Method for treating hot-rolled coils, and apparatus therefor

Abstract

The invention relates to a method for treating hot-rolled coils, wherein, after uncoiling a hot-rolled strip at the end of the hot strip mill and in particular before completion of transformation from austenite into ferrite in the microstructure of the hot-rolled strip, the hot-rolled coil is transferred from an uncoiling apparatus to an apparatus, wherein, in order to correct the shape of the coil, the coil is placed on two spaced-apart correction elements which contact the coil surface below the apex and at a distance from the transverse centre of the coil. The invention also relates to an apparatus for carrying out the method.

Description

[0001] Method for treating hot strip coils and device therefor

[0002] The invention relates to a method for treating hot strip coils and a device for carrying out the method.

[0003] Hot strip is typically produced by heating a continuously cast steel slab to a desired rolling temperature in a pusher furnace and then feeding it to the hot strip mill. The temperature of the slab is usually well above the austenitizing temperature.

[0004] In the hot strip mill, the slab's thickness is first reduced in the reversing roughing stand through several rolling passes, during which it is simultaneously elongated. Once this process has progressed sufficiently, the strip enters the actual rolling mill, where it is guided through several rolling stands and further reduced in thickness until a target thickness is reached. In order to be further processed, the hot strip, which is several hundred meters long, must first be converted into a transportable format and then cooled. The term "hot strip mill" as used herein also includes the cooling section downstream of the rolling stands.

[0005] The common transportable format is the coil, also called a bundle, into which the steel strip is wound. For this purpose, the steel strip emerging from the hot strip mill is wound on a coiler. After coiling, the strip is pulled off the mandrel onto which it was wound and then transported. Cycle times must be maintained. Between coiling and transport to the next processing station, the coil also cools. In some grades, a transformation from austenite to ferrite occurs, while the steel is comparatively soft.

[0006] The problem here is that coil sagging can occur when winding relatively soft coils. Steel grades that transform from austenite to ferrite during coil winding or transport can be particularly affected by this problem of unstable shape, especially of the coil eye.

[0007] This leads to problems familiar to the industry: reduced performance of downstream systems, rewinding costs, logistical overhead, short-term strip dropouts from the overall order, and material damage. This deformation can be particularly problematic if the coil can no longer be transported or picked up by a mandrel because the coil eye has become too flat and / or too oval. The target size of the coil eye inner diameter is 760 mm; if the smallest diameter falls below 720 mm, the coil must be rejected and reprocessed.

[0008] There is therefore a need to carry out coiling without causing damage, with reduced effort and without increasing throughput times.

[0009] EP 3774105 B1 discloses a method for preventing coil collapse in hot-rolled strip. This method involves further rotating the coil while still warm to compensate for the deformation. This method does not allow for correction within the cycle times.

[0010] DE 112017003683 T5 describes a shape correction for hot-rolled strip. This is a highly complex process involving reheating and detection of the largest diameter. This process is also practically impossible to perform within a line during ongoing operation. KR 101504837 B1 describes a coil transport device in which a coil is rotated or lifted from below to make corrections. The disadvantage of this is that the conversion point is missed and can also lead to damage to the coil.

[0011] JP 0924419 A2 discloses a coil transfer cage in which force is transmitted from the side by movable arms to correct the shape. The disadvantage of this approach is that damage to the coil is almost inevitable, and the device is so complex and requires such high forces that such an approach seems hardly practical.

[0012] The object of the invention is to create a method with which hot strip coils are produced which are dimensionally stable, in which the cycle times are not affected and which can be carried out cost-effectively, is suitable for all common coil outer diameters, is low-wear and can be carried out in a space-saving manner.

[0013] The problem is solved by a method having the features of claim 1.

[0014] Advantageous further training is indicated in the dependent subclaims.

[0015] It is a further object to provide a device for carrying out the method.

[0016] The object is achieved by a device having the features of claim 11.

[0017] Advantageous further training is indicated in the dependent subclaims.

[0018] According to the invention, after winding, and especially during the structural transformation, the oval waistband is lowered into a corset consisting of two rollers. This corset exerts a supporting effect through the waistband's own weight, and the lateral forces acting on the waistband by the rollers correct the ovality of the waistband. After the structural transformation of the waistband or further cooling, i.e., in the range of approximately 1 to 10 seconds, the waistband can be removed with an improved shape.

[0019] The basic idea of ​​the invention is thus the use of an adapted pair of rollers with a reduced distance on the coil's outer surface compared to oval, uncorrected coil outer diameters, which "forces" the coil to "slide in" accordingly and thus improves the ovality. The distance A of the correction elements, in particular rollers, is defined as the shortest distance between the respective surfaces. This is also shown as an example in Figure 1 as distance A.

[0020] Of course, more than two rollers can be provided. For example, these can be divided along the long side of the coil and each supported to accommodate a correspondingly higher weight. However, it is also conceivable to provide several pairs of rollers per side.

