省資源型二相ステンレス鋼の引張特性におよぼす温度とひずみ速度の影響

摘要

Effects of temperature and strain rate on tensile properties in a lean duplex stainless steel S32101 were investigated. In the temperature dependence on tensile properties, the uniform elongation increased from 273 K to 283 K and indicated the maximum uniform elongation at 258 K. From the x-ray diffraction experiments in the S32101, austenite was transformed to stress-induced martensite at temperatures below 283 K. The stress-induced transformation behavior at 258 K, at which the maximum uniform elongation was obtained, had things in common with the case of metastable austenitic stainless steels. When the tensile properties were compared between the S32101 and the metastable austenitic stainless steels, the increase in the uniform elongation due to TRIP effect was almost the same. At low temperatures below about 250 K, the uniform elongations of the metastable austenitic steels were smaller than that of the S32101 because of the large amount of stress-induced martensite at small strains.%二相ステンレス鋼は，フェライト(α)相とオーステナイト(γ)相が約1∶1の組織からなり，優れた機械的特性と耐腐食性を示す鉄鋼材料として広く用いられている。現在では，0.2mass％前後の窒素(N)量を含む，いわゆる第二世代の二相ステンレス鋼が広く普及し，大きく分けると標準二相ステンレス鋼，スーパー二相ステンレス鋼，省資源型二相ステンレス鋼の3種類に分類できる。NiとMo量が少なく，NとMn量の多い省資源型二相ステンレスについては，破壊靱性や熱処理による窒化物の析出などについての報告があり，γ相の加工誘起変態挙動を利用した機械的特性の向上についても研究が行われている。