Method for manufacturing a rolling or sliding bearing ring

Abstract

A method for manufacturing a rolling or sliding bearing ring (1) is disclosed, comprising: - forming (S2) a metallic ring element (1) by depositing metal using a directed energy deposition (DED) process; and - applying (S3) a load-bearing surface (11) to the formed metallic ring element (1') using a further DED process.

Description

Technical field of the invention The present invention relates to a method for manufacturing a rolling or sliding bearing ring according to claim 1. The present invention also relates to a rolling or sliding bearing ring according to claim 10. Background of the invention Rolling bearings and plain bearings are well-known mechanical components used to carry loads while allowing relative rotation between their bearing rings. Rolling bearings carry loads via rolling elements such as balls and rollers, while plain bearings, also known as sliding bearings, carry loads via sliding surfaces. A bearing ring is generally manufactured from a single piece of rolled / forged steel substrate, for example by surface cutting, grinding, and honing, until a final bearing ring component is obtained. The bearing ring is also typically subjected to a heat treatment process to increase its surface hardness and thereby achieve high fatigue strength, particularly on the load-bearing surfaces of the ring. This allows for a long service life. It is also known to provide, for example, bearing rings made from more expensive materials to offer increased performance. For instance, a bearing ring can be made from stainless steel, providing a corrosion-resistant ring. Due to the relatively high cost of stainless steel, larger bearings—such as those with an outer diameter greater than 500 mm (millimeters)—can be very expensive to manufacture due to the high material costs, or even impossible to manufacture due to limitations on the gear ratio. Instead of using an expensive material, such as stainless steel, a bearing can be manufactured from a less expensive material and coated with a high-performance material to provide additional properties like corrosion resistance. In this case, the base ring is manufactured using conventional methods, such as hot forming or rolling, and then coated. However, when manufacturing large bearings, production volumes are typically very limited, resulting in high costs and long lead times for the bearing rings. The lead time for procuring components for large bearings, such as bearing rings, is often 8 to 12 months. The costs associated with this type of procurement are also very high, as the quantities are very small and high-quality steel is required in large tonnages. Furthermore, if something goes wrong during production, a new order must be placed (again 8-12 months). This can be mitigated by building up inventories, but this can lead to high costs without knowing whether the accumulated inventory will actually be needed. It is therefore an object of the present invention to provide a bearing ring in a cost-efficient and faster manner compared to the manufacturing methods mentioned above. Summary of the invention This problem is solved by a method for manufacturing a rolling or sliding bearing ring, comprising: - forming a metallic ring element by depositing metal using a directed energy deposition process; and - applying a load-bearing surface to the formed metallic ring element using a further DED process. Based on this method, a bearing ring can be manufactured quickly and easily using only a DED process. DED is used here as a type of 3D printing of the bearing ring. Thus, in a first step, the metallic ring element is formed or 3D printed using DED. The metal can be deposited onto a support material, which can subsequently be removed. Alternatively, the support material can be part of the bearing ring and remain attached to it. The support material could, for example, be a thin metal foil made of the same material as the metallic ring element. In the second step, the load-bearing surface is also applied to the ring element, using DED. Here, DED is used to coat the formed ring element. DED is a surface welding process that creates a metallurgical bond between the load-bearing surface material and the metallic ring element (and / or between the ring element material and the substrate material), thus providing a DED-bonded surface on the metallic ring element (and / or the substrate material). Other examples of DED, besides laser cladding, include plasma powder deposition (PTA), electron beam melting (EBM), and selected laser melting (SLM). DED processes can deposit materials at very high rates (up to 10 kg per hour). Therefore, a bearing ring can be manufactured much faster compared to previous methods and, for example, produced on demand according to the user's / customer's specifications. Furthermore, DED processes offer dimensional stability, resulting in tighter tolerances for post-processing and thus