JP2021169393A - Refractory raw material for spraying and monolithic refractory for wet spraying - Google Patents

Abstract

To provide a refractory raw material for spraying, for producing a monolithic refractory for wet spraying having improved durability, more concretely, heat-resistant spalling property while maintaining good workability.SOLUTION: A refractory raw material for spraying contains a refractory raw material as a main component, silica fume and calcined alumina as sub-components, and substantially contains no alumina cement. In the refractory raw material for spraying, the total content of silica fume and calcined alumina is 0.8-22 mass% based on 100 mass% of the refractory raw material for spraying, and the mass ratio of calcined alumina to silica fume is 0.4-2.5.SELECTED DRAWING: None

Description

The present disclosure relates to refractory raw materials for spraying and amorphous refractories for wet spraying, which are suitably used for construction and repair of kilns for steelmaking and the like.

Wet spraying amorphous refractories are used for the construction and repair of blast furnaces, hot metal pots, torpedo wagons, converters, ladle, RH, TD, etc., which are kilns for steelmaking, and various industrial kilns. The non-standard refractory for wet spraying is a kneaded product of refractory powder (fireproof raw material for spraying) and colloidal silica pumped through a transport pipe by a pumping machine, and colloidal at a pre-throttle nozzle provided at the tip of the transport pipe. An alkaline quick-setting agent having a quick-binding action on silica is added, and the silica is sprayed together with compressed air from a pre-throttle nozzle.

Japanese Unexamined Patent Publication No. 11-302084

In recent years, the operating conditions of kilns for steelmaking and the like have become more and more severe, and even in amorphous refractories for wet spraying, further improvement in durability of the amorphous refractories (construction body) after spraying is required. The main form of damage to the construction body is the generation of cracks due to thermal spalling. However, the amorphous refractory for wet spraying disclosed in Patent Document 1 is intended to improve workability, and there is no specific disclosure regarding the improvement in durability.

The present disclosure has been made in view of the above circumstances, and some aspects of the present disclosure are wet spraying in which durability, more specifically, heat resistance spalling property is improved while maintaining good workability. It is an object of the present invention to provide an amorphous refractory material for use and a refractory raw material for spraying that makes it possible.

(1) One aspect of the present disclosure is a refractory raw material for spraying containing a refractory raw material as a main component, silica fume and calcined alumina as subcomponents, and substantially no alumina cement, and the silica fume. The total content of calcined alumina is 0.8 to 22 mass% with respect to 100 mass% of the refractory raw material for spraying, and the mass ratio of calcined alumina to silica fume is 0.4 to 2.5. Regarding fireproof raw materials for spraying.

(2) Another aspect of the disclosure, a refractory raw material for spraying one embodiment, includes a colloidal silica, and a quick-setting admixture, the colloidal silica comprises SiO _2, the concentration of SiO ₂ colloidal silica 100 mass The content of colloidal silica is 6 to 11 parts by mass with respect to 100 parts by mass of the refractory raw material for spraying, and the quick-setting agent is an alkali metal silicate, which is a quick-setting agent. The content relates to an amorphous refractory for wet spraying, which is characterized by having a solid content of 0.04 to 4 parts by mass with respect to 100 parts by mass of the refractory material for spraying.

A specific amount and a specific ratio of silica fume and calcined alumina are blended with the refractory raw material for spraying, and the refractory raw material for spraying is further blended with the amorphous refractory for wet spraying. This makes it possible to provide an amorphous refractory for wet spraying and a refractory raw material for spraying, which has significantly improved heat-resistant spalling property while maintaining good workability.

Hereinafter, preferred embodiments of the present disclosure will be described in detail. It should be noted that the present embodiment described below does not unreasonably limit the content of the present disclosure described in the claims, and all of the configurations described in the present embodiment are essential as a means of solving the present disclosure. Is not always the case.

