Common misassumption in induction hardening

Whenever someone is talking about induction heating, reference is often made to the phenomenon of skin effect. In most publications devoted to induction heating distributions of current density and power density (heat source distributions) along the workpiece thickness/radius are simplified, and described as exponentially decreasing from the surface into the workpiece. However, in some applications, surface hardening in particular, the power density distribution along the radius/thickness has a unique “wave” shape, which differs significantly from the commonly assumed, classical exponential distribution. Here, the power density is maximum at the surface, and decreases toward the core. But then, at a certain distance from the surface, the power density increases, reaching a maximum value before again decreasing. Article discusses frequency selection for induction surface hardening as well as electromagnetic “wave” phenomenon.

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