Why do we need to follow the water content in a quenching oil?

First of all, 18 ml of liquid water corresponds to 22.4 liters of gas. This means that the water will expand by a factor of 1,000 during the vaporisation caused by the quenching process. Thus water will lead to a risk of oil projection and fire risks. The water will also prolong the vapor blanket phase that may cause staining and/or change the cooling power of the oil and then the final characteristics of the steel. Moreover, water increases the oil oxidation through the contribution of oxygen.