The present invention relates to a two-part gunning refractory composition wherein fine powders of a refractory aggregate and superfine refractory powders are previously made into the form of a slurry containing therein a deflocculant, thereby reducing the amount of aluminous cement and also reducing the amount of water to achieve a deposit applied by gunning having a quality comparable to one produced by casting.

BACKGROUND OF THE INVENTION 
The present invention relates to a gunning refractory composition for use 
in lining troughs of blast furnaces or vessels for receiving molten pig 
iron, and more particularly it relates to a refractory composition for use 
in gunning having high adhesion ability, high strength, low porosity, and 
high corrosion resistance. 
Heretofore, the lining of the troughs of blast furnaces and vessels for 
molten pig iron was formed using refractory bricks or an monolithic 
refractory applied by stamping, casting, vibration molding and the like. 
Recently, however, casting has become the predominant technique for the 
lining of troughs of blast furnaces in order to reduce labor and costs and 
to improve working conditions. 
A casting material is composed of a castable refractory composition 
containing 15 to 25% by weight of conventional alumina cement. This 
castable refractory composition has drawbacks such as rupturing on rapid 
drying as the result of rapid dehydration of the alumina cement, poor 
strength in an intermediate temperature region, the reduction of 
resistance to slag, and the reduction of hot strength due to the presence 
of CaO in the alumina cement. These drawbacks, however, are substantially 
alleviated by employing a low cement castable refractory or an alumina 
cement free castable refractory in which superfine refractory powders and 
a deflocculant are used, while the amount of alumina cement to be used is 
made as small as possible, and the above-mentioned castable refractories, 
hereinafter referred to as low cement castable refractories, can be used 
without any problems from the standpoint of durability. 
However, casting requires blending on-site of component materials by a 
large mixer and framing operations which are quite troublesome. It has 
other drawbacks such as a long curing period at the end of which the frame 
disengages and also a long drying period. Thus, casting is not yet a 
satisfactory application technique. 
Gunning is preferable to casting as a technique for applying linings to 
troughs and vessels for molten pig iron, because it does not require 
on-site blending and framing. Thus, it permits reductions in labor and 
equipment costs and can be effectively used in repairing local damage to 
lining by cold or hot gunning. 
In the case of conventional gunning operation effected by blending water 
and a powdery gunning material at the nozzle of a spray gun, the powdery 
gunning material being transferred by pressure to the nozzle, the water 
content is rather high (10-20% by weight of the total weight of blended 
water and powdery material.) This produces a lower adhesion ratio and a 
lower packed density of the adhered material than for a cast material 
containing 4-8% by weight of water, resulting in lower durability. For 
this reason, at present, gunning is used only for repairing local damage 
to linings. Therefore, many efforts have been made in order to reduce the 
water content of gunning refractory compositions, and extensive 
investigations have been made concerning the grain size of the particles 
in the particulate component, the selection of an effective binder for 
gunning refractory compositions, the nozzle shape of the spray gun, and 
the like. However, in spite of these efforts and investigations, a 
satisfactory gunning refractory composition has yet to be achieved. For 
example, the mere addition of a deflocculant to the gunning refractory 
composition is insufficient, since it require at least 3- 5 seconds to 
deflocculate superfine refractory powders. This is too long, for it takes 
less than 1 second for the gunning refractory composition to reach the 
target surface to be coated starting from the point when water is mixed 
with a powdery composition, and thus sufficient deflocculation cannot be 
achieved. 
The present inventors have discovered that a low cement castable refractory 
composition containing a very low alumina cement, superfine powders and a 
deflocculant in combination and having a low water content can be 
successfully used as a gunning composition in order to obtain a lining of 
high packed density if a fine powder portion comprising a portion of fine 
powders of a refractory aggregate separated from a coarse/fine grain 
portions of the refractory aggregate, superfine refractory powders and a 
deflocculant are together slurried and if the resulting slurry is used in 
place of water of the conventional spray coating composition. Thus the 
slurry is mixed at a nozzle of spray gun with the remaining coarse/fine 
grains of refractory aggregate. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a two-part gunning 
refractory composition providing a lining having a high quality which is 
comparable to one resulting from casting installation with regards to its 
packed density. 
