Influence of shielding gas composition on weld structure in pulsed Nd: YAG laser welding

Subject Areas : Chemistry

M jokar ¹ , F MalekGhaini ² , M. J. Torkamany ³

1 - Department of Engineering Materials, TarbiatModares University, Tehran, Iran
2 - Department of Engineering Materials, TarbiatModares University, Tehran, Iran
3 - Department of Engineering Materials, TarbiatModares University, Tehran, Iran -Iranian National Centre for Laser Science and Technology (INLC), Tehran, Iran

Received: 2012-09-02 Accepted : 2013-01-12 Published : 2013-07-01

Keywords: Carbon dioxide, Laser Welding, Pulsed Nd: YAG laser, Argon shielding gas, Weld microstructure,

Abstract :

This work studied the effect of additions of carbon dioxide to argon shielding gas on the weld shape and microstructure of ST14 steel in pulsed Nd: YAG laser welding. By additions of carbon dioxide up to 15%,the weld area and depth/width ratio decreases while rising of carbon dioxide up to 25% causes increasing of weld area and depth/width ratio. It is observed that the weld metal microstructure is mainly constructed from polygonal ferrite under 0 to 15% CO2 additions to argon, but both polygonal and acicular ferrites are observed as the CO2 level of Ar+ CO2 mixtures increases from 15 to 25%. The shape and microstructure of pulsed Nd: YAG laser welds is believed to be closely related to laser absorption coefficient, laser energy absorption on the work-piece surface and formation of oxide layer on the work-piece surface.