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The paper focuses on rolling conditions, microstructure and mechanical properties of two different steel grades chose from the modern steel group called Advanced High Strength Steels (AHSS). The analysis carried out includes many tests and experiments such as: dilatometric and plastometric tests, Gleeble simulations of hot rolling, strip cooling after rolling and hot rolling of steel samples in laboratory conditions. For whole experimental investigations two steel grades have been chosen, namely Dual Phase (DP) and Complex Phase (CP) steels. The own casts of DP and CP steels were made, from which the samples for laboratory tests were prepared. In order to determine the cooling curves and the start and finish temperatures of phase transformations, the dilatometric investigations were performed. The designed CCT diagrams were the fundamentals of the planning of further research, e.g. computer simulation and hot rolling in laboratory conditions. On the basis of FEM analysis and plastometric tests (Gleeble), the thermo-mechanical conditions resulting in a fine-grained structure were designed. The level of diversified microstructure and thus wide range of mechanical properties by the use of laboratory hot rolling and multi-stage cooling processes were determined. It was pointed out that apart from chemical composition the thermo-mechanical rolling conditions have great influence on phase composition and mechanical properties of the investigated DP and CP steel strips. The results of the analysis carried out in this work provide useful data for the designing of thermo-mechanical rolling of DP and CP steel strips, which have multiphase microstructure and diversified mechanical properties.
Keywords: DP and CP steel, thermo-mechanical rolling, CCT curves, mechanical properties, hot workability© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.