Showing papers on "Electric resistance welding published in 1996"

Joining of aluminium based metal matrix composites

Abstract: Metal matrix composites (MMCs) are becoming more popular as structural materials, and joining them is, therefore, of paramount importance. As these new materials become available, it is necessary to define and optimise joining techniques, and a thorough understanding of each process is required. A number of joining processes have been addressed, namely: fusion welding (tungsten and metal inert gas welding, electron and laser beam welding, resistance, capacitor discharge, and plasma welding), solid state bonding (diffusion bonding, friction and magnetically impelled arc butt welding), brazing, and adhesive bonding. The advantages and disadvantages of each technique are discussed with respect to weld-parent material microstructure and the mechanical properties of the bond. Recommendations are subsequently made as to the most appropriate method for bonding aluminium based MMCs.

Programmable friction stir welding process

Abstract: A variable pin length stir friction welding method wherein the stir friction welding pin penetrates the workpiece as the workpiece translates. The stir friction welding pin starting at a zero penetration and extending to the depth needed to repair a weld or to make a weld. Then withdrawing the pin to zero penetration as the work is translated. The weld path is thus ramped into and out of the workpiece leaving no holes which need to be repaired. Circumferential welds can be made by keeping the pin extended to the welding depth for at least one complete revolution of the weld.

Plasma charge sensor for in-process, non-contact monitoring of the laser welding process

Abstract: Laser keyhole welding is an important modern manufacturing technology. During such welding a plasma cloud is generated and the behaviour of this plasma is closely coupled to the behaviour of the weld. The plasma behaviour has been observed during welding through measurement of the space charge voltage induced on an electrically insulated welding nozzle, the plasma charge sensor (PCS). It is shown both theoretically and experimentally that the induced voltage is a measure of plasma temperature and thus of the welding performance. In particular, it is shown under laboratory conditions that the PCS signal can measure weld penetration and detect a wide range of weld defects. Results have also been obtained from the PCS installed on an industrial laser can welder. An expert system has been used to analyse the PCS signal automatically and classify weld defects. It is reported that a greater than 90% success rate has been achieved in detecting and classifying defects in high-speed industrial laser can welding. The PCS is shown to be a reliable and robust non-contact method of on-line weld monitoring well suited to installation on existing laser welding stations.

Transport Phenomena During Resistance Spot Welding

Abstract: Unsteady, axisymmetric transport of mass, momentum, energy, species, and magnetic field intensity with a mushy-zone phase change in workpieces and temperature, and magnetic fields in electrodes during resistance spot welding, are systematically investigated. Electromagnetic force, joule heat, heat generation at the electrode–workpiece interface and faying surface between workpieces, different properties between phases, and geometries of electrodes are taken into account. The computed results show consistencies with observed nugget growth, electrical current, and temperature fields. The effects of the face radius and cone angle of the electrode, parameters governing welding current, electrical contact resistance, magnetic Prandtl number, electrical conductivity ratio, and workpiece thickness on transport phenomena are clearly provided.

Developments in characterization of resistance spot welding of aluminum

Abstract: Automotive industry interest in aluminum is growing rapidly in Europe and North America. Resistance spot welding and weldbonding will be key techniques in the volume production of aluminum vehicles. A monitoring system has been developed to collect process data during single-phase alternating current (AC) and medium-frequency direct current (MFDC) inverter resistance welding. Features extracted from the captured data are used to characterize spot welding and to identify a range of process phenomena. Statistical analysis has been applied to investigate the relationship between the extracted features and the conventional physical parameters, e.g., weld size and static tensile strength. Welding trials using both MFDC and AC welding equipment have been carried out using aluminum of different gauges and surface conditions. Results on the Al-Mg alloy AA-5754 have shown that the monitoring methods developed previously for steel do not appear to be generally applicable to aluminum. No single parameter can accurately quantify weld quality. Multiple regression methods can, however, provide good prediction of nugget diameter and static strength. This has proved effective even when only electrical variables are logged, removing the need for measurement of other process signals, e.g., electrode displacement or force.

Method for developing residual compressive stress in stainless steel and nickel base superalloys

Abstract: Compressive residual stresses can be developed by underwater plasma transferred arc welding. The development of these compressive stresses act to prevent hot cracking and He embrittlement that can develop during welding or stress corrosion cracking that can develop subsequent to the welding operation.

Mathematical models for control of weld bead penetration in the GMAW process

Abstract: This paper presents the effects of welding process parameters on weld bead penetration for the gas metal arc welding (GMAW) process. Welding process parameters included wire diameter, gas flow rate, welding speed, arc current and welding voltage. The experimental results have shown that weld bead penetration increased as wire diameter, arc current and welding voltage increased, whereas an increase in welding speed was found to decrease the weld bead penetration. However, the weld bead penetration is not affected significantly by gas flow rate changes. Mathematical equations for study of the relationship between welding process parameters and weld bead penetration have also been computed by employing a standard statistical package program, SAS.

