Showing papers on "Electric resistance welding published in 1989"

Ultrasonic welding of PEEK graphite APC-2 composites

Abstract: The ultrasonic welding process is modeled using a five part model that includes mechanics and vibration of the parts, viscoelastic heating, heat transfer, flow and wetting, and intermolecular diffusion. The model predicts that melting and flow occur in steps, which has been confirmed by experiments. The model also indicates the possibility of monitoring joint quality by measuring the dynamic mechanical impedance of the parts during welding, which has also been verified experimentally by indirectly monitoring the magnitude of the impedance. via measurements of both the power and the acceleration of the base. When the melt fronts of the energy directors meet, at the end of welding, the dynamic impedance of the composites' interface is shown to rise rapidly. This raises the possibility of developing closed loop control procedures for the ultrasonic welding of thermoplastic composites. Ultrasonic welding of polyetheretherketone (PEEK) graphite APC-2 composites produced joints with excellent strengths.

Apparatus and method of short circuiting arc welding

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

Ultrasonic welding of thermoplastics in the far‐field

Abstract: Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near-field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near-field ultrasonic welding of amorphous (acrylonitrile-butadiene-styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.

More creep resistant turbine rotor, and procedures for repair welding of low alloy ferrous turbine components

Abstract: A more creep resistant turbine rotor and novel methods for repairing worn surfaces of Cr-Mo-V steam turbine components are disclosed. These methods include specified alloy compositions and welding procedures that minimize weld stresses and cracking. These alloys exhibit improved creep and fatigue properties and are preferably deposited using a gas tungsten arc welding procedure. Bead sequencing, cooling side plates and the use of run-off tabs are also disclosed for minimizing welding defects in turbine rotors and discs.

Apparatus for short circuiting arc welding

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

Controller for resistance welding machine

Abstract: An inverter-type resistance welding machine includes a keyboard for inputting desired welding current command data corresponding to commanded values, a display unit for displaying, in the form of a numerical table or graph, the welding current command pattern data inputted by the keyboard, a memory for storing a plurality of the welding current command patterns set by the keyboard and from which these patterns are read out in response to a selection command from the keyboard to serve as a control command of the inverter, and acceptability decision means which successively accepts detected welding current at the time of welding for making a comparison with the reference welding current command pattern over a full range of values, checking correlation between the detected welding current and the reference welding current command pattern and determining whether the detected welding current lies within a predetermined tolerance.

Two‐Dimensional thermal analysis of resistance welded thermoplastic composites

Abstract: A transient two-dimensional thermal model for resistance welding of thermoplastic composites is presented. A parametric study is conducted that yields insight into the welding process enabling some critical process and material parameters to be identified. Time to melt is predicted by the model and is successfully compared to experimental observations. Local heating and meltthrough can also be explained by the transient thermal model in agreement with experimental observations. Mode I fracture toughness of unidirectional graphite reinforced poly(etheretherketone) resistance welded double cantilever beam specimens are conducted under various process conditions. Experimental results indicate that under optimum process conditions, the interlaminar fracture toughness of the bulk compression-molded thermoplastic composite material can be achieved using resistance heating as a joining technique.

DC resistance welding apparatus

Abstract: A DC resistance welding apparatus includes a pair of welding electrodes for sandwiching workpieces to be welded therebetween and a circuit connected to the welding electrodes for supplying a welding current to said welding electrodes. The circuit includes a plurality of parallel-connected rectifying circuits each having a welding transformer and rectifying circuit. The circuit monitors the power signal produced by inverters in the power supply to determine the proper energization time by producing a pulse signal corresponding to the waveform of the power signal. The rise and fall of the pulse signal is then detected and differentiated. The differential signal is used as a basis to control the energization time of the welding gun.

Resistance welding electrode and process.

