METHOD OF TREATING A FERROUS COMPONENT FOR SUBSEQUENT METALLURGICAL BONDING TO CAST ALUMINUM

摘要

The present invention concerns a method of treating a ferrous component, such as a cast iron cylinder liner, for subsequent metallurgical bonding to cast aluminum, such as an engine block. Initially, the cast iron cylinder liner is cleaned of grease, oil, and oxides, and is then immersed in a bath of molten aluminum at a temperature in the range of 1100-1500 DEG F, for a time period sufficient to form an Fe-Al intermetallic compound layer adjacent the surface thereof. As the cylinder liner is removed from the aluminum bath, a thin molten aluminum coating will cover the liner, and an aluminum oxide film immediately begins to form thereon. In accordance with the present invention, immediately after the liner is removed from the aluminum bath, and while the aluminum coating on the liner remains molten, the liner is quenched in a zinc alloy bath at a temperature in the range of 720-1000 DEG F. When the liner is immersed in the zinc alloy bath, the aluminum oxide film on the surface of the molten aluminum coating will wash away and float to the surface, thereby leaving a protective zinc coating on the liner which prevents the formation of any further oxides. The zinc coating will remain on the liner until the aluminum casting operation, at which, time the zinc will wash away and alloy with the cast aluminum, thereby ensuring a metallurgical bond between the liner and the casting.