A method for preparing a step-density microcrystalline foamed ceramic using industrial solid waste

Abstract

The present application relates to the technical field of foamed ceramic preparation, in particular to a method for preparing step density microcrystalline foamed ceramic by using industrial solid waste, which comprises the following steps: taking aluminum-silicon industrial solid waste as the main raw material, adding 3-15% of refractory brick waste as a foam stabilizer, 2-10% of a composite pore-forming agent composed of electrolytic manganese residue, graphite tailings and silicon carbide powder, and 0.1-0.5% of triethanolamine, mixing the above-mentioned materials by dry ball milling to obtain a uniform powder, loading the powder into a refractory mold, and then foaming the powder by high-temperature heating, partition temperature control and cooling cutting to obtain microcrystalline foamed ceramic with step density change. The method for preparing step density microcrystalline foamed ceramic by using multiple solid wastes can realize one-time firing of multiple density composite microcrystalline foamed ceramic and promote the high value-added utilization of multiple industrial solid wastes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foamed ceramic preparation, in particular to a method for preparing hierarchical density microcrystalline foamed ceramic by using industrial solid waste. BACKGROUND

[0002] Energy-saving wall materials are the basic building materials to support green buildings. At present, the main external wall insulation materials in China are organic insulation materials such as polystyrene boards (accounting for 80%), which have poor fire resistance, are prone to aging, have poor durability, and have a short service life. The main internal partition wall materials are autoclaved aerated concrete stone cuttings and sintered perforated bricks (accounting for 90%), which have poor thermal insulation performance, high water absorption, large drying shrinkage, and are prone to wall seepage and cracking. Therefore, developing new self-insulation wall materials that are fire-resistant, aging-resistant, thermal-insulating, and waterproof, and gradually replacing external wall insulation materials with self-insulation wall materials, is an important direction for the development of building materials today.

[0003] Microcrystalline foamed ceramic is a kind of porous material composed of a large number of closed pores and ceramic base pore walls, which has the characteristics of lightweight, high strength, thermal insulation, fire resistance, waterproof, frost resistance, aging resistance, and ecological environmental protection. At present, foamed ceramic has been applied in the field of building as external wall insulation board and self-insulation partition board. At the same time, a large amount of industrial solid waste is used to prepare foamed ceramic to reduce its preparation cost. For example, Chinese invention application CN202110924748.0 discloses a foamed ceramic prepared by using gold tailings and coal gangue and a preparation method. Although a large amount of industrial solid waste is used in the preparation process, long stone, talc and other fluxing components, and silicon carbide powder, calcite and other foaming agents still need to be added, and the raw material cost is still high.

[0004] On the other hand, high-density foamed ceramic (400-600 kg / m 3 ) has been used as lightweight wallboard due to its excellent strength, but due to its high thermal conductivity, it cannot meet the thermal insulation requirements of building external walls when used alone, and needs to be used in combination with low-density foamed ceramic or other high-efficiency thermal insulation materials. For example, Chinese invention application CN202010556801.1 discloses a foamed ceramic composite board, a preparation method thereof and a building wallboard. By sandwiching a layer of thermal insulation board or building waste crushed board between two foamed ceramic boards, a composite wallboard with good thermal insulation, flame retardation and waterproof performance is prepared. Although this preparation method makes the wallboard have high strength and good thermal insulation performance, the construction process is complex, which is not conducive to its large-scale application. If foamed ceramic with hierarchical density can be prepared at one time and used as building external wallboard, the wallboard can have good mechanical properties and thermal insulation performance. This not only helps to promote the efficient application of foamed ceramic in the field of building, but also helps to improve the performance of building wall.

[0005] Microcrystalline foamed ceramics are mainly prepared by powder high-temperature foaming method. The high-viscosity melt formed by the melting of the powder blank at high temperature wraps the gas generated by the decomposition of the foaming agent, so that the blank expands to form a porous foam structure, and microcrystalline foamed ceramics are obtained after cooling and solidification. Therefore, by changing the amount of foaming agent, the porosity and bulk density of the foamed ceramics can be arbitrarily controlled. Chinese invention patent CN201810339207.X discloses a one-time sintering multi-density composite foamed ceramic decorative plate and a preparation method thereof. The method is to layer the blank with different amounts of foaming agent in turn, compact it into a whole, and then sinter it at high temperature to obtain a multi-density composite foamed ceramic. Although this method can prepare multi-density composite foamed ceramics, it needs to prepare multiple powders respectively, and then layer them, which is complicated and not conducive to large-scale application. If the same blank is used to sinter the composite foamed ceramics with step density at one time, the preparation process will be greatly simplified.

