DE102014004138A1 - Process for the highly productive production of flow-through structures low component density of metallic, ceramic or metal-ceramic materials - Google Patents

Abstract

Method for the automated and thus highly productive production of high-temperature-stable molded articles of low component density and low heat capacity which can easily be flowed through in several spatial directions and made of metallic and / or ceramic materials, characterized in that a. initially single or multilayer green films are made of ceramic, metal or metal-ceramic materials, b. which are then partially coated with a suitable material for joining the green sheets, c. be stacked afterwards, d. be provided with openings at defined locations, e. then cut into multilayer strips, f. which in turn can be stacked and partially interconnected, g. wherein the method steps b to f can also take place in a different order, h. before being expanded to form a honeycomb structure, i. one or more single-component or multicomponent green films of metallic and / or ceramic and / or metal-ceramic materials are laminated on their upper and lower cover surfaces with a suitable process and the necessary auxiliaries which have a composition which seals after debindering and sintering or form porous structure, and may have the breakthroughs, or which are attached to ceramic green body to z. To stiffen freestanding walls, j. and finally, a heat treatment involving debindering and sintering is performed to make a material bond between all the individual components.

Description

The invention relates to the field of materials technology and relates to a method for the production of ceramic, metal or metal-ceramic 3-dimensional moldings, which are characterized by a low density and good flow through in at least two spatial directions. These moldings can, for. B. are used as kiln furniture or radiation shields in a heat treatment, which is essentially the sintering of ceramic or metallic components.

The molded articles must have sufficient strength even at high operating temperatures in order to securely store or transport the firing material positioned thereon. In addition, only low mechanical stresses may be thermally induced in these moldings by a suitable choice of materials and suitable constructive solutions in order to ensure a good thermal shock resistance. For the moldings materials should be used, which avoids contamination of the fuel or influencing the properties of the fuel. From an economic point of view, the moldings should have a lower heat capacity compared to all-ceramic moldings, which reduces the energy consumption during heating and the time required for cooling, as well as a more homogeneous heat input into the molded body to allow the most homogeneous heating and cooling possible.

In DE 298 16 572 U1 It is proposed to use a ceramic plate made of cordierite or cordierithaltigem material with through holes as kiln furniture. A network of interconnected, vertical webs defines a plate with lying between the webs, one-dimensional flow-through cavities. The kiln is placed on the bars for the heat treatment. In comparison to dense panels made of solid material, the web structure is characterized by the significant reduction of the mass and consequently also of the heat capacity. However, these structures have no closed surface, so that the storage of the fuel is not flat. Furthermore, the through-flow of the structure is ensured only in the thickness direction and this only if the kiln does not cover the upper region of the cavity.

The handleability poses a problem in the DE 199 31 306 A1 This kit is to be added from a variety of profile parts a component as kiln furniture. The profile parts are to be connected by an adhesive or a ceramic mass. This requires a high level of skill for the user and is only of limited suitability for use on a large scale in comparison to monolithic components.

In DE 10 2011 120 547 A1 describes lightweight ceramic kiln furniture, which are produced by forming ceramic green sheets into folded or corrugated cardboard structures. This process is difficult to automate and limits the geometry variations of the possible support structures. Although support structures resembling honeycomb bodies ensure high strength, they do not provide any significant flow through, which means that higher thermally induced stresses must occur in comparison to a flow-through structure. Although support structures with a different geometry can be flowed through well, but only in one direction, and have a lower strength.

In DE 20 2012 104 984 U1 describes high-strength ceramic lightweight structures, which are produced by the nesting of vertically arranged, partially slit strips and top surfaces applied thereto made of powder-filled papers or ceramic green sheets and then sintered. The manufacturing process is very complicated and very difficult to automate by the nesting of the individual strips. In addition, the resulting cavities are not accessible by the applied top surfaces, so that a homogeneous heating and cooling can be ensured only at low heating rates.

In the final report of the research project IGF 16485N: "Development of Novel Shaping Processes for the Production of Lightweight Ceramic Structures Using Papermaking Techniques", published by V. Beil, T. Schlordt, A. Hofenauer, N. Travitzky, F. Miletzky and P. Greil plate-shaped ceramic kiln furniture are described from pre-ceramic papers, which are sandwiched from corrugated board-like elements and a low density and good flow through, but which is present only in one direction, have. Since the structures still have a porosity of at least 20% by volume after the burn-out of the paper constituents and the subsequent sintering of the ceramic particles, the mechanical properties are significantly reduced in comparison to a dense material.

