Showing papers on "Gas metal arc welding published in 1992"

On the calculation of the free surface temperature of gas-tungsten-arc weld pools from first principles: Part I. modeling the welding arc

Abstract: A mathematical formulation has been developed and computed results are presented describing the temperature profiles in gas tungsten arc welding (GTAW) arcs and, hence, the net heat flux from the welding arc to the weld pool. The formulation consists of the statement of Maxwell's equations, coupled to the Navier-Stokes equations and the differential thermal energy balance equation. The theoretical predictions for the heat flux to the workpiece are in good agreement with experimental measurements — for long arcs. The results of this work provide a fundamental basis for predicting the behavior of arc welding systems from first principles.

Observation of metal transfer during gas metal arc welding

Abstract: The phenomenon of metal transfer has been investigated for different transfer modes using a digital high-speed video analyzer and an arc shadow-graphing system based on a laser source and related optical system. It was observed that the pinch instability phenomenon did not occur for the globular transfer mode, since the liquid globule was then spherical rather than a cylindrical molten droplet. The drop diameters and drop transfer frequencies were measured with respect to the current for different electrode extensions and different shielding gases

On the calculation of the free surface temperature of gas-tungsten-arc weld pools from first principles: Part II. modeling the weld pool and comparison with experiments

Abstract: By combining a mathematical model of the welding arc and of the weld pool, calculations are presented to describe the free surface temperature of weld pools for spot welding operations. The novel aspects of the treatment include the calculation of the heat and current fluxes falling on the free weld pool surface from first principles, a realistic allowance for heat losses due to vaporization, and a realistic allowance for the temperature dependence of the surface tension. The most important finding reported in this article is that the free surface temperature of weld pools appears to be limited by Marangoni convection, rather than heat losses due to vaporiza-tion. Furthermore, it was found that once thermocapillary flow can produce high enough surface velocities (>25 cm/s), the precise nature of the relationship between temperature and surface tension will become less important.

Method and apparatus for welding workpieces made of superalloys

Abstract: Apparatus for the deposition welding or the joint welding of a workpiece made of a superalloy by an arc welding process in which the workpiece is supported in a protective-gas container into which is placed a welding electrode and an induction coil for preheating the workpiece. Material of the same type of the workpiece is applied to the surface of the workpiece or to a welding joint thereof by arc welding produced by the welding electrode. The apparatus and associated method are particularly suitable for repairing age-hardened superalloys of engine blades.

Sensing of gas metal arc welding process characteristics for welding process control

Abstract: A method of sensing and controlling a gas metal arc welding process employs high frequency sampling of electrical signals from the welding circuit. The sampled signals are operated upon by predetermined processes to determine characteristics indicative of on-going weld quality and the future weld quality. The processes which operate upon sampled electrical signals determine shielding gas quality, the occurrence of short circuits and frequency thereof; pulse frequency and standard deviation thereof, contact tube wear and trends in the sampled electrical signals.

Electric arc spray coating with cored wire

Abstract: A method is disclosed for the electric arc spraying of powder-filled cored wires to apply hard, wear-resistant coatings to various substrates. Inert gas, preferably nitrogen, is supplied to the arc spray gun such that the mass ratio of the wire feed rate to the gas feed rate is preferably between about 0.07 and about 0.11. Operation in this range yields an optimum combination of coating hardness properties and arc spray gun operating characteristics.

Electrode and flux for arc welding stainless steel

Abstract: A flux for use in arc welding of a stainless steel workpiece with a consumable metal electrode having a precentage of chromium, which welding flux comprises a silica containing system for forming a slag on the surface of the deposited chromium-bearing alloy weld metal and a bismuth containing slag releasing agent selected from the class consisting of elemental bismuth, bismuth fluoride, bismuth sulfide, bismuth titanate, bismuth oxy carbonate, bismuth oxy-chloride and mixtures thereof. Also, there is provided an electrode employing this flux.

