Showing papers on "Arc welding published in 1984"

A new finite element model for welding heat sources

Abstract: A mathematical model for weld heat sources based on a Gaussian distribution of power density in space is presented. In particular a double ellipsoidal geometry is proposed so that the size and shape of the heat source can be easily changed to model both the shallow penetration arc welding processes and the deeper penetration laser and electron beam processes. In addition, it has the versatility and flexibility to handle non-axisymmetric cases such as strip electrodes or dissimilar metal joining. Previous models assumed circular or spherical symmetry. The computations are performed with ASGARD, a nonlinear transient finite element (FEM) heat flow program developed for the thermal stress analysis of welds.* Computed temperature distributions for submerged arc welds in thick workpieces are compared to the measured values reported by Christensen1 and the FEM calculated values (surface heat source model) of Krutz and Segerlind.2 In addition the computed thermal history of deep penetration electron beam welds are compared to measured values reported by Chong.3 The agreement between the computed and measured values is shown to be excellent.

The Physics of Welding

Abstract: Greater understanding of the physics of welding is leading to improved application and control of welding processes. Further gains in welding productivity could follow. Electric arc welding, high energy density welding and future developments are described

Short circuit transfer arc welding machine

Abstract: A short circuiting arc welding machine increases an arc current density by adding a pulsed current having upper and lower limits to a current flowing when an arc is produced, thereby increasing the depth of bead penetration into a workpiece, removing welding defects, and speeding up the welding operation. The welding machine is capable of alternately changing the direction of flow of a welding current at desired periods to produce arcs in straight, reverse and mixed polarities for achieving intermediate characteristics of arcs of straight and reverse polarities, with a resultant ability to adjust in a wide range a wire melting rate and the amount of heat applied to the workpiece.

Control for welding system

Abstract: The specification describes a control unit for use with the welding gun of an arc welding assembly. A single adjustable means in the welding gun effects changes in the control unit to regulate welding voltage as well as the speed at which the electrode wire is fed to the welding site.

Portable arc voltage wirefeed welding system

Abstract: A portable wirefeed and control apparatus for use in consumable electrode arc welding systems which is capable of being powered by conventional AC or DC variable voltage or variable current supplies without modification of the power supply or the wirefeed and control apparatus. The portable wirefeed unit incorporates a wirefeed motor, a supply of weld wire, optional gas controls, and voltage regulating and protective control circuits all powered at welding arc voltage carried by the welding current supply conductor. The unit is circuit connected to the power supply by means of a single welding electrode supply conductor and a ground return. Electrode power, weld wire, optional shielding gas supply and welding gun control switch conductors are carried in a single flexible conduit extending between the control unit and a remote welding gun and wirefeed speed and thus wirefeed rate are partially responsive to variations in welding arc voltage.

Output control of short circuit welding power source

Abstract: A method of controlling the output of a power source in consumable electrode arc welding in which a short circuiting phase and an arcing phase alternately take place between a consumable electrode and a workpiece in a shielding gas atmosphere, the method being characterized by repetition of a cycle of operation consisting of: a first stage of maintaining the output welding current at a first value of a relatively low level upon establishment of a short circuit across a gap between a consumable electrode and a workpiece; a second stage of maintaining the welding current at a second value of a relatively high level succeedingly to the first stage; a third stage of lowering the welding current to a third value of a low level upon detection of necking as a premonition of rupture of short circuiting molten metal between the electrode and workpiece; a fourth stage of, upon generation of an arc across a gap between the electrode and workpiece subsequent to the third stage, maintaining the welding current at a fourth value of a relatively high level exceeding the value of average welding current; and a fifth stage of maintaining the welding current at a fifth value of a relatively low level until the gap between the electrode and workpiece is short-circuited, under control of substantially constant current characteristics to feed current of constant level irrespective of variations in arc length.

Measurement head for welding machines

Abstract: A measurement head in an arc welding machine modulates the light intensity of a laser light beam with a modulating signal of 50 KHz or higher, and radiates the laser light beam onto an object to be measured while changing the direction of laser beam emission in one plane. A light receiving unit in the measurement head changes its direction of detecting a reflected beam in the same plane. Angles at which the light beams are emitted and detected are detected at the time a modulated signal component is detected from an output from the light receiving unit. The position of a bright spot produced on the surface by the radiated laser light beam is computed from the detected angles based on the principle of triangulation.

