Note: Descriptions are shown in the official language in which they were submitted.
1~83~
This invention relates in general to re~ractory
pr~ducts and processes and more particularly to a high density,
low poroaity re~ractory product made substantially from very
fine materials and to a process ~or making the same.
In re~ractory shapes, particularly refractory brick,
it is desirable to have high density and low porosityg and all
process0s ~or producing these refractories strive for that
end, with the exception of insulating ~irebrick whlch are
characterized by low density and high porosity. The conven~
10 tlonal dry press process produces a brick which is suitable ' '~ ~-
~or many refractory purposes. Nevert~eless, conventional dry '~
pressed brick possess a lowerjthan deslred density and a high~
er than desired porosity. Conventional ~dry pressed brick also' ''
, ~ :, . ..
have a relatively high number o~ large pores, which is unde~
sirable.
: . ,:, . .~ . .
More speci~ically, the manu~acture of re~ractory ' '
brick by the dry press process normally involves using a size
i graded mix o~ coarse, intermediate and flne sized particles.
A typical screen analysis o~ such a brick mix is~
Pass 4 mesh and retained on 10 mesh 25
Pass 10 mesh and retained on 28 mesh 20% '-
Pass 2~ mesh and retained on 65 mesh 10%
Pass 65 mesh 45% ~;~
The use of such a size graded mixture allows the '- ' '
brick to be pressed to a reasonably high density without ~orm
ing laminations in the brick perpendicular to the direction o~
,
pressing. I~ too high a proportion of the mixture:is composed
o~'the ~ine fraction (-65 mesh), there is a tendenc~ ~or the ~,
' mixture to contain ant~apped air during presa~ng~ This en-
trapped air is compressed during pressing, and, when the pres-
sure i8 released, the air expands and causes highly undesirable
--1--
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- ~ ~ 8 ~
laminations in the brick. These laminations tend tD be fur-
ther accentuated when the bricks are subJected to high temper-
atures during the firlng process
While the use of the size graded mixture allows
~orming solid brick free of laminations~ such a mixture gives
relatively low density and high porosity ~o the brick. Using
the foregoing typical size gradation, there are limits to the
values of densit~ and porosity attainable.
It is further generally recognized that in addition
to the amount of pores present in a refractory brick the siæe
of the pores is important, with the smallest size possi~le
gener~ being most desirable. When the foregoing typical
~radation is used for a refractory body, the pore si~es re-
sulting cover a wide range with an appreciable proportion of
the pores being of large size i.e., on the order of lO to 40
microns in diameter.
It is possible to improve the densit~ porosity, and
size of pores developed in a refractory body by using a fine
grained mixture. Such a procedure is used in making refrac-
tories by means of isostatic forming. Followlng is a pro-
; cedure typical of one form o~ an isostatic process: ~
a) Fine grained materials on the order of -325 mesh and ~ -
finer are mixed thoroughly in a slurr~ f~rm with suit-~
able binders;
b) The slurry is spray-dried under conditions whlch tend
to form the fines into uni~ormly sized small balls
which flow smoothly-and freely;
c) The balls are vibration packed into a rubber mold
which is sealed and con~ained in a perforated metal
container;
d) The mold and container are placed into a high pres-
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.. . ~ , , , ~
,
lOB31~4
sure vessel;
e) The balls of refractory material in khe mold are ex-
posed to a high pressure in the vessel by means of a
fluid, such as oil or water, which is pumpe~ into the
vessel to exert pre~ures up to 50,000 p5i on the
mold; and
~) The balls of refractory material are formed into an
.
ob~ect which assumes the shape of the mold.
By exerting pressure on the body in this fashionJ
the air normally entrapped in the fine grained body is removed
~ :
before it can cause pressure laminations to form. Also, the
pressure is exerted equally on all surface~ of the shape or
refractory body. This method of pressure application produces
a shape practically free of the stresses normally formed in a
i body which is exposed to forming pressures exerted primarily
. . ~ .
in one direction. Following forming, it is sometimes neces-
sary to dress the shape in the green state beiore it is ex
posed to high temperature firing.
