EP0732979A1 - Continuous casting and rolling plant for steel strip, and a control system for such a plant - Google Patents

Abstract

In the continuous casting and rolling plant and associated control system proposed, the design of the individual plant elements is optimized with respect to their combined action and the individual plant elements operated in coordinated fashion to produce steel strip which is suitable for further processing. This coordination is preferably optimized using a neurofuzzy system.

Description

Pouring salt plant for steel strips and control system therefor

The invention relates to a casting and rolling system for steel strips and a control system therefor.

Since the first casting and rolling system, as described in German Patent 52 002, casting and rolling systems have been developed in large numbers and in a wide variety of designs. Common to these developments is that they have so far only led to success for low-alloy steel if the casting device produces a so-called thin slab strand of at least 50 mm thickness (DE 37 12 537 AI), which is then introduced into the first roll stand or if stainless steel is cast into tapes, as described in EP 0 458 987 AI and EP 0 481 481 AI.

It is an object of the invention to provide a casting and rolling system for steel strips and a control system therefor, which allow steel strips of any quality to be produced within the further processing tolerances, with cast strips having a thickness between 5 and 20 mm being assumed.

The object is achieved in that individual system parts are optimized with regard to their interaction to produce a strip suitable for further processing and are operated in coordination with one another. The tuning is preferably optimized by a neurofuzzy system.

Advantageous details of the individual parts of the system and

Control systems are evident from the description below.

Starting from a pouring jet that runs out of a tundish or forehearth, it is supposed to flow through casting rolls and

Postform a hot rolled strip with a thickness of approximately

2 to 4 mm can be produced. In individual cases, one should also Thickness of 1 mm. For this, casting and rolling devices with the following, partly known, basic electrotechnical components are used:

Slider closure drive with pouring jet control on the tundish or forehearth. The pouring jet runs into a pre-cooling device, possibly also into an inlet mold, and there the pouring level, e.g. by radiometric measurement, for example with a measuring device from Dr. Berthold, set to an accuracy of ± 3 mm. This setting is independent of the cross section of the distribution and / or pre-cooling device. This can be open at the top or designed as a chamber.

A coolant control and, if necessary, a stirring device in the form of an electrical coil are provided for the distribution and precooling device. This can be made in one or more parts. The distribution and

Pre-cooling device can be designed as an inlet mold, in particular for thicker cross sections, but it can also be designed as a distribution channel or as a box-like attachment with a cover. In the training as an inlet mold, the advantageously controllable training, as described in DE 40 30 683 AI, is appropriate.

The pair of casting rolls advantageously has a coolant control as well as a power and position control and in particular a momentary shape calculation. The shape of the casting rolls is aligned to the requirements of the downstream rolling devices in such a way that they deliver a tolerance-compliant strip with a minimum of adjustment. A rectangular exit profile has been found to be particularly suitable, which advantageously has spherical edges, for example. Behind the casting rolls there is advantageously an electromagnetic belt tension control and corresponding belt deflection devices, which at least partially replace the previously usual rolls, which can give rise to surface defects or promote the occurrence of edge cracks, particularly in continuous operation. Furthermore, inductive strip temperature distribution setting devices and a pressure water descaling device are arranged directly in front of the first forming roller in this area. The casting speed is preferably approximately 6 to 10 m / min. Single or multi-part line inductors are used for edge temperature adjustment and plate inductors that can be individually switched on and off, if necessary, for temperature homogenization. With these measures, an adjustment of the inlet temperature of the cast strip into the first roll stand is possible even with a predetermined temperature profile across the width. The entry temperature of the strip into the forming rolls, like the casting temperature, is essentially set according to the alloy, ie the steel quality and the final dimension to be achieved during the rolling, ie the degree of deformation by the rolls.

Simple duo or quarto roll stands are provided as roll stands, which have at least one roll gap adjustment and a roll bending device. Here, based on the actually cast strip profile, the target profile and the target cross-section are set, as far as possible, which is also influenced by the reel pulling force.

