Refractory material, method for producing same, and use thereof

Abstract

The invention relates to a refractory material which is thermally treated at a temperature of at least 1300 °C, preferably 1300 °C to 1750 °C, such that the material has an acicular structure and a combination of a first phase, a second phase, and a third phase, wherein: the first phase comprises 2-10 wt.% C, <5 wt.% N, 30-40 wt.% O, 50-70 wt.% Al, and <5 wt.% Si, based on the total proportion of the first phase, the second phase comprises 1-7 wt.% C, 3-8 wt.% N, 25-35 wt.% O, 55-65 wt.% Al, and <5 wt.% Si, based on the total proportion of the second phase, and the third phase comprises <7 wt.% C, 14-28 wt.% N, 10-15 wt.% O, 52-63 wt.% Al, and <20 wt.% Si, based on the total proportion of the third phase, to a batch for producing the refractory material, to a main part produced from a batch, to a method for producing a refractory material, and to the use thereof.

Description

[0001]07.12.2023 / NL Refractory material, process for its production and use The present invention relates to a refractory material, a batch for producing a refractory material, a green body made from a batch, a process for producing a refractory material and the use of such materials. Refractory materials are used, for example, in industrial high-temperature processes and must therefore remain stable even under adverse conditions and at very high temperatures. They are used, for example, in the steel industry, where they are used, among other things, for the production of products such as functional products (e.g., perforated bricks or impact pots) and / or products for the lining and / or maintenance of steel ladles, tundishes, and other metallurgical units.Such metallurgical units lined with products made of refractory materials are in turn used to hold and process molten steel and other liquid metal products. Refractory materials therefore keep other substances and mixtures safe during their combustion, transformation, melting, blasting, firing, melting, and forming and must therefore withstand thermal, mechanical, and chemical stress. It is therefore desirable to provide a refractory material with good physical properties, such as high strength and high resistance to thermal shock, with which a variety of different refractory products can be manufactured. The present invention is therefore based on the object of providing a refractory material that has very good physical properties, such as in particular very good hot strength andHot abrasion resistance, good thermal shock resistance, and low thermal conductivity. Furthermore, it should also be possible to use the refractory material for a variety of different refractory products, especially more complex cast products. Therefore, it is also the object of the present invention that the refractory material with its advantageous properties can be obtained starting from a batch that has advantageous processing properties, such as, in particular, good flow properties. The invention solves this problem by a refractory material which is thermally treated at a temperature of at least 1300°C, preferably from 1300° to 1750°C, such that it has a needle-like structure and comprises a combination of a first phase, a second phase and a third phase, wherein the first phase contains 2-10 wt.% C, <5 wt.% N, 30-40 wt.-% O, ​​50-70 wt.% Al and <5 wt.% Si, based on the total proportion of the first phase, the second phase which comprises >1 wt.% C, 3-8 wt.% N, 25-35 wt.% O, 55-65 wt.% Al and <5 wt.% Si, based on the total proportion of the second phase, the third phase which comprises <7 wt.% C, 14-28 wt.% N, 10-15 wt.% O, 52-63 wt.% Al and <20 wt.% Si, based on the total proportion of the third phase. First, some of the terms used in the invention will be explained. The term “refractory material” is used in the present application in the way it is familiar to the person skilled in the art. It is therefore a material that is fire-resistant and high-temperature-resistant. The refractory material is preferably made from inorganic raw materials. In particular, the material can withstand high temperatures of at least 1500°C or higher without softening.The material preferably has a cone drop point greater than SK 17 (= ISO 150), which corresponds approximately to a temperature of 1500°C (cf. DIN 51060). The cone drop point can be determined according to ISO 528 and DIN EN 993-12. The material is therefore suitable for being in contact with liquid metal and steel products for a certain period of time without itself losing its external shape. In the context of the present invention, a "batch" is a shapeless or unshaped mass that is used to produce the refractory material. The term "green body" is used in the present application in the way that is familiar to the person skilled in the art. It is therefore a shaped or cast, but unfired mass that can still be easily processed.In the context of the present invention, a "phase" is a spatial region in a solid which differs from its surroundings both chemically and morphologically (i.e. in terms of shape, form and structure). The