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Патент USA US2406910

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Patented Sept. 3, 1946
2,406,910
UNITED STATES PATENTOFFICE
Robert A. Schoenlaub, Ti?in, Ohio, assignor to
Basic Refractories, Inc., Cleveland, Ohio, a cor
poration of Ohio
No Drawing. Application January 6, 1943,
Serial No. 471,455
6 Claims.
1
(01. 117-122)
Refractories such as chrome ore, and periclase,
casement without prior burning of the grains,
while desirable in many respects, have certain . and such as to allow full latitude in application
proclivities toward deterioration under furnace
of the refractory material in desired kinds of
condition. In exposure to high temperature
usages, and the procedure is relatively‘simple and
slags and oxide-bearing vapors, chrome ore for 01 of low cost.
instance tends to. absorb ferrous or ferric oxide,
To the accomplishment of the foregoing and
as well as some other oxides, by solid solution,
related ends, the invention, then, comprises the
the absorbed substances diffusing into ‘the
features hereinafter fully described, and partic
chrome-spinel grains and becoming an integral
ularly pointed out in the claims, the following
part thereof. This changes their physical prop
description setting forth in detail certain illus
erties, and particularly‘ important and‘destruc
trative embodiments of the invention, these being
tive is the increase in volume, and this results
indicative however, of but a few of the various
in what is variously termed “bloating,” “cauli
ways in which the principle of the invention may
?owering,” “swelling,” or “peeling,” all of which
be employed.
considerably reduce the ultimate service life of
The refractory material to be treated, as for
refractories made from chrome ore. Periclase
instance chrome ore, magnesian refractory ma
refractories are similarly affected, but to alesser
terial, etc., and designated for convenience “basic
extent. These refractories also have another dis
refractory material,” is crushed and sized to‘de
advantage in that chromite and periclase crys
sired mesh, and the grains are subjected to coat
tallize in the isometric system, usually in small 120 ing by a silicate material which permits ultimate
equi-dimensional crystals. They therefore do
moistening and molding or bringing into desired
not intrinsically possess the keying action which
shape or placement vfor use. Such silicate is in
is imparted in some refractory substances by
contrast to clays, bentonites, etc., as it is of a
prismatic crystals, such as mullite, or by tabular
chemical character not introducing deleterious
crystals such as corundum. As a consequence
alumina. Plastic hydrous magnesium silicates
they are more sensitive to spalling and structural
which with water swell to a voluminous gel, and
failure than some of the more acid types of re
are thereby distinguished from such silicates as
fractories. Commonly, in an effort to mitigate
serpentine are excellent materials for this pur
the destructive effects of absorption and the
pose, and although they may be provided syn
structural de?ciencies of basic refractories, it has 30 thetically, they may be had‘from natural de
been customary for refractory manufacturers to
posits to advantage. For instance, one such de
use as coarse a sizing as possible. Brick made
posit occurs near Hector in San Bernardino
from coarsely sized material are usually more re- -
County, California. . It is, characterized by a ra
sistant to spalling than brick made from similar
material ?nely sized. Also, by the use of coarse DD
tio of silica to magnesia usually slightly greater
than 2:1 by weight, and it usually contains al
kalies, of which lithia is notable. It differs from
the aluminous bentonite in its X-ray diffraction
sizing, the volume-surface relationship is favor
ably affected, so that a smaller amount of sur
face is exposed to destructive absorption. How
ever, as the sizing increases, therworkability of
pattern and indices of refraction. Analysis, as
freed from associated ?ne calcite, shows ignition
a refractory mixture and its permeability are ad 40 loss 5.7, MgO 25,1, SiOz 57.8,‘Naz0 2.9 per cent,
versely affected. These factors constitute prac
and traces of R203. Analysis including initially
tical limits to advantages which may be gained
associated calcite, and in the‘form in which‘it
by sizing. A common expedient is to use coarse
may also be used shows ‘ignition loss 25.55, MgO
chrome ore and to use ?ner periclase clinker,
11.09, S102 26.14, NazO 1.30, CaO 29.28 per cent,
45 and traces of R203. Physically, the material is
which is less sensitive to absorption.
