DE1111089B - Process for the production of sintered ferrites - Google Patents

Description

The increasing demands on the magnetic properties of sintered ferrites have led to that the technical raw materials used at the beginning had to give way to ever purer space. If today Many ferrites are already produced from substances that contain at most non-volatile oxidic impurities at the sintering temperatures of the ferrites may still contain one or two tenths of a percent, tomorrow it will be hundredths of a percent. the The chemical industry is in a position to meet these purity requirements, but everyone must A tenth of a percent increase in purity is bought at the cost of additional costly process steps will.

Most ferrites produced today are sintered ferrites and are currently mainly produced, by putting an intimate mixture of the starting materials in powder form in a pre-firing, a so-called "Frittung", subject, the frit (possibly mixed with raw, unfired mass) wet grinds, then dries and uses it to manufacture molded parts by any process, which ultimately be subjected to a final sintering.

The raw materials that have hitherto been used in the manufacture of sintered ferrite are known to be such Compounds of iron, zinc, manganese, nickel, magnesium (around the main components technical interesting ferrites), which can be converted into oxides when heated. It deals in detail here to oxides in different valency levels, also to oxide hydrates, hydroxides, Carbonates, oxalates, precipitated ferrites, formates and, more rarely, other compounds of the named Metals.

Attempts have now been made to move away from the classic raw materials for ferrite manufacture and these according to the invention to be wholly or partially replaced by metals, as was the case with the production of Melt ferrite is known in a special form.

According to the invention, this was also achieved with sintered ferrites, e.g. B. in the zinc-nickel ferrites, but especially in the zinc-manganese ferrites, if the divalent component or components are added in whole or in part as metal powder, but the trivalent iron is used in oxidic form. So z. B. in the highly permeable zinc-manganese ferrites, as they are used as tilting transformer cores in televisions or as pot cores for filter purposes, to replace the zinc oxide used up to now with zinc powder or the manganese oxide with manganese powder or even completely replace both raw materials with the metal powder, whereby over- Method of manufacture
of sintered ferrites

Applicant:

Steatit-Magnesia Aktiengesellschaft,

Lauf / Pegnitz,

and General Ceramics Corporation,
Keasbey, NJ (V.St.A.)

Representative: Dr.-Ing. F. Wuesthoff, Dipl.-Ing. G. Pulse and Dipl.-Chem. Dr. rer. nat. E. Frhr. v. Pechmann, patent attorneys, Munich 9, Schweigerstr. 2

Dr. Kurt Wetzel, New Brunswick, N.J. (V. St. A.),

Dipl.-Ing. Georg Zerbes, Porz / Rhine,
and Sigismund Golian, Perth Amboy, NJ

(V. St. A.),
have been named as inventors

surprisingly, the otherwise known manufacturing process for sintered ferrites can be retained can. The properties of the ferrites produced according to the invention partly from metal powders are exceeded those which are produced from technically pure oxides by known methods.

Another advantage of the invention is that the metals are of the highest purity on the market are available, e.g. B. zinc with a purity of 99.995% and electrolyte manganese with over 99.9% Mn. The powdering of these metals does not cause any significant difficulties. Equally pure oxides or other compounds of these metals are consistently two to four times more expensive, based on the Metal content. This can be explained, because with the high purity requirements for the oxides, oxyhydrates or Carbonates of zinc and manganese is four times the pure metal itself the starting product. In this In this case, a separate production of the oxides of divalent metals can be dispensed with. So you save one Work stage.

Another essential feature of the invention is therefore the oxidation of the Metals and the fritting of the ferrite mass in one

109 647/453

Step together. The finely divided iron oxide powder is located within the loose iron oxide powder Metal in a state that favors oxidation by atmospheric oxygen. Implementation of the educated Oxide with the iron oxide takes place in the same process. While otherwise oxides are bivalent Metals in their production by oxidation of powder metals with sintering easy to stick together tend, this is prevented by the presence of trivalent oxidic iron.

