AGMA 10FTM04

In many applications the high demands regarding service life oftransmission components can be reached only by the application of acustomized case hardening. This case hardening process results in awear resistant surface-layer in combination with a tough core ofthe component. However as a side-effect the components getdistorted during heat treatment. This distortion has a significantcost-impact, because distorted components often need to behard-machined after heat treatment. Therefore the proper control ofdistortion is an important measure to minimize production costs. Byapplying the technology of low pressure carburizing (LPC) and highpressure gas quenching (HPGQ) heat treat distortion can besignificantly reduced. HPGQ provides a very uniform heat transfercoefficient. The predictability of movement during quenching ismore certain and uniform throughout the load. Further improvementscan be achieved by “Dynamic Quenching” processes where thequenching severity is varied during the quench sequence by stepcontrol of the gas velocity. Proper fixturing is another factor fordistortion control. Modern CFC-materials (carbon reinforced carbon)are well suited as fixture-material for gas quenching. The paperpresents how LPC and HPGQ processes are successfully applied onInternal ring gears for a 6 speed automatic transmission. Thespecific challenge in the heat treat process was to reducedistortion in such a way that subsequent machining operations areentirely eliminated. As a result of extensive development in thequenching process and the use of specialized CFC- fixtures it waspossible to meet the design metrological requirements. The Internalring gears addressed in this report have been in continuousproduction since 2006. Subsequent testing and monitoring over a twoyear period progressively demonstrated that consistent metrologywas achieved and quality inspection was reduced accordingly.

Edition:

10

Published:

10/01/2010

Number of Pages:

16

File Size:

1 file , 1.2 MB