Synthesis Of Doloma Clinker And Its Resistance To Hydration And Slag

Natural dolomite was selected as the starting materials to prepare the MgO-CaO refractories for steel refining with a low price, and the effects of dolomite powder size, sintering temperature and additives on the density and hydration resistance of synthesized doloma clinker were also studied in this paper. Doloma bricks were prepared with clinker which was synthesized from industrial dolomite powders with sintering aids, and the slag resistance of the doloma bricks was investigated by two test methods. The results were list as following:Dolomite powder size has major effects on the density of synthesized doloma clinker. When sintered at 1650℃, 3h, dense doloma clinker can't be obtained from coarser dolomite powders containing additives which can enchance sintering by providing a path for rapid material transfer. After grinding, the fine dolomite powder can be decomposed completely at a lower temperature. And the high reactivity of the produced MgO and CaO resulting from the decomposition of dolomite would accelerate the densification of doloma clinker. As a result, the doloma clinker with 56% CaO and a density of 3.39g/cm3 can be prepared without aids(additives) at 1650℃, 3h.Sintering temperature also has some effects on the density of synthesized doloma clinker. However, the effects are no longer notable when sintering temperature over 1650℃Adding a few sintering aids into dolomite powder, there is little difference for doloma clinker sintered at different temperature, but high aids would result in much liquid at relatively low temperature, which would produce closed pores, prevent the release of CO2 from the decomposition of dolomite powder and inhibit the densification of doloma clinker.For the ground dolomite powder, sintering aids and increasing temperature just promote the growth of CaO and MgO crystal grains, but have little influence on the density and hydration resistance of synthesized doloma clinker. The hydration rate of doloma clinker is controlled by the vapor diffusion from the surface to the interior of the clinker.Sintering aids for the synthesis of doloma clinker decrease the slag resistance of doloma bricks to some extent, and the deterioration of the slag resistance is more notable when Fe2O3 was selected as sintering aid. For static crucible slag corrosion test, the eroded crucibles showed the same reactive layers for the slags with different basicity, and the layer sequence is slag layer, enriched MgO layer, cranny layer and origin layer. The slag resistance of doloma brick is mainly determined by the amount and the viscosity of the liquid at high temperature, and doloma bricks with more low-viscosity melt at high temperature will have worse resistance to slag corrosion. However, the enriched MgO layer formed in doloma bricks during slag corrasion also has notable effects on improving slag resistance.In the dynamic slag corrosion experiment conducted in vacuum induction furnace, there is no enriched MgO layer in doloma bricks, and the slag erodes doloma samples more severely than that in static crucible slag corrosion experiment. 4# samples containing more TiO2 have a bit better slag resistance than other samples. This might be contributed to the entrance of TiO2 in the melted slag and the increase of the slag viscosity in the transition layer between the sample and slag, which cushion the scouring of steel and slag against the sample surface, and prevent slag corrosion and infiltration into the samples.