JP2012200733A - Plate refractory for sliding nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance strength, oxidation resistance, corrosion resistance, and impact resistance in the intermediate temperature range of a plate refractory for a sliding nozzle.SOLUTION: The unfired plate refractory is obtained by using a fire-resistance inorganic material, 0.3-2 mass% of a carbonaceous powder raw material, and 3-15 mass% of at least one kind of aluminum-containing metal having a melting point of ≤1,000°C, and adding 2-5 mass% of an organic binder thereto. Herein, the mass of carbon originated from the organic binder and the carbonaceous powder raw material is made to fall within the range of 0.2-0.45 times of the mass of aluminum contained in an aluminum-containing alloy, thereby enhancing the strength, oxidation resistance, corrosion resistance, and impact resistance of the plate refractory for the sliding nozzle in the intermediate temperature range.

Description

  The present invention relates to a sliding nozzle plate refractory, particularly a non-fired plate refractory, which is attached to a steel ladle or tundish and controls the flow rate of molten steel.

  Plate refractories for sliding nozzles (hereinafter referred to as plate refractories) are used as a flow control device for molten metal in the steel industry. In particular, when molten steel is discharged from a molten metal container such as a ladle or tundish, it is used as a flow control device in combination of two or three plates.

  Damage forms of the plate refractories include wear and erosion due to molten steel flow, spalling cracks due to thermal shock, and rough surface of the sliding part due to oxidation and metal infiltration. Quality is required.

  The most common plate refractory is calcined alumina carbon that is heat treated at a temperature of 1000 ° C. or higher and impregnated with pitch.

  This fired alumina carbonaceous plate refractory is added with carbon raw materials such as carbon black, graphite, and pitch in order to ensure thermal shock resistance. However, since these carbons cause deterioration of the structure due to oxidation during use, it is desirable to achieve both low carbon and high thermal shock resistance.

  For example, Japanese Patent Application Laid-Open No. 2003-245770 discloses a fired plate refractory that is formed by adding a maximum of 10% by mass of expanded graphite and a maximum of 8% by mass of metal to a refractory aggregate and heat-treating it at 1000 ° C. or higher. It is.

  The fired plate refractory does not have the effect of improving the thermal shock resistance of the metal added as an antioxidant, and has improved the thermal shock resistance by adding expanded graphite. This causes a decrease and increases the roughness of the sliding portion, so that the durability is reduced.

  On the other hand, for steel types such as Ca-Si steel and high-oxygen steel, where the damage to the refractory increases, as disclosed in Japanese Patent Publication No. 60-29664, the addition of a low melting point metal and a temperature of 1000 ° C. or lower In some cases, a plate refractory called an unfired product or a lightly fired product (hereinafter referred to as “non-fired” or “light-fired” collectively as “non-fired”) by heat treatment is used.

  Advantages of the non-fired plate refractory include high hot strength by adding a large amount of metal and corrosion resistance to molten steel. On the other hand, damage factors of the non-fired plate refractory include, for example, deterioration of the structure due to disappearance of the resin bond in the intermediate temperature range, and crack peeling due to expansion of the heat receiving part due to metal oxidation / carbonization.

  Japanese Examined Patent Publication No. 60-29664 aims to improve the strength in the intermediate temperature range by melting the low melting point metal, but the oxidation resistance is not sufficient. In addition, the plate refractory after heat treatment is impregnated or coated with a silica-containing substance such as colloidal silica to generate silica at a high temperature to improve wear resistance and oxidation resistance. However, the silica component reacts with slag contained in the molten steel to produce a low melting point material, and the corrosion resistance is lowered.

  In Japanese Patent Application Laid-Open No. 07-290232, carbon is added to an aggregate such as alumina, and a silicone-modified phenol resin is added as a binder in addition to pitch, tar, and phenol resin, thereby suppressing reduction in strength in the intermediate temperature range and oxidation. Aims to prevent. However, in the method of adding the silicone-modified phenol resin in this way, even if the strength decrease in the intermediate temperature range is suppressed, silica derived from the resin generates a low-melting substance and the corrosion resistance decreases.

  In Japanese Unexamined Patent Application Publication No. 2004-82126, the addition of an aluminum-magnesium alloy and aluminum to the aggregate and the addition of a boron compound enhance the oxidation resistance and strength from the intermediate temperature range to the high temperature during use. However, when the boron compound is oxidized, a low melting point product is formed and the corrosion resistance is lowered. In this application, metallic aluminum and carbon black are added to reinforce the strength at 800 ° C. or higher. However, as described later, there is a problem of oxidation resistance due to excessive carbonaceous matter.

