DE10157742C1 - Method of operating a stretch-reducing mill and stretch-reducing mill - Google Patents

Abstract

A method for operating a stretch-reducing mill (1) for rolling a tube (2) with a finite length (L), which has at least two roll stands (3a, 3b, 3c, 3d, 3a ', 3b', 3c ', 3d', .. .), which are arranged one behind the other in the conveying direction (R) of the tube (2), at least two in each roll stand (3a, 3b, 3c, 3d, 3a ', 3b', 3c ', 3d', ...) co-operating rollers (4, 5, 6, 4 ', 5', 6 ') are arranged, each of which abuts against the tube (2) over a defined circumferential section and rolls it, and at least two drives (7, 7', 7 '', 7 '' ', 7' '' ') for driving the rolls (4, 5, 6, 4', 5 ', 6') of two different roll stands (3a, 3b, 3c, 3d, 3a ' , 3b ', 3c', 3d ', ...) is present to improve the quality of the successor processes by the steps: a) Determining the time (t¶A¶) at which the rear in the conveying direction (R) End (8) of the tube (2) leaves the roll stand (3d '' '') on the outlet side in the conveying direction (R) t; b) Definition of a time interval (DELTAT) of a predetermined duration at which the time (t¶A¶) lies at which the rear end (8) of the tube (2) in the conveying direction (R) the roll stand (3d '' '' 'on the outlet side ) leaves; c) Controlling or regulating the drive (7 '' '') of the last roll stand (3d '' '') such that during the duration of the time interval (DELTAT) the rolls of the outlet-side roll stand (3d '' '') are also driven reduced speed and the pipe runs out at a substantially constant speed.

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 be the invention relates to a device for performing the method.

A method and a device of this type are described in the essay "Stretch Reduction Ornamental Rolling Mills with Variable-Speed Group Drives "in BBC News 66, 1984, No. 5, pages 155 to 162.

In a stretch-reducing mill, the pipe to be processed passes a roll street in which a number of rolling mills one behind the other in the conveying direction of the pipe are arranged. Rolls are stored in each roll stand, which are used for rolling 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 tube is reduced to a through knife 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 Er Increase of 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 along with the conveying speed of the pipe; d. H. the sawing process can be done while the pipe is being transported. A shower of speed a flying saw is from the magazine "m + w 8/1991 - Fabrication Tech nik 3, pages 63 and 64 "known.

Furthermore, manipulators (robots) are sometimes arranged behind the rolling mill, which serve, for example, as a pusher (on the cooling bed). For all work processes (Sawing, pushing off, etc.) that take place after the rolling process is one pipe movement that is as uniform as possible is advantageous or necessary in order to achieve the required to achieve the accuracy of the processes.

In this context, there is the so-called "spit-out effect" of the stretch reduction ornamental rolling mill proved to be problematic: if the end stands of the rolling mill groups are not on the last stand of the rolling mill superimposition drives the speed in the end stands 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 significantly disrupts the succession process, at for example sawing, which is then no longer reproducible or with the required quality can be achieved. Influence parameters on the "Ausspuc kelfekt "are in particular changing interactions between the roller  scaffolding, 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 reducing the stretch Rolling process of the type mentioned and an associated device create, with which it is possible to ver existing disadvantages wrestle or eliminate entirely.

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

• a) Determine the time at which the rear end of the Tube leaves the last roll stand in the direction of conveyance;
• b) Definition of a time interval of a predetermined duration in which the time is to which the rear end of the pipe in the conveying direction is in the conveying leaves the last mill stand;
• c) Controlling or regulating the drive of the roll stand on the outlet side such that During the time interval, the rollers of the roll stand on the outlet side are also driven reduced speed and the outlet of the pipe accordingly with essentially Chen constant speed takes place.

