DE2751918A1 - Composite insulation for vehicle exhaust pipe - consists of metal grid to which ceramic is applied as slurry before heating - Google Patents

Abstract

The composite panel for high temp. insulation, for a vehicle exhaust pipe comprises a metal grid, (6) embedded in the ceramic material (18) lining the inside of the pipe. The grid mesh size lies between o.4 and 3.5 mm, and the aperture total surface area ratio is between 30 and 80%. The ceramic material is applied to the metal as a slurry, and the whole is then heated to the temp. at which the ceramic soldifies.

Description

Metal-ceramic composite. Component for the exhaust system of a

Internal combustion engine and a method for producing a high temperature insulating metal-ceramic composite The invention relates to a metal-ceramic composite, a component for the exhaust system of an internal combustion engine and a method for Manufacture of a metal-ceramic composite that insulates against high temperatures.

There are numerous examples of the need for good thermal insulation, but which is often inadequate because it is not an economically feasible material gives all the required characteristics and physical properties Has. An example of this is the obvious need for a thermally insulating Covering the exhaust system to provide an internal combustion engine, which is equipped with a catalytic converter. That's because the efficiency a catalytic converter to catalyze unburned hydrocarbons and of carbon monoxide in carbon dioxide and water or the reduction of the oxides of Nitrogen depends on the temperature of the catalytic bed.

Consequently, when the engine is started, when the catalytic Bed is cold, the efficiency is low, and the less time is needed to to heat the catalytic bed to a high temperature, the higher the Efficiency of the system. For this purpose it is desirable to have the insides Thermally isolate the exhaust system from the engine to the catalytic converter Leads so that a maximum of heat in the exhaust gases from the rotor of the catalytic bed reached to raise and maintain its temperature. Because of the removal of the Heat from the rotor to the catalytic bed becomes the overall temperature under the hood significantly reduced, which benefits the various components under the bonnet comes. Any heat insulating material used must of course be sufficient Have heat resistance to withstand the high temperatures that occur That indicates the use of ceramics, because most types of ceramics have a relatively low thermal conductivity and a high temperature resistance. One solution could be seen in the inner surfaces of the exhaust pipe with a Coating ceramic material. However, that leads because of the substantial differences in the coefficient of thermal expansion of metal and ceramics to no satisfactory Results, also because ceramic in solid monolithic form is relatively is brittle or inelastic. As a result, the ceramic material breaks and loosens away from the surfaces of the exhaust pipe. If, on the other hand, the ceramic material used does not have a solid monolithic structure, rather a fiber-like structure, this occurs Breaking and chipping due to the fact that the fibrous ceramic material does not have sufficient mechanical strength to withstand the pulsating flow of exhaust gases, which has a relatively high flow velocity can withstand, and it deteriorates therefore very quickly in its properties. In short, ceramic material in fibrous or similar structure gradually breaks or is removed from the surfaces of the exhaust pipe blown off by the exhaust gases.

So there is an urgent need for relatively inexpensive heat insulating Materials that not only have good thermal insulation properties, but also also good mechanical strength, resistance to severe crevice or other quality reductions due to thermal cycling as well as sufficient mechanical strength, deterioration or wear to be resisted by the influence of flowing and pulsating hot gases. the irfindung fulfills this need and many too other requirements.

The prior art has proposed high impact panels by producing that between tools made of graphite or the like Kerarnikarten such as aluminum oxide are hot-pressed, in which a high temperature resistance Metal grid is embedded in order to make a high-strength and therefore impact-resistant plate to produce, which consists of a composite of hot-pressed and therefore very dense sintered Ceramic and the high-temperature-resistant metal mesh embedded therein. However, the difficulties that arise are manifold. Once will imposes a severe restriction on the shapes by the requirement to hot-press, that can be made. On the other hand, the requirement to hot-press, At manufacturing costs, the resulting composite is priced from most markets exclude, for example, that market for a good, high-temperature-resistant Heat insulator. Thirdly, the high density of such a composite of It matters when impact resistance is the most important thing, but it doesn't have any Significance, can even be disadvantageous: if other properties are important, for example the properties of an effective high-temperature resistant Thermal insulation are required.

According to the invention, a material is provided that said combination of properties and which is a composite that is produced by it is that a metal mesh is coated with a ceramic slurry and thereby a layer of ceramic with the metal mesh embedded in it is created, and that then the ceramic at or under ordinary atmospheric pressure to a The temperature at which the ceramic forms a monolithic structure is fired.

