WO2004065327A2

WO2004065327A2 - Unshaped refractory products, especially refractory concrete, containing inoxidisable parts

Info

Publication number: WO2004065327A2
Application number: PCT/EP2004/000255
Authority: WO
Inventors: Dirk Uwe RÜSS; Tadeusz Von Rymon Lipinski
Original assignee: Esk Ceramics Gmbh & Co. Kg
Priority date: 2003-01-23
Filing date: 2004-01-15
Publication date: 2004-08-05
Also published as: WO2004065327A3

Abstract

The invention relates to a refractory material containing a coarse-grained, refractory constituent (coarse grain) and/or a medium-grained, refractory constituent (middle grain) and/or a fine-grained, refractory constituent (powder) and/or a finest-grained, refractory constituent (finest grain). The invention is characterised in that the material is free of carbon and contains a refractory, boronic constituent which is free of nitrogen.

Description

Unshaped refractory products, especially refractory concrete, with non-oxide components

The invention relates to unshaped refractory products, in particular refractory concrete, with non-oxide components.

Refractory unshaped products are one of the high-revenue product areas for the steel industry. The proportion of unshaped products in refractory production in the EU is currently around 43%. Japan is a pioneer in this regard, where the masses already account for almost 60%. Unshaped refractory materials account for over 55% of total refractory material production in the United States. Due to the clear technical and economic advantages, refractory masses are becoming increasingly important in industry and are displacing stone deliveries in many areas.

The most important material group of the unshaped products are refractory concretes (refractory concretes). Refractory concretes are mixtures of refractory aggregates and binders, mostly delivered dry and processed after the addition of water or another liquid. They are installed by pouring with vibration, pouring without vibration (self-flowing), by poking or, if necessary, by pounding. Binding and hardening take place without heating. After hardening, drying and heating, a furnace lining is created which, in comparison with fireproof masonry, has particularly few joints and is therefore also called "monolithic" (3). Finished parts can also be made from refractory concrete, which are usually thermally pretreated or prebaked.

The usual modern liquefied refractory concretes with their low mixing water requirement (down to 3.5% by weight) contain aggregates with grain sizes up to 10 mm, a small proportion of calcium aluminate cement (3 - 5% by weight) of fine-grained additives such as microsilica and / or alumina different rather primary crystal size (specific surface) and fineness, liquefier and setting regulator. Low-cement vibrating refractory concrete with a correct grain structure requires a water addition of 3.5 to 6% by weight. In the case of self-flowing refractory concrete, the water addition is in the range 4.5 to 7% by weight.

The calcium aluminate cement used as a binder in the hydraulically bound refractory concretes is often the weakest link in the structure of the refractory concrete. The reason for this is the relatively low-melting eutectics in the CaO-Al ₂ 0 ₃ -Si0 _{2 system} . In order to reduce these negative effects, many efforts have been made to reduce the cement content. As a result, low-cement refractory concretes or refractory concretes with an extremely low cement content were developed, see above. Parallel to the technological development of refractory concrete based on calcium aluminate, the search for new binder systems to replace calcium aluminate cement continues. The technologically relevant developments are:

In basic concretes - Mg (OH) ₂ and barium aluminate cement active A1 ₂ 0 ₃ . Its use improves concrete properties such as resistance to temperature changes (TWB) and fracture toughness. Combination of microsilica with active A1 ₂ 0 ₃ - this leads to the formation of mullite and thus to an improvement in the thermo-mechanical properties and TWB

Phosphate binding, primarily based on monoaluminium phosphate water glass synthetic resins

Various additives are used to improve the properties of the refractory concrete and its application behavior. For example, the addition of steel fibers that have a positive effect on mechanical strength and TWB is widespread (Genrong, L .; Hongliang, Z .: Influence of stainless steel fiber addition on flexural strength and thermal shock resistance of refractory castables. Int. Coll. Aachen, 1992). A Zr0 ₂ and / or Cr ₂ 0 ₃ additive in turn increases the corrosion resistance (Boquan, Z .; Hongxi, Z .: Study on slag resistance of magnesia / zirconia-based castables. Stahl Eisen (2001), p. 68- 70; Miyaji, T.; Saka oto, S.; Kudo, E .: Role of Cr ₂ 0 ₃ in Al ₂ 0 ₃ -Cr ₂ 0 ₃ castables for waste melting furnaces. Taikabutsu Overseas 22 (2002) 2, Pp. 118-121).

