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 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, to a batch composition for producing a refractory material, to a green body produced from a batch composition, to a method for producing a refractory material, and to the use of such a refractory material.

Description

[0001] Refractory material, process for its manufacture and use thereof

[0002] The present invention relates to a refractory material, a batch for producing a refractory material, a green body produced from a batch, a method for producing a refractory material and the use of such.

[0003] 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.

[0004] They are used, for example, in the steel industry, where they are used, among other things, to manufacture 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 contain 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 shaping and must therefore withstand thermal, mechanical and chemical stress.

[0005] 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 wide variety of different refractory products can be manufactured.

[0006] The present invention is therefore based on the object of providing a refractory material which has very good physical properties, such as in particular very good hot strength or hot abrasion resistance, good thermal shock resistance and low thermal conductivity. Furthermore, it should also be possible to use the refractory material for a large number of different refractory products, in particular also 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 which has advantageous processing properties, such as in particular good flow properties.It is also the object of the present invention to produce a green body from a batch which has advantageous physical and mechanical properties, such as increased strength (in particular high cold compression and cold bending strength) after drying, so that, along with this, improved handling and easier processing of the green body into the refractory material (and thus into a variety of different refractory products as described above) are made possible.

[0007] 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 comprises 2-10 wt.% C, <5 wt.% N, 30-40 wt.% 0, 50-70 wt.% Al and <5 wt.% Si, based on the total proportion of the first phase, the second phase >1 wt.% C, 3-8 wt.% N, 25-35 wt.% 0, 55-65 wt.% Al and <5 wt.% Si, based on the total proportion of the second phase, the third phase <7 wt.% C, 14-28 wt.% N, 10-15 wt.% 0, 52-63 wt.% Al and <20 wt.% Si, based on the Total share of the third phase.

[0008] First, some terms used in the context of the invention will be explained.

[0009] The term "refractory material" is used in this application as it is familiar to the person skilled in the art. It is therefore a material that is fire-resistant and resistant to high temperatures. 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 51 060). The cone drop point can be determined according to ISO 528 and DIN EN 993-12. The material is thus suitable for being in contact with liquid metal and steel products for a certain period of time without losing its external shape.

[0010] In the context of the present invention, a "batch" is a shapeless or unshaped mass used to produce the refractory material.

[0011] The term "green body" is used in this application in the manner familiar to the person skilled in the art from the prior art. It is thus a molded or cast-in-mold, but unfired mass that can still be easily processed. The term "green body after drying" is used in this application to mean a green body that has been dried to constant mass at a temperature of (110 ± 5) °C according to DIN EN ISO 1927-5.

[0012] 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., by form, shape and structure).

[0013] Preferably, the first phase 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 content of the first phase.

[0014] Preferably, the second phase comprises 1-7 wt% C, 3-8 wt% N, 25-35 wt% 0, 55-65 wt% Al and 0.001-5 wt% Si, based on the total content of the second phase.

[0015] Preferably, the third phase comprises 0.001-7 wt% C, 14-28 wt% N, 10-15 wt% 0.52-63 wt% Al and 0.001-20 wt% Si, based on the total content of the third phase.

[0016] According to the invention, the refractory material comprises a combination of the first phase, the second phase and the third phase.

[0017] According to the invention, it is preferred that the first phase comprises A14O4C or consists of A14O4C.

[0018] According to the invention, it is further preferred that the second phase comprises Al₆Cg₆N₆Gi or consists of Al₆Cg₆N₆Gi. According to the invention, it is further preferred that the third phase comprises a compound selected from SiAl₆O₂N₆, SiAl₅O₂N₆, SiAl₅O₂N₆, SiAl₅O₂N₆, and mixtures thereof. According to the invention, it is further preferred that the third phase comprises SiAl₆O₂N₆ or consists of SiAl₅O₂N₆.

