Composition of magnesia-chrome bricks and their manufacturing method

Abstract

To provide a method for manufacturing a magnesia-chromium brick that exhibits excellent hot bending strength and corrosion resistance even when a firing temperature is lowered.SOLUTION: A magnesia-chromium refractory raw material composition comprises: 50 mass% or more and 95 mass% or less of an electric fusion magnesia-chromium raw material containing 12 mass% or more and 30 mass% or less of Fe2O3; and 5 mass% or more and 35 mass% or less of a magnesia raw material containing 90 mass% or more of MgO, wherein the raw material composition is fired at 1,200°C or higher and 1,600°C or lower, thereby obtaining a magnesium-chromium brick having excellent corrosion resistance and hot bending strength.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a magnesia-chrome refractory raw material composition and a method for producing a magnesia-chrome brick. [Background technology]

[0002] Magnesia-chrome bricks have high hot strength and excellent corrosion resistance, making them ideal for use as lining materials in secondary steel refining furnaces (DH, RH, AOD, etc.), which are subject to strict operating conditions. However, their production requires high-temperature firing at over 1800°C, which places a heavy burden on the environment.

[0003] Patent Document 1 aims to lower the firing temperature without degrading the quality of the brick, and discloses a basic refractory made from clinker in which no spinel is exsolved and precipitated on the surface of the periclase and the lattice constant of the periclase is 4.206 Å or less.

[0004] Furthermore, Non-Patent Document 1 discloses the hot properties of magnesia-chrome clinker containing 10.51 mass % of Fe2O3. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 57-037552 [Non-patent literature]

[0006] [Non-Patent Document 1] Norio Yoshizawa et al., "Hot Properties of Electrofused Magnesium-Chromium Raw Materials, Refractories", 51 [1] (1999) P32-33 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 claims that high hot bending strength was achieved even at a low firing temperature of 1300°C. However, the hot bending strength after firing at 1300°C for two hours was less than half that after firing in a tunnel kiln at 1800°C. This is not a sufficient quality for use in a secondary refining furnace for steel, which requires a high load.

[0008] Furthermore, Non-Patent Document 1 discloses the hot properties of magnesia-chrome clinker containing 10.51 mass % of Fe2O3, but the firing temperature is 1750°C, which places a heavy burden on the environment as mentioned above.

[0009] The present invention has been proposed in view of the above-mentioned conventional circumstances, and its object is to provide a magnesia-chrome refractory raw material composition that exhibits excellent hot bending strength and corrosion resistance even when the firing temperature of the brick is lowered, and to provide a method for producing a magnesia-chrome brick. [Means for solving the problem]

[0010] The present invention is characterized by the Fe2O3 content 14 The magnesia-chrome refractory raw material composition contains 50% by mass or more but 95% by mass or less of an electrofused magnesia-chrome raw material having an MgO content of 90% by mass or more and 5% by mass or more but 35% by mass or less of a magnesia raw material having an MgO content of 90% by mass or more.

[0011] The present invention also provides a method for producing a magnesia-chrome brick, which comprises firing the magnesia-chrome refractory raw material composition at a temperature of 1200°C or higher and 1600°C or lower. [Effects of the Invention]

[0012] By using the magnesia-chrome refractory raw material composition, it is possible to obtain magnesia-chrome bricks that have excellent corrosion resistance and hot bending strength even when the firing temperature is 1200°C to 1600°C. In addition, by lowering the firing temperature, the environmental impact of production can be reduced. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention relates to a raw material having a composition of the following electrofused magnesia-chromium raw material and magnesia raw material.

[0014] In the present invention, a raw material containing 10% by mass or more and 30% by mass or less of Fe2O3 is used as the electrofused magnesia raw material. When a composition of an electrofused magnesia raw material containing Fe2O3 in the above range and a magnesia raw material is fired to produce a brick, sintering is promoted even at a low firing temperature, and the bonds within the brick are developed, resulting in a denser structure, and it is believed that a brick with excellent both corrosion resistance and hot bending strength can be produced.

[0015] <Electrofused Magnesium-Chromium Raw Material> The electrofused magnesia-chrome raw material has an Fe2O3 content of 10% to 30% by mass. The electrofused magnesia-chrome raw material can be produced by a known method. Specifically, calcined magnesia, magnesia clinker, chromite, iron oxide, etc. are blended and melted in an electric furnace so that the Fe2O3 content is 10% to 30% by mass.

[0016] If the Fe2O3 content is less than 10% by mass, the hot bending strength of the brick will decrease when the firing temperature of the brick is reduced to 1200°C or less. Also, if the Fe2O3 content exceeds 30% by mass, the corrosion resistance of the brick will decrease.

[0017] <Magnesia-chromium refractory raw material composition> The magnesia-chrome refractory raw material composition preferably contains 50 to 95 mass% of electrofused magnesia-chrome raw material with an Fe2O3 content of 10 to 30 mass%. By adjusting the content within this range, it is possible to produce magnesia-chrome bricks that have high hot bending strength and excellent corrosion resistance even when fired at a low temperature.

[0018] As long as the electrofused magnesia-chrome raw material having an Fe2O3 content of 10% by mass to 30% by mass is blended in an amount of 50% by mass to 95% by mass, electrofused magnesia-chrome raw materials of other compositions may be used in combination.

[0019] If the content of the electrofused magnesia-chrome raw material is 50% by mass or less, the hot bending strength and corrosion resistance of the brick will decrease, whereas if the content of the electrofused magnesia-chrome raw material is more than 95% by mass, the heat spalling resistance of the brick will decrease.

