EP2828540A1

EP2828540A1 - Method for producing a rolling bearing, and rolling bearing

Info

Publication number: EP2828540A1
Application number: EP13702780.1A
Authority: EP
Inventors: Christina Pfeuffer; Edgar Pickel; Jürgen Gegner; Wolfgang Nierlich; Armin Olschewski; Kenred Stadler; Arno Stubenrauch; Markus Volkmuth
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2012-03-20
Filing date: 2013-01-28
Publication date: 2015-01-28
Also published as: WO2013139514A1

Abstract

The invention relates to a method for producing a rolling bearing which has an inner ring (1) with an inner ring raceway (2), an outer ring (3) with an outer ring raceway (4), and rolling bodies (5) which roll on the inner ring raceway (2) and on the outer ring raceway (4). The inner ring (1) is produced from steel and is subjected to a heat treatment which serves for hardening and which is completed with the execution of a final heat treatment step at a predefined temperature. Compressive internal stresses are formed in the inner ring (1) in a surface layer by cold working in the region of the inner ring raceway (2). The inner ring (1) is burnished after the cold working.

Description

Method for producing a rolling bearing and rolling bearing

The invention relates to a method for producing a rolling bearing. Furthermore, the invention relates to a rolling bearing, in particular a rolling bearing of a wind turbine. Finally, the invention relates to a wind turbine.

In particular, in rolling bearings, which have very large dimensions and / or installed in large systems, such as rolling bearings of wind turbines, in view of the high cost of the bearings themselves and the high cost caused by a stoppage of equipped with such bearings equipment are required, a long trouble-free operation and thus a long life of the bearings. In systems with very large bearings but sometimes extreme stress situations occur, which can no longer be controlled by a simple scaling up of standard bearings. Rather, it is necessary to equip the rolling bearings with outstanding and tailored to the expected stress profiles material properties. Especially in wind turbines also very complex stress profiles occur, which can lead to premature failure of rolling bearings, which can not be predicted with conventional life models. In particular, there is the risk that temporary stresses occur which are not analyzed in detail and are not covered by the specifications of the rolling bearings. The premature failures are often based on the training of such called white cracks. These are areas of ultra-fine, nano-recrystallized carbide-free ferrite.

It is therefore an object of the invention to provide a rolling bearing, which has a very long life and a very low risk of premature failure even in an operation in which extreme stress situations occur.

This object is achieved by a method for producing a rolling bearing and by a rolling bearing according to the independent claims.

In the inventive method for producing a rolling bearing having an inner ring with an inner ring raceway, an outer ring with an outer ring raceway and rolling elements that roll on the inner ring raceway and on the outer ring raceway, the procedure is as follows:

The inner ring is made of steel and subjected to a curing heat treatment, which is completed with the implementation of a final heat treatment step at a predetermined temperature. In the inner ring, compressive stresses in an edge layer, which extends to a minimum depth below the surface of the inner ring raceway, are formed by strain hardening in the region of the inner ring raceway. After work hardening, the inner ring is burnished.

The individual steps of the process according to the invention are preferably carried out in the order mentioned above. Not all steps necessarily have to be carried out in a tight spatial or temporal context. Rather, it is possible to produce intermediates that will be further processed at a later date and / or elsewhere. The manufacturing method according to the invention reduces the susceptibility of the steel used to cracking on the surface, reduces the crack-initiating sliding friction between the rolling elements and the inner ring raceway in the highly stressed microcontact areas under extreme stress conditions and makes it difficult for hydrogen to penetrate into the inner ring raceway. This has a positive effect on the life of the rolling bearing. Accordingly, the method according to the invention has the advantage that it allows the production of rolling bearings, which even then reach a very long life, for example, if they are exposed for a short time extreme operating conditions. Thus, the inventive method is particularly suitable for the production of rolling bearings of wind turbines. Such bearings can be used for example in transmissions of wind turbines. Furthermore, such bearings can be used for example for the storage of rolls in paper machines.

