USE OF A THERMALLY INSULATING MOLDED BODY FOR ISOLATION OF MELTED METAL FROM THE ATMOSPHERE OR A METALLURGICAL VESSEL

Description

[0001] The present invention relates to the use of a heat-insulating, refractory, unfired shaped body, in particular a plate, for the thermal insulation of metal melts, in particular steel melts, and / or a solidifying cast ingot, from the surrounding atmosphere or a metallurgical vessel, in particular in the production of steel in steelworks.

[0002] The present invention relates in particular to the use of a heat-insulating cover plate for covering molten metals, in particular molten steel, and / or a solidifying cast ingot located in a metallurgical vessel.

[0003] The present invention also relates to the use of a heat-insulating, refractory, unfired shaped body for the thermal insulation of a refractory lining.

[0004] In metallurgy, it is common practice to cover the exposed surface of molten metal, especially molten steel, in an open metallurgical vessel with a covering agent. The covering agent forms a protective and thermally insulating layer. On the one hand, it shields the molten metal pool from atmospheric gases to prevent undesirable chemical reactions in the molten metal. On the other hand, it serves as insulation or thermal insulation against the atmosphere. Thus, the covering agent ensures good surface quality.

[0005] Loose fills of refractory materials, particularly rice husk ash, are commonly used as covering materials. Rice husk ash is produced in large quantities in many rice-producing countries. It is a byproduct of the combustion of rice husks (husks).

[0006] When these are burned, rice husk ash is produced, which is chemically very pure and consists of 94-96% amorphous SiO2. Rice husk ash is therefore also known as biogenic silica. It has a very high melting point of approximately 1,650°C. During production, the volatile components burn off, but a unique, microporous structure of the SiO2 is retained. This structure results in both extremely low thermal conductivity and a low bulk density of the rice husk ash. Although rice husk ash therefore provides excellent thermal insulation, its extremely fine particle size, particularly when applied to the surface of molten metal, leads to high levels of dust pollution, which can be hazardous to health and cause, for example, eye injuries. The fine dust particles can enter the human body.For this reason, for example, suction devices must be installed, which in turn lead to material losses due to the suction of the rice husk ash.

[0007] For this reason, it is also known to use granules as covering agents instead of pure rice husk ash. These granules consist of granulated refractory materials that are solidified with a binding agent. Examples of such granules are described in DE 10 2013 000 527 A1, DE 197 28 368 C1, and DE 197 31 653 C2.

[0008] The granules described in DE 10 2013 000 527 A1 contain primarily diatomaceous earth, preferably up to 90% by weight. Bentonite, water glass, or cellulose, for example, are used as binding agents. The granules may also contain polyvinylpolypyrrolidone as a binding agent. The granules melt after some time.

[0009] The granulate of DE 197 28 368 C1 comprises granules which are produced from rice husk ash, an organic, gel-forming binder in amounts of 1 to 10 wt.% and water in amounts of 20 to 100 wt.%.

[0010] The beads / pellets of the granulate described in DE 197 31 653 C2 consist of rice husk ash mixed with a surfactant and a binder. The surfactant can be sodium alginate, sodium salt of carboxymethylcellulose, sodium hexametaphosphate, or mixtures thereof. The binder can be polyvinyl alcohol, molasses, sodium hexametaphosphate, Portland cement, sodium silicate, precipitated calcium carbonate, and mixtures thereof. After mixing and pressing, the beads / pellets are dried and then fired at a temperature of 800–1400 °C.

[0011] While the granules significantly reduce dust pollution compared to pure rice husk ash, they also have a higher bulk density and thus result in poorer insulation. Furthermore, due to the manufacturing process, they are significantly more expensive than fills made from pure rice husk ash.

[0012] The metallurgical vessels to be covered are, in particular, a metal distributor, preferably a tundish, a pouring ladle, or a mold for rising or falling ingot casting. In ingot casting, the liquid metal is poured into a vertical mold (mold) and solidifies there. The filling can occur either from above (falling ingot casting) or via a feed system from below (rising ingot casting). After solidification, the mold is stripped, i.e., removed from the solidified metal, and the cast ingot is further processed.

