Duchenko A. Fluxes with low content of harmful impurities and limited oxidative ability for welding and surfacing of low alloy steels

The dissertation is devoted to the study of pyrometallurgical processes in industrial flux melting furnaces. Recommendations are developed concerning the reduction of the content of harmful impurities of sulfur and phosphorus in the slag melt. Thermodynamic models of slag melt desulfurization and dephosphorization have been developed. The influence of flux diplexing technology by the duplex process on the hydrogen content and the kinetics of its desorption at heating, the diffusion hydrogen content in weld metal using melted fluxes and agglomerated fluxes containing fused half-products in the composition have been investigated. The influence of the technology of melting by the duplex process method on the thermodynamic activity of oxygen ions in the slag melt is determined. The level and kinetics of thermodynamic activity of oxygen ions in slag melting with the introduction of deoxidants in it have been studied. The dependences of oxygen content in droplets and deposited metal, the transition of the reciprocating alloying elements (C, Si, Mn) from the electrode wire to the weld metal during welding under the fluxes of the MgO - Al2O3 - SiO2 - CaF2 system on activity of oxygen ions and silicon oxide in slag melt are obtained. Based on the developed recommendations for conducting the melting process of welding fluxes by the duplex process, the change № 4 to TU 05416923.049-99 "Fused welding fluxes " is developed and approved. According to it, the maximum sulfur content in fluxes is reduced from 0.11 to 0.09%, and phosphorus content - from 0.12 to 0.10%. The fused flux AN-69 was developed and its experimental-industrial test was performed at the State Enterprise under the Ministry of Defense of Ukraine "Kyiv Mechanical Plant" during the restorative surfacing of the vertical shaft of the excavator E652. It was proposed using of fused intermediates in the production of agglomerated fluxes. Increasing in the content of molten intermediate in the composition of the agglomerated flux leads to a decrease in the tendency of the flux to sorb moisture from the surrounding atmosphere and reduces the diffusion hydrogen content in the weld metal during welding. The developed fluxes of the ANKS-28A and ANK-43 brands with the content of the fused intermediate of 15 and 40% respectively provide the diffusion hydrogen content in the weld metal to be of 3.5 and 2.6 cm3/100 g. The agglomerated flux of the ANK-43 brand intended for welding of designs from carbon and low-alloy steels of strength category up to X80 inclusive. The agglomerated flux of the ANKS-28A brand in combination with the Sv-10NMA wire is recommended for use at production of bridge designs from 06GBD steel at operating temperature to - 40°C.