JP2019119653A - Castable refractory for blast furnace trough - Google Patents

Abstract

To enhance the generation of 9AlO2BO(9A2B) in a castable refractory for blast furnace trough.SOLUTION: A castable refractory for blast furnace trough contains alumina and/or silicon carbide, carbon raw material, and boron carbide, in which, when total amount of whole particles is set to 100 mass%, the castable refractory for blast furnace trough contains 5 to 36 mass% of alumina with a particle diameter of less than or equal to 75 μm, 0.3 to 4 mass% of boron carbide, calcium oxide of less than or equal to 0.5 mass% (including zero), carbon raw material of less than or equal to 10 mass%, and 5 to 15 mass% of an inorganic colloidal liquid by outer percentage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to castable refractories for use as linings of blast furnace weirs.

  The blast furnace crucible is a flow path for transferring the molten iron and slag discharged from the blast furnace to a predetermined place. Alumina-silicon carbide-carbonaceous castable refractories are generally used for the lining. The castable refractories for blast furnace crucibles are required to have improved corrosion resistance and wear resistance to slag and pig iron, and improvements on the composition are in progress.

  Patent Document 1 uses a silicon carbide aggregate having a SiC content of 70 wt% or more and a porosity of 10% or less, a filling bulk specific gravity of 1.25 or more for coarse particles, and 1.60 or more for medium particles, A dispersant containing 70 to 90 wt% silicon, 1 to 7 wt% carbonaceous material, 0.8 to 5 wt% boron carbide, 5 to 20 wt% alumina fine powder and 0.5 to 5 wt% ultrafine silica powder, Disclosed is a cast refractory for blast furnace outlay added with a binder.

9Al ₂ O ₃ · 2B ₂ O ₃ (following 9A ₂ B and 9 Al ₂ O ₃ · 2B ₂ O ₃ in which mullite (3Al ₂ O ₃ · 2SiO ₂ ) is solid-solved by the reaction of B ₂ O ₃ generated from the boron carbide and Al ₂ O ₃ and SiO ₂ The columnar crystals (not shown) precipitate so as to be entangled in the matrix portion and the voids, and the porosity is significantly reduced, and the high temperature hot strength is improved, and the wear resistance can be improved.

Patent document 2 contains 0.1 mass% or more and 3 mass% or less of boron carbide and 2 mass% or less of silicon as an antioxidant, and CaxSr1-xAl ₂ O ₄ and / or CaySr1-yAl as a binder. Disclosed is an alumina-silicon carbide-carbon-based amorphous refractory containing 1% by mass or more and 10% by mass or less of a component having the chemical composition (0 <x <1, 0 <y <1) of ₄ O ₇ .

Strontium (Sr) contained in the CaO-SrO-Al ₂ O ₃ based oxide has an extremely low chemical affinity with boron (B), so it does not react with the boric acid melt formed by oxidizing boron carbide. It is said that the oxidation resistance and the corrosion resistance of the refractory can be improved without inhibiting the function of preventing oxidation of carbon of boron carbide.

Patent Document 3 contains 10% by mass or more and 40% by mass or less of an Al ₂ O ₃ component contained in a raw material having a SiC component of 40% by mass to 80% by mass and a particle diameter of 45 μm or more, and 0.3% by mass of a B ₄ C component. % by weight or more 3.0 wt% or less, the content of Al ₂ O ₃ component contained in the raw material having a particle size of less than 45μm discloses a blast furnace trough for castable or less 6.9 wt%.

Since the content of the Al ₂ O ₃ component contained in the raw material having a particle diameter of less than 45 μm is limited to 6.9% by mass or less in the total amount of 100% by mass of the chemical components of the castable refractories for blast furnace slag, 9A2B is formed It is said that it is possible to prevent the occurrence of cracking and peeling of the construction body.

