JPS6024069B2 - Method for manufacturing MgO-Al↓2O↓3 quality fireproof insulation brick - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing spinel basic fireproof and insulating bricks that are resistant to attack by molten steel, molten metal, basic slag, and the like.

Fireproof and insulating bricks are widely used as energy-saving bricks, either directly on hot surfaces or on the back side of firebricks, as they have both fireproofing properties that can withstand high temperatures and insulating properties that block heat and prevent it from escaping to the outside. All of these bricks are made of silica, alumina, or mullite and are immediately eroded and damaged when they come into contact with molten steel, molten metal, or molten basic slag, so they are not suitable for use in furnaces that handle molten steel, such as mixed iron furnaces, pots, and tundishes. is not used.

Therefore, in order to insulate furnaces that handle molten steel, there has been a strong demand for the development of basic fireproof insulating bricks that are resistant to molten steel and molten slag from industries that handle molten metals, such as iron and steel manufacturing.

The production of basic fireproof and insulating bricks is fraught with difficult problems, such as reducing the weight of basic fireproofing materials such as magnesia and calcia, which are the main raw materials, and firing lightweight molded products, and the manufacturing technology is generally difficult. L, no, it has become a corporation.

In other words, the magnesia fireproof insulation brick, which was the first basic fireproof insulation brick in the world to be jointly developed by the Tokyo Industrial Research Institute and Isolite Kogyo ■, has since been discontinued, but the cause is magnesia foam particles. Not only does the use of special manufacturing equipment require special manufacturing equipment, but it is also assumed that solving various problems such as slight deformation and the occurrence of slight shrinkage cracks during firing of the molded bricks was at a standstill from both technical and profitability standpoints. .

Therefore, it can be said that it is extremely difficult to manufacture basic fireproof insulation bricks despite the demands of the demanding industry.

The refractory insulating brick of the present invention is a spinel refractory insulating brick, which is a type of basic refractory insulating brick, and is designed to meet the demands of the above-mentioned demand industry, and is suitable for use in furnaces that handle molten steel and molten metal, such as pig iron furnaces, various pots, and tundishes. The purpose of this product is to provide heat insulation and provide various effects such as energy saving and improvement of metal separation, and the manufacturing technology was discovered and completed through repeated research and testing.

The spinel fireproof insulation brick of the present invention is considered to be the most ideal basic fireproof insulation brick because spinel has low thermal conductivity and high resistance to thermal shock.

Spinel is manufactured by adding a small amount of fireclay to a pre-produced synthetic spinel pulverized material, press-molding it, and firing it, since cracks occur due to the spinel formation reaction during firing. Synthetic spinel is made by mixing equal amounts of magnesite and white bauxite, shaping and firing, and then crushing. In contrast, the spinel brick of the present invention is produced by adding a pore-forming agent to alumina, magnesia clinker powder, and a small amount of bonded clay, and producing a spinel fire-resistant and heat-insulating brick using a conventional method for producing fire-resistant and heat-insulating bricks. The key point was the discovery of the ratio of Mg0 to AI203 and the addition rate of binding clay that would not cause cracking or deformation even if spinel synthesis and brick weight reduction were performed at the same time. Of course, in the above method, there is no problem in replacing part of the sintered alumina and magnesia clinker with powder obtained by crushing broken spinel fireproof insulation bricks. Furthermore, the bonded clay referred to in this item is a raw material for obtaining 3.8 to 8.2% Sj02, and is a general term for fire-resistant clays such as Kibushi clay, Frogme clay, and kaolin. The configuration of the present invention will be explained below. When manufacturing spinel fireproof and insulating bricks, purity level 9 is required in the formulation of corpse silk alumina, magnesia clinker, bonding viscosity, and pore forming material.
20-2 parts by weight of magnesia clinker powder with a purity of 5% or more and a fineness of 150 mesh or less, 64-72 parts by weight of sintered alumina powder with a purity of 99% or more and a fineness of 150 mesh or less, and 8 parts by weight of bonded clay with a fineness of 48 mesh or less. % by weight, and the pore forming material is mixed by adding 60 k9 to 100 k9 of the above-mentioned mixed raw material, and after adding a predetermined amount of water and mixing, it is formed into a predetermined brick shape, dried, and then Fired in a tunnel kiln at 1500℃ to produce Mg○ vs. N203
The results of investigating the relationship between the ratio and firing cracks and deformation are shown in Table 1. When the N203/Mg○ ratio was in the range of 2.5 to 4, no cracking or deformation occurred, and firing was good.

Table 1 A&Q Relationship between MgO and cracking/deformation Here, the above magnesia clinker powder has a blending ratio of 20
~2 parts by weight, synergistically with the calcined alumina powder and the bonding viscosity in the above-mentioned mixing ratio, allows the spinel formation reaction to occur favorably during firing, and makes the pore-forming effect by the pore-forming material uniform and even. It has a low thermal conductivity (0.4 Isocal) with extremely stable strength without cracking or deformation
/mh℃ or less) Bricks with fireproof and heat-insulating properties can be reliably obtained.

That is, if the amount is less than 2 parts by weight, the timing of the spinel forming reaction and the pore-forming effect will be shifted, resulting in uneven pores and frequent cracking and deformation, making it extremely difficult to commercialize the product. This same problem makes commercialization extremely difficult.

The reason for using the dawn alumina powder is that the calcined alumina powder does not undergo spinelization, that is, Mg○-mountain 203 formation, during the firing process. The above-mentioned fire-resistant and heat-insulating properties can be obtained by synergistically combining the magnesia clinker powder and the binding clay to form spinel and create a uniform and evenly distributed pore-forming effect.

