Abstract: Disclosed is a gas-shield arc welding method in which chemical components of base material and weld material (gas-shield arc welding wire), chemical component ranges of weld metal based on the base material and the weld material, especially, difference (.DELTA.(Cu+Ni), .DELTA.Mo) of Cu, Ni and Mo between the weld metal and the base material, and welding conditions are limited for the purpose of improvement preferential corrosion resistance, toughness and crack resistance of the weld metal in circumferential welding of a pipe exposed into a corrosion environment including CO.sub.2.

Abstract: Chemical compositions of a base metal and a high cellulose type welding electrode are regulated within predetermined ranges, so that the chemical composition of the weld metal obtained from the welding can be regulated within a predetermined range. Particularly, with respect to the weld metal, the Mo content (Mo)1 in the weld metal and the Mo content (Mo)2 in the base metal are regulated such that the difference between the both contents .DELTA.Mo (=(Mo)1-(Mo)2) is 0.03% or more, and PCM is 0.30% or less, where PCM is defined as follows: PCM=(C)+(Si)/30+(Mn)/20+(Cu)/20+(Ni)/60+(Cr)/20+(Mo)/15+(V)/10+5(B). Here, (M) denotes a content (weight %) of a component M in the weld metal.On the other hand, a coating flux of the high cellulose type coated electrode contains relative to the total amount of the coating flux, 0.1 to 7.0% of MgO, 7 to 25% of iron oxides (in FeO equivalent), 8 to 19% of TiO.sub.2, 10 to 30% of SiO.sub.2 and 5 to 27% of Mn, and a core wire and/or the coating flux includes 0.06 to 1.

Abstract: A process for welding mechanically and/or thermally treated alloy pipes to achieve the full tensile capacity of the unwelded base alloy across the welded pipe joint is disclosed. The process comprises welding the pipes together at the beveled pipe ends to form a cap of weld metal. The weld metal cap overlaps that portion of the heat-affected zone which is created in the base alloy adjacent to the bevel of each pipe during welding. To further increase the tensile capacity of the welded joint, a low-heat buffer bead layer can be deposited on the outer surface of each pipe proximate the outer edge of each bevel, prior to depositing the weld metal between the bevels. The buffer bead layers serve to reduce the thickness of that portion of the heat-affected zone which is formed in the base alloy under each toe of the weld metal cap (upon formation of the weld metal cap) to a level having no significant reduction in the overall tensile capacity of the welded joint.

Abstract: A chamber includes a plurality of chamber elements, forming a chamber having a bottom, sides, ends and an open top, and a support wire for flexibly linking the chamber elements.

Abstract: Automatic welding apparatus of the type comprising a carriage self-propelled along a guide track encircling end-to-end adjoining metal tube sections through a welding pass therearound for forming a weld bead joint therebetween is provided with a welding head pivotally mounted on the carriage for pivotal movement thereon in the plane of the weld joint, about a pivot point located approximately at the tip end of the wire electrode projecting from the nozzle end of the welding head, between an initial forwardly inclined drag angle welding position at the top of the adjoining horizontally disposed tube sections to a rearwardly inclined push angle welding position when the welding head reaches around 120.degree. to 135.degree. of its welding pass around the weld joint.

Abstract: A method and apparatus for welding tubes to a tube sheet uses a gas tungsten arc welding (GTAW) torch assembly that is small enough to be inserted through small access holes in a box header. The welding torch is carried near the end of a rotating mandrel that is supported for rotation within a stationary tube. A centering mechanism is inserted into the tube to ensure proper radial alignment of the welding torch with respect to the tube. At the other end of the mandrel is a mechanism for rotating the mandrel and for supplying electrical power, shielding gas and cooling water to the torch and wire to the weld. Axial spacing of the welding torch is provided by a tube stop device that temporarily engages the end of the tube in combination with an axial adjustment device.

Abstract: A method and apparatus for submerged arc welding with four electrodes positioned along a line from front to rear. The first of the electrodes is supplied with direct current, and the remaining three electrodes are supplied with alternating current. The direct current electrode generate an arc that penetrates the base metal and initiates a weld. The other electrodes are supplied with alternating current having a 90.degree..+-.15.degree. current separation between the leading and trailing AC electrodes, and the trailing and middle AC electrodes. Alternating current is supplied between electrodes the trailing and middle AC electrode, having a 180.degree..+-.30.degree. current separation. The AC electrodes combine to generate an arc that deposits a filler and shapes the weld.

