Method of flame spraying refractory material

A method of flame spraying refractory material for in situ repair of, e.g., furnace linings wherein an inert carrier gas incapable of supporting combustion and particles of refractory oxide and combustible metal or other oxidizable material are delivered to a flame spraying apparatus wherein high pressure oxygen aspirates and accelerates the carrier gas-particle mixture; a controlled ratio of 5 to 1 to about 30 to 1 oxygen gas to carrier gas; allows for the use of highly combustible metals and materials such as chromium, aluminum, zirconium, and/or magnesium as heat sources without back-flash and at a deposition rate in excess of 2000 pounds per hour of refractory oxide to yield a deposited refractory mass exhibiting enhanced wear and erosion resistance.

BACKGROUND OF THE INVENTION 
1. Technical Field 
This invention relates to the repair of worn or damaged refractory linings 
and, more particularly, to a method of and apparatus for flame spraying 
refractory materials containing chromium, aluminum and/or magnesium 
oxidizable particles for in situ repair of these linings. 
2. Description Of The Related Art 
Metal processing furnaces, ladles, combustion chambers, soaking pits, and 
the like are lined with refractory brickwork or coating. These linings 
become eroded or damaged due to the stresses resulting from high 
temperature service. 
It has long been the objective of operators to repair such ovens or 
furnaces linings in situ while they are hot. Such in situ repair 
eliminates the need for cool down and heat up time periods, as well as 
thermal shock damages caused by excessive temperature change. 
The technique of flame spraying is well known in the art. By this 
technique, molten or sintered refractory particles are sprayed from a 
lance into the furnace under repair. Such a lance may be wrapped in a 
fiber protective blanket or may be provided with a water cooled outer 
jacket so as to protect it from the high temperatures encountered during 
the spraying operation. 
Previous flame spraying techniques used pulverized coke, kerosene, or 
propane gas as a fuel which was mixed with refractory powders and oxygen, 
and projected against the wall being repaired. 
British Patent Specification No. 1,151,423 teaches entraining powdered 
refractory in a stream of fuel gas. Patent Specification No. 991,046 
discloses entraining of powdered refractory material in a stream of 
oxygen, and using propane as a fuel. 
U.S. Pat. Nos. 2,741,822 and 3,684,560 and Swedish Patent No. 102,083 
disclose powdered metals as heat sources. These processes allow the 
formation of shaped masses of refractory by oxidation of one or more 
oxidants such as aluminum, silicon and/or magnesium in the presence of 
refractory oxides such as Al.sub.2 O.sub.3, MgO or SiO.sub.2. These 
processes teach the use of finely divided, oxidizable metal powders having 
a size below about 50-100 microns. This size oxidizable metal promotes 
rapid oxidation and evolution of heat so as to liquify or soften the 
entrained refractory particles as well as to soften the area being 
repaired. It is taught that these processes are dangerous due to 
flash-backs. During a flash-back, the reaction can travel back up the 
lance or the carrying hose to the machine or the operator, and can cause 
injury as well as disruption of the repair. Flash-backs are a major 
disadvantage of flame-spraying processes. 
British patent application No. GB2035524B teaches a process wherein a 
carrier gas of air or other inert gas is used to convey a powdered 
refractory and oxidizable substances to the outlet of a lance where they 
are mixed with oxygen which was separately conveyed to the outlet of the 
lance. While overcoming some of the hazard of flame spraying refractory 
and oxidizable powders, this process results in extremely low deposition 
rates. The low deposition rate is due to the small quantity of mixture 
carried in the inert gas, about 0.5 kg in 50 to 100 liters per minute. The 
large amount of oxidant necessary to overcome that proportion of air adds 
to the expense of the process and introduces further dangers, such as 
occur when the materials are mixed together. For instance, the example 
teaches the use of 40% of metal oxidants in a -100BS mesh form (about 150 
microns). This process also consumes very large volumes of oxygen to 
offset the inert gas carrier in a ratio of about 2:1 to 4:1. 
