Refractory materials, their manufacturing methods and uses

Abstract

The present invention relates to a ceramic sintered body that is heat treated at a temperature of at least 1350°C, preferably from 1300°C to 1750°C, has an acicular structure, and has a combination of a first phase, a second phase, and a third phase, wherein the first phase comprises 2-10 wt% carbon, less than 5 wt% nitrogen, 30-40 wt% oxygen, 50-70 wt% aluminum, and less than 5 wt% silicon, based on the total fraction of the first phase; and the second phase comprises 1-7 wt% carbon, 3-8 wt% silicon, based on the total fraction of the second phase. The present invention relates to a refractory material, a batch for producing the refractory material, a primary component produced from the batch, a method for producing the refractory material, and uses thereof, the refractory material comprising: 14-28 wt. % of carbon, 14-28 wt. % of nitrogen, 10-15 wt. % of oxygen, 52-63 wt. % of aluminum, and less than 5 wt. % of silicon, based on the total fraction of the third phase; 25-35 wt. % of nitrogen, 55-65 wt. % of aluminum, and less than 5 wt. % of silicon, based on the total fraction of the third phase.

Description

[Technical Field]

[0001] The present invention relates to a refractory material, a batch for producing the refractory material, a green body produced from the batch, a method for producing the refractory material, and uses thereof.

[0002] Refractory materials find their application, for example, in high temperature industrial processes and are therefore required to remain stable under adverse conditions and at very high temperatures.

[0003] They are used, for example, in the steel industry, where they serve purposes including the production of products such as functional articles (e.g., drilling blocks or shock absorbers) and / or the production of products for providing and / or maintaining steel ladles, tundishes, and other metallurgical assemblies. Consequently, such metallurgical assemblies, provided with products made of refractory materials, are used for the holding and processing of molten steel and other liquid metal products. Refractory materials therefore protect other substances and mixtures during combustion, conversion, refining, detonation, burning, melting, and forming, and are therefore required to withstand thermal, mechanical, and chemical loads.

[0004] It is therefore desirable to provide a refractory material that has excellent physical properties, such as high strength and high thermal shock resistance, and that allows a large number of different refractory materials to be manufactured. Summary of the Invention

[0005] It is therefore an object of the present invention to provide a refractory material having very good physical properties, in particular very good heat and / or hot wear resistance, good thermal shock resistance and low thermal conductivity. Moreover, said refractory material may potentially be used in many different refractory materials, including in particular more complex cast products. It is therefore a further object of the present invention to obtain a refractory material with advantageous properties, starting from a batch having advantageous processing properties, in particular good flowability.

[0006] The present invention relates to a sintered body that is heat treated at a temperature of at least 1300°C, preferably from 1300°C to 1750°C, 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% carbon, less than 5 wt% nitrogen, 30-40 wt% oxygen, 50-70 wt% aluminum, and less than 5 wt% silicon, based on the total fraction of the first phase; the second phase comprises, based on the total fraction of the second phase, greater than 1 wt. % carbon, 3-8 wt. % nitrogen, 25-35 wt. % oxygen, 55-65 wt. % aluminum, and less than 5 wt. % silicon; The objective is achieved by a refractory material in which the third phase contains less than 7 wt. % carbon, 14-28 wt. % nitrogen, 10-15 wt. % oxygen, 52-63 wt. % aluminum, and less than 20 wt. % silicon, based on the total fraction of the third phase.

[0007] First, some terms used in the context of the present invention are explained.

[0008] In this application, the term "refractory material" is used in a manner familiar to those skilled in the art from the prior art. It is therefore a fire-resistant and high-temperature resistant material. The fire-resistant material is preferably made from inorganic raw materials. The material is particularly able to withstand high temperatures of at least 1500°C without softening. The material preferably has a fire resistance of more than SC 17 (=ISO 150), which corresponds to a temperature of approximately 1500°C (see DIN 51 060). The fire resistance can be determined according to ISO 528 and DIN EN 993-12. The material is therefore suitable for possible contact with liquid metal and steel products for a certain period of time without losing its external shape.

[0009] In the context of the present invention, a "batch" is an amorphous or unshaped formulation used for the manufacture of refractory materials.

[0010] In this application, the term "green body" is used in a manner familiar to the skilled artisan from the prior art: it is thus a formulation that is molded or cast, but is not fired, and is still easily worked.

