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Alumina porcelain lamp holders production process:
The alumina ceramic currently divided into two kinds of high purity ordinary. A ceramic material of high purity alumina ceramic Al2O3 content of more than 99.9%, due to its sintering temperature of up to 1650-1990 ° C, the transmission wavelength of 1 ~ 6μm, generally made of the molten glass to replace platinum crucible: the use of its translucency and alkali metal corrosion as a sodium lamp tube; in the electronics industry can be used as the integrated circuit substrate and the high-frequency insulating material. Al2O3 contents divided into common type alumina ceramic Department 99 porcelain, 95 porcelain, 90 porcelain, 85 porcelain and other varieties, sometimes Al2O3 content in the 80% or 75%, are also classified as ordinary alumina ceramic series. 99 alumina ceramic material is used to produce high temperature crucible resistance furnace tubes and special wear-resistant materials such as ceramic bearings, ceramic seals and valve films and so on; 95 alumina ceramic is mainly used as a corrosion-resistant, wear-resistant parts; 85 porcelain because often mixed with some talc to improve the electrical properties and mechanical strength, sealing with molybdenum, niobium, tantalum, and other metals, some used as an electrical vacuum devices. Its craftsmanship as follows:
A powder preparation:
Alumina powder into the plant in accordance with different requirements and different molding process to prepare the powder material. The powder particle size below 1μm microns, if the manufacture of high purity alumina ceramic products except alumina purity 99.99%, the need to ultrafine grinding to make it uniform particle size distribution. Need to be introduced by extrusion molding or injection molding, powder binder and plasticizer, is generally a weight ratio in the 10-30% of a thermoplastic plastic or resin? The organic binder should be uniformly mixed with alumina powder at a temperature of 150-200 ℃, in order to facilitate the molding operation. Powder materials by hot press molding process, you do not need to join the binder. The use of semi-automatic or fully automatic dry pressing molding powder special process requirements, the powders by spray granulation processing, it presents a round ball, in order to facilitate to improve the powder flowability easy molding automatic filling die wall. In addition, the need to add 1 to 2 percent of a lubricant to reduce the friction of the powder and the die wall,? Such as stearic acid? And binder PVA.
For dry pressing powder spray granulation, including the introduction of polyvinyl alcohol as a binder. In recent years, a research institute in Shanghai to develop a water-soluble wax used as a binder of Al2O3 spray granulation, good mobility in the case of heating. The powder spray granulation must have liquidity loose density, the flow angle friction temperature less than 30 ° C. Particle size ratio of the ideal conditions for a larger biscuit density.
Molding method:
Dry-pressed alumina ceramics molding method, slip casting, extrusion, cold isostatic pressing, injection, casting, hot pressing and hot isostatic pressing, a variety of methods. At home and abroad in recent years has developed a filter press molding, direct solidification injection molding, gel injection molding, centrifugal slip casting and solid freeform molding technology. The different product shape, size, complex shape and precision of the product requires a different method of forming. The pick their common molding introduce:
1, dry pressure molding: alumina ceramic dry pressing technique simply limited to the shape and wall thickness of more than 1mm, length to diameter ratio not greater than 4:1 object. Uniaxial or bi-molding method. Hydraulic presses, mechanical two, was a semi-automatic or fully automatic molding. The press maximum pressure 200Mpa. Yield up to 15 to 50 per minute. Hydraulic press stroke pressure evenly, so there are differences in the powder filling repression pieces of different heights. Mechanical presses applied pressure change size because of how much the powder filling, the size easily lead after sintering shrinkage differences affect the product quality. Therefore, the process of dry-pressed powder particles uniformly distributed mold filling is very important. Accurate filling volume control affects the manufacture of alumina ceramic parts dimensional accuracy. Powder particles greater than 60μm, ranged between 60 to 200 mesh to be the largest free-flowing effect, made the best pressure molding effect.
2, slip casting method: slip casting alumina ceramic earliest forming method. As a result of the plaster mold, the large size, low cost and ease of molding, the complex shape of the member. CASTING key is the preparation of the alumina slurry. Flux medium is usually water, and then add the glue solution with a binder, after thoroughly grinding exhaust, and then poured into the plaster mold. Since the plaster mold capillary on the adsorption of water, the slurry is then cured in the mold. Hollow grouting adsorption slurry up to the required thickness needed the excess slurry is poured in the mold wall. In order to reduce the amount of body contraction, should make use of the high concentration slurry.
Alumina ceramic slurry needs to added to the organic additives to give the surface of the slurry particles to an electric double layer is formed so that the stability of the slurry suspension does not precipitate. Furthermore need to join the vinyl alcohol, methyl cellulose, alginic acid, amine, etc. binder and polyacrylamide, gum arabic, and other dispersing agents, the aim is to make a slurry suitable for the casting operation.
Third, the firing technique:
The granular ceramics preform densification and the formation of solid materials technical method called sintering. The voids between the sintered body coming billet particle exclusion, to exclude a small amount of gas and impurities organics, so that growth combined with each other in between the particles, the formation of new substances.
Firing the use of heating means, the most widely used electric furnace. In addition to normal pressure sintering? That no pressure sintering, hot pressing sintering and hot isostatic pressing. Although the continuous hot press sintering increase yield, but the equipment and tooling costs are too high, in addition, because the case of an axial heat, the article is limited in length. Hot isostatic pressing sintering using high temperature and high pressure gas as the pressure transmission medium, to evenly heat advantages, it is suitable for the sintering of complex shape products. Due to the uniform structure, material properties than SINTERED 30 ~ 50% increase. Increased by 10 to 15% than the average hot pressing sintering. Therefore, a number of high value-added alumina ceramic products or the defense industry need of special parts such as ceramic bearings, mirror, the nuclear fuel and the barrel and other products, the field using hot isostatic pressing and firing methods.
In addition, the microwave sintering, arc plasma sintering method, since the spread sintering technology is also being developed in the study., Finishing and packaging process:
Some alumina ceramic material after the sintering is complete needed for finishing. Can be used as artificial bone of the products require high surface finish, such as the mirror-like, in order to increase lubricity. Due to the high hardness of alumina ceramic material, the need to use more hard abrasive polished tile materials for finishing it. Such as SiC, B4C, or diamond. Commonly used coarse-to-fine abrasive progressively grinding, the final surface polishing. General can be <1μm micron Al2O3 the micronized or diamond paste polishing. In addition, laser processing and ultrasonic machining, grinding and polishing methods are also used. Some alumina ceramic parts are required with other materials for the encapsulation process.
Alumina ceramic lamp Strengthening Process
In order to enhance the alumina ceramic, significantly improve the mechanical strength of new foreign push an alumina ceramic strengthening process. The process is novel, simple, taken by the technical means is the surface of the alumina ceramic, using an electron beam vacuum deposition, sputtering vacuum coating, or chemical vapor deposition method, plated with a layer of a silicon compound film, was heated at 1200 ° C to 1580 ° C treatment, so that the alumina ceramic steel.
Reinforced alumina porcelain mechanical strength can be substantial growth, based on the original manufacture of ultra-high-strength alumina porcelain lamp holders.