[0021] The diameter of the rollers can be between 10 mm and 1000 mm. Preferably between 100 mm and 700 mm, particularly preferably between 200 mm and 500 mm. A comparatively small diameter can be advantageous for space utilization, while a comparatively large diameter can provide improved rigidity. The rollers can be hollow or solid.

[0022] In addition, it may be advisable to heat the rolls to avoid cold spots on the coil or curvature of the roll or to rotate them from coil to coil.

[0023] Advantageously, the rolls can be sufficiently heated by the coils during production and also remain warm.

[0024] The advantage is that it reliably prevents coils that are too oval, which cannot be used in pickling lines without rewinding. Furthermore, results can be improved by avoiding additional work such as rewinding. Logistics improvements are also achieved by reducing throughput times.

[0025] All coils in an order remain at the same processing stage. This improves results by reducing throughput time and avoiding a reduction in performance in the subsequent processing stage (slow feed of the oval coil into the pickling strip accumulator). Furthermore, scrap is minimized.

[0026] The invention thus relates in particular to a method for treating hot strip coils, wherein after the coiling of a hot strip at the end of the hot strip mill and in particular before the completion of a transformation from austenite to ferrite of the hot strip structure, the hot strip coil is placed from a coiling device onto a device, wherein for the shape correction of the coil the coil is placed on two spaced correction elements which contact the coil surface below the height center and spaced from the transverse center of the coil.

[0027] The vertical center, as defined by the invention, is the horizontal center plane through the coil, and the transverse center, as defined by the invention, is the vertical center plane through the coil. Each is measured from the frontal view of the coil. Figure 1 shows the vertical center 9 and the transverse center 10.

[0028] A further development provides that the distance A of the correction elements is set so that it is between 80% and 110%, in particular 90% and 105% of the ideally circular coil.

[0029] A further development provides that the correction elements exert a force on the surface of the coil, whereby this force is generated passively by the weight of the coil or passively and actively by a feed movement of the correction elements.

[0030] A further development provides for the correction elements to be arranged symmetrically around the transverse center. This can advantageously even out the force application to the coil. A further development provides for the use of correction elements designed as cylindrical bodies, in particular as rotating rollers, so that the coil can move on them without damaging the coil surface.

[0031] A further development provides for the use of support elements below the rollers and below the coil, which ensure that the coil sinks in a defined manner between the rollers.

[0032] A further development provides that the support elements are arranged firmly below the position of a coil and thereby vertically limit a lowering movement of the coil by the correction elements.

[0033] A further development provides for the support elements to be positioned vertically in a fixed manner depending on the diameter of a coil.

[0034] A further development provides that the support elements are vertically movable and pick up and support the coil as it is lowered onto the device and lower it in a defined manner.

[0035] A further development provides for the supporting elements to be lowered until the coil has undergone a desired shape correction.

[0036] A further development provides that the coil is lifted out of the device after the conversion has been completed.

[0037] A further aspect of the invention relates to a device for treating hot-rolled strip coils, wherein the device for correcting the shape of the coil has at least two spaced-apart correction elements onto which a coil can be placed, wherein the correction elements extend with their longitudinal axes substantially parallel along the longitudinal extent of a coil so that they bear against a coil surface, wherein the device is designed such that the correction elements contact the coil surface below the vertical center and at a distance from the transverse center of the coil. A further development provides that the correction elements have a distance from one another that is between 80% and 110%, in particular 95% and 105%, of the ideally circular coil.

[0038] A further development provides that the correction elements are designed as cylindrical bodies.

[0039] A further development provides that the correction elements are designed as rotating rollers so that the coil can move on them without damaging the coil surface.

[0040] A further development provides that at least one support element is arranged below the rollers and below the coil, which ensures a defined sinking of the coil between the rollers.

[0041] A further development provides that the support element is arranged firmly below the position of a coil and thereby vertically limits a lowering movement of the coil by the correction elements.

[0042] A further development provides that the support element is vertically fixed and adjusted to the diameter of a coil.

[0043] A further development provides that the support element is vertically movable and receives and supports the coil when it is lowered onto the device and lowers it in a defined manner.

[0044] A further development provides that the support element can be lowered until the coil has undergone a desired shape correction.

[0045] A further development provides that the support device has a curvature facing the coil for positively receiving the coil, or the device has at least two rod-like support devices that run parallel to each other and to the coil and are spaced apart from each other. A further development provides that the rollers and / or the support device have an axial longitudinal extension that corresponds at least to the axial extension of the coil.

[0046] A further development provides that the rollers of the device are arranged rotatably on support arms.

[0047] A further development provides that the support arms are designed to be movable relative to one another both in height and in delivery.

[0048] A further development provides for the rollers to be designed to be heated or cooled or both.

