極低炭素-11Ni-Mo 系鋼の低温靱性

概要

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The effects of micro-structures and molybdenum alloying on the low temperature toughness have been investigated in carbon-free 11%Ni-0 to 4% Mo steels reheated below each A_f temperature after double normalizing. In spite of very low content of C, N, P, S, and other impurities in these steels, temper embrittlement appeared in reheating or slow cooling in the range of 450° to 525℃. To inhibit this embrittlement the following two methods were shown effective. One was using substructures which had a small amount of fresh martensite and the other was alloying of 1% molybdenum. There was the optimum molybdenum content, because at higher contents age-hardening and solution hardening by this element became the enevitable cause of the low temperature brittleness. Further, it was concluded that the 1% molybdenum steel having a small amount of fresh martensite showed excellent properties in both strength at room temperature and toughness at -196℃. This steel is expected to have a good toughness also at temperatures below -196℃.
社団法人日本鉄鋼協会の論文
1979-11-01