Relaxation of 2¹/4 Cr-1 Mo Steel

抄録

Relaxation, step down and creep tests were carried out on a Cr-Mo steel at a temperature of 500°C and the characteristics of the material obtained by these tests are discussed in order to correlate them to each other. It was found that the log-log plot of stress versus strain rate in relaxation lies on a broken straight line. It may be considered that the relaxation in the higher stress range corresponds to transient creep and that in the lower stress range to steady creep. This simple correspondence dose not always hold, because the stress decrease during relaxation is accompanied by creep recovery. The predictions of relaxation using the informations obtained from other sorts of tests, which have been proposed up to this time, are not always satisfactory due to the lack of consideration of relaxation characteristics. Using the method presented by the authors, which is based on the fundamental relation between stress and plastic strain rate, the residual stress can be satisfactorily predicted. It is also found that a step down test is effective for determining the relaxation properties of materials.