Development of Shape-Controlled-Sulfide Free Machining Steel for Application in Automobile Parts

A free machining Pb-free steel was developed with shape controlled sulfide (SCS) for use in automobile applications such as rocker arms and crankshafts. This free-machining steel is characterized by its improved chip breakability, for which a technique that adds very small quantities of Ca and Ti to control sulfide shape was specifically applied. It was confirmed that this free-machining steel can offer almost equivalent machinability and equivalent or higher fatigue strength by comparison with Pb-added steel for use in rocker arms or crankshafts with S and Ti modifications.