2 while moving, the arc current is reduced to prevent the base material molten pool of the second workpiece M2 from melting too much.

[0061] 15(A), the melting start point P21 is set within the first intended melting region A1, near its inner boundary L1 and near the tip WBf of the weld bead. Note that the melting start point P21 may be located near the tip WBf of the weld bead, and may be positioned such that the base metal molten pool WP21 of the first workpiece M1 extends forward of the tip WBf of the weld bead within the first intended melting region A1. In that case, in order to prevent the formed upper weld pool WP2 from extending forward of the tip WBf of the weld bead within the second intended melting region A2, it is necessary to change the path of the heating point of the base metal by the arc discharge within the second intended melting region A2 so that it passes over the lower weld pool WP1. The melting start point P11 when forming the lower buildup portion WP1 shown in Figure 13(A) and the melting start point P21 when forming the upper buildup portion WP2 shown in Figure 15(A) are set within the first intended melting region A1 in order to sufficiently melt the first workpiece M1, which is prone to heat loss, and to reliably generate the base material molten pools WP11 and WP21.

[0062] When the heating point of the base material by the arc discharge is within the first planned melting area A1 and has not yet reached the underlying buildup portion WP1, the first workpiece M1 to be joined becomes the base material, which melts to form a base material molten pool WP21. Then, by supplying the second welding rod W2 to this base material molten pool WP21 and melting it, a molten pool of an alloy in which the first workpiece M1 and the second welding rod W2 are mixed is formed.

[0063] Furthermore, when the heated point of the base metal due to the arc discharge during movement reaches the lower metal deposition WP1, the lower metal deposition WP1 becomes the base metal, and the base metal melts, forming a base metal molten pool of the lower metal deposition WP1. Then, by supplying the second welding rod W2 to this base metal molten pool of the lower metal deposition WP1 and melting it, a molten pool of an alloy in which the lower metal deposition WP1 and the second welding rod W2 are mixed is formed. The molten pool of the alloy in which the first workpiece M1 and the second welding rod W2 are mixed together with the molten pool of the alloy in which the lower metal deposition WP1 and the second welding rod W2 are mixed together forms the upper metal deposition WP2. At the boundary between the first workpiece M1 and the lower metal deposition WP1 in the upper metal deposition WP2, the first workpiece M1 and the lower metal deposition WP1 are mixed and bonded with the second welding rod W2. The upper part of the upper buildup portion WP2 and the rear side of the first planned melting area A1 tend to have a higher proportion of the components of the second welding rod W2, the lower part of the upper buildup portion WP2 tends to have a higher proportion of the components of the lower buildup portion WP1, and the rear side of the second planned melting area A2 tends to have a higher proportion of the components of the lower buildup portion WP1.

[0064] 16, the electrode 14 moves to a position opposite the end point P22, and when the upper deposition portion WP2 is formed, the supply of the second welding rod W2 is stopped. This ends the upper deposition portion forming step ST32, and immediately thereafter, the lower deposition portion forming step ST31 is started again.

[0065] This under-deposition forming process ST31 differs from the previous under-deposition forming process ST31 in that the electrode 14 is moved so that the heating point of the base material by the arc discharge moves from the end point P22 shown in Figure 16(A) to the melting start point P11 shown in Figure 17(A), and that the melting start point P11 is set based on the under-deposition portion WP1 generated in the previous under-deposition forming process ST31, rather than the under-deposition portion WP1 generated in the first under-deposition forming process ST30.

[0066] As shown in FIG. 18, when electrode 14 moves to a position opposite end point P12 and lower banking portion WP1 is formed, lower banking portion forming step ST31 ends, and immediately thereafter, upper banking portion forming step ST32 starts again.

[0067] This upper protrusion forming step ST32 differs from the first upper protrusion forming step ST32 in that, as shown in Figure 19, the position of the melting start point P21 is located a required distance forward in the welding progress direction from the melting start point P21 in the upper protrusion WP2 formed in the first upper protrusion forming step ST32, and that, as shown in Figure 20, the trailing edge of the upper protrusion WP2 formed this time overlaps with the leading edge of the upper protrusion WP2 formed previously.

