JP3426024B2 - Construction method of refractory construction body - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a refractory lining with excellent slag resistance. 2. Description of the Related Art As one of molten steel processing apparatuses, an RH type
Vacuum degassing furnaces such as the DH type are known. Conventionally,
This vacuum degassing furnace is mainly made of magnesia
Chrome bricks are used. [0003] However, there are problems such as the high production cost due to the brick, and the special skill and many man-hours required for the furnace construction. [0004] In addition, since magnesia-chromium contains chromium, there is a problem of environmental protection after use. [0005] In recent years, there has been a strong demand for chromium removal and amorphous refractory lining of vacuum degassing furnaces. However, the lining of the vacuum degassing furnace is used under severe conditions such that the lining is always in contact with the FeO-rich slag at a high temperature of 1600 ° C. or more under vacuum. [0007] At present, it is not possible to cope with not only irregular shaped refractories but also brick materials other than magnesia-chrome bricks. [0008] Among them, an improved magnesia-shaped amorphous refractory to be constructed by pouring is considered promising. Since it is an irregular-shaped refractory, the production cost is low, and the construction work is simple. However, when a magnesia-shaped amorphous refractory is cast and poured, the drying water undergoes the following reaction with the MgO component or the CaO component during drying, causing slaking (digestion).
Causes cracks in the construction body and weakens the organization. The properties of the magnesia raw material itself, such as corrosion resistance and fire resistance, also deteriorate due to the alteration. For this reason, a sufficient effect cannot be obtained in a place where use conditions are severe such as a lining of a vacuum degassing furnace. ## STR1 ## MgO + H ₂ O → Mg (OH) ₂ CaO + H ₂ O → Ca (OH) _{2 The} magnesia raw material is dense in order to satisfy high hot strength and high corrosion resistance. Properties and high purity products are required. Since the high-purity product has few impurities, it is characterized in that silicate compounds such as monticerite and forsterite are small in the crystal grain boundaries of magnesia. Therefore, the higher the quality of the magnesia raw material, the easier it is for the magnesia crystal to come into direct contact with moisture, and therefore, the magnesia crystal is in a state of being very easily slaking. Moreover, this slaking becomes more remarkable as the ratio of the magnesia fine powder increases and as the particle size decreases. [0018] To prevent the slaking of magnesia-shaped irregular refractories, a method of adding a slaking inhibitor to the magnesia raw material to make the raw material difficult to slake, a method of adding the anti-slaking agent to the amorphous refractory as a compound, and There is. In addition to the magnesia raw material, for example, Fe
There is a method of adding ₂ O ₃ , Cr ₂ O _3, etc., and as a method of adding as a compound to the amorphous refractory, for example, a borate in Japanese Patent Application Laid-Open No.
JP-A-99177 discloses amorphous silica and JP-A-61-29.
In JP 1465, phosphates are respectively added. [0020] SUMMARY OF THE INVENTION] above, in the method of adding the slaking inhibitor magnesia raw material, is a problem that the refractory of the magnesia raw material is reduced, also, Cr ₂ O ₃
In addition, there is a problem in terms of pollution regarding the post-use treatment of the refractory. [0021] In addition, the addition as a compound also has problems of deterioration of corrosion resistance and cracking and peeling due to oversintering. For example, in the case of mixing amorphous silica,
The SiO ₂ component from the amorphous silica reacts with the MgO component from the magnesia raw material to produce a low-melting MgO—SiO ₂ —other system, which leads to a reduction in corrosion resistance and oversintering. For this reason, it is necessary to develop an irregularly shaped construction having a durability comparable to that of magnesia-chromium, and the present invention relates to corrosion resistance and construction of a cast material which is dried under reduced pressure after construction and hardening. An object of the present invention is to provide a method for constructing an amorphous refractory having both properties. Means for Solving the Problems As a method for solving the above-mentioned problems, the present inventors carried out drying under reduced pressure after construction to obtain an amorphous refractory containing a specific amount of magnesia fine powder which is easy to slake. That things can be used,
It was found that a lining construction having a durability comparable to that of magnesia-chromic brick could be obtained, leading to the present invention. According to the present invention, in a method for applying an amorphous refractory, which is cast, hardened and then dried under reduced pressure, 5 to 50 wt% of magnesia having a particle size of 0.1 mm or less is used as an aggregate.
