The use of a press quench for hardening products allows for tight dimensional control of the heat treated part. The benefit is reduced post-heat treatment grinding time, resulting in significant cost savings. Parts press quenched are typically bearing races or gears. The bearing races are made from either 52100 steel or from carburizing grades of steel which have first been carburized to the appropriate case depth required for the product. Gears which are press quenched are also first carburized and slow cooled.
For press quenching parts at Metlab, parts are placed in an atmosphere controlled Rotary Hearth Furnace. The furnace atmosphere (which is endo-based) is adjusted to match the carbon content in the part to avoid carburizing or decarburization. The furnace is able to accommodate parts up to about 18 inches in diameter. The furnace hearth, which is about 48″ in diameter, accommodates up to 8 pieces at a time. The parts are loaded sequentially, one at a time, with the furnace indexing an eighth of a turn between loading. Once the furnace is fully loaded, the number 8 piece is at the door, fully soaked out at the hardening temperature (1550°F) and is ready for quenching. The part is removed from the furnace by the operator using a robotic arm.
Operator picking up a bearing race which is at 1550°F,
from the Rotary Hearth Furnace using a robotically
controlled transfer mechanism.
The heated part is placed in the press which consists of two conical dies; an upper and a lower die. The part is placed on the bottom die, and then, the entire bottom die moved into the quench area. A tapered top die comes down to meet the part, centering the part on the die and locking it into place. The part is then quenched using high velocity oil which flows through nozzles positioned 360° around the O.D. of the part, allowing the quenched part to take a set.
Part is moved to the press quench
Part is placed on the lower die
The use of press quenching can allow for quenched and tempered product which is round and flat < 0.005″, providing for significant reductions in machining times over parts which are free quenched. Cycle times for quenching parts range from 2 ½ to 10 minutes depending the size of the part allowing for relatively high production rates.
Mark Podob
Metlab Heat Treating