With the proposed active outlet speed control or re it can be achieved to prevent the so-called "spit-out effect", which is in consequently enables a high quality to be achieved in the succession processes chen; 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 feared loading acceleration phase), the engine 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 outlet-side roll stand or Ge setup group leaves, is determined from observation or monitoring of time point of passing the rear end of the pipe at one of the outlet side upstream of the rolling stand 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 rain control of the drive of the roll stand on the outlet side also a control or re success of those drives, the upstream rolling mill in the conveying direction Most assigned and their rollers contact during the time interval have the pipe.

Finally, for the control or regulation of the speed of the drive of the a tolerance on the outlet-side roll stand that does not leave sen, 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 rolls, at least two types drives for driving the rolls of two different roll stands available 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 takes place at an essentially constant 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 which drives the last mill stands arranged in the conveying direction can at least at least three roll stands are driven.

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

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

Viewed in Fig. 1 a schematic view of two pairs of rollers in the conveying direction of the tube,

Fig. 2 corresponding to the Fig. 1 side view,

Fig. 3 shows schematically the structure of a stretch-,

Fig. 4 shows a detail from Fig. 3 with the last in the conveying direction angeord Neten rolling stands and

Fig. 5 shows the course of the speed of the rollers in the outlet-side roll stand over time.

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

In Fig. 3, the structure of a stretch-reducing mill 1 is outlined schematically. In the conveying direction R of the tube 2 , a number of roll stands 3 are arranged one behind the other. In each roll stand - as sketched in Fig. 1 and 2 - rollers are arranged. Through the rolling process, the diameter of the tube 2 is reduced slightly in each roll stand 3, wherein tension is maintained on the extension of the tube 2 between the individual roll stands. 3 Due to the decreasing diameter of the rolls from roll stand to roll stand, the following rolls have to rotate ever faster.

This is accomplished by drives 7 , 7 ', 7 '', 7 ''', 7 '''' for the five groups of roll stands 3 , 3 ', 3 '', 3 ''' and 3 '''' outlined. The drives 7 , 7 ', 7 '', 7 ''', 7 '''' are designed as overlay drives, each of which has two motors 13 , 13 ', 13 '', 13 ''' and 13 ''''and 14 , 14 ', 14 '', 14 '''and 14 ''''respectively. The motors 13 , 14 drive summation gear 12 , 12 ', 12 '', 12 ''', 12 '''', in which the rotation of the motors 13 and 14 is added. The coordination in the summation gear 12 ensures a rotational speed curve that increases from roll stand to roll stand.

Behind the rolling mill 1 , a saw device 15 is arranged, with which the ge rolled tube 2 is cut to length. The sawing device is designed as a "flying saw", ie the saw moves during the sawing process in the conveying direction R with the ejection speed of the tube, in order to produce a clean cut.

Within a group of roll stands 3 , 3 ', 3 '', 3 ''' or 3 '''- as described - the speed ratio results in a defined manner due to the superposition drive from roll stand to roll stand. If the end stands of the rolling mill 1 , namely the stands 3 c '''' and 3 d '''', are not on the rough Ge scaffolding sites of the rolling mill 1 , the speed is due to the group superposition drive 7 '''' n in the final scaffolds 3 c '''and 3 d''''too high, which is why the pipe 2 is accelerated briefly when it leaves the last scaffold locations. This "spit-out effect" disrupts the follow-up process, ie the sawing process in the exemplary embodiment.

To reduce or eliminate the "spit-out effect", proceed as follows:
Before the last group of roll stands 3 a '''', 3 b '''', 3 c '''' and 3 d '''', a sensor 10 is arranged at a monitoring point 9 . 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 or regulation 11 are supplied by the summation gear 12 '''' (or by the motors 13 '''' or 14 '''') of the values for the drive speeds of the rollers. In the open-loop or closed-loop control 11 , the point in time t _A can therefore be calculated in a simple manner at which the pipe 2 is expelled from the rolling mill 1 , ie when the pipe end 8 leaves the last rolling stand 3 d ''''.

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 open-loop or closed-loop control (via the motors 13 '''' and 14 '''') now specifically controls or regulates the speed n during the time interval ΔT, in particular of the rolls of the last roll stand 3 d '''' before, so that the outlet speed of the pipe does not leave a predetermined tolerance band ΔV.

