Showing papers on "Electric resistance welding published in 1997"

Friction stir welding with simultaneous cooling

Abstract: A method and apparatus for friction stir welding that produces a weld of significantly reduced surface roughness at significantly higher welding rates, in materials that are difficult to weld, such as non-extrudable aluminum alloys. The method includes cooling the stir welding tool during the welding process, thereby reducing the tendency of softened metal to adhere to the rotating pin and shoulder of the tool. The apparatus includes a tool with internal spaces or an external jacket, through which coolant can be pumped to remove heat and cool the tool during welding operations. In another embodiment, the apparatus includes a device for spraying a coolant onto exterior surfaces of the distal end of the welding tool to thereby remove heat from the tool, and the surrounding workpiece, during welding.

Microwave welding of high density polyethylene using intrinsically conductive polyaniline

Abstract: The use of intrinsically conductive polymers in welding of plastics and composites offers the possibility of developing new welding methods. Intrinsically conductive polyaniline (PANI) composite gaskets were used to microwave weld high density polyethylene (HDPE) bars. Two composite gaskets were made from a mixture of HDPE and PANI powders in different proportions. Adiabatic heating experiments were used to estimate the internal heat generation and electric field strength in the gasket. During welding, the effects of heating time, heating pressure and welding pressure were evaluated. It was found that increasing the heating time and the welding pressure increased the joint strength. The maximum tensile joint strength was achieved using a 60 wt% PANI gasket with a heating time of 60 sec and a welding pressure of 0.9 MPa; this resulted in a tensile weld strength of 24.79 ± 0.34 MPa, which equals the tensile strength of the bulk HDPE.

Friction welding apparatus and method

Abstract: A mobile friction welding machine is provided for creating friction weld joints in workpieces such as metal sheets, especially lead sheets is described. The machine has a track assembly to guide it across work pieces, including a caterpillar track system on the machine. The friction welding is achieved by rotating a probe and applying a downward load on the probe to urge it into the work process. The probe is preferably a pair of spaced apart probes having a crescent-shaped cross-section.

Method and material for resistance welding steel-base metal sheet to aluminum-base metal sheet

Abstract: The present invention relates to a resistance welding method suitable for use in spot welding between a steel-base metal sheet, which has been plated for rust prevention purposes, and an aluminum-base metal sheet and aims to permit a current to flow at a high density across the plated steel sheet and the aluminum-clad steel sheet, thereby realizing high-quality welding. An aluminum-clad steel sheet comprised of a steel layer having projections and an aluminum layer is interposed between the plated steel sheet and the aluminum-base metal sheet to be welded to each other. An electrode is energized by a predetermined weld current from an alternating power supply. The current path is limited to the area of the projections, and metallic melt formed by melting of the plating is accommodated between the projections, preventing the current-carrying area from being increased. Consequently, the temperature of the interface of the plated steel sheet and the aluminum-clad steel sheet can be efficiently raised, resulting in the formation of a proper nugget on both sides of the aluminum-clad steel sheet.

The effect of mechanical loading on the contact resistance of coated aluminium

Abstract: Measurements of contact resistance, related to resistance spot welding, were made using pre-treated (coated) and abraded aluminium alloy strip. With conventional domed electrodes, the contact resistance was much larger at the sheet-to-sheet (faying) contact than at the electrode-sheet contact. The effect is believed to be associated with the role of sliding in breaking down contact resistance of sheet with an insulating surface film. When the coating was removed the difference between faying surface and electrode-sheet contact was much smaller. Macroscopic shear stresses are developed by electrode-sheet contact whereas no shear stresses are present at the faying surface. The hypothesis is supported by experiments made with asymmetrical electrode pairs which give rise to varying shear stresses in faying surface contact. Some implications for the control of spot welding of different aluminium surfaces are discussed.