With the heat treatment, the formation of desired insert structure in the inner ring can be achieved. Hardening reliably protects the inner ring raceway against mechanical damage and inadmissible wear.

The inner ring may be subjected to martensite, insert or induction hardening prior to strain hardening. In this case, the temperature of the last heat treatment step may be the tempering temperature of the inner ring.

Likewise, the inner ring may be subjected to a Bainethärtung before work hardening. In this case, the temperature of the last heat treatment step may be the bainite transformation temperature of the inner ring.

Between the processing step of the work hardening and the processing step of the blackening, a mechanical surface finishing of the Inner ring are performed. As a result, damaged surface areas of the inner ring can be removed and / or the surface roughness can be reduced. The surface finishing can, for. B. done by grinding and / or honing. However, surface finishing by grinding is only possible if the removal is so small that the effects achieved by work hardening are not unduly impaired.

The burnished inner ring may be subjected to a thermal aftertreatment at a temperature below the temperature of the last heat treatment step. In particular, the inner ring may be subjected to the thermal aftertreatment at a temperature which is at least 10 K below the temperature of the last heat treatment step. The thermal aftertreatment can be carried out at a temperature of at least 100 ° C. Particularly effective is the effect of the aftertreatment, if this is carried out at a temperature which is a maximum of 100 K, in particular a maximum of 50 K, below the temperature of the last heat treatment step. As a measure of the effectiveness of the thermal aftertreatment, the decrease in the X-ray line width can be used. For example, for the half-width of the {21 1} -errite (martensite / bainite) x-ray diffraction line, a decrease of at least 0.05 ° in at least one location within the mechanically affected zone (surface and / or depth) may serve as a guideline for effective thermal aftertreatment ,

The thermal aftertreatment is preferably carried out as closely as possible below the tempering temperature for a not too long time depending on the component thickness and the thickness of the mechanically influenced edge layer, for example a maximum of 5 hours to stabilize without significant loss of hardness, the stabilization of the after heat treatment by surface treatment and work hardening Optimize microstructure. Experience has shown that there is sufficient time for the thermal aftertreatment for a maximum of 2 hours. If a bainite hardening is carried out instead of a martensite, insert or induction hardening, then those for the annealing temperature corresponding statements for the Bainitumwandlungstemperatur accordingly.

The thermal aftertreatment can be carried out in each case in such a way after the burnishing that in the meantime it does not come to a noteworthy cooling. This condition can, for example, be regarded as fulfilled if the temperature of the treated component between the browning and the thermal aftertreatment does not fall below a value of 100 ° C.

The outer ring and / or the rolling elements may be subjected to a curing heat treatment with a final heat treatment step. In each case, the same heat treatment process as the inner ring can be used. Likewise, a deviating from the heat treatment of the inner ring method may be used, since the outer ring and the rolling elements are exposed to lower loads than the inner ring usually. Furthermore, the outer ring and / or the rolling elements can be subjected to work hardening, a burnishing treatment carried out after any necessary surface finishing and / or a thermal after-treatment at a temperature below the temperature of the last heat treatment step.

The invention further relates to a roller bearing, which has an inner ring with an inner ring raceway, an outer ring with an outer ring raceway and rolling elements which roll on the inner ring raceway and on the outer ring raceway. The inner ring is made of a steel and hardened by a heat treatment. In the region of the inner ring raceway, the inner ring has compressive residual stresses formed by work hardening in an edge layer which extends to a minimum depth below the surface of the inner ring raceway. The surface of the inner ring raceway is formed by a burnishing layer. The inner ring may be made of a steel having a sulfur content of 0.002 to 0.015 mass% and / or an oxygen content of less than 15 ppm. The sulfur content may be in particular between 0.006 to 0.015 mass%. In particular, the oxygen content may be less than 10 ppm or even less than 5 ppm. The inner ring may in particular be made of a hardening bearing steel. Furthermore, the steel may contain calcium. The calcium content can be 10 to 30 ppm. The ppm figures refer to the mass ratio.

