Abstract
This investigation was sponsored by Project No. 29 of the Joint ASTM-ASME Committee on the Effect of Temperature on Properties of Metals, and was directed toward casting more light on the role of aluminum in the breakdown of iron carbide in plain carbon steels into iron and graphite at temperatures below the lower critical point of the steel. The approach to the problem was to extract the carbides from several plain carbon steels which had been deoxidized with different amounts of aluminum and had different known degrees of susceptibility to graphitization, and then to examine and analyze the extracted carbides, with particular attention to the amount and form of the aluminum therein. By comparing the aluminum found in the carbide with the aluminum of the original steel, data were obtained on the role which that element appears to play on the graphitization process. The results strongly suggest that a graphitization-resistant plain carbon steel does not differ fundamentally from one which graphitizes readily. It is tentatively concluded that, in order to promote graphitization, the aluminum is either in solid solution in the ferrite matrix, or else fixes the nitrogen as AlN. Which of these forms it takes could not be determined from the results. The results further suggested that any aluminum which might be associated with the carbide phase is not influential in determining the degree of susceptibility to graphite formation.
