Hot Cracking of Austenitic Steel Weld Metal

Abstract

It is well known that a small amount of ferrite in austenitic stainless steel weld metal is very effective for the prevention of hot cracking. But the reason seems to be not quite clear. This experiment was carried out to know the relation between the solidification phases, sulphur microsegregation and hot cracking susceptibility of Ni-Cr alloyed steels. Because it has been confirmed by previous experiment that γ iron crust of primary solidification phase through the peritectic reaction of Fe-Ni system is very responsible to the hot cracking of 3.5% nickel alloyed steel weld metal. Circular groove hot cracking test specimens were prepared by three series of Ni-Cr alloyed cast steels, which contain about 0.15% sulphur. The groove of specimen was welded by TIG and MIG welding. The experimental results obtained are as follows; (a) The weld metals which crystallize as primary γ iron are much more sensitive to hot cracking than those which crystallize as primary α iron and transform to γ iron. This result concides with the tendency of sulphur microsegreagation of weld metals, which was detected by EPMA. (b) The hot cracking susceptibility of Ni-Cr alloyed steel weld metals relates to the boundary line of primary γ or α solidification surfaces, while the ferrite amount of weld metal at the room tenperature by Schaeffler diagram seems to have no direct relation with the susceptibility. © 1972, JAPAN WELDING SOCIETY. All rights reserved.