Showing papers on "Shielding gas published in 1986"

Physical and Chemical Behavior of Welding Fluxes

Abstract: Shielded-metal arc, submerged arc, and flux-cored arc welding processes (1) all rely on a flux to achieve an acceptable weld deposit. The welding flux for each of these processes must meet specific physical and chemical requirements to perform properly (2). A flux must have a melting range such that the weld metal solidifies before the molten slag does, and the resulting slag must have a density such that it floats to the top of the weld pool and collects there. The specific ranges of melting and density vary depending on the alloy being welded. The flux must also assist in main­ taining the arc plasma, in producing a shielding gas to protect the weld deposit from the atmosphere, and in limiting the amount of splatter. The flux viscosity is important because it controls the extent to which the flux can chemically alter the weld-metal composition, and it influences weld­ metal porosity, bead morphology, and the ability to make out-of-position weld deposits (3, 4). The flux must contain specific chemical additions to influence the weld metal's composition, microstructure, and properties.

Laser welding of a sleeve within a tube

Abstract: A method for welding a sleeve within a tube of a steam generator, the sleeve being in close contact with the tube. A welding head of a weld head apparatus is positioned within the tube at a predetermined weld site, a laser beam is directed to the welding head, the beam is focused with a focusing means, the focused laser beam is reflected with a welding mirror means into contact with a portion of the sleeve to be welded to the tube, the welding mirror means is maintained a predetermined focal distance from the inside surface of the sleeve, and the welding head is rotated to complete a weld fusion path about the inner periphery of the sleeve. Shielding gas is used to shield the weld site. A robotic arm positions the weld head apparatus within the steam generator. At each end of the sleeve, multiple discrete weld paths or a continuous helical multiple weld path are welded. The sleeve is preferably welded to the tube along the weld path with a fusion width at the interface between the sleeve and tube of at least 0.045 inches and the tube is penetrated to a depth of at least 0.25 inches. The laser delivers 500 to 700 watts to the weld area.

Metal vapors in gas tungsten arcs: part ii. theoretical calculations of transport properties

Abstract: Theoretical calculations of gas tungsten arc transport properties have revealed that small amounts of low ionization potential elements such as aluminum or calcium do not have as great an effect on the electrical and thermal conductivities as has been previously reported, if the presence of other metal vapors such as iron or manganese is also considered. It is therefore concluded that the effects of minor elements on arc properties may be less important than has previously been believed in explaining the variable penetration often associated with minor element additions to the base metal, and that weld pool convection effects such as surface tension modifications are probably more important. However, the effects of vapors emitted by the tungsten electrode may have a great effect on arc properties, as the shielding gas is otherwise free of contaminants in the upper regions of the arc.

Gun and cable for gas metal arc welding

Abstract: An electrode gun and cable for feeding a welding electrode and shielding gas to a workpiece having an improved arrangement for supplying the gas to the arc and for electrifying the electrode in the contact tip. The cable is designed to resist abuse and purge air entering with the electrode. The gun nozzle has a square passage to receive the electrode guide and provide unobstructed gas passages. The trigger has a flexible member engaging the on-off switch to prevent damage thereto from too much pressure by the operator.

