EP3990200B1 - Flatness-measuring apparatus for measuring the flatness of a metal strip - Google Patents

Description

The invention relates to a flatness measuring device for measuring the flatness of a metallic strip, comprising a measuring roller which has a roller axis and which is designed to make contact with the strip for the purpose of flatness measurement, the measuring roller being connected to a cooling system with which the measuring roller can be cooled .

A flatness measuring device is from the EP 1 199 543 B1 known.

Here, a measuring roll with a circumferential section facing away from the strip to be measured is immersed in a container filled with coolant, whereby the roll is cooled. According to a further solution, the measuring roller is sprayed with cooling medium from the radial direction by cooling nozzles. The general cooling of rollers reveals this EP 0 542 640 A1 and the JP 2015-80794 A .

The US 4,188,809 A , which forms the basis for the preamble of claim 1, discloses a measuring roll in a cold rolling mill, under which a number of sensors are arranged, with which the size of a gap that forms between the sensors and the measuring roll is measured. To clean the measuring roll, it is blown on using air nozzles. The WO 2006/134696 A1 and the EP 1 199 543 B1 show similar solutions.

The present invention relates to flatness measurement in a forming process of metallic strip, in particular and preferably in a hot rolling mill. The cooling of the measuring roller during measuring operation is particularly important, especially if it is used in a hot rolling mill.

When rolling steel, optical systems are often used that can measure the flatness of the rolled strip as long as the strip head has not yet been caught by the reel. As soon as the reel has grasped the strip and puts it under tension, the flatness deviations are no longer visible and can therefore be used can no longer be detected optically or only in the case of significant deviations.

Flatness measuring systems are known from the cold rolling process that are able to measure flatness deviations that are not visible due to superimposed tensile stress. These systems measure the tension differences caused by the flatness deviation across the width of the strip. These are predominantly deflection pulleys that are equipped with sensors that are able to measure the radial force exerted on the deflection pulley by the tensile stress. By measuring the radial force in localized areas across the width, these systems are able to measure the local deviation of the tensile stress from the average tensile stress. These deviations are directly proportional to the flatness deviation.

The use of this measuring technology, known from cold rolling technology, in hot rolling places very high demands on the robustness of the system in terms of temperature and wear, while at the same time requiring high sensitivity due to the lower tensile stresses. This requires the use of highly efficient cooling that protects the sensors but has no influence on the measurement and does not disrupt the temperature control of the hot rolling process.

For previously known solutions (see the one mentioned EP 1 199 543 B1 ), the measuring roll is cooled by a cooling box arranged below the measuring roll. Since the roll has to be immersed in the belt from below, two additional rolls are necessary above the belt. These additional rollers must be pivoted to thread the belt in and out, which requires additional mechanics. Arrangements with only one additional roller lead to unfavorable geometric relationships between the distance between the rollers and the belt width, which leads to measurement errors with even the slightest alignment errors. Arranging a single roller with sufficient spacing leads to a wrap angle that is too small and thus significantly impairs the measurement accuracy. Cooling by a cooling medium located in a cooling box is not effective because the stationary medium can only achieve low relative speeds on the roller surface.

When using the spray cooling systems known from the roller cooling systems The problem arises that the measurement is disturbed due to the forces exerted on the roller surface by the cooling nozzle jet ("impact"). Furthermore, if the measuring roller is arranged above the strip, the cooling medium would influence the cooling process of the strip and thus change the quality of the product. When winding the strip, it is often necessary to completely remove the cooling medium from the strip surface for reasons of surface quality. Therefore, the use of the cooling medium in the measuring roller must be reduced to such an extent that highly efficient cooling is no longer possible. The use of wipers on a closed cooling box, which keeps the cooling medium in a closed space, also influences the measurement signal due to the pressure that these wipers exert on the measuring roller. The impact of the nozzle jets results in high temperature gradients both locally and temporally due to the locally very high heat transfer coefficient. These gradients also lead to disturbances in the measurement signal due to the deformation of the roller caused by the temperature expansion.

The invention is based on the task of developing a flatness measuring device of the generic type in such a way that it is possible to use it even at high temperatures and in particular in hot rolling mills, while at the same time ensuring that a high level of measuring accuracy can be maintained.

The flatness measuring roll should be cooled in such a way that the cooling of the roll is so effective, even at temperatures of the strip to be measured up to 1,000 °C, that a practical service life of the measuring roll can be achieved. Furthermore, the sensor system used, which is sensitive enough to measure the flatness defects that occur during hot rolling with sufficient accuracy, should be protected from excessive heat input. The cooling must not cause any thermal or mechanical disruption to the measurement. The cooling medium should be used in such a way that the quality of the product produced is not influenced by uncontrolled exposure to the cooling medium.

