DE1055431B - Method for producing a space-stable fireclay - Google Patents

Description

Process for producing a volume-stable fireclay In many Cases is the task of making refractory products, which from the raw Show as small a change in space as possible up to the fired state and that too then, when they are in the finished state, installed in the use ovens at higher temperatures are heated, show neither shrinkage nor regrowth.

In order to reduce the shrinkage in the course of production as much as possible, one worked with fireclay-rich masses, which only contained a little binding clay. However, since the chamotte itself was often fired lower or shorter as: the stones made from it., was the occurrence of a shrinkage of the stone on the whole and the formation of shrinkage cracks can hardly be ruled out. A disappearance or regrowth in the oven of use occurred in each case, if higher than that Stone burning temperatures came into play.

For obtaining a mullite chamotte that is stable even at high temperatures was recommended according to a known method, by a sufficiently refractory Alumina silicate, such as kaolin, go out with a particularly reactive one To add alumina-rich substance in addition to smaller amounts of corundum and the mixture to burn tightly at high temperatures (1600 ° C and above). Incidentally, it is known Burning fireclay from mixtures of alumina silicate and alumina-rich substances. This was done either for the purpose of reducing the clays or kaolins in the clay content by 1 up to 2% or, as in the case of the aforementioned method, products of sillimanite or mullite composition.

A mixture of alumina silicate is also used in the method of the invention and ran out of nerd rich stuff. However, the alumina silicate used is a refractory one Sin; terton, e.g. B. Kärlicher blue tone, Westerwald blue tone (Ransbach, Hillscheid, Ruppach), Palatinate binding clay, Klingenberger clay used at the normal fireclay firing temperature (SK 6 to 10) sinters. There is a certain mixing ratio of clay to alumina: ichem Applied substance, namely an initial mixture of roughly pre-shredded, pit-moist Sintered clay and bauxite or calcined alumina or corundum dust or alumina hydrate in the ratio of about 82 to 88 parts by weight to 18 to 12 parts by weight and about 5 to 15% fine-grained sintered chamotte, which is produced at temperatures of SK 6 to 10 is burned. The sintered chamotte preferably has a grain size of 0 to 0.5 or 0 to 1 mm.

The mass is worked through kneading with the addition of water, what z. B. in. A clay cutter or a sieve kneader can go on. After this Treatment that results in a plastic, stra.ngpreßbaren mass, can the mass can be pressed into lumps or other shaped bodies. On the shaping can can be omitted if the fireclay in a shaft furnace, a rotary kiln, on a sintering belt, etc. is to be fired. For the fireclay in a ring, Chamber and tunnel ovens and the like are recommended to be eaten. Chunk. In all cases is burned with normal embers (SK 6 to 10), d. H. at the burning embers, at which the starting clay would be fired into a sintered chamotte.

The use of a sinterable refractory clay as a starting material is a requirement because when starting from a non-sintering clay, there is a fading could not be ruled out.

It is also important to specify the addition of finely powdered high alumina Fabrics. Since the sinterable refractory clays almost without exception have a tendency to Have swelling, d. H. when heated above the sintering temperature, can if the addition is too small, this drift cannot be completely prevented. If, on the other hand, the addition is chosen too large, then one with a higher level of heat will be used Retaining fireclay preserved. The carried out. However, tests have shown that with regard to the amount of this addition a certain margin within the scope of the invention Range of numbers.

Another prerequisite for achieving the desired effect is the type of distribution of the fine powdery alumina-rich substance. It turned out to be proved necessary to start from pit-moist clay and the mass at the same time also add 5 to 15% fine-grain sintered chamotte. To get the most beneficial mix To obtain it has to be the use of a clay cutter or a sieve kneader proven, but less so using a pan mill. The finely divided Alumina-rich substances can also be added to the mass in liquid form, what a very appropriate special embodiment of the method according to the invention represents. To make this possible, the alumina-rich material becomes smaller Amounts of refractory clays, water and suitable electrolytes in known per se Way prepares a slip, which as such in measured partial portions the other backfill materials (sinterable clay and fireclay) is added. Nice with an addition of 20 to 30 parts by weight of dry clay to 100 parts by weight A casting slip can be prepared from calcined alumina, which does not separate, however flows well. This special design prevents the formation of agglomerations of the alumina powder as well as losses due to dust or sieve failure are prevented.