TIG welding method and welding torch therefor

Abstract: A TIG welding method is usually carried out in a manner that a tungsten electrode is inserted into a weld groove portion of a member to be welded, an electric voltage is applied to a current conducting portion provided for the tungsten electrode while flowing a shield gas means to thereby generate an arc between the tungsten electrode and the member to be welded to form a molten pool of the member, a welding wire is inserted into the molten pool, and a welding torch is then operated to perform a welding process In the improvement of the TIG welding method, the shield gas means is composed of an inner shield gas (13) flowing from a periphery of the tungsten electrode (3) to a front end thereof inserted into the weld groove portion (2a) of the member (1a) to be welded and an outer shield gas (14) flowing towards the weld groove angle from an outside of the inner shield gas (13) to prevent the molten pool from being oxidized and to prevent oxygen in air from being involved The TIG welding torch for carrying out the method is specifically provided with the inner and outer shield gas flow means, and further provided with a central shield gas flow means

Laser welded inkjet printhead assembly utilizing a combination laser and fiber optic push connect system

Abstract: A method for the solderless laser welding of two materials by using a laser light beam attached to a fiber optic system which directs the light to a region where the laser beam can shine through one of the materials to create a seam weld. By using a fiber optic system the laser beam is converted into thermal energy and weld flaws due to underheating or destruction of the materials due to overheating do not occur. A seed-metal layer and weldable-metal patterns are formed on non-metallic materials-to-allow their laser welding by this method.

Electrode for electric resistance welding

Abstract: An electrode for electric resistance welding comprises a guide hole of a circular cross-section composed of a small-diameter hole and a large-diameter hole, a guide pin composed of a small-diameter portion and a large-diameter portion, the small-diameter portion and larger-diameter portion of the guide pin being fitted into the small-diameter hole and large-diameter hole of the guide hole, respectively, so that when the guide pin is pushed down, compressed air is allowed to jet out of a gap between the small-diameter hole and the small-diameter portion. The large-diameter portion of the guide pin is firmly fitted into the guide hole, with an air passage formed in the outer circumference of the large-diameter portion and the end surface of the large-diameter portion seated on the inner end surface of the large-diameter hole.

A theoretical study on electrical and thermal response in resistance spot welding

Abstract: The effect of contact resistance including constriction and contamination resistance has been a major hurdle for the thermoelectrical analysis of the resistance spot welding process. In this paper, a simple model was suggested and used for calculating the electrical and thermal response of the resistance spot welding process to investigate the influence of contacting forces on the formation of weld nuggets. The electrode surface of the contact interface was assumed to be axisymmetric and its microasperities to have a trapezoidal cross-section. These microasperities were considered as the one-dimensional contact resistance elements in the finite element formulation. The contamination film was assumed to be a nonconducting oxide layer, which is very brittle, so that it is broken to some number of pieces when a contacting pressure is being applied. The crushed films were assumed to be distributed at regular intervals and to conserve their size and number during the welding process. The simulation results revealed that the proposed model can be successfully used to predict the effect of the contact resistance on the electrical and thermal response of the resistance spot welding process.

Method for joining two parts of different kinds by heterogeneous butt welding, and uses thereof

Abstract: An end portion of each of two parts (10, 11) is machined and the machined end portions of the parts (10, 11) are arranged in facing positions to form a welding bevel (13) extending in a longitudinal direction between the parts (10, 11), whereafter a filler metal is deposited into the welding bevel (13). The welding bevel is a narrow bevel with side walls at an aperture angle of no more than 5° relative to the longitudinal central plane of the bevel (13). A nickel alloy comprising 18-32 % of chromium is deposited into the welding bevel. The method is particularly suitable for joining a pressurised water nuclear reactor vessel tubing and an austenitic stainless steel primary circuit pipe.

High speed rotating automatic arc welding device

Abstract: PROBLEM TO BE SOLVED: To provide a high speed rotating automatic arc welding device having suitability to the welding on-site at a high position and high welding efficiency in high welding quality. SOLUTION: This device is composed of rail 5 parallel fitted with a welding line 201 extended in the perpendicular direction in a work 200 with plural magnet devices 6, an automatic welder 10 vertically welding downward by the high speed rotating arc welding with a rotation welding torch 1 through an arc sensor while travelling on the rail 5, a welding condition setting panel of a welding control device having handles for setting the welding condition and an operational pendant for finely adjusting the welding condition at an operator side. Then, a semi-automatic welding torch 20 is inserted into a connecting metallic tool at the base end side of the rotation welding torch so as to be freely attached/detached and commonly supply a welding electric source, shield gas and welding wire.

