engleski

End-quench hardenability test for gas quenched steels

Hardenability is usually characterized by the Jominy end-quenched test. For steel grades quenched in oil or water this test is enough selective, and for them a good fixed correlation between cooling time from 800 to 500 oC (t8/5) 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 conducted experiments and 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 set quenching conditions. In addition, from the conducted end-quenched tests and simulation results, the relation between hardness distribution and the cooling times t8/5 has been established for tested quench conditions.

Hardenability Jominy test; Gas quenching; Cooling time t8/5; Modeling

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