Parametric optimization for autogenous butt laser welding of sub-millimeter thick SS 316 sheets using central composite design

Abstract

Laser Beam Welding (LBW) is now well known for its high precision and greater power intensities capable of welding any type of material. LBW finds wide applications in numerous areas ranging from simple cooking utensils to complex automotive and aeronautical components. In the present study, an attempt was made to characterize the LBW process used to join sub-millimeter thick sheets of SS 316. For this purpose Ytterbium Fiber laser having 2 kW power was used and SS 316 sheets of 0.85 mm, 0.56 mm, and 0.2 mm thickness were welded in butt joint configuration. For optimizing the selected input parameters laser power, laser scan speed and focal point position, central composite design technique was used. The responses considered are ultimate tensile strength, weld width, and micro hardness. The analysis of variance of the selected quadratic models shows that, the model can adequately predict correct results within the selected limits. The microstructural, fractographic and tensile behavior analysis clearly shows the effect of base material composition and heat input on the weld quality. The input parameters are optimized to give highest tensile strength and minimum weld width and were confirmed using confirmatory experiments.