METHOD FOR REPROCESSING USED ROLLING BEARINGS AND ROLLING BEARING MANUFACTURED THEREFORE

Description

[0001] The invention relates to a method for reconditioning used rolling bearings comprising rolling bearing components made of a metallic base material, such as rolling bearing rings or rolling elements, and reconditioned rolling bearings produced thereafter.

[0002] EP 2 373 456 B1 discloses a method for repairing a metallic artifact with an open defect. This involves cold forging to close the open defect, followed by laser cladding to cover the cold-forged defect with a metal layer.

[0003] In the field of rolling bearing technology, it is already known to recondition bearing components with only moderate wear damage and reuse them by reworking the surfaces of bearing rings through material removal. To compensate for the change in ring dimensions caused by the material removal, such bearing rings are combined with correspondingly larger rolling element sets.

[0004] Bearing components made from expensive, high-performance materials are of particular interest with regard to reuse. Powder is usually processed into cylinders using hot isostatic pressing, and their outer diameters are limited by manufacturing constraints. However, the functionality of such high-performance materials is often only required in the area of ​​functional surfaces, such as the raceway of a bearing ring or rolling elements.

[0005] DE 10 2019 216 995 A1 already describes bearing components with a base body that forms the bearing component and at least one coating applied to the base body. The base body is made, in particular, of unalloyed steel, unalloyed heat-treatable steel, standard bearing steel, cast iron, or another metallic alloy. A harder material, in particular alloy steel, is applied to the base body as a coating. The coating is formed by weld overlay. It is further mentioned that weld overlay can also be used to recondition a used large bearing ring.

[0006] DE 10 2017 115 803 A1 discloses a method for manufacturing a metal component with two component sections made of different metal materials. In this process, a layer of heat-resistant steel is applied to a carrier made of a high-temperature alloy by weld overlay, and a rolling raceway is formed on this layer.

[0007] DE 10 2019 202 840 A1 describes a rolling surface element of a rolling bearing and a method for repairing the rolling surface element. The rolling surface element comprises a rolling track on which rolling elements are provided for rolling. A cavity is provided in the area of ​​the rolling track, into which an insert, fixed by means of an interference fit, is inserted, forming part of the rolling track. A rolling surface element is repaired by creating a cavity in the damaged area, inserting an insert protruding beyond the remaining rolling track into this cavity, and mechanically removing the protruding portion to create a repaired rolling track.

[0008] JP 2021 025 598 A discloses a rolling bearing and a method for repairing the running surface of a bearing ring. In this process, the entire raceway of a rotating inner ring is irradiated with a laser, coated, and the coating is then subjected to post-processing by grinding.

[0009] The object of the invention is to enable the reuse of used rolling bearings and to provide a method for reprocessing such used rolling bearings.

[0010] The task encompasses the process for reconditioning used rolling bearings, including rolling bearing components made of a metallic base material with the following characteristics.

[0011] Solved in steps: Providing the used rolling bearing comprising at least one rolling bearing ring and a number of rolling elements, wherein the rolling bearing rings and / or rolling elements formed from the metallic base material constitute recyclable rolling element components, singulating at least the recyclable rolling element components and identifying at least one rolling bearing component to be recycled from the quantity of recyclable rolling bearing components, removing a surface area of ​​the at least one rolling bearing component to be recycled, corresponding to a raceway area of ​​the rolling bearing component to be recycled, preparing a receiving area for receiving a metallic repair material, optionally applying an interlayer material to the metallic base material in the receiving area,Applying the metallic repair material in the receiving area onto the metallic base material or, optionally, onto the interlayer material, forming a raceway layer, wherein the metallic repair material is selected from steel grade 1.3344 (X 130 WMoCrV 6-5-4-3) or from martensitic stainless steel, in particular grade 1.4034 (X46Cr13), or from a cemented carbide based on tungsten carbide in a nickel binder matrix, wherein the metallic repair material is fused with the metallic base material or, optionally, the interlayer material, performing a post-processing of a free surface of the raceway layer using at least one remanufactured rolling bearing component, wherein the free surface of the raceway layer is machined and hardened.and assembly of at least one remanufactured rolling bearing component with the other rolling bearing components of the used rolling bearing to form a remanufactured rolling bearing.

