SU1339902A1 - Ceramic material for electric heaters - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to increase the service life of heaters when operating in an atmosphere of aggressive vapors. The material is intended to work to the fore. With. It contains,%: titanium disilicide 28 - 30; alumina 7 - 10; silicon dioxide 7-10; aluminosilicate fiber 7–10; raw bentonite (plasticizer) 10–14; burnt bentonite — the rest. The material obtained by sintering in a protective atmosphere. He has a high beats. resistance (500 - 600 ohms.), heat-resistant during thermal cycling modes of operation. 1 tab. (

Description

The invention relates to electrothermal conditions, namely to electric heaters made of ceramic materials used for working in corrosive environments, for example, in plastics processing.

The purpose of the invention is to increase the service life of heaters when working in an atmosphere of aggressive vapors to

Ceramic material was prepared as follows.

Mixed alumina powders (s-form (coruda), silicon dioxide (S -form (c / quartz), raw bentonite (plasticizer) and calcined in water at 50-55% of the total moisture content of Ishkhta for 3-4 hours. Aluminosilicate the fiber was mixed in hot water (or alcohol) and added to the mixture. Then, titanium disilicide powder was added and the mixture was stirred for 1 day to obtain a single-phase mass. Then the mass was dried in vacuum at 45 ° C for 16-17 h, rolled at a moisture content of 10-12% and extruded through the mouthpiece of a given profile. zhni which were dried to 4 days in the cells with an increase in temperature from 20 to 40 ° C at a humidity spizheniem therein to 20%, and sintering at a temperature of 1300-1350 C for 2.5 hours under hydrogen atmosphere.

Sterlchny pr. About a coal-shaped profile with a section of 2x8 mm, 400 mm long are received. End sections with a length of 20-30 mm metallized.

Titanium disulide powder was taken with a particle size of 1-10 microns. The limit is determined by technological difficulties, the upper one affects the stability of the electrical resistivity of the electric heater in operation. Aluminosilicate fiber (48.86%

Sio

g

50.33% AljOj with a working temperature of up to 1150 C) has a particle size of 2-3 mm, diameter up to 10 µm, which is correlated with the particle size distribution of titanium disilicy., Silicon dioxide from (the form is heat-resistant when thermally cycled to 600 ° s

Increasing the concentration of titanium disilicide (over 30%) reduces the electrical resistivity of the heaters (at 31% to 200 ohm-mm / m), and decreasing (less than 28%) dramatically increases it (at 27% - 9000 mmm2 / m). Addition of silica-alumina fiber

(/ -10%) reinforces sterles of electric heaters, which hardens them, makes them resistant to thermal shocks, slows down the formation of cracks, stabilizes the specific electrical resistance. When the fiber increases (more than 10%), pressing is complicated, the rods are deformed;

7% deterioration of strength (bending strength of 1000 kgf / cm). Increasing or decreasing beyond the indicated limits of oxide concentration leads to curvature of the rods along the length, cracking after sintering, i.e. to marriage.

The electrical resistivity of heaters from predolsennogo material 500-600 ohms .. Volume

weight 2 + 0.1 g / cm, bending strength 1550 kgf / cm, porosity 10-12%.

The tests were carried out in a cyclic mode under a current of 25 A with a watt load of 2.5-3 W / cm with heating to

600 C with suction time of 15 minutes and subsequent cooling. The test results are shown in the table.

As can be seen from the table, under thermocyclic mode of operation, the proposed

the material is more heat-resistant and retains a more stable value of electrical resistivity than the known heater.

Formula invented and

Ceramic material for electrical heaters containing metal disilicide, alumina o (forms, silicon dioxide and raw bentonite (plasticizer) and calcined, due to the fact that, in order to increase the service life of heaters when working in an atmosphere of corrosive vapors before, aluminosilicate fiber was added to it, titanium disilicide was taken as metal disilicide, and silicon dioxide was taken from the / -form with the following content of components, msec.%:

Titanium Disilicide

C / -FORMS28-30

Aluminum oxide 7-10

Silicon dioxide

of-form, 7-10

Aluminosilicate

fiber7-10

Raw bentonite 10-14

Bentonite calcined Else

Molybdenum Disilicide 31 Titanium Disilicide 31

ten

10 10

ten

- 10 10

- 0,5 12 12 12

37 36.5 38

- eao-50

+30

Watching Marriage

200 chumma is given

150

+ 20

Trio

Editor L.Gratillo

Compiled by A. Khodataeva

Tehred M. Khodanich Proofreader V. But ha

Order 4352/56 Circulation 801

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

27

38

29

thirty

ten

ten

ten

10 37

14 33

ten

12 38

150 - 380

370

420

+ 20

± 2

+5

+3

By Ow - Marriage, there are 900 cracks

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Claims (1)

Formula of the invention 35 Ceramic material for electric heaters containing metal disilicide, aluminum oxide οί forms, silica and raw bentonite 40 (plasticizer) and fired, which can be used to increase the service life of heaters when operating in aggressive atmosphere up to 600 ° C, aluminosilicate fiber was additionally introduced into it, titanium disilicide was taken as metal disilicide, and silicon dioxide was taken d-form with the titanium disilicide composition. Silicon dioxide / form is heat-resistant during thermal cycling up to 600 ° C. An increase in the concentration of titanium disilicide (more than 30%) reduces the electrical resistivity of the heaters (at 31% to 200 0m-mm * 7m), and a decrease (less than 28%) sharply increases it (at 2.7% - 900 0mmm ² / m) “Aluminosilicate additive fiber following component content, 50 ^oil: Titanium disilicide / -forms 28-30 Alumina 7-10 Silica 5θ / -forms 7-10 Aluminosilicate fiber 7-10 Raw bentonite 10-14 Calcined bentonite Rest Composition and properties Famous The proposed method 1 (control) 2 (control) 3 (control) 4 5 . 6 Molybdenum Disilicide 31 Titanium disilicide - 31 Aluminum Oxide Forms 10 10 Purified β-Form Silicon Dioxide 10 - Silicon oxide U ~ form - 10 Aluminosilicate fiber  - 0.5 Raw bentonite (plasticizer) 12 12 Calcined bentonite 37 36.5 The number of thermal shocks (in cycles) maintained by heaters (heating to 600 ° C with a holding time of 15 minutes and cooling to room temperature) 40-50 thirty 27 38 29th thirty 10 10 10 8 7 - - - - - 10 10 7 9 9 - fifteen 8 7 10 12 12 10 14 12 38 26 37 33 38 150 380 370 420 Change in specific electrical resistance laziness (± 2) at + 30 + 20 ± 2 the specified thermal cycling mode (required 500 + 102), Ohm · mm ^g / m) Watching Marriage Appearance Marriage,, given 200 are 900 spawning + 5 +3 plague