~` A modification of the isostatic process involves
elimination of the spray~drying operatiDn and forming the bod~
~ directly from a damp or tempered mixture of finely divided ma-
; terial.
The isostatic forming process n0cessitates the use
of e~uipment and processes- not common to the refractories in~
::. :.
dustry, e gO, spray-drying, isostatic pressure application~ `
green finishing, etc Thls, in turn, leads to the need for a
separate plant to manufacture product~ by this proce~s. Also,
the isostatic process is a much more expensive manuf~cturing
procedure than the conventional dry press process. This is
30 particularly true when conventional size pieces or shapes are ~;~
being manufactured However, the isostatic process is ideal
-3-
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1~33~
for forming larga pieces weighing several hundreds of pounds
and having the highly desirable properties o~ high density,
uniformity, low porosity, and high strength.
Thus, while isostatic forming allows the manufacture
of high strength, high density, and low porosity refractories
rom fine grain bodies by pressing, the isostatic process is
characterized by the need for new processing plants and high
manufaaturing costs.
The present invention provides a process for producing
a refractory brick or other refractory product, said process
comprising the steps of preparing a fine grain refractory
material capable of passing a 65 mesh screen, tempering th~
refractory material with a chemical bonding solution, forming
the tempered refractory material into larger size agglomerated
pieces, drying the agglomerated pieces so as to form the chemi-
cal bond, crushing the agglomerated pieces, sizing the crushed
pieces into a suitable mix for press:ing to a shape, moistening
the mix, pressing the mix into a desired refractory shape,
`, and firing the pressed shape in a suitable atmosphere and at
`~` 20 a temperature sufficient to form a ceramic bond and yield a
refractory product having said desired shape.
One of the advantages of the present invention is
that conventional processing equipment may be utilized for
manufacturing a refractory brick or other shape having
greater strength, high density, and lower porosity than refrac-
tory bricks made by conventional dry pressing processes. The
process of the invention is simple and economical and provides -
: :
refractory bricks or shapes which have functional character- ;
istics similar to refractory products produced by an isostatic
forming process.
The following table provides the ranges of properties
that may be obtained by the process of this invention for a ~;
7~ ) I AS;L bR~ 4 ~ ~ ~
t; : ` ` ` `: . ~ ~ ` ' :" '` :
BASIC BRICK
MADE BY T E PREDENSI~lGAI~o~ C~89'--
Bulk Denslty l90-Z20 pcf
Apparent Porosity 7.0-18.0~
Modulus o~ Rupture 1400-2600 p9 i
2700F. M0~ 700~1100 p5i `~
Median Pore Size 2.5-8.0 microns
The invention will now be described in detail. ;-
Broadly speaking, the process of the present invention involves
agglomerating or forming a very fine grained mixture o~ re~rac-
tory materials into larger particles prior to size grading and
dry pressing the larger re~ractory aggregates or particles
into a desired refractory shape by application~o~ unldirec-
tional pressing ~orce. This pretreatment inhibits the forma- ~
tion of laminatlons perpendicular to the direction of the ~ ;
pressing ~orce in the ~inal product. Any agglomerating or
.
pre-~orming technique is acceptable provided the agglomerates
~ormed thereby are suf~iciently hard and strong to withstand ` ~
subsequent processing steps, such as crushing and screening, ~ ~; ,.,7
batching, mixing, tempering a~d pressing. With all pre~ormlng
techniques, the pre~ormed shape is normally dried to develop ~
its strength and then the pre~ormed shape is crushed into par- -
ticles o~ desir~ble brick ~orming sizesO
"
All known refractory materials are amenable to
treatment according to this process, including chrome ores,
magnesite, periclase, alumina, bauxitles, fireclays, zircon
zirconia, etc. Any acid, basic, or neutral re~ractory material
may be used in the practice o~ this inventlon.
.
Speci~ic exampies to illustrate the principles o~
this inventio-n;and the benefits derived ~rom its use will be
given here`ina~ter. These speci ic example~ are chosen ~rom
: .
, . . - . .: .
33~
the basic refra~tory area fGr illustratlve purposes only and
are not to be considered restrictive to the practice of the
inventionO As previously stated, all known refractory mater-
ials are amenable to treatment according to thls process.