[0019] The refractory material may comprise a fourth phase, wherein the fourth phase comprises <5 wt% C, 26-36 wt% N, <8 wt% 0, 56-66 wt% Al and <5 wt% Si, based on the total proportion of the fourth phase, and the fourth phase preferably comprises or consists of AIN.

[0020] Furthermore, the fourth phase may comprise 0.001-5 wt% C, 26-36 wt% N, 0.001-8 wt%, 0.56-66 wt% Al and 0.001-5 wt% Si, based on the total content of the fourth phase.

[0021] The presence of the needle-like structure or phases with a needle-like structure can preferably be determined by scanning electron microscopy.

[0022] Preferably, the composition of the phases is 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.

[0023] The needle-like structure preferably has needles of a length in a range of 0.1-50 pm, preferably 0.1-30 pm, more preferably 2-30 gm and / or a thickness in a range of 0.01-8 gm, preferably 0.2-5 gm, measured by scanning electron microscopy, at an excitation voltage of 10 kV and a sample current of 1 nA.

[0024] Preferably, a minimum ratio of length to thickness (at least for some) of the needles is at least 4:1. Preferably, at least 20%, more preferably at least 40% of the needles in the needle-like structure have a minimum ratio of length to thickness of at least 4:1. Preferably, at least 20%, more preferably at least 40% of the needles in the needle-like structure in a range of at least 1000 pm x 1000 μm have a minimum ratio of length to thickness of the needles of at least 4:1. This can be determined by scanning electron microscopy, at an excitation voltage of 10 kV and a sample current of 1 nA.

[0025] Furthermore, the refractory material preferably has hole-like structures (or structures that appear circular on polished sections). Preferably, the hole-like or circular-looking structures 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.

[0026] According to the invention, it is preferred that a proportion of the 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.

[0027] 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.

[0028] The refractory material preferably comprises refractory functional products, more preferably refractory cast and / or pressed products, even more preferably refractory products in the flow control sector, and even more preferably slide plates, 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 entirely made from the refractory material and has been shaped by casting and / or molding.

[0029] The invention has the advantage that the refractory material according to the invention has very good physical properties. In particular, the refractory material displays, 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.

[0030] 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 to improved casting performance of the products obtained from the refractory material. This is because low thermal conductivity of the material prevents the deposition of solid components or particles on the refractory material, i.e., undesirable "clogging."

[0031] 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, the batch comprising 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 (magnesium aluminate 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, fine 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 from 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); f) Dry phenolic resin binder, preferably dry powdered phenolic resin binder; and g) Silica sol (silica in aqueous colloidal suspension), preferably silica containing SiO2 nanoparticles in aqueous colloidal suspension.;

[0032] The batch according to the invention is preferably produced from a dry mass (preferably comprising components a) to f)) by mixing with silica sol (silica in aqueous colloidal suspension; comprising component g)). In the dry mass, the components are chemically unchanged. Only through the addition of the silica sol (the silica in aqueous colloidal suspension) does the mass bind, which is based on a so-called sol-gel reaction. In the context of the present invention, the batch therefore already contains all the components that must be present for the production of the refractory material.

[0033] The batch comprises the granular component in the coarse fraction with a particle size in a range of 0.5-10 mm, selected from MA spinel (magnesium aluminate 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 advantageous curing time after mixing with the silica sol (silica in an aqueous colloidal suspension). This is because the bonding process (the so-called sol-gel process) is generally greatly accelerated by basic components; the use of suitable non-basic components can therefore achieve an optimum balance between processability and curing time.

[0034] The backfill also includes a granular component in the fine fraction with a particle size in the range of <0.5 mm. This serves primarily as matrix filler. Furthermore, it has been determined that the granular component in the fine fraction has a positive effect on the flow properties of the backfill, particularly during casting.

[0035] The backfill also contains carbon. Carbon is an essential source for the formation of the in-situ formed phases. In a preferred embodiment, a mixture of graphite and soot is used with a mixing ratio in a range of 1:2 to 2:1, more preferably a mixture of graphite and soot 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 tends to have a positive influence on the wetting properties (and thus the infiltration and slagging resistance), while the more reactive soot has a positive influence on the formation of the in-situ formed phases.