  In JP-A-03-32463, the thermal shock resistance is improved by adding metal (stainless) fibers to the aggregate, and the oxidation resistance is improved by adding boride / nitride / metal powder. Yes. However, the amount of carbon used is large (5% by mass or more), which is not sufficient in terms of strength and corrosion resistance. When stainless steel fibers are added as described above, the corrosion resistance decreases due to decarburization and iron oxide generation.

  In Japanese Patent Application Laid-Open No. 2004-141899, corrosion resistance is improved by using magnesia aggregate, and addition of metallic aluminum and a carbon raw material is attempted to obtain corrosion resistance and a low coefficient of friction. There is a problem that the oxidation resistance decreases.

  In Japanese Patent Application Laid-Open No. 2004-17136, the oxidation resistance is enhanced by adding boron nitride and aluminum to the alumina aggregate. However, since boron nitride is very expensive, it is preferable in terms of cost effectiveness. Absent. Further, when oxidized, a low melting point product is formed and the corrosion resistance is lowered.

Japanese Patent Publication No. 60-29664 JP 07-290232 A JP 2004-82126 A Japanese Patent Laid-Open No. 03-32463 JP 2000-327401 A JP 2003-245770 A JP 2004-141899 A JP 2004-17136 A

  As described above, a low melting point metal and a carbonaceous material are added to a refractory aggregate, and a carbonaceous material is allowed to act on the low melting point metal to improve hot strength and corrosion resistance against molten steel. . Examples of the carbonaceous material include graphite, carbon powder, and residual carbon of a resin added as a binder. In the conventional method, the amount of the carbonaceous material or the amount of the low melting point metal is determined without considering the relationship between the total amount of these carbonaceous materials and the amount of the low melting point metal.

Considering the case where the low melting point metal is aluminum, the aluminum reacts with carbon at 800 ° C. or higher to form Al ₄ C _3, and stoichiometrically, the mass ratio of carbonaceous material to aluminum is 0.33. When the carbon mass exceeds a certain range between which this value is sandwiched and excessively present, there is a drawback that sufficient oxidation resistance and corrosion resistance cannot be obtained, and improvement has been desired.

  For example, in Japanese Patent Application Laid-Open No. 2000-327401, metal powder is used in an amount of 0.5 to 5% by mass, carbon powder is used in an amount of 2 to 10% by mass, and further 3 to 10% by mass of a thermosetting resin is added. When the residual carbon ratio of a general thermosetting resin is estimated to be 20 to 40% by mass, the carbon mass relative to the aluminum mass is 0.5 to 0.6 or more, which is excessive.

  Moreover, in the said Unexamined-Japanese-Patent No. 2004-82126, since carbon black 3 mass% and the organic binder 4 mass% are added in the Example, the residual carbon ratio of a general thermosetting resin is 20-20. When the mass is estimated to be 40% by mass, the carbon mass relative to the aluminum mass is 0.7 to 1.8, and in this case too, the carbon is excessive.

  Furthermore, in the said Unexamined-Japanese-Patent No. 2004-17136, in the Example, the carbon mass with respect to the aluminum mass will be 0.5-3, and also in this case, it will be excess carbon.

  Japanese Examined Patent Publication No. 60-29664 aims to improve the strength in the intermediate temperature range by melting a low melting point metal, but has a drawback that the thermal shock resistance is lowered because it does not contain carbonaceous powder.

  The present invention has been proposed in view of the above-described conventional circumstances, and provides a non-fired plate refractory having high strength from room temperature to the temperature during use and excellent in oxidation resistance, corrosion resistance, and thermal shock resistance. It is intended to do.

  In order to achieve the above object, the present invention employs the following means.

  That is, the refractory inorganic material and the carbonaceous powder raw material are 0.3 to 2% by mass with respect to the total amount, and at least one of the aluminum-containing metals having a melting point of 1000 ° C. or less is 3 to 15 It is a non-fired plate refractory material used by mass% and added with 2 to 5 mass% of an organic binder. Here, the carbon mass derived from the organic binder and the carbonaceous powder raw material is in a range of 0.2 to 0.45 times the mass of aluminum contained in the aluminum-containing alloy.

  In the above, 0.1 to 5% by mass of a boron compound may be contained as an antioxidant.

