Alumina ceramics is an advanced ceramic material with alumina (Al2O3) as the main chemical composition, which is widely used in traditional fields and new material fields.
Alumina ceramics generally refer to alumina ceramics with alumina content more than 70%.
It is not only a traditional refractory material and wear-resistant material, but also a widely used electronic ceramic material.
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Alumina ceramic rings, spacersThe alumina powder is prepared into powder materials according to different product requirements and different molding processes. The alumina powder must be ultra-finely pulverized to make the particle size distribution uniform.
When using the injection molding method, a binder and a plasticizer must be introduced into the powder and mixed uniformly at a certain temperature to facilitate the molding operation.
If the dry pressing method is adopted, a spray drying tower is required to granulate the grinded slurry alumina powder to make it spherical, so as to improve the fluidity of the powder and facilitate automatic filling of the mold during forming.
For powder spray granulation, polyvinyl alcohol can be used as a binder. The powder after spray granulation must have good fluidity, loose density, and flow angle friction temperature less than 30&#;. Ideal particle gradation ratio and other conditions to obtain a larger green body density.
There are many methods for forming alumina ceramic products, such as dry pressing, extrusion, cold isostatic pressing, injection, casting, hot pressing and hot isostatic pressing.
Products of different shapes, sizes, complex shapes and precision require different molding methods.
The dry pressing technology of alumina ceramics is limited to ceramic parts with a simple shape, an inner wall thickness of more than 1mm, and a length to diameter ratio of not more than 4:1. The forming method is uniaxial or bidirectional.
There are two types of presses: hydraulic and mechanical, and can be semi-automatic or fully automatic operation.
Due to the uniform pressure of the hydraulic press, the height of the pressed part is different when the powder filling is different. However, the pressure applied by the mechanical press varies with the amount of powder filling, which easily leads to differences in size shrinkage after sintering, which affects product quality.
Therefore, the uniform distribution of alumina powder granular during dry pressing is very important for mold filling. Whether the filling amount is accurate or not has a great influence on the dimensional accuracy control of the manufactured alumina ceramic parts.
The ideal particle of the powder should make the powder obtain the maximum free flowability and achieve the best forming result as the goal.
Cold isostatic pressing(CIP) applies pressure from multiple directions for achieving greater uniformity of compaction (high-quality parts) and increased shape capability, compared to uniaxial pressing.
There are two methods of carrying out isostatic pressing.
In wet-bag isostatic pressing &#;
Powder is encased in a rubber sheath that is immersed in a liquid which transmits the pressure uniformly to the powder.
In dry-bag isostatic pressing &#;
Rather than immerse the tooling in a fluid, the tooling itself is built with internal channels into which high-pressure fluid is pumped.
The cold isostatic press is also known as a rubber press.
Ceramic powder and metal powder fill a rubber mold, which is then dipped into the pressure vessel.
The powder is compressed at a maximum water pressure of 400 MPa.
Isostatic actions (hydrostatic pressure) can also form complicated shapes which cannot be compressed without a uniaxial press or machine press.
The HIP process, which subjects a component to elevated temperatures and pressures to eliminate internal micro-shrinkage, helped engineers respond to the aerospace industry&#;s increasingly stringent regulations.
HIP enabled engineers to design components so they could meet specifications for use in critical, highly stressed applications.
The HIP&#;ing Process
The HIP process provides a method for producing components from diverse powdered materials, including metals and ceramics.
During the manufacturing process, a powder mixture of several elements is placed in a container, typically a steel can.
The container is subjected to elevated temperature and a very high vacuum to remove air and moisture from the powder.
The container is then sealed and HIP&#;ed The application of high inert gas pressures and elevated temperatures results in the removal of internal voids and creates a strong metallurgical bond throughout the material.
The result is a clean homogeneous material with a uniformly fine grain size and a near 100% density.
Grouting is the earliest molding method used for alumina ceramics. The grouting method has low cost and is easy to form large-sized and complex-shaped parts. The key to grouting is the preparation of alumina slurry. Usually water is used as the flux medium, and then the debonding agent and the binder are added, and the gas is exhausted after being fully ground, and then poured into the plaster mold.
The alumina ceramic slurry also needs to add organic additives to form an electric double layer on the surface of the slurry particles so that the slurry is stably suspended without precipitation. In addition, binders such as vinyl alcohol, methyl cellulose, alginate amine, and dispersants such as polypropylene amine and gum arabic must be added, all for the purpose of making the slurry suitable for grouting and molding operations.
