EP2119514A1 - Method and device for straightening a metal strip - Google Patents

Abstract

The method involves producing tensile stress which is 70 percentage of yield strength between a series of brake rolls (2.1, 2.2) and a series of traction rolls (3.1, 3.2) in a metal strip (1). Longitudinal curvatures are corrected between the brake and traction rolls in a group of straightening rolls (4.1-4.7) with straightening rolls by bending. The strip follows with selected strip tension of the curvature of straightening rolls so that the diameter (D1-D7) of the straightening rolls increases within the group of straightening rolls in a travel direction (R) of the strip from roll to roll. An independent claim is also included for a metal strip flattening system comprising straightening rolls.

Description

The invention relates to a method for straightening a metal strip, in particular a thin metal strip having a thickness of up to 1 mm, wherein in the metal strip between a brake roller set and a Zugrollensatz a tensile stress of at least 70% of the yield strength is generated, and wherein the band between the brake roller set and the Zugrollensatz is directed in a straightening roller group with multiple straightening rollers. - Metal strip means in the context of the invention, in particular a thin metal strip having a thickness of 0.02 mm to 1.0 mm, preferably 0.05 mm to 0.5 mm.

The aim of straightening a metal band is to produce a band that is as flat as possible. In principle, a distinction is made in practice between different types of bumps. In addition to band ripples and banding, which are due to differences in length across the bandwidth, band bends often occur, with a distinction being made between longitudinal curvatures (coil set) and transverse curvatures (crossbow). The straightening of ribbons is often done using strip tension, e.g. B. when drafting or stretch bending.

So you know draw lines, in which between a set of brake rollers and a Zugrollensatz a high strip tension is generated, so that finally the required for the desired stretching stretch stretching is achieved. In the course of the stretching process, the plastic elongation of the respective band is obtained from the reduction of the strip thickness and bandwidth. For example, a process is known for the continuous drawing of thin strips, in particular of metallic strips of steel, aluminum or the like with a strip thickness between 0.05 and 0.5 mm, after which the strip in a between the brake roller set and the Zugrollensatz intermediate Zugreckrollenpaar the to his stretching in the plastic area required stretching train is subjected. With the Zugreckrollenpaar while about 5% to 25% of the stretch train for plastic stretching and with the brake roller and the Zugrollensatz 75% to 95% of the stretch train for the elastic or semi-plastic stretch of the band produced. The diameter of the access rollers is 1500 times greater than the maximum strip thickness (see. DE 39 12 676 C2 ).

With the zugrecken can be generated in practice high flatness and eliminate in particular ripples and band saber. However, since the band usually runs in the plastic range on the last tensioning roller when pulling, often not inconsiderable longitudinal curvatures remain in the band when pulling, which correspond to the tensioning roller diameter minus the elastic springback. Although it is possible, this longitudinal rest curvature in z. B. to eliminate a region of low tension by an adjustable correction role. For thin tapes, however, the required diameter of the correction roller becomes very small in order to still allow a partially plastic counterbending. Therefore, it is often necessary to support such a stretch bender roll in a cassette with support rollers against deflection. In high-speed systems, such rollers tend to vibrate and can cause unwanted chatter marks on the belt surface. The vibrations can be sufficiently damped by the use of a spray liquid, but then the spray liquid is to be removed again by way of a belt cleaning, which is associated with increased equipment and operating costs. Furthermore, the position of the correction roller must be readjusted for each band thickness / band material combination.

Alternatively, tapes are often planed in practice by means of stretch bending. The tape is bent around a number of straightening rollers with a small diameter and lengthened by overlapping of bending and strip tension plastically by the degree of stretching, so that ripples (approximately) are eliminated.

