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

This work studied the effect of additions of carbon dioxide to argon shielding gas on the weld shape and microstructure of ST۱۴ steel in pulsed Nd: YAG laser welding. By additions of carbon dioxide up to ۱۵%,the weld area and depth/width ratio decreases while rising of carbon dioxide up to ۲۵% causes increasing of weld area and depth/width ratio. It is observed that the weld metal microstructure is mainly constructed from polygonal ferrite under ۰ to ۱۵% CO۲ additions to argon, but both polygonal and acicular ferrites are observed as the CO۲ level of Ar+ CO۲ mixtures increases from ۱۵ to ۲۵%. 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.

Keywords:

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