first phase preferably comprises 2-10 wt% C, 0.001-5 wt% N, 30-40 wt% O, 50-70 wt% Al and 0.001-5 wt% Si, based on the total proportion of the first phase. The second phase preferably comprises 1-7 wt% C, 3-8 wt% N, 25-35 wt% O, 55-65 wt% Al and 0.001-5 wt% Si, based on the total proportion of the second phase. The third phase preferably comprises 0.001-7 wt% C, 14-28 wt% N, 10-15 wt% O, 52-63 wt% Al, and 0.001-20 wt% Si, based on the total content of the third phase. According to the invention, the refractory material comprises a combination of the first phase, the second phase, and the third phase.According to the invention, it is preferred that the first phase comprises Al4O4C or consists of Al4O4C. According to the invention, it is further preferred that the second phase comprises Al. 28 C6N6O 21 includes or from Al 28 C6N6O 21According to the invention, it is further preferred that the third phase comprises SiAl6O2N6. According to the invention, it is further preferred that the third phase comprises a compound selected from SiAl6O2N6, SiAl5O2N5, SiAl4O2N4, Si3Al7O3N9 and mixtures thereof. The third phase preferably comprises SiAl6O2N6. According to the invention, it is further preferred that the third phase consists of a compound selected from SiAl6O2N6, SiAl5O2N5, SiAl4O2N4, Si3Al7O3N9 and mixtures thereof. The refractory material can comprise a fourth phase, wherein the fourth phase comprises <5 wt.% C, 26-36 wt.% N, <8 wt.% O, 56-66 wt.% Al and <5 wt.% Si, based on the total proportion of the fourth phase, and the fourth phase preferably comprises AlN or consists of AlN. Furthermore, the fourth phase may comprise 0.001-5 wt% C, 26-36 wt% N, 0.001-8 wt% O, 56-66 wt% Al, and 0.001-5 wt% Si, based on the total content of the fourth phase. The presence of the needle-like structure orPhases with a needle-like structure can preferably be determined by scanning electron microscopy. The composition of the phases is preferably determined by scanning electron microscopy (SEM) at an excitation voltage of 10 kV and a sample current of 1 nA with an energy-dispersive detector. The needle-like structure preferably has needles with a length in a range of 0.1-50 µm, preferably 0.1-30 µm, more preferably 2-30 µm and / or a thickness in a range of 0.01-8 µm, preferably 0.2-5 µm, measured by scanning electron microscopy at an excitation voltage of 10 kV and a sample current of 1 nA. A minimum ratio of lengths to thicknesses (at least for some) of the needles is preferably at least 4:1. Preferably, at least 20%, more preferably at least 40% of the needles of the needle-like structure have a minimum length to thickness ratio of at least 4:1.Preferably, at least 20%, more preferably at least 40% of the needles of the needle-like structure in an area of ​​at least 1000 μm x 1000 μm have a minimum ratio of the lengths to thicknesses of the needles of at least 4:1. This can be determined by means of scanning electron microscopy, with an excitation voltage of 10 kV and a sample current of 1 nA. Furthermore, the refractory material preferably has hole-like structures (or structures that appear circular on polished sections). The hole-like or circular-looking structures preferably comprise a (predominant) portion of the needle-like structures. In a preferred embodiment, a (predominant) portion of the needles is formed on the surfaces of the hole-like or circular-looking structures. According to the invention, it is preferred that the proportion of phases with a needle-like structure is at least 0.01 wt.%, preferably 0.1 wt.%, based on the total proportion of the refractory material.The refractory material preferably has an open porosity in a range of 10.0-25.0 vol.%, measured according to DIN EN ISO 1927-6, and / or a bulk density in a range of 2.95-3.70 g / cm. 3, measured according to DIN EN ISO 1927-6. The refractory material is preferably a refractory functional product, more preferably a refractory cast and / or pressed product, even more preferably a refractory product in the flow control sector, even more preferably a slide plate, interchangeable nozzles, shrouds, plugs, dip tubes, inner sleeves, weirs, dams, impact pots, and nozzles. The term "functional product" in the context of the present invention is to be understood as a product that is partially or completely made of the refractory material and has been subjected to shaping by casting and / or molding. The invention has the advantage thatthat the refractory material according to the invention has very good physical properties. In particular, the refractory material exhibits, for example, very good hot strength / hot abrasion resistance and, at the same time, very good thermal shock resistance. The refractory material according to the invention is high-temperature resistant and can withstand temperatures of at least 1700°C without softening. It has a needle-like structure with very stable phases that form in situ. The fine needles that form in many areas of the material are most likely responsible for the good thermal shock resistance. Furthermore, the refractory material according to the invention