Abstract: A process for improving nozzles extending substantially vertically through openings in the head of a nuclear reactor and which are circumferentially welded to the head through a weld lying on an inner surface of the head and on the adjacent outer surface of the nozzle which comprises forming a coaxial, circumferential groove upwardly into at least a portion of the nozzle extending into the reactor and then filling the coaxial, circumferential groove with a weld material. The nuclear reactor head is also claimed.

Abstract: A method of manufacturing tubes filled with powdery and/or granular substances, such as flux-cored welding wires. A tube filled with a powdery and/or granular substance is continuously manufactured by forming a metal strip being fed in its longitudinal direction into an unwelded tube (1a) using forming rolls (2), feeding a powdery and/or granular substance (F) into the unwelded tube (1a) being formed through its opening, butt-welding together fringing edges of the opening, and reducing the diameter of the welded tube (1b). An allowable minimum heat input below which cold cracking occurs and a maximum allowable heat input above which spatters whose diameter is not smaller than 0.83 times the inside diameter of the finished tube are generated are determined in advance, and the butt welding is performed with a heat input larger than the allowable minimum heat input and smaller than the allowable maximum heat input.

Abstract: To regulate welding current and power as a function of welding speed in welding devices for continuous longitudinal-seam welding of metal bands formed into a tube, a speed-dependent voltage value is added to an adjustable fixed voltage value.

Abstract: In a method for welding together pipe ends of pipes held mutually in line the welding process is automatically controlled subject to the angular distance traversed by the welding lance.

Abstract: A continuous manufacturing method for a metal welded tube and a manufacturing apparatus therefor, which obtains a tubular member by continuously passing a metal band coil through molding rollers, guides the tubular member to abutting rollers to bring the edges thereof in slight contact with each other so as to form a V-throat having the vertex of an edge contact portion at the upstream side of the abutting rollers, disposes an inductor of a high frequency preheating unit aiming at edge preheating at the outer periphery in front of the abutting point of the V-throat and at need disposes an impeder also at the inner surface of the V-throat, and further disposes welding torches in a single or double rows of a welding unit for melting and welding the tubular member by welding high density energy at the upstream side of the abutting rollers including the line connecting the centers thereof.

Abstract: A method and apparatus for submerged arc welding using five-electrodes having direct current (DC) connected to one electrode and alternating current (AC) connected to the other four electrodes. The electrodes are aligned in a row with predetermined angles to the direction of the weld. Alternating current is supplied to the electrodes so that a 90.degree. phase difference is applied to adjacent electrodes and a 180.degree. phase difference is applied between alternating electrodes. With such power application and the electrical connections of the electrodes, the welding process has a more stable weld puddle that suppresses welding defects at higher speeds than previously achievable.

Abstract: A method of conducting circumferential welding on electric welded steel pipes to form a continuous line pipe to be laid on the sea bottom by a reel barge method. The formation of the final welding layer is executed with a welding material having a strength which is 5 kg/mm.sup.2 or more lower than that of the welding material used for forming the welding layers underlying the final layer. Preferably, the reinforcement of weld is formed to meet the conditions of:2 mm.ltoreq.radius of curvature at the toe of weld120.degree..ltoreq.angle of toe of weld0.8 mm.ltoreq.height of reinforcement of weld.ltoreq.1.8 mmPreferably, the electric welded pipes as the base metal has the composition: containing C: 0.03 to 0.20 wt %; Mn: 0.50 to 1.5 wt %; Si: 0.05 to 0.50 wt %; Al: 0.005 to 0.060 wt %; Nb, V and Ti in total: not greater than 0.040 wt %; and the balance substantially Fe and incidental impurities, Preferably, the carbon equivalent Ceq and the weld cracking sensitivity Pcm, satisfy the following conditions of:0.20.

