Method for manufacturing a skinning roller, skinning roller and method for skinning a hot-dip coated steel strip

Abstract

According to claim 1, the invention relates to a method for manufacturing a skinning roller, wherein the skinning roller is clamped in a rotary device and set into rotation at a rotational speed w, wherein a surface of the skinning roller to be processed is treated during rotation by means of at least one laser or an optic coupled to a laser, wherein the laser is operated with a repetition rate f, with a maximum laser power P, with a focus diameter d and a pulse duration t in order to generate a stochastic structure on the surface of the skinning roller, wherein the laser is controlled and / or regulated by means of a process computer, characterized in that the surface to be treated is divided by means of a program into a pixel pattern with n x m pixels, wherein each pixel of the pixel pattern has a resolution of up to p steps with respect to a predetermined depth.wherein the pixel pattern is numerically generated with a normally distributed depth distribution and with at least one Gaussian curve or a uniformly distributed depth distribution, and the pixel pattern generated thereby is implemented in a process computer for regulating and / or controlling the laser for processing the surface of the dressing roller.

Description

[0001] The invention relates to a method for manufacturing a dressing roller, a dressing roller and a method for dressing a hot-dip coated steel strip.

[0002] In current technology, rollers with an EDT surface are used for steel production. These rollers feature stochastic structures to adjust the surface properties of the thin steel sheets. The arithmetic mean roughness (Ra) and the peak count (RPc) are linked in this process. A higher arithmetic mean roughness results in a lower peak count. This contradicts the general requirements of automotive manufacturers, significantly limiting the usable parameter space.

[0003] These parameters can be freely adjusted using non-stochastic, so-called deterministic structures, which can be introduced into the rollers, particularly through laser texturing. Deterministic structures have the disadvantage of being sensitive to optical disturbances or surface defects. The slightest changes in a regular pattern (deterministic structure) are perceived by the human eye as errors and are considered disruptive. With random distributions, such as noise, these errors cannot be detected.

[0004] Methods for manufacturing laser-textured rollers, in particular with a random (stochastic) texture, are described by way of example in EP 2 794 178 B1 and in JP 2004-106 015 A. Further prior art is described in DE 10 2012 017 703 A1.

[0005] The object of the present invention is to provide a method for manufacturing a skin-coating roller with which a parameter space encompassing topography characteristics such as arithmetic mean roughness Ra and peak number RPc can be significantly expanded. Furthermore, it is an object of the present invention to provide a skin-coating roller and a method for skin-coating a hot-dip coated steel strip with which an advantageous surface can be provided for the manufacture of vehicle components.

[0006] This problem of manufacturing a tempering roller is solved by a method with the features of claim 1, for a tempering roller is solved by the features of claim 7, and for tempering a hot-dip coated steel strip is solved by a method with the features of claim 8. Further embodiments are described in the dependent claims.

[0007] The first teaching relates to a method for manufacturing a skinning roller, wherein the skinning roller is clamped in a rotary device and set into rotation at a rotational speed w, wherein a surface of the skinning roller to be processed is treated during rotation by means of at least one laser or an optic coupled to a laser, wherein the laser is operated with a repetition rate f, with a maximum laser power P, with a focus diameter d and a pulse duration t in order to generate a stochastic structure on the surface of the skinning roller, wherein the laser is controlled and / or regulated by means of a process computer, wherein the surface to be treated is divided by means of a program into a pixel pattern with n × m pixels, wherein each pixel of the pixel pattern has a resolution of up to p steps with respect to a predetermined depth.wherein the pixel pattern is numerically generated with a normally distributed depth distribution and with at least one Gaussian curve or a uniformly distributed depth distribution, and the pixel pattern generated thereby is implemented in a process computer for regulating and / or controlling the laser for processing the surface of the dressing roller.

[0008] To process the surface of the dressing roller, the surface to be processed, or rather the area developed from it, is divided into a pixel pattern. Each pixel represents depth information. This "discretization" of the surface creates a deterministic surface. The depth information of the individual pixels is, in particular, stochastically distributed. This results in a pixel pattern that overcomes the disadvantages of a deterministic structure. For example, topographic values ​​such as the arithmetic mean roughness Ra and the peak count RPc can be precisely set. The higher the pixel and depth resolution, the closer the surface is to a stochastic surface.