[0012] To ensure the reconditioning of rolling bearing components while maintaining their internal and / or external geometry, the worn surface area is replaced, i.e., rebuilt. This is achieved by applying a raceway layer of sufficient thickness and hardness. If the repair material also exhibits higher wear resistance than the worn material of the metallic base material, the application of a raceway layer is also suitable for creating higher-quality rolling bearing components with improved wear resistance and durability properties, thus enabling upcycling.

[0013] Preferably, the surface area is removed by turning. However, other removal methods, such as milling or grinding, can also be used. A combination of different removal methods is also possible.

[0014] The at least one rolling element component to be reconditioned is, in particular, a rolling bearing ring, and the material removal in the raceway area is in the range of D / 100 to D / 20 of a diameter D of the rolling elements of the rolling bearing. Preferably, the material removal is in the range of 0.5 to 5%, more preferably 0.5 to 1.5%, of a diameter D of the rolling elements of the rolling bearing. The material removal is usually in the range of 0.4 to 10 mm.

[0015] The at least one rolling bearing component to be reconditioned is preferably a rolling bearing ring and has in particular a bore diameter of greater than or equal to 50 mm, in particular of greater than or equal to 120 mm.

[0016] The metallic base material is preferably selected from bearing steel, heat-treatable steel, structural steel or case-hardening steel.

[0017] The repair material is preferably a steel with a proportion of 0 to 10 wt.% Mo, 0 to 19 wt.% W, 0 to 5 wt.% V, 3.5 to 5 wt.% Cr, 0 to 11 wt.% Co, 0.75 to 1.2 wt.% C, balance iron and unavoidable impurities or other elements, such as Mn, Si, Cu, Ni, P, S, with a proportion of less than 0.5 wt.%.

[0018] According to the invention, in a first embodiment, steel grade 1.3344 (X 130 WMoCrV 6-5-4-3) is used. Since no heat treatment is applied, retained austenite may be present (up to approximately 30%) with a hardness of the built-up material greater than 62 HRC.

[0019] Alternatively, in a second variant, the repair material according to the invention is a martensitic stainless steel, such as one of grade 1.4034 (X46Cr13), or in a third variant, a hard metal based on tungsten carbide in a nickel binder matrix, also known on the market under the name "Cermadur".

[0020] A non-hardenable steel with a carbon content of less than 0.15% is used as the interlayer material. This is intended to improve adhesion to the base material and the application of the repair material to the interlayer material. The interlayer material is preferably applied to the base material in the same manner as the application of the repair material described below.

[0021] The application of the metallic repair material can be carried out using any material deposition process that creates a metallic bond between the base material and the repair material. In particular, application is achieved using a directed energy deposition (DED) process, for example, with a laser, electron beam, or plasma discharge. In this process, a powder or wire is melted onto the surface of the metallic base material in the receiving area or onto the interlayer material in the receiving area. This results in a wavy structure in the transition zone between the base material and the repair material, or between the interlayer material and the repair material. This structure is visible in the micrograph and can be influenced by the process parameters of the directed energy deposition process.

[0022] The resulting heat-affected zone extends, possibly across the interlayer material, into the base material, with the waviness covering an area corresponding to the measured distance between the mean of the waviness peaks and the mean of the waviness troughs, where this distance is at least 50 µm. This ensures a particularly close and pore-free bond between the base material and the repair material. The waviness and extent of the heat-affected zone depend on the application parameters, such as power, application speed, and application width.

[0023] According to the invention, the free surface of the raceway layer, which faces away from the base material, is machined and hardened. This adapts the flatness and surface roughness of the free surface of the raceway layer to the requirements of the application of the rolling bearing components. In particular, the machining process involves fine machining, preferably honing, of the raceway layer. The fine machining is performed in such a way that the amplitude density distribution exhibits a negative skewness with an Rsk value of less than -0.5, and the surface thus has a plateau-like character. Depending on the depth of the hardening, the surface is burnished (shallow depth), hot-rolled (medium depth), or ring-rolled (simultaneous heat treatment).

