The effect of solidification behaviour of austenitic stainless steel on the solidification cracking susceptibility

0Introduction Oneofthemainproblemsinweldingausteniticstain lesssteelsishotcracking1,2].Inweldingofsingle phase austeniticstainlesssteels,thetendencyofhotcrackingis moreserious3].Inordertopreventhotcrackingofthis kindofmaterial,itwasattemptedtogaintwo p…

The effect of solidification behaviour of austenitic stainless steel on the solidification cracking susceptibility

On the basis of quantitative evaluation of susceptibility to solidification cracking with Trans-Varestraint-Test, the microstructures of two stainless steels of 316L and alloy 800H with different Creq/Nieq ratios during solidification process were analyzed with several methods. It is concluded that the susceptibility to solidification cracking of 316L-stainless steel is much lower than that of alloy 800H due to different solidification behaviors of the weld metal of the two materials. The weld metal of alloy 800H solidifies in the form of primary austenite whose boundaries are straight and smooth and easily wetted by low melting-point liquid phases, which increases the susceptibility to solidification cracking; while the 316L weld metal solidifies into primary austenite/ferrite. Owing to a series of dynamic microstructure changes during solidification such as peritectic reactions, migration of austenitic boundaries and nailing of δ-ferrite to the boundaries, the grains become finer, the orientations of columnar grains get disordered and the boundaries are curved and complex. Also high temperature δ-ferrite exists, segregation of impurities at boundaries decreases and the boundaries are hard to be wetted by liquid films, which reduces the cracking susceptibility.