The use of monolithic refractory linings has the following advantages:

Possibility of mechanization of delivery and thus a

Shortening the assembly time

Lack of joints that accelerate the penetration of the lining and thus the corrosion Improve the steel cleanliness

Reduction of delivery costs by up to 50%

Reduction of specific consumption

Of all the unshaped refractory materials, the fire concrete and door locking compounds are best suited for mechanizing and automating the delivery. The ramming masses and plastic masses, which also belong to the group of unshaped products, are not so cheap in this respect. Modern refractory concrete achieves property values that can exceed that of refractory bricks.

The advantages of using monolithic linings are a great incentive for their increased use in practice both in technical and economic terms. In the meantime, unshaped refractory products and the prefabricated components made from them have been introduced in practically all areas of application of refractory materials partly replace the refractory molded materials or are alternative materials. In the iron and steel industry as the largest buyer of refractory products, the consumption of refractory concrete is also greatest. In the entire production line there is hardly any other than converters Plant in which no unshaped refractory products are used.

This development requires the refractory industry to develop new, more powerful materials and technologies. One of the most important requirements and challenges in the manufacture and use of a monolithic refractory delivery is the setting of the lowest possible mixing water content. An excessively high water content leads to a deterioration in the porosity and strength of the refractory concrete. In addition, the drying of a monolithic brick lining is a very complex and sometimes complicated undertaking. In the event of improper guidance, major damage e.g. due to material explosion due to the high water vapor pressure. From this point of view, reducing the mixing water content is one of the goals of the further development of refractory concrete.

The most important task, however, is to improve the corrosion resistance of unshaped products, especially fire-reinforced concrete. Refractory concretes are usually characterized by good corrosion resistance. It is caused, among other things, by a small pore diameter, especially in self-flowing refractory concrete. In many areas of application, for example in the steel industry, this is still not enough, so that people are looking for opportunities for further improvement. One of them is the integration into the material structure of the carbon parts. Primarily graphite and carbon black are used. Similar to shaped stones, the carbon phase brings a significant increase in corrosion resistance. However, due to the poor wettability by water, larger amounts of carbon cannot be easily introduced into a refractory concrete. Carbon-containing concretes also require higher amounts of mixing water, which, however, creates the drying difficulties described above. The use of surface-active substances provides some remedy here. To date, the protection of carbon from burning out of the structure of a refractory concrete has been largely unsolved. After carbon oxidation, pores develop in the material structure, which impair the corrosion resistance. The metallic antioxidants commonly found in molded MAGCARBON (magnesia carbon) stones can only be used to a limited extent. Since the concrete suspensions have a basic character, the metal powders can react with the components and additives dissolved in the mixing water. The resulting hydrogen represents a potential hazard (Hara, T.; Yasuda, N .; Sugiyama, K.; Shimizu, I .: Gas evolution of silicon-containing castables. Taikabutsu Overseas 22 (2002), 2, 114- 117).

Against this background, it is the object of the present invention to provide refractory unshaped masses, in particular refractory concrete, which have a significantly improved corrosion resistance compared to conventional products and can be produced on an industrial scale and economically.

The object is achieved by a refractory mass containing a coarse-grained refractory component (so-called coarse grain) and / or a medium-grained refractory component (so-called medium grain) and / or a fine-grained refractory component (so-called flour) and / or a fine-grained component Refractory component (so-called fine grain) characterized in that the mass is carbon-free and comprises a refractory boron-containing, nitrogen-free component.