The process of densifying the granular ceramic green body and forming a solid material is called sintering.
Sintering is a method of removing the voids between particles in the green body, removing a small amount of gas and impurity organic matter, so that the particles can grow and combine with each other to form a new material.
The heating device used for sintering is the most widely used electric furnace. In addition to atmospheric sintering, namely pressureless sintering, there are also hot pressing sintering and hot isostatic pressing sintering.
Hot isostatic pressing sintering uses high temperature and high pressure gas as the pressure transmission medium, which has the advantage of uniform heating in all directions and is very suitable for sintering products with complex shapes.
Roller kilns and tunnel kilns are used for wear resistant alumina ceramic sintering, such as wear protection alumina tiles and alumina grinding balls.
Some alumina ceramic materials still need finishing after sintering.
Due to the high hardness of alumina ceramic materials, it is necessary to use harder abrasive and polished tile materials for finishing, such as SIC, B4C or diamonds.
Generally, it uses coarse to fine abrasives to grind step by step to meet the required dimensional tolerance and surface finishing.
Alumina ceramic parts can also be machined before sintering, when they are green body.
This technique is commonly applied to as-pressed parts which are still in a &#;chalky&#; condition. Common metalworking machines are used to machine the part in this &#;soft&#; condition as greater material removal rates are possible than by post sintering operations such as diamond grinding.
As fired green machined components are subject to maximum tolerances of +/- 1%. To achieve tighter tolerances diamond grinding must be adopted.
Alumina wear-resistant ceramics have the characteristics of high hardness, wear resistance, high temperature resistance, corrosion resistance and low price. They are suitable for industrial applications. They have been widely used in chute liners, cement grinding systems, raw material grinding systems, ore crushing treatment system, hard material powder conveying fan impeller, wear-protection linings of coal-fired power plant pulverizing system and cement plant powder selection system, etc.
Alumina ceramic blocksAlumina ceramic blocksAlumina ceramic cylindersAlumina ceramic content: &#;92%
Density: &#;3.6 g/cm3
Rockwell hardness: &#;80 HRA
Compressive strength: &#;850 Mpa
Fracture toughness KΙC: &#;4.8MPa·m1/2
Flexural strength: &#;290MPa
Thermal conductivity: 20W/m.K
Coefficient of thermal expansion: 7.2×10-6m/m.K
Alumina grinding balls are made of alumina powder as raw material through batching, grinding, powdering (pulping, mud making), molding, drying, firing and other processes. The alumina content of high-aluminum grinding balls is above 92%, and the appearance is white spherical with a diameter of 1-100mm.
Alumina balls, alumina ceramic grinding mediaThe alumina ball has low abrasion, high hardness, corrosion resistance, impact resistance, stable performance under high temperature conditions, economical and practical.
Alumina ceramic microspheres, alumina ceramic grinding mediaIt is suitable for grinding media of ball mills, stirring mills and other equipment, and can be used in non-ferrous metal ore, industrial ceramic powder materials, non-metal powder materials, titanium dioxide, paper making, coatings, other powder materials and other fields.
As a kind of inorganic non-metallic materials, alumina ceramic materials have properties that many metal materials do not have, such as: high strength, high hardness, high elastic modulus, high temperature resistance, wear resistance, corrosion resistance, oxidation resistance, thermal shock resistance .
The current production process of alumina ceramics is mature, and alumina ceramic parts of various non-standard shapes can be made according to special applications, replacing metal as key parts.
Based on the high temperature resistance of alumina ceramics, special ceramics can be made into space shuttle insulation shells, intercontinental missile warheads, rocket nozzle parts, etc.
Alumina ceramics have a wide range of applications in civil products, such as engine combustion chambers, piston crowns, rotors, corrosion-resistant impellers, wear-resistant pipes, bearings, bushings, ball valves, seals, screws, spacers, ceramic rings, tube, &#; which can replace metal products in many applications.
The alumina ceramic parts have many characteristics such as ultra-high temperature, high hardness, high melting point, high wear resistance, acid and alkali corrosion resistance, non-conductivity, non-magnetic conductivity, low expansion coefficient, special photoelectric properties, etc., and can be used in aerospace, communications, petroleum, electricity, automobiles, electronics, photovoltaic solar energy, new energy batteries, chemicals, medical equipment, precision machinery, biological testing equipment, intelligent automation and many other fields and industries.