A model for the silicon-manganese deoxidation of steel weld metals

Abstract: From an analytical and theoretical study of flat and out-of-position gas metal arc (GMA) C-Mn steel welds containing varying additions of silicon and manganese, we conclude that the buoyancy effect (flotation obeying Stokes’ law) does not play a significant role in the separation of oxide inclusions during weld metal deoxidation. Consequently, the separation rate of the particles is controlled solely by the fluid flow pattern in the weld pool. A proposed two-step model for the weld metal deoxidation reactions suggests that inclusions formed in the hot, turbulent-flow region of the weld pool are rapidly brought to the upper surface behind the arc because of the high-velocity flow fields set up within the liquid metal. In contrast, those formed in the cooler, less-turbulent flow regions of the weld pool are to a large extent trapped in the weld metal as finely dispersed particles as a result of inadequate melt stirring. The boundary between “hot” and “cold” parts for possible inclusion removal is not well defined, but depends on the applied welding parameters, flux, and shielding gas composition. As a result of the intricate mechanism of inclusion separation, the final weld metal oxygen content depends on complex interactions among the following three main factors: (1) the operational conditions applied, (2) the total amount of silicon and manganese present, and (3) the resulting manganeseto-silicon ratio. The combined effect of the latter two contributions has been included in a new deoxidation parameter, ([pct Si][pct Mn])−0.25. The small, negative exponent in the deoxidation parameter indicates that control of the weld metal oxygen concentrations through additions of silicon and manganese is limited and that choice of operational conditions in many instances is the primary factor in determining the final degree of deoxidation to be achieved.

Joint tracking and adaptive robotic welding using vision sensing of the weld joint geometry

Abstract: An approach to the vision-guidance of welding robots and the in-process adjustment of welding conditions is presented. The implementation of a complete vision-guided adaptive robotic welding system is described. The vision-guided adaptive welding system described here has been used to track and weld a wide variety of test and production parts ranging in size from 1.6-mm (1/16-in.) sheet steel to 19.1-mm (3/4-in.) steel plate. Both conventional joint types, including square butt, lap, and V-groove, and special types, such as a multipass square butt submerged arc weld with pre-welded root passes or the axle joints were welded. Various welding procedures, such as GMA welding with a variety of shielding gases and submerged arc welding, have also been used.

Laser welding metal sheets with associated trapped gases

Abstract: A method is disclosed for laser welding two sheets of metal, the metal being of the type having associated gases tending to be trapped and expand in the weld zone during welding due to heat from the laser. These expanded gases tend to separate the upper and lower portions of the weld zone and/or expand through the weld zone toward the laser beam to create porosity in the final weld. Such metal may be coated, such as galvanized steel, in which case the zinc vaporizes into a gas in the weld zone between the adjacent sheets, or it may be poorly fitting sheets, in which case air is trapped in surface irregularities between the sheets. In either case, the method adds to the standard laser beam a surrounding stream of pressurized shield gas effective to create a pressure at the surface of the weld zone sufficient to force the molten metal of the two sheets together and force the expanded associated gases out of the weld zone in a direction away from the laser beam, whereby a non-porous weld may be created. The pressure is higher than that of shield gas in the prior art used for protection from oxygen or dispersal of plasma. Specific pressure ranges are disclosed for argon and helium.

Gas shielded, flux cored, welding electrode

Abstract: A flux cored welding electrode for use in electric arc welding with a shielded gas, which electrode includes a tube of low carbon steel having on the inside thereof a titanium dioxide based flux with fluxing ingredients including aluminum oxide in the amount of 0.1 to 0.5% of the total weight of the electrode. The improvement of the invention wherein the titanium dioxide based flux with aluminum oxide free of magnesium or compounds of magnesium.

CO/sub 2/ laser beam weldability of Zircaloy 2

Abstract: BWR (boiling water reactor) fuel rods are manufactured by stacking pellets into a zirconium alloy, cladding tube-zircaloy 2(Zr2). A fuel rod is designed as a pressure vessel in order to prevent failure of the cladding and release of radioactive fission products. As a result, there are very strict requirements from the welding methods employed. The usual welding methods for Zr2 are based on the tungsten inert gas (GTAW) resistance welding (RW) and electron beam welding (EBW) processes. There is very little information about laser beam welding (LBW) of Zr2. The recent development of multikilowatt laser systems has led to dramatic improvements in their welding performance. In the present work, laser beam welding of Zr2 was investigated. A comparison with GTA welding was carried out. The use of a high-power laser beam to weld nuclear fuel containers made of zircaloy has many advantages: (1) The high-power density of the focused laser beam enables very high welding speeds in comparison with arc welding. As a result, a narrow heat-affected zone is produced and the distortion of the parts is reduced to a minimum. (2) The beam can be transmitted to different stations alternatively, even to ones located far from one another. Itmore » also transmits to hot cells, glove boxes or any inert gas pressure chamber through suitable windows. (3) The process can easily be automated to enhance mass production. It is very simple, does not require skilled welders, and does not need the use of different electrodes, collets, etc. (4) The laser beam does not contaminate the weld metal with tungsten or other elements.« less