% Basic refractory is used. The term "drying under reduced pressure" as used herein refers to a method disclosed in Japanese Patent Application No. 5-108819 previously filed by the present inventors. And the boiling point of water (100 at normal pressure)
° C) and evaporating water at a low temperature of 100 ° C or lower and the boiling point or higher in the atmosphere, it is possible to realize both rapid drying and prevention of slaking of the refractory construction. Here, when the temperature is lower than the boiling point, the drying speed is extremely reduced. In the present invention, a specific method of drying under reduced pressure is a ladle, a converter, a vacuum degassing furnace, a lining of a molten metal container such as a mixed iron car, after pouring using a core, sealing the container, and reducing the pressure. Then, it is heated by microwave. At this time, the degree of pressure reduction is preferably 30 torr.
It is at least r and at most 250 Torr. If the pressure is less than 30 torr, microwave discharge occurs remarkably. If the pressure exceeds 250 torr, drying at a low temperature is difficult. The decompression time is determined according to the material, thickness, volume, temperature change on the back surface of the material, and the like. The magnesia raw material includes a sintered product obtained by firing magnesium hydroxide or lightly burned magnesia at a high temperature of about 1800 to 1900 ° C. and an electrofused product melted in an electric furnace. Is adjusted to coarse, medium and fine particles. In the amorphous refractory of the present invention,
Magnesia having a particle size of 0.1 mm or less is blended in an amount of 5 to 50 wt%. By mixing magnesia fine particles, the amorphous refractory improves the fluidity at the time of pouring, and a sufficient filling property can be obtained even in a narrow place. Further, the magnesia fine particles improve the densification of the refractory structure and the corrosion resistance. If the particle size is 0.1 mm or less, finer, for example, 0.05 mm or less,
Magnesia of 0.01 mm or less may be used. However, slaking easily proceeds even in the present drying method for a particle size of 0.001 mm or less. It is preferable to suppress the generation in the step of pulverizing the magnesia raw material or to reduce the mixing amount by removing as much as possible by classification. In the present invention, when the proportion of magnesia having a particle size of 0.1 mm or less is less than 5 wt%, no effect is exerted on densification of the refractory structure and improvement of corrosion resistance. Exceeding the limit of the effect of preventing slaking, the corrosion resistance is reduced due to the weakening of the refractory structure. FIG. 1 shows that a magnesia-shaped amorphous refractory is poured into the material, cured, and then heated and dried under a reduced pressure of 100 torr and when dried under a normal atmospheric pressure. 2 is a graph showing a change in the ratio of magnesia fine powder and the change in the slaking resistance (measured by a coefficient of linear expansion) of the construction body after drying. When dried under reduced pressure, even if the amount of magnesia fine powder is increased, the amount of the magnesia fine powder within the range of 50 wt% is excellent in the anti-slaking property. FIG. 2 shows the magnesia particle size of the product containing 20 wt% of magnesia in each of the case where the magnesia-type amorphous refractory was poured and heated and dried under reduced pressure of 100 torr after curing and the case where normal heating and drying were performed. 7 is a graph showing a change in slaking resistance (measured by a coefficient of linear expansion) of the construction body after drying. When dried under reduced pressure, the amount of magnesia fine powder is 0.1%.
Even with a particle size of 1 mm or less, it has excellent anti-slaking properties. The amorphous refractory used in the present invention is preferably made of magnesia as a main aggregate from the viewpoint of corrosion resistance. Therefore, magnesia of 0.1 mm or less is
If it is blended in an amount of 50 wt%, magnesia having a particle size exceeding 0.1 mm can be used for the remainder, but a refractory aggregate other than magnesia may be partially combined. For example, refractory raw materials such as alumina, zircon, zirconia, silica, and MgO—Al ₂ O ₃ spinel. The addition of a dispersant, a binder and the like is the same as in the case of conventional cast refractory. Examples of the dispersant include inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, sodium acid hexametaphosphate, sodium borate, and sodium carbonate;
Organic salts such as sodium citrate, sodium tartrate, sodium polyacrylate, and sodium sulfonate. The amount of addition is preferably 0.001 to 1 wt% with respect to 100 wt% of the refractory aggregate. As the binder, 1-15% by weight of a binder having hydraulic properties such as alumina cement and lightly burned magnesia is added as in the past. If necessary, fibers, metal powders, curing accelerators, curing retarders, ultra-fine refractory powders, silica sols, alumina sols, calcined aluminas, etc. are added to the extent that the effects of the present invention are not impaired. Is also good. . In the present invention, an amorphous refractory having the above composition is cast, cured, and dried under reduced pressure. Drying under reduced pressure can be performed at a low temperature of 100 ° C. or less because the boiling point of water is reduced, and the slaking of the magnesia raw material is suppressed. Moreover, even if some slaking occurs, the crystallization speed of water due to hydration is low, and the structure stability is maintained. As a result, effects such as corrosion resistance and simplicity of construction of the magnesia amorphous refractory blended with magnesia fine powder can be exhibited without any problems. EXAMPLES Examples of the present invention and comparative examples are shown below. Table 1 shows the composition of the amorphous refractory used in each example and the drying method. At the same time, the test results of the construction body after drying are shown. Each example is 5 to 100% by weight of refractory.