[0011] In the context of the present invention, a "phase" is a spatial region in a solid that differs from its surroundings both chemically and morphologically (ie, in shape, form, and structure).

[0012] The first phase preferably contains 2 to 10 wt. % carbon, 0.001 to 5 wt. % nitrogen, 30 to 40 wt. % oxygen, 50 to 70 wt. % aluminum, and 0.001 to 5 wt. % silicon, based on the total fraction of the first phase.

[0013] The second phase preferably contains 1-7 wt. % carbon, 3-8 wt. % nitrogen, 25-35 wt. % oxygen, 55-65 wt. % aluminum, and 0.001-5 wt. % silicon, based on the total fraction of the second phase.

[0014] The third phase preferably contains 0.001 to 7 wt. % carbon, 14 to 28 wt. % nitrogen, 10 to 15 wt. % oxygen, 52 to 63 wt. % aluminum, and 0.001 to 20 wt. % silicon, based on the total fraction of the third phase.

[0015] According to the present invention, the refractory material comprises a combination of a first phase, a second phase, and a third phase.

[0016] According to the invention, the first phase preferably comprises or consists of Al4O4C.

[0017] Furthermore, according to the present invention, the second phase is preferably Al 28 C6N6O 21 Contains or Al 28 C6N6O 21 It consists of:

[0018] Furthermore, according to the present invention, the third phase preferably comprises SiAl6O2N6.

[0019] According to the present invention, the third phase preferably comprises a compound selected from SiAl6O2N6, SiAl5O2N5, SiAl4O2N4, Si3Al7O3N9, and mixtures thereof. The third phase preferably comprises SiAl6O2N6.

[0020] Further, according to the present invention, the third phase comprises a compound selected from SiAl6O2N6, SiAl5O2N5, SiAl4O2N4, Si3Al7O3N9, and mixtures thereof.

[0021] The refractory material may include a fourth phase, wherein the fourth phase comprises less than 5 wt. % carbon, 26-36 wt. % nitrogen, less than 8 wt. % oxygen, 56-66 wt. % aluminum, and less than 5 wt. % silicon, based on the total fraction of the fourth phase, and the fourth phase preferably comprises or consists of AlN.

[0022] Furthermore, the fourth phase may contain 0.001 to 5 wt. % carbon, 26 to 36 wt. % nitrogen, 0.001 to 8 wt. % oxygen, 56 to 66 wt. % aluminum, and 0.001 to 5 wt. % silicon, based on the total fraction of the fourth phase.

[0023] The presence of acicular (needle) structures or phases with acicular structures may preferably be determined by scanning electron microscopy.

[0024] The phase composition is preferably determined by scanning electron microscopy (SEM) using an energy dispersive detector with an excitation voltage of 10 kV and a probe current of 1 nA.

[0025] The needle-like structure preferably includes 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 (or thickness) in the range of 0.01 to 8 μm, preferably 0.2 to 5 μm, as measured by a scanning electron microscope at an excitation voltage of 10 kV and a probe current of 1 nA.

[0026] The minimum length to thickness ratio of the needles (at least for some needles) is preferably at least 4:1 (or at least 4 lengths to thicknesses: ratio of the lengths to thicknesses of at least 4:1). Of the needles in the needle-like structure, preferably at least 20%, more preferably at least 40%, have a minimum length to thickness ratio of at least 4:1. Of the needles in the needle-like structure in an area of ​​at least 1000 μm x 1000 μm, preferably at least 20%, more preferably at least 40%, have a minimum length to thickness ratio of at least 4:1. This may be determined by scanning electron microscopy at an excitation voltage of 10 kV and a probe current of 1 nA.

[0027] The refractory material further preferably comprises hole-like structures (or structures that appear circular on polished sections). The hole-like structures or circular-appearing structures preferably comprise (main) portions of needle-like structures. In one preferred embodiment, the (main) portions of needles are formed on the surface of the hole-like structures or circular-appearing structures.

[0028] According to the invention, preferably the fraction of the phase with an acicular structure is at least 0.01% by weight, preferably 0.1% by weight, based on the total fraction of the refractory material.

[0029] The refractory material preferably has an open porosity, measured according to DIN EN ISO 1927-6, in the range of 10.0 to 25.0 vol. % and / or a density, measured according to DIN EN ISO 1927-6, in the range of 2.95 to 3.70 g / cm. 3 The bulk density ranges from 0.01 to 0.01.

