Preparation method of aluminum titanate-based refractory material

Abstract

The invention belongs to the technical field of refractory materials, and discloses a preparation method of an aluminum titanate-based refractory material, which comprises the following steps: 1) removing iron from high bauxite clinker, mixing with titanium dioxide, adding bismuth trioxide and gadolinium trioxide, and carrying out ball milling to obtain a first mixture; 2) adding aluminum powder into the first mixture, and carrying out ball milling to obtain a second mixture; 3) performing cold isostatic pressing on the second mixture, heating, sintering, crushing and screening to obtain aluminum titanate aggregate and aluminum titanate fine powder; (4) taking the second mixture and aluminum titanate aggregate, and additionally adding aluminum titanate fine powder and a binding agent to obtain a third mixture; and 5) carrying out cold isostatic pressing on the third mixture, heating and sintering to obtain the aluminum titanate-based refractory material. According to the invention, aluminum oxide is completely replaced by the high-alumina bauxite clinker, the high-alumina bauxite clinker and titanium dioxide are subjected to solid-phase reaction to synthesize aluminum titanate, and the prepared aluminum titanate-based refractory material has high mechanical strength, low thermal expansion coefficient and excellent thermal shock resistance and high-temperature stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of refractory materials, and particularly relates to a preparation method of an aluminum titanate-based refractory material. Background Art

[0002] Aluminum titanate (Al2TiO5) is a refractory material with excellent thermal shock resistance performance. It has advantages such as a low coefficient of thermal expansion, a high melting point, a low thermal conductivity, alkali resistance, and non-wetting with most metals. It has been widely used in industries such as steel, ceramics, metallurgy, aerospace, military, glass, medicine, and automotive manufacturing. It can be used as a heat-resistant and corrosion-resistant coating, crucible, catalytic converter, thermocouple element, etc., and has great application prospects. However, the use of aluminum titanate in refractory materials is restricted by the following problems: First, the uneven thermal expansion caused by the anisotropy of aluminum titanate crystals generates thermal stress and microcracks inside, reducing the mechanical strength of the material. At the same time, these microcracks are also the reasons for the low thermal expansion and thermal shock resistance of aluminum titanate materials. Second, aluminum titanate materials are prone to eutectoid decomposition in the range of 750 - 1280 °C, resulting in a decrease in their high-temperature stability.

[0003] The preparation of aluminum titanate usually adopts the high-temperature solid-phase synthesis method. After mixing high-purity alumina and titanium dioxide in a certain proportion, a solid-phase reaction occurs through high-temperature calcination to obtain an aluminum titanate product. However, the cost of this method is relatively high. On the one hand, it is due to the high synthesis temperature, resulting in high energy consumption. On the other hand, it is because the price of high-purity alumina is relatively high. If high-aluminum materials such as bauxite are used to replace high-purity alumina to prepare aluminum titanate, the production cost will be greatly reduced. However, after the existing technology uses high-aluminum materials to replace high-purity alumina, the strength and thermal expansion performance of aluminum titanate often further decrease, unable to meet the usage requirements of refractory materials. Therefore, producing high-performance aluminum titanate-based refractory materials under the premise of low cost is a difficult problem faced currently. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method of an aluminum titanate-based refractory material aiming at the deficiencies existing in the prior art. This method realizes the complete replacement of alumina with bauxite clinker, conducts a solid-phase reaction with titanium dioxide to synthesize aluminum titanate, and finally the prepared aluminum titanate-based refractory material has high mechanical strength, a low coefficient of thermal expansion, excellent thermal shock resistance, and high-temperature stability.

[0005] To solve the technical problems proposed by the present invention, the present invention provides a preparation method of an aluminum titanate-based refractory material, including the following steps:

[0006] 1) After removing iron from bauxite clinker, it is mixed with titanium dioxide as the first base material. After adding bismuth trioxide and gadolinium trioxide, using water as the liquid medium, wet ball milling is carried out, and then drying is performed to obtain the first mixture;

[0007] 2) After adding aluminum powder to the first mixture, dry ball milling is carried out to obtain a second mixture;

[0008] 3) Take the second mixture, after cold isostatic pressing and forming, heat sintering is carried out, and the sintered product is crushed and screened to obtain aluminum titanate aggregate and aluminum titanate fine powder;

[0009] 4) Take the second mixture and aluminum titanate aggregate as the second base material, and additionally add aluminum titanate fine powder and binder, mix evenly to obtain a third mixture;

[0010] 5) After cold isostatic pressing and forming the third mixture, heat sintering is carried out to obtain an aluminum titanate-based refractory material.

[0011] In the above solution, the Al2O3 content of the high-alumina bauxite clinker is ≥89%, the TiO2 content is ≤4%, the SiO2 content is ≤4%, the Fe2O3 content is ≤1.5%, the CaO + MgO content is ≤0.4%, and the K2O + Na2O content is ≤0.4%, all of which are mass percentage contents.

[0012] In the above solution, the particle size of the high-alumina bauxite clinker is ≤0.091mm, and the bulk density is ≥3.10g / cm 3 , and the water absorption rate is ≤4%.

