KR20090072477A - Magnesia Carbonaceous Refractory - Google Patents

Abstract

The present invention relates to a fluorinated refractory material used as an internal refractory material for steel and steelmaking equipment, and includes a main raw material composed of flaky graphite of 0.5 mm or less and 0.5 to 5% by weight of carbon black and balance magnesia aggregate. Phenol binder: 0.5 to 5 parts by weight based on 100 parts by weight of the main raw material to provide a magnesia carbonaceous fireproof material, while maintaining excellent wear resistance and oxidation resistance while reducing the carbon content, improve the service life of steelmaking productivity and It can complement the thermal shock resistance while achieving a refractory unit cost reduction.

Description

Magnesia Carbonaceous Refractory {A unburned magnesia-carbon}

The present invention relates to a fluorinated refractory material used as an internal refractory material for steel and steel making facilities, and more specifically, to improve thermal shock resistance by using flake graphite having a larger specific surface area by thinning the thickness instead of conventional impression graphite. It relates to a fluorine magnesia carbonaceous fireproof material.

Typically, in a general steel mill, C, N ₂ , O ₂ , S, P contained in the molten steel 112 of the ladle 110 by vacuuming the inside of the apparatus as one of the secondary refining facilities, as shown in FIG. 1. RH-OB facility 100 is provided to improve the quality of molten steel 112 and to produce high value-added products by degassing an element acting as an impurity in other molten steel 112 using a partial pressure difference. It is.

This RH-OB facility 100 is one of the degassing apparatus according to the R ₂ , RH-OB, RH-TOB, RH-KTB according to the oxygen blowing (O ₂ Blowing) method to the molten steel 112 in the ladle 110. It is called as RH-POSB and is used. (Hereafter, RH-OB unifies its name.)

The RH-OB facility 100 locates the ladle 110 at the bottom thereof, deposits a plurality of deposition pipes 120 from the upper side toward the molten steel 112 in the ladle 110, and the RH-OB facility. After forming a vacuum pressure in the interior of 100, and supplying argon gas (Ar Gas) through the argon injection hole 122 formed in one side of the immersion pipe 120, the immersion pipe 120 is molten steel 112 The molten steel 112 is raised from the ladle 110 to the inside of the RH-OB facility 100 by acting as a rising pipe to be raised. Then, the molten steel 112 is the molten steel 112 is lowered from the RH-OB equipment 100 to the ladle 110 again through the other side of the immersion pipe (falling pipe) 120, such molten steel 112 The flow is continuously made, and in this process, impurities in the molten steel are gasified and removed.

In order to perform degassing in the RH-OB facility 100, the deposition pipe is deposited on a ladle 110 facility containing the molten steel 112 and serves to provide a passage through the vortex of the molten steel 112. The Snorkel 120 employs an orthogonal refractory brick 124 made of various materials in its interior, and an exterior refractory 130 made of various materials due to its structural characteristics.

In the inside of the dip tube 120, plastic refractory materials have been applied to secure resistance to wear erosion against molten steel reflux, and magnesia-chromium material having excellent corrosion resistance against basic slag has been used among the plastic refractory materials. However, since the operation of the RH facility has a characteristic of depositing in the molten steel conveyed by the ladle to perform refining operation and repeatedly exposing to the atmosphere until the molten steel of the next ladle arrives, the deposition pipe located at the bottom of the RH facility Refractories attached to it will be subjected to excessive thermal shock. Therefore, the conventional calcined magnesia-chromic brick has excellent abrasion resistance to reflux of molten steel, but it is inferior to the thermal shock, and thus, there is a limit in improving the life of the immersion pipe. Therefore, in order to improve the steelmaking productivity and reduce the refractory cost by improving the life of the RH immersion pipe refractory has been required to secure an alternative material of the plastic refractory.

As an alternative material of the refractory material, the application of fluorine-magnesia-carbon bricks used in facilities such as converters, electric furnaces, ladles, etc. can be considered. Despite the excellent resistance has the following problems.

First, the fluorine-magnesia-carbon brick has a problem that the wear resistance to reflux of molten steel is lower than that of the calcined magnesia-chrome brick, and that carbon is oxidized and deteriorated by oxygen injection of RH equipment. In addition, since it contains about 10 to 20% of carbon, there is a problem in that the steel quality is degraded by carbon pick-up into steel.

In order to improve the abrasion resistance and oxidation resistance of the fluorine-magnesia-carbon brick, and to suppress the carbon pickup, the carbon content needs to be reduced. There is a disadvantage of deterioration.