When it cools down, the metal grid is under tension and the ceramic is under pressure because the grille is under pressure while it is burning is in the expanded state because of its high coefficient of thermal expansion. Especially due to the fact that the metal grid is provided, the composite has excellent mechanical strength, and because the ceramic is a solid monolithic Structure, the composite can easily handle the pulsating stream of hot gases, the one has high flow velocity, with good longevity and resistance to durability. Even if the metal mesh and the ceramic have different coefficients of thermal expansion the composite also has excellent resistance to cracking or other quality reductions due to thermal cycling - because at under most operating conditions the grid is tensile and the ceramic is compressive, and because of the relatively thin walls of the ceramic, there is a slight temperature gradient which reduces cracking or, conversely, increases heat resistance. Furthermore, the association has to be described below be becomes, a very low thermal conductivity in the direction at right angles to the plane of the metal mesh, and consequently the composite provides the excellent thermal insulation properties, that are strived for.

The mechanisms by which the composite acts as an insulation are very complex, albeit in heat exchange and ceramic technology are well documented. Based on a review of the heat exchange technology are three factors that contribute to the excellent insulation characteristics of the present invention Contribute to the composite structure, (1) the reflection and emission characteristics of multiple surfaces, (2) standing gases - in spaces between the composite layer - and (3) the low thermal conductivity from Kerainik. Of these, the first is the most important.

The Netall ceramic composites, which can be quite thin, have one excellent, indeed unusual, ability as a high temperature radiation screen to serve. There are of course many areas of application for such shielding, and this includes all high temperature systems where heat is effective \ Thermal insulation is to be preserved, or an area that is against the presence a high temperature body is to be protected. All ovens and burners, including Automobile exhaust systems, fall under this category Relative neutrality of metal-ceramic Composite parts against extremely corrosive environments and impart the ability to withstand temperatures in excess of 1100 ° C the composite parts of the invention have an unusually good ability to use as insulation, in which the characteristics of radiation transfer and multiple shielding can be exploited.

Other characteristics of the insulating composite material are as follows: The composite parts have good structural self-supporting characteristics. You can for example, preformed in their preferred state and in the scope can be easily attached without the need for additional support materials consists.

The composite parts can be pre-formed into the permanent shape and are machined can be processed, with one; 4-rinf; -st tool effort. To a cylindrical If it is to be clad, one layer of the composite can be spiralförmit; on top of each other up to the inside diameter of the cylinder before the race at the required temperature to be wrapped.

Because of the simple construction and that described below The insulation composite can be produced economically by using the manufacturing process. The type of association allows the Use of cheaper metals in zones of lower temperature for corresponding structural parts.

The composite can be inserted into an orrn and covered with melted ifetal be cast around, created by a simple method of isolating castings will.

The composite parts have very good heat-insulating characteristics with a minimum of space, as described below, and through testing will have to be demonstrated in use cases for the automotive sector.

The composite parts have good thermal shock resistance. The usage the composite insulation in an exhaust system of an automobile, in which thermal shock occur, the thermal resistance of the material has been proven. at Using the composite parts there are no serious thermal expansion problems, because multiple layers expand and contract freely independently of one another can.

The invention is explained in more detail below with reference to the drawings. In the drawings: FIG. 1 is a side view with broken parts of a Exhaust pipe incorporating the invention, Fig. 2 is a section on line 2-2 1, 3 show a detail of the lining of that shown in FIG Exhaust pipe, with parts broken away, FIG. 4 shows a representation similar to that of FIG. 1, However, another embodiment of the invention is shown, Fig. 5 is a view from the plane of the line 5-5 of FIG. 4 and FIG. 6 is an illustration similar to that of FIG. 3, however, the lining of the pipe of FIG. 4 being shown is.

In Fig. 1 a part of an exhaust pipe 2 is shown, which serves to Exhaust gases from the exhaust manifold of an internal combustion engine (not shown) to conduct a catalytic converter (also not shown). The exhaust pipe 2 is made of ordinary steel or a steel alloy, like him or her commonly used for exhaust pipes and it has a tubular liner 4, which acts as thermal insulation and which is constructed according to the invention, what will be described below.

As best seen in Figures 2 and 3, the lining is 4 a composite of a metal grid 6 and a ceramic layer 8 in which the grid is embedded. The metal mesh is usually under tensile load, the Ceramic under pressure. Because ceramics are strong under pressure, but weak in tensile load, and because metal is not only strong in pressure, but also in tensile load is, added the metal used the ceramic to improve its mechanical Properties, while the ceramic serves to protect the metal against corrosion, wear and tear etc. to protect. As the temperature of the composite increases, the greater the expansion; of the metal mesh compared to that of the ceramic at operating temperature does not exert any tensile force on the ceramic, but only reduces part of the compressive force. The end result is a composite that not only has the required heat resistance and resistance to cracking of the ceramic due to thermal cycling but also has a much higher toughness and mechanical strength in comparison to a construction made entirely of ceramic. In the one shown in Fig. 1 - 3 " Embodiment, the metal grille has the shape of a metal grate, d, h. more interwoven Metal wires. However, the metal grid can still be explained as follows will have other shapes. While in the in Fig. 1 - 3 (, ezeie, th embodiment the composite also contains only a single layer of the metal grid, it lies in the Framework of the Dfindun; to use several hunts of the composite material, which is an advantage if insulation is to be provided, the higher thermal insulation characteristics should have. Rutin complete understanding of Iletall ceramic composite construction can be obtained from the description below of a preferred method of manufacture the same.