Thus the present invention relates to an improved two-part gunning 
refractory composition for use in lining molten pig-iron receiving troughs 
and vessels comprising a refractory raw material comprising 84-98% by 
weight of a refractory aggregate consisting of coarse/fine grains and fine 
powders, 12-2% by weight of superfine refractory powders having a 
particles size of at most 10.mu., and 4-0% by weight of alumina cement, a 
deflocculant and water and/or colloidal silica, the improvement being in 
that the gunning refractory composition comprises a first-part (Part A) 
composed of coarse/fine grains of a refractory aggregate to which is 
admixed 0.05-0.5% by weight per 100 weight % of the refractory raw 
material, of a hardening accelerator, and a second part (Part B) which is 
a slurry composed of the remaining refractory aggregate fine poweders, 
superfine refractory powders, 0.01-0.5% by weight per 100 weight % of the 
refractory raw material, of a deflocculant, and 4-10% by weight per 100 
weight % of the refractory raw material, of water and/or colloidal silica, 
the alumina cement being incorporated in Part A and/or Part B. 
The present invention also contemplate to provide a process for lining the 
miner surface of troughs or vessels for molten pig iron by gunning above 
refractory compositions. 
DETAILED DESCRIPTION OF THE INVENTION 
A more detailed explanation of the present invention will be given 
hereinafter. 
The refractory composition suitable for use in the form of gunning 
composition consists of a part composed of coarse/fine grains of 
refractory aggregate and a part composed of fine powders in the form of a 
slurry (hereinafter referred to as a slurry part). 
The refractory aggregate employable in accordance with the present 
invention comprises a major part of at least one oxide raw material 
selected from alumina, alumina/magnesia-type spinel, high alumina, 
chamotte, agalmatolite, silica and the like and a minor part of at least 
one non-oxide raw material selected from silicon carbide, silicon nitride, 
ferro-silicon nitride, carbon, pitch, metallic Si, metallic Al, boron 
carbide, and the like. The amount of refractory aggregate to be 
incorporated in the refractory raw material ranges from 84 to 98% by 
weight per 100% by weight of the refractory raw material. The particle 
size of coarse/ fine grains is greater than 74 .mu.m and preferable 0.3-5 
mm. The coarse/fine grains herein referred to mean those having a particle 
size of larger than 74 .mu.m as explained hereinafter. 
To the coarse/fine grains of refractory aggregate there is added a 
hardening accelerator such as a sulfate such as sodium sultate, potassium 
sulfate, calcium sulfate, a nitrate such as sodium nitrate, potassium 
nitrate, a carbonate such as Na.sub.2 CO.sub.3, K.sub.2 CO.sub.3 and 
Li.sub.2 CO.sub.3, a silicate such as sodium silicate and potassium 
silicate, Ca(OH).sub.2, or the like. One or more of these hardening 
accelerators is used in an amount of 0.05-0.5% by weight per 100% by 
weight of the refractory raw material. It is possible to add all or a 
portion of the alumina cement to the coarse/fine grain part. The kind and 
the amount of hardening accelerator may be adjusted depending on the time 
or season to be employed and the thickness of the applied material. A 
minute amount of water can be added in order to prevent dust. 
The slurry part consists of fine powders comprising a mixture of the 
remaining refractory aggregate fine powders, a deflocculant, and superfine 
refractory powders, optinally incorporating therein alumina cement, and 
4-10% by weight, per 100% by weight of the refractory raw material, of 
water or collidal silica or a mixture of water and colloidal silica in 
order to form the slurry. The viscosity of the slurry should preferably be 
at most 1500 centi-poises (cP). The grain size of the fine powders used in 
the slurry part of the present invention corresponding to that of the fine 
powder portion of a conventional castable refractory. However, until the 
present invention, no one ever proposed separation of the fine powder 
portion from the coarse grain portion and incorporating it in a slurry. 
The particle size of the fine powder in the slurry part is determined by 
the viscosity of the slurry resulting from the deflocculating effect of a 
mixture of refractory aggregate and superfine refractory powders and the 
optimum spraying conditions such as the pore diameter of the spraying 
nozzle and the pressure applied to the conduit of the gunning equipment. 
