Hot cracking susceptibility and solidification segregation analysis by computer simulation in duplex stainless steels

Abstract

ABSTRACT Solidification cracking susceptibility in arc & laser welding of DSSs (duplex stainless steels) was quantitatively evaluated and the numerical simulation of solidification cracking susceptibility has clarified the affecting factors. The BTRs (brittle temperature ranges) of standard, lean and super DSSs in GTAW were 58 K, 60 K and 76 K, respectively. The solidification cracking susceptibilities of DSSs were lower than those of austenitic stainless steels with A-mode solidification modes. The BTRs of standard, lean and super DSSs in LBW were 40 K, 45 K and 56 K in LBW, respectively. The BTRs in LBW were reduced by 15–20 K compared to those in GTAW. These results suggested that DSSs had a significantly low risk of solidification cracking in LBW as well as GTAW. In order to clarify the affecting factors of solidification cracking, numerical simulation of solidification cracking susceptibility was carried out. The segregated concentrations of P, S and C in LBW were slightly lower than those in GTAW, suggesting that the solidification cracking susceptibility in LBW was reduced to GTAW attributed to the inhibition of solidification segregation because of the rapid solidification in LBW. In addition, we discussed that there is a difference in the hot cracking susceptibility compared with the austenitic stainless steel having the A mode. To explain this phenomenon, the segregation amounts of S and P by arc, laser and solidification modes were investigated. The segregation of Standard DSS was lower than that of Type310S when using the same amount of P and S. This clearly indicates that F mode solidification was less segregated than A mode solidification. This is because the equilibrium partition coefficient and the diffusion coefficient of the standard DSS are larger than that of Type 310S.