焼結鉄のシャルピー衝撃試験

概要

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The purpose of this investigation is to :elucidate the basic impact properties of sintered iron. Specimens were prepared from electrolytic iron powder (Husqvarna-HVA⋅Star), followed by compacting under 2-9 t/cm2, presintering for 30min at 800°C, repressing under 2-9 t/cm2 and sintering for lhr at 1200°C in hydrogen. The impact strength was measured on U-notched specimens 8×8×40mm, by a newly designed 7 Kg⋅m-Charpy tester with the distance of 30mm between the specimen supports. Results were summarized as follows. In sintered iron, as often pointed out, the impact strength increased exponentially as a function of density. And the range of transition temperature was broad. The miciofractographs of sintered irons showed some areas of ductile rupture even in tests at -90°C. These results were considered due to the notch effect of residual pores. The impact strength of some cast iron was compared with sintered ones. In this respect, it was concluded that the sintered iron with the same density as cast ones was also similar to malleable or nodular cast irons in toughness, and superior to flaky one. Abnormal brittleness was observed in sintered iron at the density range of 7.0-7.3 g/cc. The details on this brittleness will be described in the next paper.