Refractory material, method for producing refractory material, and use of refractory material

Abstract

The invention relates to a refractory material, to a method for producing a refractory material and to the use of a refractory material. The refractory material is heat treated at a temperature of at least 1300 DEG C, preferably 1300 DEG C to 1750 DEG C, to have a needle-like structure and comprises a combination of a first phase comprising 2 to 10 weight percent C, less than 5 weight percent N, 30 to 40 weight percent O, 50 to 70 weight percent Al, and less than 5 weight percent Si, based on the total fraction of the first phase, a second phase comprising 3 to 10 weight percent C, less than 5 weight percent N, 30 to 40 weight percent O, and less than 5 weight percent Si, based on the total fraction of the first phase, and a third phase comprising 3 to 10 weight percent Si, based on the total fraction of the second phase. The second phase comprises 1 to 7 weight percent of C, 3 to 8 weight percent of N, 25 to 35 weight percent of O, 55 to 65 weight percent of Al and less than 5 weight percent of Si, based on the total fraction of the second phase; the third phase includes less than 7 weight percent of C, 14 to 28 weight percent of N, 10 to 15 weight percent of O, 52 to 63 weight percent of Al, and less than 20 weight percent of Si, based on the total fraction of the third phase.

Description

Technical Field

[0001] The present invention relates to refractory materials, fillers for manufacturing refractory materials, green bodies made of the fillers, methods for manufacturing refractory materials, and applications of refractory materials. Background Art

[0002] Refractory materials are used, for example, in industrial high-temperature processes and must therefore remain stable even under adverse environmental conditions and extremely high temperatures.

[0003] Refractory materials are used, for example, in the steel industry, where refractory materials are also used to manufacture articles such as functional products (e.g., porous bricks or impact cans) and / or articles for transferring and / or maintaining steel pressings, distributors, and other metallurgical components. Such metallurgical components made of refractory materials are in turn used to receive and process molten steel and other liquid metal products. Therefore, refractory materials ensure the safety of other substances and mixtures during their combustion, transformation, melting, blasting, ignition, fusion, and shaping processes and must therefore withstand thermal, mechanical, and chemical loads.

[0004] Therefore, it is desirable to provide a refractory material having good physical properties, such as high strength and high thermal resistance, and various different refractory articles can be manufactured using the refractory material. Summary of the Invention

[0005] Therefore, an object of the present invention is to provide a refractory material having very good physical properties, such as particularly very good high-temperature strength or high-temperature wear resistance, good thermal resistance, and low thermal conductivity. In addition, it should also be possible to use the refractory material for various different refractory articles, especially more complex casting articles. Therefore, another object of the present invention is to be able to obtain a refractory material with favorable properties from a filler, the filler having favorable processing properties, such as particularly good flow properties. Another object of the present invention is to manufacture a green body from the filler, the filler having favorable physical and mechanical properties, such as increased strength after drying (especially high low-temperature compressive strength and low-temperature bending strength), so that improved manipulability and simplified processability of the green body for refractory materials (and thus for various different refractory articles as described above) can be achieved.

[0006] This object of the present invention is achieved by a refractory material that is heat-treated at a temperature of at least 1300 °C, preferably 1300 °C to 1750 °C, so that the refractory material has a needle-like structure and comprises a combination of a first phase, a second phase, and a third phase, wherein:

[0007] The first phase comprises 2 wt% to 10 wt% of C, less than 5 wt% of N, 30 wt% to 40 wt% of O, 50 wt% to 70 wt% of Al, and less than 5 wt% of Si, based on the total share of the first phase.

[0008] The second phase comprises more than 1 wt% of C, 3 wt% to 8 wt% of N, 25 wt% to 35 wt% of O, 55 wt% to 65 wt% of Al, and less than 5 wt% of Si, based on the total share of the second phase.

[0009] The third phase comprises less than 7 wt% of C, 14 wt% to 28 wt% of N, 10 wt% to 15 wt% of O, 52 wt% to 63 wt% of Al, and less than 20 wt% of Si.

[0010] First, several terms used within the framework of the present invention will be explained.

[0011] The term "refractory material" used in the present application is familiar to those skilled in the art from the prior art. That is, it is a fire-resistant and high-temperature-resistant material. The refractory material is preferably made of inorganic raw materials. This material can in particular withstand a high temperature of at least 1500 °C or higher without softening. This material preferably has a pyrometric cone point greater than SK 17 (= ISO 150), and SK 17 approximately corresponds to a temperature of 1500 °C (see DIN 51 060). The pyrometric cone point can be determined according to ISO 528 and DIN EN 993-12. Thus, this material is suitable for being able to come into contact with liquid metals and steel products for a certain period of time without losing its external shape at the same time.

[0012] Within the framework of the present invention, a "filler" is a shapeless or unformed substance used for manufacturing refractory materials.

