Showing papers on "Spot welding published in 1986"

Method of and apparatus for thermographic evaluation of spot welds

Abstract: A method of and apparatus for the non-destructive evaluation of welds joining metal bodies employing infrared thermography; the method comprising the steps of applying thermal energy to a weld and observing temperature differentials that occur on the weld's surface. The apparatus comprises a device for applying thermal energy to welds being inspected; a device for scanning the weld surface for infrared radiation being emitted therefrom; a device for capturing the emitted radiation and converting it to a signal representative of the thermophysical characteristics of the weld; and a device for visually displaying the signal in a form suitable for interpretation.

Resistance spot welding of galvanized steel: Part II. Mechanisms of spot weld nugget formation

Abstract: Dynamic inspection monitoring of the weld current, voltage, resistance, electrode displacement, and force was performed in conjunction with a detailed study of the effects of material variations and weld process parameter modifications on resistance spot welding of coated and uncoated steels. In order to determine the mechanisms of weld nugget formation and growth, scanning electron microscopy photos were taken of the developing nugget. These physical changes were then related to the dynamic inspection curves and the welding current lobe. The effects of material variations and weld process modifications, the results of which were presented in Part I, can be explained through an understanding of these mechanisms.

Method and apparatus for monitoring and controlling resistance spot welding

Abstract: A method and apparatus are disclosed for analyzing the dynamic resistance of a resistance spot welding process to determine the time of an expulsion event and use that time as the weld completion time for controlling weld termination via a weld feedback signal, controlling automatic current stepping, and identifying maintenance needs. A preconditioning pulse is used to stabilize the weld process and aid in obtaining interpretable resistance information. After an initial blanking period the resistance curve is analyzed by calculating first and second derivative values and applying several algorithms that make possible the computer recognition of characteristic resistance curve shapes resulting from weld expulsion under good geometry, bad geometry and edge weld conditions.

Resistance spot welding of galvanized steel: Part I. Material variations and process modifications

Abstract: Material variations and process modifications have been studied to determine their effects on the acceptable range of resistance spot welding conditions for galvanized steel sheet. The material variations studied include zinc coating integrity, structure, composition, thickness, roughness, oil, and the amount and type of Fe-Zn intermetallics. Process modifications studied include upsloping and downsloping of the weld current, preheat current, postheat current, electrode tip geometry, and applied force. It was found that hot-dipped galvanized materials with coatings which have a very thin Fe-Zn alloy layer have a wider range of acceptable welding conditions than the commercial galvannealed products, which have a fully alloyed Fe-Zn coating. The decreased lobe width of the galvannealed material is due to the discontinuous Fe-Zn coating structure and morphology. Small variations in the thickness of the coatings studied have no significant effect on the welding current range. Surface roughness of the coating has no effect on lobe width. Upsloping and downsloping of the weld current increase the welding range of hot-dipped products when using truncated cone electrodes, whereas sloped current has no advantage for galvannealed or uncoated materials. Radiused electrodes can increase the lobe width of hot-dipped products but are not beneficial when using sloped current or when welding galvannealed or uncoated materials.

A study on the shunt effect in resistance spot welding

Abstract: One of the important factors in practical welding situations is shunt effect which deteriorates weld quality due to a shunt current which flows in the exis- ting spot Previously, this effect has not been analytically investigated, since the mechanism of shunt effect shows very complicated phenomena in the thermal and electrical behavior In this paper this effect is extensively studied through theoretical and experimental analysis The theoretical results obtained from a numerical analysis of the modelling of shunt effect are compared with experimental ones Both results show good agreement and represent well the mechanism of shunt effect

Method and apparatus for resistance welding

Abstract: A method and apparatus are disclosed for resistance spot welding including applying a preconditioning pulse at the beginning of a welding process to stabilize the resistances at the interface of the sheets being welded and at the interface of the electrodes and the sheets. A current pulse is applied just after contact of electrodes and the workpiece when the electrode force is between about 10% and 75% of its final value to melt interface surfaces followed by a cooling time to permit dissipation of heat from the interfaces, and is finally followed by a conventional weld current schedule. The contact time is determined be electrically monitoring the conductivity between the electrodes as they are moved toward the workpiece. Alternatively, the applied electrode pressure is monitored to determine when sufficient electrode force is applied to the workpiece to achieve the proper resistance for the pulse application.

Structure and method for resistance welding with an inductively coupled power source

Abstract: Structure for and a method of resistance welding using an induction coupled power source. The structure of the invention comprises an electric coil wrapped around a flux concentrating core in close proximity to members to be welded together, a source of alternating electrical energy connected through the coil and means for applying pressure between the members to be welded. In accordance with the method of the invention the members to be welded are heated by at least one of an induced current and hysteresis loss and the heated members are then forged together by applying pressure thereon. The weld effected by the method of the invention may be either a spot weld or a continuous weld. Further in accordance with the structure of the invention the flux concentrating core may be on one or both sides of the materials to be welded and may be linear and perpendicular or at an angle to the members to be welded, or may be U-shaped or cup-shaped including a central post around which the coil is wrapped.

