Barberpole - Heat treatment defects


Figure 1: Barberpole.

Defect name: Barberpole
Record No.: 3216
Type of defect (Internal/Surface): Internal
Defect classification: Induction heating defects, heat treatment defects
Steel name: Steel
Steel composition in weight %: No data.
Note:  Spiral pattern caused by scale formation during quenching are often seen in workpieces that are scanned. When properly quenched, barbpole is a visual condition, and there is no effect on the hardened characteristics. However, if the quenching is not sufficient, two effects can occur. First, flakes of bainite may appear on the surface of the workpiece in a spiral pattern, These flakes can be seen in the microstructure and if the workpiece is centerless ground, the resulting surface finish and tolerance can be affected. Second, barbepole can be the result of self-tempering of a martensitic area as it passes from one quench impingement area to another. When microscopically viewed, the workpiece may have fully hardened case with a very shallow, tempered area spirally down to workpiece. In both cases the quenching must be improved.
Reference: Not shown in this demonstration version.

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