reduced post-processing time, further improving production in terms of both time and cost. For example, by using 3D printing, especially DED, the lead time for procuring bearing rings can be reduced to 3-4 weeks, compared to the previously required 8-12 weeks. Furthermore, the manufacturing process offers the advantage that bearing rings of different types and sizes can be easily produced using the same starting material. The manufacturing process can therefore be adapted to different bearing types and sizes based on user or customer requirements. The DED process for forming the metallic ring element and / or applying the load-bearing surface can be a steel wire and / or steel metal powder DED process. In particular, it has been found that a steel surface can be applied to the metallic ring element using a wire and / or powder-based DED process. This steel surface can be made of any metal, for example, a cost-effective metal, and preferably a high-performance steel surface. This results in a rolling or sliding bearing ring with increased service life in a cost-effective and time-efficient manner. Furthermore, by using DED, a layer of steel material of any desired thickness can be applied to the metallic ring element, resulting in a further performance improvement. Furthermore, the material of the load-bearing surface can be selected according to specific applications, such as pulp and paper applications, wind turbines, metal and mining applications, etc. This provides increased flexibility due to the adaptability of the load-bearing surface material based on the respective application. A load-bearing surface here refers to a surface intended to be subjected to loads during use, typically alternating loads. Preferably, the load-bearing surface is a raceway surface of the rolling or sliding bearing ring. However, the load-bearing surface can also be, for example, an inner circumferential surface of an inner bearing ring and / or an outer circumferential surface of an outer bearing ring.Furthermore, the load-bearing surface can be any surface of the rolling or sliding bearing ring that is intended to bear a load with a principal force component that is essentially directed straight at the surface. Additionally, when a steel wire and / or steel metal powder DED process is used, the only inventory required is drums of wire / powder for the printing process. This inventory can be significantly smaller compared to previous manufacturing methods, as the same type of inventory can be used for all storage types and sizes. The steel wire and / or steel powder for the metallic element of the ring may comprise a low-strength steel, in particular S355J2, 42CrMo4, 21CrMoV5-11, 16CrMo4 and / or 25CrMo4. Therefore, the metallic ring element can be manufactured cost-effectively using inexpensive materials such as structural steels like S355J2, 42CrMo4, low-alloy, low-carbon steels, etc. The ring element can thus be formed from a comparatively inexpensive material, while the required strength and other properties of the bearing ring can be provided by the load-bearing surface applied to the metallic ring element. For example, a less expensive material can be used for the metallic ring element, such as a standard non-stainless steel, for instance, a steel with a chromium (Cr) content below 10 wt.%. The steel wire and / or steel metal powder used for the load-bearing surface may include carbon (C) and boron (B) as hardening mechanisms. It has been recognized that DED, for example, laser cladding, of a steel wire and / or steel powder containing only carbon as a hardening mechanism may not provide a surface with sufficient hardness without a high risk of cracking. In particular, it has been found that a raceway surface coated with a steel wire and / or steel metal powder containing only carbon as a hardening mechanism may not provide sufficient surface hardness, especially for more demanding applications, without a high risk of cracking in the raceway surface.By also providing carbon (B) as a hardening mechanism, it has been found that a high surface hardness of the load-bearing surface can be achieved, suitable for more demanding applications, while also reducing the risk of cracking. For example, it has been found that a load-bearing surface with a surface hardness of at least 55 HRC, such as 55-58 HRC, can be achieved when the steel metal powder and / or steel wire includes carbon (C) and carbon (B) as hardening mechanisms. Optionally, the steel wire and / or steel metal powder can also contain 0.10-0.50 wt% carbon (C) and 0.50-1.50 wt% carbon (B). For example, it has been found that a higher surface hardness can be achieved when the aforementioned amounts of carbon (C) and carbon (B) are used, typically by using a higher amount of carbon (B) compared to the amount of carbon (C) in, for example, the steel metal powder.According to an exemplary embodiment, the total weight percentage of C and B is in the range of 0.6-1.7 wt.