[0013] In the above solution, the TiO2 content of the titanium dioxide is ≥99.0%, and the particle size is ≤5μm.

[0014] In the above solution, the Gd2O3 content of the gadolinium sesquioxide is ≥99.9%, and the particle size is ≤5μm.

[0015] In the above solution, the Bi2O3 content of the bismuth sesquioxide is ≥99.9%, and the particle size is ≤5μm.

[0016] In the above solution, the Al content of the aluminum powder is ≥99.0%, and the particle size is ≤0.147mm.

[0017] In the above solution, the binder is tetrabutyl titanate, and its Ti(OC4H9)4 content is ≥99.0%.

[0018] In the above solution, the iron removal step adopts magnetic separation method, mainly to remove iron filings in the high-alumina bauxite clinker, and the iron is removed until the content of elemental Fe is reduced to 0.1 - 0.3%.

[0019] In the above solution, in the first base material, the mass percentage content of the high-alumina bauxite clinker after iron removal is 60 - 70%, and the mass percentage content of the titanium dioxide is 30 - 40%.

[0020] In the above solution, the addition amount of the bismuth sesquioxide is 2 - 8% of the mass of the first base material.

[0021] In the above solution, the addition amount of gadolinium sesquioxide is 1-4% of the mass of the first base material.

[0022] In the above solution, the ball milling rate of the wet ball milling is 200-400 rpm, and the ball milling time is 4-10 h.

[0023] In the above solution, the ball-to-material-to-water ratio of the wet ball milling is (1-2):1:(1-2), which is a mass ratio.

[0024] In the above solution, the addition amount of aluminum powder is 2-8% of the mass of the first mixture.

[0025] In the above solution, the ball milling rate of the dry ball milling is 100-200 rpm, and the ball milling time is 1-3 h.

[0026] In the above solution, in step 3), the pressure of cold isostatic pressing is 100-200 MPa.

[0027] In the above solution, in step 3), the temperature of heat sintering is 1300-1400 °C, and the heat preservation time is 2-4 h.

[0028] Further, in step 3), the heating rate of heat sintering is 5-10 °C / min.

[0029] In the above solution, the particle size of the aluminum titanate aggregate is 0.5-2 mm, and the particle size of the aluminum titanate fine powder is ≤200 mesh.

[0030] In the above solution, in the second base material, the mass percentage content of the second mixture is 60-70%, and the mass percentage content of the aluminum titanate aggregate is 30-40%.

[0031] In the above solution, the addition amount of the aluminum titanate fine powder is 2-8% of the mass of the first base material.

[0032] In the above solution, the addition amount of the binder is 4-8% of the mass of the first base material.

[0033] In the above solution, in step 5), the pressure of cold isostatic pressing is 100-200 MPa.

[0034] In the above solution, in step 5), the temperature of heat sintering is 1200-1300 °C, and the heat preservation time is 2-4 h.

[0035] Further, in step 5), the heating rate of heat sintering is 5-10 °C / min.

[0036] In the above solution, the main crystal phase of the aluminum titanate-based refractory material is β-Al2TiO5, and the content of β-Al2TiO5 > 85%.

[0037] In the above solution, the bulk density of the aluminum titanate-based refractory material is 2.95 - 3.20 g / cm 3 , the cold compressive strength at room temperature is 150 - 240 MPa, the cold flexural strength at room temperature is 55 - 75 MPa, the thermal conductivity at room temperature is 0.9 - 1.3 W / (m·K), the temperature of 0.2 MPa load softening with 2% deformation is 1668 - 1686 °C, the thermal expansion coefficient from RT to 1100 °C is (0.4 - 1.5) × 10 -6 / °C, and the retention rate of the compressive strength after 20 water coolings at 1100 °C ≥ 72%.

[0038] The design concept of the present invention is as follows:

[0039] The first technical difficulty solved by the present invention is that bauxite clinker completely replaces alumina and undergoes a solid-phase reaction with titanium dioxide to synthesize aluminum titanate. However, since bauxite inevitably contains certain amounts of impurities such as SiO2, Fe2O3, Na2O, K2O, etc., and impurities such as elemental Fe are mixed in during the processing, they form low-melting substances with Al2O3 and TiO2 at high temperatures, resulting in an increase in the grain boundary glass phase, thereby reducing the thermal shock resistance and high-temperature mechanical properties of the material. Therefore, complete replacement is technically difficult. In response to this, the present invention has made a clever design in terms of raw materials and sintering system:

[0040] (1) Pre-select bauxite clinker with an Al2O3 content ≥ 89%, a TiO2 content ≤ 4%, and relatively low SiO2 and Fe2O3 contents, and supplement it with iron removal treatment; the small amount of TiO2 contained in the clinker helps the in-situ formation of aluminum titanate, and the mullite phase (3Al2O3·2SiO2) in the clinker has a network structure, which helps to improve the thermal stability of the material;

[0041] (2) Through the synergistic modification and high-temperature stabilization mechanism of Bi2O3 and Gd2O3, inhibit the harmful low-melting phases generated by impurities at the grain boundaries, and promote the stable formation of aluminum titanate; then, through the synergistic enhancement mechanism of two-stage sintering, obtain an aluminum titanate-based refractory material with high strength, low expansion, and high thermal shock resistance;