[0006] The amount and viscosity of the liquid phase formed at the high-temperature stage of the foamed ceramics are the main factors affecting the growth of pores. As the sintering temperature increases, the amount of liquid phase increases, the viscosity of the liquid phase decreases, and the resistance to pore growth decreases. In the same foaming and holding time, foamed ceramics with higher porosity and lower density will be formed. Therefore, if the temperature difference between the upper and lower surfaces of the blank can be controlled by adjusting the temperature of the furnace chamber during the foaming stage, the blank will foam to form a foamed ceramic plate with gradually changing density.

[0007] In view of the above defects, the inventor of the present application has finally obtained the present application after a long period of research and practice. SUMMARY

[0008] The purpose of the present application is to solve the problems of insufficient thermal insulation performance of high-density foamed ceramics, insufficient mechanical properties of low-density foamed ceramics, and complex preparation process of existing multi-density composite foamed ceramics when foamed ceramics are used as wall materials, and to provide a method for preparing foamed ceramics with step density using industrial solid waste.

[0009] In order to achieve the above purpose, the present application discloses a method for preparing foamed ceramics with step density using industrial solid waste, comprising the following steps:

[0010] S1, raw material pretreatment: dry the aluminum-silicon industrial solid waste, electrolytic manganese slag, graphite tailings and refractory brick waste to a moisture content of less than 1%, and grind them into powders respectively for use;

[0011] S2, mixing and grinding: take the aluminum-silicon industrial solid waste, and on the basis of the mass of the aluminum-silicon industrial solid waste, sequentially take 3-15% of the refractory brick waste powder, 2-10% of the composite pore-forming agent, and 0.1-0.5% of the triethanolamine, and mix all the raw materials in the ceramic ball mill for 4-10h to obtain a mixed powder;

[0012] S3, mold forming: the powder obtained in step S2 is filled into a square refractory mold assembled by refractory plates, the filling thickness is 5-10 cm, the powder is shaken to be dense, and the powder surface is scraped flat;

[0013] S4, temperature control foaming: the refractory mold filled with the powder obtained in step S3 is placed in a kiln that can be independently heated up and down and independently controlled in temperature, the temperature is increased to 1100-1250℃ at a rate of 2-8℃ / min, the temperature at the upper part of the furnace cavity is controlled to be 10-80℃ higher than that at the bottom, and the foaming firing is performed for 20-60 min;

[0014] S5, cooling and cutting: the material obtained by firing in step S4 is cooled to 800-920℃ at a rate of -10℃ / min, and the cooling stress is eliminated by keeping the temperature for 30 min, and then the material is cooled to room temperature with the furnace, and the product with regular shape is obtained after cutting.

[0015] In the step S1, the aluminum-silicon industrial solid waste includes at least one of granite sawing mud and lithium tailings, and the chemical composition satisfies: SiO2+Al2O3: 75-95wt%, Na2O+K2O: 5-12wt%, CaO+MgO: 1-6wt%, Fe2O3: 0-5wt%.

[0016] In the step S1, the electrolytic manganese residue is a solid waste discharged in the process of electrolytic manganese refining, and the chemical composition satisfies: SiO2: 20-40wt%, Al2O3: 1-10wt%, CaO: 10-20wt%, MnO+Fe2O3: 10-20wt%, SO3: 15-30wt%, and the mineral composition contains 20wt%-40wt% of CaSO4·nH2O, wherein n=0, 0.5, 2.

[0017] In the step S1, the graphite tailings are solid wastes generated in the process of graphite mining and processing, and the chemical composition satisfies: SiO2: 45-65wt%, Al2O3: 5-20wt%, CaO+MgO: 5-20wt%, Na2O+K2O: 3-8wt%, and loss on ignition: 10-20wt%.

[0018] In the step S1, the graphite tailings are solid wastes generated in the process of graphite mining and processing, and the chemical composition satisfies: SiO2: 45-65wt%, Al2O3: 5-20wt%, CaO+MgO: 5-20wt%, Na2O+K2O: 3-8wt%, and loss on ignition: 10-20wt%.

