JPH11147755A - Shaped refractory material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a Cr-free, high-quality shaped refractory material usable as e.g. a lining refractory such as for metal refining vessels in e.g. steelmaking furnaces, cement kilns and glass melting furnaces, and designed to be highly resistant to corrosion, infiltration and spalling and sufficiently durable even in case of being used in the form of a secondary refining vessel for high-grade steel. SOLUTION: This shaped refractory material consists mainly of MgAl2 O4 -Mg2 TiO4 -based solid solution and magnesia with the weight ratio: [MgAl2 O4 -Mg2 TiO4 ]/magnesia of (10:90) to (40:60), pref. (15:85) to (30:70) and also contains at least one kind of ingredient selected from spinel, chromium ore, dolomite containing <=10 wt.% CaO, alumina, mullite, carbon source(s) such as graphite, SiC, zirconia, zirocon, titania, silica and silica flour, silica rock, and metallic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention is used for metal refining vessels such as steelmaking furnaces, linings for cement kilns, glass melting furnaces, etc., and is particularly suitable for secondary refining vessels for molten steel.
The present invention relates to a shaped refractory having excellent corrosion resistance, infiltration resistance and spalling resistance.

[0002]

2. Description of the Related Art In recent years, various techniques such as oxygen blowing, vacuum degassing, argon blowing and stirring have been adopted in refining of high-grade steel. Are becoming more and more severe. For this reason, refractory linings such as metal melting furnaces and ladles must be of high quality with excellent corrosion resistance to basic slag generated during metal refining, infiltration resistance to slag, and spalling resistance. Have been.

[0003] As such high-quality refractories, magnesia-chromium refractories whose main aggregate is a magnesia raw material and chromite are known.
It is widely used in refining vessels such as furnaces and ladles for refining molten steel, and is also used as a lining material in cement kilns and glass melting furnaces.

However, magnesia-chromium refractories require a treatment for detoxifying Cr at the time of disposal after use, and the problem that the treatment cost is high has become apparent. For this reason, refractories having high quality as described above without containing Cr, that is, Cr-free high-quality refractories have been developed.

[0005] Conventional Cr-free high-quality refractories include:
Magnesia-spinel refractories are known. This refractory is made of magnesia (MgO) and spinel (MgAl ₂
It is made of a solid solution of O ₄ ) and widely used for cement kilns. Further, magnesia (MgO) -titania (TiO ₂ ) -alumina (Al ₂ O ₃ ) refractories are
It is known from JP-A-7-300361. This refractory is said to be excellent in corrosion resistance, penetration resistance and spalling resistance for lining steel making furnaces, cement kilns, glass melting furnaces and the like.

[0006]

When the above magnesia-spinel refractory is used for metal refining as described above, there is a problem in durability due to poor infiltration resistance to slag. Further, the magnesia-titania-alumina refractory described in JP-A-7-300361 is particularly suitable for use in secondary refining vessels for high-grade steel.
There is some problem in spalling resistance, and it is difficult to exhibit sufficient durability.

The present invention relates to a metal refining vessel such as a steelmaking furnace,
A Cr-free high-quality refractory used for lining of cement kilns, glass melting furnaces, etc., with excellent corrosion resistance, infiltration resistance and spalling resistance even when used for secondary refining vessels of high-grade steel. It is an object of the present invention to provide a shaped refractory having sufficient durability.

[0008]

SUMMARY OF THE INVENTION The present invention for achieving the above object comprises a MgAl ₂ O ₄ —Mg ₂ TiO ₄ -based solid solution and magnesia as main components, and the ratio between the _two is expressed by weight.
_{[MgAl 2 O 4 -Mg 2 TiO} 4]: Magnesia = 1
0:90 to 40:60. Then, [MgAl ₂ O ₄ —Mg ₂ Ti
O ₄ ]: Magnesia = 15: 85 to 30:70 is preferred. Also, spinel, chromium ore, 10% by weight
A carbon source containing the following dolomite, alumina, mullite, graphite, etc. containing CaO, one or more of SiC, zirconia, zircon, titania, silica and silica flour, silica stone, and metal powder added. Is preferred.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the shaped refractory of the present invention, the main components of MgAl ₂ O ₄ —Mg ₂ TiO ₄ based solid solution are spinel (MgAl ₂ O ₄ ) in a narrow sense and quadrulite (Mg ₂ TiO ₂ ). ₄ ) with [MgAl ₂
[O ₄ -Mg ₂ TiO ₄ ] solid solution contains unreacted substances and impurities at the time of forming the solid solution. Magnesia is M
Natural magnesite containing gO, magnesia calcined therefrom, magnesium hydroxide using seawater as a raw material, magnesia calcined therefrom, or electrofused magnesia.

