Effect of Carbon Content on High-Temperature Properties of 2%Cr-1Mo Steels

Abstract

The 2¼Cr-1Mo steel is an attractive material for liquid metal handling systems such as a liquid sodium loop of a liquid metal fast breeder reactor (LMFBR) steam generator. However, mass transfer of carbon from the chromium-molybdenum steel can occur in such applications and hence can alter the mechanical properties of the material. The object of this work was to determine the effect of low-carbon contents on the tensile, stress rupture, and low-cycle fatigue properties of 2 ¼Cr-1Mo steels at elevated temperatures. Commercial and laboratory heats of material with carbon contents of about 0.02 to 0.19 percent were tested in the annealed condition. These carbon contents were obtained by casting to the desired level and by decarburization. The results of our tests indicate that lower carbon contents decrease strength levels, stress rupture properties, and low-cycle fatigue resistance at elevated temperatures. The decarburized material may suffer greater strength losses than the cast-to-low carbon material.