Morphology and Optimisation of Impact Energy of Weldment of High Strength Low Alloy Steel.

Abstract

Morphology and optimisation of impact energy of weldment of low alloy-high strength steel were investigated in this work. The study involved the use of design of experiment via Taguchi method based on three variables, each having three levels. Minitab 16 software was used for the analysis of variance (ANOVA) and signal to noise (S/N) ratio of the impact energy. Direct current electrode positive (DCEP) was used in the electric manual metal arc (MMA) welding. The input parameters at the three levels were current (60 A, 70 A, and 80 A), metal thickness (5 mm, 7 mm, 9 mm) and root gap (2.0 mm, 2.5 mm, 3.0 mm). It was found that the input variables significantly affected the microstructure of the weldment in all the nine experiments conducted. Optimization of welding parameters was carried out to obtain the optimal input values required to give the optimal impact energy of weldment. The optimal values for the input values were 80 A for current, 9 mm thickness and 2.5 mm root gap and these were substituted in the regression equation to obtain the optimal impact energy. It was equally observed that the input variables affected the microstructure of each of the nine samples