JP2018058727A - Water-based fireproof joint mortar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve corrosion resistance while preventing hydration reaction of metal Al-containing powder from occurring, with a simple method, in an aqueous fire-proof mortar containing the metal Al-containing powder.SOLUTION: An aqueous fire-proof mortar comprises, in external addition to a fire-proof material: 0.1-10 mass% of a metal Al-containing powder; and 0.01-2 mass% of at least one of boric acid, borate, and carboxylic acid. The at least one of boric acid, borate, and carboxylic acid forms a protective colloid around the metal Al-containing powder, thereby preventing hydration reaction of the metal Al-containing powder from occurring.SELECTED DRAWING: None

Description

  The present invention relates to a water-based refractory mortar suitable for use in various kilns used in the steel industry, the industrial waste treatment industry, and the like. The water-based refractory mortar means a refractory mortar that uses water during kneading.

Conventionally, as refractories for kilns such as hot metal ladle, molten steel ladle, DH, RH, and incinerator, regular refractories, especially carbon-containing refractories, are frequently used. For the purpose of improving strength and corrosion resistance, this carbon-containing regular refractory is mixed with metal Al powder, or metal Al alloy powder such as metal Al-Si powder, metal Al-Mg powder, etc. during refractory blending. This is already well known (in this specification, metal Al powder and metal Al alloy powder are collectively referred to as metal Al-containing powder). And it is thought that the action mechanism of the performance improvement by mixing | blending of these metal Al containing powder is as follows.
(A) A strengthened structure (bond) of aluminum carbide (Al ₄ C ₃ ) is generated under a high temperature atmosphere during use.
(B) The metal Al-containing powder is oxidized in a high-temperature atmosphere to make the refractory matrix dense.
(C) The metal Al-containing powder is oxidized preferentially over carbon and acts as an antioxidant for carbon.

  On the other hand, refractory joint mortar is generally used when lining a regular refractory in a kiln. However, since conventional refractory joint mortars are inferior in corrosion resistance to regular refractories, there is a problem that the refractory joint mortar part is premelted and the life of the entire furnace is reduced.

  Therefore, it is conceivable that the metal Al-containing powder is blended in the refractory joint mortar similarly to the above-mentioned carbon-containing regular refractory, and the corrosion resistance is improved by the action mechanisms (a) to (c) described above.

  However, in the case of water-based refractory joint mortar, even if the metal Al-containing powder is simply blended, a sufficient effect of improving corrosion resistance cannot be obtained. Because, in the case of water-based refractory joint mortar, unlike the regular refractory that press-molds almost without using water, since water is used during kneading, the metal Al-containing powder reacts violently with water (hydration reaction), This is because hydrogen gas is generated.

  Here, Patent Document 1 shows that the corrosion resistance is improved by adding metal Al-containing powder to the water-based refractory joint mortar. However, as a practical use situation of the water-based refractory joint mortar, since it may be left after being kneaded with water on the day before the construction date, the metal Al-containing powder is in contact with water for a long time. . As a result, the metal Al-containing powder generates hydrogen gas by a hydration reaction with intense heat when left standing, and loses fluidity, which is an important characteristic as a refractory joint mortar. Furthermore, if it is left in a hot season such as summer, the hydration reaction occurs remarkably, and an explosion accident due to hydrogen gas may occur.

  Patent Document 2 describes that boric acid, borates, silicates, and the like are effective in suppressing the hydration reaction of metal Al powder with water. However, Patent Document 2 has the main content of adding metal Al powder as an anti-explosion agent to the castable for the purpose of preventing the explosion of the castable, and for the convenience that the castable must be self-curing. In the situation where a coagulant (lime aluminate: alumina cement) is added, the metal Al powder eventually generates heat while generating hydrogen gas, which is the purpose of this document. It functions as. That is, in Patent Document 2, it is premised that hydrogen gas is finally generated by hydrating a metal Al powder. However, when the metal Al powder is changed to aluminum hydroxide by the hydration reaction, the above-mentioned action mechanisms (a) to (c) can no longer be obtained.

