The theoretical and numerical calculation and experimental study on soft contact electromagnetic casting forming
Based on classical electromagnetic theory, the electromagnetic pressure calculation model and the formula of electromagnetic casting forming have been established. Theoretical and numerical results indicated that the frequency, current density, relative permeability of alloy melt and resistivity can also influence the effect of electromagnetic pressure. Meanwhile, the effect of metal physics properties parameters on the value of electromagnetic pressure is more complicated. The needed magnetic field for casting Al-Si alloys liquid column with length of 0.05m in experiment was very close to the theoretical value. This result indicated that the formula of electromagnetic casting forming can be used to guide experiments and the actual industrial production.
Solidification characteristics of special alloys under alternating magnetic field
Using superalloy, K403, as experimental material to investigate the solidification characteristics of the mediate/small special alloy under alterating magnetic field with the aim of understanding further the fine-crystallization mechanism and the optimization way of the solidification micro-structure. In the process of investigation, the solidification characteristics of the contactless and the soft-contact electromagnetic shaping, as well as the affection of electromagnetic stirring, susceptors and drawing speed were experimentally studied; and thereby the fine-crystallization mechanism of the solidification micro-structure of electromagnetic shaping was analyzed. The results show that, the tenuous and parallel dendrite can be obtained by using susceptors; the first dendrite arm spacing is decreased from 120μm to 80μm while the drawing speed increased from 3.2mm/min to 9.8mm/min; the main mechanism of the solidification microstructure for the contactless electromagnetic shaping is the secondary dendrite arm's peeling off amd that for the soft-contact electromagnetic shaping is the dendrite point's cracking.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.