[0030] The refractory material preferably comprises a refractory functional article, more preferably a refractory cast and / or pressed product, even more preferably a refractory product in the field of flow control, even more preferably a slide gate plate, a collector nozzle, a tube shroud, a stopper, a submerged tube, an internal nozzle, a weir, a dam, an impact absorber, and other nozzles. In the context of the present invention, the term "functional product" is understood to mean a product that is partly or wholly made from a refractory material and that is shaped by casting and / or molding.

[0031] The present invention has the advantage that the refractory material of the present invention has very good physical properties. In particular, for example, the refractory material exhibits very good heat resistance / high temperature wear resistance and, at the same time, very good thermal shock resistance. The refractory material of the present invention can withstand high temperatures, at least 1700°C, without softening. It has an acicular structure in a very stable phase that forms in situ. The fine needles that form in many regions of the material are very likely responsible for the excellent thermal shock resistance.

[0032] Additionally, the refractory material of the present invention exhibits low thermal conductivity, which not only has the advantage of providing the refractory material with excellent thermal insulation properties, but also improves the pourability of the products obtained from the refractory material, since the low thermal conductivity of the material prevents the accumulation of solids or particles on the refractory material, i.e., undesirable clogging.

[0033] A further subject of the present invention is a batch for the production of the inventive refractory material, preferably as defined in any one of claims 1 to 8, comprising the following components: a) a granular component as a coarse fraction having a particle size in the range of 0.5 to 10 mm selected from MA spinel, sintered alumina, high-grade α-alumina, brown α-alumina, gray α-alumina, mullite, bauxite, andalusite, SiC, grog, zirconium-containing components, and mixtures thereof; b) a particulate component as a fine particle fraction having a particle size in the range of less than 0.5 mm selected from sintered alumina, high-grade alpha-alumina, zirconium-containing components, and mixtures thereof; c) finely divided Al2O3, preferably calcined alumina as a fine fraction 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, even more preferably a mixture of graphite and carbon black in a ratio ranging from 1:2 to 2:1, even more preferably a mixture of graphite and carbon black in a 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 aqueous colloidal suspension.

[0034] The batches of the present invention are preferably prepared from a dry formulation (preferably comprising components a) to e) by mixing with a silica sol (silica in aqueous colloidal suspension; comprising component f). In the dry formulation, the components are in a chemically unchanged form. The bonding of the formulation based on the so-called sol-gel reaction occurs only through the addition of silica sol (silica in aqueous colloidal suspension).

[0035] In the context of the present invention, the batch therefore already contains all the components that must be present in the production of the refractory material.

[0036] The batch comprises a particulate component as a coarse fraction having a particle size ranging from 0.5 to 10 mm, selected from MA spinel, sintered alumina, high-grade α-alumina, brown α-alumina, gray α-alumina, mullite, bauxite, andalusite, SiC, grog, zirconium-containing components, and mixtures thereof. The particulate component in the coarse fraction is preferably selected from the group of non-basic components. The use of non-basic components is associated with better processing quality and more favorable setting times after mixing with silica sol (silica in aqueous colloidal suspension). This is because basic components generally facilitate the bonding process (the so-called sol-gel process).

[0037] The batch also includes a granular component as a fine fraction having a particle size of less than 0.5 mm, which is particularly useful for mold filling. Furthermore, it has been determined that the granular component in the fine fraction has a positive effect on the flow properties of the batch, particularly its castability.

[0038] The batch further comprises carbon, which is essential as a source of in-situ formed phases. In one preferred embodiment, a mixture of graphite and carbon black is used in a ratio ranging from 1:2 to 2:1, and more preferably a 1:1 mixture of graphite and carbon black. This method provides a very good trade-off between the physical properties achieved in the refractory material and the processing quality of the batch. It has been found that graphite tends to have a favorable effect on wetting (and thus resistance to wetting and slag formation), while the more reactive carbon black positively influences the formation of in-situ formed phases.

[0039] The batch further comprises a metal powder containing aluminum. An example of a usable metal alloy is a powdered Al-Si alloy (with approximately 12% Si). However, instead of this alloy, the batch may comprise a powdered mixture of Al-Met and Si-Met. The batch comprises metallic aluminum powder. Aluminum has the advantageous function of preventing, in particular, the degradation (or oxidation) of carbon. The powder preferably has a particle size of less than 0.1 mm, more preferably less than 0.075 mm, and even more preferably less than 0.065 mm.

