EP2812147A1

EP2812147A1 - Device for the laser processing of a surface of a workpiece or for the post-treatment of a coating on the outside or the inside of a workpiece

Info

Publication number: EP2812147A1
Application number: EP13704583.7A
Authority: EP
Inventors: Paul Alexander Harten; Peter Bruns; Vitalij Lissotschenko; Thomas Mitra
Original assignee: Limo Patentverwaltung GmbH and Co KG
Current assignee: Limo GmbH
Priority date: 2012-02-10
Filing date: 2013-02-11
Publication date: 2014-12-17
Also published as: CN105665934A; WO2013117754A1; KR20140122252A; US20160151862A1; CN104136163B; CN104136163A; JP2015512786A

Abstract

The invention relates to a device for the processing of a surface of a workpiece or for the post-treatment of a coating on the outside or the inside of a workpiece, in particular a metal workpiece, preferably a pipe, comprising a process head (2) that can be moved through the workpiece or outside of the workpiece, an optical fiber (5), means for feeding laser light (10) to the process head (2) or means for producing laser light in the process head (2), and optical means (7) arranged in the process head, which can apply the laser light (10) to the inside or the outside of the workpiece.

Description

DEVICE FOR LASER-PROCESSING A SURFACE OF A WORKPIECE OR FOR TREATING A COATING ON THE OUTSIDE OR THE INSIDE OF A WORKPIECE

The present invention relates to an apparatus for processing a surface of a workpiece or for the post-treatment of a coating on the outside or the inside of a

Workpiece, in particular a metal workpiece, preferably a tube. The invention further relates to a method for

Machining a surface of a workpiece or for

Post-treatment of a coating on the outside or the inside of a workpiece, in particular with a device of the aforementioned type. The invention further relates to a method for coating the outside or the inside of a workpiece.

The workpiece may in particular consist of metal or comprise metal. Furthermore, it may in particular have a cylindrical shape and be, for example, a pipe or a rod. The coatings which can be processed with the aid of the invention may comprise, for example, at least one layer which is in contact with the

High-speed flame spraying or plasma spraying or which is a spray-applied, wetting or delustered coating.

Such coatings are often intended to serve as anti-corrosion or wear-resistant coatings. As a rule, the coatings must be thermally post-processed in order to convert the applied powdered materials into a solid one

to achieve a coherent layer. The aftertreatment of a coating arranged in the interior of a pipe proves to be particularly complicated. The problem underlying the present invention is the provision of a device of the type mentioned, which can effectively treat a, in particular arranged in the interior of a pipe, coating or can effectively work a surface of a workpiece. Furthermore, methods for processing a surface of a workpiece or for the post-treatment of a coating on the outside or inside of a

Workpiece and for coating the outside or the

Indicated inside a workpiece.

This is achieved by a device having the features of claim 1 and by the method having the features of claims 16 and 18. The dependent claims relate

preferred embodiments of the invention.

According to claim 1 it is provided that the device is movable through the workpiece or outside the workpiece

Process head, an optical fiber for supplying laser light to the process head or means for generating laser light in the

Process head and optical means in the process head includes, which can act on the inside or the outside of the workpiece with the laser light. By the application of laser radiation, a surface of a workpiece can be processed effectively or the coating can be effectively reworked, with it being possible in particular for a coating, smelting or melting of coating constituents to be carried out on or into the surface of the underlying workpiece.

With the aid of a device according to the invention or a

According to the invention not only coatings are workable, but also uncoated metal surfaces. A device according to the invention allows, in a similar manner such as coatings also post-process polished and / or ground metal surfaces which have been pretreated by other methods, for example mechanical machining

Processing, dry cleaning / etching by immersion in

/ Brushing the workpiece with a solution, mechanical grinding / polishing with mechanical grinding and / or

Polishing tools.

When working on metal surfaces, these can

be melted or heated selectively below the melting point. In the case of melting smoothes at the

Surface surface tension acting surface surface with achievable roughness Ra <0.5 μηπ. When heated below the melting point, a targeted structural change takes place within the heat-affected zone at the surface of the workpiece. Such structural changes are known in various forms, for example as annealing, sintering or curing.

The last-mentioned forms (annealing, sintering, hardening) and the smoothening of a molten surface can be used in the same way for the laser after-treatment of coatings.

For example, the process header may look like one from another

Engineering areas known pig through the interior of the

in particular designed as a tube workpiece in the axial

Be moved direction.

