Preparation And Properties Of Alumina-magnesia Gunning Materials For Steel Ladles

With the development of the refining technology outside the furnace,the working conditions of the ladle lining are getting worse,but the ladle spray repair technology can shorten the maintenance time of the ladle lining and increase the ladle turnover speed.Al₂O₃-MgO gunning material has excellent mechanical properties and slag resistance,but it is prone to spalling during use.This paper first analyzes the damage mechanism of the Al₂O₃-Mg O gunning materials currently used in a factory,then prepares the Al₂O₃-MgO gunning materials with tabular corundum,fused magnesia,?-Al₂O₃ micro-powder,etc.as raw materials,calcium aluminate cement?CAC?and silica sol as binders,studies the effects of particle size composition,SiO2 micro-powder,additives on its properties.The conclusions are as follows:?1?The poor thermal shock resistance of the alumina-magnesia gunning refractories currently used in the factory lead to the erosion and penetration through the cracks generated by thermal shock to the gunning material-brick interface,causing the gunning refractories to flake off during use.?2?In the range of particle size tested in this paper,increasing the content of coarse particles can reduce sintering shrinkage of gunning refractories at high temperature;However,increasing the content of fine powder is helpful to sinter gunning refractories at high temperature.The particle size composition of gunning material has little influence on the volume density and normal temperature strength of gunning material after burning.Both sodium tripolyphosphate and FS60 can reduce the viscosity of matrix slurry.The suitable addition amount of sodium tripolyphosphate is 0.23wt%,and the suitable addition amount of FS60 is 0.16wt%-0.23wt%.?3?SiO₂ micro-powder can slow down the hydration rate of cement and magnesia and prolong the construction time of gunning refractories;SiO₂ will react with raw refractories at high temperature to generate low-melting nepheline,melilite,gehlenite,etc.,thus reducing the formation of plate-like CA₆,reducing the apparent porosity of gunning refractories,and improving the slag resistance of gunning refractories.The appropriate addition amount of SiO₂ in cement-bonded alumina-magnesia gunning material is 1.5wt%-2.0wt%.?4?Additives are introduced into cement-bonded Al₂O₃-MgO gunning materials,and the results were as follows.The addition of metal aluminum powder can improve the post-baking strength of gunning material.The organic fiber can improve the thermal shock resistance of gunning refractories.When the amount of ZrO2 added is 0.6wt%,the residual flexural strength of gunning material about 2.8MPa.Y₂O₃ generates Y?AlO₃?phase to promote sintering of gunning material to improve normal temperature strength of gunning material.La₂O₃ can inhibit the abnormal growth of CA₆ along crystal planes,and maintain the residual flexural strength about 3MPa.TiO₂ can reduce the formation temperature of MA and improve the morphology of CA₆ to increase the density of gunning material.When the amount of TiO₂ is 0.3wt%,the residual flexural strength of gunning material is 4MPa.?5?The SiO₂ colloidal particles in sol can fill the pores of gunning material and reduce the apparent porosity of gunning material after baking.Magnesia can accelerate the gelling speed of silica sol,so the content of silica sol should not exceed 6wt%;Magnesia reacts preferentially with SiO₂ to form ringwoodite phase at high temperature,so with the increase of silica sol addition,MA production decreases,thus reducing the linear expansion value of gunning material.When the addition of silica sol is 4 wt%,the residual flexural strength of gunning material reaches the highest value of 6MPa after thermal shock.