Variable polarity plasma arc welding on the Space Shuttle external tank

Abstract: Variable polarity plasma arc (VPPA) techniques used at NASA's Marshall Space Flight Center for the fabrication of the Space Shuttle External Tank are presentedd. The high plasma arc jet velocities of 300-2000 m/s are produced by heating the plasma gas as it passes through a constraining orifice, with the plasma arc torch becoming a miniature jet engine. As compared to the GTA jet, the VPPA has the following advantages: (1) less sensitive to contamination, (2) a more symmetrical fusion zone, and (3) greater joint penetration. The VPPA welding system is computerized, operating with a microprocessor, to set welding variables in accordance with set points inputs, including the manipulator and wire feeder, as well as torch control and power supply. Some other VPPA welding technique advantages are: reduction in weld repair costs by elimination of porosity; reduction of joint preparation costs through elimination of the need to scrape or file faying surfaces; reduction in depeaking costs; eventual reduction of the 100 percent-X-ray inspection requirements. The paper includes a series of schematic and block diagrams.

Arc welding system and docking assembly therefor

Abstract: In a MIG arc welding system, a docking body having utilities passages therethrough is mountable at the welding station. Means are provided at one end of the body for accepting incoming utilities such as consumable wire electrode, shielding gas, welding potential and cooling water. Different types of welding gun or torch assemblies are interchangeably manually mountable and demountable at the other end of the welding body without disturbing the docking body or the utilities coupled thereto. Plug-type water fittings on the welding gun or torch assembly are receivable in receptacles in the docking body which communicate with the water passages, actuator tips on the fittings actuating normally-closed, spring-biased check valves in the passages to prevent leakage of water from the docking body when the welding gun or torch assembly is demounted. The gun or torch assembly is held in place by a coupling nut which is threadedly engaged with the docking body. There are provided a fixed-mount embodiment, wherein all utilities but the welding wire enter the docking body radially, and a remote or movable mount embodiment, suitable for mounting on a movable mechanized or robotic support, wherein all utilities enter the docking body axially. A positioning ring on the latter embodiment accurately positions the docking body on the movable support.

Method and apparatus for arc welding

Abstract: An arc welding process is provided with a preheating step in which a consumable wire electrode is heated prior to insertion into the electrode stick-out region. This is accomplished by the circulation of current from a preheating power supply through a segment of the wire. Both gas-metal and gas-tungsten arc welding processes are disclosed, along with apparatus used in these processes.

Tubular welding electrode

Abstract: A formulation for the flux in a cored-type electric arc welding electrode which produces high impact value welds while welding vertically up or overhead and at greater melt-off rates than heretofore. The major flux ingredients are lithium oxide, iron oxide, silicon dioxide, lithium carbonate, magnesium and aluminum metal powders, all in a carefully balanced formula to give excellent operator appeal and excellent slag removal.

A Real-Time Optical Profile Sensor For Robot Arc Welding

Abstract: For robot ano automated arc welding a compact 3D vision sensor has been developed. It generates data to correct the preprogrammed welding path. It can find the starting point of toe seam, calculate the seam volume for process control and detect tack welds, all in real-time with submillimeter resolution. Mounted to the robot hand the He-Ne laser-based scanning triangulation sensor takes distance measurements to the workpiece at a 2000/s rate. Preproduction models were tested in operation for the effects of arclight, heat, smoke, spatter ano e.m.i., using various combinations of the welding_ parameters: process (MIG, TIG), mode (short cktg, globular, spray), welding current and voltage, protective gas (He, Ar, CO2) and travel speed. Included in the paper is a discussion of environmental influences and of closed-loop operation.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Method of enhancing weld pool boundary definition

Abstract: The surface of the molten weld pool and surrounding workpiece area are floodlighted during an arc welding operation by a narrowband light source such as a laser in order to highlight the pool boundary and yield an image which is easily computer processed to give the pool perimeter. An arc welding torch has built-in optical systems, one to route laser energy via a coherent optical fiber bundle to exit optics on the torch to project two spots of light onto the trailing side edges of the pool, another to image the weld region which is relayed to a remote camera. The difference between reflectance values and direction on the pool and workpiece surfaces accounts for the enhanced image.

Flux cored wire electrodes for self-shielded arc welding

Abstract: There are disclosed flux cored wire electrodes for self-shielded arc welding which comprise a steel sheath filled with a powdery flux containing as essential components thereof the following components set forth in terms of weight percentage: BaF2 (25-70), alkali metal fluoride (1-30), compound oxide composed of the oxide of an alkaline earth metal selected from among Ca, Sr, and Ba and the oxide of a metal selected from among Fe, Mn, Ni, Co, Ti, Al and Zr (1-30), Al (3-12), Mg (2-10) and Mn (0.5-10).

