WO1991017009A1 - The inspection of continuously cast metals - Google Patents

The inspection of continuously cast metals Download PDF

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Publication number
WO1991017009A1
WO1991017009A1 PCT/AU1991/000180 AU9100180W WO9117009A1 WO 1991017009 A1 WO1991017009 A1 WO 1991017009A1 AU 9100180 W AU9100180 W AU 9100180W WO 9117009 A1 WO9117009 A1 WO 9117009A1
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WO
WIPO (PCT)
Prior art keywords
strand
acoustic wave
system defined
line monitoring
continuous casting
Prior art date
Application number
PCT/AU1991/000180
Other languages
French (fr)
Inventor
Lazar Strezov
Mark Downey
Joe Herbertson
John Burgess
Original Assignee
The Broken Hill Proprietary Company Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Broken Hill Proprietary Company Limited filed Critical The Broken Hill Proprietary Company Limited
Publication of WO1991017009A1 publication Critical patent/WO1991017009A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
    • G01N29/0654—Imaging
    • G01N29/0672—Imaging by acoustic tomography
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0423—Surface waves, e.g. Rayleigh waves, Love waves

Definitions

  • the present invention relates to a system and a method for the inspection of continuously cast metals, such as steel.
  • An object of the invention is to provide a system and a method for on-line monitoring of a continuous casting process.
  • Another object of the invention is to provide a control system for a continuous casting process.
  • a system for on-line monitoring of a continuous casting process comprising: (a) a laser source for providing a pulsed beam incident on the surface of a strand drawn from a continuous caster, said pulsed beam causing generation of an acoustic wave in or on the surface of the strand;
  • system further comprises an optical fibre means to guide the pulsed beam.
  • the laser source comprises a scanning means to provide a number of acoustic wave source positions around the periphery of the strand.
  • the laser source comprises a plurality of individual laser beam sources spaced around the periphery of the strand.
  • the detector means comprises an interferometer.
  • the interferometer comprises:
  • (b) means to direct the reference beam at the surface of the strand such that the reference beam is modulated by the acoustic wave
  • (d) means to determine a measurand from said detected modulated reference beam.
  • system further comprises an optical fibre means to guide the detection beam to the surface of the strand.
  • the interferometer comprises a scanning detector means to detect the acoustic wave around the periphery of the strand.
  • the interferometer comprises a plurality of individual detectors spaced around the periphery of the strand.
  • the acoustic wave generated by the laser source is of an ultrasonic frequency.
  • the processing means comprises one or more of a tomographic imaging means, a spectral matching means, and a surface defect detection means.
  • a method of on-line monitoring of a continuous casting process comprising:
  • control system for a continuous casting process comprising, the on-line monitoring system described above, and a control means for modifying the continuous casting process in response to the on-line monitoring system.
  • Fig. 1 shows in block diagram form the main components of a preferred embodiment of the on-line monitoring and control systems of the invention in relation to a strand drawn from a continuous caster;
  • Fig. 2 shows a first configuration of a pulsed laser source and an interferometer of the on-line monitoring and control systems of the invention in relation to the strand;
  • Fig. 3 shows a second configuration of a pulsed laser source and an interferometer in relation to the strand
  • Fig. 4 shows a preferred embodiment of an interferometer for the on-line monitoring and control systems of the invention.
  • the invention is particularly applicable to continuous casting of steel and is described hereinafter in relation to this application, although it is noted the invention is not limited to this application and could be used in connection with continuous casting of any metal or alloy.
  • Fig. 1 illustrates a section of a conventional continuous caster for steel in which a strand 20 is drawn from a water cooled mould 11 through an unbending section 12 and onto roller tables (not specifically shown).
  • the strand 20 comprises a liquid core enclosed in a thin shell formed in the water cooled mould 11, and progressively the liquid core solidifies towards the center until a solid bloom is formed.
  • the bloom is then cut, typically by a torch cutter, for subsequent processing.
