Low-expansion cordierite ceramic prepared from chlorite and preparation method of low-expansion cordierite ceramic

Abstract

The invention discloses low-expansion cordierite ceramic prepared from chlorite and a preparation method of the low-expansion cordierite ceramic. The low-expansion cordierite ceramic is prepared from the following chemical components in percentage by mass: 47.3 to 48.8 percent of SiO2, 37.6 to 39.1 percent of Al2O3, 0.5 to 0.6 percent of CaO, 12.35 to 13.4 percent of MgO, 0.05 to 0.1 percent of Fe2O3, 0.01 to 0.02 percent of K2O, 0.003 to 0.009 percent of Na2O and 0.16 to 0.21 percent of TiO2. The preparation method comprises the following steps: 1, taking chlorite as a raw material, and adding kaolin and aluminum oxide to prepare a cordierite precursor; step 2, adding fused quartz into the cordierite precursor prepared in the step 1 to prepare mixed powder; and 3, molding the mixed powder obtained in the step 2, and firing to obtain the low-expansion cordierite ceramic.

Description

Technical Field

[0001] The present invention relates to the field of ceramic technology, and particularly to a low-expansion cordierite ceramic prepared from chlorite and a preparation method thereof. Background Art

[0002] As a group silicate mineral, cordierite has a hexagonal crystal structure, and the structural unit is a six-membered ring composed of [SiO4] tetrahedrons and [AlO4] tetrahedrons. This unit is arranged orderly along the c-axis direction, and the silicon-oxygen tetrahedron and the aluminum-oxygen tetrahedron are connected by sharing edges. Therefore, it has a series of excellent properties such as excellent thermal expansion performance, thermal shock resistance, and chemical stability, and can meet various requirements. Cordierite can be found in thermal industrial furnaces, electronic devices, low-expansion ceramics, kiln furniture, and lithography machines. However, the yield of natural cordierite is very low, and its performance is poor and it cannot be utilized. Therefore, cordierite needs to be synthesized artificially. Among them, the solid-phase synthesis method is a method used more in industrial production. At present, the synthesis of cordierite mostly adopts the talc-kaolin-aluminum oxide system and the kaolinite-magnesite-talc system. However, using this talc-based formulation system, since talc is often associated with dolomite or calcite, the CaO content in the formulation system is often high, generally between 3% and 8%, resulting in low purity of the synthesized cordierite, and the synthesis amount of cordierite is unstable, resulting in a large expansion coefficient of cordierite, generally between 2.8×10 -6 / °C - 3.5×10 -6 / °C fluctuates. Products such as honeycomb ceramics, kiln furniture, and heat-resistant ceramics made of this cordierite have poor thermal shock resistance, are prone to cracking, resulting in short service life and increased replacement costs. With the update and iteration of equipment and the improvement of usage scenario requirements, the requirements for the performance of cordierite powder are also getting higher and higher. Some enterprises are also using the flotation process to improve the purity of talc to increase the synthesis amount of cordierite and reduce the expansion coefficient of synthesized cordierite. However, this process causes secondary pollution and increases costs. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problem of high talc content in the raw materials for artificially synthesizing cordierite in the prior art, and to provide a low-expansion cordierite ceramic prepared from chlorite and a preparation method thereof.

[0004] The present invention is achieved through the following technical solutions: A low-expansion cordierite ceramic prepared from chlorite, characterized in that: the chemical composition of the low-expansion cordierite ceramic is as follows by mass percentage: SiO2 47.3 - 48.8%, Al2O3 37.6 - 39.1%, CaO 0.5 - 0.6%, MgO 12.35 - 13.4%, Fe2O3 0.05 - 0.1%, K2O 0.01 - 0.02%, Na2O 0.003 - 0.009%, TiO2 0.16 - 0.21%.

[0005] The preparation method of the above low-expansion cordierite ceramics is characterized by including the following steps: Step 1: Using chlorite as the raw material, after ball milling and sieving, a certain amount of kaolin and alumina are added and mixed evenly, and then wet ball milling, calcination, and pulverization are carried out to obtain a cordierite precursor; Step 2: A certain amount of fused quartz is added to the cordierite precursor prepared in Step 1, and the slurry after ball milling is placed in an oven for drying to obtain a mixed powder; Step 3: The mixed powder prepared in Step 2 is granulated, aged, dry-pressed into shape, and fired to obtain low-expansion cordierite ceramics.