Method and apparatus for measuring weld penetration in an arc welding process

Abstract: The penetration in an arc welding process is measured in real time by monitoring the natural frequency of oscillation of the weld pool. Spatial oscillations are induced in the weld pool by modulating either the shielding gas or the welding current at a plurality of different frequencies, and the light reflected from the pool at a non-specular angle is sensed and processed to determine the natural frequency of oscillation. Both pulse and swept frequency modulations are employed for excitation of the weld pool.

Baked flux for submerged arc welding

Abstract: A baked flux of high basicity for submerged arc welding which has a chemical composition suitable for use in universal combination with various types of welding wires in welding low alloying steels. The baked flux reduces the oxygen content and diffusible hydrogen content of the weld metal to form a weld metal having a high toughness, enables forming regular beads without causing weld defects such as lack of fusion and slag inclusion, and facilitates welding work. The performance of baked fluxes is described in comparison with that of the conventional baked fluxes.

Heat transfer in gas tungsten arc welding

Abstract: The heat transferred from an electrode negative, argon gas tungsten arc to an anode has been measured for a wide range of conditions suitable for mechanized welding applications The results are given as (1) the arc efficiency; and (2) the anode heat and current input distribution functional shapes and radii for various anode materials and groove shapes over a wide range of current and voltage, using different electrode geometries, as well as both He and Ar-He shielding gases The nominal arc is Gaussian with a diameter of about 4 mm and a heat transfer efficiency to the anode of about 75% Variations from these values are discussed in terms of current knowledge of the electrical and thermal energy transport mechanisms A new method of measuring the heat transferred from the arc to the anode, using a boiling liquid nitrogen calorimeter, has been developed which gives rapid, accurate values

Spectroscopic analysis of the plasma created by a double-flux tungsten inert gas (TIG) arc plasma torch

Abstract: Measurements of population densities and temperature distributions have been performed in a double-flux tungsten inert gas (TIG) arc plasma column using high-resolution spectroscopy. The experimental conditions have been chosen to mimic typical welding conditions with argon gas. The results show that the plasma is dominated by metallic vapour species in the vicinity of the molten anode, while a nearly pure argon plasma is observed in the cathodic region.

Method for overlap welding clad steels by means of an energy beam

Abstract: Welding of clad steels using laser emission. Method for overlap welding at least two clad-steel plates using a laser-emission energy beam and in which a molten weld crater is formed in the metal, the said plates being held applied against each other, characterised in that it consists in leaving a gap 6 between the contact faces of the plates 1-2.

Gas-shielded arc welding apparatus

Abstract: A gas-shielded arc welding apparatus automatically welds materials to be welded, such as rails or shape steel. The apparatus includes a gas-shielded chamber and a pair of side backing plates arranged within the chamber whereby the whole weld zone of the materials is gas shielded and a welding nozzle and shielding gas outlets are separated from each other. The apparatus also includes a welding apparatus proper and a control unit thereby performing the welding in a fully automatic manner.

Gas shield chamber for arc welding of rails

Abstract: A gas shield chamber for enclosing a welding joint of a pair of rails during the arc welding of the welding joint A pair of side backing plates are each held in contact with the groove at one side of the rails within the chamber and the side backing plates are respectively movable independently of each other by a pair of drives having manual-powered operation change-over means The ratio of respective flow rates of each shielding gas from respective injectors into the chamber is varied in accordance with the movement of the side backing plates A pair of ground terminals of a welding power source are arranged on the sides of the rails