[0013] As the molten steel solidifies in the mold, shrinkage cavities (shrinkage cavities) can form, especially in the ingot head. Components with a relatively low melting temperature are forced upward ahead of the crystallization front of higher-melting components. This, along with the flow of rising gas bubbles, can cause elements such as sulfur, phosphorus, and carbon to concentrate in the ingot head. This process, known as ingot segregation, occurs. Floated slag, thus, results in "head waste." Therefore, the affected upper section of the ingot must be removed before further processing.

[0014] Good thermal insulation of the ingot head allows the molten metal to remain liquid longer and solidify more slowly. The casting ingot is completely sealed, and the portion to be separated remains relatively small. Head insulation is therefore particularly important in ingot casting.

[0015] During vertical ingot casting in steel production, a holding plate or metal rod is typically first placed on the mold to insulate the ingot head. The holding plate is typically made of heat-generating materials (so-called "exothermic plate") consisting of mixtures of various refractory oxides with metal powder, often containing fluoride. A bag of casting powder is attached to the holding plate or metal rod by means of a rope. The bag burns after a short time due to the high heat of the molten steel, so that the casting powder is distributed over the molten steel and acts as a separating and lubricating agent between the mold and the steel bath. The holding plate or metal rod is then removed, and the respective fill material is manually applied to the molten metal surface as a covering agent. This process is very labor-intensive and, due to the close proximity to the hot mold, dangerous for the operator.

[0016] It is also known to minimize the blowhole in the ingot head by using an annular insulation hood (so-called "pouring hood"). The insulation hood is arranged as a separate component at the upper end of the mold or at the mold head and inserted into it. It thus insulates the mold head from the molten steel in the area of ​​the ingot head. The insulation hood can be designed as a one-piece component or consist of several interconnected plates. The one-piece insulation hoods and the plates are usually made of thermally insulating material.

[0017] EP 1 728 571 A1 discloses an insulating feeder for use in the foundry industry, comprising ceramic hollow spheres, hollow glass spheres, a cured binder, and optionally fiber material. The cured binder can be, for example, a thermoset former, silicate former, or starch, preferably, for example, water glass. Furthermore, EP 1 728 571 A1 discloses that the feeder can contain biogenic silica, e.g., rice husk ash, as other filler materials. The total amount of hollow glass spheres and ceramic hollow spheres is preferably in the range of 40 to 60 wt.%.

[0018] According to EP 1 728 571 A1, the riser is manufactured by mixing the components, forming the mixture into a riser, and curing the formed riser. The forming step is carried out using the slurry process or the green-state process.

[0019] GB 2 347 143 A relates to a composition for producing a product with good thermal insulation, the composition comprising biogenic silica, fibres and a binder, the biogenic silica being substantially free of cristobalite. The biogenic silica material may be rice husk ash. The products are produced, for example, using 400 litres of water to produce a slurry. The binder may comprise silica sol or the binder may be a resin. In the examples, a combination of silica sol and starch is used. In the example given, the proportion of other additives (mineral fibres, alumina, kaolin) is also significantly greater than 50% by weight.

[0020] Furthermore, GB 2 347 143 A discloses as exemplary uses for the products pouring cups and pouring ladles which are used in the metallurgical industry.

[0021] DE 28 47 807 A1 discloses a lightweight, fire-resistant, insulating material in sheet form, the components of which are dry-mixed, formed under pressure, and bonded with a chemical binder. The material is made from a dry mixture of 40-85%, preferably 50-75%, rice husk ash, 15-60%, preferably 25-50%, perlite, and 0-10%, preferably 2-5%, mineral wool. Water is added to the mixture, and the mixture is bound with a phosphate binder, preferably monoaluminum phosphate, then formed into sheet form under pressure and dried. The material is used for lining industrial furnaces.

[0022] US 3,558,591 discloses a molding compound for use in the production of casting top linings comprising 15 to 50 wt.% fiber material, 40 to 80 wt.% refractory filler, and 0.5 to 10 wt.% of a binder. The refractory filler can consist entirely or partially of lightweight filler consisting of diatomaceous earth, bubble alumina, hollow silica microspheres, calcined rice hulls, or pozzolan. Examples of binders disclosed include sodium silicate, natural gums, cereal flour, and thermosetting resins, with resins being preferred. Production is carried out according to US 3,558,591 by preparing a slurry and subsequently filtering the water out using a type of sieve. The cold bending strengths given in the examples in US 3,558,591 are only 0.45, 0.51 and 0.48 MPa, respectively.According to US 3,558,591, good gas permeability is important to dissipate the resulting casting gases and thus prevent bubble formation.

