WO2006097256A1

WO2006097256A1 - Method for producing a bearing arrangement

Info

Publication number: WO2006097256A1
Application number: PCT/EP2006/002254
Authority: WO
Inventors: Helmut Hauck; Alexander Dilje
Original assignee: Ab Skf
Priority date: 2005-03-18
Filing date: 2006-03-11
Publication date: 2006-09-21
Also published as: DE102005012602B3

Abstract

The invention relates to a method for producing a bearing arrangement (1) that has at least one bearing race (2), particularly an antifriction bearing race, and has a supporting element (3). In order to produce a durable weld joint between the bearing race and the supporting element, the method comprises the following steps: a) producing the bearing race (2) from steel by a machining and non-machining mechanical operation, this steel having a first concentration of carbon (C1); b) thermochemically enriching the entire edge layer (4) of the bearing race (2) with carbon (C) so that the entire edge layer (4) has a second concentration of carbon (C2) that is higher than the first concentration of carbon (C1); c) removing at least a portion of the carbon-enriched edge layer (4) in a partial area (5) of the bearing race (2); d) hardening the bearing race (2); e) welding the bearing race (2) with the supporting element (3), the weld seam (6) being placed in the partial area (5) in which the carbon-enriched boundary layer (4) was removed.

Description

E n g lis h

Method for producing a bearing arrangement

The invention relates to a method for producing a bearing arrangement which has at least one bearing ring, in particular a roller bearing ring, as well as a carrier element.

In many mechanical engineering applications bearing arrangements of the generic type are required, in which a bearing, in particular a roller bearing, is fixedly connected to a support member to receive and transmit the operating forces of the bearing can.

DE 199 19 201 C1, DE 199 35 469 A1 and DE 200 07 309 U1 show bearing arrangements in which roller bearings are placed in a bearing carrier, wherein at least the connection is also produced by a welding process. In this case, the production of the welded joint is not a problem because the end shield can be made of a material that is easily weldable. This is the case, in particular, for steel, which does not have too high a carbon content. The carbon concentration must generally not exceed 0.2% (weight percent), otherwise the steel at the weld embrittles.

The problem is the production of a solid and stable connection between bearing ring and support element when the material of the bearing ring itself welded must become. In order for the bearing ring to have sufficient strength for its use, it is necessary to harden it.

For hardening, however, a sufficient carbon content is known to be required. For example, typical ball bearing steel (100 Cr 6) has a carbon content of 1%. This is contrary to the requirement to keep the ring weldable; With such a carbon content, the welding inevitably leads to embrittlement of the material, which reduces the strength of the welded joint.

It is known to manufacture a bearing ring made of case hardened steel, which is subjected to hardening of a thermochemical enrichments of the surface layer with carbon (carburizing). As a result, the initially low-carbon steel is enriched in its peripheral layer with carbon such that it becomes curable. The carburizing agent can be solid, liquid or gaseous, although pastes can also be used. The carburizing itself takes place at elevated temperature (above A3).

However, carburized high carbon content material again causes the problem of poor weldability.

The invention is therefore based on the basis of creating a bearing assembly of the type mentioned, which allows both a hardening of the bearing ring and a direct welding of the ring with the support element. In this case, the production of the bearing assembly with known and in practice usually available machinery and equipment should be straightforward. So it should be an economic solution for the production of carbon-hardened bearing rings, especially rolling bearing rings, created, which are directly weldable. The weld should connect the bearing ring thereby directly to the support element. The object of this invention is characterized by a method comprising the following steps:

a) producing the bearing ring made of steel by a machining or non-cutting mechanical machining operation, wherein the steel is a first

Having carbon concentration;

b) Thermochemical enrichment of the entire surface layer of the bearing ring with carbon, so that the entire surface layer has a second carbon concentration which is higher than the first

Carbon concentration;

c) removing at least part of the carbon-enriched surface layer in a partial region of the bearing ring;

d) hardening of the bearing ring;

e) welding the bearing ring to the support element, wherein the weld is applied in the portion in which the carbon-enriched surface layer has been removed.

The invention thus provides that in a first sub-process of the bearing ring is carburized. Then the carburized area is removed there again in a subsequent step, z. B. turned off, where the support element to be welded later. After the subsequent hardening, the carrier element is then welded. Since the carburized region has been removed from the bearing ring in the connection region of the carrier element, there is a sufficiently low carbon content for welding. However, since the other surface areas of the bearing ring have remained carburized, these areas after curing to a sufficiently high hardness. The mechanical machining operation according to the above step a) is preferably a turning operation, or the operation has such.

In most cases, after the above step d) and before step e), the bearing ring is subjected to a hard machining operation; this is usually a grinding process.

The first carbon concentration is preferably so low that a firm and stable weld between the bearing ring and the carrier element can be produced. In practice, proven values are below 0.2%, preferably below 0.1%, for the carbon content or the carbon concentration.

