Title of Invention

METHOD AND APPARATUS FOR CONTINUOUS CUTTING DURING HOT ROLLING

Abstract

A method and an apparatus for cutting a rolled strip (1) which, in particular at an especially high velocity, runs out of a hot-rolling train and is cut with shears (10) arranged downstream of the hot—rolling train, a driver having two rolls (PR2) being arranged downstream of the shears (10), between which driving rollers (PR2) the metal strip (1) runs through and which exert a retaining force on the metal strip (1). The driving rollers (PR2), after the cutting of the metal strip (1), are opened so that the retaining force is essentially zero.

Full Text

-1A- Description Method and apparatus for continuous cutting during hot rolling The invention relates to a method and an apparatus for cutting a metal strip which, in particular at an especially high velocity, runs out of a hot-rolling train and is cut with shears arranged downstream of the hot-rolling train, a driver having two driving rollers being arranged downstream of the shears, between which driving rollers the metal strip runs through. In hot rolling there are particular requirements with regard to the cutting of metal strip, since the hot rolling is effected at high strip velocities. Therefore the cutting of a hot-rolled strip must also be effected at a high strip velocity. On account of the cutting at high velocities, an extremely short time is available for changing over from the conditions when slipping out the front strip to the conditions required for slipping in the rear strip. Especially the velocity of the driving rolls downstream of the shears must change very quickly. Extreme demands are therefore made on the low inertia of the drivers. However, these demands can only be met to a limited extent, so that narrow limits are-set with regard to the strip velocity when cutting hot-rolled strip. A particular problem with the cutting of high-speed metal strip, in particular in the case of metal strip which runs out of a roll stand at a velocity greater than 12 m/sec, is the reactions on the rolling process upstream of the shears. The object of the invention is accordingly to avoid the disadvantages described above. In this case, it is especially desirable to avoid or significantly reduce reactions on an upstream rolling train due to the cutting of the metal strip. - 2 - This object is achieved according to the invention by a method and an apparatus as described hereunder.An especially essential feature in this case is the moving apart or opening of the driving rolls downstream of the shears after the cut. In this way, it is possible to avoid, to the greatest extent, reactions on an upstream rolling process due to the cutting. In this way, it is possible in turn to reduce losses in quality of the rolled metal strip due to the cutting operation. The special advantage consists in the fact that cutting is also possible at high velocities without having to set such parameters at the drivers which cannot be achieved or are very difficult to achieve mechanically. The invention is used especially advantageously for the cutting of metal strips which run out of a rolling train at a velocity greater than 12 m/s. In an advantageous development of the invention, before the opening of the driving rollers, the strip tension in the metal strip between the driving rollers and the coiler is reduced. In this way, especially smooth strip running is achieved. In a further advantageous development of the invention, before the cutting of the metal strip, the strip tension in the metal strip between the driving rollers and driving rollers arranged upstream of the shears is reduced to a requisite minimum tension. This further reduces the reactions of the cutting on the rolling process and leads to an especially precise cut. Here, the term requisite minimum tension refers to that tension in the metal strip which is necessary for the metal strip -to be tightened. In a further advantageous development of the invention, the rear metal strip, which has resulted from the cutting of the metal strip, is seized by the coiler after the opening of the driving rollers. In an advantageous development, the driving rollers are closed after the seizing of the rear metal strip by the coiler. - 3 - In an especially advantageous development of the invention, driving rollers are provided upstream and downstream of the shears. In this way, in combination with the invention, especially good uncoupling between cutting and rolling is achieved. Further advantages and details can be gathered from the following description of an exemplary embodiment of the invention. In the drawing, in detail: Fig. 1 shows an exemplary development of a cutting apparatus, Fig. 2 shows an exemplary development of a speed controller, Fig. 3 shows a torque characteristic, Fig. 4 shows a tensile-stress characteristic. The following abbreviations are used in the following description of an exemplary embodiment of the invention: DC Coiler PR1 Driving rollers upstream of the shears PR2 Driving rollers downstream of the shears WR Working rolls (last stand) bstrip Strip width Fi Strip tension upstream of the plant component i hstrip Strip thickness Ji Moment of inertia of the