A novel process for manufacturing spur gear with uniform microstructure and excellent strength-ductility synergy by warm mold continuous casting

Abstract

Continuous casting spur gear with uniform microstructure and excellent performance remains challenging due to the intensive radial heat flux and nonuniform circumferential cooling in the traditional cooling mold. In this paper, a novel process for manufacturing spur gear with uniform microstructure and excellent strength-ductility synergy by warm mold continuous casting was proposed. The effects of the warm mold continuous casting process on the microstructure and mechanical properties of the QAl9–4 aluminum bronze spur gear billets were systematically studied by simulations and experiments to evaluate the effectiveness of the process. The induction heated mold reduces the radial temperature gradient while improving the vertical temperature gradient. The cooling rate was uniform at the transvers section of the spur gear and increased with increasing casting speed and mold temperature. Spur gear billets with good surface quality, dimensional precision and uniform microstructures were successfully prepared by warm mold continuous casting, and had excellent tensile stress and elongation of 692 MPa and 41%. The synchronously improved strength and ductility of the continuously cast QAl9–4 aluminum bronze spur gear billets results from a higher volume fraction of micron-sized fine α grains and numerous submicron-sized as well as nanosized coherent Fe-rich κ precipitates. The present process could be beneficial for manufacturing high-quality spur gear more efficiently and may also introduce a promising method in integrated control of shape, microstructure and performance of metallic products by continuous casting.