KR101109877B1 - Unshaped refractories - Google Patents

Abstract

The present invention relates to an amorphous refractory containing alumina as a main component, 76 to 84% by weight of alumina, 10 to 15% by weight of graphite phosphate, 2 to 3% by weight of metallic aluminum powder, 4 to 6% by weight of stainless steel fiber. It is made, including.
The present invention has the advantage of excellent corrosion resistance to high temperature molten steel, to prevent stress by reducing the stress and to suppress the progress of the crack even if a crack occurs is particularly excellent.

Description

Unshaped Refractories

TECHNICAL FIELD The present invention relates to amorphous refractory materials, and more particularly, to amorphous refractory materials used in steel ladle bottoms, impeller structures of KR plants for desulfurization, lance pipes, and the like.

Refractories are materials that can withstand high temperatures and are materials that can maintain their strength sufficiently, withstand erosion and wear due to chemical action, without softening at high temperatures at least 1000 ℃.

Refractories are classified into standard and irregular refractory materials according to their physical form.

Ordinary refractory means a refractory having a certain shape, and an amorphous refractory is a refractory that can be installed in any shape according to the part or mold to be constructed.

Among these, the amorphous refractory has advantages such as convenience in construction and long service life, so it is used in the ladle floor for steelmaking, impeller structure of KR facilities for desulfurization, lance pipe, and the like.

An object of the present invention is to provide excellent corrosion resistance against high temperature molten steel for use in steel ladle bottom, impeller structure of KR facility for desulfurization, lance pipe, etc. It is to provide an amorphous refractory material excellent in pollenability.

According to a feature of the present invention for achieving the above object, the present invention comprises alumina, graphite phosphate, metal aluminum powder, stainless fiber.

The amorphous refractory is 76 to 84% by weight of alumina relative to the total weight; 10-15 wt% graphite phosphate; 2-3 wt% of metallic aluminum powder; It comprises 4 to 6% by weight of stainless fiber.

The stainless fiber is an austenitic stainless fiber.

The amorphous refractory material is used for ladle bottoms for steelmaking, impeller structures of KR facilities for desulfurization, and lance pipes.

The amorphous refractory material of this invention consists of alumina, graphite phosphate, a metal aluminum powder, and a stainless fiber.

These components reduce the thermal stresses occurring in the refractory and inhibit the progression of cracks even if they occur. Therefore, the refractory peeling phenomenon to the thermal spalling is minimized, there is an effect that can extend the service life of the amorphous refractory.

In addition, the present invention also has a good effect on the construction properties to ensure the structural characteristics of the hearth and the speed of repair.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention is an amorphous refractory used in a ladle bottom for steelmaking in a steel mill, an impeller structure of a KR facility for desulfurization, a lance pipe, and the like, and includes alumina, graphite phosphate, metal aluminum powder, and stainless fiber.

The amorphous refractory material of the present invention is an alumina amorphous refractory material, and has excellent spalling resistance by addition of graphite phosphate and stainless fiber to alumina. Graphite phosphate is added to reduce thermal stress that causes spalling, and stainless fiber is added to suppress the progress of cracking. In addition, metal aluminum powder is added to prevent oxidation of the stainless fiber.

The spalling phenomenon is caused by cracks in the refractory material due to repeated thermal shocks due to rapid temperature differences when contacted with hot molten steel, and the cracks are developed to eventually occur as a result of peeling of the refractory material.

Refractories are subject to rapid and severe temperature changes on their surface during use, which leads to thermal stress, which causes the refractory to break or peel off.

The spalling phenomenon of the refractory is expressed by Equation 1 below.

[S: breaking strength E: elastic modulus, ν: Poisson ratio, λ: thermal conductivity, α: linear expansion coefficient, ρ: specific gravity, C: specific heat, γ: breaking energy]

Where R 'is a fracture resistance coefficient and R "represents a damage resistance coefficient.

According to Equation 1, the greater the fracture strength and thermal conductivity, the greater the resistance to the occurrence of cracking, and the greater the breaking energy, the more effective the suppression of crack propagation.