There is the possibility that the optical means comprise a component which is designed in such a way that the laser light in the component is deflected by internal reflection and / or refraction, so that it is applied to the outside to be treated or treated

Inside the workpiece passes. Such a component can be much easier to adjust and manufacture than, for example, a mirrored component on the outer sides of the laser light is reflected to the pipe inner walls.

It may be provided that the optical means such

are formed so that they can produce an annular intensity distribution of the laser light on the inside or the outside of the example formed as a pipe workpiece. These

annular intensity distribution can be determined by the movement of the

Process head in the axial direction on the inside or the

Be moved outside of the tube along, so that thereby the application of laser light can be performed very quickly.

It can be provided that the optical means a

Homogenizer agents include, for example, a

is rotationally symmetrical component and in particular has a lens array with concentric or coaxially arranged lenses. By means of such a component, the laser light can be optimally shaped and homogenized for the annular intensity distribution.

In contrast to the established and known laser methods (small spot, movement of the laser spot for planar processing by movable mirrors), the method claimed in this application is characterized in particular in that it achieves a uniformly distributed heat-affected zone, and that it

is "transitionless". Transitionless means for the workpiece that no thermal stresses occur along the surface or along the coating on the workpiece during the laser treatment, which cracks in the surface

or produce the coating. In addition, the known, for example, from the classical surfacing Material increases or "caterpillars" avoided by the invention. This difference of the invention to classical laser methods is due to the fact that the workpiece is swept evenly over the workpiece by a device according to the invention with laser radiation, whereby edge effects are minimized. Large temperature differences in a small space are in a device according to the invention on the workpiece surface only in the direction of the feed, while in the classical laser treatment with a small spot in all

Directions along the surface are large temperature differences that lead to tensions.

The optical means may be designed such that the

Intensity distribution of the laser light at the front, in which the intensity distribution moves, has a different edge shape, as on the back. The flank shape of the

Intensity distribution at the front must be optimized for material not yet irradiated and the flank form of the intensity distribution at the back must be optimized for already irradiated material.

It can be provided that during the irradiation of the workpiece, the angle of incidence is not exactly 90 °. This has the advantage that no back reflections can get into the laser light source or the laser light sources.

Other features and advantages of the present invention will become more apparent from the following description

Embodiments with reference to the accompanying

Illustration. It shows

1 shows a schematic sectional view through a tube with a partially depicted first embodiment of a device according to the invention;

Fig. 2 is a schematic sectional view of a second

Embodiment of a component of the optical means of a device according to the invention with an exemplary laser beam;

Fig. 3 is a schematic sectional view of a third

4 is a schematic sectional view of a fourth

Fig. 5 is a schematic sectional view corresponding to Fig.4 of the fourth embodiment with a wider laser beam;

Fig. 6 is a schematic sectional view of a fifth

Embodiment of a component of the optical means of a device according to the invention with an exemplary laser beam; a schematic sectional view of a sixth

Embodiment of a component of the optical means of a device according to the invention with an exemplary laser beam is a perspective view of a homogenizer means a schematic representation (l (z) / z) of a first intensity distribution of the laser light on the workpiece. a schematic representation (l (z) / z) of a second intensity distribution of the laser light on the workpiece; a schematic representation (L (z) / z) of a third intensity distribution of the laser light on the workpiece; a schematic sectional view through a pipe with a partially mapped second embodiment of a device according to the invention; a schematic view of an optical structure of the device of FIG. 12; a schematic representation (l (z) / z) of a fourth intensity distribution of the laser light on the workpiece; an exemplary illustration of a linear

Intensity distribution.

In the drawings, the same or functionally identical parts are given the same reference numerals. In the embodiment of FIG. 1, a coating has been applied in a tube 1 on the inside thereof, which consists for example of powdered material. In particular, this may be a coating applied by means of high-speed flame spraying. In particular, this can

Coating Al ₂ 0 ₃ include. For example, the coating can be a few 100 μm thick.

By the device according to the invention, the coating on the inside of the tube 1 should be aftertreated. This can be done in particular by the fact that the coating with

Laser radiation is applied. As a result, the coating can be partially melted and the individual powdery components of the layer can be firmly joined together.

The finished coatings may, for example, be an anti-corrosion layer or a wear-resistant layer. The tube 1 may in particular consist of metal or comprise metal.

The device according to the invention comprises a laser light source 16 and a process head 2, which is movable in the interior of the tube 1, in particular in the axial direction. The laser light source 16 is shown only schematically and in particular not true to scale with an optical fiber 5 connected thereto, which is also not shown to scale. Laser light is to be understood in the present application not only visible light, but any type of laser radiation, such as IR radiation or UV radiation.

