Kakhovskyi M. Self-shielding flux-cored wire for underwater welding of high-alloy chromium-nickel steels type 18-10.

Arc underwater welding is widely used in the repair of pipelines and equipment of offshore oil and gas fields and the repair of spent nuclear fuel storage pools at nuclear power plants or other elements made of high-alloy corrosion-resistant chromium-nickel steels. The thesis is devoted to the development of self-shielded flux-cored wire for mechanized and automated wet underwater welding of these steels. Physics-metallurgical features of the influence of the water environment during wet underwater welding of steel Cr18Ni10Ti on the interaction of filler metal with gases, the degree of oxidation of alloying elements, the stability of the arc combustion process, as well as the probability of hot cracks and pores in the weld metal. Using the mathematical method of experiment planning, the slag system of the powder wire core and the required number of gas-slag-forming components and deoxidizers were determined and optimized. The main factors of destabilizing influence of the aquatic environment are determined and the methods of increasing the stability of the arc combustion process by adding stabilizing components into the core of the wire are investigated. The advantages of the developed self-protective flux-cored wire over the existing manual arc underwater welding technology are the increased productivity of repair works, providing economic effect from shorter downtime of the NPP production cycle, shorter contact of divers-welders and personnel with radioactive environment and capabilities for further automation to exclude human participation in works under dangerous conditions.