The flame spraying of refractory oxides of aluminum, silicon, and/or 
magnesium is well known in the art. But when silicon and 
aluminum/magnesium are used as fuels in conjunction with these refractory 
oxides, residual silicon (SiO.sub.2) is produced so that the resulting 
deposited refractory masses are not sufficiently refractory to withstand 
the wear and tear of high erosion environments. Oxidizable powders and 
refractory powders which would yield more wear resistant deposited 
refractory masses, such as chromium fuel to deposit residual chromium 
oxide, and zirconium fuel to deposit zirconia, are highly reactive and 
have heretofore not been usable in flame spraying methods due to 
backflashes, etc. 
It would be desirable, therefore, to have a method of and apparatus for 
flame spraying entrained refractory and oxidizable powders which achieves 
significantly higher deposition rates than obtainable in the past, as well 
as which allows for the use of oxidizable and refractory powders which, up 
to now, have been deemed too reactive and too prone to induce 
back-flashing and large system explosions. 
SUMMARY OF THE INVENTION 
The invention provides a method of and apparatus for flame spraying 
refractory material for in situ repair of, e.g., furnace linings. An inert 
carrier gas incapable of supporting combustion and particles of refractory 
oxide and combustible metal or oxidizable material are delivered to a 
flame spraying apparatus wherein high pressure oxygen aspirates and 
accelerates the carrier gas-particle mixture. A controlled ratio of 
carrier gas to oxygen allows for the use of highly combustible metal 
particles such as chromium, zirconium, aluminum and/or magnesium as heat 
sources without backflash. The method and apparatus allow for a deposition 
rate in excess of 2000 pounds per hour of refractory oxide to achieve a 
high quality refractory mass having improved wear and erosion resistance. 
The process of the invention allows for the use of chromium, magnesium, 
zirconium and other highly reactive oxidizable materials and mixtures 
which impart better chemical, refractory, and high melting point 
characteristics to the resulting deposited refractory mass than silicon 
and other low melting point materials. 
The apparatus of the invention aspirates and accelerates the entrained 
particles to provide greater density and lower porosity to the resulting 
deposited refractory mass, thus improving its wear characteristics. 
The method and apparatus of the invention substantially increase the rate 
of application of the deposited refractory mass as compared to prior art 
methods and apparatuses, thus reducing the application time thereby 
rendering the method and apparatus of the present invention desirable in 
high productivity applications where non-productive down time has a high 
relative cost. 
Accordingly, the invention provides a method of forming a refractory mass 
wherein a mixture of carrier gas and entrained particles of an oxidizable 
material and an incombustible refractory material are aspirated into a 
flame spraying apparatus by means of a high pressure stream of oxygen to 
form an oxygen-carrier gasoxidizable material-refractory material stream. 
As used in the specification and claims, the term carrier gas or inert gas 
means any gas incapable of supporting oxidation of the oxidizable 
elements, and includes air as well as the noble gases such as argon. 
The aspiration is carried out to provide an oxygen to carrier gas ratio of 
from about 5 to 1 to about 30 to 1, and, more preferably from about 8 to 1 
to about 12 to 1. The ratios of oxygen to carrier gas are delivered at 
relative pressures so as to accelerate the aspirated particles. 
The oxidizable material comprises chromium or aluminum or magnesium or 
zirconium, and mixtures thereof. The refractory material comprises oxides 
of chromium or aluminum or magnesium or iron in both oxidative states as 
well as zirconium or carbon. The oxidizable material comprises about 5 to 
20% by weight, preferably 8 to 17% by weight and more preferably about 8 
to 12% by weight of the particles in the mixture. 
The refractory material may comprise silicon carbide; in such a case the 
oxidizable material may be silicon, aluminum, chromium, zirconium or 
magnesium, and mixtures thereof, and comprises 10 to 30%, preferably 15 to 
25% by weight of the particles in the mixture. 
In all instances, the oxidizable material has an average grain size of less 
than about 60 microns, and preferably, less than about 20 microns. 
