JPWO2013057756A1 - Magnesian fired brick - Google Patents

Abstract

The magnesia calcined brick according to the present invention includes a magnesia raw material as a main raw material, 2-8 wt% of a titania raw material, 3-20 wt% of a magnesia-alumina-based spinel raw material, and / or 3-20 wt% of a mullite raw material. A binder is added to 100 wt% of a composition composed of 0.3 to 3.0 wt% of a phosphate glassy raw material, kneaded and molded, and then fired. Furthermore, the corrosion resistance can be improved by adding 3 to 20 wt% of the zircon material or 0.1 to 3.0 wt% of the nickel oxide material.

Description

The present invention relates to a baked refractory for lining used in a steelmaking furnace, a refining furnace, and the like.

Conventionally, magnesia-chromium refractories having excellent corrosion resistance and spalling resistance have been used for lining refractories used in various furnaces. Since magnesia-chromium refractories produce hexavalent chromium which is harmful to the human body and environmental sanitation after use, so-called chromium-free bricks have been sought from early on.

  As chromium-free bricks, for example, magnesia-carbon bricks in which magnesia is combined with carbon have been proposed. However, magnesia-carbon bricks have the disadvantage that the brick structure becomes brittle due to carbon oxidation and cannot be used for a long time. Moreover, since carbon dioxide is generated by the oxidation of carbon, it is not preferable from the viewpoint of preventing global warming.

  Therefore, basic bricks in which titania or the like is added to magnesia have been proposed as chromium-free bricks that eliminate these drawbacks. For example, Patent Document 1 discloses magnesia-calcia-titania basic brick. In addition, refractories in which aluminum titanate is added to spinel (Patent Document 2) and magnesia-alumina-titania brick (Patent Document 3) have been proposed.

Japanese Patent Laid-Open No. 9-20550 Japanese Patent Laid-Open No. 7-300361 JP 2001-253765 A

  However, magnesium titanate produced by the reaction of magnesia and titania during firing is vulnerable to thermal expansion due to its dense structure, and its spalling resistance is very low. For this reason, magnesia-titania basic bricks have the disadvantage that they cannot withstand long-term use in an oven environment where heating and cooling are repeated.

  One countermeasure is to add alumina to the brick component. Due to the addition of alumina, the alumina reacts with magnesia during the firing of the brick to produce spinel. Due to the difference in thermal expansion coefficient between spinel and magnesia, microcracks are generated in the structure during sintering of the brick. Thereby, the space | gap margin with respect to thermal expansion arises in the structure | tissue of a brick, and spalling resistance improves. However, as the amount of alumina added increases, the number of microcracks that are generated increases. Therefore, if the amount of alumina exceeds 10 wt%, the structure weakens and the corrosion resistance decreases. For this reason, in magnesia-alumina-titania bricks, alumina cannot be added indefinitely, and the blending ratio of magnesia raw materials with a large expansion coefficient will still increase, so improving the spalling resistance There is a problem that there is a limit.

  On the other hand, it is necessary to synthesize aluminum titanate from titania and alumina, and there is a problem that the cost is high for producing the clinker.

  Furthermore, a major drawback of magnesia basic bricks is the collapse of bricks due to digestion. Digestion is a phenomenon in which magnesia, which is the main component of brick, reacts with moisture to produce magnesium hydroxide, and the brick collapses due to rapid body expansion during the reaction. Thereby, for example, in a vacuum degassing furnace, there is a problem that the brick constituting the inner surface of the dip tube collapses during drying due to moisture contained in the amorphous refractory constituting the outer layer.

  Accordingly, the present invention has been researched and developed with the object of solving the above-mentioned problems, and is excellent in corrosion resistance, slag infiltration resistance, spalling resistance and digestion resistance, and has sufficient durability. The purpose is to provide a quality fired brick.

