Method for Inductive Surface Layer Hardening

Abstract

The invention provides a method for the inductive surface layer hardening of a surface running around an annular component of a hardenable steel, which achieves uniform and uninterrupted hardening. For this purpose, a) an initial zone of the surface is surface layer hardened by it being brought to hardening temperature by means of an inductor and being quenched with a spray. b) The surface is then hardened by means of a stationarily arranged inductor arrangement and a movably arranged inductor arrangement, which each comprise a leading inductor for preheating the region of the surface covered by it, a trailing inductor offset in the direction of the initial zone for finish-heating the pre-heated region to the hardening temperature and a spray for quenching the finish-heated region, wherein the movable inductor arrangement is moved along the surface and at the same time the annular component rotates about an axis of rotation in order to move the surface to be hardened along the stationary inductor arrangement. The speed of the movable inductor arrangement along the surface is greater than its circumferential speed. c) An end zone of the surface is then hardened by the leading inductor of one of the inductor arrangements being moved temporarily in the direction of the end zone at an increased feed rate compared to its trailing inductor when the end zone is located at a certain distance from inductor arrangements such that an enlarged distance results between the leading inductor and the inductor trailing it and the leading inductor is located at the end zone by a time interval earlier, whose duration is equal to the duration required by the trailing inductor to cover the distance resulting between the trailing inductor and the leading inductor such that the at least one leading inductor arriving first at the end zone preheats the end zone until the trailing inductor is located at the end zone and finish-heats the end zone to hardening temperature. Finally, the finish-heated end zone is quenched by means of a spray.

Claims

1. A method for the inductive surface layer hardening of a surface running around an annular component consisting of a hardenable steel, which has an initial zone, which is surface layer hardened at the beginning, and an end zone, which is surface layer hardened at the end, 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 surface, to be surface layer hardened, of the annular component subsequent to the surface layer hardening of the initial zone by means of two inductor arrangements, which each comprise a leading inductor, which causes preheating of the region, respectively covered by it, of the surface be surface layer hardened, a trailing inductor, which is arranged offset with respect 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 the region, respectively previously finish-heated by the trailing inductor, of the surface to be surface layer hardened with a jet of a quenching medium, wherein the one inductor arrangement is arranged stationary, the other inductor arrangement is designed to be movable and is moved along the surface to be surface layer hardened for the purpose of surface layer hardening, and simultaneously the annular component rotates about an axis of rotation in order to move the surface to be surface layer hardened along the stationary inductor arrangement, wherein the speed at which the movable inductor arrangement moved along the surface to be surface layer hardened is greater than the circumferential speed of the surface, to be surface layer hardened, of the annular component; c) hardening of the end zone by the leading inductor of at least one of the inductor arrangements being 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 when the end zone located at a certain distance from the inductor arrangements such that an enlarged distance results between the relevant leading inductor and the trailing inductor assigned to it and the leading inductor is located at 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 resulting between the trailing inductor and the leading inductor such that the at least one leading inductor arriving first at the end zone preheats the end zone until the trailing inductor of its inductor arrangement is located at the end zone and finish-heats the end zone to hardening temperature, wherein the end zone finish-heated to hardening temperature is then quenched by means of a spray.

2. The method according to claim 1, wherein the speed at which the movable inductor arrangement is moved along the surface to be surface layer hardened is twice the circumferential speed of the surface, to be surface layer hardened, of the annular component.

3. The method according to claim 1, wherein the leading inductor of the movable inductor arrangement is moved in the direction of the end zone at increased feed rate when the end zone is located at a certain distance from the inductor arrangements.

4. The method according to claim 1, wherein the leading inductor of the stationary inductor arrangement is moved towards the end zone opposite the direction of rotation of the surface to be hardened when the end zone is located at a certain distance from the inductor arrangements.

5. The method according to claim 3, wherein the leading inductors of the movable and of the stationary inductor arrangement are simultaneously moved towards the end zone when the end zone is located at a certain distance from the inductor arrangements.

6. The method according to claim 5, wherein the feed rate of the leading inductors has the same value.

7. The method according to claim 1, wherein the end zone is quenched by one of the sprays of at least one of the inductor arrangements after being finish-heated to the hardening temperature.

8. The method according to claim 1, wherein the end zone is quenched by a spray, which is provided separately and is independent of the inductor arrangements, after being finish-heated to the hardening temperature.

9. 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The invention is explained in more detail below on the basis of a drawing representing an exemplary embodiment,

[0050] FIGS. 1-9b 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.

DESCRIPTION OF THE INVENTION

[0051] The device shown in FIGS. 1-9b is used for the surface layer hardening of a circumferential surface 2a of a bearing ring 2. It comprises an inductor arrangement 1, which is arranged stationary and which has a preheating inductor 1a, a finish-heating inductor 1b and a spray 1c. The preheating inductor 1a is arranged in a circumferential direction U in front of the finish-heating inductor 1b at the circumferential surface 2a to be hardened of the bearing ring 2. The finish-heating inductor 1b, which is also arranged closely adjacent to the circumferential surface 2a, is in turn positioned in the circumferential direction U in front of the spray 1c, which is arranged offset outwards in the radial direction with respect to the circumferential surface 2a compared to the inductors 1a, 1b.