Inert gas tungsten arc welding method

Abstract: PURPOSE:To improve the workability, quality and efficiency of welding by feeding alternately and pulsatively a welding wire and a shield gas to the center of a welding arc from the inside of a tungsten hollow electrode in case of TIG welding, and heating the welding wire on the way of feeding. CONSTITUTION:In case of TIG welding, a welding wire 13 and shield gases 19, 20 are fed pulsatively and alternately to the center of a welding arc from the inside of a hollow tungsten electrode 11. By the shield gas 20, the welding wire 13 is prevented completely from being oxidized, and a weld zone is also air-sealed together with an outside shield gas 22. Also, by a center ejected gas 19, the welding direction can be converted freely. Moreover, when the welding wire 13 is heated on the way of feeding, the welding speed becomes higher. Accordingly, the workability, quality and the efficiency of welding are improved.

Wire for gas shielded arc welding

Abstract: PURPOSE: To enable the welding work having high depositing speed and excellent arc stability by specifying the containing amount of the metalic powder of the inside of a flux ≥ the prescribed amount and the flux filling rate CONSTITUTION: The more is the metalic powder included in a flux, the better for stabilizing the arc, and in case of the containing amount being ≤ 95 wt%, the stabilized arc sufficiently satisfying is unobtainable and the deposition efficiency is therefore reduced as well, so the lower limit value is prescribed for ≥95 wt% When the filling rate of the flux included in the wire is reduced, the arc becomes unstable and the bead external appearance becomes inferior, and in case of the filling rate being too high spatters and humes are caused and the welding work is deteriorated, so the flux filling rate is prescribed for at 10W40 wt% With the use of this wire the welding of high efficiency having excellent welding operability of high deposition speed and arc stability, atc and high deposition efficiency, is enabled COPYRIGHT: (C)1987,JPO&Japio

Coated electrode for arc welding

Abstract: Disclosed is an electrode comprising a base rod and a hard coating, or a base wire which is coated with a powder or metallic coating of aluminum and optionally of hard coating material that adheres to the electrode and forms a partial pressure of arc activated reactive conductive gas agent in the shielding gas envelope surrounding the arc; and further acts as: an inert agent to shield volatile contaminants; a modifier of the shielding gas envelope's electrical properties; and a heat distributor in the area of the weld puddle by condensation in moisture or oil contaminated environment arc welding.

Flux-cored wire for welding

Abstract: PURPOSE:To obtain an excellent bead of fillet weld in fillet welding of a steel sheet coated with primer, by including the specific amounts of Mn and hydrogen- source compounds in the flux of a flux-cored wire for automatic welding. CONSTITUTION:An Mn of 1.2-5.5wt% is added for the purpose of deoxidation. The deoxidation is insufficient when the Mn is less than 1.2%, and an excessive deoxidation phenomenon is presented when the Mn is more than 5.5%. Further, other deoxidizing elements such as Si, Al, Ti, Mg, Zr and the elements such as Ni, Cr, for improving the performance of a welded metal, are added at need. As the hydrogen-source compounds; 0.8-5.0wt% of a water-containing ore such as mica, talc, asbestos, an organic compounds such as cellulose, and an inorganic compounds such as magnesium hydroxide are added. In a fillet welding of a primer-coated steel sheet in the absence of a shielding gas; a bead of fillet weld, perfectly free from surface pore, can be obtained by using a wire, in the flux of which these deoxidizing elements and hydrogen-source components are added.

Welding method for pipe material

Abstract: PURPOSE: To maintain a gas shielding atmospher and to improve the weld quality by filling up foaming and water-soluble bubbles capable of maintaining the shielding gas atomospher inside pipe materials to be butt-welded and then, butt-welding these materials. CONSTITUTION: When a spray can is made by sealing stearic acid amine water- soluble liquid and LPG and sufficiently shaked and jetted, the hard and elastic bubbles without moisture are formed immediately. The bubbles are filled up to the prescribed length from weld zones 2 of a stainless steel pipe 1 to perform the welding. After the whole welding is finished, pure water is filled up in the pipe and left as it is for a while and discharged. COPYRIGHT: (C)1987,JPO&Japio

