Abstract
1. Creep tests over periods of 25000–114000 h under stresses equal to or somewhat higher than the theoretical creep limit showed that a constant creep rate is really a variable creep rate. Therefore, the second creep period can be characterized only by some average creep rate. 2. The “constant” creep rate and the length of the second period result from the particularities of structural processes occurring in the steel. In heat-resistant steel under low stresses the plastic deformation accumulated up to the beginning of the third period is 0.2–0.5% regardless of the value of the minimum creep rate. The time preceding this degree of deformation determines the length of the second creep period. 3. One must consider the creep limit to be the stress which induces a certain degree of deformation after a given period of time at a given temperature. The theoretical creep limit determined from the constant creep rate of 1·10−5 %/h is an undependable characteristic of the resistance of a part to creep during its working life.
Published Version
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