Effect of Melting Condition on the Properties of High Chromium Ferritic Steels

Abstract

The influence of melting atmosphere and impurity elements on the hot-workability of Fe-30% Cr alloys has been studied as well as the effect of vacuum-calcium refining on the mechanical properties. The results obtained are as follows.
The deformation resistance of zone refined specimens with the lowest impurity content is from 23 to 13 Kg/mm² in the temperature range of 850° to 1300°. Increasing the interstitial elements such as carbon and nitrogen in the vacuum melted specimen raises the deformation resistance in any hot-working temperature. However, the content of oxygen (up to 0.2%), sulfur (up to 0.1%), manganese (up to 2%), silicon, and aluminium (up to 0.5%) have not any significant effect on the deformation resistance. The specimens of more than 0.017% carbon reveal intercrystalline fracture from above 1200°C. The crack initiations due to the cluster of alumina or chromium oxide inclusion are also observed. It is ascertained that the globular type inclusions found in the vacuum-calcium refined heats consist mainly of calcium aluminate, and their tensile strengths of approximately 45-65Kg/mm² with elongations of 28-35% are obtained