Layered sheet metal with rolled-on solder and process for manufacturing a honeycombed body therefrom

0001The invention relates to a method for producing a honeycomb body in which metal sheet layers are stacked and / or wound, which at least partially have a structure for the formation of channels through which a fluid can flow. In particular, the invention also relates to layered metal sheets with an outer aluminum layer for producing such honeycomb bodies, which are used above all in exhaust gas cleaning systems of motor vehicles.

0002A honeycomb body of the type mentioned above is known, for example, by WO 89/07488. The honeycomb body serves as a carrier for a catalyst which promotes the reaction of components of an exhaust gas, in particular of an exhaust gas from an internal combustion engine, into less polluting compounds. The honeycomb bodies are subjected to high mechanical and thermal stresses. In addition to the mechanical and thermal stresses, the metal sheets are exposed to a corrosion-promoting atmosphere. It is therefore desirable to use metal sheets with high corrosion resistance for producing a honeycomb body.

0003It is known from US Pat. No. 5,366,139 to use metal sheets for honeycomb bodies, which first consist of a layered material. Such sheets have at least one layer of chromium-containing steel and at least one substantially aluminum-containing layer. Such a layered sheet is subjected to heat treatment, the sheet being largely homogenized. Homogenization of the sheet is understood to be a diffusion of the aluminum into the steel so that essentially a single-layer sheet of steel with aluminum is produced.

0004DE-OS 29 24 592 discloses various methods for applying solder material to such sheets or honeycomb bodies produced therefrom. All of these methods require considerable effort and additional manufacturing steps.

0005The object of the present invention is to specify a method for producing a honeycomb body which contains as few production steps as possible, but nevertheless leads to a corrosion-resistant and mechanically load-bearing honeycomb body. In addition, a suitable metal sheet of composite material is to be produced for the production of such bodies.

0006This object is achieved by a method for producing a honeycomb body with the features of claim 1 or by a metal sheet having the features of claim 8. Advantageous further developments are the subject matter of the respective dependent claims.

0007In the production of a sheet according to the invention, the soldering material required for the subsequent external connection is also rolled up simultaneously with the rolling of the supporting metal layers. This eliminates the need for costly manufacturing steps, which have to do with the subsequent application and fixing of solder. The honeycomb body only needs to be wound or layered and can subsequently be fed to the soldering process. The application of solder material in a rolling process, in which different layers are rolled together in any case, is far less complex than the subsequent soldering of the sheets or honeycomb bodies.

0008Various types of soldering and the arrangement of soldered connections of a honeycomb body are known from the prior art. By striping the braze material on the surface of the sheets, almost all desired configurations of the later soldering sites can be achieved. Preference is given to strips of a width of 2 to 10 mm, in particular about Smm. Depending on the building type, the strips can be arranged on one or both sides and on one or both edges. In particular, it is also possible to provide only half of the sheet metal layers for soldering layers for a honeycomb body, in particular smooth sheet metal layers, while the remaining sheets are produced without solder material.

0009In the case of the particularly advantageous use of nickel-based braze for the solder material strips, these can be applied during the joint rolling process with the rolling-on of aluminum layers, the relatively harder nickel material pressing into the aluminum layer so that a nearly free surface is produced despite the strips. It is possible to use solder foils or soldered wires or scattered solder powders. In the case of the use of solder wire, this can be deformed only slightly flattened or too wide, depending on the choice of the solder material, the roller configuration and the type of the process guide.

0010Conventionally applied solder layers of, for example, a local thickness of more than 10 μm may lead to the mechanical instability of a honeycomb body, since the solder flows away during the soldering process and previously stressed honeycomb bodies can thus relax. On the other hand, the solder thickness for the finished rolled sheet must be, for example, only approximately 0.5 to 3 μm.

0011Because of the reduction in the number of process steps, the present invention makes possible a more cost-effective production of the laminated and soldered metal sheets, in particular a cost-effective production of wide sheet metal strips. The sheet strips required for honeycomb bodies are, under certain circumstances, cut in varying width therefrom. Therefore, when the solder is rolled in, care must be taken to ensure a suitable distance between the solder strips, in order to avoid superfluous waste.

0012By the method and the use of a layered material comprising at least one layer of chromium-containing steel and at least one substantially aluminum-containing layer, the braze material may be a nickel-based braze, the maximum brazing temperature being 1100 to 1150 ° C. Preferably, the brazing material contains between 0.5 and 8% boron, in particular 3 to 6% boron. Boron in the brazing material serves as a diffusion accelerator so that a time reduction of the brazing process is achieved with equivalent brazing joints. A shortening of the soldering process results in higher throughput rates being made possible by a soldering furnace. The achievable high aluminum content of the homogenized sheets can compensate for disadvantageous properties of the boron part for the corrosion resistance of the layered material.

