CN117720341A - Preparation method of magnesia-alumina spinel-carbon refractory material with rare earth as antioxidant - Google Patents

Abstract

The invention belongs to the technical field of high-temperature materials, and particularly relates to a preparation method of a magnesia-alumina spinel-carbon refractory material taking rare earth as an antioxidant. Firstly, adding the electric smelting magnesia-alumina spinel aggregate, the electric smelting magnesia-alumina spinel fine powder, the crystalline flake graphite, the phenolic resin and the lanthanum metal into a mixer according to the mass fraction ratio, fully mixing, then pressing and forming the fully mixed raw materials in a stainless steel mould, and finally carrying out heat treatment for 24 hours at 180-200 ℃ to obtain the magnesia-alumina spinel-carbon refractory material taking the rare earth element as the antioxidant.

Description

Preparation method of magnesia-aluminum spinel-carbon refractory material with rare earth as antioxidant

Technical field

The invention belongs to the technical field of high-temperature materials, and specifically relates to a method for preparing a magnesia-aluminum spinel-carbon refractory material in which rare earth is an antioxidant.

Background technique

Carbon-containing refractory materials are widely used in the linings of metallurgical kilns such as ladle converters and electric furnaces, as well as in continuous casting functional refractory materials such as immersed nozzles, long nozzles, plug rods, and slide plates. Compared with traditional carbon-containing refractory materials, magnesium-aluminum spinel-carbon refractory materials have better slag resistance and thermal shock resistance, and are potential high-performance carbon-containing refractory materials.

In order to meet the production of high-quality clean steel, it is particularly important to ensure that the carbon in carbon-containing refractory materials is not oxidized. The traditional method to improve the antioxidant properties of carbon-containing refractory materials is mainly to add antioxidants. At present, the most commonly used metal antioxidant for carbon-containing refractory materials is metal Al powder. However, the metal carbides generated during the use of metal Al powder are prone to hydration, resulting in a reduction in the performance of carbon-containing refractory materials.

Obviously, under the general trend of the metallurgical industry, it is imperative to develop high-performance carbon-containing refractory materials and find new antioxidants. Therefore, the development of high-performance carbon-containing refractory materials and the discovery of new antioxidants have become research hotspots worthy of attention.

Contents of the invention

In view of the problems in the prior art, the present invention provides a method for preparing magnesia-aluminum spinel-carbon refractory materials with rare earth as antioxidant, aiming to develop high-performance carbon-containing refractory materials and discover new antioxidants to solve the current problem of containing magnesia-aluminum spinel-carbon refractory materials. Problems with insufficient carbon refractories and antioxidants.

The technical solution of the present invention is:

A method for preparing a magnesium-aluminum spinel-carbon refractory material with rare earth as an antioxidant, including the following steps: first, fused magnesium-aluminum spinel aggregate, fused magnesium-aluminum spinel fine powder, and scales are prepared according to mass fraction ratios. Graphite, phenolic resin and metal lanthanum are added to the mixer and mixed thoroughly, and then the fully mixed raw materials are pressed into a stainless steel mold, and finally heat treated at 180 to 200°C for 24 hours to obtain magnesium with rare earth elements as antioxidants. Aluminum spinel-carbon refractory material, the mass fraction ratio of the fused magnesium aluminum spinel aggregate, fused magnesium aluminum spinel fine powder, flake graphite, phenolic resin, and metallic lanthanum is (40-50)% : (40～50)%: (10～15)%: (5～7)%: (2～6)%.

Further, the preferred method for preparing the above-mentioned magnesium-aluminum spinel-carbon refractory material in which rare earth is an antioxidant is that the chemical composition of the fused magnesium-aluminum spinel aggregate is Al ₂ O ₃ :71 ~76%, MgO: 23~28%, particle size range is 0.1~1mm.