[0036] The batch further comprises metallic aluminum powder. The metallic aluminum powder has the particularly advantageous function of preventing the decomposition (or oxidation) of carbon. The aluminum powder preferably has a particle size of <0.1 mm, more preferably <0.075 mm, and even more preferably <0.065 mm.

[0037] The batch also contains dry (preferably powdered) phenolic resin binder. The dry (preferably powdered) phenolic resin binder has the particularly advantageous function of significantly increasing the strength of the green body after drying. The phenolic resin binder used is, for example, a commercially available phenol-formaldehyde resin of the novolak type. An example of such a dry (preferably powdered) phenolic resin binder is Borofen BLR 3509. By adding this binder, the strength of the green body is significantly increased, making it easier to handle and transport after drying. This is reflected, among other things, in the greatly increased cold compressive and cold bending strength of the green body compared to a green body produced from a batch without the addition of this binder.In this way, the scrap rate in the production of refractory material due to broken green bodies can be significantly reduced. Surprisingly, it has been found that even a small addition of binder is sufficient to achieve a significant beneficial effect on the strength of the green body. At the same time, this addition does not negatively affect the refractory material's refractoriness.

[0038] The batch also includes silica sol (silica in an aqueous colloidal suspension), preferably silica containing SiO2 nanoparticles in an 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 (silica in an aqueous colloidal suspension) serves primarily as a mixing liquid and binder for the refractory material.

[0039] Preferably, a solids content (proportion of SiO2 particles) in the silica sol (in the aqueous colloidal silica suspension) is in a range of 20 to 50 wt.%, more preferably 30 to 50 wt.%, based on the total weight of the silica sol.

[0040] Replacing conventional silica with water with a silica sol, i.e. silica in an aqueous colloidal suspension, is a considerable advantage. This is because if conventional silica were used, the metal (aluminium) would react with water after the components have been mixed in certain pH ranges. This reaction is highly exothermic, and hydrogen gas (H2) would also be produced. Furthermore, if aluminum were used, an aluminum oxide layer (A12O3) 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 avoided by using a silica sol, i.e. colloidal silica ora colloidal silica suspension.

[0041] 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

[0042] 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

[0043] 19 wt.%, granular component in the fine fraction with a particle size in a range of <0.5 mm; c) 0.05-15 wt.%, preferably 2-12 wt.%, more preferably 5-10 wt.%, even more preferably about

[0044] 7 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) 3-10 wt.%, preferably 4-9 wt.%, more preferably 5-8 wt.%, even more preferably about 5 wt.%, metallic aluminum powder (Al powder); f) 0.1-4 wt.%, preferably 0.2-2 wt.%, more preferably 0.3-1 wt.%, even more preferably about 0.5 wt.%, dry (preferably powdered) phenolic resin binder; g) 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).

[0045] 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 after drying preferably has an open porosity of about 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 2.98 g / cm 3 , measured according to DIN EN ISO 1927-6.

[0046] After drying, the green body preferably has a cold compressive strength of greater than 40 MPa, more preferably greater than 50 MPa, particularly preferably greater than 60 MPa, measured according to DIN EN ISO 1927-6, and / or a cold bending strength of greater than 6 MPa, more preferably greater than 8 MPa, particularly preferably greater than 9 MPa, measured according to DIN EN ISO 1927-6. These properties of the green body result in good strength and thus very good handling and transportability of the green body.

[0047] The invention further relates to a method for producing a refractory material according to the invention, preferably a refractory material according to one of claims 1 to 8, the method comprising 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.

[0048] The preparation of the batch according to the invention in step i . preferably takes place starting from a dry mass (preferably comprising components a ) to f ) ) ) , which is produced by mixing with silica sol (silica in aqueous colloidal suspension; comprising component g ) ).

