Brake drum for a drum brake, method for producing the brake drum, and use of the brake drum in a drum brake

Abstract

The invention relates to a brake drum for a drum brake, having a first element comprising a first metallic material and a second element comprising a second metallic material, wherein the first element is joined to the second element by casting. The brake drum furthermore has a bonding layer, wherein the bonding layer is located between the first element and the second element and wherein the first element is integrally joined by intermetallic bonding to the second element by way of the bonding layer. The invention also relates to a method for producing the brake drum and to the use thereof.

Description

[0001] Brake drum for a drum brake, method for producing the brake drum and use of the brake drum in a drum brake

[0002] The invention relates to a brake drum for a drum brake, which has a first element containing a first metallic material and a second element containing a second metallic material, wherein the two elements are materially connected to one another via an intermetallic bond, a method for producing the brake drum and the use of the brake drum in a drum brake according to the preamble of the independent patent claims.

[0003] Brake drums for drum brakes are often designed in the state of the art in the form of an inner ring made of, for example, cast iron or cast steel to provide sufficient stability and, in turn, to minimize weight and ensure good heat dissipation, is embedded in an outer ring, which is typically made of a comparatively light alloy, such as an aluminum-based alloy, among other things. To prevent the inner ring from becoming detached from the outer ring and, for example, becoming mobile within it, which would ultimately lead to a loss of braking effect, a mechanical bond between the two rings is currently used according to the state of the art. This is made possible, for example, by the inner ring having a rough surface facing the outer ring and, in particular, a plurality of undercuts.Alternatively, it can also have a plurality of projections, for example.

[0004] For example, EP 2497967 B1 relates to a brake drum, wherein an inner ring made of cast iron, cast steel, or an aluminum alloy is located within an outer ring made of an aluminum or magnesium alloy. The outer ring is applied by die casting. The inner ring has projections on the outwardly facing surface, which have a tapered shape and enable a mechanical bond. It is an object of the present invention to provide improved or at least alternative embodiments for a brake drum. In particular, the present invention is concerned with the object of providing embodiments for a brake drum that enable improved load-bearing capacity of the component and / or improved heat dissipation.

[0005] This object is achieved according to the invention by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent patent claims.

[0006] According to the invention, it is provided to provide a brake drum for a drum brake, wherein the brake drum has a first element containing a first metallic material and a second element containing a second metallic material, wherein the first element is connected to the second element by casting, wherein the first element has a rough surface oriented in the direction of the second element and wherein the brake drum further has an adhesive layer, wherein the adhesive layer is located between the first element and the second element and the first element is integrally connected to the second element via the adhesive layer by means of an intermetallic bond.

[0007] The brake drum according to the invention with the features of independent patent claim 1 has the significant advantage over the prior art that a particularly good bond is provided between the inner and outer rings.

[0008] This results in a further significant advantage of the brake drum according to the invention: a greater load-bearing capacity of the component, for example, even under fluctuating thermal loads. Furthermore, the brake drum according to the invention enables very good heat dissipation. Further significant advantages of the present invention are that gap formation between the two elements is prevented, that composite stresses can be absorbed, and that forces acting on the brake drum can be effectively transmitted without causing damage to the brake drum.

[0009] Furthermore, the invention also enables the use of other casting processes in addition to the die casting process. Thus, the invention also enables the use of the permanent mold casting process, which enables a particularly dense cast structure.

[0010] This is achieved in particular by providing, in addition to the rough surface of the first element containing a first metallic material, which is oriented in the direction of the second element containing a second metallic material, an adhesive layer which serves to firmly bond the first element to the second element by means of an intermetallic bond.

[0011] The brake drum according to the invention for a drum brake, the method for producing the brake drum and the use of the brake drum are explained in more detail below, wherein the figures used in the context of the explanation of the brake drum according to the invention and the figures used in this context also apply mutatis mutandis to the method and the use and the figures used in this context and vice versa.

[0012] The present invention is based on the general idea of ​​providing a brake drum which has a first element containing a first metallic material and a second element containing a second metallic material. The first element is connected to the second element by casting. The first element has a rough surface oriented in the direction of the second element. For example, the first element is designed as a hollow cylinder and has a rough surface on the outside of the cylinder directed in the direction of the second element. The second element is also designed as a hollow cylinder, for example, and surrounds the first element. In order to effectively connect the first element to the second element, the brake drum further has an adhesive layer which is located between the first and the second element.For example, the outward-facing, rough surface of the first element can first be coated with the adhesive layer, and then the first element can be encased in a casting mold with a second metallic liquid material. Cooling and solidification of the second metallic material forms the second element, which is then firmly bonded to the first element.

[0013] Alternatively, it is also conceivable to provide a brake drum which has a first element consisting of a first metallic material and a second element consisting of a second metallic material.

[0014] For example, it is conceivable that the outer diameter of the second element ranges from a minimum of approximately 60 mm to a maximum of approximately 400 mm. Furthermore, it is conceivable, for example, that the inner diameter of the first element ranges from a minimum of approximately 30 mm to a maximum of approximately 370 mm. It goes without saying that this depends on the type of vehicle, and in particular the size of the wheels of that vehicle for which the brake drum is to be used.

[0015] To enable the first element containing a first metallic material in solid form to be cast in a casting mold with a second metallic material without changing its shape, it has proven advantageous for the melting temperature of the first metallic material to be higher than the melting temperature of the second metallic material. Preferably, the melting temperature of the first metallic material is at least 300°C higher than that of the second metallic material.

