Method for Inductive Surface Layer Hardening

Abstract

The invention relates to a method for the inductive surface layer hardening of a surface which runs around an annular component and has an initial zone, an end zone and two intermediate zones extending between the initial zone and the end zone. The initial zone is brought to hardening temperature by an inductor and quenched by a spray. Subsequently, an inductor arrangement is moved in each case along the intermediate zone to the end zone. Each inductor arrangement includes a leading inductor for preheating the region covered by it, a trailing inductor for finish-heating the preheated region and a spray for quenching the finish-heated region. After the inductor arrangements are located at a certain distance from the initial zone, the leading inductor of at least one of the inductor arrangements is moved in the direction of the end zone at an increased feed rate compared to the trailing inductor. The leading inductor thus reaches the end zone by a time interval earlier, whose duration is equal to the duration required by the trailing inductor to overcome the distance previously resulted between said trailing inductor and the leading inductor. In the meantime, the end zone is preheated by the leading inductor that reached it. When one of the trailing inductors of the inductor arrangements has arrived in the end zone, it heats the end zone to the finished hardening temperature.

Claims

1. A method for the inductive surface layer hardening of a surface which runs around an annular component consisting of a hardenable steel and which comprises an initial zone, two intermediate zones, of which the first intermediate zone is connected to the initial zone in a first circumferential direction and of which the second intermediate zone is connected to the initial zone in a second circumferential direction opposite to the first circumferential direction, and an end zone which extends between the ends of the intermediate zones facing away from the initial zone, comprising the following work steps: a) surface layer hardening of the initial zone by the initial zone being brought to hardening temperature by means of at least one inductor and being quenched by means of at least one spray, which directs a jet of a quenching medium onto the heated initial zone, b) successive surface layer hardening of the intermediate zones subsequent to the surface layer hardening of the initial zone, in each case by an inductor arrangement being moved, proceeding from a starting region of the respective intermediate zone adjoining the initial zone, along this intermediate zone to the end zone, wherein each inductor arrangement comprises a leading inductor, which causes preheating of the region of the intermediate zone respectively covered by it, a trailing inductor, which is arranged relative to the leading inductor in the direction of the initial zone and causes finish-heating of the region previously preheated by the leading inductor to hardening temperature, as well as a spray, which quenches, using a jet of a quenching medium, the region previously finish-heated in each case by the trailing inductor, ) surface layer hardening of the end zone subsequent to the surface layer hardening of the intermediate zones, by at least one of the trailing inductors of the inductor arrangements that reached the end zone heating the end zone to hardening temperature and the end zone being quenched by means of a spray, which, after heating, directs a jet of a quenching medium towards the end zone, wherein, after the inductor arrangements in work step b) are located at a certain distance from the initial zone, the leading inductor of at least one of the inductor arrangements is moved at least temporarily in the direction of the end zone at an increased feed rate compared to the trailing inductor of this inductor arrangement such that an enlarged distance results between the leading inductor and the trailing inductor and the leading inductor reaches the end zone by a time interval earlier, whose duration is equal to the duration required by the trailing inductor to cover the distance previously resulted between the trailing inductor and the leading inductor, that the at least one leading inductor arriving first at the end zone preheats the end zone until at least one of the trailing inductors of the inductor arrangements has arrived in the end zone and finish-heats the end zone to hardening temperature.

2. The method according to claim 1, wherein the electrical power of the inductor leading at increased feed rate is increased compared to the electrical power with which the relevant leading inductor is operated as long as it is moved at the same feed rate as the trailing inductor of its inductor arrangement.

3. The method according to claim 1, wherein the electrical power of the trailing inductor is increased compared to the electrical power with which the relevant trailing inductor is operated as soon as the leading inductor is moved at increased feed rate.

4. The method according to claim 1, wherein, in the work step a), the heating of the initial zone to hardening temperature is carried out by an inductor of one of the inductor arrangements.

5. The method according to claim 4, wherein the inductor is one of the trailing inductors.

6. The method according to claim 5, wherein the trailing inductor, after the initial zone is heated to hardening temperature, is moved in the direction of the starting region of the intermediate zone assigned to its inductor arrangement and in that the jet of the spray provided for quenching the initial zone is then directed to the initial zone in the space freed up by the inductor moving away.