[0024] The remanufactured rolling bearing component is either not subjected to further heat treatment, in which case the metallic repair material has a Rockwell hardness of at least 60 HRC. Alternatively, the remanufactured rolling bearing component can be subsequently heat-treated and have a Rockwell hardness of at least 63 HRC.

[0025] In a rolling bearing manufactured according to the inventive method, the metallic repair material has a Rockwell hardness of at least 60 HRC. The metallic base material preferably has a lower hardness.

[0026] In particular, the metallic repair material has a hardness greater than 62 HRC, without subsequent hardness-increasing processes such as carbonitriding or heat treatment.

[0027] The rolling bearing component is a rolling element or a bearing ring. These rolling bearing components are used particularly in rolling bearings of the ball bearing type, cylindrical roller bearing, spherical roller bearing, tapered roller bearing, and the like. In the case of ball bearings and spherical roller bearings, the rolling bearing rings are particularly suitable for reconditioning using the method according to the invention. In the case of cylindrical roller bearings and tapered roller bearings, in addition to the rolling bearing rings, the rolling elements are also suitable for reconditioning using the method according to the invention.

[0028] The thickness of the raceway layer varies according to the size of the rolling bearing component and the expected loads in the application. The at least one rolling element component to be reconditioned is preferably a rolling bearing ring, and the coating in the raceway area is applied in the range of D / 100 to D / 20 of a diameter D of the rolling elements of the rolling bearing. Preferably, the thickness of the raceway layer for rolling bearing rings corresponds to 0.5 to 5%, more preferably 0.5 to 1.5%, of the diameter D of a rolling element in the respective bearing, and is therefore usually in the range of 0.4 mm to 10 mm.

[0029] In the transition zone between the base material and the repair material, or between the intermediate layer and the repair material, the materials are fused together and thus metallurgically bonded. A drop in hardness directly adjacent to this transition zone is measurable. The transition zone exhibits a characteristic wavy profile, which is essentially achieved through the application process of directed energy input and, as described above, can be influenced by the process parameters.

[0030] The Figures 1 and 2 The inventive method and a remanufactured rolling bearing component are to be illustrated by way of example. Thus, the following is shown: Figure 1 shows a section through a used rolling bearing in the form of a ball bearing, and Figure 2 shows a micrograph of a section through a remanufactured rolling bearing component.

[0031] Figure 1Figure 1 shows a cross-section through a used rolling bearing 10 in the form of an exemplary ball bearing. A first rolling bearing component in the form of a rolling bearing ring 1a (= outer ring) is made of a metallic base material 2 (compare Figure 2). Figure 2 ) formed and has a raceway area 7. A second rolling bearing component in the form of a bearing ring 1b (= inner ring) is made of a metallic base material 2 (compare Figure 2) and has a raceway area 6. The rolling elements 1c are made of a ceramic material. A cage 9 is also provided for holding the rolling elements 1c. Here, the rolling bearing component, in the form of the bearing ring 1a or outer ring, is selected for reconditioning. The raceway area 7 of the used rolling bearing component is prepared for reconditioning by removing a surface area of ​​the bearing ring 1a corresponding to the raceway area 7 affected by wear during use of the rolling bearing 10, while preparing a receiving area for a metallic repair material 3.

[0032] The metallic repair material 3 is then applied to the receiving area, forming a raceway layer 4, whereby the metallic repair material 3 is fused with the base material 2. The free surface 5 of the raceway layer 4 (compare Figure 2The side facing away from the base material 2 undergoes post-processing. The result is a remanufactured rolling bearing component 11, which can be reused in a rolling bearing 10 as a bearing ring 1a or outer ring, together with the other, unmachined components of the used rolling bearing 10, to form a remanufactured rolling bearing. An intermediate layer material can optionally be arranged between the base material 2 and the repair material 3, in which case the intermediate layer material is first fused with the base material 2, and the repair material 3 is then fused with the intermediate layer material.

