Method and reversible rolling mill for rolling a metal strip

Abstract

The present invention relates to a method for rolling a metallic strip (2), wherein the metallic strip (2) is rolled alternately in two opposite rolling directions in at least one reversing rolling stand (3) arranged between two reversing reels (8, 9), a cooling lubricant is applied exclusively on the entry side to the work rolls (4, 5) of the reversing rolling stand (3) and / or directly to the metallic strip (2), by means of which both the work rolls (4, 5) and the metallic strip (2) are cooled and basic lubrication of the rolling process is achieved, and an additional lubricant for lubricating the metallic strip (2) is applied exclusively on the exit side to the metallic strip (2), wherein the additional lubricant is applied exclusively to the strip top of the reeled metallic strip (2) at and / or downstream of an entry point (16).Furthermore, the present invention relates to a corresponding rolling mill.

Description

[0001] The present invention relates to a method and a reversing rolling mill for rolling a metallic strip.

[0002] Operating methods for a reversing rolling mill are well known from the prior art. For example, EP 2 750 813 B2 discloses a corresponding method in which lubrication is decoupled from cooling. This is achieved by oiling the rolled stock on both sides after a rolling pass and before coiling, using a rolling oil application device, so that in a subsequent rolling pass, the lubrication effect can be achieved exclusively via the incoming, already oiled rolled stock.

[0003] Since the coil diameter changes continuously during the coiling process, and thus the inclination and position of the strip travel in the area of ​​the rolling oil application device, continuous adjustment of the rolling oil application device is essential to maintain a uniform application. Furthermore, the use of pure water for cooling produces large quantities of a mixture consisting of the cooling water and the lubricating oil washed off the strip, the treatment of which is very complex. In addition, it appears that the cooling of the rolls of the reversing rolling stand always occurs from the same side, regardless of the rolling direction. This means that for so-called even rolling passes, no strip cooling occurs to dissipate the forming heat from the preceding odd passes.This can quickly lead to overheating in the roll gap and thus to lubrication failure, as well as damage to the strip surface and / or the roll surface. Furthermore, applying the cooling medium only to one side can cause it to be carried towards the coiler, thereby impairing the lubrication performance, particularly on the strip surface.

[0004] From EP 3 733 317 B1, another method for rolling a workpiece in a reversing rolling mill is known. In one embodiment, spray bars and cooling bars are arranged on each side of the reversing rolling stand above and below the workpiece level. The spray bars are configured to discharge an aerosol mixture of a lubricating oil and a carrier gas, whereas the cooling bars are configured to discharge a coolant or a coolant emulsion. A control unit can be used to control both the spray and cooling bars such that the aerosol mixture is sprayed exclusively onto the work rolls and / or the workpiece on the exit side of a rolling pass, and the coolant or coolant emulsion is discharged exclusively onto the work rolls and / or the workpiece on the entry side of a rolling pass.

[0005] Another method for rolling a rolled product is described in EP 3 238 843 A1. In this method, a cooling lubricant is introduced into a contact zone where a contact surface of the rolled product rests against a work roll. The lubrication requirement of the contact zone is determined as a function of at least one process parameter of the rolling process. If the amount of cooling lubricant currently introduced into the contact zone does not cover the lubrication requirement, then, according to the teachings of EP 3 238 843 A1, an additional lubricant, for example, a rolling oil, is applied to the contact surface of the rolled product at a predetermined application distance in front of the roll gap.

[0006] To allow the applied additive lubricant sufficient contact time to exert its lubricating effect at any strip entry speed on the rolling stand (so-called plate-out), the application must take place at a specific minimum distance from the roll gap entry. This requires additional installation space, which is generally not available in reversing rolling mills optimized for compactness.

[0007] Against this background, the present invention aims to provide an improved method for rolling a metallic strip with simultaneously reduced installation effort compared to the prior art, as well as a corresponding reversing rolling mill. Description of the invention

[0008] The solution to the aforementioned problem is a method for rolling a metallic strip with the features of claim 1 or a reversing rolling mill with the features of claim 9.