Before going into the manufacturing process, however, it is appropriate to discuss the needs imposed by each component of the consortium are to be fulfilled.

When choosing the material for the metal mesh that will be used in the composite structure are to be used, various essential factors must be taken into account. The metal grid must have a melting temperature above the temperature required for firing the ceramic is required in a uniform structure, and it should have a higher have higher expansion coefficients than those of ceramics greater the - thermal expansion coefficient of the metal mesh compared to that the ceramic, the greater the pressure load on the ceramic and the greater is the resistance to breakage due to suc, forces at operating temperatures under the one with which the composite was burned, while vice versa applies, that the smaller the difference in the coefficient of thermal expansion of the metal mesh and the ceramic, the greater the resistance of the composite "e-cn" to ceramic fracture at operating temperatures above that with which the composite was burned. Many types of ceramics can of course withstand temperatures higher than that with which they were burned during manufacture.

The metal of the grid is preferably also chemically inert in relation to it on the ceramic composition and, in particular, if the ceramic of the composite is porous, also with respect to the atmosphere in which the composite is used target. Thus, when the metal is chosen for the grid, it is desirable to take into account whether the atmosphere in which the composite is to be used is oxidizing or reducing, carburizing, sulforating etc. is. Naturally may consider such factors as set out above Compromise may be necessary or desirable in many cases, with the further Factor of cost and availability of the ifetal is taken into account.

Numerous granularly available metals and alloys are well suited for the application according to the invention. For use in moderately high Some of the nickel alloys are well suited up to high temperature ranges. she offer high strength with a medium to high coefficient of thermal expansion, good oxidation and corrosion resistance and high toughness. Preferred marketable Nickel alloys that fall under this category are the following: Inconel 600 (1) See footnote Inconel 601 () Ni-Chromium (2) iIas-telloy X (,) (4) Another Group of metal alloys, the common stainless steels, are also suitable for many uses of the composite parts. The ferritic stainless steels are particularly suitable, they are inexpensive, have satisfactory coefficients of thermal expansion, low compared to others Metals like the austenitic ones Stainless steels and their resistance to oxidation can range from good to excellent. They are a good choice if you have inexpensive composite parts for applications with relatively high temperatures are required.

The common austenitic stainless steels are stronger than the ferritic ones Stainless steels at high temperatures. They are usually more expensive and offer a superior one Corrosion resistance and are characterized by higher coefficients of thermal expansion, roughly in the same range as the nickel alloys. Typical stainless steel on the market for use in the grid within the scope of the invention are: ferritic stainless steel austenitic Stainless steel l 1 (5) See footnote T-304 (6) see footnote T-409 (6) T-316 (6) T-430 (6) T-321 (6) T-442 (6) T-347 (6) T-446 (6) T-309 (6) KANTHAL A (7) T-310 (6) KANTHAL DS (7) RA-330 (4) MULTIMET N-155 (3) For certain applications, others can Metals are desirable. For special high-temperature applications, for example Refractory metals and their alloys can be used will. Examples of such metals are zirconium, tungsten, molybdenum, platinum, and palladium and tantalum.

The metal or the metal alloy can be in various forms be brought to form the grid, for example in the form of wire grids, stretched sheet metal or perforated sheet metal. The term "rust" means an interweaving the wires of the metal to each other. Such a grate is shown in FIG. Stretched Sheet metal is a thin sheet of metal that has slits in different shapes and positions the entire surface is provided and that at the same time or afterwards in one direction to open the slots is stretched, thereby creating a cohesive metal grid with holes in it. imine such construction is shown in Wifr, G 6. Perforated sheet or perforated sheet means that you turn Hole pattern is punched into the sheet metal to create a grid that looks the same or similar to the sheet metal produced by the stretched sheet metal.

Additional information regarding the origin and designation of the alloys: (1) The International Nickel Company, Huntington Alloys Products Division, Huntington, West Virginia; (2) Driver-Harris Company, Harrison, New Jersey; (3) Haynes Stellite Company, Kokomo, Indiana; (4) Rolled Alloys Company, Detroit, Michigan; (5) Allegheny-Ludlum Company, Pittsburg, Pennsylvania; (6) The T-Z £ 1len accordingly Descriptions are the AISI designations (American Iron and Steel Institute); (7) Kanthal Corporation, Bethel, Connecticut.

Both from the standpoint of ease of manufacture and from the standpoint creating composite parts that have optimal physical properties, preferably have the openings therein in terms of the precise construction of the grille substantially uniform shape and size, including the size of the openings in their largest dimension no more than about 9.5 mm and no less than 0.4 mm. (For example, if the openings are square, the largest dimension is the diagonal, and this should preferably not be larger than 9.5 mm and not be smaller than 0.4 mm.) Furthermore, the ratio of the sum of the opening areas is preferably to the sum of the metal surfaces between the openings such that about 30 to 82jo of the total area of the grid are formed by openings, while the rest of the Surface is metal between the openings.

