Method and Apparatus for Roll-Embossing a Strip

Abstract

Provided is a method for rolling a strip with a roll stand with at least two work rolls. A rolling gap with a pass line is defined between the work rolls. A control roll is arranged before the rolling gap of the work rolls in the rolling direction, the strip is guided into the rolling gap of the roll stand via the control roll at an entry angle relative to the pass line and the surface structure of the strip is controlled through the selection of the entry angle depending on the positioning of the control roll relative to the pass line. Also provided is an apparatus for rolling a strip with a roll stand having at least two work rolls. A rolling gap with a pass line is defined between the work rolls.

Claims

1. Method for roll-embossing a strip having a roll stand comprising a first work roll and a second work roll, wherein a rolling gap with a pass line is defined between the first work roll and the second work roll, characterised in that a control roll is arranged before the rolling gap of the work rolls in the rolling direction, the strip is guided into the rolling gap of the roll stand via the control roll at an entry angle β relative to the pass line and the embossing of the surface structure of the work roll on the strip is controlled through the selection of the entry angle β depending on the positioning of the control roll relative to the pass line an entry angle β is set within an adjustment range of +/−2α, where α is the bite angle of a work roll in a given rolling pass, for which:
α=arc cos [1−(Δh/D.sub.W)], where Δh is the difference between the thickness of the strip before rolling and the thickness of the strip after rolling in mm (pass reduction) and D.sub.W is the diameter of the work roll in mm.

2. Method according to claim 1, characterised in that at least one guide roll is used through which the strip runs before the control roll.

3. Method according to claim 2, characterised in that the at least one guide roll is positioned such that an entry angle β.sub.B is set by means of the at least one guide roll if the control roll does not touch the strip and an entry angle β is set through the positioning of the control roll, so that the difference between the entry angles β and β.sub.B is at least 0.5°, preferably at least 1.0°.

4. Method according to claim 1, characterised in that a two-high roll stand is used as roll stand, in particular a two-high roll stand with two identical work rolls.

5. Method according to claim 1, characterised in that the surface roughness of at least one surface of the strip is controlled through the positioning of the control roll during rolling in combination with a measurement of the surface roughness of the strip.

6. Method according to claim 1, characterised in that during the rolling pass a relative change in the thickness of the strip (degree of reduction) of less than 10%, preferably 1-6% takes place.

7. Method according to claim 1, characterised in that a range for the surface roughness R.sub.a or S.sub.a of at least 0.1 μm up to a maximum of 10.0 μm, preferably at least 0.4 μm up to a maximum of 4.0 μm, particularly preferably at least 0.5 μm up to a maximum of 2.0 μm can be set on at least one surface of the strip through positioning of the control roll.

8. Method according to claim 1, characterised in that at least one work roll has an EDT surface structure, an EBT surface structure, a structured chrome layer or a laser-textured surface.

9. Method according to claim 1, characterised in that a strip consisting of aluminium or an aluminium alloy is used, in particular an aluminium alloy of the type AA5xxx or AA6xxx.

10. Apparatus for roll-embossing a strip, in particular for carrying out a method according to claim 1, with a roll stand comprising a first work roll and a second work roll, wherein a rolling gap with a pass line is defined between the first work roll and the second work roll, characterised in that a control roll is arranged before the rolling gap of the roll stand in the direction of transport of the strip, means for positioning the control roll relative to the pass line are provided and the means for positioning the control roll allow the entry angle β to be adjusted within a range between +/−10° or +/−5°, preferably between +/−3°, wherein the position of the control roll can be adjusted in 0.1° increments, particularly preferably in 0.05° increments of the entry angle β.

11. Apparatus according to claim 10, characterised in that at least one guide roll is provided before the control roll in the direction of transport of the strip.

12. Apparatus according to claim 11, characterised in that means for positioning the at least one guide roll relative to the pass line are provided.

13. Apparatus according to claim 10, characterised in that a two-high roll stand is used as roll stand, in particular a roll stand with two identical work rolls.

14. Apparatus according to claim 10, characterised in that at least one measuring device is provided for measurement of the surface roughness of at least one surface of the strip.

