Influence of welding HAZ microstructure on low-temperature impact fracture behaviour in C–Mn shipbuilding steel

Abstract

The influence of microstructure on the low-temperature impact toughness of the heat-affected zones (HAZs) in C-Mn shipbuilding steels was investigated in welding thermal simulations and the Charpy impact test. Within the temperature range −80°C to −40°C, the Charpy impact energy initially increased and thereafter decreased with decreasing peak temperature of welding. The impact energy was maximised at a peak welding temperature of 850°C. The deterioration of lowtemperature impact toughness was associated with enlarging effective grain size and numerous low-angle boundaries. The distribution of dual-phase structures and martensite/austenite (M/A) constituents significantly affected the fracture mode. The impact energy fluctuations observed in the analysis are also explained.