[0052] In addition, the device has a movable second inductor arrangement 3, which can be moved along the bearing ring 2 in the circumferential direction U. The second inductor arrangement 3 comprises a preheating inductor 3a, a finish-heating inductor 3b arranged behind the preheating inductor 3a in the circumferential direction U and a spray 3c arranged behind the finish-heating inductor 3b in the circumferential direction U. The spray 3c is positioned offset outwards in the radial direction with respect to the circumferential surface 2a of the bearing ring 2 such that, in the start position in which the movable inductor arrangement 3 is located in close proximity to the stationary inductor arrangement 1 (see FIG. 1), said spray is arranged behind the finish-heating inductor 1b of the stationary inductor arrangement 1 in relation to the circumferential surface 2a, but can be moved along in front of the spray 1c of the stationary inductor arrangement 1 in relation to the circumferential surface 2a.

[0053] The bearing ring 2 aligned horizontally during the surface layer hardening is held in a workpiece holder 4 which can move it in a rotating manner about its vertically aligned central axis X in the circumferential direction U at a circumferential speed V1.

[0054] In the start position, the finish-heating inductor 3b of the movable inductor arrangement 3 is positioned in the circumferential direction U directly next to the finish-heating inductor 1b of the stationary inductor arrangement 1. The spray 1c of the stationary inductor arrangement 1 is located in relation to the circumferential surface 2a offset outwards in the radial direction behind the finish-heating inductor 3b. The bearing ring 2 stands still or is operated in an oscillating manner in a small angular range in order to homogenize the heat input when heating the initial zone A of the circumferential surface 2a to be hardened. The inductors 1a, 1b of the stationary inductor arrangement 1 and 3a, 3b of the movable inductor arrangement 3 now together heat the initial zone A (FIG. 1).

[0055] As soon as the hardening temperature is reached in the initial zone A, the bearing ring 2 is rotated about the axis X in the circumferential direction U such that the circumferential surface 2a runs around the axis X at a circumferential speed V1. The spray 1c of the stationary inductor unit 1 is switched on and quenches the initial zone A moving along it.

[0056] At the same time, the preheating inductors 1a, 3a of the stationary and of the movable inductor units 1, 3 are also switched on and the movable inductor unit 3 is moved at a speed V2 in the circumferential direction U along the circumferential surface 2a of the bearing ring 2. The speed V2 is twice the circumferential speed V1 (V2=2×V1). The spray 3c of the movable inductor arrangement 3 is also switched on as soon as it has passed the finish-heating inductor 1b of the stationary inductor arrangement 1 (FIG. 2).

[0057] During the movement along the circumferential surface 2a, the zone of the circumferential surface 2a respectively located in the operating region of the inductor unit 3 is successively hardened and quenched. In this case, the preheating inductor 3a causes preheating and the finish-heating inductor 3b causes finish-heating of the respective zone to hardening temperature, while the spray 3c quenches the zone heated to hardening temperature in order to generate hardening structures in the surface layer adjoining the circumferential surface 2a.

[0058] At the same time, the preheating inductor 1a of the stationary inductor arrangement 1 heats the zone of the circumferential surface 2a moved along it, which is then finish-heated by the finish-heating inductor 1b of the stationary inductor arrangement 1 in order to be subsequently quenched by the spray 1c of the stationary inductor arrangement 1. Due to the feed rate V2 of the movable inductor arrangement 3 being twice the circumferential speed V1, the relative speed between the inductor arrangement 3 and the circumferential surface 2 is the same as the circumferential speed V1. Accordingly, the movable inductor arrangement 3 moves at the same speed towards the end zone E of the circumferential surface 2a as the end zone E towards the stationary inductor arrangement 1 (FIGS. 2-4).

[0059] The successive hardening of the circumferential surface 2a is continued until the end zone E of the circumferential surface 2a has approached the preheating inductor 1a of the stationary inductor arrangement 1 at a certain distance. From this point on, the preheating inductor 3a of the movable inductor arrangement 3 is moved at an additionally increased feed rate V2′ compared to the feed rate V2 so as to lead the finish-heating inductor 3b of the movable inductor arrangement 3 in the direction of the end zone E. At the same time, the preheating inductor 1a of the stationary inductor arrangement 1 is moved towards the end zone E in a direction opposite the movement of the preheating inductor 3a and opposite the rotational movement of the bearing ring 2 at a speed V1′ which has the same value as the speed V2′. The finish-heating inductor 3b and the spray 3c as well as the bearing ring 2 continue to be moved unchanged during this time. In this way, the preheating inductors 1a, 3a meet above the end zone E at a position situated exactly between the finish-heating inductors 3b and 1b (FIG. 5).

[0060] Once this position is reached, both preheating inductors 1a, 3a are moved together in the direction of the stationary finish-heating inductor 1b at a feed rate that is set such that a relative movement no longer takes place between the preheating inductors 1a, 3a and the end zone E, while the finish-heating inductor 3b and the spray 3c as well as the bearing ring 2 continue to be moved unchanged until the inductor 1a is back in its original stationary position. During this phase, the end zone E is preheated together by the preheating inductors 1a, 3a (FIG. 6).

