Authors

HighTemperature Strength Analysis of Low Carbon Steels in the As - Cast State
abstract, article page 243 - 248 pdf - 788 kB

Comparison of the Forming - Limit Diagram (FLD) Models for
Drawing Quality (DQ) Steel Sheets abstract, article page 249 - 253 pdf - 385 kB

A. Ševčík - HighTemperature Strength Analysis of Low Carbon Steels in the As - Cast State

     Results of the study of the influence of chemical composition and microstructure on the strength values at high temperature tensile tests are described and discussed. By increasing the testing temperature, strength values in the low carbon steel slab continually decrease. Mathematical description of the temperature course and scatter zone of strength values was realized. Influences of the chemical composition and grain size on the strength values in a temperature interval from 900 to 1500 °C with a step of 100 or 50 °C was established by means of regression analyses. These influences are temperature-dependent. Strength values at 1400 °C, which chiefly depend on the effective grain size, were thoroughly analyzed. pdf - 788 kB

J. Slota, E. Spišák - Comparison of the Forming - Limit Diagram (FLD) Models for Drawing Quality (DQ) Steel Sheets

     In this paper a comparative investigation of three mathematical models (Marciniak - Kuczynski model, Hill - Swift model and Sing - Rao model) as well as an empirical model proposed by the North American Deep Drawing Research Group (NADDRG) has been carried out. The yield criterion (1993), recently proposed by Hill, is used for the calculation of the limit strains in connection with the Swift’s instability condition for diffuse necking and with the Marciniak - Kuczynski analysis. The emphasis of this investigation is to consider these different approaches to predicting the FLD. Experimental results have been obtained for different low carbon steel sheets of drawing quality - FeP06 G and ZStE 220P as well as rephosphorised and micro-alloyed steel. It was compared, which theoretical model showing good correlation with experiment is suitable for materials mentioned above. pdf - 385 kB

M. Besterci, O. Velgosová, F. Lofaj, L. Kováč - Superplastic Deformation of Al-Al₄C₃ Composites

     Deformation of the Al-Al₄C₃ composites with different volume fraction of Al-Al₄C₃ phase was investigated at different temperatures (293 - 723 K) and different strain rates (2,5·10^–5 s^–1 - 1,0·10^–1 s^–1). At temperatures 673 - 723 K and at the highest strain rate of 1,0·10^–1 s^–1, a significant ductility increase was observed. TEM analysis suggests the onset of superplasticity may be the result of dynamic grain polygonization, grain slip and rotation, partial recrystallization and dislocation creep in the tested system, which is known as strain induced dynamic recovery. Increase of the volume fraction of secondary phase in the studied composite resulted in a shift from slip on grain boundaries controlled mechanism to the grain rotation controlled deformation mechanism. pdf - 434 kB

I. Peruš, G. Kugler, M. Terčelj, P. Fajfar - Flow Stress Prediction of Hot Compressed Tool Steel by CAE NN and Hyperbolic-Sine Equation

    Hot compression experiments are carried out on steel workpieces by means of Gleeble 1500 thermo mechanical simulator in wide range of temperatures 800 °C - 1200 °C with strain rates 0,1 s^–1, 1,0 s^–1 and 8,0 s^–1 and true strains of 0,0 to 0,5. Hot flow curves were estimated by means of the CAE neural networks. The methods of constant smoothness parameter and non-constant (ellipsoidal) smoothness parameter were applied. The use of the latter proved more exact (up to 3,4 %) and simpler if we compare it with the existing data for the flow curve prediction of tool steel by BP NN (up to 7 %), as the proposed method yields better results. The activation energy and other parameters in hyperbolic-sine equation were calculated according to the method proposed by McQueen et al. and according to the method recently proposed by Kugler et al. The latter yields better results at predicting the maximum values of hot flow curves. pdf - 656 kB

    The paper deals with the corrosion properties of TiN coatings in a 1 % Na₂SO₄ environment, which were determined by gravimetric analysis and corrosion potential measurement. The evaluation of the corrosion effect of the test electrolyte was completed by the samples surface observation by the LEICA macroscope before and after their exposure in a sulphate environment. pdf - 453 kB

D. Ćurčija, I. Mamuzić - Optimising of Lubrication Layer on the Transversal Strip Roughness

    Solutions of differential equations for smooth surfaces and transversal strip roughness with influence of inertial lubrication forces are analyzed. Ten factors influencing the height of lubricating film at input cross section of metal deformation zone are systemized according to rheological properties of lubricants, kinematics of technological process and geometric characteristics of rolling process. At dressing processes, inertial forces of lubricants have a weak influence on the height of lubrication film at input cross-section of deformation zone. Above the nominal height of lubrication layer the roughness of strip surface also determines the form of lubrication layer in a congruent way, while under the nominal height there is an inversion - concave planes of lubricating layer are transferred into convex ones. A correction of logarithm is presented for the processes of rotary cloning of the solutions of differential equations. pdf - 665 kB

I. Mamuzić - Mechanical Properties of Blasted Steel Sheet

    Blasting results in a change of properties of the substrate surface; among others, the strain hardening, the formation of residual stress and a change in the surface morphology take place in the surface layer. The paper deals with the influence of the blasted layer on the resulting mechanical properties of blasted steel sheet RSt 37.2 (11 523.1) with the thickness from 1,5 to 3 mm. While the sheet thickness decreases, the yield point exponentially increases and the deformation properties of blasted sheet decrease. The paper analyses the nature of these changes. pdf - 282 kB

B. Arh, F. Tehovnik, H. Ploštajner - Einfluss des elektromagnetischen rührens auf das makro und mikrogefüge von im strangguss hergestellten knüppel

    Die Anwendung des elektromagnetischen Rührens (EMR) beim Stranggiessen trägt zur besseren Qualität von Knüppeln bei. Einfluss von EMR auf das Erstarrungsgefüge ist beim Stranggiessen von Knüppeln 180 × 180 mm auf der Stranggiessanlage im Stahlwerk von Štore Steel untersucht worden. Durch die Anwendung von EMR wird eine Verbesserung der Oberflächengüte von Knüppeln und des Gefüges unter der Oberfläche und des inneren Gefüges erziehlt und zwar durch die Vergrösserung des mittleren globulitischen Bereiches der gegossenen Knüppel und Vorblöcke. Im Beitrag wird der Einfluss vom elektromagnetischen Rühren auf das Makro und Mikrogefüge von gegossenen Knüppeln vorgestellt. pdf - 401 kB

W. Waszkielewicz, A. Jończyk, D. Polak, A. Górniak - Analysis of Material and Information Flows in the Logistic System of a Selected Steelworks

    Tough competition on the steel product market causes the functioning of steelworks largely to depend on their abilities to respond flexibly to the market needs and offer the right product, at the right price and in the right time. A tool which is more and more commonly used for achieving this goal is logistics. The function of logistics in a production company is the optimal shaping of the stream of materials and information flowing through the company. The article reports the result of an analysis of material and information flows on the example of a selected metallurgical enterprise. pdf - 74 kB

W. Waszkielewicz, E. Staniewska, C. Kolmasiak - The Logistic Aspects of Supply Management in a Metallurgical Enterprise

    Using logistic approach in an enterprise by organizing optimal material streams becomes an essential instrument of rationalization of storage and supply management processes. The application of proper, solutions based on logistic rules in supply administration becomes indispensable considering necessity of storage cost reduction. Optimal management in procurement sphere demands a considering a lot of parameters impacting on supply level. In this paper chosen aspects of supply management of materials and raw materials, which are subjects of supplying in a steelmaking plant, are described. pdf - 110 kB