JP3238592B2 - Irregular cast refractory moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal container having excellent durability and, more particularly, to an amorphous cast refractory molded product for lining a degassing smelting furnace.

[0002]

2. Description of the Related Art Conventionally, RH, D
Burned magnesia-chromium brick is mainly used as a refractory lining of a vacuum degassing refining furnace such as H.

[0003] However, these refractories have problems such as high cost due to the forming and firing steps in production, and special skills and many man-hours required for furnace construction.

[0004] Further, magnesia-chromic bricks contain chromium, so that there is a problem in terms of environmental preservation during disposal after use. Therefore, in the lining of a vacuum degassing smelting furnace, in recent years, dechromization and irregularization have been strongly required.

[0005] However, the refractory lining of the vacuum degassing smelting furnace is constantly in contact with high basicity (C / S) slag at a high temperature of 1600 ° C or higher under vacuum conditions, and is further subjected to physical wear due to the flow of molten steel. Due to the extremely harsh conditions of use, it is not possible to cope with bricks as well as magnesia-chromium bricks, which exhibit high corrosion resistance, as well as amorphous refractories.

[0006] For example, magnesia brick has excellent corrosion resistance to slag and molten steel, but has a defect that crack exfoliation is likely to proceed due to large thermal expansion and the slag penetration resistance is poor. The delamination phenomenon occurs remarkably, and practical use is difficult.

[0007] The use of magnesia-carbon brick has also been considered. However, since carbonaceous material is used as a raw material composition and a binder, sufficient durability cannot be obtained due to structural deterioration due to oxidation. There are also problems in steel quality, such as carbon pickup into molten steel.

Among them, a basic amorphous refractory which can be easily poured, has a small thermal expansion, and has a relatively small slag penetration, is disclosed in, for example,
An amorphous refractory comprising 86 to 96% by weight of magnesia aggregate and 14 to 4% by weight of ultrafine alumina powder and ultrafine silica powder as disclosed in Japanese Patent No. 21868 has been proposed.

This magnesia-alumina-silica-based material does not require furnace construction work because it is an amorphous refractory,
It is preferable in terms of workability. In addition, regarding the corrosion resistance to slag, since it has a high basic composition, it exhibits considerably high corrosion resistance.

[0010]

However, a material containing a silica component such as the above-mentioned amorphous refractory has a very low hot strength. In addition, the high C / S slag can easily penetrate the MgO—CaO—SiO ₂ low-melt (melting point 1500 ° C.).
Below), and the slag permeability increases.

In a degassing smelting furnace in which molten steel moves abruptly and physical wear conditions are taken into account, the infiltration layer having little strength during such heat is continuously worn by wear, and the magnesia-chromium It has extremely poor durability compared to brick.

Further, even in the case of a magnesia-alumina material containing no silica component, in the composition range of the amorphous refractory, the material functions to increase the viscosity of the slag by being dissolved in the CaO-SiO ₂ -based infiltrated slag. Al ₂ O ₃ component is small.

Instead, all of the added alumina reacts with the surrounding magnesia during use at a high temperature to cause a chemical change into spinel, and the pore diameter between the particles increases.
Therefore, it is not possible to fundamentally suppress slag penetration into the refractory.

In the case of amorphous refractories, there is no bond that does not break immediately even at high temperature and under slag infiltration, such as direct bonding of fired brick, so it is important to suppress slag infiltration as much as possible. It is also important to increase the hot strength in order to alleviate the abrasion and peeling of the penetrating layer that has occurred.

[0015] The present invention relates to a molten metal container, particularly an amorphous cast refractory for lining a degassing smelting furnace, which has an extremely excellent slag penetration resistance and a hot strength comparable to that of magnesia-chromium brick in strength. To provide a cast refractory with a service life comparable to magnesia-chrome brick.

[0016]

According to the present invention, as refractory particles, all particles have magnesia having a particle diameter of 0.1 mm or more, all particles have a particle diameter of 1 mm or less, and an average particle diameter of 1 m or less. Is an amorphous cast refractory molded body obtained by blending alumina smaller than magnesia,
An amorphous cast refractory molded article characterized in that the compounding ratio is in the range of 35 to 85 wt% of magnesia and 65 to 15 wt% of alumina, and at least the average pore diameter at the start of use of the molded article is 5 μm or less. is there.

[0017]

The basic magnesia refractory exhibits high corrosion resistance to high C / S slag in the steel refining process,
It is difficult to use in an actual furnace because the slag penetrates significantly into the material and damages such as abrasion and peeling easily occur.

The main causes of the slag infiltration are considered to be the viscosity of the infiltrated slag and the pore size level at a high temperature during use.

When the CaO—SiO ₂ slag penetrates into the pores between the magnesia particles, MgO is introduced into the slag.
It is difficult to suppress the permeation because the components dissolve and become a low viscosity slag of the MgO—CaO—SiO ₂ system.