  • Fig. 1 also illustrates, in block diagram form, the components of the preferred embodiment of the on-line monitoring and control systems of the invention which are arranged to obtain information concerning the state of the strand 20 at a number of positions 13a to 13e along the length of the strand 20. It is noted that the selection of the location and number of the positions will depend in any given situation on the particular requirements of the on-line monitoring and control systems.
  • Fig. 1 shows schematically that at each position 13a to 13e acoustic waves of ultrasonic frequency (hereinafter referred to as "ultrasonic waves”) are generated by means of pulsed laser beams that are directed to impinge on one or more points, collectively identified by the numeral 14, on the surface of the strand 20 and, after propagating through or along the surface and in either case interacting with the strand 20, the ultrasonic waves are detected at one or more points, collectively identified by the numeral 16, on the surface of the strand 20.
  • ultrasonic waves ultrasonic frequency
  • the ultrasonic waves are generated as a consequence of the pulsed laser beams causing localised heating and/or vaporization which creates mechanical stresses and induces the ultrasonic waves.
  • the ultrasonic waves propagate through and/or along the surface of the strand 20 by compression and shear mechanisms.
  • the factors that affect the nature and propagation of the ultrasonic waves include the spot size of the pulsed laser beams on the surface of the strand 20, and the energy density and intensity of the pulsed laser beams.
  • An ultrasonic wave which interacts with a material such as steel exhibits changes in velocity, spectral content and signal strength due to changes in the material. Consequently, ultrasonic waves enable the detection of the state of the material, such as regions of porosity and changes in homogeneity in the material.
  • the pulsed laser beams are generated by a pulsed laser source 22 which may be of any suitable type.
  • the ultrasonic waves are detected at the points 16 by means of an interferometer 24, and the interferometer 24 produces electrical signals that are representative of the ultrasonic waves.
  • the electrical signals are transferred from the interferometer 24 to a signal analysis and tomographic imaging system 26 for analysis to determine the physical state of the strand 20 at each position 13a to 13e and to represent the physical state by means of a tomographic image.
  • the tomographic image at each position 13a to 13e can be used for visual inspection and manual control of the continuous casting process or it can be coupled with an on-line integrated control system 28 to provide the necessary control over the continuous casting process.
  • the control is by way of process variables such as mould water flow, secondary cooling, casting speed, EMS power, roller pressure and casting power consumption.
  • Fig. 2 shows a first ultrasonic wave generation and detection configuration in relation to a partially solidified strand 20 travelling in the direction shown. This particular configuration is most suited to a determination of the solid/liquid interface, temperature profiles, the presence of internal defects, the columnar/equiaxed ratio, and the final solidification point.
  • the pulsed laser source 22 generates a pulsed laser beam that is directed onto a plurality of points 14 (only one of which is shown in the figure) around the circumference of the surface of the strand 20 at each of the positions 13a to 13e
  • the interferometer 24 is arranged to detect ultrasonic waves generated by the pulsed laser beam that propagate through the strand 20 at a plurality of points 16 (only one of which is shown in the figure) around the circumference of the surface of the strand 20 at each of the positions 13a to 13e.
  • the pulsed laser source 22 need not be located immediately adjacent the strand 20, and it could be located at a distance of some metres from the surface of the strand 20 and still provide sufficient power incident upon the surface at the required point. This configuration then has the advantage of not requiring expensive and complicated cooling systems. This is in contrast to prior art devices which require close coupling between the source and the surface of the strand 20. It is also noted that, as with the pulsed laser source 24, the interferometer 24 need not be located close to the surface of the strand 20.
  • Fig. 3 shows a second ultrasonic wave generation and detection configuration which is most suited to the determination of surface defects or cracks in the strand 20. In this configuration the pulsed beam from the pulsed laser source 22 generates ultrasonic waves which propagate along the surface of the strand 20 and these are detected by the interferometer 24 and processed as described above to provide information concerning the state of the strand 20.
  • Fig. 4 shows a preferred embodiment of the interferometer 24.
  • a laser 34 provides a continuous reference output beam 3 ] _ of a frequency f Q .
