DE202008014927U1 - Metallic seal for high temperature applications - Google Patents

Abstract

Metallic seal (1), in particular metallic flat gasket, with at least one gasket layer (2) which has at least one passage opening (3) which is enclosed by an elastically deformable sealing element (4) formed in the gasket layer (2), characterized in that at least the region (20) of the sealing layer (2) having the sealing element (4) consists of a high-alloy chromium-nickel steel having a chromium content of at least 18.5% by weight and a tensile strength Rm at room temperature of at least 900 N / mm ² exists.

Description

The The invention relates to a metallic seal and more particularly to a metallic flat gasket or pipe gasket with at least one Sealing layer, which has at least one passage opening, which of a formed in the gasket layer, elastically deformable Enclosed sealing element. The invention particularly relates to metallic Seals for high temperature applications where the Seal in operation exposed to temperatures of at least 450 ° C is. The preferred application of the seals is in the range of Internal combustion engines and here in particular in seals, the Range of engine and exhaust system can be used. To a better one Achieving power while reducing fuel consumption are getting more and more compressed engines lately used, which work at very high temperatures. Corresponding increases the thermal load on the components that be used in the area of the engine compartment and the exhaust line, ever stronger. This also applies to the seals, which are used in these areas.

In the field of internal combustion engines, metal seals of the type described above have hitherto been used in which the passageways for fluids such as fuel gas, cooling water or oil have been sealed by means of elastically deformable sealing elements such as beads. As a material for the gasket layers, which have the elastically deformable sealing elements, stainless steels such as 1.4310 or 1.4372 have traditionally been used. However, with increasing thermal stresses, these materials have neither the required chemical resistance nor adequate tensile strength at the elevated operating temperatures. As a result of material changes, for example, scaling, premature material fatigue occurs, in particular in the area of the elastically deformable sealing elements, which can no longer sufficiently follow the sealing gap changes so that leaks occur. It has therefore been proposed, instead of the previously used stainless steels, to use nickel-base alloys such as, for example, Inconel® (cf., for example, US ^Pat . DE 10 2005 041 826 A1 or US 2006/1 91 603 A1 ). However, these scale-resistant materials are several times more expensive than the stainless steels used so far. In addition, they often do not have the necessary for the functioning of the seals spring behavior.

The the same problem basically exists in others Areas where metallic gaskets by means of elastic seal deformable sealing elements, used at very high temperatures become. There was therefore a need for a metallic seal, which is inexpensive to produce, but also at very good temperatures shows a good sealing behavior. Task of Invention is to provide such a seal.

The Solution of this problem succeeds with the metallic seal according to claim 1. Preferred developments of Seal are described in the subclaims.

In its first aspect, the invention thus relates to a metallic seal with at least one gasket layer, which has at least one passage opening. This passage opening is enclosed by a molded into the gasket layer, elastically deformable sealing element and sealed in this way. At least the region of the gasket layer having the sealing element is made of a high-alloy chromium-nickel steel having a chromium content of at least 18.5% by weight and a tensile strength Rm at room temperature of at least 900 N / mm ² . The use of this chromium-nickel steel with the specified properties ensures that the sealing element formed in the gasket layer retains its elastic properties even at very high temperatures and a permanent seal of the through-hole to be sealed is achieved.

Preference is given to using those steels in which the tensile strength R m at room temperature is more than 1100 N / mm ² and particularly preferably more than 1300 N / mm ² . Particularly suitable are those steels in which the tensile strength Rm is high even at elevated temperature, namely more than 750 N / mm ² and preferably above 900 N / mm ² , in particular at 800 ° C. Usually, the chromium-nickel steels used _according to the invention have a yield strength R _p0.2 at room temperature which is at least 80%, preferably at least 85% of the value for Rm.

In addition to the relatively high chromium content, the steels used according to the invention have a comparatively low nickel content. This is, for example, significantly lower than in the case of Inconel ^® alloys, as they have been proposed as an alternative to stainless steel as a material for high temperature gaskets. While in Inconel ^® the nickel content is usually more than 50 wt .-%, the nickel content should be at least 10, although the steels used in the invention suitably wt .-%, but it is usually not higher than 20 wt .-% , It is preferred if the chromium-nickel steel used has a nickel content of 10 to 15 wt .-% and in particular from 10 to 13.5 wt .-%. This comparatively low nickel content helps to significantly reduce the cost of the material used.

in the With regard to scale resistance and elasticity of the steel used in the invention this preferably silicon and that with a weight fraction of at least 1% by weight, more preferably at least 1.4% by weight. The content of carbon is preferably no longer as 0.5 wt .-% and in particular at most 0.2 wt .-%. molybdenum is, if any, in the invention used Steels present only in a small proportion, the appropriate at most 0.5% by weight, preferably at most 0.2% by weight and in particular only up to 0.05 wt .-% is.

