Showing papers on "Gas metal arc welding published in 1991"

Method and apparatus for gmaw welding

Abstract: A method and apparatus of welding along a pass line on a steel workpiece, which method and apparatus comprises simultaneously feeding two welding wires in generally parallel relationship toward a workpiece with extended welding wires generally intersecting the workpiece at individual points spaced from each other a distance in the range about 3/16 inch to about 3/8 inch; then creating a separate arc between each of the wires and the workpiece; passing a single protective envelope of shielding gas axially along two welding wires simultaneously and around said two separate arcs extending between welding wires and the workpiece; and, causing relative movement between the two gas shielded welding wires and the workpiece in the direction corresponding to the desired pass line on the workpiece.

Process control of gmaw : sensing of metal transfer mode

Abstract: One of the requirements of a sensing system for feedback control of gas metal arc welding (GMAW) is the capability to determine the metal-transfer mode. A series of sensing experiments was performed during which the audio emissions, welding current fluctuations and welding voltage fluctuations ere recorded as a fuction of the transfer mode

Convertible arc welding system

Abstract: In a convertible TIG, MIG or plasma arc welding system, a cylindrical docking body mountable in a socket at a welding station, has utilities passages therethrough for receiving an elongated metal electrode, shielding and plasma gases, welding potential and cooling water. The electrode passage is threaded at one end to interchangeably mount any of a plurality of electrode feed assemblies for consumable wire or tungsten electrodes. An output fixture is mounted at the other end of the body to receive the electrode and the plasma or shielding gas and pass them from the body. A nozzle assembly is removably mountable on the other end of the docking body in surrounding relationship with the output fixture and the associated tip assembly and communicates with the shielding gas passage for passing shielding gas to the working end of the nozzle. The docking body has internal channels among the passages so as to circulate cooling water through both the output fixture and the nozzle assembly. The working end of the nozzle assembly interchangeably mounts any of a plurality of gas directing assemblies for directing gases relative to the arc. The system can be converted among TIG, MIG and plasma arc welding by simply changing the electrode feed assembly, the tip assembly and the gas directing assembly. Alternatively, the entire nozzle assembly can be replaced with one designed for TIG or MIG welding.

Effective heat input in pulsed current gas metal arc welding with solid wire electrodes

Abstract: In this work, the heat input of the welding arc, calculated from the measured values for voltage and current, is compared to the heat gained by the weldment for pulsed and nonpulsed current welding. The effects of shielding gas composition, arc length, weld geometry and weld position on heat transfer are examined. Methods for calculating the heat received by the weld during pulsed current welding are discussed

Analysis of arc pressure effect on metal transfer in gas-metal arc welding

Abstract: Metal transfer has been analyzed using both the static force balance method and the pinch instability theory. The influences of arc pressure as well as electromagnetic pressure in the development of instability in the cylindrical molten metal were considered. Using perturbation theory, the dispersion equation was obtained in terms of the arc current density, and the drop diameters were then calculated. The drop diameters, which were determined by considering the arc effect, were found to be greater than those drop diameters that were obtained without the arc effect. The transition current was obtained on the assumption that necking starts when the arc covers an entire drop, at which point spray transfer occurs as the molten droplet becomes cylindrical in shape. This explains why spray transfer or transition does not appear with carbon dioxide or helium shielding gas since the arc then exists only at the lower half of the droplet.

Gas metal arc welding and shielding gas therefor

Abstract: A welding method and shielding gas therefor which enables the use of gas metal arc welding to produce smooth welds with little or no surface oxidation and without encountering arc instability during the metal deposition.

Arc welding method and apparatus

Abstract: A method of consumable electrode arc welding is shown wherein the leading consumable electrode wire is mounted in parallel with a trailing filler wire, the latter inserted into a molten metal bath. Welding current is divided between the consumable electrode wire and the filler wire. These modifications improve the wettable boundary of the molten metal bath, prevent defects in the weld, and provide a high speed, highly efficient and high quality method of welding carbon steels, alloy steels, as well as aluminum and its alloys in a fully automatic as well as a semiautomatic operation. In an apparatus utilizing the above method, a single torch contains the consumable electrode and filler wire. One or more insulating contact tubes containing filler wire are mounted in a gas shield in parallel with a conductive contact tube containing consumable electrode wire. The unit is small in size and light-weight, and thus convenient for a welder to carry or hold during operation. Appropriate selection of one of the filler wires provided allows multidirectional operation without reorienting the torch. The unit produces a high-quality weld at rapid welding rates and is suitable for automatic and semiautomatic operation.

Fatigue characteristics of pulsed MIG-welded Al-Zn-Mg alloy

Abstract: Pulse-current MIG welding of Al-Zn-Mg alloy was carried out using an extruded section of base material and Al-Mg (5183) filler wire. During welding the pulse parameters such as the mean current and pulse frequency were varied and their effect on the geometry and porosity content of weld deposit as well as the fatigue life of the weldment was studied. The pulse parameters were found to affect significantly the geometry and porosity content of weld deposit and consequently the fatigue life of the weldment. For a comparative study, weldments were also prepared by using conventional continuous current MIG-welding process, where welding currents equivalent to the mean currents of pulsed process were used. The fatigue life of the weldment was correlated with the geometry and porosity content of weld deposit.