exhibits low thermal conductivity. This not only has the advantage that the refractory material has good insulation properties, but also leads tothat the casting performance of the products obtained from the refractory material is improved. This is because a low thermal conductivity of the material leads to the deposition of solid components or particles on the refractory material, i.e. undesirable "clogging", being avoided. The invention further relates to a batch for producing a refractory material according to the invention, preferably according to one of claims 1 to 8, wherein the batch comprises the following components: a) granular component in the coarse fraction with a particle size in a range of 0.5-10 mm, selected from MA spinel, sintered alumina, fine corundum, brown corundum, grey corundum, mullite, bauxite, andalusite, SiC, chamotte, zirconium-containing components and mixtures thereof; b) Granular component in the fine fraction with a particle size in a range of <0.5 mm, selected from sintered alumina, high-grade corundum, zirconium-containing components and mixtures thereof; c) Fine-particle Al2O3,preferably calcined alumina in the fine fraction with a particle size in a range of <0.5 mm; d) carbon, preferably graphite and / or carbon black, more preferably a mixture of graphite and carbon black, even more preferably a mixture of graphite and carbon black with a mixing ratio in a range of 1:2 to 2:1, even more preferably a mixture of graphite and carbon black with a mixing ratio of 1:1; e) metallic aluminum powder (Al powder); and f) silica sol (silica in aqueous colloidal suspension),Preferably silica containing SiO2 nanoparticles in an aqueous colloidal suspension. The batch according to the invention is preferably produced from a dry mass (preferably comprising components a) to e)) by mixing it with silica sol (silica in an aqueous colloidal suspension; comprising component f)). In the dry mass, the components are chemically unchanged. Only upon addition of the silica sol (silica in an aqueous colloidal suspension) does the mass bind, based on a so-called sol-gel reaction, occur. Within the scope of the present invention, the batch thus already contains all components that must be present for the production of the refractory material. The backfill comprises the granular component in the coarse fraction with a particle size in a range of 0.5-10 mm, selected from MA spinel, sintered alumina, fine corundum, brown corundum, grey corundum, mullite, bauxite, andalusite, SiC, chamotte,zirconium-containing components and mixtures thereof. The granular component in the coarse fraction is preferably selected from a group of non-basic components. The use of non-basic components results in better processability and a more favorable curing time after mixing with the silica sol (silica in an aqueous colloidal suspension). This is because the bonding process (so-called sol-gel process) is generally accelerated by basic components. The batch also includes the granular component in the fine fraction with a particle size in the range of <0.5 mm. This serves particularly for matrix filling. Furthermore, it has been determined that the granular component in the fine fraction improves the flow properties of the batch, especially during casting.positively influenced. Furthermore, the backfill contains carbon. Carbon is indispensable as a source for the formation of the in-situ formed phases. In a preferred embodiment, a mixture of graphite and carbon black with a mixing ratio in the range of 1:2 to 2:1 is used, more preferably a mixture of graphite and carbon black with a mixing ratio of 1:1. This results in a very good compromise between the achieved physical properties of the refractory material and the processing properties of the backfill. It was found that graphite has a positive influence on the wetting properties (and thus the infiltration and slagging resistance).while the more reactive soot positively influences the formation of the in-situ formed phases. Furthermore, the batch comprises metal powder containing aluminum. For example, an Al-Si alloy (with approx. 12% Si) in powder form can be used as the metal alloy. However, instead of the alloy, the batch can comprise a mixture of powdered Al-met and Si-met. The batch comprises metallic aluminum powder. The aluminum has the particularly advantageous function of preventing the degradation (or oxidation) of carbon. The powder preferably has a particle size of <0.1 mm, more preferably <0.075 mm, even more preferably <0.065 mm. Furthermore, the batch comprises silica sol (silica in aqueous colloidal suspension), preferably silica containing SiO2 nanoparticles in aqueous colloidal suspension. This is a suspension of fine amorphous,Non-porous and typically spherical silica particles in an aqueous phase. Colloidal silica is not the same as conventional (dried) silica (e.g., (dried) fumed silica). The silica sol (the silica in aqueous colloidal suspension) serves in particular as a mixing liquid and binder for the refractory material. A solids content (proportion of SiO2 particles) in the silica sol (in the aqueous colloidal silica suspension) is preferably in a range of 20 to 50 wt.