Abstract: To investigate the corrosion mechanism of MgO-C bricks for the argon-oxygen decarburization (AOD) deferrization and nickel extraction process,the used MgO-C bricks were sampled from the slag line of the AOD furnace,and their chemical composition,phase compositions and microstructure were researched.Additionally,the corrosion of deferrization slag to MgO-C bricks was simulated using FactSage thermodynamics software,and the effect on the purity of molten steel was compared with MgO-CaO bricks.The results show that,under the combined effects of smelting mechanical stress and the capillary force of refractories,the deferrization slag with high FeO content penetrates into the interface of the periclase phase.Due to the unlimited solid solubility between FeO and MgO,the bonding phase and part of the periclase phase at the phase interface dissolve into the deferrization slag,leading to the spalling of periclase in the refractories,the viscosity decrease of high-temperature liquid phases,and a reduction in the stress buffering capacity.Under the mechanical stress,the deferrization slag disturbs the refractories forming a mechanical spalling,the working surface of the used refractories is relatively flat and smooth,with a fractal dimension ranging from 1.1 to 1.2.During the dissolution of the high-temperature liquid phase into the deferrization slag,a significant amount of graphite phase in the MgO-C bricks is preserved in the strongly oxidizing environment,simultaneously reducing the impact of the MgO-C bricks on the molten nickel-iron.Compared to MgO-CaO bricks,the service life of the MgO-C brick lining is significantly improved,and the purity of the molten nickel-iron achieves the same effect.

Key words: MgO-C bricks, AOD deferrization and nickel extraction process, thermal spalling, mechanical spalling

摘要： 为了探究AOD(氩氧精炼)脱铁提镍工艺用镁碳砖的损毁原因,从AOD脱铁提镍炉下线炉衬渣线镁碳砖取样,分析了AOD脱铁提镍工艺用后渣线镁碳砖的化学和物相组成及显微结构,并采用FactSage热力学软件模拟了脱铁渣对镁碳砖的侵蚀,并对比其与镁钙砖炉衬对钢水纯净度的影响。结果表明:在冶炼机械应力和耐火材料毛细管力的双重作用下,高FeO含量脱铁渣进入方镁石相界面;由于FeO和MgO可以无限固溶,相界面的黏结相和部分方镁石相会溶解进脱铁渣中,导致耐火材料中方镁石骨料剥落,且高温液相黏度降低,耐火材料缓冲应力能力下降。在机械应力的作用下,脱铁渣对耐火材料剧烈扰动,形成机械剥落,造成用后耐火材料工作面较为平缓且光滑,分形维数在1.1~1.2。高温液相进入脱铁渣过程中,使得镁碳砖中石墨相在强氧化环境下得以大量保存,同时降低了耐火材料对镍铁水的影响;与使用镁钙砖相比,镁碳砖炉衬寿命大幅提升,镍铁水纯净度方面达到了镁钙砖相同的效果。

关键词: 镁碳砖, AOD脱铁提镍工艺, 热剥落, 机械剥落