The solution to this problem by the invention is characterized in that the measuring roller is designed as a deflection roller which is equipped with a sensor system which is able to measure the tension exerted on the deflection roller by the tensile stress To measure radial force, that the flatness measuring device is part of a hot rolling mill and that the cooling system has a nozzle bar which extends parallel to the roller axis, with at least one, preferably a number, spray nozzles being arranged on the nozzle bar, with which cooling medium is sprayed onto the surface of the in an ejection direction Measuring roller can be sprayed out, wherein the spraying direction hits a surface section of the measuring roller and the angle between the spraying direction and the tangent to the measuring roller at the location of the surface section is less than 30 °.

The angle is preferably between 0° and 20°, particularly preferably between 0° and 10°.

The spray nozzles are preferably flat jet nozzles. It is preferably provided that the flat jet nozzles emit a cooling media jet that is at least 4 times as wide as it is thick, particularly preferably at least 8 times as wide as it is thick. The width of the jet from the flat jet nozzles preferably extends in the direction of the roller axis.

Although a number of spray nozzles are preferably provided, it is also possible for only a single wide slot nozzle to be arranged on the nozzle bar.

The spray nozzles are preferably aligned so that the cooling medium is applied counter to the direction of travel of the measuring roller. The direction of movement of the ejected cooling medium is opposite to the direction of movement of the surface of the roller where the coolant contacts the roller.

The cooling system can have at least one further nozzle bar, which extends parallel to the roller axis and is arranged offset from the first, above-mentioned nozzle bar in the circumferential direction of the measuring roller, with a number of spray nozzles being arranged on the further nozzle bar, with which cooling medium is sprayed onto the surface of the in an ejection direction Measuring roller can be sprayed out, the spraying direction hitting a surface section of the measuring roller and the angle between the spraying direction and the tangent to the measuring roller at the location of the surface section being less than 30°, preferably between 0° and 20° and particularly preferably between 0° and 10 ° is.

A further development of the invention provides that the cooling system comprises an enclosure which encloses the nozzle bar(s) and a circumferential section, preferably at least 180° of the circumference, of the measuring roller. Two gaps can be formed between the housing and the measuring roller, which make it more difficult for the cooling medium to pass through. With regard to the measuring roller, the housing is preferably dimensioned so that the gaps are in the range between 0.01 mm and 2.0 mm.

Furthermore, it can be provided that means for feeding a (barrier) gas are arranged in the area of the gap, with which a gas stream can be directed into the interior of the enclosure. As a result, the escape of cooling medium from the interior of the housing can be minimized or even completely prevented. The means for feeding a gas can comprise slot nozzles which extend in the longitudinal direction of the gap, the slot nozzles preferably being integrated into the housing in the area of the gap.

The proposed concept is therefore based on spray cooling of the measuring roller, which is arranged on (at least) one nozzle bar aligned parallel to the roller axis. Flat jet nozzles are preferably used as spray nozzles. The flat jet is aligned so that the long axis of the oval surrounding the jet is preferably parallel to the roller axis; However, the angle between the long jet axis and the roller axis can be up to 10°. The spray nozzles are also aligned so that the jet hits the roller surface at a flat angle, preferably between 0° and 10°; 0° means that the beam hits the measuring roller tangentially.

The distance between the nozzles along the roll barrel is preferably chosen so that the impact on the roll surface is as uniform as possible along the impact points of the cooling medium in accordance with the geometry of the jets.

The additional nozzle bar mentioned is placed at a further position above the circumference of the roll in relation to the first-mentioned nozzle bar. The further nozzle bar can be varied in terms of its geometry and/or its arrangement and/or its orientation of the nozzles. Furthermore, with a view on the (at least one) further nozzle bar, the output of the cooling medium can vary with regard to the pressure and / or the flow rate of the cooling medium in relation to the first-mentioned nozzle bar.

The development mentioned provides that the area of the measuring roller, which is subjected to the spray cooling, is sealed off from the environment by the closed enclosure mentioned. The gap between the rotating roller and the housing is preferably minimized to such an extent that while running During operation there is no longer any contact between the housing and the rotating measuring roller.

The area of the enclosure immediately adjacent to the gap between the roll surface and the enclosure, where the rotating roll enters the enclosure, is preferably designed so that the cooling medium collects directly at the gap and so the roll surface is evenly coated with cooling medium over the entire width of the bale applied. The roller surface is preferably provided with a rough surface and is constantly kept in motion for cooling. The rotational speed of the roller should preferably not fall below a minimum specified value.

