Showing papers on "Arc welding published in 1990"

Pulse welding apparatus

Abstract: A pulse welding apparatus such as a pulse arc welding apparatus or a short-circuiting arc welding apparatus utilizing pulse discharge, wherein there is provided a pulse current waveform control circuit which feeds a desired pulse arc current to the arc welding power source that supplies pulse arc current to the welding load unit, the circuit being so designed as to effect optimum welding without adjusting or changing the circuit components. Even under various welding conditions or environments, furthermore, it is allowed to prevent defective welding during the arc welding caused by the magnetic blow phenomenon and to prevent defective welding such as undercut or sputtering caused by disturbances in the welding torch. The pulse current waveform control circuit is realized as a microcomputerized digital circuit, and the pulse arc current is controlled by the control operation of a program, in order to realize a desired current control by changing the program but without changing the circuit. By utilizing the memory, furthermore, the optimum welding current waveform parameter or a desired arc length signal is learned during the first welding, and the arc length feedback control or the current waveform control is effected during the second welding using a program prepared with the thus learned welding current waveform parameter or the desired arc length signal as a reference. Thus, the molten mass is prevented from being erroneously removed by the magnetic blow phenomenon, and a change in the arc length is suppressed that is caused by disturbance in the welding torch, contributing to improving the welding quality under various welding environments.

Flux-cored wire for gas shielded arc welding

Abstract: A flux-cored wire for gas shielded arc welding is described. The wire comprises a steel sheath and a flux composition filled in the steel sheath at a flux rate of 8 to 25 wt%. The flux composition comprises, based on the weight of the total flux, 10 to 30% of TiO₂, 0.1 to 0.6% of Na₂O provided that a ratio of TiO₂ and Na₂O is in the range of 20 to 100: 1, 0.01 to 2.0% of a metal fluoride calculated as F, and 0.005 to 0.4% of moisture. The composition may further comprise Bi₂O₃.

System and method of short circuiting arc welding

Abstract: There is provided an improvement in a short circuiting arc welding system comprising a work station with a consumable electrode and workpiece, a D.C. power supply with a positive and a negative terminal, high frequency current control means for applying a welding circuit with a given time-based profile across the work station while the electrode is short circuited and while the electrode is spaced from the workpiece, a welding current circuit means including a first means for creating a first inductive reactance in series with the current control means and work station whereby the welding current follows the time-based profile in accordance with the first inductive reactance. The improvement comprises a background current circuit means between the power supply and the work station and in parallel with the current control means and first means for applying continuously a background current across the work station. This background current circuit means includes a second means for creating a second inductive reactance substantially greater than the first inductive reactance and a resistor means for controlling the background current flowing continuously from the power supply to the work station through the background current circuit means.

Basic metal cored electrode

Abstract: A consumable welding element for arc welding comprising a steel sheath surrounding a compacted core containing metal alloying powders and an essentially 100% basic compound in an amount less than about 1.60% of the total weight of said element. The basic compound is calcium fluoride powder which is preferably in the range of about 0.1% to about 0.9% calcium fluoride powder by total weight of the element. As another feature the core of the element contains a specific agent for decreasing the amount of diffusible hydrogen in the weld metal. This new element may be a filler metal for TIG welding; however, it is preferably a consumable electrode for MIG welding.

Weldability of aluminium-lithium alloy 2090 using laser welding

Abstract: Lithium-containing aluminium alloys are of considerable current interest in the aerospace and aircraft industries because lithium additions to aluminium improve the modulus and decrease the density compared to conventional aluminium alloys. Many such alloys are under development for aircraft applications, which usually involves mechanical fastening. While aluminium-lithium alloys are fusion weldable with gas metal arc, gas tungsten arc and electron beam processes, they suffer from problems of weld porosity, heat-tearing cracking, poor penetration and low joint efficiency. In this paper, the weldability of aluminium-lithium alloys is briefly reviewed. The weldability of commercial aluminium-lithium alloy 2090 in the peak-aged condition was studied using laser welding. The quality of the welds was evaluated through mechanical tests (hardness and tensile tests) and microscopical observations. Mechanical property data and microscopical observations of the welds on prior surface-prepared (milled) material revealed a low degree of the weld surface degradation and an absence of porosity. This coupled with the attractive joint efficiencies suggest the superiority of the laser welding to conventional arc welding of this alloy. The performance of laser-welded butt joints is rationalized.