0013In particular, it is advantageous that the heat treatment is first carried out in a temperature range in which the solder material does not yet melt. After a substantial homogenization of the laminated sheets, the temperature is increased up to the melting temperature of the solder material. This method has the advantage of ensuring that a substantial homogenization of the laminated sheets is achieved and then a durable soldering connection is provided.

0014Further advantages and features of the method according to the invention are explained in more detail with reference to the drawing. Show it:<dl tsize="6"><dt>FIG</dt><dd>Schematically a honeycomb body in cross-section, according to the prior art,</dd><dt>FIG</dt><dd>A metal sheet of a stratified material having a solder layer,</dd><dt>FIG</dt><dd>A metal sheet of a stratified material with several rolled-in solder strips in a schematically perspective view, and FIG</dd><dt>FIG</dt><dd>A metal sheet of a layered material having three layers, thereof a solder layer.</dd></dl>

0015A honeycomb body 1 is shown in the FIG. The honeycomb body 1 consists of stacked and wound high temperature corrosion resistant metal sheet layers. The honeycomb body 1 is produced alternately from smooth and corrugated sheet metal layers 2, 3. The smooth and corrugated layers 2, 3 have a layered construction. However, it is also possible to manufacture a honeycomb body partly from homogeneous metal sheet layers and partly from layered material. In the case of the layered material, layers 5, 6 which essentially consist of aluminum, as can be seen in FIG. 2, are applied on both sides of an inner layer 4. The layered material shown in FIG. 2, like the one shown in FIG. 3 and FIG. 4, has an appearance as it is before the heat treatment.

0016The honeycomb body 1 has a structure for the formation of channels 7 through which a fluid can flow. Its metal sheet layers are arranged in a jacket tube 8. The jacket tube 8 preferably has, on its inner side, at least in part regions a layer consisting essentially of aluminum. However, it can also be connected to the metal sheet layers alone or additionally using conventional soldering techniques. It is also possible to produce a honeycomb body without using a prefabricated jacket tube, for example by winding a smooth sheet metal layer around a structure of stacked and wound metal sheet layers and soldering it to itself.

0017FIG. 2, FIG. 3 and FIG. 4 show various embodiments for metal sheets according to the invention. However, these embodiments are merely examples. Depending on the location, number and size of the desired solder connections, soldering layers, solder strips or other solder patterns can be rolled onto the layered material on one or both sides on the outside. It is also possible to roll soldering material into the inside of a layered material. This can be advantageous, for example, if the solder wire is first to be partially rolled. Thereafter, a layer made of softer material than the braze material can then be rolled so that the braze material passes through this layer until it reaches the surface of the layered material. Unlike in the embodiments of FIGS. 2 and 3, in which rolled solder material 9; 9a, 9b, 9c, the brazing material 9; 9a, 9b, 9c can also be rolled externally onto a metal layer of a different material, for example, as shown in FIG. 4, to an outer chromium-containing steel layer.

0018As shown in FIG. 3, it is often desirable to place the solder only in strips 9a, 9b, 9c at partial areas of the composite surface formed by rolling. This can be done on one or both sides of the sheets. Preference is given to strips 9a, 9c on at least one edge region of the metal sheets, which later lead to brazing connections on the face in the honeycomb body to be produced since the metal sheets have a width b which corresponds to the later axial length of the honeycomb body 1. Unlike in the exemplary embodiments shown in FIG. 2 and FIG. 3 with a solder material layer or with solder material strips of non-location-dependent thickness d, the solder material can also have a location-dependent thickness. By way of example, such designs can be produced by the rolling-on of solder wire and solder powder.

0019The method according to the invention is applicable to honeycomb bodies which consist wholly or partly of plate-like sheet metal layers and leads inexpensively to mechanically loadable bodies resistant to high temperature corrosion, which are particularly suitable for exhaust gas catalysts of motor vehicles.

Reference list:

0020<dl tsize="5" compact="compact"><dt>1</dt><dd>Honeycomb body</dd><dt>2</dt><dd>corrugated metal plate</dd><dt>3</dt><dd>smooth metal sheet</dd><dt>4</dt><dd>Chromium containing steel layer</dd><dt>5</dt><dd>Layer essentially containing aluminum</dd><dt>6</dt><dd>Layer essentially containing aluminum</dd><dt>7</dt><dd>channels</dd><dt>8th</dt><dd>casing pipe</dd><dt>9</dt><dd>solder material layer</dd><dt>9a-9c</dt><dd>Soldering strips</dd><dt>10-12</dt><dd>layered material</dd><dt>b</dt><dd>Width of the plates = axial length of the honeycomb body</dd><dt>d</dt><dd>Thickness of the solder material (perpendicular to the composite surface)</dd></dl>