LASER TEXTURING OF STEEL STRIP

Abstract

A method and an arrangement for finishing a steel strip including the texturing of the steel strip wherein a texture is applied to the surface of a moving steel strip by means of a single laser beam or a plurality of laser beams directed at the surface of a moving steel strip, and wherein the single laser beam or the plurality of laser beams are position controlled to apply a predetermined texture pattern on the surface of the moving steel strip.

Claims

1. A method for finishing a steel strip comprising the texturing of the steel strip wherein a texture is applied to the surface of a moving steel strip, wherein, a single laser beam or a plurality of laser beams is directed at the surface of a moving steel strip, and the single laser beam or the plurality of laser beams are position controlled to apply a predetermined texture pattern on the surface of the moving steel strip.

2. The method according to claim 1, wherein the laser beams are divided in groups each with a single laser beam or a plurality of laser beams, which groups are controlled separately.

3. The method according to claim 2, wherein the groups of laser beams are positioned over the width and/or direction of movement of the steel strip with respect to each other.

4. The method according to claim 2, wherein the groups of laser beams are controlled such that adjacent parts of the texture are applied with different groups of laser beams wherein the groups have different positions with respect to each other.

5. The method according to claim 2, wherein two or more groups of laser beams are controlled to form an interference pattern with a power density distribution suitable for texturing of the moving steel strip.

6. The method according to claim 2, wherein the control comprises the control of one or more of the laser beams and the position thereof within one or more of the different groups of laser beams.

7. The method according to claim 1, wherein the control comprises the focussing of laser beams into image points on the surface of the moving steel strip, and/or modulation of the power of the laser beam or beams and/or, shaping of the power density of the laser beam or beams.

8. The method according to claim 1, wherein the control comprises a correction for changes in the z-direction of the moving steel strip.

9. The method according to claim 1, wherein the texturing is carried out after temper rolling and/or levelling of the steel strip.

10. The method according to claim 1, wherein the line speed of the steel strip is in the range of up to and including 15 m/s.

11. The method according to claim 1, wherein the laser beam or beams or part of the beams are continuous wave laser beams.

12. The method according to claim 1, wherein the single laser beam or the plurality of laser beams are pulsed laser beams, wherein the pulse duration is in the range of 1 fs to 100 ms, the electromagnetic radiation of each laser beam has a wave length between 200 nm-11 m, and with an energy density of each laser beam in the range of 1 nJ/cm2-100 J/cm2.

13. An arrangement for the finishing of steel strip, wherein the arrangement comprises at least one laser beam source to generate a single laser beam or a plurality of laser beams to apply a texture to the surface of a moving steel strip, and control means to control the single laser beam or plurality of laser beams to apply a texture on a moving steel strip.

14. The arrangement according to claim 13, wherein the control means combine two or more laser beams to form an interference pattern with a power density distribution suitable for texturing of the moving steel strip.

15. The arrangement according to claim 13, wherein a laser beam splitter is provided for one or more of the laser beam sources to split the laser beam from a laser beam source into a plurality of laser beams.

16. The arrangement according to claim 13, wherein at least one position controlled laser beam deflector is provided in the laser beam path, to deflect the laser beam in one or more directions.

17. The arrangement according to claim 13, wherein a number of laser beam devices are positioned over the width and in the length of the path of the steel strip through the arrangement.

18. The arrangement according to claim 13, wherein the arrangement comprises a temper roll mill and wherein the temper roll mill is provided with a roll or rolls with a roughness Ra (c=2.5 mm) less than 6 m.

19. The method according to claim 1, wherein the single laser beam or the plurality of laser beams are pulsed laser beams, wherein the pulse duration is in the range of 1 fs to 100 ms, the electromagnetic radiation of each laser beam has a wave length between 200 nm-11 m, and with an energy density of each laser beam in the range of 0.1 J/cm2 to 10 J/cm2.

20. The arrangement according to claim 13, wherein the arrangement comprises a temper roll mill and wherein the temper roll mill is provided with a roll or rolls with a roughness Ra (c=2.5 mm) less than 2 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention will be further explained on hand of the example shown in the drawing, in which:

[0044] FIG. 1 shows schematically a processing order of temper rolling, tension levelling, coating and laser texturing,

[0045] FIG. 2a-d show different arrangements to apply a laser texturing to a steel strip in more detail, and

[0046] FIG. 3a-e show the typical surface results obtainable using laser texturing of a moving steel strip in more detail.

DETAILED DESCRIPTION OF THE DRAWINGS

[0047] In FIG. 1 a broad schematic is provided of the processing order. The processing starts with providing a steel strip, which in most cases will be provided with a coating such as a Zn-based coating as shown in block 1. After that the steel strip is subjected to a skin pass rolling, block 2, and to tension levelling, block 3, before a texture pattern is applied by means of laser texturing, block 4. After that, optionally a further metallic or organic coating could be applied to the textured steel strip, block 5. Of course, the laser texturing may also be conducted with or without the enveloping previous processing steps.

[0048] FIG. 2a shows an arrangement with a laser source 6 which generates one or more laser beams 7, a beam expander 8, a beam shaper 9 and a focussing element 10 to focus the laser beam on a steel strip 11.

[0049] FIG. 2b shows an arrangement which further comprises a beam splitter 12 to split the laser beam in a plurality of laser beams.

[0050] In the arrangement shown in FIG. 2c a beam deflector 13 is included which is used to deflect the laser beam in one, two, or even three dimensions.

[0051] In FIG. 2d control systems 14,15 for the arrangement are schematically indicated. Wherein control system is for the control of respectively laser source 6, beam expander 8, beam shaper 9, beam splitter 12 and beam deflector 13. Control system 15 is specifically for the control of focussing element 11.

[0052] Finally FIG. 3a-e show examples of a laser applied texture on steel samples with patterns of individual craters and/or grooves, with respectively grooves at about right angles to each other, a line of craters, an equidistant grid of craters, a regular line pattern and a cross-hatch line pattern.