Materiales Inoxidables

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UDC

Changes
Iron

of Mineral

Ore-Lime

By Fumio

Phases

Stone

during

the

processesof self-fluxingsinters with various basicities were discussed.
Introduction

It has been reported
that the metallurgical
properties of self-fluxing
sinters,
such as the mechanical
strength,'-11)
the degradability12-1s)
during
reduction
at around
550°C, and thereducibilityl,s,7,1o)
at high
temperatures,
are greatly dependent
on minerals
consisting of them.
Accordingly,
an elucidation
of the
fundamental
aspects
of the physical
and chemical
nature of the sintering processes, especially
the mineral
formation
processes,
is required
in order
to control
the qualities of self-fluxing
sinters.
Although
comprehensive
works'9-3o~
have
been
done on thisproblem,
many phenomena
in the mineral formation
processes have been left unsolved.
One
of the authors studied
this problem
basically
through

Table

**
***

(318)

of

MATSUNO** and Takeo HARADA***

In order to elucidate thefundamental aspects of the sintering processes
of self-fluxing sinters, the mineral formation processes of mixtures of iron
ore and lime stone with orwithout coke were studied. After heating between 1200° and 1350°C the sinters were examinedby microscopy,
X-ray
diffractionand EPMA.
The results indicated that the mineralformation processesof the systems
werefundamentally the same as those of 80%Fe20g CaO-Si02 system
reportedearlier. They were as follows:
(1) Molten calciumferrite was formed at the beginning.
(2) Gangue minerals dissolvedinto the melt.
(3) Iron oxides were precipitated. They were either or both of
hematite and magnetite, depending on the oxygen potential or the Si02
content of the melt.
(4) At higher temperatures, solid iron oxides and a melt coexisted,
and characteristic microstructure was formed during solidification depending on the basicity.
On the basis of the aboveresults, the microstructuresandtheformation

*

1.

Chemical

compositions

the sintering
of very simple
mixtures
consisting
of
reagents,
and several bits of interesting
information
have been obtained
especially
on the formation
processes of the secondary
or granular
hematite,
a product
detrimental
to the degradability.31,32)
However, many
complications
can be expected
on the mineral formation processes iniron ore-lime
stone systems, because
their chemical
compositions
and mineral
constituents
are very complex.
Therefore,
several iron ore-lime
stone systems are examined
in this study.

II.

Experimental

1.

Methods

Raw Materials

Lime stone, coke and seven kinds of iron ore were
used. Each of them was crushed into powder, whose
particle size was less than 0.125 mm indiameter.
Chemical compositions, main phases of iron oxides,
and gangue minerals consisting of each kind of iron
ores used were tabulated in Table 1.

2. Methods of Sintering and Examination
Mixtures of iron ore and lime stone were prepared.
The contents of lime stone in the mixtures were 5.0,
8.5, 12.0 and 18.Owt% as CaO constituent. Coke
powder was added to some of the mixtures in order
toexamine the influence of the oxygen potential on
the mineral formation processes. The coke content
was 0.5wt %, which was determined in a preliminary
experiment.
About 15 g of a mixture was pressed by means of
a steel piston in a steel cylinder of 15 mm inside diameter to a tablet of 15 mm dia. and 10 mm thick.
and

main

minerals

of

iron

ores

examined.

Originallypublished in SumitomoMetals, 31 (1979), 1, in Japanese.
English version received January 28,
Central Research Laboratories, Sumitomo Metal Industries, Ltd., Nishinagasu-hondori, Amagasaki 660.
Formerly Central Research Laboratories, Sumitomo Metal Industries, Ltd.

Research

785:669.046.557

Systems*

Synopsis

I.

Sintering

622.

Article

1980.

Transactions

These tablets...
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