The invention also provides an apparatus for forming a refractory mass 
comprising high pressure oxygen stream aspirating means for aspirating 
into a flame spraying means, a mixture comprising a carrier gas and 
entrained particles of an oxidizable material and of an incombustible 
refractory material to form an oxygen-carrier gas oxidizable 
material-refractory material stream. The aspirating means may be located 
anywhere in the flame spraying means up to its outlet. The lance may be 
insulated or water jacketed against the high temperature environment of 
use. The apparatus may include means for forming the mixture of the 
carrier gas and the entrained particles, such as an air or other carrier 
gas inlet in fluid communication with a particle inlet, such as a screw 
feed or gravity feed; the means for forming the mixture may be a motor 
driven impeller to which air or inert gas is added. 
These and other features of the invention will be better understood from 
the following detailed description taken in conjunction with the 
accompanying drawing.

DETAILED DESCRIPTION OF THE BEST MODES 
Referring to FIG. 1A, there is shown generally at 10 a flame spraying lance 
having an outlet tip 12, a body 14 surrounded by insulation 16, and an 
inlet end 18. The inlet end 18 of the lance 10 is equipped with an 
aspirator 19 having a restriction 20 wherein high pressure oxygen from a 
source S passes through a nozzle 21 to aspirate a mixture of carrier gas 
and entrained particles from the conduit 24. 
FIG. 1B illustrates another arrangement for aspiration and acceleration of 
the mixture of carrier gas and particles wherein the nozzle 21 delivers 
high pressure oxygen from source S to a point midway where conduit 22 
enters the aspirator 19. 
FIG. 2 shows a flame spraying lance 10' similar to that of FIG. 1B, except 
that instead of the aspirator 19 being located outside the body, the 
restriction 20' is located within the body 14' of the lance 10', and the 
entire lance 10' and the conduit 22' are illustrated as being sheathed in 
insulation 16'. As in FIG. 1B, oxygen is delivered via a nozzle 21' to a 
point midway where conduit 22' enters the body 14' to aspirate and 
accelerate the mixture. 
FIG. 3 illustrates the various spraying machines by which a carrier gas and 
particles are mixed to form a stream to be aspirated by the flame spraying 
apparatus of the invention. FIG. 3A illustrates a spraying machine 30 
having a hopper 31 containing particles P of oxidizable material and 
refractory material. The hopper 31 is emptied by a screw feed 32 into a 
funnel 34 in fluid communication with an aspirator 36 having a downstream 
restriction 38 into which a stream of carrier gas from source C is 
directed through nozzle 40. The venturi 38 is in fluid communication with 
conduit 24 to deliver the stream of carrier gas and entrained particles to 
a lance such as 10 in FIGS. 1A and 1B or 10' in FIG. 2. FIG. 3B 
illustrates a spraying machine 30' having a hopper 31' emptying into an 
aspirator 36' having a downstream restriction 38' with which it is in 
fluid communication. The emptying can be enhanced by providing external 
air pressure onto the contents of the hopper 31'. As in FIG. 3A, carrier 
gas from source C delivered through nozzle 40' aspirates the particles P 
to form a stream exiting the restriction 38' into the conduit 24' to be 
delivered thereby to a flame spraying lance. Instead of a venturi, FIG. 3C 
illustrates that the spraying machine 30" may have a motor driven impeller 
42 to impell the particles into which is added an appropriate amount of a 
carrier gas to form an entrained particle stream for delivery through 
conduit 24" to a flame spraying apparatus. 
The use of an aspirator in the illustrated forms on the inlet end of a 
lance or anywhere along the length of the lance introduces sufficient 
oxygen as the accelerator to optimize the oxygen-carrier gas-oxidization 
material-refractory material exit velocity at the outlet end of the lance. 