[0016] It has proven advantageous that the first metallic material contains Fe and the second metallic material contains at least one element selected from the group consisting of Al and Mg, preferably the first metallic material contains at least 90 wt% Fe, and the second metallic material contains at least 75 wt% of at least one element selected from the group consisting of Al and Mg. Alternatively, the first metallic material advantageously contains Fe, preferably at least 90 wt% Fe. Alternatively, the second metallic material advantageously contains at least one element selected from the group consisting of Al and Mg, preferably at least 75 wt% of at least one element selected from the group consisting of Al and Mg.

[0017] In particular, it is preferred that the first metallic material contains at least 90 wt% Fe, and the second metallic material contains at least 85 wt% of at least one element selected from the group consisting of Al and Mg. Alternatively, the second metallic material particularly preferably contains at least 85 wt% of at least one element selected from the group consisting of Al and Mg.

[0018] For example, this may mean that the first metallic material consists of cast iron or cast steel. A person skilled in the art defines cast iron as an iron material with a high carbon content, typically a carbon content of more than 2% by mass. A distinction can be made here between gray cast iron (grey cast iron), in which carbon is embedded in the form of graphite. In contrast, in white cast iron the carbon is embedded in the form of carbide (cementite FesC). Both types of cast iron, gray cast iron and white cast iron, can in principle be used. In the context of the present invention, a cast steel is understood to mean all steel types that can be cast into their final form as a melt. For example, the first metallic material can be a cast iron type GJL according to DIN-EN-1561:2012-01, such as the cast iron type EN-GJL-200.This is a cast iron with lamellar graphite. Furthermore, this means, for example, that the second metallic material consists of an aluminum alloy or a magnesium alloy. Aluminum alloys are alloys in which aluminum serves as the base material and other alloying elements are added to the aluminum, which can influence the material properties of the resulting alloy. For example, but not limited to, such alloying elements in aluminum alloys are Cu, Mg, Zn, Si, and Mn. Thus, a person skilled in the art knows that the main component of an aluminum alloy is aluminum and that the sum of all components amounts to 100 percent by weight. Analogously, magnesium alloys are alloys in which magnesium serves as the base material and other alloying elements are added to the magnesium.For example, but not limited to, such alloying elements in magnesium alloys are Cu, Zn, Si, Mn, Zr. In this context, “at least 75 wt% of at least one element selected from the group consisting of Al and Mg” further means that the alloy either contains at least 75 wt% Al or the alloy contains at least 75 wt% Mg or the sum of the Al and Mg contained in the alloy is at least 75 wt%. In addition, other alloying elements may be present. It goes without saying that the sum of all components contained must each add up to 100 wt%. It is also conceivable, for example, that the second metallic material is an aluminum alloy to which magnesium is added as one of the alloying elements.

[0019] For example, the second metallic material could be an EN AW-4032 alloy (wrought alloy). According to European standards (DIN EN 573-3:2009), wrought aluminum alloys are designated EN AW followed by a 4-digit number, where the number represents the composition. EN AW-4032, for example, is a representative of class EN AW-4000. The class is often alternatively specified as EN AW-4xxx, for example. It is also conceivable to use a cast aluminum alloy. Such cast aluminum alloys are designated EN AC followed by a 5-digit number according to European standards (DIN EN 1706:2021), where the number again represents the composition. An example of a cast aluminum alloy is EN AC 43300.

[0020] The chemical composition can be determined using chemical analysis methods such as ICP-OES (inductively coupled plasma optical emission spectrometry). This also applies, of course, to the chemical composition of other elements or layers described below.

[0021] In principle, all casting processes known to those skilled in the art are suitable for producing the first element containing a first metallic material, such as sand casting, centrifugal casting, permanent mold casting, or die casting. It has proven particularly advantageous if the first element is produced by centrifugal casting.

[0022] It has also proven advantageous that the first metallic material is gray cast iron. This results in particularly good compressive strength, good damping properties, and good corrosion resistance. It also enables high cost-effectiveness.

[0023] Furthermore, it has proven particularly advantageous if the first metallic material consists of grey cast iron and the second metallic material consists of an aluminium alloy.

[0024] In an advantageous development of the invention, it has also proven advantageous that the total height of the roughness profile Rt of the first element on the side of the surface facing the second element is at least approximately 500 pm and at most approximately 1200 pm. According to DIN EN ISO 4287:2010, the total height of the roughness profile Rt (also referred to as maximum roughness depth) is the sum of the height of the largest profile peak Z P and the depth of the largest profile valley Z vwithin the measurement section. Typically, the total height of the roughness profile Rt is determined by scanning the surface along a defined measurement section and recording all height and depth differences. For a detailed description of the determination of the total height of the roughness profile Rt, refer to DIN EN ISO 4287:2010.

[0025] The aforementioned overall height of the roughness profile can be achieved, for example, with the help of a refractory coating on the casting mold. This refractory coating is advantageously very porous when dry. For example, a coating with silicates with a high melting point is conceivable. If a liquid material is then poured into the casting mold, some of the liquid material flows into the pores of the refractory coating, whereupon the rough surface of the resulting component is created upon cooling. It is also conceivable, for example, for the wall of the casting mold to be covered on the inside with granules of a refractory material, which are removed from the component after it has been cast. For example, such granules can contain graphite globules.Any residues of the refractory coating or granules made of refractory material that may be adhering to the component can be removed by a cleaning process, such as a blasting process. For example, adhering residues of the refractory coating or granules made of refractory material can be removed by light sandblasting or light blasting with chilled cast grit. This means that the irradiation is sufficiently intense to remove the residues of the refractory coating or granules made of refractory material, but does not substantially change the rough surface structure of the component. This means, for example, that the total height of the roughness profile Rt of the first element on the side facing the second element after cleaning is preferably a minimum of approximately 500 pm and a maximum of approximately 1200 pm. In addition, the edges of the ring are deburred if necessary.