[0023] The object of the present invention is to provide a heat-insulating shaped body, in particular a heat-insulating plate, which is used for the thermal insulation of metal melts, in particular steel melts, from the surrounding atmosphere and / or a metallurgical vessel, in particular in the production of steel, wherein the shaped body should be simple and cost-effective to produce, should ensure good thermal insulation and should be neither harmful to health nor harmful to the environment.

[0024] In addition, such a shaped body is to be provided which is used for the thermal insulation of a refractory lining.

[0025] This object is achieved by the use of a shaped body, preferably a plate, according to claim 1 and by the use of a shaped body according to claim 15. Advantageous developments of the invention are characterized in the subsequent subclaims.

[0026] The invention is explained in more detail below using a drawing as an example. The drawings show: Figure 1: Schematically a cross-sectional section through the plate used according to the invention Figure 2: Schematically and greatly simplified a mold for the ascending ingot casting before the start of the casting process with a cover plate Figure 3: The mold according to Figure 2 during the casting process Figure 4:The mold according to Figure 2 at the end of the casting process Figure 5: Schematic and highly simplified view of a pouring distributor before the sprue Figure 6: The pouring distributor according to Figure 5 after sprue

[0027] According to a first embodiment of the invention, the shaped body 1 is used for the thermal insulation of a molten metal, in particular a molten steel, and / or a metallic cast block 14 solidifying from the molten metal.

[0028] According to a second embodiment of the invention, the shaped body 1 is used as thermal insulation in a multi-layer masonry or in heat treatment furnaces for refractory linings or as a corrosion barrier (e.g. against alkali attack) or as a fire protection lining or as a filter material for hot gases.

[0029] The unfired shaped body 1 used according to the invention ( Fig. 1-6) has a binder matrix 2 made of at least one set binder, in which aggregate grains 3 made of biogenic silica, preferably rice husk ash, are embedded or bound. The aggregate grains 3 are distributed in the binder matrix 2. The binder is a permanent binder. A permanent binder is a binder which hardens below the temperature for ceramic firing, but does not evaporate under thermal stress, in particular in an O 2 atmosphere, but rather transforms and forms a binder matrix with a ceramic or other bond. Permanent binders thus ensure the cohesion of the unfired shaped body 1 at room temperature as well as during use under thermal stress, in particular in an O 2 atmosphere. In contrast, a temporary binder burns out and evaporates under thermal stress.Permanent binders harden at temperatures below the temperature required for ceramic firing, e.g., at room temperature, e.g., hydraulically or chemically (inorganic or organic-inorganic), or organically. Under thermal stress, they form a direct ceramic bond, e.g., through sintering. Phosphate bonds and cement bonds, for example, are transformed under thermal stress but remain intact.

[0030] According to the first embodiment of the invention, the permanent binder is water glass or a sol-gel binder or a phosphate binder or alumina cement or Portland cement.

[0031] According to the second embodiment of the invention, the permanent binder is water glass or a sol-gel binder or alumina cement or Portland cement.

[0032] The binder matrix 2 can, of course, also consist of several permanent binders. This allows certain properties of the molded body 1 to be adjusted in a particularly advantageous manner.

[0033] The binder matrix 2 can also additionally comprise at least one set temporary binder. Preferably, however, the binder matrix 2 consists exclusively of one or more permanent, set binders. It is thus a permanent binder matrix 2.

[0034] According to the first embodiment of the invention, the biogenic silica according to the invention is exclusively rice husk ash.

[0035] According to the second embodiment of the invention, the biogenic silica is preferably exclusively rice husk ash. However, it can also be diatomaceous earth (kieselguhr) or siliceous slate, or radiolarian skeletons or opal sponges that have been diagenetically solidified into rock. Mixtures of different biogenic silicas can also be present as additives.

[0036] Furthermore, the molded body 1 according to both embodiments can also comprise additional aggregates made of refractory material. Aggregates within the meaning of the invention are generally substances that, or whose grains, are distributed in the binder matrix 2 and are bound or embedded therein. The aggregates do not react with the binder during setting, or only react superficially. The aggregate grains are thus essentially mechanically bound into the binder matrix 2.

