High productivity and repeatable part quality are the benefits of integrating new heat-treating equipment into a cell manufacturing installation at ZF Passau GmbH, Germany. ZF needed a double-row, pusher carburizing furnace having the capability to carburize and oil quench crown ring gears and pinions and to carburize and atmosphere gas cool crown ring gears followed by reheating in an atmosphere rotary hearth furnace for final press oil quenching. A double-track pusher furnace (Ipsen International) not only meets these requirements, but also increases heat-treating flexibility, such as the capability to simultaneously produce two different case depths.
Most of the standard gear work at ZF is carburized and oil quenched. However, more critical, higher tolerance gear components that are sensitive to distortion are carburized, then press oil quenched or atmosphere gas quenched in special protective gas cooling chambers. The atmosphere gas quench operation significantly minimizes part distortion.