Abstract: On conventional method of surfacing the interior of a pipe employing arc welding techniques is to apply a series of annular weld strips to the pipe. A simpler, more efficient method is to apply longitudinally extending strips to the interior of the pipe, while rotating the pipe between each welding metal application.

Abstract: A method for one-side root path welding of a pipe joint comprises the steps of forming a ring groove having a V-shaped bottom portion thereof at end faces of both pipes whose joint is circumferentially welded, attaching a backing material to a butt portion of the pipes from an internal side of the pipes, running an automatic welding machine along a guide rail mounted on an outer surface of the pipes in the circumferential direction thereof, controlling a position of a welding torch along a seam by means of an arc sensor, and welding root pass from the outer side of the pipes with a predetermined welding current and at a welding speed in a high-speed rotating arc welding of the pipes at a predetermined rotational speed and with a predetermined diameter of rotation. The rotational speed of arc is from 10 to 150 Hz. The rotation diameter of the arc is from 1 to 4 mm. The welding current is from 200 to 500 A. The welding speed is from 75 to 300 cm/min.

Abstract: In a process for welding a pipe string driven horizontally into the ground to a follower pipe, the pipe string buried in the ground and the follower pipe are rotated. A welder then does not need to make vertical welds but can form the weld seams in a position that is most comfortable for him.

Abstract: A pipe welding connector for joining pipe sections that have been internally coated with a heat sensitive coating material. The connector is arranged so that during the welding process, the coating remains below its degradation temperature. The connector has a first fixture at the end of one pipe section and a second fixture at the end of another pipe section. The first and second fixtures, when brought into abutting relationship, can be butt welded together to form the pipe welding connector. The second fixture is a cylinder that outwardly diverges into a bell and the opposed marginal end is of constant inside diameter and is attached about the exterior of a pipe section. Part of the pipe section extends from the belled marginal end and forms a stinger. The first fixture has an enlarged interior that telescopingly receives the stinger therein and further includes a belled marginal terminal end of a diameter equal to the diameter of the belled marginal end of the second fixture.

Abstract: An apparatus and a method for automatically welding a T-junction connector to a main pipe are disclosed. The apparatus includes a rotatable frame which is provided with a movable bracket for supporting a welding gun. The frame is preferably attached by a vertical shaft to a portable framework having a wheeled leg and a pair of spaced apart horizontal handles. The portable framework may be moved from one location to another on its wheeled leg. The frame is rotated about the shaft by a computer controlled motor. Two other motors mounted to the frame are interconnected with the bracket for supporting a welding gun or torch, and adapted to move the welding gun along axes parallel with and normal to a T-junction connector supported in a preformed hole in a main pipe.

Abstract: Disclosed is an improvement in the process of gas back-purging the root section of the weld during open-butt welding of pipe. The rates of gas flow in back-purging and in torch shielding are controlled and a ratio between the flow rates is established. The invention teaches a gas back-purging flow rate of about 40 CFH and a torch shielding flow rate of about 10 CFH under typical conditions to maintain a required 4 to 1 ratio of the flow rates.

Abstract: An apparatus method for pipe end preparation and end to end welding of pipes comprises a stationary annular clamp (4) for both clamping and round up of pipes (2). It also has one or two rotating tool carrier rings (5) mounted at one or both sides of the clamp (4) on a track (6). The rotating ring may have thereon devices for cutting, machining of grooves, welding and non-destructive testing (NDT). The round up of the pipe is performed via 6 or more clamping shoes independently operated by screw jacks (18), a wedge mechanism (15) or directly acting hydraulic cylinders.

Abstract: A welding apparatus includes a housing defining a welding chamber and an access opening at one end thereof. The access opening allows an end of a tube fitted with an end plug to pass into and from a welding position within the chamber. An end stop for supporting the end plug at the welding position is rotatably mounted to the housing and disposed in the chamber opposite from and axially aligned with the chamber access opening. The end stop has an annular collar-like portion adapted to fit over and engage the exterior of the end plug. The end stop also has an inner hollow tube-like portion adapted to fit into a central passage of the end plug and engage the interior of the end plug. The end stop has an orifice adapted to supply flow of inert cover gas into the end plug central passage and therefrom into the tube interior to purge air therefrom.

