Electric resistance welding

About: Electric resistance welding is a research topic. Over the lifetime, 16761 publications have been published within this topic receiving 154851 citations.

Gap-free lap welding of zinc-coated steel using pulsed CO2 laser

Abstract: CO2 laser welding of zinc-coated steel sheets in the lap configuration has been a major research effort for the automotive industry for many years. The introduction of a gap between the sheets is one way of solving the zinc gas explosion problem. However, this requires sophisticated clamping devices and spacer materials. A homogeneous gap is therefore difficult to realise in high volume production. This paper describes a simple but useful approach for CO2 laser welding of zinc-coated steel sheets in the lap configuration. By using a gated pulse mode, a seam welding process is developed that allows zinc-coated materials to be welded in a gap-free, overlap configuration. Laser seam welds in the lap configuration were produced in 0.7 mm-thick steel sheet with 7 μm zinc coating on both sides. A number of pulsed CO2 laser welding parameters, including peak power, duty cycle, travel speed, pulse repetition rate, and pulse energy, were identified. Furthermore, the effects of pulsed CO2 laser welding parameters on weldability were also investigated. The study shows that through the proper selection of welding parameters, it is possible to produce visually sound welds where porosity is still unavoidably formed. It was observed that decreasing the welding speed could reduce the porosity within the visually sound welds.

Modern fiber laser beam welding of the newly-designed precipitation-strengthened nickel-base superalloys

Abstract: In the present research, the modern fiber laser beam welding of newly-designed precipitation-strengthened nickel-base superalloys using various welding parameters in constant heat input has been investigated. Five nickel-base superalloys with various Ti and Nb contents were designed and produced by Vacuum Induction Melting furnace. The fiber laser beam welding operations were performed in constant heat input (100 J mm−2) and different welding powers (400 and 1000 W) and velocities (40 and 100 mm s−1) using 6-axis anthropomorphic robot. The macro- and micro-structural features, weld defects, chemical composition and mechanical property of 3.2 mm weldments were assessed utilizing optical and scanning electron microscopes equipped with EDS analysis and microhardness tester. The results showed that welding with higher powers can create higher penetration-to-width ratios. The porosity formation was increased when the welding powers and velocities were increased. None of the welds displayed hot solidification and liquation cracks in 400 and 1000 W welding powers, but liquation phenomenon was observed in all the heat-affected zones. With increasing the Nb content of the superalloys the liquation length was increased. The changing of the welding power and velocity did not alter the hardness property of the welds. The hardness of welds decreased when the Ti content declined in the composition of superalloys. Finally, the 400 and 1000 W fiber laser powers with velocity of 40 and 100 m ms−1 have been offered for hot crack-free welding of the thin sheet of newly-designed precipitation-strengthened nickel-base superalloys.

Recent developments in repair welding technologies in Japan

Abstract: Developments in some difficult repair welding technologies in Japan during the past decade are reviewed. The topics covered include the repair welding of bridges in service, the temper bead method which makes it possible to omit post-weld heat treatment (PWHT) of repaired pressure vessels, the seal welding of a reactor vessel in which stress corrosion cracks were detected, low heat input repair welding of neutron irradiated stainless steel and nickel based alloys, the prevention of solidification cracking in repair welding of aged heat resistant cast steels, the development of welding materials for the mending of single crystal nickel based superalloy turbine blades, underwater repair welding of nuclear reactors, the reduction of residual stresses in repair welding, and an ultrasonic testing method for nickel based weld metals. The local PWHT of creep resistant ferritic steel tubes is also reviewed.

Microstructure and process characterization of laser-cold metal transfer hybrid welding of AA6061 aluminum alloy

Abstract: Fiber laser-cold metal transfer (CMT) hybrid welding of an AA6061 aluminum alloy thin sheet was carried out The microstructure was analyzed by an optical microscope, scanning electron microscope, and energy-dispersive spectrometry The cross-weld tensile strength and hardness were tested to evaluate the mechanical properties of the welded joint Accepted joints with finer microstructure and free of defects were obtained The tensile strength was up to 223 MPa, 10 % stronger than that of a laser-pulse metal inert gas (PMIG) hybrid welded joint Due to the featured CMT arc current waveform, stronger constitutional supercooling and more heterogeneous nuclei were generated in the weld pool of laser-CMT hybrid welding in comparison with laser-PMIG hybrid welding It led to the results that the laser-CMT joint has a finer microstructure and narrower columnar dendrite zone compared with the laser-PMIG joint Because of the stabilization of the CMT arc on the laser-induced keyhole, spatters were seldom found during laser-CMT hybrid welding and few hydrogen pores appeared in the joint

Computerized radiographic sensing and control of an arc welding process

Abstract: This paper summarizes an effort in which real-time radiography was implemented for on-line arc welding process study and control. X-ray penetrating radiation was used for volume observation in the welding pool and the heat-affected zone during the weld process. The advantages of such a technique are online detection and monitoring of defect formation in the weld and capability to study metal fusion and filler metal/base metal interaction and metal transfer in the welding pool. This technique may also be used for postservice, real-time remote testing of weld quality.