Investigation of C92900 bronze properties obtained by permanent mold casting, continuous upcasting and hot extrusion

Abstract

In mechanical engineering, the antifriction tin bronzes, and C92900 bronze for instance are used for parts subjected to wear. The permanent mold casting into steel molds are commonly used to produce parts from C92900 bronze. This work investigates the possibility of C92900 bronze rods production by hot extrusion and upcasting methods. It has been discovered the hot extrusion temperature and ram speed, as well as the casting speed for upcasting that promote no defects in rods. It has been shown that hot extrusion leads to severe grain refinement up to 1.7 gm, and when casting upwards, on the contrary, an increase in the grain size occurs in comparison with the permanent mold casting. After hot extrusion and upcasting, the crystals of the Y-Cu3Sn intermetallic phase are refined in the bronze microstructure. At the same time, large agglomerations of (Pb) particles can be observed in the extruded bronze microstructure, which leads to a decrease in the coefficient of friction. The maximum hardness and tensile strength were obtained for rods produced by hot extrusion at 600 °C, and the highest elongation in rods obtained by the upcasting method. Tribological studies were carried out according to the «shaft — partial insert» scheme in a kerosene medium with a steel counter body showed that hot extrusion leads to a tenfold increase in wear resistance and a threefold decrease in the friction coefficient in comparison with rods obtained by permanent mold casting. At the same time, for the rods obtained by the upcast method, on the contrary, a decrease in wear resistance is observed. In connection with the mentioned results, it is possible to recommend the hot extrusion method for producing C92900 bronze rods in addition with casting technique.