# Phase Transformation Principle and Magnetite Grain Growth Law in the Magnetization Sintering Process of Oolitic Hematite Ore

## TL;DR

This study explores how to efficiently convert oolitic hematite ore into magnetite through sintering, finding optimal temperature and time conditions for the process.

## Contribution

The study identifies optimal sintering conditions and reveals how temperature affects magnetite grain growth during hematite reduction.

## Key findings

- Optimal sintering conditions are 700 °C for 45 min, achieving 68% magnetite content and 0.8% Fe/O atomic ratio.
- Magnetite grain thickness increases significantly from 9.52 μm to 76.76 μm when sintering temperature rises from 600 °C to 700 °C.
- High temperature for short duration is more effective for magnetite growth than low temperature for longer time.

## Abstract

Oolitic hematite ore represents a significant iron resource, but its utilization is challenging due to the complex multi-layered circular structure of hematite ore, which makes it difficult to be reduced. This study systematically investigated the phase transformation principle and magnetite grain growth law during the magnetization sintering of oolitic hematite ore, aiming to establish optimal conditions for efficient hematite ore to magnetite conversion. The results demonstrated that both elevated temperature and prolonged reduction duration significantly enhanced the reduction efficiency of hematite (Fe2O3) to magnetite. The optimal sintering conditions were determined to be 700 °C for 45 min, under which the magnetite content and Fe/O atomic ratio in the roasted products peaked at approximately 68% and 0.8%, respectively. However, temperatures exceeding 800 °C proved detrimental to magnetite formation, as further reduction to FeXO phases occurred. Notably, appropriate temperature elevation promoted substantial magnetite grain growth. When the sintering temperature increased from 600 °C to 700 °C, both the absolute and relative thickness of the magnetite layer exhibited remarkable enhancement, expanding from 9.52 μm to 76.76 μm and from 5.99% to 50.33%, respectively. Furthermore, comparative analysis revealed that a high sintering temperature for a short time was more effective for magnetite particle growth than a low temperature for a long time in the magnetization process of oolitic hematite ore.