1Cr-1/2Mo-1/4V鋼の応力緩和特性

抄録

Although it is important from the practical standpoint to study the effect of the initial stress of practical heat resisting steel on its stress relaxation properties, and to find thereby the phenomenological correlation between its initial stress and residual stress, it is regrettable that no systematic investigation on this problem has so far been made beyond Oding's works, Report is made in this paper of the examination made of the effect of the initial stress of 1 Cr-1/2 Mo-1/4V steel on its residual stress based on Oding's rule by varying the initial stress within the temperature range of 450∼550°C. The temperature dependence of stress relaxation rate was also discussed here.
The results obtained are as follows;
(1) The initial stress in the lower temperature range gives effect of different order on the residual stress from the effect that will be given by the initial stress in the higher temperature range. The relaxation behavior of the residual stress may even be greater when the initial stress was in the lower temperature range than what might have been expected from the property of the initial stress which was in the higher temperature range.
(2) Accordingly the so-called Oding's correlation between σ₀ and Δσ(=σ₀-σ_t) fails in this kind of low alloy steels, but is possible of success in the kinds of high chromium ferritic and austenitic steels.
(3) The temperature dependence of stress relaxation rate ε_rp for the data with same initial strain 0.15% within the temperature range of 450-550°C is represented experimentally as follows.
ε_rp=-1/E·dσ/dt={1.41×10^-13σ^21.0exp[-9.40×10⁴/RT]……18_??_σ_??_22 2.51×10^-27σ^31.8exp[-(9.25σ-13.9)×10³/RT]……10_??_σ_??_18
where, σ; stress (kg/mm²), R; gas constant (cal/mole/deg), and T; test temperature (°K).