Showing papers on "Arc welding published in 1983"

Temperature fields produced by traveling distributed heat sources

Abstract: The solution of a traveling distributed heat source on a semi-infinite plate provides information about both the size and the shape of arc weld pools. The results indicate that both welding process variables (current, arc length and travel speed) and material parameters (thermal diffusivity) have significant effects on weld shape. The theoretical predictions are compared with experimental results on carbon steels, stainless steel, titanium and aluminum with good agreement. 25 references, 23 figures, 1 table.

Arc welding method

Abstract: An arc-welding method, which comprises: arc-welding objects of welding together along the line of a groove formed between said objects of welding by continuously moving a welding electrode along the line of said groove while reciprocating said welding electrode in the width direction of said groove; characterized by: calculating at prescribed time intervals, for each one reciprocation of said welding electrode in the width direction of said groove, deviations (l-lo) of values (I) of one of arc current and arc voltage from a previously set reference value (lo), for each of left-side deviations (L) and right-side deviations (R) relative to the vertical plane which passes through the center of amplitude of said one reciprocation of said welding electrode and is parallel to the line of said groove; calculating at said time intervals, when said welding electrode moves over the left side of said groove relative to said vertical plane, differences (L-R) between said left-side deviations (L) and the immediately preceding right-side deviations (R), to controllably aligning the center of said amplitude of said one reciprocation of said welding electrode with the center of said groove In the width direction thereof at said prescribed time intervals so that said differences (L-R) become null; and, calculating at said prescribed time intervals, when said welding electrode moves over the right saide of said groove relative to said vertical plane, differences (L-R) between said right-side deviations (R) and the immediately preceding left-side deviations (L), to controllably aligning the center of said amplitude of said one reciprocation of said welding electrode with the center of said groove in the width direction thereof at said prescribed time intervals so that said differences (L-R) become null.

Robotic Arc Welding: Research in Sensory Feedback Control

Abstract: Robotic arc welding and its dependence on sensory feed-back control for successful application is discussed. Problems unique to arc weld sensing are identified and sensor requirements are categorized as a function of welding design requirements, joint imperfections, weld shape deviations, and process characteristics. The two most prevalent approaches of weld sensing, i.e., optical and through-the arc sensing, are covered.

Microprocessor controlled welding apparatus

Abstract: A microprocessor-controlled are welding power supply is disclosed. A silicon controlled rectifier ("SCR") bank is used to generate a direct current arc welding current under program control. Positive synchronization is provided by the microprocessor using a phase locked loop and a polarity detector, so that the gating signals applied to the SCRs are correctly timed. Optimum tradeoffs between hardware and software are accomplished by using look up tables to store correction factors that can be quickly accessed during execution, and by using timers as smart interface chips to fire the SCRs at the same angle during each cycle until changed or updated by the microprocessor. The arc welding power supply is capable of operating in a constant current or constant voltage mode without rewiring the circuit.

Infrared thermography for sensing the arc welding process

Abstract: This paper was presented at the Annual AWS Convention, Philadelphia, Pa., Apr. 1983. The Authors present experimental results that could aid in the development of a closed-loop feedback system capable of correcting for perturbations that arise during automatic arc-welding. Specific weld faults were intentionally introduced into an arc-welding process, and the resulting surface isotherms were observed with a scanning infra-red camera for both stationary and moving arcs, Each fault produced a recognisably different distribution of the surface temperature. The results are presented and discussed in some detail, and it is concluded that infra-red thermography appears to be a suitable sensor for incorporation into a closed-loop feedback system for continuous process and quality controlled welding.

Infrared sensor for arc welding

Abstract: An infrared detector (10) is provided with spectral filtering means (12) for direct observation of the arc region during electric arc welding operations. The filter (12) permits direct observation of the weld pool by suppressing almost all of the infrared radiation produced by the arc itself. Were this not the case, the electrical signal output from the infrared detector is totally obscured by the intense infrared radiation from the arc and would thus not permit sufficiently high resolution infrared measurements to be made on the weld pool and the work piece.