As indicated above, it is critical that the Ceramic recipe is such that one firing into the final uniform or monolithic structure at a temperature below the melting temperature of the lattice is made possible. If the metal used for the grid is such that it is a Significant reduction in quality in Zugfestirl; d t or other physical at a temperature below the melting point, it is desirable that ceramics is one that in its uniform or monolithic structure can be fired at a lower temperature than that at which the deterioration in quality of the metal occurs. It is also crucial for the invention that the ceramic slurry formulation, which is used to coat the grating is such that the slurry clings to the grid and fills the openings in it and there after drying remain. This property can best be achieved by using a binding material is included in the sludge recipe. The binder can be one or more and preferably is also of numerous inorganic agents Examples are given below and the image properties, i.e. good Wet bond strength, in the state before firing the Keranlik after drying, so that for a strong uniform or inonolithic structure in the final burned state is taken care of In this context, it should be noted that the Inorganic binder remains in the ceramic during firing and plays a part of it, although it generally reacts with other of the ceramic constituents or conversions during firing fail at least partially in others Form in the fired ceramic structure than to appear in the form in which it is the slurry has been added. For example, if the binder is a silicate or a colloidal As the examples below demonstrate, silicon oxide is can a conversion, for example by reacting with other components of the ceramic recipe, the silicon oxide in one silicate or the silicate in another silicate, for example glass, if the ceramic is finally fired. Alternatively, however or in addition to using an inorganic binder, organic Binders are used in the ceramic slurry, and in this case evaporates the organic binder or burns away during firing. If the only one The binder that is used is an organic one, so the ceramic component (s) must be used the slurry formulation must be such that the required bond is achieved during firing is created in order to ensure the uniform or itinnolithic ceramic structure. Typical examples of organic binders are polyvinyl alcohol, dextrin and the water-emulsifiable waxes used in ceramic technology as a temporary binder are known, Numerous ceramic recipes that are known for precision casting and used extensively are suitable within the scope of the invention. For example are sludges, which are made from the most varied types of ceramics individually or in groups, as given below, and composed of suitable binders are, as they are also listed below, for the production of ceramic bowls in form and investment forms for the casting of complex shapes and high temperature turbine parts used.

Typical ceramic materials that can be used in the context of the invention are, are either alone or in combination: zircon, quartz or fused Silicon oxide, i'llit, spodumene, magnesium oxide, forsterite, nagnesium oxide-aluminum oxide spinel, Silicon carbide, aluminum oxide, zirconium oxide (stabilized), chromium oxide (Cr2 () 3) and stoichiometric cordierite or composite modifications of cordierite, as is known in the art. It is desirable that the ceramic material has a small particle size, preferably with a sieve size below 325.

Although other liquids besides water are used for the sludge will be from the point of view of cost and from the point of view of Expediency as well as from all their points of view preferably water used. Accordingly, it is desirable that the binder be water soluble in the designer is or is such that it forms a colloidal suspension with water.

Examples of inorganic binders within the scope of the invention excellent one, they the following: colloidal alumina, colloidal silica, Sodium silicate, potassium silicate, calcium aluminate and kaolin or another clay. An example of an organic-inorganic binder that is used in the context of the Invention proves suitable is ethyl silicate.

The first bond of ceramic particles with the above Binders usually only requires relatively low temperatures; in many cases one cares Drying at ambient or room temperature usually for adequate bond strength before burning. However, the full bond does not arise until the structure of the Temperature has been exposed at which the ceramic recipe has a uniform or forms a monolithic structure. When the composite can be used in a field in which a high operating temperature occurs, you can use it yourself to make the final bond, The required temperature changes of course, depending on the exact recipe, like that in ceramic technology is known. In the case of ITsodium silicate and alumina ceramic systems, the as examples given below, the ultimate bond appears thereby to take place that the atriuriisilicate melts at least locally, followed by a rapid diffusion into and from at least partial reaction with the Aluminum oxide to create a structure of high bonding. The bond can also take place through binders in collcidal particle form, apparently also through solid diffusion and by at least partial reaction of the constituents with one another at the required temperature to achieve the uniform or monolithic structure let develop. The gelling of the binders in colloidal form has the advantage of to create a good dry bond strength before firing.

It is not important that the ceramic is the fired composite one has an extremely high density, and for many applications, for example for thermal insulation, even a porosity of up to 10% or higher may be desirable. By making flour, powdered wax, wood flour or some other powdery or; anic material is mixed into the slurry in the desired proportions and particle sizes The degree of porosity can be determined because when burning the combustible material burns out and leaves pores behind.

