Blast furnace taphole plugging mud material

Abstract

To provide a mud material for blocking a blast furnace tap hole excellent in corrosion resistance and opening property.SOLUTION: A mud material for blocking a blast furnace tap hole comprises alumina shot blast powder after use.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a mud material for plugging a taphole of a blast furnace. [Background technology]

[0002] Blast furnace taphole plugging mud is a clay-like material used to fill and plug the taphole of a blast furnace. In the ironmaking process, iron ore is melted in a blast furnace whose taphole is plugged with mud to produce pig iron, and the mud is then broken to open the taphole and the pig iron is extracted.

[0003] Conventional mud materials for plugging the taphole of a blast furnace are disclosed in, for example, Patent Document 1 and Patent Document 2 below. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 08-119754 [Patent Document 2] Japanese Patent Application Publication No. 11-029366 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses a mud material for plugging a blast furnace taphole, which is made by adding 10 to 17 weight percent of liquid tar as a binder to 100% refractory aggregate, which is composed of 30 to 50 weight percent alumina raw material, 2 to 5 weight percent silica raw material, 15 to 25 weight percent silicon carbide, 5 to 10 weight percent carbonaceous raw material, 15 to 30 weight percent nitride, and 5 to 15 weight percent metal powder.

[0006] Patent Document 2 discloses a mud material for plugging a blast furnace taphole, which is made by adding 100% by weight of refractory aggregate having a particle size composition consisting of 30 to 50% by weight of aluminous raw materials including calcined alumina, 2 to 5% by weight of siliceous raw materials, 15 to 25% by weight of silicon carbide, 5 to 10% by weight of carbonaceous raw materials, 15 to 30% by weight of nitrides, and 5 to 15% by weight of metal powder, with 5% by weight or less of materials with a particle size of more than 1 mm, 60 to 70% by weight of materials with a particle size of less than 0.075 mm (excluding calcined alumina with a particle size of 2 μm or less), 5 to 15% by weight of calcined alumina with a particle size of 2 μm or less, and the remainder being materials with a particle size of 1 to 0.075 mm, to which 10 to 17% by weight of liquid tar as a binder is added as an outer layer.

[0007] The mud material for plugging blast furnace tapholes disclosed in Patent Document 1 is expected to have improved strength and corrosion resistance, and is said to have good hole-opening properties, but its strength may be so high that it takes a long time to open holes.

[0008] The mud material for plugging blast furnace tapholes disclosed in Patent Document 2 is characterized by a particle size structure that uses a large amount of fine raw materials, and by using a large amount of alumina components, it has excellent resistance to molten iron and slag, but it is difficult to open holes because of its high strength and densified structure.

[0009] As described above, conventional mud materials for plugging tapholes of blast furnaces have excellent resistance to molten iron and slag, but have the problem of having a hard structure and poor hole opening properties. [Means for solving the problem]

[0010] The mud material for plugging the taphole of a blast furnace according to the present invention is characterized by the fact that it is made of alumina shot blast powder used in the processing of steel materials, oxide refractory raw materials (excluding magnesia), and , a carbonaceous raw material, and a silicon nitride raw material The point is that it includes

[0011] In the blast furnace tap hole plugging mud material according to the present invention, Note A It is preferable that the luminous shot blast powder is contained in an amount of 2% by mass to 50% by mass.

[0012] In the blast furnace tap hole plugging mud material according to the present invention, Note A It is preferable that the maximum particle size of the lumina shot blast powder is 3 mm or less. [Effects of the Invention]

[0013] In the ironworking and non-ferrous metals industries, alumina shot (alumina blasting) processing is carried out by spraying aluminum oxide abrasives (polishing agents) onto products to smooth their surface roughness, remove rust and dirt, etc. The alumina used in this processing is called post-consumer alumina shot blasting powder.

[0014] The inventors have investigated mud materials with excellent pore opening properties and have discovered that by applying used alumina shot blast powder generated after alumina shot application to mud materials, mud materials with excellent pore opening properties can be obtained while maintaining the corrosion resistance of conventional mud materials.

