Showing papers on "Electric resistance welding published in 1988"

Vibration welding of thermoplastics. Part I: Phenomenology of the welding process

Abstract: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters in vibration welding are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time. How these parameters affect weld quality, the conditions that result in the best welds, the weldability of dissimilar plastics, and the effect of fillers such as glass are of interest. To address these issues, a research vibration welding machine in which all the parameters can be independently and accurately controlled and monitored was designed and fabricated. The phenomenology of welding, as determined by experiments on the four thermoplastics polycarbonate, poly (butylene terephthalate), polyetherimide, and modified poly (phenylene oxide), is described.

Welding parameters and the grain structure of weld metal — A thermodynamic consideration

Abstract: The grain structure of the weld metal can significantly affect its resistance to solidification cracking during welding and its mechanical properties after welding. An experimental study was conducted to investigate the effect of two basic welding parameters,i.e., the heat input and the welding speed, on the grain structure of aluminum-alloy welds. Gas-tungsten arc welding was performed under various heat inputs and welding speeds, with thermal measurements in the weld pool being carried out during welding and the amounts and nuclei of equiaxed grains in the resultant welds being examined using optical and electron microscopy. The experimentally measuredG/R ratios and the clearly revealed heterogeneous nuclei together demonstrated the thermodynamic effect of the heat input and welding speed on the weld metal grain structure.

Resistance Welding of Graphite Polyetheretherketone Composites: An Experimental Investigation

Abstract: Resistance welding of preconsolidated unidirectional graphite (AS4) rein forced polyetheretherketone (PEEK) composite laminates (I.C.I. APC-2) is investigated experimentally. An apparatus is developed to conduct experiments to identify important process variables governing the efficiency of the welding process. Experiments were con ducted under displacement control and prescribed initial consolidation pressure. Heating elements consisted of a single ply of APC-2 with adjacent layers of neat film to minimize current leakage into the laminates to be welded. Temperature at the weld interface and consolidation pressure versus time were monitored and provided insight into the welding process. A strong correlation between the extent of welded surface area and process parameters such as power, energy and time in the melt were demonstrated. The quality and extent of the welded surface is quantified using ultrasonic nondestructive evaluation techniques. Experimental results indicate that superior welds exhibiting ...

Method and apparatus for building a workpiece by deposit welding

Abstract: A method and apparatus for building an axially symmetrical workpiece of desired geometry by deposit welding which uses a translatable welding head for depositing molten weld material and a rotatable, reusable shoe which translates with the welding head. The rotatable, reusable shoe forms, supports and cools the deposited molten weld material puddle while the weld material is solidifying thereby eliminating the need for a conventional preform.

Automatic arc-welding method

Abstract: An automatic arc-welding method, which comprises, when welding two objects to be welded together by means of a welding wire along a first groove formed between the objects to be welded on a first side thereof, continuously determining by calculation a target welding current, with which a depth of penetration agrees with a target value thereof, on the basis of the root gap, the material of the welding wire and the like; continuously determining by calculation a target feeding rate of the welding wire, at which an extension length of the welding wire agrees with a target value thereof, on the basis of the welding current, the material of the welding wire and the like; continuously determining by calculation a target welding speed, at which a height of the weld bead agrees with a target value thereof, on the basis of the feeding rate of the welding wire, the material of the welding wire, the root gap and the like; and on the other hand, when welding the objects to be welded together by means of the welding wire along a second groove formed on a second side of the objects to be welded, opposite to the first groove, continuously determining by calculation a target welding current and a target welding speed while taking into consideration the depth of penetration and the weld bead in the first groove; thereby automatically controlling the welding current, the feeding rate of the welding wire and the welding speed on the basis of the respective target values thus determined.

Resistance welding of aluminium

Abstract: The invention concerns a method of forming a joint between aluminium workpieces. These carry an artifically applied e.g. chromate or anodic oxide coating on their surface. A curable adhesive containing up to 40% by weight of particulate filler having a maximum particle size of 300 microns is provided between the workpieces to be joined. Resistance welding is performed using a welding electrode whose tip has a surface with an average roughness depth of at least 10 microns. This increases electrode life and makes it possible to use lower welding currents than previously recommended.