As a result of extensive experiments, the particle size of the fine powder 
portion has been determined to be preferably at most 74 .mu.m. The 
superfine refractory powders should have a particle size of at most 10 
.mu.m and preferably at most 1 .mu.m. They are selected from clay, 
kaoline, silica flour produced as a by-product of the production of 
ferro-silicon and metasilicon, hydrated silica, carbon black, silica 
formed in a gas-phase process, alumina, titanium oxide, and calcined 
alumina. One or more of these superfine refractory powders can be 
employed. The superfine refractory powders should constitute 2-12% by 
weight of the refractory raw materials. If the amount of superfine 
refractory powders is less than 2% by weight, no sufficient water 
reduction effect can be achieved, while if it is in excess of 12% by 
weight, shrinkage of the applied material after heating increases, which 
is undesirable. The particle size of superfine refractory powders should 
be at most 10 .mu.m and preferably at most 1 .mu.m. If the particle size 
is greater than 10 .mu.m the water reduction effect achievable in 
combination with the deflocculant becomes smaller. With a particle size of 
1 .mu.m or smaller, the water reduction effect becomes remarkable. 
As the aluminous cement there may preferably be used one or more of ALCOA 
CA-25 (trade name of a cement produced by ALCOA, Denka High Alumina Cement 
Super (trade name of a cement produced by Denka Co. Japan), CECAL 250 
(trade name of a cement produced by Lafarge Fondu International), JIS. No. 
1 and No. 2 aluminous cements, or calcium aluminate which constitute the 
above-mentioned aluminous cement. The total amount of the aluminous cement 
to be employed should be 4.0-0% by weight of the refractory raw material. 
If the amount of aluminous cement is greater than 4% by weight, the 
corrosion resistance and hopping resistance will decrease. 
Since the aluminous cement provides, when it is made into a slurry, an 
extensively varying viscosity upon hydration, it may be added either to 
the coarse/fine grains portion (Part A) or to the slurry (Part B) or to 
both of them depending upon the application. 
As to the deflocculant, there may be preferably employed one or more of a 
formaldehyde adduct of naphthalene sulfonic acid, lignin sulfonate salts, 
sodium phosphate, and the like. The total amount of deflocculants to be 
employed should be 0.01-0.5% by weight per 100% by weight of refractory 
raw material. If the amount of deflocculant is less than 0.01% by weight, 
adequate dispersion effect cannot be achieved, while if it exceeds 0.5% by 
weight, the optimum dispersion effect is not attained. 
Finally, the weight ratio of coarse/fine grains (Part A)/slurry (Part B) is 
preferably 60/40 to 72/25.

The following examples will illustrate the present invention more 
concretely, but it should be noted that the scope of the present invention 
is not limited to these examples. 
EXAMPLE 1 
A two-part gunning refractory composition was prepared comprising a 
coarse/fine grain part (Part A) which contained 0.15% by weight of calcium 
hydroxide as a hardening accelerator in addition to the components 
indicated in Table 1, and a slurry part (Part B) which contained the 
components indicated in Table 1, with which was admixed 0.1% by weight of 
sodium condensed phosphate having a ph of 5.5 as a deflocculant. The 
resulting coarse/fine grain part (Part A) and the slurry (Part B) were 
mixed at the nozzle portion of a continuously operating gun which 
delivered 70 kg/min. at a line pressure of 3 kg/cm.sup.2 for Part A and at 
a line pressure of 6 kg/cm.sup.2 for Part B and sprayed applied by gunning 
to the surface of agalmatolite bricks kept at ordinary temperature, 
600.degree. C., 800.degree. C., and 1000.degree. C. The quality of the 
resulting deposit was examined. 
Separately, a conventional gunning refractory composition composed of the 
same raw materials as above except that sodium silicate or aluminous 
cement was used as a binder and that no slurry part was used was coated by 
gunning using the same conditions as above. 
The results are shown in Table 2. 
TABLE 1 
______________________________________ 
Example 1 
% by weight 
______________________________________ 
Coarse/fine grain part (Part A) 
Sintered alumina (6-48 mesh) 
67.7 
pitch pellets 1 
high aluminous cement 4 
metallic aluminium powder 
0.3 
calcium hydroxide +0.15 
Slurry part (Part B) 
silicon carbide (at most 200 mesh) 
18 
calcined alumina (at most 10 .mu.m) 
7 
clay 2 
sodium condensed phosphate (pH 5.5) 
+0.05 
water +6 
______________________________________ 
Comp. Comp. Comp. 
