DE834360C - Process for the production of ceramic material, in particular for insulators of spark plugs - Google Patents

Description

Process for the production of ceramic material, in particular for Spark plug insulators The invention relates to the production of ceramic material, especially from insulators for spark plugs to racing engines.

The best spark plugs available today are mainly made up of Aluminum oxide. The remainder is usually made up of silica and small amounts Flux or other additives together. The end product consists of sintered together Crystals, the spaces between which are filled with glass.

In the manufacture of such substances arise from the required high firing temperature of 165o to 175o ° C practical difficulties. To achieve such temperatures are special 1, fuels and specially designed kilns made of the most heat-resistant materials required. The life of such material however, is limited, resulting in increased maintenance and upkeep expenses for these ovens entails. Also the control of the firing process, which is part of the guarantee Satisfactory results are essential, creates increasing difficulties.

The present invention makes use of mixtures of clay. Silicic acid and a phosphate, which have already been proposed in various forms became. So the silica and part of the clay was added as clay, and Many types, including alkaline earth phosphates, are recommended as phosphates been.

According to the present invention, there is dns Source material from a mixture of 62 to 84% clay, 12 'to 30% clay and 4 to 8% alkaline earth phosphates. The mass is shaped and, then at cone, 16, into a solid and dense., Impermeable Body burned.

The following raw materials! Can be used: Alumina As alumina It is best made at 'high temperature calcined alumina, known as fettiger Corundum, although other material, e.g. B. fused alumina, can go out.

In some cases it may prove beneficial to use a percentage to slam baked alumina at a low temperature. The clay does not need to be alkali-free, so that the: form can also be used. By the percentage Composition Hate the material constants in the desired direction influence.

A part of the alumina can be in the form of aluminum silicates with higher Aluminum oxide content as clay, e.g. as Cy amte, can be added. Erdal @ kaliphosphate Good results are obtained with the use of calcium, barium, strontium, or magnesium sulfate tablets been brought up. Of these, calcium phosphate is the most beneficial because it is smaller Quantities are required and the raw material is cheap and easy to obtain. Bone ash, a mixture of calcium phosphate and calcium carbonate, can also be used will; but there can be difficulties with regard to the difference -in the composition occur. Sometimes this can turn out to be the use of a mixture of the phosphates mentioned prove to be advantageous.

Clay has proven to be best to use kaolin or ground clay proved to be able to produce molded articles by molding, as described later enable in the plastic state.

A mixture of English ground clay is particularly suitable and Floridakaolin .. Some or all of the clay can be called montmorillonite or Beätonite to be slammed. If necessary, the sound can be replaced by equivalent Amounts of alumina and silica to be replaced, however, that requires Shaping of the pieces on a non-plastic basis. Other material additives In some In some cases it may be desirable to promise a little zirconia, but sorry including the mechanical resistance. Furthermore, the firing temperature can through The addition of talc or another common solvent can be reduced, however In the case of the 1 -, in-foldness of the Brenn @ process at cone 16, this does not become significant Advantage to be achieved.

Composition ratio of the substances The following numbers give (read the most favorable ratio of the components: Alumina ................. 84 to 62%, Sound .................... 12 - 30 "/ 0, Calcium phosphate ........ 4 - 80/0, this corresponds to Oxydgehalxen: von Aluminum oxide .... 88.74 bi, s 73.85 0/0, Silicon dioxide .... 5.58 - r3.950 / 0, Calcium oxide ...... 2.17 - 4340/0, Phosphorus pentoxide. . 1.83 - 3.66%, Water ............ 1.68 - 4.200 / 0 .. According to the development to date, the following composition has proven to be particularly favorable: English ground clay ..... 15%, Floridakaolin .................. 50/0, Calcium phosphate ............... 50 / (), tabular corundum ............... 75) / 0- Preparation of the material to be fired The tablet-like corundum is ground in such a way that it can be driven through a sieve with 130 meshes / cm. Magnetic particles are separated out in the process. Then the material is mixed with water in the above-mentioned composition in a ball mill and, after further sieving and separation, in a mixer, e.g. B. kneaded one of the well-known Laneaster or Simpson mixers. During the mixing process, the moisture content of the mass is increased to the desired amount by adding water. The resulting plastic mass is cut into narrow strips and introduced into a vacuum mortar mill, from which it is ejected in the form of cylindrical bodies. These are pre-dried and provided with the hole for the electrode. After further drying to a similar consistency, they are turned into the shape of the isolator. This is followed by complete drying and firing at about 16 in conventional tunnel ovens to form a solid, impermeable body. This process can be modified somewhat by drying the body to bone hardness and then grinding it into its final shape.

The fuel bodies can also be manufactured in other ways, e.g. B. by casting out of the doughy consistency or by pressing into rubber molds or by mixing it with a binding agent that 'burned out' after shaping will. When using the latter method, the clay is first burned. then the materials are finely ground and mixed with the binding agent before molding, the Making the fier named body is made possible by a large margin in the burn time relieved.

The firing temperatures according to Kegel 16, around 145o ° C, are usually sufficient to completely burn out the body. With an addition of more than 5% calcium phosphate A temperature of around 1400 ° C is sufficient, i.e. according to Kegel '14.

The material constants of this improved material prove that significant deficiency over ordinary porcelain and approach the qualities the sintered body, which must be at significantly higher temperatures such as 1750 ° C. The tensile strength is thus: 2246 kg / cm2 for a kiln of the invention, 2584 kg / cm2 for sintered products, 12 10 kg / cm2 for ordinary porcelain, which is used in Cone 16 was fired, The temperature at which the resistivity of the Insulating compound with a defined high-frequency alternating voltage a certain Falls below the value, i.e. the insulating effect collapses to a certain extent for the new; Candles 693 ° C versus 725 ° C for the high-temperature sintered bodies and 64o ° C for the porcelain body. The coefficient of linear expansion in the area from zoo to 600 ° C is 6.93 - 1o - 6 degrees -i compared with the new bodies 7.76 # io-s degrees -1 for the high temperature body and 4.21 - i9--6 degrees -i for the Porcelain body; the new body can be fired in the normal china-making furnace will.

Claims (4)

PATENT CLAIMS: i. Process for the production of ceramic material, characterized in that 84 to 62% alumina, 12 to 30% clay and 4 to 8% alkaline earth phosphates are mixed, shaped into the desired shape and the shaped bodies are fired at cone 16 to form a solid and impermeable body. 2. Procedure according to claim i, characterized in that the mixture of 15% ground clay, 5% kaolin, 5% calcium phosphate and 75% table corundum. 3. Ceramic Material produced by the method according to claims i and 2. 4. Ceramic material for insulators of spark plugs, characterized in that it is after chemical analysis has the following composition: 89 to 74% aluminum oxide, 5 to 14% silica, 2 to 4.5% alkaline earth oxide, 1.8 to 3.7% phosphorus pentoxide and 1.7 to 4.2% chemically bound water.