[0009] In the method for rolling a metallic strip, the invention provides that the metallic strip is rolled alternately in two opposite rolling directions in at least one reversing rolling stand arranged between two reversing reels, a cooling lubricant is applied exclusively on the entry side to the work rolls of the reversing rolling stand and / or directly to the metallic strip, by means of which both the work rolls and the metallic strip are cooled and basic lubrication of the rolling process is achieved, and an additional lubricant for lubricating the metallic strip is applied exclusively on the exit side to the metallic strip, wherein the additional lubricant is applied exclusively to the top surface of the reeled metallic strip at and / or downstream of an entry point.

[0010] Similarly, the present invention relates to a reversing rolling mill for rolling a metallic strip, which according to the invention comprises at least one reversing rolling stand arranged between two reversing reels for rolling the metallic strip, several cooling-lubricating bars arranged on both sides of the reversing rolling stand, via which a cooling-lubricating agent is applied to the work rolls of the reversing rolling stand and / or directly to the metallic strip, by means of which both the work rolls and the metallic strip can be cooled and basic lubrication of the rolling process can be achieved, wherein each reversing reel is assigned at least one additional lubricant application device and wherein each of these additional lubricant application devices is arranged such that an additional lubricant can be applied exclusively to the top surface of the reeled metallic strip at one and / or downstream of a lead-in point.

[0011] According to the invention, the additional lubricant is applied exclusively to the upper surface of the coiled metallic strip at and / or downstream of the approach point. For the purposes of this invention, the approach point is defined as the point at which the underside of the metallic strip to be wound first comes into contact with the upper surface of the topmost winding layer of the coiling coil after a rolling pass. Tests have shown that applying the additional lubricant only to the upper surface of the already wound metallic strip on the reversing coiler on one side only ensures that the underside of the subsequent winding is automatically supplied with a sufficient quantity of the additional lubricant by the pressure between the individual coil windings.Therefore, it is advantageous to forego the installation of lubricant application devices below the strip plane and in the strip direction in front of the point where the metallic strip meets the coil, thereby saving the installation space between the reversing frame and the respective reversing reel and consequently keeping the dimensional lengths of the metallic strip to a minimum.

[0012] In a preferred embodiment, it is therefore provided that the reversing rolling mill does not have any additional lubricant application devices, preferably arranged below the strip plane, in the area between the reversing rolling stand and the respective reversing reels.

[0013] Because the cooling lubricant for cooling the work rolls and the metal strip is applied exclusively to the entry side of the work rolls of the reversing rolling mill and / or directly to the metal strip in each pass, cooling lubrication always takes place on the respective entry side of a rolling pass. As a result, the metal strip then carries only residual moisture from the cooling lubricant emulsion on the exit side, which is also advantageous if an additional lubricant is to be applied to the strip surface. It has been shown that the residual moisture of the emulsion remaining on the strip surface after the rolling pass improves both the absorption and the adhesion and even distribution of the additional lubricant applied to one side between the individual coil turns. In addition, the, if necessary,The additional lubricants, which are only applied when needed, limit the total lubricant consumption in the reversing rolling mill to the necessary minimum and prevent an unfavorable increase in the lubricant concentration in the cooling-lubricant emulsion circuit.

[0014] For the purposes of the present invention, a rolling emulsion is understood to be a cooling lubricant. Such an emulsion typically comprises water, rolling oil, which is present in the emulsion at a concentration of up to 3% or more, and emulsifiers. The rolling oil generally includes further additives that improve its lubricating properties.

[0015] For the purposes of the present invention, the additional lubricant is understood to be pure rolling oil, which is used for preparing the rolling emulsion. In this respect, the additional lubricant is applied to the metallic strip in its entirety, without any water admixture.

[0016] According to one advantageous embodiment, the additional lubricant can be applied to the metallic strip only as needed (discontinuously), i.e., when it is recognized in the preceding rolling pass that the lubrication is no longer sufficient for the subsequent rolling pass. In another advantageous embodiment, the additional lubricant can be applied continuously to the metallic strip, whereby, if it is recognized in the preceding rolling pass that the lubrication is no longer sufficient for the subsequent rolling pass, the quantity applied to the metallic strip is increased accordingly to achieve sufficient lubrication.

