Abstract: A welding torch (10) for welding on a component has an electrode (12) within a nozzle (14) through which a flow of gas passes. A shield (20) defines an enclosure (22) around the nozzle (14). Means are provided for supplying weld filler material (18) into the vicinity of the electrode (12) through the shield (20). One end of the shield (20) is attached to the welding torch (10). The other end of the shield (20) is open and extends towards the component (16). An inflatable seal (28) is mounted on the end of the shield (20) to seal between the shield (20) and the component (16).

Abstract: A welding chamber having a laminar-vortex inert gas flow is disclosed. The welding chamber comprises a transparent dome that covers an open top side of a rigid generally rectanguloid enclosure. The dome includes a one-way vent for discharging ambient air from within the chamber while preventing the introduction of ambient air into the chamber. The enclosure includes a bottom and side walls that are joined at smooth, curved edges, and at least one side wall of the enclosure includes portholes with gloves for manually accessing the interior of the chamber while the dome is in a closed position. At least one gas distribution tube, a plurality of gas inlets and laminar-flow tunnels are included. In use, an inert gas is introduced into the distribution tube that substantially encircles the top of the enclosure.

Abstract: A device (10) for isolating a surface for welding in an underwater location or in high fire risk areas. The device comprises a housing (27) which is arranged to be mounted on the surface and a sealing means (30) to provide a seal between the housing and the surface. The housing (27) is provided with a sealed inlet (50) for receiving a welding apparatus, a fluid inlet (32) for the passage of gas into the housing, and a fluid outlet (34) for the passage of gas and/or liquid out of the housing. A heating means FIG. 3 is not figure) for providing heated gas to the fluid inlet is also provided. In use, an ingress of heated gas through the fluid inlet (32) facilitates an egress of gas and/or liquid, contained in a space defined by the housing and the surface, through the fluid outlet (34) in the housing. In this way an in situ dry gaseous environment is provided for welding the surface.

Abstract: For stress-crack-sensitive materials, a weld pool is formed on a substrate. The weld pool is simultaneously plastically strained and cooled while the temperature of the hot metal weld pool lies substantially within a predetermined range in which hot cracking typically occurs. The hot metal is plastically strained and cooled until the temperature of the weld material is below the predetermined temperature range associated with hot cracking or until residual stresses in the weld are sufficiently low to preclude cracking in the completed weld.

Abstract: A system (10) for conducting welding adjacent flammable materials (12) on a platform (11) is disclosed having a chamber (13) defining an interior space (16). The system also includes a welding apparatus (48) operable within the interior space. A sensor (54) is provided for sensing the presence of combustible gas within the interior space above a pre-selected level and generating a signal. An exterior sensor (57) is provided for sensing the presence of combustible gas outside the interior space above a pre-selected level and generating a signal. A controller (66) is in communication with the welding apparatus, the sensor, and the exterior sensor to control the operations of the welding apparatus in response to signals received from the sensor.

Abstract: The invention relates to electric arc processes particularly for underwater use. Electric arc processes effected under water ordinarily operate at a voltage of 20 or 30 volts, with an open circuit of e.g. 50 volts, and are at a level that does not pose a serious risk to the diver. Such as plasma arc cutting has typical voltages of 100-200 volts, and an open circuit voltage of 200-400 volts, and can put a diver at considerable risk of electric shocks at a level that can be life threatening. The object of the invention is to avoid such risks, an objective met by electric arc equipment comprising an earthed safety electrode strategically positioned close to the torch of the electric arc equipment, to create the closest earth to which current could flow, but without the striking of an arc between a torch electrode and the earthed safety electrode.

Abstract: Stainless steels are welded using a shielding gas including 88 to 98.9 mole % Ar, 1 to 10 mole % H2, and 0.1 to 2.0 mole % CO2. The shielding gas permits low sulfur, high chromium, austenitic stainless steel pipes to be joined with welds having sufficient penetration, strength, corrosion resistance and durability for practical use.