If necessary, a heat treatment zone is provided behind the last stand, one to three stands, depending on the degree of deformation required to achieve the final cross section, which has inductive devices and possibly also cooling devices. Pendulum annealing is carried out here, for example to influence the grain. Furthermore, a temperature maintenance zone in front of the reel be provided. This results in a controlled heat treatment from the rolling heat.

Thickness and profile measuring devices are advantageously located behind the rolls in order to control the roll setting, roll bending and the pull-out force from the rolls in order to achieve a tolerance-compliant strip. The entry profile into the rollers is advantageously determined by calculation, the calculation can be checked by measurement. The calculation goes e.g. from the solidification data of the alloy, the calculated instantaneous shape of the casting rolls and possibly from the strip temperature profile across the width.

The inductive devices and the casting equipment (including cooling technology) are advantageously controlled and regulated by an automation system based on Siemens "SIMATIC S5", while the casting rolls, the forming rolls and the reel advantageously control and regulation based on Siemens "Symadin D ". The automation devices are advantageously connected to one another and to a control unit by a bus system. The finished rolled strip has profile deviations below the cold rolling entry tolerance of approximately max. ± 0.025 mm for a 4 mm tape.

The individual automation and measuring devices are organized in particular in technology-related automation groups and connected to one another by a feedforward-feedback control system. In a particularly preferred embodiment, the control system has an empirical value matrix with an influencing link in the basic form of a self-optimizing neural network with fuzzy input data and automatically generated expert knowledge. This results in a superimposed control system, the relatively simple individual units in an inexpensive design for producing a crack-free strip with tolerances within the control limits of a downstream cold rolling mill can connect and thereby automatically brings with it the experience of how the individual units will react to changed input values and procedure behavior.

In special further refinements of the invention, it is provided that the tundish or forehead outflow control takes place in a pouring tube or the like, by means of slides with an electric drive, depending on the inlet casting level and predetermined requirements, such as the strip thickness. The inlet casting level or level above the casting rolls can be determined not only by radiometric, but also by optical or float measurements.

The necessary coolant control of the inlet area, etc. takes place depending on wall thermocouples or the data of the tundish outflow control in connection with an outflow measurement. An empirical value matrix is also advantageously used for this, which e.g. the alloy influences are taken into account.

The casting rolls have a speed and torque control, and the deformation energy currently required is determined very advantageously by cyclical releases of the speed and torque control. The greater the deformation energy currently required, the higher the union zone of the two solidification shells formed on the casting rolls above the connection plane of the center lines of the casting rolls and vice versa. The deformation energy currently required is therefore a good control variable. With their use, breakthroughs on the exit side can be avoided in a very advantageous manner, as can an excessively high position of the solidification shell union zone. Hanging the union zone to one side can be compensated for by selective cooling. DE 40 21 197 AI shows more about the one-sided hanging of the union zone. The unilateral hanging of the union zone is noticeable eg based on the outlet temperature profile. The casting rolls are controlled in relation to their axis position (distance, offset). Their actual position and shape can be determined, for example, by continuous IR laser measurements and corrected if necessary. The amount of coolant is adjusted, in particular according to the specifications of the inlet area and the casting roll speed. Minor crowning corrections are possible using electrical means, such as induction heating.

The extraction of the cast strip is regulated taking into account the small maximum tensile stress on the exit side of the casting rolls. This regulation can be viewed either in connection with the regulation of the roll stands, but also as the regulation of a decoupled stand with a tension regulation by electromagnetic means. A control to constant, maximum mass flow is optimal, depending on the maximum cooling capacity with an adaptation of the roll speed to the casting roll speed.

Following the exit from the casting rolls, a strip edge temperature and shape check is advantageously carried out. Both the strip edge temperature and the strip edge shape can be done by regulating the cooling and position of the side elements of the casting rolls. The side elements of the casting rolls are advantageously arranged on the circumference of the casting rolls and work advantageously in connection with an inductive heating or cooling as well as a position control, e.g. according to an empirical value matrix.

