DE974648C - Process for the manufacture of refractory products - Google Patents

Description

Process for the manufacture of refractory products. The subject of the invention is a process for the production of refractory products that are different from the known, d. H. manufactured according to older methods, by a considerably better one mechanical strength, pressure fire resistance and thermal shock resistance distinguish. The method of the invention is essentially the same Basic materials from which also after older processes for the manufacture of the products to be used.

Most of the refractory products in the form of bricks, slabs, Pipes, fittings and other components are built from non-plastic grain in fine to coarse form and a finely divided binder. The different Mass components are mixed with one another and then in a moistened state deformed. In principle, two different methods are used here. To one is of dry raw materials, such. B. ground chamotte and powdery Dry clay, gone out; the various components become dry with one another mixed, and the mixture is then added with the water necessary for shaping Mistake. This working method is mainly used when the shaping on the Ways of dry pressing or semi-dry pressing should be made. To the second method it is assumed that the clay is plastically moist. For this purpose, the ground chamotte is added and the mass, possibly among other things Added water, kneaded. Working with binding clay is a special procedure which is converted into the form of a pouring slip before it is added to the chamotte has been. However, this latter method of operation is limited to a specific one Ratio of clay to fireclay, since shaping (pressing) is only possible then is when the mass to be deformed has a very specific water content (between 6 and 8 '9 / o) and when the clay is mixed in as a casting slip, the clay component always has a certain relationship to the water content.

The construction of the refractory masses from non-plastic components on the one hand,. Binder, on the other hand, is essential for making useful products an imperative. However, there is the inelastic part in most cases is practically stable in space, d. H. does not experience any permanent room change in the event of a fire, the plastic binder, on the other hand, disappears, it is difficult to make this diverse To reconcile behavior with one another in such a way that usable products are obtained will.

It is already known that binding clay is bad on dry chamotte, on the other hand, sticks well to wet ones. Based on these observations, it was recommended that this Method mainly to use for the production of low-fired masses, since this effect is low in the case of masses rich in fireclay.

It is also known to prepare refractory masses from lean stock and make binding agent in several stages. So, according to a suggestion, it should Fireclay grub grain mixed with all the binding clay and water and put into this mixture the fine grain of fireclay can be incorporated. According to another well-known suggestion should bind concrete casting slip initially with part of the leaning agent, preferably of its finest proportions, mixed and then introduced the rest of the lean material will. A third well-known proposal is to start with a dry mix To prepare fireclay binding clay and then add electrolyte fluid to it. According to another known method, the chamotte should first be mixed with the binding clay and a small amount of electrolyte-free liquid are mixed; only Mixing water containing electrolyte should be added.

It has been found that the most important properties of the refractory Products, e.g. B. the fireclay bricks, sillimanite bricks, corundum bricks, silicon carbide bricks, decisively influenced by the strength of the integration of the inelastic grain will. If one takes a closer look at the products produced so far, one sets consistently states that there is always a more or less large part of the inelastic Grain is only insufficiently integrated in the fired product. It's a multitude of crevices and cracks. These cracks are shrinkage cracks, which are created in such a way that the binding clay, which is shrinking in the fire, is has not loosened the dwindling grain. Coarse grain in particular is one of them Shrinkage cracks surround or adhere to the binding compound only on one side or at one corner together.

According to the method of the invention, the formation of such shrinkage cracks largely switched off. The invention also creates the possibility of to work with masses that have a particularly high proportion of coarse-grained, non-plastic Have material, which has a further favorable effect on the resistance to temperature changes affects. The invention is based on the important finding that for the coming about a firm adhesion of binding clay to the grain first requirement the creation of a firm adhesion in the raw or green mass is that, however, further care must be carried so that this adhesion is reinforced in the event of fire.