Before presenting specific examples o~ this lnven-
tion, a general description of its practlce, including the
various modificati.ons of its pre~erred practice, i8 presentedO
For illustrative purposes and to aid in clarifying the descrip-
tion, a manu~acturing flow sheet depicting the Predensi~ied
10 Grain Basic Brick Process is presented hereinafter. Similar '
flow sheets can be made for other classes of re~ractoriesO
PRED~NSIFIED GRAIN_BASIC BRICK _ROCESS -~
Pre~erred Method
.
Periclase and Chrome Ore or Concentrates
(Any Combination)
Co-Ball Mill to -325 Mesh
With an Average Sub Sieve
Particle Size of 3 to 4 Microns
Batch the Mix Composed o~ 80~ o~ the Ball Milled Ml~ture
! ~ 20 and 20~ o~ -65 Mesh Periclase and -65 Mesh Chrome Ore
`~ In the Same Ratio as the Ball Mill Charge
,,
Temper With A Bond Salts Water Solution Composed o~
MgS04-7X20 and 1~ MgC12-6H20
Briquette at 40,000 psi in Briquette Rolls ~ ~
Dry Briquettes at 350~400Fo ~ ;
' For at Least 1' Hour in a Sha~t Dr~er -'
'Crush Briquettes to 3 Mesh and Fines ~'
~ Using Any Equipment Suitable ~or
` Crushing and Then Screen Into Desired Fractions ;~-
Blend and Temper the Desired Fractions With Bond Solution
Described Above ~or Briquettes or
' With an Aqueous So'lutLon o~ an Organic ~'ond
Press Brick at 11,000 psi ~ -
' ' Dry Brlck at 250-4000Fo ''~'
For at Least 8 Hours
Bùrn Brick at 3200Fo for 10 Hours
' Using a Heating and Cooling Schedule
of 50F./Xour
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~(~83~l84
Periclase or deadburned magnesite and chrome ore
are the principal ingredients of basic refractoriesJ although
other minor 3dditives are 60metimes used with these materials,
~uch as fume sLlica, alumina3 chromic oxide, olivine, etc.
The periclase and chrome ore ingredients may be used
in any proportion in the practice of thi~ ~nventionO The cho-
sen mixtureJ which is to be ~ormed into larger pieces (which
themselves are to be crushed) in the practice of this inven-
tionJ is composed of finely divided particles of periclase and
chrome ore. The finely divided mixture ma~ be prepared by
crushing and ball milling the properly proportioned mixture
together (co-ball milling). This ls the preferred methodO An ~ -
alternate method which may be used i9 to mill the ingredients
separately to the desired degree of fineness, and then to com-
bine them in the desired proportions. The degree of fineness -
of the mixture will affect the properties of the final product
but may be as coarse as 65 mesh or as fine as 325 mesh or
finer. The preferred finene6s is 325 mesh with an average
sub-6ieve size of about 3 to 4 micronsO This is true whether
20 the materials are co-ball milled or milled separatelyO ~;
~ A Fisher Sub-Sieve Sizer is preferably used to de
termine the average grain size in microns of the ball mill
.
` discharge.
When the desired finene66 of the ball mllled material
has been achieved, an addition of 65 mesh or coarser periclase ~;
and chrome ore ma~ be added for the purpose of controlling the
shrinkage during burning~ 9rick made from a mixture of fines
and 65 mesh or coarser materials are more resistant to craze
and edge cracklng o~ firing and can withstand a faster firing
schedule than brick made of all fine~. In the preferred
~,
methodg a 20~ addition of 65 mesh periclase and/or chrome ore
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is made to the mix, prior to forming into agglomerates, but
may also be added to the final brick mix instead.
