JPH05148043A - Refractory for casting - Google Patents

Abstract

PURPOSE:To improve casting property and resistance to slag permeation and corrosion resistance of a refractory by adding magnesia fine powder having specified surface characteristics as a binder to a refractory aggregate using alumina, etc., as a main material. CONSTITUTION:The objective refractory for casting is formed by adding 0.5-5wt.% magnesium fine powder to 100 pts.wt. refractory. As the refractory, alumina or alumina and MgO-Al2O3 based spinel are used as main materials. The magnesia fine powder used has surface property of 1-40mg/g iodine absorption amount. In the refractory, sufficient hardening rate and strength are obtained without adding alumina cement, fumed silica, etc., to the refractory. Consequently, the refractory is excellent in corrosion resistance, resistance to slag penetration and has an excellent resistance to sporing of constructures.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory for casting which has excellent durability.

[0002]

2. Description of the Related Art As a protective refractory material for linings of ladle, vacuum degassing furnace or lance for molten steel treatment, refractory material for pouring construction of alumina or alumina and MgO / Al ₂ O ₃ spinel material (hereinafter referred to as A casting material is used). Among the conventional casting materials, one that has been particularly effective is a MgO.Al ₂ O ₃ -based spinel having 50 to 90 wt% alumina and a particle diameter of 1 mm or less proposed by JP-A-63-111501. 40 wt
%, Alumina cement 3 to 25 wt%. However, CaO contained in the alumina cement reacts with the alumina of the aggregate to lower the corrosion resistance and the slag permeation resistance, and cause structural spalling due to oversintering,
It reduces the durability of refractories.

[0003]

Therefore, for example, as seen in Japanese Patent Laid-Open No. Hei 3-23275, a casting material using a reduced amount of alumina cement or active magnesia as a binder in order to reduce CaO has been investigated. Came. However, since a material having low CaO quality or containing no CaO is inferior in binding strength, an additional component such as fume silica is required for the purpose of promoting hardening and imparting strength to a construction body. However, since fume silica is an ultrafine powder, the pore size of the structure of the construction body is small, and it is easy to cause cracks and explosions during drying. Further, there is a problem that SiO _{2 as a} main component thereof forms an Al ₂ O ₃ —MgO—SiO ₂ -based low-melting material and reduces corrosion resistance.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive research to solve the above-mentioned conventional problems of casting materials. As a result, in the casting material of alumina or alumina-spinel material, a specific surface property is found. By using a fine powder of magnesia with a binder, excellent workability, and
The present inventors have completed the present invention, knowing that the slag penetration resistance and the corrosion resistance are remarkably improved.

A feature of the present invention is that 100 parts by weight of a refractory aggregate mainly composed of alumina or alumina and MgO.Al ₂ O ₃ type spinel has a surface texture of 1 iodine adsorption amount.
-40 Iodine mg / g magnesia fine powder 0.5-5 w
It is a refractory for pouring construction with t% added.

The alumina and MgO.Al ₂ O ₃ type spinel (hereinafter referred to as spinel) used as an aggregate in the present invention may be either an electro-melted product or a sintered product. Also,
They may be used in combination. Alumina preferably has a small amount of impurities, and preferably has an Al ₂ O ₃ content of 97% or more. Spinel is composed of MgO and Al ₂ which constitute spinel.
The ratio of each component of O ₃ does not necessarily have to be the theoretical composition, and for example, MgO: Al ₂ O ₃ is 0.4 to 1.
It may be in the range of 1: 1.1 to 0.4.

When alumina and spinel are used together in the aggregate, the ratio of both is not particularly limited, but for example, the spinel is 80 parts by weight or less in the ratio of 100 parts by weight of the total aggregate, and within that range. Therefore, it is preferable to determine it according to various conditions such as the slag component and temperature when the refractory is used. If the spinel exceeds 80 parts by weight, a low-melted material is likely to be generated due to the reaction with slag or molten steel, and the corrosion resistance decreases.

The particle size of the refractory aggregate is not particularly different from the conventional one,
For example, the maximum particle size should be 7
Approximately 3 mm, and adjusted to coarse particles, medium particles, and fine particles. The iodine adsorption amount of magnesia fine powder has been conventionally known as a criterion for evaluating the surface properties of magnesia fine powder. There are various kinds of magnesia fine powders, and there are those that do not adsorb iodine even if only commercially available products are present, and iodine adsorption amounts up to 200 mg / g. In the present invention, among them, the iodine adsorption amount is 1 to 4
Magnesia powder of 0 iodine mg / g is used. The average particle size is, for example, about 0.1 to 1 μm.

