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Important Equipment and the limit of Induction Hardening process
- Requires an Induction Coil and Tooling which relates to the Part’s Geometry
Since the part-to-coil coupling distance is critical to heating efficiency, the coil’s size and contour must be carefully selected. While most treaters have an arsenal of basic coils to heat round shapes such as shafts, pins, rollers etc., some projects may require a custom coil, sometimes costing thousands of dollars. On medium to high volume projects, the benefit of reduced treatment cost per part may easily offset coil cost. In other cases, the engineering benefits of the process may outweigh cost concerns. Otherwise, for low volume projects the coil and tooling cost usually makes the process impractical if a new coil must be built. The part must also be supported in some manner during the treatment. Running between centers is a popular method for shaft type parts, but in many other cases custom tooling must be utilized.
- Greater Likelihood of Cracking Compared to most Heat Treatment Processes
This is due to the rapid heating and quenching, also the tendency to create hot spots at features/edges such as: keyways, grooves, cross holes, threads. (Please talk to an AHT representative if you have concerns.)
- Distortion with Induction Hardening
Distortion levels do tend to be greater than processes such as ion or gas nitriding, due to the rapid heat/quench and resultant martensitic transformation. That being said, induction hardening may produce less distortion than conventional heat treat, particularly when it’s only applied to a selected area.
- Material Limitations with Induction Hardening
Since the induction hardening process does not normally involve diffusion of carbon or other elements, the material must contain enough carbon along with other elements to provide hardenability supporting martensitic transformation to the level of hardness desired. This typically means carbon is in the 0.40%+ range, producing hardness of 56 – 65 HRC. Lower carbon materials such as 8620 may be used with a resultant reduction in achievable hardness (40-45 HRC in this case). Steels such as 1008, 1010, 12L14, 1117 are typically not used due to the limited increase in hardness achievable.