Alloy 800: New stress rupture and creep data for pressurized components in high temperature reactors

In an HTR plant high temperature components of Alloy 800 materials are subjected to temperatures from about 550 to 850degC in the long term; higher temperatures may occur in the short term. Thus the creep and stress-rupture parameters govern the design of these components. Since in recent years the scope of experimental data available for Alloy 800 materials has considerably increased, a new evaluation of the creep and creep-rupture properties was performed using a data bank computer. The relationships between the characteristics of the creep and creep-rupture behaviour and the metallurgical parameters were investigated by multilinear regression analyses. On the basis of the results of these analyses and after discussion in material expert committees new material specifications were determined for different types of Alloy 800. They were included into the draft standards DIN 17459 and DIN 17460 under the material standard nos. 1.4958, 1.4958 Rk and 1.4959. Besides the new values for the 1% total plastic strain limit and the creep-rupture strength for the types of Alloy 800 under consideration, isochronous stress-strain relations were derived on the basis of creep curves of reference heats. (orig.)