  • the beam B- ⁇ is directed against the surface of the strand 20 and is modulated by the ultrasonic waves that arrive at the surface of the strand 20.
  • the frequency of modulation is given as f g .
  • the modulated beam is reflected and/or scattered a beam B 2 from the strand 20 and is detected by a photodetector in the interferometer 24.
  • the photodetector such as a photodiode, produces an electric signal which has a frequency proportional to the modulation frequency f s .
  • the electric signal is amplified and unwanted low frequency components resulting from accidental vibration, noise and mechanical instability are filtered out be the interferometer.
  • the electric signal is then sent to the tomographic processing apparatus 26.
  • an additional light source such as a laser, is used in conjunction with the interferometer 24 to illuminate the surface of the strand 20 and thereby enhance the performance of the interferometer 24.
  • an integral part of the on-line monitoring and control systems of the invention is a collection of signal processing methods enabling the determination of the physical state of the strand 20.
  • the preferred embodiment of the present invention described above in relation to Fig. 1 includes the use of tomographic imaging and this is one of the signal processing methods.
  • the signal processing methods also include:
  • Tomographic imaging is a mathematical process which can be used to form a two-dimensional representation of the internal physical state of the strand 20 having a degree of resolution in both dimensions of the order of the sample spacing. If the measurand is the time taken for the ultrasonic wave to travel through the strand 20, then a tomograph of velocity can be generated. On the other hand, if the relative amplitude of the received ultrasonic wave with respect to that generated on the strand 20 is determined, then a tomograph of attenuation can be generated. Knowing the relation between attenuation and temperature and/or velocity and temperature a two dimensional temperature profile may be displayed. Spectral analysis of received waveforms also provides information for tomographically determining solidified strand structural information such as columnar/equiaxed ratio.
  • Spectral matching can be used to determine columnar/equiaxed ratio, segregation and porosity in the strand 20 not requiring tomographic imaging. By comparing the spectral content of received waveforms with known characteristics, strand structure can be determined.
  • Surface defect detection is conducted by analysing surface waves propagating on the surface of the strand 20. By measuring amplitude, spectral content and velocity of surface waves, surface defects can be characterized and located.
  • the invention provides an integrated system for on-line monitoring and control of continuous casting and enables improved process optimization and continuous caster design.
  • the invention enables less reliance on post-mortem and accumulated impircal data and a better understanding of the solidification process in the continuously cast strand.

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  • General Health & Medical Sciences (AREA)
  • Biochemistry (AREA)
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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

A system for on-line monitoring of a continuous casting process to provide information about a continuously cast strand as a real-time event. The system comprises, a laser source for providing a pulsed laser beam incident on the surface of the strand to generate an acoustic wave in or on the surface of the strand, a detector for detecting the acoustic wave after the acoustic wave interacts with the strand, and for generating a signal representative of the state of the strand, and a processing means for analysing the signal generated by the detector.

Description

THE INSPECTION OF CONTINUOUSLY CAST METALS
The present invention relates to a system and a method for the inspection of continuously cast metals, such as steel.
Current continuous casting technology for steel involves pouring liquid steel into a water cooled mould and continuously drawing a strand from the mould. Solidification of the liquid steel starts in the mould and continues after the strand leaves the mould. In order to improve the continuous casting process it is necessary to have better control of the casting conditions. However, establishing a successful process control is only possible if a knowledge and understanding of the dynamic changes of the strand is available. An on-line monitoring system of the changes in the strand is necessary in order to have the knowledge as a real-time event.
In order to implement an on-line monitoring system in a continuous casting environment, which will provide real-time data about the changes and quality of the strand, the following criteria must be met:
(a) operational reliability;
(b) flexibility for positioning and movement along the caster;
(c) simple and effective signal analysis and display; and
(d) possibility for automation of the continuous casting process.
An object of the invention is to provide a system and a method for on-line monitoring of a continuous casting process.
Another object of the invention is to provide a control system for a continuous casting process.
