EP1314491B1 - Method of operating a stretch-reducing mill and stretch-reducing mill - Google Patents

Abstract

Process for operating a stretch reducing mill for rolling pipes comprises: determining a time point at which the rear end of the pipe leaves the roll stand in the conveying direction; establishing a time interval at which the rear end of the pipe leaves the roll stand, and controlling and regulating a drive of the roll stand. <??>Process for operating stretch reducing mill for rolling pipes comprises: determining a time point at which the rear end (8) of the pipe (2) leaves the roll stand (3d'''') in the conveying direction; establishing a time interval of a prescribed duration in which the time point lies and at which the rear end of the pipe leaves the roll stand; and controlling and regulating a drive (7'''') of the roll stand, so that the rollers of the roll stand are driven at a constant speed during the duration of the time interval. <??>An Independent claim is also included for a stretch reducing mill for rolling pipes. <??>Preferred Features: A tolerance is given for controlling and regulating the drive of the roll stand and is not exceeded. A sensor (10) is arranged in front of the roll stand for acquiring the time point when the rear end of the pipe passes the sensor.

Description

The invention relates to a method for operating a stretch-reducing mill for rolling a tube of finite length, which has at least two roll stands has, which are arranged one behind the other in the conveying direction of the tube, wherein at least two co-operating rollers are arranged in each roll stand are, each over a defined peripheral portion of the tube on this apply and roll it, and at least two drives for driving the Rolling two different roll stands are available. Furthermore concerns the invention an apparatus for performing the method. On A generic method and a generic device are e.g. known from document DE-A 3601693.

In a stretch-reducing mill, the pipe to be processed passes a rolling mill, a number of roll stands in succession in the conveying direction of the tube are arranged. Rolls are stored in each roll stand, which are given priority in the rolling process contact the pipe with a defined circumferential section. Overall, several, usually three, rollers act in this way in each roll stand together that the tube is essentially over its entire circumference of is enclosed in the rollers. The pipe is thus reduced in diameter rolled.

The rolling mill usually has one group or several groups of rolling stands, whose rollers are driven by a common drive. The drive comprises two motors (basic drive and superimposed drive), whose rotation in a summation gear is added up in such a way that the required increase the rolling speed in rolling stands arranged one behind the other results.

Sawing devices are often arranged behind the rolling mill, with which the rolled pipe can be cut to length. The sawing devices are mostly executed as "flying saws", which means that during the sawing process run with the conveying speed of the pipe; d. H. the sawing process can be done while the pipe is being transported. Furthermore, are sometimes behind the rolling mill manipulators (robots) arranged, for example, as a pusher serve (on the cooling bed). For all work processes (sawing, pushing off, etc.) that follow the rolling process is as uniform as possible Pipe movement advantageous or necessary to the required accuracy of To achieve processes.

In this context, there is the so-called "spit-out effect" of the stretch-reducing mill proven to be problematic: if the end stands of the rolling mill is not on the last stand of the rolling mill, is with group overlap drives the speed in the final scaffolding is too high, which is why Rolled material, i.e. the pipe of finite length, briefly as it emerges from the rear Scaffolding spaces is accelerated. This disrupts the follow-up process considerably, for example sawing, which is then no longer reproducible or with the required Quality can be accomplished. Influence parameters on the "spook effect" are in particular changing interactions between the rolling stands, special speed and friction conditions in the rear Scaffolding and dynamic speed changes. The pipe speed can up to 30% compared to the stationary due to the "spit-out effect" Outlet speed must be increased. An intensification of the "spit-out effect" can occur when a pipe end control is used.

