A Study on Analysis of Sinter Microstructure and Phase Morphology

Abstract

Sinter is a blast furnace input material obtained by temperature to 900-1200 oC without full melting and adhering to each other with superficial melting. It is considered as a multi-phase material with its heterogeneous microstructure. In general, the main mineral phases are hematite, magnetite, silicoferrite of calcium and aluminium (SFCA) and silicates. By determining the SFCA structure in the sinter material, the sintering process will be made more stable and important parameters affecting the quality in the sintering process will be examined. Sinter material consists of iron ore, iron and steel industry by-products and auxiliary materials. The scope of this project is the determination of the amount of SFCA formed by bonding SiO2, CaO, Fe2O3, Al2O3 and MgO compounds and monitoring this value as a parameter by sinter manufacturers. Sinter samples having different characteristic features were made ready for Xray diffraction (XRD) and optical microscopy inspections by polishing, etching and cold mounting in epoxy for mineralogical analyses. Before raw data obtained from the analysis were evaluated at Autoquan, they were converted into Autoquan format and then, read in XRD device and mineralogical composition of the sinter was revealed by XRD analyses. Detailed imaging of mineralogical compounds were made so as to complement scanning electron microscope (SEM) analyses and XRD analyses; elemental composition of the compounds and valence conditions of the elements were determined by energy dispersive spectroscopy (EDS) method. Phase structures such as hematite, magnetite, and calcium ferrite were qualitatively determined by mineralogical investigations on sinter samples. Furthermore, the variations of SFCA phases (SFCA, SFCA-I and SFCA-II) were studied through Rietveld method.