[0042] The specific explanation of the synergistic modification and high-temperature stabilization mechanism of Bi2O3 and Gd2O3 is as follows:

[0043] In the prior art, additives such as La2O3 and ZnO commonly used mainly work through a single solid-solution stabilization mechanism. In contrast, the present invention specifically selects the combination of Bi2O3 and Gd2O3, which exhibit a unique synergistic effect at high temperatures: Bi2O3 can react with TiO2 in aluminum titanate at high temperatures to form stable phases such as Bi4Ti3O 12 (BT). These phases have a layered structure and are uniformly distributed at the grain boundaries to form a dense network, acting as a "barrier"; Gd2O3 tends to form a high-melting-point solid solution with Al2O3 and dissolve into the lattice. On the one hand, it increases the lattice constant, reduces lattice distortion, and stabilizes the lattice structure. On the other hand, it cooperates with the composite phase formed by Bi2O3 to form a stable oxide network at the grain boundaries; the synergistic effect of the two results in: low-melting-point impurities such as Na2O and K2O in bauxite are "trapped" in Bi4Ti3O 12 network and cannot form a continuous glass phase at the grain boundaries, effectively suppressing the enrichment and precipitation of low-melting-point impurities at the grain boundaries; the growth of aluminum titanate grains is controlled, reducing microcracks caused by thermal stress and enhancing the toughness of the material, and more significantly reducing the decomposition tendency of aluminum titanate in the range of 750 - 1280 °C; grain boundary diffusion is enhanced, and densification can be achieved at a lower temperature; thus, even under the condition of completely using bauxite clinker to replace pure alumina, excellent high-temperature stability and mechanical strength can still be obtained;

[0044] (3) Through the chemical compatibility binding mechanism of tetrabutyl titanate, it is better chemically compatible with the aluminum titanate matrix and decomposes at high temperatures to form TiO2, which can react in-situ with the matrix, not only promoting densification but also enhancing the grain boundary binding strength; the efficient binding effect of this binder also shortens the forming and sintering time, effectively improving the mechanical properties of the material;

[0045] By the above technical measures, the problems existing in the complete use of bauxite are overcome, and the finished product reaches or even exceeds the level of using pure alumina in terms of high-temperature performance, strength, and thermal shock resistance.

[0046] The second technical difficulty solved by the present invention is to reduce the synthesis temperature, time, and energy consumption. For this, the energy-saving and efficient mechanism designed by the present invention is as follows:

[0047] (1) In-situ exothermic reaction mechanism of aluminum powder

[0048] During the first sintering process (1300 - 1400 °C), the aluminum powder undergoes the following reaction:

[0049] 4Al + 3O2 → 2Al2O3 + heat (about 3350 kJ / mol)

[0050] This highly exothermic reaction creates a local high-temperature environment inside the material, reaching above 2000 °C, which promotes the rapid formation of aluminum titanate and reduces the external energy demand. At the same time, the in-situ generated active Al2O3 particles are evenly dispersed and have a high reactivity with TiO2, significantly increasing the formation rate of the β-Al2TiO5 phase. This "self-exothermic - self-generation" in-situ synthesis mechanism significantly accelerates the formation of aluminum titanate grains, and the trace gases generated by the exothermic reaction help to expel the pores inside the material and promote densification, thereby reducing the synthesis temperature in the first stage to 1300 - 1400 °C and only requiring a holding time of 2 - 4 h, significantly reducing energy consumption.

[0051] (2) Synergistic effect mechanism of two-stage sintering

[0052] The aluminum titanate ceramics synthesized in the first stage are crushed and used as the aggregate and seed crystal in the second stage, further reducing the synthesis energy consumption. The in-situ synthesized aluminum titanate aggregate already has a stable crystal structure, which can guide the growth of new aluminum titanate crystals along its orientation during the second-stage sintering. At the same time, the seed crystal effect reduces the activation energy for the formation of aluminum titanate in the second stage, significantly reducing the nucleation barrier, reducing grain preferred orientation and grain boundary microcracks, and lowering the sintering temperature from the traditional 1500 °C to 1200 - 1300 °C. Finally, the two-stage sintering temperature and total time are significantly shorter than those of the traditional process.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] The present invention uses high-alumina bauxite clinker to completely replace alumina and undergoes a solid-phase reaction with titanium dioxide to synthesize aluminum titanate, greatly reducing the dependence on high-purity raw materials and lowering the production cost. To address the problem of performance degradation caused by the use of high-alumina bauxite clinker, mainly through the synergistic modification and high-temperature stabilization mechanism of Bi2O3 and Gd2O3, the generation of harmful low-melting phases at grain boundaries is inhibited, the stable formation of aluminum titanate is promoted, and the performance of the material is improved. At the same time, by introducing aluminum powder and combining the synergistic effect mechanism of two-stage sintering, the synthesis temperature, time, and energy consumption are further reduced. Finally, high-performance aluminum titanate-based refractory materials are produced at low cost, showing significant energy, cost, and performance advantages in industrial production. Detailed implementation manners