Friction welding of polyamides

Abstract: Results from different experiments on friction welding are used to characterize the behavior of polyamide over a wide range of welding conditions Several types and grades of polyamide were joined using the vibration and spin welding processes The quality of the welds was evaluated by short time tensile tests and microscopy In addition to the geometry of the parts being joined, the process parameters and the material were found to affect the quality of the weld, so that associated with each application is a different set of optimum welding parameters

Method of welding wallpaper alloy and arc welder modified to practice same

Abstract: A method of and welder for welding a corrosion resistant, wallpaper alloy to the inside surface of a vessel wall formed from a corrosion susceptible steel sheet after the wallpaper alloy has been affixed to the inside to provide an exposed seam of wallpaper alloy extending in a given path wherein the method and welder comprising moving a welding wire toward the seam, melting and depositing the welding wire onto the seam along the path by a short circuit arc welding process of the type having a welding cycle with a short condition and an arcing condition, which arcing condition constitutes a plasma boost portion with a set peak current level followed by a plasma portion with a current decreasing from said peak current level toward a set background current level with a given time between the plasma boost portion and the short condition andsetting the length of time of the plasma portion of the arcing condition to a value greater than 25% of the given time or greater than 2.0 ms.

CO2 laser beam welding of 6061-T6 aluminum alloy thin plate

Abstract: Laser beam welding is an attractive welding process for age-hardened aluminum alloys, because its low heat input minimizes the width of weld fusion and heat-affected zones (HAZs). In the present work, 1-mm-thick age-hardened Al-Mg-Si alloy, 6061-T6, plates were welded with full penetration using a 2.5-kW CO2 laser. Fractions of porosity in the fusion zones were less than 0.05 pct in bead-on-plate welding and less than 0.2 pct in butt welding with polishing the groove surface before welding. The width of a softened region in the-laser beam welds was less than 1/4 times that of a tungsten inert gas (TIG) weld. The softened region is caused by reversion of strengthening β″ (Mg2Si) precipitates due to weld heat input. The hardness values of the softened region in the laser beam welds were almost fully recovered to that of the base metal after an artificial aging treatment at 448 K for 28.8 ks without solution annealing, whereas those in the TIG weld were not recovered in a partly reverted region. Both the bead-on-plate weld and the butt weld after the postweld artificial aging treatment had almost equivalent tensile strengths to that of the base plate.

Plant for friction stir welding

Abstract: A plant for friction stir welding, comprising a welding probe (12), a drive unit (13) driving the welding probe, a work table (7) supporting the workpiece or workpieces (2, 3) to be welded, and at least one clamping means (5, 6) for clamping the workpieces to one another and/or to the work table, or the workpieces to the work table, respectively, during the welding operation. The plant likewise comprises a milling tool.

Apparatus for cutting and/or welding flexible packaging

Abstract: This invention involves a method and apparatus for welding and/or cutting flexible packaging material ( 1 ) using lasers. The invention is specifically directed towards the use of lasers for cutting and/or welding plastics material ( 1 ) in motion, such as in association with high speed packaging machinery. The method and apparatus of the invention enables the cutting and/or welding of adjacent webs of plastics material ( 1 ) by scanning one or more processing laser beams ( 4 ), or sub-beams ( 5, 6 ) of the or each processing laser beam ( 4 ), across said moving layers ( 1 ) at a rate controlled in relation to the rate of motion of the layers ( 1 ) of substrate. The method and apparatus may produce straight or shaped cuts and/or welds.

Method of welding

Abstract: A process for buttwelding metal workpieces (12) having bevelled joint preparations using an automatic GTAW welder (20) using filler wire (32) includes preparing the bevelled workpieces (12) with bevelled joint areas having minimal land thickness at the root extremities; placing the prepared workpiece joint sections together with an open gap between their adjacent root extremities, the gap having a minimum dimension that avoids harmful compression stress between the workpieces due to weld shrinkage and a maximum dimension that avoids filler wire penetration of the gap; fusion welding the open root area of the adjacent workpieces (12) with a root pass weld using an automatic GTAW welder (20) supplied with filler wire (32) and a shield gas including 1 to 10 % hydrogen and the balance inert gas; and then promptly overlaying the root pass weld with at least one additional filler weld pass using an automatic GTAW welder (20) supplied with filler wire (32) and hydrogen-free shield gas.