For the purposes of the present invention, carbon-free means that no unbound carbon, for example in the form of graphite, carbon black and the like, is present in the material. The invention thus also includes refractory compositions and materials which are produced using a carbon-containing binder, for example resin, tar, pitch. Masses with proportions of chemically bound carbon, such as in refractory carbides, such as silicon carbide, are also part of the invention. All typical, oxidic and non-oxidic, acidic and basic raw materials or their combination are used as coarse-grained, medium-grained, fine-grained and fine-grained refractory components. Basic metal oxides such as sintered, melted magnesia, sintered, melted spinel, sintered dolomite, sintered lime, olivine or forsterite are particularly preferred, and masses based on Al ₂ O ₃ with variable SiO ₂ and / or SiC contents are also advantageous. Combinations of these raw materials can also be present.

A particularly suitable fire-resistant boron-containing, nitrogen-free component is a compound selected from the group boron carbide BC, refractory borides and their mixtures. Refractory borides are preferably CaB _s , TiB ₂ , and ZrB ₂ . It has been found that also a mixture of several boron-containing, nitrogen-free compounds can be advantageously used ^'. The boron-containing, nitrogen-free compound is preferably present in amounts from 0.1 to 30% by weight, particularly preferably from 0.5 to 10.0% by weight.

The composition according to the invention preferably comprises an additive. In the context of the invention, additives are preferably metal powders, non-oxides such as, for example, nitrides, carbides, silicides, oxynitrides, oxycarbides, metal fibers, plastic fibers and carbon fibers, and are preferably metal powders Al, Mg, Si and non-oxides such as SiC , A1N, Si ₃ N ₄ , AlON, SiAlON. The additives are preferably present in amounts of 0.5 to 30% by weight.

For the purposes of the present invention, coarse-grained is preferably to be understood to mean grains> 1 mm, particularly preferably 1-10 mm. Grains of 0.2 to <1 mm, preferably 0.2 to 0.5 mm, are used as the middle grain.

For the purposes of the present invention, fine-grained should preferably be understood to mean grains of 0.02 to <0.2 mm, particularly preferably 0.02 to 0.1 mm. This grain fraction is usually called flour in technical parlance. Fines are reactive refractory components with an average grain size <15 μm, preferably <5 μm. For example, calcined clay, reactive clay, finely ground, refractory raw materials, microsilica, refractory clay, binding clay are used.

The unshaped refractory compositions according to the invention can be bound hydraulically, chemically or ceramic. All binder systems typical in refractory technology are suitable for this purpose. Hydraulic bonding by means of a refractory cement, preferably a calcium aluminate cement, is preferably used in an amount of up to 25% by weight, preferably 1 to 10% by weight.

Depending on the chemical composition of the refractory raw materials, all liquid binders common in the refractory industry are suitable for chemical bonding, ie as binders, both water-free and water-containing, for example resins, tar, pitch. Lignin sulfonate (sulfite liquor), polyvinyl alcohol, phosphates, MgS0 ₄ solution, water glass, levulinic acid. The amount of binder is preferably between 0.1 and 50% by weight, preferably between 1 and 10% by weight.

Ceramic bonding occurs in the compositions according to the invention when heated to temperatures> 700 ° C. This process is supported by the use of very fine grain fractions.

Depending on the type of binding, the masses are mixed with up to 40% by weight, preferably <10% by weight, of water.

In order to reduce the water content and / or to improve the rheological properties of the masses, the use of different additives, e.g. Liquefier, setting regulator, dispersing agent, advantageous. The share of this

Additive is in the range up to max. 5% by weight, preferably <1.5% by weight. The coarse-grained component is preferably present in amounts of <90% by weight, particularly preferably in amounts of 15 to 80% by weight.

The medium-grain component is preferably present in amounts of <40% by weight, particularly preferably in amounts of 3 to 20% by weight.

The fine-grained component is preferably present in amounts of <95% by weight, particularly preferably in amounts of 5 to 80% by weight.

The fine-grain component is preferably present in amounts of <50% by weight, particularly preferably in amounts of 0.1 to 35% by weight.

To increase the effect of the boron-containing components or to improve the material properties, special metallic and / or non-oxidic substances can be added to the refractory compositions according to the invention. These are preferably compounds selected from the group of metal powders Al, Mg, Si and non-oxides such as SiC, A1N, Si ₃ N ₄ , A10N, SiAlON.

