Porous refractory for porous plug, and porous plug

Abstract

The present invention provides a porous refractory for a porous plug having high air permeability and excellent durability, and a porous plug. Specifically, the present invention provides: a porous refractory 11 for a porous plug, the porous refractory containing, as refractory raw materials, at least 85 mass% of coarse particles having a particle diameter of 0.5 mm to 3 mm (exclusive of 3 mm), at most 10 mass% (including 0 mass%) of medium particles having a particle diameter of 0.1 mm to 0.5 mm (exclusive of 0.5 mm), and 5 mass% to 15 mass% (exclusive of 15 mass%) of fine particles having a particle diameter of less than 0.1 mm, wherein the porous refractory has an air permeability of at least 2×10-11 m2; and a porous plug 1 that is at least partially composed of the porous refractory 11 for a porous plug.

Description

Porous refractory material for porous plugs and porous plugs

[0001] The present invention relates to a porous refractory material and a porous plug, which are refractory components for blowing gas into molten metal in a molten metal container.

[0002] In the metal refining process, molten metals such as molten steel are subjected to bubbling with gases such as inert gases or oxygen gases to control the chemical composition of the molten metal, equalize the temperature, and separate inclusions by flotation. In this process, a refractory component containing porous refractory material called a porous plug (gas purging plug) is sometimes attached to the bottom of the container (molten steel ladle, etc.), and inert gases are blown in through the pores inside the porous refractory material.

[0003] It has long been believed that increasing the permeability of porous refractories is effective in improving refining efficiency and bubbling reliability. On the other hand, while increasing the pore size is effective in increasing permeability, as the pore size increases, molten metal (hereinafter referred to as "metal") is more likely to penetrate, so it has been said that there is a trade-off relationship between permeability and resistance to metal penetration (for example, Patent Documents 1 and 2). Patent Document 2 discloses an example in which the pore size is increased to increase the amount of air permeability, but crushed particles are used to suppress metal penetration. However, when crushed particles are used, the permeability tends to decrease compared to ordinary particles, so there is a problem that the amount of air permeability does not increase as much as the pore size increases.

[0004] JP-A-9-52168 Patent No. 7094238

[0005] The problem that this invention aims to solve is to provide a porous refractory material for porous plugs and a porous plug that has a high air permeability and high durability.

[0006] The inventors of this invention found that, contrary to the trade-off that increasing pore size makes materials more susceptible to metal infiltration, the actual cessation of metal infiltration is predominantly due to metal solidification caused by temperature gradients, and the effect of pore size is small. Furthermore, they discovered that increasing the air permeability suppresses excessive dissolution during the oxygen washing stage when the infiltrated area is dissolved and removed, thereby reducing wear, and thus completed the present invention.

[0007] In other words, according to one aspect of the present invention, the following porous refractory material for porous plugs is provided. The refractory raw material contains 85% by mass or more of coarse grains with a particle size of 0.5 mm or more and less than 3 mm, 10% by mass or less of medium grains with a particle size of 0.1 mm or more and less than 0.5 mm (including 0% by mass), and 5% by mass or more and 15% by mass or less of fine grains with a particle size of less than 0.1 mm, and has an air permeability of 2 × 10⁻⁶ －１１ I understand ２ That concludes the description of porous refractory material for porous plugs.

[0008] Furthermore, according to another aspect of the present invention, a porous plug is provided which is at least partially composed of the porous refractory material for porous plugs according to the present invention.

[0009] According to the present invention, it is possible to provide porous refractory materials and porous plugs that have high air permeability and high durability. This makes it possible to simultaneously achieve improved refining efficiency and reduced costs.

[0010] A schematic cross-sectional view of a porous plug using the porous refractory material for porous plugs according to the present invention.