While essentially the degree of stretch is generated at the first straightening rollers, the last straightening rollers are mainly used for the curvature correction. Depending on the strip tension, roll diameter and angle of wrap, the strip assumes the roll diameter at the first straightening rollers or not. At the last straightening rollers, however, the roll diameters are not accepted, since optimum ribbons of curvature must be set over the wrap angles for different ribbons. For this reason, at least the last straightening rollers are employed differently for different bands. This often results in high commissioning effort in practice. Incidentally, the disadvantage is again the use of relatively small roll diameter. Incidentally, owing to the bending and the small roller diameters in the belt, relatively high residual stresses remain over the belt thickness, which may be undesirable in the further processing of the belts. For thin strips, moreover, a large number of straightening rollers are required so that longitudinal residual curvatures are eliminated to the desired extent.

From the EP 0 790 870 B1 One knows a device for straightening metal bands, in which between a brake roller and a Zugrollensatz a stretch bending stand, a correction roller assembly and a Vielrollenrichteinheit are arranged. The Vielrollenrichteinheit has a plurality of work rolls, which are supported on support rollers. All work rolls of the stretch bender, the correction roller assembly and the multi-roller straightening unit are moved by friction between the belt and rollers, they are therefore not driven. In the multi-roll straightening unit, the diameters of the work rolls can increase from roll to roll. However, the diameters are relatively small - as is the case with multi-roller straightening or stretch bending straightening. In this known system, it is provided to adjust the position of the straightening rollers and consequently the immersion depth depending on the band properties.

The known methods (for example stretch-bending densities on the one hand and drawing on the other hand) are also combined. Thus, a method is known for the continuous straightening of thin metal strips, which on the one hand provides for stretching and, on the other hand, for stretch-bending densities (cf. DE 195 09 067 A1 ).

From the US Pat. No. 6,240,762 B1 One knows a method for leveling a metal strip by means of stretch bending or drafting, which is followed by a straightening process in a Rollenrichteinheit at low strip tension.

Finally, that describes EP 1 311 354 B1 a method and an apparatus for stretch straightening a metal strip, wherein the metal strip passes through a brake roller and a Zugrollensatz and is subjected to a stretch between the two sets of rollers in the course of its stretching and arranged in a between the brake roller and the Zugrollensatz further set of rollers to increase the degree of stretching of a bend Train is subjected. With this further set of rollers while the main part of the stretch train is generated. The traction rollers of the intermediate roller set can have a different diameter than the rollers of the brake roller set and the Zugrollensatzes. The inner traction rollers of this central roller set can have a smaller diameter compared to the rollers of the brake roller set and the Zugrollensatzes.

The invention has for its object to provide a method for straightening a metal strip and in particular a thin metal strip, which can produce low-residual bands high flatness and beyond lesser longitudinal curvatures in an economical manner. In addition, a suitable system for carrying out such a method should be specified.

To solve this problem, the invention teaches a method for straightening a metal strip, in particular a thin metal strip having a thickness ≤ 1 mm,
wherein a tensile stress below the yield strength of at least 70% of the yield strength is generated in the metal strip between a brake roller set and a roller set and the strip is directed by means of stretch bending and / or drawing,
wherein longitudinal curvatures are corrected or eliminated by bending and preferably alternating bending between the brake roller set and the train roller set in at least one straightening roller group having a plurality of straightening rollers,
wherein the diameter of the straightening rollers and the wrap angle is so large that the tape follows the curvature of the straightening rollers in the selected strip tension or assumes the curvature of the straightening rollers and
wherein the diameter increases in the strip running direction from straightening roll to straightening roll.

The longitudinal curvatures are corrected in the intermediate straightening roller group preferably by alternating bending of the belt exclusively around straightening rollers of sufficiently large diameter and with sufficiently large wrap, so that the band assumes the curvature of the rollers. Since the strip follows the curvature of the rolls, a variation of the depth of immersion has no influence on the directional result. It is in the context of the invention therefore particularly important that the position of the straightening rollers and consequently the immersion depth of a straightening roller between two adjacent straightening rollers of the straightening roller group is fixed and is not changed during the straightening of a band and / or straightening bands of different thickness.