[0055] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0056] In the following examples, the high-alumina bauxite clinker used has an Al2O3 content of 90.1%, a TiO2 content of 3.6%, a SiO2 content of 3.2%, an Fe2O3 content of 1.1%, a CaO + MgO content of 0.3%, a K2O + Na2O content of 0.2%, a particle size of 0.074 mm, and a bulk density of 3.15 g / cm3 , water absorption rate is 3.5%; the TiO₂ content of titanium dioxide is 99.0%, and the particle size is 3 μm; the Gd₂O₃ content of gadolinium sesquioxide is 99.9%, and the particle size is 2 μm; the Bi₂O₃ content of bismuth sesquioxide is 99.9%, and the particle size is 2 μm; the Al content of aluminum powder is 99.0%, and the particle size is 0.147 mm; the Ti(OC₄H₉)₄ content of tetrabutyl titanate is 99.0%.

[0057] Example 1

[0058] A preparation method of an aluminum titanate-based refractory material, comprising the following steps:

[0059] 1) First, conduct magnetic separation and iron removal treatment on the high-aluminum bauxite clinker to reduce the content of elemental Fe therein to 0.15%; then mix the two according to the mass percentage content of 60% of the high-aluminum bauxite clinker after iron removal and 40% of the mass percentage content of titanium dioxide as the first base material; then add 4% of bismuth sesquioxide and 1% of gadolinium sesquioxide based on the mass of the first base material, use water as the liquid medium, with a ball-to-material-to-water ratio of 1:1:1, conduct wet ball milling, the ball milling speed is 220 rpm, the ball milling time is 4 h, and after the ball milling is completed, dry it to obtain the first mixture;

[0060] 2) Add 5% of aluminum powder based on the mass of the first mixture, and then conduct dry ball milling, the ball milling speed is 120 rpm, the ball milling time is 1 h, to obtain the second mixture;

[0061] 3) Take a part of the second mixture, conduct cold isostatic pressing and forming under a pressure condition of 120 MPa, and then under an air atmosphere and normal pressure condition, heat it to 1300 °C at a heating rate of 6 °C / min and hold for 3 h for sintering. Crush and screen the sintered product to obtain aluminum titanate aggregate with a particle size of 0.5 - 2 mm and aluminum titanate fine powder with a particle size ≤ 200 mesh;

[0062] 4) Take the remaining second mixture, mix the two according to the mass percentage content of 70% of the second mixture and 30% of the mass percentage content of the aluminum titanate aggregate as the second base material; then add 4% of the aluminum titanate fine powder and 4% of tetrabutyl titanate based on the mass of the second base material, and put it into a high-intensity mixer to mix for 15 min to obtain the third mixture;

[0063] 5) Conduct cold isostatic pressing and forming on the third mixture under a pressure condition of 120 MPa, and then under an air atmosphere and normal pressure condition, heat it to 1250 °C at a heating rate of 6 °C / min and hold for 2.5 h for sintering to obtain the aluminum titanate-based refractory material.

[0064] The prepared aluminatotitanate-based refractory material was analyzed by X-ray diffraction. Its main crystal phase is β-Al2TiO5, and the content of β-Al2TiO5 is 85.4%. After testing, its bulk density is 2.98 g / cm 3 , the cold compressive strength at room temperature is 156.4 MPa, the cold flexural strength at room temperature is 56.3 MPa, the thermal conductivity at room temperature is 0.91 W / (m·K), the temperature of 2% deformation under a load of 0.2 MPa is 1668 °C, and the thermal expansion coefficient (linear expansion coefficient) is 0.5×10 -6 / °C (RT~1100 °C), and the retention rate of the compressive strength after 20 water coolings at 1100 °C is 76%.

[0065] Example 2

[0066] A preparation method of an aluminatotitanate-based refractory material includes the following steps:

[0067] 1) First, the bauxite clinker is subjected to magnetic separation for iron removal to reduce the content of elemental Fe therein to 0.18%; then, the bauxite clinker after iron removal and titanium dioxide are mixed according to the mass percentage content of 60% of the bauxite clinker after iron removal and 40% of the titanium dioxide mass percentage content as the first base material; then, 4% of bismuth trioxide and 1% of gadolinium trioxide are added to the first base material by mass, and using water as the liquid medium, with a ball-to-material-to-water ratio of 1.2:1:1.2, wet ball milling is carried out at a ball milling speed of 280 rpm for 6 h, and after the ball milling is completed, it is dried to obtain the first mixture;

[0068] 2) After adding 6% of aluminum powder by mass of the first mixture, dry ball milling is carried out at a ball milling speed of 150 rpm for 2 h to obtain the second mixture;

[0069] 3) Take a part of the second mixture, after cold isostatic pressing and forming under a pressure of 160 MPa, in an air atmosphere and under normal pressure, it is heated to 1400 °C at a heating rate of 7 °C / min and held for 3.5 h for sintering, and the sintered product is crushed and screened to obtain aluminatotitanate aggregate with a particle size of 0.5~2 mm and aluminatotitanate fine powder with a particle size of ≤200 mesh;

[0070] 4) Take the remaining second mixture, and mix the two according to the mass percentage content of 70% of the second mixture and 30% of the aluminatotitanate aggregate mass percentage content as the second base material; then, 8% of aluminatotitanate fine powder and 4% of tetrabutyl titanate are added to the second base material by mass, and then put into a high-intensity mixer and mixed for 15 min to obtain the third mixture;

[0071] 5) After cold isostatic pressing the third mixture under the condition of 150 MPa pressure, it is heated to 1300 °C at a heating rate of 7 °C / min and kept warm for 3 h for sintering under air atmosphere and normal pressure to obtain the aluminum titanate-based refractory material.