[0006] The chemical composition of the chlorite in Step 1 is as follows in mass percentage: SiO2 32.45 - 33.72%, Al2O3 15.86 - 16.06%, Fe2O3 0.5 - 0.6%, TiO2 0.54 - 0.64%, CaO 0.05 - 0.07%, MgO 35.54 - 35.64%, K2O 0.04 - 0.06%, Na2O 0.01 - 0.02%, loss on ignition 13.6 - 14.6%.

[0007] In Step 1, the chlorite is ball milled for 30 min and then sieved through a 80 - 120 mesh sieve, the fineness of kaolin is through a 40 - 80 mesh sieve, the fineness of alumina is through a 120 - 160 mesh sieve, and the weight ratio of chlorite:kaolin:alumina is 29.8 - 32.4:44.6 - 64.7:2.9 - 12.9.

[0008] In Step 1, the time of the wet ball milling process is 20 - 30 min, the temperature of the calcination process is 800 - 900 °C, the heat preservation time is 1 - 2 h, and the fineness of the pulverization process is through a 250 mesh sieve.

[0009] In Step 2, the weight ratio of cordierite precursor:fused quartz is 29.8 - 32.4:0.5 - 10.

[0010] In Step 2, the weight ratio of the material:water:ball mill in the ball milling process is 1:4 - 5:1.5 - 2.5, the ball milling time is 20 - 40 min, the fineness is through an 80 - 100 mesh sieve, the temperature of the drying process is 80 °C, and the drying time is 12 h.

[0011] In Step 3, the particle size of the granulation process is through an 80 - 100 mesh sieve, the time of the aging process is 2 - 4 h, the pressure of the dry pressing process is 5 - 10 MPa, and the pressure holding time is 30 - 40 s.

[0012] In the firing process in Step 3, the firing regime is as follows: the heating rate from 50 to 600 °C is 2.5 to 3.5 °C / min, the heating rate from 600 to 1000 °C is 4 to 5 °C / min, the heating rate from 1000 °C to the maximum firing temperature is 2 to 3 °C / min, the holding time at the maximum firing temperature is 2 to 4 h, and then it cools down with the furnace. The maximum firing temperature is 1300 to 1360 °C.

[0013] The crystallinity of the low-expansion cordierite ceramic obtained in Step 3 is 88.5 to 93.8%, the flexural strength is 40.12 to 43.38 MPa, the coefficient of thermal expansion from room temperature to 800 °C is 1.86 to 2.53×10 -6 / °C, the water absorption rate is 2.23 to 2.96%, and the bulk density is 2.185 to 2.445 g / cm 3 .

[0014] The present invention has the following beneficial effects: (1) The chlorite used in the present invention has a relatively high component purity and a low content of elements (Ca, K, Na) with a high coefficient of thermal expansion, and can synthesize a cordierite ceramic material with a high crystallinity and a low coefficient of thermal expansion.

[0015] (2) The present invention adds fused quartz with a low coefficient of thermal expansion, which can generate a glassy phase with low expansion at high temperatures, promotes the synthesis of cordierite crystals, reduces the water absorption rate of the cordierite ceramic, makes the structure more dense, and improves the flexural strength of the ceramic.

[0016] (3) The application method of the present invention has a simple process, low production cost, high production efficiency, low production energy consumption, is economical and environmentally friendly, preferably overcomes the problem of a relatively high talc content in the existing raw materials for preparing cordierite, and can well meet the actual production and application needs of enterprises, promoting the application and development of related industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 shows the particle size distribution and cumulative particle size detection results of the low-expansion cordierite ceramic prepared in Example 5; Figure 2 shows the XRD detection results of the low-expansion cordierite ceramics prepared in Examples 1-5; Figure 3 shows the SEM detection results of the low-expansion cordierite ceramic prepared in Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0018] To further illustrate the present invention, the technical means and effects adopted to achieve the predetermined invention purpose are described in detail below in conjunction with preferred embodiments.

[0019] Example 1

[0020] A preparation method for preparing low-expansion cordierite ceramics using chlorite, comprising the following steps: Step 1: Using chlorite as the raw material, after ball milling and sieving, a certain amount of kaolin and alumina are added and mixed evenly, and then wet ball milling, calcination, and pulverization are carried out to obtain a cordierite precursor; Step 2: A certain amount of fused quartz is added to the cordierite precursor prepared in Step 1, and the slurry after ball milling is placed in an oven for drying to obtain a mixed powder; Step 3: The mixed powder prepared in Step 2 is granulated, aged, dry-pressed into shape, and fired to obtain low-expansion cordierite ceramics.

