CN116178023A - A preparation method of thermal shock resistance and oxidation resistance Si3N4 combined with SiC refractory material - Google Patents

Abstract

The invention relates to a heat shock resistant and oxidation resistant Si ₃ N ₄ A method for preparing a combined SiC refractory material. The technical proposal is as follows: silicon carbide and molybdenum disilicide particles with the particle diameters of 1-3mm and 0-1mm are used as aggregate, silicon carbide fine powder, molybdenum disilicide fine powder and metal silicon powder with the particle diameters of less than 0.064 mu m are used as matrixes, and water-soluble resin is used as a bonding agent. Taking proper contents of the raw materials, mixing the aggregate and the binding agent uniformly in an edge mill, then adding the uniformly mixed fine powder of the raw materials, stirring uniformly, and binding properly. Then press-forming on a friction brick press, firstly drying the green body at 110 ℃ for 24 hours, and preserving heat for 3-6 hours at 1400-1450 ℃ to obtain the heat shock resistant and oxidation resistant Si ₃ N ₄ And SiC refractory material is combined. The invention is thatMainly introduces molybdenum disilicide as a second phase, and effectively improves the thermal shock resistance and oxidation resistance of the material.

Description

A preparation method of thermal shock resistance and oxidation resistance Si3N4 combined with SiC refractory material

technical field

The invention belongs to the technical field of inorganic non-metallic materials. In particular, it relates to a method for preparing a thermal shock-resistant and oxidation-resistant Si ₃ N ₄ combined with SiC refractory material.

Background technique

The refractory brick lining of the pressurized boiler is used in a very harsh environment. The refractory bricks are subjected to severe temperature fluctuations of sudden cooling and sudden heating, coupled with the frequent variable load work of the boiler during use, resulting in great thermal stress, resulting in damage to the material, which can be directly Caused the failure of the boiler, and then the loss of power of the entire ship. Therefore, the performance of the lining material directly affects the safety and reliability of the marine power plant. Silicon nitride combined with silicon carbide refractory products have excellent high-temperature performance such as acid and alkali corrosion resistance, thermal shock resistance, and erosion resistance, and are widely used in heat-resistant and wear-resistant environments such as metallurgy and chemical industry. However, according to the actual effect of long-term application, Si ₃ N ₄ combined with SiC has key application problems such as poor impact resistance and serious oxidation in service, which seriously affects the service life of refractory products and the normal operation of equipment. Improving the thermal shock resistance and oxidation resistance of Si ₃ N ₄ combined with SiC products is an important optimization direction for this type of refractory.

MoSi ₂ has the advantages of high melting point (2030°C), good electrical and thermal conductivity, excellent high temperature oxidation resistance, etc., and MoSi ₂ has good physical and chemical compatibility with SiC, especially MoSi ₂ has metal-like properties above 1000°C. The soft plasticity can greatly buffer the thermal stress of the material at high temperature. Therefore, the present invention mainly introduces MoSi ₂ in different ways and proportions into the Si ₃ N ₄ bonded SiC material to improve the high temperature thermal shock resistance and high temperature oxidation resistance of the material.

Contents of the invention

The purpose of the present invention is to solve the problems of poor impact resistance and serious oxidation of Si ₃ N ₄ combined with SiC materials in service, adopt the method of introducing the third phase molybdenum disilicide, optimize the proportion of materials, and adopt the introduction of molybdenum disilicide Granules or fine powders, granules and fine powders are jointly introduced in three different ways to regulate the material structure, and the prepared materials have better anti-oxidation and thermal shock resistance.

