Control of welding residual stress for dissimilar laser welded materials

The most common problem of welding dissimilar metals (DMWs) with respect to residual stresses is the differences in the coefficient of thermal expansion and heat conductivity of the two welded metals. In the present work, a CO2 continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless steel and low carbon steel plates. The Taguchi approach with three factors (selected welding parameters) at five levels each (L3-25) was applied to find out the optimum levels of welding speed, laser power and focal position for CO2 keyhole laser welding of dissimilar butt weld. The responses outputs were the residual stresses at different depth in the heat affected zone (HAZ). The Hole-Drilling Method technique was applied to measure the residual stress of dissimilar welded components. The results were analysed using analysis of variances (ANOVA) and signal-to-noise ratios (S/N) for an effective parameters combination. Statistical models were developed to describe the influence of the input parameters on the residual stress at different specimen levels; to predict there value within the limits of the variables under investigation. The result indicates that the developed models can predict the responses satisfactorily

Using Taguchi method to optimize welding pool of dissimilar laser welded components

In the present work CO2 continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless steel and AISI 1009 low carbon steel plates. Laser power, welding speed, and defocusing distance combinations were carefully selected with the objective of producing welded joint with complete penetration, minimum fusion zone size and acceptable welding profile. Fusion zone area and shape of dissimilar austenitic stainless steel with ferritic low carbon steel were evaluated as a function of the selected laser welding parameters. Taguchi approach was used as statistical design of experiment (DOE) technique for optimizing the selected welding parameters in terms of minimizing the fusion zone. Mathematical models were developed to describe the influence of the selected parameters on the fusion zone area and shape, to predict its value within the limits of the variables being studied. The result indicates that the developed models can predict the responses satisfactorily

Optimization of tensile strength of ferritic / austenitic laser welded components

Ferritic/Austenitic (F/A) joints are a popular dissimilar metals combination used in many applications. F/A joints are usually produced using conventional processes. Laser beam welding (LBW) has recently been successfully used for the production of F/A joints with suitable mechanical properties. In this study, a statistical design of experiment (DOE) was used to optimise selected laser beam welding parameters (laser power, welding speed, and focus length). The Taguchi approach was used for the selected factors, each having five levels (L-25; 5*3). Joint strength was determined using the notched tension strength (NTS) method. The results were analysed using analyses of variance (ANOVA) and the signal-to-noise ratios (S/N) ratio for the optimal parameters, and then compared with the base material. The experimental results indicate that the F/A laser welded joints are improved effectively by optimizing the input parameters using the Taguchi approach