鍛造球状黒鉛鋳鉄のフェライト化速度について

概要

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The authors have studied the isothermal ferritization of the uni-directionally forged spheroidal graphite cast iron. The results obtained are summarized as follows: 1) Ferritization is appreciablly accelerated by forging. The acceleration of ferritization is attributable to the increased surface area of graphite particles in unit volume of the iron. 2) Graphite nodules in iron are flattened by forging, so that the ferritization in severely forged iron can be regarded as a one-dimensional diffusion process. 3) The growth rate constants of ferrite layer obtained from the fractions of ferritization in iron and from the thickness of ferrite layer in severely forged iron coincide well with each other, and vary with the mode of transformation, -direct or indirect−, the ferritization temperature and the chemical composition of the iron. 4) When Johnson-Mehl's equation p=1−exp(−k tn) is applied to the isothermal ferritization of spheroidal graphite cast iron, n is about 0.7∼0.8 for the unforged iron and the value gradually drops down to 0.5 by increased forging.
Japan Foundry Engineering Societyの論文