The inner ring can be made of a steel with a forming ratio of at least 5: 1, in particular at least 8: 1 or at least 10: 1. This has the advantage of a comparatively low content of inclusions of critical size or distribution, which can ultimately lead to damage to the inner ring.

The inner ring may have a retained austenite content of 8 to 18% by volume. In particular, the retained austenite content can be from 10 to 16% by volume. Such a retained austenite content proves to be favorable, especially under extreme rolling stress, since cracking and growth are hindered.

The inner ring can have compressive residual stresses in the region of the inner ring raceway in the surface layer with an absolute value in the amount of a minimum value or more, and the minimum value of the absolute value of the compressive residual stresses can be 200 MPa. The minimum depth can be 0, 1 mm, in particular 0.2 mm. In particular, the minimum value of the absolute value of the compressive residual stresses may be 400 MPa or even 500 MPa. At greater depths than the minimum depth, the inner ring may have residual compressive stresses with an absolute value below the minimum value. In particular, the absolute value of the compressive residual stresses at depths greater than the minimum depth may decrease with increasing depth. The residual compressive stresses have a reduced tendency to crack of the Inner ring under local friction-induced tensile stress and thus an increased operating life of the bearing result.

The inner ring can have compressive residual stresses in the region of the inner ring raceway in the surface layer with an absolute value equal to or below the maximum value, and the maximum value of the absolute value of the compressive residual stresses can be 1500 MPa. In particular, the maximum value of the absolute value of the compressive residual stresses may be 1000 MPa or only 800 MPa.

The inner ring may have a microstructure modified by means of thermal after-treatment after formation of the burnishing layer in the surface layer. The modified microstructure in the peripheral layer of the inner ring may have dislocations to which carbon atoms are attached by the thermal post-treatment. This modification stabilizes the microstructure and can be detected by measuring the decrease in X-ray linewidth. For example, if the half width of the {21 1} ferrite (martensite / bainite) X-ray diffraction clays is lowered by at least 0.05 ° at at least one location within the boundary layer, a significant modification of the microstructure can be assumed.

The outer ring and / or the rolling elements may be burnished.

The rolling bearing may, in particular, be a rolling bearing of a wind power plant, for example a rolling bearing of a gearbox of a wind power plant.

The invention further relates to a bearing assembly for rotatably supporting a component of a transmission, wherein the bearing assembly comprises a rolling bearing according to the invention. In addition, the invention relates to a wind turbine, which has a manufactured according to the invention or inventively designed rolling bearing.

In addition, the invention relates to a bearing assembly for rotatably supporting a roller or a cylinder, wherein the bearing assembly comprises a rolling bearing according to the invention. The rolling bearing may in particular be designed as a spherical roller bearing or as a toroidal roller bearing, for example as a CA B bearing.

The roller or cylinder may be formed as a component of a paper machine. The roller or the cylinder may for example be part of a wire section, a press section, a dryer section or a calender.

The invention will be explained below with reference to the embodiment shown in the drawing.

Show it

1 shows an embodiment of an inventively

Rolling bearing in a schematic sectional view,

FIG. 2 shows a diagram for illustrating the course of the internal compressive stresses in the inner ring,

FIG. 3 shows a greatly enlarged section of the inner ring in the region of FIG

Inner ring raceway in a schematic sectional view,

Figure 4 shows an embodiment of a bearing assembly of a paper machine in a sectional view and Figure 5 shows another embodiment of a bearing assembly of a

Paper machine in section.