Ex. 1 Ex. 2 Ex. 3 
______________________________________ 
sintered alumina (6-48 mesh) 
67 74 67.7 
silicon carbide (at most 200 mesh) 
15 15 18 
calcined alumina (at most 10 .mu.m) 
7 7 7 
clay -- -- 2 
pitch pellets 1 1 1 
high aluminous cement 
10 -- 4 
powdery sodium silicate No. 3 
-- 3 -- 
aluminium phosphate -- +0.5 -- 
metallic aluminium powder 
-- -- 0.3 
sodim condensed phosphate (pH 5.5) 
-- -- +0.1 
calcium hydroxide -- -- +0.15 
______________________________________ 
Note: The symbol "+" indicates "% by weight" per total weight of the othe 
components having no "+" symbol. Hereinafter the "+" symbol has the same 
meaning. 
TABLE 2 
______________________________________ 
Comp. Comp. Comp. 
Ex. 1 Ex. 1 Ex. 2 Ex. 3 
______________________________________ 
Application Technique 
gunning gunning gunning 
casting 
Adhesion ratio (%) 
at ordinary temp. 
95 90 90 -- 
at 600.degree. C. 
95 55 85 -- 
at 800.degree. C. 
90 30 85 -- 
at 1000.degree. C. 
85 25 75 -- 
Properties of the deposit 
apparent porosity (%) 
20.3 31.3 29.3 20.2 
after gunning at 
ordinary temp. 
and burning 
at 1000.degree. C. for 3 hrs. 
Crushing strength 
350 68 75 420 
Kg/cm.sup.2 
after burning at 1000.degree. C. 
for 3 hours 
amount of water (%) 
6.0 15.0 11.0 5.5 
required for application 
at ordinary temp. 
______________________________________ 
As is apparent from Table 2, Comparative Example 1 in which an aluminous 
cement was used as a binder showed a good adhesion ratio at ordinary 
temperatures, but the adhesion ratio rapidly decreased at higher 
temperatures. Comparative Example 2 in which sodium silicate was used as a 
binder showed a similar adhesion ration to Example 1 of the present 
invention in which a 2-part refractory composition is used, but the 
Comparative Examples require much more water for gunning and the physical 
properties of the burned deposit such as the crushing strength and 
porosity are poor. It should be noted that Example 1 provides 
substantially the same quality of deposit as comparative Example 3, which 
had approximately the same refractory composition as Example 1 but which 
was applied by casting instead of gunning. Thus, the present invention can 
provide a high quality deposit equal in quality to a cast deposit but 
without the drawbacks of casting. 
EXAMPLE 2 
A two-part gunning refractory composition was prepared by mixing a 
coarse/fine grain part as shown in Table 3 with 0.1% by weight, on the 
basis of the refractory raw material, of anhydrous sodium metasilicate to 
from Part A and mixing fine/superfine powders as shown in Table 3 with 
0.1% by weight of sodium tetrapolyphosphate as a deflocculant, 4% by 
weight of colloidal silica (20% of solid SiO.sub.2), and 3.5% by weight of 
water per 100 weight % of refractory raw material, to a form slurry part 
(Part B). The resulting composition was coated by gunning onto the surface 
of agalmatolite bricks using a continuous spray gun at the nozzle portion 
of which Part A and Part B were mixed. The gunning conditions were a rate 
of 70 kg/min, and a line pressure of 3 kg/cm.sup.2 for Part A and a line 
pressure of 6 kg/cm.sup.2 for Part B. The quality of the resulting coated 
deposit was examined and the results are shown in Table 4. Separately, an 
identical composition was cast onto the surface of the same brick as 
above, The quality of the casting is also shown in Table 3. 
As is apparent from Table 3, the two-part gunning refractory composition 
according to the present invention provides a deposit having a quality 
which is comparable to that obtainable by casting application. 
