ボロンを含む 18Cr-12Ni-3Mo 系オーステナイト耐熱鋼の高温強度と組織におよぼす添加元素と熱処理の影響

概要

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The effect of alloying element such as C, B, Ti and Nb, and heat treatment on the high temperature strength and micro structure of 18Cr-12Ni-3Mo austenitic heat resisting steels containing boron were investigated. In B addition, creep rupture strength increased with increasing B content, whereas in C addition, it reached maximum at 0.2%C. These effects were ascribed mainly to a precipitation hardening due to M_<23>C_6 occurring during creep. The effects of Ti and Nb additions on creep rupture strength were given as a function of (Ti+Nb)/C (atomic percent ratis) irrespective of C contents, and gave a maximum effect at (Ti+Nb)/C=0.4∿0.8. Therefore, these effects of Ti and Nb additions were ascribed partly to a change in morphology and growth rate of M_<23>C_6, into which Ti and Nb were dissolved. Moreover, creep rupture strength increased with increasing solution temperature, up to 1250℃. Surprisingly, the eutectic structures had no negative effect upon creep rupture strength of the steels. Also, the complex borides in these alloys were identified by X ray and chemical analyses. The relation between the sort of borides and eutectic temperature was also discussed.
社団法人日本鉄鋼協会の論文
1968-01-01