Original Article

Effect of high basicity on compressive strength and microstructure of iron ore pellets containing TiO₂

¹ School of metallurgical engineering, Xi’an University of Architecture and Technology, Xi’an 710055, PR China
² Research Center of Metallurgical Engineering and Technology of Shaan Xi, Xi’an University of Architecture and Technology, Xi’an 710055, PR China
³ Technology Center of Jiuquan Iron & Steel Group Co., LTD., Jiayuguan, Gansu 735100, PR China

^* e-mail: 974987671@qq.com

Received: 1 December 2022
Accepted: 23 March 2023

Abstract

A laboratory study is carried out to characterize the effect of basicity (varying 1.5–3.5) on magnetite iron ore pellets containing TiO₂ (content 5%). Green pellets are made by the laboratory scale balling disc and roasted at a horizontal tube furnace with 1220 °C. Thermogravimetric analysis (‘TG’) is used to analyze the thermal decomposition of green pellets. X-ray diffraction (‘XRD’), scanning electron microscope and energy dispersive spectroscopy (‘SEM-EDS’) are utilized to systematically analyze the phase composition, microstructure and elemental distribution of the pellets. The findings show that as the basicity increases the porosity increases first and then decreases while the compressive strength is opposite to porosity to decrease first and then increases. With the increases of basicity, CaO responded with Fe₂O₃ and TiO₂ to form CaFe₂O₄, Ca₂Fe₂O₅ and CaTiO₃. ‘TG’ find basicity has a negative effect on pellet oxidation. Factsage7.1 software shows that with the increase of basicity, the liquid content increases. The ‘SEM-EDS’ result present that CaTiO₃ is formed around hematite, impeding the hematite connection, increasing porosity and reducing compressive strength. Being depend on the experimental results, a schematic of the oxidation mechanism is presented, providing the theoretical foundations for the study of high basicity pellets.