Tensile and Fracture Properties of an Fe-18Cr-20Ni-5Mn-0.16N Fully Austenitic Weld Metal at 4 K

Abstract: The 4-K tensile and fracture toughess properties of a fully austenitic stainless steel weld are reported. One tensile and two compact tension fracture specimens were tested. The weld was produced by gas metal arc welding using an Fe-18Cr-20Ni-5Mn-0.16N electrode and a 98 percent argon-2 percent oxygen shielding gas mixture. The yield strength of 1015 MPa and average fracture toughness, KIc (J), of 203 MPa•m are higher than those of welds produced with 308L and 316L electrodes and compare favorably with base metal properties. Examination of the fracture surfaces of all samples by scanning electron microscopy showed ductile failure by microvoid coalescence. The suitability of this alloy for welding cryogenic structures is discussed.

Production of welded overlay roll for hot rolling

Abstract: PURPOSE:To improve the toughness and wear resistance of a roll by mixing an Fe alloy contg. specific weight % of C, Si, Mn, Ni, Cr, Mo, Co, and W and VC powder at a prescribed ratio and executing plasma build-up welding. CONSTITUTION:The Fe alloy powder having the chemical compsn. adjusted, by weight %, to 0.8-1.5% C, 0.1-2.0% Si, 0.1-1.0% Mn, 0.2-1.5% Ni, 1.0-5.0% Cr, 1.0-5.0% Mo, 5.0-15.0% Co, and 5.0-15.0% W, and the VC powder are mixed at a ratio of 10-30% VC powder. A roll base body 1 is then subjected to plasma build-up welding by means of a welding torch 3, an electrode 4 and a shielding gas 10. An overlay layer 2 forms fine high hardness carbide and contributes to the improvement in both the wear resistance and toughness of the roll.

Sol-gel fluxes for flux cored welding consumables

Abstract: The feasibility of producing high purity homogeneous welding fluxes by the solgel process and the effects that these fluxes have on the welding process were determined. Reagent grade solgel welding fluxes were produced by making systematic variations of the SiO2-CaO-TiO2-l pct Na2O flux system. The resulting fluxes were made into flux cored wires and used to make bead on plate welds on a niobium microalloyed HSLA steel. Solgel fluxes were shown to have excellent homogeneity, low residual hydrogen content, and no apparent water adsorption. The welding behavior of the solgel fluxes was shown to have superior arc stability compared to a commercial flux cored wire and very low weld metal hydrogen content. The chemical behavior of this flux system was characterized with respect to elemental transfer. The weldments exhibited a primarily acicular ferrite microstructure. Analysis of nonmetallic inclusion size distributions was compared to previous investigations and found to be consistent with the formation of high toughness weld metal microstructure.

Influence of Shielding Gas in Laser Beam Welding

Abstract: During a welding process a shielding gas is used to protect the welding area from the ambient atmosphere. In laser beam welding, the shielding gas has a second function. That is - the laser induced plasma above the workpiece surface can be controlled by various gases. /1–8/

Welding torch for non-consumable electrode

Abstract: PURPOSE:To form exactly a penetration bead even in case of butt welding having no root gap by forming a non-consumable electrode of a welding torch to a hollow, and jetting a center gas by a necessary jet pressure from the hollow part. CONSTITUTION:As for a welding torch, a nozzle is constituted so that a center gas 6 can be jetted from a hollow part by providing a non-consumable electrode 2 can the hollow, and a regular shield gas 7 can be jetted from the periphery of the electrode 2. A butt part of materials to be welded 4, 5 is set so as to have no root gap, and when welding is started by igniting an arc 11 by the electrode 2, a part of a molten metal is extruded to the rear side of the materials 4, 5 by a jet pressure of the gas 6, and a penetration bead 10 is formed positively and exactly. In this way, in case of a butt welding having no root gap, the penetration bead can be formed exactly. This welding torch can execute melting by using oxygen as a center gas.