[0037] In particular, the molded body 1 comprises microsilica, preferably pyrogenic and / or precipitated silica, as an additive. The molded body 1 can also comprise expanded perlite and / or expanded vermiculite and / or expanded clay and / or inorganic fibers, preferably mineral and / or slag and / or glass and / or ceramic fibers, and / or fly ash and / or (power plant) filter dust as an additive.

[0038] Microsilica, fly ash, and / or (power plant) filter dust can also react and form the binder matrix, depending on whether reactants are present in the mixture. In this case, they are not counted as aggregates but as part of the binder.

[0039] According to the first embodiment of the invention, the aggregate of the molded body 1 consists of at least 50 wt.%, preferably at least 80 wt.%, particularly preferably at least 90 wt.%, rice husk ash, in each case based on the total content (dry matter) of aggregates. Advantageously, the molded body 1 contains exclusively rice husk ash as an aggregate. The aggregate of the molded body 1 thus advantageously consists of 100 wt.% rice husk ash.

[0040] According to the second embodiment of the invention, the aggregate of the shaped body 1 consists of at least 50 wt.%, preferably at least 80 wt.%, particularly preferably at least 90 wt.%, biogenic silica, preferably rice husk ash, in each case based on the total content (dry mass) of aggregates. Advantageously, the shaped body 1 contains exclusively biogenic silica, preferably exclusively rice husk ash, as aggregate. The aggregate of the shaped body 1 thus advantageously consists of 100 wt.% biogenic silica, preferably 100 wt.% rice husk ash.

[0041] The molded body 1 according to the invention is produced as follows: First, the dry components are mixed. The dry components are the biogenic silica, in particular the rice husk ash, and optionally the other additives, as well as optionally at least one permanent binder, if present in dry form. Water or another liquid solvent is then added to the dry mixture to dissolve, disperse, or activate the binder. However, at least one permanent binder can also be present in a dissolved or dispersed form and added in liquid form to the dry mixture of the remaining components.

[0042] The composition of the finished mixture is preferably adjusted so that after 30 seconds of vibration, the mixture has a slump, determined in accordance with DIN EN ISO 1927-4 (03 / 2013), of 200 to 500 mm, preferably 250 to 350 mm, without any separation between coarse and fine grain fractions, as is the case with pure rice husk ash.

[0043] Preferably, the finished mixture or batch for producing the shaped body 1 has the following composition with regard to the dry components based on the total dry mass, wherein the individual components add up to 100% by weight: Proportion [wt.%] preferably Rice husk ash 20.0 to 95.0 45.0 to 90.0 Permanent binder 5.0 to 30.0 10.0 to 20.0 Other aggregates 0 to 20.0 0 to 10.0 Other ingredients 0 to 30.0 0 to 25.0

[0044] Furthermore, the weight ratio of the liquid solvent, preferably water, to the dry components is preferably 2:1 to 1:9, more preferably 1:1 to 3:7.

[0045] The rice husk ash used preferably has the following chemical composition according to DIN EN ISO 12677 (02 / 2013), whereby the individual components (without loss on ignition) add up to 100 wt.%: Proportion [wt.%] preferably SiO2 92 to 98 94 to 97 P2O5 0.5 to 2.0 0.5 to 1.5 K2O 1.0 to 3.0 1.5 to 2.5 Residual oxides 0.5 to 3.0 1.0 to 2.0

[0046] The biogenic silica used, in particular rice husk ash, also preferably has the following particle size distribution according to DIN 66165-2 (04 / 1987) based on the dry mass, with the individual components adding up to 100% by weight: Grain size [mm] Proportion [wt.%] preferably ≥ 2,0 0 to 3.0 0.01 to 0.5 < 2,0 - 1,0 0.05 to 4.0 0.1 to 2.0 < 1,0 - 0,5 1.0 to 40.0. 1.5 to 35.0 < 0,5 - 0,3 3.95 to 40.0 8.39 to 30.0 < 0,3 30.0 to 95.0 40.0 to 90.0

[0047] The bulk density according to DIN EN 1097-3 (06 / 1998) of the biogenic silica used, in particular the rice husk ash, is preferably 0.05 to 0.5 g / cm 3< , more preferably 0.1 to 0.4 g / cm 3< .