The novel chamotte produced according to the invention is excellent Dimensions are also suitable for refractory products that require high dimensional accuracy, good thermal shock resistance and also high thermal resistance are important. Example 1 A mixing kneader with a capacity of 2501 is charged: 205 kg of Ruppacher Clay (38/40), fresh from the pit. The clay is worked through with the addition of water, the amount of water being adjusted so that a soft plastic mass is created.

Then 45 kg of alumina hydrate and at the same time the mixer kneader 12.5 kg of Ruppacher chamotte (0 to 1 mm) are added and the mass in the mixer worked through for a few minutes. The mass is then put on an extruder pressed into chunks, which are then placed in a shaft furnace at 1280 to 1300 ° C (throughput time 36 hours). The fireclay obtained is broken and placed on a Impact mill ground to a grain size of 0 to 5 mm.

The fired chamotte has a total porosity of 90/0. She proves after firing to temperatures of 1400, 1500 and 1550 ° C as completely stable. Example 2 Grubenfrischer Kärlicher blue tone is machined on a clay planer. on per 75 kg of this planed clay are added 10 kg of sintered chamotte from the same clay with a grain size of 0 to 1 mm and 32 kg of a slip made from 15 kg calcined clay, 5 kg clay, 121 water and 50 g of an alkaline electrolyte had been prepared. These three components are fed together to a sieve kneader, worked through in this and then formed into chunks on the extrusion press, which are fired after drying in the chamber furnace at SK 8 to 9.

The material to be fired is granulated to a grain size of 0 to 4 mm.

The following materials were prepared for testing the chamotte: a) 80 parts by weight Fireclay (0 to 4 mm) and 20 parts by weight of raw mixture from which the fireclay is burned had been. The mixture was mixed with 81% water and by dry pressing deformed to test specimens. The test specimens were fired in a gas-fired one Furnace, namely for the main part of the test specimens at SK 10.

Individual test specimens were fired at SK 14, 18 and 26.

b) 50 parts by weight of chamotte (0 to 4 mm), 30 parts by weight of corundum (0 to 1 mm), 6 parts by weight of calcined clay and 14 parts by weight of binding clay.

Processing of mass b) similar to mass a). Exam Results 1. Change in length in the event of fire: All bodies, both with SK 10 and SK Fired 14, 18 and 26 showed neither shrinkage nor expansion.

2. External condition: All bodies were fully sharp-edged, smooth on the outside, no shrinkage cracks.

3. Cold compressive strength of the bodies fired at SK 10: mass a) i. M. 475 kg / em2, mass b) 622 kg / cm2. 4. Pressure fire resistance according to DIN 1064: mass a) ta value 1490 ° C, mass b) ta value 1630 ° C.

5. Resistance to temperature changes (DIN 1068 with water).

After 50 deterrents, both masses were about halfway the specimen showed some fine cracks (between the 10th and 25th quenching), which neither increased nor increased. After 50 deterrents, the attempt was made canceled. The presumable deterrent numbers are over 100 in both cases.

Claims (2)

PATENT CLAIMS: 1. Method for producing a space-stable Fireclay made of alumina silicate and finely distributed alumina-rich substances, thereby characterized that a starting mixture of coarsely pre-crushed, pit-moist, refractory sintered clay and bauxite or calcined clay or corundum dust or Alumina hydrate in the ratio of about 82 to 88:18 to 12 parts by weight and about 5 to 151% fine-grain sintered chamotte can be used and firing temperatures at SK 6 to 10 are complied with. 2. The method according to claim 1, characterized in that that the refractory sintered clay is the finely divided alumina-rich substances in the form of a Schlickers are added from the alumina-rich substances, limited amounts Clay, water and suitable liquefying electrolytes are prepared. In. Considered publications: German patent specifications No. 662 755, 766 500, 855,674; "Unformative raw materials for ceramic masses", Niederleuthner, 1928, p.37; "Die Keramik", Salmang, 1951, p. 114; Consultation room calendar, 1928, pp. 188/189.