Papers by Author: B. Smoljan

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Authors: Imre Felde, Imre Czinege, B. Smoljan, Rafael Colás
Abstract: A novel numerical approach for testing and evaluation of quenching media and quenching systems is outlined. The technique proposed is based on determination of heat transfer coefficient from temperature signals recorded and applying it as input for simulation of quenching process. The evaluation method is based on the calculated microstructural and mechanical properties of cylindrical samples.
Authors: B. Smoljan, Dario Iljkić, N. Tomasic, Imre Felde, G.E. Totten, Tamás Réti
Abstract: The modified Jominy-test was designed for prediction of hardenability of high-hardenability tool steels and possibility of application of modified Jominy-test in computer simulation of quenching of high-hardenability tool steels has been investigated. Because of high hardenability there are limits in application of original Jominy-specimen in simulation of quenching of steels. The performance of investigated modified Jominy-test in simulation of quenching of high-hardenability tool steels was estimated by comparison of cooling curves of modified Jominy-specimen (JM®-specimen) and cylindrical specimen. The influence of dimension of JM®-specimen on cooling curves has been investigated. The time of cooling, t8/5 relevant for results of quenching was predicted. Modified Jominy-test can be applied in simulation of quenching of steel with higher hardenability rather than original Jominy-test.
Authors: Božidar Liščić, B. Smoljan
Abstract: The technology of High Pressure Gas Quenching (HPGQ) in modern vacuum furnaces has already reached the level of 20 to 25 bar pressure and up to 80 m/s gas flow velocity. By using primarily nitrogen (N2) it is possible to quench also low-alloyed steels, and to compete, in some cases successfully, with oil quenching. This depends basically on the hardenability of the steel and on the cross-section thickness of the quenched workpiece. The present work explains experimental testing of steels' hardenability when gas quenching is applied. For determination and vizualization of the hardening capacity of steels quenched by HPGQ, a computer aided method has been developed for axially symmetric workpieces of any complex shape, to show at a glance the complete hardness distribution on longitudinal section. An included database of relevant steel grades and possible gas quenching parameters enables to choose another steel grade and/or other quenching parameters, and see on the display another relevant hardness distribution, without performing additional experiments.
Authors: B. Smoljan, Dario Iljkić, Lovro Štic, Zvonimir Kolumbić
Abstract: Mathematical modelling of phase transformations and hardness distribution in non-monotonic quenched steel specimen was developed based on the results of simple experimental test i.e. Jominy test. The hardness in specimen points was estimated by the conversion of cooling time results to hardness by using both, the relation between cooling time and distance from the quenched end of Jominy specimen, and by using the Jominy hardenability curve. The cooling curve at the specimen point was predicted by numerical modelling of cooling by using the finite volume method. Developed numerical model for computer simulation of quenching was also experimentally verified. Limitations of proposed numerical model were found out as well. It has been shown that proposed numerical model can be successfully applied for purposes of simulation of continuous and interrupted quenching of carbon and low alloyed steel specimens.
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