The surfaces of the casting rolls advantageously have a structural pattern, a herringbone or zigzag pattern being particularly advantageous. The structure recesses can be cleaned, for example, by spraying water in connection with a brush system, it being advantageous to control the cleaning by a laser, which can possibly be reworked. For a perfect detachment of the strip from the casting rolls, an electromagnetically operating belt vibrating device is advantageously provided, which is supplemented if necessary by a likewise advantageous electromagnetic stage or casting roll vibrating device. If required, an image and pattern recognition unit, for example with infrared cameras, is advantageously located between the casting rolls and the first forming roll stand, with which the surface condition of the strip is checked. Assuming that visible scale cracks that exceed a maximum length are an indication of surface cracks (deviation from the normal crack pattern), and likewise scale cracks on both sides at the edges, the behavior of the electromagnetic devices is influenced accordingly and, if necessary, repair of the cracks possible by inductive partial heating performed. The error correction is carried out by targeted electrical measures, in the event of edge cracks supported by a position and / or heating / cooling control of the edge formation guide elements. This results in a tape free of macro cracks entering the first deformation frame, in which micro cracks and intercrystalline detachments are inevitably welded. A profile and thickness measuring device may be located in front of the roll stands, which in particular carries out a profile and thickness trend evaluation. This information is particularly useful for the neuro-fuzzy system with its if-then rules, but it can also be evaluated conventionally by differentiation. The same applies to the other trends that are considered.

Subsequent to the rolling, inductive heat treatment with predetermined temperature profiles is advantageously carried out, for example, pendulum annealing at 720 ° C. and / or a subsequent holding at 500 ° C. to 550 ° C. in the case of alloy steel. The downstream reel has a tension control in order to achieve the predetermined final thickness of the strip on the last roll stand while maintaining a minimum and maximum tension.

The superimposed control system, which also works largely on the basis of mathematical models with adaptation on a neuro-fuzzy basis (largely during network training), is used in particular to coordinate the profile and strip condition achieved in the casting rolls with the downstream units. It is thus possible to advantageously use the casting rolls as well as the forming rolls, e.g. to operate without complex shifting devices (forming rolls) or devices for changing the crown (casting rolls). Based on the empirical value matrix, an optimal response to the existing conditions can be achieved relatively quickly for the different entry conditions into the casting rolls, whose behavior in operation can be determined by simulation and / or tests during commissioning and for the entry conditions into the roll stands. Depending on the alloy, the running-in conditions, in particular the running-in temperature, taking into account the available cooling capacity, a tolerance-compliant band can be achieved after a relatively short time with very simple units. As a rule, estimated values of the parameters of the fuzzy sets are sufficient for the empirical value matrix, and these are improved with the aid of the self-learning neural network. The associated fuzzy rules for processing the fuzzy sets are verified after the previous effect simulation (in particular with regard to critical states) as part of the trial operation and are also included in the empirical value matrix, with the neural network weighting the fuzzy rules accordingly Requirements changed.

Under the central control system with the particularly advantageous neural network with fuzzy structure and Experience-based matrix for pre-control or direct control, also partly inventive, control structures result from the labeled Figures 1 to 4, the basics of some important fuzzy rules from the attached table and essential constructive, inventive details and an overview of the control system according to the invention Figures 5 to 8.

List of reference symbols for Figure 5

1 tundish or forehearth

2 inlet containers or molds

3 casting rolls

3a temperature measuring device

4 electrical vibration and control devices

5 surfaces and edge inductors

6 Image and pattern recognition unit with air inflation zone

7 Deformation rolling stands 7a descaling device

7b profile and thickness measuring device

7c output professional control device

8 contin. Heat treatment facility

9 reel

10 cold rolling mill

11 Neuro-fuzzy and advance calculation unit

12 empirical value matrix

13 Manufacturing tolerance entry

14 sprue inlet, casting roll and pull-out control unit

15 Neuro-fuzzy crack pattern and pattern recognition unit with air inflation zone control

16 Roll stand control and regulation

17 Heat treatment control and regulation

18 reel control

List of reference symbols for Figure 6

1 casting roller

2 casting roller

Cooling zones 1, 11 and III individually controllable cooling zones with regard to the cooling capacity