[0026] Furthermore, it has proven advantageous that the rough surface of the first element aligned in the direction of the second element has undercuts, wherein the rough surface of the first element aligned in the direction of the second element preferably has an undercut area Aue of at least approximately 0.36*10 5 pm 2 and a maximum of approximately 30*10 5 pm 2 on a distance L of 25 mm each.

[0027] The measurement of the undercut area Aue (“Undercut area”) can be carried out as follows:

[0028] First, a cross-section of the sample to be examined is created and viewed with an optical camera. In the area of ​​the rough surface of this sample, a 25 mm long section (L) is selected based on the inner diameter ID [mm] of the ring to be examined. In the area of ​​the section L [mm], a base diameter GD [mm] and an outer diameter OD [mm] are then determined, whereby the base diameter GD corresponds to a baseline of the rough surface area and the outer diameter OD corresponds to an envelope of the rough surface area. In order to obtain reproducible results, the deepest profile valleys and the highest profile peaks are filtered out beforehand. This is done by specifying a minimum height and a minimum distance between profile peaks and profile valleys, which must then be taken into account for the evaluation.For this purpose, a base area Ao is first determined based on the inner diameter ID and the starting value of the outer diameter ODo, which initially still includes all profile peaks. The outer diameter OD is then shifted in the direction of the inner diameter ID until the accumulated detected area of ​​the sample's cross-section is 90% of the base area Ao. Subsequently, an image of the sample is smoothed along the originally curved path L, and using vertical lines from the inner diameter ID toward the outer diameter OD, areas (Ai, A2, An) that form undercuts are determined. The areas thus identified are summed:

[0029] In total, typically 3 such measurements are carried out at different positions on the surface and the resulting area Aue is divided by the number of measurements.

[0030] It has also proven advantageous for the thickness of the bonding layer to be a minimum of approximately 10 μm to a maximum of approximately 500 μm; preferably, the thickness of the bonding layer is a minimum of approximately 40 μm to a maximum of approximately 200 μm. The thickness is measured perpendicular to the surface of the first element. The thickness measurement can be performed using a metallographic section, with the thickness for layers down to a minimum of approximately 1 μm being determinable by light microscopy. Analysis can also be performed using scanning electron microscopy.

[0031] The adhesion layer can, for example, have at least one layer comprising at least one element or alloy selected from the group consisting of Sn, Al, Zn, Si, Fe, AlSFe2, Sn-Al alloys, Zn-Al alloys, Al-Si alloys, Sn-Fe alloys, Sn-Al-Fe alloys, Zn-Al-Fe alloys, Al-Si-Fe alloys, Al-Fe alloys, Al-Si-Mg alloys, and Al-Mg alloys. For example, in the context of the adhesion layer, “Al-Fe alloy” means that the alloy contains Al and Fe as its main components, whereby it is conceivable that the alloy has a higher proportion (in wt%) of Al than of Fe and that the alloy has a higher proportion (in wt%) of Fe than of Al. In particular, it is also conceivable that the Fe content decreases from the surface of the first element towards the surface of the second element and the Al content increases accordingly.

[0032] In the context of the present invention, the term "alloy" can also be understood to mean so-called "intermetallic compounds". The terms alloy and intermetallic compound as such are known to those skilled in the art. An alloy is understood to be a macroscopically homogeneous material consisting of at least two components, at least one of which is a metal. A solid solution can be formed, or multiple phases can also be formed. An intermetallic compound (also referred to as an intermetallic phase) is understood to be a homogeneous chemical compound consisting of two or more metals with a lattice structure that differs from the lattice structure of the metals involved. Typically, the bond within an intermetallic compound contains both a metallic bond component and small amounts of a covalent bond and / or ionic bond.It is conceivable that an intermetallic compound has a stoichiometric composition of the metals involved and that the phase has a homogeneity region (a phase width) in the phase diagram within which the proportions of the metals involved can vary.

[0033] In the case where the bonding layer comprises an alloy containing Sn or Zn as its main component, it has also proven advantageous if a layer, for example containing chromium, has previously been electroplated onto the surface of the first element. In this context, the term "galvanic" or "electrolytic" deposition / coating refers to a deposition reaction on the surface to be coated, induced by an applied current.

[0034] Furthermore, it has proven advantageous that the adhesive layer has at least one intermetallic layer and at least one dip layer, wherein the at least one intermetallic layer is located on the surface of the first element oriented in the direction of the second element and wherein the at least one dip layer is in turn located on the at least one intermetallic layer and is oriented in the direction of the second element.

[0035] It has also proven advantageous for the thickness of the at least one intermetallic layer to be a minimum of approximately 1 μm and a maximum of approximately 50 μm. Furthermore, it has proven advantageous for the thickness of the at least one dip layer to be a minimum of approximately 9 μm and a maximum of approximately 450 μm. It goes without saying that the thickness of the adhesion layer is calculated from the sum of the thickness of the at least one intermetallic layer and the thickness of the at least one dip layer.

[0036] It has proven particularly advantageous that the thickness of the at least one intermetallic layer is at least approximately 4 pm and at most approximately 30 pm. Furthermore, it has proven particularly advantageous that the thickness of the at least one immersion layer is at least approximately 36 pm and at most approximately 170 pm.

[0037] It is also preferred that i) the at least one intermetallic layer contains at least one alloy selected from the group consisting of AlFe2, Al-Fe alloys and Al-Fe-Si alloys, and ii) the at least one dip layer contains an Al-Si alloy with a Si content of at least approximately 5 wt% to a maximum of approximately 20 wt%.

[0038] Alternatively, it is preferred that i) the at least one intermetallic layer contains at least one alloy selected from the group consisting of AlFe2, Al-Fe alloys, and Al-Fe-Si alloys. As a further alternative, it is preferred that ii) the at least one dip layer contains an Al-Si alloy with a Si content of at least approximately 5 wt% to a maximum of approximately 20 wt%.