Abstract: Welding of material such as a piping using ferrite system stainless steel, in which a back sealed gas used for conventional welding is switched from argon gas (or a hydrogen gas/argon gas mix) to an argon gas to which an oxidizing gas is doped at the time of forming a chromium oxide passivation film. Welding conditions are set at the temperature in which the inner surface of the piping does not melt at the time of forming the chromium oxide passivation film. The temperature of the welding piping is set uniformly between welding conditions in conventional welding and welding conditions at the time of forming the chromium oxide passivation film, and in order to replace gases used with conventional welding with gases used at the time of forming the chromium oxide passivation film. A cycle of one round or more is performed under the welding conditions for forming a chromium oxide passivation film, thereby, to form the chromium oxide passivation film on a weld in concurrence with welding.

Abstract: A domestic cooking or defrosting appliance including a heating region and a camera for obtaining images of food cooking or defrosting within the heating region, wherein the camera outputs video signals to a processor that drives a display means associated with the appliance and/or controls the cooking or defrosting operation of the appliance. The display means is conveniently situated on the appliance to show an easily-viewable image of the food obtained by the camera. The camera is sensitive to infra-red radiation and outputs video signals representative of the heat of the food. The processor can therefore convert infra-red information received from the camera into visible information to create a display on the display means representative of the infra-red information. Such a display is preferably color-coded in accordance with the local temperature of the food.

Abstract: An improved method for welding and passivation forms a chromium oxide passivated film over the welded portion during the welding process. In a shielding step, a backshield gas, preferably argon, is flowed around the welding site. In a welding step, an arc gas, preferably argon with approximately 10% hydrogen and less than 1 ppm moisture content, is flowed through the welding head and a welded joint is formed, for example by high speed tungsten-inert gas (TIG) orbital welding. In the passivation step, a process gas, preferably argon with approximately 30-100 ppm of oxygen and less than 1 ppm moisture content, and preferably less than 1 ppb moisture content, is flowed over the welded portion to form a chromium oxide passivated film on the welded portion. The process gas is passed through a gas purifier prior to being flowed over the welded portion to maintain its moisture level at less than 1 ppb.

Abstract: A shroud for a welding torch includes a hydrophilic skirt supported by a frame. The skirt is soft and pliable when wet and is self protected from the heat of welding by the water absorbed therein. The frame supports the skirt around the weld site and permits a good seal with the workpiece for excluding water during the welding process.

Abstract: A process and apparatus for welding a metal component (28) to a metal workpiece (40). The component (28) typically comprises a metal weld region (36) and a threaded connector region and the apparatus includes a weld head comprising a nozzle (8) for holding the weld region (36) of the component (28) adjacent the workpiece (40). The weld head induces a weld arc between the weld region (36) of the component (28) and the workpiece (40) to create a weld pool of molten material. The weld head subsequently moves the weld region into the weld pool to permanently join the component (28) to the workpiece (40). The apparatus further comprises a pressurised fluid source and a fluid flow control means for directing the pressurised fluid between the weld head and the component and weld pool so as to deflect any airborne fluid residue of the weld pool away from the connector region of the component (28).

Abstract: Realized is a welding wire containing flux used for a gas shielded arc welding of a direct current/positive polarity mode, with use of which a quantity of sputter generated is small, a good weldability is realized and a weld metal with an excellent toughness is obtained in all the welding positions under application of a welding current in the range of a low current to a medium current, or in a definite manner in the range of 50 to 300 A. The flux contains 0.7 to 3 wt % Al, 0.1 to 1.0 wt % Mg and 1.2 to 5 wt % BaF2, each content being a value in wt % to a total weight of the wire and the sum of a content of Al plus a content of Mg multiplied by 3 being in the range of 1.3 to 5 wt %, a filling ratio of the flux to the total weight of the wire is in the range of 5 to 30 wt %, a total Mn content in a steel sheath and the flux combined is in the range of 0.2 to 1.9 wt % and a total Si content in the steel sheath and the flux combined in the range of 0.001 to 0.9 wt %.

Abstract: A housing for an underwater processing device, for example, welding, includes a welding head movable laterally relative to the housing and the direction of the weld. At opposite ends, gates are provided having arcuate convex surfaces forming edge seals for engaging in the groove of the work surface. In one form, the gates are linearly slidable and biased in a direction away from the housing. In another form, the gates are pivotally mounted for engaging in the grooves. In both cases, the compliant seal about the margin of the housing, together with the arcuate seal of the gates, maintains a substantially water-free area within the housing to enable processing.