According to the invention there is provided a system for on-line monitoring of a continuous casting process comprising: (a) a laser source for providing a pulsed beam incident on the surface of a strand drawn from a continuous caster, said pulsed beam causing generation of an acoustic wave in or on the surface of the strand;
(b) means for detecting the acoustic wave on the surface of the strand following interaction with the strand and for generating signals representative of the detected acoustic wave; and
(c) a processing means for analysing the signals generated by the detector means and for producing therefrom information which is representative of the physical state of the strand.
It is preferred that the system further comprises an optical fibre means to guide the pulsed beam.
In one preferred arrangement, the laser source comprises a scanning means to provide a number of acoustic wave source positions around the periphery of the strand.
In an alternative arrangement, the laser source comprises a plurality of individual laser beam sources spaced around the periphery of the strand.
It is preferred that the detector means comprises an interferometer.
It is preferred particularly that the interferometer comprises:
(a) means for generating a reference laser beam;
(b) means to direct the reference beam at the surface of the strand such that the reference beam is modulated by the acoustic wave;
(c) means to detect the modulated reference beam;
(d) means to determine a measurand from said detected modulated reference beam.
It is preferred that the system further comprises an optical fibre means to guide the detection beam to the surface of the strand.
In one preferred arrangement, the interferometer comprises a scanning detector means to detect the acoustic wave around the periphery of the strand.
In an alternative arrangement, the interferometer comprises a plurality of individual detectors spaced around the periphery of the strand.
It is preferred that the acoustic wave generated by the laser source is of an ultrasonic frequency.
It is preferred that the processing means comprises one or more of a tomographic imaging means, a spectral matching means, and a surface defect detection means. According to the present invention there is also provided a method of on-line monitoring of a continuous casting process comprising:
(a) directing a pulsed laser beam onto the surface of a steel strand drawn from a continuous caster to generate an acoustic wave which interacts with the strand;
(b) detecting the acoustic wave on the surface of the strand after the acoustic wave has interacted with the strand;
(c) generating signals representative of the detected acoustic wave; and
(d) analysing the signals and producing therefrom information representative of the physical state of the strand.
According to the present invention there is also provided a control system for a continuous casting process comprising, the on-line monitoring system described above, and a control means for modifying the continuous casting process in response to the on-line monitoring system.
The present invention is described further with reference to the accompanying drawings, in which:
Fig. 1 shows in block diagram form the main components of a preferred embodiment of the on-line monitoring and control systems of the invention in relation to a strand drawn from a continuous caster;
Fig. 2 shows a first configuration of a pulsed laser source and an interferometer of the on-line monitoring and control systems of the invention in relation to the strand;
Fig. 3 shows a second configuration of a pulsed laser source and an interferometer in relation to the strand; and
Fig. 4 shows a preferred embodiment of an interferometer for the on-line monitoring and control systems of the invention.
The invention is particularly applicable to continuous casting of steel and is described hereinafter in relation to this application, although it is noted the invention is not limited to this application and could be used in connection with continuous casting of any metal or alloy.
Fig. 1 illustrates a section of a conventional continuous caster for steel in which a strand 20 is drawn from a water cooled mould 11 through an unbending section 12 and onto roller tables (not specifically shown). Initially, the strand 20 comprises a liquid core enclosed in a thin shell formed in the water cooled mould 11, and progressively the liquid core solidifies towards the center until a solid bloom is formed. The bloom is then cut, typically by a torch cutter, for subsequent processing.
Fig. 1 also illustrates, in block diagram form, the components of the preferred embodiment of the on-line monitoring and control systems of the invention which are arranged to obtain information concerning the state of the strand 20 at a number of positions 13a to 13e along the length of the strand 20. It is noted that the selection of the location and number of the positions will depend in any given situation on the particular requirements of the on-line monitoring and control systems.
Fig. 1 shows schematically that at each position 13a to 13e acoustic waves of ultrasonic frequency (hereinafter referred to as "ultrasonic waves") are generated by means of pulsed laser beams that are directed to impinge on one or more points, collectively identified by the numeral 14, on the surface of the strand 20 and, after propagating through or along the surface and in either case interacting with the strand 20, the ultrasonic waves are detected at one or more points, collectively identified by the numeral 16, on the surface of the strand 20.