The present invention has been made to solve the above problems, while maintaining a good wear resistance and oxidation resistance while reducing the carbon content, improving the service life while improving the steelmaking productivity and reducing the refractory unit cost magnesia complemented thermal shock resistance The purpose is to provide a carbonaceous refractory material.

The present invention relates to a main raw material composed of 1 mm or less flaky graphite: 0.5 to 10% by weight and carbon black: 0.5 to 5% by weight, and the remaining magnesia aggregate, and a phenol binder: 0.5 to 5 parts by weight based on 100 parts by weight of the main raw material. It provides a magnesia carbonaceous fireproof material comprising.

Here, 10 parts by weight or less of metal and nonmetallic additives may be further added to 100 parts by weight of the main raw material.

In addition, the flaky graphite may have a specific surface area of 10 to 30 mm 2 / g, and may replace 80 wt% or less of the flaky graphite content with impression graphite.

In this case, the magnesia carbonaceous fireproof material may have a total carbon content of less than 10% by weight.

By the magnesia carbonaceous fire retardant according to the present invention as described above, it is possible to complement the thermal shock resistance while maintaining excellent wear resistance and oxidation resistance while improving carbon life while improving carbon steel productivity and reducing refractory unit cost while reducing carbon content. have.

Hereinafter, the magnesia carbonaceous fireproof material according to an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you.

According to the present invention, unlike conventional fluorine-magnesia carbonaceous refractory bricks which mainly use impression graphite as a carbon raw material, the particle size is similar to that of impression graphite, but by using thinly flake graphite having a high specific surface area by treating the thickness thinly, The present invention relates to improving the thermal shock resistance of carbonaceous fireproof materials.

In general, the thermal shock resistance may be expressed by Equation 1 below.

Where R is thermal shock resistance, γ is fracture energy, E is elastic modulus, and α is thermal expansion coefficient.

Since the thermal shock resistance of Equation 1 has the greatest influence of the breaking energy and the elastic modulus, the thermal shock resistance is proportional to the breaking energy and inversely proportional to the elastic modulus.

In the present invention, the thermal shock resistance is improved by increasing the specific surface area of the carbon raw material. When the specific surface area is increased, the strength is slightly decreased due to the decrease in closeness, but the thermal modulus is greatly improved by increasing the thermal conductivity, increasing the porosity, and controlling the sinterability by direct contact between the magnesia aggregates. As a method for increasing the specific surface area of the carbon raw material, there may be a method of atomizing impression graphite and a method of adding flake graphite. The method of atomizing the double impression graphite is to reduce the closeness of filling in the manufacture of firebrick, not only to lower the product quality characteristics but also to improve the thermal shock resistance. Therefore, in the present invention, thermal shock resistance is improved by using a method of adding flake graphite having a small thickness to increase the specific surface area.

In the present invention, wear resistance is improved by using nano fine carbon raw materials. Abrasion resistance is evaluated by measuring the strength at the hot, the strength is characterized by the improvement when the filling resistance of the refractory brick is increased. Therefore, the wear resistance of the fluorine-magnesia-carbon fireproof material is improved by using the method of adding the carbon black which has the particle size of nano unit as a carbon raw material.

Hereinafter, the present invention will be described from the reasons for limiting the ingredients.

(A) 1 mm  The following Flaky  Graphite: 0.5 ~ 10 wt%

The flaky graphite is made from expanded graphite, which is a graphite having a small thickness to increase its specific surface area. The expanded graphite is produced by acid treatment of the graphite to produce an acid compound between the graphite layers, followed by rapid treatment at high temperature, thereby expanding the graphite layer by 100 to 300 times by the vaporization pressure of the acid compounds. When the expanded graphite is used directly for the production of refractory bricks, the volume per mass is so large that kneading is difficult and the moldability is also greatly reduced. Therefore, in the present invention, the expanded graphite is divided into layers by pulverization and used as flakes. When the particle size of the flaky graphite exceeds 1 mm, the volume is too large compared to the mass, so that the kneading property and the moldability decrease, so that the particle size is preferably limited to 1 mm or less.