This mixture is then mixed and tempered with water
and a bonding agent. The preferred bond is a water solution
of 1~ MgS04-7H~0 and 1~ MgC12 6H20, based on the weight of the
mixture belng bonded. Howeverl either of these salts alone or
in amounts greater or smaller than the preferred quantities
may be used. A180, other bonding agents such as sulfuric acid,
hydrochl~ric acid, other sulphate or chloride s~lts, lignin
liquor, etc., may be used. The bond selected, however~ must
provide agglomerates of the fine mixture having adequate hard-
ness and strength to withstand the sub~equ.ent processing re-
quired in the practice of this invention. The amount of
liquid used to temper the ~ixture must be sufficient to gi~e
the mixture the consistency required to form the desired ag-
glomerates.
The tempered mixture is then formed into agglomer- ;
ates or predensified granules of the ~ine mixture. These ag- ~-
glomerates or predensified granules may be formed by several
20 means, such as by extruding into pellets which would require a -
relatively high water content and bond content, agglomerating -
in a mixer which would generally give relatively sQft agglom-
erates, pressing into bricks or dobies on a toggle or hydraul~
ic press, briquetting with briquette rolls, etc. Of the vari~
j ous possible methods for agglomerating or predensi~ying the ~ ~-
fines, the use of briquette rolls is preferred, in whlch
briquettes of almond shape about 1 inch x 3/4 inch x 1/2 inch ; -
in size are formed under a pressure of approximately 40,000
psi. The second pre~erred method ie forming dobies of about
g inch x 4-1/2 inch x 2-1/2 inch size on a hydraulic or
toggle press under a pressure o~ approximately 10,000-15,000
... . ..... . . . .
,
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-
~ 83~
psi .
The method of ~orming the preden~ified granules in-
fluences the hardness, ~trength~ and density of the granules
which in turn influences the behavior o~ the brick made from
the granules and thelr properties. The harder and more dense
the granules the less will be the shrinkage upon firing of the
brick made from the granules. This will be illustrated in the
specific examples which follow.
After forming the briguettes, dobies, or agglomer-
ates, they are dried at a sufficient temperature ~or a 9uf~cient length of time to effect complete drying and to de~elop
the optimum qtrength from the bond added to the mixture.
DryLng may be accomplished in a batch dryer, a tun~
nel dryer, or a shaft dryer in the case of the briquetted
material. The pre~erred method ~or briquettes is to use a
- shaft dryer, exposing the briquettes to a temperature of ~ -~
350F ~400F. for a period of at least one hour, although
somewhat higher temperatures or longer times may be used. In
a shaft dryer the briquettes can be more readily exposed to
` 20 both the temperature and the flow of hot air~ thus reducing
the time required to effect the necessaryjdrying and develop-
ment of bond strength. In the cases of using a batch dryer Dr
a tunnel dryer, it is more difficult to effect the transfer of
heat from the dryer to the briquettes or dobiesO Therefore,
;~ in the batch and tunnel dryer techniquesg a temperature o~
350F.-400F or somewhat higher i9 applied for at least 8
hours. In any case, regardless of the method used to dry the
briquettes or dobies, the temperature and time of drying must
be sufficient to completely dry them and develop their optimum ;
strength.
After drying, the briquettes or dobies or other ag-
'~
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~831~
glomerates of the flne mixture are crushed in suitable equip-
ment to provide predensified grains of the proper grain si~ine
for making dry pressed brick. The grain sizing for making dry-
pressed brick is as follows:
Preferred
Pass 3 mesh on 10 mesh 60~ 40 to 60
Pass 10 mesh on 28 mesh 0 0 to 20
Pass 28 mesh 40 40 to 60
This preferred brick mix grain sizing, or any other
grain sizing that may be desired, may be achieved by screening
the crushed agglomerates into the required fractions and re-
combining these fractions in the desired proportions.
If an addition of 65 mesh or coarser periclase and
chrome was not made to the briquette mix, these materials may
be added to the brick mix otherwise consisting of the crushed ;
predensified fines. If the addition is to be made to the
brick mix, the sized fractions of the crushed predensified
`~ fines must be prepared to allow the 65 mesh materials to bé
accommodated and still retain good pressing characteristics
The fractions of predensified grain and other raw
material fractions, if added, are then mixed and blended and
tempered with water and with bonding agents if desirèd. In
the preferred method, a thick a~ueous solution of an Drganic
bond such as dextrin is used. Preferably, the mix is dry
mixed for 1 minute and then wet mixed or tem~ red for three
minutes. HoweverJ the times for dry and wet mixing may be
varied from the preferred method, as ~ong as the mix is thor
oughly mixed and tempered. A mixer with mullers can be used,
but with the mullers raised above the pan bottom, to avoid "~
excessive breakd~wn o~ thé;predensified granules.
