Mud material

Abstract

To provide a mud material capable of satisfying slipperiness, sintering property and excavation property while maintaining and improving corrosion resistance.SOLUTION: The mud material according to the invention contains refractory raw material and binder. The refractory raw material contains fly ash of 0.3 to 18 mass% and silicon nitride raw material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a mudding material particularly suitable for closing the tapping holes of blast furnaces and electric furnaces.

Background Art

[0002] The mudding material used for closing the tapping holes of blast furnaces and electric furnaces is a kneaded refractory in the form of clay that closes the tapping hole after tapping, and contains various refractory raw materials and binders. In recent years, with the increase in the scale and intensification of blast furnaces, an increase in the tapping volume, high-pressure operation, and an extension of the operating years have been demanded, and the usage environment of the mudding material has become severe.

[0003] The following performances are required for the mudding material. · It should have slipperiness that can be easily filled into the tapping hole with a mud gun. · After filling, it should have sinterability that can maintain the closure until the next opening and drillability that can be easily opened. · It should have corrosion resistance such that the expansion of the tapping hole diameter due to molten slag during tapping is small and stable tapping is possible for a long time.

[0004] Due to sinterability and slipperiness, the mudding material generally contains clay-based raw materials. However, clay-based raw materials absorb many binders. Therefore, in order to appropriately maintain the slipperiness of the mudding material containing clay-based raw materials, it is necessary to increase the content of the binder. When this binder volatilizes, the mudding material becomes porous and the corrosion resistance decreases. Also, the corrosion resistance of the mudding material decreases due to low-melting-point compounds formed from the SiO2 component, alkali component, etc. contained in the clay-based raw materials.

[0005] Therefore, various mudding materials have been developed to improve corrosion resistance. For example, Patent Document 1 discloses a tapping hole closing material (mudding material) containing 3% by weight or less of a clay component and 2 - 20% by weight of carbon black. Also, Patent Document 2 discloses a closing material (mudding material) for a blast furnace tapping hole obtained by adding a carbon raw material to a refractory raw material, adding and kneading 1 - 10 parts by weight of amorphous silica ultrafine powder having an average particle diameter of 3 μm or less and an organic binder thereto.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The milling hole plugging material of Patent Document 1 can reduce the content of clay-based raw materials. However, as the content of carbon black increases, the content of the binder also increases. For this reason, the milling hole plugging material becomes porous, and there is a problem that the corrosion resistance decreases. In addition, since carbon black has a large effect of inhibiting sinterability, there is a problem that it is difficult to maintain the plugging.

[0008] In addition, the plugging material of Patent Document 2 has a problem that as the content of ultrafine silica powder increases, the strength increases, and there is a concern that the drillability during opening decreases. In addition, since the amorphous ultrafine silica powder contains a large amount of SiO2 component, a low melting point compound is easily formed, and there is a problem that the corrosion resistance is not sufficiently improved.

[0009] Thus, it has been difficult for conventional mud materials to satisfy slipperiness, sinterability, and drillability while maintaining and improving corrosion resistance. The aspect of the present disclosure has been made in view of the above actual situation, and the object thereof is to provide a mud material that can satisfy slipperiness, sinterability, and drillability while maintaining and improving corrosion resistance.

Means for Solving the Problems

[0010] One aspect of the present disclosure is including a refractory raw material and a binder, wherein the refractory raw material relates to a mud material characterized by including 0.3 to 18% by mass of fly ash and a silicon nitride-based raw material.

[0011] Such a mud material can satisfy slipperiness, sinterability, and drillability while maintaining and improving corrosion resistance.

[0012] In one aspect of the present disclosure, it is preferable that the refractory raw material contains 0.5 to 10% by mass of fly ash and a silicon nitride-based raw material.

Mode for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the present disclosure will be described in detail. It should be noted that the embodiments described below do not unduly limit the content of the present disclosure described in the claims, and not all of the configurations described in the embodiments are essential as the solution means of the present disclosure.

