Showing papers on "Gas metal arc welding published in 1989"

Apparatus and method of short circuiting arc welding

Abstract: Apparatus and method to reduce spatter and allow better semi-automatic welding in short circuiting arc welding of the type using a single D.C. power supply for causing a welding current to pass through a welding wire extending variable distances from a holder and between the welding wire and a workpiece at a molten metal pool on the workpiece. The welding current flows in response to an arc voltage while the welding wire is fed from the holder toward the workpiece whereby the welding wire is subjected to a succession of welding cycles each of which include an arcing condition during which the wire is spaced from the pool and a short circuit condition during which a molten metal ball formed on the end of the wire contacts the metal pool and then transfers from the wire to the workpiece by a necking action. In this type of welding operation, the invention involves the application of a preselected amount of energy into the wire during the arcing condition for each welding cycle, which preselected amount of energy slightly exceeds the known value of energy necessary to melt a given volume of metal to form a consistent molten metal ball onto the end of the wire. This constant energy is divided between the resistance heating of the wire extending from the wire holder and the anode heating caused by the arc during each arcing condition of a cycle. Consequently, constant energy is inputted to the end of the wire irrespective of changes in the amount of wire extension or stick-out.

Prediction of weld pool and reinforcement dimensions of GMA welds using a finite-element model

Abstract: Mathematical models of the gas metal arc (GMA) 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. In this work, a three-dimensional (3-D), steady-state thermal model of the GMA welding process has been formulated for a moving coordinate framework and solved using the finite-element method. The model includes temperature-dependent material properties, a new finite-element formulation for the inclusion of latent heat of fusion, a Gaussian distribution of heat flux from the arc, plus the effects of mass convection into the weld pool from the melted filler wire. The influence of weld pool convection on the pool shape was approximated using anisotropically enhanced thermal conductivity for the liquid phase. Weld bead width and reinforcement height were predicted using a unique iterative technique developed for this purpose. In this paper, the numerical model is shown to be capable of predicting GMA weld dimensions for individual welds, including those with finger penetration. Also, good agreement is demonstrated between predicted weld dimensions and experimentally derived relations that describe the effects of process variables and their influence on average weld dimensions for bead-onplate GMA welds on steel plate.

Apparatus for short circuiting arc welding

Abstract: An improvement in a short circuiting arc welding apparatus comprising a single D.C. power supply causing a welding current to pass through a welding wire extending from a holder and between said wire and workpiece at a molten metal pool on the workpiece, wherein the current flows in response to an arc voltage and the welding wire is subjected to a succession of welding cycles. Each of the welding cycles includes an arcing condition during which said wire is spaced from the pool and the energy applied to said wire exceeds a given value raising the temperature at the end of the wire to a molten temperature to form a molten metal ball on the end of the wire and a short circuit condition during which the molten metal ball on the end of the wire first contacts said molten metal pool and then transfers from the wire to the workpiece by a necking action breaking the molten metal ball from the wire to initiate an arc in a subsequent welding cycle. The welding cycles have a generally fixed frequency of repetition. The improvement comprises providing the power supply with a chopper circuit for applying a succession of input current pulses across the wire and workpiece at a pulse frequency substantially greater than the generally fixed frequency of repetition of the welding cycles and a pulse width changing circuit for adjusting current flow between the wire and the workpiece many times during each of the welding cycles.

Emission spectroscopy of plasma during laser welding of AISI 201 stainless steel

Abstract: The rates of vaporization of alloying elements from the weld pool were related to the emission spectra of the plasma during pulsed laser welding of AISI 201 stainless steel under various welding conditions. The temperature distribution in the plasma was determined from the spectra obtained from various locations in the plasma plume. The extent of ionization of the plasma was calculated from the electron temperatures To understand the role of surface active elements, emission spectra and the vaporization rate of iron that resulted from the welding of ultrapure iron samples were compared with those from the welding of oxidized samples or samples that were doped with sulfur or oxygen.

