TWI Industrial Member Report Summary 455/1992
I A Jones and S T Riches
There is considerable interest in applying laser welding to aluminium alloys as a result of the high speeds and low distortions offered by this process.
However, difficulties are experienced when welding aluminium alloys caused by the material reflectivity and thermal conductivity, which are both high. Welds produced have a tendency to cracking and high levels of porosity. Use of a high quality parabolic beam focusing element increases the power density of the laser beam at focus, compared to the use of spherical focusing optics. This increase is expected to be enough to affect the reflectivity problem mentioned above.
This report is concerned with the evaluation of a parabolic beam focusing system used in conjunction with a high power CO2, laser when welding a number of 5000 series Al alloys between 2 and 8mm thick. The material surfaces were cleaned using petroleum ether prior to welding, but were otherwise in the as received condition. The resulting melt runs have been assessed in terms of tensile properties, levels of porosity and susceptibility to cracking, hardness and weld metal chemical analysis. Work has been performed on both autogenous and wire feed welding techniques. Some butt welds were carried out using the wire feed technique.