Study On The Influence Of Chromium Sol On The Properties Of Corundum Spinel Castable

Unshaped refractory castables do not need to be formed in advance and undergo high-temperature calcination treatment,and have the characteristics of relatively simple construction and high production efficiency.Therefore,they have become the main development direction of unshaped refractory materials.Refractory castables usually composed of refractory aggregates,powders,binders and admixtures will be formulated according to the use environment and purpose,so the selection of binders plays a decisive role.Corundum castables are usually used with calcium aluminate cement as a binder.Although it has the advantage of higher early strength,it also has the disadvantages of low medium temperature strength and complex curing process.With the development of bonding agent technology,aluminum and silica sol have also appeared in people’s sight as bonding agents.Among them,aluminum sol requires a strong acid environment to maintain stability,but strong acid will have a greater impact on aggregates,making refractory castables In addition,the low solid content of aluminum sol and the low strength of aluminum sol under normal temperature conditions will also affect the performance of refractory castables.In addition,when silica sol is added to the refractory,a large amount of Si O₂ will be generated inside the castable,which will affect its performance at high temperatures,and will also make its fluidity poor and affect the constructionCr₂O₃ has stable chemical properties,excellent high temperature properties,high hardness and good fire resistance,so it has been widely used in refractory materials.However,if Cr₂O₃ is used in large quantities,it will bring great pressure to environmental protection.Therefore,under the premise of maintaining the performance of refractory materials,reducing and avoiding the use of Cr₂O₃ has become the direction of refractory research and development.Introducing Cr₂O₃into the refractory material in the form of chromium sol can play a dual role of partially replacing the binder and improving the performance of the refractory material at the same time.To this end,a method for preparing chromium sol was studied.Through scanning electron microscope,transmission electron microscope,laser particle size analyzer and other material observation and detection methods,the chromium sol colloidal particle morphology,particle size,existence form and conditions required to maintain stability were analyzed.Wait.Then on the basis of preparing a suitable chromium sol,select a suitable refractory castable sol system and add it to the castable mixed according to a certain ratio,and study its influence on the microstructure,mechanical properties and thermal properties of the castable.The study analyzed the performance of corundum-spinel castables after adding different contents of chromium sol instead of aluminate cement.On this basis,it is discussed the feasibility of adding chromium sol instead of aluminate cement as a binder to refractory castables,and minimizing the amount of Cr₂O₃ in an effort to develop a relatively high-quality refractory castable.Through systematic research,the following main conclusions can be drawn:1、Using a simple method and working out a suitable preparation process,using chromium chloride hexahydrate and sodium acetate trihydrate as raw materials,a series of chromium sols with different solid content were prepared,and their particle size distribution,pH value and treatment at different temperatures The microstructure and phase composition of the product were analyzed and characterized.the result shows The stability of chromium sol is greatly affected by pH value and solid content.The higher the Ph value and solid content,the more unstable the sol system and the tendency of gelation.（1）The stability of chromium sol is greatly affected by pH and solid content.The higher the pH and solid content,the more unstable the sol system and the tendency of gelation（2）The particle size of chromium sol is greatly affected by solid content and aging time.The experiment shows that as the solid content increases,the chromium sol particles become larger;as the aging time increases,the particle size of the chromium sol particles decreases.When the system aging time is 3d,the system particle size tends to be stable、2、Combining the physical and chemical characteristics of refractory castable batching system and castable performance requirements,chromium sol with a solid content of 10%and pH=7.5 is selected and added to the refractory castable.Its characteristics are:control Cr³⁺:Ac^-=1:3 Under the ratio,the temperature is40℃and the solid content is maintained at 10%,the average particle size can be obtained at 0.9μm and it can stably exist in the environment of pH=7.5.3、The sol powder that has been dried naturally becomes a round bowl with a particle size of about 1μm.During the calcination process,the particle size tends to decrease first and then increase.After calcination at 110°C,its particle size decreased to about 200nm,and continued to heat up to 1100°C,and its particle size did not change significantly.When the temperature reached 1500°C,its particle size began to increase to about 2μm.This shows that sintering occurred after 1100°C,and the material migration and crystal growth occurred.4、When 0.5%chromium sol is added to the refractory castable,the medium temperature strength is the highest.The results show that:as the content of chromium sol increases,the fluidity of the castable system decreases;with the increase of the amount of chromium sol added,the resistance of the castable to slag erosion is reduced,but the anti-permeability of the castable slag is improved;The measurement of apparent porosity and bulk density shows that adding chromium sol can significantly increase the density of the castable;it is determined that the castable of 0.5%chromium sol can effectively promote the sintering of the castable so that the medium temperature strength is improved compared with the original,but the high temperature The increase in strength is not obvious.