[0049] The invention is explained by way of example using a drawing.

[0050] They show:

[0051] Figure 1: highly schematic representation of an oval coil deformed by its own weight;

[0052] Figure 2: the coil according to Figure 1 as used in a device according to the invention;

[0053] Figure 3: highly schematic view of the effect of the device according to the invention on the coil shape during the phase transformation;

[0054] Figure 4: a representation of a coil in a device according to the invention;

[0055] Figure 5: the arrangement according to Figure 4 in a perspective top view.

[0056] Figure 1 shows a highly schematic view of a bundle 1 or coil 1 which, due to the transformation from austenite to ferrite, was comparatively soft during winding or after winding and removal from the winding mandrel, and which accordingly collapsed under its own weight and assumed an oval shape. Additionally, the vertical center 9 and transverse center 10 are shown here. The distance A between the two correction elements 4 is also shown. Figure 2 shows the inventive method for ovality correction, wherein a coil 1 is lowered onto the inventive device 3 after winding and removal from the winding mandrel and during the transformation in the direction of arrow 2.

[0057] Here, the coil 1 is lowered onto correction elements 4 according to the invention, which are arranged on both sides of the transverse center of the coil 1 (corresponds approximately to the position of the arrow 2) and exert a force on the coil 1 according to the arrows 5.

[0058] This force can be generated passively by the weight of the coil 1 or passively and actively by a feed movement of the correction elements 4.

[0059] The correction elements 4 can be designed, in particular, as cylindrical bodies and, in particular, also as rotatable rollers 4. This is advantageous because the coil 1 can move on them without damaging the coil surface 8.

[0060] The distance A between the rollers 4 is dimensioned such that it is between 80% and 110%, in particular 90% and 105%, of the ideally circular coil 1. Preferably, it is 1 to 10% more than the diameter of a circular coil 1 (Figure 3), since a complete correction of the ovality is neither always possible nor necessary.

[0061] For example, the ideal diameter of the coil can be 2000 mm. Collapse of the coil can cause ovality, which increases the diameter at its widest point to, for example, 2300 mm. The coil eyelet can have a value of 700 mm at its narrowest point (as mentioned, the target diameter is 760 mm). The distance A between the correction elements 4 can then preferably be selected between 1600 and 2200 mm. Particularly preferably between 1800 and 2100 mm, with values ​​greater than 2020 mm being particularly preferred. When the coil 1 has then "slipped" through the correction elements set, for example, to A = 2050 mm, the ovality has already been improved, i.e., corrected to approximately 2050 mm and thus from 2300 mm to 2050 mm. The coil eyelet then has a value of 750 mm at its narrowest point. Such a correction can advantageously ensure a low risk of damage and sufficient correction of ovality.However, it is also possible for the distance A between the correction elements 4 to be set to 1600 mm. In this case, the coil cannot slip through the correction elements but is held in place by them. Nevertheless, the forces exerted by the correction elements 4 acting laterally on the coil 1 positively correct any ovality of the coil 1.

[0062] Preferably, the correction elements 4 are arranged symmetrically around the transverse center 9, but it would also be possible to offset the rollers. This may be necessary, for example, in confined spaces around the unwinder.

[0063] Of course, further support elements can also be present below the rollers 4 and below the coil 1, which ensure a defined sinking of the coil 1 between the rollers 4.

[0064] The rollers 4 have an axial longitudinal extension which corresponds at least to the axial extension of the coil 1 or is preferably larger so that a coil 1 can be easily placed thereon.

[0065] Figure 4 shows the device according to the invention, wherein the coil 1 is brought onto the device 3 according to the invention according to the method according to the invention, in particular before the complete transformation of austenite into ferrite, wherein the corresponding rollers 4 of the device 3 are rotatably arranged on support arms 6.

[0066] Here, the distance between the rollers 4 is clearly much smaller than the oval outer diameter of the coil 1 and also smaller than the diameter of an ideally round coil 1, so that the coil 1 should not slip through completely.

[0067] In addition, there are supporting elements 7 below the coil 1, which can be roller-shaped.

[0068] The support elements 7 can be fixedly arranged below the position of a coil 1, thereby vertically limiting a lowering movement of the coil 1 by the correction elements 4. Depending on the diameter of a coil 1, the support elements 7 can be vertically fixedly positioned to match the diameter.

[0069] The support elements 7 can also be vertically movable and receive and support the coil 1 as it is lowered onto the device 3. Furthermore, the support arms 6 can also be movable relative to one another both in height and in feed direction, in order to be able to react to different diameters of coils 1 if necessary.

[0070] However, this does not exclude the possibility that the rollers 4 are fixed in their position and assume a position relative to one another that is suitable for the majority of the coils.