Welding method combining laser welding and MIG welding

Abstract: Welding of deep penetration is obtained in a sustrate by a method which comprises first melting the joint portion of the substrates by MIG welding and then focusing a laser beam in the bottom surface of a crater formed in consequence of the MIG welding thereby effecting laser welding of the crater.

Finite element analysis of arc-welding processes

Abstract: Analyse du flux thermique au cours du processus de soudage a l'arc. Application au soudage en bout d'une plaque rectangulaire d'acier. Comparaison des valeurs calculees de champ de temperatures avec des donnees experimentales

Apparatus and method for providing useful audio feedback to users of arc welding equipment

Abstract: The user of electric arc welding equipment is provided with audible feedback signals which provide useful information relating to the output current and voltage of the welder. An audio tone is generated and is frequency modulated by a signal which corresponds to welder output voltage. The tone is amplitude modulated by a signal corresponding to output current thus providing the user with a synthesized feedback signal having a voltage-proportional pitch and current-proportional volume. Additional modulation means are disclosed for introducing a current-proportional warble component to said tone.

Electrical resistance-pressure welding process for welding parts of workpieces made of aluminum materials and an apparatus and electrode therefor

Abstract: Spot- and projection-welding of aluminum sheets has always been connected with difficulties mainly because of the surface layers of aluminum oxide, and even by pickling, these difficulties could be only partly eliminated. The main difficulties have always been insufficient electrode life times, the unsatisfactory quality of the weld and especially the unsolved problem of achieving good quality welding and long electrode-life when using un-pretreated aluminum sheets. The problem has been solved in principle by using electrodes having profiled contact-surfaces, by means of which the layer of oxide is broken during pre-pressing and a direct contact between the electrode and unoxidized material of the workpiece is provided, the contact-resistance of which is lower than the portion of the overall resistance of the point of weld formed by the metal of the aluminum sheets to be welded together. In an appropriate welding machine, the means for switching-on the welding current are controlled in such a manner that the welding current is switched on only after a sufficiently large contact area and therewith a sufficiently low contact-resistance of this contact has been reached.

Automatic weld line following method

Abstract: An automatic weld line following method for use with an arc welding method of welding a work by feeding a consumable electrode toward the weld line of the work through the tip of a welding torch and by oscillating the welding torch. The average and effective values of a welding current are detected, even if they are different, and fed to a computer so that the distance between the tip and the work is automatically controlled. At the same time, the oscillation angle is controlled to be symmetric at all times with respect of the weld line.

Hot wire type electric arc welding torch

Abstract: A hot wire type electric arc welding torch includes a wire heating unit which has a first guide hole therein disposed substantially parallel to a welding torch. An insulative guide is connected to the wire feeding unit and supplies a wire to the welding torch at an angle which is inclined relative to the first guide hole. An insulative spacer is disposed in the wire feeding unit, and the insulative spacer has a guide hole therein which forms an angle with the first guide hole for bending the wire. Tapered escape hole portions are formed at wire inlet and outlet sides of the insulative spacer to minimize friction.

Spectroscopic measurement of hydrogen contamination in weld arc plasmas

Abstract: The introduction of hydrogen into metals during welding is known to cause hydrogen assisted cracking and embrittlement in certain situations. It has been shown that the weld metal hydrogen content is directly related to hydrogen concentration in the weld arc plasma. In this paper we describe a simple spectroscopic technique for measuring the arc plasma hydrogen concentration in real time when an argon shield gas is used. This technique is based on the fact that the intensity ratio of the hydrogen Balmer Alpha emission line at 6563 A and an argon emission line at 6965 A was observed to be an approximately linear function of hydrogen concentration in the weld arc plasma. This technique was experimentally verified under a variety of welding conditions for gas metal arc welding and found to have an error of less than 10% when measuring hydrogen concentrations in the arc plasma as low as 0.25% by volume. This method of hydrogen measurement is also applicable when welding with shield gases not containing argon so long as a suitable ratioing line is available.

