Comparative testing for frictional properties of castings between lead-free bronze dispersed with sulfide particles, leaded bronze, and phosphor bronze was carried out. The composition of the lead-free bronze was determined by referring to calculated phase diagrams. A pin-on-disk friction tester was used for the comparative testing of the castings between the lead-free bronze and leaded bronze. A ball-on-disk friction tester was used for the comparative testing of castings between the lead-free bronze and phosphor bronze. Seizure resistance of the bronze castings was evaluated by changing the friction coefficient with sliding time at various load conditions. The influence of sulfide particles dispersion on the lead-free bronze castings was evaluated by microstructure observation before and after the friction tests and results of elemental mapping by EPMA. The seizure resistance of the lead-free bronze castings was better than that of the leaded bronze castings. Sulfide and oxide existed on the friction surface after the friction tests, suggesting that the sulfide and oxide prevent transfer to counterparts.

  The eutectic structure of hypoeutectic Al-Si alloy shows a modified structure when the amount of P is small, and an unmodified structure when the amount is large. We, therefore, developed a de-phosphorus treatment method which combines flux processing with rotary degassing processing to obtain the modified structure. Through this method, the amounts of gas, inclusions, as well as P could be reduced.