[0039] It is also particularly preferred that i) the at least one intermetallic layer contains at least one alloy selected from the group consisting of AlFe2, Al-Fe alloys and Al-Fe-Si alloys, and ii) the at least one dip layer contains an Al-Si alloy with a Si content of at least approximately 9 wt% to a maximum of approximately 13 wt%.

[0040] As a further alternative, it is particularly preferred that ii) the at least one dip layer contains an Al-Si alloy with a Si content of at least approximately 9 wt% to a maximum of approximately 13 wt%.

[0041] In principle, all casting processes known to those skilled in the art are suitable for producing the second element, such as sand casting, permanent mold casting, or die casting. However, it has proven advantageous for the second element containing a second metallic material to be a die-cast element. This means that it is advantageous for the second element containing a second metallic material to be obtained by die casting.

[0042] Alternatively, it has also proven advantageous for the second element containing a second metallic material to be a chill-cast element. This means that it is advantageous if the second element containing a second metallic material was obtained by chill-casting. The use of the chill-casting process has the particular advantage of producing a particularly dense cast structure, which leads to particularly good adhesion and stability.

[0043] Furthermore, it has proven advantageous for the brake drum to have a mean shear strength Oshear, mittei of at least 130 MPa. The mean shear strength Oshear, mittei is obtained by dividing the mean applied force by the area according to:

[0044] O'shear, medium = FA

[0045] Preferably, the shear strength is measured, as also described in Example IE1 and illustrated in Figure 4, using rings cut out of the brake drum with a width t of approximately 5 mm. These rings therefore contain both an inner ring, which consists of a section of the first element containing a first metallic material, and an outer ring, which consists of a section of the second element containing a second metallic material. This allows the samples to be easily inserted into a press. The punch is then pressed onto the part of the cut-out ring, which consists of a part of the first element containing a first metallic material (the inner ring), until the sample either breaks or the load limit of the press is reached.It is conceivable that the fracture occurs between the inner and the outer ring (the corresponding sample sections from the first element containing a first metallic material and the second element containing a second metallic material) as well as that the fracture occurs within the first or the second ring.

[0046] Furthermore, it has proven advantageous that the brake drum has an average shear strength Oshear, mittei, measured after thermal loading of the brake drum at 450°C for 4 hours, of at least 110 MPa.

[0047] This means that before measuring the shear strength, the rings are first heated to approximately 450°C and held at this temperature for approximately four hours. This thermal stress serves to simulate the heating of the brake drum during operation, particularly during repeated heavy braking. After the thermal stress, the rings are placed in a press as described above and pressed with the punch onto the part of the cut-out ring that consists of a portion of the first element containing a first metallic material (the inner ring) until the sample either fractures or the load limit of the press is reached.

[0048] The invention further relates to a method for producing a brake drum as described above, comprising the steps a) to g): a) providing a first element containing a first metallic material, wherein the first element at least partially has a rough surface, b) heating the first element containing a first metallic material, c) dipping the first element into an immersion bath, preferably with an immersion bath temperature of at least approximately 600°C to a maximum of approximately 900°C, d) leaving the first element in the immersion bath for a period of at least approximately 1 minute to a maximum of approximately 10 minutes, e) removing the first element from the immersion bath, f) introducing the first element into a casting mold and closing the casting mold, g) casting the second metallic material around the first element to form the second element, wherein the first element has a rough surface facing the second element.

[0049] In step a), a first element containing a first metallic material is initially provided. For example, the first element is designed as a hollow cylinder and has a rough surface on the outside of the cylinder. Advantageously, the first metallic material contains Fe, particularly advantageously the first metallic material contains at least 90 wt% Fe. For example, the first metallic material consists of cast iron, particularly advantageously of gray cast iron. The first element can be produced, for example, by means of sand casting, centrifugal casting, permanent mold casting, or die casting. Advantageously, the total height of the roughness profile Rt of the first element on the side that later faces the second element in step g) is at least approximately 500 pm and at most approximately 1200 pm.

[0050] Subsequently, in step b), the first element containing a metallic material is heated. The first element is advantageously heated to a temperature above the dew point. The term "dew point" is familiar to those skilled in the art. This refers to the condensation point of water in air. It is therefore dependent on the air temperature and relative humidity and can be measured, for example, with a dew-point mirror hygrometer.

[0051] After step b), in step c) the first element is immersed in an immersion bath, preferably with an immersion bath temperature of a minimum of approximately 600°C to a maximum of approximately 900°C. It goes without saying that the choice of immersion bath temperature depends on the material contained in the immersion bath. It is therefore clear to a person skilled in the art that the temperature of the immersion bath is expediently selected such that the alloy contained in the immersion bath, for example, is completely melted. Furthermore, it must be ensured that direct and complete contact of the first element with the contents of the immersion bath is possible. The element is thus immersed in the immersion bath in such a way that at least the outward-facing surface of the first element is completely wetted by the immersion bath.

[0052] The immersion bath is, for example, an immersion bath containing a melt comprising at least one element or an alloy selected from the group consisting of Al, Sn-Al alloys, Zn-Al alloys, Al-Si alloys, Al-Si-Fe alloys, Al-Si-Mg alloys, Sn-Fe alloys, Sn-Al-Fe alloys, Zn-Al-Fe alloys, or Al-Mg alloys. The immersion bath is preferably an immersion bath containing a melt comprising an element or an alloy selected from the group consisting of Al and Al-Si alloys. In particular, it is preferred that the immersion bath is an immersion bath containing a melt comprising an Al-Si alloy with a Si content of at least approximately 5 wt% to a maximum of approximately 20 wt%. It is conceivable that the melt contains additional impurities, for example Fe.In particular, it is preferred that the proportion of Fe in the melt is approximately equal to or less than 3.5 wt%.