The ferrites produced according to the invention are so pure that the desired physical properties are obtained of the finished products through surcharges of very small quantities (e.g. hundredths of a percent up to Tenths of a percent) of foreign matter can be set very precisely, which is not possible if the foreign matter from the outset are already present as impurities in larger and changing amounts.

example 1

93 parts by weight of zinc powder (purity 99.99% Zn, grain size less than 0.1 mm),

696 parts by weight of iron oxide (99.7 VoFe ₂ O ₃ , 0.1% non-volatile oxidic impurities) and

228 parts by weight of manganese (IV) oxide (0.1% non-volatile oxidic impurities)

are intimately mixed with one another in a mixer, the mixture is loosely poured into a sagger, with some grooves being drawn through the powder to allow access to the air, in particular to the metal powder. The powder mixture is kept in a gentle stream of air at 1100 ° C. for 3 hours and then cooled. 994 g of this frit are ground with 900 ecm of distilled water and 7 kg of steel balls for 14 hours in an iron ball mill, the slip is dried, then plasticized and finally pressed into toroidal cores ^{at a pressure of about 1 t / cm 2.} After a fire at 1355 ° C in an atmosphere of nitrogen with 0.4 volume percent oxygen, the toroidal core shows an initial permeability of 3000, a quality at 100 kHz of 37 and a Curie point of 173 ° C.

Example 2

11.5 parts by weight of zinc oxide (purity 99.9%),

69.8 parts by weight of iron oxide

(99.2% Fe ₂ O ₃ , <0.4% non-volatile oxidic impurities) and

13.55 parts by weight of manganese metal powder (99.9%), grain size below 0.08 mm.

are, as indicated in Example 1, prepared, fried and pressed into rings.

After a fire at 1380 ° C in nitrogen with 0.25 volume percent oxygen, the toroidal core shows an initial permeability of 2550, a quality at 100 kHz of 25, at 15 kHz of 84, a Curie point of 175 ° C, and at 20 ° C, 15 kHz and 1000 G watt losses of 26 mW / cm ^3, at 100 ⁰ C of 36 mW / cm ^3.

Example 3

89 g zinc powder (purity 99.99%, grain size

less than 0.1 mm),

702 g of iron oxide (99.2% Fe ₂ O ₃ , 0.4% non-volatile oxidic impurities) and
138 g manganese powder (purity 99.9%, grain size less than 0.06 mm)

were prepared and fritted as described in Example 1. The re-grinding took place here in following mixture: 480 g frit, 1 g calcium carbonate, 2 g titanium dioxide, 350 ecm distilled Water and 3 kg steel balls. A toroidal core that is burned at 1260 ° C in an atmosphere of water vapor showed an initial permeability of 1040, a quality of 100 kHz of 239 1 MHz of 14. The Jordanian losses were:

h = 900 cm / kA, W = lO4 ° / oo and n = 5 μβ.

Example 4

105 parts by weight of zinc powder (99.99%, grain size _2. Below 0.1 mm),

692 parts by weight of iron oxide (99.2% Fe ₂ O ₃ , less than 0.4% non-volatile, oxidic impurities) and

131 parts by weight of manganese metal powder (99.9%, grain size below 0.06 mm)

are, as indicated in example 1, prepared and fryed. 480 g of the are used for regrinding Frit with 350 ecm of distilled water and 3 kg of steel balls. Toroidal cores showed after a fire at 1430 ° C in an atmosphere of water vapor an initial permeability of 2535 and a Curie point from 169 ° C.

Claims (4)

PATENT CLAIMS: 1. A process for the production of sintered ferrites MeO-Fe ₂ O ₃ ), which are produced via a mixture of the powdery raw materials and annealing of the mixture with subsequent grinding, shaping and firing, characterized in that metal powder is used wholly or partially as divalent components. 2. A method for the production of zinc-manganese sintered ferrites according to claim 1, in which as Zinc component is used exclusively or partially zinc metal powder. 3. Process for the production of zinc-manganese sintered ferrites according to claim 1, in which manganese metal powder is used exclusively or partially as the manganese component. 4.Verfahren for the production of zinc-manganese sintered ferrites according to claim 1, in which as Zinc and manganese components exclusively or partially zinc and manganese metal powder be used. Considered publications:
German patent specifications No. 226 347, 872 203.