Further, the preferred method for preparing the above-mentioned magnesium-aluminum spinel-carbon refractory material in which rare earth is an antioxidant is that the chemical composition of the fused magnesium-aluminum spinel fine powder is Al ₂ O ₃ :71 ~76%, MgO: 23~28%, the particle size range is a mixture of two levels: ≤0.075mm and ≤0.045mm.

Furthermore, the preferred method for preparing the above-mentioned magnesia-aluminum spinel-carbon refractory material in which rare earth is an antioxidant is that the flake graphite is high-purity flake graphite with a purity of ≥99.5% and a particle size range of ≤0.180mm. .

Furthermore, the preferred method for preparing the above-mentioned magnesia-aluminum spinel-carbon refractory material in which rare earth is an antioxidant is that the phenolic resin is thermosetting, industrial grade, and the carbonization rate is 30 to 50%.

Furthermore, the preferred method for preparing the above-mentioned magnesia-aluminum spinel-carbon refractory material in which rare earth is an antioxidant is that the purity of the metal lanthanum is ≥99.5%, and the particle size range is ≤0.075mm.

Further, the preferred method for preparing the above-mentioned magnesia-aluminum spinel-carbon refractory material in which rare earth is an antioxidant is that the pressure of pressing the fully mixed raw materials in a stainless steel mold is 200-250Mpa; The heat treatment equipment is a multi-channel tunnel kiln.

Advantages and beneficial effects of the present invention:

In the present invention, metal lanthanum acts as an antioxidant because metal lanthanum has active chemical properties and is easy to react with oxygen and can be used as an antioxidant; the introduction of rare earth metal lanthanum not only delays the oxidation of carbon, but also promotes the densification of magnesium oxide in the magnesia-aluminum spinel material. layer formation. It can partially or completely replace the metal antioxidants currently commonly used in carbon-containing refractory materials, and has high promotion value and potential application prospects.

As carbon-containing refractory materials used in metallurgical equipment, the decarburization mechanism is mainly reaction and gasification with oxygen in the molten steel (C(s)+[O]=CO(g)). Therefore, how to control this reaction has a negative impact on carbon-containing refractory materials. The oxidation resistance of materials during high-temperature service has a vital impact. In the present invention, first of all, metal lanthanum has a greater affinity with oxygen than carbon, and can react with oxygen preferentially (La(s)+2[O]= La ₂ O ₃ (s)), secondly, magnesium-aluminum spinel will generate magnesium-aluminum iron spinel during the smelting process of molten steel. Magnesium-aluminum iron spinel itself is chemically stable, which reduces the corrosion of refractory materials by molten steel. ability. At the same time, magnesium oxide in magnesia-aluminum spinel reacts with carbon to form a dense layer (Mg(g)+[O]=MgO(s)) on the surface. The emergence of magnesium-aluminum spinel and dense layer prevents the oxygen in the molten steel from entering the magnesia-aluminum spinel-carbon refractory material. Therefore, the carbon of the magnesia-aluminum spinel-carbon refractory material is protected and has good oxidation resistance. Significant improvement.

Description of the drawings

Figure 1 is a morphology picture of the magnesia-aluminum spinel-carbon refractory material after oxidation at 1000°C for 2 hours in Example 1, in which (a) no metallic lanthanum is added, and (b) 2% metallic lanthanum is added.

Detailed ways

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

The oxidation resistance experiments in the examples were all conducted in a box-type resistance furnace. Set the relevant parameters according to the predetermined experimental temperature, put the magnesia-aluminum spinel-carbon refractory material samples without metallic lanthanum and with metallic lanthanum added into the resistance furnace. After the program is completed, the furnace is cooled to normal temperature and the samples are taken out. Use a cutting machine to cut in the radial direction, and use a vernier caliper to measure the radial width of the carbon oxidation, thereby calculating the proportion of the decarburized layer. The average value of three samples in each group is used to characterize the oxidation resistance of the material.

Example 1.

