Papers by Author: Balázs Verő

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Authors: Mihály Réger, Balázs Verő, Árpád Szélig
Abstract: This paper deals with the characterization of solidification, cooling and expected properties of continuously cast slabs. Semi-empirical models based on theoretical consideration and on the results of heat transfer model are used for characterization of the following: surface and inner temperature distribution of the cast semis, liquid sump depth and shape, liquid motion intensity resulting in centerline segregation, parameters of the primary dendritic structure (primary and secondary dendritic spacings, columnar to equiaxed transition position, CET). This method provides an opportunity to make a realistic comparison between the solidification and final properties of semis with different chemical compositions as a function of applied casting technologies. The final goal of this research activity in the future is to define a comprehensive quality function for optimizing continuous casting technology.
Authors: Lino Costa, Imre Felde, Tamás Réti, Zoltán Kálazi, Rogerio Colaço, Rui Vilar, Balázs Verő
Authors: Márton Takács, Balázs Verő
Abstract: Miniature structures can be produced economically by micro end milling as single parts or parts in small and medium lot sizes. The micro end milling process has to be analyzed particularly for the purpose of applying a well controlled and repeatable process. There are many specific characteristics in the micrometric scale of dimensions, whose role is negligible at the conventional processing technologies. One of these special features of micro end milling is the observation that the set value of the feed rate per tooth generally differs from the thickness of the actual removed material layer. Feed rate per tooth is practically defined as the distance, which is run by the edge lengthwise of the groove during one revolution of the tool. Accordingly the feed rate per tooth corresponds to the thickness of the material layer removed by one edge of the tool. This correspondence exists at conventional manufacturing methods but not at micro end milling. This fact is attended by more special features of the micro end milling process, which are multiple cutting, different machining conditions of the edges and tool deflection. This paper introduces the results of improvement of my earlier research on this field [1]. An enhanced flowchart was constructed, which provides the calculation of the thickness of the actual removed material layer at micro end milling under all possible circumstances.
Authors: Balázs Verő, Dénes Zsámbók, Ákos Horváth, János Dobránszky, László Kopasz, József Hirka
Abstract: At the beginning of the third millennium, the world’s annual steel production reached 900 million tons. Flat products account for the majority of the production. It is also known that around three times the amount used today would be needed if the mechanical properties of the steels produced would have stagnated on the level characteristic of the 1930s and 40s. The history of the development and production of HSLA steel in Hungary dates back to the beginning of the 1960s. For the construction of the new Erzsébet Bridge, research workers at Danube Steelworks and at Steel Industry Research Institute developed the Ti micro-alloyed steel MTA50. In the study, we will summarise the history of the development of steels of the 700MPa strength category, thereafter we will introduce the main features of the project running within the scope of the National Research and Development Programme aimed at the development of DP- and TRIP-steels, and we will finally report on the results of the first year of the three-year project.
Authors: Gábor Fehérvári, Mihály Réger, Balázs Verő
Authors: Mihály Réger, Heli Kytönen, Balázs Verő, Árpád Szélig
Abstract: Industrial data set with 400 CC (continuous casting) steel slabs were analysed by a statistical method for revealing the real connections between the technological parameters, heat transfer model results and the precisely determined centerline segregation index. Because of the poor correlations a new model was developed in which the shrinkage and deformations of the shells of the slabs can also be taken into account. It has been proved that the stopping of liquid movement below about 30 % liquid ratio plays an important role in the centerline segregation formation. The conclusions of the calculations are in good accordance with the results of the metallographical analysis.
Authors: Mihály Réger, Balázs Verő, Ibolya Kardos, Fábián Enikő-Réka, György Kaptay
Abstract: The paper deals with the stability of centerline inhomogenity of continuously cast slabs and hot rolled products. The centerline segregation is a disadvantageous failure of slabs which can affect the quality properties of the final products. During hot rolling of the slabs the centerline segregation pattern will become thin and stretched and it can also be detected in the middle part of heavy plates and coils. It is a common experience that the centerline segregation of heavy plates can not be easily decreased by post heat treatment. The pattern of the centerline segregation was modeled physically by preparing a sandwich structure of steel plates with different levels of carbon and alloying elements. Homogenization experiments were performed and the samples were examined metallographically. Diffusional calculations proved the governing role of carbon activity which is influenced by the distribution of alloying elements.
Authors: Mihály Réger, Balázs Verő, Róbert Józsa, Zsolt Csepeli
Abstract: A complex mathematical model characterizing the centerline segregation level in the mid region of continuously cast slabs was developed. The basic heat transfer and solidification model connected to the semi-empirical liquid feeding model (LMI - Liquid Motion Intensity model) gives the possibility to estimate the centerline segregation parameters of slab cast under industrial circumstances. Solid shell deformation changes the volume of the space available for the liquid inside the slab and hereby also changes the conditions of liquid supply.
Authors: Mihály Réger, Balázs Verő, Zsolt Csepeli, Zoltan Szabo, Robert Jozsa, Tibor Kelemen
Abstract: Mathematical model was developed to estimate the flow rate and direction and of the expected porosity level in the centre part of a slab. Calculations show that centreline segregation is basically affected, at a given composition and cooling technology by the setting, deformation and eccentricity of the supporting rolls. Bulging of the strand between the supporting rolls can also play role.
Authors: Anna Fauszt, Balázs Verő, Rózsa Takács, Ákos Horváth, Hartmut Schneider
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