%, more preferably 30 to 50 wt.%, based on the total weight of the silica sol. Replacing conventional silica with water with a silica sol, i.e., silica in aqueous colloidal suspension, is of considerable advantage. When using conventional silica, the metal (aluminum) would react with water in certain pH ranges after mixing the components. This reaction is highly exothermic.and hydrogen gas (H2) would also be produced. Furthermore, if aluminum were used, an aluminum oxide layer (Al2O3) would form in the edge area. These reactions must be avoided. Firstly, the formation of H2 is disadvantageous for safety reasons, and secondly, less aluminum would be available for the phases formed in situ. Furthermore, the exothermic reaction and gas formation would lead to the formation of cracks and layers in the green body. This is prevented by using a silica sol, i.e., a colloidal silica or a colloidal silica suspension. The batch may comprise one or more of the following components in the following amounts, based on the total proportion of the composition of the batch: a) 50-80 wt.%, preferably 53-70 wt.%, more preferably 55-67 wt.%, even more preferably about 59 wt.%,granular component in the coarse fraction with a particle size in a range of 0.5-10 mm; b) 5-35 wt.%, preferably 7-30 wt.%, more preferably 10-30 wt.%, even more preferably about 23 wt.%, granular component in the fine fraction with a particle size in a range of <0.5 mm; c) 0.05-4 wt.%, preferably 0.1-3 wt.%, more preferably 1-2.5 wt.%, even more preferably about 2 wt.%, finely divided Al2O3; d) 2-10 wt.%, preferably 3-8 wt.%, more preferably 3.5-6 wt.%, even more preferably about 4.5 wt.%, carbon; e) 2-8 wt.%, preferably 3-7 wt.%, more preferably 4-6 wt.%, even more preferably about 5 wt.%, a metallic aluminum powder (Al powder); f) 4-15 wt.%, preferably 5-12 wt.%, more preferably 6-8 wt.%, even more preferably about 7 wt.%, silica sol (silica in aqueous colloidal suspension), preferably silica containing SiO2 nanoparticles in aqueous colloidal suspension,wherein the solids content (proportion of SiO2 particles) is preferably in a range of 20 to 50 wt.%, more preferably 30 to 50 wt.%, based on the total weight of the silica sol (the aqueous colloidal silica suspension). The invention also relates to a green body produced from a batch according to the invention, preferably a batch according to claim 9 or 10, wherein the green body preferably has an open porosity of approximately 10-25 vol.%, measured according to DIN EN ISO 1927-6, and / or a bulk density in a range of 2.90-3.70 g / cm. 3 , preferably about 2.96 g / cm 3, measured according to DIN EN ISO 1927-6. The invention furthermore also relates to a process for producing a refractory material according to the invention, preferably a refractory material according to one of claims 1 to 8, wherein the process comprises the following steps: i. Providing a batch according to the invention, preferably according to one of claims 9 or 10; ii. Producing a green body from the batch, and iii. Heating the green body to a temperature of at least 1300°C, preferably to a temperature in a range from 1300°C to 1750°C. The provision of the batch according to the invention in step i. is preferably carried out starting from a dry mass (preferably comprising components a) to e)), which is produced by mixing with silica sol (silica in aqueous colloidal suspension; comprising component f)).Preferably, the production of the green body from the offset in step ii. involves casting and / or molding. The invention further relates to a refractory material which has a needle-like structure and comprises a combination of a first phase, a second phase and a third phase, wherein the first phase comprises 2-10 wt.% C, <5 wt.% N, 30-40 wt.% O, 50-70 wt.% Al and <5 wt.% Si, based on the total proportion of the first phase, the second phase comprises >1 wt.% C, 3-8 wt.% N, 25-35 wt.% O, 55-65 wt.% Al and <5 wt.% Si, based on the total proportion of the second phase, the third phase comprises <7 wt.% C, 14-28 wt.% N, 10-15 wt.% O, 52-63 wt.% Al and <20 wt.% Si, based on the total proportion of the third phase, produced by a process according to the invention, preferably a process according to claim 12.The invention also relates to the use of a refractory material according to the invention, preferably according to one of claims 1 to 8, of a green body produced from a batch according to one of claims 9 to 10 for the production of refractory products for steel applications, in particular steel ladles, tundishes, perforated bricks, CAS-OB bells, refractory products for the pig iron sector, in particular cast products, and / or refractory products for the flow control sector, in particular slide plates, interchangeable nozzles, shrouds, plugs, nozzles, dip tubes, inner sleeves, weirs, dams, impact pots and nozzles. In the context of the invention, products in the flow control sector are understood to mean refractory products that make it possible, for example, to contain liquid metal or steel