Chemical and structural heterogeneity of Cr13Ni6Mo type steel for castings of pumping facilities and valves

The chemical and structural heterogeneities were studied of stainless steel Cr13Ni6Mo used for castings of pumping facilities and valves for nuclear power plants. The results of the chemical analysis show that significant chemical heterogeneity occurs in this type of steel associated with the crystallization mechanism. In areas enriched with elements stabilizing ferrite and austenite, primary austenite crystallization takes place. Depending on the local level of decisive additions, austenitic phase stabilization occurs. Thus, chemical heterogeneity manifests as structural heterogeneity. The structural heterogeneity negatively affects plastic properties, mainly notch toughness. The negative effects of increased chemical heterogeneity can be suppressed at a stage of casting production by controlling the combination of important additions or a stage of subsequent heat treatment by applying the so-called double or repeat tempering. (Z.M.). 6 figs., 4 tabs., 12 refs