%, such as essentially 0.2 wt.% C and 0.9 wt.% B. Optionally, the steel wire and / or steel metal powder can be made of stainless steel wire and / or stainless steel metal powder. This allows the DED process to provide a corrosion-resistant surface, which, compared to, for example, the cost-effective material of the previously formed ring element, represents a high-performance surface. Applying the load-bearing surface can involve applying more than one layer using DED, such as 2 to 20 layers. Providing more than one layer, such as 2 to 20 layers, has been shown to result in a high-performance surface with a satisfactory thickness for more demanding applications. This can also reduce the amount of heat transferred to the previously formed metallic ring element, thus reducing the risk of cracking in the metallic ring element. Deposition of metal using directed energy deposition (DED) to form the metallic ring element involves the deposition of multiple layers using DED. These multiple layers can, for example, number in the hundreds. Thus, the metallic ring element can be built up by applying one layer after another until the desired thickness is reached. This means that any desired thickness of the metallic ring element, and therefore of the bearing ring, can be achieved by adjusting the number of layers. Furthermore, the ratio between the metallic ring element and the load-bearing surface, viewed in the radial direction of the rolling or sliding bearing ring, can be varied. By selecting a specific ratio, the ring's properties can be further adjusted. For example, the load-bearing capacity can be increased or decreased by having a higher or lower proportion of the load-bearing surface within the overall ratio. The same applies to the bearing ring's cost; that is, by having a higher or lower proportion of the cost-effective material in the ring element, the overall cost of the bearing ring can be increased or decreased. Optionally, the speed at which the load-bearing surface is applied by DED, i.e., the DED speed, can be in the range of 0.5 to 1000 meters per minute, similar to the speed used in laser cladding. According to one embodiment, the DED speed is higher than 1 meter per minute, for example, higher than 20 meters per minute, such as 80–120 meters per minute, which reduces the risk of cracking in the metallic ring element. It has been found that a higher DED speed, similar to that used in laser cladding, can reduce the risk of cracking. Therefore, by using a higher laser cladding speed, for example, an improved rolling or sliding bearing ring can be provided. Optionally, if the DED process is laser cladding, the laser power when the load-bearing surface is applied can be 1-30 kW (kilowatts), in particular 5-16 kW. Optionally, the application speed can be varied during the deposition of the steel wire and / or steel powder onto the substrate and / or the metallic ring element. This allows for the application of one or more layers with varying radial thicknesses. For example, the substrate and / or the metallic ring element can be rotated relative to an axis of rotation during the application of the load-bearing surface, with the rotational speed being varied during the deposition of the steel wire and / or steel powder. By changing the speed, less heat can be transferred to the substrate and / or the metallic ring element, as well as to subsequent layers of the metallic ring element and / or the load-bearing surface, during the DED process.According to one exemplary embodiment, the speed is varied by reducing it at least once during the application of the layers of the metallic ring element and / or the load-bearing surface. This allows a relatively high speed to be used when, for example, a first layer is applied directly to the metallic ring element, while a relatively low speed can be used when one or more additional layers are applied to the first layer. The same applies to the layers of the metallic ring element. Consequently, the first layer will be thinner than the one or more additional layers. This can result in less heat being transferred to the metallic ring element, thereby reducing the risk of cracking during the DED process, such as laser cladding. Furthermore, by varying the deposition rate, a surface with a variable radius and a load-bearing surface of substantially uniform thickness can be provided. For example, the ring of the rolling or sliding bearing can have a spherical surface with a variable radius, with the deposition rate being varied to provide a load-bearing surface of substantially uniform thickness. Accordingly, the deposition rate can be varied to achieve a constant surface velocity during the DED process. The same applies to the formation of the metallic ring element. Optionally, the final thickness of the applied load-bearing surface can be 0.25–10 µm, measured radially along the rolling or sliding bearing ring. According to another aspect, a rolling or sliding bearing ring