Alumina ceramic substrate material is the most economical and effective substrate material in microelectronics applications. The 99.6% alumina substrate has excellent thermal conductivity, mechanical strength, electrical insulation performance, chemical durability and dimensional stability, thus becoming the first choice for hybrid circuits. It is widely used in thick film circuits, thin film circuits, hybrid circuits, multi-chip components and high-power IGBT modules.
Ceramic substrate is a sheet-like material based on electronic ceramics that forms a support base for membrane circuit components and external bonding components.
Ceramic substrate has the main advantages of high temperature resistance, high electrical insulation, low dielectric constant and dielectric loss, large thermal conductivity, good chemical stability, and thermal expansion coefficient similar to that of the component.
However, the ceramic substrate is brittle, and the size of the ceramic substrate is small and the cost is relatively high.
Commonly used ceramic substrate materials are Al2O3, AlN, SiC, BeO, BN, zirconia and glass ceramics. Although the thermal conductivity of alumina ceramic substrate is not high (20W/m.K), because of its relatively simple production process, low cost and low price, it has become the most widely used ceramic substrate.
Alumina ceramic substrate has the advantages of good thermal conductivity, stable insulation, thermal shock resistance, wear resistance, acid and alkali resistance, etc., and can be used in thick film hybrid integrated circuits HTC, LED ceramic heat dissipation bases, power modules, semiconductor devices and other fields.
Inert alumina ceramic ball is not susceptible to chemical reactions, and its inherently dense texture, very low water absorption, does not act as a drying agent.
Inert alumina ceramic balls are widely used in petroleum, chemical, fertilizer, natural gas and environmental protection industries as a covering support material and tower packing for catalysts in the reactor.
Most of them are bottom-filling materials such as chemical fiber plant, alkylbenzene plant, aromatics plant and other hydrocracking refining equipment, catalytic reforming equipment, isomerization equipment, and demethylation equipment.
Inert alumina ceramic ball is resistant to high temperature and pressure, low water absorption, stable chemical function, acid, alkali and other solvents, and can compensate for temperature changes during production, and has good thermal stability.
The main application of inert ceramic balls is to increase the distribution spots of gas or liquid in a reactor, and to support and protect the activating catalyst with low strength.
Alumina foam ceramic is the earliest type of foam ceramic used. Foam ceramic material is a kind of porous material with high temperature characteristics. It has high temperature resistance, corrosion resistance, low density, high porosity and high specific strength. It is widely used in biochemistry, medical materials, electrical and electronic, metal melt filtration, heat and sound insulation materials, automobile exhaust gas treatment and other fields.
Al2O3 ceramics is currently one of the most studied and widely used new materials. In addition to the above applications, it is also widely used in other high-tech fields, such as aerospace, military industry, etc.
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The use of alumina ceramic balls in cement grinding mills is in line with the current national environmental protection industry and other policies, and can also create huge economic and social benefits for enterprises.
1. Reduce power consumption. According to our statistics, each ton of cement produced can reduce electricity consumption by 3~4kwh, and the power saving effect is very good.
2. Significantly reduce the noise of the production environment. Due to the reduction of the weight of the mill and the inherent characteristics of the alumina ceramic ball, the noise of the mill can be reduced by 10-15 decibels after replacing the alumina ceramic ball.
3. Extend the service life of the mill. Since the effective motion load of the mill itself is greatly reduced, the compliance of the relevant sliding bearing, the lining plate, the speed reducer, the motor, etc. is significantly reduced.
4. Green production, safe and environmentally friendly. Alumina ceramic balls do not produce heavy metal pollution such as chromium, and environmental protection can be said to be significant.
Of course, there are some problems with the use of alumina ceramic balls instead of steel balls:
1. The alumina ceramic ball has a small weight, and the grinding ability is slightly worse than that of the steel ball.
2. If the material of the raw material has a large water content, it will cause the temperature inside the mill to be lower and the moisture to increase, which in turn affects the yield.
3. If the enterprise is in the stage of full-load production, the electricity price will be higher.
In general, the use of alumina ceramic balls instead of steel balls in cement mill grinding can greatly reduce the power consumption of production enterprises, so that the production cost of enterprises is significantly reduced, and the service life of ceramic balls is used. Extension will also benefit cement companies in the long run.
Zibo Win-Ceramic make a recommendation, the cement factory replaces the alumina ceramic ball, it is not a simple exchange of the two balls, but a complex system engineering, which requires a lot of adjustment and cooperation, please choose experienced, quality alumina ceramic ball manufacturers.
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