The MgAl ₂ O ₄ —Mg ₂ TiO ₄ -based solid solution is prepared, for example, by mixing the particles of a magnesia source with the particles of a titania source and an alumina source and then melting or mixing the particles.
It can be manufactured by firing at a temperature of 0 ° C. or higher. At this time, the mixing ratio of each particle is TiO by weight ratio.
_It is preferable that the ratio ₂ / (TiO ₂ + Al ₂ O ₃ ) = 0.1 to 0.9.

The magnesia source used for producing the solid solution is the same as the above magnesia which is a main component of the present invention. The titania source can be natural or artificial rutile or anatase, and the alumina source can be artificial synthetic alumina or aluminum hydroxide.
It is desirable that all of these have a purity of 90% by weight or more in analysis after heat treatment at 1000 ° C.

These are mixed, granulated or molded as they are, or fired or melted to obtain Mg.
Al ₂ O ₄ -Mg ₂ TiO ₄ based solid solution can be obtained. The magnesia source, titania source, and alumina source are all granules, and the particle diameter is preferably about 100 μm or less in diameter. However, when melting, larger grains can be used. The solid solution is formed by melting or firing, and if the temperature is 1300 ° C. or higher, it can be easily formed industrially stably even by a solid reaction.

When TiO ₂ and Al ₂ O ₃ are added to MgO and melted or fired, [MgAl ₂
O ₄ -Mg ₂ TiO _4] solid solution is formed. MgO + Al ₂ O ₃ → MgO · Al ₂ O ₃ (1) 2MgO + TiO ₂ → 2MgO · TiO ₂ (2) MgO · Al ₂ O ₃ + 2MgO · TiO ₂ → [MgAl ₂ O ₄ -Mg ₂ TiO ₄ ] solid solution (3)

Here, MgO, Al ₂ O ₃ and TiO ₂
As described above, as described above, a magnesia source, an alumina source, and a titania source can be adopted, each of which is manufactured for industrial use in addition to natural ore, and all contain impurities. In addition, unreacted MgO, A exceeding the chemical equivalent of the reaction in the equations (1) and (2)
l ₂ O ₃ or TiO ₂ is also included. Therefore, in the present invention, as a form including these impurities or unreacted reactants, MgAl ₂ O ₄ -Mg ₂ of TiO ₄ based solid solution. Examples of the impurities include iron oxides such as SiO ₂ , CaO, and Fe ₂ O ₃ , B ₂ O ₃ , and MnO. Further, this solid solution does not always have a stoichiometric composition, and becomes a solid solution even if each component is increased or decreased by about ± 10%.

The MgAl ₂ O ₄ —Mg ₂ TiO ₄ -based solid solution is a solid solution formed by replacing 2Al in MgAl ₂ O ₄ with Mg and Ti. Stoichiometrically, the sum of twice the number of titanium ions and the number of aluminum ions is constant. Therefore, the amount ratio of Al ₂ O ₃ is determined by the amount ratio of TiO ₂ . MgAl ₂ O
₄ and Mg ₂ TiO ₄ are also determined.

The weight ratio of TiO ₂ / (TiO ₂
+ Al ₂ O ₃ ) = 0.1 to 0.9, it has excellent corrosion resistance, infiltration resistance and spalling resistance even when used as a secondary refining vessel for molten steel, which is a severe use condition of refractories. A raw material for refractories is obtained.

The MgAl ₂ O ₄ obtained as described above
-Mg ₂ ratio of TiO ₄ based solid solution and magnesia, at a weight _{ratio, [MgAl 2 O 4 -Mg 2} TiO 4]: Magnesia = 10: 90-40: and 60. With such a ratio, a refractory having excellent corrosion resistance, infiltration resistance and spalling resistance can be obtained even for a secondary smelting vessel of molten steel which is used under severe conditions. MgA
If the ratio of l ₂ O ₄ -Mg ₂ TiO ₄ -based solid solution is less than 10%, the infiltration resistance decreases, and if it exceeds 40%, the corrosion resistance deteriorates. It is preferable that the above ratio be 15:85 to 30:70.

