DE3620284C2 - - Google Patents

Description

The present application relates to refractory compositions for monolithic linings, which are not only for linings Applications for the most diverse types of furnaces to steel production but also for other industrial furnaces use fin can, for example for ovens for the production of non ferrous metals and in the ceramic industry.

Fireproof masses are usually used for monolithic clothes used in such a way that powdery substances in the required mixing ratio with water or an aqueous Binder solution are mixed. However, it is ver differently required that the refractory masses basi contain components such as MgO or CaO. In this case this occurs when the basic components are mixed with water called extinguishing phenomenon, causing during curing  or drying cracks or even breaks occur.

To prevent such undesirable effects, ver better method in Japanese Patent Laid-Open applications No. 52-32 908, 53-1 13 812, 57-1 29 864 and 58-99 177 described according to which certain additives are used be det. However, it can hardly be said that one of the in additives described in these publications did has properties that would make it possible that both the extinguishing phenomenon is prevented and also the good processability of the refractory in question Masses is preserved.

In Japanese Patent Application Nos. 52-32 908 and 53-1 13 812 are inhibitors in the form of organic matter lien used. In the first cited reference han it is an additive that is also used in the Production of refractory bricks acts as a binder. But then a certain effect of this additive is recognizable when the refractory material ver under pressure is molded after the aggregates with an aqueous solution have been mixed up, it turned out to be difficult sen, such an additive for pourable materials to use, due to the high concentration in the aqueous solution.  

The additive mentioned in the second prior publication is essentially only effective for materials, which are processed using the centrifugal process, but it shows not enough improvements when processing materia lien using the technique of casting, coating and Application by means of a spray gun. The use of one too Large amounts of this additive can even lead to an desired deterioration in the mechanical strength of the lead from the refractory molded body.

In Japanese Publications No. 57-1 29 864 and 58-99 177, inorganic inhibitors are recommended. The addition used in the first-mentioned publication Fabric is very effective when used in an aqueous solution and when drying in low temperature areas, he shows however, insufficient effect when drying among them Conditions like those in an autoclave at one temperature of more than 100 ° C. In the last-mentioned previous ver Silica aerosol, which is generally mean is suitable for materials which, according to Gießtech nik and coating technology are processed. A small amount this additive shows a limited effect, but can larger amounts lead to an undesirable deterioration the corrosion resistance of the basic refractory aggregates To give reason.

The object of the present invention was therefore to fire solid bulk available for monolithic linings too  places where the deletion phenomenon does not occur and therefore reduce the risk of cracking during drying is gert.

This object is achieved by refractory materials solved for monolithic linings, which ge are characterized as being a basic aggregate of magnesia Clinker and / or spinel clinker and / or magnesia chromite Clinker and / or dolomite clinker and / or lime clinker as well 0.02 to 20 parts by weight of a little or not in water soluble phosphate per 100 parts by weight of the total amount contained in basic aggregate.

The effect of a slightly water-soluble phosphate as In hibitor for the occurrence of the extinguishing phenomenon is beyond nice.

So far, phosphoric acid and water-soluble aluminum phosphate as a binder in such refractory materials uses which do not contain a basic refractory aggregate. So it is known, the very water-soluble monoaluminium sphat Al (H₂PO₄) ₃ to use as a binder for clays. Sound however, materials react neutral or weakly acidic are therefore not exposed to a hydration reaction which the Deletion phenomenon (cf. "Bull. Amer. Ceram. Soc.", Vol. 23, p. 428 (1944)).

Furthermore, it is known from DE-OS 22 44 928, the next  processability of refractory masses, which according to the Verfor be burned at 1000 ° C, and their storage stability in the flowable state by adding a water to improve soluble chromium phosphate. The eye there refractory masses are also at the bottom location of neutral or weakly acidic components, such as alumina and kaolin, d. H. occurs there too the deletion phenomenon does not occur.

With regard to the reactivity of phosphoric acid and the be knew water-soluble phosphates with basic refractories The inventors have a variety of methods and aggregates is looking for ways to eliminate the deletion prevent phenomenon to the basic refractory aggregate to stabilize. The invention is based on the consideration that only a moderate reaction with the phosphoric acid or the phos phat should occur so that only the surface of the basic refractory aggregate or only the basi dissolved in water ions would react with the phosphoric acid.