[0017] Depending on the requirements and quantity of additional lubricant, it can be applied to the metallic strip using single-component or dual-component nozzles, possibly with the aid of a carrier gas. It is also conceivable that, in cases of particularly high lubrication requirements, the additional lubricant could be applied during uncoiling before each rolling pass.

[0018] Although the application of the cooling lubricant in the form of the rolling emulsion is preferred, it goes without saying that the two components forming the cooling lubricant, i.e. essentially the water and the rolling oil, can also be applied separately under certain circumstances in order to achieve the cooling effect on the one hand and the lubricating effect on the other.

[0019] Further advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined in a technologically meaningful way and can define further embodiments of the invention. Furthermore, the features specified in the claims are specified and explained in more detail in the description, which also presents further preferred embodiments of the invention.

[0020] In an advantageous embodiment, the metallic strip can be rolled by means of two reversing rolling stands arranged between the two reversing reels. Accordingly, the reversing rolling mill preferably comprises two reversing rolling stands or a maximum of two reversing rolling stands, each with several cooling and lubrication bars arranged on both sides of the respective reversing rolling stand, via which the cooling and lubricating medium is supplied to the work rolls of the respective reversing rolling stand and / or directly to the metallic strip.

[0021] Since the additional lubricant is applied exclusively to the upper surface of the strip, it should advantageously be applied in such a quantity that the underside of the strip is coated solely through surface contact with the upper surface during coiling. Therefore, the additional lubricant is preferably applied in a quantity of 0.3 to 3.0 mL / m².

[0022] The metallic strip to be rolled in such a reversible rolling mill is typically delivered as a coil oiled after pickling to prevent rust, so that sufficient lubrication is usually present for the first rolling pass. In such a case, the additional lubricant can advantageously be applied only after the first rolling pass. After the last rolling pass, applying the additional lubricant to the metallic strip during coiling may still be beneficial if it is intended to serve as rust protection. However, an additional amount of lubricant applied can lead to increased cleaning effort in certain downstream processing steps, so the decision to apply it in the last pass should be made on a case-by-case basis. Whether the application of the additional lubricant can also be omitted after the penultimate pass should be decided within the rolling process.The metallic strip is most work-hardened and has the smallest thickness in the last pass, so a low coefficient of friction achieved through particularly good lubrication can be helpful for handling and reducing the rolling force. On the other hand, there may be other rolling parameters, such as a significant decrease in strip tension from the entry side of the reversing stand to the exit side of the reversing coiler, which, if friction is too low, can lead to process instabilities such as the flow divider emerging from the roll gap. To generally optimize lubricant consumption during the rolling process, it can be advantageous to apply the additional lubricant after the first pass and up to the penultimate or possibly even just the penultimate pass.

[0023] According to a preferred embodiment, the amount of additional lubricant applied can be varied along the strip length and / or width. For this purpose, it is preferably provided that at least one, and more preferably both, additional lubricant application devices have individually controllable lubricant nozzles, allowing the amount applied to be varied across the entire width of the metallic strip.

[0024] The lubricant nozzles of any auxiliary lubrication device can be designed as single-fluid or dual-fluid nozzles. Single-fluid nozzles are preferably used for higher quantities of auxiliary lubricant and reduce spray mist formation. Dual-fluid nozzles, on the other hand, allow the formation of an aerosol, i.e., an auxiliary lubricant-carrier gas mixture, and therefore offer a wider adjustment range for varying the application quantity. However, they also usually produce more spray mist. Air can be used as the carrier gas, although other gases such as nitrogen are also suitable.

[0025] In another advantageous embodiment, the amount of additional lubricant applied can also be varied along the strip path depending on process conditions and / or rolling parameters.