Role of the metallic phase arc discharge on arc erosion in Ag contacts

Abstract: The influence of the metallic-phase arc discharge on contact performance was studied for breaking Ag contacts. Measured parameters were whole arc duration (metallic-phase plus gaseous-phase arc duration), metallic-phase arc duration, contact resistance, bridge energy, and electrode material mass change. The tests were carried out under the various conditions of air pressure and contact current. The experimental results showed that the contact resistance increased when the arc duration in the metallic-phase arc region grew, and it was high and almost became constant when the arc reached the transition border to the gaseous phase. The material loss and transfer is log-proportional to the accumulated metallic-phase arc duration, irrespective of the air pressure condition. The effect of whole arc duration was not clear in the material mass change when the air pressure was varied. From many test results, it is concluded that the material mass change mainly depends on the metallic-phase arc rather than the whole arc duration. This means that the metallic-phase arc duration affects the material loss and transfer and the constant resistance, while the gaseous-phase arc has little influence. >

Metal Transfer in Gas Metal Arc Welding: Droplet Rate A study of droplet rates for various transfer modes verifies optimum operating parameters

Abstract: This study reports the changes in droplet-trans fer mode and rate during gas metal arc welding as the voltage is varied at a series of current levels. The droplet-transfer rate was found to be maximum (approximately 100 s_1) for the voltage/current combi­ nations that are normally suggested by the electrode manufacturers and are con­ sidered optimum in the judgment of experienced welders. At voltages above or below the TV-wide optimum range, the transfer rate decreased by about 10 s_1 per V in the vicinity of the optimum condition. Furthermore, statistical analysis of the arc current and voltage data showed that during operation outside the optimum range, the welding arc was unstable and the current output was very irregular with varying cycle time between each droplet transfer. At the maximum droplet-transfer rate, the droplet-transfer cycle time was very consistent and revealed a narrow rate range, which correlated with the high stability and lower spatter at these optimum operating conditions. The possibility of using the concept of maximum droplet-transfer rate range with minimum rate fluctuation and corresponding arc current-voltage signals as a means of short-circuiting welding process control and automation is being considered. At voltages below the optimum range, high-speed video recording confirmed that the short- circuiting transfer was very unstable and the arc reignited explosively. Above the optimum voltage, the arc became longer and the droplets became visibly larger, with mixed globular and short-circuiting transfer. The droplets, however, were no longer directed uniformly to the weld pool, resulting in increased spatter. arc (FCA), submerged arc (SA) and gas tungsten arc (GTA) welding. With the exception of GTA welding, all these pro­ cesses require a consumable electrode, which has the dual function of carrying the current that heats the weld pool and providing filler metal to complete the weld joint. This dual function has long been a topic of research. Spraragen and Lengyel (Ref. 1) reviewed the basic princi­ ples of an electric arc and summarized the development of the field of welding arc physics. In particular, they concluded that in the area of liquid metal transfer from the electrode to the weld pool, the electromagnetic pinch force, gravity, shielding gas drag force and surface ten­ sion are the major forces that act on the electrode tip. Using high-speed cinemat­ ographic techniques, Muller, Greene, and Rothschild (Ref. 2) found that large spher­ ical liquid-metal droplets in a GMA arc decreased in size with increasing current. As the electrode feed rate was continu­ ously increased, however, a sudden decrease in droplet size occurred at what was termed the transition current. In addition, they determined that with inert gas shielding, the droplet composition remained constant during the metal trans­ fer. Lesnewich (Refs. 3-5) investigated the physics of arc welding using SMA and CMA welding. Particularly, he studied the effects of welding process parameters such as current, voltage, electrode polar-

Pulse MIG welder for welding thin-walled copper-nickel pipe

Abstract: A welding station for welding thin-walled copper-nickel pipe. An electronic welding station (10) has an output circuit (13) which provides arc welding power having the arc characteristics specified by a weld parameter selection circuit (12). A welding torch and feeder assembly (11) has a controller (20) which is responsive to a predetermined event, such as the passage of time since the start of the arc, or the average temperature of the pipe (25) as indicated by two temperature-measuring devices (30, 32). The controller (20) adjusts the wire feed speed, the pulse frequency, the pulse width, the welding voltage, the welding current and/or other parameters so as to cause the arc to have the parameters most desired for welding copper-nickel pipe. The present invention provides for a hotter arc for starting the welding operation, thereby obtaining good penetration and bonding, and a cooler arc for continuing the welding operation, thereby preventing burn-through of the pipe (25).

