Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
_
The invention relates to a refractory thixotropic self-
curing vibration compound on the basis of magnesite and a process
for the vibration lining of metalluryical vessels, more particular-
ly steel plant ladles with such compound.
In the lining of metallurgical vessels with vibration of
the lining compound, use is made of the known property (thixo-
tropy) of suitable refractory substances to become liquid as a
result of vibrations and to pass into a solid state when the
vibrations terminate.
In the steel industry this lining technique has been used
for the breeches runners of blast furnaces. The refractory thixo-
tropic body is filled into the breeches runner, caused to flow by
means of a vibration template and homogenized and densified
(German OS 29 15 598) .
The technique has also been used to line low ladles in
the foundry industry ("Giesserei" 67, 1980, No. 21, Pp. 678 to
681). It has also been suggested to line steel plant ladles in this
way. Use was made of compounds of zirconium silicate and silica
with a small proportion of aluminous cement and extremely small
particles, not described in detail; a compound comprising 90% zir-
conium silicate was filled into the slag zone of the ladle and a
compound comprising 70% zirconium silicate into the steel zone
(Nippon Kokan "Technical Report Overseas", No. 37, 1983, Pp, 51 to
53) .
However, steel plant ladles are either lined with
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refractory blocks or monolithically by the ramminy or sintering of
refractory bodies. The reason is probably that heavy demands are
made on the durability of the refractory linings of steel plant
ladles, in which nowadays metallurgical treatments of the melt are
also frequently performed. All attempts to use rammed or sintered
ladles using basic compounds instead of expensive basic blocks
have therefore failed, since premature wear took place due to the
infiltration of the bodies and the shrinkage and bursting of the
lining. One cause was the high porosity of the rammed or sintered
bodies.
Steel plant ladle refractory linings built up from com-
pounds are mainly destroyed by infiltration and slagging. Due to
infiltration, the liquid slags and the melt penetrate the refrac-
tory lining, where reactions take place between the slag/melt and
the refractory material of the lining which cause the lining to
be destroyed. In addition to refractory properties and mineral
structure, the density of the refractory thixotropic compound used
is essential for the resistance of the refractory lining to slag.
Engineers in the art have hitherto obviously taken the view that
~0 the refractory linings of steel plant ladles could not be given
adequate density by vibration.
There is also the aspect that steel plant ladles with the
usual modern capacities of 80 to 320 tons have linings 3 m in
height and more. With such heights engineers in the art have not
only the problem of adequate lining density but also doubts that
the vibrated lining might not be strong enough in itself after the
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removal of the template and would collapse.
German OS 30 27 192 discloses a vibratable plastic com-
pound on the basis of magnesite which is characterized by 4 to 25~
clay minerals and an alkaline electrolyte in the form of phosphate.
However, a compound comprising 4 to 25% clay minerals and magnesite
has such low refractory properties that it cannot be used at the
temperatures of liquid steel. There is also probably the risk
that the lining will collapse when the template is withdrawn.
German OS 30 01 553 discloses a vibratable compound in
powder form on the basis of magnesite and carbon-containing mater-
ial with a grain size between 0.07 and 1 mm. Due to the absence
of a fine component < 0.07 mm, this compound cannot be used for
building up a dense body. Other disadvantages are that due to the
carbon component of the body there is a risk that higher porosity
will develop, with the consequence of heavier wear. There is also
the risk that the burning away of the carbon will further increase
porosity and accelerate wear.
A publication in "Fachberichte Huttenpraxis Metallwei-
erverarbeitung", Vol. 23, No. 5, 1985, Pp. 361 to 366 entitled:
"Monolithische Zustellung von Stahlgiesspfannen" (The Monolithic
Lining of Steel Casting Ladles) states that basic thixotropic vib-
ration compounds are being developed. However, no details such as
- composition, grain structure, etc., can be gathered from this
publication.