[0072] The prepared aluminum titanate-based refractory material was analyzed by X-ray diffraction. Its main crystal phase is β-Al2TiO5, and the content of β-Al2TiO5 is 86.1%. After testing, its bulk density is 3.02 g / cm 3 , the cold compressive strength at room temperature is 189.6 MPa, the cold flexural strength at room temperature is 63.2 MPa, the thermal conductivity at room temperature is 1.02 W / (m·K), the temperature of 0.2 MPa load softening with 2% deformation is 1672 °C, and the thermal expansion coefficient (linear expansion coefficient) is 0.6×10 -6 / °C (RT~1100 °C), and the retention rate of the compressive strength after 20 water coolings at 1100 °C is 74%.

[0073] Example 3

[0074] A preparation method of an aluminum titanate-based refractory material includes the following steps:

[0075] 1) First, the high-alumina bauxite clinker is subjected to magnetic separation for iron removal to reduce the content of elemental Fe in it to 0.22%; then, the two are mixed according to the mass percentage content of 63% of the iron-removed high-alumina bauxite clinker and 37% of the titanium dioxide mass percentage content as the first base material; then, 6% of bismuth trioxide and 2% of gadolinium trioxide are added to the first base material, and water is used as the liquid medium, and the ball-to-material-to-water ratio is 1.5:1:1.5 for wet ball milling. The ball milling speed is 320 rpm, and the ball milling time is 8 h. After the ball milling is completed, it is dried to obtain the first mixture;

[0076] 2) After adding 5% of aluminum powder to the first mixture, dry ball milling is carried out. The ball milling speed is 180 rpm, and the ball milling time is 2.5 h to obtain the second mixture;

[0077] 3) Take a part of the second mixture, after cold isostatic pressing under the condition of 180 MPa pressure, it is heated to 1350 °C at a heating rate of 8 °C / min and kept warm for 4 h for sintering under air atmosphere and normal pressure. The sintered product is crushed and screened to obtain aluminum titanate aggregates with a particle size of 0.5 - 2 mm and aluminum titanate fine powder with a particle size ≤ 200 mesh;

[0078] 4) Take the remaining second mixture, and mix the two according to the mass percentage content of 63% of the second mixture and 37% of the aluminum titanate aggregate mass percentage content as the second base material; then, 6% of aluminum titanate fine powder and 6% of tetrabutyl titanate are added to the second base material, and it is put into a high-strength mixer and mixed for 15 min to obtain the third mixture;

[0079] 5) After cold isostatic pressing the third mixture under a pressure of 180 MPa, it is heated to 1250 °C at a heating rate of 8 °C / min in an air atmosphere and under normal pressure and held for 3 h for sintering to obtain an aluminum titanate-based refractory material.

[0080] The prepared aluminum titanate-based refractory material was analyzed by X-ray diffraction. Its main crystal phase is β-Al2TiO5, and the content of β-Al2TiO5 is 88.3%. After testing, its bulk density is 3.09 g / cm 3 , the cold compressive strength at room temperature is 216.3 MPa, the cold flexural strength at room temperature is 68.4 MPa, the thermal conductivity at room temperature is 1.09 W / (m·K), the temperature of 0.2 MPa load softening with a 2% deformation is 1674 °C, and the thermal expansion coefficient (linear expansion coefficient) is 0.98×10 -6 / °C (RT~1100 °C), and the retention rate of the compressive strength after 20 water coolings at 1100 °C is 73%.

[0081] Example 4

[0082] A preparation method of an aluminum titanate-based refractory material, comprising the following steps:

[0083] 1) First, the high-alumina bauxite clinker is subjected to magnetic separation for iron removal to reduce the content of elemental Fe therein to 0.25%; then, according to the mass percentage content of 63% of the iron-removed high-alumina bauxite clinker and 37% of the titanium dioxide mass percentage content, the two are mixed as the first base material; then, 6% of bismuth trioxide and 1% of gadolinium trioxide are added to the first base material by mass, and water is used as the liquid medium, and the ball-to-material-to-water ratio is 2:1:2, and wet ball milling is carried out at a ball milling speed of 380 rpm for 10 h. After the ball milling is completed, it is dried to obtain the first mixture;

[0084] 2) After adding 7% of aluminum powder by mass of the first mixture, dry ball milling is carried out at a ball milling speed of 190 rpm for 3 h to obtain the second mixture;

[0085] 3) Take a part of the second mixture, after cold isostatic pressing under a pressure of 200 MPa, it is heated to 1400 °C at a heating rate of 10 °C / min in an air atmosphere and under normal pressure and held for 4 h for sintering. The sintered product is crushed and screened to obtain aluminum titanate aggregate with a particle size of 0.5~2 mm and aluminum titanate fine powder with a particle size of ≤200 mesh;

[0086] 4) Take the remaining second mixture, and mix the two according to the mass percentage content of 67% of the second mixture and 33% of the aluminum titanate aggregate as the second base material; then add 8% of aluminum titanate fine powder and 6% of tetrabutyl titanate based on the mass of the second base material, and put them into a powerful mixer and mix for 15 min to obtain the third mixture;

[0087] 5) After cold isostatic pressing the third mixture under the condition of 200 MPa pressure, heat it to 1250 °C at a heating rate of 10 °C / min and keep it warm for 2 h for sintering under the air atmosphere and normal pressure conditions to obtain the aluminum titanate-based refractory material.