Low hydrogen basic metal cored electrode

Abstract: A consumable welding element for arc welding comprising a steel sheath surrounding a compacted core containing metal alloying powders and an essentially 100% basic compound in an amount less than about 1.60% of the total weight of said element. The basic compound is calcium fluoride powder which is preferably in the range of about 0.1% to about 0.9% calcium fluoride powder by total weight of the element. As another feature the core of the element contains a specific agent for decreasing the amount of diffusible hydrogen in the weld metal. This new element may be a filler metal for TIG welding; however, it is preferably a consumable electrode for MIG welding.

Transient temperature distribution in arc-welding of finite thickness plates

Abstract: This paper introduces a new analytical solution to predict the transient temperature distributions in a finite thickness plate during arc welding. This analytical solution is obtained by solving a ...

Flux cored wire for gas shielded arc welding

Abstract: PURPOSE:To allow the welding of steel sheets having galvanized surfaces by kneading a flux contg specific ratios of C Si, Mn, Ni, Al, B and iron powder with a specific volume of water glass, then filling the mixture at a specific ratio of the total weight of the wire CONSTITUTION:The steel sheet having the galvanized surfaces are welded by the flux cored wire for gas shielded arc welding formed by kneading the flux consisting, by weight %, of 1 to 4 C, 1 to 5 Si, 5 to 15 Mn, 05 to 5 Ni, 1 to 5 Al, <=05 B, and 60 to 90 iron powder into the wire with the water glass of 05 to 10 of the flux weight and filling the mixture into a metallic sheath at 8 to 30 of the total weight of the wire The C in the flux is converted to CO2 which is blown from the wire sheath barrel to a molten pool to improve the arc concentratability and to active the molten pool; therefore, the pits and blowholes by the generation of Zn vapor or the like are decreased

Cavity microstructure and kinetics during gas tungsten arc welding of helium-containing stainless steel

Abstract: Helium was implanted in type 316 stainless steel, through tritium decay, to levels of 0. 18, 2. 5, 27, 105, and 256 atomic parts per million (appm). Bead-on-sheet welds were then made using the gas tungsten arc (GTA) process. Intergranular cracking occurred in the heat-affected zones (HAZs) of specimens with helium concentrations equal to or greater than 2.5 appm. No such cracking was observed in helium-free control specimens or in specimens containing the lowest helium concentration. In addition to the HAZ cracking, brittle, centerline cracking occurred in the fusion zone of specimens containing 105 and 256 appm helium. Transmission and scanning electron microscopy results indicated that both the HAZ cracking and centerline cracking in the fusion zone resulted from the stress-induced growth and coalescence of cavities initiated at helium bubbles on interfaces. For the HAZ case, the cavity growth rate is modeled and shown to predict the experimentally measured 1-second time lag between peak weld temperature and the onset of cracking.

Computerized radiographic sensing and control of an arc welding process

Abstract: This paper summarizes an effort in which real-time radiography was implemented for on-line arc welding process study and control. X-ray penetrating radiation was used for volume observation in the welding pool and the heat-affected zone during the weld process. The advantages of such a technique are online detection and monitoring of defect formation in the weld and capability to study metal fusion and filler metal/base metal interaction and metal transfer in the welding pool. This technique may also be used for postservice, real-time remote testing of weld quality.

Power source apparatus for alternating-current arc welding, capable of supplying an alternating-current welding current having any waveform

Abstract: There is disclosed a power source apparatus for an alternating-current arc welding. In the power source apparatus, a reference signal generator periodically generates a reference signal having a predetermined waveform, and a direct-current power source outputs a current periodically changing in response to the reference signal, the outputted current having a waveform corresponding to that of the reference signal. Thereafter, a switching circuit supplies an alternating-current welding current to a welding load so as to sequentially change the polarity of the welding current from a straight polarity to a reverse polarity and from the reverse polarity to the straight polarity in synchronization with the reference signal by switching the current outputted from the power source in response to the reference signal.

Welding: Theory and Practice

Abstract: 1. The geometry of gas tungsten arc, gas metal arc and submerged arc weld beads (C. Heiple, J.R. Roper). 2. Solidification and structure of welds (J.A. Brooks, K.W. Mahin). 3. The fundamentals of weld metal pore formation (R.E. Trevisan, D.D. Schwemmer, D.L. Olson). 4. Control of chemical compositions and microstructure in low carbon microalloyed steel weldments (S. Liu, J.E. Indacochea). 5. Weld-pool pyrometallurgy (C.A. Natalie, D.L. Olson, M. Blander). 6. Arc-welding processes (H. Smartt). 7. Welding automation and computer control (S.J. Marburger). 8. Electron-beam welding (R.D. Dixon). 9. Explosive bonding (R.A. Patterson). 10. Pre- and post-weld heat treatment (J.E. Jones, A. Luo). 11. computational methods for calculating weld residual stresses in pipes (E. Rybicki). 12. Application of artificial intelligence techniques to welding (J.E. Jones, A.R. Rock).