Figure 1 shows an embodiment of an inventively designed roller bearing in a schematic sectional view. The illustrated rolling bearing is designed as a tapered roller bearing and has an inner ring 1 with a conical inner ring raceway 2 and an outer ring 3 with a conical outer ring raceway 4. On the inner ring raceway 2 and the outer ring raceway 4 roll conical rolling elements 5. The rolling elements 5 are guided in a cage 6. The rolling bearing can have very large dimensions. For example, the outer diameter of the outer ring 3 may be at least 1 m. Such bearings can be formed, for example, as components of a wind turbine. In particular, the rolling bearing according to the invention can also be used in a gearbox of a wind turbine, but then usually has an outer ring 3 with a smaller outer diameter than 1 m. Likewise, the rolling bearing according to the invention may be formed as a component of another transmission. Furthermore, the rolling bearing according to the invention can be used to support a roll, in particular a roll of a paper machine.

As an alternative to the illustrated embodiment, the rolling bearing may for example be designed as a cylindrical roller bearing with cylindrical rolling elements 5, as a spherical roller bearings or as a Toroidalrollenlager, in particular a CARB bearing.

The inner ring 1 of the rolling bearing is made of a hardening steel, for example, from the bearing steel 100Cr6. Likewise, the inner ring 1 can be made of a case-hardening steel, for example of 18NiCrMol4-6 steel. The steel used is produced with a very low sulfur content and a very low oxygen content. The sulfur content is between 0.002 and 0.015 mass%, in particular between 0.006 and 0.015 mass%. The oxygen content is less than 15 ppm, in particular less than 10 ppm or after Possibility even less than 5 ppm. Furthermore, calcium may be added to the steel, which causes the sulphides formed by the sulfur to be present in a form which damages the steel to a lesser extent than does the absence of calcium. The calcium content can be 10 to 30 ppm. The ppm figures refer to the mass ratio.

The steel is transformed starting with a cast block, for example by forging or rolling to form a blank from which the inner ring 1 is produced. The ratio of the cross-sectional area of the cast block to the cross-sectional area of the blank will be referred to as the forming ratio hereinafter. A high forming ratio means that a strong deformation, in particular a strong reduction of the cross-sectional area, was carried out by pressure. Because the deformation reduces the inclusion content of critical size and distribution in the steel, a high forming ratio means a large reduction in the content of critical size and distribution inclusions in the steel. A steel with few critical inclusions is in turn less susceptible to crack formation and other damage. Therefore, for the inner ring 1, preferably a steel with a forming ratio of at least 5: 1, in particular at least 8: 1 or even better at least 10: 1 is used.

The inner ring 1 is hardened by a heat treatment. For example, a martensite hardening is carried out. The process parameters of austenitizing, quenching and tempering carried out during martensite hardening are selected such that a residual aorthenite content of between 8 and 18% by volume, in particular between 10 and 16% by volume, results.

After completion of the heat treatment, the inner ring 1 is fed to a grinding process. As part of the grinding process, the inner ring raceway 2 is formed with a predetermined geometry and a predetermined surface finish. For example, distortions can be compensated by grinding. which are caused by hardening. Honing can also be followed by grinding in order to produce a particularly smooth surface with low roughness for good tribological properties.

In a further step, work hardening of the inner ring 1 takes place in the region of the inner ring raceway 2. Cold work hardening can be achieved, for example, by shot blasting, deep rolling and / or hot oil blasting of the inner ring raceway 2. To eliminate any surface damage or plastic deformation, the inner ring raceway 2 can be ground and / or honed following work hardening. However, surface finishing by grinding is only possible if the removal is so small that the effects achieved by work hardening are not unduly impaired. Cold work hardening by deep rolling results in significantly higher surface damage than cold work hardening by shot peening. Therefore, in many cases, preference will be given to deep-rolling or similar techniques over shot peening. In the case of cold work hardening by deep rolling, grinding will generally not be necessary, at best honing.

By work hardening compressive stresses are generated in the inner ring 1 in an edge layer, which have a very beneficial effect on the life of the bearing. Size and depth profile of the residual compressive stresses are explained in more detail with reference to FIG.