[0026] In an advantageous embodiment, the reversing rolling mill is provided with a control and / or regulation device that includes at least one process model by which the application quantity of the additional lubricant before each rolling pass can be regulated and / or controlled. The process model ensures that the control and / or regulation device determines the correct application quantity of the additional lubricant for the subsequent rolling pass in the preceding pass. It is particularly preferred that the application quantity is adjusted as a function of at least one process parameter selected from the following: strip speed, strip tension, rolling force, strip geometry, material composition, surface roughness, and / or a selection thereof.

[0027] The amount of additional lubricant applied can also depend on the distance between the additional lubricant application device or its lubricant nozzles and the respective strip position on the wound coil. Therefore, it can be advantageous if at least one, and preferably both, of the additional lubricant application devices are adjustable. Alternatively or additionally, at least one of the respective reversing reels can also be adjustable. In this context, it can further be advantageous if at least one, and preferably both, of the additional lubricant application devices include distance sensors. These can, of course, be connected to the control and / or regulating unit of the reversing rolling mill via a signal system in order to determine the optimal distance and adjust it during the rolling process.

[0028] Alternatively or additionally, the optimal distance between the additional lubricant application devices or their lubricant nozzles and the respective strip position can be set via position control. In this case, the position of the respective additional lubricant application device can be controlled, for example, based on the coil diameter, which changes continuously during the rolling process. The coil diameter can be measured during the rolling process or determined using a process model.

[0029] In a further advantageous embodiment, at least one, and more preferably both, of the additional lubricant application devices can include a pressure roller which, in the event of a strip break, presses the end of the metallic strip upstream of the respective additional lubricant application device onto the coil. Advantageously, the pressure roller is guided at a predetermined distance from the coil surface, for example, in a kind of "standby position," so that it can be positioned against the outer diameter of the coil as quickly as possible in the event of a detected strip break. Alternatively, the pressure roller can also be deliberately and permanently positioned against the outer diameter of the coil in order to optimize the transfer of the additional lubricant from the top of the penultimate turn below it to the underside of the last turn by applying pressure to the outer coil. Character designation

[0030] The invention and its technical context are explained in more detail below with reference to the figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the situations explained in the figures and combine them with other elements and findings from the present description and / or figures. It should be noted in particular that the figures, and especially the depicted proportions, are only schematic. The same reference numerals denote the same objects, so that explanations from other figures can be consulted as needed. The figures show: Figure 1 shows a first embodiment of the reversing rolling mill according to the invention, and Figure 2 shows a further embodiment of the reversing rolling mill according to the invention.

[0031] First, the focus will be onFigure 1 Reference is made to a highly simplified representation of a reversing rolling mill 1 for rolling a metallic strip 2, for example a steel or aluminum strip. Figure 1 This comprises two separate presentations ( Fig. 1A and Fig. 1B ), which visualizes the inventive method in one possible embodiment.

[0032] In the illustrated embodiment, the reversing rolling mill 1 has a single reversing rolling stand 3, comprising an upper and a lower work roll 4, 5, as well as an upper and a lower backup roll 6, 7 (4-Hi). Alternatively, other reversing rolling stands can be used, such as a two-roll reversing rolling stand (2-Hi), a six-roll reversing rolling stand (6-Hi), or even a cluster reversing rolling stand comprising 18 or 20 rolls (18-Hi or 20-Hi, respectively). A reversing reel 8, 9 is arranged on each side of the reversing rolling stand 3, which can function as a coiler or a reel depending on the rolling direction. Thus, in Figure 1A A state is shown in which the metallic strip 2 is unwound via the reversing reel 8 and rewound via the reversing reel 9 after a rolling pass. In Figure 1BThe reverse case is then shown, in which the reversing reel 9 forms the unwinding reel and the reversing reel 8 forms the winding reel.

[0033] Furthermore, the reversing rolling mill 1 comprises several cooling and lubricating bars 10, 11, 12, 13 arranged on both sides of the reversing rolling stand 3, via which a cooling and lubricating agent, for example a rolling emulsion for cooling the work rolls and / or the metallic strip 2 and as basic lubrication for the rolling process, can be discharged over the entire width onto the work rolls 4, 5 of the reversing rolling stand 3 and / or directly onto the metallic strip 2.