A method for preparing magnesia-aluminum spinel-carbon refractory material with rare earth as antioxidant, the specific steps are as follows:

First, add each according to the mass fraction ratio of fused magnesia-aluminum spinel aggregate: fused magnesium-aluminum spinel fine powder: flake graphite: phenolic resin: metallic lanthanum = 45%: 40%: 15%: 7%: 2% The components are fully mixed in a mixer; then the ground and mixed raw materials are pressed into a Φ30×30mm green body in a stainless steel mold at 200MPa; finally, the final product is kept at 200°C for 24 hours.

The chemical composition of the fused magnesia-aluminum spinel aggregate is Al ₂ O ₃ : 75%, MgO: 25%, and the particle size range is 0.1 to 1 mm.

The chemical composition of the fused magnesium aluminum spinel fine powder is Al ₂ O ₃ : 75%, MgO: 55%, and the particle size range is a mixture of two levels: ≤0.075mm and ≤0.045mm.

The flake graphite is high-purity flake graphite, with a purity of ≥99.5% and a particle size range of ≤0.180mm.

The phenolic resin is thermosetting, industrial grade, with a carbonization rate of 35%

The purity of the lanthanum metal is ≥99.5%, and the particle size range is ≤0.075mm.

The prepared magnesia-aluminum spinel-carbon refractory material has an apparent porosity of 7%, a volume density of 2.90g/cm ³ , and a cured strength of 32Mpa.

The results of the antioxidant experiment in this example are as follows:

After being kept at 1000°C for 2 hours, the decarburized layer percentage of the magnesium-aluminum spinel-carbon refractory material without metallic lanthanum is 24.3%; the decarburized layer percentage of the magnesium-aluminum spinel-carbon refractory material with 2% metallic lanthanum added is 14.13%. Figure 1 shows the morphology of the magnesia-alumina spinel-carbon refractory material after oxidation at 1000°C for 2 hours.

Example 2

A method for preparing magnesia-aluminum spinel-carbon refractory material with rare earth as antioxidant, the specific steps are as follows:

First, add each according to the mass fraction ratio of fused magnesia-aluminum spinel aggregate: fused magnesia-aluminum spinel fine powder: flake graphite: phenolic resin: metallic lanthanum = 50%: 40%: 10%: 6%: 3% The components are fully mixed in a mixer; then the ground and mixed raw materials are pressed into a Φ30×30mm green body in a stainless steel mold at 220MPa; finally, the final product is kept at 180°C for 24 hours.

The chemical composition of the fused magnesium aluminum spinel aggregate is Al ₂ O ₃ : 74%, MgO: 26%, and the particle size range is 0.1 to 1 mm.

The chemical composition of the fused magnesium aluminum spinel fine powder is Al ₂ O ₃ : 74%, MgO: 26%, and the particle size range is a mixture of two levels: ≤0.075mm and ≤0.045mm.

The flake graphite is high-purity flake graphite, with a purity of ≥99.5% and a particle size range of ≤0.180mm.

The phenolic resin is thermosetting, industrial grade, with a carbonization rate of 37%

The purity of the lanthanum metal is ≥99.5%, and the particle size range is ≤0.075mm.

The prepared magnesia-aluminum spinel-carbon refractory material has an apparent porosity of 10%, a volume density of 2.80g/cm ³ , and a cured strength of 28Mpa.

The results of the antioxidant experiment in this example are as follows:

After being kept at 900°C for 2 hours, the decarburized layer percentage of the magnesium-aluminum spinel-carbon refractory material without metallic lanthanum was 20.06%; the decarburized layer percentage of the magnesium-aluminum spinel-carbon refractory material with 3% metallic lanthanum added was 10.13%.

Example 3

A method for preparing magnesia-aluminum spinel-carbon refractory material with rare earth as antioxidant, the specific steps are as follows:

First, add each according to the mass fraction ratio of fused magnesia-aluminum spinel aggregate: fused magnesium-aluminum spinel fine powder: flake graphite: phenolic resin: metallic lanthanum = 48%: 40%: 12%: 5%: 4% The components are fully mixed in a mixer; then, the ground and mixed raw materials are pressed into a Φ30×30mm green body in a stainless steel mold at 250MPa; finally, the final product is kept at 220°C for 24 hours.

