Title: The influence of different He-Ar ratios on high power CO₂ laser welding process and weld formation

Authors: Guohua Li, Yan Cai, Shijun Jia, Douglas Steyer, John Billingham, Yixiong Wu

Addresses: Laser Processing Lab., Welding Engineering Institute, Shanghai Jiaotong University, Shanghai 200030, China. ' Laser Processing Lab., Welding Engineering Institute, Shanghai Jiaotong University, Shanghai 200030, China. ' Praxair Asia Investment Co., Ltd., 69 Dongfang Road, Pudong, Shanghai 200122, China. ' Praxair Asia Investment Co., Ltd., 69 Dongfang Road, Pudong, Shanghai 200122, China. ' Praxair Asia Investment Co., Ltd., 69 Dongfang Road, Pudong, Shanghai 200122, China. ' Laser Processing Lab., Welding Engineering Institute, Shanghai Jiaotong University, Shanghai 200030, China

Abstract: Pure He is usually used as a plasma blowing gas in high power laser welding because of its high ionisation energy. Its high price however, drives researchers to put more efforts into finding the suitable alternatives. In this paper, 12 mm e-grade shipbuilding steel plates were welded using a 15 KW CO₂ laser machine, with the mixture of He and Ar as the blowing gas. The effects of different He-Ar ratios of the blowing gas on laser welding process and weld formation were studied by using a high-speed camera and spectrum was acquired simultaneously. It is found that plasma profile changes with the addition of Ar into He and the spectrum is mainly Fe spectral line even when there are 60% Ar. Sound joints can be obtained even with 40% He + 60% Ar while no acceptable joint formed when using pure Ar.

Keywords: CO2 laser welding; blowing gas; plasma; gas mixture; helium; argon; carbon dioxide; weld formation; shipbuilding steel plates; welded joints.

DOI: 10.1504/IJMMP.2010.035940

International Journal of Microstructure and Materials Properties, 2010 Vol.5 No.2/3, pp.209 - 220

Published online: 10 Oct 2010 *

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