Study On Preparation And Properties Of MgO-ZrO₂ Composite Refractories

Refractory materials are closely related to the development of refining processes.They promote each other and develop together.The quality and variety of refractory materials play a key role in the development of refining processes.The performance of the ladle gas permeable plugs is important for the efficient operation of the ladle refining process.The current gas permeable plugs are mostly corundum and corundumspinel permeable components,which are prone to blockage and damage during use.And,the developed magnesium permeable components have poor thermal shock resistance.These factors greatly affect the production efficiency and cost of the refining process.Therefore,in order to improve the thermal shock resistance of MgO gas permeable plugs and increase their service life,the paper studies the properties of MgO-ZrO2 refractory materials.In this paper,MgO-ZrO2 refractories were prepared by light-burned magnesia and monoclinic zirconia.The effect of ZrO2 addition,sintering temperature and additives on the MgO-ZrO2 refractory was studied.The influence of these factors on the sintering properties,mechanical properties,thermal shock resistance and slag corrosion resistance of MgO-ZrO2 refractories are also studied.Through the above research,the major conclusions of this paper are as follows:(1)The sintering temperature and the ZrO2 addition amount have a significant effect on the properties of MgO-ZrO2 refractories.With the increase of sintering temperature,the bulk density of MgO-ZrO2 refractories increased,the apparent porosity decreased,and the relative density of the samples increased.When the samples were kept at 1600℃ for 2 h,the MgO-ZrO2 refractories could obtain well efficiency of space filling.When the mass fraction of ZrO2 is 15%,the MgO-ZrO2 refractory has the best performance.The bulk density of this sample is 3.39 g·cm-3,apparent porosity is 5.51%,relative density is 88.91%,cold compressive strength is 205 MPa,and it has good thermal shock resistance and slag corrosion resistance.When the sintering temperature was 1600℃,ZrO2 in the MgO-ZrO2 refractory material is more evenly distributed and denser in structure with the increase of the mass fraction of ZrO2.The addition of ZrO2 significantly improves the slag corrosion resistance of MgO-ZrO2 refractories.As the ZrO2 addition amount increases,the slag erosion depth decreases significantly.(2)The addition of CeO2 has a significant effect on efficiency of space filling and thermal shock resistance of MgO-ZrO2 refractories.The addition of CeO2 increases the efficiency of space filling of the MgO-ZrO2 refractory,which reduces the apparent porosity,increases the bulk density,and increases the relative density.The MgO-ZrO2 refractory with 20%ZrO2 and 2%CeO2 have the best performance.Its bulk density of this sample is 3.54 g·cm-3,apparent porosity is 3.64%,relative density is 90.02%,and cold compressive strength is up to 269 MPa,and it has good thermal shock resistance and slag corrosion resistance.CeO2 promotes sintering of MgO grains.Simultaneously,CeO2 stabilizes ZrO2 in the sample.With the increase of CeO2 addition,the phase of ZrO2 in MgO-ZrO2 refractory material changed.The phase of ZrO2 transforms from cZrO2 to t-ZrO2 with the increase of CeO2 addition amount.Meanwhile,the addition of CeO2 improves the cold compressive strength,thermal shock resistance and slag corrosion resistance of MgO-ZrO2 refractories.(3)The addition of TiO2 significantly increases the efficiency of space filling of MgO-ZrO2 refractories.The apparent porosity of MgO-ZrO2 refractories decrease,the bulk density increases,and the relative density increases.Moreover,TiO2 improves the cold compressive strength,thermal shock resistance and slag corrosion resistance of MgO-ZrO2 refractories.The MgO-ZrO2 refractory with 10%ZrO2 and 1%TiO2 has excellent comprehensive performance.Its bulk density is 3.58 g·cm-3,apparent porosity is 1.01%,relative density is 95.75%,and old compressive strength is 325 MPa,and it has good thermal shock resistance and slag corrosion resistance.The addition of TiO2 makes the micro structure of MgO-ZrO2 refractory material compact,and the silicate phase in the sample is obviously reduced.Silicate phase and CaO·TiO2 phase exist in the inter-particle voids in the form of arc islands.Thus,the addition of TiO2 improves the overall performance of the MgO-ZrO2 refractory.