[0013] The term "green body" used in the present application is familiar to those skilled in the art from the prior art. Thus, it is a formed or molded casting but unburned substance, which can still be simply processed. The term "dried green body" used in the present application refers to a green body dried until constant mass at a temperature of (110 ± 5) °C according to the DIN EN ISO 1927-5 standard.

[0014] Within the framework of the present invention, a "phase" is a spatial region in a solid that is chemically and morphologically (i.e., by form, shape, and structure) different from its surrounding environment.

[0015] The first phase preferably comprises 2 wt% to 10 wt% of C, 0.001 wt% to 5 wt% of N, 30 wt% to 40 wt% of O, 50 wt% to 70 wt% of Al, and 0.001 wt% to 5 wt% of Si, based on the total share of the first phase.

[0016] The second phase preferably comprises 1 wt% to 7 wt% of C, 3 wt% to 8 wt% of N, 25 wt% to 35 wt% of O, 55 wt% to 65 wt% of Al, and 0.001 wt% to 5 wt% of Si, based on the total share of the second phase.

[0017] The third phase preferably comprises 0.001 wt% to 7 wt% of C, 14 wt% to 28 wt% of N, 10 wt% to 15 wt% of O, 52 wt% to 63 wt% of Al, and 0.001 to 20 wt% of Si, based on the total share of the third phase.

[0018] According to the present invention, the refractory material comprises a combination composed of the first phase, the second phase, and the third phase.

[0019] According to the present invention, preferably the first phase comprises Al4O4C or consists of Al4O4C.

[0020] According to the present invention, it is further preferred that the second phase comprises Al 28 C6N6O 21 or consists of Al 28 C6N6O 21 constitutes.

[0021] According to the present invention, preferably the third phase comprises a compound selected from SiAl6O2N6, SiAl5O2N5, SiAl4O2N4, Si3Al7O3N9, and mixtures thereof. According to the present invention, it is further preferred that the third phase comprises SiAl6O2N6 or consists of SiAl6O2N6.

[0022] The refractory material may comprise a fourth phase, wherein the fourth phase comprises less than 5 wt% of C, 26 wt% to 36 wt% of N, less than 8 wt% of O, 56 wt% to 66 wt% of Al, and less than 5 wt% of Si, based on the total share of the fourth phase, and the fourth phase preferably comprises AlN or consists of AlN.

[0023] In addition, the fourth phase may include C in an amount of 0.001 wt% to 5 wt%, N in an amount of 26 wt% to 36 wt%, O in an amount of 0.001 to 8 wt%, Al in an amount of 56 wt% to 66 wt%, and Si in an amount of 0.001 wt% to 5 wt% based on the total share of the fourth phase.

[0024] The presence of a needle-like structure or a phase having a needle-like structure can preferably be determined by means of a scanning electron microscope.

[0025] Preferably, the composition of the phase is determined by means of an energy-dispersive detector using a scanning electron microscope (SEM) at an excitation voltage of 10 kV and a sample current of 1 nA.

[0026] The needle-like structure preferably has needles having a length in the range of 0.1 to 50 μm, preferably 0.1 to 30 μm, more preferably 2 to 30 μm and / or a thickness in the range of 0.01 to 8 μm, preferably 0.2 to 5 μm, measured using a scanning electron microscope at an excitation voltage of 10 kV and a sample current of 1 nA.

[0027] The minimum ratio of the length to the thickness of the needles (at least for a part thereof) is preferably at least 4:1. At least 20%, more preferably at least 40% of the needles of the needle-like structure preferably have a minimum ratio of length to thickness of at least 4:1. Preferably, in an area of at least 1000 μm × 1000 μm, at least 20%, more preferably at least 40% of the needles of the needle-like structure have a minimum ratio of needle length to thickness of at least 4:1. This can be determined by means of a scanning electron microscope at an excitation voltage of 10 kV and a sample current of 1 nA.

[0028] In addition, the refractory preferably has a porous (or circular in cross-section) structure. The porous or circular structure preferably has a (major) part of the needle-like structure. In a preferred embodiment, the (major) part of the needles is formed at the surface of the porous or circular structure.

[0029] According to the invention, it is preferred that the share of the phase having a needle-like structure is at least 0.01 wt%, preferably 0.1 wt% based on the total share of the refractory.

[0030] The refractory preferably has an open porosity in the range of 10.0 to 25.0 volume percent, measured according to DIN EN ISO 1927-6, and / or a bulk density in the range of 2.95 g / cm 3 to 3.70 g / cm 3 measured according to DIN EN ISO 1927-6.

