SUS316L溶接金属の再熱によるM_<23>C_6及びσ相の析出過程

概要

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An author's previous paper on heat-treating of Type 316L weld metal revealed that the decomposition of δ ferrite in the weld metal (EWM) containing mainly an eutectic δ-ferrite occured rapidly as compared to that in the weld metal (PWM) containing mainly a primary δ ferrite and this reason was attributed to the difference in the lattice coherency at the δ/γ interface. In this paper, to clarify metallographically the results described above, the precipitation process of M_<23>C_6 and sigma phases was investigated by transmission electron microscopy using the weld metals heat-treated at 923 or 1123K. In the EWM specimen, at both the heat-treating temperatures, the M_<23>C_6 phase precipitated initially at the δ/γ interface and then within δ ferrite grains and the precipitation of σ phase occured finally. However, in the PWM specimen, the precipitation of M_<23>C_6 could not be observed at all within δ ferrite grains. This suggests that M_<23>C_6 formed readily in the EWM specimen, of which the δ ferrite phase contained larger amounts of molybdenum than that in the PWM specimen. On the other hand, the M_<23>C_6 at δ/γ interface in the EWM specimen precipitated rapidly and in large amount, comparing with that in the PWM specimen. Particularly, as this tendency was remarkable at 1123K, the coherency of the δ/γ interface was considered to influence considerably the precipitation of M_<23>C_6.
社団法人溶接学会の論文
1988-02-05