engleski

Controllable Heat Extraction During Gas Quenching Effect on Distortion and Depth of Hardening

In the first part of investigation, already published, a new Controllable Heat Extraction (CHE) technology for pressurized gas quenching in vacuum furnaces has been proposed. The relevant theoretical background and some experiments, using the IWT method for characterizing the quenching intensity of gases, have already been described. Present (second) part of the investigation is aimed at evaluating the effects of the CHE technology on distortion and the depth of hardening. Special distortion - prone specimens, made of a low alloyed steel, have been quenched in a high gas pressure vacuum furnace under different quenching conditions. Dimensional changes and distortion have been evalueted by measuring: diameters, lenghts, axial and radial errors in rotation, before and after quenching. Depth of hardening was evaluated by a method, based on experiments using the gas-end-quenched specimen. In order to apply the IWT method for characterizing the quenching intensity during gas quenching also in case of CHE technology, a computer programme was deweloped to calculate cooling curves in different distances from the quenched end of the relevant (Jomminy specimen like) specimen. Possible hardness prediction, based on the correlation between gas-end-quenced specimen and round bars of different diameters, as well as complicated axially symetrical workpieces, has been discussed.

Gas quenching; Distortion; Depth of hardening; Quenching intensity

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