The tempered mix is discharged from the mixer and
- 10 ~
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.
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conveyed by suitable means to a press wherea the brick are
formed. Any type of press may be used which is capable of
forming the brick to the optlmum pressed density. The prefer-
red method of forming is by use of a hydraulic or mechanical
press using a ~orming pressure of 11,000 psi. However, other
pressures may be used provided the brick formed ar~ capable of
being handled after pressing and do not contain laminations or
pressure cracks due to excessive forming pressure.
After forming, the pressed brick are dried~ depend-
10 ing on the bonding agent, from 250F. to 400F. for at least 8
hours. However, the criteria for selecting the drying condi-
tions are that the brick be sufficiently dry to avoid cracking
when exposed to high temperatures in firing and to possess
su~ficient strength to withstand handling in the case where
the brick are transferred ~rom the dryer cars to tunnel kiln
cars or to a periodic kiln. When the pressed br~ck are set
directl~ from the press to tunnel klln cars or to periodic
kiln cars, the requirement is then reduced to sufficient dry-
ing to avoid cracking in firing.
After drying the brick are set to tun~el kiln or
periodic kiln cars, assuming they are not directly set to the
; tunnel kiln or periodic kiln cars after pressing, for firing.
The preferred method of firing or burning the brick is to heat
and cool the brick at a rate of about 50F. per hour using a
top temperature of 3200Fo and holding the brick at the top
temperature ior 10 hours. However, deviations from this pre-
ferred method of firing the brick can be used which will,
within limits, provide brick of somewhat improved properties. .
Moving from the general description of the process
30 and products derived from it, specific examp~es are now given
in detail to illustrate the practice of the invention, the
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bene~its to be derived from it, and the effects of varying the
processing parameters as described prevlously.
Example No. 1
In this example a basic refractory material having a
nominal MgO content of 60~ was made using a combination of 50
Phllippine chrome ore concentrates (-10 mesh) and 50~ of a
high purity sea-water periclase grain pre crushed to -10 mesh
and fines. The characteri~tics of the~e material~ were as
~ollows:
~10 Chemical AnalysisPhilippine Chrome Ore Periclase
MgO 15.4~ 98.2%
CaO 0.29 o.67
SiO2 2.93 o.76
A1203 29.5 0.16
Fe23 14.6 0.17
Cr203 34.1 Tr.
~ulk Specl~ic Gravity, g/cc 3.84 3.33
~' True Specific Gravity, g/cc 3.98 3.56
The chrome ore and periclase were ball milled to-
gether to several degrees of fineness; i.e.l minus 65 ~esh,
. minus 150 mesh3 and minus 325 mesh. ~ ;~
Each co-ball milled mixture was mixed with a water
` solutlon of 1~ MgC12 6H20 and 1% MgS04 7H20, based o~ the dry `~-
, ~ , - , .
weight of the mixture. The dampened mixtures were then formed ~
,
on Komarek-Greaves briquetting rolls lnto almond shaped
briquettes. These briquettes were then dried at 350F. for ~;
about 16 hours in a batch dryer until the briquettes were dry
and hard.
After drying each of the types of briguettes were
crushed and sized to give a normal brick making grain-sized
` -12-
:
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1~83~
mixture approximately as follows: -
Pass 3 on 10 mesh 25
Pa5 5 10 on 28 mesh 20
Pass 28 on 65 mesh lO
Pass 65 mesh 45
Each of these grain-sized mixtures were then mixed
in a muller-type mixer with the mullers raised and with su~fi-
clent water to give the mix a suitable dry pressing consist-
ency. These mixes were then formed into brlck on a hydraulic
press using a ~orming pressure of ll,000 psl. No laminatio~s
; or pres~ure cracks were evident ln the pressed brick.
