耐熱鋼のクリープラプ・チャー試験におけるぜい性破断について

概要

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Generally speaking, austenitic heat resisting steels, when they have the tendency of age-hardening during creep test, rupture with remarkably small elongation after the lapse of a certain time in the test. This state of poor elongation is sensitive to notch and attention on it is required from design viewpoint. Now we dealt with creep ruptures of super alloy LCN-155, as its test pieces were subjected to creep rupture test at the temperature of 550℃, 650℃ and 700℃ for about 5000 hours at the longest with respect to three sorts of heat treatment ; i.e., solution treatment, solution treatment plus 700℃ aging and solution treatment plus 800℃ aging. Poor elongation ruptures were of intercrystalline rupture even when they occured after a short period. This fact is explainable if we assume that such ruptures are mainly caused by the united action of both the lattice distortion due to early stage of boundary precipitation and the voids developed by vacancy aggregation. We obtained the electron microscopic examination results which support the above assumption. Some other austenitic heat resisting steels which we examined have the same tendoncy with respect to rupture elongation. Ferritic heat resisting steels sometimes show a brittle creep rupture, and such a nature becomes specially strong when tempering of them is not sufficient. We ascertained such a tendency on two ferritic steels H 40 and H 46.
社団法人日本材料学会の論文
1959-03-15