The non-standard refractory for wet spraying of the present embodiment contains a refractory material for spraying, colloidal silica, and a quick-setting agent, and the refractory material for spraying contains the refractory material as a main component, and silica fumes and calcined alumina. As a sub-ingredient and substantially free of alumina cement, the total content of silica fume and calcined alumina is 0.8 to 22 mass% with respect to 100 mass% of the refractory raw material for spraying, and is provisionally relative to silica fume. weight ratio of the baked alumina is 0.4 to 2.5, colloidal silica comprises SiO _2, the concentration of SiO ₂ is from 7 to 43% by mass with respect to 100 wt% of colloidal silica, the content of colloidal silica It is 6 to 11 parts by mass with respect to 100 parts by mass of the refractory raw material for spraying, the quick-setting agent is an alkali metal silicate, and the content of the quick-setting agent is 0 in terms of solid content with respect to 100 parts by mass of the refractory raw material for spraying. It is .04 to 4 parts by mass.

<Fireproof raw material for spraying>
Among the refractory raw materials for spraying, the aggregate portion that is the main component includes, for example, sintered alumina, fused alumina, bauxite, bauxite, kyanite, mullite, bentonite, silica sand, silicon carbide, clay, pitch, etc. , A refractory raw material generally used for refractories can be used. In addition, the fireproof raw material for spraying does not substantially contain alumina cement.

<Silica fume>
Silica fume is an amorphous ultrafine powder obtained as a by-product mainly in the production of metallic silicon and desiliconized zirconia. The SiO ₂ purity of silica fume is preferably 94% by mass or more, more preferably 97% by mass or more. The _{higher the SiO 2} purity, the less the variation in the agglutination characteristics of the kneaded product, and the better the workability.

<Casual Alumina>
Calcinated alumina is generally obtained by the Bayer process, and ordinary soda, medium soda, and low soda can be used.

<Total content and mass ratio of silica fume and calcined alumina>
The total content of silica fume and calcined alumina is 0.8 to 22 mass% with respect to 100 mass% of the fireproof raw material for spraying, and the mass ratio of calcined alumina to silica fume is 0.4 to 2.5. As a result, the heat-resistant polling property is remarkably improved. When the total content of silica fume and calcined alumina is 0% by mass, the workability (adhesiveness) is lowered and the strength is also lowered, and when it is 25% by mass or more, cracks are generated due to sintering shrinkage. The total content of silica fume and calcined alumina is preferably 1 to 20% by mass, more preferably 8 to 20% by mass, still more preferably 11 to 20% by mass, based on 100% by mass of the fireproof raw material for spraying.

When the mass ratio of calcined alumina to silica fume is 0.3 or less, the adhesion rate and heat-resistant spalling property are lowered, and when it is 3.0 or more, the heat-resistant spalling property is lowered. The mass ratio of calcined alumina to silica fume is preferably 0.5 to 2.0, more preferably 0.5 to 1.4.

<Coroidal silica>
Colloidal silica is silica ultrafine particles having a chemical composition of SiO ₂ stably dispersed in a liquid dispersion medium. The concentration of SiO ₂ is 7 to 43% by mass with respect to 100% by mass of colloidal silica, and a commercially available product may be appropriately diluted with water to a suitable concentration before use. When _{the concentration of SiO 2} is 5% by mass or less, the function of the binder is lost and the adhesive ratio is lowered, and when it is 45% by mass or more, the quick binding property is lost and the adhesive ratio is lowered. The concentration of SiO ₂ is preferably 10 to 40% by mass, more preferably 15 to 35% by mass, still more preferably 20 to 30% by mass, based on 100% by mass of colloidal silica. The content of colloidal silica is 6 to 11 parts by mass with respect to 100 parts by mass of the fireproof raw material for spraying. When the content of colloidal silica is 5 parts by mass or less with respect to 100 parts by mass of the fireproof raw material for spraying, the kneaded material is hard and difficult to pump, the work piece becomes non-uniform, and the adhesion rate decreases. Further, in the case of 12 parts by mass or more, the kneaded product is separated, the pumping property is lowered, and the adhesive ratio is lowered. The content of colloidal silica is preferably 7 to 10 parts by mass, more preferably 8 to 9.5 parts by mass, and even more preferably 8.5 to 9.3 parts by mass with respect to 100 parts by mass of the fireproof raw material for spraying.

