End-quench Hardenability Test

Landek, B. Liščić, T. Filetin, T. Lübben:
END-QUENCH HARDENABILITY TEST FOR GAS QUENCHED STEELS

New challenges in heat treatment and surface engineering – conference in honour of prof. Božidar Liščić
(09 – 12 June 2009, Dubrovnik – Cavtat, Croatia)

ABSTRACT:
Hardenability is an inherent property of every steel, usually characterized by the Jominy endquenched test. For steel grades quenched in liquid quenchants this test is enough selective, and for them a good fixed correlation between cooling time from 800 to 500 °C (t 8/5) and the distance from the quenched end can be established. For steel grades of high hardenability, the Jominy test is not enough selective and sensitive. To establish hardenability for these steels a new hardenability testing method with the modified Jominy test specimen has been proposed after initial investigations at Stiftung Institut für Werkstofftechnik at University of Bremen. The proposed method is based on the high pressure gas end-quenching of cylindrical specimen with variations of kind of gas, pressure and its velocity to achieve more gradual decrease of cooling rates along the specimen and to make the hardenability test more selective with a broader range of lower cooling rates. The heat transfer simulation of cooling curves at different locations in the end-quenched probe gives possibilities for determination of cooling time t8/5 at different distances from the quenched end, for different quenching conditions. In addition, the relation between hardness distribution and the cooling times t8/5 has been established for tested end-quenched specimens.


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