System for use in electrode welding and gas/arc welding

Abstract: System for use in alternately electrode welding and gas/arc welding comprising a current supply cable (11) and a gas conduit in connection with a holder (10) having an associated electrode-carrying head. The holder (10) with associated current conductor member (13) is common for exchangeable first (15) and second (15') electrode-carrying heads. The first head secures the welding electrode (14) for electrode welding. The second head secures the arc electrode (14') for gas/arc welding and forms at the same time a support for a coupling member (31) for coupling to the gas conduit (32) and a control valve (33) for adjusting the supply of gas to and along the arc electrode (14').

Self organizing fuzzy linguistic control with application to arc welding

Abstract: Presents a self organizing fuzzy linguistic control strategy that is based on on-line modification of the control rules according to the extent of deviation of the process output from the output of a given reference model. Accordingly, the learning/adaptation algorithm, which is based on the hill climbing approach, modifies the parametrized characteristic functions of the fuzzy subsets describing the control rules, such that the meaning of each rule is iteratively changed to reflect new information regarding the behavior of the process. Simulation results show that this technique improves the overall response of the system in presence of asymmetric dynamic characteristics of the process, proving that this strategy can be a suitable alternative to ordinary fuzzy control. In order to study this self organizing scheme, the authors used a simulation model with similar characteristics as the gas metal arc welding process. This model simulates the variation of the peak surface temperature of the workpiece directly underneath the weld bead in response to changes in the arc current, or more accurately, changes in the electrode wire feedrate. >

Modelling the three‐dimensional fluid flow and heat transfer in a moving weld pool

Abstract: A three‐dimensional model for the fluid convection and heat flow in arc welding is proposed. It extends the previous two‐dimensional model by accounting also for the fluid flow and heat transfer in a travelling rather than a stationary mode. The model can be applied to analyse the heat‐ and fluid‐flow phenomena in welding processes. It is found that the fluid velocity in the pool front is higher than that in the pool rear. The fluid velocity field and the temperature distributions are directly proportional to the welding amperage and inversely to the welding speed. The comparison of the calculated and measured results show that the model is much more accurate than Rosenthal's theory and the pure conduction numerical method. Theoretical predictions based on the model are found to be in good agreement with experimental measurements.

Positional information detecting method in arc welding

Abstract: A method of detecting information on an arc welding position by monitoring the shape and/or position of an welding arc. When in the arc welding along a welding groove position while locating the same, the shape of the arc is picked up from above the joint portion of a member to be welded by means of an image pickup device, and the arc shape picked up is binary-coded. This binary arc shape and/or position are monitored to detect the welding groove position, the height of the welding torch, the welding start point, the welding end point, the external corner point, the internal corner point, the contact point of the welding wire with the work, and the welding groove gap.

Joint tracking with a self-teaching system

Abstract: One stage of manufacturing shipping containers includes welding long corrugated iron sheets to stringers. Before welding, the corrugated iron sheet is aligned with the stringer and the joint is defined as an intersection of two surfaces. Until recently, this weldment was performed manually. Automating this operation presents a number of difficulties and is beneficial only if the cost of the final product is lower than what it was when done manually. The preparation of weldment components, their positions on the fixture and the distortion during welding require an adaptive control system for joint tracking. A self-teaching system, where the robot is entirely guided by information provided by sensors, without any previous learning of a reference trajectory, is essential in this case. The aim of this study is to prove that it is possible to perform tracking on a plane through a self-teaching system. The paper presents the method of joint location, the operating principle of the sensor and its mechanical and metrological properties.

An experimental study of rotational behaviour of the arc during magnetically impelled arc butt welding

Abstract: This study intends to make clear experimentally physical reasons why in the case of the steel pipe with thicker wall thickness the arc rotates at low speed in the initial stage of heating and does at high speed in the final stage, why the arc rotates on the inner side of the pipe edge surface in the initial stage, and why the rotating position of the arc moves from the inner side to the outer side of the pipe edge surface as heating time passes. The results obtained were as follows:1) The low speed rotation of the arc in the initial stage of heating is due to the lower driving force resulted from the lower flux density at the inner side of the pipe edge surface, and the high speed rotation of the arc in the final stage is due to the higher driving force resulted from the higher flux density at outer side.2) The rotation of the arc on the inner side of the pipe edge surface in the initial stage is caused by the distribution of the magnetic field due to the heating current, according to the geometrical shape, the arrangement and the magnetic property of the pipe and other components for welding.3) The reason for the moving of the rotating position of the arc from the inner side of the pipe edge surface to its outer side with the increase of heating time is the variation of the magnetic field due to the heating current, which is caused by the magnetic transformation due to temperature rising near the pipe edge.

