A spur gear made of 9310 steel was carburized using acetylene in a vacuum furnace, cooled to ambient, transferred to a controlled atmosphere furnace, re-austenitized  and then oil quenched.  Final steps included deep freezing and double tempering.  Because bending fatigue strength was a critical property, the process steps were designed using computer simulation to achieve a high magnitude of residual surface compression.  This presentation will discuss the process design methods, the computer simulation results for the vacuum carburization and oil quenching steps, as well as compare these results to measured residual stress, case depth and hardness profiles.