[0031] The refractory material is preferably a refractory functional product, more preferably a refractory casting and / or pressing product, further preferably a refractory product in the field of flow control, and even further preferably a gate plate, a replaceable flushing trough, a shielding tube, a plug, a submerged tube, an inner sleeve, a weir, a dam, a baffle, and a nozzle. Herein, within the framework of the present invention, the term "functional product" should be understood to mean, in this context, a product that is partially or completely made of refractory material and is formed by casting and / or molding.

[0032] The advantages of the present invention are that the refractory material according to the present invention has very good physical properties. The refractory material particularly exhibits, for example, very good high-temperature strength / high-temperature wear resistance and at the same time also exhibits very good thermal resistance. The refractory material according to the present invention is high-temperature resistant and can withstand a temperature of at least 1700 °C without softening. The refractory material has a needle-like structure, and this needle-like structure has a very stable phase formed in-situ. The fine needles formed in many regions of the material are likely the reason for the good thermal resistance.

[0033] In addition, the refractory material according to the present invention exhibits low thermal conductivity. This not only has the advantage that the refractory material has good heat insulation performance, but also results in an improvement in the casting performance of the products obtained from this refractory material. Because the low thermal conductivity of the material causes the avoidance of the accumulation of solid components or particles on the refractory material, that is, the unwanted "blockage".

[0034] The present invention also relates to a filler for manufacturing the refractory material according to the present invention, preferably according to any one of claims 1 to 8, wherein the filler comprises the following components:

[0035] a) A granular component with a large share having a particle size in the range of 0.5 mm to 10 mm, which is selected from MA spinel (magnesium aluminate spinel), sintered clay, white fused alumina, brown fused alumina, grey fused alumina, mullite, bauxite, andalusite, SiC, refractory clay, zirconium-containing components, and mixtures thereof;

[0036] b) A granular component with a small share having a particle size in the range of less than 0.5 mm, which is selected from sintered clay, white fused alumina, zirconium-containing components, and mixtures thereof;

[0037] c) A small share of Al2O3, preferably a small share of calcined clay having a particle size in the range of less than 0.5 mm;

[0038] d) Carbon, preferably graphite and / or carbon black, more preferably a mixture of graphite and carbon black, even further preferably a mixture of graphite and carbon black with a mixing ratio in the range of 1:2 to 2:1, and even further preferably a mixture of graphite and carbon black with a mixing ratio of 1:1;

[0039] e) Metallic aluminum powder (Al powder);

[0040] f) Dry phenolic resin binder, preferably dry powder phenolic resin binder; and

[0041] g) Colloidal silica (silicic acid in an aqueous colloidal suspension), preferably silicic acid containing SiO2 nanoparticles in an aqueous colloidal suspension.

[0042] The filler according to the invention is preferably prepared by mixing dry matter (preferably comprising components a) to f)) with colloidal silica (silicic acid in an aqueous colloidal suspension; comprising component g)). In the dry matter, the components are present in a chemically unchanged manner. The binding of substances only occurs by adding colloidal silica (silicic acid in an aqueous colloidal suspension), which is based on the so-called sol-gel reaction.

[0043] Within the framework of the present invention, the filler already contains all the components that must be present for manufacturing refractory materials.

[0044] The filler includes a coarse fraction of granular components with a particle size in the range of 0.5 mm to 10 mm. The granular components are selected from MA spinel (magnesium aluminate spinel), sintered clay, white fused alumina, brown fused alumina, grey fused alumina, mullite, bauxite, andalusite, SiC, refractory clay, zirconium-containing components, and mixtures thereof. The coarse fraction of granular components is preferably selected from the group of non-basic components. By using non-basic components, better processability and a more favorable curing time are obtained after mixing with colloidal silica (silicic acid in an aqueous colloidal suspension). Because the binding process (the so-called sol-gel process) is usually greatly accelerated by basic components, an optimal balance between processability and curing time can be set here by using suitable non-basic components.

[0045] The filler also includes a fine fraction of granular components with a particle size in the range of less than 0.5 mm. This granular component is especially used for matrix filling. It is also determined that the fine fraction of granular components has a positive effect on the flowability of the filler, especially in casting.

[0046] The filler also includes carbon. Carbon is indispensable as a source for the formation of in-situ formed phases. In a preferred embodiment, there is a mixture of graphite and carbon black with a mixing ratio in the range of 1:2 to 2:1, and preferably a mixture of graphite and carbon black with a mixing ratio of 1:1. In this way, a very good compromise is obtained between the physical properties achieved in the refractory material and the processability of the filler. It can be determined here that graphite has a positive effect on the wetting property (and thus on the anti-permeability and anti-slagging property), while the more active carbon black has a positive effect on the formation of in-situ formed phases.

[0047] The filler further includes metallic aluminum powder. The metallic aluminum powder particularly has the advantageous function of preventing carbon degradation (or oxidation). The aluminum powder preferably has a particle size of <0.1 mm, more preferably <0.075 mm, and even more preferably <0.065 mm.

