Analysis of the Effect of Pre-Heating and Pre-Cooling with Variations in Duration on the Mechanical Properties of MIG Welded Joints

Abstract

This study evaluates the effect of pre-heating at 200 °C and pre-cooling at 0 °C for 5, 10, and 15 minutes on the mechanical properties of MIG welds through tensile testing in accordance with ASTM E8. The results show that preheating provides the most significant improvement, with the highest ultimate tensile strength value achieved by specimen C at 452.20 MPa, while the lowest value was found in specimen D at 304.11 MPa. In terms of ductility, the highest fracture strain was shown by specimen E (23.45%), while specimen D was again the lowest (7.89%). The improvement in performance during preheating was associated with a decrease in residual stress and the formation of a more stable microstructure in the HAZ area. Conversely, pre-cooling provided optimal results at 10 minutes, but strength and ductility decreased at 15 minutes due to excessive cooling, which resulted in a harder but less ductile microstructure. Analysis of the stress-strain curve supports these findings through an increase in peak stress and plastic deformation under the right thermal conditions. Overall, pre-heating at 200 °C proved to be the most effective in improving the mechanical performance of MIG welded joints.