Abstract: The invention relates to electric arc processes particularly for underwater use. Electric arc processes effected under water ordinarily operate at a voltage of 20 or 30 volts, with an open circuit of e.g. 50 volts, and are at a level that does not pose a serious risk to the diver. Such as plasma arc cutting has typical voltages of 100-200 volts, and an open circuit voltage of 200-400 volts, and can put a diver at considerable risk of electric shocks at a level that can be life threatening. The object of the invention is to avoid such risks, an objective met by electric arc equipment comprising an earthed safety electrode strategically positioned close to the torch of the electric arc equipment, to create the closest earth to which current could flow, but without the striking of an arc between a torch electrode and the earthed safety electrode.

Abstract: An underwater exclusion device includes a housing for a welding torch having leading and trailing arrays of pivotal fingers for engaging in grooves along a work surface to exclude water from an exclusion area within the housing containing the welding torch. The fingers are pivotally mounted and independently and individually movable under the bias of springs between retracted and extended positions. The fingers have radiussed distal ends for engaging the work surface. Upon application of the device to the work surface, the leading and trailing arrays of fingers are displaced under spring pressure to engage their distal ends against the work surface, excluding water from within the housing. The side walls of the housing carry seals for seating along the work surface to prevent water incursion in gaps between the side walls and the work surface.

Abstract: A heating apparatus and method for pre-weld heat treating, welding and post-weld heat treating a superalloy article in a single enclosure while avoiding oxidation of the article. The enclosure is preferably equipped with a one-way valve that permits the escape of gases, but otherwise seals the enclosure to prevent the ingress of air during welding and heat treatment as a result of thermal gradients induced when the article is inductively heated. To provide access to the article and a device used to weld the article, the enclosure is equipped with gloves by which the welding device and the article can be manipulated while a nonreactive atmosphere is fully maintained within the enclosure and the article is inductively heating.

Abstract: A Multi-Electrode Welding System for performing high-precision welding and joining is disclosed. One embodiment of the invention comprises a sealed chamber (13) which is enclosed by a weld head frame (11), a removable lid (12) and a chamber base (14). A generally tubular workpiece (not shown) is placed in a pair of semi-annular inserts (16) and extends into the sealed chamber (13), which is filled with an inert gas. In one embodiment, a weld head rotor (18) revolves around the longitudinal axis defined by the workpiece, and controls the motion of an inside electrode (24A) and an outside electrode (24B), which are held by inside and outside electrode holders (20 & 22). Arc welding is performed by the electrodes (24A & 24B) as they revolve around the workpiece. Inside and outside welding may be performed simultaneously. The invention provides for precise control of the relative position of the electrodes, allowing one electrode to trail the other.

Abstract: A pipe connected to a stage serving as a movable member arranged in a vacuum chamber has a double pipe structure constituted by a resin inner pipe and a resin outer pipe which covers the inner pipe including its surrounding space. The space between the inner pipe and the outer pipe is connected to a vacuum pump serving as an exhaust means. The space in the pipe is kept in vacuum by the vacuum pump.

Abstract: The present invention concerns the use of a pre-alloyed atomised powder in combination with at least one melting electrode wire in the SAW method. The electrode wire is an unalloyed or low-alloy metal wire and the metal powder is a metal powder containing a higher percentage of alloying elements than the electrode wire.

Abstract: A housing for a processing device includes a plurality of independently extendible and retractable fingers for engaging the work surface. Gas pressure supplied within the housing drives the fingers into their extended positions and assists in excluding surrounding water from the work surface within the housing. The fingers may have fixed balls, roller balls or slidable wheels at their distal ends to facilitate movement of the housing along the work surface. Flexible skirts may be provided about the fingers to assist in water exclusion from the work area.

Abstract: An improved method for welding and passivation forms a chromium oxide passivated film over the welded portion during the welding process. In a shielding step, a backshield gas, preferably argon, is flowed around the welding site. In a welding step, an arc gas, preferably argon with approximately 10% hydrogen and less than 1 ppm moisture content, is flowed through the welding head and a welded joint is formed, for example by high speed tungsten-inert gas (TIG) orbital welding. In the passivation step, a process gas, preferably argon with approximately 30-100 ppm of oxygen and less than 1 ppm moisture content, and preferably less than 1 ppb moisture content, is flowed over the welded portion to form a chromium oxide passivated film on the welded portion. The process gas is passed through a gas purifier prior to being flowed over the welded portion to maintain its moisture level at less than 1 ppb.

