In this thesis we have studied the effects of thickness on the size and distribution of ferritic crystal grains in relation to the mechanical properties obtained in the rolled and normalised states. The theoretical part deals with the basic understanding of structural steels, focusing on the steel S355J2 and the corresponding standards. This is followed by a description of hot rolling processes and their effects.
The experimental part focuses on a comparison between two different thicknesses of S355J2 steel in different states. We have compared the results from the as-rolled condition with laboratory normalised samples and additionally evaluated the influence of normalisation time and temperature on the crystal grains and mechanical properties. The mechanical tests include tensile tests, toughness and hardness measurements. The microstructural analysis was carried out using light optical microscopy.
The main objective is to understand and record the homogeneity of the microstructure over the entire thickness cross-section in correlation with the mechanical properties in both the as-rolled and normalised states. This forms the basis for research into new steels and the extension of existing thickness classifications.
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