products or to direct or prevent their flow.Products in the flow control sector require not only good physical properties, such as high strength, but also good processing properties of the mass to be processed in order to be able to manufacture the sometimes complexly shaped components. A key advantage of flow control products, preferably based on cast products, compared to ISO-pressed products, is seen in a significant reduction in costs. A further advantage of the invention is therefore that the batch according to the invention and / or the process according to the invention not only makes it possible to obtain refractory materials with very good physical properties, such as high hot strength, etc., but also to achieve good processing properties of the mass to be processed for the production of more complex components, in particular by casting.The invention will now be described by way of example using some advantageous embodiments with reference to the accompanying drawings. Fig. 1: shows an image of the refractory material according to the invention taken by light microscopy. Fig. 2: shows an image of a partial area shown in Fig. 1, taken by scanning electron microscopy. Fig. 3: an image of a further partial area of ​​the refractory material shown in Fig. 1, taken by scanning electron microscopy. Fig. 4: another image of the refractory material according to the invention taken by light microscopy. Fig. 5: an image of a region of the refractory material according to the invention taken by scanning electron microscopy. Fig. 6: an image of the other area marked in Fig. 4, taken by scanning electron microscopy. Fig. 7: another image of the refractory material according to the invention taken by light microscopy.8: A scanning electron microscopy image of the refractory material from Fig. 7. Fig. 9: The thermal shock resistance of the refractory material using a plug cold start test. Fig. 10: The thermal shock resistance of the refractory material using a further test for reusability. Fig. 11: The slag resistance of the refractory material according to the invention (left) compared to that of a known refractory material (right). Fig. 12: The results of a test with the refractory material according to the invention on softening behavior under pressure (compressive softening). Production of a refractory material: This article explains how a refractory material according to the invention can be produced starting from a batch according to the invention. First, a batch comprising the following components was produced: 58.6 wt.-% Granular component consisting of sintered alumina in the coarse fraction with a particle size in a range of 0.5-10 mm 9.2 wt.% sintered alumina (<0.5 mm) 14.0 wt.% fine corundum (<0.2 mm) 1.9 wt.% calcined alumina 1A 2.3 wt.% graphite Hunan 80 / 200 GBK 2.3 wt.% carbon black Thermal pearled 4.7 wt.% metallic aluminum powder (Al met) (<0.063 mm) 7.0 wt.% silica sol (silica in aqueous colloidal suspension), with 40 wt.% solids content (proportion of SiO2 particles), based on the total weight of the silica sol (the aqueous colloidal silica suspension). The batch was obtained by mixing a silica sol (silica in an aqueous colloidal suspension) containing SiO2 nanoparticles with a dry mass containing the remaining components of the batch. A green body was then produced from this batch by casting.The green body was then heated to a temperature of 1500°C to obtain the finished refractory material. Physical properties: The following shows the physical properties of a green body according to the invention and a refractory material according to the invention. For comparison, the physical data of a known, non-inventive material (DELTEK A115 from RHI Magnesita) are also given. Table 1: Physical properties of a green body according to the invention, a refractory material according to the invention, and a comparison material. Inventive Comparative material Material material (DELTEK A115) Green body after drying at 110°C, according to DIN EN ISO 1927-5 Bulk density (DIN EN ISO 1927-6) 2.96 2.53 [g / cm 3] Open porosity (DIN EN ISO 14.0 17.3 1927-6) [Vol.%] Cold compressive strength (DIN EN ISO 35.0 - 1927-6) [MPa] Cold bending strength (DIN EN ISO 5.0 8.4 1927-6) [MPa] Hot bending strength at 1500°C in a reducing atmosphere 17.0 8.0 (with cast samples according to DIN EN ISO 1927-5, format 130x20x20mm, measuring principle according to ISO 5013) [MPa] after heating to 1000°C in a reducing atmosphere, according to DIN EN ISO 1927-5 Bulk density (DIN EN ISO 1927-6) 3.0 - [g / cm 3 ] Open porosity (DIN EN ISO 13.0 - 1927-6) [Vol.%] Cold compressive strength (DIN EN ISO 170.0 - 1927-6) [MPa] Cold bending strength (DIN EN ISO 24.0 - 1927-6) [MPa] after heating to 1500°C in a reducing atmosphere, according to DIN EN ISO 1927-5 Bulk density (DIN EN ISO 1927-6) 3.0 - [g / cm 3] open porosity (DIN EN ISO 13.0 - 1927-6) [Vol.