Surprisingly, it is possible with the method according to the invention to produce flat and low-stress strips with minimal longitudinal residual curvatures in an economical manner. The risk of chatter marks is avoided without the use of spray liquids is required. Of particular importance is the fact that a plurality of straightening rollers is provided within a straightening roller group between Zugrollensatz and brake roller set, these straightening rollers have a relatively large diameter, and so large that the band follows the curvature of the straightening rollers in the selected strip tension, and without a change in the role of adjustment depending on strip thickness and strength ranges is required. With a suitable number of straightening rollers and consequently curvature correction rollers with suitable diameters and in particular a suitable diameter graduation, it is possible to produce belts with very small longitudinal curvatures. The selection of the number of straightening rollers and their diameter and diameter graduation can be carried out in dependence on a predetermined tolerance of the longitudinal curvatures of, for example, k = 1 / R = ± 0.001. The required number of straightening rollers and the optimal staggering of the preferably successively increasing roll diameter depends on the smallest strip thickness with the highest yield strength. The straightening roller group has z. B. three straightening rollers, preferably at least four straightening rollers, more preferably five or more straightening rollers, wherein the diameter increases within such a straightening roller group from roll to roll. As a result, the curvature of the strip decreases from roll to roll, so that the longitudinal curvatures are gradually reduced. All straightening rollers preferably have a diameter which is at least 500 times, z. B. is at least 1000 times the thickness of the band to be straightened and preferably also the maximum thickness of a straightening in such a system band. The tension between the brake roller set and Zugrollensatz is preferably set to at least 75%, more preferably at least 85% of the yield strength. It may be appropriate to adjust the tension to a value of 90% of the yield strength or more. The tensile stress may be below the yield strength, but also in the range of the yield strength or above the yield strength. Yield strength means in the context of the invention, the yield strength or plastic yield strength R _{p 0.2} , that is the stress in the pure tensile test, in which the plastic strain is 0.2%. It is therefore within the scope of the invention that between the brake roller set and Zugrollensatz straightening the band by plastic strain, z. B. by stretching and / or stretch bending takes place, but the curvature correction is done by alternating bending around the straightening rollers of the straightening roller group.

The diameter of the straightening rollers of the straightening roller group increases from roll to roll, preferably by a factor of 1.05 to 1.5, more preferably by a factor of 1.15 to 1.3. You can work with a fixed factor or a variable factor within a straightening roller group.

Always be compared to the conventional Zugrecken created bands with much lower longitudinal curvatures. The resulting residual stresses are well above the strip thickness below the residual stresses which can be achieved with the stretch bend densities.

The number of straightening rolls or curvature correction rolls and their diameter graduation is particularly preferably calculated according to a mathematical model which uses as input parameters the strip thickness, the modulus of elasticity, the transverse contraction number, the stress-strain curves, the required degree of stretch to eliminate the waviness which increases expected variations in strip tension, the expected variations in strength (within a product), the expected band thickness variations (within a product) and / or the amount of the maximum allowable longitudinal residual curvature. The mathematical model then calculates the necessary for different bands starting from a role configuration Strip tensile stresses and the resulting longitudinal residual curvatures. The required number of curvature correction rollers and the optimum gradation of the roller diameters are based on the smallest strip thickness at which a certain longitudinal residual curvature still has to lie within the tolerance. Of particular importance now is the fact that such a calculation can be carried out for certain areas due to a mathematical model and that subsequently in the course of commissioning and especially in the course of operation no variation of the parameters and in particular no variation of the immersion depth of the straightening more required is. Rather, the invention proposes that the position of the straightening rollers and consequently the immersion depth of the straightening rollers between two adjacent straightening rollers within the straightening roller group in the system is fixed and especially during straightening, but also when changing the strip material and / or the strip thickness is not changed , By suitably tuning the relatively large roll diameters, with the metal strip taking on the curvature of these rolls, with a single fixed configuration, tapes can be straightened over a certain range of thicknesses and consequently also different thickness tapes with excellent results. Even if the position of the straightening rollers and consequently the immersion depth is fixed and consequently worked with a fixed configuration, this does not exclude within the scope of the invention that the possibility of "opening" the straightening roller group and consequently the rollers apart is provided in terms of plant technology to drive (temporarily) to pass the tape without bending through the straightening roller group, z. B. when a joint between a beginning of the tape and a tape end (eg., A weld) is driven through the system. Subsequently, all straightening rollers are then brought back into the fixed predetermined or fixed configuration, in which then the bands are processed over the desired thickness range without further adaptation.

