Analysis and Experience using Process Modeling for Developing New and Corrective Heat Treat Schedules for Deep Case Carburizing

Achieving deep carburized cases in large parts, i.e. depths of 4mm or more, can oftentimes be problematic. Requiring long diffusion times at temperature, unanticipated furnace power fluctuations, changes in gas supply, inaccurate probe function, and/or atmosphere changes may result in insufficient case depth. Rising energy costs make methods for calculating efficient carburization schedules more critical. Methods used for shallow case applications may not be suitable for determining deep case schedules. The same holds for changes in alloy content, where shallow case prediction errors may be inconsequential, but highly influential for deep cases. This presentation will show new methods for calculating deep case carburizing schedules, as well as methods where corrective carburization is required when insufficient case depths are initially achieved. The computational modeling technique presented is validated against experience carburizing large AISI 3310 components for the mining industry. Practical utility of such modeling for deep case carburizing applications is presented.