Further, since magnesia has a large expansion coefficient, even when the pore diameter is small and dense at the time of construction, the level of the pore diameter increases in a high temperature state, which also has a disadvantageous effect on suppressing slag penetration.

In addition, the magnesia raw material contains impurity Si.
Due to the inclusion of the O ₂ component, it is difficult to develop high strength hot.

Further, when used as an irregularly shaped refractory, the slaking phenomenon due to the effect of the construction moisture is also a serious problem. Regarding this problem, see JP-A-6-3
The problem is solved by the drying method disclosed in Japanese Patent No. 00438.

The present invention solves the above-mentioned unsolved problems of reducing the slag permeability and improving the hot strength.
Magnesia is used for the purpose of maintaining corrosion resistance to S slag, and alumina is compounded in a matrix fine powder portion which is a permeation route for the purpose of suppressing slag permeation.

This makes it possible to drastically suppress the penetration of slag into the refractory while maintaining the high corrosion resistance of the basic refractory inherently on the slag.

This is because the alumina used in the fine powder portion has a small expansion coefficient and maintains a small pore diameter level even in a high temperature state, while the slag penetrating into the fine pores contains Al in the fine powder portion.
_{This is because the 2} O ₃ component dissolves and changes to a highly viscous slag composition of the Al ₂ O ₃ —CaO—SiO ₂ system.

When the Al ₂ O ₃ component is further dissolved, solid CaO · 6Al ₂ O ₃ having a high melting point is precipitated and acts in the direction of suppressing permeation. Also, the impurity SiO ₂ in the alumina used this time was
Since the amount is smaller than that in magnesia, a silicate bond inferior in high-temperature strength characteristics is not formed between the fine powder particles during firing, and high hot strength can be exhibited.

According to the present invention, as the refractory particles, magnesia having all particles having a particle diameter of 0.1 mm or more and alumina having all particles having a particle diameter of 1 mm or less and having an average particle diameter smaller than magnesia are used. Is an amorphous cast refractory molded article obtained by blending: 35 to 85% by weight of magnesia and 65 to 15% by weight of alumina.
Wherein the average pore size at the start of use of the molded article is at most 5 μm or less.

Here, when magnesia having a particle diameter of less than 0.1 mm is used, the pore diameter at the time of firing becomes large, and slag permeability becomes large. When alumina having a particle size exceeding 1 mm is used, the corrosion resistance to slag is significantly deteriorated.

In order to maintain a certain level of corrosion resistance, 35 w
Magnesia of t% or more is required, but if it exceeds 85 wt%, slag penetration cannot be suppressed even with alumina in the fine powder portion, expansion increases, and hot strength properties deteriorate.

The detailed particle size configuration of each part must be designed so that at least the average pore diameter at the start of use is kept at 5 μm or less. This is because if the average pore diameter of the molded body after firing exceeds 5 μm, the effect of suppressing slag penetration becomes small.

It is to be noted that a preferable mixing ratio of magnesia is optimally 40 to 70 wt%.

The magnesia and alumina clinker used in the present invention are a sintered product or an electrofused product having a residual impurity component of 2% by weight or less. When the remaining impurity component exceeds 2 wt%, the hot strength and the corrosion resistance are reduced.

In the amorphous refractory of the present invention, the thermal expansion is small and the volume stability is excellent in the range of 5 to 30 parts by weight based on 100 parts by weight of the amorphous refractory of the present invention. Alternatively, a sintered or electrofused spinel clinker, which is a magnesia-alumina compound, may be added.

If the amount is less than 5 parts by weight, the effect of addition does not appear,
If the amount exceeds 0 parts by weight, the FeO component in the slag is dissolved in the spinel and the slag permeability is increased. 5
When the content is in the range of ３０30 parts by weight, the corrosion resistance and the thermal expansion characteristics are favorably affected.

The particle size of the whole aggregate particles may be, for example, coarse particles having a particle size of 5 mm or less and exceeding 3 mm, medium particles of 3 mm or less and exceeding 1 mm, 1 mm or less and 0.1 mm or less.
Fine particles of 1 mm or more, fine particles of less than 0.1 mm and 10 μm or more, and ultrafine particles of less than 10 μm are described, and magnesia or alumina is described in these particle size ranges.

The addition of a dispersant, a binder, and the like to the compounded refractory particles is the same as in the case of the conventional refractory by casting. Examples of the dispersant include inorganic salts such as sodium tripolyphosphate and sodium hexametaphosphate, and organic salts such as sodium polyacrylate and sodium sulfonate.

The amount of addition is 0.1 to 100 parts of the refractory aggregate.
001 to 1 part is preferred. As the binder, for example, Ca
Alumina cement containing about 30 wt% of O component
Add 10 parts.

If necessary, fibers, metal powders, curing accelerators, curing retarders, ultrafine refractory powders, silica sols, alumina sols, calcined aluminas, etc. may be added as long as the effects of the present invention are not impaired. Good.