The following examples are specific application examples for ceramic slurries, which are suitable for use in the context of the invention: Example 1 112 g of distilled Water was added to 563 grams of commercial grade RU t-sodium silicate (SiO2 33.2%, Na2O @ 13.85, H2O 52.95%), and the whole thing was done with an electric Stirrer stirred to ensure complete mixing. This solution was 825; Commercial grade tabular alumina of a party size of -325 added. The addition of the alumina was done during the electrical Stirrer stirred the solution to ensure that all particles were fully wetted and the viscosity remained relatively constant. The slurry was then ready for coating of the metal grille finished.

Example 2 490 g of powdered fused silica (Nalcast P-1W) 210 g of colloidal silica (Nalcoag 1030) was added and the whole was added stirred thoroughly with an electric stirrer. Mixing became one and a half Continued for hours to ensure that the slurry was in equilibrium reached - i.e. all particles were fully wetted and the viscosity was relatively constant stayed. The slurry was then ready to coat the metal mesh.

Example 2 62 g of water became 188 g of aqueous colloidal silica (3096 solids) was added and mixed thoroughly. A complete Stirring was continued to bring about an intimate solution of the silica and water to ensure. 750 g of zirconium powder were added to this solution during a Stirring with an electric stirrer was done. This stirring was two hours long continued to ensure complete wetting of all zirconium particles and uniform Ensure viscosity. The slurry was then used to coat the metal mesh done.

The composite is produced in that the viscous ceramic slurries is applied to the grid, so that the slurry is completely all openings in the grid covers and fills, and after that the coated grid is dried and then fired, The slurry is best applied to the grid by letting the grid in the slurry is immersed. In in many cases is an additional faciies Diving desirable. So after a first dive, the sludge is left as a result, the grid has gotten dry, and then further ceramic by diving into the sludge again, etra, -en. Because the dried Ceramic slurry is usually bendable, it is possible to reshape or reshape the composite to be worked on before firing, so that it is cylindrical or otherwise Acquired after the ceramic has been placed on the grid, alternatively the grid can first be brought into a cylinder or some other shape, and the ceramic slurry is then applied to the formed grid.

Jie has been hinted at after the ceramic is applied the metal grid and, after it has dried, the ceramic with the embedded grid fired at a temperature high enough to transform the ceramic into a uniform or to bring monolithic form. The lethal grid is at the firing temperature due to its higher coefficient of thermal expansion in an expanded state, and the ceramic has a rigid monolithic structure while resting on the high temperature at which the metal grid is in its extended State. So when the cool down begins and while the cool down continues, the metal grid contracts from its expanded state, and thereby the metal grid is put under tension, while the rigid ceramic is under pressure is set. With the end of cooling the creation is finished.

Below is a specific example of the manufacturing method of a composite according to the invention, the slurry used being that which has been given in Example 1 above: A metal mesh made of Inconel 600 was degreased by washing in methanol and at low temperature dried. In order to cover the grid with the loop, it was put in the mud submerged so that the sludge clung to the wires of the grid and all Filled the gaps in the grid. After pulling out of the container with the slurry and drying in air for 30 nights (during the initial phase during drying, the covered grid was slowly rotated in a vertical plane, to prevent ceramic build-up at one end as a result of gravity) the bond in the oven with temperature increase in steps of 15 0C with a Venieilzeit Fired for about 15 minutes at each temperature step from 380C to 2600C. The temperature was increased at a relatively slow rate as described, to have a better guarantee that no gas bubbles or the ceramic came loose.

The composite was then left in air for 30 minutes at around 10,000C baked at normal atmospheric pressure and then allowed to return to room temperature cooling down. If necessary, other methods of firing and drying can be used will, for example using a vacuum oven or a microwave or induction oven, a local internal gas build-up and the associated loss of cohesion of the ceramic support structure impede.

Referring to Figures 4 through 6, there is another embodiment of the invention shown, in which several layers of the composite are provided, the successive '; end Layers are closely spaced to create thin air gaps between to form the layers. In Figs. 4 and 5, 10 denotes a metal pipe and 12 a tubular one Multi-layer composite made according to the invention and used as thermal insulation acts to prevent heat loss from hot gases or other media, that flow through the Ilohr. which can best be seen from FIG. 5, consists the composite of a grid 14, which is embedded in ceramic lu; and is spiral-shaped is wound to form a tube that has three substantially parallel or has concentric positions 18, 20 and 22, as can best be seen from iig, 6, provide at a distance an '; arranged, spirally wound heat-resistant wires 24 and 26 between the layers for the spacing and consequently the air gap between successive ones Layers, the thickness of the air gap by the diameter of the spirally wound Wires is determined. The metal grid of the exemplary embodiment according to FIGS 6 does not consist of a grid of interwoven wires, but of one stretched metal grille. A conventional and cheap method to the Manufacture of such a grid consists in a thin sheet of metal with staggered parallel rows of slots and then the sheet metal in one direction to pull across the slots so that the diamond-shaped openings as shown develop. The metal grille can be used in the exact shape specified by the Pulling arises, or it can then be passed through rollers to get it in to bring it to a flat state as shown in FIG. A metal grille with the same structure can be produced in that a sheet is punched, to allow openings to arise in it, however, this is by far more expensive because of the large amount of metal waste that is generated. Stretched metal grids are known and it is to be understood that the exact method of manufacture does not apply to the invention The shape of the openings is just as important, as long as the lattice structure is that way is that it can be pulled not only in one direction, but also in directions at right angles to each other.