Laser welding method of aluminum member

Abstract: PURPOSE:To prevent the generation of welding defects by using a gaseous mixture contg. oxygen at a specific mixing ratio as a shielding gas to execute laser welding of Al members. CONSTITUTION:The shielding gas is constituted of the gaseous mixture composed of an inert gas and oxygen and the mixing ratio of the oxygen component in the gas is controlled to 15-90%. The Al members 1 are butted to each other and are subjected to laser welding while the above-mentioned gaseous mixture is used as the shielding gas. A build-up part 2a and undercut part 2b of a weld metal 2 are formed if the mixing ratio of Al is <15%. An overlap part 2c and underfill part 2d are formed to form the weld defect if the oxygen in the gas exceeds 90%. The formation of the undercut part 2b, the underfill part 2d, etc., is prevented by the above-mentioned method, by which the defect of the weld zone is prevented.

Arc-augmented laser welding of aluminum

Abstract: Arc-augmented Laser Welding of Aluminum EdmundJ. Haas Oregon Graduate Center, 1986 Supervising Professor: Jack H. Devletian Aluminum alloys, while readily weldable with other techniques, are very difficult to weld using the laser beam welding (LBW)process. The purpose of this investigation was to examine the use of the arc -augmented LBWprocess as a possible technique for successful LBW of structural aluminum alloys. LBWparameters were examined using an industrial type 1200 watt continuous wave C02 laser. Because of the high surface reflectivity and thermal diffusivity of aluminum, power densities of greater than 106 w/cm2 were necessary to initiate and continue deep-penetration mode welding. Beam focusing optics capable of producing this high power density were limited by short depth of field which makes thick section welding impossible. Surface preparations including anodizing and grit blasting proved helpful while using longer focal length lenses. Synergy resulting from the combined action of the laser beam and the gas tungsten arc produced a far greater volume of molten metal than the individual contributions of each process added separately. This synergistic effect was seen when the laser beamwas augmented with an arc produced by a conventional gas tungsten arc welding (~) electrode. Evidence was obtained showing this increase in melted volume to be related to an increase in the efficiency of the gas tungsten arc. Measured changes in arc column resistance and current coupled with high speed videography results showing the arc rooting to the laser induced hot-spot confirm an overall increase in applied power density (mainly from the GTAWarc). Weld preheating temperatures close to the melting point of aluminum was found to promote thermal coupling of laser energy. The increase in absorption of the laser beam by aluminum was proposed as a possible mechanism of the observed arc-laser synergism in the combined process. Results from arc-augmented LaWof mild steel are provided which show the increase in melted volume to be similar to that obtained for aluminum, and based on this, the dominant mechanism of arc-laser synergism was proposed to be an increase in the GTAWefficiency. Relative to the engineering significance of this work, possible benefi ts from the arc-augmented LBWtechnique (on aluminum) would include coupling a GTAW torch to an already existing LBWapplication with increased guality or productivity as an aim. It wOuld not make economical sense to do the reverse because of the high cost of a ~ system relative to the increase in welding velocity or penetration depth one might gain from a GTAW system.

Processing head for laser welding

Abstract: PURPOSE:To remove stably plasma by providing a center nozzle which irradiates laser light and ejects a plasma-removing gas coaxially with the optical axis of the laser light and providing a shielding nozzle around the center nozzle CONSTITUTION:The center nozzle 12 irradiates the laser light 5 and ejects the plasma-removing gas in the state coaxial with the optical axis of the laser light 5 A gas inlet 121 supplies an inert gas to the nozzle 12 the shielding nozzle 13 is provided around the nozzle 12 and ejects the shielding gas which shields the processing position of a work 3 against the atm to protect the molten metal against the atm and to assure deep penetration A filter 132 for regulating the flow of the shielding gas is provided to maintain the uniform flow of the gas The always stable deep penetration bead is obtd in spite of a minor fluctuation in welding conditions and the distance (h) between a processing head 1 and the work 3 by constructing the head 1 in the above- mentioned manner