  In order to achieve the above object, the magnesia fired brick according to the present invention comprises a magnesia raw material as a main raw material, a titania raw material of 2-8 wt%, a magnesia-alumina-based spinel raw material of 3-20 wt% and / or A binder is added to a blend composition of 100 wt% composed of 3 to 20 wt% of a mullite raw material and 0.3 to 3.0 wt% of a phosphate glassy raw material, kneaded and molded, and then fired. And

As a result, perovskite (CaO · TiO ₂ ) is produced in the form of a film near the working surface of the brick by the reaction between titania and calcia in the slag, preventing other slag components from infiltrating into the brick structure. And slag infiltration resistance is improved. In addition, since spinel is generated by the reaction of alumina and magnesia contained in the spinel material or mullite material, and the cracks are formed in the brick structure due to the difference in thermal expansion coefficient between the spinel and magnesia, the space for thermal expansion Allowance. As a result, cracks and cracks are less likely to occur in bricks due to structural changes accompanying slag infiltration and thermal changes, and spalling resistance is improved. Further, forsterite (2MgO.SiO ₂ ) having a melting point lower than that of magnesia is generated by the reaction between silica and magnesia contained in the mullite raw material, and thus the brick structure becomes dense. As a result, the vulnerability of the organization due to the occurrence of a large amount of spinel is suppressed, and the spalling resistance is further improved. Furthermore, the combined use of the spinel material and the mullite material can improve the corrosion resistance and also improve the spalling resistance without weakening the brick structure.

  Further, according to the present invention, the phosphate glass reacts with magnesia, and magnesium phosphate is generated around magnesia, so that the reaction between magnesia and water is blocked, thereby improving digestion resistance. To do.

  Here, it is desirable that the magnesia fired brick is further added with a zircon material 3 to 20 wt% or a nickel oxide material 0.1 to 3.0 wt%.

  Thereby, zircon dissociates during firing and zirconia and silica are generated. Since silica produces forsterite by reaction with magnesia, the spalling resistance is improved as described above. In addition, since zirconia has a very high melting point, the corrosion resistance of the brick under high heat is improved by including it in the constituent components of the brick. On the other hand, nickel oxide has the property of repelling metal and slag according to the research results of the inventor. Therefore, the corrosion resistance is further improved by including this in the components of the brick.

  Further, it is desirable that the magnesia fired brick is further added with 1 to 5 wt% of dolomite raw material, magnesite raw material or calcium carbonate.

  As a result, dolomite, magnesite or calcium carbonate releases carbon dioxide during firing and generates micropores (fine voids) in the brick structure, increasing the apparent porosity and reducing spalling resistance. improves.

  As described above, according to the magnesia calcined brick according to the present invention, a magnesia calcined brick that is excellent in corrosion resistance, slag infiltration resistance, spalling resistance and digestion resistance and has sufficient durability is realized. In particular, the weakening of the brick structure associated with the generation of spinel is suppressed by the forsterite produced by the silica and magnesia constituting mullite and zircon, and therefore the spalling resistance can be further improved. Furthermore, since the magnesium phosphate produced by the phosphate glass blocks the reaction between magnesia and water, digestion resistance is improved.

  The magnesia fired brick according to the present invention will be described in detail below.

  The present invention comprises a magnesia material as a main material, a titania material of 2-8 wt%, a magnesia-alumina-based spinel material of 3-20 wt% and / or a mullite material of 3-20 wt%, and a phosphate glass A binder is added to 100 wt% of a composition composed of 0.3 to 3.0 wt% of raw materials, kneaded and molded, and then fired.

  Magnesia contained in the main raw material has a high melting point of about 2800 ° C. and is a highly basic substance, and therefore exhibits excellent corrosion resistance against slag. For this reason, the increase in the component ratio of magnesia leads to the improvement of the corrosion resistance of the brick. However, the coefficient of thermal expansion of magnesia is about twice as high as that of average alumina bricks. Therefore, when the component ratio of magnesia is increased, the brick structure is easily broken and the spalling resistance is improved. There is a drawback of lowering.

Titania reacts with calcia in the slag to produce perovskite (TiO ₂ + CaO → CaO · TiO ₂ ). Perovskite is generated in the form of a film near the working surface of the brick, so that the brick of the slag component is prevented from entering the tissue. Therefore, the addition of the titania-based raw material has an effect of improving the infiltration resistance against the slag.

Further, titania reacts with magnesia to produce magnesium titanate (MgO + 2TiO ₂ → MgO · 2TiO ₂ , 2MgO + TiO ₂ → 2MgO · TiO ₂ ). Magnesium titanate has a very dense structure in consideration of the apparent porosity of about 10 wt% and the apparent porosity of ordinary fired bricks is about 20 wt%. For this reason, a brick containing magnesium titanate as a component is very easily broken.

