Effect of Alloying Elements on Sulfide Morphology of Lead Free Bronze Castings with Dispersed Sulfides Particles

摘要

Transition between eutectic reaction and monotectic reaction of lead free bronze castings with dispersed sulfides particles was investigated to control sulfide morphology for improving properties, for example, pressure toughness of the lead free bonze castings for water supply products, such as, valves. The melt of Cu-Sn-Zn-S system alloy was prepared by induction furnace, and deoxidation was carried out with Cu-P alloy. The amount of alloying elements, for example, zinc and oxygen were changed to control the sulfide morphology, and the shape of sulfide particles was evaluated by an image analysis and observing three-dimensionally-images of the sulfide extracted by an electric method. Pressure toughness of the castings was improved by modifying the sulfide morphology from the eutectic structure to the monotectic structure. Spherical ratio of the sulfide particles was increased with decreasing zinc content, and machinability was improved. Tin content was not dominant for changing the sulfide morphology. The higher amount of oxygen dissolved in the melt changed the sulfide morphology from the monotectic structure to the eutectic structure.