Resistance welding electrode chip

Abstract: A welding resistance electrode chip of this invention comprises a front end to be brought into contact with a substance to be welded, an intermediate cylinder disposed on and in contact with the tail end of front end, and a main cylinder having a closed end disposed on and in contact with the tail end of front end and the tail end and the inner wall of intermediate cylinder. It is sintered and molded out of appropriate copper-based powder materials respectively satisfying the requirements of portions thereof: The front end is made of a powder material having good thermal shock resistance and wear resistance, the intermediate cylinder is made of a powder material having high tenacity to suppress the deformation of the front end, and the main cylinder is made of a powder material having high conductivity. Therefore, the durability of resistance welding electrode chip of this invention has been improved remarkably, and the operation rate of equipment has been improved.

Resistance welding of galvanized steel

Abstract: A coating for improved resistance welding of galvanized steel parts or sheets comprises a binder, and a metal phosphide pigment, preferably a ferrophosphorus pigment, having a particle size of from about 0.1 to about 30 microns. The pigment can also include up to about 40% by weight of an additional metal such as tin, aluminum or lead, which can be combined with the metal phosphide in pigment form or deposited onto the surface of the particles. The coating can be applied to either the faying or non-faying surfaces of the galvanized steel, or to the resistance welding electrode, and may be removed, if desired, after the welding operation. The advantages of the present invention include a significant reduction in welding current and an increase in the weldability lobe width, a restoration of the dynamic resistance beta peak, and an increase in electrode life.

Consumable electrode type arc welding contact tip

Abstract: A welding contact tip for use on a consumable electrode type welder has a core part (1) having a bore (3) for guiding a consumable electrode (4) and capable of supplying welding current to the consumable electrode (4), and a main part (2) which embraces and supports the core part (1). The core part (1) is made of a heat- and wear-resistant conductive metallic material such as a chromium-copper alloy, while the main part (2) is made from a less-expensive material such as copper, a copper alloy, aluminum or an aluminum alloy.

Gas tungsten arc welding machine with infinite rotating welding head and torch tilt

Abstract: This invention relates to a machine for practicing the gas tungsten arc welding process which includes means (5) for rotating the welding torch (28) continuously while welding. Means are provided for feeding the shielding gases, feed wire and electric current to the rotating torch while welding. Means (23) and (24) are also provided for tilting the torch about the point of welding. This invention makes it possible to weld continuously along a spiral path about a cylindrical object or on a flat or irregular surface.

Preweld test method

Abstract: A method for welding together the broad faces of two conductive sheets increases the reliability and consistency from weld to weld. The sheets are accessible from only one side for parallel electrical resistance welding. The electrical resistance between one sheet and the other is measured and taken as an indication of the amount of dirt or corrosion in the interface between the sheets. The measured resistance is compared with a predetermined standard. If the resistance exceeds the standard, the faces are cleaned. If the resistance is below the standard, electrical power is applied to fuse the sheets together.

Control system and method for vibration welding

Abstract: A displacement transducer is used to continuously monitor the distance between two fixtures securing parts to be welded. The signal from the displacement transducer is used to stop the welding process when a desired amount of material has been extruded from the weld. The control strategy will automatically take into account part nonuniformities that normally result in poor welds in welding processes that use time as the control variable.

Process for automatic fusion welding of rails

Abstract: A process for automatic fusion welding of rails by a combination of submerged arc welding and electroslag welding, comprising a root run for welding a rail base by submerged arc welding and, without interruption of the welding, subsequent runs for welding the rail base and welding a region from a rail web to a rail head by electroslag welding; wherein, during all of the runs, a metal mold is mounted on an upper surface of the rail base and a metal shoe is mounted on the metal mold to prevent an outflow of molten slag and molten metal and, during all of the runs, welding is performed by using a DC welding transformer having constant potential characterisitcs, a filler-wire having a diameter of from 1.2 to 2.0 mm, and a fused-type flux. The inventive process avoids the use of different fluxes and an alteration of welding machine conditions during the whole sequence of welding from the rail base through to the rail head.

A high-power-density beam welding method in combination with upset welding and apparatus therefor

Abstract: The method comprises forming along abutting edges of metal materials to be welded a continuous weld line for high-power-density beam welding by using an upset welding, and welding the metal materials by irradiation of a high-power-density beam along the weld line with an output of the high-power-density beam determined on the basis of an input heat produced by resistance exothermal reaction in the metal materials during the upset welding as well as a welding pressure given to the metal materials.

