CO₂ laser welding of interstitial free galvanized steel sheets used in tailor welded blanks

Abstract

Recently, laser welding technologies have been widely utilized to weld different automobile panels. In this research, the laser beam welding (LBW) process of interstitial free (IF) steel sheets used in the manufacturing of the car body was investigated on the basis of mathematical models. The quality indexes of LBW joints were estimated from Erichsen Cupping Test results including strength and Erichsen Cupping Index. Furthermore, three process parameters, namely laser power (P), welding speed (S), and focal position (F) were considered as the factors influencing the quality indexes. A 2.2-kW CO₂-laser beam was utilized to weld 1.2- and 0.8-mm-thick IF steel sheets. The modeling is done using experimental data which were gathered using design of experiments approach based on central composite face centered design matrix. The final regression models can be used to predict the quality indexes of laser beam-welded IF steel sheets joints at 95% confidence level. Optical metallography was utilized to characterize the weld profile and microstructures. In the second phase of this research, multi-objective genetic algorithm with the fitness function based on regression models was employed as an optimization procedure; as a result, the best quality indexes were obtained. Optimization results showed high compatibility with the actual experimental data.