CN114478018A

CN114478018A - Silicon carbide ceramic grid section and preparation method thereof

Info

Publication number: CN114478018A
Application number: CN202210365159.8A
Authority: CN
Inventors: 曹会彦; 石书冰; 张新华; 冯严宾; 黄一飞; 李�杰; 万龙刚; 吴吉光; 许海洋; 王建栋
Original assignee: Sinosteel Luoyang Institute of Refractories Research Co Ltd
Current assignee: Sinosteel Luoyang Institute of Refractories Research Co Ltd
Priority date: 2022-04-08
Filing date: 2022-04-08
Publication date: 2022-05-13

Abstract

The invention relates to a silicon carbide ceramic grid section, and belongs to the technical field of refractory and wear-resistant materials. The silicon carbide ceramic grid section uses silicon nitride, silicon oxynitride, O-SiAlON, beta-SiAlON and mullite as a combined phase, and silicon carbide as a main crystal phase; the silicon carbide ceramic grid section silicon nitride, silicon oxynitride, O-SiAlON, beta-SiAlON and mullite combined phase accounts for 10-30%, and the silicon carbide main crystal phase accounts for 70-90%. The silicon carbide ceramic grid section has the characteristics of low density, low porosity, high heat conductivity coefficient, good wear resistance, high-temperature strength, good thermal shock resistance and environmental friendliness, and is beneficial to prolonging the service lives of grid sections for the pellet process of a belt type roasting machine, grid sections for the chain-looping pellet process, grid sections for a grate furnace of a garbage incinerator and the like.

Description

Silicon carbide ceramic grid section and preparation method thereof

Technical Field

The invention relates to a silicon carbide ceramic refractory and wear-resistant material, in particular to a silicon carbide ceramic grid section which can be used as a grid section for a belt type roasting machine pelletizing process, a grid section for a chain loop pelletizing process, a grid section for a garbage incinerator furnace grate and the like, replaces expensive chromium-containing high-temperature wear-resistant alloy steel, and has the characteristics of no deformation after long-term use at 1300 ℃, capacity improvement, light overall equipment weight, energy conservation and consumption reduction, high cost performance, environmental friendliness and the like.

Background

In recent years, the roasting process of the pellets of the domestic large-scale straight grate is rapidly developed, and with the production of 400 ten thousand tons of first steel and 500 ten thousand tons of ladle steel, the pellet yield of the straight grate in 2017 accounts for about 20 percent; in 2019, in 5 months, 400-kiloton/a project engineering of a second-stage pellet engineering 3# line of Jingtang Steel United Limited company of the first Steel is ignited successfully; in 2019, the projects of 200 million pellet projects of Fujian Sanjian Minguan Yongquan, 400 million pellet projects of urban defense in 2020, 480 million pellet projects of Heiben Legting and the like all adopt a belt type roasting process; the large belt type roasting machine is a thermal device which is just emerging in recent years, and the belt type roasting pellet technology has a good development prospect in the future.

The continuous grate type roasting machine is similar to a sintering machine in appearance, but has great difference in equipment structure. The arrangement and the sealing of the upper furnace cover, the running direction of wind flow (not single air draft as a sintering machine, but both air draft and air blast), the material distribution mode, the discharge of finished products, the running speed of the trolley and the like are different, and particularly, the material of the body is completely different. In order to safely withstand the highest roasting gas temperature (1300 ℃ C.) for a long time, special alloy steel with excellent high-temperature resistance has to be adopted for the grate bars. In the development process of foreign belt type roasting machines, the development of a grate-rotary kiln which is being developed at the same time is greatly developed because the materials are not too relevant and are once frustrated. The grate-rotary kiln technology is carried out in the rotary kiln with a refractory lining at the highest temperature section in the roasting process, so the material problem in high-temperature roasting is successfully solved. The belt type roasting machine is over-closed and is greatly developed after paving the edge material by using the paving bottom and adopting the material of the high-temperature resistant alloy special steel by the trolley.

The existing high-temperature resistant alloy steel grate bars contain 24-28% of Cr element, belong to noble metal, have the service life of about 2 years generally, have the common damage mode of bearing high-temperature load deformation for a long time and influencing the functional exertion of the Cr element to be off-line, and have C element stored in the air and soil for a long time⁶⁺The pollution problem belongs to the category of products which are limited and eliminated by the nation. In order to ensure the use effect of the high-temperature-resistant alloy steel, the operation mode of the existing industrial production is that a layer of clinker is laid on the grate bar, the raw material groups which need to be roasted at 1300 ℃ are isolated by the roasted clinker and the high-temperature-resistant alloy steel, and the real service temperature of the grate bar is reduced from 1300 ℃ to 600-700 ℃. Although the method can realize stable production in a short period, the deformation of the alloy steel cannot be avoided and the productivity is reduced in a long period.

