Abstract: A method for welding copper includes steps of spraying an inert gas to copper that is an object to be welded to cover a portion to be welded on the copper with the inert gas, and performing electrical discharge to weld the portion to be welded. The inert gas that covers the portion to be welded passes a dehumidifying process that removes moisture contained in the inert gas.

Abstract: A welding system including a welding power source including power conversion circuitry adapted to receive primary power and to convert the primary power to a weld power output for use in a welding operation and a controller communicatively coupled to the welding power source are provided. The controller is adapted to determine a statistical signature of at least one parameter of a welding process and to utilize the statistical signature to determine at least one of an electrode type, an electrode diameter, and a shielding gas type during the welding operation.

Abstract: Disclosed is a method for hybrid welding in which a laser beam is applied to the welding position of objects to be welded, and at the same time, a first wire is fed to the welding position so as to perform arc welding using an arc generated between the objects to be welded and the first wire. In this method, one or more second wires are fed to a molten weld pool formed by the laser beam and arc welding, thereby increasing the amount of welding without increasing the arc current.

Abstract: A welding system is provided which can weld in narrow gap thick walled work pieces, the welding system having a magnetic field unit which contains a magnetic coil, a magnetic field probe, and a shielding gas tube and nozzle. The unit having a shape and configuration which delivers the shielding gas and magnetic field close to the welding arc so as to provide for a shielded welding arc which is manipulated as desired by the magnetic field.

Abstract: An alloy comprising about 0.5 weight percent to about 2 weight percent carbon, about 15 weight percent to about 30 weight percent chromium, about 4 weight percent to about 12 weight percent nickel, up to about 3 weight percent manganese, up to about 2.5 weight percent silicon, up to about 1 weight percent zirconium, up to about 3 weight percent molybdenum, up to about 3 weight percent tungsten, up to about 0.5 weight percent boron, up to about 0.5 weight percent impurities, and iron.

Abstract: A wire is adopted to hardfacing MIG-arc welding using a pure argon gas as a shielding gas. The wire is a flux-cored wire prepared through drawing a steel hoop or steel pipe as a sheath in which a flux is filled. The flux contains, based on the total mass of the wire, C: 0.12 to 5.00 percent by mass, Si: 0.50 to 3.00 percent by mass, Mn: 0.30 to 20.00 percent by mass, P: 0.050 percent by mass or less, S: 0.050 percent by mass or less, and at least one of TiO2, ZrO2, and Al2O3 (TiO2+ZrO2+Al2O3) in a total content of 0.10 to 1.20 percent by mass and has a total content of silicon and manganese (Si+Mn) of 1.20 percent by mass or more. The wire has a ratio of the total mass of the flux to the mass of the wire of 5 to 30 percent by mass.

Abstract: A method for root pass welding steel plate and pipe is provided that uses pulse arc welding having a current pulse waveform exhibiting a low constant background current and fixed frequency. The welding process may be performed without a backer or backing material.

Abstract: A method for welding dissimilar metals involved selecting a steel having approximately 1-3 weight % chromium (Cr) content and a first coefficient of thermal expansion at a predetermined first temperature for a first part [14], selecting a nickel-based alloy having a second coefficient of thermal expansion at a second predetermined temperature for a second part [12], the first and second coefficients of thermal expansion having a maximum difference of approximately 2-3% when the first predetermined temperature is approximately 500-550° C. and the second predetermined temperature is approximately 600-650° C., then welding the first part to the second part [12].

Abstract: The present invention provides a flux cored wire for gas shielded arc welding of high-strength steel having proof stress of 690 MPa or more, which is capable of all-position welding with a higher efficiency and exhibits an excellent cracking resistance. The flux cored wire comprising a steel sheath, and a flux filled therein, wherein the flux cored wire comprises, by mass % with respect to the total mass of the flux cored wire: C: 0.03 to 0.10%, Si: 0.25 to 0.7%, Mn: 1.0 to 3.0%, Ni: 1.0 to 3.5%, B: 0.001 to 0.015%, Cr: limited to 0.05% or less, and Al: limited to 0.05% or less, and in the flux, TiO2: 2.5 to 7.5%, SiO2: 0.1 to 0.5%, ZrO2: 0.2 to 0.9%, and Al2O3: 0.1 to 0.4%; and the remainder comprising: Fe, arc stabilizer, and unavoidable impurities; and wherein the total mount of hydrogen in the flux cored wire is in 15 ppm or less.