[0048] The filler further includes dry (preferably powdered) phenolic resin binder. The dry (preferably powdered) phenolic resin binder particularly has the advantageous function of significantly increasing the green strength after drying. The phenolic resin binder used is, for example, a commercially available Novolak type phenolic resin. An example of such dry (preferably powdered) phenolic resin binder is Borofen BLR3509. Through the addition of this binder, a significantly increased strength is achieved, and thus, a simpler manipulability and improved transportability of the green body after drying are realized. This is also reflected in the significantly increased low-temperature compressive strength and low-temperature flexural strength of the green body compared to the green body made of the filler without added binder. In this way, for example, the reject rate due to green body breakage in refractory manufacturing can be significantly reduced. Here, surprisingly, it has been found that even a small amount of added binder is sufficient to achieve the main beneficial effects on the green body strength. At the same time, the refractoriness of the refractory is not adversely affected by this addition.

[0049] In addition, the filler includes silica sol (silicic acid in an aqueous colloidal suspension), preferably silicic acid containing SiO2 nanoparticles in an aqueous colloidal suspension. This involves a suspension of fine amorphous, pore-free, and usually spherical silicic acid particles in an aqueous phase. Colloidal silicic acid is different from conventional (dry) silicic acid (such as (dry) fumed silica). Silica sol (silicic acid in an aqueous colloidal suspension) particularly serves as a mixing liquid and binder for refractories.

[0050] Based on the total weight of the silica sol, the solid fraction (the fraction of SiO2 particles) in the silica sol (aqueous colloidal silicic acid suspension) is preferably in the range of 20 wt% to 50 wt%, more preferably 30 wt% to 50 wt%.

[0051] For silica sol, i.e., silicic acid in an aqueous colloidal suspension, using water instead of common silicic acid has quite a few advantages. Because when using common silicic acid, the metal (aluminum) reacts with water within a certain pH range after mixing of the components. This reaction is strongly exothermic and simultaneously generates hydrogen gas (H2). In addition, when using aluminum, an aluminum oxide layer (Al2O3) is formed in the edge region. These reactions must be avoided. On the one hand, forming H2 is disadvantageous for safety reasons, and on the other hand, less aluminum is available for in-situ phase formation. In addition, cracks and delamination in the green body also occur due to the exothermic reaction and gas formation. By using silica sol, i.e., colloidal silicic acid or colloidal silicic acid suspension, this can be prevented.

[0052] The filler may include one or more of the following components in the following amounts based on the total share of the filler composition:

[0053] a) A coarse fraction of granular components with a particle size in the range of 0.5 mm to 10 mm, accounting for 50 wt% to 80 wt%, preferably 53 wt% to 70 wt%, more preferably 55 wt% to 67 wt%, and even more preferably about 59 wt%;

[0054] b) A fine fraction of granular components with a particle size in the range of less than 0.5 mm, accounting for 5 wt% to 35 wt%, preferably 7 wt% to 30 wt%, more preferably 10 wt% to 30 wt%, and even more preferably about 19 wt%;

[0055] c) A fine fraction of Al2O3, accounting for 0.05 wt% to 15 wt%, preferably 2 wt% to 12 wt%, more preferably 5 wt% to 10 wt%, and even more preferably about 7 wt%;

[0056] d) Carbon, accounting for 2 wt% to 10 wt%, preferably 3 wt% to 8 wt%, more preferably 3.5 wt% to 6 wt%, and even more preferably about 4.5 wt%;

[0057] e) Metallic aluminum powder (Al powder), accounting for 3 wt% to 10 wt%, preferably 4 wt% to 9 wt%, more preferably 5 wt% to 8 wt%, and even more preferably about 5 wt%;

[0058] f) A (preferably powdered) dry phenolic resin binder, accounting for 0.1 wt% to 4 wt%, preferably 0.2 wt% to 2 wt%, more preferably 0.3 wt% to 1 wt%, and even more preferably about 0.5 wt%;

[0059] g) Colloidal silica (silicic acid in an aqueous colloidal suspension), preferably silicic acid containing SiO2 nanoparticles in an aqueous colloidal suspension, accounting for 4 wt% to 15 wt%, preferably 5 wt% to 12 wt%, more preferably 6 wt% to 8 wt%, and even more preferably about 7 wt%. Based on the total weight of the colloidal silica (in the aqueous colloidal silicic acid suspension), the solid fraction (the fraction of SiO2 particles) is preferably in the range of 20 wt% to 50 wt%, more preferably 30 wt% to 50 wt%.

