Simulated Welding Heat Affected Zone Toughness and Microstructure Transformation of a Ti-Zr Microalloyed Low Carbon Steel

Abstract

Acicular ferrite (AF) can significantly improve the performance of steels and can be promoted through special inclusions. The present experimental steel was a low carbon Ti-Zr deoxidized and microalloyed steel. The welding heat affected zone (HAZ) simulation indicated that under high heat input (100 kJ/cm) and peak temperature (1400°C) conditions, the HAZ exhibited high impact toughness (150 J, -20°C) and desired microstructure. Isothermal heat treatment data suggested that grain boundary ferrite formed at ~600°C and AF formed at ~500°C. Intragranular plates sheaves formed at ~450°C. MnS coherent precipitation on ZrO2TiOx inclusions promoted AF nucleation.