Hot ductility and hot cracking susceptibility of Ti-modified austenitic high Mn steel weld HAZ

The effect of the alloying elements, the carbon, nickel, and the titanium in particular, on the hot ductility behavior of high manganese steel for cryogenic applications was investigated. A hot ductility test was carried out to clarify the mechanism of the heat affected zone (HAZ) liquation and ductility dip cracking that were observed at the HAZ of multi-pass welds. The brittle temperature range, critical strain temperature range, and overall ductility for each alloy were varied due to differences of the eutectic temperatures and the degree of dynamic recrystallization (DRX). The temperature of constitutional liquation between TiC and the austenitic matrix as well as the eutectic temperature of M3C/γ were determined based on the Ti/C ratio and Ti content in the FeTiC ternary system. The onset and degree of DRX depended on the grain size, the secondary particle distribution and the chemical composition that determines the stacking fault energy of each alloy. The HAZ cracking was consistent with aspects of liquation cracking including the constitutional liquation between the TiC and austenitic matrix, its reaction temperature, the final M3C/γ eutectic temperature, extent of liquation, followed by the ductility dip crack that was formed along with resolidified grain boundaries under the DRX temperature.