Mud material for filling blast furnace tap hole

Abstract

To provide a mud material for filling a blast furnace tap hole, in which destruction energy is large and occurrence of hole opening can be suppressed by maximizing the function of fibers in the mud material.SOLUTION: A mud material for filling a blast furnace tap hole is formed by adding 1 to 10 mass% of iron-based fibers having a diameter of 0.05 to 2 mm and a length of 5 to 35 mm at an addition rate based on the total of 100 mass% of a refractory raw material. The refractory raw material comprises 5 to 45 mass% of ferrosilicon nitride raw material having a particle size of 75 μm or less; and the balance consists mainly of one or more selected from alumina-based raw materials and silica-based raw materials.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a mud material for filling a blast furnace taphole. In this specification, the "mud material for filling a blast furnace taphole" is also simply referred to as "mud material." [Background technology]

[0002] During blast furnace operation, after the end of tapping, mud material is forced into the taphole to plug it. Then, when the time comes to tap the iron after a predetermined time (usually 2 to 5 hours), the mud material that has been baked by the furnace heat up until that point is drilled to form a runner. When drilling holes in the mud material to form a runner, it is necessary to ensure that the runner is at least a certain length. This length of the runner is called the hole depth.

[0003] In addition, while forming the runner with the drill, the mud material may fall off, causing molten iron or slag to flow into the runner from a different part. In such cases, the tip of the drill becomes worn and it becomes unable to drill. This phenomenon is called hole cut.

[0004] In recent years, there has been a demand to extend the tapping time when tapping hot metal, so it is necessary to prevent the runner from being worn down and enlarged by the molten metal and slag during tapping. The enlargement of the runner due to the wear caused by the molten metal and slag during tapping is called hole enlargement. To extend the tapping time, it is necessary to suppress hole enlargement as well as hole cutting and ensure hole depth.

[0005] The basic structure of mud is a clay-like refractory material obtained by adding a binder to refractory raw materials and kneading them. The addition of fibers to refractory raw materials has also been proposed. For example, Patent Document 1 proposes adding one or more types of fibers made of inorganic or organic materials such as steel, glass, carbon, and resin to ensure hole depth. Patent Document 2 also proposes adding one or more types of fibers made of inorganic or organic materials such as glass, carbon, and resin, with a diameter of 10 to 30 μm and a length of 7000 to 1500 μm, to ensure hole depth. Patent Document 3 also proposes adding carbon fibers to increase the tensile strength of the mud to prevent the structure from collapsing or becoming coarse. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 61-77674 [Patent Document 2] Special Publication No. 2-55395 [Patent Document 3] Japanese Patent Application Publication No. 63-288972 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, Patent Documents 1 and 2 propose adding fibers to the refractory raw materials in order to ensure the hole depth, and Patent Document 3 proposes adding fibers to the refractory raw materials in order to increase the tensile strength of the mud material and thereby prevent the structure from collapsing or becoming coarse. However, it was not entirely clear how the fibers actually function in the mud material and what properties they mainly contribute to improving.

[0008] In this regard, the inventors have conducted a detailed study on the function of fibers in the mud material and have found that the fibers primarily contribute to increasing the fracture energy of the mud material, and as a result, primarily contribute to suppressing the occurrence of the above-mentioned hole breakage.

[0009] In view of the above, the problem that the present invention aims to solve is to provide a mud material for filling blast furnace tapholes that maximizes the functionality of the fibers in the mud material, thereby having a large fracture energy and suppressing the occurrence of hole breakage. [Means for solving the problem]

[0010] The inventors of the present invention have conducted detailed studies on the material and shape of the fibers from the viewpoint of increasing fracture energy, which is the primary function of fibers in mud materials. As a result, they have found that it is effective to use an iron-based material and to set the diameter and length within specific ranges for the shape. Furthermore, they have found that adding iron-based fibers to the refractory raw materials of mud materials reduces corrosion resistance, one of the basic required properties of mud materials, and have found that an effective countermeasure to this problem is to include a specific amount of fine powder of silicon nitride iron in the refractory raw materials.