In order to produce the part according to the exemplary embodiment gellaß Fig. 4 to 6, a rectangular piece of the metal lattice is coated with the ceramic slurry, as described in connection with the exemplary embodiment according to FIGS and then after drying, spaced parallel heat-resistant Metal wires placed on the ceramic-coated metal grid. The whole thing will then spirally wound in a direction in which the metal wires extend so that the spirally wound shape arises as it is in the drawings is shown. The resulting tubular structure is then kept at a temperature fired to bring the ceramics into a monolithic structure, and then success, t a cooling to 'peel off' the T-points, e-q.

Means other than wires 24 and 26 can be used for to ensure the spacing between successive layers. For example, before spiral wrapping the ceramic coated metal mesh into a tubular shape its surface with a large number of relatively widely scattered and relatively large Ceramic grains or other refractory material will be provided, with the size the grain determines the distance between successive lances when these Construction is wrapped in a spiral. As a further alternative, the metal grille even be provided with spaced-apart humps, uia requires hen To ensure spacing between successive layers. A thin air gap between successive layers provide additional insulation; it understands however, that for certain applications, the use of multiple layers of the composite material may be desirable, but not a large spacing between the ceramic layers need to be present in which the metal grid cinjebetted is. In order to produce such a construction, it is only necessary that nitz-resistant metal wires or the other means of creating them of To omit the gap between the layers.

The composite parts according to the invention are particularly suitable for pipe shapes, as shown in the drawings; it goes without saying, however, that the Both AusfuÄirun'm, sbeispiele have a tubular shape, but composite parts according to the invention may form other shapes, for example a flat and planar shape Regarding Internal combustion engines are another application for the composite according to the invention in a thermal insulation for the combustion chamber and the engine head at the exhaust openings, in order to regulate the local heat flow to the engine coolant. That is desirable because if the heat flow to the coolant is too fast, the coolant therein can evaporate at such a point, creating gas bubbles or pockets to let that impede the flow of heat. By the thermal insulation in the head or on the If the engine block is used on the combustion chambers, better temperature control is obtained and consequently reduced pollutant emissions and better fuel consumption tongue.

The ceramic-metal grid composite according to the invention is in particular on its use as thermal insulation has been described because the composite is so exhibits remarkable thermal insulation properties.

An investigation into the insulation properties of three layers of Composite was performed in the following manner: A cylinder with a Diameter of 114mm made of stainless steel with a length of 17F? mm and a thickness The composite insulation was trimmed with three concentric cylindrical sections of 1.3 in lined. A slurry of tabular alumina and @atriunosilicate, like it was prepared in Example 2 above was made. Three cylinders Inconel grate were made by seaming the individual cylinder was joined by tack welding. These concentric cylinders were in Methanol degreased and, after drying, immersed in the sludge mixture in order to to create a viscous coating. Make the sludge dry in Air the structures were dried in the oven step by step with temperature increases of 15 °, starting at 38 ° C. After reaching 260 ° C, the structures were then at 950 ° C fired in air at normal atmospheric pressure to complete the sintering en. The metal mesh ceramic composite cylinders were then placed concentrically in the stainless steel cylinder set, the surfaces of which are spaced around the circumference Wires made from Inconel 600 were separated to leave a gap for stagnant air between to form successive cylinders. The thickness of each cylinder was about 1.6 mm, and the size dCl 'cylinder was such that the distance between successive Cylinders was about 1.5 mm. Thermocouples (T4) were attached to the outer surface of the Welded metal cylinder. Additional thermocouples (T1) were on the inner surface of innermost Verbuiidzylinders attached. Thermocouples (T2) were between the the innermost compound cylinder and the one in the middle, as well as thermocouples (T3) between the central and the outermost composite cylinders. the entire unit was placed on fireclay supports, and a burner nozzle was in set the top opening with the point down. The burner was too held by fireclay supports and covered by a layer of asbestos, in such a way that that all secondary air was supplied to the burner from outside the device. A mixture of propane and air was burned at different throttle settings, and after the temperatures stabilized, the temperatures were recorded, to provide comparative data showing the isolation effect of each successive location indicated. Table I gives the results of the test.

TABLE I INDOOR TEMPERATURE ° C TEMPERATURE ° C TEMPERATURE ° C TEMPERATURE ° C (ri) (T2) (T3) (E4) 550 525 350 235 815 735 565 385 1040 910 710 525 A second Test apparatus was set up according to the above apparatus except that instead of tubular aluminum oxide, zirconium refractory material was used. Appropriate test methods were carried out and the results are given in Table II.

