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 slabs the centerline segregation pattern will become thin and stretch 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.

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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.

A laboratory‐scale device was constructed for treating small‐size steel sheet specimens in an analogous manner to the acid pickling production line. This descaling simulator comprises three tanks for hydrochloric acid and another one for rinsing the samples, providing an automated sample transfer with a free selection of all processing parameters such as motion rate, residence time, temperature, etc. A detailed description of the simulator device will be given. Besides the pickling loss which was the primary parameter measured, surface roughness of the samples, Raman spectrum of the surface, and scale thickness were also determined in some cases. Scale‐related pickling loss and overpickling rate were determined for a number of steel qualities. The role of the pickling liquors of each tank was studied, and the descaling efficiency at various acid temperatures was assessed. A statistical analysis was used for estimating the fluctuation in the scale thickness on the hot‐rolled specimens. Results obtained with the descaling simulator were also checked with an optical imaging of the scale and a composition depth profile analysis. The scale thickness obtained from weight loss measurement was in good agreement with the direct scale thickness measurement.

A lot of phases can be present in the structure of cast iron depending on the quality and the heat treatment processes. By using the color etching, the different phases – e.g. the carbides – can exactly be identified and their quantity can be measured. The carbide of iron (cementite) or other types of carbides existing in the structure have a significant influence on the properties of cast product therefore strict prescriptions regulate their quantity mainly in case of making cast products for the motor-car industry. In the course of our experiments performed by using the color etching, we proved that carbides can be detected and their quantity can be determined by using the digital image processing method by means of the different reagents. Other different characteristics of the structure can become visible by means of the reagents used during the color etching. During the investigations, it was experienced that some of the ferrite grains are etched in different color. This is probably connected to the orientation of grains as the thickness of interference-film is different on the anode phases having different orientation and therefore they color in different tones.