Abstract: The TIG welding methods of the present invention include generating an electric arc between an electrode and an object to weld the object, wherein a first shielding gas including an inert gas flows toward the welded object surrounding the electrode, a second shielding gas containing an oxidative gas flows toward the welded object along a periphery of the first shielding gas, and the concentration of the oxidative gas in the second shielding gas is set such that the oxygen concentration in the welded metal portion of the welded object is within a range of 70 to 220 wt. ppm.

Abstract: A device and a method for welding a component are provided. The component is arranged and welded in a chamber. A welding appliance is provided, the welding appliance being arranged outside the chamber.

Abstract: The present invention includes a multi-use welding gun body configured for use in multiple locations along a welding gun assembly. In a particular embodiment, the multi-use welding gun body includes an enclosure forming an exterior surface of the body, the enclosure configured for both receiving a welding wire and a power source and directing the same toward a torch and having a first enclosure end with a wire-receiving aperture extending to an internal block-receiving cavity, the wire receiving aperture shaped to selectively receive a torch and an extension having an orifice containing both welding wire and shielding gas. The block-receiving cavity of the enclosure extends axially with a non-circular profile to a cable-receiving cavity within the housing, the cable-receiving cavity extending longitudinally to the second enclosure end. The second enclosure end includes an aperture forming an end of the cable-receiving cavity. A removable block is positioned within the block-receiving cavity.

Abstract: An air knife system includes a first set of openings and a second set of openings arranged along opposite first and second walls, respectively, of a main body. The first set of openings may be aligned with the second set of openings such that a coupling member may be inserted through each one of the first set of openings and a corresponding one of the second set of openings. The coupling members may be fixedly joined to the first and second sets of openings to maintain a desired width of a discharge slot defined by a first lip extending from the first wall and a second lip extending from the second wall. In one embodiment, the coupling members may be joined to the first and second sets of openings using a welding process.

Abstract: In response to plasma keyhole welding of a workpiece, in the case of which a plasma jet is generated using an electrode, to which a welding current is applied, and at least one process gas, wherein at least one gas composition (22) and/or a gas volume flow rate (20, 21) of the process gas is temporally changed, the gas composition (22) and/or a gas volume flow rate (20, 21) of at least one process gas are temporally changed during a welding process as a function of at least one basic condition (E1, E2) of the welding process

Abstract: The gas-metal arc welding of metal-core wile electrodes in the pure Ar shielding gas for carbon steel, low alloy steel, and ferritic stainless steel is described. Such shielding gas provides several benefits not realized ??the gas-metal arc welding process with solid wires. When compared to standard argon/oxygen containing gas mixtures normally used for metal cored wires, these benefits include reduced silicate islands on the weld surface for improved weld appearance, reduced welding fume, and lower weld spatter, all of which provide easier clean-up after the welding operation. Benefits also include reduced arc penetration desirable for welding on thinner materials or handling poor joint fit-up. Lower voltage requirement further makes it possible to weld on thinner materials. Lower oxygen content in the weld deposits provide better toughness and easier welding in all-positions.

Abstract: A system for welding a tub of a railroad tank car includes a manipulator boom adapted to move with respect to the interior surface of the tank shell. A hybrid laser arc welding head mounted to the manipulator. A supplemental gas metal arc welding head includes dual wires of welding material and is mounted to the manipulator adjacent to the hybrid laser arc welding head. An inductive heating coil is mounted adjacent to the supplemental gas metal arc welding head. The hybrid laser arc welding head welds a seam of the railroad tank car shell with the supplemental gas metal arc welding head following to generally complete filling of a resulting weld joint with welding metal. The supplemental gas metal arc welding head is followed with the inductive heating coil to provide heat to normalize the resulting weld joint.

Abstract: A wear resistant multilayer overlay includes a first layer on at least a surface of an article, and a second layer metallurgically bonded to at least a portion of the first layer. The first layer includes a first continuous metallic matrix and at least one of first hard particles, blocky diamond particles, non-blocky diamond particles, TSP diamond, cubic boron nitride particles, and PCD compacts embedded in the first continuous metallic matrix, wherein the first hard particles are at least one of transition metal carbide particles and boron nitride particles. The second layer includes a second continuous metallic matrix and at least one of second hard particles, blocky diamond particles, non-blocky diamond particles, TSP diamond, cubic boron nitride particles, and PCD compacts, embedded in the second continuous metallic matrix, wherein the second hard particles are at least one of transition metal carbide particles and boron nitride particles. Related methods and articles of manufacture also are disclosed.