The second carbon concentration is advantageous, however, so great that a hardening of the material is easily possible; proven values for the second carbon concentration in the steel are above 0.2%, preferably above 0.5%.

The removal of the carbon-enriched surface layer according to the above step c) is preferably carried out so that the bearing ring in this area after the

Removing the enriched surface layer has a carbon concentration, which is a solid and stable weld between the bearing ring and the

Carrier element allows. It is preferably provided that the

Carbon concentration at the surface of the bearing ring in the portion after removal of the enriched surface layer below 0.2%, preferably below 0.1%. Removing the carbon-enriched

Edge layer is advantageously done by a turning process.

It is not mandatory that the entire carburized layer is removed again; it only has to be removed so much surface material that a stable welding is possible. Another solution is based on the following consideration: The bearing ring can initially be manufactured with a protruding section that exceeds the intended

Protrudes final contour. This protruding portion is then removed before curing, so that the geometric final contour of the bearing ring is formed (apart from the remaining allowance for the hard fine machining). According to this concept, it is thus provided that the bearing ring according to the above step a) is produced with a preferably cylindrical outer or inner surface such that the

Bearing ring in the said portion of the bearing ring has an allowance. The radial allowance is preferably between 1 mm and 5 mm.

The welding of the bearing ring with the carrier element according to the above step e) can be carried out by means of laser beam welding or by electron beam welding. But there are also classic welding procedures possible.

The bearing ring is preferably made of case-hardened steel during its production according to the above step a).

The support member may also be formed by a spacer which holds two rolling bearings whose axes are parallel to each other at a defined distance.

A varied embodiment of the invention is based on the fact that the carrier element is formed by the ring of another rolling bearing. For example, two adjacent bearings whose axes are parallel to each other, are welded together at their outer rings, without a separate support member is used; the carrier element is rather formed by the further bearing ring. It is also possible that two bearing rings are welded together at their end faces.

With the proposed invention, a compact bearing assembly is achieved, on the one hand by a solid and stable direct weld between one of the bearing rings and the carrier element and on the other hand also comprises a bearing ring having a high hardness and thus the required wear resistance.

It is also advantageous that all process steps can be carried out with commonly available manufacturing processes and machines, so that the implementation of the inventive concept does not cause any investment costs.

It is also possible to realize almost any configuration for the bearing assembly, as far as the formation of the support member and its positioning on the bearing ring is concerned. In particular, special designs are easy to implement.

In the drawings, embodiments of the invention are shown. Show it:

1 is a bearing assembly in the finished state in section,

2 shows the bearing outer ring of the bearing assembly in a first manufacturing state in section,

3 shows the bearing outer ring of the bearing assembly in a second state of manufacture in section,

4 shows the bearing outer ring of the bearing assembly in a third state of manufacture in section,

Fig. 5 shows the bearing outer ring of the bearing assembly according to an alternative embodiment in a manufacturing state according to Fig. 3 and

6 shows the bearing outer ring of the bearing arrangement according to FIG. 5 in a manufacturing state according to FIG. 4. In Fig. 1, a bearing assembly 1 is outlined, comprising a roller bearing with a bearing outer ring 2. On the bearing ring 2, a plate-shaped support member 3 is laterally fixed, by welding. The weld is provided with the reference numeral 6.

The welding of the carrier element 3 on the bearing ring 2 was carried out here by laser welding.

The bearing assembly 1 can be defined with a screw connection 7 indicated only schematically, d. H. the carrier element 2 has corresponding through holes for screws.

The bearing assembly 1 is manufactured as follows:

In a first step, the bearing ring 2 is manufactured mechanically. The present after this process bearing ring 2 is outlined in Fig. 2. During production, machining (eg turning) or non-cutting (eg rolling) production processes can be used. In most cases, the sketched in Fig. 2 geometry is achieved by a turning operation. The bearing ring 2 consists of case steel with - still - low carbon concentration C ₁ . This is less than 0.2%, preferably less than 0.1%.

In Fig. 2, it is indicated that - which is done subsequently - carbon C is supplied to the bearing ring. By this is meant that the prefabricated bearing ring 2 is introduced into a carbon atmosphere, in which a carburizing takes place in a known manner. The result of this process step can be seen in FIG. There, it is indicated that carbon has accumulated in the boundary layer 4 of the bearing ring 2, ie on all sides of its surface, so that a carbon concentration C ₂ of more than 0.2% is present in the boundary layer 4, preferably above 0.5%.

Thus, the bearing ring surface is curable, but no longer weldable. Therefore, in the subsequent step - as can be seen from FIG. 4 - the carburized layer is removed again in a partial region 5. In the embodiment, a rectangular in radial section groove is screwed in one of the two side portions of the bearing ring 2. It is indicated in FIG. 4 that material with a low carbon concentration Ci appears again at the groove surface.

