日本金属学会誌

J. Japan Inst. Metals, Vol. 45, No. 4 (1981),
pp. 438-445

Nodular Graphite Formation in Pore-containing White Cast Iron Sintered by means of Direct Electric Resistance Heating

Kenzo Hanawa1, Zenshiro Hara2 and Kiyoaki Akechi2

1Graduate School, University of Tokyo, Tokyo
2Institute of Industrial Science, University of Tokyo, Tokyo

Abstract:

Using an electric resistance sintering aparatus, 2∼5%C flake graphite cast iron powder compacts were heated very rapidly to melt the central part of the compacts and then cooled very rapidly in order to leave the pores in a white cast iron matrix. The pore-containing white cast irons were annealed at 873∼1323 K for 1.8 ks under dry hydrogen flow, and cooled in air or in a furnace. Nodular graphite was formed according to the pore distributions which existed before annealing. However, in the pore-free specimens remelted at 1723 K for 0.6 ks, nodular graphite was not formed. The formed nodular graphite was polycrystalline and the c-axis of all crystallites was radially oriented in a way similar to that of coventional nodular graphite crystallized in a melt. These results suggest that nodular graphite can be formed by annealing of the pore-containing white cast iron, made from any kinds of cast iron powder, irrespective of carbon contents. This is explained in terms of the gas bubble theory that graphite is precipitated in the pores.


(Received 1980/11/4)

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