Of the Chromium-nickel steel used according to the invention has excellent despite its relatively high chromium content chemical and mechanical properties also in the high temperature range of at least 450 ° C and in particular of over 600 ° C. This is surprising since steels with such high chromium contents at temperatures of 450 ° C tend to form sigma phases upwards. These sigma phases lead to embrittlement of the structure, and, by chromium depletion of the matrix, to a significant reduction the corrosion resistance. Furthermore, the fatigue strength reduced in the thermal stress. Surprisingly These effects on seals from the chromium-nickel steels used in the invention however, are not observed. The steels used rather have excellent tensile strengths even at high temperatures and a very good chemical resistance, though the nickel content and thus the cost of the material comparatively are low. The springback properties of the material are at elevated temperature (up to 600 ° C) those the previously used spring-hardened stainless steels (1.4310 or 1.4372) equivalent, at temperatures beyond this Even superior to materials. Even at temperatures of over 900 ° C, the material remains spring-hard and reserves this property over a long period of time.

The chromium-nickel steels used according to the invention are usually steels having an at least predominantly austenitic structure. However, this does not exclude that a lower volume fraction of the structure has a different structure, for example a proportion of Mar tensite. Particularly preferred are those steels which are work-hardened but not annealed. For work hardening, all methods customary in the prior art are considered; they are preferably cold-rolled steels. Particularly suitable is a cold-rolled steel grade 1.4828 (X15CrNiSi 20 12) has proven. It is not the soft-annealed version of this steel that is commonly available on the market, but a stage from the manufacturing process that is not annealed. This stage is cold rolled. As used for the steel 1.4828, the stage used according to the invention has a chromium content of usually 19 to 21% by weight, a nickel content of 11 to 13% by weight, a silicon content of 1.5 to 2% by weight and a Carbon content of at most 0.2 wt .-% on. The non-annealed, work-hardened step used according to the invention has markedly increased tensile strengths, both at room temperature and at elevated temperatures, compared to the soft-annealed variant. Due to its very high tensile strength and excellent scaling resistance, this material is excellently suited for the production of high-temperature seals, which should show excellent and lasting resilience even under extreme temperature conditions. The material against Inconel ^® alloys or other nickel-rich materials is significantly less expensive.

The chromium-nickel steel described above can be used in principle for the production of all known in the prior art metallic gaskets. It is, as already mentioned, in particular for the production of such seals with molded elastically deformable sealing elements which are to be used at very high temperatures. The elastically deformable sealing element molded into the sealing layer can be, for example, a bead, the term bead here encompassing both a full bead and a half bead. Of course, several of the through-opening to be sealed from successively arranged beads act as a sealing element. In addition or as an alternative to a bead as a sealing element, it is also possible to use sealing structures which are formed from elevations and depressions which are transverse to the direction of extent of the sealing element which is usually closed to the ring. Preferably, these elevations and depressions alternate periodically and form, for example, a wave-shaped structure. The dimensions of the individual elevations and depressions are usually significantly smaller than the dimensions of a bead as a single elastically deformable sealing element. Examples of the wave-shaped structures described can be the WO 01/96768 A1 taken from the applicant. The structure of alternating elevations and depressions can also be integrated into the basic structure of a bead, as in the European Patent Application No. 08002192.6 the applicant is described. For further examples of periodic structurings of the gasket layer, moreover, reference may be made to US Pat German utility model no. 20 2008 005 712.4 and the European Patent Application No. 07010816.2 the applicant are referred. In the latter application are also wavy structurings of the gasket layer in the so-called hinterland of the Seal described. Also for the production of these structured hinterland sealing areas, the chromium-nickel steel described here is excellent. In addition, in principle to the term "elastically deformable sealing element" should be noted that this should also be understood as those sealing elements that are not only elastically deformable, but also plastically deformable or plastically deformed.

