JPH08259338A - Irregular casting cast refractory body and its construction method - Google Patents

Abstract

(57) [Abstract] [Object] The present invention relates to a cast refractory lining for a molten metal container, which is extremely excellent in slag penetration resistance and has a hot strength comparable to that of a magnesia-chromic brick. Provided is a cast refractory having developed and superior durability of magnesia-chromic bricks. [Composition] As refractory particles, all particles are 0.1m
Magnesia having a particle size of m or more and alumina having a particle size of 1 mm or less for all particles have a weight ratio of 35 to 85 wt% magnesia and 65 to 65 alumina.
It is obtained by adding and blending 1 to 15 parts by weight of zirconia in which all particles have a particle diameter of 0.1 mm or less to 100 parts by weight of the compounded to be in the range of 15 wt%, at least at the start of use, The average pore size of the molded product is 5μ
m or less.

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 a cast refractory molded product having an infinite shape for a degassing refining furnace.

[0002]

2. Description of the Related Art R, which is a secondary refining equipment for molten steel
In a vacuum degassing treatment furnace represented by H, a fired magnesia-chromic brick mainly fired at a high temperature is used as a refractory lining. However, since these refractories require a molding / firing process during manufacturing,
There are problems that the cost is high and that furnace construction requires special skills and many man-hours. In addition, since magnesia-chromic brick contains chromium, it causes a problem in waste disposal after use from the viewpoint of environmental protection. Therefore, in recent years, there has been a strong demand for dechromization and amorphousization of refractory linings in vacuum degassing furnaces.

However, the refractory lining in the vacuum degassing furnace is constantly in contact with the high basicity (C / S) slag at a high temperature of 1600 ° C. or higher under vacuum conditions, and undergoes physical wear due to molten steel flow. Due to the extremely harsh conditions of use, not only in the case of irregular-shaped refractories, but also in the case of bricks, materials other than magnesia-chromic bricks exhibiting high corrosion resistance cannot be used at present.

For example, magnesia-chromic brick has excellent corrosion resistance to slag and molten steel, but has a drawback that cracks easily occur due to large thermal expansion and peeling easily occurs, and the slag penetration resistance is poor. are doing. As a result, the peeling phenomenon of the deteriorated layer remarkably occurs, and it is difficult to actually use the layer. On the other hand, the use of magnesia-carbonaceous bricks was also investigated, but since carbonaceous materials are used for the raw material composition and the binder, the tissue deterioration due to oxidation occurs and sufficient durability cannot be obtained. In the secondary refining process, there are problems with steel quality such as carbon pickup to molten steel.

Among them, a basic amorphous refractory material which can be easily cast and has a small thermal expansion and a relatively small penetration of slag is disclosed in, for example, JP-A-60-21868. An amorphous refractory composed of 86 to 96 wt% of magnesia aggregate as disclosed in the publication and 4 to 14 wt% in total of alumina ultrafine powder and silica ultrafine powder has been proposed. This magnesia-alumina-silica-based material is an amorphous refractory and does not require furnace construction work and is preferable in terms of workability. Regarding the corrosion resistance to slag, it exhibits a considerably high corrosion resistance because of its highly basic composition.

[0006]

However, a material containing a silica component, such as the above-mentioned amorphous refractory, has a very low hot strength because the silica component melts at a high temperature. In addition, the reaction with high C / S slag facilitates MgO
To generate a -CaO-SiO ₂ system TeiTorubutsu (mp 1500 ° C. or less), the penetration of the slag is promoted. In a degassing refining furnace in which the movement of molten steel is vigorous and physical wear conditions are taken into consideration, the permeation layer, which has little strength in the hot state as described above, is continuously damaged due to wear, so it becomes stronger by high temperature firing. The durability is extremely poor as compared with magnesia-chromic bricks that form various interparticle bonds.

Also, in the case of a magnesia-alumina-based material containing no silica, it dissolves in CaO-SiO ₂ -based infiltration slag within the composition range of the above-mentioned amorphous refractory material. Originally, there are few Al ₂ O ₃ components that increase the viscosity of slag, and by using alumina added separately at high temperature, all react with the surrounding magnesia and chemically change to spinel, which exists between particles. Since the pore size becomes large, it is not possible to fundamentally suppress the penetration of slag into the refractory.

In the case of an amorphous refractory, there is no bond such as a direct bond of fired brick that is not immediately broken under high temperature and slag infiltration, so it is important to suppress slag infiltration as much as possible. Further, even if the slag permeation layer is generated, it is important to aim at high hot strength in order to alleviate wear and peeling of the layer.

The present invention relates to a molten metal container, in particular, a cast-in-place refractory lining for a degassing refining furnace, which is extremely excellent in slag permeation resistance and has a hot strength comparable to that of a magnesia-chromic brick. Provided, and as a result, a magnesia-chromic brick provides a cast refractory having superior durability.