Multiple operator welding apparatus

Abstract: A multiple operator welding apparatus is disclosed which is particularly well suited for use in stick arc welding, GTAW, FCAW, ACAC, and GMAW arc welding processes. One or more welding modules are selectively mounted in a main power frame and connected to the power source by a knife blade connector which permits removal and replacement of one or more welding modules while the power source is in use. The knife blade connector also permits one or more welding modules to be removed from the main power frame and used at a remote location. The welding module for use with the multiple operator welding apparatus incorporates an inductor which permits use of a reduced incoming module voltage while producing a satisfactory weld. The reduced incoming module voltage results in significant energy savings.

Method and apparatus for depositing molten metal

Abstract: A collector electrode and adjacent electric weld torch are placed at a selected distance from a work surface or substrate. An electric welding current is generated so that a welding current arc forms between the collector electrode and the weld torch. A feed metal is then fed into the welding current arc and is melted into molten metal adjacent to the collector electrode. The molten metal is then deposited onto a work surface. The collector electrode and weld torch are positioned so that the welding current arc between the weld torch and the collector electrodes does not penetrate the work surface or the already-deposited metal.

Digital control of torch position and weld pool in MIG welding using image processing device

Abstract: A digital computer control system for improving the stability of the torch position and weld pool shape in metal inert gas (MIG) welding is proposed. It is shown how the characteristic of the digital controller may be selected for yielding a desired transient behavior. >

Gun for gas metal arc welding

Abstract: A gas arc metal welding gun has a handle which may be rotated freely with respect to a conduit containing a current transfer wire and a gas tube and with respect to an adapter and tip assembly.

Method of welding nickel or nickel alloy products

Abstract: A method of welding metal products, at least one of which being made of nickel or a nickel alloy, comprises the steps of generating an arc between the products to be welded serving as a positive pole and a tungsten electrode held by a welding torch serving as a negative pole, emitting a shielding gas consisting of an argon-based mixed gas containing one or both of hydrogen and helium from a confining gas nozzle concentric with the tungsten electrode, thus confining the apparent flaring angle of the arc within 80 degrees, and moving the welding torch along the weld line while feeding the tip of a filler wire to a part of the molten pool directly below the arc. This method is applicable to the welding of metal products, at least one of which is made of nickel or a nickel alloy.

Monopulse investigation of drop detachment in pulsed gas metal arc welding

Abstract: The drop detachment process in pulsed welding was investigated by a novel, non-continuous method. A pendent drop was formed on a fixed electrode by a low-current arc. The drop was then detached by a single high-current pulse. The detachment process was studied by high-speed filming and by current and voltage measurements. The shielding gas was Ar with various amounts of CO2, O2, H2 and He. Comparative experiments with ordinary pulsed welding were also done. The authors found ample evidence for an upward force on the pendent drop, most likely caused by the recoil force of evaporating metal. The force increases with CO2 concentration, base current and base current duration. The recoil force gives rise to a critical concentration of the molecular additive, above which it is impossible to detach the drop almost regardless of pulse width. This critical concentration decreases with increasing base current and base current duration. It also seems to decrease with increasing dissociation energy of the molecular additive. The drop velocity decreases with increasing CO2 concentration. For 95Ar5CO2 they also present results on the effect of drop mass and pulse current on drop velocity, minimum pulse width for detachment, and shortest detachment time (tdmin). They find evidence for a minimum detachable drop mass being smallest for large pulse currents. In the pulse current range 210-350 A they observe Ip1.7 tdmin=43, and in the range 350-600 A, Ip1.2 tdmin=2.4 (basic SI-units).

Apparatus for carrying out mig welding on three-dimensional curved surface, and milling apparatus for automatically forming welding grooves

Abstract: An automatic welding apparatus and an automatic milling apparatus for machining welding grooves in order to weld a three-dimensional surface such as a ball tank or the like are disclosed A welding wire spool is accommodated within a case and a cover to prevent the welding wire from being oxidized and from being contaminated with foreign materials The automatic milling apparatus is installed to form welding grooves on the both sides of the objects to be welded, in the case where a welding is performed on a three-dimensional curved surface A guide roller having a handle is installed to control the machining depth of the grooves, and an idling type nylon guide roller is installed in closed contact with the shaft of a cutter, thereby adjusting the distance between the rail and the groove, and adjusting the deviations of the depth of the grooves, which are caused by the machining inaccuracies due to the deviations of the three-dimensional curvature