[0020] <Magnesia raw material> Known magnesia raw materials can be used as the magnesia raw material. Examples include electrofused magnesia, seawater magnesia, natural magnesia, and sintered magnesia. The MgO content in the magnesia raw material is preferably 90% by mass or more, and more preferably 95% by mass or more. By keeping the MgO content in the magnesia raw material within this range, corrosion resistance is improved.

[0021] It is preferable to mix magnesia raw material in an amount of 5 to 35% by mass. By adjusting the amount to this range, it is possible to produce magnesia-chrome bricks that have high hot bending strength and excellent corrosion resistance even when fired at a low temperature.

[0022] If the magnesia raw material is less than 5% by mass, the heat spalling resistance of the brick will decrease, while if the magnesia raw material is more than 35% by mass, the blending amount of the electrofused magnesia-chrome raw material will be too small to achieve the effects aimed at by the present invention.

[0023] <Other ingredients> Commercially available chromium oxide may be added. When chromium oxide is used, its content is preferably 10% by mass or less relative to 100% by mass of the magnesia-chrome refractory raw material composition. By adjusting the content within this range, it is possible to produce magnesia-chrome bricks that have high hot bending strength and excellent corrosion resistance, even when firing at a low temperature.

[0024] When the chromium oxide content is 10% by mass or less, it is possible to prevent a decrease in yield due to lamination after molding and cracks due to reaction with magnesia during firing. On the other hand, although it is not absolutely necessary to add chromium oxide, adding it improves the corrosion resistance of the brick.

[0025] In addition, known materials such as chromium ore, red iron oxide, and recycled magnesia-chrome bricks may be blended within the range that does not impair the effects of the present invention. Known sugars, phenolic resins, and the like can be used as binders. A magnesia-chrome refractory raw material composition can be obtained by blending and kneading these materials.

[0026] <Magnesia-chrome brick manufacturing method> The magnesia-chrome refractory raw material composition described above is press-molded in a conventional manner and fired at 1200°C to 1600°C to obtain a magnesia-chrome brick. [Example]

[0027] Table 1 shows the composition of four types of electrofused magnesia-chrome raw materials with different Fe2O3 contents.

[0028] [Table 1] Table 2 shows the formulation of the magnesia-chrome refractory raw material composition using the four types of electrofused magnesia-chrome raw materials mentioned above, and the evaluation of the magnesia-chrome bricks manufactured using them.

[0029] To prepare the test specimens, a hydraulic press was used to mold standard JIS R2101 bricks (length 230 mm, width 114 mm, thickness 65 mm). The firing temperature was varied from 1100 to 1800°C to obtain magnesia-chrome bricks.

[0030] [Table 2] <Hot bending strength> The hot bending strength was measured in accordance with JIS R 2656. The test temperature was 1400°C.

[0031] <Corrosion resistance> The amount of corrosion was measured using a horizontal rotary corrosion test. That is, the sample was lined in a drum-shaped rotary furnace, and an erosion agent was placed inside and heated to measure the amount of corrosion on the sample. The heating method was electric arc heating, the heating temperature was 1700°C, and the holding time was 5 hours. The erosion material used was slag with a CaO / SiO2 = 1.0 ratio, and was replaced with a new one every hour. After the test, the test piece was recovered, cut, and the amount of corrosion was measured. The corrosion resistance was expressed as an index, with the amount of corrosion in Example 11 being 100. A smaller index indicates less wear.

[0032] In Experimental Examples 1 to 5, the blending ratio of electrofused magnesia-chrome raw material A was fixed within the range of the present invention, and the firing temperature was varied from 1100°C to 1800°C. Good results were obtained at firing temperatures of 1200°C or higher. Although the bending strength and corrosion resistance were good even when fired at 1800°C, the reduction in environmental load by low-temperature firing, which is the object of the present invention, was not achieved.

[0033] In Experimental Examples 6 to 8, the blending ratio of the electrofused magnesia-chrome raw material was varied within the range of the present invention, and the firing temperature was fixed at 1450°C, and good results were obtained in all cases. In Experimental Examples 9 and 10, the Fe2O3 content of the electrofused magnesia-chrome raw material was varied within the range of the present invention, and the firing temperature was fixed at 1450°C, and good results were obtained in all cases.

[0034] In Experimental Example 11, the Fe2O3 content of the electrofused magnesia-chrome raw material was outside the range of the present invention, and the firing temperature was 1450°C, resulting in poor hot bending strength and corrosion resistance.

[0035] As explained above, by using an electrofused magnesia-chrome raw material with an Fe2O3 content of 10% by mass or more and 30% by mass or less, the present invention makes it possible to obtain magnesia-chrome bricks with excellent corrosion resistance and hot bending strength even at firing temperatures of 1200°C to 1600°C. In addition, lowering the firing temperature reduces the environmental impact of production.

Claims

1. Fe ２ O ３ A magnesia-chrome refractory raw material composition comprising 50% by mass or more but 95% by mass or less of an electrofused magnesia-chrome raw material having a content of 14% by mass or more but 30% by mass or less, and 5% by mass or more but 35% by mass or less of a magnesia raw material having an MgO content of 90% by mass or more.

2. A method for producing a magnesia-chrome brick by molding the magnesia-chrome refractory raw material composition described in claim 1 and then firing it at a temperature of 1200°C or higher and 1600°C or lower.

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