[0060] The subject matter of the present invention also relates to a green body which is made of a filler according to the present invention, preferably a filler according to claim 9 or 10, wherein the dried green body preferably has an open porosity of about 10 volume percent to 25 volume percent, measured according to DIN EN ISO 1927-6, and / or a bulk density in the range of 2.95 g / cm 3 to 3.70 g / cm 3 and preferably a bulk density of about 2.98 g / cm 3 . After drying, the green body preferably has a low-temperature compressive strength of greater than 40 MPa, more preferably greater than 50 MPa, and particularly preferably greater than 60 MPa, measured according to DIN EN ISO 1927-6, and / or a low-temperature flexural strength of greater than 6 MPa, more preferably greater than 8 MPa, and particularly preferably greater than 9 MPa, measured according to DIN EN ISO 1927-6. These properties of the green body result in good strength of the green body and thus excellent handling and transportability.

[0061] The subject matter of the present invention also lies in a method for manufacturing a refractory material according to the present invention, preferably a refractory material according to any one of claims 1 to 8, the method comprising the following steps:

[0062] i. providing a filler according to the present invention, preferably a filler according to any one of claims 9 or 10;

[0063] ii. manufacturing a green body from the filler, and

[0064] iii. heating the green body to a temperature of at least 1300 °C, preferably to a temperature in the range of 1300 °C to 1750 °C.

[0065] Herein, providing the filler according to the present invention in step i preferably starts from the dry matter (preferably including components a) to f)), and the dry matter is made by mixing with silica sol (silicic acid in an aqueous colloidal suspension; including component g)).

[0066] Manufacturing the green body from the filler in step ii preferably involves casting and / or molding.

[0067] In step iii of the method, heating the green body to a temperature of at least 1300 °C is completed. Herein, the green body is preferably heated to a temperature in the range of 1300 °C to 1750 °C. Thereby, the properties of the refractory material according to the present invention can be obtained in particular. Herein, the heating of the green body is preferably carried out in a gas atmosphere composed of air with a reduced oxygen content. The reduction of the oxygen content in the air is used to prevent the oxidation of the outer surface of the green body. For example, the reduction of the oxygen content is achieved by embedding the green body in coal sand.

[0068] The subject matter of the present invention also relates to a refractory material having a needle-like structure and comprising a combination of a first phase, a second phase and a third phase composition, which is manufactured by a method according to the present invention, preferably by the method according to claim 13, wherein,

[0069] The first phase comprises 2 wt% to 10 wt% of C, less than 5 wt% of N, 30 wt% to 40 wt% of O, 50 wt% to 70 wt% of Al and less than 5 wt% of Si, based on the total share of the first phase.

[0070] The second phase comprises more than 1 wt% of C, 3 wt% to 8 wt% of N, 25 wt% to 35 wt% of O, 55 wt% to 65 wt% of Al and less than 5 wt% of Si, based on the total share of the second phase.

[0071] The third phase comprises less than 7 wt% of C, 14 wt% to 28 wt% of N, 10 wt% to 15 wt% of O, 52 wt% to 63 wt% of Al and less than 20 wt% of Si, based on the total share of the third phase.

[0072] The subject matter of the present invention also relates to the use of a green body made of a filler according to any one of claims 9 to 10, preferably of a refractory material according to the present invention, preferably according to any one of claims 1 to 8, for manufacturing a refractory product, the refractory product being used in steel applications, particularly steel pressings, distributors, porous bricks, CAS-OB hoods; the refractory product being used in the pig iron field, particularly casting products; and / or the refractory product being used in the flow control field, particularly gate valves, replaceable flushing troughs, shielding tubes, plugs, dipping tubes, inner sleeves, weirs, dams, baffles and nozzles.

[0073] In the context of the present invention, products in the flow control field are understood to be, for example, refractory products that can achieve the diversion or prevention of a flow containing liquid metal (or steel products or liquid metal) or steel products. Products in the flow control field require, in addition to good physical properties (such as high strength), good processability of the material to be processed in order to be able to manufacture partially complex-shaped components. A significant advantage of flow control products (preferably based on casting products) compared to ISO-pressed products is the significant cost reduction.

[0074] Therefore, another advantage of the present invention is that, by using the filler according to the present invention and / or the method according to the present invention, not only can a refractory material with very good physical properties (such as high hot strength, etc.) be obtained, but also good processability of the material to be processed for manufacturing complex components, particularly by casting, can be obtained. Description of the Drawings

[0075] The present invention is described hereinbelow by way of example according to several advantageous embodiments with reference to the accompanying drawings. The drawings show:

[0076] Figure 1 A photograph of a refractory according to the invention taken with an optical microscope is shown.

[0077] Figure 2 A photograph taken with a scanning electron microscope is shown of Figure 1 the partial area shown.

[0078] Figure 3 Another photograph of a refractory according to the invention taken with an optical microscope is shown.

[0079] Figure 4 A photograph taken with a scanning electron microscope is shown of Figure 3 another area marked in.