If the blending ratio is less than 64 parts by weight, deformation and cracking will occur, and if it exceeds 72 parts by weight, many cracks and cracks will occur, so in either case, commercialization is difficult due to poor product yield. .

Next, we conducted a manufacturing test under the same conditions as before, increasing or decreasing the amount of bonding viscosity in 1% increments based on the standard 8%, and investigated the effect of the amount of bonding viscosity on the fired bricks. The results are shown in Table 2. As expected, there is no change in the relationship between a good product and the AI203/Mg○ ratio, but even with a good AI203/Mg○ ratio, the amount of bonding viscous added is less than 5 parts by weight, which is the amount that gives 3.8% of Si02. When the amount decreased, large cracks occurred, and when the amount of 1 weight part Si02 exceeded 8.2%, small cracks occurred.

Table 2 Relationship between the amount of addition of bonding viscosity and the occurrence of cracks From the above test results, it was found that the addition amount of bonding clay in the range of 5% to 10% was good without causing firing cracks.

In the production of the fireproof and insulating brick of the present invention, there is no problem in adding a tinning agent such as alkali fluoride, lithium carbonate, shelf acid, etc. to promote spinel formation.

The fineness of the competitive alumina, magnesia clinker powder, and bonded clay was specified as above to ensure excellent brick formability after mixing and to prevent the formation reaction of spinelization (Mg0-N203) in the firing process. It is possible to carry out the process well in a short time, to set the bulk specific gravity after firing to an appropriate value, and to stabilize the compressive strength at a high level. In other words, if a coarse powder exceeding each specified mesh is used, the moldability will be significantly reduced, and the spinel formation reaction will be significantly delayed, requiring a long firing time, which will not only be extremely uneconomical, but also cause bulk It is not preferable because the specific gravity becomes large and the pressure resistance is drastically reduced. As an effect of the present invention, spinel fireproof and heat insulating bricks can be easily manufactured using conventional fireproof and heat insulating brick manufacturing equipment without using special manufacturing equipment, thereby reducing manufacturing costs.

Moreover, the spinel fireproof insulation brick of the present invention has a thermal conductivity of 0.
．． 45Kcal/mh 1.14kcal/mmh of magnesia refractory insulating brick at 350 pm at ℃, 0.67kcal/mh of alumina refractory insulating brick. In addition to its corrosion resistance, which is smaller in size than 0, when used as heat insulating material in furnaces that handle molten metal, such as mixer furnaces, pots, and tundishes, it exhibits an excellent insulation effect and saves energy. I can do it.

Next, embodiments of this invention will be described.

Example 1 66 parts by weight of moth dressing alumina with a powder size of 325 mesh and a purity of 99% and a powder size of 200 mesh and a purity of 97.5
% magnesia clinker powder 26 parts by weight and fineness 48
After adding and mixing 8 parts by weight of frog's eye clay throughout the mesh,
As a pore-forming material, 47% of expanded polystyrene and 47% of wood chips were added and mixed to 100k9 of the above mixed raw material, an appropriate amount of water was added, and after kneading, it was poured into a specified mold, molded, and after demolding, dried with a dryer, and then formed into a tunnel. 1500q in kiln
o Baked.

The physical properties of the obtained fireproof and insulating brick were as follows.
Bulk specific gravity 0.92 Compressive strength 60k9/Earth bending strength 32k9/Geothermal conductivity
0.44kcal/mh℃ at35000
Porosity: 71% Hot linear expansion rate: 0.78% atlo00q○
Mountain 203/Mg0 2.7
3 Mineral Composition Spinel Example 2 Parts by weight of alumina 7 with a fineness of 325 mesh and a purity of 99%, and a mixture of 200 mesh and a purity of 9
24 parts by weight of 5% magnesia clinker powder and fineness 4
After adding and mixing 6 parts by weight of Kibushi clay of 8 mesh, 50 pieces of expanded polystyrene and 30 pieces of wood chips were added and mixed as a pore-forming material to 100 kg of the mixed raw material, and after kneading with an appropriate amount of water, Pour into a mold, remove the mold, dry it with a dryer, and then heat it in a tunnel kiln to 1580 ml.
q○ fired.

The physical properties of the obtained fireproof and insulating brick were as follows.
Bulk specific gravity 1.00 Compressive strength 86k9/Earth bending strength 45k9/Uniform thermal conductivity
0.4 broadside cal/mh℃ at350 pm hot linear expansion rate 0.79% atl000 pm 0 mountain 203/Mg0 3.
13 Mineral composition Spinel and a small amount of corundum Porosity 69% Cited literature Ceramic material for Aoi furnace (Gihodo) Ceramics data book 1971 (Industrial Product Technology Association) Nihon Keizai Shimbun August 15, 1968

Claims (1)

[Claims] 1. Sintered alumina powder 64 with a purity of 99% or more and a fineness of 150 mesh or less in 20 to 28 parts by weight of magnesia clinker powder with a purity of 95% or more and a fineness of 150 mesh or less
~72 parts by weight and 5~ of bound clay with a powder size of 48 mesh or less
Add 10 parts by weight and mix to obtain MgO (19.0-27.
2%), Al_2O_3 (66.3-76%), SiO
_2 (3.8-8.2%) and MgO vs. A
After setting the ratio of l_2O_3 to 1:2.5 or more and 4 or less,
MgO-Al_ characterized by adding and mixing a predetermined amount of pore-forming material, adding water, kneading, forming into a predetermined brick shape, and then performing normal drying and firing finishing processing to obtain a product.
A method for producing 2O_3 quality fireproof insulation bricks.