Abstract: A welding apparatus has a welding chamber with an access opening allowing passage of a cladding tube end fitted with an end plug to a welding position therein. A rotatable end plug stop assembly disposed in the chamber and axially aligned with the access opening is adapted to engage the end plug when inserted in the welding chamber. An end of a electrode of a girth welding assembly disposed in the welding chamber adjacent to the rotatable end plug and tube end and in generally orthogonal relation thereto is operable to form a girth weld circumferentially joining the end plug and cladding tube end. An end seal welding assembly mounted to the end plug stop assembly and having an electrode with an end disposed adjacent to and in axial alignment with an axial bore of the end plug is operable to form an end seal weld therein.

Abstract: A method of cladding a steel roll, such as a felt roll with a non-corrosive shell, ensures that the shell is tightly fitted to the core and is free to expand and contract on the core to avoid distortion problems. The method comprises the steps of preparing two stainless steel shells each having a length equivalent to the circumference of the core plus a predetermined extra, wrapping the shells about the core, side by side, leaving a predetermined circumferential gap between the shells, heating and clamping the shells tightly around the core until the longitudinal joints each attain a predetermined longitudinal gap, welding the longitudinal gaps, and circumferential gap between the shells while the shells are hot, ensuring the sheets are welded together and not welded to the core.

Abstract: An improved process for sintering extruded powder shapes comprising drying or calcining an extruded shape in a microwave furnace and rapid sintering the shape in a plasma fired furnace. Alternatively, calcining or drying may take place within a furnace heated by the plasma furnace's exhaust. The process of the invention is especially useful for silicon carbide extruded materials and for tubular shapes. This process significantly reduces sintering times and costs. Use of the process yields a high strength sintered product.

Abstract: The invention relates to a machine for automatically welding and/or cutting the junction point between a main pipe and a secondary branch pipe placed thereon. This machine comprises a positioning support on which the main pipe is placed. The positioning support comprises two servomotors which drive the main pipe in rotation about the longitudinal axis of the pipe and about a second horizontal axis perpendicular to said longitudinal axis. The machine comprises a travelling gantry crane which bears three carriages movable by three servomotors along three axes rectangular with each other, one of which is vertical. One of the carriages bears a welding or cutting head.

Abstract: This is a method for repairing low alloy steel steam turbine (both high pressure and low pressure sections) or generator rotors. The defective section of the original rotor is removed and a replacement end is used, with mating attachments machined on the replacement end and the original rotor. The inner portion of the weld joining the replacement end to the original rotor is provided by a narrow gap weld, either by gas metal or by submerged arc welding. The outer 1/2-2 inches of the weld is provided by gas tungsten arc welding. The mating attachment and at least the inside 1/4 inch of the weld is bored out to remove possible crack initiation sites and to provide a smooth inspectable bore. In this manner, a fast and reliable technique is provided which provides accurate alignment, fast, essentially distortion free welding, and the superior mechanical properties of gas tungsten arc welding in the outer, more highly stressed zones.

Abstract: A method for restarting the longitudinal welding seam when producing thin-walled tubes from a metal tape comprises the steps of starting welding with the tape in motion and the welding current amperage being gradually raised from zero to the steady state values, a steady state step in which the longitudinal welding seam is continuously produced and the welding current amperage is at its steady state value, a third step in which the welding is stopped and the welding current amperage is gradually decreased from its steady state value to nearly zero, and a restarting stage in which the welding seam is overcast partially behind the point at which it had been stopped and the welding current amperage is gradually raised from nearly zero to the steady state value once again. An apparatus for performing the method is also disclosed.

Abstract: An apparatus and a method for remotely refurbishing valve seats are disclosed herein. The apparatus generally comprises a welding assembly having a welding head for depositing a bead of metal around the valve seat, and a positioning assembly detachably mountable onto the valve body for angularly and radially moving the welding head around the valve seat at a selected point along the axis of rotation of the seat. Additionally, the apparatus includes a control means operatively connected to the positioning assembly for controlling the movement of the welding head around the valve seat. In operation, the control means, which may include a microprocessor, first angularly moves the welding head 360.degree. around the circumference of the valve seat, then moves the welding head to a different point along the axis of rotation of the valve seat, and then rotates the welding head 360.degree. around the valve seat again for as many cycles as is necessary to rebuild the valve seat.