  The raw material refractory for the plate refractory is molded with a binder and heat-treated at 100 to 1000 ° C.

  Here, the aluminum-containing metal refers to a metal having a melting point of 1000 ° C. or less among aluminum-containing metals such as Al, Al—Mg alloy, Al—Si alloy, and Al—Mg—Si alloy. Moreover, let the said aluminum mass be the total mass of the metal aluminum contained in the whole aluminum containing metal containing 1 or more types of aluminum simple substance. The carbonaceous powder raw material means carbon black, natural graphite powder, artificial graphite powder, pitch powder, coke powder, etc., and does not contain residual carbon of an organic binder added as a binder. The carbon mass is the total mass of free carbon derived from the carbonaceous powder raw material and the organic binder.

  As described above, the present invention determines the amount of carbon in relation to the amount of aluminum, so that a dense structure is obtained while ensuring the thermal shock resistance required for plate refractories, and the addition of boron results in oxidation. Suppression of strength reduction and improvement of corrosion resistance are obtained.

FIG. 1 is a photograph showing the results of an impact resistance test between the product of the present invention and a comparative example.

The inventors have intensively studied the influence of the metal additive and the amount of carbon on the characteristics of the non-fired plate, and by setting the mass ratio of not only the amount of metal but also the amount of metal to the carbonaceous material to a specific value, The metal reacts without excess and deficiency to produce a metal carbide (for example, C and Al react to produce Al ₄ C ₃ ), making a dense structure while ensuring the thermal shock resistance required for plate refractories, The present inventors have found that the metal reaction is progressed without excess and deficiency, the strength reduction due to oxidation of the unfired plate refractory is suppressed and the corrosion resistance is improved, and the present invention has been achieved.

Here, considering aluminum as a metal, the melting point of aluminum or an aluminum-containing metal is relatively low. By adding these to the refractory aggregate, it softens and melts at high temperatures during use to promote the relocation of the particles of the refractory aggregate, strengthens the structure and reduces thermal stress to increase thermal shock resistance. . Further, at 800 ° C. or higher, Al ₄ C ₃ is generated by the reaction between aluminum and carbon to increase the strength. The mass of carbon with respect to aluminum at this time is 0.33 stoichiometrically.

  The present invention has been made in consideration of the above points, and contains an aluminum having a refractory inorganic material and a carbonaceous powder raw material of 0.3 to 2% by mass with respect to the total amount and a melting point of 1000 ° C. or less. It is a non-fired plate refractory in which at least one or more of metals are used in an amount of 3 to 15% by mass based on the total amount, and 2 to 5% by mass of an organic binder is added thereto. Here, the carbon mass derived from the organic binder and the carbonaceous powder raw material is in a range of 0.2 to 0.45 times the mass of aluminum contained in the aluminum-containing alloy.

  The aluminum-containing metal is an aluminum-containing metal such as Al (melting point: 660 ° C.), Al—Mg alloy (eutectic melting point: 450 ° C.), Al—Si alloy (eutectic melting point: 580 ° C.), Al—Mg—Si alloy. To at least one having a melting point of 1000 ° C. or less. If melting | fusing point is 1000 degreeC or more, the intensity | strength of the plate refractory in a 1000 degrees C or less temperature range will become insufficient.

  The usage-amount of an aluminum containing metal shall be 3-15 mass% (preferably 5-12 mass%) with respect to the whole quantity. If the amount is less than 3% by mass, sufficient strength and corrosion resistance cannot be obtained. If the amount is more than 15% by mass, the thermal shock resistance decreases and the corrosion resistance decreases due to an increase in porosity.

  The particle size and shape of aluminum are not particularly limited, but can be properly used according to the characteristics described below.

  That is, in terms of hot reactivity, flake powder having a particle size of 100 μm or less is most excellent, but since flake powder lowers moldability, the porosity of the brick tends to increase. On the other hand, in terms of formability, it is desirable to use granular or powdery materials such as atomized powder.

  It is also effective to use a fiber having a high crack suppression effect. From the balance of moldability and reactivity, it is preferable to use atomized powder having a particle size of 100 μm or less, and flake powder, fiber, or a raw material having a particle size of 100 μm or more may be used in combination according to required properties.

  The content of the carbonaceous powder raw material is 0.3 to 2% by mass. When it is more than 2% by mass, the corrosion resistance decreases due to an increase in porosity. When the amount is less than 0.3% by mass, the thermal shock resistance is lowered due to excessive sintering of the structure.