JP-A-3-164479 Unexamined-Japanese-Patent No. 2017-19673 JP, 2014-152092, A

According to Patent Document 1, addition of boron carbide makes precipitation of 9A2B smooth and improves the hot strength at high temperature to improve wear resistance. However, although it is considered that the crystal phase to be deposited changes largely depending on the type of binder as described later, there is no specific disclosure of the binder in this document, and 9A2B in which 3Al ₂ O ₃ .2SiO ₂ is dissolved is generated. The method is not clear.

  The patent document 2 uses a strontium-containing material as a binder in order to maintain the anti-oxidant function of boron carbide to carbon. However, strontium is a rare metal, and it is not preferable to use it for refractory applications that are consumed in large quantities from the viewpoint of the cost of the product or from the viewpoint of the effective use of resources.

Patent Document 3, in order to suppress the generation of the 9A2B, but limits the content of the Al ₂ O ₃ component contained in the raw material of particle size less than 45 [mu] m, rather hot strength when suppressing the formation of 9A2B And wear resistance is degraded, which is not preferable.

  The present invention has been proposed in view of the above-mentioned conventional circumstances, and makes it possible to smoothly form 9A2B in a castable refractory for blast furnace crucible and to improve the hot strength to thereby improve the wear resistance and the corrosion resistance. It is an object of the present invention to obtain a castable refractory for blast furnace crucible which is excellent in the above.

  The present invention reduces the alumina cement as a binder and uses an inorganic colloid solution to reduce the Ca content and promote the formation of 9A2B.

  That is, the present invention is a castable refractory for blast furnace crucible containing alumina and / or silicon carbide, a carbon raw material, and boron carbide, and when the total amount is 100% by mass, alumina having a particle size of 75 μm or less is 5 ~ 36% by mass, boron carbide 0.3-4% by mass, calcium oxide 0.5% by mass or less (including zero), carbon raw material 10% by mass or less It is a castable refractory for blast furnace kilns containing 5-15 mass%.

  It is preferable to use a silica sol as the inorganic colloid.

  By reducing the amount of alumina cement and using an inorganic colloid as a binder, the amount of Ca component is reduced, the formation of liquid phase is suppressed, and the formation of 9A2B is promoted. As a result, a compact construction body is obtained, and hot strength improvement, corrosion resistance and wear resistance improvement can be obtained.

The electron micrograph of the torn surface after the hot bending test of Example 1. FIG. The electron micrograph of the torn surface after the hot bending test of Comparative Example 1. FIG.

  The present invention is a castable refractory for blast furnace kilns comprising alumina and / or silicon carbide, a carbon source and boron carbide.

<Principle>
As described above, it is considered better to form 9A2B to improve the hot strength of this castable refractory. As a result of examining in detail the formation conditions and physical properties of 9A2B, it was recognized that the Ca component in the castable would react with B ₂ O ₃ derived from boron carbide and be consumed, thus inhibiting the formation of 9A2B. Therefore, it has been recognized that the generation of 9A2B is effectively promoted, the hot strength is significantly improved, and the wear resistance is improved by reducing the Ca component in the raw material.

<Composition>
The purity of the silicon carbide raw material is preferably 85% by mass or more, more preferably 90% by mass or more, in order to reduce liquid phase formation due to impurities.

  As the alumina raw material, calcined alumina, fused alumina, sintered alumina, bauxite, bare earth shale and the like can be used alone or in combination. Further, the purity of the alumina raw material is preferably 90% by mass or more, and more preferably 95% by mass or more in order to reduce liquid phase formation due to impurities.

Alumina raw materials having a particle diameter of 1 mm or more, or 75 μm to 1 mm can be replaced with silicon carbide of the same diameter as the whole (see Example 11).
The alumina having a particle size of 75 μm or less (passing a sieve with a nominal opening of 75 μm) is preferably 5 to 36% by mass, and more preferably 7 to 36% by mass. If the amount is less than 5% by mass, the amount of 9A2B formed is reduced and the hot strength is unfavorably reduced. On the other hand, if it exceeds 36% by mass, sintering shrinkage becomes large, and cracks occur, which is not preferable.

