微量 Ti, Nb を含む 18Cr-10Ni 鋼および 18Cr-10Ni・Mo 鋼の高温強度におよぼす N, B および P の影響

概要

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It has been previously reported by one of the authors that with the combined addition of small amounts of Ti and Nb the creep rupture strength of 18Cr-8Ni austenitic steel is markedly increased. In this work, the effects of further addition of N, B, and P on the creep rupture properties of 18-10 and 18-10・Mo steels both bearing small amounts of Ti and Nb have been studied. It has been found that the combined addition of 0.1%N and 0.02%B to these steels is effective for increasing the rupture strength, and the addition of 0.3%P to 18-10・Ti・Nb・Mo steel is more effective, giving a high 700℃-10^4 hr rupture strength of 17 kg/mm^2. The cause of the strengthening effects of these elements have been discussed with relation to changes in distribution of carbide M_<23>C_6 precipitated within austenitic grains, and it has been attributed to a decrease in the misfit between matrix and the carbide M_<23>C_6, resulting in retardation of the carbide coalescence. Especially, electron microstructures of replicas extracted from 18-10 and 18-10・Mo steels bearing 0.3%P look like homogeneous precipitations of the carbide M_<23>C_6, and these fine carbide distributions have been considered to be the main cause of the strengthening action of P.
社団法人日本鉄鋼協会の論文
1973-06-01