[0048] The finished mixture is then poured into a mold and compacted therein. Compaction is carried out according to the first embodiment of the invention, and preferably by means of vibration or uniaxial pressing according to the second embodiment.

[0049] With vibratory loading, the mold is placed on a vibrating table. A weight is placed on the finished mix in the mold, the vibrating table is activated, and the mix is ​​compacted by vibration. Vibratory loading is generally used to produce smaller formats.

[0050] In uniaxial pressing, the mold filled with the finished mixture is placed in a press, with a cover plate placed over the mixture. The press's upper ram is then moved against the cover plate, compacting the mixture with a specific pressure. Preferably, multiple pressing strokes are performed. Uniaxial pressing is generally used to produce larger formats.

[0051] After compaction, the green-strength molded body is demolded and allowed to set. The setting temperature is selected so that the binder sets or hardens. It is below the temperature for ceramic firing. The molded body 1 according to the invention is therefore unfired. Cement-bonded molded bodies are preferably allowed to set at room temperature, preferably until constant weight is reached. With other binders, e.g. water glass or sol-gel binders, setting takes place in particular at 110 to 200 °C for preferably 4 to 12 hours. Phosphate-bonded molded bodies are preferably allowed to set at temperatures of 200 to 500 °C to ensure complete bonding with release of water, or up to 1000 °C to obtain a water-insoluble bond.

[0052] The shaped body 1 used according to the invention then preferably has a dry bulk density ρ 0 of 0.3 to 1.5 g / cm 3< , preferably of 0.5 to 1.3 g / cm 3< , according to DIN EN 1094-4 (09 / 1995).

[0053] In addition, the shaped body 1 preferably has a porosity of 60 to 90%, preferably 70 to 80%, according to DIN EN 1094-4 (09 / 1995).

[0054] The cold compressive strength of the shaped body 1 is preferably 1.5 to 20.0 MPa, more preferably 2.5 to 15.0 MPa, according to DIN EN 993-5 (12 / 1998).

[0055] And the cold bending strength of the shaped body 1 is preferably 1.0 to 9.0 MPa according to the second embodiment and 1.5 to 7.0 MPa according to the invention according to DIN EN 993-6 (04 / 1995) according to the first embodiment.

[0056] The hot bending strength of the shaped body 1 is preferably 1.5 to 7.0 MPa, more preferably 2.0 to 5.0 MPa, according to DIN EN 993-7 (04 / 1995).

[0057] In addition, according to the second embodiment, the molded body 1 has a softening point determined with a heating microscope according to DIN EN 51730 (09 / 2007) of 1200 to 1650 °C. And according to the first embodiment, the molded body 1 preferably has a softening point determined with a heating microscope according to DIN EN 51730 (09 / 2007) of 800 to 1700 °C, preferably 1200 to 1650 °C.

[0058] Thus, the molded body 1 is suitable for long-term or permanent use at very high temperatures.

[0059] In addition, the molded body 1 preferably has the following thermal conductivities according to DIN EN 993-15 (07 / 2005): WLF [W / mK] preferably at 26°C 0.10 to 0.14 0.11 to 0.13 at 307°C 0.12 to 0.16 0.13 to 0.15 at 700°C 0.17 to 0.21 0.18 to 0.20 at 995°C 0.25 to 0.29 0.26 to 0.28

[0060] The molded body 1 according to the invention also preferably has the following chemical composition according to DIN EN ISO 12677 (02 / 2013), wherein the individual components (without loss on ignition) add up to 100 wt.%: Proportion [wt.%] preferably SiO2 22.0 to 99.0 43.5 to 97.5 Al 2 O 3 0 to 15.0 0 to 10.0 P2O5 0.2 to 20.0 0.5 to 15.0 CaO 0 to 20.0 0 to 15.0 K2O 0.3 to 10.0 0.5 to 7.5 Na2O 0 to 10.0 0.5 to 7.5 Residual oxides 0.5 to 3.0 1.0 to 1.5

[0061] As already explained, the molded body 1 according to the first embodiment is used according to the invention for thermally insulating a molten metal, in particular a molten steel, from the surroundings. Preferably, the molded body 1 is used for thermally insulating the head block during rising ingot casting.

