DE1471430C - Process for the production of ferrites - Google Patents

Description

example

Oxides of the composition
53.0 mole percent Fe ₂ O ₃ ,
28.0 mole percent MnO and
19.0 mole percent ZnO,

which have less than 0.2 percent by weight of total impurities are ground and mixed for 8 hours on a vibrating mill with the addition of 0.4 percent by weight of zinc stearate or 0.4 percent by weight of calcium stearate. Then an alcohol-water-glycerine mixture (50: 40:10) in a ratio of 15 g of mixture to 100 g of ground oxide is added to the ground oxide. The total mixture is pressed into cores at a pressure of about 1 t / cm ^2.

The cores are heated in a 10 volume percent Säuerst-containing nitrogen atmosphere at about 1300 ⁰ C and sintered at this temperature IVa hours in the same atmosphere. Thereafter, the sintered body in 20 minutes in pure nitrogen (less than 0.02 volume percent oxygen) of 1100 is ίο rapidly cooled to 800 ⁰ C. The further cooling down to about room temperature also takes place more slowly in pure nitrogen.

With a shrinkage of the sintered cores of around 12%, the following values were achieved:

0.70
0.75

B er-χ.SS / 73

Claims (4)

It has surprisingly been shown that the addition of small proportions of stearate to the wet mixture can be dispensed with due to patent claims. This also enables the operations following wet grinding, 1. Process for the production of ferrites by 5 such as filtering, drying and repeated dry grinding, exclusively dry grinding of the initial grinding, "superfluous. A significant reduction in price substances in ball or vibratory mills, pressing the production of such ferrites is the result, and sintering, where the starting substances can in particular Small proportions of stearate are ground, after calcined grist is homogeneously finely ground. Patent 1,696,443, d a d u r c h marked io At the same time, the ground material is compressed so that net that as a lubricant stearate loss-reducing cores, which are made from this powder, the substances are used. . at least the same electrical properties 2. The method according to claim 1, characterized in that they are characterized by wet grinding draws that calcium stearate is used. are won. In addition, the pressed part, 3. The method according to claim 1 'or 2, characterized in that 15 from a grist obtained according to the invention characterized in that strontium stearate is made used, due to the higher compressibility will. a higher density and thus a lower one 4. The method according to one of the preceding shrinkage after sintering. Claims, characterized in that the with It has been shown that the type of stearate is not Stearate mixed starting substances with a 20 of no importance for the after such a alcohol-water-glycerine mixture The ceramic body to be produced is moistened. Wer- and processed to compacts. the ferromagnetic by such a process Ferrites are produced, which are used, for example, as a magnet for electrical Wash,. Transformer, head cores or the like. - 25 are used, then there is a reduction in the Losses of these ferromagnetic bodies may under certain circumstances improve the desired ferromagnetic ones Properties, e.g. B. an enlargement . ■■ '■■'. the permeability, very desirable. The invention The invention relates to a method for production 30, the object of which is the loss of ferrites of ferrites and is an additional patent to the main to reduce. patent 1 696 443. Ferrites are oxide ceramic masses The invention consists in that as a lubricant based on trivalent iron oxide in addition to other stearates of loss-reducing substances, in particular calcium second-valent metal oxides. 'cium stearate or strontium stearate, can be used. In the manufacture of such ferrites, the 35 These stearates fulfill a double task. she Starting substances, if necessary after a calcination, enable dry milling to be carried out nation, well ground, pressed and a sintering, renouncing the previously common wet grinding and subject to process. During the sintering process, the subsequent drying processes and not only bake the pressed fabrics to a me- at the same time offer the advantage of improving the chanically solid bodies together, but they experienced magnetic and electrical properties. the Ren insofar a physical conversion manufacturing costs of such ferrites can thereby process when the atoms of these ferrites decreased a certain and the quality of these ferrites improved Form order. For example, ferrite bodies are used. It is particularly advantageous to form the ferri-spinel structure on. These crystal lattices are with the starting substances, which are optionally available Application in electrical devices of particular 45 are pre-sintered, θ, 3 to 1.0 percent by weight calcium Importance. The spinel structure in ferrites is. or add strontium stearate and the mixture essential for the magnetic inherent dryness, z. B. in ball or vibrating mills, too shafts this body. grind. The addition of 0.4 percent by weight CaI- To achieve very dense sintered bodies and thus cium stearate corresponds to about 0.036 percent by weight to achieve high permeability and less 50 CaO. electrical losses, it was previously necessary that it has also been shown that for pressing Starting substances, which are optionally calcined to form a binding product of the stearate-containing dry mixes, wet fine grinding to obtain a homogeneous grist medium additive, e.g. B. polyvinyl alcohol, no longer required reach. The wet grinding requires additional that is, if the powder mixture before the processing, like filtering, drying and subsequent pressing is only moistened. In further relief Dry grinding, as the filter cake does not form the invention, the mixture with stearate without Comminution can be granulated. A ver ten starting substances with an alcohol-water layer Since then, wet grinding has led to a non-moistened glycerine mixture and to satisfactory pellets Results. As a pressing aid for friction pressing. The compacts show a sufficient reduction in raw strength one added the wet-ground, before it was mechanically solid during sintering sintered and re-ground powder mixtures form ceramic bodies. This is preferably how it will be also already lubricants, such as polyvinyl alcohol, magne-alcohol-water-glycerine mixture in a 50:40:10 silicon stearate. Zinc stearate or the like. This adding ratio mixed. The advantage of this further success immediately before pressing and making the formation of the invention is that on the cumbersome pretreatments that have to be avoided 65 Use of an additional binding agent (e.g. the The object of the invention is not superfluous. expensive polyvinyl alcohols) can be dispensed with, so According to the main patent, the starting material is that of a ferrite substance produced in accordance with the invention ground with small proportions of stearate, the core causes lower manufacturing costs.