[0071] Since the transformation from austenite to ferrite takes place within a manageable period of time, the device and method according to the invention ensure that ovality correction can be carried out reliably in an in-line process. The advantage of the invention is that ovality correction of hot strip coils during the transformation phase from austenite to ferrite can be carried out in a simple, reliable, and cost-effective manner.

Claims

Claims 1. A method for treating hot strip coils, wherein after the hot strip has been coiled at the end of the hot strip mill and in particular before the transformation of the hot strip structure from austenite to ferrite has been completed, the hot strip coil (1) is placed by a coiling device onto a device (3), wherein for the shape correction of the coil (1) the coil is placed onto two spaced-apart correction elements (4) which contact the coil surface (8) below the vertical center (9) and spaced from the transverse center (10) of the coil (1).

2. Method according to claim 1, characterized in that the distance A of the correction elements (4) is adjusted so that it is between 80% and 110%, in particular 90% and 105% of the ideally circular coil (1).

3. Method according to claim 1 or 2, characterized in that the correction elements (4) exert a force on the surface of the coil, this force being generated passively by the weight of the coil (1) or passively and actively by a feed movement of the correction elements (4).

4. Method according to one of the preceding claims, characterized in that the correction elements (4) are arranged symmetrically around the transverse center (9).

5. Method according to one of the preceding claims, characterized in that correction elements (4) are used which are designed as cylindrical bodies and in particular as rotatable rollers (4) so ​​that the coil (1) can move thereon without the coil surface (8) being damaged.

6. Method according to one of the preceding claims, characterized in that support elements (7) are used below the rollers (4) and below the coil (1), which ensure a defined sinking of the coil (1) between the rollers (4).

7. Method according to claim 6, characterized in that the support elements (7) are arranged fixedly below the position of a coil (1) and thereby vertically limit a lowering movement of the coil (1) by the correction elements (4).

8. Method according to claim 6 or 7, characterized in that the support elements (7) are vertically fixedly positioned depending on the diameter of a coil (1) and adapted to the latter.

9. Method according to claim 6, characterized in that the support elements (7) are vertically movable and receive and support the coil (1) when it is lowered onto the device (3) and lower it in a defined manner.

10. Method according to claim 9, characterized in that the support elements (7) are countersunk until the coil (1) has undergone a desired shape correction.

11. Method according to one of the preceding claims, characterized in that the coil is lifted out of the device (3) after the conversion has taken place.

12. Device for treating hot strip coils, wherein the device (3) for correcting the shape of the coil (1) has two spaced-apart correction elements (4) onto which a coil (1) can be placed, wherein the correction elements (4) extend with their longitudinal axis substantially parallel along the longitudinal extent of a coil (1) so that they bear against a coil surface (8), wherein the device is designed such that the correction elements (4) contact the coil surface (8) below the vertical center (9) and at a distance from the transverse center (10) of the coil (1).

13. Device according to claim 12, characterized in that the correction elements (4) have a distance from one another which is between 80% and 110%, in particular 95% and 105% of the ideally circular coil (1).

14. Device according to claim 12 or 13, characterized in that the correction elements (4) are designed as cylindrical bodies.

15. Device according to one of claims 12 to 14, characterized in that the correction elements (4) are designed as rotatable rollers (4) so ​​that the coil (1) can move thereon without the coil surface (8) being damaged.

16. Device according to one of claims 12 to 15, characterized in that at least one support element (7) is arranged below the rollers (4) and below the coil (1), which support element ensures a defined sinking of the coil (1) between the rollers (4).

17. Device according to claim 16, characterized in that the support element (7) is arranged fixedly below the position of a coil (1) and thereby vertically limits a lowering movement of the coil (1) by the correction elements (4).

18. Device according to claim 16 or 17, characterized in that the support element (7) is vertically fixedly positioned depending on the diameter of a coil (1) and adapted to the latter.

19. Device according to claim 16, characterized in that the support element (7) is vertically movable and receives and supports the coil (1) when it is lowered onto the device (3) and lowers it in a defined manner.

20. Device according to claim 19, characterized in that the support element (7) can be lowered until the coil (1) has undergone a desired shape correction.

21. Device according to one of claims 12 to 20, characterized in that the support device (7) has a curvature facing the coil (1) for positive reception of the coil or the device (3) has at least two rod-like support devices (7) which run parallel to one another and to the coil and are spaced apart from one another.

22. Device according to one of claims 12 to 21, characterized in that the rollers (4) and / or the support device (7) have an axial longitudinal extent which corresponds at least to the axial extent of the coil (1).

23. Device according to one of claims 12 to 22, characterized in that the rollers (4) of the device (3) are rotatably arranged on support arms (6).

24. Device according to one of claims 12 to 23, characterized in that the support arms (6) are designed to be movable relative to one another both in height and in delivery.

25. Device according to one of claims 12 to 24, characterized in that the rollers are designed to be heatable or coolable or both.

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