Precipitation examination of δ, σ, and γ phases using modified Cr/Ni equivalent ratios during the multipass welding of stainless steels

Abstract

The purpose of this study is to discuss the precipitation tendencies of δ, σ, and γ phases using a modified Cr/Ni equivalent ratio with 309L filler after welding dissimilar steels (SUS 304L and AISI 1017) while adding various Si contents of 0.25 wt.%, 0.45 wt.%, and 0.65 wt.% and hot rolling in AISI 309LSi stainless steels at 1200 °C for 2 h. The elemental compositions of δ, σ, and γ phases were performed by EDS in as-hot-rolled AISI 309LSi as well as dissimilar welded samples, and the Creq/Nieq ratios were calculated by Hammer & Svensson’s equation. In this research, the Creq/Nieq of phase and matrix were presented as [Creq/Nieq]phase and [Creq/Nieq]matrix, respectively. The modified equation ([Creq/Nieq]modified) was equal to [Creq/Nieq]phase/[Creq/Nieq]matrix, and it was used to examine the effect of materials and processes in the δ, σ, and γ phases. The results indicated the Creq/Nieq ratios of the δ, σ, and γ phases were 2.557∼1.304, over 3.143, and 1.229, respectively.