[0010]

According to the present invention, as refractory particles, magnesia in which all particles have a particle diameter of 0.1 mm or more and alumina in which all particles have a particle diameter of 1 mm or less are respectively used. The weight ratio of 35 is magnesia
1 to 15 parts by weight of zirconia in which all particles have a particle diameter of 0.1 mm or less, in 100 parts by weight of a mixture of ˜85 wt% and alumina in a range of 65 to 15 wt%.
A molded product obtained by adding and blending parts by weight, wherein the molded product has an average pore diameter of 5 μm or less when heated at least after starting use. is there. The average pore diameter referred to here is a pore diameter value corresponding to a cumulative volume percentage of 50% in the measurement of the pore diameter distribution by the mercury penetration method.

When constructing such a cast-in-place cast refractory body, the most preferable characteristics are obtained by irradiating with microwave under a reduced pressure atmosphere and drying at low temperature.

[0012]

The basic magnesia refractory exhibits high corrosion resistance against high C / S slag generated in the steel refining process. On the other hand, the penetration of slag into the material significantly progresses, and the damage due to wear and peeling increases, so that it is difficult to use in an actual furnace. The main cause of this slag infiltration is a decrease in the viscosity of the infiltration slag and an increase in the pore size level at high temperatures during use.

When the CaO--SiO ₂ slag penetrates through the pores between the magnesia particles, MgO in the slag.
Since the components are dissolved and a slag of MgO—CaO—SiO ₂ system having low viscosity is generated, it is difficult to suppress the permeation. Further, since magnesia has a large expansion coefficient, even if the pore size is small and dense during construction, the pore size level becomes large at high temperatures, which also works against the suppression of slag infiltration.

In addition, since the magnesia raw material contains a SiO ₂ component as an impurity, it is difficult to achieve high strength during hot working. Furthermore, when it is used as a castable refractory with an irregular shape, the slaking phenomenon of magnesia due to the influence of its construction moisture is also a big problem. However, this problem can be solved by practicing the drying method disclosed in JP-A-6-300438.

In order to solve the above-mentioned unsolved problems of reducing slag permeability and improving hot strength, the present invention maintains the corrosion resistance to high C / S slag as a particle composition of an amorphous refractory material. In order to suppress the penetration of slag, magnesia is used in the coarse particle portion, and alumina is mixed in the matrix fine powder portion which is the penetration route. As a result, it has become possible to dramatically suppress the penetration of slag into the refractory while maintaining the high corrosion resistance of the basic refractory that is inherent to the slag.

This is because the alumina used in the fine powder portion has a small expansion coefficient and the pore diameter level remains small even at high temperature, and the slag that has penetrated into the fine pores contains Al ₂ O in the matrix fine powder portion. ₃ components are dissolved, Al ₂ O ₃ -Ca
This is because the composition changes to an O—SiO ₂ slag with high viscosity. Further, when the Al ₂ O ₃ component is dissolved, a solid phase CaO · 6Al ₂ O ₃ having a high melting point is deposited, which works effectively for suppressing slag penetration. Further, the amount of impurity SiO ₂ contained in Al ₂ O ₃ used in this example is smaller than that in magnesia. Therefore, silicate bonds having inferior high-temperature strength properties are not formed between the fine powder particles during firing, and high hot strength can be exhibited.

The concern here is that the amount of alumina used in the fine powder portion is higher than that of magnesia used in the aggregate portion.
Since the corrosion resistance to high C / S slag is poor, in the case of heavy treatment where the treatment temperature exceeds the normal temperature of about 1600 ° C and reaches close to 1650 ° C, only the fine powder portion may be melted before the treatment. is there. As a countermeasure against this, in the present invention, zirconia is used for a part of the fine powder portion.

That is, since zirconia itself has a high melting point and is difficult to melt with respect to slag, it is possible to suppress the antecedent melting loss of the fine powder portion.
Furthermore, by adding zirconia, it is possible to suppress excessive grain growth due to sintering (spinelization) of magnesia and alumina at a high temperature, so that denseness is further developed and strength is also improved.

The present invention has been made based on the above concept, and the gist of the invention is that, as the refractory particles, all of the particles have a diameter of 0.1 mm or more, and magnesia. With alumina having a particle size of 1 mm or less, and the weight ratio of each is 35
1 to 15 parts by weight of zirconia in which all particles have a particle diameter of 0.1 mm or less, in 100 parts by weight of a mixture of ˜85 wt% and alumina in a range of 65 to 15 wt%.
A molded product obtained by adding and compounding parts by weight, and having an average pore size of 5 at least at the start of use.
The cast refractory body has an irregular shape and is characterized by having a size of not more than μm. In addition, the average pore diameter referred to here is a cumulative volume percentage of 5 in the pore diameter distribution measurement by the mercury penetration method.
It is a pore diameter value corresponding to 0%.