As mentioned, the gap between the housing and the measuring roller can be acted upon by a gaseous medium. The direction of flow of the medium is preferably directed into the interior of the enclosure. The nozzle for applying the medium is preferably designed as a slot nozzle. The slot nozzle is preferably integrated into the area of the gap.

The gap between the roller surface and the housing, where the roller surface emerges from the housing, can also be designed so that a controlled small amount of the cooling medium remains on the surface of the measuring roller.

The proposed solution ensures effective cooling of the measuring roller without disturbing the measuring signal due to the jet geometry of the cooling nozzles and the flat impact angle.

The arrangement of the nozzles against the direction of travel of the roll and the design of the enclosure advantageously prevents any influence on the quality of the measured strips, since the cooling medium is effectively contained in the enclosure can be held, collected and returned to the circulation in a controlled manner.

Through the controlled wetting of the rotating measuring roller, the cooling medium is brought into the contact area between the hot belt and the measuring roller in a controlled manner. This allows the heat transfer to be dampened and the heat input into the roll to be minimized. At the same time, wear is minimized by exploiting the aquaplaning effect.

Fig. 1

schematisch eine Planheitsmessvorrichtung mit einer Messrolle und einem Kühlsystem, wobei die Förderrichtung des nicht dargestellten zu vermessenden Bandes senkrecht auf der Zeichenebene steht,

Fig. 2

schematisch eine Spritzdüse, die Kühlmedium ausbringt,

Fig. 3

schematisch Einzelheiten des Kühlsystems, mit dem die Messrolle gekühlt wird, wobei die Rollenachse senkrecht auf der Zeichenebene steht, und

Fig. 4

schematisch die Planheitsmessvorrichtung mit einer Einhausung.

An exemplary embodiment of the invention is shown in the drawing. Show it:

Fig. 1

schematically a flatness measuring device with a measuring roller and a cooling system, the conveying direction of the strip to be measured, not shown, being perpendicular to the plane of the drawing,

Fig. 2

schematically a spray nozzle that dispenses cooling medium,

Fig. 3

schematic details of the cooling system with which the measuring roller is cooled, with the roller axis perpendicular to the drawing plane, and

Fig. 4

schematically the flatness measuring device with an enclosure.

In Figure 1 a flatness measuring device 1 can be seen, which includes a measuring roller 2, which is used to contact a metallic strip, not shown. The degree of flatness of the band can thus be determined in a manner known per se. Because the flatness measuring device 1 is part of a hot rolling mill, the measuring roll 2 must be cooled, for which a cooling system 3 is available. The cooling system 3 includes a nozzle bar 4, the longitudinal axis of which is parallel to the roller axis a, as can be seen Figure 1 results. 4 spray nozzles 5 are arranged at equal intervals on the nozzle bar; the distance is indicated by the double arrow in Figure 1 marked.

Each spray nozzle 5 delivers a jet of cooling medium that is relatively flat. This is in Figure 2 illustrated. The cooling medium is discharged from the spray nozzle 5 in the spray direction b, the spray nozzle 5 being designed as a wide slot nozzle or flat jet nozzle. Accordingly, the cooling medium reaches the surface of the measuring roller 2 with a substantially oval contact surface which has a width B and a thickness D. The contact surface that the cooling medium has on the surface of the measuring roller 2 can therefore be assigned a longitudinal axis c, which is parallel to the roller axis a. The width B is at least four times as large as the (maximum) thickness D, preferably even at least eight times as large.

In Figure 3 Details of the cooling system 3 used can be seen. The measuring roller 2 contacts the belt 12 and rotates in the direction of rotation R, whereby in Figure 3 whose roller axis a is perpendicular to the drawing plane. The cooling system 3 initially includes an (upper) nozzle bar 4 on which the spray nozzles 5 are arranged. Furthermore, it comprises a (lower) nozzle bar 7, on which spray nozzles 5 are also arranged. This nozzle bar 7 is optional and arranged offset in the circumferential direction.

The alignment of the spray nozzles 5 for cooling the surface of the measuring roller 2 is essential Figure 3 It can be seen that the spray nozzles 5, with their spray direction b, discharge their cooling medium at a point or a surface section 6 of the measuring roller 2. If you place a tangent t on the measuring roller 2 at the point or surface section 6, an angle α results between the spray direction b and the tangent t. This angle α is relatively small and is a maximum of 20°. The preferred range for the angle α is between 0° and 10°.

The two nozzle bars 4 and 7 are arranged offset in the circumferential direction over the measuring roller 2. For the angular relationships of the impact of the However, the same geometric conditions apply when the cooling medium is applied to the surface of the measuring roller in the area of the surface section 6.