[0088] The prepared aluminum titanate-based refractory material was analyzed by X-ray diffraction, and its main crystal phase was β-Al2TiO5, and the content of β-Al2TiO5 was 90.7%. After testing, its bulk density was 3.16 g / cm 3 , the cold compressive strength at room temperature was 234.1 MPa, the cold flexural strength at room temperature was 73.2 MPa, the thermal conductivity at room temperature was 1.25 W / (m·K), the temperature of 0.2 MPa load softening with 2% deformation was 1686 °C, and the thermal expansion coefficient (linear expansion coefficient) was 1.4×10 -6 / °C (RT~1100 °C), and the retention rate of the compressive strength after 20 water coolings at 1100 °C was 72%.

[0089] Comparative Example 1

[0090] The difference between Comparative Example 1 and Example 1 is only that: Bi2O3 and Gd2O3 are not added.

[0091] After testing, the content of β-Al2TiO5 in the prepared aluminum titanate-based refractory material was 70.2%, the bulk density was 2.85 g / cm 3 , the cold compressive strength at room temperature was 118.3 MPa, the cold flexural strength at room temperature was 40.5 MPa, the thermal conductivity at room temperature was 1.35 W / (m·K), the temperature of 0.2 MPa load softening with 2% deformation was 1568 °C, and the thermal expansion coefficient (linear expansion coefficient) was 2.3×10 -6 / °C (RT~1100 °C), and obvious surface cracks appeared after 14 water coolings at 1100 °C.

[0092] The results show that the content of β-Al2TiO5, mechanical properties, thermal expansion properties, high-temperature deformation resistance and thermal shock properties of Comparative Example 1 all decreased significantly compared with those of the examples. This shows that in the system using bauxite clinker as the raw material, the combined addition of Bi2O3-Gd2O3 plays an irreplaceable role in promoting the formation of the β-Al2TiO5 phase, improving the mechanical strength of the material, reducing the thermal expansion coefficient, enhancing the thermal shock stability of the material and improving the high-temperature properties. This is consistent with the aforementioned dual stabilization mechanism, that is, the synergistic effect of Bi2O3 and Gd2O3 effectively controls the harm of impurities in bauxite and simultaneously optimizes the microstructure of the material.

[0093] Comparative Example 2

[0094] The difference between Comparative Example 2 and Example 1 is only that Bi2O3 is replaced by La2O3 and Gd2O3 is replaced by ZnO, while other conditions and process parameters remain unchanged.

[0095] After testing, the prepared aluminum titanate-based refractory material has a β-Al2TiO5 content of 78.6%, a bulk density of 2.91 g / cm 3 , a normal temperature compressive strength of 135.7 MPa, a normal temperature flexural strength of 48.3 MPa, a normal temperature thermal conductivity of 1.21 W / (m·K), a temperature of 1598 °C at 0.2 MPa load softening with a 2% deformation, a thermal expansion coefficient (linear expansion coefficient) of 1.8×10 -6 / °C (RT~1100 °C), and the compressive strength retention rate after 20 water coolings at 1100 °C is 61%.

[0096] The results show that although Comparative Example 2 uses the combined addition of oxides, the use of the La2O3-ZnO combination still leads to a significant decrease in the content of β-Al2TiO5, mechanical properties, thermal expansion properties, high-temperature deformation resistance and thermal shock properties, indicating that the Bi2O3-Gd2O3 combination used in the examples of the present invention has a specific synergistic modification effect.

[0097] Comparative Example 3

[0098] The difference between Comparative Example 3 and Example 1 is only that no aluminum powder is added.

[0099] After testing, the prepared aluminum titanate-based refractory material has a β-Al2TiO5 content of 64.3%, a bulk density of 2.79 g / cm 3 , a normal temperature compressive strength of 103.7 MPa, a normal temperature flexural strength of 33.9 MPa, a normal temperature thermal conductivity of 1.14 W / (m·K), a temperature of 1545 °C at 0.2 MPa load softening with a 2% deformation, a thermal expansion coefficient (linear expansion coefficient) of 1.7×10 -6 / ℃ (RT to 1100℃), the retention rate of the compressive strength after water cooling at 1100℃ for 20 times is 58%.