The Preparation of the metallic invention Seal is with the usual so far in the art Procedure possible. Preference is given to the elastically deformable Sealing element in the gasket layer of the described chromium-nickel steel imprinted. It is possible, the gasket layer, which contains the elastically deformable sealing element, to produce a total of the steel described or only those Area around the through-hole to be sealed, which having the sealing element. It will then be known per se Just made an annular so-called insert, that in a corresponding opening of the gasket layer is used, which in its remaining areas from another Material exists. Of course, in one Gasket also several such inserts are used. These Inserts are conveniently used where the Sealing layer during operation of the seal particularly high temperatures is suspended. Individual inserts can also be spectacle-like be joined together, as is the case from the prior art is also known in principle. Both at uniform from the described chromium-nickel steel existing gasket layers as well as gasket layers with inserts made of this material all through holes with molded Sealing elements are sealed, with part of the through holes can also be sealed by a common sealing element.

Seals according to the invention comprise single-layer or multi-layer seals of which one or more layers consist at least partly of the chromium-nickel steel in the manner described above. If multilayer gaskets are used for sealing between components subjected to different temperatures, then it is preferable to manufacture at least the first gasket layer facing the more temperature-stressed component from the chromium-nickel steel. The gasket layers may be provided in a manner known per se in whole or in part, on one or both sides with a coating. In particular, this coating can also cover the elastically deformable sealing element, for example for improving the micro-seal or the sliding friction properties. In addition to metallic coatings, polymer-based coatings are also suitable; EP 0 974 630 A1 referenced temperature resistant coating referenced.

The invention is basically suitable for all types of metallic seals. Here are in particular metallic flat gaskets should be mentioned, among which are to be understood such seals that extend flat, but also have a conical or spherical basic shape due to the conical or spherical surfaces to be sealed. These seals are then considered as gaskets if their longitudinal and transverse extent is substantially greater than their thickness, namely at least five times, preferably at least ten times, is as large as the thickness. However, the invention is also suitable for use on radial seals or pipe seals, as for example in the German utility model no. 20 2008 010 025.9 the applicant are described. The term seal should also be subsumed according to the invention bipolar plates for fuel cells. Such bipolar plates are for example in the DE 102 48 531 A1 the applicant described. In such bipolar plates are metal plates, in which an elastically deformable bead is formed, which serve to seal the channels for fuel, reaction product and coolant.

Prefers becomes the metallic seal according to the invention used as a seal for internal combustion engines. in principle can the metallic seal of the invention also be used as a cylinder head gasket, are preferred applications However, flange gaskets that are located in the engine compartment or the Exhaust line are arranged and exhaust gaskets, in particular Exhaust manifold gaskets, seals in the area of the charge, z. As turbocharger seals, seals in the field of exhaust aftertreatment and - repatriation etc. The areas of the Sealing layer, which consist of the described chromium-nickel steel, are expedient at least leading to the fuel gases Through openings provided around. Further high temperature applications inventive seals are in the range Heat exchanger, reformer or gas treatment.

The Invention will be described below with reference to some embodiments explained in more detail with reference to drawings become. However, the invention is not limited to these specific embodiments limited. In the figures show schematically:

1 (a) a plan view of a metallic seal according to the invention, here a metallic flat gasket, using the example of a flange seal;

1 (b) a cross section along the line AA in 1 (a) ;

2 a partial plan view of a metallic seal according to the invention, here a metallic flat gasket, using the example of an exhaust manifold gasket;

3 (a) a partial plan view of another inventive metallic seal, again using the example of a flat exhaust manifold gasket;

3 (b) and 3 (c) Cross sections along the line BB in 3 (a) for two different embodiments;

4 (a) a section of an exhaust system consisting of cylinder head, four pipe seals, four-flow exhaust manifold and another pipe seal;

4 (b) a cross section through a built-in metallic seal according to the invention using the example of a pipe seal

5 a cross section through a metallic seal according to the invention using the example of a conical seal and

6 a partial plan view of a metallic seal according to the invention using the example of a bipolar plate of a fuel cell.

1 (a) shows a metallic seal 1 Specifically, a flange gasket for sealing the connection of two hot gas leading pipes, as described in detail in the European Patent Application No. 07020452 is described. The seal shown here 1 differs from that described in the earlier application in principle only in the choice of material for the gasket layer 2 , The flange seal 1 has a gas passage opening 3 on. In addition, there are two further passage openings 6 present in the outer area of the seal, which are screw holes.

