Induction Hardening Problems: Ferrite Banding

What were settings on induction machine? i.e. how long did you leave piece hardening for and what was amperage?

Good day

I have some experience in the tubing industry regarding heat treatment of carbon steel tubing. It is extremely common for hot rolled carbon steel to have a banded structure. The topic has been covered extensively in the literature. I will give you a short version.

Typically the segregation of Fe3C is related to the segregation of Manganese and to a lesser extent, chromium. Essentially, the Mn lowers the melting temperature of the alloy so that the area without the Mn solidifies first ejecting the carbon into the Mn rich regions. The result is chemically segregated bands of Fe3C and Fe created during the steel melting process. The hot rolling process that reduces the billet down to a sheet intensifies this banding appearance.

The banding in the steel can be dissolved by long term soaking at temperatures above AC3 and subsequent controlled slow cooling rates. The heat treatment necessary to dissolve the banding is not practical for our processes and likely yours either.