[0009] Laser processing is an ablation process. The degree of ablation can be adjusted via the maximum laser power P in conjunction with the focus diameter d. During processing, the point-to-point distance (pitch) and the line spacing, which can be set identically to the pulse interval, as well as the laser pulse duration, can be kept constant. A constant pulse duration allows the system complexity to be kept low, enabling the use of a commercially available pulsed laser. These lasers typically have a constant repetition rate. A combination of rotational speed w and repetition rate f results in a preferably constant pitch on the surface. This is essentially subject to natural fluctuations in the rotational speed of the skinning rollers and is negligible for this application.The line spacing in the axial direction is determined by the traverse speed v of the laser or the optics coupled to the laser. The traverse speed is preferably kept constant during processing. Particularly preferably, the pitch and line spacing are equal.

[0010] It is known to use random number generators with which a random, so to speak stochastic, pattern can be numerically generated. Corresponding programs are available on the market, for example, Matlab. In this program, a surface, particularly one to be processed, such as that of a dressing roller, can be transformed into a developed area and divided into n × m pixels. Thus, the area is divided into n pixels per row and m pixels per column, where n and m are integers. n and m can also be equal. Each pixel is chosen to be the same size or can vary, for example, depending on the developed area or surface. A pixel can also have a triangular, hexagonal, or other geometric shape, whereby this shape can be mapped seamlessly onto the developed area. Each pixel of the pixel pattern can preferably have a rectangular shape with a side length between 5 and 50 µm.Furthermore, each pixel of the pixel pattern has a resolution of up to p levels relative to a given depth. p corresponds to an integer and can be up to 2. 16 The number of steps can be, for example, up to 512 or 256 (8 bits: 0 to 255). The resolution of the steps can also be limited, in particular to up to 200 steps, preferably up to 150 steps, more preferably up to 128 steps, particularly preferably up to 64 steps, and more preferably up to 32 steps. A predetermined depth preferably corresponds to the deepest point that is or is intended to be created in the surface by the laser, so that the maximum or predetermined depth can be between 5 and 50 µm, in particular a maximum of 45 µm, more preferably a maximum of 40 µm, more preferably a maximum of 35 µm, and more preferably a maximum of 30 µm. One step thus corresponds to a depth of (highest step) -1× maximum or predefined depth. Each pixel thus represents depth information. The depth information of the individual pixels within the pixel pattern is therefore stochastically distributed. The pixel pattern is numerically generated using a normally distributed depth distribution and at least one Gaussian curve or a uniformly distributed depth distribution. The n × m pixels generated in this way are implemented in a process computer for regulating and / or controlling the laser for processing the surface of the tempering roller.

[0011] By selectively adjusting the aforementioned parameters on the laser using regulation and / or control, topography parameters such as arithmetic mean roughness Ra and peak number RPc on the surface of the dressing roller can be specifically or positively influenced.

[0012] According to one embodiment, the pixel pattern can be numerically generated with a normally distributed depth distribution and at least two Gaussian curves. Typically, a program numerically generates one pixel pattern with a normally distributed depth distribution and one with a Gaussian curve. For example, at least two pixel patterns, each with a normally distributed depth distribution and one with a Gaussian curve, can be numerically generated, and these two distinct pixel patterns can be combined. This means, for instance, that the even-numbered pixels in pixel pattern 1 are used and the odd-numbered pixels in pixel pattern 1 are discarded, and the odd-numbered pixels in pixel pattern 2 are used and the even-numbered pixels in pixel pattern 2 are discarded, in order to generate a "new" pixel pattern from the combination of pixel patterns 1 and 2.Thus, a "new" pixel pattern can be generated by combining two pixel patterns through alternating the arrangement of individual pixels. Preferably, pixel patterns with a normally distributed depth distribution using (exactly) two Gaussian curves are generated numerically. Here, the topography values ​​can be specifically influenced, and in particular, higher Ra values, for example greater than 3.0 µm, preferably greater than 4.0 µm, preferably greater than 5.0 µm, and lower RPc values, for example less than 100 1 / cm, preferably less than 80 1 / cm, preferably less than 60 1 / cm, can be set.