[0053] It is optionally conceivable that a layer, for example containing chromium, is first electroplated onto the first element prior to performing step c). This can increase adhesion, particularly in conjunction with an immersion bath containing a melt comprising at least one element or alloy selected from the group consisting of Sn-Al alloys and Zn-Al alloys.

[0054] In step d), the first element then remains in the immersion bath for a minimum of approximately 1 minute to a maximum of approximately 10 minutes. Care must be taken to ensure that the first element is well wetting with the melt contained in the immersion bath. In particular, it is preferred that the first element remains in the immersion bath for a minimum of approximately 2.5 minutes to a maximum of approximately 6.5 minutes. It has proven advantageous that the treatment in the immersion bath forms an adhesive layer with a thickness of a minimum of approximately 10 μm to a maximum of approximately 500 μm, preferably a minimum of approximately 40 μm to a maximum of approximately 200 μm.In this context, it has proven particularly advantageous that the treatment in the immersion bath forms an adhesive layer which has at least one intermetallic layer and at least one immersion layer, wherein the at least one intermetallic layer is located on the surface of the first element oriented in the direction of the second element and wherein the at least one immersion layer is in turn located on the at least one intermetallic layer and is oriented in the direction of the second element. In the subsequent step e), the first element is removed from the immersion bath. After removal from the immersion bath, the first element is introduced into a casting mold and the casting mold is closed in step f).

[0055] Then, in step g), the first element is encapsulated with the second metallic material, forming the second element. It goes without saying that the second metallic material must be in a molten state for this purpose. The second metallic material contains, for example, at least one element selected from the group consisting of Al and Mg, preferably at least 75 wt% of at least one element selected from the group consisting of Al and Mg. Encapsulation takes place on the rough side of the surface of the first element.For example, the casting is carried out in such a way that the second element containing the second metallic material is formed in the form of a hollow cylinder around the first element, wherein the inside of the hollow cylinder formed by the second element adheres to the outside of the hollow cylinder which is formed by the first element and which has a rough surface on the surface facing the second element.

[0056] It is particularly advantageous if steps e) to g) are carried out within a maximum period of approximately 2 minutes. This enables particularly good adhesion.

[0057] The second element can be manufactured, for example, by sand casting, permanent mold casting or die casting.

[0058] In an advantageous embodiment, the die casting process is used to enclose the first element with the second metallic material. For example, the pressure during die casting can preferably be a minimum of approximately 10 bar up to a maximum of approximately 900 bar. This enables particularly good penetration of the molten second metallic material into the rough surface structure of the first element. In another advantageous embodiment, the permanent mold casting process is used to enclose the first element with the second metallic material. This leads to particularly easy application and particularly good cost-effectiveness of the process. In addition, a particularly dense microstructure is advantageously obtained. In principle, all permanent mold casting processes known to those skilled in the art can be used. The gravity permanent mold casting process is particularly preferably used to enclose the first element with the second metallic material.

[0059] After the resulting brake drum has cooled down, it can be removed from the casting mold.

[0060] The invention also relates to the use of a brake drum as described above, preferably the use in a drum brake for use in a motor vehicle or a motorcycle, such as a passenger car, a truck, a motorcycle or an e-scooter.

[0061] Further important features and advantages of the invention emerge from the subclaims, from the drawings and the associated description of the figures as well as from the examples.

[0062] It goes without saying that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0063] They show, schematically

[0064] Fig. 1 : Perspective view of a brake drum,

[0065] Fig. 2: Representation of the sequence of a method for producing a brake drum, Fig. 3: Light micrograph of a section of the surface of the first element facing the second element, including an adhesive layer, and a section of the surface of the second element facing the adhesive layer (a), as well as an enlarged section of the surface of the first element facing the second element, including an adhesive layer (b).

[0066] Fig. 4: Representation of a section of the measuring setup for determining the average shear strength.

[0067] Fig. 5: Illustration of the method for determining the undercut area Aue with a) a representation of the measuring length L, the inner diameter ID, the base diameter GD and the outer diameter OD; b) a representation explaining the profile filtering and c) a representation for identifying individual surfaces that form undercuts.

[0068] Figure 1 shows, by way of example, a brake drum 100 with a first element 101 containing a first metallic material, which in the present Figure 1 is configured as an inner hollow cylinder. This first element 101 is surrounded by a second element 102 containing a second metallic material, which is configured as an outer hollow cylinder. Not shown in Figure 1 is the adhesive layer between the first and the second element. It is expedient for the first metallic material to contain Fe, in particular at least 90 wt% Fe. Furthermore, it is particularly preferred for the first metallic material to be cast iron or cast steel.Furthermore, it is expedient for the second metallic material to contain at least one element selected from the group consisting of Al and Mg, more preferably at least 75 wt.% of at least one element selected from the group consisting of Al and Mg, particularly preferably at least 85 wt.% of at least one element selected from the group consisting of Al and Mg. Furthermore, it is expedient for the outer diameter of the second element 102 to be from a minimum of approximately 60 mm to a maximum of approximately 400 mm. Furthermore, it is expedient for the inner diameter of the first element 101 to be from a minimum of approximately 30 mm to a maximum of approximately 370 mm. It goes without saying that the outer diameter of the second element 102 must always be larger than the inner diameter of the first element 101.Furthermore, it goes without saying that the dimensions of the brake drum depend on the type of vehicle and, in particular, the size of the wheels for which the brake drum is to be used. For example, the inner diameter of the first element 101 in a passenger car can be approximately 270 mm and the outer diameter of the second element 102 approximately 350 mm. It goes without saying that the dimensions must be correspondingly larger for a truck or construction machine, for example.