Through this, it is possible to improve the thermal spalling characteristics of the refractory by reducing the thermal stress generated in the refractory, and suppressing the progress of the crack even if a crack occurs. For reference, stresses are generated by temperature gradients in the surface and interior caused by sudden temperature changes.

Therefore, the composition of the amorphous refractory material is to suppress the formation and development of cracks due to thermal shock, thereby preventing the refractory peeling phenomenon due to thermal spalling.

The amorphous refractory material includes 76 to 84% by weight of alumina, 10 to 15% by weight of graphite phosphate, 2 to 3% by weight of metal aluminum powder, and 4 to 6% by weight of stainless fiber.

The function and content of the components constituting the amorphous refractory are as follows.

Alumina (Al ₂ O ₃ ) 76 ~ 84% by weight

Alumina slows the penetration rate of the slag and extends the life of the refractory.

Alumina has high melting point, high hardness, and thermal stability, and has erosion resistance to withstand high temperature molten steel and slag, and thermal shock resistance to accommodate extreme temperature fluctuations.

Alumina reacts with CaO, FeO and MgO contained in molten steel when molten steel penetrates into the refractory. As a result, the viscosity of molten steel becomes high and penetration is difficult, resulting in high erosion resistance.

If the alumina is less than 76% by weight, the effect of improving corrosion resistance and heat shock resistance against molten steel and slag is insignificant, and if it exceeds 84% by weight, it is difficult to improve the thermal spalling property.

Graphite Phosphate (C) 10-15 wt%

Graphite phosphate is a high thermal conductivity, low-expansion raw material, which increases the resistance to cracking of the refractory. It also has the effect of preventing oxidation of refractory and stainless fiber. Graphite phosphate is less than 10% by weight, the effect of increasing the resistance is insignificant, and when it exceeds 15% by weight, the filler is poor and weakens the hot strength.

Metal Aluminum Powder (Metal Al) 2-3 wt%

Metal aluminum powder is dispersed around the stainless fiber and added to prevent oxidation loss of the stainless fiber.

If the metal aluminum powder is less than 2% by weight, the antioxidant effect is insignificant, and if it exceeds 4% by weight, the corrosion resistance is lowered.

4 ~ 6% by weight of stainless steel fiber (SUS Fiber)

Stainless fiber has good thermal conductivity, and it is effective for spalling resistance because it can get big fracture energy by blocking the development of cracks. If the addition amount of the stainless steel fiber is less than 4% by weight, the effect is insignificant, and if the amount of more than 6% by weight, the corrosion resistance is lowered and the flow of the refractory material during the construction is deteriorated, which is disadvantageous for constructing the structure.

The stainless fiber uses austenitic stainless fiber such as SUS310, SUS302, and SUS304. Of the stainless fiber, austenitic is the best corrosion resistance, ferritic, martensitic in order to reduce the corrosion resistance in order.

The austenitic stainless fiber has a higher temperature strength than the ferritic and martensitic stainless fibers having a body centered cubic lattice (BCC) because the crystal structure is a face centered cubic lattice (FCC).

A method for producing an amorphous refractory material is alumina, graphite phosphate, metal aluminum powder, stainless fiber, mixed, pulverized, kneaded and injected into the part or mold to be applied, and then molded and refractory dry-fired to form a stable bond. Make it an organization.

Grinding is to facilitate molding and refractory to have a dense composition, and kneading is mixing the above components of different particle sizes or types by adding moisture for ease of construction.

In addition to the above-mentioned components, the amorphous refractory may further include a binder, a particle-specific adjusting additive, and the like within a range that can achieve the object of the present invention within a conventional content range.

Such amorphous refractory can be utilized as a standard refractory when molded in a mold.

In addition, the amorphous refractory material may not only be calcined after molding as described above, but may also be dried after molding by molding with a chemical binder and may not be calcined, or may be cast by melting the above-mentioned components in an electric furnace.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by the following examples.

Example Preparation of Infinite Refractories

The raw materials of the ingredients of Table 1 were ground and mixed in a dry manner, followed by addition of water. The mixture obtained by the addition of moisture was poured into the portion to be constructed and kept at room temperature for 12 hours before sintering.

Table 1 shows the spalling resistance, erosion index, workability by component of the amorphous refractory.

