Abstract
A method for the stepped rolling of a metal strip unwinds the metal strip by a feed reel device and winds-up the metal strip by a winding reel device. The metal strip is guided through a roller gap formed between two working rollers during the rolling process, and the roller gap is changed in a controlled manner during the rolling process, whereby a thickness of the metal strip is changed in steps in the longitudinal direction during the rolling process. Tension applied to the metal strip is controlled such that the rolling force applied to the metal strip by the working rollers is constant during the rolling process.
Claims
1. A method for stepped rolling of a metal strip, the method comprising: unwinding the metal strip from a decoiler apparatus, guiding the metal strip through a roll gap formed between two working rolls, changing the roll gap in targeted manner such that a strip thickness of the metal strip is changed in stepped manner, in a longitudinal direction, and concurrently controlling a strip tension applied to the metal strip, in targeted manner, so that a rolling force applied to the metal strip by the two working rolls and an elastic deformation of the two working rolls are approximately constant, and winding up the metal strip by a coiler apparatus.
2. The method according to claim 1, further comprising: controlling a forward strip tension applied to the coiler apparatus and/or controlling a reverse strip tension applied by the decoiler apparatus.
3. The method according to claim 2, further comprising: reducing the roll gap for reduction of the strip thickness, and controlling a forward strip tension applied to the coiler apparatus and increasing the forward strip tension, or controlling a reverse strip tension applied by the decoiler apparatus and increasing the reverse strip tension, or controlling a forward strip tension applied to the coiler apparatus and a reverse strip tension applied strip tension applied by the decoiler apparatus and increasing the forward strip tension and/or and the reverse strip tension.
4. The method according to claim 2, further comprising: increasing the roll gap in size for increasing the strip thickness, and controlling a forward strip tension applied to the coiler apparatus and lowering the forward strip tension, or controlling a reverse strip tension applied by the decoiler apparatus and lowering the reverse strip tension, or controlling a forward strip tension applied to the coiler apparatus and a reverse strip tension applied strip tension applied by the decoiler apparatus and lowering the forward strip tension and the reverse strip tension.
5. The method according to claim 1, further comprising: controlling in accordance with precalculated speed data: a setting speed of the working rolls and/or a speed of rotation of the working rolls, and/or a speed of rotation of the decoiler apparatus and/or a speed of rotation of the coiler apparatus.
6. A method for stepped rolling of a metal strip, the method comprising: unwinding the metal strip from a decoiler apparatus, guiding the metal strip through a roll gap formed between two working rolls, changing the roll gap in targeted manner such that a strip thickness of the metal strip is changed in stepped manner, in a longitudinal direction, and concurrently controlling a strip tension applied to the metal strip, in targeted manner, so that a rolling force applied to the metal strip by the two working rolls is approximately constant, influencing a geometry of transitions between the strip thickness of the metal strip via targeted strip tension control and targeted control of the speed of rotation and setting speed of the working rolls, and winding up the metal strip by a coiler apparatus.
7. The method according to claim 6, wherein the geometry of transitions comprises a gradient and radii of transition points.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Further characteristics, details, and advantages of the invention result from the following description and from the drawings. An exemplary embodiment of the invention is shown purely schematically in the drawings, and will be described in greater detail below. Objects or elements that correspond to one another are provided with the same reference symbols in all the figures. The figures show:
(2) FIG. 1a schematic representation of an apparatus according to the invention,
(3) FIG. 1b schematic representation of an apparatus according to the invention, with support rolls and working rolls,
(4) FIG. 2 profile contour during rolling procedure without adaptation according to the invention,
(5) FIG. 3 rolling force progression during rolling procedure without adaptation according to the invention over time,
(6) FIG. 4 strip tension of the decoiler apparatus generated without adaptation according to the invention over time,
(7) FIG. 5 strip tension of the coiler apparatus generated without adaptation according to the invention over time,
(8) FIG. 6 profile contour during rolling procedure after adaptation according to the invention,
(9) FIG. 7 rolling force progression during rolling procedure after adaptation according to the invention over time,
(10) FIG. 8 adapted strip tension of the decoiler apparatus after adaptation according to the invention over time,
(11) FIG. 9 adapted strip tension of the coiler apparatus after adaptation according to the invention over time.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(12) FIG. 1a, represented schematically, shows an apparatus according to the invention. In the exemplary embodiment shown, the metal strip 4 is guided, over its entire strip width 8, through a roll gap 3 formed by an upper working roll 1 and a lower working roll 2, in the longitudinal direction 7. In this regard, the metal strip 4 is unwound from the decoiler apparatus 5 and, after the rolling procedure, which takes place between the working rolls 1, 2, wound up by the coiler apparatus 6. As a result, the metal strip 4 moves through the roll gap 3 in the longitudinal direction 7, and is worked on by the working rolls 1, 2 over the entire strip width 8. With a change in the roll gap 3 between the working rolls 1, 2, the strip thickness of the metal strip 4 is changed in stepped manner in the longitudinal direction 7, during the rolling process, and in this way a profile contour 11 (FIGS. 2 and 6) is achieved. The profile contour 11 (FIGS. 2 and 6) occurs over the entire strip width 8, in that preferably, the setting speed and the speed of rotation of the working rolls 1, 2, the speed of rotation of the decoiler apparatus 5 and of the coiler apparatus 6 are controlled by means of a controller 9, according to precalculated speed data, and set by way of setting means (not shown).
