This time, we conclude our three-part induction discussion.
Cleanliness of the Quench-Medium Storage System
The storage system should be drained and thoroughly cleaned (piping, tank, filters induction coil and induction system) to remove any particulate matter that may have been deposited into the quench system.
Quench Spray-Head Cleanliness
The quench spray head is a trap for foreign material. If it can be afforded, have two of the same coil with quench ring. Clean one spray quench head one day and the second the next day. The spray head can make the difference between having uniformly and consistently quenched parts because of the potential of the spray quench holes becoming blocked and potentially restricting the quench medium flow to the heated workpiece.
Electrical Contact Face Cleanliness of the Inductor Coil
Each time that the inductor coil is removed or changed, clean the contact mounting faces of both the induction coil and the inductor power head. Use very soft iron wire to accomplish this and then thoroughly rinse the faces and dry completely. Also, use a torque wrench to ensure accurate and consistent tightening of the holding nuts and studs.
Mechanical Handling of the Components to be Induction Heat Treated
Check the mechanical handling system (especially if a carousel table and individual smaller rotating carousels on the main indexing table) for uniform 360-degree rotation with no off-center rotation. This will produce non-uniform case-depth formations.
Very regular and consistent preventive maintenance is perhaps the biggest single item to ensure process stability and produce uniform metallurgy. Of course, there will always be process anomalies, which can be in the steel itself as well as its prior metallurgy.