無粒界腐食型25Cr-35Ni系超高純度ステンレス鋼の高温割れ感受性 Hot Cracking Susceptibility in Anti-Intergranular Corrosion 25Cr-35Ni Extra High-Purity Stainless Steels

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The hot cracking susceptibility of type 25Cr-35Ni extra high-purity stainless steels was evaluated by the transverse-Varestraint test with varying the contents of Cr as well as P and S. Two types of hot cracks occurred in these steels by Varestraint test; solidification and ductility-dip cracks. The solidification cracking susceptibility was reduced as the amount of Cr in steels increased, and 25Cr-35Ni stainless steel was negligibly susceptible to solidification cracking. On the other hand, the ductility-dip cracking susceptibility adversely increased with an increase in Cr content as well as P and S contents in steels. There was a good linear relationship between the compositional parameter of (P+1.22S) and the DTR, as well as between (P+1.19S) and the BTR in 25Cr-35Ni stainless steel welds. Accordingly, the quantitative influence of S to an increase in the ductility-dip as well as solidification cracking susceptibility was approx. 1.2 times as large as that of P. The amount of P+1.22S in steels should be limited to approx. 90ppm in order to obtain the sufficiently low ductility-dip cracking susceptibility in 25Cr-35Ni stainless steel welds. Numerical simulation of segregation behaviours of P and S revealed that they were segregated at the grain boundary in the ductility-dip temperature range during welding. Molecular orbital analysis suggested that ductility-dip cracking was attributed to the grain boundary embrittlement due to the grain boundary segregation of P and S. In order to further inhibit the ductility-dip cracking in 25Cr-35Ni extra high-purity stainless steel welds, the effect of La addition on hot cracking susceptibility was investigated. The solidification and ductility-dip cracking susceptibilities could be improved by adding 20-70ppmLa to the extra high-purity steel containing P and S of 6-8ppm. The ductility-dip cracking susceptibility was decreased as a result of the desegregation of P and S to grain boundaries due to the scavenging effect of La.

収録刊行物

  • 溶接学会論文集 : quarterly journal of the Japan Welding Society

    溶接学会論文集 : quarterly journal of the Japan Welding Society 29(3), 187-196, 2011-12-31

    JAPAN WELDING SOCIETY

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各種コード

  • NII論文ID(NAID)
    10030150873
  • NII書誌ID(NCID)
    AN1005067X
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    02884771
  • データ提供元
    CJP書誌  J-STAGE 
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