It is therefore an object of the invention to provide a method, with the high-temperature stable and good in many directions through-flow, sintered molded body with a low component density and low heat capacity of metallic and / or ceramic materials automated and therefore highly productive can be produced, which are sintered in a heat treatment step to a monolithic component.

The components produced are intended to be at an input gas flow of 0.1 to 10 m / min, measured at room temperature and an absolute pressure of 900 to 1100 mbar a pressure drop of 0.01 to 1000 mbar / cm ² , preferably 0.1 to 200 mbar / cm ² and most preferably from 1 to 20 mbar / cm ² cause.

According to the invention, this object is achieved by a method having the features of claim 1.

Advantageous embodiments and further developments can be achieved with features described in the subordinate claims.

In the method according to the invention, the requirements for high temperature resistance are met by the use of ceramic, metallic and / or metal-ceramic materials.

The requirements for a high strength and rigidity while low density and heat capacity of the component are in the process of the invention by the use and combination of thin monolayer or multilayer green films of ceramic, metallic and / or metal-ceramic materials, which are partially connected to honeycomb bodies expanded and provided with thin cover surfaces, met. Since large-volume accumulation of material can be avoided and a very good flow through can be ensured, a high thermal shock resistance is achieved due to low thermal stresses.

The transformation of the green sheets for expansion into honeycomb bodies is possible because ceramic and / or powder metallurgical green sheets can be processed by means of paper technology due to their own bending slit and flexibility. Out US Pat. No. 3,493,450 is the processing of papers or cardboard to honeycomb bodies known.

The introduction of openings in the individual or stacked green sheets connects all the cells with each other, so that the honeycomb structure can be flowed through in all three spatial directions.

The combination of green films with different composition dense support structures can be combined with individual, defined breakthroughs with large, permeable cavities and porous and / or openwork surfaces. The dense support structures have a significantly higher strength than porous support structures. The large cavities reduce the total mass or total density of the molded part and its total heat capacity. Due to the formation of porous cover surfaces, the removal of the debindering products by the cover surface of the molded bodies is possible, so that a denser furnace occupancy can be realized. By the introduction of breakthroughs in the cover layers in the green state, z. B. by punching, the flowability of the moldings can be secured in the sintered state with top surfaces.

The partial connection of the individual film strips and the connection of the cover layers with the honeycomb structure is effected by the application of a laminating assistant and / or the action of pressure and / or temperature, wherein the laminating assistant is advantageously a suspension containing a sinterable powder, to realize a cohesive bond of the individual layers.

The sintering is preferably carried out only after the addition of all the individual components in order to allow a material bond between all individual components and to produce a monolithic molded body, preferably in a temperature range between 1000 to 2000 ° C.

Preferred field of use for the molded body produced by the method having the features of claim 1 or the subclaims is the heat treatment. The finished molded parts can be used as lightweight kiln furniture with high rigidity and strength and with low heat capacity and density. This allows faster heating and cooling rates can be realized, whereby a significant time and energy savings can be realized in the heat treatment. In addition, the low heat capacity reduces the energy required for heating the oven space and shortens the time required for cooling.

By using green film strips of varying thickness or width, which may also vary over the length of the individual strips, honeycomb support structures having one or two non-planar surfaces can be created. One or more single-component or multi-component green films of metallic and / or ceramic and / or metal-ceramic materials are applied to these surfaces after the expansion, which have already been reshaped before the joining process by a suitable method or are deformed defect-free during the joining process can be used to map the geometry of the honeycomb structure. After the final thermal processing, these structures can be considered as Brennhilfsmittel be used with a geometry adapted to the firing to z. B. rotationally symmetrical combustible goods to store or non-planar fuel not only at individual support points to prevent deformation during the heat treatment.

However, the shaped bodies with a flat or non-planar surface can also be used as radiation shields in the sintered state or can be attached green as through-flowable stiffening elements with a low density to other components and be sintered together with them.

figure description

1 shows a dry ceramic green sheet ( 27 ) as a flat wide-flat product, which serves as a starting semi-finished product and based on metallic, ceramic or a mixture of metallic and ceramic materials.

In 2 is this green foil ( 27 ) after being partially coated with a laminating aid ( 26 ) was coated.

Subsequently, these partially coated green sheets are stacked on top of each other, with the areas where the laminating aid ( 22 ) should be for overlapping films in different areas, as exemplified in 3 is shown.

After lamination of the various partially coated with laminating green sheets, the as in 4 illustrated, resulting stacks in stacking strips ( 25 ) cut like in 5 represented z. B. by punching with breakthroughs ( 22 ), wherein the introduction of the breakthroughs can also take place before cutting and the cross-section of the openings must not be made circular.