The introduction of an inert carrier gas such as air into the particle 
stream from the spraying machine will introduce sufficient dilution effect 
so as to inhibit backflash reactions when oxygen is added. Control of the 
ratio of carrier gas to oxygen eliminates or renders harmless any 
backflashes which may occur in the lance, and eliminates or minimizes the 
"tip" reactions which are found to occur at outlet end. Tip reactions 
cause buildup of refractory mass at the outlet end or along the length of 
the lance, and require the process to be discontinued until the lance is 
cleaned or replaced, causing delay. 
It is important that the oxygen to carrier gas dilution ratio be in range 
of 5-1 to 30-1. The use of the aspirator on the lance inlet or along its 
length prior to the outlet provides the flexibility for application rates 
from as little as 1 lb./min. to 50 lbs./min. 
Application rates of 100 lbs./min. can be achieved using proportionately 
larger lances and higher oxygen feed rates together with higher carrier 
gas/particle feed rates. 
The dilution effect of the inert carrier allows the process to utilize one 
or more highly reactive oxidizable materials such as chromium, aluminum, 
zirconium and/or magnesium without encountering backflash problems. 
The dilution effect of the inert carrier allows the process to utilize 
pre-fused refractory grain/powder which may contain a combination of up to 
15% of iron oxides (FeO, Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, or rust) 
which are known to cause explosions when mixed with pure oxygen without 
encountering backflash or explosion problems. 
Adjustment of the oxygen/carrier gas/particle mixture within the parameters 
set out herein will allow the use of other highly active materials such as 
finely divided zirconium metal powder or materials containing up to 80% 
iron oxide. 
The use of finely divided oxidizable powders in an aggregate amount of 
8-12% is sufficient to create a high quality refractory mass with regard 
to mass chemistry, density and porosity when using this process to create 
magnesium oxide/chromium oxide/aluminum oxide refractory matrices. Such 
powders preferably consist of one or more of chromium, aluminum, 
zirconium, and/or magnesium metals; such powders produce 
magnesia/chromite, alumina/chromite, magnesite/alumina, and 
zirconia/chromite bond matrixes and/or any combination thereof. Such bond 
matrices will improve wear resistance in high temperature environments 
over silica type bonds produced by using less reactive silicon powder used 
by the prior art as part or all of the oxidizing materials. 
Silicon powder can be used to add controlled percentages of silica to the 
final chemical analysis, thus allowing for a full spectrum of control over 
final chemical analysis. Such additions could substantially increase the 
total percentage of oxidizable powders since silicon provides relatively 
less heat of reaction than more reactive oxidizable powders such as 
aluminum or chromium or magnesium or zirconium. A typical substitution 
would be 2% of silicon for every one percent of other powder. Such 
substitution could be expected to add silica to the final refractory mass 
analysis. The use of finely divided oxidizable powders in an aggregate 
amount of 15-25% is sufficient to create a high quality refractory mass 
with regard to mass chemistry, density and porosity when using this 
process to create silicon carbide base refractories. 
The preferred particle size of the oxidizable materials is below about 60 
microns; the more preferred particle size is below about 40 microns and 
the most preferred particle size is below about 20 microns. Smaller 
particle sizes increase the rate of reaction and evolution of heat to 
result in more cohesive refractory masses being deposited. 
The very fine particles of oxidizable material are substantially consumed 
in the exothermic reaction which takes place when the oxygen-carrier 
gas-oxidizable material-refractory material stream exits the lance. Any 
residue of the stream would be in the form of the oxide of the substances 
therein or in the form of a spinel created by the chemical combination of 
the various oxides created. In general the coarser the oxidizable 
particle, the greater the propensity for it to create the oxide rather 
than to be fully consumed in the heat of reaction. This is an expensive 
method of producing oxide, however, and it is preferred generally to use 
the very fine oxidizing particles as disclosed above and to achieve the 
desired chemistry by deliberate addition of the appropriate refractory 
oxide. 
