Showing papers on "Electric resistance welding published in 1993"

Electrical contact resistance under high loads and elevated temperatures

Abstract: This research is focused on characterizing electrical contact resistance involved in resistance spot welding of thin sheet steels. It is part of a larger study in which a mathematical simulation of the welding process is being developed. A special test fixture has been fabricated that allows contact resistance at the electrode-to-sheet interface and the sheet-to-sheet interface to be measured under typical welding pressures (e.g., 14 ksi) and from room temperature to elevated temperatures. Bare and galvanized mild and HSLA steels have been considered. The nature of the contact resistance is discussed, and experimental findings are presented

Resistance welding monitor

Abstract: A welding voltage output from a power source of a resistance welder is derived on the basis of a welding current and an interelectrode voltage, and diameter of a nugget which is formed in a sheetlike work to be welded is estimated on the basis of the welding current, the welding voltage, data of material constant and a thickness of the sheetlike work, subsequently, the estimated diameter of nugget is composed with a target diameter of nugget, and thereby quality of the resistance welding is determined.

Investigation of the effect of welding parameters on weld quality of plasma arc keyhole welding of structural steels

Abstract: In the present investigation, the individual and interactive effects of the main welding parameters on weld quality of plasma arc keyhole welding of conventional structural steel, high strength microalloyed steel and strong formable microalloyed steel have been examined using welding of butt joints with a square groove in various welding positions, and welding of joint roots with a single-V-groove and the root face in the flat position. The most important welding parameters are welding current, welding speed and welding gases, especially plasma gas flow rate. Welding parameter combinations producing the best quality welds are presented. It is shown that it is possible to achieve defect-free high-quality welds with good strength and toughness properties, but the allowable range of variation of welding parameters, especially for the highest weld quality, is narrow. An argonhydrogen mixture for the plasma gas together with argon as shielding and backing gases give the best results with respect to weld quality.

Method for welding thermoplastic materials

Abstract: An improved welding rod having a solid homogeneous core of thermoplastic material and a resistance element comprised of a plurality of wires is presented with a method and apparatus for forming the welding rod. The welding rod is positioned between members of the thermoplastic material to be welded and a current and pressure is applied to the resistance element causing the thermoplastic material of the solid core and the adjacent thermoplastic members to fuse and form a unitary weld. Simultaneously the electrical resistance element is embedded in the weld, mechanically reinforcing and strengthening the connection. There is also disclosed a method for electric fusion welding of thermoplastic members wherein the welding rod is pre-attached to one of the thermoplastic members.

The effects of process variables on the weld deposit area in submerged arc welds

Abstract: The results of bead-on-plate submerged arc welding experiments are presented to determine the effects of process variables on the weld deposit area at a constant heat input of 2kj/mm. It is found that the deposit area is a function of the welding current, welding voltage, welding speed, electrode polarity, electrode diameter and electrode extension. In general, welds made using direct current electrode negative (DCEN) polarity, a small-diameter electrode, long electrode extension, high welding current, low welding voltage and high welding speed have large deposit areas. The weld deposit area is, however, not affected significantly by the power source or the flux type used in this investigation.

Thermal Analysis for Resistance Welding of Large-Scale Thermoplastic Composite Joints:

Abstract: The need for effective and reliable joining methods continues to grow as the use of thermoplastic composites becomes widespread. It is now possible to join large-scale components with the development of an automated sequential resistance welding process. The thermal history generated by the heating element placed at the interface between adherends determines the quality and performance of the welded joint. This article presents a thermal analysis for the resistance welding of large-scale components that overcomes the limitations of previous models. To simulate welding of the interface, a heat generation term was incorporated that accounts for the Joule heating of graphite fibers in the heating element. A parametric study was conducted to investigate the influence of welding parameters and assess the uniformity of interface temperatures. Components were joined by the resistance welding process to obtain experimental verification. Regions of localized overheating where potential current leakage may occur were identified as a function of process parameters. Insights on promoting more uniform heating for the resistance welding process are discussed. 11 refs.

