GB2472196A

GB2472196A - Integral Ultrasound Flatness Gauge for Cooling Machine

Info

Publication number: GB2472196A
Application number: GB0913005A
Authority: GB
Inventors: Neil Stanley
Original assignee: Siemens VAI Metals Technologies Ltd
Current assignee: Primetals Asset Management UK Ltd
Priority date: 2009-07-27
Filing date: 2009-07-27
Publication date: 2011-02-02
Also published as: GB0913005D0

Abstract

A cooling machine for a rolled metal is described. Ultrasonic tranducers are mounted in an array above the metal and are arranged to monitor the distance to the metal surface as it passes thereunder. Water from the cooling jets serves as the transmitting medium and a substantially laminar column of water is created for each device in the array. The distance measurement form the basis of an assessment of flatness upon which adjustment of the cooling sprays is made to correct flatness defects.

Description

Integral Ultrasound Flatness Gauge for Cooling Machine The invention is concerned with the metal rolling process found in plate mills and, in particular with the monitoring and control of flatness around the cooling stage.

The inclusion of at least one accelerated cooling stage during processing of plate metal is well established. In modern plate mills, a cooling machine is typically employed comprising an array of spray nozzles arranged to direct a corresponding array of coolant jets to the metal surface.

The manifest flatness of plates entering a cooling machine has a direct and detrimental effect on the performance of the cooling machine. Furthermore, incorrectly applied cooling can result in a variety of flatness defects in the plate leaving the cooling machine. In addition, internal stresses within plates entering the cooling machine can cause flatness defects to occur during cooling even if the plates are flat at the entry to the cooling machine.

Measurement of plate flatness is normally carried out using a non-contact flatness gauge. Typically these devices utilise lasers to measure the height of the material, with reference to a known position, at several points across the plate width and along the full length of this plate. This information is then converted into a recognised measure of plate flatness. Flatness gauges can be located either at the exit of the mill, at the exit of the Hot Leveller, or further down the plate processing line. However the high cost of laser type flatness gauges means that very few plate mills have them installed.

According to the invention, apparatus for cooling a metal plate comprises the features set out in claim I attached hereto.

The ultrasound transmitters and receivers may conveniently be realised as a number of dual purpose devices (transceivers) each having the ability to transmit and receive ultrasound pulses.

A first set of transceivers may be employed to perform measurements upon which adjustment of a first set of nozzles may be based, before measurements are performed by a second set of transceivers. A second set of nozzles may be adjusted responsive to the measurements performed by the second set of transceivers before measurement is performed by a third set of transceivers.

The flow of coolant to a second metal plate may be adjusted responsive to the measurements performed on a first metal plate.

The controller may be arranged to present an indication of plate flatness based on the elapsed timse between transmission and reception of ultrasound pulses.

The invention will now be described with reference to figure 1 which illustrates a typical plate mill line layout incorporating a cooling machine and figure 2 which illustrates a cooling header incorporating an array of ultrasonic transceivers.

Referring to figure 1, during a typical plate rolling process according to the prior art, a plate I exits rollers 2 before passing through cooling machine 3 and on to hot leveller 4.

Cooling machine 3 typically comprises a number of cooling headers 5 upon which are mounted spray nozzles. The spray nozzles direct cooling fluid (e.g. water) in the form of laminar (or nearly laminar) columns, to the metal plate as it passes through the cooling machine. EP0178281 describes such a cooling apparatus.

Measurement of the plate flatness directly at the entrance 6 to the cooling machine allows the flatness quality of the incoming material to be measured. This information can be used to adjust upstream processes to correct the flatness defect and to identify the cause of poor cooling performance. It may also be used to adjust the settings of the cooling machine, for example the ratio of coolant flow above and below the plate or the flow distribution across the width of the plate.

A measurement of the plate flatness directly at the exit 7 of the cooling machine provides feedback information that can be utilised to adjust the cooling machine settings in order to reduce the flatness defects. This feedback can be applied manually or via a model based control system.

A measurement of plate flatness 8 within the cooling machine can also provide feedback information that can be utilised to adjust the cooling machine settings to reduce the flatness defects.

The information obtained from plate flatness measurements at the entrance and exit of the cooling machine and the flatness measurements from within the machine may be used to adjust the cooling settings for the current plate (i.e. if the leading end is found to be not flat, adjustments can be made affecting the rest of the plate) or for the following plate if it is similar (information from one plate forms the basis of adjustments for the next plate).

According to the invention, ultrasonic transmitter/receivers 9 are mounted in an array.

