How much do you know about overburning and overheating defects caused by using high-frequency induction heating power to heat workpieces?

When the workpiece is heat treated using high-frequency induction heating power, affected by many factors, the workpiece may produce some defects, such as insufficient hardness, overheating, overburning, oxidation, etc. These defects greatly affect the service life of the workpiece. Today, let’s take a look at overheating and overburning defects.

Heating hypoeutectoid (hypereutectoid) steel for a long time at a temperature much higher than A3 or Accm will lead to a coarser actual grain size. The superheated steel has a stone-like fracture surface, and the surface of the fracture surface has a hilly coarse-grained structure. The grains have no metallic luster, as if they have been melted.

Ferrite formed by a shear mechanism is often found in superheated steels. Under high-temperature carbon diffusion transfer conditions, the actual grain size of the ferrite-Widmansite structure undergoes severe coarsening. This overheating can be corrected by diffusion annealing.

When heated by a high-frequency induction heating power supply, further heating to a temperature higher than overheating will cause overburning of the steel in the oxidizing atmosphere and the formation of iron oxides at the grain boundaries. Burnt steel has a slate-like fracture. Overheating is an irreparable defect.

When the workpiece is heat treated, some defects will inevitably occur. Among the many defects, some can be saved and some cannot be saved. Therefore, when we perform heat treatment, we must be serious and careful to avoid defects in the workpiece.