A series of fused CaF2-SiO2-CaO-based fluxes geared towards submerged arc welding has been prepared with incremental TiO2 additions. Through systematic investigation on physical properties, quantitative relationship between TiO2 content and corresponding structural information has been established, and the roles played by TiO2 have been profiled. It is found that TiO2 has been introduced into the silicate network by acting as network-former, increasing the degree of polymerization while lowering the strength of the flux.

Water-quenched nickel slags from a flash furnace are treated by using a molten oxidation method, after which, the cooling rate and holding conditions are controlled, so the iron components in the nickel slags are precipitated as magnetite phases (Fe 3 O 4 ). This study explores the influence of cooling rate, holding time, and holding temperature on the crystallization and growth of magnetite phases. The results show that, with the reduction of cooling rate, phase compositions in oxidized slags changes insignificantly, while the particle size and the magnetite crystallization content (MCC) increase with fully developed crystals. As the holding time is increased, there is sufficient time for magnetite to develop into full crystals because the slags are kept within the range of the crystallization temperature for a long time. With the decrease of holding temperature, MCC gradually increases. By describing the kinetics of the isothermal magnetite crystallization according to the JMAK equation, the growth index of crystals (n) and the crystallization activation energy (E) are calculated to be approximately 0.48 and À192.37 kJ mol À1 , respectively.

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