is provided for a rolling or sliding bearing, wherein the rolling or sliding bearing ring was manufactured by the method according to one of the embodiments of the method described above. A rolling bearing ring can be a ring of any type of rolling bearing. For example, it can be a ball bearing or a roller bearing, including but not limited to spherical roller bearings, tapered roller bearings, toroidal roller bearings, cylindrical roller bearings, self-aligning ball bearings, deep groove ball bearings, and angular contact ball bearings. A plain bearing ring can be a ring of any type of plain bearing, such as a spherical plain bearing. According to another aspect, a rolling or sliding bearing is provided which includes at least one rolling or sliding bearing ring as described above. Further preferred embodiments are defined in the dependent claims, the description, and the figures. Elements described or illustrated in combination with other elements may be present alone or in combination with other elements without deviating from the scope of protection. Brief character description Preferred embodiments of the invention are described below with reference to the drawings, which are only exemplary and do not serve to limit the scope of protection. The scope of protection is defined exclusively by the accompanying claims. The figures show: Fig. 1: a cross-sectional view of a rolling or sliding bearing ring; Fig. 2: a schematic side view of a rolling bearing comprising the ring from Fig. 1; Fig. 3: a cross-sectional view of the rolling or sliding bearing ring from Fig. 1; and Fig. 4: a flowchart of a method for manufacturing a rolling or sliding bearing ring according to Figs. 1-3. Detailed description of the invention In the following, identical or similarly functioning elements are designated with the same reference symbols. Fig. 1 shows a cross-sectional view of a rolling or sliding bearing ring 1 that can be used in a rolling or sliding bearing. The cross-sectional view is defined by a plane extending along an axis of rotation A of the rolling or sliding bearing ring 1. The rolling or sliding bearing ring 1 comprises a metallic ring element 1'. It further comprises a load-bearing surface 11 provided on the metallic ring element 1'. In order to provide a time- and cost-efficient manufacturing method for the bearing ring 1, the metallic ring element 1' and the load-bearing surface 11 are formed by a DED process. Thus, the metallic ring element 1' is first formed by depositing layers of the metallic material of the metallic ring element 1' onto a carrier material (not shown), which either remains on the bearing ring 1 or can be removed from the bearing ring 1 after the formation of the metallic ring element 1' and / or the load-bearing surface 11. The load-bearing surface 11 is then deposited onto the metallic ring element 1' by a DED process. The load-bearing surface 11 is a raceway surface, such as a raceway surface for rolling elements, i.e., balls and / or rollers. As shown, the raceway surface 11 can have a spherical shape. This allows the rolling or sliding bearing ring 1 to be aligned relative to an outer ring 2 (see Fig. 2). Thus, a rolling or sliding bearing 10, such as the one shown in Fig. 2, which includes the rolling or sliding bearing ring 1, can be able to accommodate shaft deflections during use. Other shapes of bearing rings 1 can also be formed. Fig. 2 shows a side view of a rolling bearing 10, which includes the rolling bearing ring 1, as shown, for example, in Fig. 1. The rolling bearing ring 1 is here an inner ring of the rolling bearing 10. The rolling bearing 10 further includes the outer ring 2 mentioned above and several rolling elements 3, which are provided between the outer ring 2 and the rolling bearing ring 1. It should be noted that the outer ring 2 can alternatively or additionally be provided with a load-bearing surface 11, as described above. Fig. 3 shows a cross-sectional view of a section of the rolling or sliding bearing ring 1 according to Fig. 1. As already mentioned, it comprises the load-bearing surface 11 and the metallic ring element 1', both formed by using DED. The load-bearing surface 11 has a radial thickness h1, which can be, for example, 0.25–10 mm. The radial direction of the ring 1 is perpendicular to and intersects the axis of rotation A of the rolling or sliding bearing ring 1. The metallic element of the ring 1' has a radial thickness h2, which is significantly greater than the radial thickness h1, for example, 10–500 mm. The thicknesses h1 and h2 can be adjusted depending on the intended application of the bearing ring 1.For example, for applications with higher loads the thickness h1 of the load-bearing surface 11 can be increased, while for applications with lower loads the thickness h1 of the load-bearing surface 11 can be reduced in relation to the thickness h2 of the metallic ring element 1'. It should also be noted that both the metallic ring element 