15. Apparatus according to claim 14, characterised in that at least one control means is provided by means of which the positioning of the control roll, optionally the positioning of the at least one guide roll, can be controlled depending on the measurement of the surface roughness of the at least one surface of the strip.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0049] For further embodiments and advantages of the apparatus according to the invention, reference is made to the explanations above as well as to the dependent claims of the method according to the invention, as well as to the drawing. The drawing shows:

[0050] FIGS. 1a and 1b show schematic views of the geometry during rolling;

[0051] FIGS. 2a to 2d show schematic views of the method according to the invention and the apparatus according to the invention;

[0052] FIG. 3 show measured mean roughness values S.sub.a depending on the entry angle; and

[0053] FIG. 4 shows surface topographies of the upper side and underside of strips rolled according to the invention depending on the entry angle.

DETAILED DESCRIPTION OF THE INVENTION

[0054] FIG. 1a shows a first schematic view of the geometry during rolling. A rolling gap is formed between a first (upper) work roll 2 and a second (lower) work roll 4 through which a pass line 6 is given. The pass line 6 runs through the neutral phase of the strip and is perpendicular to the connecting plane of the axes of rotation of rolls 2 and 4. A strip 8 passes through the rolling gap, being deformed by the work rolls 2, 4 into a strip 8′ of reduced thickness. Here, Δh is the difference between the thickness of the strip 8 before rolling and the thickness of the strip 8′ after rolling in mm (pass reduction).

[0055] The work rolls 2, 4 are in contact with the strip with an bite angle α. As indicated in FIG. 1a, the bite angle α is the angle between the connecting line between the two axes of the work rolls 2, 4 and the connecting line from one axis to the point of contact with the surface of the strip. The bite angle is defined through

α=arc cos [1−(Δh/D.sub.W)]

where D.sub.W is the diameter of a work roll 2, 4 in mm. In the example shown in FIG. 1a, the diameters D.sub.W of the work rolls 2, 4 are identical and thus have the same bite angle α.

[0056] The strip 8 in FIG. 1a also runs within and parallel to the pass line 6, which means that the entry angle β=0°. The contact angle between the surface of the strip 8 and the tangent of the surface of both work rolls 2, 4 is thus equal to the bite angle α.

[0057] FIG. 1b shows a second schematic view of the geometry during rolling, wherein there is an entry angle β≠0° between the path of the strip 8 and the pass line. This is drawn in, in FIG. 1b, between the pass line 6 and the centre line 10 of the strip 8. The entry angle β≠0° has the effect that the contact angle between the surface of the strip 8 and the tangent of the surface of the work rolls 2, 4 is different for both sides. In FIG. 1b, the upper work roll 2 has a contact angle of α+β and the lower work roll 4 a contact angle of α−β.

[0058] If a lubricant is used, the lubricant feed in the rolling gap is dependent on the contact angle α+β or α−β between the tangent of the surface of the respective work roll 2, 4 with the surface of the strip 8. The contact angles of the work rolls 2, 4 and thus the hydrodynamic lubricant feed can be changed through an adjustment of the entry angle β. In particular, the rolling pattern of the upper side and underside of the strip 8′ can be influenced through an adjustment of the entry angle β.

[0059] If the entry angle β exceeds the bite angle α then the strip lies tangentially against the work roll 4. In this case a further increase in the entry angle β no longer results in any significant change in the lubricant feed on the work roll 4.

[0060] FIG. 2a shows a first schematic view of the method according to the invention and the apparatus according to the invention. A roll stand is represented here in simplified form through the work rolls 2, 4, wherein at least one of the work rolls 2, 4 has a structured surface. A control roll 12 with means for positioning relative to the pass line 6 is arranged before the work rolls 2, 4 in the direction of transport of the strip. At least one guide roll 14 is provided before this in the direction of transport of the strip.

[0061] In FIG. 2a, the control roll 12 is positioned such that the control roll 12 does not touch the strip 8. The strip 8 thus runs within and parallel to the pass line 6 and the entry angle is β=0°. This represents a situation analogous to FIG. 1a, in which both contact angles of the work rolls 2, 4 with the surface of the strip 8 are equal to the bite angle α.