  Carbon black, natural graphite powder, artificial graphite powder, pitch powder, coke powder, etc. can be used as the carbonaceous powder raw material. However, an organic binder such as a phenol resin described later is not included in the carbonaceous powder raw material.

  General alumina carbonaceous plate refractories have thermal shock resistance due to the addition of carbonaceous materials, so there is a limit to reducing the amount of carbon, but in the present invention, thermal shock resistance is achieved by softening and melting low melting point metals. Therefore, the carbonaceous raw material can be greatly reduced.

  The addition amount of the organic binder is 2 to 5% by mass. If it is less than 2% by mass, a dense molded body cannot be obtained, and if it is more than 5% by mass, cracks occur during molding or heat treatment. As the organic binder, it is desirable to use a thermosetting resin such as phenol resin, epoxy resin, silicone resin, furan resin.

Carbon mass with respect to aluminum mass is 0.2 to 0.45 times (preferably 0.25 to 0.4 times). If it is smaller than 0.2 times, the production of Al ₄ C ₃ at 800 ° C. or higher does not proceed and the corrosion resistance is lowered. If it is larger than 0.45 times, the excess carbon reduces the oxidation resistance and the corrosion resistance.

Here, the aluminum mass (see Table 1) is the total mass of metallic aluminum contained in the entire aluminum-containing metal including one or more types of aluminum. The carbon mass is defined as the total mass of free carbon derived from the carbonaceous powder raw material and the organic binder. This does not include carbon that does not readily react with aluminum. For example, carbon in SiC and B ₄ C is not included in free carbon.

If a large amount of unreacted metal remains in the portion where the molten steel and the plate refractory are in contact with each other, the corrosion resistance is lowered, so that a certain amount of carbon as a metal reaction partner is required. Here, since the metal is aluminum and the reaction partner is carbon, Al ₄ C ₃ is generated by the reaction. Since the carbon mass necessary for the production of Al ₄ C ₃ stoichiometrically is 0.33 times the mass of aluminum, the validity of the carbon mass (0.2 to 0.45 times) relative to the aluminum mass is Led.

  In the present invention, it is preferable to further add a boron compound. The said boron compound is added 0.1-5 mass% with respect to whole quantity. Boron compounds have an excellent antioxidation effect in that they oxidize preferentially and produce a low melting point material after oxidation to form a protective film that suppresses the invasion of oxygen. If the addition of the boron compound is less than 0.1% by mass, the oxidation resistance is not sufficient, and if it is greater than 5% by mass, the corrosion resistance decreases.

  In the present invention, after the raw materials mixed in the above ratio are formed, heat treatment is performed in the range of 100 ° C to 1000 ° C.

  The purpose of the heat treatment is to remove and cure the organic binder. If it is less than 100 ° C., the removal of volatile matter and the curing are insufficient, and the strength decreases. If it exceeds 1000 ° C., the thermal shock resistance decreases due to oxidation and carbonization of the metal. Further, at 300 to 1000 ° C., the porosity is increased and the strength is decreased due to the decomposition of the organic binder. In this case, pitch impregnation treatment may be performed as necessary. Moreover, you may heat-process at 100-600 degreeC after pitch impregnation for volatile matter removal. When it is necessary to suppress oxidation of the plate refractory during the heat treatment, known means such as reduction firing or firing in a nitrogen atmosphere may be used.

  As an aggregate material for non-fired plate refractory bricks, use one or more of aggregate materials generally used as refractory materials such as alumina, alumina zirconia, zirconia mullite, magnesia, spinel, etc. To do. Moreover, about the particle size, the size generally used for a plate refractory may be sufficient, and it is not specifically limited.

  In addition to the above, a metal not containing aluminum such as metallic silicon may be used. Further, it is preferable to use a thermosetting resin as the organic binder.

  An organic binder is added to these aggregate raw materials, aluminum-containing metal and other metals, carbonaceous powder, and boron compounds, and kneaded with a container-fixed type or container-driven type mixer. The kneaded compound is molded by an impact pressure press such as a friction press or a static pressure press such as an oil press, and then heat-treated at a temperature of 100 to 1000 ° C.

  As described above, since the carbon amount is set to an appropriate amount corresponding to the aluminum amount, an unfired plate refractory having excellent strength, oxidation resistance and corrosion resistance in the intermediate temperature range, and excellent impact resistance in the high temperature range is obtained. Obtainable.

