An investigation on laser induced downward expanded vapour region in laser weld butt joint of AISI 316L stainless steel

Abstract

The physics of laser - AISI 316 stainless steel interactions discussed stage-by-stage including the formation of plasma plume around the keyhole during the laser welding. This work reveals that the pulsed laser heat input is a highly successful tool to join 2 mm thick 316L stainless steel welding by a single pass, that too autogenously! However, inadequacy in laser input power leads to the incomplete penetration at weld joint and poor bead formation and whereas excess heat input causes root concavity (loss of material) at the bottom. It has observed a vapour region near bottom of the keyhole while the joint fully penetrated and it slightly expanded due to excess heat input, known as downward expanded vapour region. Consequently, downward expanded vapour region results in excess melting; it leads to loss of material by spatter during welding that causes root concavity at the bottom, which will affect the joint integrity. Therefore, it is important to identify and control the expansion of vapour region by optimizing the input power of the laser. To ensure optimization of the operating parameters and the integrity of weld joints are qualified through Vickers micro hardness test and X-ray radiography test.