含硼素強靱鋼に關する研究 (I)

概要

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Effects of boron addition on grain sizes, critical temperatures, Jominy hardenabilities and isothermal transformation diagrams were studied with several kinds of constructional alloy steels prepared from commercial and experimental heats. The results obtained were summarized as follows. 1. The perfect deoxidation and nitrogen fixing of the heat by proper addition of Al+Ti, prior to the boron addition was proved to be effective to increase hardenability and also to avoid grain coarsing tendency of boron steel. 2. The intensity of the boron effect on hardenability was apparently larger in Mo-containing steels especially in complex low alloy steels than in simple alloy steels. 3. Boron appeared to retard nucleation of ferrite both in continuous cooling and isothermal transformations, accordingly it seemed to retard the begining of proeutectoid ferrite, intermeadiate and pearite transformations in hypoeutectoid steel. Decreasing effect of boron in higher carbon steels and practically no effect at eutectoid and hypereutectoid steels was considered to prove that boron only delayed the nucleation of ferrite but it did not affect on the nucleation of carbide. 4. A"boron constituent" at the austenitic grain boundary was observed, after the grain coarsing by heating at 1200℃ followed by slow cooling.
1953-06-25