The chemical composition of the fused magnesium aluminum spinel aggregate is Al ₂ O ₃ : 76%, MgO: 24%, and the particle size range is 0.1 to 1 mm.

The chemical composition of the fused magnesium aluminum spinel fine powder is Al ₂ O ₃ : 76%, MgO: 24%, and the particle size range is a mixture of two levels: ≤0.075mm and ≤0.045mm.

The flake graphite is high-purity flake graphite, with a purity of ≥99.5% and a particle size range of ≤0.180mm.

The phenolic resin is thermosetting, industrial grade, with a carbonization rate of 40%

The purity of the lanthanum metal is ≥99.5%, and the particle size range is ≤0.075mm.

The prepared magnesia-aluminum spinel-carbon refractory material has an apparent porosity of 9%, a volume density of 2.85g/cm ³ , and a cured strength of 30Mpa.

The results of the antioxidant experiment in this example are as follows:

After being kept at 1100°C for 2 hours, the decarburized layer percentage of the magnesium-aluminum spinel-carbon refractory material without metallic lanthanum was 26.03%; the decarburized layer percentage of the magnesium-aluminum spinel-carbon refractory material with 4% metallic lanthanum added was 18.83%.

Claims (7)

1. A method for preparing a magnesium-aluminum spinel-carbon refractory material with rare earth as an antioxidant, which is characterized in that it includes the following steps: first, fuse the fused magnesium-aluminum spinel aggregate and the fused magnesium-aluminum tip according to the mass fraction ratio. Spar fine powder, flake graphite, phenolic resin and metallic lanthanum are added to the mixer and mixed thoroughly, and then the fully mixed raw materials are pressed into a stainless steel mold, and finally heat treated at 180 to 200°C for 24 hours to obtain a rare earth seed. Magnesium-aluminum spinel-carbon refractory material whose elements are antioxidants. The mass fraction ratio of the fused magnesium-aluminum spinel aggregate, fused magnesium-aluminum spinel fine powder, flake graphite, phenolic resin, and metallic lanthanum is: (40～50)%: (40～50)%: (10～15)%: (5～7)%: (2～6)%. 2. A method for preparing a spinel-carbon refractory material in which rare earth is an antioxidant according to claim 1, characterized in that the chemical composition of the fused spinel aggregate is Al ₂ O ₃ : 71～76%, MgO: 23～28%, particle size range is 0.1～1mm. 3. A method for preparing a magnesium-aluminum spinel-carbon refractory material in which rare earth is an antioxidant according to claim 1, characterized in that the chemical composition of the fused magnesium-aluminum spinel fine powder is Al ₂ O ₃ : 71～76%, MgO: 23～28%, the particle size range is ≤0.075mm and ≤0.045mm. 4. A method for preparing a magnesium-aluminum spinel-carbon refractory material in which rare earth is an antioxidant according to claim 1, characterized in that the flake graphite is high-purity flake graphite with a purity of ≥99.5% and a particle size of ≤ 0.180mm. 5. A method for preparing a magnesia-aluminum spinel-carbon refractory material in which rare earth is an antioxidant according to claim 1, characterized in that the phenolic resin is thermosetting, industrial grade, and has a carbonization rate of 30 to 50%. 6. A method for preparing a magnesia-aluminum spinel-carbon refractory material in which rare earth is an antioxidant according to claim 1, characterized in that the purity of the metal lanthanum is ≥99.5% and the particle size range is ≤0.075mm. 7. A method for preparing a magnesia-aluminum spinel-carbon refractory material in which rare earth is an antioxidant according to claim 1, characterized in that the pressure of pressing the fully mixed raw materials in a stainless steel mold is 200 ~250Mpa.