[0068] Therefore, in the weld bead forming step ST3, an arc discharge is constantly generated between the TIG welding electrode 14 and the base metal, and the heated point on the base metal by the arc discharge is moved in the width direction of the weld bead WB from a melting start point P11 in the first intended melting region A1, which is set at a position further forward a required distance from the tip of the weld bead being formed, to near the inner boundary L2 of the second intended melting region A2. At the same time, the first welding rod W1 is melted and added to the molten base metal pool of the first workpiece M1 and the molten base metal pool of the second workpiece M2, which are generated by heating by the arc discharge, to form an underlayment forming step ST31 in which an underlayment portion WP1 extending in the width direction of the weld bead WB is formed. The welding bead WB can be formed by alternately repeating the steps of: returning the base material M1 to the melting start point P21, which is set near the rear boundary of the first melting region A1 and near the start of the underlayer portion WP1, and moving it over the first workpiece M1 toward the underlayer portion WP1; further, moving the heating point on the base material by the arc discharge onto the underlayer portion WP1 within the first melting region A1 and moving it over the underlayer portion WP1 in the width direction of the weld bead to near the end of the underlayer portion WP1; and melting and adding the second welding rod W2 to the base material molten pool of the first workpiece M1 and the base material molten pool of the underlayer portion WP1 created by heating by the arc discharge, thereby forming an upper layer portion WP2 that extends from near the rear boundary L1 of the first melting region A1, over the underlayer portion WP1, to near the end of the underlayer portion WP1.

[0069] By forming the weld bead WB in this manner, the underlay portion WP1 generated using the first welding rod W1 is mainly composed of the second workpiece M2 and the first welding rod W1 melted and mixed together in the second intended melting region A2, and is mainly composed of the first workpiece M1 and the first welding rod W1 melted and mixed together in the first intended melting region A1.

[0070] The upper protrusion WP2 is composed of a portion in the first intended melting region A1 where the first workpiece M1 and the second welding rod W2 are mainly melted and mixed together, and a portion on the second intended melting region A2 side of the upper protrusion WP2 where the lower protrusion WP1 and the second welding rod W2 are mainly melted and mixed together. In the second intended melting region A2, the upper protrusion WP2 is composed of a portion where the lower protrusion WP1 and the second welding rod W2 are mainly melted and mixed together.

[0071] As a result, in the width direction of the weld bead WB, the side facing first workpiece M1 contains more of the metal component of the first workpiece M1, and the side facing second workpiece M2 contains more of the metal component of the second workpiece M2; the lower part of the weld bead WB contains more of the metal component of the first workpiece M1 in the first planned melting region A1, and more of the metal component of the second workpiece M2 in the second planned melting region A2; the upper part of the weld bead WB contains more of the metal component of the first workpiece M1 because the second welding rod W2 is made of the same type of metal as the first workpiece M1; and the middle part of the weld bead WB in the thickness direction contains more of the metal component of the first welding rod W1. Therefore, when looking at the weld bead WB as a whole, the metal component gradually changes in the vertical and width directions.

[0072] The lower weld portion WP1 and the upper weld portion WP2 fuse together and become one unit, extending in the width direction of the weld bead WB and spanning the first planned weld region A1 and the second planned weld region A2. The lower weld portion WP1, which is directly fused to the second workpiece M2 and extends to the first planned weld region A1, and the upper weld portion WP2, which is directly fused to the first workpiece M1 and extends to the second planned weld region A2, are aligned in the direction of welding, so that the boundaries between the lower weld portion WP1 and the upper weld portion WP2, which are adjacent in the extension direction of the weld bead WB, extend in the width direction of the weld bead. Therefore, when a tensile load is applied to the weld portion between the first workpiece M2 and the second workpiece M1, the ratio of the cross-sectional area of ​​the boundary portion created by welding to the cross-sectional area of ​​the entire weld portion that receives the tensile load is small, and even if the boundary portion has a low tensile strength, the tensile strength of the weld portion is only slightly reduced. Therefore, even if a boundary portion with low mechanical strength occurs between the previously generated lower weld portion WP1 and upper weld portion WP2 and the newly generated lower weld portion WP1 and upper weld portion WP2 during welding due to insufficient heating or the like, the tensile stress acting on the weld portion is significantly reduced compared to when the boundary portion extends in the weld bead elongation direction as in the conventional case, and the decrease in mechanical strength of the weld portion can be kept small, making it possible to obtain a dissimilar metal welded product of the first weld material M1 and the second weld material M2 with sufficient mechanical strength.