[0019] In the step S1, the refractory brick waste includes at least one of cordierite refractory brick waste, spinel refractory brick waste, and corundum refractory brick waste.

[0020] In the step S1, the ground raw material needs to pass through the 200 mesh standard sieve; wherein, the electrolytic manganese residue and the graphite tailings need to be ground to pass through the 500 mesh standard sieve, and the refractory brick waste needs to be ground to pass through the 1000 mesh standard sieve.

[0021] In the step S2, the composite pore-forming agent is composed of the electrolytic manganese residue, the graphite tailings and the silicon carbide powder, and the mass ratio is 3:5:0.2.

[0022] The median particle size of the silicon carbide powder is 8-13 μm.

[0023] In the step S4, the refractory mold needs to be placed in the kiln in the air, so that the distance between the mold and the heat source on the top and bottom surfaces of the furnace is the same, and the heating mode is electric heating or flame heating.

[0024] The present application proposes a method for preparing the step density microcrystalline foamed ceramics from industrial solid wastes, which not only utilizes the granite sawing mud and lithium tailings, such low melting point aluminum-silicon industrial solid wastes, but also uses the electrolytic manganese residue and the graphite tailings which can produce gas at high temperature as the pore-forming agent. When the above raw materials are mixed in a certain proportion, the high-temperature liquid phase produced by partial melting at high temperature can wrap the gas produced by the decomposition of the pore-forming agent, and form a foam structure. At the same time, the amount of liquid phase produced in the range of 1100-1250℃ of the blank made of the preferred raw material ratio of the present application will gradually increase with the increase of temperature, resulting in the decrease of the viscosity of the blank body, and the decrease of the growth resistance of the pores, so that the foamed ceramics with higher porosity and lower density will be formed. Based on this principle, the up-down temperature control foaming process is adopted, so that a certain temperature difference is formed on the upper and lower surfaces of the blank body, and the microcrystalline foamed ceramics with gradually changing density are prepared.

[0025] In the implementation of the technology, not only the composition characteristics and the mixing ratio of the raw materials are considered to obtain the blank with the gradually increasing amount of high-temperature liquid phase with the increase of temperature, but also the sintering temperature of the temperature control foaming is considered to avoid the high sintering temperature, which leads to the rapid growth of the pores and causes the pores to float and break. The preferred stable foam agent plays an important role in avoiding the abnormal growth of the bubbles.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1. The step density microcrystalline foamed ceramics obtained by the present application has high strength and low thermal conductivity, and when it is used to build the building outer wall, only two mirror image foamed ceramics with bulk density are stacked, and the low-density thermal insulation core material is not needed between the boards, and the process is simple.

[0028] 2、The present application adopts low-melting-point lithium tailings and granite saw mud as main raw materials, electrolytic manganese slag, graphite tailings and composite SiC powder capable of high-temperature decomposition to produce gas as a composite pore-forming agent, and refractory brick waste powder as a foam stabilizer, so that the full-solid-waste-prepared foamed ceramics are realized, which not only reduces the raw material cost of the foamed ceramics, but also promotes the resource utilization of solid waste.

[0029] 3、The present application adopts a formula, and through one-time piling and forming and one-time calcination, the composite foamed ceramics with gradient density are obtained, without the need of preparing multiple formula powders, so that the process is simple and helps large-scale popularization and use. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A cross-sectional morphology of the gradient density microcrystalline foamed ceramics prepared in Example 1 of the present application;

[0031] Figure 2 An XRD graph of the gradient density microcrystalline foamed ceramics prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0032] The above and other technical features and advantages of the present application will be explained in more detail with reference to the accompanying drawings.

[0033] Example 1

[0034] The present embodiment provides a method for preparing gradient density microcrystalline foamed ceramics by using industrial solid waste, comprising the following steps:

[0035] (1) The lithium tailings, electrolytic manganese slag, graphite tailings and spinel refractory brick waste are dried to a water content of less than 1%, and the lithium tailings are ground to pass through a 200-mesh standard sieve, the electrolytic manganese slag and the graphite tailings are ground to pass through a 500-mesh standard sieve, and the spinel refractory brick waste is ground to pass through a 1000-mesh standard sieve.