The shaped refractory of the present invention has the M
gAl ₂ O ₄ -Mg ₂ as a main component TiO ₄ solid solution and magnesia, impurities such as described above, unreacted Al ₂ O ₃
And TiO _2, etc., as well as unavoidable contents or intentional additives. For example, carbon sources such as spinel, chromite ore, dolomite containing 10% by weight or less of CaO, alumina, mullite, graphite, one or two kinds of SiC, zirconia, zircon, titania, silica and silica flour, silica stone, metal powder, etc. It can contain more than one species. However, corrosion resistance,
It is desirable to adjust the addition amount and the particle size according to the use conditions of the refractory so as not to deteriorate properties such as infiltration resistance and spalling resistance.

The fixed refractories of the present invention include fired bricks and unfired bricks. In any case, the solid solution and magnesia in the form of granules or powder, and additives to be added as necessary, a binder is added as necessary, kneaded, molded by a press or the like, and then dried at 100 to 500 ° C. The fired brick is fired at 1500 to 1900 ° C., and the unfired brick is fired using high heat during use.

The binder may be water, and pulp waste liquor, phenol resin, furan resin, bittern, calcium lignin sulfonate, sodium silicate, aluminum phosphate, polyvinyl alcohol, and the like can also be used. Molding is
Pressure molding is performed by a friction press, oil press, rubber press, etc. according to the application and equipment used for the brick.

[0021] The shaped refractory of the present invention is used in a metal refining vessel,
When used for lining of cement kilns, glass melting furnaces, etc., it has excellent corrosion resistance, infiltration resistance and spalling resistance. In particular, in the secondary refining of molten steel, oxygen is blown, vacuum degassed, argon is blown, and agitation is performed, so that the steel has sufficient durability even under severe conditions involving an increase in the temperature of the molten steel, a prolonged residence time, and the like.

The reason why the fired brick made of MgAl ₂ O ₄ —Mg ₂ TiO ₄ based solid solution and magnesia has high durability will be considered below. The TiO ₂ component in the solid solution reacts with CaO in the infiltrated slag to form a high melting point CaT.
Generate iO ₃ . For this reason, it seems that further infiltration of the slag can be suppressed. The thickness of the altered layer due to slag infiltration can be suppressed to a small value, and the melting point of the slag infiltrated portion is small, so that it is considered that the corrosion resistance is high. In the refractory structure, voids are formed around and inside the coarse particles of the solid solution. This effectively suppresses the growth of cracks caused by thermal stress, and is considered to exhibit high spalling resistance.

[0023]

[Embodiment 1]: MgAl ₂ O ₄ —Mg ₂ Ti
An O ₄ -based solid solution was prepared by a firing method, and a brick was manufactured using this and magnesia, and the characteristics were evaluated. As a raw material of the solid solution, a magnesia source having a particle size of 4
99% pure seawater sintered magnesia having a particle size of 4 μm or less, industrial rutile powder as a titania source, and a sintered alumina fine powder having a particle size of 100 μm or less and a purity of 99% for a refractory as an alumina source were prepared.

The mixing ratio of each raw material depends on the magnesia source 41.
2% by weight, 29.4% by weight of titania source, alumina source 2
It was 9.4% by weight. To these, 2% by weight of water was added as a kneading material and kneaded with a fret mixer. Then 300t
Molded at normal temperature with a friction press
Dried for hours. This is the maximum firing temperature of 1 in a tunnel kiln.
By firing at 700 ° C., MgAl ₂ O ₄ —Mg ₂ T
A sintered body composed of an iO ₄ -based solid solution was obtained. Further, this sintered body was pulverized and adjusted to a particle size suitable for refractory production.

The raw material thus obtained and sintered magnesia having a purity of 99% were mixed in a weight ratio of 0: 100 to 50:50.
The particle size range of the solid solution was 1 to 3 mm, or the entire particle size range. In addition, the particle size composition of the whole brick is
The amount ratio of the solid solution and magnesia in each particle size range was adjusted so that the weight%, 1 mm or less was 33% by weight, and the mill powder of 100 μm or less was 7%. Also prepared were the above-mentioned titania source, alumina source and unstabilized zirconia having a particle size of 100 μm or less and a purity of 95% or more. 4% by weight of these are added as a kneading liquid to knead, and kneaded.
They were molded in a regular shape by a friction press, dried at 120 ° C. for 24 hours, and then fired in a tunnel kiln having a maximum sintering temperature of 1750 ° C.

