I have been pulling my hair out trying to obtain the information and formula for calculating the pressure in pounds on a Gleason-type quench press. We outsource our heat treatment and have had good success in the past with our vendors. We are now having an issue with a large-diameter ring gear over expanding. I am trying to calculate the starting pressure of the Gleason expander. If you could advise me, I would be very grateful.
As you know, press quenching is all about oil flow and tooling design. If we are talking about a Gleason hydraulic press, I am told most people start with an expander pressure of 200-250 pounds and a cylinder pressure of about 250-300 pounds with the pulse control on (if available). Remember, you are attempting to control shrinkage to a repeatable size (time after time) as the part comes out of the unit. Too low of pressure may result in an out-of-round or undersize condition, while too high of pressure may cause excessive taper. It depends on the part geometry.
Consideration and regulation of the following press parameters have been found to help control distortion:
- Transfer time from furnace to press (consistent)
- Manipulator contact (area, duration)
- Part positioning on the die
- Die design
- Die pressure (clamping force, expander force) applied to hold the component
- Quenchant temperature
- Direction of quenchant flow
- Quenchant pressure
- Quantity of quenchant
- Location of points of contact on the component
- Duration of quenching (at various flow rates)
- Flow paths to and through the lower die for the quenchant to reach top and bottom simultaneously
- Die set maintenance and repair
- “Pulsing” feature (optional)
The "pulse" feature allows a part to expand and contract normally while still controlling shape. Without it, stresses are induced because the part is not allowed to contract and expand. Pulsing reduces the friction caused by constant pressure and clamping on the ring as it contracts during cooling. This friction promotes stresses that result in eccentricity and out-of-flatness. Properly applied, the pulsing technique finds the die in contact with the part throughout, but the pressure is released and re-applied every two seconds during the entire quench cycle. The expander pressure is normally not pulsed.