New technology for production of granular adding material with nanomodifying additives for steel arc welding

The chemical analysis of metal seam showed that introduction of titanium dioxide with MCA intensifies transition of Al2O3 from slag into metal pool and provides double concentration of titanium in the seam compared to the one which appears in the interaction of bathtub with melted flux AH-47 without TiO2 additives. The presence of oxides of titanium and aluminium of endogenous origin in the melt leads to formation of refractory particles with the center of TiO2 and Al2O3 in it. These particles are the centers of crystallization in the tail part of the molten pool and they remain in seam metal in the form of evenly distributed fine nonmetallic inclusions, which have crystallographic affinity with a matrix (а-iron). That provides the fine-grained seam structure with the raised and stable strength characteristics. This article compares the existing and developed technologies for production of MCA. The granulometric analysis of the powder TiO2 has demonstrated that when MCA is processed in the planetary mill, particles of titanium dioxide are crushed to a nanodimensional order. It is shown that the preparation of MCA in high-energy planetary mill (due to double increase of durability in coupling of the modifier with granulate) provides its stable structure, increases the cold resistance (20-25%) and stability of strength characteristics along the length of welded seam. Metalgraphic researches determined that the fine-grained structure which linear size of grain is twice smaller than the one obtained in the old technology welding is formed in a seam. However the direct introduction of nanomodifiers in a molten pool through the flux or an electrode wire is not efficient because of their deactivation and high temperature in welding zone. Therefore it was offered to use modifiers in the mix with the cooling macroparticles in case of automatic welding of a bridge metalware under flux using metalchemical additive (MCA). The MCA consists of a chopped welding wire (granulate), the powdering modifying chemical additive TiO2 in the mixer with the displaced rotation axis «piyanay bochka» accorfint to the existing technology. However this MCA's technology doesn't provide the stable durability of modifier's coupling with the granulates surface and it is not able to control its structure under production conditions that, certainly, negatively affects on stability of welded connections' properties. Therefore one of the main task in this research was to improve the existing technology to increase durability of the modifier' coupling with granulate. Welding is one of the main technological methods to connect details and nodes in production process. However 70-80% of metalware destruction occuring in operational process are related to welded connections. These destructions are mainly fragile. The increased firmness of welded connections against the fragile destruction is needed due to development of northern and east regions in Russia. The most perspective method to increase cold resistance of welded connections is the crush of seam metal grain by means of nanomodification.