The Effect of Melting Condition on the Properties of High Chromium Ferritic Steels(Metallurgy)

概要

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The influence of melting atmosphere and impurity elements on the hot workability of Fe-30%Cr alloys and the effect of vacuum and Ca refining on the mechanical properties have been studied. The results obtained are as follows. The deformation resistance of zone refined heat with the lowest impurity content is from 23 to 13 kg/mm^2 in the temperature range of 850°to 1300℃. Increasing the interstitial elements such as C and N in the vacuum-melted heat raises the deformation resistance in any hot-working temperature. However, the contents of O up to 0.2%, S up to 0.1%, Mn up to 2%, Si and Al up to 0.5% have not any significant effect on the deformation resistance. The heats of more than 0.017%C reveal intercrystalline fracture from above 1200℃. 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 and Ca refined heats consist mainly of calcium aluminate, and their tensile strengths are approximately 45 to 65 kg/mm^2 with elongations of 28 to 35% at room temperature -72°and -120℃, and the ductile fracture with a fine dimple pattern is observed.
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