The use of chromic oxide as part of the chemistry of refractory masses used 
in high temperature conditions has long been recognized as a valuable 
addition to reduce thermal shock or spalling tendencies and enhance wear 
and erosion resistance characteristics. Chromium oxide occurs naturally in 
various parts of the world; although it is heat treated in various ways, 
such as by fusing, it contains by-products which are difficult or 
expensive to eliminate. One particular source has a high proportion of 
iron oxide as a contaminant. This material has proved to impart 
particularly good wear characteristics to refractory masses in certain 
applications. 
Another material is produced by crushing refused grain brick such as was 
produced by Cohart. Some are known commercially as Cohart RFG or Cohart 
104 Grades. Again some of these materials typically contain 18-22% of 
Cr.sub.2 O.sub.3 and 6-13% of iron oxide. When using these materials in 
the presence of pure oxygen, violent backflashes occur. When diluted with 
an inert carrier before oxygen is added, however, backflashes are 
eliminated or reduced to a non-dangerous, non-violent level. 
The ratio of carrier gas to oxygen has an important effect on the ability 
to create the correct conditions for the exothermic reaction. Too much air 
will dampen or cool the reaction resulting in high porosity of the formed 
mass and hence reduce wear characteristics of the mass. In addition, it 
will substantially increase the rebound percentage and hence increasing 
the cost of the mass. It can make the exothermic reaction difficult to 
sustain. It has been found that a spraying machine conveying the particles 
using air as the aspirant most preferably operates at 5-15 psi air, 
conveying the particles to the flame spraying apparatus using oxygen as 
the aspirant, preferably at 50-150 psi oxygen. In this case the same size 
nozzles for air and oxygen give an average most preferred dilution volume 
ratio of 10 to 1 oxygen to air. Dilution ratio as low as 5 to 1 oxygen to 
air and as high as 30 to 1 oxygen to air can be effective although at 30 
to 1, one can begin to experience backflashes with particularly active 
materials such as iron oxide or chromium metal. The most ideal operating 
pressures are 8-12 psi air and 80-120 psi oxygen and as close as possible 
to 10 to 1 operating pressures, i.e., 8 psi air to 80 psi oxygen, and 12 
psi air to 120 psi oxygen. 
By adjusting the oxidizing/refractory oxide ratio to compensate for the 
melting point changes of the different refractory oxides, it is possible 
to create refractory masses of almost any chemical analysis. It has been 
found that when flame spraying MgO/Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3 
materials, oxidant mixtures of one or more of aluminum/chromium and/or 
magnesium allow accurate chemical analysis reproduction, low rebound 
levels (material loss) and high quantity and high quality refractory mass 
production with regard to density and porosity. The most ideal percentage 
by weight of oxidizing material in this type of mass was 81/2-10 1/2%. 
The refractory oxide materials used can vary over a wide range of mesh 
gradings and still produce an acceptable refractory mass. High quality 
masses are obtained using refractory grains screened -10 to dust USS and 
containing as low as 2% -200 mesh USS. Other high quality masses are 
formed using refractory grains sized -100 to dust USS and containing over 
50%-200 USS. In general, refractory mass build up is faster when coarser 
particles are used. Excessive percentages of coarse material can cause 
material settling in the feed hose and lower rates of refractory mass 
formation. 
A major benefit of this invention is that refractory masses have been 
formed at rates of over 2,000 lbs. per hour. By increasing the feed rate 
of the carrier gas/particle mixture and increasing the size of the venturi 
and/or lance, it is projected that feed rates of 6,000 lbs. per hour and 
up can be achieved. It is important to maintain the oxygen/carrier gas 
ratio of between 5-1 oxygen/carrier gas and 30-1 oxygen/carrier gas in 
this scale up. 
The best modes of practicing the invention can be further illustrated by 
the following examples. 
EXAMPLE I 
Refractory blocks/bricks in the tuyere line of a copper smelting converter 
were repaired in situ at or close to operating temperature by a process 
according to the invention using a mixture consisting of 91% of Crushed 
RFG bricks known in the trade as Cohart RFG containing screened -12 dust 
USS Mesh grading; 5% aluminum powder of 3 to 15 micron particles size 
average and 4% chromium powder 3 to 15 micron particles size average. The 
mixture was transported in a stream of air at 10 psi to the venturi on the 
inlet end of the lance where it was projected at a rate of 1700 lbs. per 
hour by a stream of oxygen at a pressure of 100 psi against the worn 
tuyere line which was at a temperature in excess of 1200.degree. F. to 
form an adherent cohesive refractory repair mass. 
