加速試験条件下における 2.25Cr-1Mo 鋼のクリープ挙動解析

概要

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Creep behavior has been studied of a 2.25 Cr-1Mo steel under accelerated test conditions. The experimental results show that the minimum creep rate, ε_m, is well expressed by an equation from wihch an Arrhenius term is absent. This fact implies that the state equation for minimum creep rate fails to reflect the unique rate controlling process relevant to the creep mechanism. In a strain region where ε>ε_m (ε_m : strain corresponding to ε_m), the value of ln ε increases linearly with increasing strain, and the slope of the straight lines decreases with increasing initial stress. This fact shows implicitly that microstructure becomes hard at high stresses and soft at low stresses although creep rate increases with increasing time. The relation between creep life (t_r) and ε_m is expressed by an equation, ε_m^Y・t_r=K_<M-G> or ε_m^<Y'>・(t_r/ε_r)=K_<D-M>, where Y, Y', K_<M-G> and K_<D-M> are constants. The time to minimum creep rate (t_<mln>) was connected with creep life irrespectively of stress and temperature by an equation of t_<mln>=0.111×t_r^<1.07>. When the extent of structural degradation is expressed by a minimum creep rate ratio of used to unused specimens, the remaining creep life of degraded materials is readily converted into the minimum creep rate ratio.
社団法人日本鉄鋼協会の論文
1993-09-01