%] cold compressive strength (DIN EN ISO 140 - 1927-6) [MPa] cold bending strength (DIN EN ISO 24.0 - 1927-6) [MPa] thermal conductivity (acc. to Dr. Klasse*) [W / mK]: 200°C 5.2 14.7 400°C 5.2 13.7 600°C 4.9 12.4 800°C 4.6 12.0 1000°C 4.7 11.7 *Klasse, F.; Heinz, A.; Hein, J.: Comparison method for determining the thermal conductivity of ceramic materials. Ber. DKG 34 (1957), pp. 183-189. Table 1 shows that the refractory material according to the invention exhibits high strength. Furthermore, the refractory material exhibits only low thermal conductivity compared to the known material. The significantly lower thermal conductivity of the refractory material according to the invention ensures better insulation properties and thus has a positive influence on the flow properties of the material, as undesirable clogging can be prevented. Clogging refers to the deposition of solid components orParticles in a component or pouring system that can disrupt the casting process and thus reduce the casting performance of the refractory material. Measurement methods: For measurements in accordance with DIN EN ISO 1927-6, geometry D specified in this standard was used. The refractory material was examined using light and scanning electron microscopy. Light microscopy examinations were carried out using a NIKON Eclipse LV150. Scanning electron microscopy analyses were performed using a JEOL JSM-6460 or a JEOL JSM-7900F scanning electron microscope. The composition of the individual phases was determined using scanning electron microscopy at an excitation voltage of 10 kV and a sample current of 1 nA with an energy-dispersive detector. The scanning electron microscopy images were generated using a BSE detector. Fig.Figure 1 shows a light microscopy image of a refractory material according to the invention, revealing the needle-like structure of the material. In particular, areas with hole-like or circular-looking structures can also be seen, in which the needle-like structures of the material are preferably formed. The needles preferably have a small thickness in a range of 0.01-8 µm, more preferably 0.2-5 µm. It is assumed that the fine needles that form in many areas are most likely responsible for the very good thermal shock resistance of the refractory material. In addition, it is assumed that the circular structures in the refractory material can prevent crack propagation. Figure 2 shows a scanning electron microscopy image of the refractory material from Figure 1, wherein Figure 2 shows the right-hand area of ​​the areas marked in Figure 1. Figure 2 shows the right-hand area of ​​the areas marked in Figure 1.2, the needle-like structure of the material is even more clearly visible. In Fig. 2, areas 1 and 2 are shown, which correspond to the first phase, in particular the Al4O4C phase. Fig. 3 also shows an image of the refractory material from Fig. 1, created by scanning electron microscopy. The section shown in Fig. 3 corresponds to the left of the areas marked in Fig. 1. The section shows a structure that appears circular, on the surface or in the middle of which a needle-like structure has formed in-situ. In areas 1 and 2 shown in Fig. 3, phases are present that correspond to the second phase, in particular the Al. 28 C6N6O 21-phase. Fig. 4 shows a further image of the refractory material according to the invention taken by light microscopy, from which further areas with a hole-like structure can be seen, in which the needle-like structures of the material have formed in situ. Fig. 5 shows an image of the upper area marked in Fig. 4, taken by scanning electron microscopy. In this area too, the refractory material has a needle-like structure. In area 1 shown in Fig. 5, a phase is present which corresponds to the second phase, in particular the Al 28 C6N6O 21-phase. Furthermore, Fig. 5 also shows the region 2 in which a phase is present which corresponds to the third phase, in particular the SiAl6O2N6 phase. Fig. 6 also shows an image of the refractory material from Fig. 4, produced by scanning electron microscopy. The section shown in Fig. 6 corresponds to the lower of the areas marked in Fig. 4. In this area, the refractory material also has a needle-like structure. The section shows a circular-looking structure, on the surface or in the center of which a multitude of fine needles have formed. In the region 1 shown in Fig. 6, a phase is present which corresponds to the second phase, in particular the Al 28 C6N6O 21-phase. Furthermore, Fig. 6 shows region 2 in which a phase is present which corresponds to the third phase, in particular the SiAl6O2N6 phase. Furthermore, Fig. 6 also shows region 3 in which a phase is present which corresponds to the fourth phase, in particular the AlN phase. Fig. 7 shows a further image of the refractory material according to the invention taken by light microscopy, from which a circular region can be seen in which the needle-like structure of the refractory material is again present. Fig. 8 again shows an image of the refractory material with a needle-like structure shown in Fig. 7, produced by BSE scanning electron microscopy. Fig. 8 shows regions 1 and 3 which correspond to the first phase, in particular the Al4O4C phase. Furthermore, regions 2 and 4 are also shown in Fig. 8, which correspond to the third phase, in particular the SiAl6O2N6 phase.Thermal