Fe-Cr合金の水素環境脆化に及ぼすクロムの影響

Abstract

Tensile properties of Fe-Cr alloys of chromium content up to 30% were investigated from 1.1 to 39.3 MPa of hydrogen and in 0.6 MPa of argon at room temperature by using a specially designed equipment. The results obtained are as follows.1. Annealed Fe-Cr alloys of Cr content up to 30%Elongation and reduction of area of the annealed alloys decreased with increase in hydrogen pressure, while hydrogen showed no effect on 0.2% proof stress and tensile strength. Hydrogen environment embrittlement (HEE) was minimized at 4∼8% of chromium content, and HEE increased with increase in chromium content above 12%. It is considered that the crack formed by hydrogen on the surface propagated rapidly, when plastic deformation occurred near the maximum load point in stress-strain diagram.2. Fe-Cr alloys of 16∼30%Cr content aged at 748 KHydrogen susceptibility of aged alloys of 16 to 20% chromium content from was larger than that of annealed alloys, and HEE behavior was the same as that of annealed ones. In the aged alloys of 25 to 30% chromium content, the tensile strength, elongation and the reduction of area greatly decreased with increase both in hydrogen pressure and chromium content, while hydrogen showed no effect on 0.2% proof stress. It is considered that the aging at 748 K enhanced the cleavage fracture sensitivity, and a small crack formed by hydrogen with small plastic deformation induced the cleavage fracture easily, thus the aging at 748 K increased the HEE sensitivity.