JP6951951B2 - Amorphous refractory for tundish lining - Google Patents

Description

The present invention relates to an amorphous refractory for tundish lining.

A technique of using an amorphous refractory as a refractory for a tundish lining is known, but such an amorphous refractory has a problem that cracks occur due to sintering shrinkage if there is no residual expansion. Therefore, it is known to use pyrophyllite or silica stone as a refractory raw material as a technique for imparting residual expandability to an amorphous refractory (see, for example, Patent Documents 1 and 2).

However, the temperature range when the amorphous refractory for tundish lining is used is as wide as about 600 ° C to about 1500 ° C (operating surface side about 1500 ° C, back side about 600 ° C). For this reason, if a large amount of pyrophyllite or silica stone with rapid thermal expansion characteristics is used, the expansion difference between the operating surface side and the back surface side becomes large, and this expansion difference causes cracks inside the amorphous refractory for tundish lining. Will occur. In addition, there is also a problem that the abrupt expansion causes tissue destruction of the amorphous refractory for the tundish lining, and buckling and protrusion due to the decrease in strength occur.

Japanese Unexamined Patent Publication No. 2-141445 Japanese Unexamined Patent Publication No. 4-160066

An object of the present invention is to suppress the occurrence of cracks and the occurrence of buckling and protrusion in an amorphous refractory for tundish lining.

In order to solve the above-mentioned problems, the present inventors have focused on andalusite from the idea that it is necessary to have a characteristic of slowly expanding without abrupt expansion. That is, as shown in FIG. 1, andalusite expands more slowly than pyrophyllite and silica stone. Therefore, the present inventors have focused on andalusite, and as a result of detailed examination of the amount (content) used, the particle size composition, and the like from the viewpoint of solving the above-mentioned problems, they have come up with the present invention.

That is, according to one aspect of the present invention, the following amorphous refractory material for tundish lining is provided.
Andalsite quality of 40% by mass or more and 80% by mass or less in 100% by mass of the fireproof raw material, and 75 μm or less in particle size in 100% by mass of the total amount of the andalcite material. Containing 2% by mass or more and 50% by mass or less of the raw material ,
The ratio of the content of the andalustotic raw material having a particle size of 75 μm or less in the refractory raw material to the total content of the silica ultrafine powder and alumina cement in the refractory raw material containing silica ultrafine powder and alumina cement in the refractory raw material. An amorphous refractory for tundish lining having (content of andalsite material having a particle size of 75 μm or less / total content of silica ultrafine powder and alumina cement) of 0.2 or more.

According to the present invention, by setting the content and particle size composition of the andalusite raw material within a specific range, rapid expansion is suppressed while exhibiting predetermined residual expandability, so that crack generation is suppressed and buckling is suppressed. The occurrence of bending and protruding is also suppressed.

The figure which shows the thermal expansion property of andalusite, pyrophyllite and silica stone.

The amorphous refractory for tundish lining of the present invention (hereinafter, also simply referred to as "amorphous refractory") contains 40% by mass or more and 80% by mass or less of the andalitic material in 100% by mass of the total amount of the refractory material. contains. If the content of the andalusite raw material is less than 40% by mass, the predetermined residual expandability cannot be obtained, and cracks are likely to occur due to the sintering shrinkage of the fireproof raw material after receiving heat. On the other hand, if the content of the andalusite raw material exceeds 80% by mass, the residual expandability becomes too large and buckling or protrusion occurs. The preferable content of the andalusite raw material is 50% by mass or more and 70% by mass or less in 100% by mass of the total amount of the fireproof raw material.

Here, in the present invention, the andalusite quality raw material includes andalusite (diffraction surface is 110 planes (including the vicinity thereof)) among those having the third highest peak intensity in the X-ray diffraction of the raw material. _{And, the content of Al 2} O ₃ in the raw material is in the range of 50% by mass or more and 75% by mass or less, and _{the content of SiO 2} is in the range of 20% by mass or more and 45% by mass or less, and contains andalusite. In addition to those obtained from natural minerals (silimanite group minerals) and the like, those obtained by crushing fire-resistant materials (post-use products) containing andalusite are also included.

Further, as the particle size composition of the andalusite material in the present invention, the andalusite material having a particle size of 75 μm or less is contained in an amount of 2% by mass or more and 50% by mass or less in 100% by mass of the total amount of the andalusite material. When the content of the andalusite raw material having a particle size of 75 μm or less is less than 2% by mass, the residual expandability of the fine powder portion (matrix portion) becomes small, and cracks due to sintering shrinkage are likely to occur. On the other hand, when the andalusite raw material having a particle size of 75 μm or less exceeds 50% by mass, the expansion of the fine powder portion (matrix portion) becomes too large, the structure is destroyed greatly, and the strength decreases. As a preferable particle size composition of the andalusite material, 10% by mass or more and 30% by mass or less of the andalusite material having a particle size of 75 μm or less is contained in 100% by mass of the total amount of the andalusite material.