The process head 2 has in the illustrated embodiment to on its outside guide rollers 3, which on the

Can lie inside the tube 1. The process head 2 is with a guide tube 4, through which the laser light from an external laser light source can be supplied to the process head 2 via an optical fiber 5. Alternatively, in or on the

Process head 2 may be provided a laser light source.

The guide tube 4 can also be used to

To move process head 2 through the tube 1, in particular the process head 2 into the tube 1 and push it out of the tube 1. Through the guide tube 4 can continue

at least one line for process gases to be passed, for example, if the post-treatment of the coating to be carried out to be carried out under a protective gas atmosphere. From Fig. 1, nozzles 6, in particular annular nozzles 6 for the exit of the process gas can be seen.

In the process head 2, optical means 7 are arranged, which form the emerging from the end 8 of the optical fiber 5 laser light and can deflect to the inside of the tube 1. By way of example, the optical means comprise a cone-shaped component 9 which is particularly reflective on the outside and which can divert the laser light outwards onto the inner sides of the tube 1 such that an annular intensity distribution of the laser light arises there. This annular intensity distribution can be moved along the inside of the tube 1 in the axial direction by the movement of the process head 2, so that the application of laser light can thereby be effected very effectively.

The direction of movement of the process head 2 and thus the

Intensity distribution in the axial direction can be selected according to the application. It is thus either possible to move the process head 2 to the right in FIG. 1 or to the left in FIG. A criterion for the direction of movement can be, for example, whether the coating on the inside of the tube 1 before the irradiation is resistant enough to come in contact with the guide rollers 3, for example.

FIGS. 2 to 7 show further rotationally symmetrical components 9 which are not mirrored on their outside. In this case, FIGS. 2 to 4 and FIGS. 6 and 7 each show only a part of the laser light 10, which is incident off-center and is therefore deflected only to one side. Fig. 5, however, shows the incidence of a broad, the optical axis or the axis of symmetry of

9 component symmetrical laser light 10, the corresponding

is deflected radially outwards. In FIG. 5, this can be seen from the fact that a part of the laser light 10 is deflected both downwards and upwards.

In the exemplary embodiments according to FIGS. 2 to 5, the incident laser light 10 enters the component 9 through a planar surface 11 oriented perpendicularly to the laser light 10, experiences a total internal reflection on a further surface 12 and passes through a further surface 13 out. Due to the rotational symmetry of the component 9, this results in an annular intensity distribution of the

Laser light 10 on the inside of the tube. 1

In the embodiment according to FIG. 2, the laser light 10 is deflected overall by an angle of approximately 75 °. Both

Embodiments according to FIG. 3 to FIG. 5, the laser light 10 is deflected in total by an angle of about 90 °.

In the embodiments according to FIGS. 6 and 7, this occurs

Laser light 10 in a plane, inclined to the direction of incidence of the laser light 10 surface 11 in the component 9 a. In the embodiment of FIG. 6, the laser light passes without internal reflection by a Surface 13 of the component 9 from. In the embodiment according to FIG. 7, the laser light 10 experiences a total internal reflection on a further surface 12 and exits through a surface 13.

In the embodiment according to FIG. 6, the laser light 10 is deflected overall by an angle of approximately 55 °. In which

Embodiment of FIG. 7, the laser light 10 is deflected in total by an angle of about 90 °.

The optical means 7 may further at least one

Homogenizer 14 include, which may consist of a lens array with concentric or coaxially arranged lenses 15 in the case of a desired annular intensity distribution (see an embodiment in Fig. 8). Such a thing

Homogenizer means 14 may be designed so that it emits an angular distribution of the laser radiation with an M-profile. A comparable lens array is in WO 2012/095422 A2

described.

In FIGS. 9 to 11 are possible examples

Intensity distributions 17, 18, 19 of the laser light 10 on the

Inside of the tube 1 shown. In each case, the axial direction z is applied to the right, so that the representations show the profile of the laser radiation in the transverse direction of the ring. The arrow 20 indicates the direction of advance of the intensity distribution on the inside of the tube 1.

With the intensity distribution 17 shown in FIG. 9, a controlled post-heating of the coating can be achieved. The dashed line 21 indicates an exemplary Gaussian profile. From such a profile, the intensity distribution 17 deviates through a region 22 which is the rear edge of the distribution increases, so that after the maximum intensity 23, a phase longer reheating is achieved.

