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Michalek K.,VSB - Technical University of Ostrava | Gryc K.,VSB - Technical University of Ostrava | Tkadleckova M.,VSB - Technical University of Ostrava | Moravka J.,Materials and Metallurgical Research. Ltd. | And 3 more authors.
Archives of Metallurgy and Materials | Year: 2013

This work compares the experimental results of nickel concentration measurements in the intermixed zone of the continuously cast round blooms with a diameter of 525 mm using two types of submerged entry nozzles (SEN) - a straight-through nozzle and one with 5-ports. Based on determination of the system and optical interface in the blooms a detailed study of concentration profiles on the bloom surface in a small radius area, on the right side and then also on a cross-section of the blooms, was carried out. The results were further analysed using approximation models, and were to be used to verify the proposed model for predicting intermixed zones for a continuous casting machine, developed based on the results of physical and numerical modelling. © Warszawa - Krakow 2013. Source


Michalek K.,VSB - Technical University of Ostrava | Gryc K.,VSB - Technical University of Ostrava | Tkadleckova M.,VSB - Technical University of Ostrava | Moravka J.,Materials and Metallurgical Research. Ltd. | And 3 more authors.
Materiali in Tehnologije | Year: 2012

This work compares the experimental results of nickel-concentration measurements in the intermixed zone of the continuously cast round blooms with a diameter of 525 mm using two types of submerged entry nozzles (SEN) - a straight-through nozzle and the one with 5-ports. Based on the determination of the system and optical interface in a bloom, a detailed study of the concentration profiles on the bloom surface in a small-radius area, on the right-hand side, and then alsoon the cross sections of the blooms was carried out. The results were further analysed using the approximation models, and were used to verify the proposed model predicting the intermixed zones for the continuous-casting machines. The developed model was based on the results of the physical and numerical modelling. Source


Mohyla P.,VSB - Technical University of Ostrava | Kubon Z.,Materials and Metallurgical Research. Ltd. | Cep R.,VSB - Technical University of Ostrava | Janasek A.,VSB - Technical University of Ostrava | Samardzic I.,Josip Juraj Strossmayer University of Osijek
Metalurgija | Year: 2014

The T24 steel represents the new generation of low-alloyed creep resistant steels with higher creep resistance and lower carbon content. It was designed as prospective material for membrane waterwalls of ultra super critical (USC) power plants, enabling to avoid preheating and post weld heat treatment (PWHT) during welding. However, our investigations concerning secondary hardening of vanadium containing low-alloyed steels show that non-tempered welded joints undergo a significant increase in hardness during exposure to operating temperature. The results then imply that PWHT of T24 steel welds is necessary and this idea is at present supported by the occurrence of several troubles with new installations of USC blocks in Europe. Source


Mohyla P.,VSB - Technical University of Ostrava | Kubon Z.,Materials and Metallurgical Research. Ltd. | Cep R.,VSB - Technical University of Ostrava | Samardzic I.,Josip Juraj Strossmayer University of Osijek
Metalurgija | Year: 2014

This work is focused on testing and evaluation of creep properties of P92 base material (BM) and welded joints (WJ) as well. Up to date results of creep rupture test of P92 base metal and welds are presented in this article. Creep rupture strength (CRS) of WJ initially reaches values close to the BM, with longer times to fracture and especially at higher temperatures, creep strength of WJ decreases and the data is closer to the lower 40 % tolerance band. Source


Strilkova L.,Materials and Metallurgical Research. Ltd. | Kubon Z.,Materials and Metallurgical Research. Ltd. | Vodarek V.,VSB - Technical University of Ostrava
METAL 2010 - 19th International Conference on Metallurgy and Materials, Conference Proceedings | Year: 2010

Two variants of P23/P91 heterogeneous welds were studied. The composition of filler material in Weld A corresponded to that of P91 steel, whilst for Weld B the low alloy filler material of P23 type composition was used. Results of creep rupture tests on the cross weld specimens are close to, or slightly below, the lower limit of the ±20% scatter band around the standardized curve for creep strength of the P23 steel. Creep rupture tests were performed at temperatures of 500, 550 and 600°C with time to rupture up to 60 000hours. Optical microscopy investigations and hardness measurements were carried out on longitudinal sections through ruptured cross weld specimens in order to reveal the effect of testing parameters (temperature, stress) on the preferred location of creep failure. It has been found that in both weld variants creep damage can develop simultaneously in several parts of the cross-weld specimens. The preferred failure locality during testing at 550 and 600°C was the partly decarburized zone of the low alloy P23 steel (or WM23). © 2010 TANGER Ltd., Ostrava. Source

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