[0011] That is, according to the present invention, the following mud material for filling a taphole of a blast furnace is provided. A mud material for filling a taphole of a blast furnace, which is obtained by adding iron-based fibers having a diameter of 0.05 to 2 mm and a length of 5 to 35 mm at an addition rate of 1 to 10 mass% relative to 100 mass% of a total amount of refractory raw materials, The refractory raw material is a mud material for filling a blast furnace taphole, containing 5 to 45 mass% of silicon nitride iron raw material having a particle size of 75 μm or less, and the remainder consisting mainly of one or more materials selected from alumina raw materials and silica raw materials. [Effects of the Invention]

[0012] According to the present invention, the fracture energy of the mud material is increased, and as a result, the occurrence of hole breakage can be suppressed. DETAILED DESCRIPTION OF THE INVENTION

[0013] One of the features of the mud material of the present invention is that iron-based fibers having a diameter of 0.05 to 2 mm and a length of 5 to 35 mm are added at a rate of 1 to 10 mass % relative to the total amount of 100 mass % of the refractory raw materials. If the diameter of the iron-based fiber is less than 0.05 mm, the effect of increasing the fracture energy cannot be obtained, while if the diameter of the iron-based fiber is more than 2 mm, the workability when filling the mud material decreases and the corrosion resistance of the mud material decreases. Furthermore, if the length of the iron-based fiber is less than 5 mm, the effect of increasing the fracture energy cannot be obtained, while if the length of the iron-based fiber is more than 2 mm, the workability of filling the mud material decreases. In the present invention, when the fiber is curved or otherwise not linear, the length refers to the entire length along the shape of the fiber.

[0014] In addition to iron-based fibers, organic materials such as resins and inorganic materials such as glass and carbon are known as fiber materials. However, organic fibers burn up in the temperature range where the fiber's fracture energy-increasing effect is particularly needed, i.e., the temperature range (maximum temperature of approximately 500°C) at which the binder in the mud material hardens and develops a predetermined strength, and therefore the fracture energy-increasing effect is not substantially achieved. On the other hand, inorganic fibers can solve the problem of burn-up, but they break during mud material production, specifically when added to the refractory raw material and kneaded with the binder, and their length becomes much shorter than the initial length, resulting in substantially no fracture energy-increasing effect. In the present invention, stainless steel is preferably used as the iron-based fiber material, but carbon steel can also be used.

[0015] If the iron-based fiber content is less than 1% by mass, the effect of increasing the fracture energy cannot be obtained. On the other hand, if the iron-based fiber content exceeds 10% by mass, corrosion resistance and workability during mud filling decrease, and the fracture energy becomes too large, resulting in a decrease in hole opening during tapping. The iron-based fiber content is preferably 2 to 8% by mass.

[0016] As mentioned above, when iron-based fibers are added to the refractory raw material of a mud material, corrosion resistance, which is one of the basic required properties of the mud material, is reduced. Therefore, in the present invention, in order to compensate for the reduction in corrosion resistance caused by the addition of iron-based fibers, the refractory raw material is made to contain 5 to 45 mass% of silicon nitride iron raw material having a particle size of 75 μm or less (hereinafter referred to as "silicon nitride iron fine powder"). If the silicon nitride iron fine powder content is less than 5 mass%, corrosion resistance is insufficient. On the other hand, if the silicon nitride iron fine powder content exceeds 45 mass%, workability during filling of the mud material is reduced. The silicon nitride iron fine powder content is preferably 10 to 40 mass%. In the present invention, the particle size refers to the size of the sieve openings when the refractory raw material particles are sieved to separate them. For example, silicon nitride with a particle size of 75 μm or less refers to silicon nitride that passes through a sieve with 75 μm openings, and silicon nitride with a particle size of more than 75 μm refers to silicon nitride that does not pass through a sieve with 75 μm openings.

[0017] The silicon nitride iron powder not only contributes to improved corrosion resistance but also to increased fracture energy. Specifically, the silicon nitride iron powder reacts with the C component in the mud material or the CO in the blast furnace gas to form SiC bonds. This strengthens the mud material matrix, improving corrosion resistance and increasing fracture energy. The reaction to form these SiC bonds progresses significantly above 1200°C. In other words, while the fracture energy-increasing effect of adding iron-based fibers in the present invention is lost at around 1200°C, the formation of SiC bonds maintains the effect at high temperatures above 1200°C. Thus, in the present invention, the fracture energy-increasing effect is achieved throughout the entire temperature range of the mud material, thereby suppressing the occurrence of hole breakage.

[0018] In the mud material of the present invention, the refractory raw material contains 5 to 45 mass% silicon nitride fine powder, with the remainder, similar to conventional mud materials, primarily consisting of one or more materials selected from alumina-based raw materials and siliceous raw materials. Here, the alumina-based raw material refers to a refractory raw material containing more than 50 mass% Al2O3 as a chemical component, such as alumina and bauxite. The siliceous raw material refers to a refractory raw material containing more than 50 mass% SiO2 as a chemical component, such as silica and pyrophyllite. In the present invention, the remainder of the refractory raw material primarily contains one or more materials selected from these alumina-based raw materials and siliceous raw materials. Specifically, when the remainder of the refractory raw material is taken as 100 mass%, the remainder of the refractory raw material contains more than 50 mass% of the alumina-based raw materials and siliceous raw materials in total. The remainder of the refractory raw materials in the mud material of the present invention may contain, as in conventional common mud materials, carbon raw materials such as coke and carbon black, and other refractory raw materials such as clay, silicon carbide, metallic silicon, etc. The particle size composition of the remainder of the refractory raw materials in the mud material of the present invention is also adjusted appropriately to within a particle size range of 3 mm or less, as in conventional common mud materials.