[0049] Preferably, the production of the green body from the batch in step ii involves casting and / or molding.

[0050] In step iii of the process, the green body is heated to a temperature of at least 1300 ° C. The green body is preferably heated to a temperature in the range from 1300 to 1750 ° C. This makes it possible, in particular, to obtain the properties of the refractory material according to the invention. The green body is preferably heated in a gas atmosphere comprising air with a reduced oxygen content. The reduction of the oxygen content in the air serves to prevent external oxidation of the green body. The reduction of the oxygen content can be achieved, for example, by embedding the green body in coal grit.

[0051] The invention furthermore also 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 contains 2-10 wt.% C, <5 wt.% N, 30-40 wt.% O,

[0052] 50-70 wt% Al and <5 wt% Si, based on the total content of the first phase, the second phase >1 wt% C, 3-8 wt% N, 25-35 wt% O,

[0053] 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 13.

[0054] 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, shadow tubes, plugs, nozzles, immersion pipes, inner sleeves, weirs, dams, impact pots and nozzles.

[0055] For the purposes of the invention, flow control products are understood to be refractory products that make it possible, for example, to contain liquid metal or steel products or to direct or prevent their flow. Flow control products require not only good physical properties, such as high strength, but also good processing properties of the material 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 cost reduction.

[0056] A further advantage of the invention is therefore that with the batch according to the invention and / or the method according to the invention, not only can refractory materials with very good physical properties, such as high hot strength, etc., be obtained, but also good processing properties of the mass to be processed can be achieved for the production of more complex components, in particular by casting.

[0057] The invention will now be described by way of example with reference to some advantageous embodiments and the accompanying drawings. They show:

[0058] Fig. 1: a photograph of the refractory material according to the invention taken by light microscopy.

[0059] Fig. 2: a scanning electron microscopy image of a portion shown in Fig. 1.

[0060] Fig. 3: another image of the refractory material according to the invention taken by light microscopy.

[0061] Fig. 4: a scanning electron microscopy image of the other area marked in Fig. 3.

[0062] Fig. 5: The slag resistance of the refractory material according to the invention (left) compared to that of a known refractory material (right). Fig. 6: The results of a test with the refractory material according to the invention and comparison materials on softening behavior under pressure (compression softening).

[0063] Production of a refractory material:

[0064] This document explains how a refractory material according to the invention can be produced starting from a batch according to the invention.

[0065] First, a batch was prepared comprising the following components:

[0066] 58.4 wt.% Granular component consisting of sintered alumina in

[0067] Coarse fraction with a particle size in a range of 0.5-10 mm

[0068] 9.4% by weight of sintered alumina (<0.5 mm)

[0069] 8.9 wt.% corundum (<0.2 mm)

[0070] 6.5 wt% calcined alumina 1A

[0071] 2.3% by weight graphite Hunan 80 / 200 GBK

[0072] 2.3 wt.% carbon black thermally pearled

[0073] 4.7 wt% metallic aluminum powder (Al met) (<0.063 mm)

[0074] 0.5 wt.% dry (powdered) phenolic resin binder 7.0 wt.% silica sol (silica in aqueous colloidal

[0075] Suspension) , with 40 wt.% solids content (proportion of SiO2 particles) , based on the total weight of the silica sol (the aqueous colloidal silica suspension) .

[0076] The batch was obtained by mixing a silica sol (silica in an aqueous colloidal suspension) containing SiO2 nanoparticles with a dry mass comprising 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 in a gas atmosphere (air with reduced oxygen content). The reduction of the oxygen content in the gas atmosphere was achieved by embedding the green body in coal grit. In this way, the refractory material according to the invention was obtained.

[0077] Physical properties:

[0078] The following shows the physical properties of a green body according to the invention and a refractory material according to the invention, which were produced by the process described above. For comparison, the physical data of two refractory materials not according to the invention are also compared. These are DELTEK A115 from RHI Magnesita and a green body and a refractory material, respectively, which were produced from a batch without the addition of dry (powdered) phenolic resin binder by the process described above. Table 1: Physical properties of a green body according to the invention, a refractory material according to the invention and two comparison materials.