Abstract: Resistance welding electrodes and processes using the same are provided. The electrodes have a base portion and an integral nose portion projecting therefrom, with the nose portion terminating in a welding tip face. The nose portion tapers inwardly between said base portion and said welding tip face with a concave profile taper such as a frustum of a vortical surface. The electrodes used may be made up of a conventional copper material having copper combined with one or more metals selected from the group consisting of chromium, zirconium, cadmium, cobalt, nickel, beryllium, tungsten, aluminum, tungsten carbide, iron, and molybdenum. The electrodes may be used in a welding process, which provides for a generally linear increase in current stepping with reduced or eliminated conditioning of the electrodes. The welding tip face has a convex curvature which may range between about a two inch and a eight inch radius of curvature, and which preferably has a radius of curvature of about four inches. Both male and female electrodes may be used with cooling recesses in the electrodes. The diameter of the welding tip face may be about equal to the length of the nose portion.

Resistance welding control system

Abstract: A resistance welding control system is disclosed which comprises a resistance detection unit for detecting an interelectrode resistance by measuring welding current and voltage applied between electrodes; a compensation section for comparing a resistance value as detected with a predetermined model resistance value and determining an amount of compensation of the welding current in accordance with the difference therebetween; and a current control section for controlling the welding current on the basis of the amount of compensation of the compensation section.

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

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

Welding apparatus coated with spatter-resistant and electrically conductive film

Abstract: A welding contact tip or a weld nozzle is provided with a coating comprising a film of tungsten disulfide or other low friction material. The film provides resistance to weld spatter without interrupting electrical contact between the contact tip and electrode wire.

Welding of coated metals

Abstract: The invention provides a method and apparatus for welding together two metal workpieces, at least one of which has thereon a coating material which enters a fluid or visco-elastic phase at a temperature below the melting temperature of the workpieces, the method comprising the steps of subjecting the workpieces to a preliminary preparative treatment at a zone to be welded and thereafter applying (preferably be means of a high-energy beam such as a laser beam) sufficient heat to the workpieces at the weld zone to effect there the welding together thereof, wherein the preliminary preparative treatment comprises preheating the workpieces to the said lower temperature and pressing them together, at the zone to be welded, with a force sufficiently great to expel coating material from between the workpieces at the weld zone, thereby to improve the quality of the subsequent weld.

Resistance-weldable composite

Abstract: The invention concerns three-layer composites with their plastic core so uniformly enriched with an appropriate percentage by volume of a ferrosilicon with an appropriate particle size that the composites can be securely joined to each other and to sheets of metal alone by resistance welding. The property applies to composites with either a viscously elastic or an impact-resistant core.

Resistance welder using an inverter

Abstract: A dc resistance welder includes a first rectifier circuit for converting the ac power from an ac power supply into dc power, an inverter for converting the dc power into ac power having a desired frequency, a welding transformer connected to the inverter, a second rectifier circuit for rectifying the output current of the welding transformer and for supplying welding current to a workpiece, a first element for setting welding current in accordance with the nature of the workpiece, a second element for sensing actual welding current for the purpose of sensing magnetic saturation of the welding transformer, and a third element for comparing the welding sent by the first element with the actual welding current sensed by the second element and for varying the output frequency of the inverter by inverting the direction of the output current of the inverter when the actual welding current reaches the set welding current

Friction welding apparatus

Abstract: A friction welding apparatus for preparing weldments by fictional contact of the weld members which includes sensors for measuring torque, axial forces, and other variables important to the control of the welding process, and for facilitating the obtainment of process information useful in correlating process conditions with weld quality. The apparatus includes means for the substantially frictionless coupling of the component providing the axial normal force on the aligned shafts upon which the weld pieces are mounted. The coupling, which contributes to accurate torque measurements, comprises a substantially frictionless, single-contact-point coupling provided by the point of contact between two adjacent spherical surfaces. The welding apparatus is also provided with a vacuum-braked air drive assembly for substantially instantaneously stopping relative rotation between the weld members after fusion of the members has occurred, thereby preventing undesirable over-run and resulting stress formation in the weld zone.

