Creep and Creep-Rupture Properties of 2 1/4Cr1Mo Steel for Fast Breeder Reactor in High Temperature Sodium
1976 Volume 25 Issue 270 Pages 263-270
Details
1976 Volume 25 Issue 270 Pages 263-270
In providing the basis of designing structural components for the secondary sodium cooling system of a fast breeder reactor and for determining the optimum service condition of these components, it has been required to obtain creep and creep-rupture properties of 21/4Cr1Mo steel in sodium and also to clarify effects of sodium corrosion on these properties.
The creep and creep-rupture tests under uniaxial tension were made using the specimens extracted from seamless tubes of normalized and tempered 21/4Cr1Mo steel of domestic heat at temperatures of 500°, 550° and 600°C in flowing sodium with the oxygen level of 10wppm. The similar tests were carried out at the same temperatures in air for the purpose of comparison.
The similar tests were made also in air at 550°C for the specimens exposed to sodium under various conditions. Corrosion rate and carbon loss were examined simultaneously for these specimens exposed to sodium.
The results obtained are summarized as follows:
(1) At 500° and 550°C, the values of creep-rupture strength in flowing sodium and those in air were not significantly different. The rupture strength at 600°C, however, was significantly lower in the sodium environment than in air. The decrease of rupture strength became greater as the exposure time in sodium was increased, and coincidence was noted with the tendency of the relative increase in the minimum creep rate. This apparent reduction in rupture strength was accompanied by the significant increase in carbon loss due to decarburization of the specimens tested.
(2) The creep-rupture strength in air at 550°C for the specimens after exposure to flowing sodium was found to reduce almost proportionally to the carbon loss in the specimens of 0.10 to 0.03w/o.
(3) The rate of average metal loss in 21/4Cr1Mo steel was calculated to be 1.2±0.1μm/year from the values of weight loss after the exposure to flowing sodium containing 10wppm of oxygen for about 10000hrs in. the temperature range of 545° to 560°C.