The silicon carbide ceramic grate bar is sintered at the high temperature of 1450 ℃ through 1350-^-3The alloy steel 1/3 is wear-resistant alloy steel, and has the characteristics of large yield, light weight, less heat storage, energy conservation, consumption reduction, environmental friendliness and the like.

Disclosure of Invention

The invention aims to provide a silicon carbide ceramic grid and a preparation method thereof, which can prolong the service life of grids for a pelletizing process of a belt type roasting machine, grids for a chain-loop pelletizing process, grids for a furnace of a garbage incinerator, and the like, furthest exert the design productivity of related processes, reduce the use of high-temperature-resistant and wear-resistant alloy steel which is expensive and contains a large amount of Cr elements, and realize the environment-friendly and energy-saving consumption-reducing large-scale stable production of the related processes.

The invention adopts the following technical scheme for achieving the purpose:

a silicon carbide ceramic grid section takes silicon powder, alumina micro powder, silicon dioxide micro powder, silicon carbide micro powder and silicon carbide particles as raw materials; silicon powder and silicon dioxide micropowder are subjected to a common nitridation reaction to generate silicon nitride and silicon oxynitride; the aluminum oxide micro powder is dissolved in silicon nitride generated by silicon powder nitridation to generate beta-SiAlON; the aluminum oxide micro powder is dissolved in silicon oxynitride generated by nitriding the silicon dioxide micro powder and the silicon powder together to generate O-SiAlON; all these reactions and the formation of the binding phase were carried out at 1350-; the silicon carbide ceramic grid section takes silicon nitride, silicon oxynitride, O-SiAlON, beta-SiAlON and mullite as a combined phase, and silicon carbide as a main crystal phase; the silicon carbide ceramic grid section silicon nitride, silicon oxynitride, O-SiAlON, beta-SiAlON and mullite combined phase accounts for 10-30%, and the silicon carbide main crystal phase accounts for 70-90%.

The raw materials comprise the following components in percentage by mass: the mass content of the silicon powder is 8-15 percent,

the mass content of the alumina micro powder and the silica micro powder is 2-12%, the mass content of the silicon carbide micro powder is 2-10%, and the mass content of the silicon carbide particles is 65-80%.

The fine silica powder D₅₀Less than or equal to 0.2 micron, D of the alumina micropowder₅₀Less than or equal to 2 microns; d of the silicon carbide micro powder₅₀Less than or equal to 10 microns.

SiO of the fine silica powder₂The content is more than or equal to 95 percent, and the impurity K in the silicon dioxide micro powder₂O+Na₂The content of O is less than or equal to 0.5 percent.

A preparation method of the silicon carbide ceramic grid section comprises the following steps: firstly, uniformly mixing silicon carbide particles, then adding a bonding agent accounting for 3-5% of the total amount of the raw materials and a solvent accounting for 0.5-3.5% of the total amount of the raw materials, uniformly mixing the bonding agent on the surfaces of the silicon carbide particles to form uniform films, then adding the mixed fine powder of the pre-mixed silicon powder, silicon dioxide micro powder, aluminum oxide micro powder and silicon carbide micro powder, uniformly mixing, then pressing a sample, putting the dried sample into a sintering furnace, heating to 1350-1450 ℃ in a segmented manner under the nitrogen atmosphere of 0.1Mpa, preserving the temperature for 6-10 h at the temperature, then replacing the nitrogen with air, controlling the temperature to be 1100-1300 ℃, preserving the temperature for 3-6 h, and obtaining the silicon carbide ceramicA ceramic grid section; the density of the silicon carbide ceramic grid section prepared by the method is 2.60-2.75 g-cm^-3The porosity is 8-10%, and the long-term service temperature is more than 3 years under the condition of 1300 ℃ natural gas or coal gas air combustion.

Replacing nitrogen with air after the nitridation and solid solution reactions are finished, preserving heat at 1100-1300 ℃, eliminating adverse effects of partial residual silicon dioxide and aluminum oxide micro powder and silicon carbide or silicon nitride or silicon oxynitride or beta-SiAlON or O-SiAlON on silicon oxide and aluminum oxide generated by co-oxidation and possibly existing impurity glass relative to grain boundaries in the system, converting the silicon oxide and aluminum oxide into a high-temperature resistant mullite crystal phase, purifying a system free glass phase, prefabricating a partial oxygen-containing crystal phase in a combined phase system taking nitride as a main component, the nitride-bonded silicon carbide air holes are blocked, the influence of the service environment atmosphere on the high-quality nitride bonding phase is shielded to the maximum extent, and meanwhile, adverse factors brought by the difference of thermal expansion coefficients brought by the existence of cristobalite or free alumina to the thermal shock stability of a system are eliminated, and the stability of the material structure under the long-term high-temperature service condition is realized.