On the other hand, the addition of spinel material and mullite material has the effect of making bricks difficult to break. That is, spinel is generated by the reaction of alumina and magnesia contained in these during firing (MgO + Al ₂ O ₃ → MgO · Al ₂ O ₃ ), and the expansion coefficient of spinel and magnesia is different, so the structure of the brick Microcracks are generated inside. Thereby, a spatial margin is generated in the brick structure, and the spalling resistance is improved. If the amount of the spinel material added is increased, the influence of densification of the brick structure is suppressed, so that the spalling resistance is further improved. However, if it is added too much, microcracks increase in the brick structure and the structure becomes brittle.

When the mullite raw material is added, in addition to the generation of spinel, silica contained in the mullite raw material reacts with magnesia to generate forsterite (SiO ₂ + 2MgO → 2MgO · SiO ₂ ). Since forsterite plays a role of densifying the structure of the brick, when a mullite raw material is added, weakening of the structure of the brick due to an increase in microcracks is suppressed.

  In the present invention, instead of the spinel material, only the mullite material may be used, or the spinel material and the mullite material may be used in combination. In addition, when all of these addition amounts are less than 3 wt%, the amount of spinel generation is insufficient, and the spalling resistance is not improved. Moreover, when these addition amounts exceed 20 wt%, the structure tends to become brittle, and this causes a decrease in corrosion resistance.

The phosphate glass reacts with magnesia during firing to produce magnesium phosphate (Mg (H ₂ PO ₃ ) ₂ ). By generating this around magnesia, the reaction (MgO + H ₂ O → Mg (OH) ₂ ) between magnesia and water is blocked. Therefore, the addition of phosphate glassy raw material is effective in improving digestion resistance. In addition, if the addition amount of the phosphate glassy raw material is less than 0.3 wt%, the effect of digestion resistance is small, and if it exceeds 3 wt%, the melting point of the phosphate glass is relatively low, so the corrosion resistance of the brick This is not preferable because it leads to a decrease in

Zircon dissociates into zirconia and silica during calcination (ZrSiO ₄ → ZrO ₂ + SiO ₂ ). Silica reacts with magnesia in the brick to produce forsterite (SiO ₂ + 2MgO → 2MgO · SiO ₂ ), and forsterite has the effect of densifying the structure of the brick, thus improving the spalling resistance. On the other hand, zirconia improves corrosion resistance due to its high melting point. However, if the amount of the zircon material is less than 3 wt%, the effect is small. Moreover, since it is an expensive raw material, it is economically unpreferable to use too much.

  Nickel oxide has a property of repelling molten metal and slag, and the corrosion resistance of bricks is improved by including this in the constituent components. However, if the addition amount of the nickel oxide raw material is less than 0.1 wt%, the effect is small. Moreover, since it is an expensive raw material, it is economically unpreferable to use too much. In addition, when adding a nickel oxide raw material, the method of adding, after preparing a suspension in a liquid binder previously so that the effect may fully be exhibited is desirable.

Dolomite (Ca (Mg (CO ₃ ) ₂ )), magnesite, or calcium carbonate all release carbon dioxide during calcination (Ca (Mg (CO ₃ ) ₂ ) → CaO + MgO + 2CO ₂ , MgCO ₃ → MgO + CO _2. , CaCO ₃ → CaO + CO ₂ ). As a result, micropores are formed in the brick tissue. Spinel and mullite have the effect of improving the spalling resistance, but if added too much, the structure is weakened. Therefore, by adding dolomite or the like and forming micropores in the brick structure by carbon dioxide generated during firing, a spatial effect equivalent to microcracks is produced. Therefore, by adding these, the spalling resistance can be improved without weakening the brick structure.

  Next, the constituent materials of the magnesia fired brick according to the present invention will be described in detail.

  As the magnesia material, either electrofused magnesia or sintered magnesia may be used. A purity of 97 wt% or more is sufficient. Particle sizes of 3 to 1 mm, 1 mm or less, and 74 μm or less are appropriately mixed and used.