The magnesia fine powder used in the present invention is
It reacts with construction moisture to produce magnesium hydroxide, which accelerates the hardening of the construction body. The formation of the hydroxide has the same effect as the hardening caused by the alumina cement forming CaO hydroxide, and improves the strength of the construction body after curing and drying.

Further, magnesium hydroxide returns to magnesia fine powder in response to a high temperature atmosphere when the refractory is used. The magnesia fine powder generated through the hydroxide is fine and has extremely high reactivity with the main aggregate, alumina. The fine powder of magnesia produces spinel when it reacts with alumina, but due to the high reactivity of the fine powder of magnesia, the production of this spinel is carried out from a low temperature region around 900 ° C. INDUSTRIAL APPLICABILITY In the present invention, the effect of slag permeation resistance can be obtained by the spinel produced by the reaction between the magnesia fine powder and the alumina of the aggregate.

On the other hand, the normal magnesia fine powder added to the conventional casting material does not become a hydroxide even when it comes into contact with the working water, and has little effect of imparting strength to the working body. Further, since magnesia fine powder is inferior in reactivity, spinel is produced from around 1300 to 1400 ° C., and a sufficient spinel production amount is not ensured at the time of molten steel contact,
The effect of preventing slag penetration is poor.

Fine powder of magnesia is known as a curing agent for casting materials. However, conventionally, in order to secure the strength of the construction body, magnesia fine powder as a curing agent for the pouring material,
For example, JP-A-2-233564 or JP-A-3-232
As seen in Japanese Patent Publication No. 75, an amine silicate, fume silica and the like are added together. Addition of amine silicate, fume silica, and the like causes cracks and explosion during drying as described above, and further deteriorates corrosion resistance and slag penetration resistance.

Further, magnesia fine powder has been conventionally used as a binder for a grindstone. However, in this case as well, the magnesia fine powder is not alone, but is used in combination with magnesium chloride to form magnesia cement to form a connective structure of the grindstone. In the present invention, the surface texture is an iodine adsorption amount of 1 to 4
By using 0 iodine mg / g of magnesia fine powder, sufficient curing characteristics can be obtained even with magnesia fine powder alone. Therefore, since it is not necessary to add amine silicate, fume silica, etc., it is possible to prevent cracking and explosion during drying, and at the same time, it is possible to exert excellent effects on corrosion resistance and slag penetration resistance.

Each of the figures is a graph showing the relationship between the amount of iodine adsorbed by the magnesia fine powder and the characteristics of the casting material in the alumina casting material to which the magnesia fine powder is added. In the test in which each property was measured, the addition amount of magnesia fine powder was 2 parts by weight. Further, each test was the same as the method shown in the section of Examples below.

FIG. 1 shows the iodine adsorption amount of magnesia fine powder,
The relationship between the curing strength and the dry strength of the cast material is shown.
FIG. 2 shows the relationship between the amount of iodine adsorbed by the magnesia fine powder, the rate of change in the firing line of the cast material, the slag penetration resistance, and the corrosion resistance. FIG. 3 shows the amount of iodine adsorbed by magnesia fine powder and the rate of change in the firing line of the cast material.

As shown in FIG. 1, good results have been obtained with a material to which magnesia fine powder having an adsorbed amount of iodine within the range of the present invention is added for both dry strength and curing strength. It can be seen from FIG. 2 that the materials to which magnesia fine powder having an iodine adsorption amount within the range of the present invention is added are also excellent in corrosion resistance and slag resistance. Magnesia powder exhibits residual expansiveness when it reacts with alumina to form spinel, but as shown in Fig. 3, when the iodine adsorption amount is 1 iodine mg / g or more, there is little change in the firing line and the structural stability of the refractory structure. Excellent in

The present invention is composed of the above-mentioned compounds, but within a range that does not impair the effects of the present invention, organic / inorganic / mineral known as additives for casting materials are used.
Fibers such as metal, metal powder, and other refractory raw materials may be added. Further, in order to impart fluidity during construction, a dispersant is poured over the entire material to be 0.01 to 5 wt.
% Addition is the same as the conventional casting material. Specific examples of the dispersant include sodium hexametaphosphate, sodium tripolyphosphate, sodium polyacrylate and the like. Construction is the same as the usual method, with 4 to 4 outside of the pouring material
A water content of about 8 wt% is added, and casting is performed using a mold. In order to improve the filling property at the time of casting, a vibrator is generally attached to the mold, or a rod-shaped vibrator is inserted in the casting material.

