JPH11180779A - Monolithic refractory and its structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a monolithic refractory structure used in an iron mill, etc. SOLUTION: The objective refractory structure is manufactured by using a blend of monolithic castable refractories with 5-60 wt.% blocks of monolithic castable refractories having the same compsn. or applying monolithic castable refractories while adding 5-60 wt.% blocks of monolithic castable refractories having the same compsn. The blocks are preferably subjected to heat treatment such as drying and firing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an irregular-shaped refractory which can reduce the occurrence of cracks in the field of refractories and has high durability, and a structure thereof.

[0002]

2. Description of the Related Art Amorphous castables have been increasingly used in various heat-resistant structures, such as lining of molten steel pots and tundishes used in steelworks and the like.

[0003] The reason is that it is easy to mechanize at the time of construction and can be automated (labor-saving) as compared with a fixed refractory, and since it is an unfired product, the energy cost of the refractory required to use it is low (energy saving). It is said that there is an advantage that there is no uneven wear such as joint erosion due to the absence of joints.

However, on the other hand, since it is a large monolithic structure, it generates internal strains during its drying or use at high temperatures, causing cracks, and peeling and peeling of the amorphous castable from the surface to be used. Such wear is frequently seen and is a problem.

Since the castables are exfoliated by excessive sintering of the castables at a high temperature or by excessive shrinkage due to reaction with molten steel or slag intruding from the surface to be used, various castables are separated from each other. Measures have been taken, but the fundamental solution has not yet been reached.

[0006]

In general, as a method of relieving thermal stress generated in a refractory, a different material having a different expansion amount is mixed, and a minute material formed at a boundary between the different material and a base material during heating is used. A method of absorbing strain with cracks has been adopted.

For example, in the case of alumina-spinel castable, there are addition of alumina particles larger than the particle diameter used for the castable and addition of stainless steel fiber.

[0008] These methods are effective in that microcracks are generated in the castable in advance, but since the composition differs from that of the castable matrix, the microcracks gradually expand during use, and They have the disadvantage that they are connected to each other to form large cracks, and finally to castable peeling.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above points, and in order to solve the above-mentioned problems, an amorphous castable is formed by adding a mass of irregular castables having the same composition to 5 to 60 masses. Provides an amorphous refractory and its structure characterized by being blended in a weight percent, alleviating the internal strain that occurs in the integrated castable that has become an integral structure, and continuously suppressing the generation and propagation of cracks In addition, the castable peeling phenomenon can be reduced.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The amorphous refractory and its structure according to the present invention are characterized in that, when the amorphous castable is cast into a predetermined container or mold, a lump formed beforehand by the same castable is 5 to 60% by weight. By adding and pouring, cracks generated inside the construction body during use are suppressed, and deterioration of the construction body does not occur even if the construction body is continuously used. It should be noted that the above-mentioned composition can be cast into an amorphous castable from the beginning.

[0011] The principle lies in the use of a connection between an irregular castable of the cast body and a pre-solidified mass of the same castable. In other words, the present inventors have found out that even if the castable composition has the same composition, once the solidified mass is put in a fluid castable, it does not completely adhere to each other and is used.

[0012] At this stage, microcracks capable of relaxing internal strain are formed around the irregular castable mass. The construction body obtained in this way gradually changes its structural structure with the passage of time and the rise in temperature (curing, drying, furnace operation), but the micro cracks created first are necessary for sintering. If a sufficient temperature is not applied, the material will not disappear, and as described above, the phenomenon of crack propagation as seen in the addition of a material different from the base castable will not occur. That is, it becomes possible to maintain a very stable microcrack up to near the sintering temperature of the composition.

It has been clarified that the effect of the disappearance of the microcracks near the sintering temperature on the construction body is rather good. For example, if you look at the state of being installed on the inner wall of a molten steel pot, the sintered body starts sintering after receiving molten steel and because there is a large temperature gradient inside the installed body, so-called sintering The thickness called the layer is limited to only the very surface of the construction body.

As is well known, this surface layer is a place where a molten material such as molten steel or slag comes into contact and undergoes physicochemical erosion such as erosion and penetration. In such a place, it is clear that the micro-cracks that alleviate the stress in the construction body are no longer necessary, and it is more preferable that the number of pores including the cracks is smaller. As described above, it is possible to obtain a construction body that is resistant to the attack of molten steel and slag on the surface side, and has a small crack whose size is stable on the inside side, thereby hardly causing cracks.