Welding method of aluminum foil

Abstract: A welding method of an aluminum foil, which permits the direct resistance welding of an aluminum foil, with a chemical conversion coated layer of Al 2 O 3 formed thereon, to a lead wire, includes placing an aluminum foil, with a chemical conversion coated layer formed on the surface thereof, on a back bar made of a material having good electrical insulating property and heat resistance, arranging an electrically-conductive metal on the aluminum foil, bring first and second electrode tips into contact under pressure with the surface of the electrically-conductive metal with the electrode tips spaced from each other and then causing a welding current to flow between the first and second electrode tips, thereby conducting the series resistance welding of the aluminum foil to the electrically-conductive metal.

Welding method for rotating shafts

Abstract: An improved welding method is provided for repairing rotating shafts, particularly cracked high pressure steam turbine rotors The welding method preferably employs a 225Cr--10Mo--03V-type welding filler metal, preferably deposited using a narrow groove automatic gas tungsten arc welding technique A narrow groove is formed in the rotor to remove the crack The groove is preheated, filled with the welding filler metal, and postheated, resulting in a strong, high temperature resistant, long lasting weld

Arc welding method using special protecting gas

Abstract: The invention relates to a protective-gas arc welding method using a melting electrode for relatively highly and highly alloyed, corrosion resistant steels, especially nickel materials and special steels, in which the welding process is carried out under protective gas. Welding methods of this type are associated, owing to the normally present oxygen contents or the contents of oxygen-carrying compounds in the protective gases, with undesirable oxidation at the welding point. Said oxidising proportions, on the other hand, do contribute to effective welding. According to the invention, a welding process is now proposed in which a protective gas having a proportion of carbon dioxide or a proportion of oxygen or a proportion of a mixture of said gases of from 0.01 to 0.5% by volume, preferably from 0.02 to 0.1% by volume is used. This results in an advantageous welding outcome while welding proceeds surprisingly well.

Ultra high vacuum diffusion bonded NbAl2O3 and CuAl2O3 joints—The role of welding temperature and sputter cleaning

Abstract: Polycrystalline niobium and copper are welded in UHV (2 × 10−10mbar) to alumina (99.7 wt%) at various temperatures. Prior to joining the surfaces of the metal and ceramic to be welded are sputter-cleaned by argon ions at 3–5 keV with a maximum dose of 5 × 1019Ar+/cm2. The amount of bonded area at the interface depend on welding temperature and welding time. After 1 h welding time the fraction of bonded area is 98% for Nb Al2O3 joints at 0.65Tm (Tm = melting point of the metal in K). The amount of unbonded regions at the interface of Cu Al2O3 joints decrease from 20% after 1 h welding time to 5% after 3 h welding time at 1010°C. Plastic flow and creep determine the pre closure mechanism at the metal-ceramic interface. Fracture energy Gc and the fracture resistance Kc of the UHV bonded metal-ceramic joints depend strongly on welding temperature and the amount of bonded area. For Cu Al2O3 joints sputter-cleaning is a prerequisite for reliable measurements of the fracture energy. Without sputter-cleaning most of these joints did not withstand the cutting procedure during fabrication of four-point bend test beams. The fracture energy of Nb Al2O3 joints manufactured without sputter-cleaning is low and can only be determined for joints welded above 1500°C. Impurities at the metal-ceramic interface are assumed to be responsible for the decrease in bond strength of joints manufactured without sputter-cleaning.

Development of low-frequency pulsed MIG welding for aluminium alloys

Abstract: (1992). Development of low‐frequency pulsed MIG welding for aluminium alloys. Welding International: Vol. 6, No. 7, pp. 580-583.

Computer simulation of three‐dimensional convection in travelling mig weld pools

Abstract: Mathematical models of the metal‐inert gas (MIG) welding process may be used to study the influence of various welding parameters on weld dimensions, to assist in the development of welding procedures, and to aid in the generation of process control algorithms for automated applications. A three‐dimensional model for convection and heat transfer in MIG weld pools has been formulated and solved using the finite difference technique. The energy exchange between the pool and the molten filler metal droplets via spray transfer, and the interaction of electromagnetic, buoyant, surface tension, droplet impact and plasma jet forces were considered. MIG welding was carried out using mild steel plate with heat input from 7 to 17.5 KJ/cm. The calculated and experimentally observed weld bead dimensions were compared. Occurrence of finger penetration phenomena only in MIG welds are adequately explained through the application of the proposed model. Good agreement is demonstrated between predicted weld dimensions and experimentally measured ones.

