DE975757C - Process for the production of sintered ferromagnetic ferrite bodies - Google Patents

Description

Process for the production of sintered ferromagnetic ferrite bodies Magnetizable cores for coils, especially for high frequency coils of high Goodness, are made from ferrite in many cases. Here z. B. _ mixed or oxides or hydroxides precipitated together from solutions of the metal salts in question first compressed and then subjected to a sintering process. The compression will designed so that a core of the desired shape is created. Possibly Ferrite that has already been sintered and then crushed again can also be sintered again will. It is expedient if the shapes are cylindrical or prismatic is the extrusion process for forming the pre-pressings prior to sintering used, whereby the starting powder is a plastic for better processability or liquid binder is added.

According to the invention it is now proposed as an additive in the Forming the pre-presses, e.g. B. in extrusion to use silicones, namely either vaporizable or less vaporizing, e.g. B. curing silicones. Through this a number of advantages are achieved. Silicones can be found in practically all of them desired viscosity grades can be produced, so that for each type of powder silicones suitable toughness can be used. When using silicone with less Evaporation rate at room temperature you can also finish prepared mixtures can be stored if necessary without affecting the plasticity properties suffer, in contrast to the binders commonly used up to now, which in water, Spirit or the like. Be dissolved.

In addition, certain silicones are almost temperature-independent Viscosity, so that the processability of the masses due to fluctuations in the Room temperature is not affected. If it is desired that the additive before sintering without any residues remaining, which in some cases could reduce the quality of the If the finished ferrite core is to be removed, then silicones are used used, which evaporate at a higher temperature, usually at a few 100 ° C, see above that they are after extrusion, but before sintering, by heat treatment a few 100 ° C can be driven out of the extruded core.

Finally, it is sometimes desirable to add silica to the ferrite powder add to z. B. to increase the sinterability. The silica must be natural be distributed as uniformly as possible in the starting material. Used in this case one liquid, non-evaporating or difficult to evaporate, so z. B. curable silicones. At the When heated, these remain wholly or partially in the core and disintegrate at the high level Temperature, in which case the desired silica as a decomposition product in the finest Distribution in the ferrite mass remains.

Claims (5)

PATENT CLAIMS: i. Process for making sintered ferromagnetic Ferrite bodies, in particular magnetizable ferrite cores for high-frequency coils from high quality, in which mixed or jointly made solutions of the metal salts in question Precipitated oxides or hydroxides or ferrite powder, which are already made by grinding sintered ferrite were obtained, initially with the addition of a plastic or liquid binder compacted and then subjected to a sintering process, characterized in that exclusively or partially silicones are used as binders be used. 2. The method according to claim i, characterized by the use of silicones with low evaporation rate at room temperature. 3. Procedure according to claim i, characterized by the use of silicones with a, almost temperature-independent viscosity. 4. The method according to claim i, characterized through the use of silicones that evaporate at higher temperatures without leaving any residue. 5. The method according to claim i, characterized by the use of silicones, which disintegrate when heated, so that silica is finely distributed in the ferrite mass remains. Considered publications: Swiss patent specification No. 243,724; French Patent No. 906,784; U.S. Patent No. 1946,964; Electronics Buyers' Guide, June 1948, pp. M-8; "Radio-Mentor", 1948, issue 9, p. 394> '' Die Technik '' 1947, pp. 457, 458.