[0040] The batch further comprises a 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 (dry) silica (e.g., (dry) fumed silica). Silica sol (silica in aqueous colloidal suspension) is particularly useful as a mixing liquid and binder for refractory materials.

[0041] The solid content (fraction of SiO2 particles) in the silica sol (in the aqueous colloidal silica suspension) is preferably in the range of 20 to 50% by weight, more preferably 30 to 50% by weight, based on the total weight of the silica sol.

[0042] Substituting silica sol, i.e., silica in an aqueous colloidal suspension, for regular silica offers significant advantages. The reason is that, when regular silica is used, in certain pH ranges, the metal (aluminum) can react with water after the components are mixed. This reaction is highly exothermic and can also generate hydrogen gas (H). Furthermore, the use of aluminum can result in the formation of an aluminum oxide layer (Al2O3) in the surrounding area. These are reactions that should be avoided. First, the generation of H2 is a safety hazard, and second, it can reduce the aluminum available for in-situ phase formation. Furthermore, the exothermic reaction and gas formation can lead to the formation of cracks and layers in the green body. This is prevented by the use of silica sol, i.e., colloidal silica or colloidal silica suspension.

[0043] The batch may include one or more of the following ingredients in the following amounts, based on the total fraction of the batch composition: a) 50 to 80% by weight, preferably 53 to 70% by weight, more preferably 55 to 67% by weight, and even more preferably about 59% by weight of a granular component as a coarse particle fraction having a particle size in the range of 0.5 to 10 mm; b) 5 to 35% by weight, preferably 7 to 30% by weight, more preferably 10 to 30% by weight, and even more preferably about 23% by weight of a particulate component as a fine particle fraction having a particle size in the range of less than 0.5 mm; c) 0.05 to 4 wt. %, preferably 0.1 to 3 wt. %, more preferably 1 to 2.5 wt. %, and even more preferably about 2 wt. % finely divided Al2O3; d) 2 to 10 wt. %, preferably 3 to 8 wt. %, more preferably 3.5 to 6 wt. %, and even more preferably about 4.5 wt. % carbon; e) 2 to 8 wt %, preferably 3 to 7 wt %, more preferably 4 to 6 wt %, and even more preferably about 5 wt % of metallic aluminum powder (Al powder); f) Silica sol (silica in aqueous colloidal suspension) of 4 to 15 wt%, preferably 5 to 12 wt%, more preferably 6 to 8 wt%, even more preferably about 7 wt%, preferably silica containing SiO2 nanoparticles in aqueous colloidal suspension, with the solid fraction (fraction of SiO2 particles) preferably in the range of 20 to 50 wt%, more preferably 30 to 50 wt%, based on the total weight of the silica sol (aqueous colloidal silica suspension).

[0044] A further subject of the present invention is a green body produced from the batch according to the invention, preferably from a batch according to claim 9 or 10, which preferably has an open porosity, measured according to DIN EN ISO 1927-6, of about 10 to 25% by volume and / or a density, measured according to DIN EN ISO 1927-6, of 2.90 to 3.70 g / cm 3 in the range of about 2.96 g / cm 3 It has a bulk density of

[0045] A further subject of the present invention is also a method for producing a refractory material according to the invention, preferably according to any one of claims 1 to 8, comprising the following steps: i. providing a batch according to the invention, preferably a batch according to claim 9 or 10; ii. Producing a green body from the batch; iii. Heating the green body to a temperature of at least 1300°C, preferably in the range of 1300°C to 1750°C.

[0046] Here, the provision of the inventive batch in step i preferably occurs starting from a dry formulation (preferably comprising components a) to e)) prepared by mixing with a silica sol (silica in aqueous colloidal suspension; comprising component f)).

[0047] The production of the green body from the batch in step ii preferably involves casting and / or moulding.

[0048] A further subject of the present invention is a granular granule having a needle-like structure and a combination of a first, second and third phase such as: a first phase comprising, based on the total fraction of the first phase, 2-10 wt. % carbon, less than 5 wt. % nitrogen, 30-40 wt. % oxygen, 50-70 wt. % aluminum, and less than 5 wt. % silicon; a second phase comprising, based on the total fraction of the second phase, more than 1 wt. % carbon, 3-8 wt. % nitrogen, 25-35 wt. % oxygen, 55-65 wt. % aluminum, and less than 5 wt. % silicon; a third phase comprising less than 7 wt. % carbon, 14-28 wt. % nitrogen, 10-15 wt. % oxygen, 52-63 wt. % aluminum, and less than 20 wt. % silicon, based on the total fraction of the third phase; 12. A refractory material comprising:

[0049] Likewise, a subject of the present invention is the use of the refractory material according to the invention, preferably the refractory material according to any one of claims 1 to 8, or the green bodies produced from a batch according to claim 9 or 10, for the manufacture of refractory products for steel applications, in particular steel ladles, tundishes, perforated blocks, 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 gate plates, collector nozzles, tube shrouds, stoppers, spouts, immersed pipes, internal nozzles, weirs, dams, shock absorbers and other nozzles.