Efforts have been made to improve chrome
unctuous and’ swells copiously to a voluminous,
ore or periclase refractories by providing the
stable gel when immersed in water. These gels
grains with encasements of refractory silicates‘by
are ‘variously tacky and plastic, depending upon
means of calcium and magnesium silicates fused
the . amount of water used and other factors.
on the clinker grains by high temperature firing 50 Such‘ physical characteristics of plastic hydrous
in a rotary kiln. The cost- of this is prohibitive
magnesium silicate materials allow emplacement
for what advantages result. In accordance with
of a thin, persistent layer on the refractory grains
the present invention however, basic refractory
materials, chrome , ore, magnesia refractories,
treated; This may be applied alone as the coat
ing material, or it may carry other material, as
_etc.,~'m_ayebe coated with a bene?cial silicate en .55 a thick gelatinous suspension. The‘ refractory
2,406,910
3
4
jected to elevated temperature, in burning or in
grains in such addition or additions may be
mixed in suitable mixing apparatus, as for in
stance a pan mixer, the suspension being added
furnace use.
As an example: A massive chrome ore analyz
ing CI'zOs 34.5 per cent, CaO 1.0, MgO 16.1, $102
4.0, F6203 15.4, and A1203 29.7 is crushed and
sized, and with 45 parts of -—~8 +20 mesh par
ticles and 20 parts of ~20 +50 mesh particles
to the refractory grains, allowing suf?cient time
for good distribution of the water and silicate
material. The coated grains may then be pressed
into brick or shapes which can be ?red, or alter
and 22 parts of -150 mesh chrome ore there
natively, with suitable bonding materials well
are incorporated 3 parts of —150 mesh hydra
known in the art, may as chemically bonded
brick be sold and applied as un-?red brick. Al 10 tion-resistant high magnesia clinker, and 3.8
parts of —200 mesh hectorite (MgO 25 per cent,
S102 5'7 per cent), and 2.8 parts of extremely
ternatively also, the coating material can be in
corporated dry with the refractory grains, and
may ?nally be tempered with water in amount
?nely divided magnesium hydrate, and 2 parts of
7
“goulao” or waste sulphite liquor bond. After
for desired molding condition.
mixing in a pan mixer and tempering to desired
As indicated, the plastic hydrous magnesium
silicate may be applied alone to the refractory
grains, or it may be used with other materials.
For the latter, there may be employed for in
pressing consistency the material is formed into
shapes under high pressure, dried and ?red. Al
ternatively, the dried bricks may be set in a fur
stance magnesium hydrate. The plastic hydrous
nace in un-?red condition. In the latter case,
it may be desired to also incorporate in the ma
terial a chemical bond.
magnesium silicate or hectorite, and the magnesia
can conveniently for instance be added dry to
the refractory grains. On mixing, and temper
ing with water, the coating substance will be
distributed over the particles. With small
amounts, the material may be applied as a thick
slurry in water. By coating refractory grains
Other modes of applying the principle of the
invention may beemployed, change being made
as regards the details described, provided the
features stated in any of the following claims, or
the equivalent of such, be employed.
I therefore particularly point out and distinctly
thus with plastic hydrous magnesium silicate and
claim as my invention:
magnesium hydrate, and exposing to a high tem
*1. A process of treating refractory material,
perature, as in the furnace heat if the material
is applied un~burned, or in the ?ring process if 30 which comprises coating the surface of basic
refractory material particles with an alkaline
molded bricks or shapes are burned before being
earth compound of the group consisting of mag
used, there is a reaction, hectorite '(free from
nesium and calcium hydroxides and oxides, and
lime) and the magnesium hydrate forming
to react therewitha substantially non-aluminous
2MgO.SlO2. Amounts of for instance 2 to 10
per cent of the magnesium silicate and particu 35 gel-forming hydrous magnesium silicate of the
composition of hectorite from 'San Bernardino
larly a range around 5 per cent give very desir
County, California, and contacting the reaction
able results, and for example for one part of
mixture with water for swelling the gel-forming
hectorite 1/2 part or more of magnesium oxide
material, and compacting the coated particles
or its equivalent in magnesium hydrate may make
40 ‘together.
up the reaction materials.