[0062] In contrast, in FIG. 2b the control roll 12 is positioned, via the means for positioning, such that the control roll 12 touches the strip 8, deflects it and thus creates an entry angle β≠0° between the strip 8 and the pass line 6. This situation is comparable with that in FIG. 1b.

[0063] By changing the entry angle β, the contact angle of the work rolls 2, 4 and thus in particular the hydrodynamic lubricant feed to the respective work roll 2, 4 can be changed. Thus, the rolling pattern on the upper side and underside of the strip 8′ or the surface structure of the rolled strip 8′ can be controlled by changing the entry angle β via the means for positioning the control roll 12.

[0064] FIG. 2c shows a further embodiment of the method according to the invention and the apparatus according to the invention in a further schematic view. Means for positioning the at least one guide roll 14 relative to the pass line 6 are also provided here.

[0065] Here, the at least one guide roll 14 is positioned such that an entry angle β.sub.B would be set without the control roll 12 coming into contact with the strip 8. Through the positioning of the control roll 12, an entry angle β is set, wherein the difference between the entry angles β and β.sub.B is at least 0.5°, preferably 1.0°.

[0066] A positioning of control roll 12 and guide roll 14 of this type ensures that the control roll 12 has sufficient traction on the strip 8 in order to avoid any slipping between the strip 8 and the control roll 12. Consequently, undesired grinding or scratching effects on the surface of the strip 8 caused by the control roll 12 are avoided.

[0067] FIG. 2d shows a further embodiment of the method according to the invention and the apparatus according to the invention in a further schematic view. A measuring device 16 is provided here for measurement of the surface roughness of at least one surface of the strip 8′. The rolling patterns can be monitored by means of the measuring device 16. The measuring device 16 can pass on the measured values to a control means 18. The control means 18 hereby exerts influence on the means for positioning the control roll 12 on the basis of the measured values from the measuring device 16. Therefore, the control means 18 can be used to control the surface roughness of the strip 8′ during rolling. Optionally, the control means 18 can also control the means for positioning the at least one guide roll 14.

[0068] FIG. 3 shows measured mean roughness values S.sub.a depending on the entry angle β from a test series. Here, an aluminium alloy strip of the alloy type AA6016 with a thickness of 2.4 mm was rolled in a roll stand. The bite angle α of the embossing roll stand was around 1.3° during the tests.

[0069] The strips were rolled with different entry angles β, which were set by means of the control roll. For entry angle β>α=1.3°, the bite angle α of the lower work roll was exceeded. No great variation was therefore observed in the mean roughness value S.sub.a for the underside of the strip. Rather, the underside of the strip lay tangentially against the surface of the lower work roll, which meant that a constant rolling pattern was produced practically independently of the entry angle β. However, for the upper side, a surprisingly high dependence of the mean roughness value Sa on the entry angle β was observed. It was found that by changing the entry angle β through the positioning of the control roll a wide range of different roughnesses can be achieved on the upper side of the strip and the respective mean roughness values S.sub.a can be specifically set. The dependence of the mean roughness value S.sub.a on the entry angle β within the measured range is approximately linear.

[0070] FIG. 4 shows surface topographies of the upper side and underside of strips rolled according to the invention as a function of the entry angle β from the same test series as shown in FIG. 3. Here too it can be seen that while, due to the exceeding of the bite angle α, the topography of the underside only varies slightly with the entry angle α, the topography of the upper side can be controlled very effectively by adjusting the entry angle β by means of the control roll. For example, the control roll can be used, in a reliable manner, to set the same roughness on both sides of the strip.

[0071] The control roll can also be used to react to a changing of, or wear on, the work rolls. In this test series, following an increase of the entry angle β from 0.97° to 2.20°, the entry angle β=1.74° was set again. As can be seen in FIGS. 3 and 4, a slightly changed topography or a slightly changed roughness was observed in comparison with the previous test at β=1.74°. This was probably attributable to an accretion of material or a soiling of the work rolls. However, in such a case a uniform rolling pattern can be achieved again simply by once again adjusting the entry angle β, without the work rolls needing to be reconditioned or replaced.

[0072] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0073] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0074] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.