Research On Fabrication And Performance Of The Active Flux-cored Wire For Arc Welding Of Titanium Alloy

The gas tungsten arc welding is one of the most commonly used processing methods in joining titanium and its alloys, which can produce stable arc and high quality welds. On the other hand, the penetration of the weld is so small that the gas tungsten arc welding is not suitable for the welding of the thick plates. The E. O. Paton Institute has proved that the A-TIG process can effectively increase the penetration depth in a single pass and reduce the sensitivity of pore. They also have successfully applied the A-TIG process for a variety of metal, such as steel and titanium. In recent years, the A-TIG process has become a hot topic in the field of welding. The main weaknesses of A-TIG process are the uneven coating and the inaccurate content of the flux pastes. In this thesis, the flux cored wire is introduced to the welding of the titanium, and a new flux cored wire with excellent performance is investigated.The effects of five fluorides on the arc stability are explored, including magnesium fluoride, rare earth fluoride, sodium fluosilicate, potassium fluosilicate and cryolite, as well as the formation of weld and the cross section of weld. The results suggest that three fluorides(magnesium fluoride, rare earth fluoride, sodium fluosilicate) have positive impacts on the welding usability.After confirming the sort and proportion of the fluorides, the effects of the chloride and oxide on the welding usability are investigated. The experimental results are as following: DC TIG as welding model, the optimized formula of Mg F2-Rare earth fluoride-Ca F2- Cd Cl2, the powder filling ratio matching the current value. Then, the mechanism of the flux-cored wire is studied, and the deep penetration can be inferred to the arc constriction and the increase of the heat production in the anode.The weld microstructure of weld zone is hexagonal martensite, and the hardness is higher than that of the heat affected zone and the base metal. The main components of slag are Mg F2, Rare earth fluoride and Ca F2. The mechanical property of weld is in normal range.