The ~ormed brick from each mix were then dried in a
batch dryer for about ~4 hours at 350F. Theidried brick were
set and fired in a gas-fired periodic kiln at 3150F. ~or lO
hours u6ing a heating and cooling rate of about 50F. per
; hour.
~ After cooling, the brick from each mix were tested
- and examined. No laminations were evident in the fired brick
a}though some cra~ing and edge cracking was noted. The brick
~; 20 properties are given in Table I along with properties usually
obtained on brick of similar composition but made using normal
dry press brick-making techniques and to properties usually
obtained on brick of similar composition but made by the iso
static ~orming process.
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33~84
TABLE I
Conventional ~ -
Isostatic Dry Press
A B C Process Process
MgO Content ~ -- 60% ----------------------
Mix:
Agglomerate A 100%
Agglomerate B 100~
Agglomerate C 100%
10 Water -------~ 4% -~~~~~~~
Firing
~'emperature ----- 3150F.------_
Manufacturing
Shrinkage 7.4~ 5.9~ 3.1
Bulk Density~
pc~ 216 203 194 212 189-195 ~ :~
Modulus of
Rupture
psi 2315 1405 1685 5000 600-goo ~; .
20 Hot
Modulus
of Rupture,
2700F., psi1020 895 740 ~ -
Apparent
Porosity 7.5~ 13.5% 17.2~ 8.5% 16-19%
Apparent
` Speci~ic
~ravity,
~/cc 3,74 3.76 3.78 3072 3.71-3075 -
30 Median Pore
Size, No
Microns 2.7 6.2 Data 1.8 18.8
Agglomerate A - Briquetted co-ball milled -325 mesh mixture o~
50~ periclase and 50~ chrome ore concentrates.
` Agglomerate B - Briquetted co-ball milled -150 mesh mixture of
50~ periclase ~nd 50~ chrome ore concentrates.
Agglomerate C - Briquetted co-ball milled -65 mesh mixkure of
50~ periclase ~nd 50~ chrome ore concentrates
:
As may be seen, as the ~ineness o~ the predensi~led
materials decreases, the density and stren~th decrea~es and the
porosity and pore size increases. The brick made by this in~
vention using -325 mesh material have superior properties to
.:
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' ' : ~ . . ' . , '
' ~ "' ' ' ' ' ' ' ". ' "'. " ', ' ' ',, '
1~38~
conventional dry pressed brick and properties approaching
those of isostatically formed brick.
~ e No. 2
When brick are made from all predensified fine ma-
terlal according to this invention, they undergo the highest
amount of shrinkage on firing. Thi~ sometimes results in
b~ick having some surface craze cracking and edge cracking,
which is probably due to heating them on a schedule too fast
to accommodate the hlgh shrinkage. While the cracking is con-
~ined to the surface with the interior of the brick being
sound and crack free, this surface and edge cracking may be
considered at times to be ob~ectionable.
It was found that one method for elim~nating this
cracking or reducing it to an acceptable minimum, aside from
slower firing schedules, was to increase the grain size o~ ~he
mixtures to be brlquetted; i.e., by increaslng the grain size
~rom the preferred -325 mesh size to -150 mesh or -65 mesh
slzes. However, as seen from the data given ln Ta~le I, in-
creasing the grain size in this manner resulted ln decreased
density and increased porosity.
In this example~ another method of elimlnating or
reducing the surface crazing and edge cracking is de~cribed.
A basic refractory having a nomlnal MgO content of 60~ was
made ln the same manner as described ln Example 1 usin~ the
~325 mesh co-ball mllled mixkure. In addltion, another basic
.: :
~ refractory o~ similar composltlon ~as ~adeJ but in this caseJ
.~ .
` ~ 85% of the brick mix wa~ composed o~ granules of the preden
sified brlquette ~ines and 15% o~ the brick mix was composed
of 7.5% of -65 mesh chrome ore concentrates and 7.5% of -65
mesh periclase. All other aspects o~ the manuPacture of the
brick of this second basic refractory were the s~me as de-
-15-
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~83~t34
scribed in Example 1. The properties of the brlck mad0 by
these two techniques are given in Table II.