Analyses of Electrode Heat Transfer in Gas Metal Arc Welding In-depth investigation offers insight into the practicality of modeling the GMAW process

Abstract: Heat and fluid flow in the electrode during gas metal arc welding are considered approximately, experimen­ tally, analytically and numerically for ranges of electrodes and materials of practical importance. Estimation of the governing nondimensional parameters and pertinent time scales provides insight into droplet formation and detachment while demon­ strating that the behavior of the solid electrode may be considered to be quasi- steady. The time scale estimates show that a steady-state, spherical flow calculation for the droplet would be inappropriate and possibly misleading. Experimental ob­ servations of the formation of a tapering tip, forming as electrical current is in­ creased in steel electrodes shielded by ar­ gon gas, are found quantitatively consis­ tent with numerical simulations based on the hypothesis that additional thermal en­ ergy is evolved along the cylindrical side surface of the electrode due to electron condensation.

Shielding gas mixture for welding superalloys

Abstract: This invention discloses a novel shielding gas mixture for use in gas shielded arc welding processes. The shielding gas of this invention may be used in a wide variety of processes when welding various superalloy compositions. In the broad range, the composition contains, in percent by volume, 5 to 12 helium, 0.1 to 0.9 carbon dioxide and the balance argon. The typical composition contains about 10 helium, about 0.25 to 0.55 carbon dioxide and the balance argon plus impurities.

Welding material for low coefficient of thermal expansion alloys

Abstract: The invention provides a welding material for welding iron containing low CTE alloys. The filler metal contains 25-55% nickel, 0-30% cobalt, 0.05-0.5% carbon, 0.25-5% niobium and balance iron with incidental impurities. The welding material also is operable with fluxes for submerged arc welding. In addition, the welding material may be configured to function as a flux coated or flux-cored electrode.

A Study on Prediction of Welding Current in Gas Metal arc Welding Part 1: Modelling of Welding Current in Response to Change of Tip-to-Workpiece Distance:

Abstract: A model of the welding arc in gas metal arc welding (GMAW) is very useful for the analysis and automation of the welding process. Thus a mathematical model that is able to predict the welding curre...

Method of fabricating metallic workpieces with a welding apparatus, and apparatus for carrying out the method

Abstract: With an apparatus for shaping by hardfacing, welding material is deposited in track-like layers starting on the surface of a parent body (2), and a workpiece (1) is thus produced, in which case the parent body (2) can be a component of the workpiece (1). The progress of the track-like layers as well as the approximate deposition rate of the welding material are calculated by a computer unit (11), starting from a software, two- or three-dimensional model of the workpiece (1), and are preset for the system control (10), which mutually positions the welding torch (7) by means of the robot (5) as well as the workpiece (1) fixed on a rotary table (4) with a clamping device (3) and regulates the deposition rate of welding material at the welding apparatus (8) in such a way that the liquid welding material adheres to the underlying layer without flowing off and irregularities in the track-like layers are compensated for. Thus metallic workpieces with the most diverse body shapes, theoretically of any size and of any wall thickness, and even consisting of different metallic materials, can be produced by shaping by hardfacing without auxiliary cores or other devices supporting the liquid welding material.

Analyses of electrode heat transfer in gas metal arc welding

Abstract: The present study examines the thermal processes occurring in moving electrodes for GMAW with the objectives of 1) determining which phenomena are important in controlling the melting rate and 2) explaining the formation of a tapering tip observed for some combinations of electrode materials and shielding gases

Shielding gas for arc welding of aluminum

Abstract: A shielding gas for the arc welding of aluminum consists of argon or mixtures of argon and helium. The shielding gas also includes an admixture of 80 ppm to 250 ppm of nitrogen.

A Study on Prediction of Welding Current in Gas Metal arc Welding Part 2: Experimental Modelling of Relationship Between Welding Current and Tip-to-Workpiece Distance and its Application to Weld Seam Tracking System

Abstract: The weld joint tracking sensor is indispensable to improve the flexibility of the arc welding robot application. Recently, some sensing methods that utilize the electric arc signal, or more correct...

Vacuum arc deposition device

Abstract: A vacuum arc deposition device comprising a vacuum vessel with a vacuum arc evaporation source disposed in the vacuum vessel, a plurality of arc current introduction portions are disposed to the vacuum arc evaporation source along with a plurality of arc discharge power sources for supplying arc electric power correspondingly to the plurality of arc current introduction portions. The vacuum arc vapor deposition device provides a large evaporation area and a high film formation rate.

Laser Welding of Titanium Alloy

Abstract: (1991). Laser Welding of Titanium Alloy. Welding International: Vol. 5, No. 5, pp. 346-351.