FIG. 2 shows a diagram for illustrating the course of the internal compressive stresses in the inner ring 1. The abscissa shows the depth below the surface of the inner ring raceway 2. The ordinate shows the value of the residual stress for the respective depth. Negative values of the residual stress mean that it is a compressive residual stress, positive values mean that it is a tensile residual stress. The residual stress has negative values in the whole illustrated range, which can be equated with the mentioned boundary layer, so that it is a compressive residual stress throughout. On the surface of the inner ring raceway 2, the absolute value of the compressive residual stress is slightly lower than 600 MPa, which is a typical value after honing. With increasing depth, the absolute value of the compressive residual stress first decreases to slightly above 400 MPa at a depth of approximately 0.01 mm. With increasing depth, the absolute value of the compressive residual stress increases again and approaches a value of 800 MPa at a depth of 0.20 mm to 0.25 mm, without, however, reaching it. At even greater depths, the absolute value of the residual compressive stress decreases again continuously.

It has been shown that a long life of the rolling bearing can be achieved if the absolute value of the residual compressive stresses does not fall below a minimum value to a minimum depth. The minimum depth should be 0, 1 mm, in particular 0.2 mm. The minimum value for the absolute value of the residual compressive stresses should be 200 MPa, in particular 400 MPa or 500 MPa. At greater depths than the minimum depth, the inner ring 1 can have residual compressive stresses with an absolute value below the minimum value. In particular, the absolute value of the compressive residual stresses at depths greater than the minimum depth may decrease with increasing depth. Furthermore, the absolute value of the residual compressive stresses over the entire depth range should not exceed a maximum value. The maximum value may be 1500 MPa, in particular 1000 MPa or even 800 MPa.

After work hardening and a possibly necessary to achieve suitable roughness mechanical surface finishing of the inner ring 1 is burnished. The blackening can be carried out in a manner described in DE-A-102007061 193. The burnished inner ring 1 is shown in FIG. Figure 3 shows a greatly enlarged section of the inner ring 1 in the region of the inner ring raceway 2 in a schematic sectional view.

The surface of the inner ring raceway 2 is formed by a thin burnishing layer 7. The thickness of the burnishing layer 7 can be less than 1 μηι or up to a few μηι. Thus, in the curve shown in FIG. 3, the burnishing layer 7 lies completely within the area of the first rise beginning at the surface, ie. H. within the range of decreasing values for the absolute value of compressive residual stress. The burnishing layer 7 is very dense and has a deep black color. In particular, the burnishing layer 7 is formed liquid-tight.

After burnishing, the inner ring 1 is subjected to a thermal aftertreatment. The thermal post-treatment is carried out at a temperature which is at least 10 K below the tempering temperature of the inner ring 1, for example in a range of 190 to 230 ° C. In any case, a temperature above 100 ° C should be selected. The thermal aftertreatment is particularly effective if it is carried out at a temperature which is a maximum of 100 K, better still a maximum of 50 K, below the tempering temperature. The temperature of the thermal aftertreatment can also be brought closer than 10 K to the tempering temperature. However, then a relatively accurate temperature control is to ensure to avoid exceeding the tempering temperature. The thermal after-treatment ensures that the structure of the inner ring 1 stabilizes. In this case, carbon atoms, comparable to Cottrell clouds, deposit on dislocations which form energetically favorable configurations (eg dipoles, multipoles) during plastic deformation during work hardening and surface hard machining by the sliding processes triggered thereby and thus stabilize these favorable dislocation arrangements , The running under Wälzbeanspruchung processes (eg Wälzermüdung) are thereby influenced advantageous, ie slowed down in particular in their material damaging effect. With the implementation of the thermal treatment of the inner ring 1 is completed and can be used to assemble the bearing.

Instead of martensite hardening, bainite hardening may be provided as the heat treatment. In this case, the thermal post-treatment is carried out at a temperature which is at least 10 K below the Bainitumwandlungstempe- temperature. The comments made in the case of martensite hardening on the temperature limits apply analogously.