[0021] The chemical composition of the chlorite in Step 1 is as follows in mass percentage: SiO2 32.45%, Al2O3 16.06%, Fe2O3 0.5%, TiO2 0.64%, CaO 0.05%, MgO 35.64%, K2O 0.04%, Na2O 0.02%, loss on ignition 14.6%.

[0022] In Step 1, the chlorite is ball milled for 30 min and then sieved through a 120-mesh sieve, the fineness of kaolin is through an 80-mesh sieve, the fineness of alumina is through a 120-mesh sieve, and the weight ratio of chlorite:kaolin:alumina is 29.8:60.7:9.5.

[0023] In Step 1, the time of the wet ball milling process is 20 min, the temperature of the calcination process is 900 °C, the holding time is 1 h, and the fineness of the pulverization process is through a 250-mesh sieve.

[0024] In Step 2, the weight ratio of cordierite precursor to fused quartz is 29.8:0.5.

[0025] In Step 2, the weight ratio of the material:water:ball mill in the ball milling process is 1:4:1.5, the ball milling time is 30 min, the fineness is through an 80-mesh sieve, the temperature of the drying process is 80 °C, and the drying time is 12 h.

[0026] In Step 3, the particle size of the granulation process is through an 80-mesh sieve, the time of the aging process is 2 h, the pressure of the dry pressing process is 10 MPa, and the pressure holding time is 40 s.

[0027] The firing system of the firing process in Step 3 is as follows: the heating rate from 50 to 600 °C is 2.5 °C / min, the heating rate from 600 to 1000 °C is 4 °C / min, the heating rate from 1000 to 1300 °C is 3 °C / min, the holding time at the highest firing temperature is 3 h, and then it cools down with the furnace.

[0028] The chemical composition of the low-expansion cordierite ceramic is as follows in mass percentage: SiO2 47.8%, Al2O3 38.2%, CaO 0.5%, MgO 13.4%, Fe2O3 0.1%, TiO2 0.19%, K2O 0.01%, Na2O 0.009%.

[0029] Example 2

[0030] A preparation method for preparing low-expansion cordierite ceramic using chlorite includes the following steps: Step 1: Using chlorite as the raw material, after ball milling and sieving, a certain amount of kaolin and alumina are added and mixed evenly, and then wet ball milling, calcination, and pulverization are carried out to obtain a cordierite precursor; Step 2: A certain amount of fused quartz is added to the cordierite precursor obtained in Step 1, and the slurry after ball milling is placed in an oven for drying to obtain a mixed powder; Step 3: The mixed powder obtained in Step 2 is granulated, aged, dry-pressed into shape, and fired to obtain a low-expansion cordierite ceramic.

[0031] The chemical composition of the chlorite in Step 1 is as follows in mass percentage: SiO2 33.72%, Al2O3 15.86%, Fe2O3 0.6%, TiO2 0.54%, CaO 0.07%, MgO 35.54%, K2O 0.06%, Na2O 0.01%, loss on ignition 13.6%.

[0032] In Step 1, the chlorite is ball milled for 30 min and then sieved through a 80-mesh sieve, the fineness of kaolin is through a 40-mesh sieve, the fineness of alumina is through a 120-mesh sieve, and the weight ratio of chlorite:kaolin:alumina is 32.4:54.7:12.9.

[0033] In Step 1, the time of the wet ball milling process is 30 min, the temperature of the calcination process is 800 °C, the holding time is 2 h, and the fineness of the pulverization process is through a 250-mesh sieve.

[0034] In Step 2, the weight ratio of cordierite precursor to fused quartz is 29.8:10.

[0035] In Step 2, the weight ratio of the material:water:ball mill in the ball milling process is 1:4:1.5, the ball milling time is 20 min, the fineness is through an 80-mesh sieve, the temperature of the drying process is 80 °C, and the drying time is 12 h.

[0036] In Step 3, the particle size of the granulation process is through an 80-mesh sieve, the time of the aging process is 2 h, the pressure of the dry pressing process is 5 MPa, and the pressure holding time is 40 s.

