Brake element

Abstract

A brake element (1) according to the invention comprises a main part (2) and a frictional layer (3), the frictional layer (3) containing a steel that has the following typical composition: 10 – 15 wt.% Mn, 18 – 24 wt.% Cr, < 1 wt.% Si, < 1 wt.% N, < 0.1 wt.% C, remainder Fe.

Description

[0001] Brake element

[0002] The invention relates to a brake element comprising a base body and a friction layer.

[0003] The invention further relates to a method for producing a braking element according to the invention.

[0004] Brake elements of the type mentioned above are known from the prior art. Here, a moving, e.g. rotating, element is contacted on its surface by brake pads, so that friction arises between the moving element and the brake pad. This friction causes the kinetic energy of the moving element to be converted into thermal energy and thus to be decelerated. One example of this is a disc brake, in which a rotating brake disc can be braked as required by means of brake blocks having the brake pads that can be pressed optionally onto the brake disc.

[0005] During braking, the braking elements, such as brake discs, are subjected to high loads. On the one hand, material is abraded from the braking element due to the mechanical load, and on the other hand, the braking element becomes extremely hot due to the thermal load. This means that braking elements must be replaced with new braking elements at regular intervals or when a wear limit is reached in order to ensure that the braking elements and thus the respective braking system function properly. Known braking elements, in particular brake discs, are made of gray cast iron, steel or ceramic, for example. Furthermore, brake discs with a double coating are known, for example from WO 2020 / 043712 A1. In this case, an intermediate layer, which in turn carries a cover layer, is arranged on the base body.The intermediate layer, formed from a Ni or Cr alloy, is intended in particular to compensate for temperature-related stresses, while the top layer, consisting of a stainless steel matrix with embedded hard materials, is as hard as possible in order to achieve long durability.

[0006] EP 0902099 A1 describes a coating with the following composition (each in mass percent):

[0007] - 12 to 25% chromium (Gr)

[0008] - 0 to 15% manganese (Mn)

[0009] - 2 to 6% molybdenum (Mo)

[0010] - 0 to 15% nickel (Ni)

[0011] - 1%, preferably 2 to 12% vanadium (V)

[0012] - 0 to 5% nitrogen (N)

[0013] - Rest iron and technically usual impurities.

[0014] A disadvantage of the known brake elements, however, is that the pressure exerted by the brake pads during braking can damage or wear the surface of the brake elements, particularly the friction layer. This material removal inadvertently exposes the material layer originally located beneath the surface of the brake element and exposes it to the environment. This allows for the undesirable formation of corrosion on the brake elements and reduces the service life of the

[0015] Brake elements clearly.

[0016] It is therefore an object of the invention to provide a brake element that is less susceptible to corrosion. In particular, the brake element should exhibit less wear of the friction layer during operation and improved damping.

[0017] According to the invention, in a brake element of the type mentioned at the outset, the friction layer comprises a steel having the following directional analysis:

[0018] 10 - 15 wt% Mn (manganese)

[0019] 18 - 24 wt.% Gr (chromium)

[0020] < 1 wt% Si (silicon)

[0021] < 1 wt% N (nitrogen)

[0022] < 0.1 wt% C (carbon) balance Fe (iron).

[0023] The steel therefore contains no other elements besides the elements mentioned above, apart from minor impurities.

[0024] In order to further reduce the susceptibility to corrosion, the steel preferably has the following standard analysis:

[0025] 10 - 11 wt% Mn (manganese)

[0026] 18 - 20 wt.% Gr (chromium)

[0027] < 1 wt% Si (silicon)

[0028] < 1 wt% N (nitrogen)

[0029] < 0.1 wt% C (carbon) balance Fe (iron).

[0030] Preferably, the friction layer is made of steel. The friction layer closes any openings in the surface of the base body, thereby simultaneously increasing corrosion protection against the environment. It also improves wear and damping of the brake element. This, in particular, extends the service life of the brake element until it needs to be replaced.

[0031] Particularly preferably, the steel has the following

[0032] Target analysis on:

[0033] 10 - 11 wt% Mn (manganese)

[0034] 18 - 20 wt% Cr (chromium)

[0035] < 1 wt% Si (silicon)

[0036] < 1 wt% Ni (nickel)

[0037] < 0.1 wt% C (carbon)

[0038] 0.06 wt% P (phosphorus)

[0039] 0.03 wt% S (sulfur)

[0040] 0.4 - 0.65 wt% N (nitrogen)

[0041] < 1 wt% Mo (molybdenum)

[0042] Rest Fe (iron) .

[0043] The steel is preferably a manganese hard steel, particularly preferably a manganese hard steel 1.3820 (X8CrMnN20-10).

