A formula for high-temperature lightweight mullite bricks and its firing process

Abstract

The present invention discloses a formula for high-temperature lightweight mullite bricks and a firing process thereof, relating to the technical field of refractory materials. According to the invention, by weight, the following components are included: 40-44 parts of alumina, 18-24 parts of cyanite, 10-15 parts of soft clay, 18-23 parts of high-temperature mullite, 25-35 parts of sawdust, 15-23 parts of burn-out polyethylene balls and a reinforcing agent; the sawdust is used to form microscopic air channels and reinforce the pores; the sintering temperature of the mixture is 1200°C-1800°C; the reinforcing agent is quartz powder; to solve the problem of the low strength of the lightweight heat-insulating refractory materials prepared by the burn-out method.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory materials, and specifically, to a formula for high-temperature lightweight mullite bricks and a firing process therefor. Background Art

[0002] There are many methods for preparing heat-insulating lightweight refractory materials, mainly including the hollow sphere bonding method, the burnout method, the foam gelling method, etc. The most commonly used methods in actual production are the hollow sphere bonding method and the burnout method. Different preparation methods have great differences in the performance of lightweight heat-insulating materials. For the burnout method, the thermal conductivity of the produced refractory material is small and the heat-insulating effect is good. However, its structure is loose and its strength is far less than that of the refractory material prepared by the hollow sphere bonding method.

[0003] The burnout method adds a certain amount of pore-forming agent to the raw material formulation. During the sintering process, the pore-forming agent leaves the matrix leaving voids, thereby obtaining a porous structure. Generally speaking, when firing porous refractories, the sintering temperature should not be too high. After a high sintering temperature, a large amount of collapse will occur in the formed porous structure, thus affecting the heat-insulating performance of the material. Although sintering at a higher temperature can greatly improve the transformation of the matrix ceramic phase and improve the mechanical properties of the refractory. However, it has a greater impact on the heat-insulating performance of the matrix. Summary of the Invention

[0004] The purpose of the present invention is to provide a formula for high-temperature lightweight mullite bricks and a firing process therefor, so as to solve the problem of low strength of the lightweight heat-insulating refractory material prepared by the existing burnout method.

[0005] To solve the above problems, the present invention adopts the following technical means:

[0006] A high-temperature lightweight mullite brick, by weight, comprises the following components: 40-44 parts of alumina, 18-24 parts of cyanite, 10-15 parts of soft clay, 18-23 parts of high-temperature mullite, 25-35 parts of sawdust, 15-23 parts of burnout-type polyethylene balls, and a reinforcing agent;

[0007] The sawdust is used to form microscopic air channels and reinforce the pores;

[0008] The sintering temperature of the mixture is 1200°C to 1800°C;

[0009] The reinforcing agent is quartz powder.

[0010] Preferably, by weight, the alumina is 40 parts, the cyanite is 20 parts, the soft clay is 15 parts, the high-temperature mullite is 20 parts, the sawdust is 30 parts, the burnout-type polyethylene balls are 20 parts, and the reinforcing agent is 10 parts.

[0011] Furthermore, the sintered mixture is kept warm for 2.5 to 8 hours, and the higher the sintering temperature, the longer the keeping warm time.

[0012] Furthermore, the soft clay has a silicon dioxide content of not less than 52.6%, and an aluminum oxide content of not less than 32%.

[0013] Furthermore, the high-temperature mullite is γ-mullite, and the iron oxide and titanium dioxide dissolved in the mullite are used to promote the formation of the ceramic phase during the sintering process and avoid the airway collapse caused by high-temperature sintering.

[0014] In addition, a method for preparing a high-temperature lightweight mullite brick is provided, wherein 40 to 44 parts of alumina, 18 to 24 parts of kyanite, 10 to 15 parts of soft clay, 18 to 23 parts of high-temperature mullite, 25 to 35 parts of sawdust, 15 to 23 parts of burnt polyethylene balls and a reinforcing agent are mixed, pressed to form a brick embryo, sintered at 1800°C, and kept warm for 8 hours.