[0036] (2) 1.0 kg of lithium tailings powder, 120 g of spinel refractory brick waste powder, 60 g of composite pore-forming agent (containing 21.95 g of electrolytic manganese slag, 36.59 g of graphite tailings and 1.46 g of silicon carbide micro powder with a median particle size of 11 μm), and 2 g of triethanolamine are weighed. All the raw materials are added to a ceramic ball mill for dry mixing for 6 h to obtain a mixed powder;

[0037] (3) The obtained powder is loaded into a square refractory mold assembled by refractory plates, the loading thickness is 8 cm, the powder is lightly shaken several times until it is compacted, and the powder surface is scraped flat.

[0038] (4) Put the refractory mold into the electric furnace which can independently control the temperature of the upper and lower parts, adjust the temperature controller, and make the upper part of the furnace cavity heat up to 1200℃ at a rate of 4℃ / min, the lower part of the furnace cavity heat up to 1140℃ at the same time, and keep the temperature for 60min to foam and sinter.

[0039] (5) After the sintering is completed, heat down to 880℃ at a rate of -10℃ / min, keep the temperature for 30min, and then cool down to room temperature with the furnace, cut to form a product with regular shape, i.e. the stepped density microcrystalline foamed ceramic sample 1.

[0040] The cut and formed stepped density microcrystalline foamed ceramic sample has the physical properties shown in Table 1. The pore structure of the sample is shown in Figure 1 , and the XRD diffraction pattern of the upper and lower surfaces of the sample is shown in Figure 2 .

[0041] Table 1 Properties of the stepped density microcrystalline foamed ceramic sample 1

[0042]

[0043] Example 2

[0044] The present example provides a method for preparing a stepped density microcrystalline foamed ceramic using industrial solid waste, comprising the following steps:

[0045] (1) Pretreat the lithium tailings, electrolytic manganese residue, graphite tailings, and corundum refractory brick waste, and the specific steps and parameters are the same as those in Example 1.

[0046] (2) Take 1.0kg of lithium tailings powder, 100g of corundum refractory brick waste powder, 80g of composite pore-forming agent (containing 29.27g of electrolytic manganese residue, 48.78g of graphite tailings, and 1.95g of silicon carbide micro powder with a median particle size of 11μm), and 2g of triethanolamine. Mix all the raw materials in a ceramic ball mill for 8h to obtain a mixed powder;

[0047] (3) Put the obtained powder into a square refractory mold assembled by refractory plates, fill the thickness of 5cm, shake several times until the powder is compacted, and scrape the surface of the powder.

[0048] (4) Put the refractory mold into the electric furnace which can independently control the temperature of the upper and lower parts, adjust the temperature controller, and make the upper part of the furnace cavity heat up to 1240℃ at a rate of 4℃ / min, the lower part of the furnace cavity heat up to 1160℃ at the same time, and keep the temperature for 60min to foam and sinter.

[0049] (5) After the sintering is completed, heat down to 890℃ at a rate of -10℃ / min, keep the temperature for 30min, and then cool down to room temperature with the furnace, cut to form a product with regular shape, i.e. the stepped density microcrystalline foamed ceramic sample 2.

[0050] The different physical properties of the step density microcrystalline foamed ceramic sample 2 are shown in Table 2.

[0051] Table 2 Properties of step density microcrystalline foamed ceramic sample 2

[0052]

[0053] Example 3

[0054] The present example provides a method for preparing step density microcrystalline foamed ceramic using industrial solid waste, comprising the following steps:

[0055] (1) The lithium tailings, electrolytic manganese residue, graphite tailings, and cordierite refractory brick waste were pretreated. The specific steps and parameters were the same as those in Example 1.

[0056] (2) 1.0 kg of lithium tailings powder, 60 g of cordierite refractory brick waste powder, 50 g of composite pore-forming agent (containing 18.29 g of electrolytic manganese residue, 30.49 g of graphite tailings, and 1.22 g of silicon carbide micro powder with a median particle size of 11 μm), and 1.5 g of triethanolamine were weighed. All raw materials were added to a ceramic ball mill and dry mixed for 6 h to obtain a mixed powder;

[0057] (3) The obtained powder was loaded into a square refractory mold assembled by refractory plates, with a packing thickness of 10 cm. The powder was compacted by gently shaking several times, and the powder surface was scraped flat.

[0058] (4) The refractory mold was placed in an electric furnace with independent temperature control on the upper and lower parts. The temperature controller was adjusted to raise the upper part of the furnace to 1180℃ at a rate of 4℃ / min, and the lower part of the furnace to 1150℃ at the same time, and maintain the temperature for 60 min for foaming and sintering.