[0034] According to the invention, the reversing rolling mill 1 further comprises an additional lubricant application device 14, 15 assigned to each of the respective reversing reels 8, 9, wherein each of these additional lubricant application devices 14, 15 is configured such that an additional lubricant, preferably pure rolling oil, can be applied exclusively to the upper surface of the coiled metallic strip 2 at and / or downstream of an approach point 16. For the purposes of the present invention, the approach point 16 is to be regarded as the point at which the underside of the metallic strip 2 to be wound first comes into contact with the upper surface of the top winding layer of the coil 17.

[0035] To ensure optimal application of the additional lubricant to the strip surface across the entire coil structure, an optimal distance between the additional lubricant application device 14, 15 and the coil surface must be maintained. For this purpose, each of these additional lubricant application devices 14, 15 is adjustable. The distance is advantageously detected by distance sensors (not shown), which are arranged, for example, on the respective additional lubricant application device 14, 15. Furthermore, each of the two additional lubricant application devices 14, 15 has a plurality of lubricant nozzles 141, 151 arranged side by side, which are preferably individually controllable, so that the lubrication can be adapted to the respective strip width and strip speed and / or other rolling process parameters.

[0036] In Figure 2A further embodiment of the reversing rolling mill 1 according to the invention is shown. In contrast to the first embodiment, the two additional lubricant application devices 14, 15 each comprise a pressure roller 18, 19 in its protective housing, which, in the event of a detected strip break, is to be positioned against the outer diameter of the coil 17 as quickly as possible. Alternatively, the pressure rollers 18, 19 can also be permanently positioned against the coil 17.

[0037] The process is explained below according to one embodiment. For rolling a metallic strip 2, a pre-oiled coil 17 is typically provided first. During the rolling process, this coil then passes through the reversing rolling stand 3, located between the two reversing reels 8, 9, with alternating directions of travel, thereby reducing its thickness. The direction of travel is determined by the Figures 1A, 1B , 2A and 2B sketched using the arrows.

[0038] In Fig. 1A The metallic strip 2 is unwound from the reversing reel 8, then passes through the roll gap formed between the work rolls 4, 5, whereby its thickness is reduced in a rolling pass, and is subsequently wound up by the reversing reel 9, which acts as a winding reel. As the Figure 1A As can be seen, a cooling lubricant is supplied to the work rolls 4, 5 of the reversing rolling stand 3 and / or directly to the strip 2 via the cooling lubrication bars 10, 12 which are switched on exclusively on the inlet side.

[0039] If necessary, i.e., if lubrication is required in the preceding rolling pass, the additional lubricant for the following rolling pass is applied to the upper surface of the strip only via the additional lubricant application device 14 at and / or downstream of the approach point 16. For the subsequent rolling pass, the metallic strip 2 is unwound from the reversing reel 9 and wound onto the reversing reel 8, as described in the Figures 1B or as shown in Figure 2B. Here, the metallic strip 2 passes through the reversing rolling mill 3 from right to left, thereby reducing its thickness again. Based on the illustration in the Figures 1BFigure 2B shows that the metallic strip 2 and the work rolls 4, 5 are again supplied with cooling lubricant exclusively on the entry side via the cooling-lubricating bars 11, 13, and that the metallic strip 2 is additionally lubricated as needed exclusively on the exit side via the additional lubricant application device 15. The process is repeated until the metallic strip 2 has reached its target thickness, whereby no additional lubrication is required for the last and / or penultimate rolling pass, since no further rolling passes take place after the last pass or sufficient lubrication is provided by the preceding rolling passes. Reference symbol list

[0040] 1 Reversing rolling mill 2 Metallic strip 3 Reversing rolling stand 4 Upper work roll 5 Lower work roll 6 Upper backup roll 7 Lower backup roll 8 Reversing reel 9 Reversing reel 10 Cooling / lubricating bar 11 Cooling / lubricating bar 12 Cooling / lubricating bar 13 Cooling / lubricating bar 14 Additional lubricant application device 141 Lubricating nozzles 15 Additional lubricant application device 151 Lubricating nozzles 16 Lead-in point 17 Coil 18 Pressure roller 19 Pressure roller