[0013] According to one embodiment, a repetition rate f between 10 and 8000 kHz can be used or set. In particular, the repetition rate f can be between 50 and 2000 kHz.

[0014] According to one embodiment, a maximum laser power P between 10 and 1000 W can be used or set. The maximum laser power can be, in particular, at least 15 W, preferably at least 20 W. The maximum laser power can be, in particular, a maximum of 700 W, preferably a maximum of 300 W. Preferably, the pulse energy can be varied in order to control the ablation and thus the depth depending on the maximum laser power.

[0015] According to one embodiment, a focus diameter d can be used or set which corresponds at most to the pixel size. If, for example, a pixel has a square shape with a side length of 20 µm, then the focus diameter corresponds at most to 20 µm. As a minimum, the smallest possible laser diameter d can be used or set. In particular, the focus diameter d can correspond at most to half the pixel size, preferably at most to one-third of the pixel size, and preferably at most to one-quarter of the pixel size, whereby several pulses are accordingly triggered in each pixel to achieve a corresponding ablation depending on the set depth.

[0016] According to one embodiment, a pulse duration t between 300 fs and 500 ns can be used or set.

[0017] A distance L between 20 and 300 mm can be used or set.

[0018] A rotational speed w between 1 and 25 m / s can be used or set. The rotational speed is typically the product of pitch and repetition rate.

[0019] A travel speed v depends on the rotational speed and the roller diameter, and in particular on the number of passes to achieve the desired depth.

[0020] Therefore, the laser can be targeted in each pixel as often as necessary until the specified depth, according to the (depth) level, has been achieved. In particular, the focus diameter can be selected such that the pixel to be processed is targeted multiple times in one plane, thus allowing for successive ablation within a pixel.

[0021] The second teaching of the invention relates to a skinning roller with a laser-processed stochastic texture on the surface, preferably manufactured according to the first teaching, wherein the surface of the skinning roller has a topography with an arithmetic mean roughness Ra between 0.8 and 8.0 µm and with a peak number RPc between 30 and 250 1 / cm, wherein Ra and RPc are determined according to DIN EN 10049:2014-03.

[0022] The surface of the dressing roller can have a surface roughness (Ra) of at least 0.9, 1.0, 1.1, 1.2 µm, preferably at least 1.3, 1.4, 1.5, 1.6 µm, preferably at least 1.7, 1.8, 1.9, 2.0 µm, particularly preferably at least 2.2, 2.5, 2.7, 3.0 µm, and more preferably at least 3.5, 4.0, 4.5, 5.0 µm.

[0023] According to one embodiment, the surface of the dressing roller can have an RPc of at least 30 1 / cm and in particular a maximum of 240, 230, 220, 210 1 / cm, preferably a maximum of 200, 190, 180, 170 1 / cm, preferably a maximum of 160, 150, 140, 130 1 / cm, particularly preferably a maximum of 120, 110, 100, 90 1 / cm, further preferably a maximum of 80, 70, 60, 50 1 / cm.

[0024] According to an alternative embodiment, the surface of the dressing roller can have an RPc of a maximum of 250 1 / cm² and in particular at least 55, 60, 65, 70 1 / cm², preferably at least 75, 80, 85, 90 1 / cm², more preferably at least 95, 100, 105, 110 1 / cm², particularly preferably at least 115, 120, 125, 130 1 / cm², more preferably at least 135, 140, 145, 150 1 / cm².