[0044] In a preferred embodiment, the friction layer further comprises an alloy having the following standard analysis: 4 - 6 wt.% Mn (manganese) 22 - 28 wt.% Cr (chromium) 3 - 5 wt.% B (boron)

[0045] < 1 wt% Si (silicon)

[0046] 0.4 - 0.6 wt% C (carbon)

[0047] Rest Fe (iron) .

[0048] In this preferred embodiment, the friction layer consists of a mixture of the steel with the above-mentioned standard analysis and the alloy. The mixing ratio between the steel and the alloy is preferably approximately 80:20, 60:40, 40:60, or 20:80. By providing a mixture of the steel and the alloy, the hardness and strength of the friction layer can be further improved. The steel and the alloy are preferably mixed together in a liquid (molten) state to obtain a substantially homogeneous friction layer.

[0049] Preferably, the friction layer contains essentially no nickel. The friction layer preferably contains less than 0.2 wt.% nickel, particularly preferably less than 0.1 wt.% nickel, and further particularly preferably less than 0.01 wt.% nickel. Nickel is considered hazardous to human health. Providing a nickel-free friction layer prevents nickel from being released into the ambient air through abrasion during braking and subsequently inhaled.

[0050] Furthermore, it is preferably provided that the friction layer contains essentially no CMR substances. The friction layer preferably contains less than 0.2% by weight of CMR substances, particularly preferably less than 0.1% by weight of CMR substances, and further particularly preferably less than 0.01% by weight of CMR substances. CMR substances are carcinogenic, mutagenic, or reproductively toxic substances that are or could be dangerous to humans. Examples of these are acrylamide, beryllium, or chromium trioxide. To prevent toxic substances from entering the environment through abrasion of the friction layer during use, these substances are preferably not contained in the friction layer.

[0051] Preferably, the friction layer has a thermal conductivity greater than 1.1 times the thermal conductivity of the base body. The thermal conductivity of the friction layer is preferably 1.1 to 10 times greater than the thermal conductivity of the base body. Particularly preferably, the thermal conductivity of the friction layer is approximately 1.12 to 1.36 times greater than the thermal conductivity of the base body. This design allows the thermal energy generated during braking to be largely dissipated via the friction layer, and the thermal energy dissipated via the base body is reduced. This allows a reduction in the thermal mass of the base body and thus a reduction in the weight of the braking element.

[0052] The friction layer preferably has a thermal conductivity of approximately 65 to 85 W / mK. Gray cast iron, a preferred material for the base body, typically has a thermal conductivity of approximately 48 to 52 W / mK.

[0053] Preferably, the friction layer is formed from a stainless steel matrix with hard material particles embedded therein. This provides a particularly hard friction layer, reducing wear on the friction layer and thus on the brake element. The hard material particles preferably comprise or are chromium carbide particles and / or vanadium carbide particles.

[0054] In this case, it is preferably provided that the base body is made of grey cast iron or comprises grey cast iron. The grey cast iron is, for example, EN GJL 150. Grey cast iron contains carbon in the form of graphite. This graphite can, for example, be used to form hard material particles in the friction layer during application of the friction layer with the aid of a heat source and a welding filler, for example a powder, whereby the hard material particles form as primarily precipitated hard materials when the applied melt solidifies. The heat source, for example a laser, interacts with the welding filler, for example a powder, and the graphite in the grey cast iron to form the hard material particles in the friction layer. The hard material particles are therefore formed in the melt and not supplied from an external source. The resulting hard material particles consist, for example, of chromium carbide and / or vanadium carbide.The hard material particles preferably have an average grain size of approximately 3 to 5 μm. Furthermore, the proportion of hard material particles in the friction layer is preferably approximately 20 to 70 vol.%, preferably 35 to 55 vol.%, particularly preferably 40 to 50 vol.%, in order to ensure both high hardness and sufficient strength of the friction layer.

[0055] The thickness of the friction layer is preferably 3.5 mm or more. The friction layer is preferably arranged directly on the base body, i.e. without an intermediate layer. This allows the heat to be dissipated directly from the friction layer to the base body. This structure also allows simple production of the brake element. The invention further relates to a brake disc, comprising at least one brake element according to the invention. The brake disc is preferably a brake element according to the invention, wherein the base body is particularly preferably annular. The base body of the brake disc can be coated on one side with a friction layer according to the invention. It is preferably provided that the base body of the brake disc is coated on both sides, on two essentially opposite surfaces, with a friction layer according to the invention. This makes it possible to exert pressure on the brake disc on both sides during the braking process.