1' and the load-bearing surface 11 can consist of several individual layers which are applied on top of each other by using a DED process. Fig. 4 shows a flowchart of a process for manufacturing the bearing ring 1 of Fig. 1, Fig. 2 to Fig. 3. In a first step S1, a support material is provided on which the metallic ring element 1' can be formed. This step S1 is optional, and it should be noted that other methods of forming the metallic ring element 1' are also possible, such as using a mold or the like. In a second step S2, the layers of the metallic ring element 1' are applied or deposited using a DED process. During this DED process, for example by laser cladding, steel wire and / or steel metal powder is melted layer by layer to form the metallic ring element 1'. This step S2 can be carried out until a desired thickness h2 of the metallic ring element 1' is reached. In a third step, S3, the load-bearing surface 11 is applied to the metallic ring element 1'. This can be done with the same machine or device as in step S2, requiring only the steel wire and / or steel powder to be changed to provide the load-bearing surface 11 and the metallic ring element 1' with different characteristics or properties. Thus, only one production facility is required for steps S2 and S3. It should be noted that the layers of the metallic ring element 1' and the load-bearing surface 11 can also comprise different materials. For example, the layers of the metallic ring element 1' can consist of alternating layers of two or more materials, such as different types of steel. The same applies to the load-bearing surface 11. This can offer the advantage that additional features, properties, and / or characteristics can be added to the metallic ring element 1' and / or the load-bearing surface 11. Once the desired thickness h1 of the load-bearing surface 11 has been reached, the process can end or continue with step S4, in which the support material from step S1 can be removed. It should be noted that if a support material is used, this support material can also be removed after step S2 and before step S3. In summary, the manufacturing process described here and the corresponding bearing ring offer a flexible approach to producing a bearing ring in terms of its type and size. For example, the thickness and materials of the layers can be adapted to the specific requirements of the intended application. Furthermore, the bearing ring can be easily manufactured using the same production equipment by simply exchanging the added wire / powder. Reference symbol list 1 Rolling or sliding bearing ring 1' Metallic ring element 2 Outer ring 3 Rolling element 10 Rolling bearing 11 Load-bearing surface A Axis of rotation h1 Thickness of the load-bearing surface h2 Thickness of the metallic ring element S1-S4 Process steps

Claims

Method for manufacturing a rolling or sliding bearing ring (1), comprising: - forming (S2) a metallic ring element (1) by depositing metal using a directed energy deposition (DED) process; and - applying (S3) a load-bearing surface (11) to the formed metallic ring element (1') using a further DED process. Method according to claim 1, wherein the DED process for forming the metallic ring element (1') and / or for applying the load-bearing surface (11) is a steel wire and / or a steel metal powder DED process. Method according to claim 2, wherein the steel wire and / or the steel metal powder for the metallic ring element (1') comprises a low-strength steel, in particular S355J2 and / or 42CrMo4. Method according to claim 2 or 3, wherein the steel wire and / or steel metal powder for the load-bearing surface (22) comprises carbon (C) and boron (B) as hardening mechanisms. Method according to claim 4, wherein the steel wire and / or steel metal powder for the load-bearing surface (1) comprises 0.10-0.50 wt.% of C and 0.50-1.20 wt.% of B. Method according to any one of claims 2 to 5, wherein the steel wire and / or the steel metal powder for the load-bearing surface (11) is each a stainless steel wire and / or a stainless steel metal powder. Method according to one of the preceding claims, wherein the application of the load-bearing surface (11) comprises the application of more than one layer by using DED, such as 2-20 layers. Method according to one of the preceding claims, wherein the application of metal by using a directed energy deposition (DED) process to form the metallic ring element (1') comprises the application of multiple layers by using DED. Method according to one of the preceding claims, wherein the ratio between the metallic ring element (1') and the applied load-bearing surface, as seen in a radial direction of the rolling or sliding bearing ring, is variable. Rolling or sliding bearing ring (1) for a rolling or sliding bearing (10), wherein the rolling or sliding bearing ring (1) was manufactured by the method according to one of the preceding claims.

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