Intercritical Interrupted Jominy Test Mihály RÉGER 1,a , Balázs VERİ 2,b ,Zsolt CSEPELI 3,c and Peter PINKE 4,d 1 Budapest Tech, Bánki Donát Fac. of Eng.,1081Budapest, Népszínház u. 8., Hungary 2 Bay Zoltán Inst. for Mat. and Techn., 1116 Budapest, Fehérvári út 130., Hungary 3 DUNAFERR Co., 3515 Dunaújváros, Vasmő tér 1-3., Hungary 4 Slovak University of Technology, Faculty of Material Science and Technology, Paulínska 16, 91724 Trnava, Slovak Republic a reger.mihaly@bgk.bmf.hu , b vero@bzaka.hu , c zscsepeli@rt.dunaferr.hu , d peter.pinke@stuba.sk Keywords: intercritical annealing, Jominy End Quench Method, modeling, DP, TRIP Abstract. The final microstructure of DP and TRIP assisted steels can evolve after hot working (hot rolling) or during post heat treatment process. In the formation of the final structure a number of different technological parameters have important role, e.g. finishing temperature of rolling, cooling rates, temperature of intercritical annealing, etc. As a result of the individual factors and their combinations a lot of production technology routes are feasible. The effect of the different combinations of these technological parameters on the microstructure can be mapped by a special Jominy end-quench test (so called intercritical Jominy end-quench test) described in this paper. Unlike the traditional Jominy test, in this case there is a partial austenizing between A 1 and A 3 temperatures which results in a given amount of ferrite in the microstructure before quenching. The amount of ferrite depends on the temperature. In some cases the quenching process was interrupted for a given period of time in order to model the cooling process on the run-out table. During cooling each point of the Jominy specimen has a different cooling rate, so the effect of cooling rate on the microstructure can be evaluated along the length of the specimen. Introduction The characteristic multiphase structure of DP and TRIP steels can be evolved by hot rolling or by post heat treatment. Only this latter case is discussed in this paper. The transformation processes which result in the expected microstructure and ratio of constituents are controlled by the technological parameters of the treatment. Although the number of affecting parameters is not so large, the determination of important parameters’ values (intercritical temperature, cooling rate, temperature and duration of quasi isothermal stage) needs numerous pre-experiments before industrial production. The paper describes a new simple method which can be applied for mapping the effect of technological parameters on the microstructural properties. This technique was elaborated in the frame of a Hungarian national industrial project which aims at the introduction of DP and TRIP steels’ production into the Hungarian industrial practice. The project is still under way, so the first results of application of this technique is discussed here. The thermal and physical metallurgical simulation of intercritical annealing is aimed at the complete scanning of possible routes producing multiphase structure (DP and TRIP) and at the determination of heat cycle parameters necessary for optimal microstructure. In addition to the increase of technological reliability the model can help in the prediction of structural and mechanical properties. Experimental material Some DP and TRIP steel compositions produced in the frame of the research project can be seen in Table 1. The first four grades were smelted in an electric induction furnace and were cast into Materials Science Forum Vols. 537-538 (2007) pp. 549-554 online at http://www.scientific.net © (2007) Trans Tech Publications, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net . (ID: 213.81.187.90-02/03/07,15:56:25)