For the purpose of reinforcing the structure and / or improving the drying process, the addition of metal fibers is also advantageous.

The carbon-free refractory compositions according to the invention are distinguished by a number of positive properties. Due to the relatively high thermal conductivity of the boron-containing additives, they have an improved thermal shock resistance compared to compositions without additives.

Due to the high affinity for oxygen, the boron-containing compounds show good oxidation resistance in the material structure. This behavior is supported by the formation of passivation layers on the surface of the material, which make contact with oxygen more difficult. The added boron-containing substances are poorly wetted by ionic melts, which limits the wetting by molten slags. This improves the corrosion resistance and contributes to increasing the durability of these new refractory compounds.

The formation of refractory, stable oxides due to the reaction of the borides with oxygen also has a positive effect on the corrosion resistance of the new materials. Since the reactions with a partially accompanied by considerable volume increase, they lead to a densification of the material structure, which in turn contributes to improving the corrosion resistance and the strength of the infeed. Borides and boron carbide are able to reduce the critical components of metallurgical slags and thereby reduce their aggressiveness.

A high compression of the material structure is important for the corrosion resistance of the refractory materials. This can include can be improved by an appropriate grain distribution. The following grain structure has proven to be advantageous for the offset according to the invention:

Coarse grain component: <90% by weight> 0.2 mm. Portions of 15 to 80% by weight of the grain fraction 1-10 mm are preferred.

Medium grain component: <40% by weight of the grain fraction 0.2 to 1 mm. Portions of 3 to 20% by weight of the grain fraction 0.2-0.5 mm are preferred.

Fine grain component: <95% by weight <0.2 mm, preferably 5 to 80% by weight

Fine grain component: <50% by weight <15 µm, preferably 0.1 to 35% <5 µm

Boron-containing, nitrogen-free compound: 0.1 to 30% by weight -325 mesh (<45 µm), preferably 0.5 to 5% by weight. The refractory compositions according to the invention are produced at the refractory manufacturer or on-site at the refractory user, preferably in the following steps:

Production of a homogeneous mixture of the refractory components mentioned in the weight percentages mentioned.

Adding a binder and / or additives and / or mixing water and further homogenizing the batch.

Addition of additives and further homogenization of the batch. If necessary, substances are added to the mixture, which take on certain functions in the finished masses. Examples are metal powder and non-oxide materials such as carbides, nitrides, silicides, metal fibers, plastic fibers, carbon fibers, which further improve the resistance to oxidation, strength, drying behavior, corrosion resistance and the thermal shock resistance of the material.

The homogenized mixture is ready for use and can be made using techniques familiar in refractory technology, e.g. Pouring, vibrating, spraying, door locking, pounding, etc., are processed into a monolithic refractory lining or a functional mass.

Prefabricated components can also be produced from the refractory materials according to the invention. For this purpose, the masses produced as described above are brought into a metal, or wood _, or plastic mold. The mass can be further compacted by subsequent vibration, pounding, pressing, etc. After the mass has hardened, the component is shaped and dried and / or tempered at 80 to 700 ° C. If necessary, the dried or tempered component can be fired. The firing conditions essentially depend on the chemical and mineralogical composition of the refractory mass as well as the shape and geometry of the component. After drying or tempering or firing, the prefabricated components according to the invention are ready for use. The unshaped refractory compositions according to the invention can be used in the furnaces and plants of the non-ferrous industry, steel industry, cement industry, glass industry, waste incineration plants, etc.