[0011] The porous refractory material for porous plugs according to the present invention (hereinafter also referred to as "porous brick") is mainly manufactured from relatively high-purity refractory raw materials with a refractoriness of 1500°C or higher, such as alumina, mullite, silica, magnesia, zirconia, and chromia. Specifically, these refractory raw materials are adjusted to a predetermined particle size configuration, then a binder is added to the refractory raw materials, kneaded and molded, and then subjected to appropriate heat treatment to obtain the porous brick. In the present invention, the particle size configuration of the refractory raw materials is adjusted so that 85% by mass or more of coarse grains with a particle size of 0.5 mm or more and less than 3 mm, 10% by mass or less of medium grains with a particle size of 0.1 mm or more and less than 0.5 mm (including 0% by mass), and 5% by mass or more and 15% by mass or less of fine grains with a particle size of less than 0.1 mm. By adjusting the particle size configuration of the refractory raw materials in this way, the air permeability of the porous brick is increased to 2 × 10⁻⁶ －１１ I understand ２ The above can be achieved. And the permeability of the porous brick is 2 x 10 －１１ I understand ２ By doing so, it is possible to achieve both high air permeability and excellent resistance to metal penetration. Furthermore, from the viewpoint of stably ensuring high air permeability and high air volume, it is preferable that the apparent porosity of the porous brick be 28% or higher.

[0012] In this invention, the particle size of the refractory raw material refers to the size of the sieve opening when the refractory raw material is separated by sieving. For example, a refractory raw material with a particle size of less than 0.5 mm is a refractory raw material that passes through a sieve with an opening of 0.5 mm, and a refractory raw material with a particle size of 0.5 mm or more is a refractory raw material that does not pass through a sieve with an opening of 0.5 mm.

[0013] Figure 1 conceptually shows a porous plug using the porous brick of the present invention in cross-section. The porous plug 1 shown in the figure has its central part composed of the porous brick 11 of the present invention. In Figure 1, reference numeral 12 denotes a dense brick, reference numeral 13 denotes a metal case, and reference numeral 14 denotes a gas introduction pipe. This porous plug 1 is used, for example, to be attached to a molten steel ladle and to blow in an inert gas supplied from the gas introduction pipe 14. Note that the configuration of the porous plug shown in Figure 1 is just one example, and the configuration of a porous plug using the porous brick of the present invention is not limited to this. For example, the single-stage porous brick 11 shown in Figure 1 can be made into a two-stage structure, with the porous brick of the present invention used only in the upper stage.

[0014] The following shows examples and comparative examples that were actually obtained. Based on the particle size composition of the refractory raw materials shown in each table (mixing ratio of coarse, medium, and fine particles), and the evaluation results of the apparent porosity, permeability, and amount of wear due to oxygen washing of the obtained porous bricks, the gist of the present invention will be reinforced and the usefulness as a porous plug will be specifically explained. Here, the porous bricks in each example shown in each table were produced by adding phenolic resin as a binder to the refractory raw materials in each example shown in each table, kneading them in a mixer, then press-molding them in a 500t oil press, drying them, and firing them at 1500°C for 5 hours.

[0015] The apparent porosity and air permeability of the porous bricks were measured in accordance with JIS-R2205 and JIS-R2115, respectively. In addition, the evaluation of the amount of wear associated with oxygen lancing was carried out according to the following procedure. A porous plug test piece produced by incorporating a porous brick having a cylindrical shape with a tip diameter of 45 mm and a length of 120 mm is immersed in molten steel at 1600°C melted in a high-frequency induction furnace, and vacuum suction is performed from the back surface to allow molten steel to penetrate into the pores of the porous brick. After holding this state for about 10 minutes, the test piece is pulled out of the molten steel, and oxygen lancing is performed while flowing nitrogen gas from the back surface at a pressure of 0.1 MPa. The oxygen lancing is stopped when the nitrogen gas flow rate reaches 100 NL / min, and after cooling, the test piece is cut and the cross-section is observed. At this time, the metal penetration depth and the maximum wear depth due to oxygen lancing were measured, and the sum thereof was taken as the wear amount. The evaluation was performed by marking cases where the wear amount was less than 45 mm as ⊚ (excellent), cases where the wear amount was 45 mm or more and less than 50 mm as ○ (good), and cases where the wear amount was 50 mm or more as × (poor), and ⊚ or ○ were regarded as acceptable.

