Press quenching

Quenching a component whilst it is restrained in a jig clamped shut by a press in order to control its final dimensions after hardening. Press quenching is generally used on simple-shaped, flat components which are prone to distortion, particularly gears and thin rings.

After being heated to the hardening temperature, the component is taken from the furnace and placed in a die on a quench press. As the press closes, it clamps the component between two specially-made dies and immediately, oil flows over the component and hardens it. The component keeps its dimensions because it is clamped under very high pressure between the dies.

The geometry of some components, such as clutch plates, synchromesh sleeves, and helical, worm, ring and spur gears, present increased risks of component distortion at the quenching stage, if free quenching is applied, even when optimum controls are employed. Press quenching provides an effective solution. Very close fitting dies can be manufactured and the austenitised component transferred to them prior to quenching. This is carried out with the dies pressed together in a suitable press quench apparatus and the constrained component cooled by either immersion in, or spray cooling with, the quenchant, usually oil or a polymer mixture. Press quenching allows precise control of finished dimensions and can greatly improve the yield by reducing scrap due to distortion, as well as reducing or removing the need for expensive finish grinding. Simple shapes such as rings can be plug quenched when it is required to inhibit bore shrinkage or increase compressive stresses to enhance fatigue resistance. The method is a piece part process and may also be labour intensive but it is nonetheless an economic proposition for precision components. When large production volumes are available it is possible to automate the process and thus reduce unit costs.

See also cold die quenching.