On the Structure of the Steel Carburized by Various Hydrocarbons

Abstract

Under the probable assumption that one of the chief causes for the formation of the abnormal structure in carburized steel exits in O₂ contained in steel in large quantity, the author carried out some experiments to prevent the formation of the structure in question. As the specimens, Armco iron was first adopted which was determined by analysis to have 0.0₆₇ per cent of 0₂. It was found that the abnormal structure was scarcely developed in the specimens which were carburized in some gaseous hydrocarbons such as CH₄ , C₂H₄ or C₂H₂ and in CO containing the vapour of liquid hydrocarbons such as C₆H₆, C₇H₈, C₅H₁₂, C₆H₁₄, C₇H₁₆ or C₈H₁₈ in spite of its prevailing in those carburized by some commercial solid carburizers _and in the mixture of charcoal and 40 per cent. of BaC0₃. These phenomena can be easily understood if the assumption before mentioned is, true, because hydrocarbons deoxidize and carburize steel simultaneously at high temperatures. The 3 kinds of other commercial steel were then carburized with C₂H ₂ and CO containing C₆H₅ or C₅H₁₂ which were found to be very effective for the improvement of the structure of carburized steel in the preceeding experiments. A similar effect from these carburizers, however, was not observed in this case, notwithstanding the fact that the oxygen content of these steel specimens is less than or almost equal to that of Armco iron. This is doubtless due to the fact that the cause for the formation of the abnormal structure in carburized steel is not so simple as before assumed.