Manufacture of spark plug

Abstract: PURPOSE: To provide a spark plug with improved heat resistance by carrying out plating after an earthing electrode welded to main metal fittings is temporarily curved into almost the same shape as the final shape. CONSTITUTION: An earthing electrode 11 is joined to a tip end face of a cylindrical part of main metal fittings 4 by resistance welding. The earthing electrode 11 is bent into an L-shape which is almost the same shape as that in the final state to be assembled. Then, after the metal fittings 4 are pickled to remove oxides and powders due to cutting, corrosion resistant at high temperature and hardly processible surface treatment is carried out for the inner circumference and the outer circumference of the metal fittings 4 and the earthing electrode 11 by plating. Next, an insulator built in a middle axis 2 is assembled with the metal fittings 4 and a spark gap 12 is formed between the earthing electrode 11 and the middle axis 2. After that, if necessary, a gap gauge 13 is inserted in the spark gap 12 and the spark gap 12 is finely adjusted by lightly hitting the earthing electrode 11 from the outside. Troubles such as cracking and peeling of the plating scarcely occur in the obtained spark plug 1. COPYRIGHT: (C)1996,JPO

Process and apparatus for welding or heat treating by laser

Abstract: Method and apparatus for welding, cutting, surface machining or heat treating workpieces by a laser beam which includes providing an optical element in the path of the laser beam to modify the pattern of the laser beam such that different geometric patterns can be projected on the focal plane, and this beam pattern spans at least the width of the heat treatment, cutting, surface machining or welding zone on the workpieces.

Intermetallic alloy welding wires and method for fabricating the same

Abstract: Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined.

Process for the electric welding of two weld parts

Abstract: The invention relates to a process for the electric welding of two weld parts by the flow of electric current through a welding point and the use of fluid such as an inert or protective gas to inhibit or prevent or eliminate oxidation at the welding point. The fluid is supplied through a continuous bore in one weld part and is directed toward the welding point, so that the fluid sweeps over the welding point radially from the bore. The fluid may be an inert gas such as argon or nitrogen, optionally mixed with carbon dioxide; alternatively the fluid may be aqueous liquid, the water being vaporized in the region of the welding point.

A model for heat and mass input control in GMAW

Abstract: This work describes derivation of a control model for electrode melting and heat and mass transfer from the electrode to the work piece in gas metal arc welding (GMAW). Specifically, a model is developed which allows electrode speed and welding speed to be calculated for given values of voltage and torch-to-base metal distance, as a function of the desired heat and mass input to the weldment. Heat input is given on a per unit weld length basis, and mass input is given in terms of transverse cross-sectional area added to the weld bead (termed reinforcement). The relationship to prior work is discussed. The model was demonstrated using a computer-controlled welding machine and a proportional-integral (PI) controller receiving input from a digital filter. The difference between model-calculated welding current and measured current is used as controller feedback. The model is calibrated for use with carbon steel welding wire and base plate with Ar-CO[sub 2] shielding gas. Although the system is intended for application during spray transfer of molten metal from the electrode to the weld pool, satisfactory performance is also achieved during globular and streaming transfer. Data are presented showing steady-state and transient performance, as well as resistance to external disturbances.

Resistance welding process for aluminum and aluminum alloy materials

Abstract: A resistance welding process for aluminum and aluminum alloy materials for enabling the remarkable improvement of the electrode life comprises the steps of preparing an insert material having the overall thickness of 0.02 to 1 mm including a sheet-like core material consisting of iron, steel, copper or copper alloy and coated layers each having the thickness of 1 to 100 μm, consisting of any one of Ni, Ni alloy, Ti, Ti alloy, Nb, Nb alloy, Mo, Mo alloy, W, W alloy, Cr, Cr alloy, Co and Co alloy and formed on both surfaces of the core material, or an insert material consisting of Ti foil or Ni foil; interposing the insert material between each of upper and under electrodes and each portion of overlapped materials to be welded consisting of aluminum or aluminum alloy; pressurizing the materials to be welded by the upper and under electrodes to join the materials to be welded together. The coated layers on both surfaces of the core material may consist of the same metal or different metals from each other. When the core material of the insert material consists of iron or steel, the insert material having the coated layer consisting of Ti and formed on one surface is interposed between each electrode and each portion of the materials to be welded in such a state that the coated layer faces each material to be welded, and the materials to be welded are pressurized and jointed together.

