Effect of Microstructure on Fracture Toughness of SUS329J1 Duplex Stainless Steel Welds

概要

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Relationship between the microstructure and the impact fracture toughness of welds on SUS329 J1 stainless steel (Fe-25Cr-5Ni-0.1N) has been studied. Volume fraction of γ phase of base metal decreases at HAZ when it is heated over 1400 K. At the region heated over 1600K, the morphology of γ also changes to Widmanstatten structure and the Kurdjumov-Sachs relationship holds between γ and α phase, so good coherancy is observed at the phase boundary. When the Charpy test is performed at room temperature, tearing or voids occur in a region of fracture surface and the fracture toughness increases with an increasing γ volume fraction. At low temperature, cleavage fracture occurs in α phase, at the same time γ phase slightly plays the part of an obstacle to crack propagation. Charpy impact value of Widmanstatten type γ slightly increases with an increasing volume fraction of γ phase. On the other hand, band type γ, separation of α-γ phase boundary occurs and the crack propagates zigzag manner, so in this case the impact value increases more substantially than Widmanstatten type γ.
1989-10-01