This invention seeks to provide a reEractory thixotropic
self-curing basic vibration compound which has the required high
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stability under load and wear resistance attack by erosion.
One particular aim is to improve the infiltration-
inhibiting and slag-repelling effect of the lining.
SUMMARY OF THE INVENTION
This invention provides a refractory thixotropic self-
curing vibration compound on the basis of sintered magnesite and
having the following chemical composition (in % by weight):
0.1 to 2.0 % SiO2
0.1 to 30 % A1203
0.5 to 3.0 % P205
0.2 to 1.5 % K20 plus Na20 plus LiO2
0.1 to 2.0 % Fe203
0.1 to 0.5 % B203
0.1 to 3.0 % CaO
residue MgO
The invention also counteracts slag attack and its con-
sequences for the refractory material by suitable steps as regards
both structure (mineralogical structure) and texture (density, gas
permeability, grain distribution, porosity).
~o The composition of this invention has the following
crystallographic analysis (in % by weight):
0 to 30 % corundum
0.1 to 0.5 % boric acid
0.5 to 4 % alkali polyphosphates
residue sintered magnesite.
The balanced composition on the basis of magnesite or
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magnesite/corundum advantageously enables the refractory lining
to be constructed in areas for the steel zone and the slag zone.
To obtain a vibration density of at least 3.0 g/cm3 the
compound has the following grain frac-tions:
10 to 50 ~ : < 0.06 mm
5 to 20 % : 0.06 to 0.5 mm
30 to 85 ~ as residue : 0.5 to 2 mm
The sintered magnesite used preferably has the following
grain spectrum:
15 to 35 ~ :< 0.06 mm
5 to 15 ~ : 0.06 to 0.5 mm
50 to 80 ~ : 0.5 to 2 mm
The corundum used preferably has the following grain
spectrum:
50 to 85 ~ < 0.3 mm
15 to 50 %:0.3 to 0.6 mm
This results in reduced cracking due to volumetric expan-
sion in the magnesite/corundum reaction.
Cracking can be further reduced if according to a further
feature use is made of a corundum having a grain size all below
0.06 mm.
It is also advantageous to use as the sintered magnesite
a product having the following chemical composition (in % by
weight):
0 to 3.0 % CaO
0.1 to 2.0 % SiO2
residue MgO and impurities.
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Preferably the sintered magnesite should have a raw
grain density of at least 3.35 g/cm3 and a total porosity of 7%
and less.
Also advantageously a product is used having the follow-
ing composition (in % by weight):
97 to 99.5 % A1203
residue impurities.
The corundum should preferably have a raw grain density
of at least 3.40 g/cm3 and a total porosity of 15% and less.
According to a further feature of the invention the vib-
ration compound contains 0.5 to 2% by weight of pulverulent CaO-
containing materials as hardener, for example, in the form of
ferrochromium slag, electric furnace slag or calcium hydroxide. The
addition of such a hardener gives optimum control of the template
withdrawal time. According to a further feature of the invention,
the quantity of water for mixing is 4.0 to 7.0 kg per 100 kg of
dry compound.
Another object of the invention is to provide a suitable
process for the vibration lining of metallurgical vessels, more
particularly steel plant ladles, using the refractory thixotropic
compound according to the invention.
The process according to the invention for the vibration
lining of metallurgical vessels, more particularly steel plant
ladles, using the refractory thixotropic self-curing basic compound
according to the invention is characterized in that the components
of the mass are intensively mixed in the dry condition; the
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quantity of water for mixing is added before vibration starts; the
moist compound is mixed for about 4 minutes and filled with con-
stant vibration into the space between an introduced template and
the ladle wall; and the lining is heated after the removal of the
template.
According to a preferred feature of the invention the
quantity of water is added with a precision of at least 0.1% and
the moist compound is mixed for 4 minutes at the most.