The invention is therefore based on the object of providing a stretch-reducing rolling method of the type mentioned at the outset and an associated device with which or with which it is possible to reduce the existing disadvantages or to eliminate them entirely.

a) Ermitteln des Zeitpunktes, zu dem das in Förderrichtung hintere Ende des Rohres das in Förderrichtung letzte Walzgerüst verlässt;

b) Festlegung eines Zeitintervalls vorgegebener Dauer, in dem der Zeitpunkt liegt, zu dem das in Förderrichtung hintere Ende des Rohres das in Förderrichtung letzte Walzgerüst verlässt;

c) Steuern oder Regeln des Antriebs des letzten Walzgerüsts so, dass während der Dauer des Zeitintervalls der Auslauf des Walzgutes mit im wesentlichen konstanter Geschwindigkeit erfolgt.

This object is achieved in that the generic method has the following method steps:

a) determining the point in time at which the rear end of the tube in the conveying direction leaves the last rolling stand in the conveying direction;

b) Definition of a time interval of a predetermined duration at which the time lies at which the end of the tube in the conveying direction leaves the last roll stand in the conveying direction;

c) Controlling or regulating the drive of the last rolling stand in such a way that the rolling stock runs out at a substantially constant speed for the duration of the time interval.

With the proposed active outlet speed control or regulation it can be achieved to prevent the so-called "spit-out effect", which in consequently enables high quality to be achieved in the succession processes; in particular, the cutting tolerances during the sawing process are improved. The proposed method reduces or eliminates the period in which the "spit-out effect" is to be expected (ie during the acceleration phase to be feared), the motor speed of the basic and superimposed drive in the rear scaffolding group, which ensures a constant outlet speed of the Pipe from the rolling mill is ensured.

According to a further development, it is provided that the point in time at which the Conveying direction at the rear end of the pipe is the roll stand or stand group on the outlet side leaves, is determined from observation or monitoring of the point in time passing the rear end of the pipe at the outlet end Rolling mill upstream in the conveying direction, taking into account the Rolling speed of the pipe from the monitoring point to the last one Rolling stand.

In the case of long pipes, it may make sense to do this in addition to the control or regulation a control or regulation of the drive of the roll stand on the outlet side of those drives takes place, the upstream rolling stands in the conveying direction are assigned and their rollers contact with during the time interval have the pipe.

Finally, for the control or regulation of the speed of the drive of the a tolerance that does not leave, d. h may be exceeded.

The stretch-reducing mill according to the invention for carrying out the method has at least two roll stands with rollers, at least two drives for driving the rolls of two different roll stands are. According to the invention it is provided that means for determining the point in time, to which the rear end of the pipe in the conveying direction is in the conveying direction Leaving mill stand leaves, are available as well as means for control or Regulating the drive of the roll stand on the outlet side so that during the duration a drive of the rollers of the outlet side of a predetermined time interval Roll stand with reduced speed.

According to a further development, one is in the conveying direction in front of the roll stand on the outlet side Sensor arranged to detect the time of passing the end of the pipe is suitable. Furthermore, the sensor can send its measured signal to a Control or regulation transmit on the drive of the outlet side Acts on the roll stand.

At least the drive of the roll stands last arranged in the conveying direction of the stretch-reducing mill can be designed as an overall superposition drive be, which has a summation gear and two motors. From the drive that drives the mill stands last arranged in the conveying direction can at least three rolling stands are driven.

A sawing device is preferred in the conveying direction behind the outlet-side roll stand is arranged; this can have a "flying saw". Further an automatic manipulator can be arranged behind the last rolling stand his.

Fig. 1

schematisch die Ansicht zweier Walzenpaare in Förderrichtung des Rohres betrachtet,

Fig. 2

die zu Fig. 1 zugehörige Seitenansicht,

Fig. 3

schematisch den Aufbau eines Streckreduzierwalzwerks,

Fig. 4

einen Ausschnitt aus Fig. 3 mit den letzten in Förderrichtung angeordneten Walzgerüsten und

Fig. 5

den Verlauf der Drehzahl der Walzen im auslaufseitigen Walzgerüst über der Zeit.