It is within the scope of the invention that between the brake roller set and Zugrollensatz only a single straightening roller group is provided, in which the diameter increases from roll to roll, so consequently all the rollers of the straightening roller group have a different diameter. However, the invention also includes embodiments in which within such a straightening roller group with a total of rising roller blade (each) two adjacent rollers have an identical roll diameter. It is also within the scope of the invention that the straightening roller group upstream and / or downstream of one or more other additional straightening rollers. Thus, it may be expedient, for example, if the straightening roller group is preceded by one or more additional straightening rollers, wherein the diameter of these upstream straightening rollers is preferably less than or equal to the diameter of the first straightening roller of the straightening roller group. Preferably, however, a diameter is chosen which corresponds to at least 500 times (minimum) strip thickness also in these additional straightening rollers. These upstream additional straightening rollers can also be arranged between brake roller set and Zugrollensatz. However, the invention also includes embodiments in which a band treatment in several treatment zones, for. B. several Zugreckzonen, takes place, which consequently several sets of clamping rollers to form a plurality of treatment zones, for. B. Zugreckzonen, are connected in series. The straightening roller group according to the invention for eliminating longitudinal curvatures is then always in the last treatment zone, z. B. last Zugreckzone arranged. After the correction of curvature by the straightening rollers, plastic deformation no longer takes place, so that the final result of the straightened and, in addition, longitudinally curvature-free band is maintained.

It is within the scope of the invention that all straightening rollers of the straightening roller group are not driven. However, the invention also includes embodiments in which one, several or all straightening rollers of the straightening roller group are driven. Such a possibility is, for example, then, when (very) large straightening rollers with large moments of inertia are used. By driving one or more straightening rollers, it is then possible in particular to avoid slippage when starting up the installation.

The invention also relates to a system for straightening a metal strip, in particular a thin metal strip having a thickness ≤ 1 mm, according to a method of the type described. Such a system has at least one brake roller and a Zugrollensatz to build the desired tension and at least one between brake roller and Zugrollensatz arranged straightening roller group with multiple straightening rollers. The diameter of the straightening rollers within the straightening roller group increases in the direction of belt travel from roll to roll. In this case, such a straightening roller group at least three rollers, preferably at least four rollers, more preferably at least five rollers. The diameter of the straightening rolls is at least 500 times the (minimum) strip thickness and preferably at least 1000 times the (minimum) strip thickness. The diameter of the straightening roller group increases from roll to roll by a factor of 1.05 to 1.5, preferably 1.15 to 1.3. In practice, for. B. straightening rollers in the straightening roller group with a diameter of 100 mm to 2000 mm, z. B. 200 mm to 1600 mm, preferably 300 mm to 1500 mm are used.

Fig. 1

eine erfindungsgemäße Anlage zum Richten eines Metallbandes mit dem erfindungsgemäßen Verfahren,

Fig. 2

eine abgewandelte Ausführungsform des Gegenstandes nach Fig. 1 und

Fig. 3

ausschnittsweise eine weitere Ausführungsform der Erfindung.

In the following the invention will be explained in more detail with reference to a drawing showing only one exemplary embodiment. Show it:

Fig. 1

a system according to the invention for straightening a metal strip with the method according to the invention,

Fig. 2

a modified embodiment of the article according to Fig. 1 and

Fig. 3

a detail of a further embodiment of the invention.