Claims

1. A method for rolling a metallic strip (2), wherein the metallic strip (2) is rolled alternately in two opposite rolling directions in at least one reversing rolling stand (3) arranged between two reversing reels (8, 9), a cooling lubricant is applied exclusively on the entry side to the work rolls (4, 5) of the reversing rolling stand (3) and / or directly to the metallic strip (2), by means of which both the work rolls (4, 5) and the metallic strip (2) are cooled and basic lubrication of the rolling process is achieved, and an additional lubricant for lubricating the metallic strip (2) is applied exclusively on the exit side to the metallic strip (2), wherein the additional lubricant is applied exclusively to the top surface of the coiled metallic strip (2) at and / or downstream of an entry point (16).

2. Method according to claim 1, characterized by the fact thatthe additional lubricant is applied continuously or discontinuously.

3. Method according to claim 1 or 2, characterized by the fact that the metallic strip (2) is rolled alternately in two opposite rolling directions by means of two reversing rolling stands (3) arranged between two reversing reels (8, 9).

4. Method according to any one of the preceding claims, characterized by the fact that The additional lubricant is applied in such a quantity that the underside of the strip is coated solely through surface contact with the top side of the strip during winding.

5. Method according to any one of the preceding claims, characterized by the fact that the additional lubricant in a quantity ranging from 0.3 to 3.0 mL / m 2 is applied.

6. Method according to any one of the preceding claims, characterized by the fact that that the order quantity is varied across the belt length and / or the bandwidth.

7. Method according to any of the preceding claims, characterized by the fact that that the order quantity is set depending on a process parameter selected from the range including strip speed, strip tension, rolling force, strip geometry, material composition, surface roughness and / or a selection thereof.

8. Method according to any one of the preceding claims, characterized by the fact that The additional lubricant is applied during unwinding.

9. Reversing rolling mill (1) for rolling a metallic strip (2), comprising at least one reversing rolling stand (3) arranged between two reversing reels (8, 9) for rolling the metallic strip (2), several cooling and lubricating bars (10, 11, 12, 13) arranged on both sides of the reversing rolling stand (3), via which a cooling and lubricating agent can be applied to the work rolls (4, 5) of the reversing rolling stand (3) and / or directly to the metallic strip (2), by means of which both the work rolls (4, 5) and the metallic strip (2) can be cooled and basic lubrication of the rolling process can be achieved, wherein each reversing reel (8, 9) is assigned at least one additional lubricant application device (14, 15), wherein each of these additional lubricant application devices (14, 15) is configured such thatthat an additional lubricant can be applied exclusively to the upper surface of the coiled metallic strip (2) at and / or downstream of a ramp-up point (16).

10. Reversing rolling mill (1) according to claim 9, characterized by the fact that this has no additional lubricant application devices in the area between the reversing rolling stand (3) and the reversing reels (8, 9).

11. Reversing rolling mill (1) according to one of the preceding claims 9 or 10, characterized by the fact that this has a control and / or regulation device which includes at least one process model by which the amount of additional lubricant applied before the respective rolling pass can be regulated and / or controlled.

12. Reversing rolling mill (1) according to any one of the preceding claims 9 to 11, characterized by the fact that that at least one of the additional lubricant application devices (14, 15) and / or at least one of the reversing reels (8, 9) are adjustable.

13. Reversing rolling mill (1) according to any one of the preceding claims 9 to 12, characterized by the fact that the additional lubricant application devices (14, 15) include at least one distance sensor.

14. Reversing rolling mill (1) according to any one of the preceding claims 9 to 13, characterized by the fact that at least one of the additional lubricant application devices (14, 15) includes a pressure roller (18, 19).

15. Reversing rolling mill (1) according to any one of the preceding claims 9 to 14, characterized by the fact that at least one of the additional lubricant application devices (14, 15) comprises individually controllable lubricant nozzles (141, 151).

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