In the drawing, an embodiment of the invention is shown. Show it:

Fig. 1

schematically viewed the view of two pairs of rollers in the conveying direction of the tube,

Fig. 2

1 associated side view,

Fig. 3

schematically the structure of a stretch-reducing mill,

Fig. 4

a section of FIG. 3 with the last rolling stands arranged in the conveying direction and

Fig. 5

the course of the speed of the rolls in the outlet-side roll stand over time.

1 and 2 it can be seen schematically how two pairs of rollers 4, 5 and 6 or 4 ', 5' and 6 'roll a tube 2 in a stretch-reducing mill. The rollers 4, 5 and 6 belong to a first roll stand 3a, while the rolls 4 ', 5' and 6 ' belong to a second roll stand 3b. Both mill stands 3a and 3b belong again to a first group of roll stands of the stretch-reducing mill, such as described below. So that a tube 2 with a finite length L at Pass through the stretch-reducing mill over its entire circumference is rolled evenly, the rolls of two successive roll stands 3a, 3b each rotated by 60 ° around the tube axis, as is shown in FIGS. 1 and 2 is clearly visible.

In Fig. 3, the structure of a stretch-reducing mill 1 is outlined schematically. In Conveying direction R of the tube 2, a number of roll stands 3 are arranged one behind the other. Rollers are arranged in each roll stand, as sketched in FIGS. 1 and 2. Due to the rolling process, the diameter of the Tube 2 somewhat reduced, with one between the individual roll stands 3 Tension for stretching the tube 2 is maintained. Because of the from roll stand to roll stand of decreasing diameter of the rolls the subsequent rollers turn faster and faster.

This is accomplished by drives 7, 7 ', 7 ", 7"', 7 "" for the five groups outlined Roll stands 3, 3 ', 3 ", 3"' and 3 "". The drives 7, 7 ', 7 ", 7"', 7 "" are superimposed drives trained, the two motors 13, 13 ', 13 ", 13"' and 13 "" and 14, 14 ', 14 ", 14'" and 14 "" respectively. The motors 13, 14 drive summation gears 12, 12 ', 12 ", 12"', 12 "" in which the rotation of the motors 13 and 14 is added. The tuning in the summation gear 12 ensures one of Roll stand to roll stand increasing rotational speed curve.

Behind the rolling mill 1, a sawing device 15 is arranged, with which the rolled Pipe 2 is cut to length. The sawing device is called a "flying saw" trained, d. H. the saw moves in conveyance during the sawing process direction R with the ejection speed of the tube to ensure a clean Generate cut.

Within a group of roll stands 3, 3 ', 3 ", 3"' and 3 "" results - as described - The speed ratio due to the superposition drive of Roll stand to roll stand in a defined way. If the end stands of the rolling mill 1, namely the scaffolding 3c "" and 3d "", not in the last scaffolding locations of the rolling mill 1 are due to the group superposition drive 7 "" the speed n in the end stands 3c "" and 3d "" high, which is why tube 2 briefly as it exits the last scaffolding locations is accelerated. This "spit-out effect" disrupts the follow-up process, in the exemplary embodiment the sawing process, considerably.

To reduce or eliminate the "spit-out effect", proceed as follows:

A sensor 10 is arranged at a monitoring point 9 in front of the last group of roll stands 3a "", 3b "", 3c "" and 3d "". As shown in particular in FIG. 4, the sensor 10 detects when the rear end 8 of the tube 2 passes the point 9. The signal detected by the sensor 10 is sent to a controller 11. The control system 11 is supplied by the summation gear 12 "" (or by the motors 13 "" or 14 "") for the drive speeds of the rollers. In the open-loop or closed-loop control 11, the point in time t _A at which the pipe 2 is ejected from the rolling mill 1, ie when the pipe end 8 leaves the last rolling stand 3d "" can therefore be calculated in a simple manner.

A time interval .DELTA.T is also predetermined for the control or regulation, which - as can be seen from FIG. 5 - is defined in such a way that the calculated time t _A comes to lie at the end of the time interval .DELTA.T. The control or regulation now (via the motors 13 "" and 14 "") selectively controls or regulates the rotational speed n, in particular the rollers of the last roll stand 3d "" during the time interval .DELTA.T, so that the outlet speed of the pipe increases does not leave the specified tolerance band ΔV.

