Formation mechanism of vermicular and lacy ferrite in austenitic stainless steel weld metals

Abstract

Solidification and subsequent transformation of austenitic stainless steel weld metals that solidified in the ferritic–austenitic mode were investigated from the viewpoint of crystallography. The formation mechanisms for the vermicular and lacy ferrite observed in the weld metals were clarified. The ferrite morphology is determined by both the crystallographic orientation relationship between ferrite and austenite established at the stage of ferrite nucleation and the relationship between the welding heat source direction and the preferential growth directions of ferrite and austenite. In particular, for the formation of continuous lacy ferrite, it is necessary that the ferrite continues to grow with the Kurdjumov–Sachs orientation relationship with austenite that is established at the stage of ferrite nucleation.

<I>In-Situ</I> Observation for Weld Solidification in Stainless Steels Using Time-Resolved X-ray Diffraction

“…Naturally, these results correspond to those of the X-ray diffraction. These results for the growth mode of the secondary phase may also correspond to those of the microstructure observation of the liquid-tin quenched metal by Inoue et al 11,12) …”

“…So the solidification morphology of the weld metal has been estimated by the SEM observation of microstructure, using the liquid-tin quenching method. [10][11][12] In late nineties, Elmer et al [13][14][15] has been used a intense synchrotron radiation as a probe and directly revealed the phase mapping around the heat spot, during pure titanium welding. After that, Babu et al investigated the primary weld solidification in the Fe-C-Al-Mn weld steel [16][17][18] using the Time-Resolved X-Ray Diffraction (TRXRD) technique.…”

Two-Dimensional Time-Resolved X-ray Diffraction Study of Directional Solidification in Steels

“…So the solidification morphology has been observed by the Scanning Electron Microscope (SEM), using the liquid-tin quenching method in high alloys that have some influence on solid-transformation. [1][2][3] Since late nineties, Elmer et al [4][5][6] has used intense synchrotron radiation and has directly revealed the phase mapping around the heat source, during pure titanium welding. After that, Babu et al investigated the primary weld solidification in the Fe-C-AlMn steel weld [7][8][9] using the Time-Resolved X-Ray Diffraction (TRXRD) technique.…”

Influência do gás de purga na formação da raiz do cordão de solda em tubos de aço inoxidável AISI 304

“…Em função das características citadas anteriormente, intrínsecas ao material, podem ser retidas quantidades variáveis de ferrita  (delta) a temperatura ambiente (INOUE, 2000;MODENESI, 2001).…”

“…Uma análise prévia no modo de solidificação das fases do aço inox austenítico poderá então ajudar a prevenir falhas como suscetibilidade a trincas e melhorar a resistência a eventuais trincas (INOUE, 2000;MODENESI, 2001;SHANKAR, 2003).…”