In Figure 4 It can be seen that the flatness measuring device 1 can also have a housing 8, which accommodates the nozzle bars 4 and 7 (not shown here) and encloses the measuring roller over a circumferential section of a good 180 °. Small gaps 9 and 10 ensure that only a small amount of cooling medium escapes from the inside of the enclosure. By applying sealing air (as described above), liquid leakage can be completely prevented.

Inside the housing 8, cooling medium 11 collects, which cools the measuring roller 2 over its entire width as it rotates. However, the geometry explained when aligning the spray nozzles 5 ensures that the measuring function of the measuring roller 2 is not impaired. This is not the case with previously known solutions.

List of reference symbols:

1

Flatness measuring device

2

measuring roller

3

Cooling system

4

nozzle bar

5

spray nozzle

6

Surface section of the measuring roller

7

another nozzle bar

8th

Enclosure

9

gap

10

gap

11

accumulated cooling medium

12

tape

a

Roller axis

b

Spray direction

c

Longitudinal axis of the applied cooling medium

t

Tangent to the measuring roller

b

Width of the coolant jet

D

Thickness of the coolant jet

R

Direction of rotation

α

angle

Claims (10)

1. Planarity measuring device (1) for measuring the planarity of a metallic strip, comprising a measuring roller (2), which has a roller axis (a) and which for the purpose of planarity measurement is constructed for making contact with the strip, wherein the measuring roller (2) is connected with a cooling system (3) by which the measuring roller (2) can be cooled,
   characterised in that

   the measuring roller (2) is constructed as a deflecting roller equipped with a sensor system which is in a position of measuring through tensile stress the radial force exerted on the deflecting roller,

   the planarity measuring device (1) is a component of a hot-rolling mill and

   the cooling system (3) comprises a nozzle bar (4) extending parallel to the roller axis (a), wherein at least one spray nozzle (5), preferably a number of spray nozzles (5), by which cooling medium can be sprayed onto the surface of the measuring roller (2) in a spraying direction (b) is arranged at the nozzle bar (4), wherein the spraying direction (b) is incident on a surface section (6) of the measuring roller (2) and wherein the angle (α) between the spraying direction (b) and the tangent (t) to the measuring roller (2) at the location of the surface section (6) is less than 30°.
2. Planarity measuring device according to claim 1, characterised in that the angle (α) is between 0° and 20°, preferably between 0° and 10°.
3. Planarity measuring device according to claim 1 or 2, characterised in that the spray nozzles (5) are fan nozzles preferably delivering a cooling media jet which is preferably at least four times as wide (B) as thick (D), particularly preferably at least eight times as wide as thick.
4. Planarity measuring device according to claim 3, characterised in that the width (B) of the jet of the fan nozzles (5) extends in the direction of the roller axis (a).
5. Planarity measuring device according to any one of claims 1 to 4, characterised in that the spray nozzles (5) are oriented so that the cooling medium is applied against the running direction of the measuring roller (2).
6. Planarity measuring device according to any one of claims 1 to 5, characterised in that the cooling system (3) comprises at least one further nozzle bar (7), which extends parallel to the roller axis (a) and is arranged to be offset with respect to the first nozzle bar (4) in the circumferential direction of the measuring roller (2), wherein a number of spray nozzles (5) by which cooling medium can be sprayed onto the surface of the measuring roller (2) in a spraying direction (b) is arranged at the further nozzle bar (7), wherein the spraying direction (b) is incident on a surface section (6) of the measuring roller (2) and wherein the angle (α) between the spraying direction (b) and the tangent (t) to the measuring roller (2) at the location of the surface section (6) is smaller than 30°, preferably between 0° and 20° and particularly preferably between 0° and 10°.
7. Planarity measuring device according to any one of claims 1 to 6, characterised in that the cooling system (3) comprises a housing (8) surrounding the nozzle bar or bars (4, 7) as well as a circumferential section, preferably at least 180° of the circumference, of the measuring roller (2).
8. Planarity measuring device according to claim 7, characterised in that two gaps (9, 10) hampering the passage of cooling medium are formed between the housing (8) and the measuring roller (2).
9. Planarity measuring device according to claim 8, characterised in that means for feeding a gas into the region of the gaps (9, 10) are arranged, which can conduct a gas flow into the interior of the housing (8).
10. Planarity measuring device according to claim 9, characterised in that the means for feeding a gas comprise slot nozzles extending in the longitudinal direction of the gaps (9, 10), wherein the slot nozzles are preferably integrated in the housing (8) in the region of the gaps (9, 10).

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