[0037] In the firing process of Step 3, the firing regime is as follows: the heating rate from 50 to 600 °C is 3.5 °C / min, the heating rate from 600 to 1000 °C is 4 °C / min, the heating rate from 1000 to 1320 °C is 2 °C / min, the holding time at the highest firing temperature is 4 h, and then it is cooled down with the furnace.

[0038] The chemical composition of the low-expansion cordierite ceramic is as follows in mass percentage: SiO2 48.3%, Al2O3 38.8%, CaO 0.5%, MgO 12.35%, Fe2O3 0.05%, TiO2 0.16%, K2O 0.02%, Na2O 0.003%.

[0039] Example 3

[0040] A preparation method for preparing low-expansion cordierite ceramic using chlorite includes the following steps: Step 1: Using chlorite as the raw material, after ball milling and sieving, a certain amount of kaolin and alumina are added and mixed evenly, and then it is wet ball milled, calcined, and pulverized to obtain a cordierite precursor. Step 2: A certain amount of fused quartz is added to the cordierite precursor prepared in Step 1, and the slurry after ball milling is dried in an oven to obtain a mixed powder. Step 3: The mixed powder prepared in Step 2 is granulated, aged, dry-pressed into shape, and fired to obtain a low-expansion cordierite ceramic.

[0041] The chemical composition of the chlorite in Step 1 is as follows in mass percentage: SiO2 32.76%, Al2O3 15.965%, Fe2O3 0.55%, TiO2 0.6%, CaO 0.06%, MgO 35.6%, K2O 0.05%, Na2O 0.015%, loss on ignition 14.4%.

[0042] In Step 1, the chlorite is ball milled for 30 min and then sieved through a 120-mesh sieve, the fineness of kaolin is through an 80-mesh sieve, the fineness of alumina is through a 160-mesh sieve, and the weight ratio of chlorite:kaolin:alumina is 29.8:63.5:6.7.

[0043] In Step 1, the time of the wet ball milling process is 30 min, the temperature of the calcination process is 850 °C, the holding time is 1.5 h, and the fineness of the pulverization process is through a 250-mesh sieve.

[0044] In Step 2, the weight ratio of cordierite precursor to fused quartz is 29.8:0.5.

[0045] In the second step, the weight ratio of the material, water, and ball mill in the ball milling process is 1:5:2.5, the ball milling time is 30 min, the fineness is passing through a 80-mesh sieve, the temperature in the drying process is 80 °C, and the drying time is 12 h.

[0046] In the third step, the particle size in the granulation process is passing through a 100-mesh sieve, the time in the aging process is 4 h, the pressure in the dry pressing forming process is 10 MPa, and the pressure holding time is 30 s.

[0047] In the third step, the firing system in the firing process is as follows: the heating rate from 50 to 600 °C is 2.5 °C / min, the heating rate from 600 to 1000 °C is 5 °C / min, the heating rate from 1000 to 1360 °C is 2 °C / min, the heat preservation time at the highest firing temperature is 2 h, and then it cools down with the furnace.

[0048] The chemical composition of the low-expansion cordierite ceramic is as follows in mass percentage: SiO2 47.3%, Al2O3 39.1%, CaO 0.6%, MgO 12.9%, Fe2O3 0.1%, TiO2 0.18%, K2O 0.015%, Na2O 0.004%.

[0049] Example 4

[0050] A preparation method for preparing low-expansion cordierite ceramic using chlorite includes the following steps: Step 1: Using chlorite as the raw material, after ball milling and sieving, a certain amount of kaolin and alumina are added and mixed evenly, and then through wet ball milling, calcination, and pulverization, a cordierite precursor is obtained; Step 2: A certain amount of fused quartz is added to the cordierite precursor prepared in Step 1, and the slurry after ball milling is put into an oven for drying to obtain a mixed powder; Step 3: The mixed powder prepared in Step 2 is granulated, aged, dry pressed into shape, and fired to obtain a low-expansion cordierite ceramic.

[0051] The chemical composition of the chlorite in Step 1 is as follows in mass percentage: SiO2 32.6%, Al2O3 15.965%, Fe2O3 0.58%, TiO2 0.63%, CaO 0.06%, MgO 35.6%, K2O 0.05%, Na2O 0.015%, loss on ignition 14.5%.