7. The method according to claim 1, wherein the leading inductors of both inductor arrangements are moved at least temporarily in the direction of the end zone at an increased feed rate compared to the trailing inductor of this inductor arrangement, after the inductor arrangements in work step b) are located at a certain distance from the initial zone.

8. The method according to claim 7, wherein the inductors leading at increased feed rate preheat the end zone together after they reach the end zone.

9. The method according to claim 7, wherein of the inductors leading at increased feed rate, after they reach the end zone, one is removed from the end zone, while the other preheats the end zone.

10. The method according to claim 1, wherein the end zone is finish-heated by the trailing inductors of the inductor arrangements together to hardening temperature.

11. The method according to claim 1, wherein an additional spray is used to quench the end zone, which is independent of the sprays of the inductor arrangements and is in a waiting position during the heating of the end zone.

12. The method according to claim 1, wherein the component is moved in a rotary manner during its surface layer hardening at least temporarily in at least one of its circumferential directions.

13. The method according to claim 1, wherein the inductor respectively provided for the preheating and/or finish-heating of the end zone is moved relative to the end zone during the preheating and/or finish-heating.

14. The method according to claim 1, wherein the increased feed rate of the leading inductors is 240-1800 mm/min.

15. The method according to claim 1, wherein the feed rate, at which the trailing inductors are moved along the intermediate zones, is 180-1200 mm/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention is explained in more detail below on the basis of a drawing representing an exemplary embodiment.

[0045] FIGS. 1-8 each show a device for surface layer hardening in different phases of the method according to the invention schematically and not to scale in plan view.

[0046] The device 1 represented in FIGS. 1-8 is for example used for the surface layer hardening of a race surface 2 which runs around the outer circumference of a bearing ring 3 for a large-size rolling bearing consisting of a suitable steel material known for this purpose.

[0047] For this purpose, the device 1 comprises a horizontally aligned workpiece holder 4, which can optionally be rotated about a central vertical axis X and in which the bearing ring 3 is clamped in a horizontal orientation.

[0048] The race surface 2 of the bearing ring 3 is composed without interruption of an initial zone A, two intermediate zones Z1, Z2, and an end zone E. The intermediate zones Z1, Z2 are each connected with their starting regions S1, S2 to an assigned edge of the initial zone A. The one intermediate zone Z1 thereby extends in a first circumferential direction U1 and the second intermediate zone Z2 extends in a circumferential direction U2 of the bearing ring opposite to the first circumferential direction U1. The end zone E extends between the end regions B1, B2 of the intermediate zones Z1, Z2 assigned to it and is arranged opposite the initial zone A here. While the intermediate zones Z1, Z2 each extend approximately over half of the arc plotted by the race surface 2, the initial zone A and the end zone E each occupy only one correspondingly short section of the circumferential length of the race surface 2 compared to the length of the intermediate zones.

[0049] The device 1 further comprises four inductors 5, 6, 7, 8, each of which are supported by actuating devices not shown here, which move the inductors 5-8 in all degrees of freedom required here.

[0050] The device 1 also comprises sprays 9, 10, 11, of which the sprays 9, 10 are also carried by actuating devices which move the sprays 9, 10 in the manner required here. In contrast, the spray 11 is arranged stationary in the vicinity of the end zone E of the race surface 2 of the bearing ring 3. It can be pivoted out of a waiting position, in which it is located outside the space in which the inductors 5-8 and the sprays 9, 10 move, to an operating position in which it directs jets of a suitable quenching medium known for these purposes towards the end zone E. The quenching medium can be, for example, water or an aqueous polymer solution.

[0051] In FIGS. 1-8, the inductors 5-8 and the sprays 9-11, which are switched on in the operating state represented in the respective figure, are represented as black-filled rectangles, while those inductors 5-8 and sprays 9-11, which are not switched on in the respective operating state, are represented as white-filled rectangles.

[0052] The inductors 5, 6 and the spray 10 together form a first inductor arrangement 12 indicated in FIG. 1 by a dashed border, while a second inductor arrangement 13 is formed by the inductors 7, 8 and the spray 9, which in FIG. 1 is indicated by a dot-dashed border.

