Development and metallurgical evaluation of centrifugally cast solid bronze bushes

Abstract

A study has been carried out into a novel centrifugal casting method which allows gunmetal bushes, within a restricted size range, to be cast simultaneously. The method involves the incorporation of sodium silicate bonded and segmented sand moulds in a conventional die. A range of centrifuging speeds was employed to study the effect on microstructure and properties. Test specimens were machined from standard positions from each casting and homogeneity and property evaluations were made. Casting techniques are discussed and their effects on tensile and yields strengths are considered. Elongation, reduction in area, porosity and microstructure assessments were also made. An optimum speed of rotation of the mould was established which provided consistently improved properties with respect to bushes cast by the conventional static method. Centrifugally cast bushes were finally tested in a special tribological test rig under high load and boundary lubrication conditions. The parameters measured included the coefficients of friction, Talyrondness and weight loss during the test. The properties were compared with those of conventionally cast bushes and an overall enhancement of properties was observed.