[0073] Furthermore, even if a boundary is formed between the previously formed lower weld portion WP1 or upper weld portion WP2 and the currently formed lower weld portion WP1 or upper weld portion WP2 due to insufficient melting of the two, the boundary extends in the width direction of the weld bead WB, so when a potential difference is applied between the first workpiece M1 and the second workpiece M2 to pass an electric current, the boundary portions that extend in the width direction of the weld bead and cause an increase in electrical resistance will line up in the extension direction of the weld bead, and the electrical resistance of all the boundary portions will act as a combined resistance when the electrical resistances of the individual boundary portions are connected in parallel. Therefore, the increase in electrical resistance of the weld can be sufficiently suppressed compared to the conventional case in which there are many boundary portions that extend in the longitudinal direction of the weld bead WB and the electrical resistance of all the boundary portions acts as a combined resistance when the electrical resistances of the individual boundary portions are connected in series. [Example]

[0074] A 5 mm-thick copper plate made of 99.9% pure copper was used as the first joined material M1, a 3 mm-thick stainless steel plate made of stainless steel (SUS304) was used as the second joined material M2, a 2 mm-diameter pure nickel rod was used as the first welding rod W1, and a 2 mm-diameter pure copper rod was used as the second welding rod. The first and second joined materials M1 and M2 were joined using the first and second welding rods W1 and W2 by the dissimilar metal welding method of the present invention. As a result, a dissimilar metal joined product having the welded portion shown in FIGS. 21 and 22 was obtained. FIG. 21 shows the appearance of the welded portion between the first and second joined materials M1 and M2, and FIG. 22 shows a cross-section of the weld bead at the welded portion. This welded portion between the copper plate and the stainless steel plate exhibited good mechanical strength and electrical properties. This welding method can suppress an increase in electrical resistance in the welded area, and is therefore effective for producing dissimilar metal joined products in which electricity needs to flow between the first material to be joined M1 and the second material to be joined M2 during use, such as for producing base plates used in copper refining. Second Embodiment

[0075] FIG. 23 is a plan view of a welding rod holder according to a second embodiment of the present invention, and FIG. 24 is a cross-sectional view taken along the line AA in FIG. 23 . In FIG. 24 , the welding rod holder 1 is shown in the same position as the welding rod holder 1 in FIG. 4 . This welding rod holder 1 differs from the welding rod holder 1 of the first embodiment in that the three welding rods W1, W2, and W3 it can hold are not all the same in outer diameter. That is, among the three welding rods W1, W2, and W3, the first welding rod W1 and the second welding rod W2 have the same outer diameter, but the third welding rod W3 has a larger outer diameter than the other two welding rods W1 and W2. Therefore, the through hole 33 corresponding to the third welding rod W3 has an inner diameter that matches the outer diameter of the third welding rod W3, and the individual operation roller 6 has a V-shaped groove that matches the outer diameter of the third welding rod W3. The through holes 31 and 32 have an inner diameter that fits the outer diameter of the welding rods W1 and W2, and the individual operation rollers 4 and 8 have a V-shaped groove that fits the outer diameter of the welding rods W1 and W3, respectively. A U-shaped groove may be formed instead of this V-shaped groove.

[0076] The dissimilar metal welding method according to the second embodiment of the present invention differs from the first embodiment in that, in the welding rod preparation step ST1, a first welding rod W1 made of a metal that has affinity for each of the first workpiece M1 and the second workpiece M2, a second welding rod W2 made of the same type of metal as the first workpiece M1 and that has affinity for the first welding rod, and a third welding rod W3 made of the same type of metal as the second welding rod W2 but with a different outer diameter than the second welding rod W2 are attached to the welding rod holder 1 shown in Figures 23 and 24, and in that, in the upper weld portion formation step ST32 of the weld bead formation step ST3, the second welding rod W2 and the third welding rod W3 are switched between use while forming the upper weld portion WP2.