[0016]

[0017] Table 1 shows examples in which the blending ratio of coarse particles, medium particles and fine particles, that is, the particle size composition of the refractory raw material, was changed. All of Examples 1 to 5 shown in Table 1 have the particle size composition of the refractory raw material within the scope of the present invention, and the air permeability is 2×10 －１１ m ２ or more, the wear amount was as small as about 42 to 47 mm, and high durability was exhibited. On the other hand, in Comparative Example 1, the content of coarse particles was as low as 80% by mass, and the air permeability was 1.7×10 －１１ m ２ , and the wear amount increased to 54 mm. Further, in Comparative Example 2, the content of medium particles was as high as 12% by mass and the content of fine particles was as low as 3% by mass, and the air permeability was 1.9×10 －１１ m ２ , and the wear amount also reached 52 mm. These results show that by adopting the particle size composition of the present invention, high air permeability is secured and wear amount is suppressed.

[0018]

[0019] Table 2 shows examples where the proportion of particles with a particle size of 0.5 mm or more and less than 2 mm was varied within the coarse grains. Specifically, in Examples 6 to 10 shown in Table 2, the coarse grain content in the refractory raw material was set to 90% by mass, and the proportion of particles with a particle size of 0.5 mm or more and less than 2 mm within the coarse grains was varied within the range of 70 to 90% by mass. As a result, the air permeability was 2.1 × 10⁻⁶. －１１ I understand ２ ~2.4 x 10 －１１ I understand ２ As a result, the amount of wear was 46 mm or less in all cases. Furthermore, in Examples 7 to 10, where the proportion of coarse particles with a particle size of 0.5 mm or more and less than 2 mm was 75% by mass or more, the air permeability was further increased, and the amount of wear could be reduced to 44 mm or less, indicating a more preferable configuration.

[0020]

[0021] Table 3 shows examples where the content of medium-sized particles in the refractory raw material is varied. Specifically, in Examples 1, 2, and 11 shown in Table 3, the content of medium-sized particles is 5% by mass, 10% by mass, and 7% by mass, respectively. The air permeability is 2.1 × 10⁻⁶. －１１ I understand ２ ~2.4 x 10 －１１ I understand ２ As a result, the amount of wear was 47 mm or less in all cases. Furthermore, in Example 1, where the content of medium grains was 5% by mass or less, a high air permeability was ensured, and the amount of wear could be reduced to 42 mm, indicating a more preferable configuration.

[0022]

[0023] Table 4 shows examples where the content of fine particles in the refractory raw material was varied. Specifically, in Examples 1, 2, 5, and 12 shown in Table 4, the content of fine particles was 10% by mass, 5% by mass, 15% by mass, and 12% by mass, respectively. Fine particles greatly contribute to sinterability and pore formation, and a comparison between Example 5 and Example 12 confirms that by adjusting the content of fine particles to 12% by mass or less, an optimal pore structure can be obtained, achieving both high permeability and low wear.

[0024] The porous brick according to the present invention can be used not only in steel refining but also as a refractory material in non-ferrous metal refining and other applications. As described above, by obtaining a porous refractory material for porous plugs that satisfies the constituent requirements of the present invention, it is possible to simultaneously achieve improved refining efficiency by gas bubbling and high durability. Such porous plugs that combine high permeability and high durability are extremely useful in the field of metal refining.

[0025] 1. Porous plug 11. Porous brick (porous refractory material for porous plugs) 12. Dense brick 13. Metal case 14. Gas introduction pipe

Claims

1. As a refractory raw material, it contains 85% by mass or more of coarse grains with a particle size of 0.5 mm or more and less than 3 mm, 10% by mass or less of medium grains with a particle size of 0.1 mm or more and less than 0.5 mm (including 0% by mass), and 5% by mass or more and 15% by mass or less of fine grains with a particle size of less than 0.1 mm, with an air permeability of 2 × 10⁻⁶ －１１ I understand ２ That concludes the description of porous refractory material for porous plugs.

2. The porous refractory material for porous plugs according to claim 1, wherein the proportion of particles with a particle size of 0.5 mm or more and less than 2 mm among the coarse grains is 75% by mass or more.

3. The porous refractory material for porous plugs according to claim 1 or 2, wherein the content of the medium grains in the refractory raw material is 5% by mass or less (including 0% by mass).

4. The porous refractory material for porous plugs according to claim 1 or 2, wherein the content of the fine particles in the refractory raw material is 5% by mass or more and 12% by mass or less.

5. A porous plug comprising at least a portion of the porous refractory material for porous plugs described in claim 1 or 2.

Images