Transmission shaft made of iron alloy - with outer hardened and inner relatively unhardened layers

摘要

A shaft transmitting a rotational movement is produced by casting a shaft preform of Fe with alloying material, heat treating to produce a predetermined microstructure, machining to produce the final shape and surface hardening to produce a hard outer layer with a relatively unhardened inner layer. Pref. the Fe alloy is heat treated to produce a pearlite, bainite or tempered martensite microstructure. The outer surface is hardened by induction hardening. ADVANTAGE - Is cheaper to produce than a similar steel shaft. An iron alloy requires less working than a steel and can be easily cast while a steel shaft has to be forged.