Abstract: Control apparatus for a gas-shielded welding arrangement which includes a monitor for logging welding parameters, a gas surge tank, the volume of which is adjustable to take account of the pressure of a gas-supply source, and a lockable device which prevents unauthorised access to a pressure regulator on the surge tank.

Abstract: A new method of process control for fusion welding maintains a controlled weld pool size or volume, for example in some applications a substantially constant weld pool size or volume. The invention comprises a method of linking machine and process variables to the weld pool size or volume in real time, thereby enabling constant weld pool volume control. The invention further comprises a method of using thermal inverse models to rapidly process real-time data and enable models-based control of welding processes so as to implement constant weld pool volume control.

Abstract: A shielding gas (SG) flow controller for an arc welder includes SG input/output with a controllable valve therebetween, and having a control input, and a controller having a first input receiving a welding signal representing arc current and a gas flow setting controller generating a flow setting output based on the welding signal, representing a desired SG flow. Input and output pressure sensors provide SG input and out pressure to second and third controller inputs, respectively. A flow setting output modifier modifies the flow setting output of the gas flow setting controller based on the SG input/output pressure, the welding signal, and a characteristic of the controllable valve into a control signal input to the control input of the controllable gas valve to maintain a substantially constant SG flow corresponding to the flow setting output substantially independent of actual SG input/output pressures.

Abstract: The present invention relates to arc welding torch and a method of extracting fume gas from a welding site. The torch comprises a metal electrode and at least one shield gas port adapted to direct a shield gas curtain around the metal electrode and a welding site. At least one shroud gas port is spaced radially outward from the shield gas port and adapted to impart to an exiting shroud gas a radially outward component of velocity. Fume gas is preferably extracted from a position radially intermediate the shield gas curtain and the shroud gas curtain.

Abstract: Electrically isolated gas cups for plasma transferred arc welding torches, plasma transferred arc welding torches including such gas cups, and related methods are disclosed. In one embodiment a gas cup includes a dielectric portion sized and configured to couple with a torch body and electrically isolate the gas cup from the torch body. In additional embodiments, a plasma transferred arc welding torch includes an anode, a cathode, a torch body coupled to the anode and the electrode, and a gas cup at least partially surrounding the anode and electrically isolated from the torch body. In further embodiments, a method of coupling a gas cup to a plasma transferred arc welding torch includes coupling a dielectric structure to a gas cup and coupling the dielectric structure to a torch body to electrically isolate the gas cup from the torch body.

Abstract: A spool gun having a quick connector connectable to an electrical power source and a gas source is disclosed. A connection line extends from the spool gun and is attached to a connector. The connector both fluidly connects the spool gun to a shielding gas source and electrically connects the spool gun to a power source constructed to generate a welding-type power. Such a spool gun is quickly and efficiently connectable to the gas and power systems required for performing welding processes.

Abstract: A welding apparatus for welding a work piece is provided that has a weld gun with a nozzle body having an inner surface defining a cavity, and a distal opening forming a nozzle orifice. An electrode extends in the cavity and is configured to be positionable proximate the work piece. The weld gun is configured to provide a flow of shielding gas through the nozzle orifice. The welding apparatus is configured to position the nozzle orifice at a distance from the work piece sufficient to cause the inner surface to direct weld spatter to a weld pool on the work piece adjacent the nozzle. Additionally, the distance is such that laminar flow of the shielding gas is maintained under the predetermined gas flow rate.

Abstract: Provisions of shields for protecting welds as well as providing heat treatments are advantageous. Previously such shields were bespoke constructions produced iteratively and empirically for particular applications and uses. By utilisation of accurately cut sheets of material within which labyrinths are created it is possible to produce an output flow which is even and incorporates no vortexes. In such circumstances problems with regard to edge entrainment of oxygen causing possible oxidation problems in output flows as well as variations in heat treatments can be avoided. The shield also avoids use of welds which may become distorted during welding or heat treating processes. For reproducibility the shield is formed from accurately produced reproducibility components such that shields can be made at a number of sites to provide the same shield function.

