SURFACE-HARDENED, ROTATIONALLY SYMMETRICAL WORKPIECE, HARDENING METHOD AND HARDENING APPARATUS

Abstract

The invention relates to a surface-hardened, rotationally symmetrical workpiece, to a hardening method and to a hardening apparatus. The proposed hardening apparatus comprises a machine frame on which two coaxially arranged rotary bearings designed to support a rotationally symmetrical workpiece are arranged, at least one rotary bearing being operatively connected to a drive device to generate rotation of the workpiece; and at lease one laser apparatus for generating focussed, high-energy radiation is arranged on said rotary bearing, said laser apparatus being movable in the axial direction, and the radiation being directed toward the workpiece.

Claims

1. A method, comprising: obtaining a rotationally symmetrical workpiece with a lateral surface and a longitudinal axis, wherein at least a portion of the lateral surface comprises hardened portions of differing diameters formed by: generating, via at least one laser device, concentrated high-energy laser radiation that acts on an area of action of the lateral surface; moving the at least one laser device along the longitudinal axis of the workpiece such that the laser radiation acts on differing portions of the lateral surface along the longitudinal axis of the workpiece; rotating the workpiece about its longitudinal axis at a first rotational speed when the laser radiation acts on a first portion of the lateral surface along the longitudinal axis having a first local diameter to form a first hardened portion; and rotating the workpiece about its longitudinal axis at a second rotational speed that differs from the first rotational speed when the laser radiation acts on a second portion of the lateral surface along the longitudinal axis having a second local diameter that differs from the first local diameter to form a second hardened portion, wherein the first and second rotational speeds of the workpiece are dependent on the radiation output of the laser device, the size of the area of action and the respective first and second local diameters of the workpiece, such that an energy per unit area that is introduced into the first and second portions is substantially constant.

2. The method of claim 1, wherein the workpiece is configured as a shape roll for a rolling mill.

3. The method of claim 2, wherein the shape roll comprises a shaft with at least one caliber arranged thereon, and wherein outer lateral surface portions of the at least one caliber comprises the hardened portions.

4. The method of claim 1, wherein the workpiece is configured as a crusher cone.

5. The method of claim 1, wherein the workpiece is configured as a drive shaft.

6. The method of claim 5, wherein the drive shaft comprises a bearing seat arranged thereon, and wherein outer lateral surface portions of the at least one bearing seat the hardened portions.

7. The method of claim 1, wherein the second local diameter is less than the first local diameter, and the second rotational speed is greater than the first rotational speed.

8. The method of claim 1, wherein the second local diameter is greater than the first local diameter, and the second rotational speed is less than the first rotational speed.

9. The method of claim 1, wherein the laser device is held fixed in place in relation to the longitudinal axis of the workpiece for at least one full revolution of the workpiece when the laser radiation acts on a portion of the first portion of the lateral surface and the workpiece is rotated at the first rotational speed, and when the laser radiation acts on a portion of the second portion of the lateral surface and the workpiece is rotated at the second rotational speed.

10. The method of claim 9, wherein the laser device is moved along the longitudinal axis by a selectable axial adjusting displacement after being held fixed in place for the at least one full revolution such that the laser radiation acts on other portions of the respective first and second portions of the lateral surface.

11. The method of claim 10, wherein cycles of the laser device being held fixed in place for the at least one full revolution and then moved along the longitudinal axis by the selectable axial adjusting displacement are repeated one or more times such that the laser radiation acts on all of the first and second portions of the lateral surface.

12. The method of claim 10, wherein the selectable axial adjusting displacement is less than or equal to an axial extent of the area of action.

13. The method of claim 12, wherein cycles of the laser device being held fixed in place for the at least one full revolution and then moved along the longitudinal axis by the selectable axial adjusting displacement are repeated until the area of action of the laser device passes over all of the first and second portions of the lateral surface without any gaps.

14. The method of claim 1, wherein, during the rotation of the workpiece at at least one the first rotational speed and the second rotational speed, the laser device moves continuously along the longitudinal axis.

15. The method of claim 14, wherein the laser device moves continuously along the longitudinal axis in a pattern that comprises: moving axially from a first axial position to a second axial position in relation to the lateral surface, and after moving axially from the first axial position to the second axial position, moving axially back from the second axial position to the first axial position.

16. The method of claim 14, wherein the laser device moves along the longitudinal axis of the workpiece at an axial speed that is dependent on the rotational speed of the workpiece and the axial extent of the area of action such that the area of action of the laser device passes over at least the first and second portions of the lateral surface of the workpiece without any gaps.

17. A hardening apparatus for the surface hardening of a rotationally symmetrical workpiece, comprising: a frame; two coaxially-arranged rotary bearings that are arranged on the frame and are configured to receive a rotationally symmetrical workpiece, wherein at least one rotary bearing is operatively connected to a drive device configured to rotate the workpiece about a longitudinal axis thereof; at least one laser device that is arranged on the frame and is configured to generate concentrated high-energy radiation that acts on an area of action of a lateral surface of the workpiece when the workpiece is rotated by the drive device and rotary bearings; and a control device configured to: rotate the workpiece about its longitudinal axis at a first rotational speed via the drive device and rotary bearings, and generate the laser radiation via the at least one laser device such that the laser radiation acts on a first portion of the lateral surface along the longitudinal axis having a first local diameter to form a first hardened portion; and rotate the workpiece about its longitudinal axis at a second rotational speed that differs from the first rotational speed via the drive device and rotary bearings, and generate the laser radiation via the at least one laser device such that the laser radiation acts on a second portion of the lateral surface along the longitudinal axis having a second local diameter that differs from the first local diameter to form a second hardened portion, wherein the first and second rotational speeds of the workpiece are dependent on the radiation output of the at least one laser device, the size of the area of action and the respective first and second local diameters of the workpiece, such that an energy per unit area that is introduced into the first and second portions is substantially constant.

