A novel method for preparing TiN / AlON-Al2O3 composite refractory material

Abstract

This invention relates to a novel method for preparing TiN / AlON-Al2O3 composite refractory materials, belonging to the field of refractory materials. The preparation method of the composite material includes ball milling and premixing titanium corundum and fine aluminum powder, mixing them uniformly with other raw materials and binders, pressing and drying to obtain a composite green body, and firing it at 1400-1550℃ under a nitrogen atmosphere. To ensure that the final composite material matrix bonding phase is TiN and AlON, three nitrogen flow rates and two holding periods were designed during the heating process to regulate the nitriding sequence of aluminum and Ti2O3, achieving synergistic reinforcement of the material by AlON and TiN. The designed novel TiN / AlON-Al2O3 composite material exhibits excellent thermal shock stability, superior oxidation and wear resistance compared to aluminum-carbon materials, and superior erosion resistance compared to chromium corundum materials, achieving excellent anti-sparing and anti-erosion properties of corundum materials under carbon- and chromium-free conditions.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, and particularly relates to a novel method for preparing TiN / AlON-Al2O3 composite refractory materials. Background Technology

[0002] The steel industry is moving towards low-carbon and ultra-low-carbon steel, making it crucial to address the issue of carbonization-free refractory materials during steelmaking. Key refractory materials in steelmaking, including permeable bricks for ladle refining and the three main components of continuous casting, are primarily corundum-based. Due to the characteristics of slag erosion, thermal shock from molten steel, and intermittent operation in steelmaking, refractory materials must possess excellent resistance to erosion, thermal shock, and spalling. Therefore, permeable bricks for ladle refining are typically made of chromium corundum, offering excellent erosion resistance, while the three main components of continuous casting are mostly made of alumina-carbon materials, with carbon-bonded materials providing excellent thermal shock resistance. However, alumina-carbon materials can increase the carbon content of molten steel, which is detrimental to the smelting of ultra-low-carbon steel, and chromium corundum has been controversial due to chromium contamination issues. AlON-bonded spinel sliding gates have the potential to replace carbon-bonded materials, exhibiting superior oxidation resistance, wear resistance, and resistance to molten iron erosion, making them a promising candidate for development.

[0003] AlON is a series of solid solutions in the AlN-Al2O3 binary system; multiple AlON phases have been found in the AlN-Al2O3 binary system; based on their crystal structures, these phases can be divided into two groups: one group belongs to the wurtzite structure, and the other belongs to the spinel structure; the spinel structure AlON has a crystal structure of space group F3dm, with nitrogen and oxygen occupying the anion positions in the spinel structure, and aluminum ions occupying the octahedral and tetrahedral interstitial positions; the AlON phase is only stable when the octahedral interstitial positions are disordered. AlON has a melting point of 2140℃ and a coefficient of thermal expansion of (5.6×10⁻⁶). -6 ℃ -1 The value compared to fused alumina (8.2 × 10⁻⁶) -6 ℃ -1AlON has low thermal conductivity, comparable to fused alumina, excellent high-temperature chemical stability and thermal shock resistance, and is carbon- and chromium-free, making it a recognized ideal refractory material in modern times. Studies have found that it can improve the erosion and thermal shock resistance of trough materials. The introduction of AlON into trough materials has shown a significant increase in erosion resistance, and thermal shock resistance also increases with the increase of AlON content. It has also been found that the introduction of AlON does not affect the workability. The introduction of some AlON into Al2O3-C sliding gate nozzles has shown that the pore size increase rate is 20% lower than that of nozzles without AlON, improving the life of the sliding gate and the erosion and spalling resistance of the immersion nozzle. Foreign studies have shown that AlON-bonded spinel has significantly improved erosion resistance in permeable bricks compared to chromium alumina. The application of AlON in continuous casting sliding gate nozzles has enhanced stability compared to Al2O3-ZrO2-C.

[0004] The current methods for introducing AlON binder phases into refractory materials include carbothermic reduction, aluminothermic reduction, and solid-state sintering. Carbothermic reduction nitriding uses readily available raw materials. Although the initial reaction temperature is around 1300℃, the sintering temperature for generating the AlON binder phase is relatively high, at 1650-1700℃, and it requires the addition of excessive carbon, which is not conducive to low-carbon designs. Aluminothermic reduction introduces both metallic aluminum and corundum into the refractory material simultaneously. Nitriding sintering generates the AlON binder phase in situ during application, with a reaction temperature above 1500℃. Phenolic resin is required as a binder to prevent the formation of large amounts of molten aluminum, and Al-OC non-oxide phases are preferentially generated. Solid-state sintering, using AlN and Al2O3 as raw materials, has a reaction temperature above 1600℃ and suffers from high cost and low yield.