Method of automatically welding rails

Abstract: In a method of automatically welding rails, welding of bottom portions of the rails is carried out as root pass welding of a first layer according to CO2 gas shielded arc weld technique, and as continuous multilayer welding of layers above the first layer according to CO2 gas shielded arc weld technique without discontinuing the welding of a second layer and upper layers. In welding of ankle portions (R2) of the rails, a flux is rapidly added to promptly shift to electroslag weld. Then, welding is conducted to head surfaces (R5) of the rails by continuing electroslag weld technique. This automatic welding method enables high efficiency field welding of rails, obviating the need for any complicated switching operation of the electric power source and use of several kinds of welding materials.

Simultaneous In-Process Control of Heat-Affected Zone and Cooling Rate during Arc Welding A model is developed for independently regulating the time-temperature relationship of the HAZ and the centerline cooling rate

Abstract: The problem of process con­ trol in welding involves not only regulation of weld bead geometry, but also ther­ mally induced changes such as distortion, residual stresses and metallurgical trans­ formations near the weld. This paper ad­ dresses the last of these, and poses it as a feedback control problem. The objective is transformed to one of controlling the surface temperature field in-process, and using temperature feedback to implement such a scheme. A control model of the process is presented, and a parameter adaptive controller is designed to ensure consistent control system performance. A series of numerical simulations and exper­ iments using CMA welding is presented that confirms the model and illustrates the desired properties of the controller. With this system, the heat-affected zone and cooling rate (through their correlates in surface temperature-time relationships) can be regulated independent of each other, and gross disturbances to the tem­ perature field rejected totally in the steady- state. In addition, dynamic performance of the control system is illustrated, and the limits imposed by current hardware are discussed.

Device for monitoring qualities of electric welding

Abstract: PURPOSE: To improve sensitivity and reliability by constituting to obtain a reject limiting value width which encloses an average welding parameter profile based on a selectable probability to the reject of many can bodies which are recognized to be excellent and can bodies itself which are excellent. CONSTITUTION: An average welding parameter profile Fm which is stored in a memory 24 as a first welding parameter profile is obtained. And the average value of the welding parameter value measured to a first welding profile and the product of a standard deviation of the parameter value preliminarily fixed as a normal distribution multiplied by one or more sensitivity coefficients are obtained. Thus, a reject limiting value width which encloses the profile Fm is obtained, and an evaluation for a statistical evaluation of the welding parameter value, wherein the number of existence of can bodies 10 which are judged to be excellent is measured, is executed. Also, whether a second welding parameter profile measured lies within the reject limiting value width to the can bodies 10 which are successively produced is detected by a comparator 26.

Arc welding current/voltage control method

Abstract: A control method capable of effecting satisfactory arc welding by automatically controlling arc welding current and voltage. A processor calculates (106, 112) errors (eI, eV) between mean value (I, V) of actual welding currents and voltages periodically detected a predetermined number of times and target values IO, VO) of the welding current and voltage. If the welding current error falls outside an allowable range, a wire feeding speed correction amount is determined (ΔFW) (109) by substituting the mean value (I) of the welding currents and a welding current correction amount (ΔI) equivalent to the product of the calculated welding current error and a current gain into a calculation formula containing a first-degree polynomial (g'(I)) for the welding current and a welding current change amount (ΔI) as variables. The wire feeding speed correction amount is input to a welding machine. If the welding voltage error falls outside an allowable range, the processor determines a power supply output correction amount (ΔU) (115) by substituting the welding current correction amount (ΔI) and a welding voltage correction amount (ΔV) equivalent to the product of the calculated welding voltage error and a voltage gain into a calculation formula containing welding current and voltage charge amounts (ΔI, ΔV) as variables. The power supply output correction amount is input to the welding machine. The welding machine adjusts the wire feeding speed and power supply output, to rationalize the welding current and voltage.