Arc welding torch with integral vision sensor

Abstract: A gas tungsten arc welding torch has an integral optical system which images the weld puddle on the face of a fiber optic cable, and is suitable for industrial welding. The copper torch body has cover gas, electrical power, and coolant connections and an integral slim profile electrode holder. The optical lens is located directly above the electrode; the holder is out of focus and is not seen in the image of the weld region. A concentric torch configuration is more compact and has a large field of view at the weld area. When coupled to a remote video camera and monitor components, the torch-vision system permits control of torch manipulation and of the weld process.

A Study on the Metallurgical Properties of Steel Welds with Underwater Gravity Welding

Abstract: The main object of this study is to clarify the effects of water pressure on the metallurgical properties of steel welds such as blowhole occurrence, crack sensitivity, formation of diffusible hydrogen and oxide inclusions etc. with underwater gravity welding. Underwater welding were carried out at water pressure 0.03 to 10 kgf/cm2 (0.003 to 1 MPa) in the experimental tank and some facts were made clear.

Method for controlling output of welding power source

Abstract: PURPOSE:To obtain a flat bead shape and to decrease generation of a spatter by supplying high welding current from the stage when an arc is generated and decreasing the welding current when the sign for a short-circuit is detected thereby performing consumable electrode type arc welding. CONSTITUTION:A high current period maintaining the welding current to be supplied from a welding power source 14 at a high level is provided as long as possible to form a flat bead shape in a consumable electrode type arc welding method which repeats alternately the short-circuit and arc generation between a welding wire 1 fed by a welding wire feed motor 13 and base metals 4. A voltage fluctuation is further detected by a welding voltage detecting circuit 16 and is inputted via an arc detecting circuit 15 and a differentiating circuit 21 to a short-circuit predicting circuit 18. When the sign for the short-circuit is detected in said circuit by the fluctuation of the welding voltage inputted thereto, a switch 19 is changed over from the terminal 19a on the side of a high current setting circuit 20 to the terminal 19b on the side of a low current setting circuit 22 to decrease the welding current to a low level and to maintain the low current thereby waiting for the short-circuit between the wire 1 and the base metals 4.

Hot-wire arc welding apparatus

Abstract: A hot-wire arc welding apparatus comprises a non-expendable electrode, means for supplying a current to initiate an arc between the nonexpendable electrode and a workpiece, an arc current control means for controlling the current from the supplying means, a wire feed means for feeding a filler wire into the arc, a wire feed control means for controlling the wire feed means to feed the filler wire at a given rate of feed, a voltage applying means for applying a voltage between the filler wire and the workpiece, a wire voltage control means for controlling the voltage from the voltage applying means, and a reference voltage generator for generating an output voltage which increases gradually or incrementally with time, each of the arc current control means, the wire feed control means, and the wire voltage control means being connected to the reference voltage generator and responsive to the output voltage therefrom for controlling the operation thereof. A delay circuit such as an integrator may be connected between the reference voltage generator and the wire feed control means for applying a delayed output voltage to the latter.

Vehicular arc welder

Abstract: An arc welder, designed to receive its source of power from a vehicle's alternator through a special controlled battery charger. The first portion of energy used in welding comes from the vehicle's battery charger and the balance of energy used in welding comes from the welder's battery pack. Between spurts of actual welding, the welder's batteries are re-charged by the vehicle's special controlled battery charger. The batteries in said battery pack are so arranged as to give the operator a choice of voltage for welding and inductors are used to control the current. Also, the batteries can be used direct by by-passing said inductors for extra-heavy cutting and/or extra-heavy duty welding thus giving the operator an extremely wide range of current to fit his needs.

Real-time ultrasonic sensing of arc welding processes

Abstract: NDE techniques are being investigated for fusion zone sensing of arc welding processes for closed-loop process control. An experimental study of pulse-echo ultrasonics for sensing the depth of penetration of molten weld pools in structural metals during welding indicates that real-time ultrasonic sensing is feasible. Results on the detection of liquid/solid weld pool interfaces, the determination of interface location, and effects of high temperature gradients near the molten zones on ultrasonic wave propagation are presented. Additional work required and problems associated with practical application of the techniques are discussed.

