Influence of Si Addition on the Hot Cracking Susceptibility of Fe-Mn-C-Si Steel

The effects of Si on the weldability of high Mn steel were investigated. A multiple bead Varestraint technique was utilized to evaluate simultaneously the hot cracking susceptibility of the base metal heat affected zone (HAZ), weld metal HAZ and fusion zone. Considering Total Crack Length (TCL) and Maximum Crack Length (MCL), the addition of Si noticeably increased the hot cracking susceptibility of high Mn steel. The segregations of Si, Mn and C extensively occurred at dendritic- and grain boundaries in the weld metal. Accordingly, they contributed to the increase in hot cracking susceptibility of high Mn steel by the enlargement within solidification temperature range. Also, the volume fraction of low-melting eutectic phases along the grain boundary in the vicinity of cracks significantly increased in comparison with that of Fe-Mn-C steel. Since, the Si addition enhanced the eutectic phase formation, decreasing a carbon equivalent of eutectic point. In conclusion, the segregation and the eutectic phase formation dominated by Si addition mainly deteriorated the hot cracking susceptibility of high Mn steel.