[0077] In the second embodiment, the second welding rod W2 and the third welding rod W3 correspond to the second welding rod W2 in the first embodiment, and function similarly to the second welding rod W2 in the first embodiment in steps other than the upper projection forming step ST32. The third welding rod W3 has a larger outer diameter than the first welding rod W1 and the second welding rod W2 in the second embodiment.

[0078] Fig. 25 is an explanatory view of the welding operation in the top buildup formation step ST32 of the dissimilar metal welding method according to the second embodiment of the present invention, and corresponds to Fig. 16 in the first embodiment. In this top buildup formation step ST32, as the heated point of the base metal by the arc discharge moves from the melting start point P21 toward the melting end point P22, the second welding rod W2 is supplied to the molten base metal pool until the heated point of the base metal by the arc discharge reaches the welding rod switching point P3, which is a required distance before the boundary Lb between the first workpiece M1 and the second workpiece M2, and then the third welding rod W3 is supplied to the molten base metal pool after passing the welding rod switching point P3, which is different from the first embodiment. The reason for switching between the second welding rod W2 with a smaller outer diameter and the third welding rod W3 with a larger outer diameter at the welding rod switching point P3 is to eliminate the fact that, if the third welding rod W3 is not used, a large amount of the second welding rod W2 would be needed near the boundary Lb between the first workpiece M1 and the second workpiece M2, but with the second welding rod W2 with a smaller outer diameter, it would take a long time to melt it into the base metal molten pool and add it, which would reduce efficiency. The welding rod switching point P3 is set by the welder so that the top weld portion WP2 is formed appropriately, observing the formation state of the top weld portion WP2. (Third embodiment)

[0079] A welding rod holder according to a third embodiment of the present invention will be described with reference to Figures 26 to 30. This welding rod holder 1 differs from the welding rod holder 1 of the second embodiment mainly in that it allows for easy replacement of third welding rods W3 with different outer diameters. The guide unit 3 of this welding rod holder 1 includes a through-hole 34 provided in the holder body 2 and having an inner diameter large enough to accommodate a welding rod of the largest conceivable diameter; a movable body 35 having a V-shaped groove 351 at its tip; a guide groove 36 that accommodates the movable body 35 and guides it in a direction perpendicular to the longitudinal direction of the third welding rod W3; and a movable body advance / retract unit 37 that advances the movable body 35 until the V-shaped groove engages with the outer circumferential surface of the third welding rod W3 and the outer circumferential surface of the third welding rod W3 opposite the movable body 35 abuts the inner circumferential surface of the through-hole 34. The guide units 3 are provided at the front and rear ends of the base 21 of the holder body 2, respectively, for each of the welding rods W1, W2, and W3. In this embodiment, the movable body advance / retract portion 37 is made of a compression coil spring 371 that presses and biases the movable body 35 against the third welding rod W3. A cover plate 24 for holding the movable body 35 in the guide groove 36 is fixed to the end face of the base 21 of the holder main body 2, and the cover plate 24 has an elongated hole 241 that receives the knob 352 and a through hole 242 with the same inner diameter and at the same position as the through hole 34.

[0080] 26 holds a third welding rod W3 having a small outer diameter, and to replace the third welding rod W3 having a small outer diameter with a third welding rod W3 having a large outer diameter as shown in FIG. 28, the third welding rod W3 having a small outer diameter is removed, and then the knob 352 is manually pulled up to retract the movable body 35 upward from the through-hole 34. In this state, the third welding rod W3 having a large outer diameter is inserted into the through-hole 34. After insertion, when the knob 352 is released, the movable body 35 is lowered by the action of the compression coil spring 371, and the side surface of the V-shaped groove 351 abuts against the outer peripheral surface of the third welding rod W3, and the third welding rod W3 is sandwiched between the movable body 35 and the lower part of the inner peripheral surface of the through-hole 34. The spring constant of the compression coil spring 371 is selected so that the frictional force between the third welding rod W3 and the through hole 34, which is generated by the pressing force of the compression coil spring 371, is large enough not to prevent the third welding rod W3 from being removed. Note that Figure 28 shows the end faces of the guide part 3 and the base 21 without the cover plate 24.