According to the invention, the coarse-grained, inelastic material is first used slightly moistened by itself. This moistening can be done with water, though the interfacial tension between water and grain is small. Isn't she so the interfacial tension is to be suppressed by additives so that one really good wetting of the coarse, inelastic grain is achieved. Suitable additives are on the one hand commercially available organic agents, such as alkylbenzenesulfonates, on the other hand, weak acids, e.g. B. acetic acid or salts, e.g. B. Aluminum sulfate or calcium sulfate or borax can be used. The additional amounts are small. In most cases, an addition of the same order of magnitude is sufficient from o, oi to o, i ° / o (based on the amount of grain).

After the coarse grain has been wetted, a small one is produced Amount of binding clay added in finely powdered form and incorporated by mixing. For example, one uses in the production of chamotte, sillimanite stones u. Like. 1 to 3% of the binding clay intended for the mass in dry, finely powdered Form and work through mixing the mass. You can already see that every single grain is covered with a thin, but very firmly adhering layer of the Bindetons is coated. Then the remaining amount of the required mass components, Fine plastic materials and binding clay, mixed in and finally the total mass by adding water immediately before shaping to the correct shape brought.

When choosing the substances that reduce the interfacial tension If possible, those should be selected that have a certain flux or mineralizer character exercise. Such substances can be added when the coarse grain is moistened will. With fireclay masses, a small amount of lime or calcium sulfate is very effective cheap. In other cases, the addition of phosphate or fluoride can be advantageous be. However, the amounts must be very small in order to be fire-resistant Flux effect cannot occur. Will the amount of these additives but kept below 0.05'11 / o, no damage was found.

The shape of the masses prepared in the manner described can in any convenient way, e.g. B. by deformation on the extruder and re-pressing or by deformation by hand or by pressing on punch presses or finally by pounding or pounding. Further treatment - drying, Post-processing, firing - is also done in a generally known manner.

The method of the invention is primarily aimed at Processing of such non-plastic materials, which are dense or nearly dense, because the measures of the invention have a particularly strong effect on these raw materials the end. Such raw materials are z. B. Sintered chamotte, burnt sillimanite or cyanite, Corundum, silicon carbide. The use of such raw materials - compared to porous, like chamotte - has the advantage that compounds with particularly good thermal properties, especially good resistance to chemical attack can be obtained. It is precisely the secure integration of such dense coarse grains that has previously caused difficulties.

The superiority of the invention over older methods is expressed in the following values: Dry pressing method old I new method Cold compressive strength 24o kg / cm2 290 kg / cm2 DFB-ta value. . 134o ° C 137o ° C TWB number ....... 16 depreciation 24 depreciation (The above values relate to chamotte material that was produced from the same mass offset and raw materials of the same type. With the old method, the total amount of chamotte moistened, then the binding clay was added, mixed and the remaining amount of the water required was added during the mixing process of the binding clay are mixed in dry, then the fine chamotte and other i2n / o binding clay are mixed in and the remaining amount of water is then added.

Claims (4)

PATENT CLAIMS: i. Process for the production of refractory products from practically stable, non-plastic raw materials on the one hand, finely divided binding clays on the other hand, whereby the lean substances are divided into coarse and fine grain, the preparation of the mixture of lean substance, binding clay and water takes place in several stages, the finished mass is then shaped, dried and is fired, characterized in that the coarse grain moistened for itself is intimately mixed with a small proportion of binding clay, which is preferably mixed with small amounts of a flux or mineralizer, this mixture is then processed with the fine-grained lean fraction and the remaining binding clay and that water required for shaping is only incorporated immediately before shaping. 2. Procedure according to Claim i, characterized in that the wetting water for the coarse grain is small Quantities of substances are added, which reduce the interfacial tension between the surface of coarse grain and water. 3. The method according to claim i and 2, characterized characterized in that the non-plastic materials used are those which are dense or are almost impervious, such as sintered chamotte, burnt sillimanite, corundum, silicon carbide. 4. The method according to claim i to 3, characterized in that non-plastic coarse grain is used in predominant quantities. Publications considered: German Patent Nos. 621 283, 625 400; P. O. B u d n i k o w, »Technology of the ceramic Products «, 195o, pp. 2o6 to 21o; A. B. Searle, "Refractory Materials," 195o, P. 38i.