Effect of Pre and Post-Heat Treament on the Heat-Affected-Zone (HAZ) of Austenitic Stainless Steel

Abstract

Stainless Steel is an important class of engineering alloys which are iron-base alloys grouped as iron-chromium-nickel alloys used in both wrought, cast and fabricated form for a wide range of applications and in many industries. Residual stresses in weld joints can be reduced by heat treatment The goal of this research work carried out by Legend Builders Limited in collaboration with the Lagos state Laboratory test Center, Center for Energy and Research Development(CERD) Osun chapter and Universal Steels Limited Lagos. This project is aimed to improve the performance of austenitic stainless steels weldment used in Universal Steels Limited, joined using Shielded Metal Arc Welding (SMAW) welding with stainless steel electrodes at constant welding current, through preheating and stress relieving post weld heat treatment by determining the effect of preheating temperature on the micro structure of heat affected zone, the effect of post weld; annealing, normalizing and quenching on the micro structure of heat affected zone, hardness value of the heat affected zone. The result shows that the post weld heat treatments; annealing, normalizing and quench hardened generally decreases the hardness values of the stainless steel and by extension improve the mechanical properties of the steel weldment e.g. strength, toughness, etc. Increase in annealing temperature also improves the mechanical properties of the stainless steel and decrease the hardness values.