TABLE II ININ @@@ LT @ATOR ° C TEMPERATURE ° C TEMPERATURE ° C TEMPERATURE ° C (T1) (T2) (T5) (T4) 540 465 315 220 815 715 540 355 1040 925 710 520 These tests show a pronounced drop in temperature through about @@@ m of the pre-bundle insulation with small air gaps between successive layers.

In another application, the insulation became concentric wrapped on itself to form three layers totaling 4 to be thick and placed in a cylindrical stainless steel container having a diameter of was 95 mm high and 254 mm long. A reducing agent used in the automotive sector catalyst was then placed in the insulation, and the container was and exhaust pipes welded shut to direct engine exhaust through the catalytic converter. This test shows a marked drop in temperature through approximately 4.8 mm of insulation with minimal air gaps between the layers. Thermocouples were in the middle of the catalyst and placed on the surface of the stainless steel container, its metal thickness 1 mm. The catalyst canister was to the standard exhaust manifold connected to a Plymouth engine type 318 CID-V8 from an independent test laboratory, to do a dynamometer test. It was made with constant loads and throttle settings driven, and after temperatures stabilized, the gas temperatures were measured in the catalytic converter and surface temperatures. These are listed in Table III, and they show the pronounced effect of insulation on temperature reduction.

X IJI exhaust gas temperature ° C canister surface temp. 480 127 575 ° C 141 615 170 665 205 730 225 785 260 Another jIest with an insulated catalyst canister and an insulated exhaust manifold similar to that of the foregoing stationary dynamometer testing was carried out by an independent testing laboratory carried out.

This test was carried out on a 1975 Plymouth Fury automobile 318-CID-V8 carried out with a built-in catalyst container, and an assembly was carried out at the same time with thermocouples to determine gas and surface temperatures. The automobile became placed on a Chansis roller dynamometer and according to EPA hot start CVS mission test regulations drove. The exhaust temperatures and the canister and gas manifold surface temperatures were recorded. The exhaust manifold was insulated. The results are in Table IV included. As can be seen, these are the insulating properties of the composite material outstanding.

Table IV Exhaust gas temperature ° C Canister surface temp. Surface temperature- ° C pertaur exhaust manifold ° C 860 210 257 700 240 257 715 250 265 750 260 262 745 295 320 Table IV gives results which are somewhat scattered compared to those of the Table III, namely the type of tests conducted. The data of the table III were achieved in a dynamometer test constant running conditions while the data in Table IV was obtained during an ETA hot start CVS test of which the engine temperatures are in an over angsstatus during most of the time are.

It will be understood that the composite parts according to the invention many other Can find applications, for example, as components that have a high level of heat resistance require. It should also be mentioned that the composite parts according to the invention, not only demonstrate excellent thermal insulation properties, but also excellent acoustic insulation properties. This is important, for example, when the composite parts for the exhaust systems of motor vehicles because they are not only used for provide good thermal insulation, but also offer acoustic insulation properties, so that the noise level is reduced, which is normally found in such exhaust systems occurs.

In addition, the composite parts according to the invention allow development von, Jerkstoffen r.lit special properties that cannot be achieved using other methods can be achieved, for example, heat-resistant catalyst supports. One such an application can be illustrated with reference to the exemplary embodiment, which has been described in connection with FIGS. The shown forms Composite the liner in the exhaust pipe that goes from the engine to a catalytic converter of a motor vehicle. By catalyzing the inner surfaces of the tubular Liner, the liner serves not only as thermal insulation and as one acoustic insulation, but also as a catalytic device for catalyzing the oxidation of unburned and partially burned hydrocarbons in the Exhaust gases in carbon dioxide and water or, alternatively, to reduce the oxides of nitrogen in the exhaust. The catalytic materials that have catalytic activity Show performance of such functions are known, for example platinum, palladium, Copper and the transition metals or the oxides of these metals. To such a one The catalytic I; aterial in powder form can be incorporated into the composite for example applied to the surface of the ceramic before firing, or alternatively it can be inserted directly into the ceramic itself.

Claims (1)