Spectroscopic Study Of Laser-Induced Plasma In The Welding Process Of Steel And Aluminium

Abstract: Results of spectral diagnostics of the plasma produced by intense laser radiation during the welding process of steel and aluminium with CO2 lasers are presented. The experiments were carried out in an intensity range I = 106 ÷ 107 W/cm and with He, N2, Co2, Ar as shielding gases. The electron plasma temperature T and density n were measured under various processing and shielding gas conditions.It is shown that the time-averaged plasma temperature correlates with the welding results such as e.g. a welding depth obtained by varation of the welding speed and process gas. In this way it is demonstrated that spectral characteristics of the plasma can be used in the monitoring of the plasma and in the optimalization of the welding process. Furthermore, it is shown that spectroscopic results help to explain the influence of the process gas. Examples of cooling, heating and shielding effects caused by process gases are shown and discussed in view of the efficiency of the welding process.

Welding flux and welding electrode

Abstract: A welding flux and welding electrode containing a copper-nickel core is described which results in very low porosity when used in the overhead welding position as well as all other welding positions.

Spray mode gas metal arc welding process

Abstract: A spray mode gas metal arc welding process employing a shielding gas mixture consisting essentially of (A) 3 to 8 volume percent carbon dioxide, (B) 30 to 40 volume percent argon and (C) the balance helium

Device and process for short circuit arc welding

Abstract: The invention relates to a device and a process for reducing the spatter effect when welding and for improving the welding work, particularly in the case of semi-automatic short-circuit arc welding using a direct-current supply. The welding current flows as a function of the arc voltage while the welding wire is fed towards the workpiece from the holder, the welding wire being subjected to a series of welding cycles. Each welding cycle comprises an arc phase and a short-circuit phase. In the case of this kind of welding, the invention makes provision for the supply of a predetermined amount of energy to the welding wire during the arc phase in each welding cycle, the said amount of energy exceeding the amount of energy, whose energy level is known, which is required to melt a certain volume of metal at the end of the welding wire into a coherent globule (droplet) of molten metal. This constant energy is divided between the resistance heating of the free end of welding wire projecting beyond the welding-wire holder and the anode heating which is effected by the arc in the arc phase of the welding cycle.

Flux cored wire for gas shielded arc welding for heat resistant steel

Abstract: PURPOSE: To improve high temp. characteristic of a welded metal by containing the specific contents of Mo and Nb in a metal fluoride series flux cored welding wire. CONSTITUTION: In the flux cored wire for gas shielded arc welding packing 8-25% of the flux containing 1.0-10.0% metal fluoride and 1.0-6.0% deoxidizer to the total wire wt. in cavity part of a steel-made outer shell, 0.10-0.50% Mo, 0.005-0.025% Nb and further, 0.1-0.4% of (0.5 Mo + 10 Nb) to the wire wt. are contained in one or both of the steel-made outer shell and the packed flux. Nb and Mo form fine carbon-nitride and further, Mo increases high temp. strength with solid-solution strengthening. High temp. characteristic of the welded metal can be improved and can be used to structure without fire resistant covering. COPYRIGHT: (C)1990,JPO&Japio

