Photon Factory Activity Report 2014 #32 (2015) B

BL-6C/2014C203

In situ observation of sintering in CaO-Fe2O3 system at high temperatures (II)“The first “Continuous cooling transformation (CCT)” concept for iron ore sintering

Masao KIMURA1,2*and Reiko Murao1
Adv. Tech. Res. Lab., Nippon Steel & Sumitomo Metal Co., Chiba 293-8511, Japan2
Photon Factory, Institute of Materials Structure Science, High Energy Accelerator ResearchOrganization, Tsukuba, 305-0801, Japan
1

3 Results and Discussion
The specimens Fe2O3: CaO = 64:36, 80:20, and 90:10(mass%) were heated up from 300 to 1773 K at 5.0 × 10−1
K/s, and cooled down to 300 K with different coolingrates: −3.3 K/s, −8.3 × 10−1 K/s, and −8.3 × 10−2 K/s, forsimulation of industrial processes. Reaction schemes arebasically the same as expected from the quasibinary
phase diagram, but in situ observation both of crystal
structure and microstructure successfully revealed theeffects of heating and cooling rates on the sintering
reaction in the CaO-Fe2O3 system with special attention
to overheating and overcooling phenomena.
In situ observation both of crystal structure andmicrostructure successfully revealed the effects of heating
and cooling rates on the sintering reaction in the CaOFe2O3 system with special attention to overheating and 
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2 Experiment
A special reaction cell for in situ X-ray diffraction wasdeveloped [1]. Powder specimens are heated in various
gas up to T = 1773 K. The reaction cell was mounted on a
special goniometer [2] which can maintain the specimen
in a near-horizontal position while scanning a detector inboth an in-plane and out-of-plane directions [3]. An area
detector, PILATUS® (PIxeL ApparaTUs for the SLS,DECTRES and Rigaku), was used in order to measure apart of diffraction Debye-ring in a short period.
Powder specimens, a mixture of Fe2O3 and CaO withvarious ratios, were mounted in the center of thereaction cell. They were heated in air up to to T = 1773
K, and the change in the diffraction patterns weremeasured using an X-ray beam with a size of 1 × 1 mm2and λ = 0.178897 nm. Experiments were conducted at abending beam-line of BL-6C at PF, KEK, Tsukuba, Japan.
In situ and real-time observation of microstructures
were performed using an in situ laser microscope.

overcooling phenomena. The first continuous coolingtransformation (CCT) concept for iron ore sintering wasproposed to understand overcooling phenomena when themolten oxide cooled down to room temperature andmagnetite (Fe3O4), hematite (Fe2O3), and various types ofcalcium ferrite were formed. Figure 1 shows the first
CCT diagram for sintering of specimen with Fe2O3: CaO= 90:10 (mass%). Solid lines show the time-temperature
curves for cooling rates: (i) −3.3 K/s, (ii) 8.3 × 10−1 K/s,and (iii) −8.3 × 10−2 K/s.
The CCT diagram for sintering provides crucial andfundamental information on the sintering accompanying
solidification, precipitation, and formation of calcium
ferrites from the molten oxide, and can be used as aguideline for controlling sintering processes [4].

Temperature,    T/ K

1 Introduction
Phase equilibrium of Fe2O3-CaO system has a great
importance in the process of iron making. Sintered ironores with lime stone are used as raw material for ablast furnace. The process of sintering proceeds at atemperature higher than 1773 K and the sintered ores
are cooled down before the thermal equilibrium
attained. The required properties for sintered ores, suchas the mechanical strength and the reactivity withreduction gas, are largely affected by the types ofcoexisting phases and their fractions, and its
microstructure. Thus in situ observation of the changeof structure during sintering processes is of a greatimportance.

Time,   t/ sFigure 1 the first CCT diagram for sintering of specimen
with Fe2O3: CaO = 90:10 (mass%).
References[1] Kimura, M. et al.: ACR2012, 225 (2013).
[2]Kimura, M., Kihira, H., Ohta, N., et al.: Corros. Sci.,
47, 2499-2509 (2005).
[3]Kimura, M., Acosta, A., Fujioka, H., et al.: J. Appl.
Phys., 93(4), 2034-2040 (2003).
[4]Kimura, M., & Murao, R.: ISIJ Int. 53, 2047 (2013).
* masao.kimurakek.jp