Source of power for arc welding

Abstract: Power sources for welding applications and the like are provided in accordance with the teachings of the present invention. An inverter arrangement comprising a plurality of inverters, having inputs connected in series, receive portions of a d.c. load from a plurality of series connected smoothing capacitors. The smoothing capacitors are connected to form a voltage divider and apply the resulting portions of the d.c. load to the plurality of inverters. This enables the plurality of inverters to be dimensioned in a manner so as to withstand the smaller portions of the d.c. load resulting from the voltage division.

Heat Flow during the Autogenous GTA Welding of Pipes

Abstract: A theoretical and experimental study of heat flow during the welding of pipes was carried out. The theoretical part of the study involves the development of two finite difference computer models: one for describing steady state, 3-dimensional heat flow during seam welding, the other for describing unsteady state, 3-dimensional heat flow during girth welding. The experimental part of the study, on the other hand, includes: measurement of the thermal response of the pipe with a high speed data acquisition system, determination of the arc efficiency with a calorimeter, and examination of the fusion boundary of the resultant weld. The experimental results were compared with the calculated ones, and the agreement was excellent in the case of seam welding and reasonably good in the case of girth welding. Both the computer models and experiments confirmed that, under a constant heat input and welding speed, the size of the fusion zone remains unchanged in seam welding but continues to increase in girth welding of pipes of small diameters. It is expected that the unsteady state model developed can be used to provide optimum conditions for girth welding, so that uniform weld beads can be obtained and weld defects such as lack of fusion and sagging can be avoided.

Long wearing contact tip for inert gas arc welding

Abstract: A long wearing contact tip for an inert gas arc welder comprises an elongated cylindrical copper member having a longitudinal bore therethrough. A portion of the bore is enlarged for receiving a steel liner formed of either spiral wound steel wire or steel tubing. Circumferential grooves are cut into the external surface of the contact tip to afford better cooling of the tip by the inert gas flowing past the tip.

Method of controlling the output characteristic of a welding power source, apparatus for arc welding, and electrical circuit to be used for such apparatus

Abstract: A method and apparatus for arc welding particularly regarding a pulse arc welding machine comprising a welding power source having an output characteristic control circuit, an overload protection circuit, a driving circuit, and a main power circuit, and a wire feeding unit having a wire feeding control circuit, a motor driving circuit and a wire feed motor. The output characteristic control circuit comprises a welding arc autoregulating control system which provides the power source with a multi-segmental and moving output characteristic with varying slope, a circuit for connecting arbitrary number of output characteristic segments with arbitrary or varying slope, and a scanning circuit for obtaining the output characteristic segment with varying slope. A particular use of the control system is in an easy to operate autoregulating controlled GMA welding machine with one-knob control of wire feed rate without having to adjust the other welding parameters.

Arc welding torch having integrated wire feed

Abstract: A compact gas tungsten arc welding torch, which may have an integral puddle view optical system, utilizes an inert gas supply line and coolant supply and return lines, one carrying current for the weld process. The torch body has passages for flow of cover gas from a connection tube to the gas nozzle. The gas supply hose additionally carries the filler wire for the weld process, which passes into the gas connection tube and out of the torch body to an integral wire feed guide tube that is alternatively inside or outside of the gas nozzle.

Consumable electrode type arc welding method

Abstract: PURPOSE:To suppress the generation of defective shape beads such as welding defects lacking in fusion, etc., and drooping of beads in attitude welding by repreating alternately by an optional number of times each a short-circuit shift and a spray shift for controlling a heat input and controlling the bead shape. CONSTITUTION:Electric conduction is executed between a wire 31 and a material to be welded 35 from a welding power source 37 while supplying a shielding gas (g) from a feed port 32b, the wire 31 is melted by generating an arc (a) and dropped down onto a base metal 35, and a welding torch 32 is moved and the base metal is deposited by heating it and making molten pool (m). Its welding condition and a wire 31 feed speed are set by setting devices 40, 41, and an output of the power source 37 and rotation of a motor 46 are controlled by a controller 42 so as to reach said set condition. The welding condition is controlled by monitoring a welding current level, but a welding current and a current waveform being the origin of this control are obtained from an output of a welding current detector 38, for instance, short-circuit and pulse shifting periods Ta, Tb are as shown by waveforms in the figure. This waveform is processed by a device 39, and each shifting time T1, T2 is detected.

