各種リフォーマ・チューブ材料のクリープ・疲労特性と寿命推定法

概要

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Since the reformer-tubes used in fuel cell systems are subjected to frequent load- and temperature-cycling in the creep range, it is necessary to take account of creep-fatigue interaction for material selection and structural design. in order to find the most suitable materials and life estimation method for this application, creep rupture and low-cycle-fatigue properties at 800 and 1000℃ were investigated on various centrifugally-cast materials. The following conclusions were obtained; (1) A Nb- and Ti-containing 25Cr-35Ni steel (HP-BST-M) was superior i creep rupture strength and creep-fatigue properties to conventional HK40 and HP-Nb at both 800 and 1000℃. (2) A low carbon HP-Nb showed equally as good creep-fatigue properties as HP-BST-M had at bother temperatures. This material had almost the same creep rupture strength as HK40 had at 800℃, but had higher strength than HK40 at 1000℃(3) The superior creep-fatigue properties of HP-BST-M and low carbon-HP-Nb were attributed to the excellent creep ductility. (4) The linear cumulative damage rule (φ_c+φ_f=1) gave the extremely conservative life estimation at 800℃, but gave the unconservative one at 1000℃. On the other hand, the strain-range-partitioning method gave an accurate prediction irrespective of temperature by selection appropriate partitioning.
1988-03-15