[0062] A block casting device 4 ( Fig. 2 and 3) for the vertical casting of metal, in particular steel, typically comprises a base frame 5 with a pouring channel 6 for supplying the molten metal, in particular steel. Furthermore, the ingot casting device 4 comprises a tubular mold 7 for receiving a metal bath 8 of molten metal. The mold 7 has a lower and an upper, open mold end 7a;b. The upper mold end 7b forms a mold head 9 of the mold 7.

[0063] According to an advantageous aspect of the invention, the mold body 1 is used as a cover plate 10 for covering the upper, open mold end 7b. For this purpose, the cover plate 10 is applied before the start of the ingot casting ( Fig. 2) is placed on the mold head 9. The placement on the mold 7 thus takes place without direct contact with the metal bath 8. The metal bath 8 is thus thermally insulated indirectly, i.e. without direct contact, by the cover plate 10. A casting powder bag 11 filled with casting powder is attached to the cover plate 10 in such a way that it hangs down from the cover plate 10 into the mold 7. To attach the casting powder bag 11, the cover plate 10 preferably has a central recess 12 running continuous from one plate surface to the other.

[0064] Now the molten metal, in particular the molten steel, is poured through the pouring channel 6 from below into the mold 7 and rises upwards ( Fig. 3). The metal bath 8, in particular the steel bath, typically has a temperature of approximately 1550°C. The casting powder bag 11 therefore burns after a short time due to the high heat of the molten steel, so that the casting powder is distributed over a metal bath surface 8a and forms a superficial casting powder layer 13. The casting powder is also distributed between the mold 7 and the metal bath 8 and acts as a separating and lubricating agent.

[0065] The metal bath 8 rises during the sprue up to the cover plate 10 and forms a solidifying cast block 14 with an upper block head 15 ( Fig. 4 ). The cover plate 10 insulates the block head 15 from the atmosphere and thus ensures slow cooling of the block head 15.

[0066] According to a further advantageous aspect of the invention, the molded body 1 is used as an insulating plate 16 for a casting hood or insulating hood 17 for thermally insulating the ingot head 15 from the mold 7, in particular from the mold head 9. The annular insulating hood 17 consists of several interconnected insulating plates 16 arranged adjacent to one another in the circumferential direction of the mold 7. It serves as the inner lining of the mold head 9. The insulating hood 17 thus rests on the inside against a mold wall 18. It can also protrude beyond the mold 7 at the upper mold end 7b (not shown). In this case, it is used in particular together with a loose fill to insulate the metal bath surface 8a, which is vacuumed off at the end of the casting process.

[0067] The insulating hood 17 can also be formed in one piece and the molded body 1 can thus be used as an insulating hood 17.

[0068] The molded body 1 can also advantageously be used as a cover plate for covering or insulating the free metal bath surface 8a in another metallurgical vessel open at the top. In particular, the molded body 1 can be used as a cover plate 19 for a pouring distributor 20 ( Fig. 5 and 6 ), preferably a continuous casting tundish is used.

[0069] Before the sprue, the pouring distributor 20 is preferably covered with several cover plates 19 ( Fig. 5 During the casting process, the metal bath 8 rises to the cover plates 19. These form a continuous, insulating covering layer covering the metal bath surface 8a.

[0070] The molded body 1 can also be used advantageously as a cover plate for covering or insulating the free metal bath surface 8a in a casting ladle or in troughs.

[0071] The molded body 1 can also be placed directly on the metal bath surface 8a so that it floats on it.

[0072] The molded body 1 used according to the invention exhibits low thermal conductivity at both low and high temperatures, thus providing excellent thermal insulation properties. When used for block head insulation in vertical ingot casting, this ensures consistently good block head quality. The good thermal insulation results in particular from the excellent thermal insulation properties of the biogenic silica and its very high melting point of approximately 1650 °C.

[0073] Furthermore, molded body 1 is free of harmful substances. Furthermore, rice husk ash is a natural recycling product.

[0074] When the cover plate 10 is used simultaneously as a holding plate for the casting powder bag 11 and subsequently for insulating the block head 15, an additional process step is eliminated. This is because removing the holding plate and subsequently applying the loose rice husk ash is no longer necessary.

