University of Oulu

Kemppainen, A., Ohno, K., Iljana, M., Mattila, O., Paananen, T., Heikkinen, E., Maeda, T., Kunitomo, K., Fabritius, T. (2015) Softening Behaviors of Acid and Olivine Fluxed Iron Ore Pellets in the Cohesive Zone of a Blast Furnace. ISIJ International, 55 (10), 2039-2046.

Softening behaviors of acid and olivine fluxed iron ore pellets in the cohesive zone of a blast furnace

Saved in:
Author: Kemppainen, Antti1; Ohno, Ko-ichiro2; Iljana, Mikko1;
Organizations: 1Process Metallurgy Group, University of Oulu, P.O Box 4300 FI-90014, Finland
2Department of Materials Science and Engineering, Faculty of Engineering, The Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka, 819-0395 Japan
3SSAB Europe, Rautaruukintie 155, FI-92100 Raahe, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.7 MB)
Persistent link:
Language: English
Published: Iron and Steel Institute of Japan, 2015
Publish Date: 2021-01-20


A ferrous burden loses its permeability in the cohesive zone of a Blast Furnace (BF) which has an effect on the flow of reducing gases. Iron ore pellets with various chemical compositions have different softening properties. Due to the occurrence of numerous simultaneous phenomena the clarification of different variables is difficult. In this study the effect of Reduction Degree (RD) on the softening behavior of individual acid and olivine fluxed iron ore pellets was experimentally tested under inert conditions. The acid pellet softened rapidly at 1150°C and reached about 40% contraction at 1200°C. The olivine fluxed pellet softened gradually in the range of 1150 and 1350°C and reached 30–35% contraction. The RDs of 50–70% for acid and 50–65% for olivine fluxed pellet had no significant effect on the softening behavior. However, the highest contraction-% was reached with the lowest RD. The results indicate that softening of the pellets is caused by the softening of the pellet core. The early softening of the acid pellet was attributed to high SiO₂ content and formation of fayalite slag with high wüstite solubility. The superior properties of the olivine fluxed pellet were attributed to the low SiO₂ content and favorable effects of fluxes to prevent wüstite dissolution. FactSage V6.4 -software and its FToxid-database was used to compute the phase equilibrium of a pre-reduced pellet with a quaternary FeO–SiO₂–CaO–MgO system in the core region. The computed phase equilibrium provided additional information about the effects of different components in the phase equilibrium.

see all

Series: ISIJ international
ISSN: 0915-1559
ISSN-E: 1347-5460
ISSN-L: 0915-1559
Volume: 55
Issue: 10
Pages: 2039 - 2046
DOI: 10.2355/isijinternational.ISIJINT-2015-023
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: This research is a part of the Systems Integrated Metal Processes (SIMP) research program coordinated by the Finnish Metals and Engineering Competence Cluster (FIMECC). SSAB Europe and the Finnish Funding Agency for Technology and Innovation (TEKES) are acknowledged for funding this work.
Copyright information: © 2015 by The Iron and Steel Institute of Japan.