[0079] *Klasse , F . ; Heinz , A. ; Hein, J . : Comparison method for determining the thermal conductivity of ceramic materials . Ber . DKG 34 ( 1957 ) , pp . 183 - 189 .

[0080] Table 1 shows that the green body according to the invention has a significantly higher strength after drying than a green body which was produced from a batch without the addition of dry (powdered) phenolic resin binder. This is reflected in the significantly increased values ​​for the cold compressive and cold bending strength and thus enables undamaged transport of such green bodies according to the invention to the customer as well as safe use of such green bodies according to the invention by the customer. In addition, the refractory material according to the invention has only a low thermal conductivity compared to the known material DELTEK A115. The considerably 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, since undesired clogging can be prevented.Clogging is the accumulation of solid components or particles in a component or pouring system, which can lead to a disruption in the casting process and thus to a reduced casting performance of the refractory material.

[0081] Measurement methods:

[0082] For the measurements of the properties according to DIN EN ISO 1927-6, the geometry D specified in this standard was used.

[0083] The refractory material was examined using light and scanning electron microscopy. Light microscopy was performed using a Nikon Eclipse LV150. Scanning electron microscopy analyses were performed using a JEOL JSM-6460 or a JEOL JSM-7900F scanning electron microscope.

[0084] The composition of the individual phases was determined by 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 with a BSE detector.

[0085] Fig. 1 shows a micrograph of a refractory material according to the invention taken by light microscopy, from which the needle-like structure of the material is evident. In particular, areas with hole-like or circular-looking structures can 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 pm, more preferably 0.2-5 pm. 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. Fig. 2 shows a scanning electron microscopy image of

[0086] Image of the refractory material from Fig. 1, with Fig. 2 depicting the area marked in Fig. 1. The needle-like structure of the material is even more clearly visible in Fig. 2. Regions 1 to 4 are marked in Fig. 2, in which the four phases described in this application are present.

[0087] Fig. 3 shows a further image of the refractory material according to the invention by means of 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.

[0088] Fig. 4 shows a scanning electron microscopy image of the area marked in Fig. 3. The refractory material also exhibits a needle-like structure in this area. Also marked in Fig. 4 are areas 1 to 4, in which the four phases described in this application are present.

[0089] Slag resistance test:

[0090] The refractory material according to the invention was tested for slag resistance against both acidic (C / S = 0.8) and basic slag compositions (C / S = 3.2). Slag resistance is the ability of the refractory material to withstand the damaging effects of molten slag. The refractory material according to the invention demonstrated very good slag resistance, particularly in comparison to a known refractory material for steel ladles (comparison material COMPRIT 185HMV from RHI Magnesita) (see Fig. 5, the inventive material is shown on the left, and the comparison material COMPRIT 185HMV from RHI Magnesita is shown on the right). Pressure softening test (softening behavior under pressure):

[0091] Furthermore, a test was conducted on the refractory material to determine its softening behavior under pressure (compression softening). For this test, the refractory material according to the invention and a refractory material produced from a batch without the addition of dry (powdered) phenolic resin binder according to the process described above, as well as a known refractory material (ANKO 85MR5A from RHI Magnesita), were used as reference materials.

[0092] The test was conducted using a cast sample according to DIN EN ISO 1927-5. The sample was dried to constant mass at a temperature of 110°C according to DIN EN ISO 1927-5.

[0093] Test specimen: cylinder (height (h): 50 mm, diameter (d): 40 mm, inner bore: 16 mm, measurement method according to ISO 5013)

[0094] The measurements for softening behavior under pressure (compression softening) were conducted in accordance with 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 specimen decreased by 0.5%. The maximum measurement temperature is limited to 1700°C.