[0033] Figure 2Figure 1 shows a micrograph of a section through a remanufactured rolling bearing component 11. The base material 2 has a raceway layer 4 made of the repair material 3, formed by a directed energy input process. In the transition zone 12, where the base material 2 is fused with the repair material 3, a wavy structure is present. The distance A between the mean of the wave crests and the mean of the wave troughs (see dashed lines) is at least 50 µm. The free surface 5 of the raceway layer 4, which faces away from the base material 2, has been post-processed by grinding. Reference symbol list

[0034] 1a, 1b Rolling bearing ring 1c Rolling element 2 Metallic base material 3 Metallic repair material 4 Raceway layer 5 Free surface of the raceway layer 6 Raceway area 7 Raceway area 9 Cage 10 Rolling bearing 11 Reconditioned rolling bearing component 12 Transition area A Distance

Claims

1. A method for reprocessing used rolling bearings (10) comprising rolling bearing components made of a metallic base material (2) having the following steps: providing the used rolling bearing (10) comprising at least one rolling bearing ring (1a, 1b) and a number of rolling bodies (1c), wherein the rolling bearing rings (1a, 1b) and / or rolling bodies (1c) formed from the metallic base material (2) constitute reprocessable rolling body components, separating at least the reprocessable rolling body components and identifying at least one rolling bearing component to be fed for reprocessing from the quantity of reprocessable rolling bearing components, removing a surface region of the at least one rolling bearing component to be reprocessed that corresponds to a raceway region (6, 7) of the rolling bearing component to be reprocessed so as to prepare a receiving region for receiving a metallic repair material (3), optionally applying an interlayer material to the metallic base material in the receiving region, applying the metallic repair material (3) in the receiving region to the metallic base material or optionally to the interlayer material to form a raceway layer (4), the metallic repair material (3) being selected from steel of grade 1.3344 (X 130 WMoCrV 6-5-4-3) or from martensitic stainless steel, in particular of grade 1.4034 (X46Cr13), or from a cemented carbide based on tungsten carbide in a nickel binder matrix, the metallic repair material (3) being fused with the metallic base material (2) or optionally the interlayer material, carrying out finishing of a free surface (5) of the raceway layer (4) by providing at least one reprocessed rolling bearing component (11), the free surface (5) of the raceway layer (4) being machining finished and finish-hardened, and assembling the at least one reprocessed rolling bearing component (11) with the other rolling bearing components of the used rolling bearing (10) to form a reprocessed rolling bearing.

2. The method according to claim 1, wherein the removal of the surface region is carried out by means of rotation.

3. The method according to either one of claims 1 or 2, wherein the at least one rolling body component to be reprocessed is a rolling bearing ring (1a, 1b) and the removal in the raceway region (6, 7) is in the range of D / 100 to D / 20 of a diameter (D) of the rolling bodies (1c) of the rolling bearing (10).

4. The method according to any one of claims 1 to 3, wherein the at least one rolling bearing component to be reprocessed is a rolling bearing ring (1a, 1b) and has a bore diameter of more than 50 mm.

5. The method according to any one of claims 1 to 4, wherein the metallic base material (2) is selected from rolling bearing steel, quenched and tempered steel, structural steel or case-hardened steel.

6. The method according to any one of claims 1 to 5, wherein the interlayer material selected is a non-hardenable steel having a carbon content of less than 0.15%.

7. The method according to any one of claims 1 to 6, wherein the application of the metallic repair material (3) is carried out by means of a directed energy input method.

8. The method according to any one of claims 1 to 7, wherein the reprocessed rolling bearing component (11) is subsequently fine-machined.

9. The method according to claim 8, wherein the machining finishing is a fine machining and is carried out in such a way that an amplitude density distribution has a negative skewness with an Rsk value less than -0.5 and the finished surface thus has a plateau character.

10. The method according to any one of claims 1 to 9, wherein for finish-hardening the finished surface is smooth-rolled or deep-rolled or ring-rolled, wherein in the case of ring rolling a simultaneous heat treatment is carried out.

11. A reprocessed rolling bearing produced according to a method according to any one of claims 1 to 10, wherein the metallic repair material (3) has a Rockwell hardness of at least 60 HRC.