rollers including gearing, motor, etc. Li Length between adjacent plant components upstream of the component i MFF,i Preset torque Mi Motor torque MN,i Rated torque of the motor NBel%,i Motor torque in % relative to the rated torque Ri Roller radius VAdd,i Additional setpoint of the rotational speed or of the roller peripheral velocity - 4 - V1 Rotational speed or roller peripheral velocity V1* Setpoint of the rotational speed or of the roller peripheral velocity VStrip Nominal value of the strip velocity si Specific strip tension upstream of the plant component i sMFFf,i Preset torque converted to specific strip tension sMI Motor torque converted to specific strip tension sOP,1 Specific strip tension at the working point upstream of the plant component i t Time Index i designates the plant components coiler (DC) , driving rollers (PR1) upstream of the shears, driving rollers (PR2), or working rolls (WR) of the last stand of a rolling train upstream of the cut setting. Fig. 1 shows a cutting apparatus. This cutting apparatus has shears 10, a stand having driving rollers PR1 upstream of the shears 10, a stand having driving rollers PR2 downstream of the shears 10, a coiler DC, and a computing device 11. Via a data line 1*2, which is designed in an exemplary development of the bus system, there is a data connection between the computing device 11 and the drives of the driving rollers PR1 and PR2, the coiler DC and the shears 10. In Fig. 1, reference numeral 1 designates a metal strip, and the arrow designated by reference numeral ,2 designates the running direction of the metal strip 1. As viewed in the running direction of the metal strip 1, a rolling train for rolling the metal strip 1 is arranged upstream of the cutting apparatus. In this case, WR designates the working rolls of the last stand of this rolling train. After the metal strip 1 has been cut by the shears 10, the metal strip 1 is divided into a front part 13 and a rear part 14. The coiler DC is configured - 5 - in such a way that it winds the front metal strip 13 and the rear metal strip 14 into different coils. A motor torque Mi, where i = WR, ' PRl, PR2, DC, i.e. the working rolls WR, the driving rollers PR1 and PR2, and the coiler DC, is fed to the individual plant components. The plant reacts to this with the rotational speeds or roller peripheral velocities Vi, where i = WR, PR1, PR2, DC, and with the strip tensions Fi or the specific strip tensions si where i = WR, PRl, PR2, DC. In an exemplary development, a speed controller, which has a PI controller 3, is provided according to Fig. 2 for each of the components, driving rollers PRl, PR2 and coiler DC. The desired velocity Vi* and the actual velocity vi are applied to the input of this PI controller 3. A predetermined torque MFF,I acts on the limit of the PI controller 3. To simulate secondary current control, a PT2 element 4', at the output of which the motor torque Mi is obtained, is connected in series with the PI controller 3. The speed controllers may be operated in two modes: Mode 0 (switch 5 to the left) In this position of the switch 5, the PI controller 3 works as a normal speed controller and keeps the rotational speed at its setpoint. Mode 1 (switch 5 to the right) An additional setpoint vAdd,i of the rotational speed or the velocity is added at the input of the PI controller 3. The output of the PI controller 3 is limited by limit 31 on one side. As a result, the velocity, in the event of any crack in the metal strip 1, can only increase until it deviates from the setpoint by vAdd,i. In this operating mode, the preset torque MFF,I comes into effect directly as motor torque Mi. A reliable operating sequence is achieved in this way. The speed controllers are controlled by being preset with the mode and the torque MFF,± to be added. The - 6 - transmission of these preset inputs to the speed controllers is effected via dead times, which simulate the actual transmission dead times. In order to be able to better evaluate the motor torque Ml, the relative motor torque is calculated as a percentage with the rated torque MN,i: In an exemplary development, the sequence of the cutting of the metal strip per unit of time is subdivided into the following phases: Phase 1:Initial state Phase 2:Reduce strip tension between PR1 and PR2 to a minimum tension Phase 3:Cutting and compensate for the minimum tension present beforehand Phase 4:Reduce strip tension between PR2 and DC Phase 5: Open PR2 and wind front metal strip 14 to the end Phase 6:Coiler seizes new strip and builds up tension Phase 7:Close PR2 and continue to build up coiler tension Phase 8:Final state = initial state with new strip Fig. 3 and the following table disclose how the speed controllers are controlled in the individual phases: Phase WR Mod PR1 e PR2' DC sMFF,PR1 Preset torques [N/mm2] sMFF,DC 1 0 1 1 1 0 -4.8 12 2 0 1 1 1 0 ? 6 -4.8 ? -10.8 12. 3 0 1 1 0 6 ? 7.2 -10.8 12 ? 10.8 4 0 1 1 0 7.2 -10.8 ? 0 10.8 ? 0 5 0 1 0 0 7.2 0 0 - 7 - 6 0 1 0 1 7.2 ? 0 0 0 ? 7.2 7 0 1 1 1 0 0 ? -4.8 7.2 ? 