2. A process of treating refractory material,
If desired, instead of allowing reaction with
which comprises applying to the surface of basic
plastic hydrous magnesium silicate to the forma
refractory material particles a coating of mag
tion of 2MgO.SiO2 as ultimately ?red, the coating
nesium hydroxide, and to react therewith a sub
material may be chosen to eventuate in
stantially non-aluminous gel-forming hydrous
2CaO.SiO2. For this, lime-bearing hectorite may
magnesium ‘silicate of the composition of hec
be used, and correcting lime, such as ?nely
torite from San Bernardino County; California,
ground, chemical grade hydrate may be added to
and contacting the reaction mixture with water
bring up the molecular ratio of vlime to silica as
2:1. Borax to give for instance 0.05 per cent of 5.1 for swelling the gel-forming material, and com
pacting the coated particles together.
B203 or slightly more in the ?nished refractory
3. A process of ‘treating refractory material,
may be added, as with the tempering water. Sili
which comprises applying to the surface of basic
cate for coating purposes should not be added in
refractory material particles a coating of lime,
amount larger than required for effective coat
and to react therewith a substantially non
ing. It is generally more susceptible than other
constituents to fluxing. Consequently, a desir or CA aluminous gel-forming hydrous magnesium sili
cate of the composition of ‘hectorite from San
able balance may be made between the absorp
Bernardino County, California, and contacting
tion mitiation and fluxing tendency. Usually, 3
the reaction mixture with water for swelling the
to 1-5 per cent of coating silicate material is
gel-forming material, and compacting the coated
satisfactory. Other silicates, present as impur
2
particles
together.
ities or otherwise, are omitted from present con
4. A process of treating refractory material,
sideration.
which comprisesapplying to the surface of un
Refractory particles so coated with plastic
?red basic refractory material particles a coating
hydrous magnesium silicate, with optional inclu
of an alkaline earth compound of the group con
' sisting of magnesium and calcium hydroxides
sion of a reactive alkaline earth compound, such
as hydrate or oxide or carbonate, with a suit
and oxides, and to react therewitha substantially
able amount of moistening and tempering water,
non-aluminous gel-forming ihydrous magnesium
may be compacted to form furnace linings, or
molded shapes, etc. And, it is a particular con
Bernardino County, California, and contacting
silicate of the composition of hectorite from San
venience that such refractory materials, involv 10 the reaction mixture with water for swelling the
ing particles of chromite or of magnesia char
gel-forming material, compacting the coated par
ticles together, and ?nally heating to react the
acter, may thus be employed in either un-?red
coating.
or in ?red condition, the ?nal reaction of the
-5. A process of ‘treating refractory material,
plastic hydrous magnesian silicate to a refrac
tory silicate occurring when the material is sub 75 which comprises applying to the surface of basic
I
2,406,910
refractory material particles a coating 01' mag
nesium hydroxide, and to react therewith a sub
which comprises applying to the surface of basic
refractory material particles a coating of lime,
stantially non-aluminous gel-forming hydrous
and to react therewith a substantially non-alumi
nous gel-forming hydrous magnesium silicate of
the composition of hectorite from San Bernardino
County, California, and contacting the reaction
mixture with water for swelling the gel-forming
magnesium silicate of the composition of hec
torite from San Bemardino County, California,
and contacting the reaction mixture with water
for swelling the gel-forming material, compact
ing the coated particles together,‘ and ?nally
heating to react the coating.
6. A process of treating refractory material, 10.
‘material, compacting the coated particles to
gether, and finally heating to react the coating.
'
ROBERT A. SCHOENLAUB.
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