[0061] The preheating inductor 3a of the movable inductor arrangement 3 is now switched off and moved to a waiting position remote from the circumferential surface 2a. The preheating inductor 3a is moved further at the speed V2′ in the direction of the stationary finish-heating inductor 1b, while the finish-heating inductor 3b and the spray 3c as well as the bearing ring 2 continue to be moved unchanged until the preheating inductor 3a has approached the finish-heating inductor 3b (FIG. 7).

[0062] The preheating inductor 3a is now also switched off and moved into a waiting position, while the movable finish-heating inductor 3b is moved further with the spray 3c at the speed V2 in the circumferential direction U towards the stationary finish-heating inductor 1b, while the bearing ring 2 continues to move at the circumferential speed V1 until the moving finish-heating inductor 3b is in a position directly adjacent to the stationary finish-heating inductor 1b. The movement of the bearing ring 2 is now stopped and the finish-heating of the end zone E, which is now exactly below the finish-heating inductors 1b, 3b, is carried out together by the finish-heating inductors 1b, 3b (FIG. 8).

[0063] Alternatively, it would also be possible here to switch off both preheating inductors 1a, 3a and bring them into the waiting position as soon as they have approached one another, and then to continue the movements of bearing ring 2 and movable finish-heating inductor 3b and spray 3c until the finish-heating inductor 3b has reached its position next-adjacent to the finish-heating inductor 1b and situated above the end zone E.

[0064] If the hardening temperature is reached in the end zone E, according to a first variant, the finish-heating inductors 1b, 3b are pivoted away from the end zone E and the quenching is carried out by means of an additional spray 5 (FIG. 9a) or, according to a second variant, the bearing ring 2 rotates at fast speed in the circumferential direction U until the end zone E is arranged under the stationary spray 1c, which then performs the quenching (FIG. 9b).

[0065] The invention thus provides a method for the inductive surface layer hardening of a surface 2a running around an annular component of a hardenable steel, which achieves uniform and uninterrupted hardening. For this purpose, an initial zone A of the surface 2a is surface layer hardened by it being brought to hardening temperature by means of an inductor 1a, 1b, 3a, 3b and being quenched with a spray 1c, 3c. The surface 2a is then hardened by means of a stationarily arranged inductor arrangement 1 and a movably arranged inductor arrangement 1, 3, which each comprise a leading inductor 1a, 3a for preheating the region of the surface 2a covered by it, a trailing inductor 1b, 3b offset in the direction of the initial zone A for finish-heating the pre-heated region to the hardening temperature and a spray 1c, 3c for quenching the finish-heated region, wherein the movable inductor arrangement 3 is moved along the surface 2a and at the same time the annular component 2 rotates about an axis of rotation X in order to move the surface 2a to be hardened along the stationary inductor arrangement 1, wherein the speed V2 of the movable inductor arrangement 3 along the surface 2a is greater than its circumferential speed V1. An end zone E of the surface 2a is then hardened by the leading inductor 1a, 3a of one of the inductor arrangements 1, 3 being moved temporarily in the direction of the end zone E at an increased feed rate V1′, V2′ compared to its trailing inductor 1b, 3b when the end zone E is located at a certain distance from the inductor arrangements 1, 3 such that an enlarged distance results between the leading inductor 1a, 3a and the inductor 1b, 3b trailing it and the leading inductor 1a, 3a is located at the end zone E by a time interval earlier, whose duration is equal to the duration required by the trailing inductor 1b, 3b to cover the distance resulting between the trailing inductor and the leading inductor such that the at least one leading inductor 1a, 3a arriving first at the end zone E preheats the end zone E until the trailing inductor 1b, 3b is located at the end zone E and finish-heats the end zone E to hardening temperature. Finally, the finish-heated end zone E is quenched by means of a spray 1c, 3c, 5.

REFERENCE NUMERALS

[0066] 1 Stationary inductor arrangement [0067] 1a Preheating inductor of the inductor arrangement [0068] 1b Finish-heating inductor of the inductor arrangement [0069] 1c Spray of the inductor arrangement [0070] 2a Circumferential surface of the bearing ring 2 to be hardened [0071] 2 Bearing ring (=annular component) [0072] 3 Movable inductor arrangement [0073] 3a Preheating inductor of the inductor arrangement 3 [0074] 3b Finish-heating inductor of the inductor arrangement 3 [0075] 3c Spray of the inductor arrangement 3 [0076] 4 Workpiece holder [0077] 5 Additional spray [0078] A Initial zone of the circumferential surface 2a to be hardened [0079] E End zone of the circumferential surface 2a to be hardened [0080] U Circumferential direction [0081] V1 Circumferential speed of the bearing ring 2 [0082] V1′ Feed rate of the preheating inductor 1a [0083] V2 Movement speed of the movable inductor arrangement 3 [0084] V2′ Increased feed rate of the preheating inductor 3a [0085] X Vertically aligned central axis of the workpiece holder 4