12 8 0 1 1 1 0 -4.8 12 In order to be able to directly read off the effect of the preset torques MFF,i on the specific strip tensions si, the values sMFF,I are specified in N/mm2, from which the preset torques are calculated with the equation: MFF,i = sMFF,i . bstrip . hstrip . Ri, where i = WR, PR1, PR2, DC. The same correspondingly applies to the motor torques: Mi = sMi . bstrip . hstrip . Ri, where i = WR, PR1, PR2, DC. The phases 3 and 4 follow one another directly without a pause, so that the coiler tension is reduced from 12 to 0 N/mm2 without interruption. Likewise, the phases 6 and 7 follow one another directly, so that the coiler tension is built up from 0 to 12 N/mm2 with a continuous slope. Fig. 4 shows the characteristic of the strip tensions sPR1 and sPR2 between the working rolls and the driving rollers upstream of the shears and respectively between the shears and the driving rollers downstream of the shears plotted against time t. In this case, the following numerical values are taken as a basis: LPR1 = 23955 mm LPR2 = 2480 mm LDC = 4715 mm (front metal strip 14) 2272 mm (rear metal strip 13) RWR = 290 mm RPR1 = 250 mm RPR2 = 250 mm RDC = 1000 mm (front metal strip 14) 375 mm (rear metal strip 13) JWR = 21380 kgm2 JPR1 = 234 kgm2 JPR2 = 234 kgm2 - 8 - JDC = 14351 kgm2 (front metal strip 14) 2495 kgm2 (rear metal strip 13) bstrip = 1000 mm hstrip = 3 mm Vstrip = 16 m/s SOP, PR1= 7.2 N/mm2 SOP, PR2 = 7.2 N /mm2 sop, DC = 12 N /mm2 MN,WR = 382000 Nm MN MN,PR2 = 20400 Nm MN,DC = 50000 Nm The cutting of the metal strip 1 starts at about 380 m/sec. The characteristic of the tensile stress sPR1 in the metal strip 1 between the working rolls WR and the driving rollers PR1 upstream of the -shears 10 clearly shows the effect of the method according to the invention on the tensile stress downstream of the working rolls WR. This tensile stress, as Fig. 4 shows, remains virtually constant downstream of the working rolls WR during the cutting operation. Thus cutting process and rolling are uncoupled, that is, the cutting of the metal strip does not affect the rolling of the metal strip., -9-WE CLAIM: 1. Method of cutting a metal strip (1) which, in particular at an especially high velocity, runs out of a hot-rolling train and is cut with shears (10) arranged downstream of the hot-rolling train, at least one driver having at least two driving rollers (PR2) being arranged downstream of the shears (10), between which driving rollers (PR2) the metal strip (1) runs through and which exert a retaining force on the metal strip (1), characterized in that the driving rollers (PR2), after the cutting of the metal strip (1), are opened so that the retaining force is essentially zero. 2. Method as claimed in claim 1, wherein before the opening of the driving rollers. (PR2), the strip tension in the metal strip (1) between the driving rollers (PR2) and the coiler (DC) is reduced. 3. Method as claimed in claim 1 or 2, wherein before the cutting of the metal strip (1), the strip tension in the metal strip (1) between driving rollers (PR1) arranged upstream of the shears (10) and driving rollers (PR2) arranged downstream of the shears (10) is reduced to a requisite minimum tension. 4. Method as claimed in claim 1, 2 or 3, the metal strip (1), by the cutting of the metal strip (1), being divided into a rear metal strip (13) and a front metal strip (14), wherein the rear -10- metal strip (13), which has resulted from the cutting of the metal strip (1), is seized by the coiler (DC) after the opening of the driving rollers (PR2). 5. Method as claimed in claim 4 wherein the driving rollers (PR2) are closed after the seizing of the rear metal strip (13) by the coiler (DC). 6. Method as claimed in claim 1,2,3,4 and 5 wherein the metal strip (1) runs out of the rolling train at more than 12 m/s. 7. An apparatus for cutting a metal strip (1) for carrying out the method as claimed in claim 1 which, in particular at an especially high velocity, runs out of a hot rolling train, having shears (10) and two driving rollers (PR2) arranged downstream of the shears (10), between which driving rollers (PR2) the metal strip (1), runs through and which exert a retaining force on the metal strip (1), wherein the apparatus for cutting the metal strip (1) has a computing device (11), which opens the driving rollers (PR2) after the cutting of the metal strip (1) in such a way that the retaining force is essentially zero. -11- 8. Apparatus as claimed in claim 7, wherein at least two driving rollers (PR1) are provided upstream of the shears (10). 9. Apparatus as claimed in claim 7 or 8 wherein the shears (10) and the driving rollers(PRl, PR2) have a data connection to the computing device (11). 10. Apparatus as claimed in one of claims 7, 8, 9 wherein there is a data connection between the coiler (DC) and the computing device (11). A method and an apparatus for cutting a rolled strip (1) which, in particular at an especially high velocity, runs out of a hot-rolling train and is cut with shears (10) arranged downstream of the hot—rolling train, a driver having two rolls (PR2) being arranged downstream of the shears (10), between which driving rollers (PR2) the metal strip (1) runs through and which exert a retaining force on the metal strip (1). The driving rollers (PR2), after the cutting of the metal strip (1), are opened so that the retaining force is essentially zero.