Laser edge welding member and its welding method

Abstract: PROBLEM TO BE SOLVED: To enhance productivity by forming a weld zone in which plural superposed parts formed on the end face of a weld joint are connected and alternately crossed and thereby laser-welding the superposed part in one welding operation. SOLUTION: While a laser welding machine 9 is moved along a welding line, it is also moved in the width direction of a weld joint 4 in the manner of continuously and alternately crossing a first and a second superposed part 6, 7 formed on the end face of the weld joint 4. Then, a laser beam is emitted from the laser welding machine 9, heating the end face of the weld joint 4 to form a weld zone 8. Thus, the superposed part is surely welded, with the formation of welding defects effectively eliminated.

Studs for boilers and other high temperature applications

Abstract: Disclosed is a stud for a boiler or other high temperature application, such as a furnace. The stud is made of an iron aluminum alloy which comprises about 81 to 91 wt. % iron, about 8 to 13 wt. % aluminum, about 0.01 to 0.3 wt. % carbon, and zero to about 3 wt. % of a refractory metal and/or zero to about 1.5 wt. % zirconium. The studs are welded to a surface of a component of the boiler or furnace by arc or resistance welding. The aluminum of the iron aluminum alloy imparts good oxidation and sulfidation resistance to the studs. The alloy also has a good electrical resistance which makes the alloy especially useful for arc or resistance welding. The aluminum content acts as a getter to eliminate gas porosity in the resulting welds. The present invention is particularly useful for making boiler heat exchange surfaces or refractory covered surfaces wherein the studs function as refractory anchors.

Friction welding of Al-Al, Al-steel, and steel-steel samples

Abstract: Friction welding of Al- Al, Al- steel, and steel- steel studs is compared. Transient heat generation and temperature rise during the welding process were modeled. Tensile tests and microhardness measurements across the weld zone were carried out. The metallurgical changes in the heat- affected zone were examined by SEM. Temperature rise at the interface plane was computed and related to weld properties. The affecting parameters on weld quality were identified by statistical analysis. Results show that interaction of weld parameters significantly affect yield, tensile, and breaking strength, and the heat- affected zone on the Al side is wider for Al-steel welds.

An Experimental Study of Resistance Spot Welding in 1 mm Thick Sheet of Low Carbon Steel

Abstract: Investigations on the influence of welding parameters such as welding current, electrode force and weld time in resistance spot welding processes have been carried out with the help of a specially developed simulator. The effect of these parameters on dynamic contact resistance as well as on the quality of weld joint in terms of weld joint strength, nugget diameter, etc., was studied and conclusions have been made. Experiments have been carried out on 1 mm thick St1203 (DIN 1623) type of steel. Experimental observations were analysed statistically to obtain an empirical relationship between weld strength and the welding process parameters and subsequently a polynomial relation of second order has been fitted with a satisfactory degree of reliability. From these results welding lobes were also drawn which will provide information on different conditions needed for specified weld strength and also ensure a minimum guaranteed strength at those combinations. The possibility of using dynamic contact resistance...

Preventing weld hot cracking by synchronous rolling during welding

Abstract: Based on the mechanical point of view of hot cracking in weldments, a new method, accomplished by synchronous rolling during welding (SRDW) along both sides of the weld at a suitable distance behind the welding arc, has been developed for preventing weld hot cracking. The theory behind this method was also examined. Three-dimensional simulative computations of displacement and strain fields produced by SRDW were carried out by means of the finite element method to reveal the mechanism of the new method and provide a theoretical basis for parameter choice. With a specially developed equipment for welding and synchronous rolling, experiments were performed to investigate the effectiveness and feasibility of this method in preventing weld hot cracking in high-strength aluminum alloy 2024-T4. Results show that weld hot cracking in 2024-Al alloy can be effectively prevented and the mechanical properties of welded joints can also be improved by the new method. It is an important new solution to weld hot cracking in welding of sheet metals.

Narrow gap laser beam welding method

Abstract: PROBLEM TO BE SOLVED: To accomplish a narrow gap of joining part by irradiating a filler wire through narrow gap width with supplying a filler wire and executing build up welding from an inner part toward an outer part. SOLUTION: For example, when a thick plate 1 is butt welded, a narrow gap width 7 of a part to be welded is set narrower. A filler wire 9 is inserted into a welding part in the gap 7a. The filler wire part 9 is irradiated with a laser beam from a torch 2 through a gap 7a and a weld metal 4 is formed. Further, while the filler wire 9 is supplied to an irradiating part, a layer is formed with moving the torch 2 in the vertical direction. By repeating this, a multi-layer welding is quickly executed while building up one by one layer. Thus, the gap width 7 is made smaller as a result, welding deformation is turned to smaller, good welding is made possible and cost is reduced as well.