In the figures, a system for straightening a metal strip, in particular a thin metal strip 1 with a thickness d ≦ 1 mm is shown. Such a system has in its basic structure a brake roller set 2 and a Zugrollensatz 3. In the exemplary embodiment, the brake roller set 2 only a pair of rollers and consequently two brake rollers 2.1 and 2.2, while the Zugrollensatz 3 also has only one pair of rollers and consequently two tension rollers 3.1 and 3.2. Of course, the invention also includes embodiments with pulley sets with more roles, eg. B. four roles or six roles. With the aid of these tensioning roller sets (brake roller set 2 and tension roller set 3) a strip tension or a tensile stress is generated in the metal strip 1 which is at least 75% of the yield strength, preferably at least 90% of the yield strength. Between the brake roller set 2 and the Zugrollensatz 3 now a straightening roller group 4 with a plurality of straightening rollers 4.1, 4.2, 4.3, 4.4, 4.5, 4.6 and 4.7 is arranged within the scope of the invention. In this straightening roller group 4, longitudinal curvatures of the band are eliminated by means of alternating bending. The diameter D1 - D7 of the rollers of this straightening roller group 4 is relatively large and indeed so large that the band 1 follows the curvature of all of these straightening rollers within the straightening roller group 4 in the selected strip tension. It is in Fig. 1 recognizable that the diameter D1, D2, D3, D4, D5, D6, D7 of the straightening rollers 4.1 to 4.7 of the straightening roller group 4 increases in the direction of tape R from roll to roll and thus becomes larger. In the exemplary embodiment, the straightening roller group 4 has seven straightening rollers, wherein the roller diameter D1 to D7 increases from roller to roller by a factor of about 1.25. The position of the straightening rollers 4.1 to 4.7 is fixed within the system. An adjustment of the position or immersion depth is not provided in the context of the invention. Rather, succeeds by a one-off interpretation of the parameters, a proper straightening and low residual longitudinal curvatures for different thicknesses without an adjustment of the immersion depth of the individual roles is required.

While Fig. 1 a first embodiment shows, in which between the brake roller set 2 and the Zugrollensatz 3 only the straightening roller group 4 is arranged, shows Fig. 2 a modified embodiment in which the straightening roller group 4 with the straightening rollers 4.1 to 4.6 further auxiliary rollers 5.1, 5.2 and 5.3 are arranged upstream. The diameter D 'of these additional rollers 5.1 to 5.3 corresponds to the diameter D1 of the first straightening roller of the straightening roller group 4th

Fig. 3 shows an embodiment in which the straightening rollers 4.1 to 4.7 of the straightening roller group 4 four more additional straightening rollers 5.1 to 5.4 are arranged upstream. These additional straightening rollers 5.1 to 5.4 have a relatively small diameter D 'and form as it were stretch bends. For this reason, each of these straightening rollers 5.1 to 5.4 is supported by support rollers 6. In this embodiment, the straightening roller group according to the invention is therefore preceded by a stretch bender roller group 5.1 to 5.4. Brake roller set and pull roller set are in Fig. 3 not shown.

If necessary, the wrap angles can be made substantially larger in practice than indicated in the figures. There are wrap angles of up to 180 ° or even more conceivable. In this respect, the first roller 3.1 of the Zugrollensatzes 3 (at the same time) be part of the straightening roller group 4 and consequently also contribute to the plastic deformation of the belt by bending.