[0005] Titanium nitride (TiN) has the characteristics of high melting point (2950℃), high hardness, high thermal conductivity, wear resistance and is not easily wetted and corroded by molten metal, slag, etc. It has excellent high-temperature chemical stability and is an ideal high corrosion-resistant non-oxide refractory material.

[0006] Titanium corundum is a byproduct of titanium-iron alloy smelting. It is obtained by improving the traditional titanium-iron smelting process by adding CaO. The titanium element exists in the Ti2O3 phase, which is a separate phase from the Al2O3 corundum phase. It is a new type of raw material in which Ti2O3 and Al2O3 exist independently but are intertwined. Summary of the Invention

[0007] Based on the excellent performance of AlON and TiN in refractory materials, a novel method for preparing TiN / AlON-Al2O3 composite refractory materials was designed. By utilizing the trace oxygen released from Ti2O3 in titanium corundum during high-temperature nitriding, it combines with the AlN precursor generated by the nitriding of metallic Al to form the AlON phase. A fine powder ball milling premixing process and a sintering process combining a specific heating curve and atmosphere were designed to ensure that metallic aluminum is fully nitrided before melting, guaranteeing the generation of sufficient AlN precursor and achieving AlN coating. This solves the production problem of difficulty in achieving complete nitriding due to molten aluminum agglomeration during heating. Simultaneously, it achieves efficient synthesis of the AlON phase at medium and low temperatures (1400~1550℃), realizing low-cost sintering of AlON-containing materials.

[0008] The technical solution adopted by the present invention to achieve the above objectives is as follows: A method for preparing a TiN / AlON-Al2O3 composite refractory material includes the following steps: (1) Weigh out titanium corundum fine powder and metallic aluminum powder with a particle size of 0.1-0 mm according to the proportioning ratio, and premix them by ball milling to obtain mixed fine powder; (2) Weigh out the various raw materials according to the proportion, mix them evenly, and knead them to obtain mud; (3) Press the prepared clay into shape and dry it; (4) The dried blank is fired at high temperature to obtain the required refractory material. During the high-temperature firing, three nitrogen flow rates are designed for the heating process: the nitrogen flow rate is 1.5 times the furnace volume per minute for temperatures ≤700℃, 1 times the furnace volume per minute for temperatures <700℃ and ≤1100℃, and 0.5 times the furnace volume per minute for temperatures >1100℃. Two holding periods are also designed for the heating process: the first period is 500-700℃, and the holding time is 1-3h; the second period is 1200-1300℃, and the holding time is 2-6h. The sintering process combining the above heating curve with atmosphere control is used to control the nitriding sequence of aluminum and Ti2O3 to achieve the synergistic enhancement of the material by AlON and TiN.

[0009] Premixing time for fine powder ball milling: 0.5 to 2 hours.

[0010] The drying temperature is 120-200℃, and the holding time is 12-48h.

[0011] The firing temperature is 1400-1550℃, the heating rate is 3-5℃ / min, the holding time is 8-16h, and the firing atmosphere is nitrogen.

[0012] The raw material composition of the refractory material is: 55-70wt% Al2O3, 20-35wt% titanium corundum, 5-12wt% metallic aluminum, plus 2%-6% dextrin as a binder.

[0013] The Al2O3 includes tabular alumina, white alumina, brown alumina and dense alumina, and the titanium content of the titanium alumina is 20-40 wt%. Among the added titanium alumina, the proportion of titanium content ≥25 wt% is not less than 50 wt%.

[0014] The Al2O3 has two particle sizes: 3-1 mm and 1-0.1 mm; the titanium corundum has two particle sizes: 1-0.1 mm and 0.1-0 mm; and the metallic aluminum has a particle size of 0.1-0 mm. The ratio of the three different particle sizes is as follows: 3≤particle size<1mm 25%—35% 1 ≤ Particle size < 0.1 mm 30%–50% 0.1 ≤ particle size < 0 mm 15%–35%

[0015] This invention proposes a novel TiN / AlON-Al2O3 composite refractory material and its preparation method. Using the above technical solution, it has the following beneficial effects: (1) The novel corundum composite refractory material with TiN and AlON as the bonding phase has excellent thermal shock stability, and its anti-oxidation and wear resistance are superior to those of aluminum-carbon materials. Its anti-corrosion performance is superior to that of chromium corundum materials. This realizes that corundum materials can simultaneously have excellent anti-stripping and anti-corrosion performance under carbon-free and chromium-free conditions.