The preparation and the properties of the products according to the invention are explained below using a few examples. In the offsets of the examples, as is customary in ceramics, a "basic offset" is first produced, which is already 100%. In order to obtain variations, additives are added in different amounts to this basic offset. Their% details ^" refer to the 100% value of the basic approach.

example 1

4 self-flowing corundum concretes with variable BC components were produced. Their composition and grain structure were as follows:

Sintered corundum (T60) 1 - 3 mm 45.0% by weight

Sintered corundum (T60) 0.5 - 1 mm 10.0% by weight

Sintered corundum (T60) 0 - 0.3 mm 10.0% by weight Sintered corundum (T60) <45 by 12.0% by weight

Calcined alumina CTC 50 16.0% by weight

Calcium aluminate (CA 270 alumina cement) 5.5% by weight

Additives: Disperging aluminas (ADSl + ADW1 in a ratio of 3: 1) 1.5% by weight

All raw materials and additives are available under the names mentioned from ALCOA Germany.

The raw materials and additives were mixed with variable B ₄ C components, -325 mesh (<45 μm), from Wacker Chemie GmbH, Munich, and mixing water. It was shown that the amount of water required decreased with increasing BC content. Standard test specimens 50x50 mm were produced from the masses. The The test specimens were produced by pouring them into a plastic mold, curing them at room temperature for 24 hours, and then drying them at 110 ° C. for 24 hours. The dried test specimens were characterized by the determination of the cold compressive strength, KDF, (DIN EN 9935), bulk density, RD, (DIN EN 993) and open porosity, OP, (DIN EN 993). The results obtained are summarized in the table below.

BC additive mixing water KDF RD OP

(% By weight) (% by weight) (MPa) (g / cm3). *.

0 5.6 82 3.15 18.9

1 4.7 81 3.14 19.1

3 4.6 75 3.02 19.9

5 4.4 71 2.99 21.1

The results show that the amount of mixing water in the concretes according to the invention can be reduced by adding boron carbide. Corundum concretes with a relatively high BC content also have good property values.

Example 2

A bauxite refractory concrete was made with the following composition:

Sinter bauxite 1 - 3 mm 45.0% by weight

Sintered bauxite 0 - 1 mm 25.0% by weight

Sintered corundum T60 <45 by 12.0% by weight

Calcined alumina CTC 50 12.0% by weight CA 270 alumina cement 5.0% by weight

Additives: Disperging aluminas (ADS1 + ADW1 in the ratio 1: 1) 1.5% by weight

Sintered bauxite (sinter bauxite) is a commercially available product. Sintered corundum T60, calcined alumina CTC 50, alumina cement CA 270 and additives can be obtained, for example, from ALCOA Germany. 2% by weight of boron carbide from Wacker Chemie GmbH, Munich, were added to the mixture. The mixture was then made into a concrete with 5.7% by weight of mixing water. Cylindrical test crucibles for testing corrosion resistance were made from the concrete. As shown in Example 1, the production was carried out by pouring the liquefied concrete into a plastic mold. The casting mold was constructed in such a way that a round recess with a diameter of 30 mm and a depth of 10 mm was created on one side of the test cylinder. The depression was used to hold a test metal melt. After curing at room temperature, 24 h and drying at 110 ° C, 24 h, 20 g of pure aluminum powder were placed in the well of the crucible. The crucible was then aged at 800 ° C for 72 hours in an electric oven with no air. After cooling, the test crucible was examined for any signs of corrosion, such as chemical reaction with the metal and infiltration of the metal into the material structure. For comparison, a crucible test was made from the same refractory concrete without BC addition and examined under the same conditions. The bauxite B ₄ C refractory concrete according to the invention showed no infiltration and a significantly better corrosion resistance compared to the Al melt in comparison to the material without boron carbide.

Example 3

Spinel AR78 0 - 3 mm 40.0% by weight

Spinel AR78 0 - 1 mm 20.0% by weight Spinel AR78 0 - 0.5 mm 10.0% by weight

Sipnell AR78 <45 by 12.0% by weight

Calcined spinel / alumina CTC 55 12.0% by weight

CA 270 alumina cement 5.0% by weight Additives: Disperging aluminas (ADS1 + ADW1 in a ratio of 3: 1) 1.0% by weight

The spinel raw materials are a sintered Al ₂ 0 ₃ -rich magnesium-aluminum spinel, which is available from ALCOA Germany can be obtained. The other components, calcined spinel / alumina CTC 55, alumina cement and additives can also be obtained from this company. 3% by weight of zirconium boride from Wacker Chemie GmbH, Munich, were added to the mixture. The mixture was then 5.2

