Composition of magnesia-chromium brick and method for manufacturing the same

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 magnesia-chrome bricks.

Background Art

[0002] Magnesia-chrome bricks have high hot strength and excellent corrosion resistance, and are therefore suitably used as lining materials for secondary steel refining furnaces (such as DH, RH, AOD, etc.) with severe operating conditions. On the other hand, in the production of magnesia-chrome bricks, high-temperature firing at 1800°C or higher is required, which places a large burden on the environment.

[0003] Patent Document 1 addresses the problem of reducing the firing temperature without sacrificing brick quality, and discloses a basic refractory using a clinker in which spinel separated and precipitated on the surface of periclase is absent and the lattice constant of the periclase is 4.206 Å or less.

[0004] Also, Non-Patent Document 1 discloses the hot properties of a magnesia-chrome clinker containing 10.51% by mass of Fe 2 O 3 .

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Patent Document 1 states that even at a low firing temperature of 1300°C, high hot bending strength can be obtained. However, the hot bending strength after firing at 1300°C for 2 hours is less than 1 / 2 compared to that after firing in an 1800°C tunnel kiln. This cannot be said to be of sufficient quality for application to secondary refining furnaces for steel with high loads.

[0008] Also, Non-Patent Document 1 discloses the hot properties of magnesia-chrome clinker containing 10.51 mass% of Fe 2 O 3 , but the firing temperature is 1750°C, and as described above, the load on the environment is large.

[0009] The present invention has been proposed in view of the above conventional circumstances, and an object thereof is to provide a magnesia-chrome refractory raw material composition excellent in hot bending strength and corrosion resistance even when the firing temperature of bricks is lowered, and to provide a method for manufacturing magnesia-chrome bricks.

Means for Solving the Problems

[0010] The present invention is a magnesia-chrome refractory raw material composition containing 50 mass% or more and 95 mass% or less of an electrically fused magnesia-chrome raw material having a Fe 2 O 3 content of 10 mass% or more and 30 mass% or less, and 5 mass% or more and 35 mass% or less of a magnesia raw material having a MgO content of 90 mass% or more.

[0011] Also, it is a method for manufacturing magnesia-chrome bricks by firing the magnesia-chrome refractory raw material composition at 1200°C or higher and 1600°C or lower.

Effects of the Invention

[0012] When the magnesia-chrome refractory raw material composition is used, magnesia-chrome bricks excellent in corrosion resistance and hot bending strength can be obtained even when the firing temperature is 1200°C to 1600°C. Also, by lowering the firing temperature, the environmental load during production can be reduced.

Modes for Carrying Out the Invention

[0013] The present invention uses raw materials composed of the following electrofused magnesia-chrome raw materials and magnesia raw materials.

[0014] As the electrofused magnesia-chrome raw material, in the present invention, Fe 2 O 3 uses a raw material with 10% by mass or more and 30% by mass or less. When firing a composition of the electrofused magnesia-chrome raw material and the magnesia raw material in which Fe 2 O 3 is within the above range to produce bricks, sintering is promoted even when the firing temperature of the bricks is low, the bonds inside the bricks develop, the structure becomes dense, and it is considered that bricks excellent in both corrosion resistance and hot bending strength can be produced.

[0015] <Electrofused magnesia-chrome raw material> The electrofused magnesia-chrome raw material is an electrofused magnesia-chrome raw material with a Fe 2 O 3 content of 10% by mass or more and 30% by mass or less. The electrofused magnesia-chrome raw material can be produced by a known method. That is, calcined magnesia, magnesia clinker, chromite ore, iron oxide, etc. are blended so that the content of Fe 2 O 3 becomes 10% by mass or more and 30% by mass or less, and it is produced by melting in an electric furnace.

[0016] Fe 2 O 3 When the content is less than 10% by mass, when the firing temperature of the bricks is lowered to 1200 °C or lower, the hot bending strength of the bricks decreases. Also, when the Fe 2 O 3 content exceeds 30% by mass, the corrosion resistance of the bricks decreases.

[0017] <Magnesia-chrome refractory raw material composition> In the magnesia-chrome refractory raw material composition, Fe 2 O 3It is preferable to blend 50 mass% or more and 95 mass% or less of an electrofused magnesia-chrome raw material having a content of 10 mass% or more and 30 mass% or less. By setting it within this range, magnesia-chrome bricks with high hot bending strength and excellent corrosion resistance can be produced even when the firing temperature is lowered.

[0018] Fe 2 O 3 If 50 mass% or more and 95 mass% or less of an electrofused magnesia-chrome raw material having a content of 10 mass% or more and 30 mass% or less is blended, electrofused magnesia-chrome raw materials of other compositions may be used in combination.

[0019] When the content of the electrofused magnesia-chrome raw material is 50 mass% or less, the hot bending strength and corrosion resistance of the brick decrease. On the other hand, when the content of the electrofused magnesia-chrome raw material exceeds 95 mass%, the thermal spalling resistance of the brick decreases.