3 shape and position scanning lasers, working trigonometrically or with pulse counting

5 coolant (water, salt solution) supply and discharge lines A, B, C, for applying a controlled vibration conveyed by speed and stroke-adjustable piston pump

9 electrical, e.g. inductive casting roll shape correction means

10 cast roller edge heating agents

11 Position and coolant or heating-adjustable casting area side limits

12 lateral temperature measuring devices, e.g. Thermocouples in cladding tubes or ultrasonic vibrators to take advantage of the temperature response of the steel density

13 cranked edges that can be influenced by temperature and shape

14 shape-influencing agents, e.g. inductive devices or hydraulic adjustment cylinders, for the casting roll edge

15 height and position adjustment devices for the lateral casting space limits in order to set the sealing gap between the lateral casting space limits and the casting rolls, List of reference symbols for Figure 7

1.2 casting rolls

3 Casting chamber middle heat sink, possibly also acting as a distributor, adjustable in length and cooling intensity

4 directional arrows

5 coolant holes

6.7 ultrasonic thermometer or thermocouple cladding 8.9 solidification shells

10 cast tape

11 one- or multi-part electromagnetic axial tension control, guiding and / or vibration device, optionally adjustable in coordination with coolant vibration pumps for 1 and 2

12 strip profile, strip thickness measuring devices, e.g. designed as laser measuring devices, integrated edge profile measuring devices,

13 temperature distribution sensors

14 position sensors

15 vibration sensors

Reference symbol list for picture

1 Midsection of the herringbone pattern

2 bones of the herringbone pattern

3 zigzag pattern lines

Casting roll surface parts, e.g. made of copper beryllium, possibly coated with tungsten carbide or other carbides

Claims

claims 1. Casting and rolling system for steel strips and control system for making sure that individual parts of the system are designed with regard to their interaction to produce a strip suitable for further processing and are operated in coordination with one another. 2. Casting-rolling system according to claim 1, d a d u r c h g e k e n n e e c h n e t that the coordination of the individual parts of the system to each other and the behavior of the individual units is optimized by a control system, in particular a neuro-fuzzy control system. 3. Casting-rolling system according to claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t that the control system generates an empirical value matrix that for the control and regulation, in particular for pilot controls, the individual parts of the system and their Components. 4. Casting-rolling system according to claim 1, 2 or 3, that the optimization comprises, among other things, a behavior simulation in various, in particular critical, input states. 5. Casting and rolling system according to claim 1, 2, 3 or 4, characterized in that the casting roll positions and the positions of the associated elements are controlled by actuators with absolute position sensors or the like, the control system specifying the values of the absolute position controllers and the result on Band or band segments on correction circles. 6. Casting-rolling system according to claim 1, 2, 3, 4 or 5, that a correction of correction values for control are preferably taken from the empirical value matrix, the neurofuzzy system carrying out the linking and mutual influencing, in particular taking into account the time behavior of the correction effects. 7. Casting-rolling plant according to claim 1, 2, 3, 4, 5 or 6, so that a main controlled variable of the casting rolls is the position of the union zone of the band shells formed, the position of the union zone being determined by the instantaneous forming force requirement of the casting rolls. 8. Casting-rolling system according to claim 1, 2, 3, 4, 5, 6 or 7, so that it has electromagnetic means for longitudinal and transverse movement and / or guiding of the strip in the area behind the casting rolls. 9. Casting-rolling plant according to one or more of the preceding claims, that a and a c e n c e n c e n c e that a strip preforming mold is arranged in front of the casting rolls, so that the casting rolls essentially act as deformation rolls. 10. Casting and rolling system according to claim 9, d a d u r c h g e k e n n z e i c h n e t that the neuro-fuzzy control system and the empirical value matrix includes the strip preforming mold and its behavior.