[0059] (5) After the sintering was completed, the temperature was lowered to 860℃ at a rate of -10℃ / min, and maintained for 60 min. Then, the furnace was cooled to room temperature. After cutting, the product with regular shape, i.e., step density microcrystalline foamed ceramic sample 3, was obtained.

[0060] The different physical properties of the step density microcrystalline foamed ceramic sample 3 are shown in Table 3.

[0061] Table 3 Properties of step density microcrystalline foamed ceramic sample 3

[0062]

[0063] Example 4

[0064] The present example provides a method for preparing step density microcrystalline foamed ceramic using industrial solid waste, comprising the following steps:

[0065] (1) Pretreatment of granite sawing mud, electrolytic manganese residue, graphite tailings, and spinel refractory brick waste, the specific steps and parameters are the same as those of Example 1.

[0066] (2) 1.0 kg of granite sawing mud, 50 g of spinel refractory brick waste powder, 20 g of composite pore-forming agent (containing 7.31 g of electrolytic manganese residue, 12.20 g of graphite tailings, and 0.49 g of silicon carbide micro powder with a median particle size of 11 μm), and 3 g of triethanolamine were weighed. All raw materials were added to a ceramic ball mill and dry mixed for 6 h to obtain a mixed powder;

[0067] (3) The obtained powder was loaded into a square refractory mold assembled by refractory plates, with a packing thickness of 10 cm, and lightly shaken several times to compact the powder. The powder surface was scraped flat.

[0068] (4) The refractory mold was placed in an electric furnace with independent temperature control of the upper and lower parts. The temperature controller was adjusted to raise the upper part of the furnace to 1200°C at a rate of 5°C / min, and the lower part of the furnace to 1140°C at the same time, and maintain the temperature for 60 min for foaming and sintering.

[0069] (5) After the sintering was completed, the temperature was lowered to 800°C at a rate of -10°C / min, and maintained for 60 min. Then, the furnace was cooled to room temperature. After cutting, the product with regular shape, i.e., the hierarchical density microcrystalline foamed ceramic sample 4, was obtained.

[0070] The different physical properties of the hierarchical density microcrystalline foamed ceramic sample 4 were measured and shown in Table 4.

[0071] Table 4 Properties of hierarchical density microcrystalline foamed ceramic sample 4

[0072]

[0073] Example 5

[0074] The present embodiment provides a method for preparing hierarchical density microcrystalline foamed ceramics using industrial solid waste, comprising the following steps:

[0075] (1) Pretreatment of granite sawing mud, electrolytic manganese residue, graphite tailings, and spinel refractory brick waste, the specific steps and parameters are the same as those of Example 1.

[0076] (2) 1.0 kg of granite sawing mud, 100 g of spinel refractory brick waste powder, 100 g of composite pore-forming agent (containing 36.59 g of electrolytic manganese residue, 60.98 g of graphite tailings, and 2.44 g of silicon carbide micro powder with a median particle size of 11 μm), and 4 g of triethanolamine were weighed. All raw materials were added to a ceramic ball mill and dry mixed for 8 h to obtain a mixed powder;

[0077] (3) The obtained powder is loaded into a square refractory mold assembled by refractory plates, with a loading thickness of 10 cm, and shaken several times until the powder is compacted, and the powder surface is scraped flat.

[0078] (4) The refractory mold is placed in an electric furnace with independent temperature control, the temperature controller is adjusted, the upper part of the furnace is heated to 1200℃ at a rate of 3℃ / min, the lower part of the furnace is heated to 1140℃ at the same time, and the temperature is maintained for 60 min to foam and sinter.

[0079] (5) After the sintering is completed, the temperature is decreased to 820℃ at a rate of -10℃ / min, and maintained for 60 min, then the furnace is cooled to room temperature, and the product is cut to form a product with regular shape, i.e. the stepped density microcrystalline foamed ceramic sample 5.

[0080] The different physical properties of the stepped density microcrystalline foamed ceramic sample 5 are shown in Table 5.

[0081] Table 5 Properties of the stepped density microcrystalline foamed ceramic sample 5

[0082]

[0083] The chemical composition of the solid waste raw material used in Examples 1-5 is shown in Table 6.

