EP3927478B1 - Method for setting different cooling courses for rolled material over its width in a cooling line of a hot-strip mill or heavy-plate mill - Google Patents

Description

The invention relates to a method for adjusting the cooling process of metal strips or metal sheets (rolling stock) across the strip width of a cooling section, e.g. in a hot strip or heavy plate mill or cooling in a continuous annealing/heat treatment.

Cooling plays an important role in improving the quality of hot strip or heavy plate. For this purpose, a targeted computer-assisted control of the cooling is known, for example to prevent the strips or sheets from buckling and/or bulging. If there is a lack of control and regulation of the temperature, the desired qualities can no longer be set. So it happens that if the strips or sheets are bent or bulged too much, this cannot be corrected in a subsequent roller conveyor to ensure quality. The consequences are tape errors and an associated increased reject rate.

In order to avoid this, methods for cooling a rolling stock are known in which a control device for the rolling stock determines and sets the optimal coolant quantity and coolant quantity profile for the passage through a cooling section. This is intended to ensure the optimal flatness and evenness of the rolling stock to be cooled.

A disadvantage of this is that the strip width areas are cooled differently in a targeted manner in order to improve the flatness of the strip or sheet. This is done taking into account measured temperatures, but these are taken from the surface. After cooling, the temperature distribution in the strip or Sheet metal is not homogeneous and therefore not meaningful in relation to the actual energy content in the material.

From the DE 10 2008 011 303 B4 the energy content of the rolling stock to be cooled is taken into account as an input variable for controlling the cooling section and for determining the amount of coolant in order to specifically remove a certain amount of heat from the rolling stock. A single, fixed value is always assumed here as the starting and target variable. Furthermore, no indication is given as to how the target value can be determined.

The JP S64 622 08 A discloses a generic method which serves to uniformly cool hot strip in the width direction over its entire length. This improves the material quality and prevents the generation of an incorrect shape of the hot strip. To do this, the centers of a pair of movable plates are brought into agreement with the center position in the width direction of the hot strip being passed. The temperature difference T between the temperatures of the middle part and the end part of the hot strip is calculated by comparison arithmetic and compared with a target temperature difference T0. When T is larger than T0, a signal for narrowing the distances between the movable plates is transmitted to a drive motor controller. At the same time, the center position of the hot strip is calculated based on the two end positions using the comparison arithmetic.

Proceeding from this, it is the object of the present invention to specify an improved method for checking and adjusting the planarity or flatness and/or the mechanical properties of the rolling stock in a hot-rolled and heavy-plate mill. Further advantageous measures are the subject of dependent claims.

This object is achieved starting from the preamble of claim 1 by the initial enthalpy distribution over the calculation of the cooling

Material width of the rolling stock is determined before cooling, based on which a target enthalpy distribution is determined, taking into account a calculation of the flatness and the mechanical properties using a microstructure model in the width and length direction of the rolling stock, and after this the amount of coolant and the coolant flow of the cooling section are set.

Based on an enthalpy distribution across the width at the start of the cooling section, a target enthalpy distribution across the width after the cooling section is defined. The input enthalpy distribution can be determined from a computer program, for example. In principle, another thermodynamic potential can also be used instead of the enthalpy.

The target enthalpy distribution can be set using various parameters. For example, this is a numerical calculation of the flatness of the strip after the cooling line, which can be optimized based on the target value. With the help of modelling, it is basically possible to calculate the flatness of the finished product in the cold state (i.e. after coil cooling). This is not possible with the help of a measuring device when it is warm. Another option is to define this using a microstructure model so that the goal of setting homogeneous mechanical properties across the width can be met. This is not necessarily the case with uniform cooling and this is also not necessarily the case with uniform enthalpy distribution across the width. Furthermore, the results of various measuring devices that measure a quality variable as a function of the width can also be used as control parameters. This can be, for example, a flatness measuring roller or another flatness measuring device, but also measuring devices for recording the mechanical properties (e.g. Impoc or others).

A wide variety of measures can be used as actuators within the cooling section, which make it possible to achieve different enthalpies depending on the width. This can be, for example, edge masking, heating of edges, targeted cooling using multiple control loops across the width, or similar. The target enthalpy distribution can also be determined by optimizing other parameters or empirically based on measurements after cooling.

Starting from the initial enthalpy distribution, the target enthalpy distribution can be adjusted inhomogeneously across the width. A control can dynamically change the target enthalpy distribution in the rolling stock over the width while the rolling stock is running through the cooling section. The enthalpy calculation can be based on the Gibbs energy, for example.

Databases in the SGTE (Scientific Group on Thermodata Europe and MatCalc database) can be used to determine the Gibbs energy, for example to specify the structural components in the rolling stock and to set the cooling to a constant structural phase proportion that is homogeneously distributed over the strip width of the rolling stock and thus to regulate and control the mechanical properties depending on the target enthalpy distribution.

An immediate comparison can be made with the mechanical properties calculated in the microstructure model via a measuring point located after the cooling system, and a possible deviation in the target enthalpy distribution can be corrected immediately by activating or switching off the cooling system.