[0015] Furthermore, since used alumina shot blasting powder is discharged and discarded in the scale of several hundred tons per month in large-scale steel product manufacturing industries, for example, by using used alumina shot blasting powder as a recycled raw material for mud material, it is possible to significantly reduce the amount of waste. DETAILED DESCRIPTION OF THE INVENTION

[0016] The mud material for plugging a taphole of a blast furnace according to the present invention comprises a known refractory aggregate and used alumina shot blast powder.

[0017] In the present invention, used alumina shot blast dust refers to the shot blast dust generated after processing such as deburring, surface polishing, precision grinding, etc. by projecting granular alumina onto the surface of a workpiece made of steel material, etc. Although the mechanism by which the effects of the present invention are achieved is not completely clear, it is presumed that the metal powder adhering to the alumina surface contributes to this.

[0018] The preferred Fe content, as well as the preferred Al2O3 content, particle size, and particle shape, when the used alumina shot blast powder contains, for example, Fe in the present invention, will be described in detail below.

[0019] <Fe content> The content of Fe in the used alumina shot blast powder is preferably 2 to 25% by mass, more preferably 5 to 20% by mass. Incidentally, the Fe content can be measured using the bromine methanol method or the like. The mud material during tapping will be exposed to 1400 °C or higher. When the used alumina shot blast powder contains an Fe component, it is considered that the Fe component functions as a reaction catalyst for the reaction between silicon nitride and carbon contained in the mud material, promoting the following reaction in which SiC and nitrogen gas are generated. Reaction formula: 3Fe + Si3N4 + 2C → Fe3Si + 2SiC + 2N2 (reaction temperature range: about 1400 °C)

[0020] The generation of SiC bonds in the matrix part of the mud material is promoted, improving the corrosion resistance of the mud material. At the same time, the generated nitrogen gas makes the mud material porous, improving the porosity. Therefore, when the used alumina shot blast powder contains an Fe component, it becomes easier to obtain a mud material excellent in corrosion resistance and porosity.

[0021] <Al2O3 content> The content of Al2O3 in the used alumina shot blast powder is preferably 70 to 98% by mass, more preferably 80 to 95% by mass. Incidentally, the content of Al2O3 can be measured by fluorescence X-ray analysis using glass beads according to the provisions of Japanese Industrial Standard JIS R 2216. The Al2O3 component contained in the used alumina shot blast powder improves the corrosion resistance and slag resistance of the mud material.

[0022] <Particle size> The maximum particle size of the used alumina shot blast powder is not particularly limited, but is preferably 3 mm or less, more preferably 1 mm or less, and even more preferably 0.075 mm or less. Regarding the reactivity of the used alumina shot blast powder with silicon nitride, iron, and carbon, it is preferable that the maximum particle size of the used alumina shot blast powder is 3 mm or less, since it disperses well in the mud material. The particle size in this case is determined by sieving using a JIS Z 8801-1 sieve.

[0023] <Particle shape> The particle shape of used alumina shot blasting powder is preferably rounded. For example, an average roundness of 0.3 or more is preferable, and an average of 0.5 or more is more preferable. The average roundness can be calculated by comparing each particle of used alumina shot blasting powder with Krumbein's roundness impression diagram. An average roundness of 0.3 or more is more likely to exert a ball-bearing effect, which reduces friction between raw materials during mixing and increases fluidity, and the amount of binder added to achieve the necessary plasticity for the mud can be reduced. In a mud structure with reduced binder addition, the raw materials are closer together, increasing the reactivity of used alumina shot blasting powder with silicon nitride iron and carbon.

[0024] The mud material for plugging a blast furnace taphole of the present invention preferably contains 2 to 50 mass % of used alumina shot blast powder.

[0025] Examples of refractory aggregates that can be used in the blast furnace taphole plugging mud material of the present invention include one or more oxide refractory raw materials selected from alumina raw materials, alumina-silica raw materials, clay raw materials, and silica raw materials, carbonaceous raw materials, silicon carbide raw materials, silicon nitride raw materials, etc. Only one of these raw materials may be selected, or two or more may be used in combination.