% By weight of mixing water processed into a concrete. Cylindrical test crucibles for testing corrosion resistance were made from the concrete. For this purpose, the concrete was filled into a plastic mold and then compacted on a vibrating table. The shape was constructed in such a way that a round recess with a diameter of 30 mm and a depth of 10 mm was created on one side of the test cylinder. The recess was used to hold a test slag. After curing at room temperature / 24 h and drying at 110 ° C / 24 h, 20 g of a ladle slag from the steel industry were placed in the well of the crucible. The crucible was then fired in air at 1500 ° C for 6 hours in an electric furnace. After cooling, the test crucible was examined for any signs of corrosion, such as chemical reaction with the slag and its infiltration into the material structure. For comparison, a crucible test was made from the same refractory concrete without ZrB ₂ and examined under the same conditions. The spinel concrete according to the invention with ZrB ₂ addition showed a significantly better infiltration and corrosion resistance compared to the material without addition.

Example 4

A chemically bound, basic mass with the following composition was produced:

Coarse grain, high-purity magnesia sinter 1 - 3 mm 50% by weight

Medium grain, high-purity magnesia sinter 0.2 - 0.5 mm 5% by weight

Fine grain, high-purity magnesia sinter <0.1 mm 40% by weight titanium boride <45 μm 5% by weight

The magnesia sinter is a sintered high-purity magnesia, for example from NEDMAG. Titanium boride (e.g. titanium di boride) can be obtained, for example, from Wacker Chemie GmbH, Munich.

The components were dry homogenized and then prepared into a sprayable mass by mixing with 12% by weight Na water glass. The mass was applied to a fired magnesia stone and fired at 1550 ° C for 2 hours. After the fire, the mass adhered very well to the stone surface and showed very good oxidation resistance and corrosion resistance compared to a steel converter slag. The mass is suitable for performing both cold and hot repairs of the refractory deliveries.

Example 5

Al ₂ 0 ₃ -SiC ramming mass with phosphate bond

There was a chemically bound Al ₂ 0 ₃ -SiC mass with the following

Composition made:

Coarse grain, sintered corundum (T60) 1 - 3 mm 45% by weight

Medium grain, sintered aluminum oxide (T60) 0.2 - 0.6 mm 10% by weight fine grain, sintered aluminum oxide (T60) <0.1 mm 30% by weight

Silicon carbide powder <45 μm 12% by weight

Silicon powder <45 μm 3% by weight

Sintered corundum raw materials can be obtained from ALCOA Germany.

A product from ESK-SiC GmbH was used as silicon carbide powder and a commercially available product was used as silicon powder. The components became dry with 3% by weight of ZrB ₂ (from Wacker

Chemie GmbH, Munich) and then processed by mixing with 6.5% by weight of a monoaluminum phosphate solution (50%) from BUDENHEIM into a tamped mass. Test specimens with a diameter of 50 mm and a height of 50 mm were produced from the mass by stamping in a steel mold. A round recess with a diameter of 30 mm and a depth of 10 mm was pressed in on one side of the test cylinder during the pressing process to receive the test slag. In the 20 g of a steel converter slag were placed in the well. The crucible was then fired at 1500 ° C in an electric furnace for 6 hours in air. For comparison, a crucible was made from the offset without ZrB ₂ and tested under the same conditions. After cooling, the test crucibles were examined for any signs of corrosion, such as chemical reaction with the slag and its infiltration into the material structure. The Al ₂ 0 ₃ SiC ramming mass according to the invention with ZrB ₂ showed a significantly better infiltration and corrosion resistance compared to the material without addition.

Example 6

A self-flowing corundum concrete B ₄ C and steel fiber additive with the following composition was examined.