Abstract: A method of replacing a defective circumferential butt joint in a metal pipe is disclosed. An annular metal bridge ring, having a smaller wall thickness than the pipe but the same inside diameter, is positioned coaxial with the pipe in the relatively wide gap created by the removal of the defective joint. The ring becomes an integral part of the weld by being welded in place, thereby partially filling the gap between the edge surfaces of the pipe exposed by the removal of the defective joint. Subsequent layers of fusible material are weld deposited in place on top of the ring until the gap is filled to the exterior pipe surface. Use of the ring in the gap enables replacement of the defective joint with a single weld.

Abstract: A method and system for enclosing a gas at a preselected pressure in a nuclear reactor fuel rod having two ends open to its interior. Hermetically enclose each end in a separate airtight chamber. Introduce the gas into the first chamber and open the second chamber to purge the fuel rod interior and both chambers of residual atmosphere. After purging close the open second chamber and determine the gas pressure in the fuel rod interior. When the pressure reaches the preselected value, hermetically seal each fuel rod end while in its respective chamber. After sealing, remove the fuel rod from the chambers.

Abstract: A method for performing automatic circumferential welding around the circumference of a butt joint of a fixed pipe or the like. First, an initial set-up operation is performed wherein a welding head is moved around the welding circumference while producing pulses indicative of the amount of movement of the welding head. The number of pulses required to move the welding head one complete revolution is counted. Next, angles at which the welding conditions are to be changed are specified. These angles are converted to the form of pulses from a start point using the number of pulses previously counted. For the actual welding operation, pulses are again counted while moving the welding head. Each time the pulse count reaches one of the specified angles, a controller instructs a new set of welding conditions to the welding head.

Abstract: In order to join a tube to a tubesheet of a heat exchanger, the end of the tube is inserted into a socket at the end of a hole that passes through the tubesheet. The socket is large enough to receive the tube, but the hole is not, so the tube bottoms out in the socket and is thus located both radially and axially by the socket. A ring mold is fitted around the tube and moved against the tubesheet, so that its end fits into an annular groove that surrounds the socket in the back face of the tubesheet. The ring mold has a chamfered confining surface that surrounds the tube where the tube emerges from the socket. Once the ring mold is in place the portion of tube that is within the socket is welded autogenously to the tubesheet by rotating an electrode within the hole. The molten weld metal flows outwardly to the confining surface, but is prevented by that surface from flowing circumfentially, even when the welding is performed with the tube in a horizontal position.

Abstract: An improved system (50) for shielding a circumferential region about elongate workpieces from air contamination during welding or heat treatment includes a pair of generally cylindrical shields (52, 54) which define central openings for receiving the workpieces, and which are positioned in longitudinally spaced apart relationship about the joint or region to be welded or heat treated. The shields (52, 54) are of symmetrical but otherwise identical construction. For example, the shield (52) includes a first annular chamber (70) and associated annular diffuser positioned adjacent the process zone, and a second annular chamber (86) and associated cylindrical diffuser (90) extending away from the zone. The chambers (70, 86) are connected to independent sources of inert gas, which flows both into and out away from the process zone to eliminate air contamination from aspiration and the like.

Abstract: An improved welding method for welding an inner seam of a longitudinally welded steel pipe along an inner groove by welding electrodes held by a boom which is supported by a tracing roller moving along the inner groove of the steel pipe. According to the invention, at least one metal plate is urged against at least one end of the steel pipe after tack welding the seam on an opposite side of the inner groove of the steel pipe to be welded. Lateral angular deformations of the end of the steel pipe are prevented on both sides of the seam. Such deformations are due to the load of the boom when the tracing roller leaves the end of the steel pipe for the metal plate. Thus, the invention provides for prevention of hot cracking at the end of the pipe.