  The purity of boron carbide is preferably 90% by mass or more, more preferably 95% by mass or more, in order to reduce liquid phase formation due to impurities.

The boron carbide having a particle diameter of 75 μm or less is preferably 0.3 to 4% by mass, and more preferably 0.6 to 2.5% by mass. If the amount of boron carbide is less than 0.3% by mass, 9A2B is not sufficiently generated and the hot strength is inferior. If it is more than 4% by mass, a boron-derived liquid phase which does not become 9A2B is generated and the hot strength is inferior. Besides boron carbide, boron-containing raw materials such as B ₂ O ₃ , ZrB ₂ , MgB ₂ and BN can also be used.

  Incidentally, by setting the particle diameter of the alumina and the boron carbide to 75 μm or less, 9A 2 B can be effectively produced by reaction.

  As a carbon raw material, carbon black, pitch, coke, phosphorous graphite and the like can be used alone or in combination. 10% or less of the carbon raw material which passes the said 75-micrometer nominal sieve is preferable. The purity of the carbon raw material is preferably 80% by mass or more, more preferably 95% by mass or more, in order to reduce liquid phase formation due to impurities.

  The calcium oxide having a particle diameter of 75 μm or less is preferably 0.5% by mass or less, and more preferably 0.125% by mass or less. When the content of calcium oxide exceeds 0.5% by mass, it reacts with boron originating from boron carbide to reduce the formation of 9A2B and cause a decrease in hot strength.

  The overall grain size configuration can be adjusted accordingly depending on the construction characteristics. When the preferable particle size configuration is exemplified, the whole is 100% by mass, 20 to 60% by mass of less than 0.3 mm, 3 to 17% by mass of 0.3 to 1 mm, 23 to 77% by mass of 1 mm, more preferably Of less than 0.3 mm is 30 to 50% by mass, 0.3 to 1 mm is 5 to 15% by mass, and 1 mm or more is 35 to 65% by mass.

  As an additive, a dispersing agent, a curing time regulator, an anti-crack agent, etc. can be used.

  Examples of the dispersant include substances generally used for amorphous refractories, such as alkali metal phosphate, alkali metal carboxylate, alkali metal humate, naphthalene sulfonic acid formalin condensate salt, polycarboxylate and the like, and , Substances which can obtain the same effect as these can be used. Moreover, multiple types of dispersants can be used in combination.

  The curing time adjuster includes a curing accelerator and a curing retarder. As the curing accelerator, for example, slaked lime, calcium chloride, gypsum, magnesia, sodium aluminate, lithium carbonate and the like can be used, and a plurality of curing accelerators can be used in combination. As the curing retarder, for example, boric acid, oxalic acid, citric acid, gluconic acid, sodium carbonate, sugar and the like can be used, and a plurality of curing retarders can be used in combination. For example, aluminum lactate, an organic fiber or the like can be used as the explosion-proof agent, and a plurality of explosion-proof agents can be used in combination.

As the inorganic colloid solution, silica sol, alumina sol, zirconia sol and the like can be used alone or in combination. Inorganic colloid solution and water can also be mixed and used. When a silica sol is used, one having a SiO ₂ concentration of 20 to 40% by mass can be suitably used.

  A knoWn method can be adopted for kneading the raw materials. For example, a vortex mixer, a mortar mixer, an omni mixer, etc. can be used. Further, additives such as a curing agent, a dispersing agent, a curing time regulator, an anti-crack agent, an antioxidant and the like can be separately added without being mixed with the refractory material.

<Example>
Examples and comparative examples are shown in Table 1, and comparative examples are shown in Table 2 to explain the superiority of the castable refractory for blast furnace gutter of the present invention. The present invention is not limited to the following examples.