Device for spot welding, in particular for joining hardware to a workpiece

Abstract: 1. Apparatus for spot-welding small parts to a workpiece, comprising welding tongs (1) for a manipulator, which welding tongs consist of two tong arms (2, 3) and comprise an electromagnet, characterized in that the electromagnet is mounted to be displaceable along the electrode (8) of one tong arm (3) of the welding tongs (1) and consists of a lifting magnet (7) for transporting the small parts to be spot-welded.

Method for reconditioning spot welding electrodes

Abstract: A method and an apparatus for reconditioning worn electrodes for resistance welding. The worn electrodes are pressed into a die by a punch and thus restored to their original shape or given a different shape.

MIG welding torch

Abstract: In a MIG welding torch for partially or fully mechanised spot welding with consumable wire electrodes, the wire electrode is guided in the wire guide bore (Dfb) of a contact tube (Kr). In order to ensure at the front end of the torch in the delivery area of the wire electrode reliable and defined current transfer to the wire electrode, uniform material transfer during welding and uniform burn-back of the wire electrode, the front end of the contact tube (Kr) axially displaceable in the torch body (Bk) carries a collet (Sz) which can be released by the feed of the wire electrode against the force of a closing spring.

The Measurement and Monitoring of Resistance Spot Welds Using Infrared Thermography

Abstract: The ability to monitor the spot welding process and provide a real time inspection is of interest to the automotive, aircraft, and aircraft turbine industries. A series of experiments was performed using the infrared radiometer during the welding operation when welding coated and uncoated automotive gage steels. It has been determined that the isotherm radiated at the electrode/base material surface contains apometric information that can be used in the detection of the weld nugget and its quality. Weld nugget measurement and tensile shear tests results show good correlation between isotherm geometry, weld joint strength, and weld nugget size.

Contact wire for a roller seam welding machine

Abstract: The contact wire (30) for a roller seam welding machine is provided on its front face with grooves (32) which are formed in the longitudinal direction of the wire and which are bounded by sharp longitudinal edges (34). The contact wire (30) is particularly well suited for welding metal sheets, the surfaces of which are heavily soiled or provided with coatings which are poor electrical conductors or electrically non-conducting. During the welding operation, the longitudinal edges (34) cut open the sheets to be welded or their oxide layer or coating which is a poor electrical conductor or non-conducting, and render possible a direct passage of the welding current to the actual metal sheet. Dirt as well as semi-plastic and vaporized coating material are reliably carried away to the front and rear in the longitudinal grooves so that the contact wire (30) cannot "float" during the welding operation. A preferred application for the contact wire (30) is the welding of fuel tanks from sheets which are coated so as to be poor electrical conductors or non-conducting on both sides, on a resistance roller seam welding machine.

Thermal Modeling of Spot Welds

Abstract: Solidification structure and austenite decomposition in some spot welded 0.05% C-0.3% Mn steels have been studied with the aid of a numerical thermal model. The model is a one dimensional finite difference formulation, and accounts for melting, temperature dependent thermal properties, effective heat transfer in the liquid, and contact resistances. The model was used to predict solidification conditions during resolidification of the nugget. These solidification conditions were correlated with the primary dendrite spacing using available primary dendrite spacings modeling. The model was also used to predict cooling rates in the temperature regime for austenite decomposition. These cooling rates were used to interpret the underlying microstructure.

Embossed steel plate

Abstract: PURPOSE:To provide the titled steel plate to which a stable and intensifying welding is subjected with bettering the lapping accuracy and widening the current values range of holding the required intensity without generating expulsion and surface flash by performing a spot welding with forming the lap welding part of a corrugated embossed steel plate on the plane face in advance. CONSTITUTION:The lap welding part 2 of corrugated embossed steel plates 4, 5 is made in advance a plane face with a press and subjected to a lap spot welding. The steel plates 4, 5 are not slid by the press due to the overlapping condition of the waveforms and the lapping accuracy thereof is bettered. The range o the current value for spot welding which keeps the required welding intensity without generating expulsion and surface flash widened as well to weld better even in case of the change in the current.

