Comparison of (D)CCT diagram of studied steels. Selected steels are used for manufacturing seamless tubes. Compared materials are steels 4130, X70 and P620Q. Diagrams were compared based on phases and their position. Metallographic analysis and hardness measurements were also made. Main focus of the study was dilatometric tests with(DCCT) and without(CCT) previous deformation. Third set of tests were performed to evaluate the effect of high austenitization temperature on resulting structure. Samples were heated with a constant rate to austenitisation temperature and then cooled with selected cooling rates in case of CCT and deformed before cooling in case of DCCT. Effects of the high austenitization temperature were much larger than that of deformation alone. Hardness tests showed very similar values for the samples with a deformation difference and more significant difference in the case of high austenitization temperature. Tests were made on plastometer Gleeble 3800 with optical module in VSB-Technical University of Ostrava.Keywords: Seamless tubes, dilatometric tests, 4130, X70, P620Q
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