[0069] Figure 2 schematically shows the sequence of a method for producing a brake drum. In step a), a first element containing a first metallic material is provided 200, the first element having at least a partially rough surface. In the subsequent step b), the first element is heated 201. Subsequently, in step c), the first element is immersed 202 in an immersion bath, preferably with an immersion bath temperature of at least approximately 600°C to a maximum of approximately 900°C. Optionally, before carrying out step c), a layer, for example containing chromium, can first be electroplated onto the first element. This is particularly preferred in conjunction with an immersion bath containing a melt comprising at least one alloy selected from the group consisting of Sn-Al alloys and Zn-Al alloys. This optional additional step is not shown in Figure 2.In step d), the first element remains in the immersion bath 203 for a minimum duration of approximately 1 minute to a maximum duration of approximately 10 minutes. Subsequently, in step e), the first element is removed from the immersion bath 204. Then, in step f), the first element is introduced into a casting mold, which is closed 205. Subsequently, in step g), the first element is encased in the second metallic material, forming the second element 206. This naturally means that the second metallic material must be in a molten state during encasement. The second element is obtained by encasement. As already mentioned, the first element has a rough surface which faces the second element. The second element can generally be cast by sand casting, permanent mold casting, or die casting. In particular, it is advantageous if the casting is carried out by die casting or permanent mold casting.After casting and cooling the second element, the resulting brake drum can be removed from the casting mold. Unless otherwise stated, the above statements regarding the process steps apply to all process steps a) to g).

[0070] Figure 3a) shows a light micrograph of a section of the surface of the first element facing the second element, including an adhesive layer, and a section of the surface of the second element facing the adhesive layer. Figure 3b) shows an enlarged section of the surface of the first element facing the second element, including an adhesive layer. Both Figures 3a) and 3b) show a section of the first element 300, which in this case is a rough-cast ring made of a NiResist alloy. An adhesive layer 301 is located on the surface of this first element 300. In particular, Figure 3b) shows that this adhesive layer 301 in turn has two layers: an intermetallic layer 302 and a dip layer 303.In the present case, the intermetallic layer 302 contains an Al-Fe alloy and the dip layer 303 contains an Al-Si alloy with a Si content of at least approximately 5 wt% to a maximum of approximately 20 wt%. Furthermore, the thickness of the dip layer 307 is shown in Figure 3a) and the thickness of the intermetallic layer 306 in Figure 3b). The thickness of the dip layer 307 for the section of a brake drum shown in Figure 3 is a minimum of approximately 62 pm to a maximum of approximately 76 pm and the thickness of the intermetallic layer 306 for the section of a brake drum shown in Figure 3 is a minimum of approximately 10 pm to a maximum of approximately 19 pm. Above the dip layer 303, as can be seen in Figure 3a), there is a section of the second element 304. The second element 304 has a second metallic material which consists of an Al alloy and has at least 75 wt% Al.In addition, the total height of the roughness profile Rt of the first element 305 is also shown schematically in Figure 3a.

[0071] Figure 4 illustrates a section of the measurement setup for determining the average shear strength 400. Here, a sample ring 401 is placed on a support 402 and held in place by a hold-down device 403. On the side facing the hold-down device 403 is the punch 404 of a press, with which the sample ring 401 can be pressed. The punch is designed such that the pressing takes place on the inner ring (the first element 405). The sample ring 401 is a ring cut out of the brake drum to be tested, with a width t of the sample ring 411 of approximately 5 mm. Figure 4 illustrates the first element 405, which is advantageously a rough cast iron ring, an optional adhesive layer 406 between the first and second elements, and the second element 407.The sample ring 401 has an inner diameter, wherein the inner diameter is the inner diameter 408 of the first element, which is, for example, approximately 90 mm. Figure 4 further illustrates the outer diameter 409 of the first element, which is, for example, 100 mm, and which is then adjoined by either the optional adhesive layer 406 or the second element 407. The second element 407, in turn, has an outer diameter 410, which is, for example, 120 mm. During the test (not shown here), the punch is pressed onto the first element 405 until the sample either breaks or the load limit of the press is reached.

[0072] Figures 5a, 5b and 5c illustrate the described method for determining the undercut area Aue. As previously described, a cross-section 500 of the sample to be examined is created, which is illustrated in Figure 5a. In addition, Figure 5a shows the measuring length L, which is selected to be 25 mm, as well as the inner diameter ID, the base diameter GD and the outer diameter OD of the sample ring to be examined. Figure 5b illustrates the profile filtering. As already described above, a base area Ao is first determined based on the inner diameter ID and the starting value of the outer diameter ODo, which initially still includes all profile peaks. The outer diameter OD is then shifted in the direction of the inner diameter ID until the summed detected area of ​​the cross-section of the sample is 90% of the base area Ao.Figure 5c illustrates the determination of the undercut area Aue by summing individual areas (Ai, A2, .An) which form undercuts.

[0073] In the following, the invention is described in detail using examples, without limiting the scope of the invention thereto:

[0074] Inventive Example IE1 a) According to the inventive example IE1, a brake drum was produced, wherein the first element having a hollow cylindrical shape was produced from gray cast iron by means of a centrifugal casting process and the total height of the roughness profile Rt of the first element on the side facing the second element was at least approximately 500 pm and at most approximately 1200 pm. On the outside, i.e. the side facing the second element, an adhesive layer with a thickness of at least approximately 70 pm to a maximum of approximately 100 pm was first applied. The adhesive layer was applied by immersion in an immersion bath containing a melt comprising an Al-Si alloy with a Si content of at least approximately 5 wt% to a maximum of approximately 20 wt%.An adhesion layer was obtained which had an intermetallic layer and a dip layer, wherein the intermetallic layer formed on the surface of the first element oriented towards the second element, and a dip layer in turn formed on this intermetallic layer. The intermetallic layer contains an Al-Fe alloy and the dip layer an Al-Si alloy with a Si content of a minimum of approximately 5 wt% to a maximum of approximately 20 wt%. The thickness of the resulting intermetallic layer was a minimum of approximately 10 μm to a maximum of approximately 20 μm. The thickness of the dip layer was a minimum of approximately 60 μm to a maximum of approximately 80 μm. On the side of the dip layer facing away from the intermetallic layer, the second element was obtained by casting an Al alloy of the MAHLE M174 type, which contains a minimum of approximately 11 to a maximum of approximately 13 wt% Si, using the gravity die casting process.For the exact composition of Al alloys of the type MAHLE M174, please refer to US 7533649 B2.

