Disclosed is an apparatus for arc welding, comprising: a torch body comprising a power supply line and a gas supply line; two or more metal segments movable relative to one another being sized and shaped to surround a seam between two elongated objects to be welded together, the two or more metal segments being in electrical communication with the power supply line; and a gas jacket attached to each of the metal segments.

An electrode in which the metallurgical structure of the active surface includes incoherent chromium precipitates, more than 90% of which have a surface of projection of less than 1 m.sup.2, the incoherent chromium precipitates having a size at least between 10 and 50 nm. The electrode further has a fibrous structure that is visible in a cross-section of the active surface of the electrode following surfacing and chemical etching. The fibrous structure includes a plurality of radial fibers having a thickness of less than 1 mm and of a substantially central fiberless region that has a diameter of less than 3 mm. The electrical conductivity of the electrode is greater than 85% IUPAC. The method for obtaining the electrode in a continuous casting process as well as to a use of the electrode in a resistive spot welding process.

An electrode unit for inert gas welding by means of a non-consumable. The electrode unit includes an electrode holder and an electrode held firmly and undetachably in the electrode holder and having an electrode tip at a front end. The electrode protrudes beyond the electrode holder by means of the electrode tip on a first longitudinal end of the electrode holder. A gas guide channel is formed in the electrode holder, with an inlet opening located toward a second longitudinal end of the electrode holder. At least one outlet opening is oriented transversely with respect to a longitudinal extent of the electrode holder and located offset from the inlet opening, when viewed in the direction of the longitudinal extent, toward the first longitudinal end. The electrode unit is able to be efficiently cooled during the welding operation and has a reduced tendency to jam or wedge due to thermal expansions.

An electrode tip for resistance spot welding includes a main body with tip and base portions. The tip portion has a bottomed and substantially cylindrical shape. The base portion has a substantially cylindrical shape and merges into the tip portion. The main body is made of a copper alloy such as chromium copper. The tip portion has a bottom part and a barrel part. The bottom part has a pressure-contact surface that is not recessed with respect to a workpiece to be pressed. The barrel part has a substantially cylindrical shape and merges into the bottom part. The electrode tip may have an inner diameter ratio (inner diameter of the barrel part to an outer diameter of the base portion) of 0.4 to 0.6, and may also have a bottom thickness ratio (thickness of the bottom part to the outer diameter of the base portion) of 0.15 to 0.5.

An electrode in which the metallurgical structure of the active surface includes incoherent chromium precipitates, more than 90% of which have a surface of projection of less than 1 m.sup.2, the incoherent chromium precipitates having a size at least between 10 and 50 nm. The electrode further has a fibrous structure that is visible in a cross-section of the active surface of the electrode following surfacing and chemical etching. The fibrous structure includes a plurality of radial fibers having a thickness of less than 1 mm and of a substantially central fiberless region that has a diameter of less than 3 mm. The electrical conductivity of the electrode is greater than 85% IUPAC. The method for obtaining the electrode in a continuous casting process as well as to a use of the electrode in a resistive spot welding process.

A method of joining together adjacent overlapping copper workpieces by way of resistance spot welding involves providing a workpiece stack-up that includes a first copper workpiece and a second copper workpiece that lies adjacent to the first copper workpiece. The faying surface of the first copper workpiece includes a projection that ascends beyond a surrounding base surface of the faying surface and makes contact, either directly or indirectly, with an opposed faying surface of the second copper workpiece. Once provided, a compressive force is applied against the first and second copper workpieces and an electric current is passed momentarily through the first and second copper workpieces. The electric current initially flows through the projection to generate and concentrate heat within the projection prior to the projection collapsing. This concentrated heat surge allows a metallurgical joint to be established between the first and second copper workpieces.

A TIG welding filler metal is provided that has a composition including, by mass %, C: 0.20 to 0.80%, Si: 0.15 to 0.90%, Mn: 15.0 to 30.0%, P: 0.030% or less, S: 0.030% or less, Cr: 6.0 to 15.0%, and N: 0.120% or less, the balance being Fe and incidental impurities. Where necessary, the filler metal may contain one or two selected from Ni and Mo, may further contain one, or two or more selected from V, Ti, and Nb, and may additionally contain one, or two or more selected from Cu, Al, Ca, and REM. This configuration reduces the occurrence of welding cracks during TIG welding, that is, realizes excellent hot crack resistance, and allows for easy production of a weld joint having high strength and excellent cryogenic impact toughness.

A domed copper electrode tip has a refractory insert inserted thereinto extending from the apogee of the dome into the interior of the electrode. The refractory insert is, preferably, a tungsten insert which is force-fitted into the interior of the electrode tip.

A method of joining together adjacent overlapping copper workpieces by way of resistance spot welding involves providing a workpiece stack-up that includes a first copper workpiece and a second copper workpiece that lies adjacent to the first copper workpiece. The faying surface of the first copper workpiece includes a projection that ascends beyond a surrounding base surface of the faying surface and makes contact, either directly or indirectly, with an opposed faying surface of the second copper workpiece. Once provided, a compressive force is applied against the first and second copper workpieces and an electric current is passed momentarily through the first and second copper workpieces. The electric current initially flows through the projection to generate and concentrate heat within the projection prior to the projection collapsing. This concentrated heat surge allows a metallurgical joint to be established between the first and second copper workpieces.

An arc welding/brazing process is disclosed that is useful to join together a first copper piece and a second copper piece without damaging more heat-sensitive materials that may be located nearby is disclosed. The arc welding/brazing process includes using a non-consumable electrode wire, which electrically communicates with a weld control in a straight polarity orientation, to strike an arc across a gap established between a leading tip end of the electrode wire and the first copper piece. The current that flows through the arc when the arc is established heats the first copper piece such that the first copper piece becomes joined to a second copper piece. The joint between the first copper piece and the second copper piece may be an autogenous weld joint or a braze joint.