The following is from the technical booklet "Houghton on Quenching":
As a general guideline during steel quenching, for a single quench, 10 liters of oil for each kilogrm of total charge weight will give an acceptable rise in oil temperature. However, with successive quenches some form of cooling may be necessary to prevent the oil from overheating.
D. Scott MacKenzie from Houghton International is one of the world's foremost experts on quenching. I recommend contacting him for additional information.
Maybe. A good heat exchanger only addresses the issue of heat removal in order to reduce the temperature to the desired range. It does not address the issue of having a sufficient oil volume to absorb all of the heat from the metal without being degraded (change in viscosity, smoking, fire, etc.). Good agitation and a good heat exchanger may allow for a smaller ratio such as 8:1.
Just a caution in case you are using coupons (samples) of some type that are not actual parts to be quenched to establish your heat treat cycle. We had a supplier of a specially designed product by a major company with their own heat treat facility. One of the components was carburized 8630 steel that had insufficient core hardness. Part of the problem is that they were using wedge shaped samples of only a portion of the actual part. This in no way represented the actaul mass and mass/exposed surface area to quenchant especially since they were quenching multiple parts simultaniously and craning them from the furnace to another room to the quench tank.
