Product Code: ICAL07_M607

The Micro-Welding Ability of 100W High Brightness Fibre Laser on 316L Stainless Steel
Authors:
C J Kong, Welding Engineering and Metal Science Centre, School of Applied Sciences, Cranfi; Bedfordshire Great Britain
S. Williams, Welding Engineering and Metal Science Centre, Cranfield University; Bedfordshire Great Britain
G. Lopes, Welding Engineering and Metal Science Centre, Cranfield University; Bedforshire Great Britain
P. Colegrove, Welding Engineering and Metal Science Centre, Cranfield University; Bedfordshire Great Britain
Presented at ICALEO 2007

Fibre lasers are an attractive option for laser micro-welding applications because of their high beam quality which gives a small spot size. In this paper, the results of an investigation into the micro-welding of stainless steel using a 100 W fibre laser are reported. Continuous and pulsed modes of operation were investigated in terms of penetration depth, top bead width and focus position sensitivity. For the continuous mode, penetration depths of 550 μm were obtained at welding speeds of 5 mm/s. When the welding speed was increased to 30 mm/s the penetration depth was still greater than 400 μm. In the pulsed welding mode, the pulse duration and frequency were varied to give duty cycles of 10% and 50%. There was a significant increase in the penetration depth when the pulse duration was less than 0.5 ms (with the 50% duty cycle) due to the pulse enhancement of the laser at the very short pulse durations. At the same time, the top bead width reduced by over 50% for the lowest pulse duration (0.05 ms) giving a weld with an aspect ratio of 11:1. The fast cooling rate in the short pulse weld changes the final microstructure to pure austenite rather than austenite with ferrite which was obtained with the continuous mode laser welds. In all cases, the deep penetration conditions were very sensitive to focus position.