[0015] During use, the present invention has the following beneficial effects:

[0016] The burn-out polyethylene balls are burned out during the sintering process to form cavities, and the cavities are connected by microscopic air channels formed by the burning of sawdust, thereby connecting the cavities with the outside. On the one hand, the air permeability of the refractory material is improved, and on the other hand, the carbon dioxide and water vapor generated during the burning of polyethylene can be discharged, thereby preventing water vapor and carbon dioxide from remaining in the matrix and affecting the formation of the matrix ceramic phase during the subsequent sintering process. Moreover, when the sawdust is burned at 1800°C, a large amount of sawdust can be carbonized, and the carbonized sawdust can be attached to the inner wall of the formed microscopic airway in large quantities, while the unattached carbonized sawdust can be discharged together with the carbon dioxide and water vapor discharged during the burning process of polyethylene. The attached carbonized sawdust can combine with a small amount of metal crystals included in the high-temperature mullite at 1800°C to form a C-metal alloy phase, thereby reinforcing the inner wall of the microscopic airway formed after the sawdust is burned out, and avoiding the collapse of the pores of the microscopic airway due to high-temperature sintering under high-temperature conditions of 1800°C. In addition, for the cavities formed after the polyethylene is burned, the inner wall of the cavities is coated by melting the quartz powder at high temperature. At the same time, the quartz powder is used to form a molten state during the sintering process with kyanite and alumina to reduce the stress contraction formed in the matrix during the high-temperature sintering process, thereby reducing the collapse rate of the cavities. In this way, the refractory material can not only have the strength of high-temperature sintering, but also have the advantages of good thermal insulation performance of a large number of gaps unique to the burn-out method. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will describe the technical solutions in the embodiments of the present invention clearly and completely in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0018] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0019] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0020] Example 1

[0021] A high-temperature lightweight mullite brick, by weight, comprises the following components: 40 parts of alumina, 18 parts of cyanite, 10 parts of soft clay, 18 parts of high-temperature mullite, 25 parts of sawdust, 15 parts of burnable polyethylene balls, and 10 parts of a reinforcing agent;

[0022] The sawdust is used to form microscopic air channels and reinforce the pores;

[0023] The sintering temperature of the mixture is 1200°C to 1800°C;

[0024] The reinforcing agent is quartz powder.

[0025] The sintered mixture is heat-insulated for 2.5 to 8 hours. The higher the sintering temperature, the longer the heat-insulation time.

[0026] The silica content of the soft clay is not less than 52.6%, and the alumina content is not less than 32%.

[0027] The high-temperature mullite is γ-mullite, and the iron oxide and titanium dioxide dissolved therein are used to promote the formation of the ceramic phase during sintering and avoid the collapse of the air channels caused by high-temperature sintering.

[0028] Example 2

[0029] A high-temperature lightweight mullite brick, by weight, comprises the following components: 44 parts of alumina, 24 parts of cyanite, 15 parts of soft clay, 23 parts of high-temperature mullite, 35 parts of sawdust, 23 parts of burnable polyethylene balls, and 10 parts of a reinforcing agent;

[0030] The sawdust is used to form microscopic air channels and reinforce the pores;

[0031] The sintering temperature of the mixture is 1200°C to 1800°C;

[0032] The reinforcing agent is quartz powder.

[0033] The sintered mixture is kept warm for 2.5 to 8 hours. The higher the sintering temperature, the longer the holding time.

[0034] The silica content of the soft clay is not less than 52.6%, and the alumina content is not less than 32%.

[0035] The high-temperature mullite is γ-mullite, and the iron oxide and titanium dioxide dissolved in it are used to promote the formation of the ceramic phase during sintering and to avoid airway collapse caused by high-temperature sintering.

[0036] Example 3

[0037] A high-temperature lightweight mullite brick, by weight, comprises the following components: 40 parts of alumina, 20 parts of kyanite, 15 parts of soft clay, 20 parts of high-temperature mullite, 30 parts of sawdust, 20 parts of burnable polyethylene balls, and 10 parts of a reinforcing agent;

[0038] The sawdust is used to form microscopic airways and reinforce the pores;

[0039] The sintering temperature of the mixture is 1200°C to 1800°C;

[0040] The reinforcing agent is quartz powder.

[0041] The sintered mixture is kept warm for 2.5 to 8 hours. The higher the sintering temperature, the longer the holding time.

[0042] The silica content of the soft clay is not less than 52.6%, and the alumina content is not less than 32%.

[0043] The high-temperature mullite is γ-mullite, and the iron oxide and titanium dioxide dissolved in it are used to promote the formation of the ceramic phase during sintering and to avoid airway collapse caused by high-temperature sintering.

[0044] The refractory materials with different dosages in Examples 1 to 3 are prepared. At a large temperature range, with the excessive addition of sawdust, that is, when the proportion of sawdust in alumina and kyanite is too large, due to the formation of excessive microscopic airways, the matrix cannot effectively bear the cavities. Therefore, compared with Examples 1 and 2, the porosity of Example 3 is the best choice.

[0045] Example 4

[0046] On the basis of Example 3, the sintering temperature is selected as 1200°C and the holding time is 2.5 hours.