If magnesia having a particle size of less than 0.1 mm is used, the pore size becomes large at the time of firing, and slag penetration becomes large, which is not preferable. In addition, 1m
If alumina having a particle size exceeding m is used, the corrosion resistance to slag is significantly deteriorated. In order to maintain sufficient corrosion resistance, that is, in order for the erosion dimension after the rotary erosion test to be 10 mm or less, 35 wt% or more magnesia is required. Further, if it exceeds 85 wt%, it is not possible to prevent the slag infiltration even with the finely powdered alumina,
The expansion becomes large and the hot strength property becomes inferior. In addition, the more preferable compounding ratio of magnesia is 40 to 70.
wt%.

On the other hand, when zirconia having a particle size of more than 0.1 mm is added, the particles are too large and the uniform dispersibility in the fine powder portion is deteriorated, and it does not act favorably to suppress the preceding dissolution loss of the fine powder portion. With respect to the addition amount, if the addition amount is less than 1 part by weight, the effect of the addition is not exhibited, and the preceding powder loss of the fine powder portion occurs during high temperature treatment. On the other hand, if it exceeds 15 parts by weight, the balance of the particle constitution is lost, the pore diameter level becomes large, and the strength is lowered. The detailed particle size composition of each of the coarse particle portion and the fine powder portion is such that at least the average pore diameter when starting use and heating is 5 μm.
It must be designed to keep: This is because when the average pore size of the molded body after heating and firing exceeds 5 μm, the effect of suppressing penetration of slag is reduced.

The magnesia clinker and alumina clinker used in the present invention are preferably a sintered product or an electromelted product having a residual impurity component of 2 wt% or less. If the residual impurity component exceeds 2 wt%, the hot strength and corrosion resistance decrease.
The zirconia used in the present invention is an unstabilized product, or a sintered product or an electromelted product partially or completely stabilized with magnesia, calcia, yttria, or the like.

The particle size composition of the aggregate particles is, for example, coarse particles having a particle diameter of 5 mm or less and more than 3 mm, 3 mm.
It is controlled in five particle size regions of the following: medium particles in the range of more than 1 mm, fine powder of 1 mm or less and 0.1 mm or more, fine powder of less than 0.1 mm and 10 μm or more, and ultrafine powder of less than 10 μm, and magnesia, alumina, and zirconia are controlled. According to the grain size condition of the present invention, these five grain size ranges are allocated.

The addition of a dispersant, a binder and the like to the blended refractory particles is carried out in the same manner as in the conventional castable amorphous refractory material. As the dispersant, for example, inorganic salts such as sodium tripolyphosphate and sodium hexametaphosphate, organic salts such as sodium polyacrylate and sodium sulfonate, and the like can be used. The addition amount is preferably 0.001 to 1 part by weight with respect to 100 parts by weight of the refractory particles. As the binder, for example, 1 to 10 parts by weight of alumina cement containing about 30 wt% of CaO component is added. In addition, if necessary, fibers, metal powder, curing accelerator, curing retarder,
Refractory fine powder, silica sol, alumina sol, calcined alumina, etc. may be added within a range that does not impair the effects of the present invention.

[0025]

EXAMPLES Examples of the present invention and comparative examples will be described below. Table 1 summarizes the characteristics of the examples and the comparative examples of the irregular shaped refractory molded articles according to the present invention. Further, Table 2 summarizes the characteristics of the amorphous refractory moldings according to Example 1 of the present invention for each drying method.

In the actual machine test, 4 to 6 parts by weight of the working water was added to 100 parts by weight of the amorphous refractory, and after sufficient kneading, the inside of the lower tank of the RH vacuum degassing and refining furnace was subjected to medium The molding was performed by pouring while applying vibration using a child, and subjected to a predetermined drying treatment. The drying treatment was carried out either by a microwave heating method under a reduced pressure atmosphere or circulating hot air, or by a general gas burner heating method.

The apparent porosity, average pore diameter, hot bending strength, slag penetration resistance, corrosion resistance, and spall resistance are the results of test pieces sampled in a specific shape from the molded body after drying. For magnesia-chromic bricks, the test results of 1800 ° C fired products are listed.

Each test method is as follows. Apparent porosity: According to JIS-R2205. Average pore size: The pore size distribution of each sample after drying and firing at 1500 ° C. was measured by the mercury intrusion method, and a pore size value of 50% in cumulative volume percentage was adopted. Hot bending strength: After being held at 1500 ° C. for 1 hour, the bending strength was measured.