(13) In FIG. 1b, a single-framework 4-roll reversing framework is shown schematically from the roll axis direction. The working rolls 1, 2 are supported by two support rolls 23. The broken-line arrows represent forces, speeds, and torques, and are supposed to illustrate the rolling process.
(14) The drawings according to FIG. 2 and FIG. 6, as a diagram, show the profile contour 11 of a metal strip 4 (FIG. 1a), as an example, which strip has a length L after a rolling procedure, with the diagram reaching from 0 L to 1.12 L. Here, L represents a freely selectable value for the profile length produced. The profile height h plotted in the diagram is measured from the center of the metal strip 4 (FIG. 1a), in the height direction, and for this reason, the metal strip 4 (FIG. 1a) has twice as high a metal strip thickness after the rolling process. In the examples considered below, a metal strip 4 (FIG. 1a) having an intake thickness of H.sub.0 is used, wherein H.sub.0 is any desired value for the intake thickness and preferably lies between 1.2 mm and 5 mm. During this rolling process, the strip thickness is reduced to a profile height h of 0.425 H.sub.0, in other words a metal strip thickness of 0.85 H.sub.0, wherein subsequently, further stepped setting of the working rolls 1, 2 (FIG. 1a) is undertaken, and the material strip 4 is reduced, in sections, to a profile height h of 0.2875 H.sub.0, in other words a metal strip thickness of 0.575 H.sub.0. Transitions are situated between the level sections, level 16, level 18, level 20 of the metal strip profile 11, which transitions have a gradient, reference symbols 17 and 19. The profile contour 11 shown in FIG. 2 and FIG. 6 has the transition points 12, 13, 14, and 15 between the level sections level 16, level 18, level 20 and the gradients 17, 19, which points will be used for the further explanation. In FIG. 2, it can be seen that the profile contour 11 that can be achieved by means of setting of the roll deviates from the profile contour 11 according to FIG. 6, particularly at the transition point 13, to the effect that the radius that can be achieved in the transition point 13 is clearly smaller and actually can hardly be recognized in FIG. 2.
(15) In FIG. 3, the rolling force progression 21 can be seen as a diagram over a time interval T of the rolling procedure shown in FIG. 2. The rolling force W begins with W.sub.0 kN, wherein W.sub.0 is a value that occurs for the rolling force, and increases after the transition point 12 during setting of the working rolls 1, 2 (FIG. 1a). The rolling force W reaches its maximum at the transition point 13 with 2.32 W.sub.0 kN. Subsequently, the rolling force W is constant at 2.0 W.sub.0 kN during the level section, level 18, between the transition points 13 and 14, before it decreases again after the transition point 14, as a result of renewed setting of the working rolls 1, 2 (FIG. 1a), and reaches a value of W.sub.0 kN again after the transition point 15.
(16) Over the same time interval T being considered, FIGS. 4 and 5 show the stress progressions of the strip tensions as a diagram.
(17) In FIG. 4, the strain progression 22 of the reverse strip tension .sub.0 of the decoiler apparatus 5 (FIG. 1a) can be seen, which is constant during the entire rolling process at .sub.0* MPa. In contrast, the strain 22 of the forward strip tension .sub.1 of the coiler apparatus 6 (FIG. 1a) changes during the time interval T being considered. As is evident from FIG. 5, the strain of this strip tension increases during the rolling procedure, between the transition points 12 and 13, to maximally 1.23 .sub.1* MPa, before the strain drops again after the transition point 14. .sub.0* and .sub.1* represent strain values that lie in the range of 15% to 60% of the flow strain at the strip-profile position being considered.