[0047] Example 5

[0048] On the basis of Example 3, the sintering temperature is selected to be 1200° C. and the holding time is 3 hours.

[0049] Example 6

[0050] Based on Example 3, the sintering temperature was selected to be 1200° C. and kept at this temperature for 8 hours.

[0051] After the performance evaluation of the refractory materials prepared in Examples 4 to 6, their mechanical properties are improved to a certain extent with the increase of the insulation time. However, after measuring the apparent porosity of different materials in Examples 4 to 6, it is obviously found that the apparent porosity of the materials gradually decreases with the increase of the insulation time. The reason is that under the insulation condition of 1200°C, sawdust and polyethylene can only be burned away. Even after carbonization, sawdust and polyethylene are difficult to combine with the solid solution material of high-temperature mullite, and cannot form a reinforcement layer for microscopic airways and cavities. Therefore, with the increase of the insulation time, the cavities and microscopic airways formed by burning out the polyethylene balls and sawdust collapse in large quantities, resulting in a decrease in apparent porosity and an increase in density, thereby increasing the density and improving the mechanical properties.

[0052] Example 7

[0053] Based on Example 3, the sintering temperature is selected to be 1800° C. and the temperature is kept for 2.5 hours.

[0054] Example 8

[0055] On the basis of Example 3, the sintering temperature was selected to be 1800° C. and kept at this temperature for 3 hours.

[0056] Example 9

[0057] Based on Example 3, the sintering temperature is selected to be 1800° C. and kept at this temperature for 8 hours.

[0058] Example 10

[0059] Based on Example 3, the sintering temperature was selected to be 1800° C. and kept at this temperature for 9 hours.

[0060] The performance of the above-mentioned Examples 4 to 10 was tested, as shown in the following table.

[0061]

[0062] From the comparison between Example 7 and Example 8, when the sintering temperature is 1800 °C, as the holding time increases, the strengthening effect of the C-metal alloy on the inner wall of the relative micro air passage becomes more obvious. Therefore, a large number of formed micro air passages can be maintained, and the apparent porosity is higher. Moreover, under high-temperature sintering, the melting of quartz can occur, so a good high-temperature sintering strengthening effect can also be produced on the cavities. When the holding time is too long, the strengthening effect of the C-metal alloy formed inside the matrix on the micro air passage is difficult to support high-temperature sintering. Therefore, some micro air passages collapse, resulting in a decrease in apparent porosity. However, due to the long high-temperature sintering time, its overall normal-temperature milk pressure strength is higher.

[0063] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-temperature lightweight mullite brick, characterized in that: By weight, it includes the following components: 40 - 44 parts of alumina, 18 - 24 parts of cyanite, 10 - 15 parts of soft clay, 18 - 23 parts of high - temperature mullite, 25 - 35 parts of sawdust, 15 - 23 parts of burn - off polyethylene balls, and a reinforcing agent; The sawdust is used to form microscopic air channels and reinforce the pores; The sintering temperature of the mixture is 1200°C - 1800°C; The reinforcing agent is quartz powder; The high - temperature mullite is γ - mullite, and iron oxide and titanium dioxide are solid - solved in the high - temperature mullite.

2. The high-temperature lightweight mullite brick according to claim 1, characterized in that: By weight, it is 40 parts of alumina, 20 parts of cyanite, 15 parts of soft clay, 20 parts of high - temperature mullite, 30 parts of sawdust, 20 parts of burn - off polyethylene balls, and 10 parts of the reinforcing agent.

3. The high-temperature lightweight mullite brick according to claim 1, characterized in that: The sintered mixture is heat - insulated for 2.5 - 8 hours. The higher the sintering temperature, the longer the heat - insulation time.

4. The high-temperature lightweight mullite brick according to claim 1, characterized in that: The silica content of the soft clay is not less than 52.6%, and the alumina content is not less than 32%.

5. The high-temperature lightweight mullite brick according to claim 1, characterized in that: The iron oxide and titanium dioxide solid - solved in the high - temperature mullite are used to promote the formation of ceramic phases during sintering and avoid airway collapse caused by high - temperature sintering.

6. A preparation method of the high-temperature lightweight mullite brick according to any one of claims 1 to 5, characterized in that: After blending 40 - 44 parts of alumina, 18 - 24 parts of cyanite, 10 - 15 parts of soft clay, 18 - 23 parts of high - temperature mullite, 25 - 35 parts of sawdust, 15 - 23 parts of burn - off polyethylene balls, and the reinforcing agent, it is pressed into a brick blank and sintered at 1800°C for 8 hours of heat - insulation.

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