In general, the thermal aftertreatment can be carried out at a temperature which is below, preferably at least 10 K below, the temperature of a last heat treatment step. In the case of martensite hardening, the last heat treatment step is tempering. Accordingly, the temperature of the last heat treatment step is the tempering temperature. In bainite hardening, the last heat treatment step is bainite transformation. Accordingly, the temperature of the last heat treatment step is the bainite transformation temperature.

The outer ring 3 and / or the rolling elements 5 may be made of the same material as the inner ring 1. When processing the outer ring 3 and / or the rolling elements 5, the process steps described for the inner ring 1 can be used individually or in combination. However, it is also possible to use modified process steps. Since the outer ring 3 is generally exposed to lower loads than the inner ring 1, it is not necessary to take over all the process steps described for the inner ring 1 also for the outer ring 3. For example, a work hardening in the outer ring 3 is not mandatory.

A premature failure of the rolling bearing is usually not by the permanent operation of the bearing permanently present nominal load, but rather by peak stress conditions associated with a momentary failure of the bearing kinetic. These critical operating conditions, which result from the action of vibrations on the bearing, are characterized in particular by high local sliding friction (high coefficient of friction) combined with high Hertzian pressure and can occur, for example, during starting and braking operations or emergency stops. Thus, by acting on the contact surface as a result of acting on the bearing, in practice often multi-dimensional vibrations locally, for. B. band or speckled, occurring mixed friction very high tensile stresses in the area near the surface occur, which can lead to the formation of cracks by typically 0.05 to about 0.2 mm deep brittle violent fracture. The cracks initiated at or near the raceway surface, with the assistance of the penetrating, aging lubricant, branch out into the material in a branching and expanding manner relatively rapidly due to vibration crack corrosion (corrosion fatigue), which leads to peelings, for example due to crack retractors, during further operation.

Overall, a reduction in the risk of premature failure and thus an increase in the life are achieved in the rolling bearing according to the invention by a tailor-made interaction of various measures. These measures include passivation, the use of a particularly pure steel, at least for the most stressed component, and strengthening deep below the surface, at least for the most stressed component.

Passivation can be achieved by stabilizing the near-surface microstructure, increasing resistance to (tribo) chemical attack, reducing local sliding friction under peak load and improving shrinkage. In particular, in view of the purity of the steel, oxygen and sulfur impurities are important because they are associated with inclusions such as oxides or sulfides. These inclusions constitute a risk for damage to the Rolling when they occur in near-surface areas, for example, to a depth of 200 μηι below the surface. Such near-surface inclusions represent critical weak points (stress concentrations) in the material at which the described friction stress-induced brittle fractures can be triggered more easily.

Compressive stresses of sufficient minimum thickness (eg 400 MPa) produced by work hardening to a sufficient depth (eg 0.4 mm) below the surface cause an increase of the material resistance against the formation of brittle surface force fracture cracks and also impede crack propagation below the Surface. This can be done by means of the generation of residual compressive stresses in the surface layer which has already been described in detail.

The measures described can significantly reduce the risk of premature failure of the rolling bearing.

The rolling bearing according to the invention can be used, for example, in a bearing arrangement of a paper machine. There, the rolling bearing according to the invention, in particular in a wire section for rotatably supporting a former roll or a suction roll, in a press section for rotatably supporting a screen roll or a suction roll, press roll, in a dryer section for supporting a felt roll, a drying cylinder or a Yankee cylinder or in a calender for Storage of a felt roll or a thermoroll are used. Some of these bearing arrangements are described in more detail below.

Figure 4 shows an embodiment of a bearing assembly of a paper machine in a sectional view. The bearing arrangement shown serves for the storage of press rolls and is operated with an oil circulation lubrication.

