Preparation And Properties Of Unfired Al₂O₃-MgO-CaO Compound Phase Ladle Lining Brick

China's iron and steel metallurgy industry is in the stage of structural industry upgrading under the new normal,which is changing from traditional quantity to quality to high-quality refinement.With the continuous progress of clean steel smelting technology,secondary refining as the main means of clean steel smelting process,the requirements for ladle lining refractory materials are constantly improving,so it is urgent to study the new non-carbon steel lining materials.Based on the theory of hypoxia potential,Al₂O₃-MgO-CaO composite material(AMC composite material in this paper)with CA₆and MA as main crystal phase was synthesized by domestic and foreign scholars by sintering method.This material has potential application value in the field of iron and steel metallurgy.However,AMC complex phase material prepared by solid phase sintering method has small volume density,large obvious porosity and poor mechanical properties.AMC complex phase material prepared by hot pressing sintering method has compact structure,but high production cost and difficulty in mass production.The analysis of Al₂O₃-MgO-CaO ternary system is based on thermodynamics,dynamics,with industrial alumina,light burning magnesium powder and quick lime powder as raw material,using the synthesis method of AMC fused heterogeneous material,testing different smelting area synthesis of AMC of material bulk density,porosity,using X-ray diffraction(XRD)and scanning electron microscopy(SEM)on the phase composition and microstructure were characterized,and its high temperature melting and cooling crystallization mechanism analysis.The results showed that AMC multiphase material showed stepwise crystal evolution,the main crystal phase of the synthetic material was CA₆and MA,a small amount of CM₂A₈and corundum phase,with the decrease of cooling rate,the main crystal phase gradually changed to CA₂and MA,and the CM₂A₈gradually disappeared.The bulk density of the composite material was up to 3.2 g·cm^-3,and the apparent porosity was3.8%.Due to the different cooling rates of each region inside the molten lump,the composition of the synthetic material is different,and a large number of platy CA₆is generated near the sand area,with good MA crystallization.Due to the slow cooling rate,the central region of the molten lump has less CA₆production,and there are more unreacted corundum phases.Synthesis method of AMC in the fused,on the basis of heterogeneous materials,based on the tabular corundum,magnesium aluminate spinel,fused magnesia,homemade fused AMC complex phase material as raw material,with aluminum magnesium cementing agent as binder,preparation of ladles with baking-free brick,testing its bulk density,porosity,strength and line after burning rate,thermal residual strength retention after the quake,slag resistance,and by using X-ray diffraction(XRD)and scanning electron microscopy(SEM),the phase composition and microstructure were characterized,and the results showed that with the introduction of 3%AMC composite material as the substrate,the maximum flexion strength of the burning-free brick reaches 15.6 MPa,the thermal shock performance is the best,and the retention rate of thermal shock residual strength is14.3%,which is 19%higher than that of the burning-free brick without AMC.When6%AMC composite material is introduced,the compressive strength of burning-free brick reaches 86 MPa,and the slag resistance of burning-free brick is the best.However,with the introduction of more than 6%,the sintering performance of the burnt-free brick decreased significantly,and the thermal shock and slag resistance of the burnt-free brick also decreased.The introduction of AMC aggregate improves the thermal shock performance of burning-free brick obviously.With the decrease of particle size,the introduction of 1?0 mm granular aggregate makes the binding of aggregate and matrix more closely.The compressive strength of the burnt-free brick is increased by 15%,and the retention rate of thermal shock residual strength reaches14.5%,which is 21%higher than that of the burnt-free brick without AMC aggregate.