Spot welding gun device

Abstract: PURPOSE:To prevent the damage and entanglement of a power feed cable as a result of the rotation of a welding gun by constituting a spot welding gun device in such a manner that the power feed cable is not connected to the welding gun. CONSTITUTION:The rod parts 36b, 37b of contact driving cylinders 36, 37 are pushed out and power source side contacts 38, 39 are brought into contact with gun side contacts 26, 31 respectively under substantial pressing forces in the stage of welding. The power feed cable 40 is thereby connected to a movable electrode tip 16 via the contact 38, the contact 26, a connecting metal 24, an ounce copper plate 32 and a rod part 15b. On the other hand, a power feed cable 41 is electrically connected to a stationary electrode tip 21 via the contact 39, the contact 31, connecting metals 29, 33, an ounce copper plate 34 and an arm 20. Stop welding is thus executed in the conventional manner. Since the mechanical connection of the power feed cable to the rotating part such as the welding gun is obviated by the above-mentioned method, the damage of the cable as a result of the rotation of the gun is thoroughly eliminated.

Apparatus for spot welding of metal thin plate part

Abstract: For the welding of tongues (12) onto rupturable can members (10) of tin plate, a pair of welding electrodes (20, 22) is provided which are movable cyclically towards and away from one another and are additionally movable cyclically transversely to this movement in such a manner that successive spot welds are carried out by different portions of electrode.

Electrode for spot welding

Abstract: PURPOSE:To increase the durability of an electrode by forming a nickel plated layer on the outer surface of the electrode including the pointing face of the electrode which press-contacts the material to be welded in the copper alloy made electrode for spot welding. CONSTITUTION:The electrode for spot welding is made by forming the nickel plate layer 3 on the outer surface including the point face 2 of a copper alloy made electrode 1. This electrode is mainly composed of the copper alloy having good electric conductivity and heat conductivity. The point part of the electrode has higher melting point than the melting point of a copper with good high temp. intencity and wear resistance, and yet the nickel plated layer having smaller reactivity to a zinc or tin compared to that of a copper is formed. The deformation of the point shape of the electrode and the adhesion of spatters are prevented, therefore, without damaging the surface of the material to be welded and the good welding quality is maintained over long term. Consequently the man-hour in the shape correction of the electrode point part and the change of the electrode, etc. is saved.

Projection welding machine

Abstract: PURPOSE:To provide a titled device which executes welding with high positioning accuracy for welding a nut to be welded and high welding quality by providing retractably a guide pin having a tapered surface part which can be put into and out of the screw hole of the nut into a welding electrode CONSTITUTION:This projection welding machine executes welding by mounting an upper electrode 4 to the lower part of a supply head rod 3 of a pressurizing cylinder attached to a welding machine body 1, attracting the nut 7 to be welded which is fed by a nut catcher mechanism 16 provided with a chute 23, a guide 19, a nut receiving part 20, etc at the top end thereof by the excitation of an attraction coil 9 and lowering the electrode 4 so as to contact with the panel (not shown) on a lower electrode The guide pin 10, attached to the piston 11 in a cylinder chamber 13, is vertically movably provided into the electrode 4 of the above-mentioned machine and the attracted screw 7 is positioned by projecting the pin rod part 12 of the pin from the electrode 4 and pressing the tapered surface provided in the mid-way thereof to the aperture edge of the screw hole 7A of said nut The pin 10 is held retracted during the welding operation to prevent the deterioration in weld quality

Electrode shaping method for spot welding

Abstract: PURPOSE:To extend an electrode to a long life without deteriorating a welding quality by forming a projecting part for constituting a passage in which a current density of a welding current is constant, on the surface of the tip side of an electrode for spot welding CONSTITUTION:Dome-shaped recessed parts 20, 22 which are fitted to the surface of the tip side of spot welding use electrodes 16, 18 are formed on an upper face 12 and a lower face 14 of a jig 10 for constituting a cube In the center parts of the recessed parts 20, 22, annular grooves 24, 26 are formed, respectively The surface of the tip side of the electrodes 16, 18 is made to abut on the inside of the recessed parts 20, 22 of the jig 10, and the electrodes 16, 18 are pressed against the jig 10 by a pressing force of the time of welding or the stronger pressing force than said force When the electrodes 16, 18 pressed against the jig 10, projecting parts 28, 30 for constituting a passage in which a current density of a welding current is constant are formed on the surface of the tip side of the electrodes 16, 18 by a forging pressure action

Method and apparatus for projection welding

Abstract: Two metal plates 1a, 1b are projection welded together using a truncated conical projection 12 on a first one of the plates having a spherical end surface. The plates are pressed together through the projection, and a welding current pulse is applied which reaches a maximum value in less than 2 milli-seconds. The shape and dimensional limitations of the projection coupled with the high amplitude, short duration current spike result in a thin welding nugget 9 and prevent any thermal distortion of the outer plate surface due to localized overheating.