Abstract: Apparatus for coating an internal wall of a curved conduit (50) with a layer of protective material, characterized in that it comprises a guide means (46, 46a), a longitudinally flexible member (44) which is transversely substantially rigid associated with the guide means, means for mounting a coating means (62) adjacent a first end of the flexible member for incremental rotation with the flexible member, a drive means (28) for driving the flexible member relative to a curved conduit (50) to be coated, so that the coating means can enter the curved conduit in use and so that the coating means can deposit a strip of protective material longitudinally of the conduit, and means (32, 34, 36) acting on the flexible member for automatically stepping the flexible member and consequently the coating means by a rotational increment after the coating means has completed a traverse of the conduit and for automatically reversing the drive means so that the apparatus deposits a strip of protective material adjacent the fi

Abstract: For the manufacture of heat exchanger tubes having a metal strip (tangential surface) welded to the surface of the tube, the metal strip is fastened to the surface of the tube by through-welding with welding current of alternating value.

Abstract: A method and machine for weld cladding, particularly for welding material to a cylindrical plate, such as hardfacing or corrosion resistant alloys normally applied as claddings. The machine has a mandrel extending from it for supporting and rotating the plate. The mandrel is supported by beams and driven either by hand or by a motor. Rotating the mandrel rotates the plate supported on the mandrel through the path of a welding apparatus. Flanges can be provided to hold the plate on the mandrel. Bearings can be provided in the beams to facilitate the rotation of the mandrel.

Abstract: Welding of tubes to tube plates using a non-consumable electrode to locally melt the wall of a tube and an adjacent area of the tube plate where the tube has been entered into a hole in the tube plate and including an initial weld preparation comprising the machining of one face of the tube plate to produce respective annular grooves concentrically around the holes into which the tubes are subsequently to be entered for welding.

Abstract: The h.f.-heated edges of a split tube are prepared prior to heating by means of contour-rolling the edges in order to obtain a convex contour in which the temperature is isothermically distributed, parallel to the convex edges.

Abstract: In a welding procedure for joining of adjacent, possibly partially enclosed metal components, such as pipe sections, wherein the welding procedure can be of a gas tungsten arc type such as a heli-arc type, or similar process, and wherein oxidation of metal frequently occurs within the components at the joinder point due to presence of oxygen in the region of weld during the welding procedure; introducing under pressure and at least initially pressure blowing, at a relatively high pressure, an inert gas into the interior of the components in a substantial swirling and interior surface wiping motion. The inert gas is blown through the components, from the entry end, beyond the weld region to rapidly, and substantially completely remove from the interior and weld region, any oxygen or other possible deleterious gas or material. Subsequently a lower pressure introduction of gas will serve to maintain the interior free of oxygen and the like.

Abstract: A tungsten electrode (35) is positioned adjacent the root face (15) of a tube (10) with the tube and the electrode being connected to a source of direct current (40) such that the electrode is positive with respect to the tube. The electrode is mounted in an assembly (30), and the assembly is provided with a shielding gas from a source (48). The electrode assembly is mounted for rotation on an orbiting head (60) with the electrode axially spaced from the root face. As the electrode is rotated about the tube, the root face (15) and a portion (20) of the inner surface and a portion (25) of the outer surface are simultaneously cathodically cleaned. Preferably, the electrode (35) cleans the root face from two to four times in preparation for a subsequent welding operation.

Abstract: A crucible for containing molten magnesium, and a process for forming the crucible. The crucible is formed from ferritic stainless steel, and particularly type 444 stainless steel plate. The method involves forming ferritic stainless steel plate into component parts of the crucible, while maintaining the ferritic stainless steel plate at temperatures above about 200.degree. F. but below the "blue brittle" temperature range. Further, the method involves special techniques for welding the crucible parts. Specifically, the crucible parts are preheated to a temperature of 100.degree. -150.degree. C. and are completely welded by a process utilizing multiple welding passes with a special metal inert gas shielded welding technique before any cool down of the crucible parts below 100.degree. C. is allowed. The welds extend completely through the crucible walls, which are the thickness of steel plate, and completely incorporate the crucible parts while being essentially free of cracks.

Abstract: The method of and apparatus for welding of a pair of in-line pipes which utilizes a pair of insert rings. Initially, in the root area of the weld there is located an inner insert ring, which is welded to the pair of abutting pipes by a root welding path. An outer insert ring which is constructed of two identical pieces is located exteriorly about the inner insert ring between the pair of in-line pipes. The outer insert ring includes a laterally extending flange which is to be tack welded to the exterior surface of the pipe which is abuts. The main section of the outer insert ring is then melted to fuse together the pipes. The tack welding of the flange to the pipes keeps the main section of the outer insert ring located between the abutted edges of the in-line pipes.

