PURPOSE: To easily measure the degree of the deterioration of 12% Cr-based heat resisting steel with time by using the close correlation between an experimental expression showing the relation among a Laves phase deposition amount, absolute temperature, and elapsed time and the degree of deterioration.
CONSTITUTION: A constant C depending upon the Laves phase deposition amount of 12% Cr-based heat-resisting steel in use is expressed by the experimental expression C=T(C1+log t), where T is the absolute temperature, (t) is the elapsed time, and C1 is the constant depending upon the material. Further, a relational expression has close correlation with the degree of deterioration. For the purpose, a characteristic graph showing the relation between the amount of Laves phase deposition by X-ray diffraction and elapsed time as to a test piece under the condition of constant temperature and constant stress is drawn and used as a deterioration evaluation reference curve. Consequently, the degree of deterioration, i.e. which position up to rupture is indicated is easily decided.
NAKABASHI MASAKO
TAKEDA HIROMITSU
YAMADA MASAYUKI
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