Abstract: A water-repellent film is applied on to the surface of a welding member such as of a welding backing member disposed backside a joint defined between two mating welding bevels, a welding bevel of a base member to be welded, and a coated welding rod formed by coating a metallic core wire with a flux. The water-repellent film is formed of a hydrophobic material having a contact angle of 90.degree. or above and providing minute concavities and convexities. In a highly humid environment, during rainfall or in water, welding can be effected without weld defects such as blow holes, cracks and the like.

Abstract: A heating apparatus and method for welding a superalloy article. The apparatus and method of this invention provide for pre-weld and post-weld heat treatments to be performed on an article within the same enclosure in which the welding operation is performed. The apparatus accurately controls the temperature of the component to be welded throughout the temperature treatment profiles with the use of means for welding the article, means for heating the article, and means for sensing the article temperature. The apparatus also works in conjunction with a memory storage device that stores appropriate pre-weld and post-weld heat treatment temperature profiles and a welding temperature profile for the article.

Abstract: An apparatus for underwater welding has a housing and a diverter. The diverter is inside the housing and has an outer sheath and an inner sheath. A gap between the housing and diverter passes a screening fluid to form an outer screening jet that prevents water from flowing into a weld site near the electrode. The inner sheath forms a pair of channels in the inner diverter. One channel passes a shielding fluid that shields the weld site. The other channel forms an exhaust line for venting the weld site during welding.

Abstract: Metal workpieces are subjected to laser treatment in a liquefied gas, by passing the laser beam through a layer of liquid nitrogen in direct contact with the metal surface to be treated, thereby creating an amorphous state.

Abstract: A MIG and Flux Core wire feed and containment system for filler wire distribution for both manual and robotic underwater and terrestrial welding applications has a sensor feedback pressure sensor system that detects deflective and deformative pressures acting on the filler wire by surrounding environmental objects which the operator may not be aware of while setting up the task and which prevents the filler wire from being bent if the welding torch is inadvertently pressed against solid objects in robotic applications, thereby eliminating the need to manually straighten the wire, and enabling the capability of providing a filler wire distribution assembly at great water depths or at locations distant from the welding controls and in close proximity to the torch head.

Abstract: A submersible thermal processing apparatus including a welding torch having an electrode, a housing and an inlet for pressurized gas; a shielding gas nozzle mounted to the torch housing and surrounding at least a portion of the electrode; and a fluid-permeable baffle made of elastic, heat-resistant spring material arranged in a closed loop and mounted to a distal end of the shielding gas nozzle. This water exclusion device acts as a movable, flexible, gas-flow permeable baffle, and is used in contact with and/or close proximity to the workpiece surface. One preferred shape of the cross section of the device is elliptical, with the coils of the spring inclined at an angle to the general path around the device so as to allow the overall helix shape to be readily compressed and released through larger deflections than the conventional design of baffle.

Abstract: The apparatus of the invention forms a sealed pocket area which excludes water or other liquid fluent directly over a portion of an angled configuration that is to be welded, where the angled configuration is created by teeing two pieces of material together at an angle and joining them by fillet welding.

Abstract: A water exclusion device for underwater arc welding comprises a chamber having flexible gas permeable surface contact member at the lower end. A wire mesh material is the preferred gas permeable material.

Abstract: An improved underwater arc-welding apparatus that includes a handheld torch assembly connected to an housing that delivers electrical power, a pressurized shielding gas, and a consumable wire electrode to the site of the weldment. The housing is configured such that the diver/operator, himself, can control such welding parameters as the voltage level of the electrical power, the duration of the flow of the shielding gas, and the delivery rate of the electrode. In addition, the housing is configured to allow the entry of water into the space between its components, and these components, including an electric motor that advances the consumable wire electrode, are sealed individually from the water. Electrical connections between the components are effected using underwater cables and connectors.

Abstract: Stress corrosion cracking damage to stainless steels and nickel base superalloys is repaired by underwater plasma transferred arc welding which under conditions which reduce residual tensile stresses in the weld and adjacent portions of the repaired structure.

