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These days, nickel-base superalloy has been applied to reduce the valve weight of motorcycles. Inconel 751 is excellent in performance but expensive in cost. Therefore, we verified the constituents of nickel-base superalloys corresponding to the requirements of valves and we succeeded in developing a new superalloy and applying it to motorcycle exhaust valves. The characteristics are summarized as follows: 1. The basic composition is Fe-46Ni-18Cr-4Ti-1Al-0.3C-0.004B. It is a precipitation-hardened nickel alloy characterized by precipitation of Ni3 (Al,Ti) and, crystallization and dispersion of fine TiC. 2. It has the following distinctive features. (1) Superior to Inconel 751 in wear and heat resistance. (2) Superior to 20-11P steel in resistance to lead oxide corrosion. (3) Applicable to both unleaded and low-lead gasoline. 3.

A β-titanium alloy wire with a tensile strength of 210 kgf/mm2 (2060 MPa) was made for automotive valve springs. The fatigue of the β-titanium valve springs were heavily affected with the existence of the oxide layer on the surface. The repeated contact of coils to the ends also gives rise to heavy abrasion during the service, indicating the necessity of some measures to prevent it. Through this investigation, technological basis for β-Ti valve springs was established.