[0052] The chlorite in Step 1 is ball milled for 30 min and then passes through a 100-mesh sieve, the fineness of kaolin is passing through a 60-mesh sieve, the fineness of alumina is passing through a 160-mesh sieve, and the weight ratio of chlorite:kaolin:alumina is 32.4:44.6:2.9.

[0053] In the first step, the time of the wet ball milling process is 30 min, the temperature of the calcination process is 900 °C, the heat preservation time is 2 h, and the fineness of the pulverization process is passing through a 250-mesh sieve.

[0054] In the second step, the weight ratio of the cordierite precursor to fused quartz is 32.4:10.

[0055] In the second step, the weight ratio of the material, water, and ball mill in the ball milling process is 1:5:2.5, the ball milling time is 30 min, the fineness is passing through a 100-mesh sieve, the temperature of the drying process is 80 °C, and the drying time is 12 h.

[0056] In the third step, the particle size of the granulation process is passing through a 100-mesh sieve, the time of the aging process is 3 h, the pressure of the dry pressing forming process is 8 MPa, and the pressure holding time is 35 s.

[0057] In the third step, the firing regime of the firing process is that the heating rate from 50 to 600 °C is 2.5 °C / min, the heating rate from 600 to 1000 °C is 4.5 °C / min, the heating rate from 1000 to 1360 °C is 3 °C / min, the heat preservation time at the highest firing temperature is 2 h, and then it is cooled down with the furnace.

[0058] The chemical composition of the low-expansion cordierite ceramic is as follows in mass percentage: SiO2 48.8%, Al2O3 37.6%, CaO 0.6%, MgO 12.9%, Fe2O3 0.1%, TiO2 0.21%, K2O 0.016%, Na2O 0.005%.

[0059] Example 5

[0060] A preparation method for preparing low-expansion cordierite ceramic using chlorite includes the following steps: Step 1: Using chlorite as the raw material, after ball milling and sieving, a certain amount of kaolin and alumina are added and mixed evenly, and then through wet ball milling, calcination, and pulverization, a cordierite precursor is obtained; Step 2: A certain amount of fused quartz is added to the cordierite precursor prepared in Step 1, and the slurry after ball milling is placed in an oven for drying to obtain a mixed powder; Step 3: The mixed powder prepared in Step 2 is granulated, aged, dry pressed into shape, and fired to obtain a low-expansion cordierite ceramic.

[0061] The chemical composition of the chlorite in the first step is as follows in mass percentage: SiO2 33.1%, Al2O3 15.965%, Fe2O3 0.58%, TiO2 0.63%, CaO 0.06%, MgO 35.6%, K2O 0.05%, Na2O 0.015%, loss on ignition 14.0%.

[0062] In Step 1, the chlorite is ball-milled for 30 minutes and then screened through a 80-mesh sieve. The fineness of kaolin is passing through an 80-mesh sieve, and the fineness of alumina is passing through a 140-mesh sieve. The weight ratio of chlorite:kaolin:alumina is 30:64.7:5.5.

[0063] In Step 1, the time of the wet ball-milling process is 25 minutes, the temperature of the calcination process is 800 °C, the heat preservation time is 1 hour, and the fineness of the pulverization process is passing through a 250-mesh sieve.

[0064] In Step 2, the weight ratio of cordierite precursor:fused quartz is 30:5.5.

[0065] In Step 2, the weight ratio of the material:water:ball mill in the ball-milling process is 1:4.5:2, the ball-milling time is 40 minutes, the fineness is passing through a 90-mesh sieve, the temperature of the drying process is 80 °C, and the drying time is 12 hours.

[0066] In Step 3, the particle size of the granulation process is passing through a 90-mesh sieve, the time of the aging process is 3 hours, the pressure of the dry pressing forming process is 10 MPa, and the pressure holding time is 40 s.

[0067] In Step 3, the firing system of the firing process is that the heating rate from 50 to 600 °C is 3 °C / min, the heating rate from 600 to 1000 °C is 4 °C / min, the heating rate from 1000 °C to 1320 is 2.5 °C / min, the heat preservation time at the highest firing temperature is 3 hours, and then it cools down with the furnace.

[0068] The chemical composition of the low-expansion cordierite ceramic is as follows in mass percentage: SiO2 48.25%, Al2O3 38.33%, CaO 0.55%, MgO 12.7%, Fe2O3 0.07%, TiO2 0.19%, K2O 0.015%, Na2O 0.005%.

[0069] For the low-expansion cordierite ceramics prepared in Examples 1-5, the test results are shown in the following table.