EXAMPLE II 
The process of Example I was repeated substituting 20% of crushed 93% 
Cr.sub.2 O.sub.3 bricks with a typical mesh grading of -60 to dust mesh 
for 20% of the RFG bricks in Example I. 
EXAMPLE III 
The process of Example I was repeated using 0.5% magnesium powder and 1% 
additional chromium powder both with an average micron size of between 
3-15 microns. 
EXAMPLE IV 
The process of Example I was repeated except that 1% aluminum powder was 
replaced by 1% of RFG bricks giving 92% RFG bricks, 4% aluminum powder and 
4% chromium powder. 
EXAMPLE V 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
Amount by Weight 
Average Grain 
% Size 
______________________________________ 
MgO 59-68% -12 to dust USS 
Cr.sub.2 O.sub.3 
13-23% -12 to dust USS 
Fe.sub.2 O.sub.3 
5-9% -12 to dust USS 
Al metal powder 
5% 3-15 microns 
Cr metal powder 
3% 3-15 microns 
Mg metal powder 
.5% 3-15 microns 
Si metal powder 
2% 3-15 microns 
______________________________________ 
EXAMPLE VI 
the process of Example I was repeated, but using the following mixture: 
______________________________________ 
MgO 49-53% 
Cr.sub.2 O.sub.3 25-27% 
Fe.sub.2 O.sub.3 4-6% 
SiO 1-2% 
Al metal powder 9% 
Cr metal powder 6% 
Mg metal powder .5% 
______________________________________ 
EXAMPLE VII 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
MgO 49-53% 
Cr.sub.2 O.sub.3 25-27% 
Fe.sub.2 O.sub.3 4-6% 
SiO 1-2% 
Al metal powder 9% 
Cr metal powder 7.5% 
Mg metal powder .5% 
______________________________________ 
EXAMPLE VIII 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
Purity % By Weight 
of Material 
in Recipe 
______________________________________ 
MgO 96% 63% 
Cr.sub.2 O.sub.3 
93% 23% 
Al Metal 99.7% 5% 
Powder 
Cr Metal 99.9% 7% 
Powder 
______________________________________ 
EXAMPLE IX 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
% By Weight 
in Recipe 
______________________________________ 
MgO 63% 
Cr.sub.2 O.sub.3 
23% 
Al Metal 7% 
Powder 
Cr Metal 7% 
Powder 
______________________________________ 
EXAMPLE X 
The process of Example I was repeated using the following mixture: 
______________________________________ 
Variance Purity 
% by Weight 
of Material in Recipe 
______________________________________ 
MgO 96% 61.5% 
Coke Dust 97% Carbon 25% 
Al Metal 99.7% 5% 
Powder 
Cr Metal 99.9% 9% 
Powder 
Mg Metal 99.9% .5% 
Powder 
______________________________________ 
EXAMPLE XI 
The process of Example I was repeated using the following mixture: 
______________________________________ 
% by Weight 
in Recipe 
______________________________________ 
MgO 60.5% 
Coke Dust 25% 
Al Metal 7% 
Powder 
Cr Metal 7% 
Powder 
Mg Metal 5% 
Powder 
______________________________________ 
EXAMPLE XII 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
Purity of % by Weight 
Material in Recipe 
______________________________________ 
MgO 97.3% MgO 88.5% 
Al Metal 99.7% 6% 
Powder 
Cr Metal 99.9% 5% 
Powder 
Mg Metal 99.9% 0.5% 
Powder 
______________________________________ 
EXAMPLE XIII 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
Purity % By Weight 
of Material 
in Recipe 
______________________________________ 
Al O 99.8% 87% 
Refractory 
Grain 
Al Metal 99.7% 4.5% 
Powder 
Cr Metal 99.9% 8% 
Mg Metal 99.9% 0.5% 
______________________________________ 
EXAMPLE XIV 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
% By Weight 
in Recipe 
______________________________________ 
Al O 87% 