Advances in welding metallurgy of steel

Abstract: Progress in welding with regard to ferritic, austenitic, and duplex-microstructure grade steels is discussed. In transformable ferritic steels, the influence of second-phase particles on welding behaviour is an important theme and examples given include their effect on: (a) heat affected zone (HAZ) microstructure, hardenability, and toughness; (b) HAZ reheat cracking; (c) weld-metal microstructure and toughness; and (d) weld-pool behaviour during arc welding. The improved quantitative understanding of factors controlling solidification and hydrogen-induced cracking in weld deposits is also discussed. In high-alloy austenitic grades, a greater awareness of the advantages of fabricating low-C grades is noted, together with recognition of the important role of residual stress in the development of intergranular stress-corrosion cracking. Factors controlling the creep properties of austenitic weld metal have been clarified, and methods of producing highly aligned columnar grains in multipass austeniti...

Arc welding system with vision

Abstract: An arc welding system with image acquisition utilizing a non-planar beam of electro-magnetic radiation, such as, a hollow conical beam of light, to illuminate at least a portion of the welding object is disclosed. The conical beam of light is generated by impinging a light beam on the surface of a concave, cylindrical reflector having a longitudinal axis that preferably is parallel to the longitudinal axis of the welding torch. The light beam enters the concave cylindrical reflector through the hollow shaft of a motor. Rotation of the motor angularly positions the reflected light beam on the welding object. The illuminated portion of the object is imaged on an array of photosensitive elements to produce corresponding signals that are representative of the image on the array. These signals are used to obtain identification information concerning the welding object and guidance information for a plural axis manipulator that guides the welding torch tool along a welding seam. The image acquisition apparatus is optically and physically shielded from the welding arc by a replaceable shield.

Resistance welding of zinc-coated steel

Abstract: A method for resistance welding zinc-coated steel members is described wherein at least one member comprises a copper layer intermediate the steel and the zinc coating. The copper layer melts during welding and seals fissures within the fused steel to produce a hermetic weld. The copper layer also protects exterior surfaces where the zinc coating is disrupted by the welding operation.

Prediction of weld-metal composition during flux-shielded welding

Abstract: It is well known that the slag and metal do not reach equilibrium during fluxshielded welding, due to the short reaction times and large thermal gradients inherent in the process. Nonetheless, many investigators have attempted to define the effective equilibrium by empirical analysis of experimental data. The results of these analyses have generally been contradictory and, in most cases, have lacked a firm scientific basis.

Flexible trailing shield for welding reactive metals

Abstract: A flexible trailing shield for providing nonreactive gas shielding to arc lding operations comprises a housing formed of interlocking transverse segments adapted to flexibly cover weld surfaces having varying configurations. The housing has a torch entrance port for slidably receiving a welding torch, a conduit for receiving gas into the housing, a foraminous material to uniformly distribute the gas within the housing, and a pervious structure through which the gas is dispersed over the weld surface.

Welding Under Water and in the Splash Zone — a Review

Abstract: The author reviews the parameters controlling underwater welding especially arc welding with covered electrodes, MIG, TIG and with cored wire. It describes wet welding and hyperbaric welding, with the use of nitrogen and noble gases for shielding and in the welding chamber. The specific problems of underwater welding are described in detail: hardness of the HAZ, cold cracking by hydrogen, method of calculating the thermal input, consequences of pressure on fusion characteristics.

Measurement of Fusion Boundary Energy Transport During Arc Welding

Abstract: An experimental technique is presented to identify fusion boundary (liquid/solid interface) energy transport mechanisms during welding procedures. The gas-tungsten-arc-spot-welding procedure, using a low melting (point specimen material (lead), was chosen to demonstrate the methods. Vaporization energy losses were found to be important during the growth of the fusion boundary. Significant thermal convection was absent within the weld pool for applied currents less than about 1000 A, and for such cases the location of the fusion boundary was found to be governed primarily by heat conduction. At the current levels of almost 300 A significant weld pool convection was found to exist, expecially at the (inner) stagnation point, causing a deeper penetration of the fusion boundary there.