RO104541B1 - Production method of an electro-insulating ceramic material - Google Patents

Abstract

The invention relates to a process for obtaining of an insulating ceramic material, with compactness high, for the incorporation of resistances electric heating, used in manufacturing discs, plates and tubes of heaters metal. The electro-insulating ceramic material, according according to the invention, it is made up, in percentage of weight, from: milled talc 52 + 58%, kaolin washed 15 + 18%, calcined alumina 15 + 18%, feldspar 3 + 5%, which is added as an inorganic binder, by mixing, sodium polyphosphate (NaPO3) n • H 2 O) 2 + 4%.

Description

The present invention relates to a process for obtaining an electrically insulating ceramic material, with high compactness, for the incorporation of electric heating resistors, used in the manufacture of metal discs, plates and tubes.

It is known the method of fixing the resistors of the heaters in ceramic bodies, which, in turn, are mounted in metal discs.

These have the disadvantages that the heat transmission is made at a low efficiency, due to the fact that the contact surface between the ceramic body and the surface of the heating disk is small and also a rapid oxidation of the resistance to the operating temperature occurs, due to the permanent contact with ambient air

It is also known as an electrically insulating ceramic material, which encompasses the entire heating resistance, thus protecting the incandescent resistance to the oxidizing effect of the air.

This electro-insulating ceramic material has the disadvantage that it is not compact enough, which leads to heat loss and gives your friable ones. Also, metal discs, which are paste with this electrically insulating ceramic material, can no longer be used after they have been pierced.

The object of the invention is to make a ceramic material with high compactness, which has high technical characteristics and the possibility of reusing the metal disk when troubleshooting.

The technical problem pa that solves the invention is to make a mixture based on. known components, which, by adding an inorganic binder, ensures a high compactness of the ceramic electrically insulating mass, eliminating the combustion operation of the mixture.

The process according to the invention removes the disadvantages presented above, in that: 52-5-58% milled talc, 15418% kaolin and 3 ± 5% felds2 bed are mixed, to which 2-5-4% sodium polyphosphate is added. presses the mixture obtained at a pressure of ... 1004120 daN / cni in a first layer of thickness 3-5-4 mm, over which the resistance is fixed by pressing with a second layer with a thickness of 7-5-10 mm , after which, finally, the pressed products are subjected to drying at a temperature of 345 + 36 & C. for 20 min.

An example of the invention is given below.

A mixture, by weight, is formed of: milled thallium 52458%, washed eaolin 15,418%, feldspar 3 45% -, to which is added as inorganic binder, by mixing, sodium polyphosphate [(NaPOs) n · H2O ] 244%. The mixture thus obtained is pressed into a layer of thickness a, over which the resistance is fixed by pressing with a second layer of thickness b. The electro-insulating ceramic material in which the resistance was compacted is subjected to a drying process in an electric oven, at a temperature between 345 and 360 ° C.

The characteristics of the ceramic material obtained are:

- apparent density: l „942.1g / cnT;

- apparent porosity: below 5%:

- mechanical resistance to compression:

3004350 kg.f / cm ²

Compared to these values, the usual masses of the shock type, used as materials for incorporating the heating resistors. it is presented as follows:

- apparent density: 2,642.8 g / cm ⁰ ;

- apparent porosity: 10.0420.0%

- compressive strength: 150,4200 kg.f / W

The recipe for the ceramic material is as follows:

- ground talc: 52458%;

- washed aeoline: 15-5-18%;

- calcined alumina: 15418%:

- feldspar: 3 -5%;

to which is added, by mixing, sodium polyphosphate Na (POsjn.HzO in gravimetric percentages of 244%.

The disk in which the ceramic table with the embedded resistance is located is con104541 li

4 made of cast iron (energofag material).

The process according to the invention allows the ceramic material to be removed from the damaged disk, which can be reused by re-drying and drying in the electric oven. 5

Electric disk repositioning automatically results in significant metal savings, as opposed to the old solutions used in the manufacture of the electric heating disc, which did not allow this. 10

The process according to the invention has the following advantages:

- a highly compact, electrically insulating ceramic material is obtained, which has corresponding use characteristics;

- presents a simple technology:

- compactness of the electrically insulating ceramic material gives it the possibility to be removed relatively easily from the metal disk. 20 at the occurrence of the piercing phenomenon, the metal disc thus being able to be reused;

- the mechanical strength of the electrically insulating ceramic mass with high compactness is higher than that used up to 25 at present:

- the yield of the discs pasted with the electro-insulating ceramic material according to the invention, amounts to SO-t-82% values.

Claims (1)

Claim Process for obtaining an electrically insulating ceramic material, used in the manufacture of metal discs, plates and tubes, by pressing a mixture of raw materials and drying at the appropriate temperature, characterized by the fact that, in order to produce high-compactness products, to include the resistances. electric, as well as simplifying the technological flow, mix 52 - ^ - 58% milled talc 15-el8% kaolin and 3 - * - 5% feldspar, to which is added 2 ^ -4% sodium polyphosphate, pressing the obtained mixture at a pressure of 100-rl20 daN / cm ' ¹ ' in a first layer of thickness 3 ... 4 mm, above which the resistance is pressed by pressing with a second layer with a thickness of 7 ... 10 mm. after which, finally, the pressed products are subjected to drying at a temperature of 345 - * - 360 ° C, for 20 minutes.