WO2001017704A1

WO2001017704A1 - Method and device for cooling a hot rolled steel strip that runs off a roll stand

Info

Publication number: WO2001017704A1
Application number: PCT/DE2000/003039
Authority: WO
Inventors: Otto Gramckow; Rüdiger DÖLL; Rolf-Martin Rein; Klaus Weinzierl
Original assignee: Siemens Aktiengesellschaft
Priority date: 1999-09-10
Filing date: 2000-09-04
Publication date: 2001-03-15
Also published as: DE19943403A1

Abstract

The invention relates to a method and a device for cooling a hot rolled steel strip (1, 30, 40, 50) that runs off a roll stand (2). Cooling is carried out by means of a cooling device (3, 4, 5, 6, 7, 8, 9, 10) and at least two temperature measuring devices (20, 21, 33, 34, 35, 41, 42, 51, 52, 53) that are arranged in the longitudinal direction of the steel strip (1, 30, 40, 50). The cooling devices (3, 4, 5, 6, 7, 8, 9, 10) are controlled according to the measured values of the at least two temperature measuring devices (20, 21, 33, 34, 35, 41, 42, 51, 52, 53).

Description

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In this context, the term cooling device means an active cooling device, i.e. a cooling device that is switched on and not a cooling device that is switched off.

In a further advantageous embodiment of the invention, for cooling a hot-rolled steel strip, in particular a hot-rolled strip made of carbon steel, the cooling device is regulated as a function of measurements of the temperature of the steel strip at at least two locations in the longitudinal direction of the steel strip, advantageously at least one measurement of the temperature of the steel strip at a distance of 0 to 80 cm behind the cooling device.

In a further advantageous embodiment of the invention, for cooling a hot-rolled steel strip, in particular a hot-rolled strip made of carbon steel, the cooling device is regulated in dependence on measurements of the temperature of the steel strip at at least two locations in the longitudinal direction of the steel strip such that the essential γ-α Transition takes place in the steel strip between the at least two locations in the longitudinal direction of the steel strip, at which the temperature of the steel strip is measured. In this way, a particularly high quality steel is produced.

In a further advantageous embodiment of the invention, for cooling a hot-rolled steel strip, in particular a hot-rolled strip made of CMn steel, at least one measurement of the temperature of the steel strip takes place in the area of the cooling device.

In a further advantageous embodiment of the invention, at least one measurement of the temperature of the steel strip in the area of the cooling device and at least one further measurement of the temperature of the steel strip in the area of the cooling device or at a distance of 0 to 80 cm behind the cooling device take place. In a further advantageous embodiment of the invention, the ferrite grain size in the steel strip is determined from the measurement of the temperature of the steel strip in the area of the cow device. In a further advantageous embodiment of the invention, the chemical composition of the steel strip is also used to determine the ferrite grain size in the steel strip.

In a further advantageous embodiment of the invention, the ferrite grain size in the steel strip is regulated as a function of the measurement of the temperature of the steel strip in the area of the cooling device or advantageously as a function of the determined ferrite grain size by adjusting the cooling device.

Further advantages and details emerge from the following description of exemplary embodiments. In detail show:

1 shows a cooling system for a hot-rolled steel strip,

2 shows a further cooling system for a hot-rolled steel strip,

3 shows a temperature control system for adjusting the temperature of a steel strip,

4 shows an exemplary embodiment of the arrangement of temperature measuring devices, FIG. 5 shows an advantageous embodiment of a measuring head which is part of a temperature measuring device on which the principle according to the invention is based,

6 shows a further advantageous embodiment of a measuring head which is part of a temperature measuring device which is based on the principle according to the invention,

7 shows an advantageous embodiment of a temperature measuring device which is based on the principle according to the invention.

