Study of the Properties of C92900 Bronze Obtained by Permanent Mold Casting, Upward Casting, and Hot Extrusion

Antifriction tin bronzes and, in particular, C92900 bronze are used in mechanical engineering to manufacture parts subject to friction. Permanent mold casting into steel molds is commonly used to produce parts from C92900 bronze. The feasibility of producing C92900 bronze rods by hot extrusion and upward casting methods is explored. The hot extrusion temperature and ram speed, as well as the upward casting speed at which defects do not emerge in rods is determined. Hot extrusion is shown to result in a significant refinement of grains down to 1.7 μm, while upward casting, on the contrary, results in an increase in the grain size in comparison with permanent mold casting. Regarding microstructure, γ-Cu3Sn intermetallic phase crystals are refined in hot extrusion and continuous upward casting. Large agglomerations of Pb particles can be observed in the extruded bronze microstructure, which presumably lead to a decrease in the coefficient of friction. Maximum hardness and tensile strength are characteristic of the rods produced by hot extrusion at 600°C, while the highest elongation at fracture is obtained in the rods produced by upward casting. Tribological studies conducted using the “shaft–partial insert” setup in a kerosene medium with a steel counter body show that hot extrusion leads to a tenfold increase in wear resistance and a threefold decrease in the coefficient of friction in comparison with the rods obtained by permanent mold casting. The rods obtained by the upward casting method, on the contrary, exhibit a decrease in wear resistance. Given these results, hot extrusion may be recommended along with the casting technique for manufacturing bronze C92900 rods.