Addition of boron and carbon in sintered steel as a promising substitute for copper was tried in order to promote recycling of used steel from scrapped cars. Atomized iron powders mixed with amorphous boron and/or graphite, or 1.5mass%Cu and 1.0mass%C were pressed into 5 mm cube under 600MPa. Most compacts were heated in vacuum in a differential dilatometer with a rate of 10K/min up to 1430 K, and held for 60 min.
Similar differential dilatometric curves were observed in Fe-0.05mass%B-1.0mass%C and Fe-1.5mass%Cu-1.Omass%C compacts. Their dimensional changes during sintering were similar too, yet the dimensional change of the former material was smaller. In 1.Omass%C compacts, Fe-B-C eutectic liquid did not appear with the boron addition of 0.05 mass%. In high boron compacts of Fe-0.5mass%B-1.Omass%C sintered at 1430 K for 60 min and cooled slowly, iron particles surrounded by the eutectic liquid were remarkably spherodized, and cores and cases of them became pearlite and ferrite, respectively.