Abstract: Persistent compressive stresses sufficient to suppress hot cracking, reheat cracking and stress corrosion cracking are developed in welds containing alloys of plural materials by quenching of the weld after onset of solidification but while the weld remains soft or "mushy" at a temperature above the melting point of eutectic alloys which may form. Control of the time of quenching is preferably established during submerged welding by a cup-shaped exclusion fitting which is sized relative to the dimensions of a molten weld pool and the speed of travel of a welding heat source such as a plasma transfer arc torch. The cup-shaped exclusion fitting provides improved protection of the weld and heat source with inert gas supplied thereto while also permitting submerged welding at higher hydrostatic pressures than has heretofore been possible.

Abstract: An electric welding device using welding or filler material supplied to a welding site located in a wet environment. The device provides for the supply of the welding material to the welding site in a water-free environment that extends up to the welding site.

Abstract: An enclosure enveloping a work area with a controlled gaseous atmosphere. It is particularly useful as a welding enclosure for welding metals in a total atmosphere of inert gas. The enclosure consists of a basal portion which rests on a table or work bench of similar dimensions and geometry. A short lower portion is preferably of somewhat smaller horizontal cross section than an attached much larger upper portion. A gas diffusion ring is located inside about midway between the top and bottom. There is a recloseable gas tight opening in or adjacent the top for introducing workpieces and a one way vent valve at or adjacent the highest point on the top. When ready for introducing the workpiece the hood drapes neatly and uniformly around the workbench and the gas diffusion ring is enclosed at the lowest part of the draped portion. Argon is the inert gas of preference. When it is introduced it displaces any remaining air ahead of it and ultimately out the vent valve.

Abstract: A welding method for forming an oxide passivation film having corrosion resistance and an extremely small emission quantity of an outgas during welding at a weld portion and portions nearby, and a process apparatus requiring an ultrahigh-clean atmosphere. A back-shielding gas comprising an inert gas containing 1 ppb to 50 ppm of oxygen gas is caused to flow during a welding process, and an oxide passivation film comprising chromium oxide as a principal component is formed on the surface of the weld portion. In a process apparatus using welding for installing the apparatus, a back-shielding gas comprising an inert gas containing 1 ppb to 50 ppm of oxygen gas is caused to flow during a welding process and an oxide passivation film comprising chromium oxide as a principal component is formed on the surface of a weld portion.

Abstract: A welding electrode suitable for underwater welding is manufactured from a welding rod with a flux layer thereon by forming a protective coating of a waterproofing material at least over this layer and subjecting it to a pressure at least as great as the pressure at a depth of water at which the welding electrode is intended to be used such that the waterproofing material is driven into pores and interstices of the flux to impregnate it. Waterproofing materials which do not produce organic residues at welding are preferred, such as liquid sealant with metallic aluminum powder, polyurethane, resins and epoxy-based coatings.

Abstract: A method for thermal insulation of a wet shielded metal arc welds including insulating a weld joint between workpieces to be welded with a synthetic insulator is provided. An apparatus for thermally insulating a wet shielded metal arc weld including a synthetic insulator is also provided.

Abstract: A welding enclosure includes a central work chamber; a plurality of horizontally spaced welding work stations within the central work chamber; an exhaust chamber beneath and generally coextensive with the central work chamber; a floor over the exhaust chamber, underlying and substantially coextensive with the central work chamber, and including vents operative to allow air to pass through the floor between the central work chamber and exhaust chamber; an exhaust fan for exhausting air from the exhaust chamber; a blower arranged to establish a positive air pressure in the plenum chamber; and a ceiling over and substantial coextensive with the central work chamber, underlying the plenum chamber, and including air registers operative to pass air downwardly through the ceiling from the plenum into the central work chamber for passage downwardly through the central work chamber and through the floor vents into the exhaust chamber for removal by the exhaust fan.

Abstract: Disclosed is a multi-point welding method capable of certainly welding an object having a number of points to be welded for a short time. First, an approximately cylindrical base body is formed by alternately laminating a flat sheet and a corrugated sheet and then winding them in a spiral shape. In this case, there exist a number of contact points of the flat sheet to the corrugated sheet, that is, points to be welded. Next, there is provided an electrode apart from one end surface of the base body by a specified interval and facing to the end surface. After that, by intermittently applying a current across the electrode and the one end surface of the base body thereby intermittently generating electric discharges between the electrode and the one end surface of the base body, to thus fuse and weld the points to be welded of the flat sheet to the corrugated sheet.

Abstract: Disclosed are a device and a method for inert gas plasma welding in a low pressure or vacuum environment.