[0050] In the present invention, products in the field of flow control are understood to be refractory products that make it possible to obtain, for example, liquid metal or steel products or to guide or prevent the flow of such products. Products in the field of flow control require not only good physical properties such as high strength, but also good processing qualities in the formulation for processing, in part so that parts with complex shapes can be produced. The main advantage of flow control products, preferably based on cast products, is the potential for significantly greater cost savings compared to isostatically pressed products.

[0051] A further advantage of the present invention is therefore that by means of the inventive batch and / or the inventive method it is not only possible to obtain refractory materials with very good physical properties, such as high heat resistance, but also to achieve good processing qualities, in particular in processing formulations for the manufacture of relatively complex parts by casting. [Brief explanation of the drawings]

[0052] The invention will now be described, by way of example only, through some advantageous embodiments with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows an image of the refractory material of the present invention obtained by optical microscopy. [Figure 2] FIG. 2 shows an image of the sub-region shown in FIG. 1 generated by a scanning electron microscope. [Figure 3] FIG. 3 shows an image of a further sub-region of the refractory material shown in FIG. 1 produced by scanning electron microscopy. [Figure 4] FIG. 4 shows a further image of the refractory material of the present invention obtained by optical microscopy. [Figure 5] FIG. 5 shows an image of a region of the refractory material of the present invention produced by scanning electron microscopy. [Figure 6] FIG. 6 shows an image of the area marked in FIG. 4 produced by scanning electron microscopy. [Figure 7] FIG. 7 shows a further image of the refractory material of the present invention obtained by optical microscopy. [Figure 8] FIG. 8 shows an image of the refractory material of FIG. 7 produced by scanning electron microscopy. [Figure 9] FIG. 9 shows the thermal shock resistance of the refractory material by the stopper cold start test. [Figure 10] FIG. 10 shows the thermal shock resistance of the refractory material with further testing for recyclability. [Figure 11] FIG. 11 shows the slag resistance of the refractory material of the present invention (left) compared to that of known refractory materials (right). [Figure 12] FIG. 12 shows the results of testing the pressure softening characteristics (pressure softening) of the fire-resistant material of the present invention.

[0053] Refractory material manufacturing: We now describe how the refractory material of the invention can be manufactured starting from the batch of the invention.

[0054] First, a batch was prepared containing the following ingredients: 58.6% by weight of a granular component consisting of sintered alumina as a coarse fraction, with particle sizes ranging from 0.5 to 10 mm; 9.2 wt.% sintered alumina (<0.5 mm); 14.0 wt.% high-grade α-alumina (<0.2 mm); 1.9 wt.% of calcined alumina 1A; 2.3 wt.% graphite (Hunan 80 / 200 GBK); 2.3% by weight of beaded thermal black; 4.7 wt.% metallic aluminum powder (Al met) (<0.063 mm); 7.0 wt. % of silica sol (silica in aqueous colloidal suspension) with 40 wt. % solids (fraction of SiO2 particles) based on the total weight of the silica sol (silica in aqueous colloidal silica suspension).

[0055] The batch was obtained by mixing a silica sol (silica in aqueous colloidal suspension) containing SiO2 nanoparticles with a dry formulation containing the remaining components of the batch. Green bodies were then produced from the batch by casting. The green bodies were then heated to a temperature of 1500°C to give the finished refractory material.

[0056] Physical properties: Below we reproduce the physical properties of the green body according to the invention and of the refractory material according to the invention, together with the physical data of a known material (DELTEK A115, manufactured by RHI Magnesita) which is not according to the invention, for comparison.

[0057] [Table 1] TIFF2026500411000003.tif166147 * Klasse, F.; Heinz, A.; Hein, J.: "Comparative methods for determining the thermal conductivity of ceramic materials", Ber. DKG 34 (1957), pp. 183-189.

