DD148929A1 - PROCESS FOR PRODUCING WET-PRESSED FERRITE FORMKOERPER - Google Patents

Abstract

The invention relates to the preparation of the Ferritschlickers for Naszpressen of Ferrritformkoerpern. The object of the invention is to increase the productivity of the nascent pressing process and to improve the magnetic characteristics by reducing the paramagnetic content in the material. This is achieved by giving up the resulting in the wet fine grinding of the reaction sintered product Ferritschlicker before molding a continuously operating centrifuge. The invention is particularly suitable for the production of anisotropic ferrite moldings.

Description

218879

Dietrich Kätzel P 722

Manfred Lübke C 04.B, 35/26

Karlheinz Urban 21.1.1980 Wolf-Dieter Bartsch

Title of the invention

Process for producing wet-pressed ferrite molded bodies

Field of application of the invention

The invention relates to a process for producing wet-pressed shaped ferrite bodies, in particular anisotropically wet-pressed shaped bodies of Ba, Sr, Pb ferrites. These are permanent magnetic products with elevated magnetic characteristics.

Characteristic of the known technical solutions

It is known that wet-pressed ferrite moldings have higher magnetic characteristics than dry-pressed, because the ferrite particles are more mobile in the water during pressing under the action of a magnetic field, than in air and therefore can be better aligned. The customary production takes place according to ceramic technology (Heimke, G. ceramic magnets - Springer Verlag 1976 p. 82 ff), in which the mixed and comminuted raw materials are reaction sintered, then pre-comminuted and finely ground. The resulting low-viscosity slip is conveyed via pipe

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fed lines to the presses, where the shaping of the body takes place (DD-PS 97 326). Da.hierbei not only a compression, but at the same time also a drainage must be made, the pressing times are much higher than dry pressing.

It is also known to change the optimum for fine grinding water content of the slurry of about 60% before Verprassen anything (Heimke, G. Ceramic Magnets - Springer Verlag 1976, p 97), by the Schlick initially passed through settling tank becomes. However, this type of Schlickervorentvs / ässerung takes a few days, especially in the last phase of grinding the liquor often liquefiers, binders and pressing aids are added, the u.a. just to prevent sedimentation of solids,.

It has also been proposed to reduce the water content by adding dried mass to the ground sludge. (YiP C 04 B / 205 029). With increasing solids content, however, the uniform stirring in of the dry mass becomes more and more difficult. In addition, the agglomerates formed in the dry mass are difficult to remove. In general, the wet processing method has shown that the theoretically possible magnetic parameters are not fully achieved because i.a. a certain paramagnetic component occurs in the material.

Object of the invention

The object of the invention is to increase the productivity of the wet-pressing process, as well as to further improve the magnetic characteristics.

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Explanation of the essence of the invention

The invention is therefore based on the object to develop a process for producing wet-pressed ferrite moldings by ceramic technology by mixing and comminuting the raw materials, reaction sintering, pre-crushing, wet fine grinding, shaping, drying and sintering of the moldings. The preparation of the Ferritschlickers should be changed so that shorten the pressing times and the paramagnetic content in the material is reduced.

This is achieved by the present invention in the wet fine grinding resulting ferrite slip is abandoned before shaping a continuously operating centrifuge.

Exemplary embodiment

In one embodiment, the invention will be explained in more detail o

Sr ferrite is micromilled in an attritor to a fineness of 1.0 to 1.5 μm. The resulting Sr-ferritic leacher has a water content of about 60 %, then the slurry is pumped continuously through a horizontal centrifuge with Schnecken.Danach, the slip now has a residual moisture content of 30% and is pressed anisotropically on the usual presses. Subsequently, the shaped bodies are dried and sintered. From Figures 1 and 2, the results can be seen, which were achieved with centrifuges with a drum diameter of 135 to 325 mm and drum speeds up to 5000 min, which corresponds to centrifugal accelerations of I70 to 3074 g ". From Figure 1 it can be seen that the residual moisture remaining in the centrifuged slurry depends not only on the acting central acceleration, but also on the mass flow rate. The larger the mass flow rate becomes

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the degree of dewatering becomes lower.

Fig. 2 shows that a Sr ferrite slip with a water content of about 60%, as is commonly obtained in the technology of Sr ferrite, already by low centrifugal accelerations, ie low drum speeds in the screw centrifuge to the desired residual moisture content of 2j ? - JO % can be brought. Depending on the particle size distribution, the ferrite particles are still so mobile in this residual moisture that they can be aligned in the magnetic field and magnetic losses on the shaped body can not be determined. The solids content in the Fugat was less than 1% in all experiments. The geometric dimensions of the rotating drum determine the solids content remaining in the fugate. Depending on the Tromiaelgeometrie desired classification of the slurry can be achieved. As a result, the superparamagnetic fines of the slurry can be separated, which accounts for about 1% of the solids content. This has an advantageous effect on the magnetic properties of the ferrite material.

In addition, the process leads to a significant increase in productivity. Thus, the time for Schlickervorentwässerung is shortened from a few days to a few seconds, eliminating the need for space for sedimentation, rapid pre-drainage of the slip to minimum residual moisture is possible, the compression paths are shortened, the filling and pressing times decreased

Claims (1)

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I OOIW "5" P 722 invention claim A process for producing wet-pressed Perritformkörper ceramic technology by mixing and comminuting the raw materials, reaction sintering, pre-crushing, wet fine grinding, shaping, drying and sintering of the moldings, characterized in that the incurred in the wet pulverization Ferritschlicker is abandoned before shaping a continuously operating centrifuge , See. ^ "Pages Drawings