[0026] The completed brick was mixed with a magcro direct bond brick (samples A and B) and MgAl ₂ O in advance.
₄ -Mg ₂ magnesia without producing a TiO ₄ solid solution simply adding titania source 6.6 wt% and alumina source 8.4 wt% was evaluated in comparison with kneading molding fired bricks (Sample C) . The results are shown in Tables 1 and 2. Samples DS in Table 2 were prepared by temporarily preparing a solid solution from a magnesia source, a titania source, and an alumina source, and adding magnesia thereto.

The corrosion resistance was evaluated by a rotary drum type erosion test using an oxygen-propane burner as a heat source, and the spalling resistance was evaluated by a hot metal immersion spall test. The erosion test conditions were a sample surface temperature of 1700.
℃, time 5 hours, the erosion material is CaO-SiO ₂ slag, C / S of slag is 3, the amount of slag is 40 per time
After cooling, the residual thickness at the most eroded position of the sample and the thickness of the portion where the slag was not infiltrated were measured and measured in advance. The residual thickness was subtracted from the original thickness to give the erosion depth, and the thickness of the portion where the slag was not infiltrated was subtracted from the residual thickness to give the slag infiltration depth. The spalling resistance test is 40 × 40
A sample having a size of × 160 mm was immersed in hot metal at 1600 ° C. to a depth of 50 mm in the longitudinal direction for 15 seconds, then taken out and allowed to cool, and the number of repetitions until the immersion portion of the sample was chipped off was examined.

The erosion depth, the slag infiltration depth, and the number of repetitions before chipping are shown in Table 1 as indices with the value of sample A being 100, that is, the erosion index, the infiltration index, and the Spor index. The smaller the values of the erosion index and the infiltration index,
The larger the value of the Spall index is, the better the characteristics are.

Regarding the erosion index, MgAl ₂ O ₄ -M
g ₂ TiO ₄ -based solid solution and magnesia in a mixing ratio of 40: 6
Sample F exceeding 0 was large. Regarding the infiltration index, D and E in which the mixing ratio of the same solid solution and magnesia is less than 10:90
Was bad. In addition, the sports index was poor at less than 10:90. Therefore, the ratio is 10: 90-40:
Must be 60. The same ratio is 15:85 to 30:
H, J, K, L, N, P, Q, R, and S of 70 were particularly excellent in each property.

Example 2 An unfired brick was manufactured using the same raw materials and method as in Example 1 except for the firing step, and the characteristics were evaluated in the same manner as in Example 1.
Table 3 shows the results. Although the unfired brick of the present invention has almost the same corrosion resistance as the magcro brick (sample A) of the comparative example, it has excellent slag infiltration resistance and spall resistance, and can be said to be excellent overall.

Example 3 A sample H of the fired brick of the present invention shown in Table 2 was test-stretched on a 300 tRH side wall.
After use, the state of wear and remaining dimensions of the bricks remaining in the tank were investigated. As a result, the surrounding conventional material (A in Table 1) was cracked and peeled off, whereas the sample H was hardly cracked or peeled off. Also, the wear rate of Sample H was 25% less than A.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

The shaped refractory of the present invention is used for metal refining vessels such as steelmaking furnaces, linings for cement kilns, glass melting furnaces and the like, and secondary refining vessels for high-grade steels such as DH, RH and AOD. It is excellent in corrosion resistance, infiltration resistance, and spalling resistance even when used for applications, and contributes to improving the durability of these containers and the like. In addition, bricks that do not use chromium ore do not contain Cr, so that disposal after use does not require high processing costs.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Dosuni 1-3-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside Harima Ceramics Co., Ltd. (72) Inventor Minoru 1-3-3, Niihama Araimachi, Takasago City, Hyogo Prefecture No. 1 Harima Ceramics Co., Ltd.

Claims (3)

[Claims] 1. A composition comprising a MgAl ₂ O ₄ —Mg ₂ TiO ₄ -based solid solution and magnesia as main components, and the ratio of the two is [MgAl ₂ O ₄ -Mg ₂ TiO ₄ ]: magnesia = 1.
A fixed refractory having a ratio of 0:90 to 40:60. 2. The fixed refractory according to claim 1, wherein [MgAl ₂ O ₄ —Mg ₂ TiO ₄ ]: magnesia = 15: 85 to 30:70. 3. Spinel, chromite ore, carbon sources such as dolomite, alumina, mullite, graphite containing 10% by weight or less of CaO, SiC, zirconia, zircon, titania, silica and silica flour, silica stone, and metal powder 3. The refractory according to claim 1, wherein one or more of the following are added.