[0014] The mud material of this embodiment includes a refractory raw material and a binder. The refractory raw material includes 0.3 to 18% by mass of fly ash and a silicon nitride-based raw material. Such a mud material can satisfy slipperiness, sinterability, and drillability while maintaining and improving corrosion resistance.

[0015] <Refractory raw material> The refractory raw material of this embodiment is not particularly limited as long as it is generally used in mud materials except for fly ash and silicon nitride-based raw materials. For example, it may include oxide raw materials, carbonaceous raw materials, silicon carbide-based raw materials, etc. Note that fly ash is one type of oxide raw material, and the content of the oxide raw material in this specification includes the content of fly ash.

[0016] <Fly ash> Fly ash is fine-grained and spherical particles obtained by collecting the ash generated when pulverized coal burns in a coal-fired power plant or the like. The main components are SiO2 and Al2O3. The content of fly ash in the refractory raw material is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass. The preferred chemical composition, mineral composition, and particle size of fly ash in this embodiment are described in detail below.

[0017] The chemical composition of fly ash is not particularly limited, but preferably SiO2 is 45 to 70% by mass, more preferably SiO2 is 45 to 60% by mass. Although the detailed reaction mechanism is not clear, when fly ash and silicon nitride raw materials are included in the mud material, SiO2 and Al2O3 in the silicon nitride raw material and fly ash react at a temperature of 1400 °C or higher to form a Si-Al-O-N based compound. Thereby, it is considered that the sinterability is improved and at the same time the corrosion resistance is improved. The chemical composition of fly ash can be measured by Japanese Industrial Standard JIS R 2216 (Fluorescent X-ray Analysis Method for Refractory Products), etc.

[0018] The mineral composition of fly ash is not particularly limited, but preferably quartz is 3 to 15% by mass, more preferably quartz is 5 to 10% by mass. When fly ash contains 3% by mass or more of quartz as the mineral composition, when heated to 1250 °C or higher, microcracks are formed due to the volume expansion accompanying the phase transition from quartz to cristobalite, so over-sintering is suppressed and good workability can be maintained. The content of quartz in fly ash can be measured by the calibration curve method of powder X-ray diffraction using calcium fluoride as an internal standard sample.

[0019] The particle size of fly ash is not particularly limited, but preferably the particle size of 45 μm or less is 60 to 80% by mass, more preferably the particle size of 45 μm or less is 65 to 70% by mass. When the particle size of 45 μm or less is 60 to 80% by mass, fly ash is well dispersed in the mud material, and the binder can be reduced by the ball bearing effect. At the same time, the improvement of the strength during heating can be suppressed. The particle size of fly ash can be measured by laser diffraction particle size distribution measurement.

[0020] <Silicon nitride raw material> Examples of the silicon nitride-based raw materials include silicon nitride obtained by reducing and nitriding silica, silicon nitride obtained by directly nitriding metallic silicon, and ferrosilicon nitride obtained by directly nitriding ferrosilicon. The content of the silicon nitride-based raw material in the refractory raw material is not particularly limited, but is preferably 3 to 45% by mass, more preferably 10 to 40% by mass. When it is 3% by mass or more, the corrosion resistance can be improved, and when it is 45% by mass or less, the cost can be reduced.

[0021] <Oxide raw material> Examples of the oxide raw materials other than fly ash include sintered alumina, fused alumina, bauxite shale, bauxite, chamotte-based raw materials, wollastonite, mullite, andalusite, silica, and silica fume. The content of the oxide raw material in the refractory raw material is not particularly limited, but is preferably 5 to 85% by mass, more preferably 30 to 75% by mass. When it is 5% by mass or more, the porosity can be reduced, and when it is 85% by mass or less, the corrosion resistance can be improved.

[0022] <Carbonaceous raw material> Examples of the carbonaceous raw materials include graphite, amorphous graphite, coal coke, petroleum coke and powders of these cokes, graphite electrode scraps, carbon black, coal pitch, and petroleum pitch. The content of the carbonaceous raw material in the refractory raw material is not particularly limited, but is preferably 1 to 20% by mass, more preferably 4 to 16% by mass. When it is 2% by mass or more, the penetration of slag and over-sintering can be suppressed, and when it is 20% by mass or less, the sinterability can be maintained.