Consumable electrode type arc welding apparatus having a selectable start current

Abstract: A consumable electrode type arc welding apparatus in which arcing can be positively started under a variety of welding conditions. A start current detector selects a predetermined limited start current according to the welding conditions. A start current period setting unit sets a start current period, also in accordance with the welding conditions. A start current control circuit supplies the predetermined limited start current to the workpiece and the wire electrode for the predetermined period of time at the start of arcing.

Fatigue strengths of truss made of high strength steels

Abstract: This study investigates the fatigue behavior of trusses. Various types of panel-point-structures were designed for the purpose of obtaining compact and strong nodal joint, and fatigue tests of the structural models on the scale of about one quarter were carried out. Based on the previous study, details of nodal joint were improved and the process of corner weld was changed from manual shielded arc welding to submerged-arc welding. The local stresses distribution in the vicinity of nodal joint and their influences on the fatigue strength are also shown through the finite element stress analysis.

Pneumoconiotic effects of welding-fume particles from mild and stainless steel deposited in the lung of the rat

Abstract: Rats were exposed to single periods of inhalation of fumes generated by arc welding. Two processes were compared: either manual metal arc (MMA) using flux-coated mild steel (MS) electrodes or metal inert-gas (MIG) welding with stainless steel (SS). Widespread but small deposits of fume particles were cleared effectively from alveoli and airways. Peribronchial and subpleural aggregates of particle-laden macrophages remained. More massive and persistent lung-burdens were established by intratracheal administration of suspensions of fume-particles (10 mg and 50 mg, single doses).

Short arc welding method

Abstract: PURPOSE:To stabilize a welding arc and to prevent generation of a welding defect by detecting short circuit and detachment of a droplet, controlling welding current and oscillating a welding torch in the axial direction of the top end of a welding wire CONSTITUTION:The voltage from a welding power source 7 is impressed between a welding wire 2 and objects 6 to be welded through a wire feeder 5, a welding torch body 11, etc by which welding is progressed A voltage decider 17 judges the short circuit or detachment of a molten metal upon receipt of information from a welding voltage detector 16 and outputs a signal to an electromagnet controller 19 and a power source controller 29 On the other hand, the controller 19 controls the polarity change-over of the current flowing in an electromagnet 15 according to the time set in a time setter 18 with the signal from the decider 17 as a trigger The controller 20 controls also a welding power source 7 according to the time set in a time setter 18 with the signal from the decider 17 as a trigger thereby increasing or decreasing the welding current

Welding wire feeder system for electric arc welding apparatus

Abstract: A welding wire feeder system for an electric arc welder in which the wire feed motor M is powered from a pulse width modulated power supply comprising a power transistor Q10 controlled by a pulse signal on line 31 from a pulse width modulator comprising an integrated circuit A3. A control voltage proportional to the arc voltage and a feedback voltage indicative of the feed motor speed are generated and applied to respective inputs of a high gain amplifier A4-1 whose output error signal is either high or low dependent upon the relative values of the control and feedback signals. Control is effected in such a manner that an increase in welding arc voltage causes a corresponding increase in the welding wire feed rate, and vice versa.

Pulsed arc welding apparatus

Abstract: A method of pulsed arc welding and an apparatus for carrying out the method, employ welding current pulses having an amplitude greater than the value of a background current. The arc voltage is sensed to provide a signal for controlling the frequency of the welding current pulses to counteract variations in electrode wire feed speed or spacing of the electrode from the workpiece.

Arc welding apparatus

Abstract: A method and apparatus are provided for removing spatter from a torch of a gas shielded arc welding apparatus. After a series of welding operations are completed, pressurized air mixed with a small amount of oil is injected through a passage defined between a member supplying a welding electrode and a gas nozzle. This oil emitted adheres to the surface of the electrode supply member and the gas nozzle, thereby generating an oil film thereon. The pressurized air removes any spatter on the apparatus and the oil film prevents any further spatter from adhering to the surface.

Infrared Thermography As A Control For The Welding Process

Abstract: A feasibility study was performed to determine if infrared thermography could be used to detect perturbations in the arc welding process which result in defects. Data were gathered using an infrared camera with a resolution of .2°C which was trained on the molten metal pool during welding. Several defects were then intentionally induced and the resulting thermal images were preserved on film. These images revealed that different types of weld defects induce different characteristic changes in the thermal image by detectably altering the temperature field around the weld. These perturbations in the temperature field can be used to identify and locate defects such as arc misalignment, plate gap, puddle impurities etc. Macrostructural examinations permitted investigations into the relationships between weld puddle penetration depth and the temperature field. Using computer aided processing of these thermal images, it is expected that the welding process can be controlled to a higher degree than is presently possible.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.