The silicon carbide ceramic grid section provided by the invention has the density of 2.60-2.75 g-cm^-3The porosity is 8-10%, and the preparation of the silicon carbide ceramic grid section with the structural characteristics of low density, low porosity, high strength, high wear resistance and the like is mainly attributed to the following aspects: SiO₂Fine powder of Al₂O₃The three micro powder systems of micro powder and SiC micro powder are cooperatively introduced, and the effective physical filling effect on blank pores is more obvious than that of single micro powder in the aspect of effective physical filling of blank pores through the gradient arrangement of the particle sizes of three different micro powders D50; 2. SiO 2₂The plasticizing effect of the micro powder is far better than that of Al₂O₃The micro powder is better in the aspects of ensuring the molding stability of the silicon carbide ceramic grid section and the density uniformity of a blank body. 3. The nitride formed by nitriding the main system with silicon powder gives the bonding phase high strength and high wear resistance, and can absorb SiO₂Fine powder and Al₂O₃The Si-O-Al bond brought by the micro powder on the chemical bond is converted into silicon oxynitride or beta-SiAlON or O-SiAlON, and the shape of the chemical bond of Si-O-N, Al-O-N, Si-O-Al-N is accompanied in the processDuring the process of converting silicon powder into silicon nitride by nitridation, the porosity of the blank is reduced by the weight increasing reaction of nitridation, and Al₂O₃In the solid solution process of the silicon nitride or the silicon oxynitride, along with the lattice distortion, the material is also endowed with smaller and lower porosity and more reasonable pore diameter distribution, and the wear resistance and the high-temperature strength are improved. 4. The silicon carbide ceramic grid section is formed by firstly generating high-strength and high-wear-resistance silicon nitride, silicon oxynitride, beta-SiAlON or O-SiAlON complex phase combination phase in nitrogen atmosphere and then processing the combination phase in air atmosphere to form mullite combination phase, so that the silicon carbide ceramic grid section with nitride and high-temperature-resistant oxide synergistic enhancement, high wear resistance and high stability is formed.

The silicon carbide ceramic grid section provided by the invention has the characteristics of low density, low porosity, high heat conductivity coefficient, good wear resistance, high-temperature strength, good thermal shock resistance and environmental friendliness, is beneficial to prolonging the service lives of grid sections for a belt type roasting machine pellet process, grid sections for a chain-looping pellet process, grid sections for a waste incineration furnace grate furnace and the like, furthest exerts the design productivity of related processes, reduces the use of high-temperature-resistant wear-resistant alloy steel which is expensive and contains a large amount of Cr elements, and realizes the environment-friendly, energy-saving and consumption-reducing large-scale stable production of the related processes.

Detailed Description

The present invention will be described in detail with reference to specific examples:

example 1:

the final phase composition of the silicon carbide ceramic grid section comprises: the proportion of silicon carbide is 70 percent, and the proportion of silicon nitride, silicon oxynitride, beta-SiAlON, O-SiAlON and mullite is 30 percent. The amount of Si powder introduced as a raw material was 15%, and SiC fine powder (D)₅₀=8 μm) was incorporated in an amount of 5%, SiO₂Micropowder (D)₅₀=0.2 μm) was incorporated in 2%, Al₂O₃Micropowder (D)₅₀=1 μm), and the amount of 0.1 to 1.43mmSiC particles introduced is 68%. The binder is water-soluble amino resin, the apparent porosity of the product is 8.0%, and the volume density is 2.75g/cm³Normal temperature bending strength of 55.0MPa, 1300 deg.C high temperature bending strength of 60.0MPa, and abrasion resistance of 2.5cm³。