Universal quality assurance method for resistance spot welding based on dynamic resistance

Abstract: Welding of mild steel is one of the most common processes in spot welding. Numerous methods for ensuring high-quality welds are based on dynamic resistance. However, in general, these methods are only useful over a relatively narrow range of welding parameters. This article presents a universal quality assurance method based on dynamic resistance that is valid over a wide range of welding time, welding current, electrode force and electrode tip geometry (up to and including complete tip mushrooming). This method was constructed on the basis of models describing current density redistribution at the faying surface during the welding process. Validation of the method has been confirmed experimentally. The comparison of results shows that the method provides the maximum nugget size.

Method of welding in the horizontal position and welding apparatus therefor

Abstract: The object of this invention is to prevent the occurrence of welding defects such as undercuts, overlaps and faulty angles of fusion, and to increase the efficiency of welding in the horizontal position. Auxiliary wires 5a and 5b are inserted into molten pool 12, and a unidirectional current is made to flow between them. A magnetic field 9 is induced which is approximately orthogonal to the surface of the parent material so as to generate an upward Lorentz force (opposite the pull of gravity) in molten pool 12. This force supports the molten metal and prevents it from dripping, resulting in a better-shaped bead.

Absorption and transport of hydrogen during gas metal arc welding of low alloy steel

Abstract: Although hydrogen induced cracking remains a major problem in the welding of steels, the present methods of managing hydrogen in the weldment are mostly empirical in nature. In recent years, numerical modelling of heat transfer and fluid flow has provided detailed insight into the physical processes in welding. However, very little effort has been made in the past to use these transport phenomena based calculations to understand the dissolution of hydrogen in the weld metal and its subsequent transport in the liquid and solid regions. The aim of the present work was to address this important need. Heat transfer, fluid flow, and hydrogen transport calculations in transient, three-dimensional form are used to predict the spatial distribution of hydrogen concentration in the weld metal during gas metal arc welding of mild steels for different welding conditions. The enhanced hydrogen solubility in the weld metal above that predicted by Sieverts law was determined from a model for the partitioning of ...

Spark plug and its manufacturing method

Abstract: A hole is formed on a central electrode A chip has a leg portion A distal end of the leg portion is entirely united with a bottom surface of the hole by resistance welding A plurality of fused portions are formed at a boundary between the chip and the central electrode The fused portions integrate the chip and the central electrode by fusing them together Each fused portion extends in a radial direction of the chip The entire periphery of a pointed end of each fused portion penetrates radially inside the outer cylindrical surface of the leg portion of the chip

Method and apparatus for controlling resistance welding

Abstract: An apparatus for controlling resistance welding defines a weld time for series welding as a plurality of (e.g., two) weld periods. In one embodiment, a control successively switches a bidirectional switch in a first polarity during the first weld period so that welding current flows through workpieces of different metals in one direction by passing through a series of welding points of the workpieces. In the second weld period, the control successively switches the bidirectional switch in the reversed polarity so that welding current flows through the workpieces in the other direction so as to compensate for Pertier effect on the welding points. A polarity changing technique is used to minimize welding energy loss in shifting weld periods for better weld quality. In another embodiment, thyristors are controlled such that they are fired in the second half cycle of the supply voltage at an angle smaller than the firing angle in the first half cycle.

Ultrasonic energy welds copper to aluminium

Abstract: Attempting to weld copper to aluminum by conventional means through the application of thermal energy to melt and fuse the two metals (fusion welding) can result in an unreliable weld. The oxide layer on aluminum is difficult to remove, the melt temperatures of the two metals are not close, the two metals exhibit high thermal conductivity and alloying of the two metals creates a brittle intermetallic that is mechanically and electrically unreliable. An alternative for design engineers is to weld copper to aluminum by applying ultrasonic energy, which joins the metals without melting. The ultrasonic process creates a high quality weld both mechanically and electrically without forming a brittle intermetallic and without intermediate steps. Ultrasonic welding of copper to aluminum has been shown to be efficient and effective as demonstrated by a number of practical production applications. The problems of tough oxides, high thermal conductivity, high electrical conductivity, intermetallics and brittle alloys are not significant with the ultrasonic welding process. And similarly, the problems associated with pre and postweld cleaning, fluxes, hot metal and high energy costs are eliminated. Modern ultrasonic welding equipment is capable of monitoring energy and controlling the critical welding process variables.