(18) FIG. 6, as an example, shows the profile contour 11 of the metal strip 4 (FIG. 1a) after a rolling procedure. As has already been mentioned above, the strip thickness is reduced to a profile height h of 0.425 H.sub.0, in other words a metal strip thickness of 0.85 H.sub.0, wherein subsequently, stepped setting of the working rolls 1, 2 (FIG. 1a) is undertaken, and the material strip 4 (FIG. 1a) is reduced, in sections, to a profile height of 0.2875 H.sub.0, in other words a metal strip thickness of 0.575 H.sub.0. There are transitions between the level sections, level 16, level 18, level 20 of the metal strip profile 11, which transitions have a gradient, reference symbol 17 and 19. In FIG. 6, it can be seen that the profile contour 11 that can be achieved by setting of the rolls 1, 2 (FIG. 1 a) deviates from the profile contour 11 according to FIG. 2, particularly at the transition point 13, to the effect that the radius that can be achieved in the transition point 13 is clearly greater and corresponds to the radius in the transition point 14. This profile contour 11 is only possible by means of targeted adaptation of the strip tensions, roll speed of rotation, and setting speed during the rolling process.
(19) The diagram that is evident from FIG. 7 shows the rolling force progression 21 over the time interval T of the rolling procedure shown in FIG. 6. The rolling force W begins at W.sub.0 kN and increases minimally after the transition point 12, during setting of the working rolls 1, 2 (FIG. 1a). The rolling force W reaches its maximum at the transition point 13, with just 1.14 W.sub.0 kN. Subsequently, the rolling force W is constant during the level section, level 18, between the transition points 13 and 14, before it decreases again after the transition point 14, as a result of renewed setting of the working rolls 1, 2 (FIG. 1a), and reaches a value of W.sub.0 kN again after the transition point 15.
(20) Over the same time interval T being considered, FIGS. 8 and 9 show the strain progressions of the strip tensions in diagrams. In FIG. 8, the strain progression 22 of the reverse strip tension .sub.0 of the decoiler apparatus 5 (FIG. 1a) can be seen, which is adapted during the rolling process. The strip tension is adapted to a tension strain of 6.7 .sub.0* MPa during setting of the working rolls 1, 2 (FIG. 1a) between the transition points 12 and 13. This tension strain is maintained for the rolling process, until the transition point 14, before the strip tension of the decoiler apparatus 5 (FIG. 1a) is reduced again. The strain 22 of the forward strip tension .sub.1 of the coiler apparatus 6 (FIG. 1a) also changes during the time interval T being considered. Thus, the strain 22 of this strip tension increases during the rolling procedure, between the transition points 12 and 13, to 8 .sub.1* MPa, before the strain 22 drops again after the transition point 14.
(21) The invention can be summarized as follows: An increase in the rolling force W (FIG. 1a) is effectively prevented in that the shape change state and the strain state in the roll gap 3 (FIG. 1a) is changed by means of the strip tensions .sub.0, .sub.1 that are applied to the metal strip 4 (FIG. 1a). Usually, the vertical strain increases as the result of a reduction in the roll gap, and this results in a greater rolling force W (FIG. 1a). With the adaptation of the strip tensions .sub.0, .sub.1, in contrast, the result is achieved that in order to achieve flow conditions in the roll gap 3 (FIG. 1a), a lower resulting vertical strain is required.
(22) Control of the strip tensions .sub.0, .sub.1 takes place by way of the change in the reel speeds of rotation, wherein for targeted control of the strip tensions .sub.0, .sub.1, the coil diameter must be taken into consideration, so that a desired reel moment is achieved by means of the change in the reel speeds of rotation, which moment acts on the strip tensions .sub.0, .sub.1. With control of the strip tensions .sub.0, .sub.1, the flow condition in the roll gap 3 (FIG. 1a) is thereby achieved and maintained in targeted manner, without the vertical strains and thereby the rolling force W (FIG. 1a) being significantly changed as a result. Of course, the exemplary embodiment of the invention, as described, can still by modified in multiple respects, without departing from the basic idea.
REFERENCE SYMBOL LIST
(23) 1 upper working roll (upper roll) 2 lower working roll (lower roll) 3 roll gap 4 metal strip 5 decoiler apparatus 6 coiler apparatus 7 longitudinal direction 8 strip width 9 controller 10 strip tension measurement roller 11 profile contour 12, 13, 14, 15 transition point 16 level 17 gradient 18 level 19 gradient 20 level 21 rolling force progression 22 strain progression 23 support rolls W rolling force in kN W.sub.0 starting value for rolling force h profile height in mm H.sub.0 intake thickness of the metal strip l rolled profile length in mm L value for total profile length, t time in s T time interval .sub.0 reverse strip tension in MPa .sub.0* starting value for reverse strip tension .sub.1 forward strip tension in MPa .sub.1* starting value for forward strip tension