[0080] Figure 5 The slag resistance of a refractory according to the invention (left) is shown compared to the slag resistance of a known refractory (right).

[0081] Figure 6 The test results of the softening behavior under pressure (pressure softening) using a refractory according to the invention and a comparative material are shown. Detailed Description of the Embodiments

[0082] Manufacture of the refractory:

[0083] It is explained herein how a refractory according to the invention can be manufactured starting from a filler according to the invention.

[0084] First, a filler is manufactured comprising the following components:

[0085] A granular component consisting of 58.4 weight percent of sintered clay with a coarse fraction having a particle size in the range of 0.5 mm to 10 mm,

[0086] 9.4 weight percent of sintered clay (<0.5 mm),

[0087] 8.9 weight percent of white fused alumina (<0.2 mm),

[0088] 6.5 weight percent of calcined clay 1A,

[0089] 2.3 weight percent of graphite Hunan80 / 200GBK,

[0090] 2.3 weight percent of carbon black Thermalgeperlt (hot beaded),

[0091] 4.7 wt% metallic aluminum powder (Al met) (<0.063 mm),

[0092] 0.5 wt% dry (powdered) phenolic resin binder,

[0093] 7.0 wt% silica sol (silicic acid in an aqueous colloidal suspension), having a solid fraction of 40 wt% (fraction of SiO2 particles), based on the total weight of the silica sol (aqueous colloidal silica suspension).

[0094] The filler is obtained by mixing the silica sol (silicic acid in an aqueous colloidal suspension) containing SiO2 nanoparticles with the dry matter of the remaining components of the filler. Subsequently, a green body is formed from the filler by casting. Then, the green body is 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 is achieved by embedding the green body in coal sand. In this way, the refractory according to the invention is obtained.

[0095] Physical properties:

[0096] The physical properties of the green body according to the invention and the refractory according to the invention, manufactured using the above method, are described below. For comparison, the physical data of two refractories not according to the invention are also listed for reference. Here, it refers to DELTEK A115 from RHI Magnesita and the green body or refractory made from the filler using the above method without adding dry (powdered) phenolic resin binder.

[0097] Table 1: Physical properties of the green body according to the invention, the refractory according to the invention, and two comparative materials.

[0098]

[0099]

[0100]

[0101] *Klasse, F.; Heinz, A.; Hein, J.: Vergleichsverfahren zur Ermittlung der keramischer Werkstoffe (comparative method for determining the thermal conductivity of ceramic materials). Ber. DKG 34 (1957), pages 183 to 189.

[0102] Table 1 shows that the green body according to the present invention has significantly higher strength after drying than the green body made of a filler without added dry (powdered) phenolic resin binder. This is mainly reflected in that the values of the low-temperature compressive strength and the low-temperature bending strength increase significantly, and thus such a green body according to the present invention can be transported to the customer intact and used safely at the customer's place. In addition, compared with the known material DELTEK A115, the refractory material according to the present invention exhibits only a low thermal conductivity. The significantly lower thermal conductivity of the refractory material according to the present invention ensures better heat insulation performance, and thus has a positive impact on the flowability of the material, because unwanted blockages can be prevented. Blockage is understood as the accumulation of solid components or particles in a component or a casting system, which can interfere with the casting process and thus lead to a reduction in the casting efficiency of the refractory material.

[0103] Measurement method:

[0104] When measuring the properties according to DIN EN ISO 1927-6, the geometry D specified in this standard was used.

[0105] The refractory material was examined by means of an optical microscope and a scanning electron microscope. The optical microscopy was carried out using a NIKON Eclipse LV150. The analysis by means of the scanning electron microscope was carried out using a JEOL JSM-6460 or a JEOL JSM-7900F scanning electron microscope.

[0106] The composition of each phase can be determined by means of an energy-dispersive detector in the scanning electron microscope at an excitation voltage of 10 kV and a sampling current of 1 nA. The scanning electron microscope images were generated using a BSE detector.

[0107] Figure 1 A photograph of the refractory material according to the present invention taken by means of an optical microscope is shown, from which the needle-like structure of the material can be seen. In particular, regions with a porous or circular structure can also be seen, in which the needle-like structure of the material is preferably formed. The needles preferably have a small thickness in the range from 0.01 μm to 8 μm, more preferably in the range from 0.2 μm to 5 μm. It is presumed that the excellent heat resistance of the refractory material is very likely due to the fine needles formed in many regions. In addition, it is also presumed that the circular structure in the refractory material can prevent crack propagation.

[0108] Figure 2 A photograph taken by means of a scanning electron microscope of the Figure 1 refractory material in Figure 1 is shown, where the Figure 2 marked region in Figure 2 is shown. The needle-like structure of the material can be seen more clearly fromFigure 2 Regions 1 to 4 are marked therein, where the four phases described in the present application are present accordingly.