Fig. 1

eine schematische Darstellung der Anlage und des Flusskonzeptes;

Fig. 2

Darstellung der einlaufenden Enthalpieverteilung (oberes Bild),

Fig. 2a

der Zielenthalpieverteilung (mittleres Bild)

Fig. 2b

und der Differenz der beiden Enthalpieverteilungen über die Breite des Walzgutes gesehen;

Fig. 3

die Darstellung möglicher Zielverteilungen für die mechanischen Eigenschaften und

Fig. 3a

der Planheit über der Breite gesehen.

The invention will be explained in more detail below on the drawings. It shows:

1

a schematic representation of the system and the flow concept;

2

Representation of the incoming enthalpy distribution (upper picture),

Figure 2a

the target enthalpy distribution (middle image)

Figure 2b

and the difference between the two enthalpy distributions across the width of the rolling stock;

3

the representation of possible target distributions for the mechanical properties and

Figure 3a

of flatness across the width.

The figure 1 shows schematically part of a possible hot strip or heavy plate plant for processing metal strips and/or metal sheets. After the last stand 1 of the hot strip or heavy plate mill is a measuring device 2 arranged. The measuring device 2 can be a flatness roller or the like and is arranged in front of the actual cooling section 3 . The measuring device records an actual value of the rolling stock 6 before the cooling section 3.

The cooling section 3 can include laminar cooling or intensified cooling or also compact cooling. After the cooling section 3 there is at least one further measuring device, for example a flatness roller or the like, which measures the actual value, for example the flatness of the hot strip/rolled stock 6 after it has passed through the cooling section 3 .

A calculation model 5 receives the measurement data from the measuring devices 2 and 4 and specifies the amounts of cooling medium to be used accordingly in the cooling section 3 in order to set the target enthalpy distribution. As a result, it can be ensured virtually online that the desired qualities of the rolling stock/hot strip 6 can be adjusted and immediately thereafter coiled into a coil 7 for further processing. Other units, for example more measuring devices, descalers, thermal insulation hoods, scissors, etc. can be arranged in the area before and after the cooling system 3 .

The Figures 2, 2a, 2b illustrate the enthalpy distribution in the hot strip across the width at the beginning of the acquisition and at the end of the acquisition as well as the difference between the two enthalpies at the beginning and end.

Figures 3 illustrates the mechanical properties of yield point and tensile strength (Rp and Rm) across the width of the hot strip. The Figure 3a shows the flatness of the rolling stock across the width.

Reference sign

1

last scaffold

2

Measuring device in front of the cooling section

3

cooling line

4

Measuring device after the cooling section

5

model

6

Rolled steel / hot strip

7

coil/spool

Claims (8)

1. Method for setting the cooling course of rolling material (6) consisting of metal strips or metal sheets over the strip width or width of the sheet in a cooling path (3) of a hot-strip rolling train or heavy-plate rolling train or cooling in continuous annealing / heat treatment, characterised in that the initial enthalpy distribution over the material width of the rolling material (6) is determined prior to cooling, wherein starting therefrom and with consideration of a computation of planarity and/or mechanical properties a target enthalpy distribution is determined in width direction and length direction of the rolling material (6) by a structural model and the coolant quantity and coolant course of the cooling path (3) are set according thereto.
2. Method according to claim 1, characterised in that starting from the initial enthalpy distribution the target enthalpy distribution over the width is set inhomogeneously.
3. Method according to claim 2, characterised in that the initial enthalpy distribution is dynamically changed during the strip running and the coolant quantity is correspondingly and subsequently recalculated.
4. Method according to claim 3, characterised in that regulation during the rolling material running dynamically changes the target enthalpy distribution in the rolling material over the width.
5. Method according to claim 4, characterised in that the enthalpy computation is carried out on the basis of Gibbs energy.
6. Method according to claim 5, characterised in that for determination of the Gibbs energy reference is made to databanks in the Scientific Group on Thermodata Europe (SGTE) so as to indicate the structural components in the rolling material (6) and the cooling is regulated and controlled in dependence on the target enthalpy distribution to a constant structural phase component distributed homogenously over the strip width of the rolling material (6).
7. Method according to claim 6, characterised in that an immediate comparison with the mechanical properties computed in the structural model is carried out by way of a measuring point and a possible deviation of the target enthalpy distribution is thereby corrected immediately by activating or switching-off the cooling.
8. Method according to one or more of claims 2 to 7, characterised in that the setting of different enthalpy courses H(x) is carried out in such a way with the width co-ordinates x of rolling material (6) consisting of metal strips or metal sheets over the strip width or width of the sheet in a cooling path (3) of a hot-strip rolling train or heavy-plate rolling train or the cooling in a continuous annealing / heat treatment that the initial enthalpy distribution over the material width of the rolling material (6) is determined prior to the cooling, wherein starting therefrom and with consideration of a computation of the planarity and/or the mechanical properties a target enthalpy distribution is determined in width direction and length direction of the rolling material (6) by a structural model and the coolant quantity and the coolant course of the cooling path (3) are set according thereto.

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