Naumeiko S. Development of self-shielding flux-cored wire for welding low-alloyed steels in all attitude

The thesis is dedicated to problems of development of self-shielding flux-cored wire for all position welding of low-carbon low-alloyed steels. The processes of formation of gas shielding are investigated at melting of self-shielding flux-cored wire. The results of researches and calculations of processes of gas-generation are considered having taken into account kinetic parameters of reactions calculated on the basis of experimental data. Metallurgical and technological ways of lowering of nitrogen content in weld metal are studied. Perspective compositions gas and slag forming of the core of flux-cored wire for the solution of the given problem are determined. Conditions of a formation of multipass weld metal microstructure alloyed with nitrideforming elements are considered, and the alloying effects on the characteristics of strength and impact toughness are studied. In result of the carried out researches, the rational alloying system C-Si-Al-Mn-Ni-Zr and ranges of alloying are determined to ensurethe required mechanical properties of the weld metal. Results of development of an experimental-calculation method for prediction of welding and technological properties of self-shielding flux-cored wire on the basis of physical and chemical properties of salt-oxide slag systems are given. The effectiveness of application of the developed flux-cored wire is analysed.