Parametric analysis of resistance spot welding lobe curve

Abstract: A linearized lumped parameter heat balance model was developed and is discussed for the general case of resistance welding to see the effects of each parameter on the lobe shape. The parameters include material properties, geometry of electrodes and work piece, weld time and current, and electrical and thermal contact characteristics. These are then related to heat dissipation in the electrodes and the work piece

Metal transfer mechanisms

Abstract: This article describes the basic mechanisms involved in the transfer of metal from the electrode to the weld pool in consumable electrode arc welding processes. The transfer modes observed in practice are explained and an indication of the resultant process characteristics is given. A brief introduction to the theoretical background of the subject is also provided.

Welding method by energy beam

Abstract: PURPOSE:To effect a strong welding with small energy by forming a thin part in the range of overlapping a pair of base metals to be welded by piling them up each other and projecting an energy beam on this thin part CONSTITUTION:A thin part 3 is formed in the overlapping range of a pair of base metals 1, 2 to be welded by piling up each other and the base metals 1, 2 are subjected to a lap resistance welding by projecting an energy beam 4 in opposition to this thin part 3 A flat bottomed recessed part 5 is provided on the projecting face of the base metal 1 at the projecting side of the energy beam 4 on the thin part 3 The lap part where the energy beam 4 of the thin part 3 is projected and said projecting part of the base metal 2 of the other part is thus heated and melted, and both base metals 1, 2 are welded each other The thermal capacity of this projecting part is small and the temp up is faster, the heat conduction to the base metal 2 of the other part becomes fast as well and less energy will do

Automatic stepper for resistance welding

Abstract: A method is disclosed for controlling the magnitude of current delivered through welding electrodes to a workpiece to be welded using resistance welding techniques, in order to prevent weld expulsion and concomitant diminishment of weld quality. Weld expulsion is detected by determining changes in resistance during formation of the weld, by periodically determining the power factor, and the primary circuit of the welding transformer. The power factor is determined by determining the relative timing between the commencement of the applied voltage, the zero crossover point of the applied voltage, and the ensuing zero point of the applied current.

Production of target for sputtering

Abstract: PURPOSE:To make it possible to join the body of a target and a backing plate to each other with satisfactory strength by directly joining them by a specified method without interposing a material for adhesion. CONSTITUTION:The body of a target and a backing plate are directly joined to each other without interposing a material for adhesion such as an adhesive or soft solder. A pressure welding method such as explosive welding, resistance welding, hot rolling with rolls or diffusion bonding is adopted as the direct joining method. Defective joining due to unsatisfactory wetting property of a material for joining to the body of the target, etc., is prevented and high joining strength is obtd. between the body of the target and the backing plate.

Method for heat-treating straight bead welded pipes

Abstract: A method for welding and heat treating straight bead welded pipes made of austenitic, ferritic or austenitic-ferritic rust-resistant steel includes welding a straight bead on a pipe forming a welding seam region, a heat affected zone and a remaining region, and annealing the pipe after welding the straight bead by only partially solution-annealing in the welding seam region and the heat affected zone, while heat treating the remaining region at a reduced temperature. An apparatus is also provided for carrying out the method.

Microstructure effects on dynamic welding of Ag/W contacts

Abstract: A computer-controlled device was used to simulate contact bounce on closing to evaluate the dynamic weld strength of some silver-tungsten contact materials. The effects of composition, microstructure modifications (such as different tungsten particle sizes), and the thickness of the silver-rich surface layer on the tendency to weld were evaluated. Probability analysis showed that silver has the highest tendency to weld. The addition of tungsten lowers the weld strength, with a minimum in the range of 35-62 vol.% of tungsten. The weld probability is lower than that predicted by a volume-mixing-rule calculation. The tungsten particle size was found to be a very important parameter in determining weld tendency. The optimum tungsten particle size for lowest weld tendency was dependent on the volume percent of tungsten. In general, an increase in tungsten particle size increased welding tendency. Silver enrichment of the contact surface by electrochemical etching also increased weld tendency. The welding tendencies were found to be related to the metallurgical properties of the contacts and the welding process. >

Transport arrangement for the welding-wire feed on welding equipment

Abstract: The invention deals with the control of the welding-wire feed on welding equipment. In order to deliver the welding wire (2) at constant force even in the face of unfavourable actions of force and avoid tensile or compressive stresses, the welding wire (2) is guided between a pushing drive (3) and a pulling drive (6) through a yielding part (4) and a curved tube (8). The tube tension is assisted by a spring (11). The yielding part (4, 9) is coupled to a control member (13) which measures the yielding travel of the yielding part (4, 9) when compressive or tensile stresses develop at the welding wire (2) and feeds it to a control system for compensation via speed control of the first drive (3). In this way, even very soft and thin welding wires (2), for example made of tin, aluminium or the like, can be delivered without problem.