The flake graphite prepared as described above exhibits the characteristics shown in Table 1 below.

division Flaky graphite Impression graphite Ingredient (% by weight) Fixed carbon 85 or more 85 or more Ash 12 or less 12 or less moisture 0.5 or less 0.5 or less Granularity 1 mm or less 1 mm or less Specific surface area (mm2 / g) 10-30 1 to 3

As can be seen in Table 1, the flaky graphite has a similar particle size compared to that of the impression graphite, but because the thickness of the graphite is thin, the specific surface area is 10 to 30 mm 2 / g, and the specific surface area is 10 times larger than that of the impression graphite. Have. In addition, the purity of flaky graphite is preferably 85% by weight or more of fixed carbon similar to that of impression graphite.

If the content of the flaky graphite is less than 0.5% by weight, the characteristics of the magnesia carbonaceous refractory bricks do not appear, and when the content of the flaky graphite is more than 10% by weight, the strength of the refractory bricks is decreased, the physical properties due to carbon oxidation, carbon pickup into the steel, and the like. Since this occurs, it is preferable to limit the content to 0.5 to 10% by weight.

(B) carbon black: 0.5-5% by weight

Carbon black is a product widely used for strength reinforcement of rubber and ink materials for printing, and various kinds are commercially available. In the present invention, any of these various carbon blacks may be used. If the content of the carbon black is less than 0.5% by weight, the characteristics of magnesia-carbon refractory bricks do not appear, and when the content of the carbon black exceeds 5% by weight, the amount of the phenol binder is excessively increased so that the properties of the refractory bricks such as filling properties are lowered. Since this occurs, it is preferable to limit the content to 0.5 to 5% by weight.

In addition, in the present invention, it is possible to replace a part of the flaky graphite or carbon black with impression graphite. When the amount of the impression graphite replacing the flaky graphite or carbon black exceeds 80% by weight of the total carbon raw material, the thermal shock resistance of the flaky graphite cannot be improved, thereby replacing the flaky graphite. It is desirable to limit the amount of the graphite to 80% or less. In the case of the above-mentioned graphite which is partially used as the carbon raw material, all of graphite, artificial graphite, etc. can be used in addition to the graphite, but it is preferable to use the graphite having crystallinity in terms of erosion resistance. In addition, the purity of the graphite is preferably 85% by weight or more of fixed carbon.

In addition to the above compositions, the remainder is composed of magnesia aggregate and other unavoidable impurities. The magnesia aggregate can be used both natural sintered products, natural melted products, seawater sintered products and seawater melted products.

(C) phenol binder: 0.5 ~ 5 parts by weight

A phenol binder: 0.5-5 weight part is added with respect to 100 weight part of main raw materials comprised as mentioned above.

The phenolic binder is a binder, when less than 0.5 parts by weight of the moldability is lowered, when added in excess of 5 parts by weight of the pores when used in real increase the quality characteristics, so the addition amount is 0.5 to 5 to 100 parts by weight of the main raw material It is preferable to limit to parts by weight.

(D) Metal and Nonmetallic Additives: 10 parts by weight  Below

In addition, 10 parts by weight or less of the metal and nonmetallic additives may be additionally added to 100 parts by weight of the main raw material formed as described above.

The metal and nonmetallic additives are added to prevent oxidation of the refractory brick, to improve the strength and to improve the erosion resistance, and the like, and metal additives such as Al, Si, Mg, Mg / Al, Al / Si, Ca / Si, or B ₄ It is possible to add one or more of nonmetallic additives such as C, CaB ₆ , MgB, SiC, AlN, and BN. If the metal and nonmetallic additives are added in excess of 10 parts by weight, the erosion resistance and thermal shock resistance are lowered, and therefore, the amount of the metal and nonmetallic additives is preferably added in an amount of 10 parts by weight or less based on 100 parts by weight of the main raw material.

As described above, the magnesia carbonaceous refractory material (A) 1 mm or less flaky graphite: 0.5 to 10% by weight and (B) carbon black: 0.5 to 5% by weight and the remaining raw material composed of magnesia aggregate and 100 parts by weight of the main raw material (C) phenol binder: 0.5 to 5 parts by weight, with respect to 100 parts by weight of the main raw material (D) metal and nonmetallic additives: 10 parts by weight or less may be further added.