Claims (16)

Method for straightening a metal strip, in particular a thin metal strip having a thickness ≤ 1 mm,
wherein in the metal strip between a brake roller set and a Zugrollensatz generates a tensile stress of at least 70% of the yield strength and the metal strip z. B. is directed by means of stretch bending and / or drawing,
wherein longitudinal curvatures are corrected by bending between the brake roller set and the train roller set in at least one straightening roller group with a plurality of straightening rollers,
wherein the diameter of the straightening rollers is so large that the band follows the curvature of the straightening rollers in the selected strip tension and
wherein the diameter of the straightening rollers increases within the straightening roller group in the tape running direction from roll to roll. A method according to claim 1, characterized in that the position of the straightening rollers and consequently the immersion depth of a straightening roller between two adjacent straightening rollers of the straightening roller group is fixed, and is not changed during the straightening of a band and / or straightening bands of different thickness. A method according to claim 1 or 2, characterized in that the straightening roller group has at least three straightening rollers, preferably at least four straightening rollers, more preferably at least five straightening rollers with roll-to-roll increasing diameter. Method according to one of claims 1 to 3, characterized in that the diameter of the straightening rollers is at least 500 times, preferably at least 1000 times the thickness of the band to be straightened. Method according to one of claims 1 to 4, characterized in that the tensile stress of at least 75%, preferably at least 85%, z. B. is at least 90% of the yield strength. Method according to one of claims 1 to 5, characterized in that the diameter of the straightening roller group increases from roller to roller by a factor of 1.05 to 1.5, preferably by a factor of 1.15 to 1.3 increases. Method according to one of claims 1 to 6, characterized in that the number of straightening rollers of the straightening roller group and their diameter gradation is calculated according to a mathematical model which as input parameters, the strip thickness or the band thickness range, the modulus of elasticity, the transverse contraction number, the stress-strain curves, the degree of stretch required to eliminate the waviness, the anticipated strip tension variations, the expected strength variations, the expected strip thickness variations and / or the amount of maximum allowable longitudinal deflection. Method according to one of claims 1 to 7, characterized in that the thickness of the band to be straightened 0.02 mm to 1.0 mm, z. B. 0.05 mm to 0.5 mm. Method according to one of claims 1 to 8, characterized in that the straightening roller group upstream of one or more additional additional straightening rollers and / or are arranged downstream, wherein the diameter of the additional straightening rollers is preferably less than or equal to the diameter of the first straightening roller of the straightening roller group. Plant for straightening a metal strip (1), in particular a thin metal strip having a thickness d ≤ 1 mm, according to a method according to one of claims 1 to 9, comprising at least one brake roller set (2) and a pull roller set (3) and at least one between the Brake roller set 2) and the Zugrollensatz (3) arranged straightening roller group (4) with several straightening rollers (4.1 to 4.7), wherein the diameter (D1 to D7) of the straightening rollers (4.1 to 4.7) is so large that the band (1) in the The selected strip tension follows the curvature of the straightening rollers (4.1 to 4.7) and the diameter (D1 to D7) of the straightening rollers (4.1 to 4.7) increases in the direction of travel (R) from roller to roller. Installation according to claim 10, characterized in that the position of the straightening rollers (4.1 to 4.7) and consequently the immersion depth of a straightening roller between two adjacent straightening rollers of the straightening roller group (4) is fixed. Plant according to claim 10 or 11, characterized in that the straightening roller group (4) has at least three rollers, preferably at least four rollers, more preferably at least five rollers with roller to roller increasing diameter (D1 to D7). Installation according to one of claims 10 to 12, characterized in that the diameter (D1 to D7) of the straightening rollers of the straightening roller group (4) is at least 500 times, preferably at least 1000 times the thickness (d) of the band to be straightened. Installation according to one of claims 10 to 13, characterized in that the diameter D1 to D7) of the straightening rollers (4.1 to 4.7) of the straightening roller group 4 from roll to roll by a factor of 1.05 to 1.5, preferably of 1.15 increases to 1.3. Installation according to one of claims 10 to 14, characterized in that the straightening roller group (4) one or more further additional straightening rollers (5.1 to 5.3) are arranged upstream and / or downstream. Plant according to one of claims 10 to 15, with several belt treatment zones, e.g. B. one or more Zugreckzonen and / or one or more stretch bending zones, characterized in that the straightening roller group (4) in the last band treatment zone, z. B. in the last Zugreckzone, or forms the last band treatment zone.

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