shock resistance tests: In the following tests, the thermal shock resistance of the refractory material according to the invention was tested. a. Plug cold start test: In a first test, the refractory material, in the form of a plug, was directly immersed in liquid steel at a temperature of 1650°C without preheating. The refractory material was then removed from the liquid steel and cooled to room temperature. This process was repeated in three cycles. The refractory material according to the invention shows very good thermal shock resistance (see Fig. 9). b. Reusability test: In a further test, the refractory material, in the form of a steel ladle, this time with preheating, was immersed in liquid steel at a temperature of 1650°C. The refractory material was then removed from the liquid steel and cooled to room temperature.This process was repeated in three cycles. The refractory material according to the invention also demonstrated very good thermal shock resistance in this test (see Fig. 10). Slag resistance test: Slag resistance is the ability of the refractory material to withstand the damaging effects of molten slag. Slag resistance is determined by the volume or weight loss of a refractory material upon exposure to slag. In the present test, the refractory material according to the invention was tested against both an acidic (C / S = 0.8) and a basic slag composition (C / S = 3.2). In addition to the refractory material according to the invention (Fig. 11, left), a known refractory material for steel ladles (COMPRIT 185HMV from RHI Magnesita) (Fig. 11, right) was also tested as a reference material.The refractory material according to the invention demonstrated very good slag resistance, particularly in comparison to the known refractory material for steel ladles (comparison material COMPRIT 185HMV from RHI Magnesita) (see Fig. 11). Pressure softening test (softening behavior under pressure): Furthermore, a pressure softening test was conducted with the refractory material. For this purpose, the refractory material according to the invention and a known refractory material (ANKO 85MR5A from RHI Magnesita) were used as reference materials. The test was carried out with a sample cast in accordance with DIN EN ISO 1927-5. The sample was dried at a temperature of 110°C in accordance with DIN EN ISO 1927-5.Test specimen: cylinder (height (h): 50 mm, diameter (d): 40 mm, inner bore: 16 mm, measurement method according to ISO 5013) The measurements for softening behavior under pressure (compression softening) were carried out according to DIN EN ISO 1893. A load of 0.2 MPa and a heating rate of 5°C / min in a reducing atmosphere were selected. The result was a T0.5 value of >1700°C. This is the temperature at which the maximum thermal expansion of the test specimen has decreased by 0.5%. The maximum temperature of the measurement is limited to 1700°C. In contrast to the known refractory material, no softening could be detected with the material according to the invention up to a temperature of 1700°C (Fig. 12). Test to measure the thermal conductivity according to Dr. Class: The thermal conductivities of the material according to the invention and the comparison material (DELTEK A115 from RHI Magnesita) given in Table 1 were determined according to the method of Dr.Class (Klasse, F.; Heinz, A.; Hein, J.: Comparative method for determining the thermal conductivity of ceramic materials. Ber. DKG 34 (1957), pp. 183–189). The values ​​given for 1000°C were extrapolated.

Claims

Claims 1. Refractory material which is thermally treated at a temperature of at least 1300°C, preferably from 1300°C to 1750°C, such that it has a needle-like structure and comprises a combination of a first phase, a second phase and a third phase, wherein: the first phase comprises 2-10 wt% C, <5 wt% N, 30-40 wt% O, 50-70 wt% Al and <5 wt% Si, based on the total proportion of the first phase, the second phase comprises 1-7 wt% C, 3-8 wt% N, 25-35 wt% O, 55-65 wt% Al and <5 wt% Si, based on the total proportion of the second phase, and the third phase comprises <7 wt% C, 14-28 wt% N, 10-15 wt% O, 52-63 wt% Al and <20 Wt.% Si, based on the total proportion of the third phase.

2. Refractory material according to claim 1, characterized in that the first phase comprises Al4O4C or consists of Al4O4C. 3.Refractory material according to claim 1 or 2, characterized in that the second phase is Al. 28 C6N6O 21 encompasses or consists of Al 28 C6N6O 21 4. Refractory material according to one of claims 1 to 3, characterized in that the third phase comprises a compound selected from SiAl6O2N6, SiAl5O2N5, SiAl4O2N4, Si3Al7O3N9 and mixtures thereof or consists of a compound selected from SiAl6O2N6, SiAl5O2N5, SiAl4O2N4, Si3Al7O3N9 and mixtures thereof.

5. Refractory material according to one of claims 1 to 4, characterized in that the refractory material comprises a fourth phase, wherein the fourth phase comprises <5 wt% C, 26-36 wt% N, <8 wt% O, 56-66 wt% Al and <5 wt% Si, based on the total proportion of the fourth phase, and the fourth phase preferably comprises AlN or consists of AlN.