[0075] This resulted in a brake drum. The outer diameter of the first element (joining diameter of the brake drum) was approximately 98.1 mm. b) To further investigate the properties of this brake drum, sample rings with a width t of approximately 5 mm were cut from the brake drum. With the joining diameter of the brake drum or the cut-out sample rings D of approximately 98.1 mm, the total area to be tested was 1541 mm. 2 , which served as the basis for further calculations.

[0076] One test (Ring 1) was carried out without prior thermal stress. Three further tests were carried out after thermal stress. To ensure good reproducibility, three sample rings of the same brake drum were tested for each measuring point and the results were averaged. For the test after thermal stress, the sample rings were heated to approximately 400°C (Ring 2), approximately 450°C (Ring 3) and approximately 500°C (Ring 4) and held at each temperature for approximately 4 hours. The idea behind this temperature stress was to simulate the heating of the brake drum during operation, particularly during repeated heavy braking.

[0077] To test the cohesion of the first and second elements, the sample rings were each placed in a press (Zwick 200 kN) and a punch was pressed onto the sample rings from above (see also the test setup illustrated in Figure 4). The punch was pressed onto the inner ring (made of the first element and containing a metallic material) of the sample ring. The punch was moved forward at 10 mm / min. Although a fracture was observed for each of the samples, this did not occur at the adhesive layer but rather within the second metallic material. The following Table 1 lists the area A, the temperature of the thermal load, the exerted average force Faverage, the average shear strength Oaverage and the result for all samples.

[0078] The average shear strength Oshear, average is calculated by dividing the average applied force by the area according to:

[0079] Oshear, medium = FA

[0080] Table 1

[0081] These results for the shear strength of the sample rings Ring-1, Ring-2, Ring-3, and Ring-4 thus demonstrate particularly good adhesion between the first element containing a metallic material and the second element containing a metallic material due to the proposed adhesive layer. c) Furthermore, the specific thermal contact resistance for the heat transfer between the first element containing a metallic material and the second element containing a metallic material was determined. This plays a role in the dissipation of heat generated during braking. For this purpose, sample rings were first cut out as described under point b), and a cross-section was then cut out of these sample rings. The specific thermal contact resistance can be calculated from the thickness of a sample (d) and the thermal conductivity of the material (X) as follows:

[0082] The thermal conductivity required for calculating the specific thermal contact resistance was determined using the laser flash method using a NETZSCH LFA 467 Hyperflash® apparatus. A short energy pulse heats the front of a plane-parallel sample. An infrared detector records the associated temperature increase on the back of the sample. From this temperature increase, the thermal diffusivity a (T) and the specific heat capacity c can be determined. p (T). Using the density (T), the thermal conductivity can then be calculated as follows:

[0083] 2(T) = a(T) xc p (T) xp(T)

[0084] A specific thermal contact resistance of approximately 2.6 * 10' 6 m 2 K / W. The measurement error was approximately ± 5.2 *10' 7 m 2 K / W determined.

[0085] Comparative Example CE1 a) For comparison, a brake drum was produced according to Comparative Example CE1, wherein the first element having a hollow cylindrical shape was produced from gray cast iron using a centrifugal casting process and the total height of the roughness profile Rt of the first element on the side facing the second element was at least approximately 500 pm and at most approximately 1200 pm. In contrast to the inventive example IE1, however, no adhesive layer was subsequently applied, but rather the second element was obtained directly on the first element by encapsulating it with an Al alloy (EN AB-46000 according to DIN EN 1676 and DIN EN 1706, also referred to as AISi9Cu3) using a die-casting process.

[0086] This resulted in a brake drum. The outer diameter of the first element (joining diameter of the brake drum) was approximately 87.7 mm. b) To further investigate the properties of this brake drum, sample rings with a width t of approximately 5 mm were cut from the brake drum. With the joining diameter of the brake drum or the cut-out rings D of approximately 87.7 mm, the total area to be tested was 1378 mm. 2

[0087] The procedure was then analogous to the inventive example IE1. Tests were conducted (ring 5, ring 6, and ring 7) after thermal stress. To ensure good reproducibility, three sample rings of the same brake drum were tested for each measurement point, and the results were averaged.

[0088] The results are summarized in Table 2. For all sample rings, a fracture was observed at the boundary of the first and second elements and a lower mean shear strength Oshear was observed than for the sample rings of the inventive example IE1.

[0089] Table 2 c) Analogous to the inventive example IE1, the specific thermal contact resistance was also determined for the comparative example CE1. This resulted in a specific thermal contact resistance of approximately 1.1 * 10' 5 m 2 K / W. The measurement error was approximately ± 1.5 *10 -6 m 2 K / W determined.

[0090] This means that the heat generated during braking can be dissipated significantly faster for the inventive example IE1 than for the comparative example CE1.

