Qingcai Liu

Determination of CC slab solidification using nail shooting technique

Abstract The technology of nail shooting was improved and used to study the transverse shape of the solidified shell during steel continuous casting. Three locations across the slab width (1/2, 1/4 and 1/8) were measured by nail shooting and which indicated a larger solidification coefficient and longer liquid core in the slab at higher casting speeds. The solidified shell across the slab width direction was non-uniform due to uneven secondary spray cooling. The point of final solidification at locations 1/8 and 1/4 was much longer than the position between the slab centre and location 1/4, leading to a long solidification end of >2 m, which is poor for the application of dynamic soft reduction. A mathematical model was developed to simulate the growth of the solidified shell and which was in good agreement with the measurements measured by nail shooting. Based on the measurements and simulations, the water spray pattern was improved, making the solidified shell more uniform. Dynamic soft reduction was then optimised resulting in reduced centreline segregation.

Corrosion resistance of MgO–C refractory to smelting reduction slag containing titania

Abstract Interactions between smelting reduction slags containing titania (0·2-20 wt-%TiO2) and MgO-C refractories have been investigated by stationary immersion and rotary immersion at temperatures of 1773-1923 K. The relationship between the concentration of TiO2 in the slag and the corrosion rate of the refractories, the effects of slag basicity (CaO/SiO2), and the effect of the temperature of the molten bath on the corrosion rate were examined. Increasing the TiO2 concentration in the slag caused an increase in the corrosion rate of the MgO-C refractories. The corrosion rate also increased when the temperature was increased. Increasing the basicity of the acid slag decreased the corrosion rate, but this effect was not evident when the basicity of slag exceeded 1·0. The corrosion mechanism of MgO-C refractories in smelting reduction melts containing titania involves the oxidation of graphitic carbon by TiO2 and the formation of a deterioration layer containing Ti and TiC, together with the reaction of matrix MgO with slag to form MgAl2O4, MgCaSiO4, and MgSiO3.

Distribution of heavy metals from iron bath-melting separation process applied to municipal solid waste incineration fly ash.

Fly ash generated from municipal solid waste (MSW) incineration is frequently classified as hazardous material and requires special disposal. The management of the large amount of fly ash has caused increasing problems in China. This work describes a novel approach for melting MSW incineration fly ash, and the distribution of heavy metals was characterized during the iron bath‐melting separation process. Four hundred grams of pelletized fly ash was fed into the furnace in molten iron bath atmosphere. After the melting separation process, the distribution of heavy metals in samples and the leaching characteristics of the slag were investigated. The results indicated that iron bath‐melting promoted the transfer of Cr, Mn and Cu from the slag phase to the iron phase, which also improved Zn and Pb volatilization. The leaching concentrations, determined by the Chinese Standard Method (rollover leaching procedure) of the target metals of the slag from leaching tests were lower than the Chinese regulatory thresholds. Therefore, this method was proposed as an environmentally friendly technology to achieve a satisfactory solution for MSW incineration fly ash management.

Weldability and Microstructure of Nickel-Silicon Based Alloy

The NiSix based alloy typically has poor weldability due to its lower ductility. A limited amount of work has been performed on the weldability of NiSix based alloys. Therefore, the effect of heat treatment and welding parameters on weldability of the alloys, and the relationship between the weldability and microstructure were studied. The results show that the as-cast Ni-Si-Nb-B alloy (Ni 76. 5%, Si 20%, Nb 3%, and B 0. 5%) could be successfully welded after preheating at 600 °C. The welding procedure should be performed on the alloys before any heat treatment and a preheating at 600 °C should be used. The fusion zone is harder than the matrix due to a large amount of γ phase and a finer microstructure. The cracks are predominantly intergranular in heat affected zone and associated with the needle-like γ phase. The heat treatment before welding increases the tendency of cracking in the fusion zone.