  As the titania material, a material having a particle size of 45 μm or less and a purity of 85 wt% or more is used.

  A spinel material having a particle size of 74 μm or less is used. A theoretical composition having an alumina component of about 70 wt% and a magnesia component of about 30 wt% is effective.

  Since mullite raw materials are rarely produced in nature, synthetic mullite is used. The particle size is 74 μm or less, the alumina component is about 70 wt%, and the silica component is about 30 wt%.

  The zircon raw material has a particle size of 74 μm or less, a zirconia component of about 67 wt%, and a silica component of about 33 wt%.

  As the nickel oxide raw material, those having a particle size of 74 μm or less can be used, but 45 μm or less is desirable. This is because the reactivity of nickel oxide with magnesia and titania is improved when a finer particle size is used. Further, by reducing the particle size, the raw material is easily dispersed throughout the brick during kneading, so that there is an advantage that the amount of the nickel oxide raw material added can be further reduced. Purity should just be 80 wt% or more in consideration of economical efficiency.

  The commercially available dolomite raw material, magnesite raw material and calcium carbonate can be used as they are.

As the phosphate glassy raw material, a phosphorous oxide component (P ₂ O ₅ ) of 60 to 65 wt%, a sodium oxide component (Na ₂ O) of 20 to 30 wt%, and an alumina component of about 8 to 10 wt% are used. To do.

  Next, the magnesia fired brick according to the present invention will be described in more detail with reference to examples and comparative examples. The following examples and comparative examples show the influence of the amount of each constituent material added on the brick properties.

The raw materials are prepared at the blending ratios shown in the following tables, the liquid of calcium lignin sulfonate (pulp waste liquid) is kneaded as a binder, and pressure-molded into a parallel shape (230 x 114 x 65 mm) with a 300-ton friction press did. The molded body was dried at a temperature of 150 ° C. for 24 hours, and then fired at a temperature of 1700 ° C. for 6 hours using a shuttle kiln. The fired body was cut into a predetermined size, and the characteristics of the examples and comparative examples were examined by the following evaluation items.
(1) Apparent porosity and bulk specific gravity: The bulk specific gravity and the apparent porosity were measured based on JIS standard (JIS R2205).
(2) Spalling resistance: A sample having a size of 40 × 80 × 20 mm is quickly put in an electric furnace maintained at a temperature of 1200 ° C., heated for 15 minutes, then quickly removed and put into water. It repeated until it disintegrated and evaluated the spalling resistance by the number of times. In this test, the greater the number of times, the better the spalling resistance.
(3) Corrosion resistance: Corrosion resistance was evaluated using a rotary erosion tester. The operation of adding 300 g of erodible material of steel: slag (basicity 3.0) = 6: 4 per one time and replacing it every 30 minutes was repeated a total of 10 times. The temperature is 1730 ° C. and the test time is 5 hours. The results were expressed as an index (melting loss index) with the amount of magnesia-chrome brick melting as 100. In this test, the smaller the erosion index, the smaller the erosion amount.
(4) Digestion resistance: A sample having a size of 50 × 50 × 50 mm was placed in an autoclave, heated at a temperature of 130 ° C. for 5 hours, and digestion resistance was evaluated by whether or not the sample was cracked. . In addition, the pressure at the time of a heating is about 0.3 MPa.

  Further, in the following, Comparative Example 1 is a conventional magnesia-chromium brick made of sintered magnesia 40 wt%, chromium ore 60 wt%, and chromium oxide 6 wt%, and has a chromium content of about 30 wt%.

  Table 1 shows the influence of the amount of titania added on the brick properties. According to this, Comparative Example 2 with a small addition amount of titania is inferior to Comparative Example 1 in which magnesia-chromium brick is used, and Comparative Example 3 with a large addition amount is in spalling resistance. ing. In contrast, Examples 1 to 3 are superior to Comparative Example 1 in corrosion resistance, spalling resistance and digestion resistance. Therefore, it can be seen that the addition amount of titania is preferably 2 to 8 wt%.

  Moreover, according to Table 1, the apparent porosity is falling with the increase in the addition amount of titania. This indicates that the densification of the structure proceeds with a decrease in the amount of titania added.