According to another feature of the invention the vib-
ration compound on the basis of magnesite and corundum is filled
with constant vibration into the space between an introduced tem-
plate and the ladle wall in the area of the steel zone; and then
the vibration compound on the basis of magnesite is filled with
constant vibration into the space between the introduced template
and the ladle wall in the slag zone.
This structure is advantageous, since the purely magnes-
ite compound is particularly resistant to slag, while the spinel-
forminq body of magnesite and corundum has a reduced resistance to
slag, it is true, but grows when heated by the liquid steel, thus
~0 reducing the slight shrinkage.
After the removal of the template, the lining is prefer-
ably heated to 150C at a maximum speed of 8C/hour.
Example l
A thixotropic self-curing vibration compound according to
the invention for lining a steel plant ladle having a capacity of
230 tons had the following refractory components in % by weight:
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25 % sintered magnesite with a grain size 0 to 0.1 mm
10 % sintered magnesite with a grain size 0 to 0.5 mm
10 % sintered magnesite with a grain size 0.5 to 1 mm
55 ~ sintered magnesite with a grain size 1 to 2 mm
2.5 % sodium polyphosphate
0.2 % boric acid
0.25% calcium hydroxide as hardener
The sintered magnesite used had the following chemical
composition (in % by weight):
0.20 % SiO2
2.0 % CaO
> 97 % MgO
The raw grain density was 3.38 g/cm3 and the total
porosity 5.0%.
The refractory components were intensively mixed in the
dry condition in a mixer and packed in plastic bags.
The chemical analysis of the compound was as follows (in
by weight):
0.55 % SiO2
0.32 % A12O3
1.47 % P2O5
0.54 % Na2O
0.23 % Fe2O3
2.3 % CaO
residue MgO
The grain fraction was in the range.
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10 to 50 % ~ 0.06 mm
5 to 20 % 0.06 to 0.5 mm
50 to 80 % 0.5 to 2.0 mrn.
The compound was free from clay and hydraulic bonding
agent and therefore had no water of crystallization. There was
therefore no risk of explosion during rapld heating. In a ladle
lined with this compound it was possible to perform desulphuriza-
tion treatments with lime-containing substances with better results
and to cast steels with high manganese contents.
At a steel works the dry compound was introduced into a
mixer in charges of 2 tons each and intensively mixed with the
addition of 6.7 kg of water per 100 kg of dry compound. The water
was metered with a precision of 0.1% using an electrical impulse
control system. The mixing time following the addition of the water
was 4 minutes. Then the compound was removed from the mixer and
transported to the steel casting ladle to be lined. The mixture
was filled into the space between an introduced template and the
ladle wall and vibration was performed within a period of 4 minutes~
After vibration the template was removed. The lining was then
heated at a speed of 8C/hour to 150C and then brought to operat-
ing temperature.
The finishing lining had the following properties:
Vibration density (raw density): 3.05 g/cm3
Total porosity 110 C: 17.0% by volume
Thermal expansion up to 1,000 C: 1.2%
Cold compressive strength after prefiring 1,000C: 40
N/mm .
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For purposes of comparison, a portion of the steel cast-
ing ladle had been lined in the usual manner with dolomite blocks.
On completion of the ladle campaign, the lining with the vibration
compound according to the invention showed 20~ less wear than the
dolomite block lining.
Example 2:
A thixotropic self-curing vibration compound according
to the invention for lining a steel casting ladle having a capacity
of 230 tons had the following refractory components in % by weight:
20 % corundum with a grain size ~ 0.06 mm
15 % sintered magnesite with a grain size 0 to 0.5 mm
13 % sintered magnesite with a grain size 0.5 to 1 mm
50 % sintered magnesite with a grain size 1 to 2 mm
2.5 % sodium polyphosphate
0.2 % boric acid
The chemical composition of the sintered magnesite used
and also its raw grain density and total porosity corresponded to
the values in Example 1.
The corundum used has the following chemical composition
~n (in % by weiyht):
> 99.5 % A12O3
residue impurities
The refractory components were intensively mixed in the
dry condition in a compulsory mixer and packed in plastic bags.