Detection of metal-transfer mode in GMAW

Abstract: One of the requirements of a sensing system for feedback control of gas metal arc welding (GMAW) is the capability to detect information about the metal-transfer mode. Because the operating boundary for the desired transfer mode, expressed as a function of mass input and heat input, may vary due to conditions beyond the control of the system, a means of determining the transfer mode during welding is necessary. A series of sensing experiments is performed during which the ultrasonic emissions, audio emissions, welding current fluctuations, and welding voltage fluctuations are recorded as a function of the transfer mode. In addition, high speed movies (5000 frame/s) of the droplet formation and detachment are taken synchronously with the sensing data. An LED mounted in the camera is used to work the film at the beginning and end of the data acquisition period. A second LED is pulsed at a 1 kHz rate and the pulses are recorded on film and with the sensor data. Thus events observed on the film can be correlated with the sensor data. Data acquired during globular transfer, spray transfer, and stiff spray or streaming transfer are observed to correlate with droplet detachment and arc shorting. The audio,more » current, and voltage data can be used to discriminate among these different transfer modes. However, the current and voltage data are also dependent on the characteristics of the welding power supply. 4 refs., 5 figs.« less

Automatic soldering or welding unit for small parts - has hydrogen oxygen gas mixt. plus alcohol gas, if required, fed under pressure to workpiece location

Abstract: Soldering or welding unit esp. for automatic processing of small components utilises a stream of pressurised heated gas, more specifically hydrogen and oxygen, which is fed via piping (4) to a torch nozzle (9) directed at the soldering or welding position. The tubular section of the nozzle is eccentrically mounted on the unit relative to its vertical axis (5) about which it is swivable. The solder in wire form (41) is fed from an exchangable magazine (37) via an automatic advancing unit (55). The nozzle movement and solder wire feed are program controlled. The gas mixte is produced by the electrolysis of mineral-free water. Hydrocarbon gas, e.g. alcohol gas, can be fed along with the combustion gas mixture in order selectively to adjust the flame temp.' ADVANTAGE - The soldering or welding head design facilitates compact, intensive action at the soldering or welding points, rapid progression of the individual processes, improved application of soldering flux and the elimination of oxydation reaction during working.

Magnetically impelled arc butt welding of aluminium pipes

Abstract: (1989). Magnetically impelled arc butt welding of aluminium pipes. Welding International: Vol. 3, No. 11, pp. 941-946.

Method for joining galvanized steel plates

Abstract: PURPOSE: To prevent the development of blow hole by using a wire containing the specific quantity or more of Cu and brazing under argon gas atmosphere in the method joining galonized, steel plates under superposing or butting plural pieces with laser beam heating source or plasma heat source. CONSTITUTION: By using a plasma welding machine, the galanized steel plates 1 are joined with a butt joint by using the wire containing ≥ 60% Cu. The brazing layer 1a is made at the joined part 10. In the case of using the plasma welding machine, the galvanized steel plate as the base material and the wire are heated by arc generated with W electrode. In the case of being the prescribed welding condition and the prescribed or lower welding current, the brazing is executed without existence of diffusion layer and in the case of being more than the prescribed welding current, the liquid phase diffusion brazing is executed. This plasma welding is executed under shield gas atmosphere of argon gas. By this method, the development of blow hole is prevented and the joined part having extremely good outward appearance can be obtd. COPYRIGHT: (C)1991,JPO&Japio

Welding joining method of surface treated steel plates

Abstract: PURPOSE: To reduce the scattering of molten metal during welding and to improve corrosion resistance and rust prevention of a weld zone by removing surface treating coating films of the weld zone and then, performing welding thereon and further, forming metallic sprayed deposit on the bead surface. CONSTITUTION: Surface treating coating films 2a and 2b of both surfaces in the vicinity of the end faces to be a welding joining part of secondary material 2 in lap joint fillet welding or only a surface treating coating film 2a in the vicinity of the end face left side to be a welding joining part of the secondary material 2 in Tee joint fillet welding are removed partially respectively and welding is performed. Further, after cleaning treatment of the bead 3 surface after welding is carried out, metallic sprayed deposit 5 or nonmetallic sprayed deposit 6 is formed thereon. Accordingly, since the surface treating coating films 1a, 2a and 2b are removed in advance, these are not evaporated and scattered during welding. In addition, since a welded bead 3 is covered with the metallic sprayed deposit 5 with high corrosion prevention, the corrosion resistance is improved and welding joining with high reliability can be performed. COPYRIGHT: (C)1990,JPO&Japio