[0023] <Silicon carbide-based raw material> Examples of the silicon carbide-based raw materials include silicon carbide-based raw materials produced by the Acheson method and silicon carbide-based raw materials obtained by reducing and carbonizing silica. The content of the silicon carbide-based raw material in the refractory raw material is not particularly limited, but is preferably 5 to 50% by mass, more preferably 10 to 30% by mass. When it is 5% by mass or more, the corrosion resistance against slag can be improved, and when it is 50% by mass or less, the strength after sintering can be improved.

[0024] <Other raw materials> If it is within the range where the desired properties can be obtained, a clay-based raw material may be included as a refractory raw material to improve the slipperiness. Examples of the clay-based raw material include ball clay, water frog-eye clay, kibushi clay, sericite clay, etc. These clay-based raw materials contain kaolin group minerals (mainly kaolinite {Al2Si2O5(OH)4}, nacrite, dickite, halloysite), and due to the layer structure of this mineral, water and tar components can be incorporated between the layers. Note that if the kaolin group mineral is simply replaced with a compound composed of the chemical components Al2O3 and SiO2, the buffering action of binder retention cannot be exerted. The content of the clay-based raw material in the refractory raw material is not particularly limited, but is preferably 2 to 10% by mass, more preferably 3 to 6% by mass. When it is 2% by mass or more, it can be well dispersed in the mud material and the slipperiness can be improved. When it is 10% by mass or less, the content of binders such as tar, SiO2 components, and alkali components can be reduced, so the porosity and low melting point compounds can be reduced and the corrosion resistance can be improved.

[0025] As other raw materials, one or more kinds of metal powders may be added as necessary. Examples of the metal powder include metallic aluminum, metallic silicon, and metallic aluminum-silicon alloy.

[0026] <Binder> The binder used in the mud material of this embodiment is not particularly limited as long as it is generally used in mud materials. Examples include coal tar, phenolic resin, petroleum pitch, coal pitch, etc. The form is also not particularly limited, and examples include liquids, granules, and powders. Two or more kinds of the binder type and form may be combined.

[0027] <Manufacturing method> A mud material can be manufactured by charging refractory raw materials into a mixer, adding and kneading a predetermined amount of binder and, if necessary, a curing agent or the like. The kneading time is not limited as long as they are sufficiently mixed. For example, 10 to 120 minutes can be mentioned.

Example

[0028] Hereinafter, examples of the present disclosure will be described in detail.

[0029] First, the extrusion load of a mud material containing fly ash with a particle size of 100 μm or less was measured, and the influence of fly ash on the slipperiness was evaluated.

[0030] A mud material containing fly ash with a particle size of 100 μm or less was put into a mold with an inlet diameter of Φ60 mm and an outlet diameter of Φ20 mm, and extruded at a volume rate of 2.82 cm 3 / s with a Marshall tester, and the extrusion load (kgf) was measured. Taking the extrusion load measured at 60 °C as 100 as a reference, the extrusion load measured at 100 °C was indexed. When the index is 100 or less, it can be evaluated that the slipperiness during filling is excellent.

[0031] The index of the mud material containing fly ash with a particle size of 100 μm or less was less than 100, and it was found that the slipperiness during filling was excellent. This is presumably because the fly ash is fine and spherical particles, and exhibits a ball bearing effect.

[0032] Next, refractory raw materials were put into a universal mixer kept at 60 °C, anhydrous tar was added as a binder, and kneaded for about 20 minutes to obtain a mud material. The addition amount of anhydrous tar was adjusted so that the extrusion load of the mud material was 300 ± 50 (kgf / cm 2 ) at 60 °C. The formulation of the refractory raw materials and the binder is shown in Table 1.

