Volume 1, Issue 1
Local Film Boiling and Its Impact on Distortion of Spur Gears During Batch Quenching
The paper discusses results of computer simulation connected with the double distortion during batch quenching of spur gears caused by a local film boiling between teeth. A carburized gear, outside diameter 2.5 in., was intensively quenched in conditions that provided heat transfer coefficient (HTC) equal to 25 000 Wm−2K−1. In some places between teeth local film boiling took place where HTC was 800 Wm−2K−1. Computer simulation showed that maximum displacement is observed between teeth where local film boiling took place. The authors came to the conclusion that increasing critical heat flux densities and elimination of local film boiling can result in decreasing distortion of spur gear. That is true for different sizes of gear during their quenching when using the second type of intensive quenching process (IQ-2) technique (a two or three-step quenching process). It is underlined that critical heat flux densities have a great effect on distortion during batch quenching. The authors also came to the conclusion that a small amount of special additives can decrease significantly distortion during quenching of gears. That is why a global database on cooling capacity of quenchants should be available which must contain critical heat flux densities of different kinds of quenchants.