二相ステンレス鋼溶接部におけるシグマ相ぜい化(<特集>フラクトグラフィ)

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The effect of σ phase precipitation on the toughness of duplex stainless steel and its weld metal was investigated by means of fractography. The material used was SUS329J1 steel, and the samples were welded using SMAW SUS329J4L (DP3) electrode and SUS329J3L (DP8) electrode. The materials were reheated at 1 023K and 1 123K for various times. ne toughness was evaluated by Charpy impact test at 273K. The fine secondary austenite ( γ^* ) was formed from the ferrite and then σ phase was precipitated by reheating both base metal and weld metal. The σ phase precipitation in DP3 and DP8 weld metals was much faster than that in the base metal. The lowering of toughness by σ phase precipitation for the weld metals was much larger than that of the base metal. The fracture morphology showed that brittle cracks occurred in the σ phase and at the interface between the matrix and the σ phase in every sample. In case of the base metal, the fracture morphology showed a dimple pattern at the region around the σ phase. The lowering of toughness was affected by the large volume fraction of σ Phase, because of the wide region of ferrite. In case of the weld metals, the primary austenite and the secondary austenite were fine and crowded and the ferrite region was fine. The fracture morphology showed brittle fracture with fairly tear ridge. Only a small amount of σ phase was enough to cause the lowering of toughness in the weld metals, because of fine σ phase precipitation by reheating.
社団法人日本材料学会の論文
1997-06-15

二相ステンレス鋼溶接部におけるシグマ相ぜい化(<特集>フラクトグラフィ)

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