[0100] The results show that under the same external temperature conditions, in Comparative Example 3, without adding aluminum powder, the content of β-Al2TiO5, mechanical properties, thermal expansion properties, high-temperature deformation resistance and thermal shock properties are all significantly lower than those in Example 1. This indicates that the in-situ exothermic reaction of aluminum powder not only significantly reduces the external energy input required for the preparation of aluminum titanate, promotes the formation of aluminum titanate phase and the densification of the material, but also comprehensively improves the physical properties of the material; the strong exothermic reaction of aluminum powder at high temperature creates a local high-temperature environment inside the material, significantly accelerating the formation of aluminum titanate grains, reducing microcracks, and increasing the grain boundary bonding strength, thus achieving the comprehensive optimization of the material properties.

[0101] Comparative Example 4

[0102] Comparative Example 4 adopts a single-sintering process. The specific preparation method is as follows:

[0103] 1) First, conduct magnetic separation to remove iron from bauxite clinker to reduce the content of elemental Fe to 0.15%; then mix the iron-removed bauxite clinker and titanium dioxide according to the mass percentage content of 60% for the bauxite clinker and 40% for titanium dioxide as the first base material; then add 4% bismuth trioxide and 1% gadolinium trioxide based on the mass of the first base material, use water as the liquid medium, with a ball-to-material-to-water ratio of 1:1:1, carry out wet ball milling at a ball milling speed of 220 rpm for 4 h, and dry after ball milling to obtain the first mixture;

[0104] 2) After adding 5% aluminum powder based on the mass of the first mixture, carry out dry ball milling at a ball milling speed of 120 rpm for 1 h to obtain the second mixture;

[0105] 3) After adding 4% tetrabutyl titanate based on the mass of the second mixture, put it into a high-intensity mixer and mix for 15 min to obtain the third mixture;

[0106] 4) After cold isostatic pressing the third mixture under a pressure of 120 MPa, heat it to 1500℃ at a heating rate of 6℃ / min in an air atmosphere and under normal pressure and hold for 4 h for sintering to obtain the aluminum titanate-based refractory material.

[0107] After testing, the content of β-Al2TiO5 in the prepared aluminum titanate-based refractory material is 81.2%, and the bulk density is 2.85 g / cm 3, the normal temperature compressive strength is 131.5 MPa, the normal temperature flexural strength is 45.8 MPa, the normal temperature thermal conductivity is 1.18 W / (m·K), the temperature at 0.2 MPa load softening with 2% deformation is 1592 °C, and the thermal expansion coefficient (linear expansion coefficient) is 1.1×10 -6 / °C (RT~1100 °C), and the compressive strength retention rate after water cooling at 1100 °C for 20 times is 52%.

[0108] The results show that although Comparative Example 4 uses the same raw materials and dosages as Example 1, due to the use of a single sintering process and the absence of the two-stage sintering method, its performance is significantly worse than that of the example. The bulk density, mechanical properties, and high-temperature stability are all significantly reduced. In terms of thermal shock performance, although the thermal expansion coefficient of 1.1×10 -6 / °C is within the scope of the present invention, the thermal shock performance is significantly poor, which is directly reflected in the strength retention rate of only 52% after water cooling at 1100 °C for 20 times. Microscopic analysis reveals that although the thermal expansion coefficient values of the two materials are similar, the grain orientation distribution in Comparative Example 4 is uneven and the grain boundary bonding is weak, resulting in easier stress concentration and crack propagation during thermal shock. This indicates that there are more defects in the microstructure formed under the single sintering process that are unfavorable to thermal shock stability.

[0109] Comparative Example 5

[0110] Comparative Example 5 uses a traditional process of pure alumina to prepare the aluminum titanate-based refractory material. The specific preparation method is as follows:

[0111] 1) Mix pure alumina (Al2O3 content ≥ 99.5%, particle size ≤ 5 μm) and titanium dioxide according to the mass percentage content of 60% and 40% respectively. Use water as the liquid medium, with a ball-to-material-to-water ratio of 1:1:1, conduct wet ball milling at a ball milling speed of 220 rpm for 4 h, and dry after ball milling to obtain the first mixture;

[0112] 2) After cold isostatic pressing the mixture under a pressure of 120 MPa, heat it to 1500 °C at a heating rate of 6 °C / min in an air atmosphere and under normal pressure, and hold for 4 h for sintering to obtain the aluminum titanate-based refractory material.

[0113] After testing, the content of β-Al2TiO5 in the prepared aluminum titanate-based refractory material is 70.3%, and the bulk density is 2.65 g / cm 3 , the normal temperature compressive strength is 98.6 MPa, the normal temperature flexural strength is 30.2 MPa, the normal temperature thermal conductivity is 1.42 W / (m·K), the temperature at 0.2 MPa load softening with 2% deformation is 1520 °C, and the thermal expansion coefficient (linear expansion coefficient) is 2.8×10 -6 / °C (RT~1100 °C), and obvious surface cracks appear after water cooling at 1100 °C for 11 times.

[0114] The results show that after using bauxite chamotte with lower cost to replace pure alumina with higher cost in the embodiments of the present invention, through the synergistic effect of the Bi2O3-Gd2O3 composite additive and the optimization of the two-stage sintering process, not only the adverse effects of impurities in the bauxite chamotte are successfully overcome, but also the performance comprehensively superior to that of the traditional pure alumina process is obtained. This technical route of "achieving high performance with low-cost raw materials" subverts the limitation of "only high-purity raw materials can obtain high performance" in traditional cognition, and provides a solution with great economic and technical significance for the industrial application of aluminum titanate-based refractory materials.