Sintered corundum (T60) 1 - 3 mm 45.0% by weight

Sintered corundum (T60) 0.5 - 1 mm 10.0% by weight

Sintered corundum (TβO) 0-0.3 mm 10.0% by weight Sintered corundum TβO <45 μm 12.0% by weight

Calcined alumina CTC 50 15.0% by weight

CA 270 alumina cement 5.0% by weight

B4C, <45 μm 2.0% by weight additive dispersing aluminas (ADS1 + ADW 1 in the vehicle 1: 1) 1.0% by weight

The sources of supply for raw materials, additives and additives are as mentioned in the previous examples.

The raw materials and additives were dry premixed with 2.0% by weight of steel fibers (D = 0.3mm, length = 20mm) and then processed into a concrete with 6.7% by weight of mixing water. Standard test specimens 50x50 mm were made from the concrete. The test specimens were produced by pouring them into a

Plastic mold, curing at room temperature for 24 h, and then drying at 110 ° C, 24 h. The dried test specimens were determined by determining the cold compressive strength, KDF, (DIN EN 9935), bulk density, RD, (DIN EN 993), open porosity, OP, (DIN EN 993) and thermal shock resistance TWB (DIN EN 993-11). For comparison, test specimens without the addition of steel fibers were produced and examined under the same conditions. After drying, the test specimens had the following characteristic values:

with steel fibers without steel fibers

Cold compressive strength (MPa) 94 84

Bulk density (g / cm3) 2.91 2.85

Open porosity (%) 20.8 19.2

TWB (cycles) ^' > 20 14 ^'

The results show that the addition of steel fibers can improve the thermal shock resistance of the concretes according to the invention.

Claims

claims

1. Refractory mass, containing a coarse-grained refractory component (so-called coarse grain) and / or a medium-grained refractory component (so-called medium grain) and / or a fine-grained refractory component (so-called flour) and / or a fine-grained refractory component (so-called Fine grain) characterized in that the mass is carbon-free and comprises a refractory boron-containing, nitrogen-free component.

2. Composition according to claim 1, characterized in that the coarse-grained, medium-grained, fine-grained and fine-grained refractory component is selected from the group of, oxidic and non-oxidic, acidic or basic raw materials.

3. Mass according to claim 2, characterized in that the refractory components are selected from the group of basic metal oxides such as Sintered, melted magnesia,

Sintered, melted spinel, sintered dolomite, sintered lime, olivine or forsterite, the masses based on Al ₂ 0 ₃ with a variable Si0 ₂ and / or SiC content and their combinations.

4. Composition according to one of claims 1 to 3, characterized in that the boron-containing nitrogen-free component is selected from the group boron carbide, refractory borides and mixtures thereof.

5. Composition according to one of claims 1 to 4, characterized in that the boron-containing, nitrogen-free component is present in amounts of 0.1 to 30% by weight.

6. Composition according to one of claims 1 to 5, characterized in that it also comprises an additive which is preferably selected from the group consisting of metal powders, non-oxides such as, for example, nitrides, carbides, silicides, oxynitrides, Oxycarbide, metal fibers, plastic fibers and carbon fibers.

7. Composition according to claim 6, characterized in that the additive is present in amounts of 0.5 to 30 parts by weight.

8. Composition according to one of claims 1 to 7, characterized in that it also comprises a binder, preferably a liquid binder common in the refractory industry.

9. Composition according to one of claims 1 to 8, characterized in that it also comprises an additive, preferably selected from the group of plasticizers, setting regulators and dispersants.

10. Composition according to one of claims 1 to 9, characterized in that the coarse-grained refractory component is present in amounts <90% by weight.

11. Composition according to one of claims 1 to 10, characterized in that the medium-grain refractory component is present in amounts of <40 wt .-%.

12. Composition according to one of claims 1 to 11, characterized in that the fine-grained refractory component is present in amounts of <95 wt .-%.

13. Composition according to one of claims 1 to 12, characterized in that the fine-grained refractory component is present in amounts of <50 wt .-%.

14. Composition according to one of claims 1 to 13, characterized in that it also comprises water, preferably in an amount of up to 40% by weight.

5. Composition according to one of claims 1 to 14, characterized in that it also contains additives such as e.g. Liquefier, setting regulator, dispersant.