[0025] According to one embodiment, the surface of the skinning roller can have a surface area (Ra) of at least 0.9, 1.0, 1.1, 1.2 µm, preferably at least 1.3, 1.4, 1.5, 1.6 µm, more preferably at least 1.7, 1.8, 1.9, 2.0 µm, particularly preferably at least 2.2, 2.5, 2.7, 3.0 µm, more preferably at least 3.5, 4.0, 4.5, 5.0 µm and an RPc of at least 30 1 / cm² and in particular a maximum of 240, 230, 220, 210 1 / cm², preferably a maximum of 200, 190, 180, 170 1 / cm², more preferably a maximum of 160, 150, 140, 130 1 / cm², more preferably a maximum of 120, 110, 100, 90 1 / cm, preferably with a maximum of 80, 70, 60, 50 1 / cm.

[0026] According to an alternative embodiment, the surface of the dressing roller can have a surface area (Ra) of at least 0.9, 1.0, 1.1, 1.2 µm, preferably at least 1.3, 1.4, 1.5, 1.6 µm, more preferably at least 1.7, 1.8, 1.9, 2.0 µm, particularly preferably at least 2.2, 2.5, 2.7, 3.0 µm, more preferably at least 3.5, 4.0, 4.5, 5.0 µm and an RPc of at most 250 1 / cm² and in particular at least 55, 60, 65, 70 1 / cm², preferably at least 75, 80, 85, 90 1 / cm², more preferably at least 95, 100, 105, 110 1 / cm², particularly preferably at least 115, 120, 125, 130 1 / cm, preferably at least 135, 140, 145, 150 1 / cm.

[0027] The third teaching of the invention relates to a method for dressing a hot-dip coated steel strip, wherein the hot-dip coated steel strip is passed between two dressing rollers having a stochastic texture and thereby dressed, wherein at least one dressing roller is used according to the second teaching, and in particular is manufactured according to the first teaching.

[0028] Preferably, both dressing rollers conform to the second doctrine and are manufactured in particular according to the first doctrine.

[0029] To avoid repetition, reference is made to the explanations of the first and second doctrines.

[0030] According to one embodiment, the steel sheet comprises a zinc-based coating. In addition to zinc and unavoidable impurities, the coating may contain additional elements such as aluminum with a content of up to 8 wt.%, in particular up to 5 wt.%, and / or magnesium with a content of up to 8 wt.%, in particular up to 5 wt.%. Steel sheets with a zinc-based coating offer very good cathodic corrosion protection and have been used in automotive manufacturing for many years. If improved corrosion protection is required, the coating additionally contains magnesium with a content of at least 0.3 wt.%, in particular at least 0.6 wt.%, preferably at least 0.9 wt.%. Alternatively or additionally, aluminum may be included with magnesium with a content of at least 0.1 wt.%, in particular at least 0.3 wt.%.A certain percentage of the coating must be present to, for example, improve the bond between the coating and the steel sheet and, in particular, to essentially prevent the diffusion of iron from the steel sheet into the coating during heat treatment of the coated steel sheet, thus ensuring, for example, good adhesion. The coating thickness on each side can be between 1.5 and 30 µm, particularly between 2 and 25 µm, preferably between 3 and 20 µm. Below the minimum limit, sufficient cathodic corrosion protection cannot be guaranteed, and above the maximum limit, joining problems can occur when connecting the steel sheet according to the invention, or a component manufactured therefrom, to another component. In particular, if the coating thickness exceeds the specified maximum limit, a stable thermal joining or welding process cannot be ensured.

[0031] If the coating contains magnesium and aluminum in addition to zinc and unavoidable impurities, it is known in the scientific community as zinc-magnesium, ZM or Zn-Al-Mg.

[0032] In a preferred variant, the aluminium content in the coating is 1.1 to 8 wt.%, in particular 1.2 to 5 wt.%.

[0033] In a preferred variant, the magnesium content in the coating is 1.1 to 8 wt.%, in particular 1.2 to 5 wt.%.

[0034] The coating may also contain only zinc with small amounts of aluminum up to 0.3 wt.% in addition to unavoidable impurities, known in technical circles as "Z".