Abstract: A method of producing welded, thin-wall straight-seamed tubes comprises forming a strip in rolls of a tube-forming mill into a tube skelp, and then subjecting the latter to the inert-gas-shielded non-consumable electrode welding. The tube skelp is formed with a gap between edges being 1/500 to 1/30 to the tube-diameter-to-wall-thickness ratio, taken in mm. The rate of welding and the level of welding current are selected in accordance with the rate of heat release in the welding zone, which should be sufficient to close joint due to heat expansion of the tube skelp material and the formation of welding joint.

Abstract: When metal inert gas (MIG) welding is carried out at normal atmospheric pressure, the electrode is made positive with respect to the workpiece because the use of a negative electrode gives little penetration. In undersea welding, as the pressure increases the arc stability and metal transfer in MIG welding become erratic and there is copious fume evolution. According to the present invention, MIG welding at pressures greater than 7 bars is carried out with the electrode negative with respect to the workpiece and with an electrode wire of diameter not greater than 1.4 mm; the slope of the power supply, as seen from the welding arc, is preferably between 6 and 15 V/100 A, which is higher than the 3 to 4 V/100 A used in positive-electrode MIG welding at normal atmospheric pressure.

Abstract: A welding apparatus for pipes which provides for a guide means which is to be fixedly secured to the pipe adjacent the welding area, a first carriage and a second carriage is movably supported upon the guide means with each of the carriages supporting a pair of spaced apart welding heads. Attached to the guide means is a driving chain. Mounted on each of the carriages are motor means which, in turn, operate through the driving chain to move the carriages in a prescribed manner with respect to the guide means. The welding heads of each of the carriages move within the same plane but each are movable in a separate one hundred and eighty degree arc thereby forming a continuous circle. Associated with each welding head is a weld groove tracking system which automatically maintains each welding head correctly aligned within the welding groove. The entire apparatus of this invention, when combined with appropriate electronic computer equipment, automatically welds an adjoined pair of piping sections.

Abstract: The invention relates to a method and an apparatus to perform plasma welding, by providing a cooling water temperature detector at the inlet side of cooling water in the plasma welding torch, controlling the temperature at the inlet side of the cooling water running into the plasma welding torch at a set temperature of more than 4.degree. C. and less than 18.degree. C., starting a plasma arc when the temperature of the cooling water reaches a specified point after starting to pass the cooling water, and moving the base metals and the torch relatively upon lapse of a specified time allowed to form a keyhole after start of the plasma arc.

Abstract: A method of longitudinally seam-welding steel pipes comprises the steps of providing a conductive net-like enclosure tube around a cable for supplying a direct electric current from the power source to the welding head; and conducting a direct electric current through the enclosure tube and through the steel pipe in a direction opposite to that in which the direct current runs through the cable. Apparatus for longitudinally seam-welding steel pipes comprises an electrical cable coupled to a welding head, a net tube surrounding the cable, and a device for supplying a direct electric current to the cable in a first direction and to the net enclosure tube and steel pipe in the opposite direction. The direct currents flowing in the enclosure tube and in the steel pipe is adjustably controlled to minimize the magnitude of a magnetic field created around the net enclosure tube and producing a welded steel pipe seam.

Abstract: A method and apparatus for welding girth joints in pipelines using two welding heads comprises the steps of moving each of the welding heads upwards around the pipeline along the respective section of the girth joint, feeding a welding wire to each of the welding heads so that the welding wire is fed substantially tangentially with respect to the surface of the pipe, and forming a circumferential weld by moulding it to hold the molten metal of the welding bath in the welding zone. An apparatus for carrying out the method for welding girth joints in pipelines comprises an annular track structure having at least two carriages mounted thereon which are connected with drives adapted to impart a translatory motion to the carriages. Each of the carriages carries a welding head provided with a welding wire feeder and a weld moulding member arranged opposite to the joint being welded.