[0056] According to the invention, a method for producing a brake element according to the invention is further provided, wherein the friction layer is applied to the base body by build-up welding. Thus, first the base body is provided, which is then coated with a friction layer containing the composition according to the invention by means of a build-up welding process. During build-up welding, the welding filler material is melted by a heat source, for example a laser beam, and applied to the base body. After the applied material has solidified, a solid friction layer is formed. Build-up welding is suitable for this purpose because it is a tried and tested method which can be used simply, quickly and cost-effectively to produce the brake element according to the invention.

[0057] Furthermore, it is possible for hard phases to be formed in the friction layer during deposition welding, which further reduce wear on the friction layer. Preferably, the base body is made of or comprises gray cast iron (e.g., EN GJL 150), whereby hard material particles form from the graphite flakes during deposition welding, as described above. Preferably, a laser is used as the heat source during deposition welding, and a powder is used as the filler material. Preferably, no carbides are added to the friction layer, but rather the hard material particles are formed exclusively from the melt during deposition welding.

[0058] Preferably, the friction layer is cooled in a controlled manner after application. Cooling is therefore not achieved by simple cooling in air, but rather the removal or, if necessary, introduction of heat to the brake element is controlled to achieve the desired cooling curve. The desired cooling behavior depends in particular on the precise composition of the friction layer. Controlled cooling ensures that cracks or other damage in the friction layer or in the transition area between the friction layer and the base body are reduced or avoided as much as possible.

[0059] After application of the friction layer, the friction layer or the base body is preferably cooled at a substantially linear cooling rate of 25°C per 10 seconds to 35°C per 10 seconds, particularly preferably approximately 30°C per 10 seconds. The controlled cooling preferably takes place until the brake element temperature reaches approximately 30°C.

[0060] After the base body has been coated with the friction layer, the friction layer can be further processed, for example by partially removing the surface of the friction layer in order to obtain a friction layer with an essentially homogeneous thickness.

[0061] The invention is explained in more detail below with reference to an exemplary embodiment shown schematically in the drawing. In this drawing, Fig. 1 shows a braking element according to the invention, and Fig. 2 shows a schematic representation of a method according to the invention.

[0062] Fig. 1 shows a brake element 1 according to the invention, comprising a base body 2 and a friction layer 3 applied on both sides. During operation, the friction layer 3 interacts with a brake pad, e.g., brake blocks, to decelerate the moving brake element 1. With this design, brake pads can be arranged on both sides of the base body 2 in order to exert pressure on the brake element 1 on both sides and thus brake it.

[0063] Fig. 2 shows a schematic representation of a method according to the invention for applying a friction layer 3 according to the invention to a base body 2. The base body 2 is made of gray cast iron. A processing device 4 applies a laser beam 5 and powder 6 to both sides of the laser beam 5 onto the surface of the base body 2. The heat of the laser beam 5 creates a local melt from the powder 6 and part of the material of the base body 1, so that the friction layer 3 bonds to the base body 1. The base body 1, which is made of gray cast iron, contains graphite lamellae 7 which, during the application of the friction layer 3, together with the powder 6, form hard material particles 8 which, after solidification, are arranged in the friction layer 3. This produces a particularly hard friction layer 3 which is both less susceptible to wear and less susceptible to corrosion and therefore has a longer service life.

Claims

Patent claims:

1. Brake element comprising a base body (2) and a friction layer (3), characterized in that the friction layer (3) comprises a steel having the following Indicative analysis shows: 10 - 15 wt% Mn 18 - 24 wt% Cr < 1 wt% Si < 1 wt% N < 0.1 wt% C, balance Fe.

2. Brake element according to claim 1, characterized in that the friction layer (3) further comprises an alloy having the following directional analysis: 4 - 6 wt% Mn 22 - 28 wt% Cr 3 - 5 wt% B < 1 wt% Si 0.4 - 0.6 wt.% C, balance Fe.

3. Brake element according to claim 1 or 2, characterized in that the friction layer (3) contains substantially no nickel.

4. Brake element according to claim 1, 2 or 3, characterized in that the friction layer (3) contains substantially no CMR substances.

5. Brake element according to one of claims 1 to 4, characterized in that the friction layer (3) has a has a thermal conductivity that is greater than 1.1 times the thermal conductivity of the base body (2).

6. Brake element according to one of claims 1 to 5, characterized in that the friction layer (3) is formed from a stainless steel matrix with hard material particles (8) embedded therein.

7. Brake disc comprising at least one braking element (1) according to one of claims 1 to 6.

8. A method for producing a brake element (1) according to one of claims 1 to 6, characterized in that the friction layer (3) is applied to the base body (2) by build-up welding.

9. Method according to claim 8, characterized in that the friction layer (3) is cooled in a controlled manner after application.

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