[0058] Table 1 shows that the refractory material of the present invention has high strength. Moreover, the thermal conductivity of the refractory material of the present invention is low compared to conventional materials. The significantly lower thermal conductivity of the refractory material of the present invention provides better thermal insulation and also has a positive effect on the flow properties of the material, since it can prevent undesirable clogging. Clogging is understood as the accumulation of solid components and / or particles in the part or pouring system, which can interrupt casting and thus reduce the pouring ability of the refractory material.

[0059] Measurement method: For measurements according to DIN EN ISO 1927-6, the geometry D specified in that standard was used.

[0060] The refractory materials were examined by optical and scanning electron microscopy. Optical microscopy was performed using a NIKON Eclipse LV150. Scanning electron microscopy was performed using a JEOL JSM-6460 or JEOL JSM-7900F scanning electron microscope.

[0061] The composition of each phase was determined by scanning electron microscopy using an energy dispersive detector with an excitation voltage of 10 kV and a probe current of 1 nA. Scanning electron microscope images were generated using a BSE detector.

[0062] FIG. 1 shows an image of the refractory material of the present invention obtained by optical microscopy, revealing the needle-like structure of the material. In particular, the visible regions contain structures with a hole-like or circular appearance, and in these regions the needle-like structure of the material is preferentially formed. The needles have a low thickness, preferably in the range of 0.01 to 8 μm, more preferably 0.2 to 5 μm. It is highly likely that the fine needles that form in the numerous regions contribute to the exceptional thermal shock resistance of the refractory material. In addition, it is believed that the circular structures in the refractory material may (or may prevent) crack propagation.

[0063] Figure 2 is an image of the refractory material of Figure 1 produced by scanning electron microscopy, showing the right side of the area shown in Figure 1. The acicular structure of the material is much more evident in Figure 2. Figure 2 shows regions 1 and 2, which correspond to the first phase, more specifically the Al4O4C phase.

[0064] FIG. 3 also shows an image of the refractory material of FIG. 1, produced by scanning electron microscopy. The detail shown in FIG. 3 corresponds to the left side of the area shown in FIG. 1. This detail shows a circular-looking structure with needle-like structures formed in situ at the surface or center. Areas 1 and 2 shown in FIG. 3 contain a second phase, more specifically Al. 28 C6N6O 21 There are phases corresponding to the phases.

[0065] FIG. 4 shows a further image of the refractory material of the present invention obtained by optical microscopy, revealing further areas of hole-like structures formed in situ by the needle-like structures of the material.

[0066] In this regard, Figure 5 shows an image of the upper part of the region shown in Figure 4, produced by scanning electron microscopy. In this region, too, the refractory material has a needle-like structure. Region 1 shown in Figure 5 contains a second phase, more specifically Al. 28 C6N6O 21Furthermore, Figure 5 also shows region 2, which contains a third phase, more specifically a phase corresponding to the SiAl6O2N6 phase.

[0067] FIG. 6 also shows an image of the refractory material of FIG. 4, produced by scanning electron microscopy. The detail shown in FIG. 6 corresponds to the lower part of the region shown in FIG. 4. In this region, the refractory material also has an acicular structure. The detail shows a circular-looking structure with many fine needles formed on the surface or in the center. Region 1 shown in FIG. 6 contains a second phase, more specifically Al. 28 C6N6O 21 6 also shows region 2, where a phase corresponding to a third phase, more specifically, the SiAl6O2N6 phase, exists. Additionally, FIG. 6 also shows region 3, where a phase corresponding to a fourth phase, more specifically, the AlN phase, exists.

[0068] Figure 7 shows a further image of the refractory material of the present invention obtained by optical microscopy, which again reveals circular areas where the needle-like structures of the refractory material are present.

[0069] Similarly, Figure 8 shows an image produced by BSE scanning electron microscopy of the refractory material with the needle-like structure depicted in Figure 7. Figure 8 shows regions 1 and 3, which correspond to the first phase, more specifically the Al4O4C phase. In addition, Figure 8 also shows regions 2 and 4, which correspond to the third phase, more specifically the SiAl6O2N6 phase.

[0070] Thermal shock resistance test: The following test evaluated the thermal shock resistance of the fire-resistant materials of the present invention.

[0071] a.Stopper cold start test:

[0072] In the first test, a stopper-shaped refractory material was immersed directly into molten steel at a temperature of 1650°C without preheating, after which the refractory material was removed from the molten steel and allowed to cool to room temperature.