[0095] In contrast to the known refractory material ANKO 85MR5A, no softening was observed in the material according to the invention up to a temperature of 1700°C. The addition of dry (powdered) phenolic resin binder had no negative influence on the softening behavior under pressure, as is particularly evident in comparison to the material produced without the addition of phenolic resin binder (Fig. 6).

[0096] Experiment to measure thermal conductivity according to Dr. Klasse: The thermal conductivities of the material according to the invention and the comparison materials (DELTEK A115 from RHI Magnesita and the material produced without the addition of dry (powdered) phenolic resin binder) given in Table 1 were determined according to the method of Dr. Klasse (Klasse, F.; Heinz, A.; Hein, J.: Comparative method for determining the thermal conductivity of ceramic materials. Her. DKG 34 (1957), pp. 183-189). The values ​​given for 1000°C were extrapolated.

Claims

Patent claims 1. Refractory material which is thermally treated at a temperature of at least 1300°C, preferably from 1300°C to 1750°C, so 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% 0, 50-70 wt% Al and <5 wt% Si, based on the total content of the first phase, the second phase comprises 1-7 wt% C, 3-8 wt% N, 25-35 wt% 0, 55-65 wt% Al and <5 wt% Si, based on the total content of the second phase, and the third phase <7 wt% C, 14-28 wt% N, 10-15 wt% 0, 52-63 wt% Al and <20 wt% Si, based on the total content of the third phase, includes.

2. Refractory material according to claim 1, characterized in that the first phase comprises or consists of A14O4C.

3. Refractory material according to claim 1 or 2, characterized in that the second phase A1 28 C6N6O 21 includes or from A1 28 C6N6O 21 consists.

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, SiAlA^CpNg and mixtures thereof or consists of SiAl6O2N6.

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 AIN or consists of AIN.

6. Refractory material according to one of claims 1 to 5, characterized in that the needle-like structure has needles of a length in a range of 0.1-50 pm, preferably 0.1-30 pm, more preferably 2-30 pm and / or a thickness in a range of 0.01-8 pm, preferably 0.2-5 pm, measured by means of 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 a proportion of the phases with a needle 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 (magnesium aluminate spinel), sintered clay earth, high-grade 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) 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 aluminium powder (Al powder); f) dry phenolic resin binder, dry, preferably powdered phenolic resin binder;and g) silica sol (silica in aqueous colloidal suspension), preferably silica containing SiO2 nanoparticles in 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 19 wt.%, granular component in the fine fraction with a particle size in a range of <0.5 mm; c) 0.05-15 wt.%, preferably 2-12 wt.%, more preferably 5-10 wt.%, even more preferably about 7 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) 3-10 wt.%, preferably 4-9 wt.%, more preferably 5-8 wt.%, even more preferably about 5 wt.%, metallic aluminum powder; f) 0.1-4 wt.%, preferably 0.2-2 wt.%, more preferably 0.3-1 wt.%, even more preferably about 0.5 wt.-%, dry (preferably powdered) phenolic resin binder; g) 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 SiG2 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 after drying 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 a range of 2.90-3.70 g / cm 3 , preferably about 2.98 g / cm 3f measured according to DIN EN ISO 1927-6.

12. Green body produced from a batch according to claim 9 or 10, characterized in that the green body after drying preferably has one or more of the following properties: - a cold compressive strength of greater than 40 MPa, preferably greater than 50 MPa, particularly preferably greater than 60 MPa, measured according to DIN EN ISO 1927-6; - a cold bending strength of greater than 6 MPa, preferably greater than 8 MPa, particularly preferably greater than 9 MPa, measured according to DIN EN ISO 1927-6.

13. A method for producing a refractory material according to any one of claims 1 to 8, the method comprising 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.

14. Use of a refractory material according to one of the 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 Pig iron sector, in particular cast products, and / or refractory products for the flow control sector, in particular slide plates, interchangeable nozzles, shadow pipes, plugs, dip pipes, inner sleeves, weirs, dams, impact pots and nozzles.

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