After adding 7 wt% of working water, kneading, pouring into a vibrating mold, hardening, and drying. The size of the construction body is 200 × 200 ×
The thickness was 40 mm. Magnesia-chrome brick is 1
800 ° C. calcined product was used as it was. The drying under reduced pressure is carried out by putting in a vacuum
orr (sample temperature 70-80 ° C.) × 20 hours and 35
Microwave irradiation was performed in a reduced pressure atmosphere of 0 torr (sample temperature 90 to 95 ° C.) × 20 hours. The test method is as follows. Slaking resistance: Expansion after drying was determined by a linear change rate (according to JIS-R2553). The compact expands due to slaking. Therefore, those having a large linear change rate have poor slaking resistance. Bulk specific gravity / porosity: According to JIS-R2205. Corrosion resistance; Steel slag by weight ratio: converter slag = 6
Using a 0:40 erosion agent, a rotational erosion test was performed at 1600 ° C. for 3 hours, and the erosion size after the rotational erosion was measured. Slag penetration resistance: After rotating erosion, the slag penetration dimension was measured. Actual machine test: Materials of some examples and comparative examples were lined in a lower tank of an RH type vacuum degassing furnace, and the wear rate was determined in mm / charge. As can be seen from the test results, the embodiment of the present invention is superior in corrosion resistance and slag penetration resistance to the conventional examples 1 and 2 in which the magnesia in the fine powder portion is small, and the conventional example 3
In comparison with the magnesia-chromic bricks, the results showed less corrosion and slag penetration. Comparative Examples 1 and 2 were obtained by ordinary heat drying, while Comparative Examples 3 and 4 were obtained by drying under reduced pressure
It exceeds 0 torr and is inferior to Examples of the present invention in all test results such as volume stability (linear change rate) after drying, denseness (bulk specific gravity, porosity), corrosion resistance and slag penetration resistance. The effect of the present invention is also confirmed from the results of the actual machine test. [Table 1] As described above, according to the present invention, a basic amorphous refractory containing a specific amount of magnesia as a fine powder is poured, and after drying, it is dried under reduced pressure, whereby the durability equivalent to magnesia-chrome brick is obtained. Lining can be formed. Therefore, according to the construction according to the present invention,
For example, in the lining of a vacuum degassing furnace, it enables amorphous refractories and dechromization.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the change in the ratio of magnesia fine powder and the slaking resistance (measured by the coefficient of linear expansion) of a construction body after drying, in the case of drying under reduced pressure and in the case of normal heating drying, respectively. It is a graph. FIG. 2 is a graph showing a change in particle size of magnesia fine powder and a change in a slaking resistance (measured by a coefficient of linear expansion) of a construction body after drying in each of a case where drying is performed under reduced pressure and a case where normal heating and drying are performed. .

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyoto Kasai 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Kiyohiro Hosokawa 1-3-3, Araimachi Shinama, Takasago-shi, Hyogo Prefecture -1 Inside Harima Ceramic Co., Ltd. (72) Inventor Tetsuro Fujii 1-3-1 Shinhama, Araimachi, Takasago City, Hyogo Prefecture Inside Harima Ceramic Co., Ltd. (56) References JP-A-5-238839 (JP, A) Hei 4-116379 (JP, A) JP 62-25633 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F27D 1/16 C04B 35/66 C21C 7/10

Claims (1)

(57) [Claims 1] An irregular-shaped refractory containing 5 to 50 wt% of magnesia having a particle size of 0.1 mm or less as an aggregate is poured and hardened, and after hardening, 30 Torr or more and 250 Torr or less.
A method for constructing an irregular-shaped refractory construction body, which comprises irradiating a microwave under a reduced pressure to perform drying.