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为了减缓海绵铁的高温再氧化,在以含碳球团制备海绵铁的过程中,在含碳球团表面包覆一层约0.25mm厚的Al2O3-MgO-CaO-SiO2陶瓷料浆作为保护层,研究了有无防护层的海绵铁在制备过程中的金相组织及微观形貌,分析了氧化产物的物相组成,测试了球团的金属化率,考察了包覆层对含碳球团还原过程的影响,探讨了涂层防护含碳球团的还原行为和防护机理。研究结果表明,含碳球团“自还原”过程中表层还原产物FeO在高温下通过塑性变形进入包覆层,并包裹其中的功能组元MgO颗粒,两者发生固溶反应生成主要成分为(MgO)0.239(FeO)0.761的致密层,该致密层可进一步氧化生成内层为“针状”的Fe2.95Si0.05O4、外层为“补丁”状的MgFe2O4尖晶石结构的防护层,防护层的总厚度为0.20mm,可通过挤压形变处理的方式使其从海绵铁基体上完整剥落。涂层防护改变了海绵铁疏松多孔的氧化皮结构,致密的防护层很好地维持含碳球团内部的还原性气氛,防止生成的海绵铁被高温氧化性炉气二次氧化,在富氧炉况下取得了80%的金属化率(与无防护涂层的含碳球团相比,金属化率提高了59.5个百分点)。
In order to reduce the high temperature reoxidation of sponge iron, in the process of preparing sponge iron from a carbon-containing pellet, the surface of the carbon pellet is coated with a layer of Al2O3-MgO-CaO-SiO2 ceramic slurry with a thickness of about 0.25 mm as a protective layer , Studied the presence or absence of protective layer of sponge iron in the preparation process of the microstructure and morphology, analysis of the phase composition of the oxidation product, test the metalization rate of the pellet, investigated the effect of the coating on the carbon-containing ball Group reduction process, the reduction behavior and protective mechanism of coating-protected carbon-containing pellets were discussed. The results show that during the process of carbon-containing pellet “self-reduction ”, FeO, a surface reduction product, enters into the coating through plastic deformation at high temperature and wraps the functional component MgO particles therein, and the two react in solution to form the main component Is a dense layer of (MgO) 0.239 (FeO) 0.761, which can be further oxidized to produce Fe2.95Si0.05O4 with inner layer of “needle ” and outer layer of “patch ” shape of MgFe2O4 spinel Structure of the protective layer, the protective layer of the total thickness of 0.20mm, by extrusion deformation of the way it made from sponge iron substrate completely peeled off. Coating protection changed sponge iron porous porous oxide structure, dense protective layer well maintain the reducing atmosphere inside the carbon-containing pellets to prevent the sponge iron generated by the high temperature oxidizing gas secondary oxidation, oxygen-rich Metallization rates of 80% were obtained in the furnace (59.5% increase in metallization compared to uncoated carbonaceous pellets).