In Fig. 5, the curve is shown by dashed lines, which would result without these measures. The speed v increases up to the time t _{A of} the pipe discharge, which considerably disturbs the subsequent sawing process. The described procedure 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.

A speed increase in pipe ejection is thereby effectively prevented, while at the same time the stretching of the pipe between the individual roll stands 3 a '''', 3 b '''', 3 c '''' and 3 d '''' is maintained ,

In addition to the control or regulation of the drive 7 '''' of the roll stand 3 d '''' on the outlet side, a control or regulation in the conveying direction R of further upstream drives, e.g. B. 7 ''', provided that the rollers of the corresponding roll stands have contact with the tube 2 in the time interval ΔT. This prevents undesirable stresses in the pipe. As a rule, however, it will be sufficient to influence the drive 7 '''' of the last group of roll stands 3 a '''', 3 b '''', 3 c '''' and 3 d ''''.

Both the values for the length of the time interval ΔT and the height of the tole ranzbandes 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 depending on the corresponding input in the control or regulation currently possible. If necessary, optimal data from the Interpolati on known values for existing stretch reduction rolling mills.

It is particularly advantageous to provide the described method at least in the last three roll stands. In the exemplary embodiment, the control or regulation takes place for the last four roll stands 3 a '''', 3 b '''', 3 c '''' and 3 d ''''.

LIST OF REFERENCE NUMBERS

1

stretch

2

pipe

3

rolling mills

3

a,

3

b

3

c,

3

d first group of roll stands

3

a ',

3

b '

3

c ',

3

d 'second group of mill stands

3

a ",

3

b "

3

c "

3

d "third group of roll stands

3

a '' ',

3

b '' '

3

c '' ',

3

d '''fourth group of mill stands

3

a '' '',

3

b '' '',

3

c '' '',

3

d '''' fifth group of mill stands

4

.

4

'

5

.

5

'

6

.

6

'' Rollers

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

'''' Summation gear

13

.

13

'

13

''

13

'' '

13

'''' Engines

14

.

14

'

14

''

14

'' '

14

'''' Engines

15

sawing
L tube length
R direction of conveyance
t time
t _A

Time of pipe ejection
ΔT time interval
v Pipe runout speed
ΔV 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 ) with a finite length (L),
which has at least two roll stands ( 3 a, 3 b, 3 c, 3 d, 3 a ', 3 b', 3 c ', 3 d',...), which in the conveying direction (R) of the tube ( 2 ) are arranged one after the other,
wherein in each roll stand ( 3 a, 3 b, 3 c, 3 d, 3 a ', 3 b', 3 c ', 3 d',...) at least two interacting rolls ( 4 , 5 , 6 , 4 ' , 5 ', 6 ') are arranged, each because of a defined peripheral portion of the tube ( 2 ) on this and roll it, and
wherein at least two drives ( 7 , 7 ', 7 '', 7 ''', 7 '''') for driving the rollers ( 4 , 5 , 6 , 4 ', 5 ', 6 ') of two different roll stands ( 3 a, 3 b, 3 c, 3 d, 3 a ', 3 b', 3 c ', 3 d',...) Are present,
characterized by
that the process comprises the steps:

• a) determining the point in time (t _A ) at which the end ( 8 ) of the tube ( 2 ) which is at the rear in the conveying direction (R) leaves the last, on the outlet side, roll stand ( 3 d '''') in the conveying direction (R);
• b) Definition of a time interval (ΔT) of a predetermined duration at which the point in time (t _A ) lies at which the rear end ( 8 ) of the tube res ( 2 ) in the conveying direction (R) rests on the outlet-side roll stand ( 3 d '''')leaves;
• c) controlling or regulating the drive ( 7 '''') of the roll stand on the outlet side ( 3 d '''') such that during the duration of the time interval (ΔT) the rolls of the roll stand of the outlet side ( 3 d '''') are driven ) at a reduced speed and the pipe runs out at a substantially 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 ) in the conveying direction (R) the roll stand ( 3 d '''' on the outlet side in the conveying direction (R) '), is determined from monitoring the time at which the rear end ( 8 ) of the tube ( 2 ) passes at a point ( 9 ) upstream of the roll stand ( 3 d'''') in the conveying direction (R), taking into account the rolling speed of the pipe ( 2 ) from the monitoring point ( 9 ) to the outlet stand ( 3 d ''''). 3. The method according to claim 1 or 2, characterized in that in addition to the control or regulation of the drive ( 7 '''') of the Auslaufsei term rolling stand ( 3 d '''') also a control or regulation of those to drives ( 7 '''), the upstream rolling stands ( 3 a ''', 3 b''', 3 c ''', 3 d''') are assigned and their rollers come into contact with the pipe during the time interval (ΔT) ( 2 ) have. 4. The method according to any one of claims 1 to 3, characterized in that a tolerance (ΔV) is predetermined for the control or regulation of the speed of the drive ( 7 '''') of the roll stand ( 3 d '''') on the outlet side, that must not be left. 5. stretch-reducing mill ( 1 ) for rolling a tube ( 2 ) with finite length (L) for carrying out the method according to one of claims 1 to 4,
which has at least two roll stands ( 3 a, 3 b, 3 c, 3 d, 3 a ', 3 b', 3 c ', 3 d',...), which in the conveying direction (R) of the tube ( 2 ) are arranged one after the other,
wherein in each roll stand ( 3 a, 3 b, 3 c, 3 d, 3 a ', 3 b', 3 c ', 3 d',...) at least two interacting rolls ( 4 , 5 , 6 , 4 ' , 5 ', 6 ') are arranged, each because of a defined peripheral portion of the tube ( 2 ) on this and roll it, and
wherein at least two drives ( 7 , 7 ', 7 '', 7 ''', 7 '''') for driving the rollers ( 4 , 5 , 6 , 4 ', 5 ', 6 ') of two different roll stands ( 3 a, 3 b, 3 c, 3 d, 3 a ', 3 b', 3 c ', 3 d',...) Are present,
characterized,
that means ( 10 , 11 ) for determining the point in time (t _A ) at which the rear end ( 8 ) of the tube ( 2 ) in the conveying direction (R) leaves the outlet stand ( 3 d '''') are present as well as means ( 11 ) for controlling or regulating the drive ( 7 '''') of the roll stand ( 3 d '''') on the outlet side, such that during the duration of a predetermined time interval (ΔT) the rolls of the roll stand ( 3 d '''') takes place at an essentially constant speed. 6. The device according to claim 5, characterized in that a sensor ( 10 ) is arranged in front of the outlet-side roll stand ( 3 d ''''), which is suitable for detecting the time of passing the end ( 8 ) of the raw res ( 2 ) is. 7. The device according to claim 6, characterized in that the sensor ( 10 ) transmits its measured signal to a control or re regulation ( 11 ), which on the drive ( 7 '''') of the outlet-side rolling stand ( 3 d '''') acts. 8. Device according to one of claims 5 to 7, characterized in that at least the drive ( 7 '''') in the conveying direction (R) last arranged mill stands ( 3 a '''', 3 b '''', 3 c '''', 3 d '''') of the stretch-reducing mill ( 1 ) is an overall superimposition drive which has a summation gear ( 12 '''') and two motors ( 13 '''', 14 '''') , 9. The device according to claim 8, characterized in that of the drive ( 7 '''') at least three roll stands ( 3 a '''', 3 b '''', 3 c '''', 3 d '''') are driven. 10. Device according to one of claims 5 to 9, characterized in that a sawing device ( 15 ) is arranged behind the outlet-side roll stand ( 3 d ''''). 11. The device according to one of claims 5 to 10, characterized in that an automatic manipulator is arranged behind the outlet-side roll stand ( 3 d '''').