[0035] Unavoidable impurities, such as elements from the group consisting of silicon, antimony, lead, titanium, calcium, manganese, tin, lanthanum, cerium and chromium, may be present individually or in combination in the coating in amounts up to 0.5 wt.%, in particular up to 0.3 wt.%, preferably up to 0.1 wt.%, preferably up to 0.05 wt.%.

[0036] The steel strip consists of a steel material which, in addition to iron and unavoidable impurities, contains alloying elements such as carbon, silicon, manganese, and aluminum. Other components, such as titanium and chromium, may also be present, either individually or in combination, and can be selected depending on the application and strength class. It is well known in technical circles which steel materials are particularly suitable for the production of cold-formed components in the automotive industry, depending on the application.

[0037] According to a preferred embodiment, the steel strip is a cold-rolled strip. A cold-rolled strip is a cold-rolled steel strip. The production of cold-rolled strips is common practice.

[0038] The invention also includes any combinations of the embodiments and alternatives described above.

[0039] The invention is explained in more detail with reference to the following exemplary embodiments in conjunction with the drawing.

[0040] Standard sizes of skinning rollers have a working surface width between 1200 and 2200 mm and a diameter between 350 and 650 mm. Thus, a typical skinning roller's working surface could have a developed area of ​​2200 × 1500 mm. 2The program specifies the following parameters: These parameters are entered into the example program Matlab, and based on predefined parameters or by the program itself, the developed area is divided into a pixel pattern with n x m pixels. Each pixel of the pixel pattern can preferably be rectangular, preferably square, with a side length between 5 and 50 µm and a resolution of, for example, up to 512, and in particular up to 256, steps relative to a given depth. The program also includes routines for determining topography parameters, in accordance with DIN EN 10049:2014-03, so that Ra and RPc can be determined. The Fig. Figures 1 to 3 show three different partial views of a pixel pattern, which were numerically generated using the Matlab program. The [images] are for the Fig. The results presented in points 1 to 3 refer to numerical or simulated data.

[0041] In Fig. Figure 1 shows an example of a partial view of a pixel pattern with a normally distributed depth distribution and a Gaussian curve. The partial view of the pixel pattern shown in this case corresponded to a square shape with an area of ​​0.7 × 0.7 mm. 2 Each pixel was square with a side length of 50 µm. A resolution of 6 levels with a predefined depth of 25 µm was chosen. Level 6 in the Fig. Level 1 on the left shows the brightest point (white) at 25 µm on the scale and thus corresponds to an untreated area on the surface of the skinning roller. Level 0 shows the darkest point (black) at 0 µm on the scale and thus corresponds to a treated area on the surface of the skinning roller with the deepest material removal. Topography parameters Ra = 3.7 µm and RPc = 46 1 / cm were determined using routines stored in the Matlab program.

[0042] In Fig. Figure 2 shows an example of a partial view of a pixel pattern with a normally distributed depth distribution and two Gaussian curves. The partial view shown in this case corresponded to a square shape with an area of ​​0.9 × 0.9 mm. 2 Each pixel was square with a side length of 30 µm. A resolution of 256 steps with a predefined depth of 15 µm was chosen. Step 255 in the Fig. Level 2 on the left shows the brightest point (white) at 15 µm on the scale and thus corresponds to an untreated area on the surface of the skinning roller. Level 0 shows the darkest point (black) at 0 µm on the scale and thus corresponds to a treated area on the surface of the skinning roller with the deepest material removal. Topography parameters Ra = 3.08 µm and RPc = 55 1 / cm were determined using routines stored in the Matlab program.

[0043] In Fig. Figure 3 shows an example of a partial view of a pixel pattern with a uniform depth distribution. The partial view shown in this case corresponded to a square shape with an area of ​​0.9 × 0.9 mm. 2 Each pixel was square with a side length of 30 µm. A resolution of 256 steps with a predefined depth of 20 µm was chosen. Step 255 in the Fig. Level 3 on the left shows the brightest point (white) at 20 µm on the scale and thus corresponds to an untreated area on the surface of the skinning roller. Level 0 shows the darkest point (black) at 0 µm on the scale and thus corresponds to a treated area on the surface of the skinning roller with the deepest material removal. Topography parameters Ra = 3.21 µm and RPc = 51 1 / cm were determined using routines stored in the Matlab program.