[0026] The amount of the oxide refractory raw material is preferably 5% by mass or more and 85% by mass or less, more preferably 30% by mass or more and 75% by mass or less. If the amount exceeds 85% by mass, corrosion resistance decreases, and if it is less than 5% by mass, the porosity tends to be too high. Examples of the oxide refractory raw material that can be used include sintered alumina, fused alumina, aluminium shale, bauxite, chamotte raw material, pyrolite, mullite, andalusite, and silica fume.

[0027] Examples of carbonaceous raw materials constituting the refractory aggregate include graphite, amorphous graphite, coal coke, petroleum coke and powders of these cokes, graphite electrode scrap, carbon black, coal pitch, and petroleum pitch. The carbonaceous raw materials are added to suppress slag penetration and over-sintering, and the blending amount is preferably 3% by mass or more and 20% by mass or less, and more preferably 4% by mass or more and 16% by mass or less. A blending amount of the carbonaceous raw materials less than 3% by mass is undesirable because it results in over-sintering, while a blending amount exceeding 20% ​​by mass is undesirable because it results in reduced strength.

[0028] Examples of silicon carbide raw materials that can be used to form the refractory aggregate include silicon carbide raw materials produced by the Acheson process and silicon carbide raw materials obtained by reducing and carbonizing silica. The silicon carbide raw material is added to improve corrosion resistance against slag, and its blending amount is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 30% by mass. The blending amount of the silicon carbide raw material is desirably 5% by mass to 50% by mass. A blending amount of less than 5% by mass does not contribute much to improving corrosion resistance, and a blending amount of more than 50% by mass reduces the strength after sintering.

[0029] If necessary, a silicon nitride raw material may be added to improve corrosion resistance. Examples of such silicon nitride raw materials include silicon nitride obtained by reducing and nitriding silica, silicon nitride obtained by directly nitriding metallic silicon, and silicon ferronitride obtained by directly nitriding ferrosilicon. The amount of silicon nitride raw material added is preferably 3% by mass to 45% by mass, and more preferably 10% by mass to 40% by mass. The amount of silicon nitride raw material added is desirably 3% by mass to 45% by mass. If the amount is less than 3% by mass, it is difficult to obtain a sufficient effect in improving corrosion resistance. On the other hand, if the amount is more than 45% by mass, the silicon nitride raw material is relatively expensive among mud material raw materials, and it is difficult to obtain the effect of adding the silicon nitride raw material that is worth the cost of the mud material.

[0030] If necessary, one or more kinds of metal powders may be added, such as aluminum metal, silicon metal, and aluminum-silicon alloy.

[0031] If necessary, coal tar or phenol resin for mud materials may be used as an organic binder. The amount of organic binder added can be adjusted appropriately depending on the usage situation of the mud material and the required performance.

[0032] The blast furnace taphole plugging mud material according to the present invention can be produced by mixing at least the above-mentioned refractory aggregate and used alumina shot blast powder using a known mixing device or method, such as a Fukai-type Conner mixer, an upper mixer, or an Eirich mixer, although the mixing device is not particularly limited.

[0033] The method for filling and plugging the taphole of a blast furnace using the taphole plugging mud material of the present invention is not particularly limited, and any commonly used filling and plugging method may be used. [Example]

[0034] Table 1 below shows an example of the mud material for blocking blast furnace tapholes of the present invention, which contains used alumina shot blast powder, and a comparative example of the mud material not containing used alumina shot blast powder. [Table 1]

[0035] Each of Examples 1 to 4 in Table 1 is a mud material made by mixing a refractory aggregate based on a blend of pyrophyllite, alumina, carbon, silicon carbide, clay, and silicon nitride iron, with post-consumer alumina shot blast powder, and adding anhydrous tar as an organic binder.Comparative Examples 1 and 2 are mud materials with a blend that does not contain post-consumer alumina shot blast powder.