  For this reason, in Patent Document 3, a boehmite layer is formed on the surface of the metal Al powder, and a phosphate coating film is formed on the boehmite layer, thereby suppressing hydration reaction and It is stated that the occurrence is suppressed.

  However, since the method of Patent Document 3 requires a step of forming a boehmite layer, there is a problem that time and cost are required for practical use.

JP-A-8-283074 JP-A-53-66917 Japanese Patent No. 2909582

  The problem to be solved by the present invention is to improve the corrosion resistance of a water-based refractory mortar containing a metal Al-containing powder while suppressing the hydration reaction of the metal Al-containing powder by a simple method.

  In the water-based refractory joint mortar containing the metal Al-containing powder, the present inventors almost completely completed the hydration reaction of the metal Al-containing powder by adding an appropriate amount of at least one of boric acid, borate and carboxylic acid. The inventors have found that this can be prevented, and have completed the present invention.

That is, according to the present invention, the following water-based refractory joint mortars (1) to (4) are provided.
(1) 0.1 to 10% by mass of metal Al-containing powder and 0.01 to 2% by mass of at least one of boric acid, borate, and carboxylic acid are blended on the refractory material. Water-based fireproof joint mortar.
(2) The water-based refractory mortar according to (1), wherein the refractory material includes a basic oxide raw material.
(3) The water-based refractory joint mortar according to (1), wherein the refractory material contains a neutral oxide raw material.
(4) The water-based refractory joint mortar according to any one of (1) to (3), wherein the refractory material contains 1 to 20% by mass of at least one of a carbon raw material and a silicon carbide raw material.

  According to the present invention, the hydration reaction of the metal Al-containing powder can be suppressed by a simple method of blending at least one of boric acid, borate, and carboxylic acid. The mechanism of action (a) to (c) described above can be fully exhibited, and the corrosion resistance can be improved.

The test sample used for the rotational erosion test for evaluating corrosion resistance is shown conceptually. The amount of erosion after the rotation erosion test is conceptually shown.

  The water-based refractory joint mortar of the present invention is an outer shell for the refractory material, 0.1 to 10% by mass of metal Al-containing powder, 0.01 to 2 of at least one of boric acid, borate and carboxylic acid. It is blended by mass%. Thus, by blending an appropriate amount of at least one of boric acid, borate and carboxylic acid, the hydration reaction of the metal Al-containing powder can be almost completely prevented as described above. Specifically, at least one of boric acid, borate, and carboxylic acid forms a protective colloid around the metal Al-containing powder, and suppresses the hydration reaction of the metal Al-containing powder.

The water-based refractory joint mortar of the present invention is used as a mortar for secondary refining containers such as RH on which magcro bricks are lined, and a mortar blended with a carbon raw material is particularly excellent as a joint mortar for carbon-containing bricks. Demonstrate. For example, MgO-C bricks in hot metal and ladle, MgO-Al ₂ O ₃ -C bricks, or carbon-containing bricks such as Al ₂ O ₃ -SiC-C bricks lined on kneading cars etc. It is suitable as a joint mortar.

  Hereinafter, specific examples of the refractory raw materials used in the present invention, blended raw materials blended with the refractory raw materials, and appropriate blending ratios thereof will be described.

  The basic oxide raw material used for the refractory raw material in the present invention is typically a magnesia raw material, and either a sintered product or an electromelted product is used. Natural products such as Further, in terms of particle size, it is preferable to adjust to 0.3 mm or less so as not to impair workability and the like, as in the case of conventional mortar. The basic oxide raw material is preferably contained in the refractory material in an amount of 65 to 99% by mass.

  The neutral oxide raw material used for the refractory raw material in the present invention is typically an alumina raw material, and either a sintered product or an electromelted product is used. Natural products may be used. Further, in terms of particle size, it is preferable to adjust to 0.3 mm or less so as not to impair workability and the like, as in the case of conventional mortar. The neutral oxide raw material is preferably contained in the refractory material in an amount of 65 to 99% by mass.

