November 2022 Volume 4

MATERIALS

quench is entirely enclosed under atmosphere and automated, which greatly simplifies this step of the process from both a repeatability and safety standpoint. There is also a fair degree of flexibility in the types of forgings that can be processed in an IQ furnace. On the large side, a user can process an individual workpiece up to the volumetric size of the work zone or up to the max weight rating of the furnace. Conveniently, there is effectively no low limit to how small of a forging that could be processed in this type of equipment. Special baskets and fixtures can be used to run multiple layers of small forgings that may not be well suited to processing in a box furnace using an open transfer mechanism. There are a few significant limitations to IQ furnaces. First, while it is possible to run larger work pieces in these furnaces, it is not the ideal setup if there are high volumes of larger parts due to overall weight capacity limits on these furnaces. These limits typically fall between 3000-6000 pounds. Second, users are typically constrained to using oil as the quench media in this furnace configuration. This limitation precludes running many forgings that are made from lower hardenability steels such as 1045 or 4130. Third, because these are fired using radiant tubes, the maximum operating temp would typically be capped at 1750F unless special internal alloy is equipped in which case the user may be able to run up to 1900F.

IQ furnaces tend to be reliable and robust when PMs are performed, however, they have a significantly higher maintenance burden than a simple box furnace. The internal alloy components distort over time and must be replaced to prevent jams from occurring in the handling mechanism. The internal brick jambs and arch must also be maintained regularly and can easily be damaged by a load that is built improperly. Failure tomaintain these features can result in heat leaking to the furnace shell which can cause catastrophic damage. Chuck Hartwig is the Director of

Operations for Carburizing and Batch Hardening at ThermTech in Waukesha, WI. He holds a B.S. in Metallurgical Engineering from Colorado School of Mines. Email: chuck.hartwig@thermtech.net

FIA MAGAZINE | NOVEMBER 2022 45