Method for one-side root pass welding of a pipe joint

Abstract: A method for one-side root path welding of a pipe joint comprises the steps of forming a ring groove having a V-shaped bottom portion thereof at end faces of both pipes whose joint is circumferentially welded, attaching a backing material (16) to a butt portion of the pipes from an internal side of the pipes, running an automatic welding machine (1) along a guide rail (12) mounted on an outer surface of the pipes in the circumferential direction thereof, controlling a position of a welding torch (2) along a seam by means of an arc sensor, and welding root pass from the outer side of the pipes with a predetermined welding current and at a welding speed in a high-speed rotating arc welding of the pipes at a predetermined rotational speed and with a predetermined diameter of rotation The rotational speed of arc is from 10 to 150 Hz The rotation-diameter of the arc is from 1 to 4 mm The welding current is from 200 to 500 A The welding speed is from 75 to 300 cm/min

Pulsed arc welding apparatus

Abstract: A pulsed arc welding for carrying out arc welding or short-circuit transfer type arc welding by utilizing the pulsed discharge generated at the tip of a wire electrode. The propensity of wire electrode curvature causes irregular changes in the contact point of the wire electrode and variations in the arc length between the wire electrode tip and workpieces. Consequently, the invention detects arc voltage and current and checks the instantaneous variation in the arc length. The arc voltage value thus detected is converted to a reference arc voltage variable. Then the detected arc voltage value is compared with the reference value to compute a true arc length. A simulation arc length signal, which varies as welding proceeds, and a reference simulation welding current waveform are set, to compare the simulation arc length signal with the computed arc length signal. The reference simulation welding current waveform is corrected according to this difference signal to form and output a welding current waveform, which is controllable instantaneously to provide an ideal target arc length. Welding can be carried out with stability since the wire electrode is allowed to hold the simulation arc length during each welding process.

Effect of weld cooling rate on delta-ferrite content of austenitic weld metals

Abstract: The present study attempts to vary the weld cooling rate by the use of water-cooled copper backing (so far not tried) by keeping the heat input constant. It also takes into account the Cr eq /Ni eq ratio. In the present study two austenitic stainless steel strips (0.5 mm thick), type 308 Cb and 309 Cb (Table I) were used. Microplasma arc welding (5 A, 20 V, 20 cm min -1 , direct current electrode negative) was used to make autogenous beads using the melt-in technique

Manual keyhole plasma arc welding system

Abstract: A manual keyhole plasma arc welding system including a power source; a manual arc welding torch assembly which includes, a) a hollow shield cup, b) a orifice subassembly concentrically disposed within the shield cup, and c) an electrode concentrically disposed within the orifice subassembly; a shield gas source; and a plasma gas source. A shield gas discharge annulus is formed between a terminal edge of the shield cup and the terminal end of the orifice subassembly. The terminal edge of the shield cup is extended beyond the terminal end of the orifice subassembly to produce a laminar shield gas discharge flow through the discharge annulus, providing cooling of the orifice subassembly. A plasma gas discharge annulus is formed between the terminal end of the orifice subassembly and a terminus of the electrode. A first terminal of the power source is connected to the electrode and a second terminal of the power source is connected to the workpiece. The power source provides a sinewave alternating current. A transferred arc is formed between the electrode and the workpiece. The power density is sufficient to provide keyhole welding, the reversing sinewave polarities providing simultaneous keyhole penetration and cathodic cleaning, eliminating the requirement of substantial workpiece surface preparation and/or removal of internal workpiece defects.

Effect of electrochemical reactions on submerged arc weld metal compositions

Abstract: The purpose of this work is to investigate the relative influence of electrochemical and thermochemical reactions on the weld metal chemistry in a direct current submerged arc welding process. Chemical analyses were carried out on the melted electrode tips, the detached droplets and the weld metal for both electrode-positive (reverse) polarity where the welding wire is anodic and electrode-negative (straight) polarity where the welding wire is cathodic

Simultaneous in-process control of heat-affected zone and cooling rate during arc welding

Abstract: The problem of process control welding involves not only regulation of weld bead geometry, but also thermally induced changes such as distortion, residual stresses and metallurgical transformations near the weld. This paper addresses the last of these, and poses it as a feedback control problem. The objective is transformed to one of controlling the surface temperature field in-process, and using temperature feedback to implement such a scheme. A control model of the process is presented, and a parameter adaptive controller is designed to ensure consistent control system performance. A series of numerical simulations and experiments using GMA welding is presented that confirms the model and illustrates the desired properties of the controller. With this system, the heat-affected zone and cooling rate (through their correlates in surface temperature-time relationships) can be regulated independent of each other, and gross disturbances to the temperature field rejected totally in the steady-state. In addition, dynamic performance of the control system is illustrated, and the limits imposed by current hardware are discussed.

Monitoring of arc welding by analyzing modulation of radiation from carrier signals superimposed on weld current

Abstract: A carrier signal is superimposed on the arc current during an arc welding operation, and radiation, either acoustic or light, emitted by the arc is detected and analyzed, with the results being used to control weld penetration.