[0044] Not shown, further pixel patterns with a normally distributed depth distribution and a Gaussian curve were numerically generated. The partial view considered in these cases corresponded to a square shape with a cell area of ​​0.9 × 0.9 mm. 2 A resolution of 256 steps with a predefined depth of 20 µm was chosen. The side lengths of the pixels were varied in a square shape, see Table 1. Table 1 Pixelgröße in µm 10 20 30 Ra in µm 1,06 1,08 0,9 RPc in 1 / cm 139 73 36

[0045] By increasing the pixel side length from 10 to 30 µm, the peak count in this example can be reduced from 139 1 / mm to 36 1 / mm. However, even at 30 µm, a reduction in the arithmetic mean roughness can be observed.

[0046] Not shown, further pixel patterns with a normally distributed depth distribution and a Gaussian curve were numerically generated. The partial view considered in these cases corresponded to a square shape with a cell area of ​​0.9 × 0.9 mm. 2 A resolution of 256 steps was chosen, with a predefined square pixel size of 20 µm. The ablation depth was varied, see Table 2. Table 2 Abtragtiefe in µm 10 20 30 Ra in µm 0,54 1,08 1,61 RPc in 1 / cm 45 73 83

[0047] The arithmetic mean roughness can be adjusted, in particular, via the maximum cutting depth. The greater the maximum cutting depth, the higher the arithmetic mean roughness. However, the cutting depth also affects the number of peaks.

Claims

[1] Method for manufacturing a skinning roller, wherein the skinning roller is clamped in a rotary device and rotated at a rotational speed w, wherein a surface of the skinning roller to be processed is treated during rotation by means of at least one laser or optics coupled with a laser, wherein the laser is operated with a repetition rate f, with a maximum laser power P, with a focus diameter d and a pulse duration t in order to generate a stochastic structure on the surface of the skinning roller, wherein the laser is controlled and / or regulated by means of a process computer, characterized by, that the surface to be processed is divided by means of a program into a developed area into a pixel pattern with n × m pixels, wherein each pixel of the pixel pattern has a resolution of up to p steps with respect to a given depth, wherein the pixel pattern is numerically generated with a normally distributed depth distribution and with at least one Gaussian curve or a uniformly distributed depth distribution, and the pixel pattern generated thereby is implemented in a process computer for regulating and / or controlling the laser for processing the surface of the dressing roller. [2] Method according to claim 1, wherein the pixel pattern is numerically generated with a normally distributed depth distribution using at least two Gaussian curves. [3] Method according to any of the preceding claims, wherein a repetition rate f between 10 and 8000 kHz is used or set. [4] Method according to any of the preceding claims, wherein a maximum laser power P between 10 and 1000 W is used or set. [5] Method according to any of the preceding claims, wherein a focus diameter d is used or set which corresponds to a maximum of one pixel size. [6] Method according to any of the preceding claims, wherein a pulse duration t between 300 fs and 500 ns is used or set. [7] Dressing roller with a laser-processed stochastic texture on the surface manufactured according to one of the preceding claims, characterized by , that the surface of the dressing roller has a topography with an arithmetic mean roughness Ra between 0.8 and 8.0 µm and with a peak number RPc between 30 and 250 1 / cm, where Ra and RPc are determined according to DIN EN 10049:2014-03. [8] Method for dressing a hot-dip coated steel strip, wherein the hot-dip coated steel strip is passed between two dressing rollers having a stochastic texture and having a dressing gap, characterized by , that at least one dressing roller according to claim 7 is used. [9] Method according to claim 8, wherein the hot-dip coated steel strip comprises a zinc-based coating. [10] Method according to claim 8 or 9, wherein the hot-dip coated steel strip contains a coating comprising, in addition to zinc and unavoidable impurities, additional elements such as aluminium and magnesium, each with a content of up to 8 wt.%. [11] Method according to any one of claims 8 to 10, wherein the steel strip is a cold-rolled strip.

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