The amorphous refractory of the present invention preferably contains silica ultrafine powder from the viewpoint of increasing fluidity and strength.

Further, the amorphous refractory of the present invention is generally used as a binder of amorphous refractories such as alumina cement, hydraulic transition alumina, Portland cement, magnesia cement, silicate and phosphate. The one used is available. In addition, a part or all of the binder may form a cohesive binding portion by a combination of magnesia fine powder having a particle size of 75 μm or less and silica ultrafine powder. Among the above-exemplified binders, alumina cement is preferably used because of its high early strength and excellent corrosion resistance.

In the present invention, when alumina cement and silica ultrafine powder are contained, they promote sintering shrinkage. Therefore, from the viewpoint of further suppressing the generation of cracks due to sintering shrinkage, the ratio of the content of the andalcite material having a particle size of 75 μm or less to the total content of the silica ultrafine powder and the alumina cement (andalsite quality with a particle size of 75 μm or less). The content of the raw material / the total content of the silica ultrafine powder and the alumina cement) is preferably 0.2 or more.

The amorphous refractory of the present invention can be used as a refractory raw material in addition to the above-mentioned andalusitic raw material, silica ultrafine powder and alumina cement, as well as a clay raw material, an alumina-silica raw material such as mullite, an alumina raw material, a silicon carbide raw material and a carbon raw material. Etc. can be contained.

Further, the amorphous refractory of the present invention may contain an expansive aggregate containing α-quartz as a mineral and having a particle size of more than 1 mm, such as pyrophyllite and silica stone, as a refractory raw material. In order to prevent problems such as cracking and tissue destruction from occurring remarkably, the content thereof is preferably less than 2% by mass and 1.5% by mass or less in 100% by mass of the total amount of the refractory raw materials. It is more preferable, and it is most preferable that the content is 0% by mass (the mineral contains α-quartz and does not contain an expansive aggregate having a particle size of more than 1 mm). Further, an expandable raw material having a particle size of 1 mm or less containing α-quartz in the mineral may be contained as long as it is in a trace amount, and the content thereof is preferably 3% by mass or less in 100% by mass of the total amount of the fireproof raw material.

The amorphous refractory of the present invention may contain various additives generally used for the amorphous refractory, such as a dispersant and a curing modifier, in addition to the refractory raw material. Further, the amorphous refractory of the present invention may contain large coarse particles (particle size exceeding 10 mm) generally used for the amorphous refractory. In the amorphous refractory of the present invention, large coarse particles are not included in the refractory raw material. That is, in the amorphous refractory of the present invention, the large coarse particles are added externally to 100% by mass of the refractory raw material. Further, auxiliary raw materials such as metal powder, metal fiber, and organic fiber may be added to the amorphous refractory, but these auxiliary raw materials are not included in the refractory in the amorphous refractory of the present invention. , It shall be added externally to 100% by mass of the refractory raw material.

Table 1 shows the raw material formulations and evaluation results of Examples, Reference Examples and Comparative Examples of the present invention. The evaluation items and evaluation methods in Examples , Reference Examples and Comparative Examples are as follows. In Table 1, "other fireproof raw materials" are mullite (particle size 10 mm or less) and alumina raw material (particle size 1 mm or less). Further, in Table 1, "other raw materials" are additives such as dispersants and curing modifiers and auxiliary raw materials such as organic fibers, and the blending amount thereof is shown by the mass% of the outer weight with respect to 100% by mass of the fireproof raw material. There is.

<Remaining line change rate>
The residual line change rate was measured at 1000 ° C. and 1500 ° C., respectively, in accordance with JIS-R2554. As a result of the investigation by the present inventors, it was found that the temperature of the portion where many cracks occur in the amorphous refractory for the tundish lining is about 1000 ° C. The temperature near the operating surface is about 1500 ° C. Therefore, the residual line change rates were measured at 1000 ° C. and 1500 ° C. At 1000 ° C, cracks due to sintering shrinkage were assumed, and at 1500 ° C, buckling and protrusion were assumed, and the standard was set. Specifically, the evaluation was made on a four-point scale of ⊚ (excellent), ○ (good), Δ (possible), and × (poor) according to the following criteria.
Residual line change rate at 1000 ° C ◎ (excellent): -0.05 or more, 〇 (good): -0.1 or more and less than -0.05, Δ (possible): -0.2 or more and less than -0.1, × (impossible): Less than -0.2 (unit%)
Residual line change rate at 1500 ° C ◎ (excellent): 0 or more and less than 1, 〇 (good): 1 or more and less than 1.5, △ (possible): 1.5 or more and less than 2, × (impossible): 2 or more (unit) %)

