A customer quenches small cylindrical parts using induction hardening, followed by dropping the parts into a quench ring. A polymer quenchant is used to control distortion and residual stresses. In a small percentage of parts, the cylinders would experience soft spots on the cylinder sides. This was usually just a single location, where the hardness could be as much as 20HRC below the targeted minimum. At first, the focus was on the polymer quenchant, and its degradation. The concentration of the polymer was reduced from a nominal 10% to 4%. This improved the situation and reduced the number of soft spots observed. However, reducing the concentration of the polymer quenchant did not eliminate the soft spots occurring.
Investigation of the method of quenching and the resultant microstructure was conducted using CFD and SIMHEAT™.