[0020] <Magnesia raw material> As the magnesia raw material, known magnesia raw materials can be used. For example, electrofused magnesia, seawater magnesia, natural magnesia, sintered magnesia, etc. may be mentioned. The MgO content in the magnesia raw material is preferably 90 mass% or more, and more preferably 95 mass% or more. By setting the MgO content in the magnesia raw material within this range, the corrosion resistance is improved.

[0021] It is preferable to blend 5 mass% or more and 35 mass% or less of the magnesia raw material. By setting it within this range, magnesia-chrome bricks with high hot bending strength and excellent corrosion resistance can be produced even when the firing temperature is lowered.

[0022] When the content of the magnesia raw material is 5 mass% or less, the thermal spalling resistance of the brick decreases. On the other hand, when the content of the magnesia raw material exceeds 35 mass%, the blending amount of the electrofused magnesia-chrome raw material decreases, and the effects aimed at in the present invention cannot be obtained.

[0023] <Other raw materials> Commercially available chromium oxide may be additionally used. When using chromium oxide, the content is preferably 10% by mass or less based on 100% by mass of the magnesia-chrome refractory raw material composition. By setting it within this range, even if the firing temperature is lowered, magnesia-chrome bricks with high hot bending strength and excellent corrosion resistance can be produced.

[0024] When the chromium oxide is 10% by mass or less based on the internal addition, it is possible to prevent a decrease in yield due to the occurrence of lamination after molding and cracks due to the reaction with magnesia during firing. On the other hand, chromium oxide does not necessarily need to be added, but adding it improves the corrosion resistance of the bricks.

[0025] In addition, within the range that does not inhibit the action of the present invention, known chrome ore, red iron oxide, magnesia-chrome brick recycling raw materials, etc. may be blended. As the binder, known saccharides, phenolic resins, etc. can be used. By blending and kneading these raw materials, a magnesia-chrome refractory raw material composition is obtained.

[0026] <Method for manufacturing magnesia-chrome bricks> By pressure molding the above-mentioned magnesia-chrome refractory raw material composition according to a conventional method and firing it at 1200 °C or higher and 1600 °C or lower, magnesia-chrome bricks are obtained.

Example

[0027] Table 1 shows the compositions of 4 types of fused magnesia-chrome raw materials with different Fe 2 O 3 contents.

[0028]

Table 1

[0029] A hydraulic press was used to fabricate test pieces by molding standard bricks (length 230 mm, width 114 mm, thickness 65 mm) in accordance with JIS R2101. The firing temperature was varied from 1100 °C to 1800 °C to obtain magnesia-chrome bricks.

[0030]

Table 2

[0031] <Corrosion resistance> The erosion amount was measured by a horizontal rotary erosion test. That is, the sample was lined inside a drum-type rotary furnace, and an erosion agent was placed inside and heated to measure the erosion amount of 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 CaO / SiO 2 = 1.0, which was replaced with a new one every hour. After the test, the test pieces were recovered and cut to measure the erosion amount. The corrosion resistance was indicated by an index with the erosion amount of Example 11 taken as 100. A smaller index indicates less wear.

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

[0033] In Experimental Examples 6 to 8, the blending ratio of the electrofused magnesia-chrome raw material was varied within the scope 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 to 10, the Fe 2 O 3 content of the electrofused magnesia-chrome raw material was varied within the scope of the present invention, and the firing temperature was fixed at 1450 °C, and good results were obtained in all cases.

[0034] Experimental Example 11 used a Fe content in the electrofused magnesia-chrome raw material outside the scope of the present invention and had a firing temperature of 1450°C, resulting in inferior hot bending strength and corrosion resistance. 2 O 3 As described above, according to the present invention, by using an electrofused magnesia-chrome raw material with an Fe content of 10% by mass or more and 30% by mass or less, even when the firing temperature is 1200°C to 1600°C, magnesia-chrome bricks excellent in corrosion resistance and hot bending strength can be obtained. Further, by lowering the firing temperature, the environmental load associated with production can be reduced.

[0035] As described above, the present invention 2 O 3 By using an electrofused magnesia-chrome raw material with a content of 10% by mass or more and 30% by mass or less, magnesia-chrome bricks excellent in corrosion resistance and hot bending strength can be obtained even when the firing temperature is 1200°C to 1600°C. Also, the environmental load associated with production can be reduced by lowering the firing temperature.

Claims

1. Fe ２ O ３ A magnesia-chrome refractory raw material composition containing 50% by mass or more and 95% by mass or less of an electrofused magnesia-chrome raw material having an Fe content of 10% by mass or more and 30% by mass or less, and 5% by mass or more and 35% by mass or less of a magnesia raw material having an MgO content of 90% by mass or more.

2. A method for manufacturing magnesia-chrome bricks, which is obtained by firing the magnesia-chrome refractory raw material composition after molding at a temperature of 1200°C or higher and 1600°C or lower.

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