The Effects of Heat Treatment on the Tensile Properties of Camshaft made of GGG70 Series Spherical Graphite Cast Iron.

The aim of this study is to investigate the effects of austempering and induction hardening on the tensile properties of GGG70 ductile cast iron for camshaft production. For this purpose, camshafts have been produced by sand mould casting method. For nodulizing process, Fe-Si-Mg alloy has been used and Fe-Si-Ba-Ca-Al alloy has been for inoculation process. The casting has been done between 1420-1440 °C and the pouring time was in between 11-13 s. The casted camshafts have been austenitized at two different temperatures and time under controlled furnace atmosphere. The austenitized camshafts have been quenched into the molten salt bath at 320 °C temperature and held 90 min and then cooled in air. By this way, austempering heat treatment has been applied. After that, surface hardening process was conducted by induction hardening machine with medium frequency. Microstructures of camshafts have been examined by optical and mechanical tests (hardness and tensile tests) have been performed. The fracture surfaces of tensile specimens were examined by SEM analysis. Results show that austempering heat treatment increases the tensile strength of camshaft as-cast condition. Tensile strength of the cam shaft increases with increasing austenitizing temperature, time and induction hardening. The highest tensile strength 1285 MPa, has been obtained from the induction hardened camshaft austenitized at 900 °C and 90 min time. [ABSTRACT FROM AUTHOR]