Mechanism of film boiling elimination during quenching in mineral oils caused by oligomeric additives

Abstract

Previously, it has been shown by authors [1–3] that the addition of a special additives, for example PIB (polyisobutylene oligomer), creates an insulating layer on the surface of steel parts during quenching in mineral oils that eliminates film boiling without affecting physical properties of the oil. Insulating layer decreases initial heat flux density which becomes less than critical one. In current paper, the detailed investigations are provided concerning the mechanism of film boiling elimination or its cardinal decreasing due to presence a small amount of PIB in mineral oil. Experiments were made using Inconel 600 probe (10 mm in diameter and 30 mm long) which was quenched from 810 °C in I-8A, I-12A and I-20A oils. Effect of viscosity and molecular weight of PIB was investigated by authors. By elimination film boiling during quenching, it is possible to govern intensity of cooling and provide uniformity of hardening process. A phenomenon of eliminating film boiling due to presence a small amount of PIB in mineral oil is called EFB effect which has an important practical use.