Slag permeation resistance: Using a corrosive agent of steel slab: converter slag = 60: 40 in weight ratio, a rotary erosion test was carried out at 1650 ° C. for 3 hours, and then the permeation size of the slag was measured. . Corrosion resistance: After performing the slag penetration resistance rotary erosion test, the erosion size of the test piece was measured. Spor resistance: The work of heating at 1500 ° C. for 20 minutes and then air cooling in the atmosphere was repeated, and the number of times until peeling was determined. The larger the value, the better the spall resistance.

Actual machine test: The refractories of Examples or 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. First, all the properties shown in Table 1 are material properties after microwave heating and drying in a reduced pressure atmosphere of 100 Torr.

[0031]

[Table 1A]

[0032]

[Table 1B]

[0033]

[Table 1C]

[0034]

[Table 1D]

As shown by the test results, Examples 1 to 9 which are the shaped amorphous refractory products of the present invention have a lower pore size level after firing as compared with Comparative Examples 10 to 16 of the shaped amorphous refractory products, It has excellent resistance to slag penetration and high hot strength, and exhibits strength almost equal to that of magnesia-chromic bricks. However, in Example 9, since the magnesia aggregate used is of low purity, the strength is slightly low, the melt loss dimension is large, and the corrosion resistance tends to be poor.

Although Comparative Examples 10 and 11 are both excellent in slag penetration resistance, Comparative Example 10 is poor in corrosion resistance because Comparative Example 10 uses alumina even in a portion having a large particle size of more than 1 mm. In Example 11, the amount of alumina used was too large and the corrosion resistance was extremely poor. Comparative Examples 12 and 13
Although both have excellent corrosion resistance, Comparative Example 12 uses too much magnesia, and Comparative Example 13 uses magnesia even in the fine powder portion of less than 0.1 mm, so both have extremely high slag penetration resistance. Inferior to.

In Comparative Example 14, the amount of zirconia used was too small, and the effect of adding zirconia was not exhibited in terms of strength and corrosion resistance. On the contrary, in Comparative Example 15, the amount of zirconia used was too large, and Denseness is impaired, porosity increases,
This leads to a decrease in strength. Regarding Comparative Example 16, the particle size of zirconia was too large, the zirconia was not uniformly and effectively dispersed in the fine powder portion, and the preceding dissolution loss of the fine powder portion could not be suppressed.

Further, the evaluation results of the fireproof molded products shown in the examples of the present invention using an actual machine show that in all cases, the durability is equal to or higher than that of the current magnesia-chromic brick (Example 17). There is. This is because although the bricks that have undergone the firing process are superior in hot strength and corrosion resistance, the examples 1 to 9 of the present invention are by far superior in terms of slag penetration resistance and spall resistance. As a result, the amorphous refractory molded product of the present invention has better durability in an actual furnace.

The refractory molding of the present invention can withstand any drying method, but as shown in Table 2, low temperature drying by vacuum microwave drying can suppress slaking of magnesia as much as possible. Most desirable.

[0040]

[Table 2]

[0041]

INDUSTRIAL APPLICABILITY As described above, the amorphous refractory molded article of the present invention obtained by casting an amorphous refractory having a specific viscosity composition and chemical composition, curing it, and then drying it has a slag penetration resistance. , Exhibits excellent properties in hot strength.
Its durability is superior to that of the existing magnesia-chromium brick, and when it is used as a refractory lining for a vacuum degassing and refining furnace, for example, it is possible to save the labor of the furnace construction work and to reduce the cost of the refractory material.

Continuation of the front page (72) Inventor Shiro Yunari No. 1 Nishinosu, Oita City, Oita Prefecture Nippon Steel Co., Ltd. Oita Works

Claims (3)

[Claims] 1. As the refractory particles, all particles have a particle size of 0.
Magnesia having a particle diameter of 1 mm or more and alumina having all particles having a particle diameter of 1 mm or less were used in a weight ratio of 35 to 85 wt% magnesia and 6 alumina.
Compounded to be in the range of 5 to 15 wt% 100
A molded body obtained by adding and blending 1 to 15 parts by weight of zirconia having all particles having a particle diameter of 0.1 mm or less in parts by weight, wherein the average pore size of the molded body is at least at the start of use. A castable refractory body having an irregular shape, characterized by having a size of 5 μm or less. 2. The irregular cast porosity refractory body according to claim 1, wherein the average pore size is a pore size value corresponding to a cumulative volume percentage of 50% in the measurement of the pore size distribution by mercury porosimetry. . 3. An amorphous cast refractory molding characterized by irradiating with a microwave in a reduced pressure atmosphere and drying when the molded amorphous cast refractory molding according to claim 1 or 2 is constructed. Body construction method.