Abstract: An inert gas nitrogen mixture is used as a shielding gas to prevent weld hot cracking in superalloys containing zirconium and/or boron. The gas mixture preferably contains argon and about 2 to 8% by volume nitrogen. Test data show excellent results are obtained when gas tungsten arc welding HAYNES 214 alloy which normally contains boron and zirconium and a minimal content of titanium.

Abstract: An apparatus for torch cutting and welding which is safe, easy to use, accurate, provides an exceptionally clean cut of any desired shape, and can be brought into a non-operating state by the operator underwater. The apparatus includes a body having at least a first chamber and a second chamber, a hydraulic motor fitted in the first chamber and communicating with an external source of a pressurized liquid medium. At one end of a movable shaft of the motor, an elongated electrode is connected, at least a portion of which is adapted to extend out of the body through an opening in the body. Via the shaft, the motor transmits a rotating or reciprocating motion to the electrode. An electric current is conducted from an external power supply source to the electrode via an electrically conductive member which is fitted in the second chamber around at least a portion of the electrode.

Abstract: A glove box for establishing an inert gas working environment. The glove box has a housing defining a work chamber and a stovepipe section. Flexible glove sections are connected to the housing and can be inserted into the work chamber. A valve is connected to the stovepipe section for exiting gas from the work chamber and stovepipe section. The valve includes a rigid member with a seal connected thereto. The rigid member is biased by elastic members onto the stovepipe section with the seal therebetween.

Abstract: A gas/arc electrode for use under vacuum conditions wherein a first housing encloses a second housing, with an end of the second housing extending through an opening in the first housing and having therein an outlet orifice. Provisions are made for circulating a coolant through the first housing to surround and cool the second housing. An electrical current and a gas, such as argon, as passed through the second housing, with the current flowing through a narrow stream of the ionized gas flowing through the outlet orifice to a workpiece to be treated. The second housing forms a chamber which has a cross sectional area, in a plane perpendicular to the direction of gas flow, of at least ten times the cross sectional area of the outlet orifice such that a gas pressure can be maintained in the chamber to reduce erosion of the chamber walls.

Abstract: The present invention relates to an exothermic cutting electrode. The electrode includes an outer hollow conductor, an inner conductor disposed inside the and outer hollow conductor. The inner conductor is configured so as to form the boundaries of two chambers and configured to form a third chamber between the outer hollow conductor and an inner conductor. The three chambers are of substantially equal cross-sectional size whereby even gas flow is proudced and even consumption of the electrode is provided.

Abstract: Method of underwater arc welding comprising the steps of placing a welding electrode nearby a parent material to be welded, immerged in water; generating a high frequency voltage between the electrode and the parent material for starting a striking arc and supplying a high frequency current to said electrode, after said striking arc has been initiated; generating a welding voltage for producing a weld at the parent material and; simultaneously sustaining the high frequency current, superimposed to the welding current, for stabilizing said welding arc during the time duration of the underwater arc welding.

Abstract: An exothermic cutting electrode or burning bar having an oxidizable metal fluid conduit (tube) surrounded by alternate layers of wire wound helically in opposite directions, the entire structure covered with an outer oxidizable metallic tube, either end of the electrode being adapted for connection to a source of oxidizing fluid and electric current, so that an arc can be struck between a work-piece and the free end of the electrode to produce a cutting flame. By proper selection of the type and size of materials of construction the electrode will burn after the electric current has been turned off.

Abstract: A physical vapor deposition system is disclosed for routinely achieving unprecedented processing uniformity of thin films on substrates of a size comparable to or larger than the source. The system includes a plurality of substrates; a plurality of deposition, etching, and/or heating sources; a plurality of mobile in-situ process monitors for obtaining the fundamental processing profiles that characterize the processing properties of each source; and mobile fixturing responsive to the fundamental processing profiles for effecting prescribed motion scenarios of the substrate relative to the source; to thus provide the means for achieving extremely uniform as well as an unprecedented range of prescribed non-uniform final thin film processing profiles, irrespective of the size of the substrate relative to the size of the source.

Abstract: A novel weld chamber and process for using such weld chamber are disclosed. A flow of shielding gas through the weld chamber is regulated to provide a constant pressure in the weld chamber while the shielding gas flow sweeps away metal vapors.