Solidification Crack Susceptibility in Weld Metals of Fully Austenitic Stainless Steels (Report I) : Fundamental Investigation on Solidification Behavior of Fully Austenitic and Duplex Microstructures and Effect of Ferrite on Microsegregation

概要

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It has been well known that weld metals of fully austenitic stainless steels exhibit greater susceptibility to hot cracking and austenitic weld metals containing a small amount (in the order of 5%) of delta (δ) ferrite are much more resistant during welding. However, it has not been clarified completely why the presence of some δ-ferrite prevents hot cracking in Cr-Ni weld metals. Therefore, the authors have investigated the structual change during solidification from a metallographic standpoint for the both weld metals of fully austenitic stainless steel AISI 310S (25Cr-20Ni ; Japanese Industrial Standard: SUS 310S) and austenitic stainless steel AISI 304 (18Cr-8Ni ; JIS ; SUS 304) containing a small amount of δ-ferrite to which sulphur and phosphorus were added as harmful impurities. Each specimen was rapidly quenched in water during TIG arc bead-on-plate welding, so that each bead showed the instantaneous structures from solidification front to room temperature along welding direction. Solidification behaviors of the fully austenitic and the duplex microstructures, microsegregation (especially S and P) during solidification and distribution of alloying elements between δ-and γ-phases at high temperature were investigated.
大阪大学の論文