[0115] The above embodiments are merely examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here, and the obvious changes or modifications thus extended are still within the protection scope of the present invention.

Claims

1. A preparation method of an aluminum titanate-based refractory material, characterized in that, It includes the following steps: 1) After removing iron from bauxite clinker, mix it with titanium dioxide as the first base material. After adding bismuth trioxide and gadolinium trioxide, use water as the liquid medium for wet ball milling, and then dry it to obtain the first mixture; 2) Add aluminum powder to the first mixture and then perform dry ball milling to obtain the second mixture; 3) Take the second mixture, perform cold isostatic pressing and then heat sintering. Crush and screen the sintered product to obtain aluminum titanate aggregate and aluminum titanate fine powder; 4) Take the second mixture and aluminum titanate aggregate as the second base material, and additionally add aluminum titanate fine powder and binder, and mix evenly to obtain the third mixture; 5) Perform cold isostatic pressing on the third mixture and then heat sintering to obtain the aluminum titanate-based refractory material.

2. The preparation method of the aluminum titanate-based refractory material according to claim 1, characterized in that The bauxite chamotte has an Al2O3 content of ≥ 89%, a TiO2 content of ≤ 4%, a SiO2 content of ≤ 4%, an Fe2O3 content of ≤ 1.5%, a CaO + MgO content of ≤ 0.4%, a K2O + Na2O content of ≤ 0.4%, a particle size of ≤ 0.091 mm, and a bulk density of ≥ 3.10 g / cm 3 , and a water absorption rate of ≤ 4%; magnetic separation is used for iron removal, reducing the elemental Fe content of the bauxite chamotte to 0.1 - 0.3%.

3. The preparation method of the aluminum titanate-based refractory material according to claim 1, characterized in that, In the first base material, the mass percentage content of iron-removed bauxite clinker is 60-70%, and the mass percentage content of titanium dioxide is 30-40%; the addition amount of bismuth trioxide is 2-8% of the mass of the first base material; the addition amount of gadolinium trioxide is 1-4% of the mass of the first base material.

4. The preparation method of the aluminum titanate-based refractory material according to claim 1, wherein For the wet ball milling, the ball-to-material-to-water ratio is (1-2):1:(1-2), the ball milling rate is 200-400 rpm, and the ball milling time is 4-10 h.

5. The preparation method of the aluminum titanate-based refractory material according to claim 1, wherein The addition amount of aluminum powder is 2-8% of the mass of the first mixture; the ball milling rate of the dry ball milling is 100-200 rpm, and the ball milling time is 1-3 h.

6. The preparation method of the aluminum titanate-based refractory material according to claim 1, characterized in that, In step 3), the pressure for cold isostatic pressing is 100-200 MPa, the heating rate for heat sintering is 5-10 °C / min, the sintering temperature is 1300-1400 °C, and the holding time is 2-4 h; the particle size of the aluminum titanate aggregate is 0.5-2 mm, and the particle size of the aluminum titanate fine powder is ≤200 mesh.

7. The preparation method of the aluminum titanate-based refractory material according to claim 1, characterized in that, In the second base material, the mass percentage content of the second mixture is 60-70%, and the mass percentage content of the aluminum titanate aggregate is 30-40%; the addition amount of the aluminum titanate fine powder is 2-8% of the mass of the first base material; the addition amount of the binder is 4-8% of the mass of the first base material.

8. The preparation method of the aluminum titanate-based refractory material according to claim 1, wherein In step 5), the pressure for cold isostatic pressing is 100-200 MPa, the heating rate for heat sintering is 5-10 °C / min, the sintering temperature is 1200-1300 °C, and the holding time is 2-4 h.

9. The preparation method of the aluminum titanate-based refractory material according to claim 1, characterized in that The main crystal phase of the aluminosilicate refractory is β-Al2TiO5, with the content of β-Al2TiO5 > 85%, the bulk density being 2.95 - 3.20 g / cm 3 , the cold crushing strength at room temperature being 150 - 240 MPa, the cold bending strength at room temperature being 55 - 75 MPa, the thermal conductivity at room temperature being 0.9 - 1.3 W / (m·K), the temperature of 2% deformation under a load of 0.2 MPa being 1668 - 1686 °C, the thermal expansion coefficient from RT to 1100 °C being (0.4 - 1.5) × 10 -6 / °C, and the retention rate of the crushing strength after 20 water coolings at 1100 °C being ≥ 72%.

10. The preparation method of the aluminum titanate-based refractory material according to claim 1, characterized in that, The TiO2 content of the titanium dioxide ≥99.0%, and the particle size ≤5 μm; the Gd2O3 content of the gadolinium trioxide ≥99.9%, and the particle size ≤5 μm; the Bi2O3 content of the bismuth trioxide ≥99.9%, and the particle size ≤5 μm; the Al content of the aluminum powder ≥99.0%, and the particle size ≤0.147 mm; the binder is tetrabutyl titanate, and its Ti(OC4H9)4 content ≥99.0%.