In the example shown, there is the flange seal 1 , as in 1 (b) shown, made of two gasket layers 2 and 2 ' , which have both sealing elements for sealing the passage openings and therefore as functional layers 2 . 2 ' be designated. Over their entire surface are both functional layers 2 . 2 ' produced according to the invention from the described chromium-nickel steel. The elastically deformable sealing elements 4 . 4 ' which the gas passage opening 3 surround and seal these are each as full beads 40 . 40 ' executed. Due to the production of functional layers 2 . 2 ' from the chrome-nickel steel have the sealing elements 4 . 4 ' for the gas passage openings 3 excellent springback properties, which are retained because of its excellent scale resistance even with the large temperature exposure in this area. This ensures a permanent seal.

In the 1 (b) underlying functional position 2 ' has a larger surface area than the functional layer 2 which does not reach into the area of the screw openings 6 enough. To compensate for the resulting reduced overall thickness of the seal in this area, this area is used as a support area 7 educated. The support area 7 serves further in a conventional manner to prevent distortion between the adjacent components in this area. It is designed here in the form of a wave-shaped structuring.

2 shows a section of a Mehrflutigen exhaust manifold gasket 1 in which two gas passages 3 are reproduced. The seal has only one gasket layer 2 on, this is made up of a sealing plate 25 and inserted insert sealing elements, so-called inserts, 5 together. The gas passage openings 3 are each from an insert 5 enclosed, that also the respective sealing element 4 wearing. The sealing elements 4 are as in the previous example as Vollsicken 40 educated. The sealing plate 25 and the inserts 5 preferably have the same material thickness. To secure attachment of the inserts 5 in the gasket plate, these are over puzzle-shaped extensions 5 * attached. In the embodiment shown is not the entire gasket layer 2 made from the described chromium-nickel steel, but only the inserts 5 , since in the present application, only the closer environment of the gas passage openings 3 exposed to oxidative gases that can lead to scaling. The sealing plate 25 can be made of metal with a lower yield strength, since it does not have to have sealing elements or stable embossing.

3 (a) shows a partial plan view of another Mehrflutige exhaust manifold gasket 1 , again with two gas passage openings 3 are reproduced. Unlike the previous embodiment, however, this seal is designed as a two-layer seal, as shown 3 (b) , which shows the gasket layers simplified as lines, becomes clear. It points next to a bottom layer 8th , which is designed without sealing elements or other structures, a functional position 2 on, in which the sealing elements 4 are formed. The sealing elements 4 are here but not designed as ordinary full beads, but have a wave structure 41 with five wave crests 43 superimposed on an arch form. This sealing structure also gives the described chromium-nickel steel, from which at least the entire functional position 2 is formed, excellent springback properties even at high operating temperatures.

3 (c) illustrates another variant in which the sealing element 4 only from a wavy structuring 41 the functional position 2 consists. Unlike in the previous examples, this embodiment has on both surfaces of the functional layer 2 a coating 20 on, in the example shown in the troughs 42 a greater material thickness than on the wave crests 43 or in the unstructured area 44 the functional position 2 has. The top layer 8th is executed here without coating. The functional position 2 is in turn made of the described chromium-nickel steel, whereas the top layer 8th can be made of this or another metallic material. In addition to this sectional view, it should be noted that the layer sequence compared to the 3 (a) and 3 (b) is reversed.

4 shows in partial pictures 4 (a) and 4 (b) a completely different type of seal, namely a pipe seal 1 , This has a tubular body of usually only one gasket layer 2 on top of the passage opening 3 encloses. Preferably at both ends of the tubular base body (see 4 (a) ), but at least once in the course of the tubular body (see 4 (b) ) has the seal 1 a the passage opening 3 circumferential sealing element 4 on. This can be performed, for example, as shown in the previous flat gaskets as a full bead, as in 4 (a) is indicated or as in the 4 (b) as unbalanced double bead. While the exhaust manifold gaskets the 2 and 3 between a cylinder head 100 and an exhaust manifold 200 be installed that they lie flat between these two and are fastened by bolts or screws to both, the pipe seal is the 4 with one end into a gas outlet 102 of the cylinder head 100 and with its other end in the gas inlet opening 201 the exhaust manifold 200 inserted as in 4 (b) shown, at least one of these two components may have a stop. Especially in these pipe seals, the described chromium-nickel steel unfolds its advantages, since often a considerable portion of the inner surface of the seal is exposed to the aggressive hot gases.