[0019] The mud material of the present invention is obtained by adding iron-based fibers to the above-mentioned refractory raw material, and then adding a binder and kneading them. Tar-based binders and resin-based binders are known as binders for mud materials, and either binder can be used in the present invention, and it is also possible to use a tar-based binder and a resin-based binder in combination. [Example]

[0020] Table 1 shows the raw material compositions of the mud materials according to the examples of the present invention and the comparative examples, and also shows the evaluation results of workability, fracture energy, and corrosion resistance.

[0021] [Table 1]

[0022] For each example shown in Table 1, iron-based fiber was added to 100% by mass of the total refractory raw materials, except for Comparative Example 9, and carbon fiber was added to Comparative Example 9. A binder was also added and kneaded to obtain mud material samples (hereinafter referred to as "mud material samples"). The mud material samples were used to evaluate workability, fracture energy, and corrosion resistance as follows. The kneading conditions for the mud material sample preparation process were a kneading temperature of 70°C and a kneading time of 20 minutes.

[0023] <Workability> Workability was evaluated using a Marshall test. A stainless steel sample holder was filled with a mud sample kept at 60°C. The sample holder was 220 mm long, had an upper inner diameter of 70 mm, a lower inner diameter of 20 mm, and was funnel-shaped, with the inner diameter tapering from 150 mm from the top. The resistance was measured when the mud sample was extruded from the top of the sample holder at 50 mm / min using an extrusion rod with an outer diameter the same as the upper inner diameter. The workability was evaluated based on the extrusion resistance of Comparative Example 1, i.e., a mud material sample without added fiber, as the standard. When the binder addition rate was adjusted to the same extrusion resistance value, the workability was evaluated on the following four-point scale based on the increase in the binder addition rate, with ◎ or ○ being considered pass. The binder addition rate increment is within 1% by mass. ◎ (Good): When the increase in binder addition rate is 1% by mass or less. ○ (Acceptable): When the increase in binder addition rate is more than 1% by mass and 2% by mass or less. △ (Not acceptable): When the increase in binder addition rate is more than 2% by mass and 2.5% by mass or less, or when the dispersion state of the fiber is poor. × (bad): When the increase in the binder addition rate exceeds 2.5% by mass, or when the fibers cannot be dispersed and kneaded.

[0024] <Destructive Energy> Each mud specimen was molded into a 40 x 40 x 160 mm shape at 60°C and 11 MPa. The specimens were then degreased by heating them at 500°C for a set time while restrained in a metal frame. After natural cooling to room temperature, the fracture energy was evaluated at room temperature. The degreased specimens were then embedded in coke, heated to 1200°C at a rate of 300°C / h, held there for three hours, then naturally cooled and evaluated at room temperature. The fracture energy was evaluated using a three-point bending strength tester, and the area under the stress-strain curve up to 10% of the maximum load was used as the fracture energy. The fracture energy was evaluated on the following four-point scale based on the fracture energy of Comparative Example 1, that is, the mud material sample without added fiber, with ⊚ or ◯ being considered pass. ⊚ (Good): The fracture energy after firing at 500°C and after firing at 1200°C was at least 2 times but less than 20 times that of the case without fiber addition (Comparative Example 1). Good (Acceptable): The fracture energy after firing at 500°C and after firing at 1200°C was 1.5 times or more and less than 2 times that of the specimen without fiber addition (Comparative Example 1). △ (Fail): The fracture energy after firing at 500°C and after firing at 1200°C was 1.2 to less than 1.5 times, or 20 times or more, of that without fiber (Comparative Example 1), respectively. × (bad): The fracture energy after firing at 500°C and after firing at 1200°C was less than 1.2 times that of the sample without fiber addition (Comparative Example 1).