The purpose of the present invention is achieved by the following technical solutions:

A method for preparing a thermal shock-resistant and oxidation-resistant Si ₃ N ₄ bonded SiC refractory material. The main raw materials of the thermal shock-resistant and oxidation-resistant Si ₃ N ₄ bonded SiC refractory material are silicon carbide particles and fine powder, molybdenum disilicide particles and fine powder Powder, metal silicon powder; and water-soluble resin is used as binder; it is characterized in that: the mass percentage of raw materials is: 15~30% of silicon carbide particles with a particle size of 1-3mm, and 15~25% of silicon carbide particles with a particle size of 0-1mm Silicon carbide particles, 10-20% of silicon carbide fine powder with a particle size of less than 0.062mm, 10-20% of molybdenum disilicide particles with a particle size of 1-3mm, and 5-15% of molybdenum disilicide particles with a particle size of less than 0.062mm Molybdenum fine powder, 5-15% metal silicon powder with particle size less than 280 mesh and 2-6% water-soluble resin; silicon carbide particles and molybdenum disilicide particles are aggregates; The aggregate and water-soluble resin are mixed evenly in the wheel mill, and then the fine powder mixed in advance is added to the raw materials, and it is fully stirred in the wheel mill. After the mixture is processed by bundling; Brick machine press molding; firstly dry the body at 110°C for 24h, then heat treatment at 1400~1450°C under nitrogen atmosphere for 3~6h heat treatment, you can get Si ₃ N ₄ combination with good thermal shock resistance and oxidation resistance SiC refractories.

The SiC content of the silicon carbide particles is greater than 98.0%.

The SiC content in the silicon carbide fine powder is greater than 98.0%

The MoSi ₂ content in the molybdenum disilicide particles is greater than 98.0%.

The _MoSi2 content in the molybdenum disilicide fine powder is greater than 98.0%.

The Si content in the metal silicon powder is greater than 98.0%.

The binder used is water-soluble resin.

Using the above technical scheme, different from the in-situ synthesis of molybdenum disilicide by the infiltration method reported in the literature, the present invention directly adds pre-synthesized molybdenum disilicide particles or powder, and can directly add the treated used molybdenum silicon rod as a raw material, The recycling of waste materials is realized, which responds to the concept of sustainable development; the invention has the following advantages:

The introduction of pre-synthesized second phase molybdenum disilicide can effectively improve the oxidation resistance of Si ₃ N ₄ combined with SiC refractories, and effectively alleviate the structural damage caused by rapid oxidation of materials during use.

2. Molybdenum disilicide becomes metal-like soft plasticity above 1000°C. Using this property, the high-temperature plasticity of Si ₃ N ₄ combined with SiC refractories can be improved, thereby improving the thermal shock resistance of the material.

Implementation

The present invention will be further described below in combination with specific embodiments.

Embodiment 1: A kind of preparation method of thermal shock resistance, anti-oxidation Si ₃ N ₄ combined with SiC refractory material, its raw material composition and parts by weight are: 30% silicon carbide particles with a particle diameter of 1-3mm, 15% with a particle diameter of 0~1mm silicon carbide particles, 20% silicon carbide fine powder with particle size ≤0.062mm, 15% molybdenum disilicide particles with particle size 1~3mm, 10% molybdenum disilicide fine powder with particle size ≤0.062mm, 10 % metal silicon powder, 4% water-soluble resin.

Embodiment 2: A kind of preparation method of thermal shock resistance, anti-oxidation Si ₃ N ₄ combined with SiC refractory material, its raw material composition and parts by weight are: 25% of silicon carbide particles with a particle size of 1-3 mm, 20% with a particle size of 0~1mm silicon carbide particles, 25% silicon carbide fine powder with particle size ≤0.062mm, 10% molybdenum disilicide particles with particle size 1~3mm, 10% molybdenum disilicide fine powder with particle size ≤0.062mm, 10 % metal silicon powder, 4% water-soluble resin.

Embodiment 3: A kind of preparation method of thermal shock resistance, anti-oxidation Si ₃ N ₄ combined with SiC refractory material, its raw material composition and parts by weight are: 25% silicon carbide particles with a particle size of 1-3mm, 20% with a particle size of 0~1mm silicon carbide particles, 25% silicon carbide fine powder with particle size ≤0.062mm, 20% molybdenum disilicide particles with particle size 1~3mm, 10% metal silicon powder, 4% water-soluble resin.

Embodiment 4: A kind of preparation method of thermal shock resistance, anti-oxidation Si ₃ N ₄ combined with SiC refractory material, its raw material composition and parts by weight are: 25% silicon carbide particles with a particle diameter of 1-3mm, 20% with a particle diameter of 0~1mm silicon carbide particles, 25% silicon carbide fine powder with particle size ≤0.062mm, 20% molybdenum disilicide fine powder with particle size ≤0.062mm, 10% metal silicon powder, 5% water-soluble resin.