New results on the spin welding of plastics

Abstract: Short welding times make spin welding particularly suitable for mass production. This paper presents an analysis of the friction phase, which makes it possible to estimate the influence of the welding parameters and the material being welded on the temperature in the welded zone, the melt rate, and the torque in the spin welding of semicrystalline thermoplastics. A comparison of experimental and calculated results shows an acceptable correlation. In addition, the influence of speed, axial pressure, and braking on the weld seam quality of different amorphous and semicrystalline thermoplastics is discussed.

Process and machine for the welding together of plastic parts processing a built-in winding

Abstract: The invention relates to the automatic welding of plastic parts possessing a built-in winding. In order to carry out an automatic welding operation without risking damaging the parts by subjecting them to an excessive welding temperature, there are regulating means for varying the electrical energy supplied to the winding, in order, during the welding phase, to maintain the temperature of the winding between a minimum temperature, below which welding cannot be carried out, and a maximum temperature, beyond which the parts will be damaged. The invention is used particularly for the production of systems for the distribution of gas under pressure by means of plastic pipelines.

Resistance welding control method

Abstract: A resistance welding control system is dis­closed which comprises a resistance detection unit (5) for detecting an interelectrode resistance by measuring welding current (I) and voltage (V) applied between electrodes; a compensation section (3) for comparing a resistance value as detected with a predetermined model resistance value and determining an amount of compensa­tion of the welding current in accordance with the difference therebetween; and a current control section (8) for controlling the welding current on the basis of the amount of compensation of the compensation section.

Method for controlling machine parameters in friction welding

Abstract: In vibration welding the process takes place in a number of phases. The qity of the welding connection depends on which phase is reached during vibration and which conditions prevail in the phase 3 of the vibration process. According to the invention the welding machine is provided with a measuring and controlling system for the displacement distance to determine when the phase 3 of the process is safely reached and to control the joining velocity in this phase.

Portable impedance meter for resistance welding equipment

Abstract: A portable meter for measuring the impedance of a resistance welding circuit between first and second points on the apparatus The meter is powered by conventional alternating current and conducts a test alternating current through the welding apparatus at such an amperage so that the voltage measured between the first and second points is equal to the impedance therebetween

Welding of filled sintered polytetrafluoroethylene

Abstract: A method for welding together filled sintered polytetrafluoroethylene components. The ends of the components to be welded are carefully tapered to form reverse mated surfaces and then assembled in position to be welded. The actual welding step is carried out under heat and pressure followed by cooling under pressure. The process is particularly useful in the fabrication of very large gaskets or other very large planar objects.

Circuit for measuring the voltage difference between the welding electrodes of a resistance-welding machine

Abstract: What is described is a circuit for measuring the effective voltage drop at the welding position (30) between the welding electrodes (14,16) of a resistance seam welding machine. A first measuring loop (40) for measuring a first loop voltage is secured to the lower welding arm (28) close to the lower welding electrode (16) and is in communication with the upper welding electrode (14) through a sliding contact (44). The second measuring loop (60) is taken close to the welding electrodes (14,16) through the head portion of the Z-rail (12). The conductor turns (42,62) of both measuring loops, which lead to an evaluation circuit (48), are twisted together. Thus the stray effects picked up in the two measuring loops are the same. The difference between the two loop voltages formed in the evaluation circuit (48) is the effective voltage drop which is further processed in the usual manner to monitor the quality of the welding seam produced.

Pre-resistance-welding resistance check

Abstract: A preweld resistance check for resistance welding machines uses an open circuited measurement to determine the welding machine resistance, a closed circuit measurement to determine the parallel resistance of a workpiece set and the machine, and a calculation to determine the resistance of the workpiece set. Any variation in workpiece set or machine resistance is an indication that the weld may be different from a control weld.