  The carbon raw material used as the refractory raw material in the present invention is not only carbon black but also artificial graphite, coke, earthy graphite, scaly graphite, etc., but it is sufficient that the carbon raw material has a purity of 90% or more. Moreover, the particle diameter is preferably 0.3 mm or less, and more preferably 0.1 mm or less. Further, the silicon carbide raw material used as the refractory raw material in the present invention can be used without any problem as long as the silicon carbide raw material has a purity of 90% or more, and the particle diameter is preferably 0.3 mm or less, more preferably 0.1 mm or less. . These carbon raw materials and silicon carbide raw materials are preferably contained in the refractory material in an amount of 1 to 20% by mass from the viewpoint of improving the corrosion resistance by preventing infiltration of slag and the like.

  As the refractory raw material for the water-based refractory joint mortar of the present invention, refractory clay is used in the same manner as ordinary mortar in addition to the above-mentioned raw materials. Refractory clay is plastic clay such as Kibushi clay, ball clay, bentonite, and the like, and is also useful for imparting workability such as elongation during construction. Further, although the mechanism is not clear, in the presence of refractory clay, as described above, at least one of boric acid, borate and carboxylic acid is added, and these boric acid, borate and carboxylic acid are mixed. At least one of them forms a protective colloid around the metal Al-containing powder, and the effect of suppressing the hydration reaction of the metal Al-containing powder is remarkable.

  Among the boric acid, borate and carboxylic acid blended with the refractory raw material in the present invention, examples of boric acid include orthoboric acid, metaboric acid, and tetraboric acid, and orthoboric acid is preferred. The borate is a general term for salts such as orthoboric acid, metaboric acid, and tetraboric acid, but may be natural products such as borax. The carboxylic acid is a compound having a carboxyl group, such as citric acid, malic acid, oxalic acid, and lactic acid, and citric acid is particularly preferable.

  The blending amount of these boric acid, borate and carboxylic acid is required to be 0.01% by mass or more in order to exert the effect of suppressing the above-mentioned hydration reaction. It reacts with the raw material components to produce a low melt, resulting in a decrease in corrosion resistance. In addition, the preferable compounding amount of boric acid, borate and carboxylic acid is 0.2 to 0.5% by mass when a basic oxide raw material is used for the refractory material, and a neutral oxide raw material is used for the refractory material. When it does, it is 0.05-0.3 mass%.

  The metal Al-containing powder blended externally to the refractory raw material in the present invention exhibits the above-mentioned action mechanisms (a) to (c), and is particularly a main raw material component of its own oxidation or mortar in a high temperature range. And the function of densification by the reaction and the anti-oxidation function when the carbon raw material coexists, thereby contributing to the improvement of corrosion resistance. The metal Al-containing powder is a concept including Al alloy powder as described above, and Al alloy includes Al-Mg alloy, Al-Si alloy, Al-Mg-Si alloy, Al-Mg-Ca alloy, and the like. is there. The particle diameter of the metal Al-containing powder is preferably 0.3 mm or less, more preferably 0.1 mm or less. If the amount of the metal Al-containing powder is 0.1% by mass or less, the effect cannot be confirmed, and if it exceeds 10% by mass, the corrosion resistance is lowered and the cost is increased. The preferable compounding quantity of metal Al containing powder is 0.5-5 mass%.

In addition to these, the water-based refractory mortar of the present invention uses boron compounds other than boric acid and borate as refractory materials, such as boron carbide (B ₄ C) and zirconium boride (ZrB ₂ ), as antioxidants. On the other hand, it may be blended with an outer shell and does not inhibit the effect of the present invention. Moreover, dextrin, gum arabic, CMC, sodium lignin sulfonate and the like may be appropriately selected and used as the work imparting agent.

  On the other hand, the water-based refractory joint mortar of the present invention does not contain a binder such as alumina cement.

  About the water-system refractory joint mortar of each example shown in Table 1 and Table 2, the gas generation state and corrosion resistance were evaluated in the following way, and comprehensive evaluation was performed based on these evaluation results.

Gas evolution state An appropriate amount (about 15 to 35% by mass) of construction water is added and kneaded with respect to the composition of each example shown in Tables 1 and 2, and this kneaded product (mortar) is placed in a cylindrical container. And left for 1 day under the condition of 20 ° C. and evaluated by visually observing the presence or absence of gas generation.