A systems approach to the control of welding fumes at source

Abstract: This paper presents a systematic approach to fume control by process modification. The effects on the rate of fume formation of the various welding parameters: the type of welding system, voltage, current, wire feed rate, gas shield and the type of materials to be welded are described

Resistance welding gun and apparatus

Abstract: A resistance spot welding apparatus (10) includes a base (11) mounted on a sliding track (12) along a fixed orientation to a rotary part (14) to be balanced. An arm (18) is pivotable about pin (20) which is rigidly attached to the base (11). The arm (18) provides a platform for a welding gun assembly (26). Electrodes (27, 29) provide current to weld a balance weight (28) to the rotary part (14). The welding gun assembly's electrode (27) is positionable by cylinder rod (46) rigidly attached to a positioning bracket (42). The position of the positioning bracket is determined by linear variable displacement transducer (LVDT) (58). The position of the bracket (42) is used to determine electrode positioning faults and weld quality.

Fast response weld head

Abstract: A fast response weld head (2) and a control system (60) allows user control of critical welding parameters such as speed, force, position, and duration. In one embodiment, the control system (60) includes a position servo loop (64, 66, 16, 50, 70) attached to a motor driven output shaft (36) on which a welding electrode (38) is mounted utilizing a follow-up spring assembly (44). During a weld cycle, the control system (60) moves the welding electrode (38) toward a workpiece (46) at a rapid user-defined rate. Just prior to contact this rate is reduced to prevent damage to the parts. When contact is made, the force exerted by the electrode (38) on the workpiece (46) is measured until the measured force equals a user-defined optimum welding force. When the weld is complete, the welding electrode (38) is automatically raised by the control system (60) releasing all pressure on the workpiece (46).

Apparatus for removing an electrode chip from a shank of a resistance welding machine

Abstract: An apparatus for removing an electrode chip of a resistance welding machine from a shank holding the electrode chip thereon comprising a shank holder to hold the shank, an electrode chip holder having a pair of holder halves to hold the electrode chip on the shank therebetween and means to move the electrode chip holder in a direction which is parallel to an axis of the shank so that the electrode chip holder move far away from the shank.

Corrosion resistant welding of stainless steel

Abstract: A process for welding stainless steel tubing in the presence of an inert gas comprising a silicon base gas, in particular silane SiH₄. During the welding operation, a suitable quantity of silicon is deposited by chemical vapor deposition at the weld joint to significantly improve the corrosion resistance of the weld.

Electric fusion welding of thermoplastic materials

Abstract: An improved welding rod having a solid homogeneous core of thermoplastic material and a resistance element comprised of a plurality of wires is presented with a method and apparatus for forming the welding rod. The welding rod is positioned between members of the thermoplastic material to be welded and a current and pressure is applied to the resistance element causing the thermoplastic material of the solid core and the adjacent thermoplastic members to fuse and form a unitary weld. Simultaneously the electrical resistance element is embedded in the weld, mechanically reinforcing and strengthening the connection. There is also disclosed a method for electric fusion welding of thermoplastic members wherein the welding rod is pre-attached to one of the thermoplastic members.

Weld nugget development and integrity in resistance spot welding of high-strength cold-rolled sheet steels

Abstract: Spot welds were produced using a high-strength cold-rolled sheet steel 0.08-in. (1.9-mm) thick. The welding parameters were systematically varied to examine their effects on nugget formation, microstructure, and mechanical properties. Following welding, several spot welds were cross-sectioned and mechanically polished for metallographic examination. Other spot welds were submitted to shear tensile tests. It is observed that welding current and weld time are more significant parameters than applied electrode force in affecting expulsion. In all the spot welds examined, it was found that solidification cracking could be reduced but not eliminated, and it was observed that for this particular steel, a weld cycle of 18 and a holding cycle of 15 resulted in the least amount of solidification cracking. Nugget displacement to one side of the faying surface, also known as 'stuck weld,' was observed in some samples that showed banding from rolling. Prior to melting, it appears that solid-state metallic bonding occurs during nugget development.

Resistance Welding of Graphite-Polyarylsulfone/Polysulfone Dual-Polymer Composites

Abstract: A statistically designed experimental approach was used to determine the optimum weld processing parameter values for a lap shear coupon prepared from a resis tance welded dual-polymer material system. The adherends used were 16-ply quasi isotropic laminates formed from T-750 graphite and polyarylsulfone prepreg (Radel®) with neat polysulfone comolded to each surface. The heating elements were made from a single layer of the Radel® prepreg with neat polysulfone comolded on each side. Electrical con nections were made through an expanded foil mesh conductor tab that was ultrasonically attached to each end of the heating element. The design-of-experiment approach was used for the experimental set-up and analysis. A series of response surface plots was prepared that allowed the optimum processing parameter values to be identified. Photomicrographs and C-scans were prepared from the welded region and compared to the lap shear strength values obtained. The relationship between the bondline thickness and the la...