A Study on an Arc Sensor for Gas Metal Arc Welding of Horizontal Fillets An S-shaped fillet weld was successfully tracked using the quadratic curve-fitting method for sensing

Abstract: The weld joint tracking sensor is indispensable for improving the flexibil­ ity of arc welding robot applications. Re­ cently, some sensing methods that utilize the electric arc signal, or more correctly the welding current in GMA welding, have been developed and are prevalently in use. The welding current is directly af­ fected by the contact tip-to-workpiece distance for the given welding voltage and wire feed speed. Armed with a means of measuring the welding current, the tip-to- workpiece distance and then the weld joint geometry can be obtained by weav­ ing the arc back and forth across the line of travel. Knowledge of the weld joint geometry relative to the welding gun per­ mits the welding gun to trace the joint. In this study, the welding current signal was fitted to a curve, which is inversely proportional to the trace of contact tip- to-workpiece distance by using the qua­ dratic curve-fitting method in order to ex­ tract useful information on the welding gun position from the welding current sig­ nal. Furthermore, the availability of the curve-fitted welding current signal was in­ vestigated and a joint tracking system for horizontal fillet joints was developed by using this curve-fitting method.

Evidence from inclusion chemistry of element transfer during submerged arc welding

Abstract: The complex changes in composition during the submerged arc welding of C-Mn steels have been related to flux composition and weld metal inclusions, which form the final reaction products. High-temperature reactions in the arc plasma (particularly those involving oxygen, fluorine, calcium and magnesium) are followed at lower temperatures by reactions in the slag and the weld pool

Method for controlling arc start of pulse mag welding

Abstract: PURPOSE: To prevent spattering by setting shifting time from completion of conducting hot start current to the starting time of conducting pulse current and conducting plural shifting pulse currents changed over to pulse width of the above pulse current during this shifting time step by step. CONSTITUTION: When tip part of a wire 1 comes into contact with a material 2 to be welded at the time of starting the welding, the hot start current Ih having current larger than the mean value of pulse current Iw during welding is sent and after that, pulse MAG welding arc start control method for sending the pulse current is executed. The shifting time period from the time at sending completion of the above hot start current to the time at sending start of the above pulse current is set. During the above shifting time period, plural shifting pulse currents It changed over step by step from the pulse width having width larger than pulse width in the above pulse current to the pulse width of the above pulse current is sent. By this method, the spattering and burn back developed with short circuit of the tip part of wire with molten particles due to sudden variation of wire melting speed can be prevented. COPYRIGHT: (C)1992,JPO&Japio

Tig welding method in combination with laser beam

Abstract: PURPOSE:To provide the TIG welding method in combination with a laser beam where feed space of filler metal is secured and the occurrence of inside defects of a weld zone, etc., are prevented. CONSTITUTION:The laser beam welding side is constituted of an optical fiber 3 to transmit the laser beam 2, a condenser lens 5 and a hollow part of a hollow electrode 1 arranged on the same axis in front thereof. The TIG welding side is constituted of the hollow electrode 1 and an electrode fitting body 16. The optical fiber is protected by a fiber protecting tube 6 and fitted to lens housing 4, an irradiation part is formed of the optical fiber, the condenser lens and the lens housing and the optical fiber is inserted into the electrode fitting body, by which two welding means are formed into one system on the same axis. The electrode fitting body receives an electric current carried through a feeder 9 from a welding power source 7 which is passed to the hollow electrode and a TIG arc 22 is generated between the electrode 1 and welding base metal 23.

A study on an arc sensor for gas metal arc welding of horizontal fillets

Abstract: The weld joint tracking sensor is indispensable for improving the flexibil­ ity of arc welding robot applications. Re­ cently, some sensing methods that utilize the electric arc signal, or more correctly the welding current in GMA welding, have been developed and are prevalently in use. The welding current is directly af­ fected by the contact tip-to-workpiece distance for the given welding voltage and wire feed speed. Armed with a means of measuring the welding current, the tip-to- workpiece distance and then the weld joint geometry can be obtained by weav­ ing the arc back and forth across the line of travel. Knowledge of the weld joint geometry relative to the welding gun per­ mits the welding gun to trace the joint. In this study, the welding current signal was fitted to a curve, which is inversely proportional to the trace of contact tip- to-workpiece distance by using the qua­ dratic curve-fitting method in order to ex­ tract useful information on the welding gun position from the welding current sig­ nal. Furthermore, the availability of the curve-fitted welding current signal was in­ vestigated and a joint tracking system for horizontal fillet joints was developed by using this curve-fitting method.

Particulate fume generation during gmaw and gtaw

Abstract: For the past five or six years BOC Limited has carried out a series of investigations into particulate fume generated during welding. Various gas shielded processes were studied and the amount of fume emitted and its chemical composition were analysed. In this paper the authors present the results of these investigations and discuss the significance of the findings.

Orbital welder for high purity welding

Abstract: An orbital welder for welding tubes includes a welding head and a hinged clamp arrangement which grasps the tubes and holds them in abutment for welding. The clamp is constructed to discharge shielding gas into the welding region. By supplying gas only from the clamp, a high purity weld is achieved.