NK-40, 25Cr-35Ni 遠心鋳造管材の熱疲労強度

概要

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The strain controlled thermal fatigue test was carried out on HK-40 and 25Cr-35Ni centrifugal casting tube materials being used for heat transfer tubes of chemical apparatus at about 1 000℃. In addition to the general thermal fatigue properties, the evaluation of creep damage, behaviour of welding joint and metallurgical crack appearance were also investigated. The results are summarized as follows : (1) The results of thermal fatigue properties fall on straight lines when plotted Δε_T against N_f in the logarithmic scale. The slope of the line for T_<max>=1 100℃ differs from those below T_<max>=1 050℃. This difference is considered to arise from the oxidation effect. (2) It has been generally said that as the damage of trapezoidal wave pattern rupture occurs when Φ_h(=Φ_f+Φ_c) reaches unity. However, the present results show that it occurs whenΦ_h is more than unity at low temperatures and less than unity at high temperatures. Furthermore, the considerable effects of creep recovery and oxidation besides creep damage and fatigue damage are noticed.
社団法人日本材料学会の論文
1973-03-15