[0070]

[0071] As Figure 2 shown, the diffraction peaks in the XRD test results of the low-expansion cordierite ceramics prepared in Examples 1-5 are consistent with the main crystal phase of cordierite (PDF#97-015-6362).

[0072] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, and improvements made within the principle and spirit of the present invention shall be included within the protection scope of the present invention.

Claims

1. A low-expansion cordierite ceramic prepared from chlorite, characterized in that: The chemical composition of the low-expansion cordierite ceramic is as follows by mass percentage: SiO2 47.3 - 48.8%, Al2O3 37.6 - 39.1%, CaO 0.5 - 0.6%, MgO 12.35 - 13.4%, Fe2O3 0.05 - 0.1%, K2O 0.01 - 0.02%, Na2O 0.003 - 0.009%, TiO2 0.16 - 0.21%.

2. The preparation method of the low-expansion cordierite ceramic according to claim 1, wherein It includes the following steps: Step 1: Using chlorite as the raw material, after ball milling and sieving, a certain amount of kaolin and alumina are added and mixed evenly, then wet ball milling, calcination, and pulverization are carried out to obtain a cordierite precursor; Step 2: A certain amount of fused quartz is added to the cordierite precursor obtained in Step 1, and the slurry after ball milling is dried in an oven to obtain a mixed powder; Step 3: The mixed powder obtained in Step 2 is granulated, aged, dry-pressed into shape, and fired to obtain a low-expansion cordierite ceramic.

3. The preparation method according to claim 2, wherein: The chemical composition of the chlorite in Step 1 is as follows by mass percentage: SiO2 32.45 - 33.72%, Al2O3 15.86 - 16.06%, Fe2O3 0.5 - 0.6%, TiO2 0.54 - 0.64%, CaO 0.05 - 0.07%, MgO 35.54 - 35.64%, K2O 0.04 - 0.06%, Na2O 0.01 - 0.02%, loss on ignition 13.6 - 14.6%.

4. The preparation method according to claim 2, characterized in that: In Step 1, the chlorite is ball milled for 30 mins and then sieved through a 80 - 120 mesh sieve, the fineness of kaolin is through a 40 - 80 mesh sieve, the fineness of alumina is through a 120 - 160 mesh sieve, and the weight ratio of chlorite:kaolin:alumina is 29.8 - 32.4:44.6 - 64.7:2.9 - 12.

9.

5. The preparation method according to claim 2, wherein: In Step 1, the time of the wet ball milling process is 20 - 30 min, the temperature of the calcination process is 800 - 900 °C, the holding time is 1 - 2 h, and the fineness of the pulverization process is through a 250 mesh sieve.

6. The preparation method according to claim 2, wherein: In Step 2, the weight ratio of cordierite precursor:fused quartz is 29.8 - 32.4:0.5 - 10.

7. The preparation method according to claim 2, characterized in that: In Step 2, the weight ratio of the material:water:ball mill in the ball milling process is 1:4 - 5:1.5 - 2.5, the ball milling time is 20 - 40 min, the fineness is through an 80 - 100 mesh sieve, the temperature of the drying process is 80 °C, and the drying time is 12 h.

8. The preparation method according to claim 2, characterized in that: In Step 3, the particle size of the granulation process is through an 80 - 100 mesh sieve, the time of the aging process is 2 - 4 h, the pressure of the dry pressing process is 5 - 10 MPa, and the holding pressure time is 30 - 40 s.

9. The preparation method according to claim 2, characterized in that: In Step 3, the firing system of the firing process is that the heating rate from 50 - 600 °C is 2.5 - 3.5 °C / min, the heating rate from 600 - 1000 °C is 4 - 5 °C / min, the heating rate from 1000 °C to the highest firing temperature is 2 - 3 °C / min, the holding time at the highest firing temperature is 2 - 4 h, and then it cools down with the furnace, and the highest firing temperature is 1300 - 1360 °C.

10. The preparation method according to claim 2, characterized in that: The crystallinity of the low-expansion cordierite ceramic obtained in the third step is 88.5-93.8%, the flexural strength is 40.12-43.38 MPa, the coefficient of thermal expansion from room temperature to 800 °C is 1.86-2.53×10 -6 / °C, the water absorption rate is 2.23-2.96%, and the bulk density is 2.185-2.445 g / cm 3 .

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