TABLE 3 
______________________________________ 
% by weight 
______________________________________ 
Coarse/fine grain part (Part A) 
sintered alumina (6-48 mesh) 
57.7 
silicon carbide (14-200 mesh) 
12 
graphite (pitch treated, at most 1 mm) 
3 
anhydrous sodium metasilicate 
+0.1 
water +0.2 
Slurry part (Part B) 
silicon carbide (at most 200 mesh) 
18 
calcined alumina (at most 10 .mu.m) 
7 
clay 2 
boron carbide (at most 200 mesh) 
0.3 
sodium polytetraphosphate 
+0.1 
colloidal silica (20% of solid SiO.sub.2) 
+4 
water +2.5 
______________________________________ 
Application 
technique gunning Casting 
______________________________________ 
Properties of deposit 
linear change 
110.degree. C. - 24 hrs. 
-0.03 -0.09 
1000.degree. C. - 3 hrs. 
-0.06 -0.06 
1500.degree. C. - 3 hrs. 
-0.06 -0.03 
crushing strength 
110.degree. C. - 24 hrs. 
156 120 
(kg/cm.sup.2) 
1000.degree. C. - 3 hrs. 
750 590 
1500.degree. C. - 3 hrs. 
970 880 
apparent porosity 
110.degree. C. - 24 hrs. 
17.5 17.3 
(%) 1000.degree. C. - 3 hrs. 
19.6 19.1 
1500.degree. C. - 3 hrs. 
19.4 19.2 
amount of water 6.0 6.0 
employed (%) 
______________________________________ 
EXAMPLE 3 
A two-part gunning refractory composition was prepared by mixing the 
coarse/fine grain components set forth in Table 4 with 0.3% by weight of 
anhydrous sodium metasilicate as a hardening accelerator to form Part A 
and by mixing fine/superfine powders as set forth in Table 4 with 0.1% by 
weight of sodium tetrapolyphosphate as a deflocculant, 3.5% by weight of 
colloidal silica and 4.0% by weight of water, per 100 weight % of 
refractory raw material, to form a slurry part (Part B). The resulting 
two-part compositions were coated by gunning using the same conditions as 
in Example 2. Separately, casting was also carried out with the same 
composition except that the slurry (Part B) was not used. The quality of 
the deposit thus obtained was examined and the results are shown in Table 
4. 
As is apparent from Table 4, the present example provides the same quality 
obtainable by casting application. 
TABLE 4 
______________________________________ 
% by weight 
______________________________________ 
Coarse/fine grain part (Part A) 
burned bauxite (6-48 mesh) 
62.8 
silicon carbide (at most 48 mesh) 
5 
pitch pellets 2 
high aluminous cement 
0.2 
anhydrous sodium metasilicate 
+0.3 
Slurry part (Part B) 
burned bauxite (at most 48 mesh) 
8 
silicon carbide (at most 200 mesh) 
10 
calcined alumina 9 
silica flour 3 
sodium tetrapolyphosphate 
+0.1 
colloidal silica (20% solid SiO.sub.2) 
+3.5 
water +4 
______________________________________ 
Application technique gunning casting 
______________________________________ 
linear change (%) 
105.degree. C. - 24 hrs. 
0.00 -0.06 
1000.degree. C. - 3 hrs. 
-0.06 -0.00 
1500.degree. C. - 3 hrs. 
+0.28 +0.46 
crushing strength 
105.degree. C. - 24 hrs. 
120 100 
(kg/cm.sup.3) 1000.degree. C. - 3 hrs. 
530 490 
1500.degree. C. - 3 hrs. 
480 310 
apparent porosity (%) 
105.degree. C. - 24 hrs. 
19.9 19.8 
1000.degree. C. - 3 hrs. 
23.0 22.8 
1500.degree. C. - 3 hrs. 
22.1 22.3 
______________________________________ 
The two-part gunning refractory composition comprising the coarse/fine 
grain part (Part A) and slurry part (Part B) according to the present 
invention can be used for gunning application using gunning equipment 
comprising a conventional batch-type or continuously operating gun, a 
slurry tank and a nozzle for gunning by mixing the coarse/fine grain part 
(Part A) with the slurry part (Part B) at the nozzle. The present 
invention using the two-part gunning refractory composition can increase 
the adhesion ratio of applied refractory material and also the packed 
density of the deposit and thus provides the same quality deposit obtained 
by casting application.