[0016] (2) A fine powder ball milling premixing process was designed to ensure that the titanium corundum powder and aluminum powder in the matrix are dispersed as a whole and locally aggregated, which is conducive to the simultaneous formation of titanium aluminum alloy and the nitriding reaction of metallic aluminum; a sintering process combining a specific heating curve and atmosphere control was designed to control the nitriding sequence of metallic aluminum and Ti2O3, so as to achieve the synergistic enhancement of materials by AlON and TiN. Holding the temperature at 500-700℃ with a high flow rate of nitrogen can promote the full nitridation of metallic aluminum before melting, ensuring the formation of sufficient AlN precursor, achieving AlN coating, preventing the agglomeration of molten aluminum during the heating process, and avoiding excessive participation of metallic aluminum in the reduction reaction of Ti2O3. 1200~1300℃ is the optimal nitriding temperature of Ti2O3. Reducing the nitrogen flow rate and holding the temperature can promote the full nitridation of Ti2O3. During the nitriding process, Ti2O3 loses oxygen step by step, integrates into the precursor AlN, promotes the formation of Al-ON solid solution, and achieves efficient synthesis of AlON phase at medium and low temperature (1400~1550℃), realizing low-cost sintering of AlON-containing materials. Detailed Implementation

[0017] The present invention will be described in detail with reference to specific embodiments: Example 1:

[0018] The mixture consists of 32 wt% white corundum (3-1 mm), 30 wt% tabular corundum (1-0.1 mm), 15 wt% titanium corundum (1-0.1 mm, 20 wt% titanium content), 15 wt% titanium corundum (0.1-0 mm, 40 wt% titanium content), 8 wt% aluminum powder (0.1-0 mm), and 4 wt% dextrin as a binder. During production, the 0.1-0 mm titanium corundum powder and aluminum powder are weighed according to the formula and pre-mixed by ball milling for 2 hours to obtain a mixed fine powder. Then, all raw materials are weighed according to the formula, mixed evenly, and kneaded to obtain a mud. This mud is then pressed into shape using a friction press, dried at 180℃ for 32 hours, and then fired in an electrically heated shuttle nitriding kiln at 1400℃ under a nitrogen atmosphere for 8 hours, with a heating rate of 3℃ / min. During the heating process, the nitrogen flow rate is ≤700℃. The nitrogen flow rate was 1.5 times the furnace volume per minute, and the temperature was maintained at 550℃ for 1 hour; for temperatures between 700℃ and 1100℃, the nitrogen flow rate was 1 times the furnace volume per minute; for temperatures ≥ 1100℃, the nitrogen flow rate was 0.5 times the furnace volume per minute, and the temperature was maintained at 1250℃ for 3 hours. The calcined phase consisted of corundum, various AlON phases, TiN, and a small amount of AlN. The physical properties of the obtained product were: apparent porosity 18.3%, bulk density 3.01 g / cm³. 3 It has a compressive strength of 96.0 MPa at room temperature and a flexural strength of 19.0 MPa at room temperature. Example 2:

[0019] The mixture consists of 30 wt% dense corundum (3-1 mm), 35 wt% tabular corundum (1-0.1 mm), 12 wt% titanium corundum (1-0.1 mm, 20 wt% titanium content), 15 wt% titanium corundum (0.1-0 mm, 40 wt% titanium content), and 8 wt% metallic aluminum powder (0.1-0 mm), with 4 wt% dextrin as a binder. During production, the 0.1-0 mm titanium corundum powder and metallic aluminum powder are weighed according to the formula and pre-mixed by ball milling for 2 hours to obtain a mixed fine powder. Then, various raw materials are weighed according to the formula, mixed evenly, and kneaded to obtain a clay mixture. This clay is then pressed into shape using a friction press, dried at 180℃ for 32 hours, and then fired in an electrically heated shuttle nitriding kiln at 1500℃ under a nitrogen atmosphere for 8 hours at a heating rate of 5℃ / min. During the heating process: for temperatures ≤700℃, the nitrogen flow rate is 1.5 times the furnace volume per minute, and the temperature is held at 550℃ for 1 hour; for temperatures 700℃ < 1100℃, the nitrogen flow rate is 1 times the furnace volume per minute; for temperatures ≥1100℃, the nitrogen flow rate is 0.5 times the furnace volume per minute, and the temperature is held at 1300℃ for 3 hours; the calcined phase consists of corundum, various AlON phases, and TiN; the physical properties of the obtained product are: apparent porosity 16.9%, bulk density 3.14 g / cm³. 3 The compressive strength at room temperature is 142 MPa, and the flexural strength at room temperature is 24.4 MPa. Example 3:

[0020] The mixture consists of 30 wt% brown corundum (3-1 mm), 40 wt% tabular corundum (1-0.1 mm), 10 wt% titanium corundum (1-0.1 mm, 23 wt% titanium content), 15 wt% titanium corundum (0.1-0 mm, 38 wt% titanium content), and 5 wt% aluminum powder (0.1-0 mm), with 5 wt% dextrin as a binder. During production, the 0.1-0 mm titanium corundum powder and aluminum powder are weighed according to the formula and pre-mixed by ball milling for 1.5 hours to obtain a mixed fine powder. Then, various raw materials are weighed according to the formula, mixed evenly, and kneaded to obtain a clay material. This clay is then pressed into shape using a friction press, dried at 200℃ for 28 hours, and then fired in an electrically heated shuttle nitriding kiln at 1450℃ under a nitrogen atmosphere for 8 hours at a heating rate of 4℃ / min. During the heating process: for temperatures ≤700℃, the nitrogen flow rate was 1.5 times the furnace volume per minute, and the temperature was held at 650℃ for 2 hours; for temperatures 700℃ < 1100℃, the nitrogen flow rate was 1 times the furnace volume per minute; for temperatures ≥1100℃, the nitrogen flow rate was 0.5 times the furnace volume per minute, and the temperature was held at 1300℃ for 4 hours. The calcined phase consisted of corundum, various AlON phases, and TiN. The physical properties of the obtained product were: apparent porosity 17.2%, bulk density 3.10 g / cm³. 3 The compressive strength at room temperature is 105 MPa, and the flexural strength at room temperature is 20.3 MPa.

[0021] The foregoing description illustrates and describes several preferred embodiments of the present invention, but the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing a TiN / AlON-Al2O3 composite refractory material, characterized in that: Includes the following steps: (1) Weigh out titanium corundum fine powder and metallic aluminum powder with a particle size of 0.1-0 mm according to the proportioning ratio, and premix them by ball milling to obtain mixed fine powder; (2) Weigh out the various raw materials according to the proportion, mix them evenly, and knead them to obtain mud; (3) Press the prepared clay into shape and dry it; (4) The dried blank is fired at high temperature to obtain the required refractory material. During the high-temperature firing, three nitrogen flow rates are designed for the heating process: the nitrogen flow rate is 1.5 times the furnace volume per minute for temperatures ≤700℃, 1 times the furnace volume per minute for temperatures <700℃ and ≤1100℃, and 0.5 times the furnace volume per minute for temperatures >1100℃. Two holding periods are also designed for the heating process: the first period is 500-700℃, and the holding time is 1-3h; the second period is 1200-1300℃, and the holding time is 2-6h. The sintering process combining the above heating curve with atmosphere control is used to control the nitriding sequence of aluminum and Ti2O3 to achieve the synergistic enhancement of the material by AlON and TiN.

2. The preparation method of a TiN / AlON-Al2O3 composite refractory material as described in claim 1, characterized in that: Premixing time for fine powder ball milling: 0.5 to 2 hours.

3. The preparation method of a TiN / AlON-Al2O3 composite refractory material as described in claim 1, characterized in that: The drying temperature is 120-200℃, and the holding time is 12-48h.

4. The preparation method of a TiN / AlON-Al2O3 composite refractory material as described in claim 1, characterized in that: The firing temperature is 1400-1550℃, the heating rate is 3-5℃ / min, the holding time is 8-16h, and the firing atmosphere is nitrogen.

5. The preparation method of a TiN / AlON-Al2O3 composite refractory material as described in claim 1, characterized in that: The raw material composition of the refractory material is: 55-70wt% Al2O3, 20-35wt% titanium corundum, 5-12wt% metallic aluminum, plus 2%-6% dextrin as a binder.

6. The preparation method of a TiN / AlON-Al2O3 composite refractory material as described in claim 5, characterized in that: The Al2O3 includes tabular alumina, white alumina, brown alumina and dense alumina, and the titanium content of the titanium alumina is 20-40 wt%. Among the added titanium alumina, the proportion of titanium content ≥25 wt% is not less than 50 wt%.

7. The preparation method of a TiN / AlON-Al2O3 composite refractory material as described in claim 5, characterized in that: The Al2O3 has two particle sizes: 3-1 mm and 1-0.1 mm; the titanium corundum has two particle sizes: 1-0.1 mm and 0.1-0 mm; and the metallic aluminum has a particle size of 0.1-0 mm. The ratio of the three different particle sizes is as follows: 3≤particle size<1mm 25%—35% 1 ≤ Particle size < 0.1 mm 30%–50% 0.1 ≤ particle size < 0 mm 15%–35%