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.

Mechanism and possible solution for transverse solidification cracking in laser welding of high strength aluminium alloys

Abstract: In laser and hybrid laser/arc welding of high strength aluminium alloys, a large number of transverse cracks were found in the weld fusion zone. The cracking behaviour was evaluated experimentally and scanning electron microscopy images of crack surfaces confirmed that the cracks occurred when the weld fusion zone was in the semi-solid state. Thermal histories in the workpiece under representative welding conditions were measured and constitutive modelling of thermo-mechanical behaviour in the weld was performed. It was found that the cracking is related to the elongated temperature distribution in the welding direction, which induces a transverse tensile strain in the weld fusion zone during the cooling phase. One of the possible solutions to the cracking problem is to use an additional heat source to alter the temperature distribution and thus to reduce the cracking tendency. The effect of welding with an appropriately placed secondary heat source was verified by experimental tests.

Laser Beam Welding of AA5052, AA5083, and AA6061 Aluminum Alloys

Abstract: The present investigation was mainly concerned with characteristics of autogeneous laser butt welding of 2 mm thickness nonheat treatableAA5052-H12,AA5083-H12 and 2 mm, 3 mm thickness heat treatableAA6061-T6aluminum alloys. The effect of laser welding parameters, surface cleaning, filler wire addition, and backing strip on quality of laser welded joints was clarified using 5 kW C O 2 laser machine. It was found that all the investigated alloys showed tendencies for porosity and solidification cracking, particularly, at high welding speed ( ≥ 4 m/min). Porosity was prevented by accurate cleaning of the base metal prior to welding and optimizing the flow rate of argon shielding gas. Solidification cracking was avoided through two different approaches. The first one is based on the addition of filler metal as reported in other research works. The other new approach is concerned with autogeneous welding using a backing strip from the same base metal, and this could be applicable in production. Preventing solidification cracking in both cases was related mainly to a considerable decrease in the stress concentration at the weld metal center as a result of improving the fusion zone profile. The implementation of the new approach could help in producing weldments with a better quality due to the absence of the filler metal, which is known as a source for hydrogen-related porosity. It can also have a positive economic aspect concerning the manufacturing cost since welding is done without the addition of filler metal. Not only quality and economic positive aspects could be achieved, but also high productivity is another feature since high quality autogeneous weldments were produced with high welding speed, 6 m/min. Hardness measurements and tensile test of AA6061 alloy welds indicated a remarkable softening of the fusion zone due to dissolution of the strengthening precipitates, and this was recovered by aging treatment after welding. For alloys AA5052 and AA5083, softening of the fusion zone due to the loss of its work-hardened condition was much less in comparison with AA6061 alloy.

Characteristics of resistance welding of lap shear coupons. Part I: Heat transfer

Abstract: A transient three-dimensional finite element model for resistance welding of thermoplastic matrix composite lap shear specimens was established. The basic model assumes orthotropic heat conduction in the composite parts and accounts for heat losses by radiation as well as natural convection, involving latent heat effects. The rough contact surface between the heating ply and composite adherends was simulated by means of a thermal gap-conductance concept. Heat generation through the bundles of fibres in the heating ply was modelled. Different welding configurations of lap shear specimens were evaluated, namely APC-2 laminate/PEEK film, APC-2 laminate/PEI film and CF-PEI laminate/PEI film. `Time to melt' and `time to cause thermal degradation' were predicted and compared with experimental data available in the literature, and close agreement was obtained. Localised thermal degradation at the bonding interface was identified for high input power levels, and heat flow to the bulk laminate for long processing times was exhibited.