<Rapid binder>
The quick-setting agent is an aqueous solution of silicate, aluminate, carbonate, sulfate, etc. (solid content), and known ones can be used. Alminates have a high pH and require careful handling. Alkali metal silicates are preferred, and sodium silicates are particularly preferred. As the sodium silicate, sodium silicate Nos. 1 to 3 and sodium metasilicates 1 to 2 specified in JIS K 1408 can be preferably used. The concentration of the solid content of the quick-setting admixture can be appropriately changed according to the handling time. The content of the quick-setting admixture is 0.04 to 4 parts by mass in terms of solid content with respect to 100 parts by mass of the fireproof raw material for spraying. If the content of the quick-setting agent is 0 parts by mass in terms of solid content with respect to 100 parts by mass of the fire-resistant raw material for spraying, the quick-setting property is lost, and if it is 5 parts by mass or more, the quick-setting property becomes excessive and the adhesiveness is poor. descend. The content of the quick-setting admixture is preferably 0.05 to 3.5 parts by mass, more preferably 1 to 3.5 parts by mass, and further 2 to 3 parts by mass with respect to 100 parts by mass of the fireproof raw material for spraying. preferable.

<Dispersant>
Sodium tripolyphosphate can be added up to 0.5 parts by mass with respect to 100 parts by mass of the fireproof raw material for spraying as a dispersant for improving the fluidity of the kneaded product and facilitating pumping. If it exceeds 0.5 parts by mass, the viscosity of the kneaded product increases and the adhesiveness decreases. The content of sodium tripolyphosphate is more preferably 0.05 to 0.15 parts by mass with respect to 100 parts by mass of the fireproof raw material for spraying.

<Construction method>
A known wet spraying method can be applied to the refractory raw material for spraying and the amorphous refractory for wet spraying of the present embodiment. A kneaded product obtained by kneading a fireproof raw material for spraying and colloidal silica is pumped through a transport pipe by a concrete pump (pumping machine). An alkaline quick-setting admixture is added to the pressure-fed kneaded material at a pre-throttle nozzle provided at the tip of the transport pipe, and the kneaded product is sprayed together with compressed air.

The refractory raw material for spraying and the amorphous refractory for wet spraying of the present embodiment can significantly improve the heat-resistant spalling property while maintaining good workability.

Hereinafter, examples of the present disclosure will be described.

[experimental method]
Fireproof raw materials for spraying, colloidal silica, quick-setting admixtures and dispersants were prepared so as to have the blending ratios shown in Tables 1 and 2. The actual n and the ratio n in the table represent Example n and Comparative Example n, respectively. The mass ratio of calcined alumina to silica fume is shown in parentheses because the unit is dimensionless.

Sintered alumina was used for the aggregate part, which is the main component of the fireproof raw material for spraying. In Examples 1 and 2 and Comparative Examples 1 and 2, the mass ratio of calcined alumina to silica fume was fixed at 1.5, or both components were not contained, and the total content of silica fume and calcined alumina was set to fire resistance for spraying. It was changed between 0 and 25% by mass with respect to 100% by mass of the raw material. In Examples 3 to 5 and Comparative Examples 3 to 4, the total content of silica fume and calcined alumina was fixed at 12% by mass with respect to 100% by mass of the fireproof raw material for spraying, and the mass ratio of calcined alumina to silica fume was set to 0. It was varied between 3 and 3.0. In Examples 4, 6 to 7 and Comparative Examples 5 to 6, _{the concentration of SiO 2} was changed between 5 and 45% by mass with respect to 100% by mass of colloidal silica. In Examples 4, 8 to 9 and Comparative Examples 7 to 8, the content of colloidal silica was changed between 5 and 12 parts by mass with respect to 100 parts by mass of the fireproof raw material for spraying. In Examples 4, 10 to 11 and Comparative Examples 9 to 10, the content of the quick-setting admixture was changed between 0 and 5 parts by mass in terms of solid content with respect to 100 parts by mass of the fireproof raw material for spraying.