Patent claims @ etall-ceramic composite as high-temperature insulation, a stiff metal wall, a monolithic layer made of ceramic, which is located on the metal wall and in which a metal grid with Openings is embedded that are substantially the same size and shape, wherein the composite is produced by coating the metal grid in such a way that the (Iitteropeniuigen are filled with Koramic sludge and a layer of the ceramic is created is, in which the Motallgitter is embedded, the ceramic layer with the one located in it Metal mesh is heated to a temperature at which the ceramic has a monolithic Ceramic body forms, and then the ceramic body with the Iletallgitter located therein is cooled, wherein the metal grid has a melting temperature that is higher than is the ambient temperature at which the ceramic forms the monolithic ceramic body, and wherein the metal grid has a higher thermal expansion; skoef- Efficient than the ceramic and the grid openings have a size of about 0.4 to 1.5 and the sum of the areas of the openings about 30 to 0 of the total area of the grid matters. 3. Metal-ceramic composite according to claim 1, d a d u r c h e k e n n notices that the composite contains at least two layers of the metal grid, which are spaced apart by the ceramic. 3. Metal-ceramic composite according to claim 1, d a d u r c h g e k e n z e i n e t that the metal mesh is an elongated metal mesh that consists of Sheet metal is made. 4. Metal-ceramic composite according to claim 1, d a d u r c h e e k lc e n n n c i c h n e t that the metal grille is a metal grate. 5. Metal-ceramic composite according to claim 1, d a d u r c h g e k e n It is noted that several layers of the ceramic are provided, in each of which a metal grid is embedded, and that successive layers of the ceramic lie at a distance from each other. 6. Metal-ceramic composite according to claim 1, d a d u r c h g e k e n It is not indicated that the composite is in the form of a tube. 7. Metal-ceramic composite according to claim 6, d a d u r c h e It is not noted that the composite has a cylindrical shape. 8. Metal-ceramic composite according to claim 7, d a d ü r c h g e K e n n z e i c h n e t that the composite consists of a spiral wound layer of the Ceramic is formed with a grid embedded therein, such that a number all, cj: lein concentric positions of the grid are provided, s embedded in the lteramic is. 9. Metal-ceramic connection according to claim 1, o. & D u r c n p It is not noted that the ceramic is alumina. 10. Component for the exhaust system of an internal combustion engine after a of claims 1 to 9, that it is hollow and has an inner liner that forms insulation, the insulating Lining has a monolithic layer of ceramic material in which a metal grid is embedded with openings that are closed by the ceramic material. 11. Component for the exhaust system of an internal combustion engine after a of claims 1 to 9, d a d u r c h r e k e n xi -z e i c h n e t t that it is hollow and is made of a metallic material and has an inner liner has, which forms a thermal insulation, the heat-insulating lining has a monolithic layer of ceramic material, in which a metal grid with öffnunüen is embedded, which are closed by the ceramic material, 12. Brn.teil for the exhaust system of an internal combustion engine according to one of claims 1 to 9, d a d u r c h g e -k e n n n z e i c h n e t that it is hollow and made of a metallic material ilaterial is made and has an inner liner that provides thermal insulation forms, the heat-insulating lining from a metal grid and a layer Has Keramthnaterial in which the gate is embedded by the fact that the grid is coated with a ceramic slurry and then the ceramic slurry is heated to a temperature at which the slurry forms a monolithic ceramic body forms, wherein the grid has openings through the ceramic material of the monolithic Ceramic body are developed, 15. Component for the exhaust system of an internal combustion engine according to one of claims 1 to 9, d a d u r c h g e -k e n xi z e i c h n e t, that it is hollow and has an inner lining that forms insulation, wherein the heat insulating liner comprises a metal mesh and a sheet of ceramic material has, in which the grid is embedded in that the grid with a ceramic slurry is coated and then heated the ceramic slurry to a temperature becomes, in which the mud has a monolithic Kerani bodies forms, wherein the metal grid has a melting temperature that is higher than the Teinperatur in which the slurry forms the monolithic ceramic body, and where the Metal mesh has a higher thermal expansion coefficient than the ceramic material has, in such a way that the grid is put under tension and the ceramic body under pressure as the heated liner cools down. 14. Hollow cylindrical component for the exhaust system of an internal combustion engine according to one of claims 1 to 9, g e -k e n n z e i c h n e t d u r c h an inner one Lining that provides thermal insulation of the same, the thermal insulating Liner comprises a metal grid which is wound in a spiral shape, such that that at least two grid layers are created around the hollow cylindrical component, wherein the lining comprises a monolithic ceramic material in which the third is embedded, and the grid has openings through the ceramic material are closed. 15. Hollow cylindrical component in metallic design for the Exhaust system of an internal combustion engine according to one of claims 1 to 9, ç e k e n n z e i c nn e t d u r c h an inner liner that is used for thermal insulation of the same, the heat-insulating lining being a monolithic layer made of ceramic material, in which a metallic grille is embedded, the openings has that by the ceramic material are closed. 16. Process for the production of a high-temperature insulating composite made of metal and ceramic according to one of claims 1 to 15, d a d u r c h g e k It is noted that a metal grid is coated with ceramic slurry and this creates a layer of ceramic in which the net lattice is embedded, the layer made of ceramic with the metal grid located therein to a temperature is heated, during which the Kerar! lik forms a Jionolithic body, then the ceramic with the metal grid located therein is cooled, the metal grid has a melting temperature that is higher than the temperature at which the ceramic the monolithic ceramic body forms, and the metal mesh has a higher coefficient of thermal expansion than the ceramic, and has a metallic layer and the ceramic layer in a la; e are brought together.