Corrosion resistance test Corrosion resistance was evaluated by a rotational erosion test. Specifically, an appropriate amount (about 15 to 35% by mass) of construction water is added and kneaded with respect to the formulation of each example shown in Table 1 and Table 2, and this kneaded product (mortar) is operated. A refractory having a shape of a cylinder having a diameter of 25φ × 35 mm perpendicular to (a MgO—C brick in the example shown in Table 1 and Al ₂ O ₃ —SiC—C in the example shown in Table 2. Brick was used) and used as a test sample (Fig. 1). Originally, in order to simulate actual use conditions, we wanted to use mortar after standing for one day after kneading, but in the boric acid-free system shown in the comparative example, generation of hydrogen gas as mentioned above As described above, the mortar immediately after kneading having fluidity was cast into a regular refractory and left to stand at 20 ° C. for 1 day. Later, the portion raised from the horizontal surface due to the generation of gas was scraped off and dried to obtain the test sample of FIG.
These test samples were lined on the inner surface of a drum having a horizontal rotating shaft, slag was added, and the mortar surface was eroded by heating. The heating source was an oxygen-propane burner, the test temperature was 1500 ° C., the slag composition was CaO / SiO ₂ = 1.0, FeO = 1.5 mass%, and slag discharge and charging were repeated 10 times every 30 minutes. .
After the test is completed, the sample is cut at the center, and the erosion amount is calculated by measuring the size of the maximum erosion part of each mortar (Fig. 2). In the case of each example 1, the erosion amount of “Comparative Example 1” in Table 1 was expressed as a erosion index with 100 (the erosion index in Table 1 = 100 × the erosion amount (cm ³ ) of each example / comparison. Erosion amount of Example 1 (cm ³ )). In addition, in each case of Table 2 mainly composed of a neutral oxide raw material (sintered alumina powder), the erosion amount of “Comparative Example 11” in Table 2 was expressed as a erosion index with 100 (Table 2). Index of erosion = 100 × the amount of erosion in each example (cm ³ ) / the amount of erosion in Comparative Example 11 (cm ³ )). This melting loss index indicates that the smaller the numerical value, the better the corrosion resistance.

Comprehensive evaluation O (good) when no gas is generated in the evaluation of the gas generation state and the erosion index is less than 90, and X is when the gas generation is present or the erosion index is 90 or more in the evaluation of the gas generation state. (Defect).

  Each example in Table 1 uses a basic oxide raw material (sintered magnesia powder) as a refractory raw material. Hereinafter, Table 1 will be described by dividing into (1-1) to (1-4).

(1-1)
Comparative Example 2 is an example in which metal Al powder is blended with respect to Comparative Example 1 in which metal Al powder is not blended, but since none of boric acid, borate and carboxylic acid is blended, metal Al powder As a result of the generation of hydrogen gas and an increase in porosity, the corrosion resistance decreased significantly. On the other hand, in Examples 1 to 3, since boric acid, borate or carboxylic acid is blended, unlike Comparative Example 2, there is no generation of hydrogen gas and the porosity does not increase, so the corrosion resistance is greatly increased. Improved.

(1-2)
Comparative Example 3 is an example in which the amount of boric acid is too small, which causes generation of hydrogen gas from the metal Al powder and increases the porosity, so that the corrosion resistance is lowered. On the other hand, Comparative Example 4 is an example in which the amount of boric acid is too large, and although hydrogen gas is not generated from the metal Al powder, it reacts with boric acid itself or sintered magnesia powder to produce a low melt. No improvement in corrosion resistance was observed. On the other hand, in Examples 4 and 5 in which the blending amount of boric acid is within the range of the present invention, the generation of hydrogen gas is not generated, and the production of low melt is small, so the corrosion resistance is improved.

(1-3)
Comparative Example 5 is an example in which the blending amount of the metal Al powder is too small, and the effect of improving the corrosion resistance by the metal Al powder was not observed. On the other hand, Comparative Example 6 is an example in which the blending amount of the metal Al powder is too large, and the metal Al powder reacts with the sintered magnesia powder to generate excessive spinel, and the corrosion resistance is lowered due to the component relationship. On the other hand, in Examples 6 and 7 in which the blending amount of the metal Al powder is within the range of the present invention, the metal Al powder forms a bond with heat to be densified, and excessive spinel is not generated. Corrosion resistance improved.

