抄録
The investigations on the characteristics of sintering and the age-hardenability of sinte red maraging steels, were carried out. Specimens were prepared from the mixed powder of Fe-18% Ni-7% Co-5% Mo and the atomized alloy powder, followed by compacting under 4-8t/cm2 and sintering or 0.5-5hrs. at 1150-1300°C in hydrogen. The results obtained are summarized as follows.
1) After air cooling from the sintering temperature, the sintered compact was relatively soft (<100HR B) with low carbon martensitic structure, which made it amenable to sizing. Subsequent age-hardening given to it for 5hrs. at 500°C, increased its hardness (>30HR c) with negligible contraction.
2) For compacts made from the mixed powder, the increase in compacting pressure and sintering temperature or in time was effective in raising the aged hardness, which might be due to the homogenization of alloying elements and the densification during sintering. Under identical conditions of compacting and sintering, the aged hardness of sintered com-pacts produced by mixing the reduced iron powder was, on the average, 2-4 HR c higher than that of electrolytic iron powder.
3) Coining and normalizing attempted in advance to age-treatment were not effective for the increase of the age-hardenability of compacts.
4) With atomized alloy powder, it was difficult to obtain the densities of more than 7.1g/c.c., even when it was repressed at 4-8t/cm2 and resintered for 1hr. at 1300°C. This may be ascribed to the relatively low aged hardness.