Self-cleaning nozzle for a gas welding torch

Abstract: A welding torch for gas metal arc welding has a torch body which conducts electricity, receives a cable for directing a welding wire, and defines a passage for directing a shielding gas. A conductor tube has an inner end portion secured to the torch body and a free outer end portion, and a contact tip is secured to the outer end portion of the conductor tube. The contact tip has a central bore which directs the welding wire through the tip, and a diffuser directs the shielding gas around the contact tip and conducts electrical power to the contact tip. A tubular welding nozzle body is formed of a porous polycrystalline graphite material and has a slightly tapered inner surface which surrounds the contact tip for collimating the gas while substantially reducing the accumulation of spatter on the nozzle body. The contact tip may also be covered with the same graphite material to impede spatter accumulation, and the porous graphite material is impregnated with petrolatum and wax to extend the service life of the body. The tubular nozzle body may be protected by a surrounding copper jacket, and an interfitting band of ceramic material retains the body within the jacket.

Process for seam welding of sheet metal blanks

Abstract: As preparation for the seam welding of different thickness sheet metal blanks (10 and 12), at least the thicker (10) of the two blanks is reduced in thickness, preferably by chip machining, in its edge region (11) which is intended for welding. Since the edge regions (11 and 13) which are to be welded then approximate to each other in their thicknesses (t1+t2), practically symmetrical conditions with regard to the joint plane exist for the welding operation, so that the welding can proceed with substantially the same controllable welding parameters as in the seam welding of sheet metal blanks of equal thickness. The process is suitable mainly for use in mash seam welding, but also in other seam welding processes, such as for example, in laser welding.

A mercury-free electrodeless metal halide lamp

Abstract: A mercury-free electrodeless metal halide lamp has an arc tube (21). The arc tube (21) is made of glass having an inner surface defining an arc discharge space (23). A metal oxide layer (31, 35) is coated on the inner surface of the arc tube (21). A filling gas disposed in the arc discharge space (23) includes metal halide and a rare gas. Excitation means (27,29) couple radio-frequency energy to the filling gas for generating an arc discharge. The mercury-free electrodeless metal halide lamp suppresses an increase of an arc voltage of the lamp during its lifetime.

Method for defect free keyhole plasma arc welding

Abstract: A plasma arc welding process for welding metal of increased thickness with one pass includes operating the plasma arc welding apparatus at a selected plasma gas flow rate, travel speed and arc current, to form a weld having a penetration ratio to weld height to weld width, and maintaining the penetration ratio at less than 074 Parameters for the plasma gas flow rate, travel speed and arc current are adjusted to a steady state condition during a start up period and maintained during the steady state condition to complete a weld During a terminal stopping period, the travel speed is stopped and instantaneously replaced by filler wire which adds material to fill the keyhole that had been formed by the welding process Parameters are subsequently adjusted during the stopping period to terminate the weld in a sound manner

Spectroscopic study of a magnetically rotating arc between opper electrodes in contaminated argon

Abstract: The effects of N2 and CO contaminants in atmospheric-pressure argon on an arc rotating between two concentric copper electrodes has been studied using optical spectroscopy of copper lines. The axial temperature of the magnetically driven arc in Ar + %N2 was determined to be around 10,000 K for arc currents of SO to 200 A. The diffusion process of the copper vapor from the cathode was also studied. A copper density maximum 1 mm from the cathode along the arc column was found in Ar + %N2. Removal of the contaminated cathode surface layers by the arc when contaminant injection in the plasma gas was stopped was found to be a slow process with a time scale depending on the type of the gas contaminant. The presence of gas contaminant in the electrode material controls the cathode erosion mechanism and the overall arc behavior in the transition between a contaminated to a pure argon arc.

Laser welding of aluminium alloy 5456

Abstract: (1992). Laser welding of aluminium alloy 5456. Welding International: Vol. 6, No. 6, pp. 425-435.