The cooling ability of vacuum oils

P. Danev, R. Radeva:

Proceedings of the 8th Seminar of the International Federation for Heat Treatment and Surface Engineering , IFHTSE 2001, Dubrovnik- Cavtat, Croatia, 12 – 14 September 2001.

The hardening of workpieces of rolled instrumental and constructional steels in vacuum furnace is most often done in oils. A lot of firms nowadays, like “TEXACO”, “Karl Burgdorf”, “SHELL”, “BP” and so on, produce a large variety of vacuum-quench oils. The aim of the paper is to define their cooling ability at lowered pressure (vacuum) and to compare it to that at normal (atmospheric) pressure.
A vacuum installation for studying of the cooling ability of quenchants has been used. Two problems have been solved:
1. The influence of the kind of the oil, at constant temperature of 60°C and pressure of 1 mbar without agitation, on the cooling during quenching of the sample is determined.
2. The influence of the depth of the vacuum for some of the tested oils on their cooling ability is studied as well.
Quantity estimations of the cooling of the important for the steels pearlitic and martensite temperature intervals have been made. A lowering of their cooling ability with the decrease of the pressure was determined. This substantial disadvantage can easily be eliminated in the multi-camera vacuum furnaces for heat treatment and chemical heat treatment by following inert gas into the cooling camera.

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