Example 5: A method for preparing a thermal shock-resistant and oxidation-resistant Si ₃ N ₄ bonded SiC refractory material, its raw material composition and parts by weight are: 20% silicon carbide particles with a particle size of 1 to 3 mm, and 15% with a particle size of 0~1mm silicon carbide particles, 20% silicon carbide fine powder with particle size ≤0.062mm, 20% molybdenum disilicide particles with particle size 1~3mm, 15% molybdenum disilicide fine powder with particle size ≤0.062mm, 10 % metal silicon powder, 4% water-soluble resin.

According to the above ingredients and appropriate content, first mix the aggregate and binder uniformly in the wheel mill, then add the fine powder mixed in advance of the raw materials, fully stir it in the wheel mill, bales. It is then machine-pressed on a friction brick press. Firstly, the green body is dried at 110°C for 24 hours, and then heat-treated at 1400-1450°C for 3-6 hours in a nitrogen atmosphere to obtain a Si ₃ N ₄ bonded SiC refractory material with good thermal shock resistance and oxidation resistance. After relevant performance tests, this kind of refractory material has high thermal shock stability, more than 20 times of water-cooled thermal shock, and the high-temperature oxidation weight loss rate has dropped significantly.

Claims (6)

1. Thermal shock resistant and oxidation resistant Si ₃ N ₄ Preparation method of combined SiC refractory material, thermal shock resistant and oxidation resistant Si ₃ N ₄ The main raw materials of the SiC-combined refractory material are silicon carbide particles, fine powder, molybdenum disilicide particles, fine powder and metal silicon powder; and water-soluble resin is adopted as a bonding agent; the method is characterized in that: the mass percentages of the raw materials are as follows: 15-30% of silicon carbide particles with the particle size of 1-3mm, 15-25% of silicon carbide particles with the particle size of 0-1mm, 10-20% of silicon carbide fine powder with the particle size of less than 0.062mm, 10-20% of molybdenum disilicide particles with the particle size of 1-3mm, 5-15% of molybdenum disilicide fine powder with the particle size of less than 0.062mm, 5-15% of metal silicon powder with the particle size of less than 280 meshes and 2-6% of water-soluble resin; silicon carbide particles and molybdenum disilicide particles are aggregate; according to the above components and proper content, the aggregate and the water-soluble resin are firstly mixed uniformly in an edge mill, and then the raw materials are addedFully stirring the fine powder which is mixed in advance in an edge mill, and bundling the mixture; then pressing and forming on a friction brick press; firstly, drying the blank at 110 ℃ for 24 hours, and then, preserving heat for 3-6 hours under the nitrogen atmosphere at 1400-1450 ℃ for heat treatment, thus obtaining Si with good thermal shock resistance and oxidation resistance ₃ N ₄ And SiC refractory material is combined.

2. A heat shock resistant and oxidation resistant Si according to claim 1 ₃ N ₄ The preparation method of the combined SiC refractory material is characterized by comprising the following steps: the SiC content of the silicon carbide particles is greater than 98.0%.

3. A heat shock resistant and oxidation resistant Si according to claim 1 ₃ N ₄ The preparation method of the combined SiC refractory material is characterized by comprising the following steps: the SiC content of the silicon carbide fine powder is more than 98.0%.

4. A heat shock resistant and oxidation resistant Si according to claim 1 ₃ N ₄ The preparation method of the combined SiC refractory material is characterized by comprising the following steps: moSi in the molybdenum disilicide particles ₂ The content is more than 98.0 percent.

5. A heat shock resistant and oxidation resistant Si according to claim 1 ₃ N ₄ Preparation method of combined SiC refractory material, wherein MoSi in molybdenum disilicide fine powder ₂ The content is more than 98.0 percent.

6. A heat shock resistant and oxidation resistant Si according to claim 1 ₃ N ₄ The preparation method of the combined SiC refractory material is characterized by comprising the following steps: the Si content in the metal silicon powder is more than 98.0%.