TWI Industrial Member Report Summary 264/1985
M N Watson
The use of wire feed with laser welding offers three potential advantages: the tolerance to gaps at the joint line is improved, the weld metal composition can be modified to control properties, and multipass welds can be made to allow thicker sections to be welded than is possible with a single pass.
Therefore laser welding trials have been conducted to demonstrate the feasibility of the wire feed technique. Welds were made in 8mm thick C-Mn-Si-Al-Nb structural steels to BS 4360 Grade 50D , using a 5kW laser and a wire feed system to fill a joint gap. Standard 1.2mm diameter Cu coated MIG welding wires were used. Gaps up to 2mm wide could be welded satisfactorily and the wire feed technique was found to be simple and straightforward to use. Some welds suffered from porosity, but its occurrence was not fully understood. Weld metal microstructures containing acicular ferrite were favoured by low weld metal carbon equivalents. Impact testing of half size Charpy specimens showed that good results could be obtained (13.5J temperatures of below -40°C). In addition to single pass wire feed welds, the possibility of multipass welding was demonstrated; this allowed thicker materials to be welded (up to 25mm in this case).