[0025] <Corrosion resistance> Corrosion resistance was evaluated using a rotating drum corrosion test. In the rotating drum corrosion test, mud samples were baked in a reducing atmosphere at 500°C for 4 hours, assembled into a drum, and 100g of blast furnace slag was placed inside the drum as the corrosion material. The drum was then held at 1500-1550°C for 30 minutes. The corrosion material was replaced every 30 minutes, and this test cycle was repeated a total of 10 times. The corrosion depth of the mud samples was measured after the test. The corrosion resistance was evaluated on the following four-point scale based on the corrosion depth of Comparative Example 1, that is, the mud material sample without added fiber, with ⊚ or ◯ being considered acceptable. ⊚ (Good): When the increase rate of the melting damage depth is less than 5% compared to the case where no fiber is added (Comparative Example 1). Good (Acceptable): When the increase in melting damage depth is 5% or more and less than 10% compared to the case without fiber addition (Comparative Example 1). △ (unacceptable): When the increase rate of the melting damage depth is 10% or more but less than 15% compared to the case where no fiber is added (Comparative Example 1). × (bad): When the increase rate of the melt damage depth is 15% or more compared to the case where no fiber is added (Comparative Example 1).

[0026] <Overall rating> The workability, fracture energy, and corrosion resistance were evaluated based on the results, and the evaluation was made on the following four levels, with ◎ or ○ being considered a pass. ◎ (Good): When all evaluation results are ◎. 〇 (Acceptable): At least one evaluation result is 〇, and there are no △ or × evaluations. △ (Fail): At least one evaluation result is △ and there are no × evaluations. × (bad): When at least one of the evaluation results is ×.

[0027] In Table 1, Examples 1 to 3 are examples in which the addition rate of iron-based fibers differs, but all are within the range of the present invention, and good evaluation results were obtained in the evaluation of workability, fracture energy, and corrosion resistance. In contrast, Comparative Example 1 is an example in which no iron-based fibers were added, and the fracture energy was evaluated as × (bad). On the other hand, Comparative Example 2 is an example in which the addition rate of iron-based fibers exceeds the upper limit value of the present invention, and workability and corrosion resistance decreased. Furthermore, the fracture energy of Comparative Example 2 is more than 20 times that of Comparative Example 1, and when filled into the taphole of a blast furnace, there is a problem in that the hole opening during tapping decreases.

[0028] Examples 4 to 7 are examples in which the content of silicon nitride iron fine powder differs, but all are within the range of the present invention, and good evaluation results were obtained in the evaluation of workability, fracture energy, and corrosion resistance. In contrast, Comparative Example 3 is an example that does not contain silicon nitride iron fine powder, and the corrosion resistance was reduced and the fracture energy was evaluated as × (poor).On the other hand, Comparative Example 4 is an example in which the content of silicon nitride iron fine powder exceeds the upper limit of the present invention, and the workability was reduced and the fracture energy was insufficient.

[0029] Examples 8, 2 and 9 are examples in which the diameter of the iron-based fiber is different, but all are within the range of the present invention, and good evaluation results were obtained in all evaluations of workability, fracture energy and corrosion resistance. In contrast, Comparative Example 5 is an example in which the diameter of the iron-based fiber is below the lower limit of the present invention, and the fracture energy was evaluated as × (poor).On the other hand, Comparative Example 6 is an example in which the diameter of the iron-based fiber is above the upper limit of the present invention, and workability and corrosion resistance were reduced.

[0030] Examples 10, 2, and 11 are examples in which the length of the iron-based fiber is different, but all are within the scope of the present invention, and good evaluation results were obtained in all evaluations of workability, fracture energy, and corrosion resistance. In contrast, Comparative Example 7 is an example in which the length of the iron-based fiber is below the lower limit of the present invention, and the evaluation of the fracture energy was × (bad).On the other hand, Comparative Example 8 is an example in which the length of the iron-based fiber is above the upper limit of the present invention, and the workability was reduced.

[0031] Comparative Example 9 is an example in which the iron-based fiber was replaced with carbon fiber in the mud material of Example 2. The carbon fiber broke during kneading, and its length became much shorter than the initial length, resulting in an evaluation of fracture energy of × (bad).

Claims

1. A mud material for filling a taphole of a blast furnace, comprising: an iron-based fiber having a diameter of 0.05 to 2 mm and a length of 5 to 35 mm, added at an addition rate of 1 to 10 mass% relative to a total amount of 100 mass% of a refractory raw material; The refractory raw material is a mud material for filling a blast furnace taphole, containing 5 to 45 mass% of silicon nitride iron raw material having a particle size of 75 μm or less, and the remainder consisting mainly of one or more materials selected from alumina raw materials and silica raw materials.

2. The blast furnace taphole filling mud material according to claim 1, wherein the content of the silicon nitride iron raw material having a particle size of 75 μm or less is 10 to 40 mass %.

3. The blast furnace taphole filling mud material according to claim 1 or 2, wherein the iron-based fiber has a diameter of 0.1 to 1 mm, a length of 10 to 30 mm, and an addition rate of the iron-based fiber of 1 to 10 mass%.

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