  Table 2 shows the influence of the amount of spinel added on the brick properties. According to this, Comparative Example 4 with a small amount of spinel is inferior to Comparative Example 1 in spalling resistance, and Comparative Example 5 with a large amount of addition is inferior to Comparative Example 1 in corrosion resistance (melting loss index). In contrast, Examples 4 to 6 are superior to Comparative Example 1 in corrosion resistance, spalling resistance, and digestion resistance. Therefore, it is understood that the amount of spinel added is preferably 3 to 20 wt%.

  Table 3 shows the influence of the added amount of mullite on the brick properties. According to this, even when the amount of mullite added is increased, no significant change in apparent porosity is observed compared to the case where spinel is added. The reason for this is that when spinel is generated by the reaction between the alumina component of mullite and magnesia, forsterite is generated by the action of microcracking in the structure and the reaction between the silica component of mullite and magnesia. In this case, it is presumed that the effect of the organization trying to be densified cancels out.

  Moreover, according to Table 3, the comparative example 6 with a small amount of mullite added shows no improvement in the spalling resistance, and the comparative example 7 with a large amount added does not show an improvement over the comparative example 1 in the corrosion resistance. In contrast, Examples 7 to 9 are superior to Comparative Example 1 in corrosion resistance, spalling resistance, and digestion resistance. Therefore, it is understood that the added amount of mullite is preferably 3 to 20 wt%.

  Table 4 shows the effect of the addition amount of both on the brick characteristics when spinel and mullite are used in combination. According to this, even when spinel and mullite are used in combination, the change in apparent porosity is not so different from the case where only mullite is added. The reason for this is that, as in the case of adding only mullite, the denseness of forsterite produced by the reaction of the silica component of mullite with magnesia reduces the effect of microcracks generated by the thermal expansion of spinel. Presumed to be. Therefore, it can be seen that by using spinel and mullite together, spalling resistance can be improved without impairing corrosion resistance even if the amount of spinel added is increased.

  Moreover, according to Table 4, the comparative example 8 with a small addition amount of both does not show an improvement over the comparative example 1 in the spalling resistance, and the comparative example 9 with a large addition amount is compared with the comparative example 1 in the corrosion resistance. Inferior. In contrast, Examples 10 to 12 are superior to Comparative Example 1 in corrosion resistance, spalling resistance, and digestion resistance. Therefore, when spinel and mullite are used together, it can be seen that the addition amount of both is preferably 3 to 20 wt%.

  Table 5 shows the effect of the addition amount of phosphate glass on the properties of bricks. According to this, Comparative Example 10 with a small addition amount of phosphate glass does not show the effect of digestion resistance, and Comparative Example 11 with a large addition amount shows a digestion resistance effect, but is compared in terms of corrosion resistance. Inferior to Example 1. In contrast, Examples 13 to 15 are superior to Comparative Example 1 in corrosion resistance, spalling resistance, and digestion resistance. Therefore, it can be seen that the addition amount of phosphate glass is preferably 0.3 to 3.0 wt%.

In addition, according to Table 5, with the increase in the addition amount of phosphate glass, the bulk specific gravity decreases slightly, and the apparent porosity increases. The reason for this is presumed to be that pores are formed in the structure of the brick by part of phosphorus oxide (P ₂ O ₅ ) contained in the phosphate glass being vaporized.

  Table 6 shows the influence of the amount of zircon added on the brick properties. According to this, it can be seen that as the amount of zircon added increases, the bulk specific gravity increases, and the apparent porosity and melting index decrease. This is because zircon dissociates during firing to produce zirconia and silica, and forsterite produced by the reaction of silica and magnesia densifies the brick structure as described above, and zirconia has a melting point. Since it is very high, it is presumed that this is because the corrosion resistance is increased by being contained in the constituent components.

  Further, according to Table 6, Comparative Example 12 with a small amount of zircon added does not have a sufficient effect in corrosion resistance and poling resistance. In contrast, Examples 16 to 18 are superior to Comparative Example 1 in corrosion resistance, spalling resistance and digestion resistance. Moreover, also in Comparative Example 13 in which the addition amount is further increased, improvement is observed in these evaluation items. Therefore, it can be seen that the amount of zircon added is effective in the range of at least 3 to 21 wt%. However, since zircon is an expensive raw material, it is preferable to keep the addition amount at 3 to 10 wt% in consideration of economic problems.