1 shows a cooling system for a hot-rolled steel strip 1, in particular a hot-rolled steel strip made of carbon steel. The Rolls 2 indicate the last stand of a hot rolling mill. Behind this frame, cow devices 3, 4, 5, 6, 7, 8, 9, 10 are provided for cooling the steel strip 1. The cooling of the steel strip 1 can be adjusted via the amount of coolant by means of the cooling devices 3, 4, 5, 6, 7, 8, 9, 10. For this purpose, the cooling devices have 3,4,5,6,7,8,9,10 valves. These valves are set by means of a cooling controller 22. For reasons of clarity, the connections of the cooling controller 22 to the cow devices 7, 8, 9, 10 are not shown. The cooling controller 22 regulates the cow devices 3, 4, 5, 6, 7, 8, 9, 10 as a function of measured values which are supplied by temperature measuring devices 20 and 21. The temperature measuring devices 20, 21 are arranged in front of a reel 12 for reeling the steel strip 1. In a particularly advantageous embodiment, the temperature measuring device 20 is arranged in an area immediately behind the rear cooling devices 6 and 10 or in an area between 0 and 80 cm behind the rear cooling devices 6 and 10. By means of the two temperature measurements which the cooling controller 22 compares, the cooling controller 22 controls the cow devices 3, 4, 5, 6, 7, 8, 9, 10 in such a way that the γ- conversion is not cooled by one of the cow devices 3 , 4,5,6,7,8,9,10. Furthermore, the cooling controller 22 controls the cow devices 3, 4, 5, 6, 7, 8, 9, 10 in such a way that the γ-α conversion in the steel strip 1 in front of the reel 12 is completed. γ-α transformation is the transformation of austenite (γ) into ferrite (α).

2 shows a cooling device for a steel strip 30, in particular a steel strip made of unalloyed CMn steel. The rolls designated by reference number 2 in turn represent the last stand of a hot rolling mill. Reference numerals 3,4,5,6,7,8,9,10 denote cow devices and reference numeral 12 a reel. The cooling of the steel strip 30 by means of the cooling devices 3, 4, 5, 6, 7, 8, 9, 10 takes place as a function of a predetermined target value d ^ for the ferrite grain size d _α . For this purpose, a ferrite grain size controller 31 is provided, of the valves of the Kuhlemrichtungen 3,4,5,6,7,8,9,10 in / dependence of a calculated actual value of _α d for Ferritkorngroße and the target value _α d for Ferritkorngroße such controls, that the computed actual value for _α d Ferrite grain size corresponds to the target value d _{α for} the ferrite grain size. Under

Ferrite grain size is to be understood as the mean size of ferrite crystals in steel strip 30. For reasons of clarity, the connections between the cooling devices 3, 4, 5 and 6 and the femt grain controller 31 are not shown.

To determine an actual value d _{α of} the ferrite grain size, an e-grain size observer 32 is provided. The grain size observer 32 determines an actual value for the ferrite grain size dα from temperature measurement values for the temperature of the steel strip 30 at at least two points in the longitudinal direction of the steel strip 30. In the exemplary embodiment, three temperature measuring devices 33, 34, 35 are provided for measuring the temperature of the steel strip 30. This is an advantageous embodiment. However, a ferrite grain size observer can also be provided, who determines an actual value for the ferrite grain size d _α from the temperature measured values of two temperature measuring devices 33 and 34, 33 and 35 or 34 and 35. The temperature measuring device 33 is advantageously arranged directly in front of the first cooling devices 3 and 7. The temperature measuring device 34 is advantageously arranged between the cooling devices 3 or 7 and 4 or 8 between the temperature measuring devices 4 or 8 and 5 or 9 or between the temperature measuring devices 7 or 9 and 8 or 10. The temperature measuring device 35 is advantageously arranged directly behind the last temperature measuring devices 6 and 10, in particular at a distance between 0 and 80 cm. It is advantageous to provide a setpoint generator which determines the setpoint d _α for the ferrite grain size from predetermined material properties, such as tensile strength, and specifies it to the ferrite grain size controller. 3 shows a temperature control system for adjusting the temperature of a steel strip 40, which runs out of a hot rolling mill, indicated by the rollers 2. To cool the steel strip there are 40 cooling devices between the hot rolling mill and a reel 12 for winding the steel strip

3,4,5,6,7,8,9,10. These are regulated by means of a controller 43. For reasons of clarity, the connections between the controller 43 and the cooling devices 3, 4, 5, 6 are not shown. To regulate the temperature of the steel strip 40, this is measured by means of the temperature measuring devices 41 and 42 at two different points in the longitudinal direction of the steel strip 40. For this purpose, it is advantageously provided to provide only one cooling device 3 or 7, 4 or 8, 5 or 9 or 6 or 10 between the two temperature measuring devices 41 and 42. The measured values TI and T2 of the temperature measuring devices 41 and 42 are fed to the controller 43, which controls the valves of the cooling devices 3, 4, 5, 6, 7, 8, 9, 10. It has been shown that this configuration enables a significantly faster regulation to be achieved than with a single temperature measuring device in front of the reel 12. It is advantageously provided that the controller 43 uses the difference between the values TI and T2 to control the effectiveness of the cooling device or the cooling devices (if several cooling devices are provided between the temperature measuring devices) between the two temperature measuring devices 41 and 42 and the actuator effectiveness is taken into account when regulating the cooling devices 3,4,5,6,7,8,9,10.