Abstract: A MIG welded joint between aluminum and steel members is obtained by overlapping the aluminum member and the steel member each other and performing MIG welding using a filler wire made of a 4000 or 5000 series aluminum alloy on an end face of the overlapped aluminum member, wherein the aluminum member has a thickness P ranging from 0.5 to 2.0 mm, and the steel member has a thickness Q satisfying the following formula: 0.6?Q/P?0.8, whereby a penetration depth of the steel member is equal to or less than 5% of the thickness Q thereof.

Abstract: A drawn arc welding process that includes the steps of a) providing a welding device having a fastener, b) providing a power supply and controller linked with the welding tool, c) providing a work piece, d) energizing a main welding current in the welding tool locally melting the workpiece and forming a weld pool, e) changing the energizing current to a predetermined plunge current, and f) plunging the fastener into the locally melted workpiece at the predetermined plunge current forming a weld between the fastener and the work piece.

Abstract: An apparatus for improved narrow-gap welding is provided. The apparatus includes an inert gas tube within which a contact tube is arranged, the contact tube includes a wire feed for a melting wire. The end of the inert gas tube is ceramic. In another embodiment, the inert gas tube of the apparatus includes a plurality of materials with a high thermal conductivity. A first metallic material at the end of the inert gas tube has a higher thermal conductivity than a second material at a start of the inert gas tube. The first metallic material is molybdenum, tungsten, an alloy of molybdenum or tungsten, or copper or a copper alloy.

Abstract: An apparatus for improved narrow-gap welding is provided. The apparatus includes an inert gas tube within which a contact tube is arranged, the contact tube includes a wire feed for a melting wire. In one embodiment, the inert gas tube includes a plurality of cooling tubes in order to provide active cooling. In another embodiment, the inert gas tube is rectangular.

Abstract: The present invention provides a method of manufacturing a core shroud for a nuclear plant and a nuclear power plant structure in which a groove portion is easily assembled in the case of manufacturing the core shroud having a weld structure of a nuclear power plant by a laser welding, and it is possible to obtain a weld joint portion in which a plastic distortion region and a residual stress are as small as possible, going with a solidification shrinkage of the weld portion. At a time of welding butted portions of a plurality of members constructing a core shroud, a root face is provided in the butted portion, a length of the root face is set to 25% to 95% of a thickness of the thinner one of the butted portions of a plurality of members, a narrow groove is provided in the other than the root face, and the butted portions are welded by a laser welding using a weld wire.

Abstract: The present invention relates to a system and method for automated or “robotic” application of hardfacing to the surface of a steel-toothed cutter of a standard earth-boring rock bit or a hybrid-type rock bit. In particular, the system incorporates a grounded adapter plate and chuck mounted to a robotic arm for grasping and manipulating a rock bit cutter, particularly a hybrid rock bit cutter, beneath an electrical or photonic energy welding source, such as a plasma arc welding torch manipulated by a positioner. In this configuration, the torch is positioned substantially vertically and oscillated along a horizontal axis as the cutter is manipulated relative along a target path for the distribution of hardfacing. Moving the cutter beneath the torch allows more areas of more teeth to be overlayed, and allows superior placement for operational feedback, such as automatic positioning and parameter correction.

Abstract: In a plate assembling step, a gap (5) is formed between a leading end portion (3A) of a groove (3) provided on an upright plate (2) and a lower plate (1). An arc is generated from a welding wire (7) toward a back surface (3C) side of the groove (3) through the gap (5), to form a satisfactory penetration bead (8) on the back surface (3C) side of the groove (3). Next, the welding wire (7), the lower plate (1), the groove (3) of the upright plate (2) and the penetration bead (8) are fused to form a first-layer welding bead (9), thereby firmly joining the lower plate (1) and the groove (3) of the upright plate (2). The first and second welding steps are performed continuously after performing the plate assembling step, to enhance workability at the time of welding the lower plate (1) and the upright plate (2).

Abstract: Apparatus and method for controlling blanket gas flow in an electrical welding facility, wherein welding is performed using a welding electrode in electrical connection with a welding machine unit. The apparatus includes an electric measuring device having a current sensor for determining the magnitude of an electrical welding current carried in a circuit incorporating the welding electrode and having a current sensor output adapted to provide a I signal indicating the current magnitude, and a voltage sensor for determining the magnitude of electrical voltage applied to the welding electrode and having a voltage sensor output for providing a U signal indicating the voltage magnitude, and a control device having inputs connected to the current sensor output and the voltage sensor output, respectively, and a control signal output for providing a control signal to a blanket gas flow controller.