Study of Friction Welding of Titanium and SUS 304L Austenitic Stainless Steel

Abstract: It is well known that fusion welding between titanium and foreign materials is almost impossible because of occurring brittle intermetallic compound in its weld metal. From this reason, there are few research reported for the welding titanium to other steels up to date. And also, there are a few investigations reported for it by using other welding process except fusion welding.In this study, to establish the welding process between titanium and SUS 304L austenitic stainless steel by using friction welding process with argon shielding, the effect of welding conditions on the tensile strength and metallurgical characteristics of the weld joint was evaluated. The results obtained are as follows:(1) There was little or no deformation observed in SUS 304L after weld.(2) The welding conditions, which increase the tensile strength, are, a. low rotational speed, b. high upsetting pressure andc. polishing of the faying surface of SUS 304L before welding.(3) Upsetting pressure was the most effective to tnesile strength than the other factors.(4) The tensile strengths of the joints, which were welded by using conditions described in (2), were from 348MPa to 378MPa.(5) The characteristics of the faying surface of SUS 304L before joining affected the tensile strength of the joint. That is, the roughness and foreign materials on the faying surface decrease the degree of metal bonding.

Electrode for resistance welding

Abstract: PURPOSE:To obtain an electrode for spot welding having the high number of spots without electrode deposition and cracking by forming the electrode of triple structure of core material, inner material and sheath material and laminating electric conductivity and vickers hardness of each material and specifying a ratio of a diameter to an outside diameter thereof. CONSTITUTION:The electrode used for spot welding is constituted of the triple structure of the core material 1, the inner material 2 and the sheath material 3 in order in the direction of the outside from the central axis of the electrode. The core material 1 has >=20% electric conductivity IACS (%) and vickers hardness in the range of 130-200 and the inner material 2 has >=70% electric conductivity and vickers hardness in the range of 90-160 and the difference in hardness between the core material 1 and the inner material 2 is made to >=30. Further, the sheath material 3 has >=40% electric conductivity and vickers hardness in the range of 130-200. When the diameter of the core material 1, the outside diameter of the inner material 2 and the outside diameter of the sheath material 3 are denoted by d1, d2 and d3 respectively, the ratio of respective parts is made in the range of d1/d3=0.12-0.32 and constitution is arranged so as to be in the range of d2/d3=0.5-0.75.

Electric resistance seam welding method

Abstract: An electric resistance seam welding method for a hard-to-weld steel sheet is disclosed which prevents the occurrence of flashes The steel sheet has metal harder than tin and an intermetallic compound as coating layers, the sheet thickness of the steel sheet is 05 mm or less and portions of the sheet are overlapped for welding with an overlapping width in a range from 20 times to 23 times the sheet thickness

Nd-YAG laser welding of bare and galvanised steels

Abstract: Until recently, one of the problems that has held back the introduction of lasers into car body fabrication has been the difficulty of integrating the lasers with robots Nd-YAG laser beams can be transmitted through fibre optics which, as well as being considerably easier to manipulate than a mirror system, can be mounted on more lightweight accurate robots Although previously only available at low powers, recent developments in Nd-YAG laser technology mean that lasers of up to 1kW average power will soon be available, coupled to a fibre optic beam delivery system The increasing usage of zinc coated steels in vehicle bodies has led to welding problems using conventional resistance welding as well as CO/sub 2/ laser welding The use of Nd-YAG lasers may be able to overcome these problems This paper outlines work carried out at The Welding Institute on a prototype Lumonics 800W pulsed Nd-YAG laser to investigate its welding characteristics on bare and zinc coated car body steels

Device and process for short circuit arc welding

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

Method and apparatus for supplying electric power to resistance welding gun

Abstract: A welding electric current is suppled to a tiltable resistance welding gun having a pair of electrodes which grip a workpiece while effecting resistance welding thereon. A power receiver terminal on the resistance welding gun and a power supply unit are connected to each other when the electrodes grip the workpiece therebetween, and the welding current is supplied from the power supply unit to the power receiver terminal. When the electrodes are separated from the workpiece, the power receiver terminal and the power supply unit are disconnected from each other.