Apparatus for assembling and welding final end plugs to nuclear fuel-containing cladding tubes and inspecting the welds, all on an automated basis

Abstract: In an automated final weld apparatus, a transporter conveys nuclear fuel-loaded cladding tubes successively to a check station to verify the presence of a plenum spring in the open end of each cladding tube, a reader station where a unique first end plug serial number is read, an evacuation/backfill station where the cladding tube is backfilled with helium, a seam welding station where a final end plug is welded to the cladding tube open end, and a seal weld station where the tube is pressurized with helium through a pressurization hole in the final end plug, whereupon the pressurization hole is welded closed. After checking for helium leakage, the seam weld is inspected in a succession of inspection stations, and, depending on inspection results, the finished nuclear fuel rods are sorted into accepted and rejected lots.

Fixed point welding gun

Abstract: A resistance welding gun which is adapted to prevent asymmetrical impacting of two or more metal sheets to be welded. The resistance welding gun includes a pair of rotatably connected arms, each of which has a corresponding working end and actuation end. An electrode tip is located at each working end to provide a pair of opposed welding electrodes, while a cylinder is attached to the actuation ends of the arms to provide rotation therebetween. Between the actuation ends there is provided an equalizing mechanism including a crank and a pair of linkages which serve to equalize the movement of the arms about their pivot. In cooperation with the pivot of the arms, the crank establishes a fixed or datum point at which the electrode tips of the resistance welding gun are targeted such that, when properly positioned on opposite sides of the metal sheets, the electrode tips contact the metal sheets substantially simultaneously and apply substantially equal forces to the opposite sides of the metal sheets. As a result, the equalizing mechanism substantially prevents unilateral contacting and asymmetrical impacting by the electrode tips on the metal sheets.

Laser Welding of Lightweight Structural Steel Panels

Abstract: The Applied Research Laboratory, The Pennsylvania University (ARL Penn State) has developed a relatively low heat input high power carbon dioxide (CO2) robotic laser beam welding (LBW) technique for fabrication of lightweight corrugated core steel sandwich structures. Both HSLA 80 and type 316L stainless steel structures have been produced. Over 276 test panels ranging in size from 3″ × 5″ to 8′ × 8′ have been produced.Specimens have been rigorously tested by the Carderock Division of the Naval Surface Warfare Center (NSWC) private industry and foreign Governments and have been evaluated in terms of static and dynamic strengths, fatigue, fire, acoustics, thermal and insulation performance, and corrosion resistance. Lightweight corrugated core steel panels (LASCOR) fabricated by ARL Penn State have been shown to have exceeded or met the performance requirements established by NSWC in the areas of weight, fire, weld fatigue, static strength, thermal and insulation performance. Additional work has been conducted by NSWC in the area of blast analysis.Development of fabrication procedures, testing and evaluation procedures, and results to-date will be reviewed.The Applied Research Laboratory, The Pennsylvania University (ARL Penn State) has developed a relatively low heat input high power carbon dioxide (CO2) robotic laser beam welding (LBW) technique for fabrication of lightweight corrugated core steel sandwich structures. Both HSLA 80 and type 316L stainless steel structures have been produced. Over 276 test panels ranging in size from 3″ × 5″ to 8′ × 8′ have been produced.Specimens have been rigorously tested by the Carderock Division of the Naval Surface Warfare Center (NSWC) private industry and foreign Governments and have been evaluated in terms of static and dynamic strengths, fatigue, fire, acoustics, thermal and insulation performance, and corrosion resistance. Lightweight corrugated core steel panels (LASCOR) fabricated by ARL Penn State have been shown to have exceeded or met the performance requirements established by NSWC in the areas of weight, fire, weld fatigue, static strength, thermal and insulation performance. Additional work has been condu...