Documents:

01940-cal-1998-abstract.pdf

01940-cal-1998-claims.pdf

01940-cal-1998-correspondence.pdf

01940-cal-1998-description(complete).pdf

01940-cal-1998-drawings.pdf

01940-cal-1998-form-1.pdf

01940-cal-1998-form-2.pdf

01940-cal-1998-form-3.pdf

01940-cal-1998-form-5.pdf

01940-cal-1998-g.p.a.pdf

01940-cal-1998-priority document others.pdf

01940-cal-1998-priority document.pdf

1940-CAL-1998-(12-10-2012)-FORM-27.pdf

1940-CAL-1998-CORRESPONDENCE 1.1.pdf

1940-CAL-1998-FORM-27.pdf

1940-cal-1998-granted-abstract.pdf

1940-cal-1998-granted-claims.pdf

1940-cal-1998-granted-correspondence.pdf

1940-cal-1998-granted-description (complete).pdf

1940-cal-1998-granted-drawings.pdf

1940-cal-1998-granted-examination report.pdf

1940-cal-1998-granted-form 1.pdf

1940-cal-1998-granted-form 2.pdf

1940-cal-1998-granted-form 3.pdf

1940-cal-1998-granted-form 5.pdf

1940-cal-1998-granted-gpa.pdf

1940-cal-1998-granted-letter patent.pdf

1940-cal-1998-granted-priority document.pdf

1940-cal-1998-granted-reply to examination report.pdf

1940-cal-1998-granted-specification.pdf

1940-cal-1998-granted-translated copy of priority document.pdf

1940-CAL-1998-PA.pdf