Research of Properties and Microstructure on High-Strength Casting of Turbo-Charger

Abstract

Combining with productive practice, production of intermediate castings in high-strength turbochargers under the condition of intermediate frequency furnaces is analysed in this paper. By adopting measures of compound inoculation and increasing Sulfur, 95% type A graphite and high-strength intermediate castings whose tensile strength is 300 MPa are acquired. Furthermore, moderate amounts of S and Mn as well as CE values are determined according to test results. As for thin-wall gray cast iron with high strength and complicate structure, whenwSis low andwCis high, castings with good graphite form can be produced. But it is not stable and the strength is low. Adding inoculants like Calballoy and Si-Ca-Ba can significantly improve the graphite form on the edge of thin-walls. WhenwCis stabilized at about 4.1, stable and continuous production of high strength gray cast iron with good graphite form can be guaranteed by adding sulfur and controlling the amount of Mn. The proportion of A type graphite and that of pearlite are both more than 90%.When high-strength gray cast iron is produced in intermediate frequency furnaces,wSshould be controlled between 0.1% and 0.12% andwMnshould be controlled between 0.5% and 0.55%.