Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1941-05-10


ed is mounted on rollers and can
be titled forward or backward,
which allows blowing various mix
lures CT air. oxygen. and fluxes
through the oil-cooled tuyere and
into the molten chromium-iron
metal. Electrothermal energy can
De applied while blowing.
Preliminary Bessemer trials on
$50 to 200 Ib. of molten ferro-
chrome baths. in contact with high
silica slags. were made with oxy-
gen and with air-oxygen mixtures.
Bessemerizing of high-iron fer
rochrOme oxides the chromium
more rapidly than either the car
bon or the iron. However, the OK
idation is to slow to justify fur
Their investigation.
SBLEGTIVE CARBON REDUC-
TION OF IRON IN CHROMITE.
Bogitch IN. G. Bogitch) gives da-
ia liable IX) on the ferroalloys
produced by varying the carbon on
the charge The analysis of high
grade chromium mineral used was:
Cr2O3, SIP; Fec, 1865; MgO,
1874; Sio2, 3.5; Al2O3, 14.9.
SELECTIVE CARBON REDUC-
TION OF IRON IN DOMESTIC
CHROMITE. The selective reduction
OF iron from Montana chromium
concentrates has been demonstrated
in the pilot electric furnace.
Analysis of the slags or benefit
ciated chromite from which the
excess iron has been removed is,
on 3-12-40; Or, 27.5 per cent; Fe,
1912 per cent The ratio of chrom-
ium to iron is 81. This Stag when
poured to the second pilot furnace
temperature 1850 to 1900 deg,
C.-is reduced by petroleum coke
to standard ferrochromium alloy.
DECENTRALIZATION OF DO
MESTIC HIGH-IRON FERRO-
CHROMIUM. Stag Resistance Fur
naces.
Bogitch shows as low as 0.3 per
cent carbon in the high-iron alloy
selectivity reduced from a high
grade chromite smelt. The furnace
used by Bogitch was a direct-arc
type with automatic voltage cleo
trode control. The electrodes were
not in contact with the bath.
The pilot smelling furnaces in
the Boulder laboratory are of the
submerged electrodes slag-resist-
ance type, and the lowest carbon
made was 2.3S per cent in the
chromium alloy produced in selec-
lively reducing the iron. This al
10y analysed 20 per cent Or, rs
per cent Fe and DAB per cent 81.
When automatic voltage-control
eleetrOde equipment is available,
comparative smelts are anticipated.
INDUCTION FURNACE DECAR-
BURIzATION. Crucibles were made
in the laboratory Of domestic chro-
mite concentrates and commercial
magnesia. These were pressed I'M
der 10000 lib. per So. in. pressure,
dried and fired in place in the in
ductiOn furnace They served sat
isfactorily at temperatures of 1900
deg. C. in these small scale inves-
legations.
High iron-chromium alloy used
for tests / 2, 3, 4 and 5 liable
XII contained 54.56 per cent Or,
34.16 Fee, 6.62 C, and COS Mn.
The metal was held in the mol
ten state approximately one hour
in contact with the decarburiZer.
The induction furnace power sup
ply was held at Is to II XIV.
Use of high-iron chromite for
decentralization of high-iron high
carbon ferrochrOme is questionable
because Of the ease of reduction of
the iron from the high-iron chro
mite concentrates and consequent
dilution of the chromium alloy.
These standardization data are to
be considered as only indicative be-
cause of the small surface contact
between the oxidiZing Stag and the
alloy and because the Stag is al
ways at a lower temperature than
the alloy. Proper mixing of the two
is not effected under these Undue
ton furnace conditions. The lar
ger scale Decentralization investi-
cations are planned to be carried
out in a standard direct arc furnace
with several type of decarburizing
slags.
MONTANA CHROMITE CON-
GENERATES AS METALLURGICAL
RBFRACTORIES. Table XII gives
the comparative analysis of several
standard chromite refractories US
ed in steel and copper furnaces
The crucibles and furnace Innings
of domestic chrome concentrates
can be made to withstand tempera-
lures and corrosive slagging action
as well as the standard products in
laboratory use.
According to Sell (G.E. Seil)
For refractory purposes the per-
centage Cr203 in itself is not a
decisive factor and ores relatively
low in ehrome-oxide content are
used if the percentage Al2O3 is
relatively high"
According to at least one au-
thority (Nonmetallic Mineral Indus
try Bureau of Mines, 1. C. 71O6,
p. 81, the most satisfactory all
around mixture is rs per cent
chrome ore and 25-per cent dead
burned magnesia."