In the basic aggregates used according to the invention, it is the most diverse on the market Trade clinker types, for example seawater magnesia Clinker to natural magnesia clinker to electric melted magnesia clinker to sintered spinel clinker, electrically melted spinel clinker, natural Dolomite clinker, sintered lime clinker and electric melted lime clinker.  

To allow a free choice regarding the particle size Lichen, clinker are preferably in the form of crushed large chunks or in the form of classified Particles of various particle sizes are used.

The relevant clinker types can be used as such or in Mi application. In addition, the inventions inventive refractory masses also the most varied other refractory components, provided they are stable against water and steam, like aluminum oxide, bauxite, Mullite, chamotte, silica, chrome ores and olivine. The An parts in which these components in the invention refractory masses are also not subject to any special limitation and depend on the operating conditions different types of furnace, for the lining of which refractory masses are determined.

Preferably, they should be used as inhibitors in the context of the invention used insoluble or only slightly soluble in water phosphates are soluble in water at one temperature of less than 40 ° C of less than 2.5 g / 100 ml of water point. In addition, it is appropriate that the concern the phosphates in the form of an aqueous suspension Have a value less than 7. If namely the Soluble Phosphate in water of less than 40 ° C too large then there is a quick implementation between the basi refractory unit during the mixing process or the application of the refractory mass takes place and leads to flocculation or other defects, which makes handling the refractory Mass becomes difficult. If the phosphate is in the form of an aqueous  Suspension has a pH of more than 7 the inhibitory effect on the extinguishing phenomenon only rela tiv limited.

Although the type of used as an inhibitor according to the invention water-soluble or only slightly water-soluble phosphates connections are not particularly limited gene used, which orthophosphate or polyphosphate group and have a salt of aluminum, chromium, iron, Magnesium, calcium, potassium, sodium, lithium, boron, zinc, lead, Are barium, bismuth or silver. For example, an aluminum minium phosphate of the formula Al (H₂PO₄) ₃ water-soluble and therefore not usable within the scope of the invention. Aluminum phosphates the formulas AlH₃ (PO₄) ₂, Al₂ (HPO₄) ₃ and AlPO₄, however, are insoluble in water and can therefore be used within the scope of the invention be used. In the group of aluminum phosphates with the formula AlPO₄ etc. there are those of the most varied Crystal types and also amorphous compounds, and each of these Modifications can be used within the scope of the invention. In addition, there are also polyphosphates, such as aluminum meta phosphate, aluminum tripolyphosphate etc. only a little in water soluble and can therefore also within the scope of the invention be used. The same considerations apply to this Lich other phosphates than aluminum phosphate as well composite phosphates consisting of two or more Phosphates exist, or with regard to phosphates, which one form a solid solution with each other.  

The amount of the phosphate, which is insoluble or only slightly soluble in water in the refractory compositions according to the invention depends on the type the clinker used and the special recipe. If For example, clinker can be used, the relatively Wassersta are like magnesia chromite clinker or spinel clinker that are rich in aluminum oxide, then one extra is enough really small amount of the phosphate to make a corresponding To achieve effect. In refractory masses that contain magnesium contain oxide-rich spinel clinker or magnesia clinker, however, the amount of phosphate must be increased more or less. In addition, when using dolomite clinker and Lime clinker, which contains a large proportion of CaO and are therefore water-active, using a larger amount of the phosphate be used. The amount of phosphate varies also according to the crystalline state and the Crystal size of MgO and CaO in each clinker type. If Wed. If clinker types are used, the amount of Phosphate depending on the specific type of use ten aggregates can be determined. In any case, it should Phosphate concentration in the range of 0.02 to 20 parts by weight per 100 parts by weight of total amount of basic aggregate. If the amount of phosphate is below 0.02 part by weight, cracking during drying in autoclave conditions occur. An addition of more than 20 parts by weight However, phosphate has no further additional effect and is therefore economically inappropriate.

In the refractory according to the invention  Masses can also be used with other common components the, for example inorganic binders such as cements, Na trium silicate, water-soluble sodium phosphate, or organic Binders, such as the various types of resin, and also dispersing agents medium, such as the various water-soluble sodium phosphates and carboxylates. Means of controlling the Curing process can be used, such as sulfates, carbonates, Hydroxides, chlorides, borides and carboxylic acids. For the practical The use of the refractory compositions according to the invention is dependent but the use of a binder is not always required Lich, especially if they are intended for casting processes. This is due to the fact that the pH increases to the extent increases like divalent magnesium and calcium ions from the Clinker material are eluted so that only very little phosphorus acid is eluted with, which then creates connections with the magne Sium and calcium ions are formed, which the structure of the Reinforce molded body.