With the intensity distribution 18 shown in FIG. 10, a controlled preheating of the coating can be achieved. The dashed line 21 again indicates an exemplary Gaussian profile. From such a profile gives way to the

Intensity distribution 18 by an area 24 from which the

front flank of the distribution increases, so before the

Intensity maximum 23 a phase of preheating is achieved.

The intensity distribution 19 shown in FIG. 11 is a

exemplary combination of the intensity distributions 17, 18. With the intensity distribution 19 shown in Fig. 11, therefore, both a controlled preheating, as well as a controlled reheating of the coating can be achieved.

It is quite possible to provide other optical means which can produce a linear or a point-like intensity distribution of the laser light on the inside of the tube 1. In this case, then, the line-shaped or a point-like intensity distribution of the laser light by a rotational movement of the process head 2 or the optical means or the tube 1 in

Circumferential direction to be moved over the inside of the tube.

An example of such embodiments is shown in FIGS. 12 and 13. Fig. 13 shows the optical structure in which the

Optic means 7 a collimating lens 25, preferably

uniaxial two-stage homogenizer 26, a mirror 27 and a Fourier lens 28 include.

It may be provided that a line-shaped angular distribution of the laser light 10 is generated by the optical means 7, wherein the longitudinal direction of the line extends in the radial direction of the tube 1. Furthermore, the mirror 27, which is inclined at an angle of, for example, 45 ° to the axial direction of the tube 1, the line-shaped intensity distribution of the laser light 10 on the

Apply inside of the schematically indicated tube 1.

Here, the mirror 27 can be rotated together with the homogenizer 26 and possibly also with the other optical means 7 about the axial direction.

Through the mirror 27 is a in the axial direction Z

extending linear intensity distribution applied to the inside of the tube 1, which is moved by the rotation of the mirror or the optical means 7 and the feed of the process head 2 spirally over the inside of the tube 1. Fig. 12 illustrates this spiral movement schematically, wherein for clarity, the spiral has been stretched, so that between the individual

irradiated areas 29 unirradiated areas 30 can be seen. This structure is for illustrative purposes only. In practice, of course, a gapless or preferably overlapping action on the inside of the tube 1 with the laser light 10 is provided.

Fig. 14 shows an example of a possible intensity distribution 31 of the laser light 10 on the inside of the tube 1 as a function of z. In each case, the axial direction z is applied to the right, so that the representations show the profile of the laser radiation in the longitudinal direction of the linear intensity distribution. The arrow 20 again indicates the direction of advance of the intensity distribution 31 on the inside of the tube 1.

Fig. 14 illustrates that even in the linear

Intensity distribution 31 the flank 32, the unprocessed material irradiated and the edge 33, the illuminated material already irradiated, can be designed differently. However, the design can be adapted in detail to the thermal properties of the sample and the rotational speed of the line.

Fig. 15 shows once again the line-shaped intensity distribution 31 in plan view. It is schematically indicated that the extension of the beam cross-section in the z-direction (from left to right in FIG. 15) is significantly greater than in the direction perpendicular thereto (from top to bottom in FIG. 15), that of the circumferential direction of the tube 1 equivalent.

It is quite possible, the invention

Apparatus for the aftertreatment of coatings on the

Inside to use non-tubular workpieces.

Furthermore, the outsides of workpieces can be aftertreated with the device according to the invention.

For example, on the outside of a cylindrical workpiece, which may be a pipe but also a rod, a

circumferential annular intensity distribution of the laser radiation are generated. This "outer laser ring" can then be moved in the axial direction along the cylindrical workpiece.

Examples of preferred embodiments to be processed

Surfaces are polished and / or ground metal surfaces.

The laser radiation used in the processing of the surface or the aftertreatment of the coating may have a wavelength between 192 nm and 10700 nm. Furthermore, in the processing of the surface or the aftertreatment of

Coating used laser radiation have a power between 300 W and 300 kW. Furthermore, in the processing of the Surface or the aftertreatment of the coating laser radiation used have an intensity between 6 kW / cm ² and 1000 kW / cm ² .

Furthermore, the laser radiation used in the processing of the surface or the aftertreatment of the coating may have an extension of the line focus in the long axis between 1 mm and 6000 mm. Furthermore, the laser radiation used in the processing of the surface or the aftertreatment of the coating can have an extension of the line focus in the short axis between 50 μm and 5 mm.

The relative speed between the workpiece surface and the laser beam can be between 1 mm / s and 1000 mm / s.

