Reduction and subsequent carburization of pre-oxidation magnetite pellets  

预氧化磁铁矿球团的还原和渗碳行为研究

作　　者：CHEN Suo CHEN Dong LYU Ya-nan WU Fei-bao YIN Wei-ang 陈琐;陈栋;吕亚男;吴飞豹;阴伟昂(School of Iron and Steel,Soochow University,Suzhou 215131,China;Department of Mechanical and Electrical Engineering,Suzhou Institute of Industrial Technology,Suzhou 215104,China)

机构地区：[1]School of Iron and Steel,Soochow University,Suzhou 215131,China [2]Department of Mechanical and Electrical Engineering,Suzhou Institute of Industrial Technology,Suzhou 215104,China

出　　处：《Journal of Central South University》2022年第6期1856-1868,共13页中南大学学报（英文版）

基　　金：Project(U1960104)supported by the National Natural Science Foundation of China;Project(LYU Ya-nan)supported by the Jiangsu Colleges and Universities Qing Lan Project,China。

摘　　要：Magnetite is a kind of iron ore that is difficult to carburize.In order to improve the carburizing performance of magnetite pellet,pre-oxidation treatment was carried out,and the oxidation,reduction and carburization behaviors of magnetite pellet were investigated in this study.The magnetite pellet was oxidized in the air and carburized in CO-CO_(2)-H_(2) gas mixtures,the oxidation,reduction and carburization behaviors were demonstrated by detecting phase change,microstructure,carburizing index via thermogravimetry,X-ray diffraction(XRD),infrared carbon-sulfur analyzer,and scanning electron microscope(SEM).The results show that the dense magnetite particles inside pellet are oxidized to porous hematite particles,and the Fe_(3)O_(4) transforms to Fe_(2)O_(3) with high lattice defect concentration during the pre-oxidation process.Then the porous hematite particles and newly formed Fe_(2)O_(3) significantly promote the reduction efficiency.Porous metallic iron particles are produced in the reduction process.Finally,both high reduction efficiency and the porous structure of metallic iron particles dramatically enhance the carburization efficiency of pellet.High preoxidation temperature favors to the carburization of magnetite pellet.However,the carburized index decreases due to the recrystallization of iron oxide when the temperature extends to 1000℃.The optimum pre-oxidation temperature for magnetite pellet carburization is 900℃.磁铁矿是一种难渗碳的铁矿石。为了提高磁铁矿球团的渗碳性能,本文对磁铁矿球团进行了预氧化处理,并进一步研究了磁铁矿球团的氧化、还原和渗碳行为。磁铁矿球团在空气中进行氧化并在CO-CO_(2)-H_(2)气氛中进行渗碳,利用热重分析仪、X射线衍射仪(XRD)、红外碳硫分析仪和扫描电子显微镜(SEM)研究产物的渗碳指数、微观结构和物相变化,以揭示磁铁矿的氧化、还原和渗碳行为。结果表明:在预氧化过程中,球团中致密的磁铁矿颗粒被氧化为多孔的赤铁矿颗粒,Fe_(3)O_(4)转化为晶格缺陷较高的Fe_(2)O_(3),多孔的赤铁矿颗粒和新生的Fe_(2)O_(3)显著提高了球团的还原速率;在还原过程中,多孔的赤铁矿颗粒被还原为多孔的金属铁颗粒,球团的高还原速率和金属铁颗粒的多孔结构显著提高了球团的渗碳效率;较高的预氧化温度有利于磁铁矿球团的渗碳,但当氧化温度增加到1000℃时,由于氧化铁的再结晶,其预氧化球团的渗碳指数反而有所降低;磁铁矿球团渗碳的最佳预氧化温度为900℃。

关 键 词：MAGNETITE PRE-OXIDATION CARBURIZATION porous particle recrystallization 

分 类 号：TF046.6[冶金工程—冶金物理化学]