[0039]

EXAMPLES Examples of the present invention and comparative examples are shown below.

Table 1 summarizes the characteristics of Examples and Comparative Examples of the amorphous refractories according to the present invention.

In the actual machine test, 4 to 6 parts of construction moisture was externally added to 100 parts of the amorphous refractory, and after sufficient kneading, a core was placed inside the lower tank of the RH vacuum degassing refining furnace. Was carried out while applying vibrations, and the drying was performed on a construction body formed by performing predetermined drying. Drying was performed by microwave heating or general gas burner heating under a reduced-pressure atmosphere or under circulation of hot air.

The apparent porosity, average pore diameter, hot bending strength, slag penetration resistance, corrosion resistance, and spall resistance of a sample sampled in a specific shape from the dried construction were determined. For magnesia-chrome brick,
The test results of 1800 ° C fired products are listed.

Each test method is as follows. Apparent porosity; according to JIS-R2205. Average pore diameter: The pore diameter distribution of the sample after drying and after calcination at 1500 ° C. was measured by a mercury intrusion method, and the pore diameter value was determined to be 50% by cumulative volume percentage. Hot bending strength: After holding for 1 hour at 1500 ° C., the bending strength was measured. Slag penetration resistance; weight ratio: billet: converter slag = 60: 4
Using a zero erosion agent, a rolling erosion test was performed at 1600 ° C. for 3 hours to measure the permeation size of the slag. Corrosion resistance: The erosion dimension after the above-mentioned rotational erosion test was measured. Spall resistance: After heating at 1500 ° C. for 20 minutes, the operation of air cooling in the atmosphere was repeated, and the number of times until peeling was obtained. The higher the value, the better the spall resistance. Actual machine test: Some of the examples and comparative examples were actually used in the RH lower tank, and the durability was determined by the average wear amount per channel mm / ch. The smaller the value, the better the durability.

As shown by the test results, Examples 1 to 9, which are the amorphous refractories of the present invention, are comparative examples 10 of the amorphous refractories.
As compared with Nos. To 14, the pore size level after firing is low, the slag penetration resistance is excellent, the hot strength is high, and the strength is almost equivalent to that of magnesia-chromium brick. However, in Example 9, the strength of the magnesia aggregate used was low and the strength tends to be slightly low, and the erosion size tends to be large.

On the other hand, Comparative Examples 10 and 11 are both excellent in slag penetration resistance. However, in the case of Comparative Example 10, 1
Corrosion resistance is poor because alumina particles are also used in the large particle size portion exceeding mm, and in Comparative Example 11, the amount of alumina used is too large and the corrosion resistance is extremely poor.

Although Comparative Examples 12 and 13 both have excellent corrosion resistance, Comparative Example 12 uses too much magnesia, and Comparative Example 13 also uses magnesia in a fine powder portion of less than 0.1 mm. Therefore, both have extremely poor slag penetration resistance. In Comparative Example 14, too much spinel was used, and both the corrosion resistance and the slag penetration resistance were poor.

Further, as a result of evaluating the constructions shown in the examples of the present invention with actual machines, in all cases, the durability was equal to or higher than that of the current magnesia-chromium brick (Example 15).

This is because bricks that have undergone the firing step have better hot strength and corrosion resistance, but Examples 1 to 9 of the present invention are far superior in terms of slag penetration resistance and spall resistance. Specifically, the amorphous material of the present invention resulted in better durability in an actual furnace.

Although the material of the present invention can withstand any drying method, low-temperature drying by reduced pressure microwave drying is most desirable.

[0050]

[Table 1]

[0051]

As described above, the irregular-shaped refractory construction body of the present invention, which is obtained by pouring in an irregular-shaped refractory having a specific particle size composition and chemical composition, curing it, and subjecting it to predetermined drying, provides a slag-resistant material. It exhibits excellent properties in terms of permeability and hot strength. Its durability is equal to or higher than that of the existing magnesia-chromium bricks.For example, if it is used as a refractory lining in a vacuum degassing smelting furnace, it can save labor for furnace construction work and reduce the cost of refractory materials. Become.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shiro Yunari 2-6-3 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Steel Corporation (56) References JP-A-5-238839 (JP, A) JP-A-6-116048 (JP, A) JP-A-7-300371 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/66

Claims (1)

(57) [Claims] 1. As refractory particles, all particles have a particle size of 0.1.
Magnesia having a particle diameter of 1 mm or more, and all the particles have a particle diameter of 1 mm or less, the average particle diameter is an amorphous cast refractory molded body obtained by blending smaller alumina than magnesia, An amorphous cast refractory molded article characterized in that the compounding ratio is in the range of 35 to 85% by weight of magnesia and 65 to 15% by weight of alumina, and at least the average pore diameter of the molded article at the start of use is 5 μm or less.