A kneaded product obtained by kneading a fireproof raw material for spraying and colloidal silica is pumped through a transport pipe by a concrete pump (pumping machine), and a quick-setting admixture is added at a tip drawing nozzle provided at the tip of the transport pipe to add compressed air. At the same time, it was sprayed on the construction surface to obtain a construction body. The following evaluations were made on the obtained construction body.

<Adhesion rate>
From the mass (A) of the material (construction body) adhered to the construction surface and the total mass (B) of the rebound loss, the adhesion ratio was calculated by the following formula. The closer the adhesive ratio is to 100, the smaller the rebound loss, indicating that the adhesiveness is good.
Adhesion rate (%) = A ÷ B × 100

<Porosity, flexural strength>
An amorphous refractory for wet spraying was sprayed onto a 40 × 40 × 160 mm mold, and the obtained work piece was dried at 105 ° C. for 24 hours and then heated at 1000 ° C. for 3 hours to obtain a sample. For the obtained sample, the apparent porosity based on JIS R 2205 and the bending strength based on JIS R 2553 were measured. Generally, the lower the porosity, the higher the bending strength, but if it is too low (too dense), the heat-resistant spalling property is lowered. Therefore, a porosity that does not lower the heat-resistant spalling property is required.

<Heat-resistant polling property>
An amorphous refractory for wet spraying was sprayed onto a 230 mm × 114 mm × 65 mm mold, and the obtained work body was dried at 105 ° C. for 24 hours to obtain a sample. Using a box-type electric furnace, the sample was heated at 1300 ° C. for 45 minutes and air-cooled at room temperature of 20 ° C. for 15 minutes, which was repeated eight times. The sample was cut, the state of cracks on the cut surface was confirmed, and the evaluation was made in the following five stages A to E.
A: Less than 3 cracks with a width of 1 mm or more and a length of 10 mm or more B: 3 or more and less than 5 cracks with a width of 1 mm or more and a length of 10 mm or more C: 5 cracks with a width of 1 mm or more and a length of 10 mm or more More than 8 cracks D: 8 or more cracks with a width of 1 mm or more and a length of 10 mm or more and less than 10 E: 10 or more cracks with a width of 1 mm or more and a length of 10 mm or more

[Evaluation results]
The evaluation results are shown in Tables 3-4.

In each of the examples, the adhesion rate was high, the porosity was low, the bending strength was high, and the heat-resistant spalling property was excellent. On the other hand, in the comparative examples, at least one of the adhesive ratio, the porosity, the bending strength, and the heat-resistant spalling property was inferior, and in particular, many of them were inferior in the heat-resistant spalling property.

Although the present embodiment has been described in detail as described above, those skilled in the art will easily understand that many modifications that do not substantially deviate from the new matters and effects of the present disclosure are possible. Therefore, all such variations are within the scope of the present disclosure. For example, in the specification, a term described at least once with a different term having a broader meaning or a synonym may be replaced with the different term at any part of the specification.

Claims (2)

A refractory raw material for spraying that contains a refractory raw material as a main component, silica fume and calcined alumina as subcomponents, and substantially no alumina cement.
The total content of the silica fume and the calcined alumina is 0.8 to 22% by mass with respect to 100% by mass of the fireproof raw material for spraying.
A fireproof raw material for spraying, wherein the mass ratio of the calcined alumina to the silica fume is 0.4 to 2.5. The fire-resistant raw material for spraying according to claim 1, colloidal silica, and a quick-setting agent are included.
The colloidal silica contains SiO ₂ and contains
The concentration of SiO ₂ is 7 to 43% by mass with respect to 100% by mass of the colloidal silica.
The content of the colloidal silica is 6 to 11 parts by mass with respect to 100 parts by mass of the fireproof raw material for spraying.
The quick-setting agent is an alkali metal silicate,
An amorphous refractory for wet spraying, wherein the content of the quick-setting admixture is 0.04 to 4 parts by mass in terms of solid content with respect to 100 parts by mass of the refractory raw material for spraying.