Papers by Keyword: MgO·Al₂O₃

Abstract: Consumable electrodes of H13 die steel with different magnesium contents were produced by medium frequency induction furnace. Effects of magnesium on deoxidation rate and inclusions in consumable electrode were studied. Results show that the deoxidization ability of Fe-Al-Mg alloy is better than that of aluminum and the dissolved oxygen content is decreased with the increase of magnesium content in liquid steel. The deoxidation rate is less than 15 % for steel without magnesium and more than 24 % for steel with 20 × 10^-4 wt% magnesium content. The number of inclusions is decreased with the increase of the magnesium content in steel. Because tiny MgO·Al₂O₃ inclusions are generated in the steel containing magnesium, the number of inclusions with size less than 2 μm is increased obviously and the number of inclusions with size larger than 5 μm is decreased. Some VN and VN-TiN inclusions with size less than 10 μm are precipitated taking MgO·Al₂O₃, MgO, MgS as cores in the steel containing magnesium.

Abstract: Micron, sub-micron and nanometer sized MgO•Al2O3 ultra-fine powders were prepared by gel precipitation, solid-phase synthesis, sol-gel and flame throwing pyrogenation methods. XRD analysis showed that all of the ultra-fine powder is pure with the single MgO•Al2O3 spinel phase. The powder size was measured by laser granularity analyzer and the average size is 1780, 505 and 60 nm with a quite uniform distribution of particle size. MgO•Al2O3 spinel powder with different granularity were sprayed into molten low carbon steel in MgO crucible and MoSi2 furnace at 1873 K. Quantitative microscopic examination showed that big particle inclusions reduce and small particle inclusions increase, as a result, the average size reduce. Data comparison from spraying powders with different size showed that spraying MgO•Al2O3 of nanometer tends to cause more small inclusions in molten steel. The sprayed steel samples were rolled and heat treated for the mechanical properties tests, which showed spraying nanometer MgO•Al2O3 is the best way to improve mechanical property of steel.