Method and apparatus for stretch-leveling metal strip

Abstract

A metal strip is gripped by an upstream set of infeed tension rollers and, downstream therefrom in a strip-travel direction, by a downstream set of outfeed tension rollers. These tension rollers are rotated so as to tension the strip between the upstream and downstream sets and move the strip downstream in the strip-travel direction. Between the sets the strip first passes around individually supported relatively rotatable stretch rollers to increase a plastic stretch ratio of the strip, and then through a plurality of straightening rollers to reduce curvature and residual tension of the strip and also to increase the plastic stretch ratio of the strip.

Claims

1. A method of stretch-leveling metal strip, the method comprising the steps of: gripping the strip with an upstream set of infeed tension rollers and, downstream therefrom in a strip-travel direction, with a downstream set of outfeed tension rollers; rotating the upstream and downstream tension rollers so as to tension the strip between the upstream and downstream sets and move the strip downstream in the strip-travel direction; passing the strip between the sets around individually supported relatively rotatable stretch rollers spaced in the travel direction to plastically stretch the strip; engaging the strip downstream of the stretch rollers and upstream of the downstream set with a plurality of straightening rollers spaced in the travel direction to reduce curvature and residual tension of the strip and also to plastically stretch the strip; and relatively orienting the straightening rollers and a furthest upstream roller of the stretch rollers such that the strip engages the straightening rollers in a region extending angularly over a wrap angle that decreases downstream from roller to roller and such that at the stretch rollers the wrap angle of the strip decreases in the travel direction by a greater amount than in the plurality of straightening rollers.

2. The stretch-leveling method defined in claim 1, wherein at least 5% of the plastic stretch is generated with the straightening rollers and at least 5% of the plastic stretch is generated with a furthest upstream roller of the straightening rollers.

3. The stretch-leveling method defined in claim 1, wherein, at least starting at a furthest upstream straightening roller, the wrap angle of the strip decreases from roller to roller by at least 5%.

4. The stretch-leveling method defined in claim 1, wherein from a furthest upstream stretch roller to the first straightening roller, the wrap angle decreases from roller to roller by a first constant difference, and from the second straightening roller to the last straightening roller it decreases from roller to roller by a second smaller difference.

5. The stretch-leveling method defined in claim 1, wherein from a furthest upstream stretch roller to a furthest upstream straightening roller, the wrap angles decrease from roller to roller by differences that become smaller going downstream.

6. An apparatus for stretch-leveling metal strip comprising: an upstream set of rotatable infeed tension rollers gripping the strip; downstream therefrom in a strip-travel direction, a downstream set of outfeed rotatable tension rollers also gripping the strip, the upstream and downstream tension rollers rotating so as to tension the strip between the upstream and downstream sets and move the strip downstream in the strip-travel direction; individually supported relatively rotatable stretch rollers downstream of the upstream set, around which the strip passes, spaced in the travel direction, and operable to plastically stretch the strip; and downstream of the stretch rollers and upstream of the downstream set, a plurality of straightening rollers spaced in the travel direction and engaging the strip so as to reduce curvature and residual tension of the strip and also so as to plastically stretch the strip, the straightening rollers and a furthest upstream roller of the stretch rollers being relatively oriented such that the strip engages the rollers in a region extending angularly over a wrap angle that decreases downstream from roller to roller and such that at the stretch rollers the wrap angle of the strip decreases in the travel direction by a greater amount than in the plurality of straightening rollers.

7. The stretch-leveling apparatus defined in claim 6, wherein the downstream straightening rollers has an upper leveling cassette holding a plurality of the rollers and a lower leveling cassette holding another plurality of the straightening rollers, at least one of the leveling cassettes being adjustable with respect to height and inclination.

8. The stretch-leveling apparatus defined in claim 6, wherein a furthest downstream stretch roller can be adjusted with respect to its position.

9. The stretch-leveling apparatus defined in claim 6, wherein the stretch rollers are formed by upper and lower interleaved stretch rollers, and the stretch rollers can be adjusted individually with respect to position.

10. The stretch-leveling apparatus defined in claim 6, wherein spacings in the travel direction between two directly succeeding stretch rollers and between a furthest downstream stretch roller and a furthest upstream straightening roller are generally identical or increase in the strip-travel direction.

11. The stretch-leveling apparatus defined in claim 6, wherein a spacing between two directly succeeding stretch rollers and between the furthest downstream stretch roller and the furthest upstream straightening roller are each at least 300 mm.

12. The stretch-leveling apparatus defined in claim 6, wherein spacings between two directly succeeding stretch rollers and between the furthest downstream stretch roller and the furthest upstream straightening roller are each at least one third of the width of the strip or of a maximal width of the strip.

13. The stretch-leveling apparatus defined in claim 6, wherein there are at least four of the stretch rollers.

14. The stretch-leveling apparatus defined in claim 6, wherein there are at least eight straightening rollers.

15. The stretch-leveling apparatus defined in claim 6, further comprising: an infeed deflection roller upstream of the first stretch roller.

16. The stretch-leveling apparatus defined in claim 6, further comprising: between the upstream set of infeed tension rollers and the downstream set of outfeed tension rollers, a strip-tension sensor formed at least partly by at least one deflection roller.

17. The stretch-leveling apparatus defined in claim 6, further comprising: respective drives of the set of infeed tension rollers and the set of outfeed tension rollers; respective positioners of the stretch rollers and of the straightening rollers; and a controller connected to the drives and positioners.

