定荷重クリープ試験における 2.25Cr-1Mo 鋼の状態方程式の構築

概要

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Creep testing was conducted on the pre-crept specimens of a 2.25Cr-1Mo steel under constant load. The amount of pre-strain was between 4.4 and 12.0%, and the range of temperature and initial stress was 853 to 903 K and 78.4 to 127.4 MPa, respectively. The relation between creep rate, εand creep strain, ε was expressed as below over a wide range of creep strain : ε=ε_0exp(sε), where s is the acceleration factor, ε_0 is the imaginary initial strain rate, and the stress and temperature dependence of ε_0 is given as : ε_0=Aσ^nexp(-Q_0/RT), where Q_0 is the apparent activation energy for creep of the magnitude of 400±10kJ・mol^<-1>, σ is the true stress, n is the stress exponent of the magnitude of 9.7 and A is the mechanically defined structure factor expressed as below : A=A_0exp[(m-n)ε_p], where A_0 is the structure factor for virgin specimens and m is the constant. These experimental facts lead to the conclusion that pre-strain and creep strain do not alter the creep mechanism but cause the increase in the mechanically defined structure factor, and creep life, t_r is given by t_r=1/(sε_0).
1994-10-01