Hodnocení svařitelnosti oceli S690QL

Abstract

The bachelor's thesis deals with the evaluation of the weldability of high-strength quenched and tempered steel S690QL. The theoretical part of the work is focused on the metallurgical properties of the material, factors influencing the formation of cold cracks and the specifics of temperature cycles at high cooling rates. The experimental part is devoted to the implementation of welded joints on sheets with a thickness of 4 mm using a fiber laser with a power of 4.5 kW. The research focuses on surface preparation for process stability and the resulting mechanical properties. The main output of the work is the analysis of the hardness of HV10 and HV5, which found a significant increase in hardness in the heat-affected zone due to the formation of a martensitic structure. The results are compared with the requirements of the ČSN EN ISO 15614-1 and ČSN EN ISO 15614-11 standard and technological recommendations are formulated on their basis, in particular the need for preheating to reduce the maximum hardness of the joints.