[0081] 29 includes a support shaft 62 held by the base 21 and side plate 22 of the holder body 2, a pair of roller bodies 63 each having a truncated cone-shaped inclined surface 631 facing each other and slidably mounted on the support shaft 62, and compression coil springs 64, 64 that bias the pair of roller bodies 63 toward each other. The individual receiving roller 7 also includes a similar support shaft 72, a pair of roller bodies 73 each having a truncated cone-shaped inclined surface 731, and compression coil springs 74, 74.

[0082] When the third welding rod W3 is held by the guide portion 3 of the holder body 2, the third welding rod W3 is inserted between the inclined surfaces 631 of the pair of roller bodies 63 of the individual operation rollers 6 and the inclined surfaces 731 of the roller bodies 73 of the individual receiving rollers 7, and the upper outer peripheral surface of the third welding rod W3 is clamped in the left-right direction by the inclined surfaces 631 of the pair of roller bodies 63, while the lower outer peripheral surface of the third welding rod W3 is clamped in the left-right direction by the inclined surfaces 731 of the pair of roller bodies 73 and is also clamped in the up-down direction by the inclined surfaces 631 of the pair of roller bodies 63 and the inclined surfaces 731 of the pair of roller bodies 73. In this state, the third welding rod W3 can be moved in the longitudinal direction by placing fingers on the outer peripheral surface of the roller body 63 of the individual operation roller 6 and turning the roller body 63. When the welding rod holder 1 holds a third welding rod W3 having a large outer diameter as shown in FIG. 30 instead of the third welding rod W3 having a small outer diameter as shown in FIG. 29, the pair of roller bodies 63 and the pair of roller bodies 73 move backward along the support shafts 62 and 72 against the pressing forces of the compression coil springs 64, 64 and the compression coil springs 74, 74, and maintain a state in which the third welding rod W3 is clamped in the vertical and horizontal directions. [Industrial Applicability]

[0083] The welding rod holder of the present invention can be used not only for TIG welding but also for other welding and brazing processes that do not consume electrodes.

[0084] 1...Welding rod holder 2...Holder body; 21...Base; 22...Side plate; 23...Cover plate; 24...Cover plate; 211...Recess; 231...Opening; 241...Slot; 242...Through hole in cover plate 3...Guide portion; 31...First through hole; 32...Second through hole; 33...Third through hole; 34...Through hole; 35...Movable body; 36...Guide groove; 37...Movable body advance / retract portion; 351...V-shaped groove; 352...Knob; 371...Compression coil spring 4... Individual operation roller; 41... Operation unit 5...Individual support roller 6... Individual operating roller; 61... Operating part; 62... Support shaft; 63... Roller body; 64... Compression coil spring; 631... Inclined surface 7... Individual support roller; 72... Support shaft; 73... Roller body; 74... Compression coil spring; 731... Inclined surface 8... Individual operating roller; 81... Operating unit 9...Individual support roller 10...Common operation roller 11...Common receiving roller 12... Movable holding portion; 121... Movable support; 122... Leaf spring; 123... Pressed body; 124... Receiving hole; 125... Through hole; 126... Convex portion; 127... Machine screw 13...Torch 14...Electrode A1: First melting area A2: Second planned melting area L1: The inner boundary of the first melting area L2: The inner boundary of the second planned melting area Lb: Boundary between the first and second materials to be welded M1…First material to be joined M2…Second material to be joined WP1…Lower fill part WP2: Upper mound P01: Welding start point P11, P21...Start of melting P02, P12, P22...End point P3: Welding electrode switching point ST1: Welding rod preparation process ST2…To be joined material preparation process ST3... Weld bead forming process; ST30... First underlay forming process; ST31... Underlay forming process; ST32... Toplay forming process W1...First welding rod W2: Second welding rod W3...Third welding rod WB...weld bead; WBf...tip of weld bead

Claims

1. A rod-shaped holder body that can be held in one hand, a plurality of guide portions provided on the holder body for individually slidably holding a plurality of welding rods so as to penetrate the holder body; a plurality of pairs of individual operating rollers and individual receiving rollers arranged in a row in the longitudinal direction of the holder body so as to be manually rotated, the individual operating rollers and individual receiving rollers individually clamping the outer peripheral surface of the welding rod held by the guide portion in pairs; A welding rod holder comprising:

2. 2. The welding rod holder of claim 1, A welding rod holder characterized in that the holder body is provided with the individual operation rollers and individual support rollers, as well as a common operation roller and a common support roller arranged in a row in the longitudinal direction of the holder body, so that the outer peripheries of the multiple welding rods can be clamped and rotated with the fingers only when the multiple welding rods are fed out simultaneously.

