| 摘要 |
PURPOSE:To inexpensively manufacture the sintered material excellent in mechanical properties, by mixing graphite powder in high-oxygen alloyed steel powder, subjecting the mixture to the reactions of sintering-reducing-alloying with C in the step of sintering, and then heat treating it. CONSTITUTION:Alloyed steel powder containing, by wt%, 0.4-0.7% one or two of Mn<=2.3% anc Cr<=5.5% and 0.25-1.0% O is prepared. Graphite and a selective lubricant are then added to this alloyed steel powder, to prepare a powdery mixture having C content controlled at 0.25-1.0%. Thereafter, this powdery mixture is compression-formed to obtain a compressed powdery body having compression density above 6.0g/cm<3>. This compressed powdery body is then heated at a temp. of 1,150-1,300 deg.C in an unoxidizing atmosphere such as H2 gas having a dew point below -30 deg.C for a predetermined time, to obtain a sintered body of 0.2-0.5% C and 0-0.25% O. This sintered body is then quenched in a cooling medium of cooling power above 0.16cm<-1> from the temp. range of the point Ac3- the point Ac3+100 deg.C in an unoxidizing atmosphere having a dew point below -30 deg.C and tempered, to obtain the objective high-strength sintered material. |