Spot welding method

Abstract: PURPOSE:To improve an electrode life and welding quality by conducting electricity through belt-like conductors inserted between pressing rollers and materials to be welded to generate heat in the materials to be welded thereby welding said materials. CONSTITUTION:The belt conductors 12 are inserted between the disk-shaped pressing rollers 10 and the materials 16 to be welded. Electricity is supplied to the conductors 12 from reel parts 14, 18 on which said conductors are wound. The welding current is passed to the weld zone pressurized by the rollers 10 to generate a nugget 22, by which the weld zone is welded. The pressurization and supply of electricity are shared by the above-mentioned method, by which the electrode life and the welding quality are improved.

Electrode device for spot welding machine

Abstract: PURPOSE:To increase the operation rate of a welding machine without any suspension in welding work by fitting a tomatically the next electrode to an electrode holder and by withdrawing the used electrode as well as continuing the welding with a new electrode by turning the electrode holder after performing the spot welding with suspension of the electrode in the prescribed times. CONSTITUTION:The body to be worked on a counter electrode 21 is spot-welded with an electrode 190 by suspending a rotary shaft 2 and electrode holder 1 together with an arm 6 by air pressure device 5. The electrode holder 1 is turned 90 deg. by a motor 7 after welding in the prescribed times and the welding is continued by an electrode 191. Simultaneously the next electrode 192 is fitted by the air pressure device 15 and the used electrode 19r(19o) is withdrawn by hammering it by operating a hammer 17 with the air pressure device 28. The suspension in welding work by the change of electrode 19 is eliminated and the operational efficiency of welding machine is increased.

Spot welding device

Abstract: PURPOSE:To automate a welding work efficiently extending over many hours by placing a lower electrode placing base and a polishing means on a horizontal movable table, executing a spot welding to an object to be welded, on the placing base by a descent of an upper electrode, and polishing and regenerating suitably the tip of the upper electrode CONSTITUTION:A placing base 4 being a lower electrode and an upper electrode 2 tip rotating 9 polishing means 7 are placed on a table 5 which can move horizontally in the X and Y directions The upper electrode 2 is made to descend by an upper pressure means 1, and an object to be welded 3 on the placing plate 4 is brought to a spot welding Also, the tip of the upper electrode 2 is repolished by the polishing means 7 by shifting the table, and the tip is regenerated satisfactorily By said control operation, the welding work is automated efficiently extending over many hours

Production of corrosion resistant net

Abstract: PURPOSE:To increase a strength, to eliminate a burr generation and deformation and to increase a corrosion resistance by subjecting to spot welding the cross point of the wire netting consisting of aluminum coated steel wire or aluminum alloy wire, also by coating a boehmite film on the surface. CONSTITUTION:The boehmite film 1b is subjected to a boehmite treatment by heating to the prescribed temp. the ion exchange water added with triethanolamine, by dipping for the prescribed time aluminum coated steel wire 1a in this heated water. A weld zone 2a is subjected to spot welding with the prescribed electrode pressurizing force under the welding conditions of welding current, squeeze time, welding time and holding time. The aluminum coated steel wire subjected to boehmite treatment has less burrs and the recess of steel core, nor bend and deformation. The corrosion resistance is increased about three times more than those which are not treated and it has the corrosion resistance nearly close to ten times compared with a zinc plated steel wire netting.

Method for controlling welding current of spot welding device

Abstract: PURPOSE:To obtain optimum welding current by detecting the substantial pressurization of power feed terminals and changing over selectively the welding current value conforming to the conditions of a spotting position on a timer side in accordance with the detected output. CONSTITUTION:Groups A, B, C, D consisting of the plural 1st spot welding guns are respectively different in the conditions for the spotting position such as the thickness and quality of materials to be welded. The timer 16 is disposed with start switches 9a, 9b, 9c, 9d for making change-over operation in accordance with the groups A, B, C, D and is connected with a phase change-over control part 10 for controlling the phase change-over. The welding conditions conforming to the spotting position of the group A are selected by the operation of the start switch 9a of the timer 16 when the current conduction of the 1st spot gun of the group A is detected by a sensor 8. The optimum conditions are successively selected to the groups B, C, D as well and the respectively optimum welding currents are obtd.

Projection welding method

Abstract: PURPOSE:To prevent the reduction in a welding strength by arranging a magnetic body on the part of a high dense magnetic field generating around a projection by a welding current and by removing the magnetic field. CONSTITUTION:Magnetic bodies 11, 12 are arranged on the outer side of the projections 5, 6 of a welding material 4. When a welding current is flowed to the lower part electrode 9 via the projections 5, 6 and the material 3 to be welded from the upper part electrodes 7, 8, a magnetic field is caused clockwisely around the projections 5, 6 and the magnetic field is made highly dense on the outer side of the projections 5, 6. The generation of an electromagnetic force can be controlled by arranging the magnetic bodies 11, 12 generating the magnetic field having nearly the same strength in the direction of denying the magnetic field on said part of high dense magnetic field. Consequently the movement at the welding time of the projections 5, 6 is prevented and the reduction in the welding strength of welding materials 4, 3 is prevented.