2001 Volume 19 Issue 1 Pages 92-99
Precipitation behavior of sigma (σ) phase was investigated for duplex stainless steel and its weld metals by reheating. The material used was SUS329J1 base metal, and the samples were single-pass welded using SMAW 329J4L (DP3) electrode and SMAW 329J3L (DP8) electrode.
The fine secondary austenite (γ*) was formed at primary austenite (γ) /ferrite (α) phase boundaries and grew into ferrite, and then σ phase began to precipitate at γ*/α phase boundaries and grew into ferrite for SUS329J1 base metal. In case of weld metals, γ* was formed both at γ/α phase boundaries and in the interior of ferrite matrix, and thereafter precipitation of a phase at γ*(γ)/α phase boundaries occurred. Time-Temperature-Precipitation (T-T-P) diagrams of sigma (σ) phase were constructed in order to investigate beginning of precipitation of sigma (σ) phase for SUS329J1 base metal and 329J4L (DP3), 329J3L (DP8) weld metals. As a result, the nose position in TTP diagram of σ phase was located at 1123 K for 0.06 ks for 329J4L (DP3) weld metal, while its position was located at 1123 K for 0.3 ks in case of 329J3L (DP8) weld metal which was lower chromium content.