[0109] Figure 3 Another photograph of the refractory material according to the invention taken by means of an optical microscope is shown, from which another region with a pore-like structure can be seen, where the acicular structure of the material has been formed in-situ.

[0110] Figure 4 shown by means of a scanning electron microscope Figure 3 photograph of the marked region in. In this region, the refractory material also has an acicular structure. In Figure 4 Regions 1 to 4 are also marked therein, where the four phases described in the present application are present accordingly.

[0111] Slag resistance test:

[0112] The slag resistance of the refractory material according to the invention against acidic (C / S = 0.8) slag compositions and basic (C / S = 3.2) slag compositions is tested. The slag resistance refers to the ability of the refractory material to resist the destructive action of molten slag. In particular, compared with a known refractory material for steel pressings (comparative material COMPRIT 185HMV from RHI Magnesita), the refractory material according to the invention shows very good slag resistance here (see Figure 5 , on the left is the material according to the invention, and on the right is the comparative material COMPRIT 185HMV from RHIMagnesita).

[0113] Pressure softening test (softening behavior under pressure):

[0114] In addition, a test on the softening behavior under pressure (pressure softening) of the refractory material was carried out. For this purpose, on the one hand, the refractory material according to the invention, on the other hand, the refractory material manufactured from a filler without adding a dry (powdered) phenolic resin binder according to the above method, and a known refractory material (ANKO 85MR5A from RHI Magnesita) were used as comparative materials.

[0115] This test was carried out using samples cast according to DIN EN ISO 1927-5. The samples were dried at a temperature of 110 °C until a constant mass according to DIN ENISO 1927-5.

[0116] Test sample: cylinder (height (h): 50 mm, diameter (d): 40 mm, inner hole: 16 mm, measurement method according to ISO5013).

[0117] The measurement of the softening behavior under pressure (pressure softening) was carried out in accordance with DIN EN ISO 1893. Here, a dynamic load of 0.2 MPa in a reducing atmosphere and a heating rate of 5 °C / min were selected. As a result, a T0.5 value of > 1700 °C was obtained. That is to say, this is the temperature at which the maximum thermal expansion of the sample drops by 0.5%. The maximum temperature for the measurement was limited to 1700 °C.

[0118] Compared with the known refractory material ANKO 85MR5A, no softening was found in the material according to the invention at temperatures up to 1700 °C. The addition of a dry (powdered) phenolic resin binder has no adverse effect on the softening behavior under pressure, as can be seen especially in comparison with materials produced without the addition of a phenolic resin binder ( Figure 6 ).

[0119] Test for measuring the thermal conductivity according to Dr. Klasse:

[0120] The thermal conductivities given in Table 1 for the material according to the invention and the comparative materials (DELTEK A115 from RHI Magnesita and the material produced without the addition of a dry (powdered) phenolic resin binder) were determined according to the method of Dr. Klasse (*Klasse, F.; Heinz, A.; Hein, J.: Vergleichsverfahren zur Ermittlung der keramischer Werkstoffe (comparative method for determining the thermal conductivity of ceramic materials). Ber. DKG 34 (1957), pages 183 to 189). Here, the value given for 1000 °C was obtained by extrapolation.

Claims

1. A refractory material, which is heat-treated at a temperature of at least 1300 °C, preferably 1300 °C to 1750 °C, so that the refractory material 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 wt% to 10 wt% of C, less than 5 wt% of N, 30 wt% to 40 wt% of O, 50 wt% to 70 wt% of Al and less than 5 wt% of Si, based on the total share of the first phase; The second phase comprises 1 wt% to 7 wt% of C, 3 wt% to 8 wt% of N, 25 wt% to 35 wt% of O, 55 wt% to 65 wt% of Al and less than 5 wt% of Si, based on the total share of the second phase; and The third phase comprises less than 7 wt% of C, 14 wt% to 28 wt% of N, 10 wt% to 15 wt% of O, 52 wt% to 63 wt% of Al and less than 20 wt% of Si, based on the total share of the third phase.

2. The refractory material according to claim 1, characterized in that, The first phase comprises or consists of Al4O4C.

3. The refractory material according to claim 1 or 2, characterized in that, The second phase includes Al 28 C6N6O 21 or is composed of Al 28 C6N6O 21 constituting it.

4. The refractory material according to any 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 SiAl6O2N6.

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

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

7. The refractory material according to any one of claims 1 to 6, characterized in that, The minimum ratio of the length to the thickness of at least a part of the needles is at least 4:

1.

8. The refractory material according to any one of claims 1 to 7, characterized in that Based on the total share of the refractory material, the share of the phase having the needle-like structure is at least 0.01 wt%, preferably 0.1 wt%.

