Abstract
Effects of the addition of phosphorus (0.2-0.8%) to Cu-9% Sn compacts which was standard composition of conventional bronze oil impregnated sintered bearings were examined during sintering process. The bearing running test was also carried out under the heavy load condition for Cu-base oil impregnated bearings on Cu-9%Sn-0.4%P bearing.
The results obtained were as follows;
1) By the addition of phosphorus, Cu-Sn compacts were remarkably strengthened. For example, the radial crushing strength of the compact added 0.4% phosphorus, pressed at 2 t/cm2 and sintered at 700°C for 30 min., was 11 kg/mm2 higher than that of the non-phosphorus compact.
2) On the case of addition of phosphorus above 0.4%, the swelling phenomena during sintering process, which occur above peritectic temperature (798°C) in ordinary mixed Cu-Sn powder compacts were not observed. The reason was seemed that owing to the addition of phosphorus alloying of Sn had progressed sufficiently through the sintering below peritectic temperature.
3) Sinterability of mixed Cu-Sn powder compacts was extremely enhanced by the addition of phosphorus. With the progress of sintering, large pores became larger, but on the contrary small pores became smaller and gradually disappeared. So, the oil impregnated sintered Cu-Sn-P bearings having large size pores and high strength can be produced by selecting the proper sintering conditions.
4) In the running test, Cu-9%Sn-0.4%P bearings showed excellent bearing performance even under the heavy load condition (P=20 kg/cm2, N=4, 000 rpm, PV=2, 000 kg/cm2m/min) in which the oil impregnated pores were closed by the plastic flow of the rubbing surface in the conventional sintered Cu-9%Sn bearings.