18. The hardening apparatus of claim 17, wherein the at least one laser device comprises a plurality of laser devices that are arranged and aligned at a respective radial distance from the lateral surface of the workpiece, and distributed about the longitudinal axis of the workpiece, and wherein the plurality of laser devices are configured such that the generated radiation impinges on the workpiece over an entirety of a circumference of the workpiece.

19. The hardening apparatus of claim 17, wherein the at least one laser device is operatively connected to a second drive device that is configured to longitudinally move the at least one laser device relative to the workpiece.

20. The hardening apparatus of claim 17, wherein the control device is further configured to longitudinally move the at least one laser device at a speed that is dependent on the rotational speed of the workpiece and an axial extent of the area of action such that the area of action of the at least one laser device passes over at least the first and second portions of the lateral surface of the workpiece without any gaps.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0036] The invention is explained in more detail below on the basis of exemplary embodiments and associated drawings, in which

[0037] FIG. 1 shows a schematic representation of two shape rolls interacting in a steel rolling mill,

[0038] FIG. 2 shows a crusher cone of a cone crusher, and

[0039] FIG. 3 shows the surface hardening of a shape roll by means of two laser devices.

DETAILED DESCRIPTION

[0040] FIG. 1 shows two interacting, oppositely running shape rolls 1, as are used in steel rolling mills for the production of steel profiles. The term “caliber” 2 relates to the shaping in the roll barrel for the rolling of long products. The circumferential grooves in the shape rolls 1 along with the grooves of the counter roll and the roll spacing produce the shape. The closed calibers 2 shown here, respectively formed by the interaction of the upper and lower shape rolls 1, allow all-round shaping. Shape rolls 1 are subject to a very high level of wear in their life cycle. This wear can be reduced, and their lifetime thereby increased considerably, by a hardened surface layer of the shape roll 1.

[0041] FIG. 2 shows by way of example the structure of a cone crusher, which is used for breaking up rock. In a crusher housing 3, a crusher cone 4 is arranged at a distance from the inner wall of the crusher housing 3 that becomes smaller from the top downward. The crusher cone 4 is fitted in such a way as to rotate about its vertical axis. Pieces of rock fed in from above are broken up by the friction to which the rock is subjected between the inner wall of the crusher housing 3 and the outer lateral surface of the crusher cone 4. The fragments thereby produced fall further into the downwardly tapering annular gap between the crusher housing 3 and the crusher cone 4 and are in turn broken up. This process continues until the fragments produced are so small that they are no longer held in the annular gap and therefore fall downward out of the cone crusher. Because of the action of the pieces of rock, the crusher cone 4 is also subjected to a very high level of wear. This wear can be reduced by a hardened surface layer of the lateral surface of the crusher cone 4, and its lifetime thereby increased considerably.

[0042] With the proposed hardening method it is possible either to subject the lateral surface of the crusher cone 4 to a complete surface hardening, or only to harden the lateral surface selectively, for example in strips. In this case it is also possible for example to produce hardened strips that form a rhomboid pattern. The selective hardening has the effect that the pieces of rock wear away the unhardened areas more, so that over time erosion effects that increase the breaking-up effect of the cone crusher occur between the hardened areas.

[0043] FIG. 3 shows a first method variant for the surface hardening of a shape roll 1 in the area of the calibers arranged on it. For this purpose, the shape roll 1 is rotatably mounted in a hardening apparatus, which generates a controlled rotational movement of the shape roll 1.

[0044] Arranged on or alongside the hardening apparatus is at least one laser device 5, which may be held for example by an industrial robot that is movable in all directions. The laser device 5 projects a laser beam directly onto the shape roll 1. By means of a control device, the laser beam follows the geometry of the shape roll in a spiral, lines or other conceivable forms.

[0045] By this method, hardness traces with a hardening depth of about 1 mm are produced on the shape roll 1. The hardness is determined by the material and may be an increase of up to about 30% in comparison with the base material.

[0046] Unfortunately, the formation of traces has an adverse influence on the geometry of the rolled stock. This formation of traces occurs if the laser beam does not have the necessary width to cover the entire profile, so that many traces have to be laid next to one another in a spiral in the radial direction, or where the laser bombardment begins and ends.

[0047] To avoid the formation of traces, the overlapping of adjacent traces may be increased such that a uniform hardness layer is produced, for example in that adjacent traces overlap by 5 mm or 10 mm.

[0048] A further possibility for avoiding the formation of traces is to irradiate the shape roll 1 with two laser devices 5, which move around the shape roll 1. For this purpose, the laser devices 5 may begin with the irradiation together at any desired point on the shape roll 1 and then move on an encircling path around the shape roll 1. The two laser devices 5 meet on the exactly opposite side (180°) of the shape roll 1 and end the irradiation.

[0049] Alternatively, one laser device 5 may be fixedly arranged, the shape roll 1 set in a rotational movement and the second laser device 5 moved in a circling manner as far as the starting point (360°).

LIST OF DESIGNATIONS

[0050] 1 Shape roll [0051] 2 Caliber [0052] 3 Crusher housing [0053] 4 Crusher cone [0054] 5 Laser device