Strip flatness automatic control is a knowledge-based control technology, without which today is unthinkable production of high-quality rolled products.
In the former USSR countries, in the cold rolling mills AFC of foreign design and manufacture were used, providing flatness measurement by contact method with, as a rule, sectioned measuring rollers (stress meters).
In the developed (firstly in CIS) AFC the effective innovative control algorithms were implemented, developed by MTM and ISI NASU staff, having years of experience in the theory and technology of production processes of rolled strips. As a strip flatness meter it is used a non-contact optoelectronic measuring device IP-4М of our partners - JSC "Inkomet".
Software components of AFC
The set of AFC includes:
- control program that implements the flatness control algorithm (the development of MTM) via the channels of bending, tilting and rolls selective cooling. The control program also provides the interface between local subsystems;
- visualization system - the operator keypad or workstation;
- data archiving system, implemented on a remote SQL Server;
- system for the analysis of process variables and parameters of the strip. This client application is installed on the remote workstation and allows the enterprise engineering and technological personnel to receive extensive (mathematically processed) information on the majority of process parameters;
- web-reports (shift reports) contain information about rolled coils, their total mass, the main parameters of quality, etc.;
- implemented a remote maintenance of system.
Particularities of the AFC algorithms
In the controls algorithm of the selective rolls cooling, several important new features
are realized that are not used in existing systems for automatic flatness control of the strips.
In particular, that:
- Particularities of control in the period of rolls heating (when the coolant does not cool, but warms up the rolls), ensuring the continued effectiveness of control in the rolling process (control efficiency during rolling may be lost);
- the system offers several solutions that allow to create conditions, under which the strips flatness control by the selective rolls cooling is most effective. This channel, as the research has been shown, can provide about half of the range of flatness tolerance, i.e., its effective use is very fruitful;
- method is implemented of continuous diagnostics of nozzles and valves of selective cooling system by the data of effectiveness of impacts on the strips flatness in each controlled zone.
Differences and competitive advantages
The main differences and competitive advantages of the developed system are as follows:
- achievement of thermo-flattening effect on strips (because target curves of the strip flatness depend on current measured temperature field in the strip);
- considered the outer profile line of winding coils, which irregularity distorts the measured strip flatness. Profile of the outer line of coil either is calculated from data on transverse profile of hot rolled strip taking into account the calculated stress-strain state of the roll on a winder reel, or can be measured by means of a triangular laser system;
- model of control is designed in such a way that does not depend on the specific conditions of rolling, as based on physical laws of the rolling process, and therefore can be used for various sheet rolling mills, including the hot strip rolling mills.
Firstly created AFC in the CIS, introduced in temper mill TM-1 NLMK has provided improved by 10-30% flatness of the finished strips.
MTM offers the comprehensive services that enhance the flatness of rolled wide strip lines in the hot and cold rolling.