As may be seen from these data, adding the -65 mesh
periclase and chrome ore decreased density and manufacturing
shrinkage and increased strength, porosity, and pore size.
TABLE II
MgO Content ~ - 60% ---~
Mix: A _ A-1
A~glomerate A 100~ 85~ .
lO Pericilase, -65 mesh, ball milled 7.5
Chrome ore concentrates, -65
mesh ball milled ,7.5 : -
Water --~ 4% ~
Firing Temperature ----- 3150F.------
Manu~ac~turing shrinkage 7.4~ 6.9% : :
Bulk density~ pc~ 216 210
Modulus o~ rupture, psi 2315 2640
Hot modulus of rupture,
2700F., psi . 1020 1315 :~
20 Apparent porosity 7.5~ 10.2
Asparent speci~ic gravity
Median Pore slze, microns 2.7 7.6
Example No. 3
In addition to making brick using all ~ine materials
as described in the previous examples, it was ~ound that addi
tions o~ predensified granules o~ -325 mesh fine materials to -
a normal brick mix of a 60~ MgO type product resulted in im-
pro~ed properties In~this example, predenqi~ied granules of
co ball milled -325 mesh materials were crushed to -3 mesh and
fines and were then added to a normal brick mix in increasing
amounts as shown in Table III. As~ay be seen, as the amount
~,
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~ . . ~, . , .. , , ~ . . . .
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~383~
o~ predensified granules in the mix increased, the density in-
creased and the porosity decreased.
TABLE III
Mix D E F G
Periclase
Pass 4 mesh and
retained on 65
mesh~ ~ 3 22.5 15 7.5
Ball milled and
passing 65 mesh 25 18.75 12.5 6.25
Chrome Ore Concentrakes
Pass 10 mesh and
retai~ed on 65 mesh 25 18.75 12.5 5.25
Ball milled and
passing 65 mesh 20 15, lo 5
Agglomerate B,
(Table II), 3 mesh
and fines 0 25 5 75
Water -- 4%
20 Firing Temperature F. -- 3150F~
Manu~acturing
Shrinkage +0. 75% +0.25% -1.3%-3~ 5
Bulk density, pcf 182 185 lgo 195
` - Modul~s of rupture,
`; psi 515 55 67~ 1210 - `
Hot modulus o~
rupture, 2700F., psi 735 455 445 580
~ Apparent porosity 22.5~ 20.6% 18.7%16.7%
i~ Apparent specific
30 gravity 3.76 3.74 3.753.76
Example No. 4
~:A wide variety o~ compositions can be made using the
predensified grain brick process. Table IV illustrates proper-
'ties o~ brick made-in nominal 30~ MgO and 80% MeO composLtions
and ~rom the same raw materials as were used in the previous
examples but in different proportions. For-comparison, similar
17
.:
~;: ' - '' ':
- , ,
i : . . . ~ .
, .
data for isostatically ~ormed, and conventionally processed
brick are ~hown.
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.
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o u~ ~ ~ )~ ~o o
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~19-
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Example ~o. 5
In brick mixes made with the same agglomerated grain, ~.
it is possible to alter the grain size of the additlon made to
the brick mix with corresponding alterations in the brick
properties. This is illustrated by Mixes H and I shown in
Table V.
: Both brick mixes were constituted of 80% of the same
agglomerate crushed to 3 mesh and fines. To brick mix H was
added 10% each Df -65 mesh periclase and -65 mesh chrome ore,
- 10 while to brick Mix I was added lO~ each o~ -28+65 mesh peri-
clase and chrome ore.
It can be seen that the mix with the -65 mesh addl-
tions had a higher manufacturing shrinkage and produced brick
with higher bulk density, modulus of ruptu.re and lower appar- :
ent porosity, but that the brick made ~rom tha m~ with the ~ ;
-28+65 mesh additions had slightly better thermal shock re- :
sistance. ~ ~
. 1
?1
~ ,,
; ~' ,,
'~, ' ;'' '
~ '~','' ~',
' '
, ~ . .
~ ~, ' , ~ . ' ' ; ' .
: . .