Abstract: Welding repairs are performed in an underwater environment adjacent the bottom head of the nuclear reactor vessel. To provide a dry welding environment, segments of a lower caisson are passed through the core plate holes and assembled along the interior surface of the bottom head. The assembled segments are held down by brackets and sealed to one another and to the bottom head by a water curable polymer. An upper caisson is passed through the core plate hole to sealingly engage the lower caisson. The caissons are pumped dry and welding equipment is passed through the caissons to effect weld repairs about the stub tube or along the bottom head cladding.

Abstract: A method is disclosed including operations for repairing a component. The method includes providing a component including one of titanium and a titanium alloy, providing a laser deposition device, and providing a shielding means that ensures an oxygen content remains below a first threshold and that a water vapor content remains below a second threshold in a target area of the component. The method further includes depositing a metal material on the component, where the depositing includes operating the deposition device along a tool path including a plurality of tool passes, wherein the tool path further comprises a deposition device velocity specification, a laser power specification, and a specified delay time between each of the plurality of tool passes.

Abstract: Provided are butt welds and methods of making such butt welds using a combination of fusion root welding and friction stir welding to yield welds with decreased propensity for dropout during friction stir welding without the need for a back-up support plate. In one form of the present disclosure, the butt weld includes: two or more abutting structural steel components beveled on faying surfaces on one side of the components to form a suitably shaped fusion root weld groove and unbeveled on faying surfaces on the opposite side of the components and interconnected with a first fusion root weld on the beveled side of the components and a second friction stir weld on the unbeveled side of the components, wherein the first fusion root weld has a width ranging from 7 mm to 30 mm, a penetration depth ranging from 2 mm to 20 mm, and an overfill ranging from 2 mm to 5 mm, and wherein the stir zone of the second friction stir weld penetrates the first fusion root weld.

Abstract: A method of consumable electrode type gas shield arc welding characterized in that a shield gas consisting of an inert gas is fed toward a consumable electrode and an addition gas consisting of a mixture of oxidizing gas and inert gas toward an outer edge of welding pool. Further, there is provided a welding torch for use in the method. Thus, in the welding of steel material in accordance with GMA welding technique, the dissolved oxygen concentration of the weld metal can be reduced to 100 ppm or less, and while maintaining arc stability, desirable bead formation can be attained.

Abstract: A shielding gas for MAG welding wherein a carbon steel solid wire is used for lap fillet welding of a galvanized steel sheet; wherein the shielding gas is a mixed gas composition consisting of 8 to 15% by volume of oxygen, 20 to 30% by volume of carbon dioxide, and residual % by volume of argon.

Abstract: A method of gas-shielded metal arc joining using a consumable electrode having an alternating polarity (GMA-AC). A shielding gas containing argon is used to improve process stability and working speed.

Abstract: The invention relates to a device for automatic under-water welding for making a welding joint (3) on a surface (2), of the type comprising a welding torch (20) including an electrode (21) surrounded by a protection envelope (23) that defines together with said electrode (21) an annular channel (24) connected to means for supplying a protection gas. The welding torch (20) is provided axially at the centre of a set (30) of two concentric envelopes (31, 32), one of which at least is capable of axial displacement and can be adjusted relative to said surface (2), said envelopes defining between them an annular gap (34) for injecting a flow for drying the welding area and keeping it away from the water.

Abstract: Methods for arc welding unalloyed or low-alloy steels with consumable electrode under protective gas are suggested, in which the protective gas is a mixture comprising at least helium and an active gas as well as a further inert gas. In the general case, the proportion of the active gas in the total volume of the protective gas is to be in the range from more than 0.5% to approximately 1,5% and the proportion of helium in the total volume of the protective gas is to be more than 30%. In case an electrode having a lowered or medium Si content of approximately 0.2% to approximately 0.4% is used, the proportion of the active gas in the total volume of the protective gas is to be approximately 1% to approximately 5%. If an electrode with a low Si content of approximately 0.05% to approximately 0.1% is used, the proportion of the active gas in the total volume of the protective gas is to be approximately 3% to approximately 10%.

Abstract: The invention relates to a MIG- or MAG-welding gun, comprising a hand-held grip for supporting, handling and aiming the welding gun during a welding process, the grip including a body member (1). The grip further includes a grip member (2) pivotable relative to the body member (1) and lying alongside the body member over at least part of the same lengthwise extent as the body member. The grip member (2) has its free end pivotable to such a distance from the body member (1) that a hand grasping around the pivotable grip member (2) fits between the body member (1) and the pivotable grip member (2), the body member (1) resting on top of the hand. When the pivotable grip member (2) has its free end is in its position pivoted into the engagement with the body member (1), these two components constitute jointly a handle for the hand to grasp around.

