Corrosion Behavior Of Alumina Refractories By Molten Slags Under High Temperature And Weak Static Magnetic Field

Alumina refractories are the fundamental material for high-temperature industries such as metallurgy.The high alumina content slag during the smelting process of low-density high-strength steel not only seriously affects the safe and efficient operation of furnaces,but also leads to the formation of non-metallic inclusions in the steel,which is one of the key bottlenecks restricting the development of high-quality steel smelting.Traditionally,the improvement of slag resistance of refractory mainly relies on the improvement and optimization of it’s composition and structure.Using of external field effects such as electromagnetic fields to develop new technologies for corrosion resistance of refractories has gradually attracted attention.Different from the external field effect of electric field,high intensity magnetic field or alternating magnetic field,it was also found that the weak static magnetic field with a millitesla magnetic flux density has the potential to improve the slag resistance of refractories.However,there is still a lack of in-depth understanding of how weak static magnetic field affects the complex interfacial reaction between refractory and slag and its inhibition mechanism.The corrosion behavior of alumina refractories by high alumina Ca O-Al₂O₃-Si O₂slags under high temperature and weak static magnetic field was studied based on the developing and utilizing high-temperature visualisation technology in this work.The dissolution behavior of corundum refractories in slags,the wetting behavior of slags to corundum refractories,and the slag penetration corrosion behavior to alumina refractories under high temperature and weak static magnetic field were explored.The influence of magnetic flux density of external magnetic field on the slag corrosion to alumina refractories under different temperatures and slag basicity（Ca O wt%/Si O₂wt%）was explored,and it’s slag resistance mechanism were discussed,this is helpful for the development and application of magnetic field composite alumina refractory.The main conclusions are as follows.（1）The dissolution rate of corundum refractory in slags were obviously exhibits weak magnetic effect,the refractory dissolution rate curve presented troughs type with the increasing of magnetic flux density of the static magnetic field,and the dissolution rate can be inhibited obviously within a specific flux density weak static magnetic field（5～30Gs）,which transformed the dissolution mechanism from diffusion controlling into reaction controlling.The reaction in oxide melts can be promoted with the increasing of the temperature,but the magnetic flux density thresholds for the inhibition of reactions didn’t change.Based on the molecular dynamics calculations combined with EPR test results,it was found that there are abundant free radicals in the slag.The addition of a weak static magnetic field with flux density of 5～30 Gs can regulate the electron spin state of free radicals,thereby affecting the radical reaction between slag and corundum refractory and changing its dissolution behavior.（2）The apparent wetting angle of slag on corundum refractory can be affected by weak static magnetic field,and the influence law of the magnetic field for the same slag is similar at different temperatures.The wetting behavior of slag and the corundum refractory ceramics at high temperature is reactive wetting,which caused the forming of the calcium alumina products at the interface and the increasing roughness even denting of interface.External weak static magnetic field can reduce the forming of calcium aluminates reaction layer and the decreasing denting degree of interface by inhibiting the interfacial radical reaction of slag and corundum refractory.Taking slag with basicity of 5as an example,when there was external static magnetic field of 10 Gs,the thickness of calcium aluminates reaction layer at the interface decreased by 36.7%,the denting depth of interface decreased by 35.6%,and the wettability of slag on the interface of corundum refractory decreased significantly.（3）The free radical reaction involving superoxide radicals appeared at the interface of high alumina slag and alumina refractories,the imbalanced distribution of·O₂^-and·Ca⁺in reactants and products caused the appearance of Turing pattern corrosion patterns at the reaction interface.External static magnetic field of 10～15 Gs can significantly reduce the interfacial reaction degree corundum refractory and slag,reducing the thickness of calcium aluminate reaction layer,and significantly inhibit the Turing pattern corrosion,the height of the corrosion peak decreased by 20%～30%.The spin state of the free radicals can be changed through the inter-system crossing excited by static magnetic field,thus reducing the bonding number and alleviating uneven distribution of reactant in auto-catalysis reaction,and finally inhibited the interfacial reaction and the development of Turing patterns.（4）The penetration and corrosion of slag on alumina refractory mainly includes three stages:penetration,penetration and alumina dissolution,and new phase precipitation caused by the interaction between slag and refractory,which will cause the structure peeling or thermal peeling of refractory as the forming of deteriorative layer and temperature fluctuations.The stress produced in the stage of slag penetration and alumina dissolution coupled with the formation of CA₆is the largest and about 1.20 times than that caused by the slag penetration.The rapid increasing in strain was weakened with external magnetic field of Gaussian level,the reduction of corundum dissolution rate limited the decreasing rate in wall thickness of the slag corrosion channel,thus reducing the slag penetration stress and delaying the formation of new phase,and the deformation of alumina refractories caused by slag corrosion was significantly decreased,the strain caused by slag corrosion reduced up to 50%.It was also found that weak static magnetic field can significantly improve the slag resistance of alumina refractories in complex smelting environments,indicating that it have great potential in large-scale applications in high temperature industrial processes.