5, the curve is drawn in dashed lines which would result without these measures. The speed v increases until the time t _{A of} the pipe ejection, which considerably disturbs the subsequent sawing process. The procedure described ensures, however, that the tolerance band ΔV of the speed v shown in broken lines is not left. As a result, the sawing process can be carried out precisely.

This effectively prevents an increase in pipe ejection speed, at the same time the stretching of the tube between the individual Roll stands 3a "", 3b "", 3c "" and 3d "" are maintained.

In addition to the control or regulation of the drive 7 "" of the roll stand on the outlet side 3d "" can also control in the conveying direction R. upstream drives, e.g. B. 7 "', if the rollers of the corresponding Roll stands in the time interval ΔT have contact with tube 2. This will unwanted tensions in the pipe avoided. As a rule, however, it will be sufficient be the drive 7 "" of the last group of rolling stands 3a "", 3b "", 3c "" and To influence 3d "".

Both the values for the length of the time interval ΔT and the height of the tolerance band ΔV are given to the control system, the Values are determined empirically for specific applications. The values can be displayed on the rolling mill's visualization PC. An adjustment the data is available at any time by appropriate input in the control system possible. If necessary, optimal data can also be obtained from the interpolation known values can be obtained for existing stretch reduction rolling mills.

It is particularly advantageous to use the method described, at least in the last to provide three rolling stands. In the exemplary embodiment, the control or Regulation for the last four roll stands 3a "", 3b "", 3c "" and 3d "".

LIST OF REFERENCE NUMBERS

1

stretch

2

pipe

3

rolling mills

3a, 3b, 3c, 3d

first group of roll stands

3a ', 3b', 3c ', 3d'

second group of roll stands

3a ", 3b", 3c ", 3d"

third group of roll stands

3a '' ', 3b "', 3c '' ', 3d' ''

fourth group of roll stands

3a "", 3b '' '', 3c "", 3d ""

fifth group of roll stands

4, 4 ' 5, 5 ' 6, 6 '

roll

7, 7 ', 7 ", 7 "', 7" "

Drives (superposition drives)

8th

rear end of the tube

9

Location of the sensor (observation point)

10

sensor

11

Control / regulation

12, 12 ', 12 ", 12 '' ', 12 ""

summing

13, 13 ', 13 ", 13 "', 13" "

Engines

14, 14 ', 14' ', 14 "', 14" "

Engines

15

sawing

L

tube length

R

conveying direction

t

time

t _A

Time of pipe ejection

.DELTA.T

time interval

v

Outlet speed of the pipe

.DELTA.V

Tolerance for the outlet speed of the pipe

Claims (11)

1. A method for operating a stretch-reducing mill (1) for rolling a tube (2) of finite length (L),
   wherein said mill comprises at least two roll stands (3a, 3b, 3c, 3d, 3a', 3b', 3c', 3d', ...) that are arranged in series referred to the transport direction (R) of the tube (2),
   wherein at least two cooperating rolls (4, 5, 6, 4', 5', 6') are arranged in each roll stand (3a, 3b, 3c, 3d, 3a', 3b', 3c', 3d', ...) and respectively contact and roll the tube (2) over a defined circumferential section thereof, and
   wherein at least two drives (7, 7', 7", 7"', 7"") are provided for driving the rolls (4, 5, 6, 4', 5' 6') of two different roll stands (3a, 3b, 3c, 3d, 3a', 3b', 3c', 3d', ...),
   characterized in that the method comprises the following steps:

   a) determining the time (t_A), at which the rear end (8) of the tube (2) referred to the transport direction (R) emerges from the last roll stand (3d"") on the outlet side referred to the transport direction (R);