18. The stretch-leveling apparatus defined in claim 17, wherein the controller stores predetermined target roller settings that are determined by calculation beforehand, and are subsequently entered into the controller.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

(2) FIG. 1 is a side-schematic view of the apparatus according to the invention for stretch-leveling metal strip in a simplified side view;

(3) FIG. 1A is a large-scale view of the detail indicated at 1A in FIG. 1;

(4) FIG. 2 is a graph of the development of the (relative) stretch ratio from roller to roller in an apparatus according to FIG. 1, and

(5) FIG. 3a, 3b show examples of two different settings for the wrap angles at the rollers.

SPECIFIC DESCRIPTION OF THE INVENTION

(6) As seen in FIG. 1 an apparatus for stretch-leveling metal strip B is provided with a set of infeed tension rollers A for applying tension to the strip and a set of outfeed tension rollers E for relieving tension in the strip B. The tension rollers A and E displace the strip B in a normally horizontal travel direction D. Between the set of infeed tension rollers A and the set of outfeed tension rollers E, a deflection roller U and downstream therefrom, five individually supported stretch rollers 1, 2, 3, 4, 5 are arranged, around which the strip B is bidirectionally bent, thereby increasing the stretch ratio. The infeed and outfeed rollers E and A are rotated by respective drives as illustrated at 18 for rollers E, with the output rollers A rotating slightly faster than the input rollers E in order to maintain tension in the strip B and to take up the extra length imparted as described below to the strip B.

(7) Downstream of the last stretch roller 5, a multiroller straightening set V is provided that has a plurality of straightening rollers 6 to 16 around which the strip is bidirectionally bent for reducing strip curvature and/or residual tension. The multiroller straightening set V is directly downstream of the last stretch roller 5, without further tension roller sets being between the last stretch roller 5 and the multiroller straightening set V. The multiroller straightening set V is thereby basically comprised of an upper leveling cassette K1 and a lower leveling cassette K2, the upper leveling cassette being adjustable with respect to height and inclination by one or more positioning actuators 17 operated by a controller 19. Each of the straightening rollers 6 to 16 of the multiroller straightening set V is supported by unillustrated backing rollers, that is, between rollers and backing rollers, and the individual rollers of the upper leveling cassette K1 on the one hand and the individual rollers of the lower leveling cassette K2 are frictionally interconnected by the backing rollers, that is synchronized, like a 1:1 transmission. This is not illustrated in the figures.

(8) In the illustrated embodiment, the three upper stretch rollers 1, 3, and 5 of the individual stretch rollers 1 to 5 can be adjusted by positioning actuators 17 such as shown for the straightening roller 1 and 15. As for the others, the spaces between two stretch rollers 1-5 directly following one another as well as between the last, that is the furthest downstream, stretch roller 5 and the first straightening roller 6 increase in the strip-travel direction D.

(9) With the illustrated apparatus, metal strip, and in particular high-strength metal strip, can be stretch-leveled according to a method of the type described above. To this end, the apparatus is operated such that the plastic stretch ratio is not exclusively generated with the stretch rollers 1 to 5, but proportionally also by the upper rollers 1, 9, 11, 13, and 15 and the lower rollers 6, 8, 10, 12, 14, and 16 of the multiroller straightening set V, and particularly by the first, that is the furthest upstream, straightening roller 6.

(10) This can be seen in FIG. 2. There, the (relative) stretch ratios of each of the rollers 1-16 are graphically illustrated. The stretch ratio develops from roller to roller in the following manner, where the respective proportion of the total stretch ratio after each roller 1-16 is indicated.

(11) TABLE-US-00001 Proportion of the stretch ratio Roller No. after each roller 1 0.27 2 0.47 3 0.64 4 0.78 5 0.89 6 0.97 7 0.99 8 1.00 9 1.00 10 1.00 11 1.00 12 1.00 13 1.00 14 1.00 15 1.00 16 1.00

(12) A proportion of the stretch ratio after roller 1 of 0.27 consequently corresponds to a stretch ratio of 27% of the total stretch ratio after this roller 1. In this illustrated embodiment, after roller 8, a proportion of the stretch ratio of 1.0, and consequently, the total stretch ratio is reached. The same holds true for the data in FIG. 2. There, the respective proportion of the total stretch ratio after each of the rollers is indicated.

(13) It becomes clear from the table, that is, from FIG. 2, that particularly with the first straightening roller 6 of the multiroller straightening set V, a substantial portion of the stretch ratio of more than 10% is still being generated. This is possible because the first straightening roller 6 is neither frictionally connected to the preceding stretch roller 5, nor to the subsequent straightening roller 7.

(14) It is also important according to the invention that by the individual position setting, the wrap angle can be flexibly adjusted. According to the invention, a slow decrease of the wrap angle occurs. To this end, there are various possibilities. FIG. 3a shows a first variation, where the wrap angles decrease from roller to roller from the first stretch roller 1 to the first straightening roller 6 by a first constant difference so that the dots to rollers 1 to 6 are basically connected by a straight line with a first gradient. Thereafter, the wrap angles decrease from the second straightening roller 7 to the last or furthest downstream straightening roller 16 by a second constant difference that is lower than the first difference. In this way, the dots to the rollers 7 to 16 can basically be connected by a second straight line with a second gradient that in terms of amount is less.

(15) FIG. 3b shows a modified mode of operation where the wrap angles from the first stretch roller 1 to the first straightening roller 6 decrease by smaller and smaller differences. From the second straightening roller 7 to the last straightening roller 16, once again basically constant differences are set.

(16) Either way, such modes of operation are characterized by an evenly degrading bending effect, because the wrap angles decrease fluidly, so to speak, from roller to roller.