[0075] In addition, dust pollution is significantly reduced. Placing the cover plates 10; 19 on the mold 7 or the pouring manifold 20 is also significantly easier than applying a loose fill to the metal bath surface 8a. Furthermore, this can be done before the molten metal is poured in, which means a significantly lower temperature stress for the operator.

[0076] It is also within the scope of the invention that production advantageously takes place by granulating the biogenic silica, in particular the rice husk ash, with water and / or at least one binder before mixing it with the other components of the shaped body, and then mixing the soft or plastic, not yet set granules with the remaining components. The binder is preferably the same binder(s) used for the shaped body. During compaction or pressing, the plastic granules are destroyed, so that the shaped body according to the invention with the additive grains of biogenic silica is created. The advantage of this process variant is that dust development is lower. Example:

[0077] A plate according to the invention was produced from a batch with the following composition by means of load vibration: Proportion [wt.%] Water glass (Betol 52 T) 50 Rice husk ash NERMAT BF - E 50

[0078] The finished mixture was compacted for 30 seconds at a frequency of 50 Hz and an amplitude of 0.8 mm. The weight per unit area of ​​the applied weight was 0.005 N / mm 2 . The panel was demolded and dried on a metal sheet in a drying cabinet at 150°C for 12 hours, and allowed to set. The panel had the following dimensions: 500 x 500 x 300 mm 3 . The manufactured panel had the following properties: Dry bulk density ρ 0 (DIN EN 1094-4 (09 / 1995)) 0.73 g / cm 3 Porosity (DIN EN 1094-4 (09 / 1995)) 70,00 % Cold pressure resistance (DIN EN 993-5 (12 / 1998)) 4.4 N / mm 2 Cold bending strength (DIN EN 993-6 (04 / 1995)) 2.4 N / mm 2

Claims

1. Use of an unfired, refractory molded body (1), comprising a binding agent matrix (2) containing at least one set, permanent binding agent and aggregate grains (3) of rice husk ash, which grains (3) are incorporated into the binding agent matrix (2), wherein the aggregate of the molded body (1) consists of at least 50 wt-% of rice husk ash, relative to the total dry mass of aggregates materials, and wherein the at least one permanent binding agent pertains to water-glass or a sol-gel binder or a phosphate binder or alumina cement or Portland cement, and wherein the molded body (1) comprises a cold bending strength from 1.0 to 9.0 MPa, preferably from 1.5 to 7.0 MPa according to DIN EN 993-6 (04 / 1995), for thermal isolation of molten metal, especially of molten steel, and / or of a metallic ingot (14) solidifying from the molten metal, wherein a molded body (1) is used which is produced with the following method steps: a) Preparation of a mixture having the aggregate grains (3) of the rice husk ash, the at least one, permanent binding agent, and potentially a solvent for the permanent binding agent, b) Filling the mixture into a mold, c) Compacting the mixture by means of superimposed load vibration or uniaxial pressing, d) Removing the green molded body (1) from the mold, e) Letting the molded body (1) set.

2. Use according to claim 1, characterized in that the molded body (1) is used for thermal isolation of the molten steel and / or of the ingot (14), preferably of an ingot head (15) of the ingot, for the production of steel, preferably in rising ingot casting.

3. Use according to one of the preceding claims, characterized in that the molded body (1) is used for thermal isolation of the molten metal, in particular of the molten steel, located in a metallurgical vessel, and / or of the ingot (14) located in a metallurgical vessel, from the vessel itself and / or from the atmosphere.

4. Use according to one of the preceding claims, characterized in that the molded body (1) is a plate (1).

5. Use according to claim 4, characterized in that the molded body (1) is used as covering plate (10) for covering and for thermal isolation of a metal bath (8), in particular a steel bath, located in a ingot mold (7), preferably in falling or rising ingot casting, and / or as covering plate (19) for covering and for thermal isolation of a metal bath (8), in particular a steel bath, located in a casting distributor (20).

6. Use according to one of the preceding claims, characterized in that the aggregate of the molded body (1) consists of at least 80 wt-%, preferably of at least 90 wt-%, particularly preferably of 100 wt-% of rice husk ash, relative to the total dry mass of aggregates materials.