The particle size of the basic aggregates in the Invention according refractory masses is chosen so that the aggre Gate size for the most diverse types of manufacture and manufacture improvement of monolithic linings is suitable, for. B. by means of casting technology, by means of the spray gun, by means of the Covering and by stamping. In addition, ge if desired, other components can be added, such as clay, finely divided silica, finely divided aluminum oxide, in order to this way certain properties regarding the castability, to improve the consistency and the like.  

Although the refractory compositions according to the invention are water-insoluble contain phosphates which are only slightly or slightly soluble in water, so that the compositions are stable to water and hence after mixing with water during their practical Application hardly react, it has been shown that the pH after adding water over time in the Measure increases like divalent magnesium and calcium ions the clinker material are eluted, which then also released a very small amount of phosphoric acid components which is linked to the magnesium and calcium ions form, which ultimately causes the formation of cracks or Fractures that otherwise result from the deletion phenomenon would not occur.

Embodiments Example 1

There are different recipes according to the information in the Table I below from the required ingredients produced and 6.5 parts by weight of water each 100 Parts by weight of these recipes added. After mixing are these refractory masses in Casting molds of dimensions 40 × 40 × 160 mm and cast Hardened for 24 hours at room temperature. In this way corresponding test samples are obtained.  

After drying each molding for 24 hours at 110 ° C the modulus of rupture and the porosity are determined. Other Un test samples are immediately taken after curing Autoclave test subjected (3 hours at 5.07 · 10 · Pa). The Untersu samples that had passed this autoclave test were subsequently discussed regarding the Burch module and the Porosi activity examined.

The results obtained are shown in Table I below summarized.

From Table I it can clearly be seen that in the investigation samples from refractory compositions according to the present invention even under the harsh conditions of the autoclave test Cracking and no breakage occurred. In addition, the Bending strength of the test samples by the autoclave test increased after drying, while the porosity was reduced. In contrast, they showed Test samples of the comparative examples of signs of breakage or reduced strength. In addition, recipes doors which soluble and acidic phosphates, such as Al (H₂PO₄) ₃ contained, not be used in practice, because already with the Mixing appropriate reactions occurred.  

Table I

Example 2

There were recipes according to the information in the Table II prepared, which water in quantities was set as required for the specified types of application was such. After mixing, these became refractory Mass blocks with dimensions 230 × 230 × 300 mm and these moldings were then at room for 24 hours hardened temperature and then at 3 hours 110 ° C and then dried again at 200 ° C for 24 hours. To the Finally, the appearance of these mold blocks after drying visually assessed. Because the internal vapor pressure of the molded body is not identical due to different porosities, such a drying test on large blocks is a rea Listed method to evaluate the extent to which Defects during drying in an oven in practical use need to occur.

As can be seen from Table II, the Comparative examples Cracks or breaks observed, weh rend the refractory compositions of the invention a good Ver showed workability and no ver change could be determined.  

Table II

Claims (5)

1. Refractory masses for monolithic linings, as characterized by the fact that they are used as basic aggregate Ma gnesia clinker and / or spinel clinker and / or Magnesia chromite clinker and / or dolomite clinker and / or lime clinker and 0, 02 to 20 parts by weight of a phosphate which is insoluble or only slightly soluble in water per 100 parts by weight of the total amount of basic aggregate. 2. Refractory compositions according to claim 1, characterized in that they additionally as a further component (s) sintered aluminum oxide, Bauxite, mullite, chamotte, silica, chrome ores and / or contain olivine. 3. Refractory masses according to claim 1 and 2, characterized records that they have a compound as a phosphate inhibitor an orthophosphate or polyphosphate group in the molecule ten, which is a salt of aluminum, chromium, iron, magnesium, Cal cium, potassium, sodium, lithium, boron, zinc, lead, barium, bismuth or is silver. 4. Refractory compositions according to claim 3, characterized in that the phosphate inhibitor connects to a water solution Possibility of less than 2.5 g / 100 ml of water at temperatures is below 40 ° C.   5. Refractory compositions according to claim 3, characterized in that the phosphate inhibitor is a compound which in the form an aqueous suspension has a pH below 7.