3. 2. The welding rod holder of claim 1, 2. A welding rod holder according to claim 1, wherein the outer diameter of at least one of the plurality of welding rods is different from the outer diameters of the other welding rods.

4. A dissimilar metal welding method for TIG welding a first workpiece and a second workpiece made of dissimilar metals, comprising: The thermal conductivity of the first material to be joined is greater than the thermal conductivity of the second material to be joined, a welding rod preparation step of preparing in advance a first welding rod made of a metal having an affinity for each of the first material to be joined and the second material to be joined, and a second welding rod made of the same metal as the first material to be joined or a metal having an affinity for the first material to be joined and having an affinity for the first welding rod; a welded member preparation process in which the first and second workpieces are arranged side by side, and a portion of the first workpiece that is inward by a required width from the side edge of the first workpiece on the side of the second workpiece is set as a first intended melting region, and a portion of the second workpiece that is inward by a required width from the side edge of the second workpiece on the side of the first workpiece is set as a second intended melting region; a weld bead forming step of forming a weld bead by TIG welding, the weld bead spanning the first intended melting region and the second intended melting region and extending along a boundary portion between the first workpiece and the second workpiece, In the weld bead forming step, Arc discharge is generated between the TIG welding electrode and the base material throughout the process, an underlayment forming step of moving a heating point on a base material by the arc discharge from a melting start point in the first intended melting region, which is set at a position further forward a required distance from the tip of the weld bead being formed, to near the inner boundary of the second intended melting region in the width direction of the weld bead, and melting the first welding rod into a molten base material pool of the first workpiece and a molten base material pool of the second workpiece, which are generated by heating by the arc discharge, thereby forming an underlayment extending in the width direction of the weld bead; an upper build-up forming step in which, immediately after the underbuild-up forming step is completed, the heated point on the base material by the arc discharge is returned to a melting start point set within the first intended melting region near the inner boundary of the first intended melting region and near the start of the underbuild-up, and moved over the first workpiece toward the underbuild-up; further, the heated point on the base material by the arc discharge is moved over the underbuild-up within the first intended melting region, and moved over the underbuild-up in the width direction of the weld bead to near the end of the underbuild-up; and the second welding rod is melted and added to the molten base material pool of the first workpiece and the molten base material pool of the underbuild-up, which are generated by heating with the arc discharge, thereby forming an upper build-up extending from near the inner boundary of the first intended melting region, over the underbuild-up, to near the end of the underbuild-up; and forming the weld bead by alternately repeating the steps of:

5. The dissimilar metal welding method according to claim 4, In the underlayment forming step, a welding current is increased when the underlayment is formed in the first intended melting region, and a welding current is decreased when the underlayment is formed in the second intended melting region; a welding current for forming the upper protrusion in the first intended melting region and a welding current for forming the upper protrusion in the second intended melting region, the welding current being increased in the upper protrusion forming step;

6. The dissimilar metal welding method according to claim 4, In the welding rod preparation step, the first welding rod and the second welding rod are attached to the welding rod holder according to any one of claims 1 to 3, a welding rod holder for selectively using the first welding rod and the second welding rod during welding;

