Finishing and quality of mechanically brushed 316L stainless steel welded joints using MIG process: hardness modeling by L9 TAGUCHI design

The present work aims to optimize the mechanical brush finishing of Metal Inert Gas (MIG) welded joints on AISI316L thin steel sheet. The innovative methodology is based on the experimental design methodology of the Taguchi design (L9) and the analysis of variance (ANOVA) with objective function of microhardness in brushed layers. A “Signal to Noise” approach is adopted with the objective of “Large is Better”. The speed of rotation of the brush, the speed of advance of the sample, the number of brushing passes, and the depression ratio of the brush fibers are the four three-level factors of the L9 design. The study of the effects of these factors showed the major influence of the depression and the number of passes on the magnitude of hardening of the brushed layers in the various zones of the weld. Minor interactions, found in the regression model, are noted between the different factors. Measurements of microhardness in the depths of each zone reveal distinct cure rates from one zone to another. The melted zone of the weld undergone the minimum hardening, unlike the heat affected zone (HAZ), whose microhardness contribution reaches 30% compared with the non-brushed welded sample. It is revealed that the main results lie in the microhardness contribution, of the order of 30% at the joint, while keeping the same level of magnitude of the mechanical strength using the optimal parameters.