(1-4)
Comparative Example 7 is an example in which silicon carbide powder (silicon carbide raw material) and earthy graphite powder (carbon raw material) were used as the refractory raw material, but the corrosion resistance was hardly improved. Further, Comparative Example 8 is an example in which metal Al powder is blended with the refractory raw material of Comparative Example 7, and it seems that the corrosion resistance is improved by blending of the metal Al powder. did. On the other hand, in Examples 8 to 10, since boric acid, borate or carboxylic acid is blended, unlike Comparative Example 8, there is no generation of hydrogen gas, and the porosity is not increased. A sufficient antioxidant effect of the raw material and a densification effect of the matrix portion were obtained, and the corrosion resistance was greatly improved.

  Each example in Table 2 uses a neutral oxide raw material (sintered alumina powder) as a refractory raw material. Hereinafter, Table 2 will be described by dividing into (2-1) to (2-4).

(2-1)
Comparative Example 12 is an example in which a metallic Al powder is blended with respect to Comparative Example 11 in which a metallic Al powder is not blended, but since none of boric acid, borate and carboxylic acid is blended, the metallic Al powder As a result of the generation of hydrogen gas and an increase in porosity, the corrosion resistance decreased significantly. On the other hand, in Examples 11 to 13, since boric acid, borate or carboxylic acid is blended, unlike Comparative Example 12, there is no generation of hydrogen gas and the porosity does not increase, so the corrosion resistance is greatly increased. Improved.

(2-2)
Comparative Example 13 is an example in which the amount of boric acid is too small, which causes generation of hydrogen gas from the metal Al powder and increases the porosity, so that the corrosion resistance is lowered. On the other hand, Comparative Example 14 is an example in which the amount of boric acid is too large, and although hydrogen gas is not generated from the metal Al powder, it reacts with boric acid itself or sintered alumina powder to produce a low melt. No improvement in corrosion resistance was observed. On the other hand, in Examples 14 and 15 in which the blending amount of boric acid is within the range of the present invention, there is no generation of hydrogen gas, and the production of low melt is small, so the corrosion resistance is improved.

(2-3)
Comparative Example 15 is an example in which the blending amount of the metal Al powder is too small, and the effect of improving the corrosion resistance by the metal Al powder was not seen. On the other hand, Comparative Example 16 is an example in which the blending amount of the metal Al powder is too large, and the effect of improving the corrosion resistance was not observed. On the other hand, in Examples 16 and 17 in which the blending amount of the metal Al powder was within the range of the present invention, the metal Al powder formed a bond hot and densified, and the corrosion resistance was improved.

(2-4)
Comparative Example 17 is an example in which silicon carbide powder (silicon carbide raw material) and earthy graphite powder (carbon raw material) were used as the refractory raw material, but the corrosion resistance was hardly improved. Further, Comparative Example 18 is an example in which metal Al powder is blended with the refractory raw material of Comparative Example 17, and it seems that the corrosion resistance is improved by blending of the metal Al powder, but the porosity is increased due to the effect of gas generation, rather it is deteriorated. did. On the other hand, in Examples 18 to 20, since boric acid, borate or carboxylic acid is blended, unlike Comparative Example 18, there is no generation of hydrogen gas, and the porosity does not increase. A sufficient antioxidant effect of the raw material and a densification effect of the matrix portion were obtained, and the corrosion resistance was greatly improved.

Claims (4)

  A water-based fireproof joint containing 0.1 to 10% by mass of metal Al-containing powder and 0.01 to 2% by mass of boric acid, borate and carboxylic acid as an outer shell with respect to the refractory material. mortar.   The water-based refractory joint mortar according to claim 1, wherein the refractory material includes a basic oxide raw material.   The water-based refractory joint mortar according to claim 1, wherein the refractory material contains a neutral oxide raw material.   The water-based refractory joint mortar according to any one of claims 1 to 3, wherein the refractory material contains 1 to 20 mass% of at least one of a carbon raw material and a silicon carbide raw material.