[0018]

EXAMPLES Examples of the present invention and comparative examples will be described below. Table 1 shows the iodine adsorption amount of the magnesia fine powder used in each example. Magnesia A is obtained by crushing magnesia fired at 1800 ° C. to 100 mμ or less. B ~
I is a light-burning magnesia fine powder fired at 1000 to 1300 ° C. Among these, C to H are magnesia fine powders having an iodine adsorption amount limited in the present invention. The amount of iodine adsorbed was measured according to JIS-K6338, which is known as a measurement of the surface properties of magnesia fine powder as an additive for rubber.

Table 2 shows examples of the present invention, comparative examples and conventional examples, and test results thereof. In each case, an appropriate amount of water suitable for workability was added, and vibration casting was performed in the mold. After molding, cure for 48 hours and then 200 ℃
It was dried by heating for 16 hours.

[0020]

[Table 1]

[0021]

[Table 2A]

[0022]

[Table 2B]

The test method is as follows. Curing property: For construction, it is preferable to cure within 2 to 4 hours after addition of water. If it is shorter than that, it hardens before construction. If it is longer than that, the construction efficiency deteriorates. In this test of the curing characteristics, what was cured within 2 to 4 hours after the addition of water was defined as “good”. Porosity: Measured according to JIS R-2205. Strength of the construction body: Bending strength after curing and after drying is measured according to JIS-R2553. Rotational erosion: Steel slab: converter slag = 60:40 (weight ratio) was used as a solvent, and rotational erosion at 1700 ° C x 5 hours was repeated 5 times to measure the melt loss dimension and the slag infiltration dimension. Line change rate: Curing, heat drying, baking at 1250 ° C, J
It was measured according to IS-R2553.

As shown in Table 2, good test results are obtained in all the examples of the present invention. On the other hand, in Conventional Example 1,
It is a material with the same amount of iodine adsorbed as magnesia fine powder used in conventional casting materials and high-alumina cement, and is inferior in slag resistance and corrosion resistance and has a large linear change rate. Conventional Example 2 is a material to which high alumina cement is added and magnesia fine powder is not added, and is inferior in slag resistance and corrosion resistance.

Comparative Example 1 is a material in which no alumina cement is added and magnesia fine powder having the same iodine adsorption amount as that used in the conventional casting material is added, and the slag resistance and the corrosion resistance are inferior. The contraction of the rate of change is large. Comparative Example 2 is a material in which magnesia fine powder having an iodine adsorption amount larger than the range of the present invention is added, and the workability is poor due to the slightly rapid curing, and the strength of the construction body is also poor. In Comparative Example 3, since the addition amount of the magnesia fine powder is small, it takes 24 hours or more for curing, and the strength of the construction body and the slag penetration resistance are poor. In Comparative Example 4, the addition amount of the magnesia fine powder was too large and the workability was poor due to the rapid hardening, and the obtained construction product had a large porosity and was poor in strength and slag penetration resistance.

[0026]

As described above, according to the present invention, by adding magnesia fine powder having a specific surface property to an alumina or alumina-spinel casting material, it is possible to add alumina cement, fume silica and the like. Sufficient curing speed and strength of the construction body can be obtained. Therefore, by not adding alumina cement, fume silica, etc., which cause the formation of low melting point substances, it is possible to obtain a casting material with excellent corrosion resistance, slag penetration resistance and structural spalling resistance, and without crevices or explosions during drying. I was able to do it.

[Brief description of drawings]

FIG. 1 shows the relationship between the iodine adsorption amount of magnesia fine powder and the curing strength and dry strength of the cast material.

FIG. 2 shows the relationship between the iodine adsorption amount of magnesia fine powder and the dissolution / penetration size.

FIG. 3 shows the relationship between the iodine adsorption amount of magnesia fine powder and the linear change rate (%) after firing at 1500 ° C.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Tsutsui 5-3 Tokai-cho, Tokai-shi, Aichi Pref.Nippon Steel Corporation (72) Inventor Takeshi Matsuda 5-Tokai-cho, Tokai-shi, Aichi 3 Nippon Steel Co., Ltd. Nagoya Steel Works (72) Inventor Kiyohiro Hosokawa 1-3-1 Niihama, Arai-cho, Takasago-shi, Hyogo Prefecture Inside Harima Ceramics Co., Ltd. (72) Inventor Hitoshi Nishiwaki 1- Niihama, Arai-cho, Takasago-shi 1- 3-1 Inside Hari Ceramics Co., Ltd. (72) Inventor Koichi Nishi 1-3-1 Niihama, Arai Town, Takasago City, Hyogo Prefecture

Claims (1)

[Claims] 1. Alumina or alumina and MgO.Al
100 parts by weight of refractory aggregate mainly composed of ₂ O ₃ spinel,
Refractory for pouring construction in which 0.5 to 5 wt% of magnesia fine powder having a surface property of 1 to 40 iodine mg / g in iodine adsorption amount is added.