<Strength>
The strength was evaluated by the cold compressive strength. Specifically, it was evaluated by the compressive strength after firing at 1000 ° C. for 3 hours. The compressive strength was measured in accordance with JIS-R2553. The evaluation was made on a four-point scale of ◎ (excellent), ○ (good), Δ (possible), and × (poor) according to the following criteria.
◎ (excellent): 40 or more, ○ (good): 35 or more and less than 40, Δ (possible): 30 or more and less than 35, × (impossible): less than 30 (unit MPa)

<Heat-resistant impact resistance>
The thermal shock resistance was evaluated by repeating forced heating and forced air cooling for 30 minutes in an electric furnace at 1500 ° C. after firing the test piece at 1000 ° C. for 3 hours, and the number of repetitions when a large crack occurred. Regarding the judgment of a large crack, the width of the crack in the test piece was confirmed by a feeler gauge according to JIS-B7524, and the case where the width of the crack was 0.5 mm or more was regarded as a large crack.
The evaluation was made on a four-point scale of ◎ (excellent), ○ (good), Δ (possible), and × (poor) according to the following criteria. In this evaluation, it is shown that the higher the number of repetitions when a large crack occurs, the better the thermal impact resistance.
◎ (excellent): 16 times or more, ○ (good): 13 times or more and 15 times or less, △ (possible): 10 times or more and 12 times or less, × (impossible): 9 times or less

<Comprehensive evaluation>
In any of the above evaluations, the overall evaluation is ◎ (excellent) when there are 3 or more ◎, 〇 (good) when there are 2 ◎ and 2 〇, and × when there is × in any of them. It was evaluated as (defective).

As shown in Table 1, in Examples 1 , 2, 4 to 11 within the scope of the present invention, the overall evaluation was ⊚ (excellent) or 〇 (good), and good evaluation results were obtained.

Comparative Example 1 is an example in which the content of the andalusite raw material is small. It was judged that the residual line change rate at 1000 ° C. was less than −0.2% and the predetermined residual expandability could not be obtained.
Comparative Example 2 is an example in which the content of the andalusite quality raw material is high. It was judged that the rate of change of the residual line at 1500 ° C. was 2% or more, and the residual expandability was too large to cause buckling or protrusion.

Comparative Example 3 is an example in which the andalusite raw material having a particle size of 75 μm or less is not contained as the particle size composition of the andalusite raw material. The residual expandability of the fine powder portion (matrix portion) is reduced, and cracks are likely to occur due to sintering shrinkage, resulting in a decrease in thermal impact resistance.
Comparative Example 4 is an example in which the content of the andalusite raw material having a particle size of 75 μm or less is large as the particle size composition of the andalusite raw material. As a result of the expansion of the fine powder portion (matrix portion) becoming too large and the destruction of the tissue becoming large, the strength decreased.

Claims (4)

Andalsite quality of 40% by mass or more and 80% by mass or less in 100% by mass of the fireproof raw material, and 75 μm or less in particle size in 100% by mass of the total amount of the andalcite material. Containing 2% by mass or more and 50% by mass or less of the raw material ,
The ratio of the content of the andalustotic raw material having a particle size of 75 μm or less in the refractory raw material to the total content of the silica ultrafine powder and alumina cement in the refractory raw material containing silica ultrafine powder and alumina cement in the refractory raw material. An amorphous refractory for tundish lining having (content of andalsite material having a particle size of 75 μm or less / total content of silica ultrafine powder and alumina cement) of 0.2 or more. Andalusite quality with a particle size of 75 μm or less in 100% by mass of the total amount of the refractory raw material containing 50% by mass or more and 70% by mass or less of the andalusite material, and 100% by mass of the total amount of the andalusite material. The amorphous refractory for tundish lining according to claim 1, which contains 10% by mass or more and 30% by mass or less of a raw material. Claim 1 or 2 in which the content of the expandable aggregate containing α-quartz in the mineral and having a particle size of more than 1 mm is less than 2% by mass (including 0) in the total amount of the fireproof raw material of 100% by mass. Atypical fireproof material for tundish lining described in. The third aspect of claim 3, wherein the content of the expandable aggregate containing α-quartz in the mineral and having a particle size of 1 mm or less is less than 3% by mass (including 0) in the total amount of the fireproof raw material of 100% by mass. Atypical fireproof material for tundish lining.

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