[0084] Table 6 Chemical composition of the solid waste raw material used in Examples 1-5

[0085]

[0086] The above description is only the preferred embodiments of the present application, which is only illustrative but not limiting. Those skilled in the art understand that many changes, modifications, and even equivalents can be made to the present application within the spirit and scope of the present application as defined in the claims, and all of them will fall within the protection scope of the present application.

Claims

1. A method for preparing a step-density microcrystalline foamed ceramic using industrial solid waste, characterized by, The method comprises the following steps: S1, raw material pretreatment: dry the aluminum-silicon industrial solid waste, electrolytic manganese residue, graphite tailings, and refractory brick waste to a moisture content of less than 1%, and grind them into powders respectively for standby; S2, mixing and grinding: take the aluminum-silicon industrial solid waste, and on the basis of the mass of the aluminum-silicon industrial solid waste, sequentially take 3-15% of the refractory brick waste powder, 2-10% of the composite pore-forming agent, and 0.1-0.5 wt % of triethanolamine, mix all the raw materials in a ceramic ball mill for 4-10 hours by dry method to obtain a mixed powder; S3, mold forming: put the powder obtained in step S2 into a square refractory mold assembled by refractory plates, fill the powder to a thickness of 5-10 cm, shake gently to compact the powder, and scrape the surface of the powder; S4, temperature control foaming: put the refractory mold containing the powder obtained in step S3 into a kiln that can be independently heated and controlled in temperature from top to bottom, heat to 1100-1250 ℃ at a rate of 2-8 ℃ / min, control the temperature of the upper part of the furnace cavity to be 10-80 ℃ higher than that of the bottom, and keep the temperature for 20-60 min for foaming and sintering; S5, cooling and cutting: cool the material obtained by sintering in step S4 to 800-920 ℃ at a rate of -10 ℃ / min, keep the temperature for 30 min to eliminate cooling stress, and then cool to room temperature with the furnace, cut to obtain products with regular shapes; In step S1, the refractory brick waste includes at least one of cordierite-based refractory brick waste, spinel-based refractory brick waste, and corundum-based refractory brick waste; In step S1, the ground raw materials need to pass through a 200-mesh standard sieve; wherein the electrolytic manganese residue and the graphite tailings need to be ground to pass through a 500-mesh standard sieve, and the refractory brick waste needs to be ground to pass through a 1000-mesh standard sieve; In step S2, the composite pore-forming agent is composed of electrolytic manganese residue, graphite tailings, and silicon carbide powder, and the mass ratio is 3:5:0.

2.

2. The method of claim 1, wherein the method of preparing the step-density microcrystalline foamed ceramics using industrial solid waste is characterized by, In step S1, the aluminum-silicon industrial solid waste includes at least one of granite sawing mud and lithium tailings, and the chemical composition satisfies: SiO2+ Al2O3: 75-95 wt %, Na2O+K2O: 5-12 wt %, CaO+MgO: 1-6 wt %, Fe2O3: 0-5 wt %, and the total chemical composition mass percentage is 100%.

3. The method of claim 1, wherein the method is characterized by, In step S1, the electrolytic manganese residue is a solid waste discharged in the process of electrolytic manganese production, and the chemical composition satisfies: SiO2: 20-40 wt %, Al2O3: 1-10 wt %, CaO: 10-20 wt %, MnO+Fe2O3: 10-20 wt %, SO3: 15-30 wt %, and the mineral composition contains 20 wt %-40 wt % of CaSO4·nH2O, wherein n=0, 0.5, 2.

4. The method of claim 1, wherein the method of preparing the step-density microcrystalline foamed ceramics using industrial solid waste is characterized by, The graphite tailings in the step S1 are solid wastes generated in the graphite mining and processing, and the chemical composition satisfies: SiO2: 45~65 wt %, Al2O3: 5~20 wt %, CaO+MgO: 5~20 wt %, Na2O+K2O: 3~8 wt %, loss on ignition: 10~20%.

5. The method of claim 1, wherein the method of preparing the step-density microcrystalline foamed ceramics using industrial solid waste is characterized by, The median particle size of the silicon carbide micro powder is 8~13 μm.

6. The method of claim 1, wherein the method of preparing the step-density microcrystalline foamed ceramics using industrial solid waste is characterized by, In the step S4, the refractory mold needs to be placed in the kiln in the air, so that the mold is at the same distance from the heat source on the top surface and the bottom surface of the hearth, and the heating mode is electric heating or flame heating.

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