Process for controlling the welding operation in the production of a spigot joint

Abstract: In a process for controlling the welding operation in the production of a spigot joint for heat-insulated conduits, in which the temperature of a heating wire provided for generating the welding heat is monitored, the temperature of the heating wire is determined by measuring the wire resistance.

Welded joint between plastic parts

Abstract: The invention relates to a welded joint between plastic parts, the welding quality of which can be checked in a non-destructive way. In particular, a coating of an X-ray contrast medium, of sharply set-off contour and of specific outline shape, is introduced, before welding, in the region of the welding gap. The coating is narrower or smaller than the zone to be welded. It can be a strip of specific width or a pattern comprising recurring contour parts. The coating can be printed on or take the form of an inserted auxiliary film. Coloring pigments based on heavy metal, metal powder, rock dust, powdered glass or ceramic powder come under consideration as X-ray contrast media.

Method and apparatus for determining the power factor of a circuit

Abstract: Structure for and method of controlling the firing point of thyristors in a phase controlled contactor in a resistance welding circuit in accordance with variations in current line voltage and/or one of resistance and inductive impedance in the welding circuit including structure for and the method of determining the firing point in a cycle of alternating electrical energy fed to the welder in terms of its distance from zero voltage cross over point and determining the current lag after a subsequent zero voltage cross over point of the voltage signal, determining the power factor of the welding circuit from these angular measurements and selecting a new firing delay for the contactor in accordance with the circuit power factor and the percent heat selected in the welding circuit, and subsequently correcting the firing delay in accordance with the percent heat selected in view of changes in the line voltage and circuit current.

Method and apparatus for resistance projection welding with quality monitoring of the welding

Abstract: Resistance welding methods were hitherto scarcely suitable for carrying out quality monitoring of the welding in the welding machine during the continuous production. This was because of the welding and measuring methods, which did not permit measurement of the joining occurring between the welded parts, because, during the welding, on the one hand the welded parts thermally expand due to their pronounced heating and on the other hand the plasticised material is deformed by the electrode pressure forces. In a procedure according to the novel method, the quality monitoring of the welding is made possible directly following the welding operation. In a resistance welding method with welding energy density optimised by spatial limiting of the welding zone and by minimum welding duration as well as maximum reproducibility of the welding parameters, the depression displacement of the welded parts into one another is measured by a high-resolution displacement sensor. This depression displacement is the best suitable measuring variable in order to determine the extent to which the parts to be welded have joined to one another. With uniform preparation of the welded parts and welding parameters set once to the welded parts, quality monitoring which goes beyond the method according to the invention is only necessary in exceptional cases. Quality monitoring of the welding.

Laser welding process

Abstract: Laser welding process in which the laser beam (10) produces a melting zone in the workpiece during welding, which melting zone has a vapour capillary in it which is open at least towards the beam source. In order to improve the process in such a way that phenomena disturbing the welding operation do not form in the melting zone, the procedure is to apply the laser beam at an inclination producing an essentially vertical melting front and directed against the relative beam feed direction. At lower welding speeds but under extreme conditions, e.g. when lap welding coated plates, the laser beam is inclined in the other direction in order to produce a vapour capillary opened wide in the direction of the impinging beam.

Computer control of gas metal arc welding

Abstract: The state of an arc weld is determined by the composition of the weld and base metal and its thermomechanical history. The composition of the deposited weld metal depends primarily on the amount of filler metal dilution which occurs. The heat input to the weld, comprising pre-heat and process heat, is the controlling factor in the thermal cycle to which the material responds metallurgically, to produce a specific set of weld properties. Thus, control of the arc welding process should focus on rational specification and real-time control of the heat and mass input to the weld. A process control model has been developed for the gas metal arc welding (GMAW) process using the state variables, time-domain method. The governing equations have been solved for the process parameters as functions of the desired heat input (in terms of heat per unit length) and mass input (in terms of transverse reinforcement area) to the weld. The resulting nonlinear model has been used with a simple proportional controller with deadband and variable coefficients to control the weld heat input and reinforcement area independently. A welding machine has been developed for this work, consisting of a computer-controlled welding head, positioning table, and operator panel,more » which is the front end for a conventional 300 A constant voltage power supply. Software for the system is written in the HPL language. System components communicate over an IEEE-488 bus. 9 refs., 6 figs.« less