At both axial ends of a not figuratively shown and formed as a press roller roller a pin 8 is formed, the region of the inner ring 1 is included. Accordingly, two bearings per roller and thus two rolling bearings are provided according to the invention. In the embodiment of Figure 4, both bearings are identical and arranged mirror-symmetrically to each other. Therefore, only one bearing point is shown in FIG. By means of a nut 9, which is screwed onto a thread 10 of the pin 8, the inner ring 1 of the rolling bearing is secured on the pin 8. The inner ring 1 has two axially juxtaposed concave inner ring raceways 2, on which roll two sets of axially adjacent barrel-shaped rolling elements 5. The rolling elements 5 are guided in two axially adjacent cages 6 and continue to roll on a concave outer raceway 4 of an outer ring 3 from. Alternatively, a single cage 6 may be provided for both sets of rolling elements. The outer ring 3 is arranged in a bearing housing 1 1, which may be firmly anchored, for example, in a side wall of the paper machine not shown figuratively. The bearing housing 1 1 is sealed by a seal assembly 12 and a further seal assembly 13, which are arranged on one side axially adjacent to the rolling bearing, against the pin 8. The seal assembly 12 is disposed at a closer distance to the roller than the rolling bearing and the further seal assembly 13 at a greater distance from the roller than the rolling bearing. In the area of the further sealing arrangement 13, the housing 11 has a cover 14.

Figure 5 shows another embodiment of a bearing assembly of a paper machine in a sectional view. The bearing assembly shown in Figure 5 is used for storage of felt guide rollers in the dryer section of the paper machine and is operated with an oil lubrication.

Analogous to the exemplary embodiment of FIG. 4, according to FIG. 5, the roller, which is not shown in the figures and embodied as a felt guide roller, has a journal 8 at both axial ends which is received in regions by an inner ring 1 of the rolling bearing. Accordingly, in the exemplary embodiment of FIG. 5, in each case two bearing points and thus two rolling bearings according to the invention are provided per roller. seen. In contrast to Figure 4, the two bearings are formed differently in the embodiment of Figure 5 and therefore both shown in Figure 5.

The bearing shown on the left in Figure 5 has a rolling bearing, which is designed as a single-row Toroidalrollenlager, especially as a CA B bearing, and in addition to the inner ring 1 with a concave inner ring raceway 2, an outer ring 3 with a concave outer ring raceway 4 and a Set barrel-shaped rolling elements 5, which are guided in a cage 6 and roll on the inner ring raceway 2 and the outer ring raceway 4. The inner ring 1 is arranged on the pin 8 and fixed by means of a nut 9, which is screwed onto a thread 10 formed on the pin 8, on the pin 8. The outer ring 3 is arranged in a bearing housing 1 1. The bearing housing 1 1 is sealed by a seal assembly 12, which is arranged at a smaller distance from the roller than the rolling bearing, against the pin 8. In addition, the housing 1 1 is closed by a cover 14 which is arranged at a greater distance from the roller than the rolling bearing,

The bearing point shown on the right in Figure 5 is formed except for the configuration of the rolling bearing itself analogous to the bearing point shown on the left in Figure 5 and arranged mirror-symmetrically to this. The rolling bearing of the bearing point shown on the right in Figure 5 is designed as a double-row spherical roller bearings and has an inner ring 1 with two axially juxtaposed concave inner ring raceways 2, an outer ring 3 with a concave outer ring raceway 4 and two axially juxtaposed sets of barrel-shaped rolling elements 5, which are guided in one or in a common cage 6 and roll on the inner ring raceways 2 and the outer ring raceway 4. In a modification of the bearing assembly according to Figure 5, the bearing point shown on the left is formed analogous to the bearing point shown on the right and arranged mirror-symmetrically to this.