3LS~1~3~
TABLE V
MgO Content ------ 60% ------
Mix: H
-
Ag~lomerate Mix
Co-Ball Milled to 5 microns
Periclase 50% 50%
Chrome Concentrate 50 50
MgSO4 (Extra)
MgC12 (Extra
Moisture 4 4
(Bri~uetted at 40,000 psi)
Brick Mix
Agglomerate, Crushed, 3 M/F 80% 80%
:Periclase, -28+:65 Mesh 0 10
Periclase, -65 Mesh 10 0
Chrome Concentrate, -28+65 Mesh 0 10
Chrome Concentrate, -65 Mesh 10 0 - -
Dextrin (Extra) 2 2
Moisture (Extra) 2 2
Firing Temperature -------3200F.------
Manufacturing Shrinkage 5.8% 4.0%
Bulk Density, pcf 206 202 :::
Modulus of Rupture, psi 2030 1~.65 :~
Apparent Porosity, % 12.2 13.8 :-
Apparent Specific Gravity, g/cc 3.76 3.76
Prism Spalling, Cycles to Fail 5 7
EXAMPLE No. 6 :
This example illustrates the preferred way to add a
coarser fraction to the otherwise very fine ingredients to con-
trol shrinkage and densification of the brick, and at the same
time permit effective and economical utilization of fine grained
low silica Phili~pine Chrome concentrates marketed as "Losil"
(R.T.M.) This material is also referred to as 100 mesh concen-
trates, whereas screen analysis indicates it to be all essen-
tially -65+325 mesh. It should be pointed out that these high
;, .
purity chrome concentrates could have been substituted for the ~:
10 mesh concentrates in all of the previous examples except ~:
Example No. 5 in which a -28+65 mesh chrome concentrate was
added to the brick mix. This fraction is.not available in
-21-
':
~ - . - . , ,, . , . : ~
- : . .
.,:~. , . . , ~ .
8~
the Philippine "Losil" chrome concentrates.
Mix J in Table 6 shows additions of 11% -6S mesh
periclase and 9~ of Losil chrome ore to the brick mix other-
wise consisting of 80% crushed agglomerated grain, whereas in
Mix K, the additions of 11~ -65 mesh pericalse and 9~ Losil
chrome ore were blended with the co-ball milled periclase and
chrome prior to briquetting.
After the briquettes were drled and crushed to 3
mesh and fines, to facilitate pressing, the -10~28 mesh frac~
tion was removed by screening, crushed to pass 28 mesh and
fines) and blended back to the 3 mesh and fines. ~
Mix K brick made by adding -65 mesh material to the ~ -
briquette mix had a slightly higher manu~acturing shrinkage
and density, lower porosity~ and smaller pore size than brick
made by the first method. The brick made by the second method
had a slightly smoother texture than brick made by the fir
method.
: .. ; ';' ' '.,',
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. '
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-22-
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~83~
TABLE VI
Mix: J K
Agglomerate Mixes
Pericalse, -65 mesh 0
"Losil" chrome Conc.
(100 mesh, a~ rec'd) 0 9
Co-Ball milled to 4.0 microns
Periclase 55 44
"Losil" Chrome Conc. 45 36
MgC12, Extra
MgS04, Extra
Moisture, Extra 4 4
(Briquetted at 40,000 psi)
Brick Mixes
Agglomerate, 3/10 mesh 60% 60%
Agglomerate, 28/F mesh 20 40
Periclase, 65/F 11 0
"Losil" Chrome Conc.
(100 mesh, as rec'd) 9 0
Dextrin, Extra 2 2
Moisture~ Extra 2 2
Firing Temperature ~ - 3200F. ~
Agglomerate, Bulk DensityJ g/cc 3.00 3. o6
Manufacturing Shrin~ge, ~ 5.0 5.5
Bulk Density, pcf 200 203
Apparent Poroslty, ~ 14.7 13.1
Apparent Specific Gravity, g/cc 3.77 3.75
Modulus of Rupture, psi 1955 2235
2700F. Modulus of Rupture~ psi 895 890
30 Medlan Pore Slze, i~lcrons9.7 6.2
.~
' ' '' ' .
:
23-