[0091] List of reference symbols: : brake drum : first element of a brake drum : second element of a brake drum : providing a first element containing a first metallic

[0092] Material: Heating the first element containing a first metallic

[0093] Material : Immersion of the first element in a dipping bath : Remaining of the first element in the dipping bath : Removing the first element from the dipping bath : Inserting the first element into a casting mold and closing the

[0094] Casting mold : Casting of the second metallic material around the first element to form the second element : Section of the first element : Bonding layer comprising an intermetallic layer and a dip layer : Intermetallic layer : Dip layer : Section of the second element : Total height of the roughness profile Rt of the first element : Thickness of the intermetallic layer : Thickness of the dip layer : Section of the measuring setup for determining the shear strength : Sample piece (specimen ring) : Support for sample piece (specimen ring) : Hold-down device for sample piece (specimen ring) : Stamp : first element 406: optional bonding layer

[0095] 407: second element

[0096] 408: Inner diameter of the first element

[0097] 409: Outer diameter of the first element

[0098] 410: Outer diameter of the second element

[0099] 411 : Width t of the sample piece (sample ring)

[0100] 500: Cross section of the sample to be examined to determine the undercut area Aue

[0101] L: Length of a measuring section for determining the undercut area Aue, related to the inner diameter ID

[0102] ID: Inner diameter of a sample to determine the undercut area

[0103] Floodplain

[0104] GD: Base diameter of a sample to determine the undercut area

[0105] Floodplain

[0106] OD: outer diameter of a sample to determine the undercut area Aue

[0107] ODo: outer diameter of a sample for determining the

[0108] Undercut area Aue before profile filtering

[0109] Ao: Base area based on the inner diameter ID and the outer diameter of a sample to determine the undercut area Aue before profile filtering

[0110] Ai, A2,, A n: individual surfaces that form undercuts

Claims

Claims 1. Brake drum (100) for a drum brake, comprising a first element (101 ) containing a first metallic material and a second element (102) containing a second metallic material, - wherein the first element (101) is connected to the second element (102) by casting, - wherein the first element (101) has a rough surface oriented in the direction of the second element (102), - wherein the brake drum further comprises an adhesive layer (301), - wherein the adhesive layer (301) is located between the first element (101) and the second element (102), - wherein the first element (101) is integrally connected to the second element (102) via the adhesive layer (301) by means of an intermetallic bond.

2. Brake drum (100) according to claim 1, characterized in that the melting temperature of the first metallic material is higher than the melting temperature of the second metallic material.

3. Brake drum (100) according to one of the preceding claims, characterized in that the first metallic material contains Fe, and / or that the second metallic material contains at least one element selected from the group consisting of Al and Mg, preferably the first metallic material contains at least 90 wt% Fe, and / or the second metallic material contains at least 75 wt% of at least one element selected from the group consisting of Al and Mg.

4. Brake drum (100) according to one of the preceding claims, characterized in that the first metallic material consists of gray cast iron.

5. Brake drum (100) according to one of the preceding claims, characterized in that the total height of the roughness profile Rt according to DIN EN ISO 4287:2010 of the first element (101) on the side of the surface facing the second element (102) is at least approximately at least 500 pm and at most approximately 1200 pm.

6. Brake drum (100) according to one of the preceding claims, characterized in that the rough surface of the first element oriented in the direction of the second element has undercuts, wherein the rough surface of the first element oriented in the direction of the second element preferably has an undercut area Aue of at least approximately 0.36*10 5 pm 2 and a maximum of approximately 30*10 5 pm 2 on a distance L of 25 mm each.

7. Brake drum (100) according to one of the preceding claims, characterized in that the thickness of the adhesive layer is at least approximately 10 pm to a maximum of approximately 500 pm, preferably the thickness of the adhesive layer is at least approximately 40 pm to a maximum of approximately 200 pm.

8. Brake drum (100) according to one of the preceding claims, characterized in that the adhesive layer (301) has at least one intermetallic layer (302) and at least one dip layer (303), wherein the at least one intermetallic layer (302) is located on the surface of the first element oriented in the direction of the second element and wherein the at least one dip layer (303) in turn is located on the at least one intermetallic layer and is aligned in the direction of the second element.

9. Brake drum (100) according to one of the preceding claims, characterized in that i) the at least one intermetallic layer (302) contains at least one alloy selected from the group consisting of AlFe2, Al-Fe alloys and Al-Fe-Si alloys, and / or ii) the at least one dip layer (303) contains an Al-Si alloy with a Si content of at least approximately 5 wt% to a maximum of approximately 20 wt%.

10. Brake drum (100) according to one of the preceding claims, characterized in that the second element (102) containing a second metallic material is a die-cast element.

11. Brake drum (100) according to one of the preceding claims, characterized in that the second element (102) containing a second metallic material is a die-cast element.

12. Brake drum (100) according to one of the preceding claims, characterized in that the average shear strength Oshear, medium is at least 130 MPa.

13. Brake drum (100) according to one of the preceding claims, characterized in that the average shear strength Oshear, medium, measured after thermal loading of the brake drum at 450°C for 4 hours, is at least 110 MPa.

14. A method for producing a brake drum (100) according to any one of the preceding claims, comprising steps a) to g): a) Providing a first element (101) containing a first metallic material, wherein the first element (101) at least partially has a rough surface, b) Heating the first element (101) containing a first metallic material, c) Immersing the first element (101) in an immersion bath, preferably with an immersion bath temperature of at least approximately 600°C to a maximum of approximately 900°C, d) Leaving the first element (101) in the immersion bath for a duration of at least approximately 1 minute to a maximum of approximately 10 minutes, e) Removing the first element (101) from the immersion bath, f) Inserting the first element (101) into a casting mold and closing the casting mold, g) Casting the second metallic material around the first element (101) to form the second element (102), wherein the first element has a rough surface facing the second element.

15. Use of a brake drum (100) according to one of claims 1 to 13 in a drum brake, preferably a drum brake for use in a motor vehicle or a motorcycle.

Images