LIST OF REFERENCE NUMBERS

1 inner ring

2 inner ring raceway

3 outer ring

4 outer ring raceway

5 rolling elements

6 cage

7 burnishing layer

8 cones

9 mother

10 threads

1 1 bearing housing

12 sealing arrangement

13 further sealing arrangements

14 lids

Claims

P atentansprü che method for producing a rolling bearing and roller bearings

1. A method for producing a rolling bearing having an inner ring (1) with an inner ring raceway (2), an outer ring (3) with an outer ring raceway (4) and rolling elements (5) on the inner ring raceway (2) and on the outer ring raceway (4) unroll, where

- The inner ring (1) is made of steel,

- the inner ring (1) is subjected to a curing heat treatment, which is completed with the implementation of a last heat treatment step at a predetermined temperature,

- In the inner ring (1) by strain hardening in the region of the inner ring raceway (2) compressive stresses in an edge layer, which extends to a minimum depth below the surface of the inner ring raceway (2) are formed, and

- The inner ring (1) is browned after work hardening.

2. The method of claim 1, wherein the inner ring (1) is subjected to a martensite, insert or induction hardening before the work hardening and the temperature of the last heat treatment step is the tempering temperature of the inner ring (1).

3. The method of claim 1, wherein the inner ring (1) is subjected to a bainite hardening before the work hardening and the temperature of the last heat treatment step is the Bainitumwandlungstemperatur the inner ring (1).

4. The method according to any one of the preceding claims, wherein between the processing step of the work hardening and the processing step of the blackening, a mechanical surface finishing of the inner ring is performed.

5. The method according to any one of the preceding claims, wherein the burnished inner ring (1) is subjected to a thermal post-treatment at a temperature below the temperature of the last heat treatment step.

6. The method according to any one of the preceding claims, wherein the outer ring (3) and / or the rolling elements (5) of a curing heat treatment with a final heat treatment step, a work hardening, a burnishing treatment and / or a thermal post-treatment at a temperature be subjected to below the temperature of the last heat treatment step.

7. rolling bearing having an inner ring (1) with an inner ring raceway (2), an outer ring (3) with an outer ring raceway (4) and rolling elements (5), which roll on the inner ring raceway (2) and on the outer ring raceway (4) , in which

- The inner ring (1) is made of steel,

the inner ring (1) is hardened by a heat treatment,

- The inner ring (1) in the region of the inner ring raceway (2) in an edge layer which extends to a minimum depth below the surface of the inner ring raceway (2), formed by work hardening Druckeigenspan- has and

- The surface of the inner ring raceway (2) by a burnishing layer (7) is formed.

8. Rolling bearing according to claim 7, wherein the inner ring (1) is made of a steel having a sulfur content of 0.002 to 0.015 mass% and / or an oxygen content of less than 15 ppm.

9. Rolling bearing according to one of claims 7 or 8, wherein the inner ring (1) has a estaustenite content of 8 to 18% by volume.

10. Rolling bearing according to one of claims 7 to 9, wherein the inner ring (1) in the region of the inner ring raceway (2) in the boundary layer compressive stresses with an absolute amount equal to or above a minimum value and the minimum value of the absolute value of the compressive residual stresses 200 MPa.

1 1. Rolling bearing according to one of claims 7 to 10, wherein and the minimum depth is 0.1 mm.

12. Rolling bearing according to one of claims 7 to 1 1, wherein the inner ring (1) in the region of the inner ring raceway (2) in the surface layer compressive stresses with an absolute amount equal to a maximum value or less and the maximum value of the absolute value of the compressive residual stresses is 1500 MPa.

13. Rolling bearing according to one of claims 7 to 12, wherein the inner ring (1) in the edge layer by means of a thermal post-treatment after formation of the burnishing layer (7) modified microstructure.

14. Rolling bearing according to one of claims 7 to 13, wherein the outer ring (3) and / or the rolling elements (5) are burnished.

15. Bearing arrangement for rotatably supporting a component of a transmission, wherein the bearing arrangement comprises a rolling bearing according to one of claims 7 to 14.

16. Wind energy plant with a rolling bearing according to one of claims 7 to 14.

17. Bearing arrangement for rotatably supporting a roller or a cylinder, wherein the bearing arrangement comprises a roller bearing according to one of claims 7 to 14.

18. Bearing arrangement according to claim 17, wherein the roller or the cylinder is formed as a component of a paper machine.