4 shows a particularly advantageous exemplary embodiment for the / arrangement of temperature measuring devices. The rolls designated by reference number 2 denote the last stand of a hot rolling mill, reference numbers 3,4,5,6,7,8,9,10 cooling devices and reference number 12 a reel. Reference numeral 50 denotes a steel band which corresponds to the steel band 1, 30 or 40. Reference numerals 51, 52, 53 denote temperature measuring devices which run in the transverse direction of the steel strip 50 are arranged. The arrangement of the temperature measuring devices 51, 52, 53 can each replace one temperature measuring device 20, 21, 33, 34, 35, 41, 42 in the sense that, instead of these temperature measuring devices, at least two, advantageously three, temperature measuring devices in the transverse direction of the steel strip 1, 30 and 40 are arranged. In this way it is possible

- to determine or set the γ-α conversion also in the transverse direction of the steel strip 1 (FIG. 1), - to set the ferrite grain size d _α in the steel strip 30 also in the transverse direction of the steel strip 30 (FIG. 2) or

- To regulate the temperature in the transverse direction of the steel strip 40 (FIG 3).

7 shows a particularly advantageous embodiment of a temperature measuring device 20, 21, 33, 34, 35, 41, 42, 51, 52, 53.

5 and 6 show advantageous and alternative configurations of the measuring head 130 in FIG. 7. To measure the temperature, infrared rays 112 are passed on via a glass fiber cable 110. The measuring head 79 in FIG. 5 has a compressed air inlet opening 78 through which compressed air is blown into its interior. The measuring head 79 also has a squeegee 74 with an air outlet opening 113 through which the compressed air flows against the steel strip 1. An air flow indicated by the arrows 72 and 73 is formed between the squeegee 74 and the steel strip 1. The geometry of the squeegee 74 and its distance from the steel strip 1 are matched to the flow velocity of the air 72 and 73 flowing between the squeegee 74 and steel strip 1 in such a way that an aerodynamic paradox occurs. This creates a balance between air pressure and suction between the suction foot 74 and the steel strip 1. It is particularly advantageous to connect the suction foot 74 to the remaining part of the measuring head 79 via a flexible connecting piece 76. If a stable gas cushion builds up due to the aerodynamic paradox, the squeegee 74 hovers over the steel belt 1 ⁾ cυ IV) N) P ¹ P »

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P> P ¹ CΛ;

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the steel strip 1 hits. A particularly precise measurement of the temperature of the steel strip is achieved in this way.

The temperature measuring devices with the measuring heads 79 and 114 according to FIGS. 5 and 6 advantageously have a pyrometer (not shown) as a sensor at the end of the glass fiber cable 110.

In FIG. 7, reference numeral 130 designates a measuring head which, in a correspondingly modified form, can also be replaced by corresponding configurations according to FIG. 5 or FIG. 6. Due to the aerodynamic paradox, the measuring head 130 hovers over a steel strip 1. Infrared light emitted from the steel strip 1 is fed via a glass fiber cable 132 to a pyrometer 136, by means of which a measured value for the temperature of the steel strip 1 is determined. The fiber optic cable 132 is accommodated with a compressed air line 133 in a flexible protective cable 134. Via the flexible protective cable 134, the compressed air lines 133 and the glass fiber cable 132 are led into a protective housing 138, which also accommodates the pyrometer 136. By means of the compressed air line 133, compressed air is blown into the measuring head 130 via a compressed air connection 137, which hits the steel strip 1 via an outflow opening 139.

