Numerical Modeling of δ-Ferrite Dissolution Kinetics in Austenitic Stainless Steels

Abstract

In the present paper a numerical model that describes the diffusion processes of Ni and Cr between ferrite and austenite in Fe‐Cr‐Ni ternary systems has been developed by using the finite difference method (FDM). The model employed the tie‐line relationships given by Kajihara and Kikuchi. The moving ferrite/austenite interface was determined by solving the mass balance equations using the Newton‐Raphson method. The model has been applied to predicting the dissolution kinetics of ferrite in austenitic stainless steels, which were processed by welding, continuous casting and strip casting, respectively. The accuracy of the model has been confirmed to be quite satisfactory as compared with measured values, with advantages over another numerical model developed by Vitek et al. This model was reproduced in the present work.

Kinetic Model to Investigate the Effect of Cooling Rate on δ-Ferrite Behavior and Its Application in Continuous Casting of AISI 304 Stainless Steel

“…However, in austenitic stainless steel, the peritectic reaction through the entire solidification process either for fast or slow cooling rates occurs by diffusional transformation [10][11][12][13][14]. In view point of the δ-ferrite decomposition kinetics in ASSs, former studies have shown that diffusion rate of major alloying elements contributing to the δ-ferrite and austenite have the most important effect on the δ-ferrite decomposition at high temperatures [15][16][17]. There is usually an M-shaped distribution of retained δ-ferrite fraction through the thickness of continuously cast products of 304 ASSs with increasing depth from the surface of the slab (surface) to its center of the thickness (center) [18][19][20].…”