Effect of SiO2 on the Mechanical Property and Reduction of Calcium Ferrite

Abstract

SiO 2 -Fe 2 O 3 -CaO (SFC) is believed to be the transition phase during the SiO 2 -Fe 2 O 3 -CaO-Al 2 O 3 (SFCA) formation process. The effect of SiO 2 on the mechanical property and reduction of the CaO-Fe 2 O 3 -SiO 2 system was inspected in this study. Experiments were carried out under air at 1200 • C with different amounts of SiO 2 mixed with Fe 2 O 3 and CaO. The mechanical properties and reduction of samples were studied. Results indicate that the hardness of samples gradually increases with the increase of SFC content. That may be caused by SiO 2 solid solution in calcium ferrite. The larger the amount and smaller size of acicular calcium ferrites in samples, the greater the fracture toughness. The solid solution of SiO 2 in calcium ferrite is beneficial to decrease the initial reduction temperature. The apparent activation energy values of the samples with the different content of SiO 2 from 0% to 5% are 167. 23, 84.36, 87.90, 96.02, 92.44 and 107.83 kJ·mol −1 , respectively. The microstructure of lump samples after reduction consists of four phases, i.e., CF (CaFe 2 O 4 ), SFC, calcio-wüstite (CW) and Fe. It was not difficult to find the Fe in the samples reduced from CW. Scanning electron micrograph images have revealed that the acicular-like calcium ferrites are more easily reduced than the platy-like ones.

Synthesis and Mechanical Testing of Calcium Aluminosilicoferrite Crystals with High Alumina Content

“…Compared with the results from earlier studies [18][19][20][21][22], this work provides a new view on the determination of mechanical properties. The obtained data are difficult to compare with classical Vickers microhardness, but on the other hand, the values were obtained with an accurate method allowing for rigorous comparison with the future examination of mechanical properties of sinter phases.…”

“…In most cases the hardness was measured using Vickers microindentation. However, there are some elementary problems with these measurements, such as too little information about the elastic constants or insufficient size of the crystals, so that the surrounding phases influence the measurements [18][19][20][21][22]. For this reason, in this study SFCA phases were synthesized in the laboratory to attain grain sizes of tens of micrometers, for which the mechanical properties can be quantified using advanced mechanical testing such as nanoindentation.…”

Understanding Chromium Slag Recycling with Sintering–Ironmaking Processes: Influence of Cr2O3 on the Sinter Microstructure and Mechanical Properties of the Silico–Ferrite of Calcium and Aluminum (SFCA)

“…Shi et al [23] and Zhou et al [24] found that with the increase in MgO content, the formation of MgO•Fe 2 O 3 by the reaction between MgO and Fe 2 O 3 increased the formation temperature of the liquid phase in the sinter, resulting in a decrease in the liquid phase content and calcium ferrite mass fraction, which leads to a decrease in the strength of the sinter. Wang et al [25,26] found that increasing the SiO 2 content in the sinter to 4 wt% promoted the formation of calcium ferrite. Further increasing the SiO 2 content caused the formation of silicate, which reduced the contact surface between CaO and Fe 2 O 3 , inhibited the formation of calcium ferrite, and reduced the strength of the sinter.…”