DESCRIPTION OF THE INVENTION

[0053] At the beginning of the surface layer hardening (FIG. 1) of the race surface 2, the inductor 7 of the second inductor arrangement 13 is positioned directly opposite the initial zone A and switched on in order to heat the initial zone A to the hardening temperature. The second inductor 8 of the inductor device 13 is simultaneously switched off in a waiting position in the circumferential direction U2 offset with respect to the inductor 8 above the starting region S2 of the intermediate zone Z2 directly adjoining the initial zone A.

[0054] The spray 10 of the inductor arrangement 12, which is also switched off, is offset in the radial direction and arranged behind the inductor 8 in relation to the bearing ring 3.

[0055] Inductors 5 and 6 and spray 9 are also switched off and are in a waiting position. Thus, the inductor 6 is arranged next-adjacent to the inductor 7 above the starting region S1 of the intermediate zone Z1, the inductor 5 is arranged offset to the inductor 6 in the circumferential direction U1 also above the starting zone S1 and the spray 9 is positioned behind the inductor 6 offset in the radial direction in relation to the bearing ring 3. The distance of the spray 9 to the bearing ring 3 is smaller than the distance of the spray 10 to the bearing ring 3. In this way, the sprays 9 and 10 can be moved past one another in the respective circumferential direction U1, U2 without colliding.

[0056] In the case of the inductor arrangement 12, in relation to a movement in the circumferential direction U1, the inductor 5 is therefore a leading inductor in relation to the inductor 6 and the inductor 6 is a trailing inductor in relation to the inductor 5. In contrast, in the case of the inductor arrangement 13, in relation to a movement in the circumferential direction U2, the inductor 8 is a leading inductor in relation to the inductor 7 and the inductor 7 is a trailing inductor in relation to the leading inductor 8.

[0057] As soon as the initial zone A is heated to hardening temperature (FIG. 2), the inductors 7 and 8 and with it the assigned spray 9 are moved suddenly and rapidly in the circumferential direction U1 along the intermediate zone Z2 such that the trailing inductor 8 frees up the space previously occupied by it at the initial zone A and the spray 9 is located opposite the initial zone A. It is situated in this position between the bearing ring 3 and the spray 10 of the inductor arrangement 12. The spray 9 now directs a jet of the quenching medium onto the initial zone A such that said initial zone A is quenched by forming hardening structures in a surface layer adjoining the race surface 2. At the same time, the inductors 5, 6, 7, 8 of the inductor arrangements 12, 13 are switched on and moved along the respectively assigned intermediate zone Z1, Z2 at a continuous feed rate V1, V2 (V1=V2). The respectively leading inductors 5, 8 each carry out preheating of the regions covered by their electromagnetic field, whereas the respectively trailing inductors 6, 7 heat up the previously preheated regions of the intermediate zones Z1, Z2 to hardening temperature.

[0058] The trailing inductors 6, 7 are followed by the respectively assigned spray 9, 10, which direct the quenching media towards the regions of the intermediate zones Z1, Z2 previously heated to hardening temperature and quench them by forming hardening structures in the respective region of the surface layer (FIG. 3).

[0059] In order to keep the inductors 5-8 in each case in tangential orientation and at a constant distance from the race surface 2, the inductor arrangements 12, 13 are moved in a manner known per se not only in the horizontal plane along the bearing ring 3, but also additionally rotated about a vertical axis.

[0060] As soon as the inductor arrangements 12, 13 are each located at a certain distance a from the initial zone A, which corresponds, for example, to 60%, 70%, 80% or 90% of the length of the intermediate zones Z1, Z2 measured in the circumferential direction, the leading inductors 5, 8 of the inductor arrangements 12, 13 are moved at increased speed V1′, V2′ (V1′=V2′) in the direction of the end zone E along the respectively assigned intermediate zone Z1, Z2. The trailing inductors 6, 7, on the other hand, continue to be moved at the feed rate V1, V2 with the sprays respectively assigned to them. As a result, the distance b between the trailing and the leading inductors 5, 6 and 7, 8 of the inductor arrangements 12, 13 is enlarged continuously until the leading inductors 5, 8 reach the end zone E (FIG. 4, 5).