Refractory 
Grain 
Al Metal 9% 
Powder 
Cr Metal 3.5% 
Mg Metal 0.5% 
______________________________________ 
EXAMPLE XV 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
Purity % by Weight 
of Material 
in Recipe 
______________________________________ 
Zr.sub.2 O.sub.3 
99.5% 87% 
Refractory 
Grain 
(-50 + 100 Mesh) 
Al Metal 99.7% 4.5% 
Powder 
Cr Metal 99.9% 8% 
Powder 
Mg Metal 99.9% 0.5% 
Powder 
______________________________________ 
EXAMPLE XVI 
The process of Example I was repeated, but using the following mixture: 
______________________________________ 
% By Weight 
in Recipe 
______________________________________ 
Zr.sub.2 O.sub.3 87% 
(-50 + 100 Mesh) 
Al Metal 9% 
Powder 
Cr Metal 3.5% 
Powder 
Mg Metal 0.5% 
Powder 
______________________________________ 
EXAMPLE XVII 
A mixture was prepared containing by weight 79% of 99% silicon carbide 
graded -50-100 USS mesh and 16.25% and 98% pure silicon metal powder 
graded -325 USS mesh, 4% of pure aluminum powder graded -325 USS mesh and 
0.75% and 99.9% pure magnesium powder graded -325 USS mesh. This mixture 
was projected through a double venturi air oxygen system in the same way 
as specified in Example I against a silicon carbide tray column used in 
the fire refining of zinc powder. Zince liquid metal and zinc oxide leaks 
were cooled and an adherent fused refractory coating was formed. 
EXAMPLE XVIII 
The process of Example XII was repeated, using the following mixture: 
______________________________________ 
% by Weight 
in Recipe 
______________________________________ 
SiC 99.5% - 200xD Uss Mesh 
79% 
SiO.sub.2 powder - 325xD 
16.25% 
Al powder - 325xD 4% 
Mg powder - 325xD 0.75% 
______________________________________ 
EXAMPLE XIX 
The process of Example XII was repeated, using the following mixture: 
______________________________________ 
% By Weight 
in Recipe 
______________________________________ 
SiC 99.5% - 200xD Uss Mesh 
80.5% 
SiO.sub.2 powder - 325xD 
14% 
Al powder - 325xD 5% 
Mg powder - 325xD 0.5% 
______________________________________ 
EXAMPLE XX 
The process of Example XII was repeated, using the following mixture: 
______________________________________ 
% by Weight 
in Recipe 
______________________________________ 
SiC 99.5% - 200xD Uss Mesh 
77% 
SiO.sub.2 powder - 325xD 
19.5% 
Al powder - 325xD 3% 
Mg powder - 325xD 0.5% 
______________________________________ 
The processes in Examples I, IV were performed using pure oxygen at 100 psi 
injected at the spraying machine venturi and aspirating these the recipes 
of Examples I and IV at approximate rates of 1 lb. per minute. Back 
flashes were encountered which made the recipes unusable. The examples 
were then repeated using a dilution and relative pressures of 8:1 to 12:1 
oxygen to air as described at application rates of 1 lb. per minute, 3 
lbs. per minute, 9 lbs. per minute, 15 lbs. per minute, and 33 lbs. per 
minute, without encountering backflashes serious enough to prevent their 
usage. The most desirable recipes in terms of buildup and quality and 
rebound was that of Example I and Example XVII, but all mixtures tested 
produced adherent fused refractory masses. 
Variations and modifications of the invention will be apparent to those 
skilled in the art from the above detailed description. Therefore, it is 
to be understood that, within the scope of the appended claims, the 
invention can be practiced otherwise than as specifically shown and 
described.