Relaxation of 21/4 Cr-1 Mo Steel

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  • 21/4 Cr-1 Mo鋼のリラクゼーションについて
  • 21 4Cr-1 Mo コウ ノ リラクゼーション ニ ツイテ

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Relaxation, step down and creep tests were made at a temperature of 500°C to obtain relaxation characteristics of Cr-Mo steel and to its relationship to creep properties under constant load. The conclusion may be summarized as follows : Log-log plot of stress vs. plastic strain rate of relaxation consists of two straight lines. It was proved in both relaxation and also step down tests. At a higher stress range the strain rate depends on the initial total strain, but at a lower stress range its dependency is small, so that it is almost definite irrespective of the total strain. It may be said that the observed strain rate in a higher stress range corresponds to the transient creep and that of a lower stress range, to the steady creep. The correspondencies do not always exist because of creep recovery, which inevitably follows the stress decrease due to relaxation. All the methods, which have been so far presented to extrapolate the residual stress of relaxation are not exactly correct due to the lack of consideration of relaxation characteristics. Using the method by the present author, which is based on relation between stress and plastic strain rate, the residual stress can be correctly estimated.

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