鋳鉄粉・Fe-Si-C系・Ni-C系焼結体の球状黒鉛(2) : 組織と機械的性質

概要

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The mechanism of graphite nodularization and how to control graphite morphologies in sintered products of cast iron swarf powder, Fe-Si-C mixed powders, or Ni-C mixed powders have been investigated.<BR>When the powder contains carbon less than the maximum solubility at the given sintering temperature, all carbon atoms dissolve in solid solution (γ-Fe or Ni-phase) during sintering and precipitate as the graphite into the pores during cooling. Consequently, if the pores in the sintered products are spherical by long-time sintering or powder forging processes, spherical frames for the graphite to grow in nodular morphology, can be provided. Then for example, the products (Imass%C) made from mixtures of cast iron swarf powder and reduced iron powder show the high tensile strength of 95 kgf/mm<SUP>2</SUP> by long-time sintering (1150°C⋅20 hr).<BR>On the other hand, when carbon contents are more than the maximum solubility, no nodular graphite can be obtained because of residual undissolved graphite.
社団法人粉体粉末冶金協会の論文