In the further course (which is not illustrated any more in the figures), the carrier element 3 (see Fig. 1) is inserted into the groove-shaped recess and then welded into it. The welded connection has high strength because the welded joint between the material of the carrier element (low carbon content) and the material of the bearing ring 2 at the point of contact with the carrier element 3 with low carbon content C _{1 is} produced.

In FIGS. 5 and 6 an alternative exemplary embodiment is sketched:

Here, the bearing ring 2 is rotated in its mechanical production with an oversize x. Ie. the cylindrical outer surface of the bearing ring 2 has in the portion 5 radially a larger amount, namely a larger by the allowance x radius.

In Fig. 5, the state after carburizing is shown. As can be seen, the entire edge region of the bearing ring 2 again has a higher carbon concentration C ₂ , which is higher than the carbon content C _{1 of} the remaining ring.

Before hardening, the allowance x is removed, ie, turned off, for example, so that the contour sketched in FIG. 6 results. As can be seen there further, there is a low carbon concentration ci on the surface of the subregion 5, which is later welded to the carrier element 3, which enables optimum welding. Ie. the carburized region present in subregion 5 is removed or at least significantly reduced until a sufficiently low carbon concentration for welding is present.

LIST OF REFERENCE NUMBERS

1 bearing arrangement

2 bearing ring

3 carrier element

4 edge layer

5 subarea

6 weld

7 screw connection

C ₁ first carbon concentration

C ₂ second carbon concentration x allowance C carbon

Claims

P atentansprü CH eVerfahren for producing a bearing assembly

1. A method for producing a bearing arrangement (1) which has at least one bearing ring (2), in particular a roller bearing ring, and a carrier element (3), the method comprising the steps:

a) producing the bearing ring (2) from steel by a machining or non-cutting mechanical machining operation, the steel having a first carbon concentration (C ₁ );

b) thermochemically enriching the entire surface layer (4) of the bearing ring (2) with carbon (C) so that the entire surface layer (4) has a second carbon concentration (c ₂ ) which is higher than the first carbon concentration (C ₁ );

c) removing at least part of the carbon-enriched surface layer (4) in a partial region (5) of the bearing ring (2);

d) hardening of the bearing ring (2);

e) welding of the bearing ring (2) with the support element (3), wherein the weld seam (6) in the portion (5) is mounted, in which the

Carbon-enriched surface layer (4) was removed.

2. The method of claim I _5, characterized in that the mechanical machining operation according to step a) of claim 1 is a turning operation or has such.

3. The method according to claim 1 or 2, characterized in that after step d) and before step e) according to claim 1, the bearing ring (2) is subjected to a hard machining operation.

A method according to claim 3, characterized in that the hard machining operation is or includes a grinding operation.

5. The method according to any one of claims 1 to 4, characterized in that the first carbon concentration (C ₁ ) is so low that a solid and stable

Welded connection between the bearing ring (2) and the carrier element (3) can be produced.

6. The method according to claim 5, characterized in that the first carbon concentration (C ₁ ) in the steel below 0.2%, preferably below 0, 1%.

7. The method according to any one of claims 1 to 6, characterized in that the second carbon concentration (c ₂ ) is so large that a hardening of the material is possible.

8. The method according to claim 7, characterized in that the second carbon concentration (c ₂ ) in the steel above 0.2%, preferably above 0.5%.

9. The method according to any one of claims 1 to 8, characterized in that the removal of the carbon-enriched surface layer (4) according to step c) of claim 1 is carried out so that the surface of the bearing ring (2) in this region (5) Removing the enriched surface layer has a carbon concentration which is a solid and stable

Welded connection between the bearing ring (2) and the support element (3) allows.

10. The method according to claim 9, characterized in that the carbon concentration on the surface of the bearing ring (2) in the

Subregion (5) after removal of the enriched edge layer (4) below 0.2%, preferably below 0, 1%.

11. The method according to any one of claims 1 to 10, characterized in that the removal of the carbon-enriched surface layer (4) according to

Step c) of claim 1 by a turning operation.

12. The method according to any one of claims 1 to 11, characterized in that the bearing ring (2) according to step a) of claim 1 with a cylindrical outer or inner surface is made so that the bearing ring (2) in the

Part area (5) of the bearing ring (2) has an allowance (x).

13. The method according to claim 12, characterized in that the radial allowance (x) is between 1 mm and 5 mm.

14. The method according to any one of claims 1 to 13, characterized in that the welding of the bearing ring (2) with the carrier element (3) according to step e) according to claim 1 by means of laser beam welding.

15. The method according to any one of claims 1 to 13, characterized in that the welding of the bearing ring (2) with the carrier element (3) according to step e) according to claim 1 by means of electron beam welding.

16. The method according to any one of claims 1 to 15, characterized in that the bearing ring (2) is made in its manufacture according to step a) according to claim 1 of case-hardened steel.

17. The method according to any one of claims 1 to 16, characterized in that the carrier element (3) is formed by a ring of another rolling bearing.