[0033] In Examples 1 to 3, the content of fly ash in the refractory raw material was changed. In Examples 4 and 5, the content of fly ash in the refractory raw material was fixed at 5% by mass, and the content of quartz in the fly ash was changed. In Example 6, the content of fly ash in the refractory raw material was fixed at 5% by mass, and the content of SiO2 in the fly ash was reduced. In Examples 7 and 8, the content of fly ash in the refractory raw material was fixed at 5% by mass, and the particle size in the fly ash was changed. In Examples 9 and 10, the content of fly ash in the refractory raw material was fixed at 5% by mass, and the contents of silicon carbide and ferrosilicon nitride were changed. In Example 11, the content of fly ash in the refractory raw material was fixed at 5% by mass, without containing clay raw material and silica ultrafine powder, and the content of carbon black was increased. In Example 12, the content of fly ash in the refractory raw material was fixed at 5% by mass, without containing clay raw material, the content of carbon black was reduced, and the content of silica ultrafine powder was increased. On the other hand, Comparative Examples 1 to 4 did not contain fly ash. Among them, in Comparative Examples 2 and 3, the fly ash of Example 11 was replaced with carbon black and silica ultrafine powder respectively, and in Comparative Example 4, the fly ash of Example 12 was replaced with silica ultrafine powder. In Comparative Examples 5 and 6, the content of fly ash in the refractory raw material was reduced and increased respectively.

[0034] The obtained mud material was put into a mold of 40 mm × 40 mm × 160 mm, pressure molded at 5.0 MPa, and dried at 300 °C for 12 hours to obtain a sample. The following measurements and evaluations were performed on the obtained samples.

[0035] <Flexural strength> The sample was buried in coke breeze and reduction heated at 1500 °C for 3 hours, and a three-point bending test was performed using the apparatus specified in JIS R 2553 (Test method for strength of castable refractories) to measure the flexural strength.

[0036] A larger numerical value of flexural strength means that the sinterability required for closing the tapping hole is obtained. On the other hand, for the drillability during hole opening, a smaller numerical value of flexural strength is preferable. Therefore, the flexural strength was evaluated as follows. 6.0 MPa or more and less than 7.5 MPa: Excellent (◎) Above 7.5 MPa and less than 8.5 MPa: Good (〇) Less than 6.0 MPa or 8.5 MPa and above: Not acceptable (×)

[0037] <Corrosion resistance> The sample was buried in coke breeze, reductively heated at 800 °C for 3 hours, and subjected to a rotary drum erosion test. Pig iron and blast furnace slag (C / S = 1.2) were used as the erosion agents and were replaced every hour. The test temperature was approximately 1550 °C and the test time was 3 hours. After the test, the erosion depth was measured, and the erosion depth of Comparative Example 1 was taken as 100 as a reference for indexing.

[0038] A smaller erosion depth index indicates better corrosion resistance, and the corrosion resistance was evaluated as follows. Less than 90: Excellent (◎) 90 and above and less than 100: Good (〇) 100 and above: Not acceptable (×)

[0039] The results of the measurement and evaluation are shown in Table 1.

Table 1

[0040] For Comparative Example 1 without fly ash, in Examples 1 to 3 where the fly ash content was varied, the addition amount of the binder could be reduced. This is presumably because fly ash has a fine particle size and a spherical shape, thus exhibiting a ball bearing effect. Also, a mud material with excellent corrosion resistance, appropriate strength, and workability was obtained. This is presumably because the main components of fly ash are SiO2 and Al2O3, which react with the silicon nitride raw material at 1500 °C to form Si - Al - O - N - based compounds, promoting sintering and moderately improving the strength. On the other hand, in Comparative Example 5 where the fly ash content was reduced, the effect of reducing the binder was not obtained, resulting in inferior corrosion resistance. This is presumably because the fly ash content was insufficient. Also, in Comparative Example 6 where the fly ash content was increased, while a large effect of reducing the binder was obtained, the flexural strength was high, the workability was poor, and the corrosion resistance was also inferior. This is presumably because the fly ash content was excessive, forming many low - melting - point compounds. From the above, it is considered that the fly ash content in the refractory raw material is 0.3 to 18% by mass, preferably 0.5 to 10% by mass, and more preferably 1 to 5% by mass.