(Unit: wt%) division Al ₂ O ₃ C
Impression Graphite metal
Al SUS Fiber Spalling resistance Erosion Index Workability Example 1 80 10 4 6 ○ 105 ○ Example 2 80 13 3 4 ◎ 100 ○ Example 3 78 15 3 4 ◎ 100 ○ Comparative Example 1 85 5 4 6 Ｘ 115 ○ Comparative Example 2 76 18 2 4 Ｘ 120 Ｘ Comparative Example 3 82 13 One 4 Ｘ 110 ○ Comparative Example 4 76 13 6 5 ◎ 120 Ｘ Comparative Example 5 81 15 2 0 Ｘ 100 ○ Comparative Example 6 76 12 4 8 ◎ 140 Ｘ Comparative Example 7 Alumina-Spinel Type Amorphous Refractories Ｘ 110 ○ Comparative Example 8 Alumina-magnesia amorphous refractory Ｘ 105 ○

<Spalling Resistance Test>

The spalling resistance was obtained by cutting the amorphous refractory of Table 1 into a size of about 70 × 70 × 65 mm, loading it into molten steel with an experimental temperature of 1500 ± 5 ° C., and repeating 25-minute holding-quenching for 25 minutes to observe the crack state.

◎: no crack or fine crack

○: small crack

Ｘ: large crack

According to Table 1, spalling resistance was inferior in Comparative Examples 1 to 3, Comparative Example 5, Comparative Example 7, and Comparative Example 8.

Comparative Example 1 and Comparative Example 2 did not satisfy the content of the 10 ~ 15% by weight of the graphite to lower the thermal stress, Comparative Example 3 was low in the content of metal aluminum having an antioxidant effect.

Comparative Example 5 was inferior in spalling resistance because no stainless fiber was added to prevent the progress of cracking.

Comparative Example 7 and Comparative Example 8 is alumina-Spinel-based, alumina-magnesia (MgO) -based amorphous refractory to reduce the penetration rate of the slag to improve the life of the refractory. However, as the thermal shock caused by the temperature difference is repeated upon contact with the hot molten steel, cracks occur in the refractory, and the crack develops, resulting in spalling, which is a peeling damage of the refractory.

On the other hand, Examples 1 to 3 were excellent in spalling resistance.

Erosion Index

Cut the amorphous refractory into the size of about 70 × 70 × 65mm, dig a hole in the center of 70 × 70mm, insert the slag crushed to 710㎛ or less, and heat it uniformly for 2 hours at the experiment temperature 1500 ± 5 ℃. After maintenance, turn off the power and let it cool naturally. After the test, the cut surface was cut and the surface area of the eroded and dissolved parts, the softening, deformation, and infiltration state of the amorphous refractory material were examined and expressed as an index.

The erosion indices of Examples 1 to 3 were generally lower than Comparative Examples 1 to 8.

In Comparative Example 6, too much stainless fiber was added to reduce corrosion resistance, and the workability was also poor.

Through this, spalling resistance is produced by producing amorphous refractory materials including graphite phosphate which reduces thermal stress in high alumina, stainless fiber which prevents the progress of cracking even if cracks occur, and metal aluminum powder which prevents oxidation of stainless fiber. It can be seen that the amorphous refractory material having excellent excellent corrosion resistance can be produced.

Within the scope of the basic technical idea of the present invention, many other modifications are possible to those skilled in the art, and the scope of the present invention should be interpreted based on the appended claims. will be.

Claims (4)

An amorphous refractory comprising alumina, graphite phosphate, metal aluminum powder and stainless fiber. The method according to claim 1,
The amorphous refractory is
About the total gross weight
76 to 84% by weight of alumina;
10-15 wt% graphite phosphate;
2-3 wt% of metallic aluminum powder;
An amorphous refractory comprising 4 to 6% by weight of stainless fiber. The method according to claim 1,
The stainless fiber is an amorphous refractory, characterized in that the austenitic stainless fiber. The method according to any one of claims 1 to 3,
The amorphous refractory is
Indefinite refractory, characterized in that used in steel ladle bottom, impeller structure of KR facilities for desulfurization, lance pipe.