7. Use according to one of the preceding claims, characterized in that the molded body (1) comprises a dry apparent density p0 from 0.3 to 1.5 g / cm3, preferably from 0.5 to 1.3 g / cm3 according to DIN EN 1094-4 (09 / 1995) and / or a porosity from 60 to 90%, preferably from 70 to 80% according to DIN EN 1094-4 (09 / 1995).

8. Use according to one of the preceding claims, characterized in that the molded body (1) comprises a cold compression strength from 1.5 to 20.0 MPa, preferably from 2.5 to 15.0 MPa according to DIN EN 993-5 (12 / 1998) and / or a hot bending strength from 1.5 to 7.0 MPa, preferably from 2.0 to 5.0 MPa according to DIN EN 993-7 (04 / 1995).

9. Use according to one of the preceding claims, characterized in that the molded body (1) comprises a softening point from 800 to 1700 °C, preferably 1200 to 1650 °C, determined with a hot stage microscope according to DIN EN 51730 (09 / 2007).

10. Use according to one of the preceding claims, characterized in that the molded body (1) comprises the following thermal conductivities (TC) according to DIN EN 993-15 (07 / 2005): TC [W / mK]preferablyat 26°C0.10 to 0.140.11 to 0.13at 307°C0.12 to 0.160.13 to 0.15at 700°C0.17 to 0.210.18 to 0.20at 995°C0.25 to 0.290.26 to 0.2811. Use according to one of the preceding claims, characterized in that a molded body (1) is used which is produced from a mixture whose composition is adjusted such that the mixture after 30 s under vibration, has a slump of 200 to 500 mm, preferably 250 to 350 mm, determined in reference to DIN EN ISO 1927-4 (03 / 2013).

12. Use according to one of the preceding claims, characterized in that a molded body (1) is used which is produced from a mixture which comprises the following composition relative to the total dry mass, wherein the individual constituents add up to 100 wt-%: Amount [wt-%]preferablyRice husk ash20.0 to 95.045.0 to 90.0Permanent binding agent5.0 to 30.010.0 to 20.0Other aggregate materials0 to 20.00 to 10.0Other constituents0 to 30.00 to 25.

013. Use according to one of the preceding claims, characterized in that a molded body (1) is used which is produced in that before mixing with the other constituents of the mixture, the aggregate grains (3) from the biogenic silicic acid are agglomerated with water and / or with at least one binding agent to form granulate grains and the granulate grains in the ductile state are mixed with the other constituents of the mixture.

14. Use according to one of the preceding claims, characterized in that the binding agent matrix (2) contains reacted microsilica, reacted fly ash and / or reacted (power plant) filter dust.

15. Use of an unfired, refractory molded body (1), comprising a binding agent matrix (2) containing at least one set, permanent binding agent and aggregate grains (3) of biogenic silicic acid, preferably of rice husk ash, which are incorporated into the binding agent matrix (2), wherein the aggregate of the molded body (1) consists of at least 50 wt-% of biogenic silicic acid, preferably of rice husk ash, relative to the total dry mass of aggregates materials, and wherein the at least one permanent binding agent pertains to water-glass or a sol-gel binder or alumina cement or Portland cement, and wherein the molded body (1) comprises a softening point from 1200 to 1650 °C, determined with a hot stage microscope according to DIN EN 51730 (09 / 2007), for thermal isolation of a refractory lining, especially in a multiple-layer brick wall or in a heat-treatment furnace, or as a corrosion barrier, e.g. against alkali attack, or as a fire protection lining or as filter material for hot gasses.

16. Use according to claim 15, characterized in that the molded body (1) comprises a cold bending strength from 1.0 to 9.0 MPa, preferably from 1.5 to 7.0 MPa according to DIN EN 993-6 (04 / 1995).

17. Use according to claim 15 or 16, characterized in that a molded body (1) is used which is produced with the following method steps: a) Preparation of a mixture having the aggregate grains (3) with and / or biogenic silicic acid, the at least one, permanent binding agent, and potentially a solvent for the permanent binding agent, b) Filling the mixture into a mold, c) Compacting the mixture, d) Removing the green molded body (1) from the mold, e) Letting the molded body (1) set.

18. Use according to one of claims 15 to 17, characterized in that a molded body (1) with the features of one of claims 4, 7 to 14 is used.