SUS329J1二相ステンレス鋼溶接部の破壊靱性に及ぼす金属組織の影響

概要

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Relationship between the microstructure and the fracture behavior of welds which were tested by Charpy impact on SUS329J1 (Fe-25Cr-5Ni-0.1N) stainless steel has been studied. Volume fraction of γ phase decreases at HAZ which has been heated over 1400K. At the region over 1600K, the morphology of γ also change to Widmanstatten and the Kurdjumov-Sachs relation exists between γ and α phase, so the phase boundary has good coherency. There is certain relationship between crack propagation and microstructure. When the Charpy test performed at room temperature, tearing or voids occur in α region, because the ductility and strength of γ phase are higher than ones of α. γ phase is deformed at the circumference of dimple and γ maintains the ductility of duplex steel. Consequently, the fracture toughness increases with increasing the γ volume fraction. At low temperature, cleavage fracture occurs in α phase, same time γ phase plays the part of a little obstacles to crack propagation. In Widmanstatten like γ, Charpy impact value slightly increases with increasing the volume fraction of γ phase. In band like γ, a separation of α-γ phase boundary occurs and the crack propagates zigzag manner, so the impact value increases more substantially than widmanstatten like γ in the case of crack propagation normal to the γ phase.
1990-02-05