MICROATMOSPHERE SINTERING OF Cr–Mn STEEL IN FURNACE ATMOSPHERES OF FLOWING HYDROGEN AND TECHNICAL NITROGEN

Abstract

Chromium-containing steels must be sintered in dry atmospheres with low partial pressures of oxygen, such as nitrogen–hydrogen mixtures. The conventional endogas atmospheres have a potential to carburize the main steel and simultaneously oxidize alloying elements, e.g. Cr and Mn, preventing proper sintering. Fe–1.5% Mn–1.5% Cr–0.25% Mo–0.4% C steel is successfully sintered in flowing technical nitrogen by controlling the local microatmosphere, through the use of semi-closed container/getter/activator combinations. Then, the necessary reducing reactions are induced in the dry microatmosphere within and around the specimens. As manganese has a higher affinity for oxygen than chromium, chromium oxide is reduced by relying only on carbon and manganese in the semi-closed container. Mechanical properties of the specimens sintered in technical nitrogen do not significantly differ from those sintered in dry hydrogen.