[0061] The leading inductor 8 of the inductor arrangement 13 is now switched off and moved to a waiting position. At the same time, the leading inductor 5 of the inductor arrangement 12 is positioned centrally over the end zone E and starts with the preheating of the end zone E (FIG. 6). This preheating is continued until the trailing inductors 6, 7 reach the end regions B1, B2 of the intermediate zones Z1, Z2. As soon as this has occurred, the leading inductor 5 arranged above the end zone E is switched off and moved to a waiting position. As a result, the trailing inductors 6, 7 are arranged together above the end zone E so that they together heat the end zone E to hardening temperature. Meanwhile, the sprays 9, 10 quench the end regions B1, B2 of the intermediate zones (FIG. 7). Alternatively, it would also be possible to switch off one of the trailing inductors and to also move it to a waiting position and use only the other trailing inductor to heat up the end zone E to hardening temperature.

[0062] When end zone E is heated to hardening temperature, the trailing inductors 6, 7 are also removed from the end zone E, switched off and moved to a waiting position. The sprays 9, 10 are also switched off and moved to a waiting position. The end zone E is quenched using the spray 11 which, after the trailing inductors 6, 7 have been removed from the end zone E, is pivoted into the space freed up as a result. Proceeding from their waiting positions, the leading and trailing inductors 5, 6; 7, 8 and sprays 9; 10 belonging to the respective inductor arrangement 12; 13 are returned to their initial positions shown in FIG. 1. The slip-free surface layer hardening of the race surface 2 is thus completed.

[0063] The invention thus provides a method for the inductive surface layer hardening of a surface running around an annular component, which is composed of an initial zone, an end zone and two intermediate zones extending between the initial and end zone. The initial zone is brought to hardening temperature by an inductor and quenched by a spray. Subsequently, an inductor arrangement is moved in each case along the intermediate zone up to the end zone E. Each inductor arrangement comprises a leading inductor for preheating the region covered by it, a trailing inductor for finish-heating the preheated region and a spray for quenching the finish-heated region. After the inductor arrangements are located at a certain distance from the initial zone, according to the invention, the leading inductor of at least one of the inductor arrangements is moved in the direction of the end zone at an increased feed rate compared to the trailing inductor. The leading inductor thus reaches the end zone by a time interval earlier, whose duration is equal to the duration required by the trailing inductor to overcome the distance previously resulted between said trailing inductor and the leading inductor. In the meantime, the end zone is preheated by the respectively leading inductor, which reached to the end zone with a time advantage over the trailing inductor assigned to it. When one of the trailing inductors of the inductor arrangements has arrived in the end zone, it finish-heats the end zone to hardening temperature.

REFERENCE NUMERALS

[0064] 1 Device for the surface layer hardening of the race surface 2 [0065] 2 Race surface of the bearing ring 3 [0066] 3 Bearing ring [0067] 4 Workpiece holder [0068] 5, 8 Leading inductors [0069] 6, 7 Trailing inductors [0070] 9, 10 Moving sprays [0071] 11 Stationary spray [0072] 12 First inductor arrangement comprising the leading inductor 5, the trailing inductor 6 and the spray 10 [0073] 13 Second inductor arrangement comprising the leading inductor 8, the trailing inductor 7 and the spray 9 [0074] a Distance between the inductor units 12, 13 and the initial zone A [0075] b Distance between the trailing inductors 6, 7 and the leading inductors 5, 8 of the inductor units 12, 13 [0076] A Initial zone of the race surface 2 [0077] B1, B2 End regions of the intermediate zones Z1, Z2 [0078] E End zone of the bearing surface 2 [0079] S1, S2 Starting regions of the respective intermediate zones Z1, Z2 [0080] U1 First circumferential direction [0081] U2 Circumferential direction opposite the first circumferential direction U1 [0082] V1, V2 Feed rates [0083] V1′, V2′ Increased feed rates [0084] X Vertical axis of the workpiece holder 4 [0085] Z1, Z2 Intermediate zones of the race surface 2