Control method in multi-layer welding

Abstract: In a multi-layer welding, weld line and a gap width of workpieces (A, B) to be welded are detected by a laser sensor mounted on a robot, during a welding for a first layer, whereby, a welding torch mounted on the robot is made to follow the weld line and welding conditions are adjusted in accordance with the detected gap width. The detected gap width is stored in the storage means together with the weld line data. Then, weldings for a second and subsequent layers are performed by using the stored data in such a manner that the welding torch is made to follow the weld line, and the welding conditions are adjusted in accordance with the gap width.

Spot welding method and its device

Abstract: PROBLEM TO BE SOLVED: To prevent generation of expulsion and welding defects by actually applying a proper pressurizing force between members in a weld zone, in a spot welding method in which the weld zone of a liquid tank is held between a pair of electrode tips, pressurized and energized for welding. SOLUTION: In the servo gun electrode tips oppositely vertically arranged with a weld zone of a liquid tank in between, the upper electrode tip is advanced by a servo motor, pressurizing a weld zone (S4). With the inter- electrode distance detected based on the output signal of the servo motor (S5), and with the distance equalized to the total thicknesses of a work in the weld zone (S6), the pressurizing force to the weld zone by the electrode is detected and stored (S8). The weld zone is pressurized with the value in which the detected pressurizing force is added to the preset proper pressurizing force required for welding (S9, 10, 11).

Aluminium sheet product and method of welding structural components

Abstract: In the welding of aluminium alloy structural components, e.g. in the aerospace industry, one of the welded components is a sheet product (1) having a core (2) and a clad layer (3) of filler material. During welding, the clad layer (3) provides filler for the welding pool, and the core (2) remains substantially unmelted. Consequently adhesion between the core and the clad layer maintains its strength, e.g. keeps at least 80 % of its pre-welding strength.

Apparatus and method for resistance welding tubular parts

Abstract: An apparatus and method for resistance welding tubular parts. The apparatus includes a weld gun having electrodes with arcuate contact faces engaging the parts. The electrodes are displaceable relative to each other. The contact faces are designed to distribute the force applied to the parts to prevent deformation and to hold the parts together steadily in order to minimize the amount of undesired electrode displacement caused by these effects. A test computer monitors the amount of electrode displacement occurring as a result of penetration of the parts into each other during welding. When the displacement between the electrodes falls within a predetermined displacement range, which is indicative of a proper weld between the parts, the computer cooperates with a weld controller to terminate the welding power, thereby inhibiting any substantial further penetration of the parts. The apparatus and method is suitable for tube-to-tube and wire-to-tube applications commonly performed in the manufacture of automobile seats.

Welding method and welding material

Abstract: A welding method for two members adapted to be welded and formed of a low-alloy steel for structural purposes causing the weld metal to develop martensite transformation during cooling after welding, so that the weld metal becomes expanded to a greater degree at room temperature than at a temperature at which the martensite transformation initiates. The welding material comprises a ferrous alloy containing C, Cr, Ni, Si, Mn, Mo and Nb, all of which meet substantially with the contents of the following equation (1): ##EQU1##

Resistance welding electrode with guide pin

Abstract: In an electrode for welding with a retractable guide pin so received in a guide hole of the electrode that air blows out from a gap between the guide hole and the guide pin as the guide pin is pushed in to prevent intervention of foreign matters between an end face of an electrode and a steel sheet part or at a sliding portion of the guide pin, a large-diameter hole (33) and a small-diameter hole (34) are provided at a portion through which passes a small-diameter portion (7) of the guide pin (6) so as to form a receiving face (35) with the difference in diameter between the two, and an exhaust passage is provided near the receiving face (35) to establish communication between the large-diameter hole (33) and outside of the electrode.

Dual welding method of laser beam and consumable electrode arc

Abstract: PROBLEM TO BE SOLVED: To provide a dual welding method of laser beam and arc capable of welding a thick plate at a high speed. SOLUTION: On a welding route 6 of plates 1, 2 to be welded, a laser beam machining nozzle 3, a plasma torch 4 and an assist injection nozzle 5 are arranged. A laser beam is preceding and an arc is succeeding, a distance between a laser beam irradiating position (a) and a welding wire targeting position (b) of an arc is set to a appropriate value, a gap of the welding route of the plates 1, 2 to be welded are set to >=10% of a plate thickness and <= laser beam diameter.