One array may be located at the entrance 6 of the machine and another array may be located at the exit 7 of the machine. The arrays are incorporated into the cooling headers 5. Water is used as the transmitting medium and a laminar column of water is created for each ultrasonic device in the array. Periodically, ultrasonic pulses are transmitted down the column and the time taken to receive the return pulse is measured. This time can be directly translated into a distance, which corresponds to the length of the water column. From this, the distance of the plate surface from the ultrasonic device can be calculated. This distance, and the distance taken from the other devices in the array, when combined with a plate speed signal, can be converted in to a measure of flatness by calculation algorithms which are similar to those employed for laser based flatness measuring devices and which are know to persons skilled in the art.

A controller (not shown) is arranged to receive data from the ultrasound transceivers and combine this with a knowledge of the transceiver loci to perfom a calculation of metal flatness. The controller is linked to, and arranged to control, the spray nozzles therby performing flatness adjustments responsive to the measured flatness.

As the cooling headers are located at the top and the bottom of the plate, ultrasonic arrays can be mounted to detect either the upper or lower surface distance, or both.

Varying widths of metal can be accommodated by utilising only the part of the ultrasonic arrays.

Another array of transmitters/receivers 8 may be incorporated within the cooling machine, between the entrance and exit. Use of multiple arrays allow one or more flatness measurements to be made, followed by adjustment and subsequent further measurement. A particular advantage of using ultrasound transceivers incorporated into the cooling headers within the cooling machine is that it would be extremely difficult to measure the flatness within the cooling machine by using lasers or similar methods.

For example, in the three array device, the flatness can be measured as the metal enters the cooling machine followed by adjustment of flow from some or all of the nozzles. A further measurement is made within the machine followed by further adjustment of some or all of the nozzles before a measurement is made as the metal exits the machine followed by further adjustment of some or all of the nozzles.

In many instances, a plate entering the cooling machine appears flat, but is subject to internal stresses which cause deformation on application of the coolant. The facility for measurement and adjustment within the cooling machine is particularly uesful in addressing this problem.

Alternatively, flatness measurements may be performed on one metal plate which form the basis of adjustments made to the cooling apparatus for the next plate to enter.

Claims

Claims 1. Apparatus for cooling a metal plate comprising: at least one cooling header and means for passing the metal plate below or above the cooling header; wherein each cooling header comprises one or more nozzles, each nozzle arranged to direct a column or curtain of cooling water on to the plate; a plurality of ultrasound transmitters located in the cooling header, each transmitter being arranged to transmit an ultrasonic pulse through cooling water towards the metal; a plurality of ultrasound receivers arranged to receive an ultrasonic pulse reflected through cooling water from the metal; characterized by a controller in data communication with the ultrasound transmitters, receivers and nozzles, the controller being arranged to vary the flow of water from at least one of the nozzles, thereby varying the distribution of cooling water responsive to data received from the transmitters and receivers.
2. Apparatus according to claim I where the ultrasound transmitters and ultrasound receivers are realised as a plurality of transceivers, each transceiver performing a transmit and receive function.
3. Apparatus according to claim 2, wherein the controller is arranged to vary the flow of water in a first set of nozzles responsive to data received from a first set of transceivers, and to receive data from a second set of transceivers.
4. Apparatus according to claim 3, where the controller is arranged to vary the flow of water in a second set of nozzles responsive to data received from the second set of transceivers and to received data from a third set of transceivers.
5. Apparatus according to claim I where the controller is arranged to vary the flow from the nozzles impinging on a second metal plate responsive to data acquired from the transceivers during cooling of a first metal plate.
6. Apparatus according to any preceding claim, where the controller is arranged to present an indication of flatness of the plate based on the time elapsed between transmission and reception of ultrasound pulses.
7. A method cooling a metal plate comprising: passing the plate through a plurality of columns or curtains of flowing water; transmitting ultrasonic pulses from transmitters, through the water to the plate; receiving ultrasonic pulses reflected from the plate through the water to receivers measuring the time elapsed between transmission and reception of pulses and varying the flow of water through at least some of the nozzles, thereby varying the distribution of cooling water, responsive to time elapsed between transmission and reception of pulses.
8. A method according to claim 7, further comprising varying the flow of water in a first set of nozzles responsive to time elapsed between transmission and reception of a first set of pulses and measuring the time elapsed between transmission and reception of a second set of pulses.
9. A method according to claim 8, further comprising varying the flow of water in a second set of nozzles responsive to time elapsed between transmission and reception of a second set of pulses and measuring the time elapsed between transmission and reception of a third set of pulses.
10. A method according to claim 7, comprising varying the flow from the nozzles impinging on a second metal plate responsive to time elapsed between transmission and reception of pulses during cooling of a first metal plate.
11. A method according to any of claims 7 -10, further comprising displaying an indication of metal flatness derived from time elapsed between transmitting and receiving pulses.