高強度12Cr鋼のクリープ変形挙動と組織の関連
1996 年 82 巻 3 号 p. 249-254
詳細
1996 年 82 巻 3 号 p. 249-254
The creep curves of 12Cr steel tested at 873948K up to about 3000h were analized using the modified θ projection concept based on the following equation. Subsequently, the correlations between all three parameters obtained and the structural degradation were investigated.
ε = A{1-exp (-αt)}+B{exp (αt) }-1
where ε is the strain, t is the time, and A, B and α are the parameters determined by curve fitting.
Both values of strain hardening parameter A and weakening parameter B increased with lowering the stress or raising the temperature, i.e., to the long term condition. The degree of their increases depended on the amount of recovery in tempered martensite occurred during creep. For the parameter α related to the recovery rate, the structural degradation brought about the lowering of stress exponent. Such behavior of all parameters corresponded with vanishing the VN finely precipitated during tempering and creep testing.
The estimation curve for creep rupture life at 873K showed good agreement with the experimental data up to about 10 times the longest rupture data. In addition, this method could predict long term rupture lives with high accuracy compared with Larson-Miller parameter method.