<Examples and Comparative Examples>
Alumina, alumina zirconia as aggregate, Al, Al-Mg alloy, Al-Si alloy as metal, carbon black as carbon powder raw material, B ₄ C as boron compound, and phenol resin as organic binder in proportions shown in Table 1 Then, after kneading at room temperature for about 30 minutes, a plate formed using a 500 t vacuum friction press was heat-treated at a temperature of 250 to 1500 ° C. to obtain a plate refractory.

  Of the mass ratio of carbon to aluminum (C / Al) shown in Table 1, the aluminum mass was calculated from the aluminum content of each raw material and the additive amount of the raw material known in advance. About carbon mass, it computed from the carbon content (800 degreeC residual-carbon ratio) of each raw material (carbonaceous raw material and organic binder) known beforehand, and raw material usage-amount.

  With respect to Examples 1 to 6 and Comparative Examples 1 to 9 shown in Table 1, the apparent porosity and 600 ° C. hot bending strength were measured, and an oxidation resistance test, a thermal shock test, and a corrosion resistance test were performed. Apparent porosity was measured based on the method of JIS (R2205). The hot bending strength was measured in a nitrogen atmosphere at 600 ° C. The oxidation resistance test was evaluated based on the thickness of the decarburized layer on the cut surface of the sample after being heated at 1000 ° C. for 3 hours in the atmosphere, and was evaluated in three stages. In the thermal shock resistance test, a 30 × 30 × 230 mm sample was immersed in a hot metal at 1550 ° C. for 90 seconds, air-cooled, and evaluated by the amount of cracks generated in the sample. For the corrosion resistance test, normal steel and mill scale were used as erosion materials, and the erosion amount was evaluated by heating at 1650 ° C. for 4 hours by the rotary drum erosion method. The smaller the value, the better the corrosion resistance.

  Examples 1 to 6 all showed higher hot bending strength and corrosion resistance than Comparative Examples 1 and 2. In Examples 1 to 6, the oxidation resistance and the thermal shock resistance are equal to or higher than those of Comparative Examples 1 to 6, and each characteristic is well-balanced.

  In Comparative Example 1, the amount of aluminum-containing metal is small, and the oxidation resistance, hot strength, and corrosion resistance are not sufficient. In Comparative Examples 2 and 4, C / Al is large, the carbon amount is excessive, the oxidation resistance is low, and the hot strength is not sufficient. Further, Comparative Example 3 has an excessive amount of aluminum-containing metal and low thermal shock resistance.

  Since Comparative Example 5 does not contain a boron compound, the oxidation resistance is not sufficient. Conversely, Comparative Example 6 has an excessive amount of boron compound and low corrosion resistance.

  Comparative Example 7 is a baked plate refractory obtained by heat-treating the same composition as Example 3 in a reducing atmosphere at 1500 ° C., and the metal is oxidized and carbonized to strengthen the bond. Impact is low (see FIG. 1).

  Comparative Example 8 was aimed at densification by increasing the amount of organic binder, but cracks occurred during drying.

  Since Comparative Example 9 does not contain a carbonaceous powder raw material, there is no problem in oxidation resistance, but the thermal shock resistance decreases.

  FIG. 1 is a photograph showing the results of thermal shock resistance of Comparative Example 7 (upper side) and Example 3 (lower side). Although Example 3 is in a state where there are no cracks (good evaluation of three stages), Comparative Example 7 can confirm a state where there are many cracks (evaluation of three stages of bad).

  As described above, the present invention can obtain a non-fired or light-fired refractory excellent in strength, oxidation resistance and corrosion resistance in the intermediate temperature range of the refractory for the non-fired sliding nozzle plate, in the steel industry. Usefulness is extremely high.

Claims (3)

  A refractory raw material composition containing at least one or two or more of a refractory inorganic material and an aluminum-containing metal having a melting point of 1000 ° C. or less in an amount of 3 to 15% by mass and a carbonaceous powder raw material in an amount of 0.3 to 2% by mass. A sliding nozzle plate refractory having an organic binder added thereto, heat-treated at a temperature of 100 to 1000 ° C. after molding, and having a carbon mass in the range of 0.2 to 0.45 times the aluminum mass.   The plate refractory for a sliding nozzle according to claim 1, which contains 0.1 to 5% by mass of a boron compound as an antioxidant.   The plate refractory for sliding nozzles according to claim 1 or 2, which is produced by adding 2 to 5% by mass of an organic binder.