The chemical analysis of the compound was as follows
(in % by weight):
t
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21421-234
0.4~ % SiO2
20.1 % A12O3
1.47 % P2O5
0.59 % Na2O
0.2 % B2O3
0.18 % Fe2O3
1.6 % CaO
residue MgO
The grain fraction corresponded to that set forth in
Example 1.
This composition was also free from clay and hydraulic
bonding agent. At a steel plant dry compound was introduced into a
mixer in charges of 2 tons each and intensively mixed with the
addition of 3.5 kg of water per 100 kg of dry compound. The water
was metered with a precision of 0.1% using an electrical impulse
control system. The mixing time following the addition of the
water was 4 minutes. Then the compound was removed from the mixer
and transported to the steel casting ladle to be lined; the mixture
was filled into the space between an introduced template and the
ladle wall and vibration was performed within a period of 4 minutes.
After vibration the template was removed. The lining
was then heated at a speed of 8C/hour to 150C and then brought
to operating temperature.
The finished lining had the following properties:
Vibration density (raw density): 3.02 g/cm3
Total porosity 110 C: 15.8% by volume
Thermal expansion up to 1 000 C: 1.1%
Cold compressive strength after 1 000C: 90 N/mm2.
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For purposes of comparison, a poxtion of the steel plant
ladle had been lined in the usual manner with dolomite blocks. On
completion of the ladle campaign, the lining with khe vibration
compound according to the invention showed 10% les6 wear than the
dolomite block lining.
Example 3:
A thixotropic self-curing vibration compound according
to the invention for lining a steel plant ladle having a capacity
of 230 tonshad the following refractory components in % by weight:
10 % corundum with a grain size ~ 0.6 mm
25 ~ sintered magnesite with a grain size 0 to 0.5 mm
10 % sintered magnesite with a grain size 0.5 to l mm
55 % sintered magnesite with a grain size 1 to 2 mm
2.5 % sodium polyphosphate
0.2 % boric acid
The chemical composition of the sintered magnesite used
was (in % by weight):
0.20 % SiO2, 2.0 % CaO, more than 97% MgO
The raw grain density was 5.38 g/cm3 and the total
~0 porosity 5.0%.
The corundum used had the following chemical composition
(in ~ by weight):
99.5 % A12O3
residue impurities
The refractory components were intensively mixed in the
dry condition in a compulsory mixer and packed in plastic bags.
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The chemical analysis of the compound was as follows
(in % by weight):
0.50 % SiO2 0.21 % Fe2O3
10.2 % A12O3 1.80 % CaO
1.47 % P2O5 residue ~gO
0.57 % Na2O
The grain fractions were:
20 % : ~0.06
9 % : 0.06 to 0.5 mm
69 % : 0.5 to 2 mm
This compound was also free from clay and hydraulic bond-
ing agent. At a steel works the dry compound was introduced into
a mixer in charges of 2 tons each and intensively mixed with -the
addition of 7.0 kg of water per 100 kg of dry compound. The water
was metered with a precision of 0.1% using an electrical impulse
control system. The mixing time following the addition of the
water was 5 minutes. The compound was then removed from the mixer
and transported to the steel casting ladle to be lined
After vibration the template was removed; the lining was
~0 then heated at a speed of 8C/hour to 150C and then brought to
operating temperature.
The finished lining had the following properties:
Vibration density (raw density): 2.96 g/cm3
Total porosity 110 C: 20 % by volume
Thermal expansion up to 1000C: 20 N/mm2
Cold compressive strength after prefiring 1000C:
20 N/mm .
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21421-234
For purposes of comparison, a portion of the steel cast-
ing ladle had been lined in the usual manner with dolomite blocks.
On completion of the ladle campaign, the lining with the vibration
compound accordiny to the invention showed 10% less wear than the
dolomite block lining.
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