Libor Čamek

Industrial Application Of Two Numerical Models In Concasting Technology

This paper deals with the causes of a transversal crack in a steel slab with a 1300x145 mm cross-section by means of two numerical models. Samples were taken from and around the crack in order to analyze the concentration, as well as the chemical heterogeneity y of the constituent elements and impurities. Simultaneously, the concentration of elements at the surface of the crack was measured after the crack was opened. The heterogeneity of elements was analyzed by the JEOL JXA 8600/KEVEX device. The measurement results were processed using mathematical statistics. The chemical heterogeneity of elements in the steel matrix around the crack, and at the crack surface, had been evaluated with the help of heterogeneity y parameters, i.e. the arithmetic mean of concentration, the standard deviation of concentration and the index of heterogeneity of the analyzed elements. The results proved that there was an internal crack initiating immediately below the solidus temperature and consecutively propagating.

Optimization of a Concasting Technology via a Dynamic Solidification Model of a Slab Caster

Solidification and cooling of a continuously cast steel slab and the heating of the mould is a very complicated problem of transient heat and mass transfer. This original three-dimensional (3D) numerical model is capable of simulating the temperature field of a caster. The numerical computation has to take place simultaneously with the data acquisition—not only to confront it with the actual numerical model, but also to make it more accurate throughout the process. The utilization of the numerical model of solidification and cooling plays an indispensable role in practice. An important step in this analysis is to determine the necessary quantities in the course of concasting. The software enables data acquisition in real time, which is necessary for optimization. This is ensured by the correct process procedure: real process → input data → numerical analysis → optimization → correction of process. This procedure is necessary for optimization (i.e. maximization of the quality of the process)—especially when reacting to specific needs and conditions in the operation.

Prediction Of Cracks Of The ContinuouslyCast Carbon-steel Slab

This paper deals with surface morphology, the mechanism of origination and causes of cross cracking of a concast low alloy manganese steel slab. The cross cracking was identified in a steel slab with a sectional size of 145x1300 mm and the length of the asymmetrical cracking was approximately 600 mm. The light microscopy and the scanning electron microscopy have been applied for determination of the metallographic structure of steel and for the study of micro-morphology and the trajectory of cracking. The chemical microheterogeneity of the steel matrix and the surface of cracking have been estimated by means of an X-ray micro-analyser JEOL JXA 8600/KEVEX. The analyses of Al, Si, P, Ti, Cr, Mn and Fe on the metallograpic samples of the matrix of steel, of the neighbourhood of cracking and of the surface of cracking have been realized. It has been found that the cross cracking is characterized by high macro-heterogeneity of manganese, carbon and sulphur. The causes of cross cracking have been explained by means of a thermokinetic calculation of a slab transient temperature field and by mean of an application of the theory of physical similarity and dimensionless criteria. It has been confirmed that two solidification cones are formed asymmetrically in the course of slab solidification and it is probable that the asymmetrically passing crack initiated on one of these two apexes. Computer Methods and Experimental Measurements for Surface Effects and Contact Mechanics VII 111