9. A filler for manufacturing a refractory material according to any one of claims 1 to 8, wherein, The filler comprises the following composition: a) A granular component with a coarse fraction having a particle size in the range of 0.5 mm to 10 mm, which is selected from MA spinel (magnesium aluminate spinel), sintered clay, white fused alumina, brown fused alumina, grey fused alumina, mullite, bauxite, andalusite, SiC, refractory clay, zirconium-containing components and mixtures thereof; b) A granular component with a fine fraction having a particle size in the range of less than 0.5 mm, which is selected from sintered clay, white fused alumina, zirconium-containing components and mixtures thereof; c) A small fraction of Al2O3, preferably a small fraction of calcined clay having a particle size in the range of less than 0.5 mm; d) Carbon, preferably graphite and / or carbon black, more preferably a mixture of graphite and carbon black, still more preferably a mixture of graphite and carbon black with a mixing ratio in the range of 1:2 to 2:1, and still 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 powder phenolic resin binder; and g) Colloidal silica (silicic acid in an aqueous colloidal suspension), preferably silicic acid containing SiO2 nanoparticles in an aqueous colloidal suspension.

10. The filler according to claim 9, wherein The filler comprises one or more of the following components in the following amounts based on the total share of the composition of the filler: a) 50 wt% to 80 wt%, preferably 53 wt% to 70 wt%, still preferably 55 wt% to 67 wt%, and still more preferably about 59 wt% of a coarse fraction of granular components having a particle size in the range of 0.5 mm to 10 mm; b) 5 wt% to 35 wt%, preferably 7 wt% to 30 wt%, still preferably 10 wt% to 30 wt%, and still more preferably about 19 wt% of a fine fraction of granular components having a particle size in the range of less than 0.5 mm; c) 0.05 wt% to 15 wt%, preferably 2 wt% to 12 wt%, still preferably 5 wt% to 10 wt%, and still more preferably about 7 wt% of a small fraction of Al2O3; d) 2 wt% to 10 wt%, preferably 3 wt% to 8 wt%, still preferably 3.5 wt% to 6 wt%, and still more preferably about 4.5 wt% of carbon; e) 3 wt% to 10 wt%, preferably 4 wt% to 9 wt%, still preferably 5 wt% to 8 wt%, and still more preferably about 5 wt% of metallic aluminum powder; f) 0.1 wt% to 4 wt%, preferably 0.2 wt% to 2 wt%, still preferably 0.3 wt% to 1 wt%, and still more preferably about 0.5 wt% of (preferably powdered) dry phenolic resin binder; g) 4 wt% to 15 wt%, preferably 5 wt% to 12 wt%, still preferably 6 wt% to 8 wt%, and still more preferably about 7 wt% of colloidal silica (silicic acid in an aqueous colloidal suspension), preferably silicic acid containing SiO2 nanoparticles in an aqueous colloidal suspension, wherein, based on the total weight of the aqueous colloidal silicic acid suspension, the solid fraction (the fraction of SiO2 particles) is preferably in the range of 20 wt% to 50 wt%, and still preferably 30 wt% to 50 wt%.

11. A green compact made of the filler according to claim 9 or 10, characterized in that, The green body after drying preferably has one or more of the following characteristics: An open porosity of about 10 to 25 volume percent, measured according to DIN EN ISO 1927-6, Bulk density measured according to DIN EN ISO 1927-6, in the range of 2.9 g / cm 3 to 3.7 g / cm 3 and preferably about 2.98 g / cm 3 .

12. A green body made of the filler according to claim 9 or 10, characterized in that, The green body after drying preferably has one or more of the following properties: A low-temperature compressive strength of greater than 40 MPa, more preferably greater than 50 MPa, and particularly preferably greater than 60 MPa, measured according to DIN EN ISO 1927-6; A low-temperature flexural strength of greater than 6 MPa, more preferably greater than 8 MPa, and particularly preferably greater than 9 MPa, measured according to DIN EN ISO 1927-6.

13. A method for manufacturing a refractory material according to any one of claims 1 to 8, wherein, The method comprises the following steps: Providing a filler according to any one of claims 9 or 10; Manufacturing a green body from the filler, and Heating the green body to a temperature of at least 1300 °C, preferably to a temperature in the range of 1300 °C to 1750 °C.

14. Use of a refractory according to any one of claims 1 to 8, a green body made of a filler according to any one of claims 9 to 10 for manufacturing a refractory product, the refractory product being for steel applications, in particular steel pressings, distributors, perforated bricks, CAS-OB hoods; the refractory product being for the pig iron field, in particular casting products; and / or The refractory product being for the flow control field, in particular gate valves, replaceable flushing troughs, shielding tubes, plugs, dipping tubes, inner sleeves, weirs, dams, baffles and nozzles.

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