In addition, the magnesia carbonaceous refractory material prepared as described above may have a total carbon content of 10% by weight or less. When masonry is made of fluorinated magnesia carbonaceous refractory material with a total carbon content of 10% by weight or less and used as a refractory inside the sedimentation pipe, the amount of carbon pickup into the steel is reduced and the steel quality due to carbon pickup is solved. Can be.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

To prepare a brick with a magnesia carbonaceous refractory material having a composition as shown in Table 2, the general physical properties such as volume specific gravity, porosity, compressive strength, hot bending strength after reducing plasticity and elastic modulus after reducing plasticity were measured, the results are shown in Table 2 As shown. The reducing firing was performed at 1200 ° C., and the thermal shock resistance was relatively evaluated by measuring the bending strength and elastic modulus after the reducing firing. Since the thermal shock resistance is inversely proportional to the elastic modulus, the lower the elastic modulus, the better the thermal shock resistance. In addition, the wear resistance was evaluated by measuring the hot bending strength, indicating that the higher the hot bending strength, the better the wear resistance.

division Example Comparative example One 2 3 4 5 One 2 3 4 Composition Magnesia aggregate (5 mm or less, weight%) 97 95 93 95 95 97 95 93 85 Impression graphite (1 mm or less, weight%) - - - 2 - 3 5 7 15 Flaky Graphite (1 mm or less, wt%) 3 5 7 3 3 - - - - Carbon black (wt%) 2 Additive (extrapolation) ○ ○ ○ ○ ○ ○ ○ ○ ○ Phenolic binder (extrapolation) ○ ○ ○ ○ ○ ○ ○ ○ ○ General property Volume specific gravity 3.07 3.02 2.98 3.05 3.12 3.12 3.08 3.02 2.97 Porosity (%) 5.3 5.6 6.1 4.4 0.9 3.5 3.1 2.7 1.7 Compressive strength (MPa) 64.4 57.0 41.5 62.0 75.2 72.3 65.2 52.7 42.3 Thermal shock resistance Modulus of elasticity after reducing firing 29.3 22.4 18.9 27.4 26.8 39.5 34.1 28.5 22.5 Wear resistance Hot bending strength 16.7 15.1 13.8 16.3 20.9 20.1 19.2 17.8 13.2

As can be seen in Table 2, Examples 1 to 3 in which flaky graphite was added alone as a carbon component, and Example 4 in which flaky graphite and impression graphite were added were mixed. Comparative Example 1 in which impression graphite was added alone. Compared to 4 to 4, the volume specific gravity, porosity, and compressive strength at the same carbon content were slightly decreased. This is a result of declining closest packing property by using flaky graphite with a large specific surface area.

However, the thermal shock resistance, which is one of the most important quality characteristics in the present invention, includes Examples 1 to 3, in which flaky graphite is added alone, and Examples 4 and Comparative Examples 1 to 4, in which flaky graphite and impression graphite are added. In comparison, it can be seen that the same carbon content is more improved.

Table 3 shows the fluorine-magnesia-carbon refractory material according to an embodiment of the present invention and the conventional fired magnesia-chromium refractory material.

division Example 6 Conventional example material Fluorine Magnesia-Carbon Calcined Magnesia-Chrome Composition Impression graphite (1 mm or less, weight%) One - Flaky Graphite (1 mm or less, wt%) One - Carbon black (wt%) One - General property Volume specific gravity 3.14 3.19 Porosity (%) 2.7 16.3 Compressive strength (MPa) 16.8 Thermal shock resistance Modulus of elasticity after reducing firing 27.6 42.1 Wear resistance Hot bending strength 20.3 20.5

As can be seen from Table 3, Example 6 of the magnesia-carbon refractory material in which impression graphite, flaky graphite, and carbon black were mixed and added as a carbon component was compared with the conventional examples of magnesia-chromium material, and the thermal shock resistance was comparable. It can be seen that this has been improved.

Although the technical spirit of the present invention has been described in detail according to the above-described preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

1 is a cross-sectional view showing the RH-OB equipment of a general steelmaking process.

Claims (5)

Magnesia comprising 1-10 mm or less flaky graphite: 0.5 to 10% by weight and carbon black: 0.5 to 5% by weight and a main raw material composed of the balance magnesia aggregate, and a phenol binder: 0.5 to 5 parts by weight based on 100 parts by weight of the main raw material. Carbonaceous Refractory. The magnesia carbonaceous fireproof material according to claim 1, wherein 10 parts by weight or less of metal and nonmetallic additives are added to 100 parts by weight of the main raw material. The magnesia carbonaceous fireproof material according to claim 1, wherein the flaky graphite has a specific surface area of 10 to 30 mm 2 / g. The magnesia carbonaceous fireproof material according to claim 1, wherein up to 80% by weight of the flaky graphite content is replaced with impression graphite. The magnesia carbonaceous fireproof material according to claim 1, wherein the magnesia carbonaceous fireproof material has a total carbon content of 10% by weight or less.

Images