Vliv teploty předehřevu na tvrdost TOO heterogenního svarového spoje

Abstract

This diploma thesis focuses on studying the influence of preheating temperature on the properties of a heterogeneous welded joint, specifically on the hardness and microstructure within its heat-affected zone (HAZ). The experimental part deals with a single-layer fillet joint formed between fine-grained carbon ferritic-pearlitic steel and corrosion-resistant austenitic steel. Welding was carried out using the gas-shielded metal arc welding method (MAG) utilizing a rutile flux-cored wire. The primary variable monitored in this work is the preheating temperature, which influences subsequent metallurgical processes in the heat-affected zone during the cooling of the weld joint. To comprehensively assess the quality of the welded joint, both non-destructive testing (NDT) and destructive tests were employed. These included Vickers hardness testing, microhardness measurements and detailed metallographic examinations of the macrostructure and microstructure using light microscopy and scanning electron microscopy. The aim of the thesis is to analyse hardness changes in the HAZ as a function of the preheating temperature and to verify whether the achieved values meet the acceptance criteria according to relevant standards, such as ČSN EN ISO 15614-1.