[0041] In Examples 4 and 5, even when the quartz content in the fly ash was varied, the corrosion resistance was excellent and the workability was also good. The mineral composition of fly ash is not particularly limited, but it is considered that preferably quartz is 3 to 15% by mass, and more preferably quartz is 5 to 10% by mass.

[0042] In Example 6, even when the amount of SiO2 component in the fly ash was reduced, the corrosion resistance was excellent and the workability was also good. The chemical composition of fly ash is not particularly limited, but it is considered that preferably SiO2 is 45 to 70% by mass, and more preferably SiO2 is 45 to 60% by mass.

[0043] In Examples 7 and 8, even when the particle size of 45 μm or less in the fly ash was increased or decreased, excellent corrosion resistance and good workability were obtained. In particular, Example 8 in which the particle size of 45 μm or less in the fly ash was reduced resulted in excellent corrosion resistance and workability. The particle size of the fly ash is not particularly limited, but is preferably 60 to 80% by mass with a particle size of 45 μm or less, and more preferably 65 to 70% by mass with a particle size of 45 μm or less.

[0044] In Examples 9 and 10, even when the contents of silicon carbide and ferrosilicon nitride were increased or decreased, excellent corrosion resistance and good workability were obtained. In particular, Example 10 in which the content of ferrosilicon nitride was reduced resulted in excellent corrosion resistance and workability. The content of silicon carbide raw material in the refractory raw material is not particularly limited, but is preferably 5 to 50% by mass, and more preferably 10 to 30% by mass. Also, the content of silicon nitride raw material in the refractory raw material is not particularly limited, but is preferably 3 to 45% by mass, and more preferably 10 to 40% by mass.

[0045] In Example 11, even when the contents of the clay raw material and the silica ultrafine powder were reduced and the content of carbon black was increased, excellent workability and good corrosion resistance were obtained. Also, in Example 12, even when the contents of the clay raw material and carbon black were reduced and the content of silica ultrafine powder was increased, the workability and corrosion resistance were good. On the other hand, Comparative Examples 2 and 3 in which the fly ash of Example 11 was replaced with carbon black or silica ultrafine powder resulted in inferior bending strength and corrosion resistance. This is considered to be due to insufficient sinterability. Also, Comparative Example 4 in which the fly ash of Example 12 was replaced with silica ultrafine powder had too high bending strength, resulting in inferior workability and also inferior corrosion resistance. The content of the clay raw material in the refractory raw material is not particularly limited, but is preferably 2 to 10% by mass, and more preferably 3 to 6% by mass. Also, the content of the carbonaceous raw material in the refractory raw material is not particularly limited, but is preferably 1 to 20% by mass, and more preferably 4 to 16% by mass.

[0046] From the results of Examples 1 to 12, the content of the oxide raw material in the refractory raw material is not particularly limited, but is preferably 5 to 85% by mass, more preferably 30 to 75% by mass.

[0047] Although the present embodiment has been described in detail as above, those skilled in the art will easily understand that many modifications can be made without substantially departing from the novel matters and effects of the present disclosure. Therefore, all such modifications are included in the scope of the present disclosure. For example, in the specification, a term described at least once together with a broader or synonymous different term can be replaced with that different term anywhere in the specification. Further, the configuration of the present embodiment is not limited to that described in the present embodiment, and various modifications are possible.

Claims

Claim 1 comprising a refractory raw material and a binder, wherein the refractory raw material comprises 0.3 to 18% by mass of fly ash and a silicon nitride-based raw material, and is characterized as a ramming material. Claim 2 comprising a refractory raw material and a binder, wherein the refractory raw material comprises 0.5 to 10% by mass of fly ash and a silicon nitride-based raw material, and is characterized as a ramming material.

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