7. A dissimilar metal welding method for TIG welding a first workpiece and a second workpiece made of dissimilar metals, comprising: The thermal conductivity of the first material to be joined is greater than the thermal conductivity of the second material to be joined, a welding rod preparation process in which a first welding rod made of a metal having an affinity for each of the first material to be joined and the second material to be joined, a second welding rod made of the same metal as the first material to be joined or a metal having an affinity for the first material to be joined and having an affinity for the first welding rod, and a third welding rod made of the same metal as the second welding rod and having an outer diameter larger than that of the second welding rod; a welded member preparation process in which the first and second workpieces are arranged side by side, and a portion of the first workpiece that is inward by a required width from the side edge of the first workpiece on the side of the second workpiece is set as a first intended melting region, and a portion of the second workpiece that is inward by a required width from the side edge of the second workpiece on the side of the first workpiece is set as a second intended melting region; a weld bead forming step of forming a weld bead by TIG welding, the weld bead spanning the first intended melting region and the second intended melting region and extending along a boundary portion between the first workpiece and the second workpiece, In the weld bead forming step, Arc discharge is generated between the TIG welding electrode and the base material throughout the process, an underlayment forming step of moving a heating point on a base material by the arc discharge in a width direction of the weld bead from a melting start point set at a position advanced a required distance from the tip of the weld bead being formed within the first intended melting region to near the inner boundary of the second intended melting region, and melting the first welding rod into a molten base material pool of the first workpiece and a molten base material pool of the second workpiece created by heating by the arc discharge, thereby forming an underlayment extending in the width direction of the weld bead; Immediately after the underlayment forming step is completed, the heated point on the base material by the arc discharge is returned to the melting start point set in the first planned melting region near the inner boundary of the first planned melting region and near the start end of the underlayment, and moved on the first workpiece toward the underlayment, and further the heated point on the base material by the arc discharge is moved onto the underlayment within the first planned melting region and moved on the underlayment in the width direction of the weld bead to near the end of the underlayment, and an upper bank formation step of melting the second welding rod into the molten base metal pool of the first workpiece and the molten base metal pool of the underlayment, which are generated by heating with the arc discharge, until the second workpiece is located a required distance before the boundary with the second workpiece, and then melting the third welding rod into the molten base metal pool of the underlayment when the heated point on the base material by the arc discharge passes a required distance before the boundary between the first workpiece and the second workpiece, thereby forming an upper bank extending from near the rear boundary of the first intended melting region, over the underlayment, to near the end of the underlayment; and forming the weld bead by alternately repeating the steps of:

8. A method for manufacturing a dissimilar metal joined product, which is formed by joining a first workpiece and a second workpiece made of dissimilar metals by TIG welding, comprising: The thermal conductivity of the first material to be joined is greater than the thermal conductivity of the second material to be joined, a welding rod preparation step of preparing in advance a first welding rod made of a metal having an affinity for each of the first material to be joined and the second material to be joined, and a second welding rod made of the same metal as the first material to be joined or a metal having an affinity for the first material to be joined and having an affinity for the first welding rod; a welded member preparation process in which the first and second workpieces are arranged side by side, and a portion of the first workpiece that is inward by a required width from the side edge of the first workpiece on the side of the second workpiece is set as a first intended melting region, and a portion of the second workpiece that is inward by a required width from the side edge of the second workpiece on the side of the first workpiece is set as a second intended melting region; a weld bead forming step of forming a weld bead by TIG welding, the weld bead spanning the first intended melting region and the second intended melting region and extending along a boundary portion between the first workpiece and the second workpiece, In the weld bead forming step, Arc discharge is generated between the TIG welding electrode and the base material throughout the process, an underlayment forming step of moving a heating point on a base material by the arc discharge from a melting start point in the first intended melting region, which is set at a position further forward a required distance from the tip of the weld bead being formed, to near the inner boundary of the second intended melting region in the width direction of the weld bead, and melting the first welding rod into a molten base material pool of the first workpiece and a molten base material pool of the second workpiece, which are generated by heating by the arc discharge, thereby forming an underlayment extending in the width direction of the weld bead; an upper-layer build-up forming step in which, immediately after the underlayer build-up forming step is completed, the heated point on the base material by the arc discharge is returned to a melting start point set near the innermost boundary of the first intended melting region and near the beginning of the underlayer build-up in the first intended melting region, and moved over the first workpiece toward the underlayer build-up; further, the heated point on the base material by the arc discharge is moved over the underlayer build-up within the first intended melting region, and moved over the underlayer build-up in the width direction of the weld bead to near the end of the underlayer build-up; and the second welding rod is melted and added to the molten base material pool of the first workpiece and the molten base material pool of the underlayer build-up created by heating with the arc discharge, thereby forming an upper-layer build-up extending from near the innermost boundary of the first intended melting region, over the underlayer build-up, to near the end of the underlayer build-up; and forming the weld bead by alternately repeating the steps of:

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