  Boron carbide having a purity of 95% by mass was used. The alumina used had a purity of 99% by mass. The alumina cement used that whose CaO content is 25 mass%. Silicon carbide having a purity of 97% by mass was used. As a carbon raw material, coal tar pitch having a softening point of 110 ° C. and a fixed carbon of 60% by mass was used. As the silica sol, one having a SiO2 concentration of 30% by mass was used. Further, as various additives, dispersants such as alkali metal phosphates and naphthalenesulfonic acid formalin condensate salt based dispersants, and organic fibers as anti-bursting agents were added.

  The amount of calcium oxide in Examples 1 to 3 is within the scope of the present invention. In Comparative Example 1, the amount of calcium oxide is outside the scope of the present invention.

  Examples 4 to 7 have boron carbide amounts within the scope of the present invention. In Comparative Examples 2 and 3, the amount of boron carbide is outside the scope of the present invention. In Examples 8 to 10, the amount of alumina having a particle size of 75 μm or less is within the range of the present invention. In particular, Example 10 uses the entire amount of alumina. The amount of alumina of Comparative Example 4 is outside the range of the present invention. The present invention relates to Example 11 in which the particle diameter of alumina is 75 μm to 1 mm, and 1 mm or more is zero, and 7% by mass of silicon carbide having a particle diameter of 75 μm to 1 mm and 53% by mass of silicon carbide of 1 mm or more. Within the scope of Water or silica sol was added to these compounding materials, and the flow value was adjusted to 120 to 160 according to JIS R 2521.

  The kneaded material was poured into a 40 × 40 × 160 mm mold, aged at 30 ° C. for 24 hours and then deframed, and dried at 110 ° C. for 24 hours to obtain a sample. The sample was subjected to one heating and natural cooling at 1500 ° C. for 3 hours in coke breeze, and then the hot bending strength was measured according to JIS R 2656. The test was performed in a nitrogen atmosphere. The sample having a hot bending strength of more than 2.5 MPa was evaluated as ◎, the sample having 1.5 to 2.5 MPa as ○, and the sample having less than 1.5 MPa as x. It can be understood that the example has excellent hot bending strength as compared with the comparative example.

  The fractured surface after the hot bending test was observed with an electron microscope. In Example 1 having a composition within the scope of the present invention, a large amount of 9A2B (needle-like crystals) is formed on the fracture surface (FIG. 1), which is consistent with the result of high hot strength. Further, in Comparative Example 1 having a composition outside the scope of the present invention, 9A2B was not generated on the fracture surface (FIG. 2), and the hot strength was low. It was confirmed that the composition within the scope of the present invention promotes the formation of 9A2B and significantly improves the hot bending strength.

As described above, the present invention promotes the formation of the 9Al ₂ O ₃ · 2B ₂ O ₃ component in which mullite is solid-solved by reducing the Ca component, so a castable for blast furnace crucibles having high hot strength. You can get

That is, the present invention is a castable refractory for blast furnace crucible containing alumina and / or silicon carbide, a carbon raw material, and boron carbide, and when the total amount is 100% by mass, alumina having a particle size of 75 μm or less is 5 to 36% by weight, mean particle diameter of 75μm or less of boron carbide is 0.3 to 4 wt%, less calcium oxide particle size 75μm or less 0.5 wt% (including zero), the particle size 75μm or less of the carbon raw material It is 10 mass% or less, and is a castable refractory for blast furnace gutter which further contains 5 to 15 mass% of inorganic colloid liquid outside.

Claims (3)

  A castable refractory for blast furnace crucible containing alumina and / or silicon carbide, a carbon raw material, and boron carbide, and when the total amount of all particles is 100% by mass, the alumina having a particle diameter of 75 μm or less is 5 to 5 36% by mass, boron carbide 0.3 to 4% by mass, calcium oxide 0.5% by mass or less (including zero), carbon raw material 10% by mass or less Castable refractories for blast furnace kilns characterized by containing -15 mass%.   The castable refractory for blast furnace kiln according to claim 1, wherein the inorganic colloid is silica sol. The castable refractory for blast furnace gutter according to claim 1, wherein B ₂ O ₃ , ZrB ₂ , MgB ₂ or BN is used in place of or in addition to the boron carbide.