Abstract
[Background and purposes]Most existing research have focused on the corrosion of refractories by molten slag,whereas studies on matte-induced corrosion remain scarce.In this work,high-temperature corrosion tests were conducted at 1200℃for 2,4,8 and 12 h,to evaluate the interaction between magnesia-chrome refractory bricks and three grades of molten matte under simulated smelting conditions.The corroded samples were sectioned and mounted,then characterized by using XRD,SEM/EDS and TG-DSC.Macroscopic observations showed that copper in the matte completely penetrated the bricks after firing.Increasing matte grade markedly accelerated the corrosion rate.SEM-EDS analyses results revealed that Cu migrated preferentially along grain boundaries,generating a dendritic network.The boundaries constituted mainly by MgO and spinel thus provide the principal penetration path and are the key factor governing the structural degradation of the refractory bricks.In copper pyrometallurgy,the longevity of magnesia-chrome refractory linings in smelting furnaces is critically challenged by the corrosive attack of molten matte.While slag-induced corrosion has been extensively studied,the specific mechanisms of matte corrosion,especially under high matte grades,remain insufficiently understood.Industrial observations consistently indicate that increased matte grade accelerates the deterioration of magnesia-chrome bricks,leading to shortened service life and elevated operational costs.This work was aimed to elucidate the corrosion mechanism of magnesia-chrome refractory bricks by different grades of molten matte,with a focus on phase evolution and the corresponding microstructural degradation.
[Methods]Three industrial matte grades(57-58%,59-60%,and～61.5%Cu)were employed to corrode commercial magnesia-chrome bricks in Ar at 1200℃for durations of 2,4,8,and 12 h.The as-received refractory brick,composed primarily of MgO(49.26%)and Cr2O3(23.32%)with significant contents of Fe2O3(12.49%)and Al2O3(8.68%),was characterized by using XRF and XRD.Post-corrosion samples were sectioned,mounted,polished and meticulously examined using SEM-EDS for elemental distribution and microstructural analysis.Thermal behavior of the mattes was examined by using TG-DSC.
[Results]Copper penetration was intensified markedly with both increasing matte grade and prolonged exposure time.After corrsion for 12 h,complete penetration of Cu through the bricks was observed,accompanied by severe structural spalling.SEM images and EDS mapps unequivocally demonstrated that Cu preferentially infiltrated along the grain boundaries between MgO and spinel phases,forming an interconnected dendritic network.Elemental maps showed a strong spatial correlation between Cu-rich areas and the depletion of Cr at the grain boundaries,suggesting chemical interaction.Critically,XRD analysis of the corroded samples identified the formation of new crystalline phases,magnesium-iron-aluminate spinel(AlFeMgO4)and copper chromite(Cr2CuO4),alongside the remaining periclase(MgO).TG-DSC results indicated that higher-grade mattes possessed lower melting points,facilitating earlier melt formation and more aggressive corrosion.The corrosion mechanism is identified as a combination of physicochemical processes.The infiltration of low-viscosity matte along grain boundaries initiates the attack.The reaction of Cu(from the matte)with Cr2O3(from the refractory's spinel phase)to form copper chromite(CuCr2O4).This reaction consumes the crucial Cr2O3 component,leading to the decomposition of the reinforcing MgCr2O4 spinel skeleton.Furthermore,CuCr2O4 likely forms low-melting-point phases that severely weaken the grain boundary cohesion.The simultaneous incorporation of Fe into the grain boundaries,reacting with MgO and Al2O3 to form a(Mg,Fe)(Al,Fe)2O4 solid solution(AlFeMgO4).This alters the original chemical and physical properties of the grain boundaries,making them more susceptible to penetration and attack.The synergy between the destructive formation of CuCr2O4 and the alteration of grain boundaries by AlFeMgO4 create a rapid pathway for melt ingress,culminating in macroscopic structural failure.The enhanced corrosion rate with higher matte grades is attributed to their earlier melting and greater fluidity,which accelerate these coupled physical and chemical degradation pathways.
[Conclusions]The corrosion of magnesia-chrome bricks by molten matte is governed by grain boundary attack,which is dramatically exacerbated by higher matte grades and prolonged exposure.Increasing matte grade significantly accelerates the corrosion process,with high-grade matte causing the most severe structural failure characterized by deep root-like Cu penetration networks.Prolonged exposure leads to a progression from initial localized Cu penetration to complete microstructural breakdown via interconnected grain boundary channels.The fundamental mechanism is the chemical corrosion at the grain boundaries,primarily through the in-situ formation of copper chromite(CuCr2O4),which destroys the refractory's spinel reinforcement and creates grain-boundary weakening phases,coupled with the formation of a magnesium-iron-aluminate spinel(AlFeMgO4)that modifies the grain boundary chemistry.This synergistic chemical attack is the root cause of the severe deterioration of the refractory's structural integrity.These insights provide a scientific basis for developing next-generation refractory materials with improved resistance to chemical corrosion by copper mattes,potentially through grain boundary engineering and the stabilization of the chromium oxide phase.关键词
冰铜/镁铬耐火砖/侵蚀/晶界Key words
molten matte/magnesia-chrome refractory brick/corrosion/grain boundary分类
化学化工