   b) determining a time interval (ΔT) of predetermined duration that contains the time (t_A), at which the rear end (8) of the tube (2) referred to the transport direction (R) emerges from the roll stand (3d"") on the outlet side, and

   c) controlling or regulating the drive (7"") of the roll stand (3d"") on the outlet side in such a way that the rolls of the roll stand (3d"") on the outlet side are driven with a reduced rotational speed over the duration of the time interval (ΔT) and the exit of the tube accordingly takes place with an essentially constant speed.
2. The method according to Claim 1,
   characterized in that the time (t_A), at which the rear end (8) of the tube (2) referred to the transport direction (R) emerges from the roll stand (3d"") on the outlet side referred to the transport direction (R), is determined by monitoring the time, at which the rear end (8) of the tube (2) passes a point (9) that is arranged upstream of the roll stand (3d"") on the outlet side referred to the transport direction (R), and by taking into account the rolling speed of the tube (2) from the monitoring point (9) to the roll stand (3d"") on the outlet side.
3. The method according to Claim 1 or 2,
   characterized in that not only the drive (7"") of the roll stand (3d"") on the outlet side is controlled or regulated, but also those drives (7"') that are assigned to upstream roll stands (3a"', 3b"', 3c"', 3d"'), the rolls of which are in contact with the tube (2) during the time interval (ΔT).
4. The method according to one of Claims 1-3,
   characterized in that a predetermined tolerance (ΔV) for controlling or regulating the rotational speed of the drive (7"") of the roll stand (3d"") on the outlet side must be observed.
5. A stretch-reducing mill (1) for rolling a tube (2) of finite length (L), namely for carrying out the method according to one of Claims 1-4,
   wherein said stretch-reducing mill comprises at least two roll stands (3a, 3b, 3c, 3d, 3a', 3b', 3c' 3d', ...) that are arranged in series referred to the transport direction (R) of the tube (2),
   wherein at least two cooperating rolls (4, 5, 6, 4', 5', 6') are arranged in each roll stand (3a, 3b, 3c, 3d, 3a', 3b', 3c' 3d', ...) and respectively contact and roll the tube (2) over a defined circumferential section thereof, and
   wherein at least two drives (7, 7', 7", 7"', 7"") are provided for driving the rolls (4, 5, 6, 4', 5', 6') of two different roll stands (3a, 3b, 3c, 3d, 3a', 3b', 3c' 3d', ...),
   characterized in that means (10, 11) are provided for determining the time (t_A), at which the rear end (8) of the tube (2) referred to the transport direction (R) emerges from the roll stand (3d"") on the outlet side, and in that means (11) are provided for controlling or regulating the drive (7"") of the roll stand (3d"") on the outlet side in such a way that the rolls of the roll stand (3d"") on the outlet side are driven with a reduced rotational speed over the duration of a predetermined time interval (ΔT).
6. The device according to Claim 5,
   characterized in that a sensor (10) is arranged upstream of the roll stand (3d"") on the outlet side, wherein said sensor is suitable for determining the time, at which the end (8) of the tube (2) passes.
7. The device according to Claim 6,
   characterized in that the sensor (10) transmits its measuring signal to a control or regulating device (11) that acts upon the drive (7"") of the roll stand (3d"") on the outlet side.
8. The device according to one of Claims 5-7,
   characterized in that at least the drive (7"") of the last roll stands (3a"", 3b"", 3c"", 3d"") of the stretch-reducing mill (1) referred to the transport direction (R) consists of a total contact ratio drive that contains a compound gear (12"") and two motors (13"", 14"").
9. The device according to Claim 8,
   characterized in that at least three roll stands (3a"", 3b"", 3c"", 3d"") are driven by the drive (7"").
10. The device according to one of Claims 5-9, characterized in that a sawing device (15) is arranged downstream of the roll stand (3d"") on the outlet side.
11. The device according to one of Claims 5-10,
    characterized in that an automatic manipulator is arranged downstream of the roll stand (3d"") on the outlet side.

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