The castables according to the present invention include all castables generally used as refractories,
For example, an alumina-spinel system, an alumina-magnesia system, a zircon system, an alumina-silica system, or the like can be used.

[0016] As a method of hardening into a lump,
For example, casting into a mold or molding under pressure,
And crushing them with a crusher. The lumps are dried, baked, etc.
More effective.

The reason why the addition amount of the lump is limited to 5 to 60% by weight is that if the amount is less than 5% by weight, it is not possible to form a microcrack enough to alleviate the stress generated in the entire construction, and to add 60% by weight. % Or more, too many micro-cracks are generated too much, and eventually the cracks are connected to each other, resulting in a decrease in the strength of the entire construction.

[0018]

Next, as an example, the case of an alumina-spinel castable will be described below. The chemical composition of the alumina-spinel castable used was 91% by weight of Al ₂ O ₃ , 5% by weight of MgO, 3% by weight of CaO,
iO ₂ is a cement bond product of 0.5% by weight. Table 1 shows a comparison of the physical properties of the construction body when the irregular castable was used as a base, the amorphous castable was once formed into a lump, and then added in a predetermined amount to the base amorphous castable.

The spalling property in the table is based on JISR2657.
Investigation was conducted by heating and cooling with water at 1400 ° C. according to 1995 “Spalling test method for refractory bricks and refractory bricks”. After repeating 10 times, the ultrasonic wave propagation velocity was measured in the 114 mm direction of the sample to determine the elastic modulus, and the thermal spalling property was represented by the ratio to the value before the test. The higher the value, the higher the spalling resistance.

Table 1 Comparison table

[Table 1]

The slag erosion ratio was determined by comparing the corrosion resistance by a rotary slag test method. Temperature and temperature
Time is 1650 ° C, 5 hours, the erosion agent is converter slag (Ca
O / SiO ₂ = 2.5). The center of the test piece after the test was cut, the erosion area was measured, and the erosion amount in Comparative Example 1 was set to 100 and expressed relative to each other.

As a result, as shown in FIG. 1 and 2 are N of the comparative example, which is a construction body made of only the base castable.
o. It shows a good result that the elastic modulus is lower than that of No. 1, excellent in thermal spalling property, and the resistance to slag is almost the same. And the No. of the embodiment. As shown in FIG. 3, the effect of the block treated at 500 ° C. is larger.

Further, in Comparative Example No. The results of Nos. 2 and 3 were no effect, or were very poor in resistance to slag. Furthermore, in the comparative example No. In the product using 40% by weight of alumina particles of No. 4, the resistance to slag was remarkably inferior because the structure was greatly deteriorated.

In this embodiment, No. 2 for 250 at a certain steel mill
When constructed and used as a lining material for molten steel pots,
No. 325 charge, comparative example no. 1 of 2
The result was much higher than 63 charges, demonstrating the remarkable effect of the present invention.

The top size of the alumina-spinel castable used in Table 1 was 5 mm, and the particle size of the lump was 2 mm.
It was 0 to 10 mm. In addition, 50 tons of molten steel pot has 50
〜30 mm lumps were used.

As for the particle size of the lump, it is preferable that the top size is about one third of the construction thickness, and the lower limit is the top size of the base amorphous castable. If the thickness is larger than one-third of the work thickness, the workability when used in a large amount is unfavorably reduced.

[0027]

As described above, according to the present invention, it is possible to form an appropriate amount of microcracks around an irregular castable mass to alleviate internal strain, and since the base and the mass have the same composition, the cracks are formed. , The extremely stable micro-cracks can be maintained up to near the sintering temperature of the composition, and a durable construction body in which cracks are less likely to occur can be obtained.

[0028] Then, dried into a mass of irregular castables,
By applying a heat treatment such as firing, the microcracks can be reliably maintained at the sintering temperature, and the above-mentioned effects can be further exerted.

Claims (4)

[Claims] 1. An amorphous refractory comprising an amorphous castable and a castable mass of the same composition in an amount of 5 to 60% by weight. 2. An amorphous refractory structure in which an amorphous castable having the same composition is blended in an amount of 5 to 60% by weight when the amorphous castable is constructed. 3. The amorphous refractory according to claim 1, wherein the amorphous castable mass is subjected to a heat treatment such as drying and baking. 4. The amorphous refractory structure according to claim 2, wherein the lump of the amorphous castable is subjected to a heat treatment such as drying and firing.