[0073] This procedure was repeated for three cycles.

[0074] The fire-resistant material of the present invention exhibits excellent thermal shock resistance (see Figure 9).

[0075] b. Reusability testing:

[0076] In a further test, a steel ladle-shaped refractory material was immersed in molten steel, this time preheated, at a temperature of 1650°C. The refractory material was then removed from the steel and allowed to cool to room temperature.

[0077] This procedure was repeated for three cycles.

[0078] In this test as well, the fire-resistant material of the present invention exhibited excellent thermal shock resistance (see Figure 10).

[0079] Slag resistance test: Slag resistance is the ability of a refractory material to withstand the harmful effects of molten slag. Slag resistance is determined through the volume or mass loss of the refractory material when exposed to slag.

[0080] In this test, the refractory material of the present invention was evaluated against both acidic (C / S=0.8) and basic (C / S=3.2) slag components. In addition to the refractory material of the present invention (Fig. 11, left), a known refractory material for steel ladles (COMPRIT 185HMV manufactured by RHI Magnesita) (Fig. 11, right) was also evaluated as a comparative material.

[0081] In particular, the refractory material of the present invention exhibited very excellent slag resistance compared to a known refractory material for steel ladles (comparison material: COMPRIT 185HMV manufactured by RHI Magnesita) (see FIG. 11).

[0082] Pressure softening test (softening properties under pressure): Furthermore, the refractory material was tested for its softening properties under pressure (pressure softening).

[0083] The tests were carried out using firstly the fire-resistant material of the invention and secondly a known fire-resistant material (ANKO 85MR5A, manufactured by RHI Magnesita) as a comparison material.

[0084] The tests were carried out on cast specimens according to DIN EN ISO 1927-5. The specimens were dried at 110°C according to DIN EN ISO 1927-5.

[0085] Test piece: Cylinder (height (h): 50 mm, diameter (d): 40 mm, inner hole: 16 mm, measurement method conforms to ISO 5013)

[0086] The measurement of the softening properties under pressure (pressure softening) was carried out in accordance with DIN EN ISO 1893. In this case, an applied load of 0.2 MPa and a heating rate of 5°C / min in a reducing atmosphere were selected. The result obtained was T0.5 above 1700°C. This value is the temperature at which the maximum thermal expansion of the test specimen decreases by 0.5%. The maximum temperature in the measurement is limited to 1700°C.

[0087] In contrast to known refractory materials, no softening was observed in the material of the present invention up to 1700° C. (FIG. 12).

[0088] Thermal conductivity measurement test according to Dr. Klasse method: The thermal conductivities of the materials of the invention and the comparative material (DELTEK A115, manufactured by RHI Magnesita) reported in Table 1 were determined by the method of Dr. Klasse (Klasse, F.; Heinz, A.; Hein, J.: "Comparative Methods for Determining the Thermal Conductivity of Ceramic Materials", Ber. DKG 34 (1957), pp. 183-189.), where the values ​​reported at 1000°C were estimated by extrapolation.

Claims

1. 1. A refractory material having an acicular structure and heat treated at a temperature of at least 1300°C, preferably from 1300°C to 1750°C, to contain a combination of a first phase, a second phase, and a third phase, the first phase comprises, based on the total fraction of the first phase, 2 to 10 wt. % carbon, less than 5 wt. % nitrogen, 30 to 40 wt. % oxygen, 50 to 70 wt. % aluminum, and less than 5 wt. % silicon; the second phase comprises, based on the total fraction of the second phase, 1-7 wt. % carbon, 3-8 wt. % nitrogen, 25-35 wt. % oxygen, 55-65 wt. % aluminum, and less than 5 wt. % silicon; 1. A refractory material, wherein the third phase comprises less than 7 wt. % carbon, 14 to 28 wt. % nitrogen, 10 to 15 wt. % oxygen, 52 to 63 wt. % aluminum, and less than 20 wt. % silicon, based on the total fraction of the third phase.

2. The first phase is Al ４ O ４ Contains C or Al ４ O ４ Refractory material according to claim 1, characterized in that it consists of C.