Abstract: A joining device for joining a component to a workpiece. The device includes a component holder which moves the component along an axis in a first direction towards the workpiece in order to connect the component to the workpiece, and has a protective gas feed in order to carry out a welding process in a protective gas atmosphere. During the welding process the protective gas is discharged essentially in a second direction which is opposed to the first direction. An elastic sealing sleeve including folding bellows is arranged in relation to the component holder in such a way that a welding space, which is bounded by the workpiece, the component holder, the component and the sealing sleeve and through which the protective gas flows, is sealed off from the external surroundings during the welding process so that the protective gas can escape only in the second direction.

Abstract: An arc welding method using a welding material having a low transformation temperature, characterized in that it is carried out by the use of a shielding gas consisting of a rare gas alone or a mixed gas of a rare gas and a small amount of an oxygen gas; and an additional welding method using a welding material having a low transformation temperature, characterized in that it is carried out while moving a weld line in the form of a straight line. The former method allows the enhancement of a Charpy value in combination with improved fatigue strength, and the latter allows the experience of heat history of the material having a low transformation temperature to be suppressed, resulting in the prevention of weld crack in combination with an improved fatigue strength.

Abstract: A purge arrangement for welding backup of a seam between two surfaces selected for welding together along respective runs which define the seam includes a ventilated tubeform and an adhesive tape attached for forming a seal across the back of the seam and sealing in the ventilated tubeform. The ventilated tubeform adapted for flooding with a purge gas by a source thereof. The adhesive tape's seal across the back of the seam traps the flood of the purge gas in the interspace between the tape and seam and ultimately flushes the as-yet un-welded portions of the seam with the purge gas.

Abstract: An underwater fastener welding apparatus that includes a welding tool positioned within a watertight housing. The housing includes an inlet coupled to a source of pressurized gas. The housing is pressurized to balance a pressure internal to and external to the housing when the underwater welding apparatus depth level is changed.

Abstract: A method and apparatus for MIG-MIG welding includes at least first and second sources (104,114) of wire, and first and second sources of power (102,112). The first source of wire provides a first wire (106) to a main arc between the first wire (106) and a workpiece (110). The first source of power (102) provides MIG power to a first current path including the first wire (106) and the workpiece (110). The second source of wire provides a second wire to a filler arc between the first wire (106) and the second wire (116). The second source of power (112) provides MIG power to a second current path including the first wire (106) and the second wire (116).

Abstract: Systems for coupling end portions of two elongated heater portions and methods of using such systems to treat a subsurface formation are described herein. A system may include a holding system configured to hold end portions of the two elongated heater portions so that the end portions are abutted together or located near each other; a shield for enclosing the end portions, and one or more inert gas inlets configured to provide at least one inert gas to flush the system with inert gas during welding of the end portions. The shield may be configured to inhibit oxidation during welding that joins the end portions together. The shield may include a hinged door that, when closed, is configured to at least partially isolate the interior of the shield from the atmosphere. The hinged door, when open, is configured to allow access to the interior of the shield.

Abstract: A porosity free weld is formed at the surface of an aluminum object. The object is enclosed in a welding box that is sealed and purged with an inert gas, and preheated to at least 100° C. Welding of one pass of the weld using a gas-tungsten arc welding method with AC current and shielding gas mixture of argon and helium is followed by removal of the top portion of the bead. The process of preheating, formation of a weld bead and top portion removal are repeated to achieve the desired weld thickness or build-up.

Abstract: A consumable electrode gas shield arc welding torch (20) includes a torch body (21), a tip body (22) mounted to a front end of the torch body, a tip holder (23) mounted to a front end of the tip body, a spring (26) provided in the tip body (22) in contact with the front end of the torch body (21), a pressing shaft (27) provided in the tip body (22) in contact with a front end of the spring 26) and a power feed tip (28) pressed by the pressing shaft (27) and the tip holder (23). The tip (28) includes a side surface having a projection contacting with a base end (23a) of the holder (23), with a space (29) defined between an inner surface of the holder (23) and a front end (28a) of the tip (28) when the front end (28a) of the tip (28) is inserted into the holder (23).