Method of controlling welding current in direct-current resistance welding machine

Abstract: A workpiece is welded successively at a plurality of welding points by a direct-current resistance welding machine with a constant current in a welding current supply period at each of the welding points, and the constant current is varied depending on whether expulsions are produced on the workpiece when it is welded, to determine an expulsion-producing limit current value as a maximum current beyond which expulsions will be produced. The workpiece is welded with a first stepped welding current having a first current value that is smaller than the expulsion-producing limit current value by a predetermined value and a second current value that is greater than the expulsion-producing limit current value, and an average current value higher than the expulsion-producing limit current value, and also with a second stepped welding current having a variation of the second current value based on whether expulsions are produced or not on the workpiece when it is welded with the first stepped welding current.

Shut off check valve for a welding gun

Abstract: A shut off check valve for controlling cooling fluid flow to weld tips of a resistance welding gun. The valve is disposed within the weld gun housing and selectively interrupts cooling fluid flow between fluid inlet and outlet ports.

Joining method and joining structure by spot welding using together press welding

Abstract: PURPOSE: To improve the strength of a coupler by spot welding by drawing down a spot welding electrode and the periphery of contact part of a material to be welded by using an insulater indenter when a power is supplied. CONSTITUTION: When the spot welding is performed, the material 13 to be welded is drawn down by bringing into contact with the spot welding electrode 11. Press welding is performed by drawing down the spot welding electrode 11 and the periphery of contact part of the material 13 to be welded by using the insulator indenter 12 when the power is supplied. In such a case, the width of a corona bond part 14 in the periphery of a nugget 15 is set at a value between 20-100% of a nugget diameter 17. In this way, solid joining can be performed by the synergetic effect of temperature and pressure, and a large corona bond part can be formed in the periphery of the nugget on which the spot welding is performed. Therefore, the coupler strength of a joint can be increased to expand a joining area from only a nugget area to the one on which a corona bond area is added. COPYRIGHT: (C)1995,JPO

Welding complicated, difficult-to-weld metal components

Abstract: The present invention is a method for welding difficult-to-weld metal components as illustrated in the welding of a receiver for a weapon. The method reduces net distortion by a number of techniques, including: (1) cooling the weld with Carbon Dioxide (CO 2 ) preheated with the welding torch tip; (2) use of not more than approximately 4% oxygen in the shield gas to enable hotter, faster welding; (3) the use of a reduced voltage and wire feed rate at the end of a weld to avoid cracking; (4) the intentional use of distortion to reduce net distortion; and (5) sequencing of welds to reduce distortion. Distortion can be introduced in the stamped parts as they are made or when placed in a fixture for welding that, when welded, have less distortion than before. Distortion can also be countered by welding parts in a sequence where a subsequent weld reduces the distortion of a previous weld. The process is illustrated as applied to a receiver for a weapon made by welding non-compatible and low carbon steels in a low tolerance configuration.

Laser-beam welding of SiC fibre-reinforced Ti-6Al-4V composite

Abstract: Three- and ten-ply SiC fibre-reinforced Ti-6Al-4V composites were joined using a laser beam. With a 300 μm thick Ti-6Al-4V filler metal, fully penetrated welds without apparent fibre damage, could be obtained in welding directions both parallel and transverse to the fibre direction by controlling the welding heat input. Excess heat input resulted in the decomposition of SiC and subsequent TiC formation, and also caused degradation of joint strength. The welding of the three-ply composite in which full penetration was achieved at lower laser power, exhibited higher flexibility in heat input than that of the ten-ply composite. Heat treatment at 1173 K after welding improved the joint strength because of the homogenization of the weld metal and decomposition of TiC. The strengths of the transverse weld joints after the heat treatment were approximately 650 and 550 MPa for the three- and ten-ply composites, respectively. With the welding direction parallel to the fibre direction, the strengths both parallel and transverse to the weld joint were equivalent to those of the base plate.

Welding apparatus having coaxial welding electrodes

Abstract: A resistance welding apparatus for welding a wire to a metallic pad of an integrated circuit. The welding apparatus has coaxial welding electrodes with the outer electrode being in the form of a tube. The inner electrode is a cylindrical rod and is located in the outer electrode. The end of the outer electrode has two opposed open-ended V-shaped slots. The slots receive and position the wire. With the wire located in the slots, the end of the outer electrode is engaged with the pad and the inner electrode pushes the wire against the pad. Welding current can now be applied to the electrodes. Each electrode is associated with a load cell that senses electrode force. Welding current is applied to the electrodes only after the electrode force of each electrode attains certain predetermined values.