3. The second phase is Al ２８ C ６ N ６ O ２１ Contains Al ２８ C ６ N ６ O ２１ The fire-resistant material according to claim 1 or 2, characterized in that it consists of

4. The third phase is SiAl ６ O ２ N ６ , SiAl ５ O ２ N ５ , SiAl ４ O ２ N ４ , Si ３ Al ７ O ３ N ９ and mixtures thereof, or SiAl ６ O ２ N ６ , SiAl ５ O ２ N ５ , SiAl ４ O ２ N ４ , Si ３ Al ７ O ３ N ９ and mixtures thereof, The fire-resistant material according to any one of claims 1 to 3.

5. the refractory material comprises a fourth phase; the fourth phase comprises less than 5 wt. % carbon, 26-36 wt. % nitrogen, less than 8 wt. % oxygen, 56-66 wt. % aluminum, and less than 5 wt. % silicon, based on the total fraction of the fourth phase; The fourth phase preferably comprises or consists of AlN. The fire-resistant material according to any one of claims 1 to 4, characterized in that

6. 6. The refractory material according to any one of claims 1 to 5, characterized in that the needle-like structures comprise needles with 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, as measured by scanning electron microscopy at an excitation voltage of 10 kV and a probe current of 1 nA.

7. 7. The fire-resistant material according to claim 1, wherein at least some of the needles have a minimum length to thickness ratio of at least 4:

1.

8. 8. Refractory material according to any one of claims 1 to 7, characterized in that the fraction of the phase with an acicular structure is at least 0.01% by weight, preferably 0.1% by weight, based on the total fraction of the refractory material.

9. A batch for producing a refractory material according to any one of claims 1 to 8, comprising the following composition: a) a particulate component as a coarse fraction having a particle size in the range of 0.5 to 10 mm selected from MA spinel, sintered alumina, high-grade alpha-alumina, brown alpha-alumina, gray alpha-alumina, mullite, bauxite, andalusite, SiC, grog, zirconium-containing components, and mixtures thereof; b) a particulate component as a fine particle fraction having a particle size in the range of less than 0.5 mm selected from sintered alumina, high-grade alpha-alumina, zirconium-containing components, and mixtures thereof; c) Finely divided Al ２ O ３ , preferably as a fine particle fraction 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, even more preferably a mixture of graphite and carbon black in a ratio ranging from 1:2 to 2:1, even more preferably a mixture of graphite and carbon black in a ratio of 1:1; e) metallic aluminum powder (Al powder); and f) Silica sol (silica in aqueous colloidal suspension), preferably SiO ２ Silica containing nanoparticles.

10. 10. The batch of claim 9, characterized in that one or more of the following components are present in the amounts set forth below, based on the total fraction of the batch composition: a) 50 to 80% by weight, preferably 53 to 70% by weight, more preferably 55 to 67% by weight, and even more preferably about 59% by weight of a particulate component as a coarse fraction having a particle size in the range of 0.5 to 10 mm; b) 5 to 35% by weight, preferably 7 to 30% by weight, more preferably 10 to 30% by weight, and even more preferably about 23% by weight of the particulate component as a fine particle fraction having a particle size in the range of less than 0.5 mm; c) 0.05 to 4 wt. %, preferably 0.1 to 3 wt. %, more preferably 1 to 2.5 wt. %, and even more preferably about 2 wt. % finely divided Al ２ O ３ ; d) 2-10 wt. %, preferably 3-8 wt. %, more preferably 3.5-6 wt. %, and even more preferably about 4.5 wt. % carbon; e) 2 to 8 wt. %, preferably 3 to 7 wt. %, more preferably 4 to 6 wt. %, and even more preferably about 5 wt. % of metallic aluminum powder, Al powder; and 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 at a solids content (SiO ２ The SiO sol (fraction of silica particles) is preferably in the range of 20 to 50% by weight, more preferably 30 to 50% by weight, based on the total weight of the silica sol (aqueous colloidal silica suspension). ２ Silica containing nanoparticles.

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

12. A method for producing a refractory material according to any one of claims 1 to 8, comprising the following steps: i. providing a batch according to claim 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 in the range of 1300°C to 1750°C.

13. Use of a green body produced from a refractory material according to any one of claims 1 to 8 or a batch according to claim 9 or 10, comprising: Use for the manufacture of refractory products for iron and steel applications, in particular steel ladles, tundishes, perforated blocks, CAS-OB bells; Use for the manufacture of refractory products, in particular cast products, in the pig iron sector, and / or Use for the manufacture of refractory products in the field of flow control, in particular slide gate plates, collector nozzles, tube shrouds, stoppers, immersed pipes, internal nozzles, weirs, dams, shock absorbers and other nozzles.

Images