6 shows different, with breakthroughs ( 22 ) provided stacking strips ( 25 ), which are arranged one behind the other and by means of partially applied laminating ( 26 ) into a quasi-endless compound ( 24 ) from individual green sheets, but which are always only partially connected with each other, be joined, the in 7 is shown.

In 8th is a honeycomb structure ( 2 ), which arises when the areas on which the laminating assistant ( 26 ), of green sheet ( 27 ) to green film ( 27 ) are arranged centrally offset and the quasi-endless compound ( 24 ) in the thickness direction of the green sheets ( 27 ) is pulled apart (expanded). In this case, a transformation of the green sheets ( 21 ), so that between large cavities are formed, which are above the breakthroughs ( 22 ) also by the transformed green sheets ( 21 ) are interconnected. The width of the film strips after cutting into stack strips ( 25 ) remains unchanged during forming and defines the height of the formed structure.

By the in 9 illustrated lamination of one or more green sheets with introduced breakthroughs ( 31 ) as the lower (4) and upper ( 3 ) on the expanded honeycomb structure and the final, common heat treatment for debinding and sintering of the materials used, a high-temperature-stable and in many spatial directions well flow-through molding of low component density and low heat capacity ( 1 ), which is exemplary in 10 is shown.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 29816572 U1 [0003]
• DE 19931306 A1 [0004]
• DE 102011120547 A1 [0005]
• DE 202012104984 U1 [0006]
• US 3493450 [0014]

Cited non-patent literature

• IGF 16485N: "Development of Novel Shaping Methods for the Production of Lightweight Ceramic Structures Using Papermaking Techniques", published by V. Beil, T. Schlordt, A. Hofenauer, N. Travitzky, F. Miletzky and P. Greil [0007]

Claims (8)

Method for the automated and thus highly productive production of high-temperature-stable shaped articles which can be easily flowed through in several spatial directions, low component density and low heat capacity of metallic and / or ceramic materials, characterized in that a. initially single or multilayer green films are made of ceramic, metal or metal-ceramic materials, b. which are then partially coated with a suitable material for joining the green sheets, c. be stacked afterwards, d. be provided with openings at defined locations, e. then cut into multilayer strips, f. which in turn can be stacked and partially interconnected, g. wherein the method steps b to f can also take place in a different order, h. before being expanded to form a honeycomb structure, i. one or more single-component or multicomponent green films of metallic and / or ceramic and / or metal-ceramic materials are laminated on their upper and lower cover surfaces with a suitable process and the necessary auxiliaries which have a composition which seals after debindering and sintering or form porous structure, and may have the breakthroughs, or which are attached to ceramic green body to z. To stiffen freestanding walls, j. and finally, a heat treatment involving debindering and sintering is performed to make a material bond between all the individual components. A method according to claim 1, characterized in that the strip-shaped or partially coated joints of two adjacent film strips are arranged offset. A method according to claim 1 or 2, characterized in that green sheets can be combined with different compositions. Method according to one of the preceding claims, characterized in that green foil strips with different geometry are partially connected to each other and so a honeycomb structure is realized with at least one non-planar top surface. Process according to claims 1 to 4, characterized in that the components produced according to the method with an input-side gas flow of 0.1 to 10 m / min, measured at room temperature and an absolute pressure of 900 to 1100 mbar a pressure drop of 0.01 to 1000 mbar / cm ² , preferably 0.1 to 200 mbar / cm ² and very particularly preferably from 1 to 20 mbar / cm ² cause. Method according to one of Claims 1-5, characterized in that, for the production of metallic foils, powders of the refractory metals are used which mainly contain elements such as tungsten, molybdenum, tantalum, titanium, niobium, chromium, etc., or powders of alloys on iron, Cobalt or nickel base, which have sufficient mechanical and special thermal properties, such as oxidation resistance and corrosion resistance. Method according to one of claims 1-5, characterized in that the preparation of the films ceramic oxide or non-oxide powder are used, such as alumina, calcium oxide, calcium carbonate, (partially) stabilized zirconia, zirconia-reinforced alumina, alumina-reinforced zirconia, titania, aluminum titanate, aluminum nitride , Aluminum silicate, silicon carbide, silicon nitride, silicon dioxide, porcelain, steatite, cordierite, beryllium oxide, magnesium oxide, boron nitride, boron carbide and mixtures thereof, which have sufficiently mechanical and particular thermal properties, such as oxidation resistance and corrosion stability. Method according to one of claims 1-5, characterized in that for the production of the films some of the mentioned in claims 6 and 7 metallic and ceramic powders are used in combination, such as. For example, 17-4PH, 316L or CroFer22APU in conjunction with yttria partially or fully stabilized zirconia.

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