  Table 7 shows the influence of the addition amount of nickel oxide on the brick characteristics. According to this, it turns out that corrosion resistance improves with the increase in the addition amount of nickel oxide. The reason for this is presumed to be that the penetration of slag into the brick is prevented by the nature of nickel oxide and the ability to repel slag.

  Moreover, according to Table 7, Comparative Example 14 with a small amount of nickel oxide added is poor in corrosion resistance, and Comparative Example 15 with a large amount added has poor superiority over Comparative Example 1 in spalling resistance. In contrast, Examples 19 to 21 are superior to Comparative Example 1 in corrosion resistance, spalling resistance, and digestion resistance. Therefore, it can be said that the addition amount of nickel oxide is effective at 0.1 to 3 wt%. However, since nickel oxide is also an expensive raw material like zircon, it is not practical from an economic viewpoint to increase the amount of addition. Considering the above, it can be said that the addition amount of nickel oxide is preferably 0.5 to 1 wt%.

  Table 8 shows the influence of the added amount of calcium carbonate on the properties of bricks. According to this, with the increase of the addition amount of calcium carbonate, the apparent porosity increases. The reason for this is presumed to be that calcium carbonate releases carbon dioxide during firing and generates micropores in the brick tissue.

  Further, according to Table 8, Comparative Example 16 with a small amount of calcium carbonate added is poor in the corrosion resistance over Comparative Example 1, and Comparative Example 17 with a large amount added is inferior to Comparative Example 1 in the corrosion resistance. Yes. On the other hand, Examples 22-24 are superior to Comparative Example 1 in corrosion resistance, spalling resistance, and digestion resistance. Therefore, it can be said that the addition amount of calcium carbonate is preferably 1 to 5 wt%. The same conclusion can be obtained by using a dolomite material or a magnesite material instead of calcium carbonate.

  The reason why the corrosion resistance suddenly deteriorated in Comparative Example 17 is estimated as follows. In general, about 46 wt% of carbon dioxide is released from dolomite and calcium carbonate, and about 49 wt% of carbon dioxide is released from magnesite to generate micropores. Thereby, especially the spalling resistance is improved. However, if the addition amount is large, a low melting point product is generated by CaO and other components, and conversely the corrosion resistance is lowered.

In Example 17, microcracks were observed. The cause of this is that calcium carbonate releases carbon dioxide and changes to calcia upon firing, which reacts with the water vapor in the autoclave to produce calcium hydroxide (CaO + H ₂ O → (Ca (OH) ₂ )), which expands. This is presumed to be because Therefore, it can be seen that adding calcium carbonate in excess of 5 wt% is not preferable from the viewpoint of the influence of calcium hydroxide.

  Although the magnesia fired brick according to the present invention has been described based on the embodiment, the present invention is not limited to this, and the scope of the present invention can be achieved and does not depart from the gist of the invention. Various design changes are possible within the scope of the present invention, and they are all included within the scope of the present invention.

  The present invention relates to a ladle for steel making, a vacuum degassing furnace, a VOD furnace, an AOD furnace, an aluminum smelting furnace, a zinc smelting furnace, a copper smelting furnace, an ash melting furnace for melting and treating incinerated ash generated by incineration, and gasification It can be widely used as a refractory brick for use in melting furnaces, waste liquid incinerators, rotary kilns for cement firing, and the like.

Claims (3)

  The main raw material magnesia raw material, titania raw material 2-8 wt%, magnesia-alumina-based spinel raw material 3-20 wt% and / or mullite raw material 3-20 wt%, phosphate glassy raw material 0.3 A magnesia fired brick, which is obtained by adding a binder to 100 wt% of a blending composition consisting of ˜3.0 wt%, kneading and molding, and firing.   2. The magnesia fired brick according to claim 1, wherein 3-20 wt% of a zircon material or 0.1-3.0 wt% of a nickel oxide material is further added to the magnesia fired brick.   2. The magnesia fired brick according to claim 1, wherein 1 to 5 wt% of dolomite raw material, magnesite raw material or calcium carbonate is further added to the magnesia fired brick.