Properties of Low Cost TiAl Automotive Valves Produced by Cold Wall Induction Melting and Permanent Mold Centrifugal Casting

摘要

Initiated by ALD Vacuum Technologies GmbH a new manufacturing process for an economical mass production of TiAl valves has been developed by a joint research project which is financially supported by the Federal Ministry for Education and Research of Germany. The new process enables the production of TiAl valves in high annual volumes and at cost comparable to conventional steel exhaust valves. The expected price is feasible through the very high level of process integration. Melting, alloying, purification and casting are integrated in single step. The two main features of the manufacturing process are the use of a modified induction cold crucible and a heatable metallic permanent mold in an evacuable centrifugal casting unit. Based on the results of numerical process simulation as well as casting experiments a pilot plant has been built. In order to minimize the effort for the optimization of melting and casting parameters, regarding the mechanical properties of the valve, an experimental programme based on modem DoE-technique was performed. The development of the process and the results of this programme will be presented.