There is a general possibility that the intensity distribution of the laser light at the front side, in which the intensity distribution moves in the axial direction of the tube 1, has a different flank shape than at the rear side. In this case, the flank shape of the intensity distribution at the front can be optimized for not yet irradiated material and the flank shape of the intensity distribution can be optimized at the back for already irradiated material.

Claims

claims:

1. Apparatus for processing a surface of a workpiece or for the aftertreatment of a coating on the

Outside or inside of a workpiece, in particular a metal workpiece, preferably a tube, comprising a process head (2) movable through the workpiece or outside the workpiece, an optical fiber (5) for supplying laser light (10) to the process head (2) or means for generating laser light in the process head (2), in the process head (2) arranged optical means (7) which can act on the inside or the outside of the workpiece with the laser light (10).

2. Device according to claim 1, characterized in that the optical means (7) comprise a component (9) which is designed such that the laser light (10) in the component (9) by internal

Reflection and / or refraction is deflected so that it reaches the machined or nachzubehandelnde outside or inside of the workpiece.

3. A device according to claim 2, characterized in that the component (9) is a rotationally symmetrical component.

4. Device according to one of claims 1 to 3, characterized

characterized in that the optical means (7) are designed such that they have an annular intensity distribution of

Laser light (10) on the inside of the particular as a tube (1) can produce trained workpiece or the outside of the particular cylindrical workpiece.

5. Device according to one of claims 1 to 4, characterized

characterized in that the optical means (7) a

Homogeniser include.

6. Apparatus according to claim 5, characterized in that the homogenizer means (14) is a rotationally symmetrical component and in particular a lens array with concentric or coaxially arranged lenses (15).

7. Device according to one of claims 1 to 3, characterized

in that the optical means (7) are designed such that they can produce a linear intensity distribution (31) of the laser light (10) on the inside or the outside of the workpiece, wherein the linear intensity distribution (31) is in particular in the axial direction (z ) of the particular cylindrical workpiece and can be moved spirally over the inside of the particular designed as a pipe (1) workpiece.

8. Device according to one of claims 1 to 7, characterized

in that the optical means (7) are designed in such a way that the intensity distribution of the laser light (10) at the front side, in which the intensity distribution moves, has a different flank shape than at the rear side.

9. Device according to one of claims 1 to 8, characterized

characterized in that the process head (2) in the axial direction through the tube (1) or outside of the cylindrical

Workpiece can be moved.

10. Device according to one of claims 1 9, characterized in that the process head (2) comprises means for dispensing process gas, in particular at least one nozzle (6).

11. Device according to one of claims 1 to 10, characterized

characterized in that the device comprises at least one

Laser light source (16) for generating laser light (10), wherein the laser light source (16) outgoing laser light (10) in particular via the optical fiber (5) to the process head (2) can be supplied.

12. Device according to one of claims 1 to 11, characterized

characterized in that the device comprises a guide tube (4) which is connected to the process head (2), wherein the guide tube (4) can serve to move the process head (2) relative to the workpiece.

13. The apparatus according to claim 12, characterized in that the optical fiber (5) extends through the guide tube (4).

14. Device according to one of claims 1 to 13, characterized

characterized in that the process head (2) on its

Outside guide means, in particular guide rollers (3), which may rest against the inside of the tube 1.

15. Device according to one of claims 1 to 14, characterized

characterized in that the coating is a thermal

sprayed coating is, in particular a through

High-speed flame spraying or plasma spraying applied coating, or that the coating is applied by spraying, by wetting and by coating applied coating.

16. A method for processing a surface of a workpiece or for the post-treatment of a coating on the

Outside or inside of a workpiece, in particular a metal workpiece, preferably a tube,

in particular with a device according to one of claims 1 to 15, characterized by the following method steps:

A process head (2) is moved, preferably in the axial direction, through the workpiece or outside the workpiece;

Laser light (10) is generated and applied by the process head (2) to the inside or outside of the workpiece for processing a surface of the workpiece or for post-treating the coating.

17. The method according to claim 16, characterized in that an annular intensity distribution of the laser light (10) on the inside of the particular as a tube (1) formed workpiece or on the outside of the particular

cylindrical workpiece is generated.

18. A method for coating the outside or the inside of a workpiece, in particular a metal workpiece, preferably a tube, characterized by the following method steps:

On the inside or the outside of the workpiece, a coating is applied, in particular by high velocity flame spray; the coating is aftertreated by a method according to one of claims 16 or 17.