[0036] The mud material obtained above was placed in a 40 x 40 x 160 mm mold, molded under a pressure of 5.0 MPa, and dried in a dryer at 300°C for 12 hours. After drying, the sample was embedded in coke breeze and heated at 1500°C for 3 hours to prepare a test specimen.

[0037] <Bending strength> A bending test was conducted to evaluate hole opening property. The bending test was performed by measuring test pieces in accordance with JIS R 2553. When the bending strength was 10 MPa or more, the strength was high and the corrosion resistance was excellent, but the strength was too high and the hole opening property was judged to be poor. When the bending strength was less than 10 MPa, the hole opening property was judged to be excellent.

[0038] The mud materials of Examples 1 to 4 containing used alumina shot blast powder were found to have better pore opening properties than the mud materials of Comparative Examples 1 and 2 containing no used alumina shot blast powder.

[0039] Next, the formulations and test results of Examples 5 to 22 and Comparative Examples 3 to 5, which were tested with a focus on the particle size composition of the raw materials, are shown in Table 2 below. [Table 2]

[0040] The bending test was carried out in the same manner as in Table 1. The corrosion resistance was evaluated by carrying out tests on the molten iron resistance index and the slag resistance index as follows.

[0041] <Hot metal resistance index> Molten iron resistance tests were conducted, and evaluations were performed by calculating indices. Molten iron corrosion resistance was evaluated by a sample lining test using a high-frequency induction furnace. A mold was filled with mud material, and the specimens were embedded in coke breeze and heated at 800°C for 3 hours to prepare test pieces. Each test piece was combined into a crucible shape, and 20 kg of pig iron was added as an erosion agent to the crucible. The test was performed by holding the crucible at 1550 to 1600°C for 4 hours. The corrosion volume of the sample after the test was measured, and an index was calculated for evaluation. The corrosion volume of Comparative Product 1 was set to 100, and the index for each Example and Comparative Example was calculated using the following formula. A smaller index indicates better molten iron resistance. Molten iron resistance index = (erosion volume of each test piece ÷ erosion volume of Comparative Example 1) × 100

[0042] <Slag resistance index> Slag resistance tests were conducted, and an index was calculated for evaluation. Corrosion resistance against blast furnace slag was evaluated using a rotating drum corrosion test. A mold was filled with mud material, and the material was embedded in coke breeze and heated at 800°C for 3 hours to prepare a test specimen. Each test specimen was combined into a drum shape, and 1 kg of blast furnace slag was placed inside the drum as an erosion agent, and the drum was held at 1550 to 1600°C for 4 hours. The erosion agent was replaced every hour during the test. After the test, the corrosion depth of the mud material sample was measured, and an index was calculated for evaluation. Comparative product 1 was set to 100, and the index for each example and comparative example was calculated using the following formula. A smaller index indicates better slag resistance. Slag resistance index = (erosion depth of each test piece ÷ erosion depth of Comparative Example 1) × 100

[0043] In Examples 5 to 9, used alumina shot blast powder with a particle size of greater than 1 mm was used and the blending amount was varied. In Examples 10 to 14, used alumina shot blast powder with a particle size of 0.075 mm to 1 mm was used and the blending amount was varied. In Examples 15 to 22, used alumina shot blast powder with a particle size of less than 0.075 mm was used and the blending amount was varied.

[0044] As shown in Table 2, all of Examples 5 to 22 were excellent in corrosion resistance and pore opening property. [Industrial Applicability]

[0045] The mud material according to the present invention can be suitably used, in particular, as a mud material for plugging a taphole of a blast furnace.

Claims

1. A mud material for plugging tapholes in a blast furnace, comprising alumina shot blast powder used in the processing of steel materials, oxide refractory raw materials (excluding magnesia), carbonaceous raw materials, and silicon nitride raw materials.

2. The mud material for plugging a blast furnace taphole according to claim 1, comprising the alumina shot blast powder in an amount of 2 mass% to 50 mass%.

3. 3. The mud material for plugging a taphole of a blast furnace according to claim 1, wherein the maximum particle size of the alumina shot blast powder is 3 mm or less.

Images