SU810640A1 - Method of making ceramic billets - Google Patents

Description

(54) METHOD FOR MAKING CERAMIC PREPARATIONS

The invention relates to the field of producing ceramic preforms, preferably ferrite, containing polyvinyl alcohol as a binder.

A known method for producing ceramic blanks, p, rl (of which a press powder containing the required amount of binder, plasticizer, lubricant, is poured into the mold and pressed one-sided (OR double-sided pressing. Humidity of the press bladder should be limited to this) one.

LI (Insufficient humidity of pressed powder; pressed products have low mechanical strength, chipping occurs, and cracks appear.

In addition, the low strength of the workpieces immediately after pressing requires careful handling of them, and the presence of a significant amount of moisture, which is dried in the process of firing.

A known method of making ceramics products, including ferrite ones, by preparing a press with the introduction of an organic binder having a melting point of 60-63 ° C in an amount of .30-60% by volume, followed by molding at a temperature of up to 200 ° C. 21.

However, this method is similar to pho / immanu by injection molding with the inherent disadvantages of this method in contrast to the molding by the method of dry extrusion.

The closest to the invention is a method of manufacturing ferrite products, including preparing a pressing agent with the introduction of an aqueous solution of polyvinyl alcohol as a binder, pressing the products with their subsequent roasting, in which romany ammonium 3 is introduced into the solution of polyvinyl alcohol to improve compressibility.

The disadvantage of this method is the low mechanical strength of compacts.

The purpose of the invention is to improve moldability and increase the mechanical strength of the blanks.

This goal is achieved by the fact that in the known method of making ceramic preforms by preparing press powder using an aqueous solution of polyvinyl alcohol as a binder by means of dry pressing, the pressing is carried out in a mold heated to 40 to 200 ° C.

FIG. 1 is a graph of the change in mechanical strength of blanks pressed from a powder with a moisture content of 0.2% obtained by spray drying.

It can be seen from the graph that the strength of the blanks increases with the temperature of the mold, reaching a maximum at a temperature of 180-200 ° C. A further increase in temperature leads to a decrease in the strength of the blanks caused by the decomposition of polyvinyl alcohol.

FIG. 2 are presented graphs of the change in the strength of blanks pressed from press powders obtained by different methods from the time of drying at room temperatures.

Curve, / - pressing powder O (B, crawled by wiping through a sieve (, 5%, P 1.5 t / cm) at a mold temperature of 170-180 ° C.

| KriVa 2 - irrescent of powders obtained by spray drying (W 0.2%, P 1.5 t / cm) at a mold temperature of 190-200 ° C.

Curve 3 - pressing of powders obtained by wiping through a | Sieve (W 1.5%, P, 6 t / cm) at a mold temperature of 20 ° C.

Curve 4 - pressing of powders obtained by spray drying (W 0.2%, R 1.5 t / cm) at a mold temperature of 20 ° C.

From the graph, it follows that the billet pressed into a hot mold has the greatest strength directly during pressing.

In the case of press | Vani at room temperature of the mold, the strength of blanks pressed from the press powder obtained by rubbing through a sieve increases with increasing time, the drying time reaches a maximum after 2-3 days, and obtained by spray-drying, mechanical strength practically does not increase with increasing time.

An example of the method.

As the initial charge, Mn-Zn ferrite powder with a polyvinyl alcohol content in the amount of 1% was used, obtained by both spray drying and wiping through a sieve.

Rings with an outer diameter of 17.6 mm, an internal diameter of 10 mm and a height of 10 mm were pressed from the press powder.

The mechanical strength of the rings was determined by their destruction during compression in

radial direction. The pressing was carried out under a pressure of 1.5 t / cm and a temperature of the mold from 20 to 210 ° C.

Data on mechanical strength (kg / cm) blanks are given in the table.

The use of the proposed method for the manufacture of ceramic products will improve the formability of the press powder, improve the mechanical strength of the blanks.

The most effective method of pressing is in a hot press mold for press powders obtained by spray drying, especially for those with humidity equal to or close to zero.

The maximum strength of the blanks pressed in the hot mold, depending on the press powder, is 4-7 times higher than the strength of the blanks pressed at room temperature.

Claims (3)

1.Zhuravlev G. I. “Chemistry and technologists qbeppitov, Publishing house“ Himi, M., 1970, p. 151-168. 2. The UK patent number 1006518, cl. From 1 J, pub. 1965. 3. USSR author's certificate number 324656, cl. H 01 F 1/22, 1969.