6. Refractory material according to one of claims 1 to 5, characterized in that the needle-like structure has needles with a length in a range of 0.1-50 µm, preferably 0.1-30 µm, more preferably 2-30 µm, and / or a thickness in a range of 0.01-8 µm, preferably 0.2-5 µm, measured by scanning electron microscopy, at an excitation voltage of 10 kV and a sample current of 1 nA.

7. Refractory material according to one of claims 1 to 6, characterized in that a minimum ratio of lengths to thicknesses is at least 4:1 for at least some of the needles. 8.Refractory material according to one of claims 1 to 7, characterized in that the proportion of phases with an acicular structure is at least 0.01 wt.%, preferably 0.1 wt.%, based on the total proportion of the refractory material.

9. Batch for producing a refractory material according to one of claims 1 to 8, wherein the batch comprises the following composition: a) Granular component in the coarse fraction with a particle size in a range of 0.5-10 mm, selected from MA spinel, sintered alumina, fused alumina, and brown alumina. Grey corundum, mullite, bauxite, andalusite, SiC, chamotte, zirconium-containing components and mixtures thereof; b) Granular component in the fine fraction with a particle size in a range of <0.5 mm, selected from sintered alumina, noble corundum, zirconium-containing components and mixtures thereof; c) Finely divided Al2O3, preferably calcined alumina in the fine fraction with a particle size in a range of <0.5 mm; d) Carbon, preferably graphite and / or carbon black, more preferably a mixture of graphite and carbon black, even more preferably a mixture of graphite and carbon black with a mixing ratio in a range of 1:2 to 2:1, even more preferably a mixture of graphite and carbon black with a mixing ratio of 1:1; e) Metallic aluminum powder (Al powder); and f) silica sol (silica in an aqueous colloidal suspension), preferably silica containing SiO2 nanoparticles in an aqueous colloidal suspension. 10.Batch according to claim 9, characterized in that one or more of the following components are present in the following amounts, based on the total proportion of the composition of the batch: a) 50-80 wt.%, preferably 53-70 wt.%, more preferably 55-67 wt.%, even more preferably about 59 wt.%, granular component in the coarse fraction. with a particle size in a range of 0.5-10 mm; b) 5-35 wt.%, preferably 7-30 wt.%, more preferably 10-30 wt.%, even more preferably about 23 wt.%, granular component in the fine fraction with a particle size in a range of <0.5 mm; c) 0.05-4 wt.%, preferably 0.1-3 wt.%, more preferably 1-2.5 wt.%, even more preferably about 2 wt.%, finely divided Al2O3; d) 2-10 wt.%, preferably 3-8 wt.%, more preferably 3.5-6 wt.%, even more preferably about 4.5 wt.%, carbon; e) 2-8 wt.%, preferably 3-7 wt.%, more preferably 4-6 wt.%, even more preferably about 5 wt.%, metallic aluminum powder; f) 4-15 wt.%, preferably 5-12 wt.%, more preferably 6-8 wt.%, even more preferably about 7 wt.%, silica sol (silica in aqueous colloidal suspension), preferably silica containing SiO2 nanoparticles in aqueous colloidal suspension, wherein the solids content (proportion of SiO2 particles) is preferably in a range of 20 to 50 wt. %, more preferably 30 to 50 wt. %, based on the total weight of the aqueous colloidal silica suspension.

11. Green body produced from a batch according to claim 9 or 10, characterized in that the green body preferably has one or more of the following properties:. - an open porosity of approximately 10-25 vol%, measured according to DIN EN ISO 1927-6; - a bulk density in the range of 2.90-3.70 g / cm 3 , preferably about 2.96 g / cm 3 ,measured according to DIN EN ISO 1927-6.

12. A method for producing a refractory material according to any one of claims 1 to 8, wherein the method comprises the following steps: i. Providing a batch according to any one of claims 9 or 10; ii. Producing a green body from the batch; and iii. Heating the green body to a temperature of at least 1300°C, preferably to a temperature in a range of 1300°C to 1750°C. 13.Use of a refractory material according to one of claims 1 to 8, of a green body produced from a batch according to one of claims 9 to 10 for the production of refractory products for steel applications, in particular steel ladles, distributors, perforated bricks, CAS-OB bells, refractory products for the pig iron sector, in particular cast products, and / or refractory products for the flow control sector, in particular slide plates, interchangeable nozzles, shadow tubes, plugs, dip tubes, inner sleeves, weirs, dams, impact pots and nozzles.

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