CA1273964A

CA1273964A - Refractory thixotropic vibration compound and process for the vibration lining of metallurgical vessels with such compound

Info

Publication number: CA1273964A
Application number: CA000536471A
Authority: CA
Inventors: Gert Konig; Alexander Markov
Original assignee: Martin and Pagenstecher AG
Current assignee: Martin and Pagenstecher AG
Priority date: 1986-05-07
Filing date: 1987-05-06
Publication date: 1990-09-11
Anticipated expiration: 2007-09-11
Also published as: DE3615506A1; FI872009A0; ATE48831T1; EP0248171B1; DE3761207D1; FI85366C; DE3615506C2; FI85366B; FI872009L; EP0248171A1

Abstract

ABSTRACT
The invention relates to a refractory thixotropic self-curing vibrationcompound on the basis of magnesite having the following composition 0.1 to 2.0 % SiO2 0.1 to 30 % Al2O3 0.5 to 3.0 % P2O5 0.2 to 1.5 % K2O+Na2O+LiO2 0.1 to 2.0 % Fe2O3 0 to 0.5 % B2O3 0.1 to 3.0 % CaO
residue MgO.

Description

~2~3~

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 ~73~ 21421-234 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 ~3~ 21421-234 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 ~2739~ 21~21-23~

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 ~7~ 21421-234 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.
D

~ 3~ 21421-234 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 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:

~2~ 21421-234 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.

~ 21421-234 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 .

~3~ 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 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 .

3~

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.

~7~ 21421-234 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.

~2~3~ 21421 234 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 .

~2~39~

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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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A refractory thixotropic self-curing vibration compound on the basis of magnesite, characterized by the following chemical composition (in % by weight):
0.1 to 2.0 % SiO2 0.1 to 30 % Al2O3 0.5 to 3.0 % P2O5 0.2 to 1.5 % K2O+Na2O+LiO2 0.1 to 2.0 % Fe2O3 0 to 0.5 % B2O3 0.1 to 3.0 % CaO
residue MgO

2. A compound according to Claim 1 for producing a vibra-tion density of at least 3.0 g/cm3, characterized by the following crystallographic analysis (in % by weight):
0 to 30 % corundum 0.1 to 0.5 % boric acid 0.5 to 4.0 % alkali polyphosphates residue sintered magnesite and the following grain fraction:
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.

3. A compound according to Claim 2, characterized in that the sintered magnesite 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

4. A compound according to Claim 2, characterized in that the corundum has the following grain spectrum:
50 to 85 % < 0.3 mm 15 to 50 % 0.3 - 0.6 mm

5. A compound according to Claim 2, characterized in that the corundum has the following grain spectrum:
100 % < 0.06 mm

6. A compound according to Claim 1, characterized in that the sintered magnesite has the following chemical composition (in % by weight):
0.1 to 3.0 % CaO
0.1 to 2.0 % SiO2 residue MgO and impurities and possesses a grain density of at least 3.35 g/cm3 and a total porosity of 7% and less.

7. A compound according to Claim l, characterized in that the corundum has the following chemical composition (in % by weight):
97 to 99.5 % Al2O3 residue impurities

8. A compound according to Claim 1, characterized in that it contains 0.5 to 2 per cent by mass of pulverulent CaO-containing materials as hardener.

9. A compound according to Claim 1, characterized in that the quantity of water for mixing is 4.0 to 7.0 kg per 100 kg of dry compound.

10. A process for the vibration lining of metallurgical ves-sels, with a refractory thixotropic compound according to Claim l, characterized in that the components of the mass are intensively mixed in the dry condition; the quantity of mixing water is added before vibration starts; the moist compound is mixed for about 4 minutes and filled with constant vibration into the space between an introduced template and the ladle wall; and the lining is heated after the removal of the template.

11. A process according to Claim 10, characterized in that the quantity of water for mixing is added with a precision of at least 0.1% and the moist compound is mixed for 4 minutes at the most.

12. A process according to Claims 10 and 11 characterized in that the vibration compound on the basis of magnesite and corun-dum is filled with constant vibration into the space between an introduced template 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.

13. A process according to Claims 10 or 11, characterized in that after the removal of the template, the lining is heated to 150°C at a maximum speed of 8°C/hour.

14. A process according to claim 10 wherein the metallurgical vessel is a steel plant ladle.

15. A steel plant ladle having as a protective lining a refractory self-curing vibration compound as defined in Claim 1 which has been cured.