Device for controlling a stretch-reducing mill

Abstract

The disclosure relates to a method for controlling a stretch-reducing mill. Tube ends of stretched tubes are optimized by controlling one or more motors of the stretch-reducing mill. The method includes at least one outlet-side wall thickness measurement and an automatic adjustment of the value of a speed change of the motors to the tube wall thickness profile. The progression of the speed changes over time of individual or all motors is also automatically adjusted on the basis of the tube wall thickness measured values.

Claims

1. A method for controlling a stretch-reducing mill in which tube ends of stretched tubes are optimized by controlling motors of the stretch-reducing mill by a programmable logic controller, comprising: measuring outlet-side wall thicknesses of the stretched tubes by a sensor that is operatively connected to the programmable logic controller; and automatically adjusting speed changes of the motors while stretching a following tube based on a tube wall thickness profile of an earlier stretched tube, wherein the programmable logic controller calculates, based on the measured wall thicknesses of the earlier stretched tube, for each of the speed changes of individual ones of the motors a start time of the speed change, an end time of the speed change, and a rate of speed change.

2. The method according to claim 1, wherein the method is combined with a wall thickness control system for automatically controlling wall thicknesses outside of thickened ends.

3. The method according to claim 1, wherein wall thickness measurements along ends of the stretched tubes are examined for cyclic patterns and wherein the cyclic patterns are considered in controlling the motors.

4. The method according to claim 1, wherein a measurement of an incoming shell wall thickness profile is carried out, and wherein the speed changes are adjusted to the measurement of the incoming shell wall thickness.

5. The method according to claim 4, wherein the method is combined with a wall thickness control system for automatically controlling a wall thicknesses outside thickened ends.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic illustration of a stretch-reducing mill with its control system.

DETAILED DESCRIPTION

(2) A stretch-reducing mill comprises several rolls in roll stands 1, which are driven by controllable motors. Thereby, the stretch reduction of a rolled material 2 is achieved by means of a selective control of the motors with different speeds, such that the rolled material is put under tensile stress between the rolls.

(3) The motors are supplied with electrical energy via a programmable logic controller (PLC) 3. The PLC 3 takes over the query and/or calculation of the speeds of the motors during the rolling process.

(4) The PLC 3 is connected via a network 4 in the form of a Fieldbus system with sensors 5, 6, such that measured values flow directly into the PLC. The sensors 5 are exemplary position sensors, for example in the form of light barriers. The sensors 6 determine further measured values for monitoring the rolling process, in particular diameter, wall thickness and temperature of the rolled material.

(5) The PLC 3 can also communicate with a process control computer 7a at a process control level via a network 7 that is not real-time capable.

(6) On a stretch-reducing mill described as an example above, a method in accordance with the disclosure for controlling a stretch-reducing mill can be carried out. In this process, tube ends of stretched tubes are optimized by controlling one or more motors of the stretch-reducing mill.

(7) At least one outlet-side wall thickness measurement is carried out by the sensors 6 and an automatic adjustment of the value of a speed change of the motors to the measured tube wall thickness profile is performed. The progression of the speed changes over time of individual or all motors is also automatically adjusted on the basis of the measured tube wall thickness values.

(8) The progression of the speeds over time is characterized by the start time of the speed change and the end point of the speed change. In particular, the progression over time is also characterized by a rate of change of the speeds.

(9) An evaluation of the wall thickness curve is carried out on at least three sections of the wall thickness profile.

(10) In addition, the evaluation of the wall thickness curve is made from several target values.

(11) The method for controlling the tube end thickness is combined with a wall thickness control system for the automatic control of the wall thickness outside the thickened ends.

(12) The measured values by the sensors 6 are analyzed by means of programs, wherein the wall thickness curves at the ends are examined for cyclic patterns and such patterns are taken into account in the control of the motors.

(13) In addition to a measurement of the wall thicknesses of the (partially) stretched tubes, a measurement of an incoming shell wall thickness profile is carried out, wherein the values and the progression of the speed changes over time of the tube end control are adjusted to shell wall thickness measurements.

(14) Thereby, the wall thickness curves at the shell ends are examined for cyclical patterns and such patterns are taken into account.

(15) As a whole, the method is combined with a wall thickness control system for the automatic control of wall thicknesses outside the thickened ends.

LIST OF REFERENCE SIGNS

(16) 1 Roll stand with rolls and motors 2 Rolled material 3 PLC=programmable logic control 4 Bus system, Fieldbus 5 Sensors, Position sensors 6 Sensors for diameter, wall thickness, temperature, etc. 7 Network at process control level 7a Process control computer