5 represents a flat gasket 1 is that already protrudes in its base from the plane, since the at least one gasket layer 2 is conically shaped. The illustrated embodiment has two the passage opening 3 enclosing sealing elements 4 and 4 ' on, the former as a full bead 40 and the latter as wave-shaped profiling 41 is executed. In principle, for most applications of this type of seal, which is usually used as a pipe seal, already a single of these sealing elements 4 . 4 ' sufficient for the sealing function. Again, at least the functional position 2 made from the described chromium-nickel steel.

Finally clarified 6 in that the metallic seal can also be a plate of a fuel cell, here a bipolar plate. This has inter alia a media passage opening 3 , For example, for air or hydrogen, that of a sealing element 4 , here a half-bead, is enclosed. In the lower right area is the so-called Flowfield 9 the bipolar plate arranged. The at least one metallic layer is in turn formed from the chromium-nickel steel described, whereby the bipolar plate also offers very good sealing properties at high temperatures.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102005041826 A1 [0002]
• US 2006/191603 A1 [0002]
• WO 01/96768 A1 [0011]
• - EP 08002192 [0011]
• - DE 202008005712 U [0011]
• EP 07010816 [0011]
• - EP 0974630 A1 [0013]
• - DE 202008010025 U [0014]
• - DE 10248531 A1 [0014]
• EP 07020452 [0026]

Claims (11)

Metallic seal ( 1 ), in particular metallic flat gasket, with at least one gasket layer ( 2 ), which has at least one passage opening ( 3 ), which from one into the gasket layer ( 2 ) molded, elastically deformable sealing element ( 4 ) is enclosed, characterized in that at least the sealing element ( 4 ) ( 20 ) of the gasket layer ( 2 ) consists of a high-alloy chromium-nickel steel having a chromium content of at least 18.5 wt .-% and a tensile strength Rm at room temperature of at least 900 N / mm ² . Metallic seal according to claim 1, characterized in that the chromium-nickel steel has at least one of the following properties: a tensile strength Rm at room temperature> 1100 N / mm ² , preferably> 1300 N / mm ² , - a tensile strength Rm at 800 ° C of> 750 N / mm ² , preferably> 900 N / mm ² , - a yield strength R _p0.2 > 80%, preferably> 85% Rm at room temperature. Metallic seal according to claim 1 or 2, thereby in that the chromium-nickel steel at least one has the following properties: - a chromium content from 18.5 to 25% by weight, in particular from 19 to 21% by weight, - one Nickel content of ≥ 10 wt .-%, preferably 10 to 20, especially preferably 10 to 15% by weight and in particular 10 to 13.5% by weight, - one Silicon content of> 1 Wt .-%, preferably> 1.4 Wt .-%, - a molybdenum content of ≤ 0.5 Wt .-%, preferably ≤ 0.2 wt .-% and in particular ≤ 0.05 Wt .-%, - a carbon content of ≤ 0.5 Wt .-%, preferably ≤ 0.2 wt .-%. Metallic seal according to one of the claims 1 to 3, characterized in that the chromium-nickel steel a Steel with at least predominantly austenitic structure is. Metallic seal according to one of the claims 1 to 4, characterized in that the steel is work hardened and not annealed. Metallic seal according to claim 5, characterized in that that the steel is the work-hardened, not soft-annealed Stage of steel 1.4828 (X15CrNiSi 20 12). Metallic seal according to one of claims 1 to 6, characterized in that the elastically deformable sealing element ( 4 ) a bead ( 40 ) or one in the gasket layer ( 2 ), in particular embossed structure ( 41 ) with transversely to the direction of extension of the sealing element preferably closed to the ring ( 4 ) alternating surveys ( 42 ) and depressions ( 43 ), especially a wavy structure. Metallic seal according to one of claims 1 to 7, characterized in that the sealing element ( 4 ) ( 20 ) as an insert ( 5 ) formed in a corresponding opening ( 21 ) of the gasket layer ( 2 ) is used. Metallic seal according to one of claims 1 to 7, characterized in that the sealing layer ( 2 ) is a corrugated sheet, in particular a bipolar plate, monopolar plate or distributor plate of a fuel cell. Metallic seal according to one of the preceding claims, characterized in that the at least one sealing layer ( 2 ) is coated at least partially on at least one of its surfaces, in particular with a metallic and / or polymer-based coating ( 20 ) is coated. Metallic seal according to one of the claims 1 to 10, namely gasket for internal combustion engines, in particular exhaust gasket, flange gasket, bipolar plate for a fuel cell, seal for heat exchangers, Reformer or for gas treatment.