Example 2:

the final phase composition of the silicon carbide ceramic grid section comprises: the proportion of the silicon carbide is 80 percent, and the proportion of the silicon nitride, the silicon oxynitride, the beta-SiAlON, the O-SiAlON and the mullite is 20 percent. The amount of Si powder introduced as a raw material was 12%, and SiC fine powder (D)₅₀=8 μm) was incorporated in an amount of 5%, SiO₂Micropowder (D)₅₀=0.2 μm) was incorporated in an amount of 0.5%, Al₂O₃Micropowder (D)₅₀=1 μm) of the components, the content of 0.1-1.43mmSiC particles is 77.5%, the bonding agent is phenolic resin, the apparent porosity of the product is 9.5%, and the volume density is 2.60g/cm³Normal temperature bending strength of 45.0MPa, 1300 deg.C high temperature bending strength of 50.0MPa, and abrasion resistance of 3.5cm³。

Example 3:

the final phase composition of the silicon carbide ceramic grid section comprises: the proportion of silicon carbide is 90 percent, and the proportion of silicon nitride, silicon oxynitride, beta-SiAlON, O-SiAlON and mullite is 10 percent. The amount of Si powder introduced as a raw material was 8%, and SiC fine powder (D)₅₀=8 μm) is 10%, SiO₂Micropowder (D)₅₀=0.2 μm) was incorporated in an amount of 0.5%, Al₂O₃Micropowder (D)₅₀=1 μm), the incorporation amount of 0.1-1.43mmSiC particles is 80%, the binder is dextrin and calcium lignosulfonate, the apparent porosity of the product is 9.0%, and the bulk density is 2.7g/cm³Normal temperature bending strength of 50.0MPa, 1300 deg.C high temperature bending strength of 65.0MPa, and abrasion resistance of 4.0cm³。

Claims

1. A silicon carbide ceramic grid section is characterized in that: the silicon carbide ceramic grid section takes silicon powder, alumina micro powder, silicon dioxide micro powder, silicon carbide micro powder and silicon carbide particles as raw materials; silicon powder and silicon dioxide micropowder carry out nitridation reaction together to generate silicon nitride and silicon oxynitride; the aluminum oxide micro powder is dissolved in silicon nitride generated by silicon powder nitridation to generate beta-SiAlON; the aluminum oxide micro powder is dissolved in silicon oxynitride generated by nitriding the silicon dioxide micro powder and the silicon powder together to generate O-SiAlON; all these reactions and the formation of the binding phase were carried out at 1350-; the silicon carbide ceramic grid section takes silicon nitride, silicon oxynitride, O-SiAlON, beta-SiAlON and mullite as a combined phase, and silicon carbide as a main crystal phase; the silicon carbide ceramic grid section silicon nitride, silicon oxynitride, O-SiAlON, beta-SiAlON and mullite combined phase accounts for 10-30%, and the silicon carbide main crystal phase accounts for 70-90%.

2. The silicon carbide ceramic grid according to claim 1, wherein: the raw materials comprise the following components in percentage by mass: the mass content of the silicon powder is 8-15%, the mass content of the alumina micro powder and the silica micro powder is 2-12%, the mass content of the silicon carbide micro powder is 2-10%, and the mass content of the silicon carbide particles is 65-80%.

3. The silicon carbide ceramic grid section of claim 1, wherein: the fine silica powder D₅₀Less than or equal to 0.2 micron, D of the alumina micropowder₅₀Less than or equal to 2 microns; d of the silicon carbide micro powder₅₀Less than or equal to 10 microns.

4. The silicon carbide ceramic grid section of claim 1, wherein: SiO of the fine silica powder₂The content is more than or equal to 95 percent, and the impurity K in the silicon dioxide micro powder₂O+Na₂The content of O is less than or equal to 0.5 percent.

5. The preparation method for preparing the silicon carbide ceramic grid section of any one of claims 1 to 4 comprises the following steps: firstly, uniformly mixing silicon carbide particles, then adding a bonding agent accounting for 3-5% of the total amount of the raw materials and a solvent accounting for 0.5-3.5% of the total amount of the raw materials, uniformly mixing the bonding agent on the surfaces of the silicon carbide particles to form uniform films, then adding the mixed fine powder of the pre-mixed silicon powder, silicon dioxide micro powder, aluminum oxide micro powder and silicon carbide micro powder, uniformly mixing, then pressing a sample, putting the dried sample into a sintering furnace, heating to 1350-1450 ℃ in a segmented manner under the nitrogen atmosphere of 0.1Mpa, preserving heat for 6-10 h at the temperature, then replacing nitrogen with air, controlling the temperature to be 1100-doped 1300 ℃ and preserving heat for 3-6 h to obtain silicon carbide ceramic grid bars; the density of the silicon carbide ceramic grid section prepared by the method is 2.60-2.75 g-cm^-3The porosity is 8-10%, and the long-term service temperature is more than 3 years under the condition of 1300 ℃ natural gas or coal gas air combustion.