Control apparatus for resistance welding machine

Abstract: A control apparatus for a resistance welding machine comprises a welding current detecting device (5; 205) for detecting a welding current, interelectrode voltage detecting device (6; 206) for detecting an interelectrode voltage, a calculating section (13; 213) for predicting a nugget growth or estimating an expulsion & surface-flash generation probability, and control section (16, 17, 18; 212, 215) for controlling the welding current so that the nugget growth or the expulsion & surface-flash generation probability can be adjusted to a predetermined value.

Method and apparatus for electrical resistance spot welding

Abstract: An improved welding apparatus and method of use including a pair of opposed electrodes mounted on arms which are fixed against outward displacement during the application of the welding current. One of the arms includes a cylinder for moving an electrode to and away from the work piece. The cylinder includes a pilot operated check valve which permits a one-way flow of hydraulic fluid while the weld current is applied. The check valve prevents movement of the electrode away from the work piece during expansion of the weld nugget, however, permits inward movement of the electrode after the nugget is softened.

Control device of resistance welding equipment

Abstract: PROBLEM TO BE SOLVED: To provide a set nugget by comparing the estimated temperature distribution of a weld zone with a target nugget to control the output of a welding machine. SOLUTION: A control device is provided with a welding current detecting means 5, an inter-electrode voltage detecting means 6, a temperature distribution estimating means 9 to estimate the temperature distribution, an inductance characteristic value operating means 14, an adjusting means 24 to adjust the temperature distribution estimating means 9 by comparing the temperature distribution estimated by the temperature distribution estimating means 9 with the temperature distribution estimated by using the inductance characteristic value, and a control means 13 to control the welding condition by the temperature distribution. The temperature distribution estimated by the adjusted temperature distribution estimating means 9 is compared with the target nugget to control the welding condition. COPYRIGHT: (C)1997,JPO

Method for joining two parts by heterogeneous welding and use thereof

Abstract: The machined ends of two parts (2, 4) are arranged in facing positions to form a welding bevel (6) between the parts (2, 4). A series of layers of filler metal are deposited one on top of the other in the welding bevel (6) in a direction thereof corresponding to the width of the parts (2, 4), by melting a wire (14) supplied at a predetermined feed rate to an electric arc between the parts to be welded and an electrode (13) supplied with a predetermined welding current and voltage. Each layer of filler metal essentially consists of a single weld bead across the full width of the bevel (6). The electric welding current and voltage and the feed rate of the wire (14) are predetermined in accordance with the width of the bevel (6).

Resistance welding machine

Abstract: PROBLEM TO BE SOLVED: To provide a resistance welding machine which ensures the supply of a work, which facilitates an operation for correcting an electrode tip wear, which eases an operation for adjusting an original point position, and which reduces wear and tear of a guide pin, by independently driving the guide pin. SOLUTION: This machine is equipped with an upper and lower electrodes 2, 3, and structured so that a projection nut can be welded to a work W that is set on the upper face of the lower electrode 3. An electrode tip 4 is arranged in the lower electrode 3, as are a guide pin 5 and an electrode holder 6; a main shaft 11 and a piston rod 22 are movably connected to the lower part of the guide pin 5, with a detection rod 14 connected through the main shaft 11 and a coil spring 13. The piston rod 22 is arranged so as to make it slidable in a cylinder case 21 in the lower part of the electrode holder 6. This structure enables the movement of the two strokes of the guide pin 5. In addition, a dog 17 and a sensor 30 are attached to the lower end of the detection rod 14, thereby detecting the movement of the guide pin 5. COPYRIGHT: (C)1997,JPO

Friction Welding of 2017 and 6061 Aluminum Alloys to S45C Carbon Steel.

Abstract: Joint performance of two types of friction welded butt joints, A2017/S45C and A6061/S45C, fabricated under several welding conditions was investigated. In the case of A2017/S45C joint, the joint strength decreased with an increase in forging pressure, and the intermetallic compounds of Al7Cu2Fe and iron -aluminum alloy were observed at the weld interface. On the other hand, in the case of A6061/S45C joint, the joint strength increased with an increase in forging pressure, and iron-aluminum alloy was observed at the weld interface. Such a difference in the effect of forging pressure on microstructure at the weld interface depends on the deformation property of each aluminum alloy at elevated temperature. And the thinner was the intermetallic compound or the iron-aluminum alloy, the higher was the joint strength.