Claims

claims

1. A method of cooling a hot-rolled steel strip (1, 30, 40, 50) running out of a rolling stand (2) by means of a cooling device (3, 4, 5, 6, 7, 8, 9, 10), characterized in that the temperature of the steel strip (1, 30, 40, 50) is measured at at least two locations in the longitudinal direction of the steel strip (1, 30, 40, 50).

2. A method for cooling a hot-rolled steel strip (1, 30, 40, 50), in particular a hot-rolled steel strip (1) made of carbon steel, according to claim 1, characterized in that at least one measurement of the temperature of the steel strip (1, 30, 40 , 50) behind the cooling direction (3, 4, 5, 6, 7, 8, 9, 10).

3. The method according to claim 1 or 2, characterized in that at least one measurement of the temperature of the steel strip (1, 30, 40, 50) m a distance of 0 to 80 cm behind the Kuhlemrichtung (3, 4, 5, 6, 7, 8, 9, 10).

4. The method, in particular for cooling a hot-rolled steel strip (1) made of carbon steel, according to claim 1, 2 or 3, characterized in that the cooling direction (3, 4, 5, 6, 7, 8, 9, 10) in dependence measurements of the temperature of the steel strip (1, 30, 40, 50) at at least two locations in the longitudinal direction of the steel strip (1, 30, 40, 50) are regulated, advantageously at least one measurement of the temperature of the steel strip (1, 30, 40 , 50) m at a distance of 0 to 80 cm behind the cooling direction (3, 4, 5, 6, 7, 8, 9, 10).

5. The method, in particular for cooling a hot-rolled steel strip (1) made of carbon steel, according to claim 4, characterized in that the cooling device (3, 4, 5, 6, 7, 8, 9, 10) as a function of measurements of the temperature of the steel strip (1, 30, 40, 50) at at least two locations in the longitudinal direction of the steel strip (1, 30, 40, 50) is regulated such that the essential ^" γ-α transition in the steel strip (1, 30, 40, 50) takes place between the at least two locations in the longitudinal direction of the steel strip (1, 30, 40, 50), at which the temperature of the steel strip (1, 30, 40, 50) is measured.

6. A method for cooling a hot-rolled steel strip (1, 30, 40, 50), in particular a hot-rolled strip (30) made of CMn steel, according to claim 1, 2 or 3, characterized in that at least one measurement of the temperature of the steel strip (1 , 30, 40, 50) in the area of the cooling device (3, 4, 5, 6, 7, 8, 9, 10).

7. The method according to claim 6, characterized in that at least one measurement of the temperature of the steel strip (1, 30, 40, 50) in the region of the cooling device (3, 4, 5, 6, 7, 8, 9, 10) and that at least a further measurement of the temperature of the steel strip (1, 30, 40, 50) in the area of the cooling device (3, 4, 5, 6, 7, 8, 9, 10) or at a distance of 0 to 80 cm behind the Cooling device (3, 4, 5, 6, 7, 8, 9, 10) takes place.

8. The method according to claim 6 or 7, characterized in that from the measurement of the temperature of the steel strip (1, 30, 40, 50) in the region of the cooling device (3, 4, 5, 6, 7, 8, 9, 10) Ferrite grain size (d _α ) in the steel strip (1, 30, 40, 50) is determined.

9. The method according to claim 6, 7 or 8, characterized in that the ferrite grain size (d _α ) in the steel strip (1, 30, 40, 50) depending on the measurement of the temperature of the steel strip (1, 30, 40, 50) in the area of the cooling device (3, 4, 5, 6, 7, 8th,

9. 10) or advantageously as a function of the determined ferrite grain size (d _α ) by adjusting the cooling device (3, 4, 5, 6, 7, 8, 9, 10).

10. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the temperature is measured at at least two, advantageously at least three, locations in the transverse direction of the steel strip (50).

11. Device for cooling a hot-rolled steel strip (1, 30, 40, 50) running out of a roll stand (2), in particular according to a method according to one of the preceding claims, wherein a cooling device (3, 4, 5, 6, 7, 8 , 9, 10) for cooling the steel strip (1, 30, 40, 50) is provided, characterized in that the device for cooling the steel strip (1, 30, 40, 50) has at least two temperature measuring devices (20, 21, 33, 34 , 35, 41, 42, 51, 52, 53) for measuring the temperature of the steel strip (1, 30, 40, 50) at at least two locations in the longitudinal direction of the steel strip (1, 30, 40, 50).