The actual configuration of the points of ultrasonic wave generation and detection on the surface of the strand 20 in any given situation will depend on the particular requirements of the on-line monitoring and control systems. Two examples of preferred configurations are described hereinafter with reference to Figures 2 and 3.
The ultrasonic waves are generated as a consequence of the pulsed laser beams causing localised heating and/or vaporization which creates mechanical stresses and induces the ultrasonic waves. The ultrasonic waves propagate through and/or along the surface of the strand 20 by compression and shear mechanisms. The factors that affect the nature and propagation of the ultrasonic waves include the spot size of the pulsed laser beams on the surface of the strand 20, and the energy density and intensity of the pulsed laser beams. An ultrasonic wave which interacts with a material such as steel exhibits changes in velocity, spectral content and signal strength due to changes in the material. Consequently, ultrasonic waves enable the detection of the state of the material, such as regions of porosity and changes in homogeneity in the material.
The pulsed laser beams are generated by a pulsed laser source 22 which may be of any suitable type.
The ultrasonic waves are detected at the points 16 by means of an interferometer 24, and the interferometer 24 produces electrical signals that are representative of the ultrasonic waves.
The electrical signals are transferred from the interferometer 24 to a signal analysis and tomographic imaging system 26 for analysis to determine the physical state of the strand 20 at each position 13a to 13e and to represent the physical state by means of a tomographic image.
The tomographic image at each position 13a to 13e can be used for visual inspection and manual control of the continuous casting process or it can be coupled with an on-line integrated control system 28 to provide the necessary control over the continuous casting process. Typically, the control is by way of process variables such as mould water flow, secondary cooling, casting speed, EMS power, roller pressure and casting power consumption.
Fig. 2 shows a first ultrasonic wave generation and detection configuration in relation to a partially solidified strand 20 travelling in the direction shown. This particular configuration is most suited to a determination of the solid/liquid interface, temperature profiles, the presence of internal defects, the columnar/equiaxed ratio, and the final solidification point.
With reference to Fig. 2, the pulsed laser source 22 generates a pulsed laser beam that is directed onto a plurality of points 14 (only one of which is shown in the figure) around the circumference of the surface of the strand 20 at each of the positions 13a to 13e, and the interferometer 24 is arranged to detect ultrasonic waves generated by the pulsed laser beam that propagate through the strand 20 at a plurality of points 16 (only one of which is shown in the figure) around the circumference of the surface of the strand 20 at each of the positions 13a to 13e. By appropriate selection of the position and number of the ultrasonic wave generation and detection points 14, 16 around the circumference of the strand 20 it is possible to generate a two-dimensional tomographic representation of the strand 20 at each position 13a to 13e.
It is noted that the pulsed laser source 22 need not be located immediately adjacent the strand 20, and it could be located at a distance of some metres from the surface of the strand 20 and still provide sufficient power incident upon the surface at the required point. This configuration then has the advantage of not requiring expensive and complicated cooling systems. This is in contrast to prior art devices which require close coupling between the source and the surface of the strand 20. It is also noted that, as with the pulsed laser source 24, the interferometer 24 need not be located close to the surface of the strand 20. Fig. 3 shows a second ultrasonic wave generation and detection configuration which is most suited to the determination of surface defects or cracks in the strand 20. In this configuration the pulsed beam from the pulsed laser source 22 generates ultrasonic waves which propagate along the surface of the strand 20 and these are detected by the interferometer 24 and processed as described above to provide information concerning the state of the strand 20.
Fig. 4 shows a preferred embodiment of the interferometer 24. A laser 34 provides a continuous reference output beam 3]_ of a frequency fQ. The beam B-^ is directed against the surface of the strand 20 and is modulated by the ultrasonic waves that arrive at the surface of the strand 20. The frequency of modulation is given as fg. The modulated beam is reflected and/or scattered a beam B2 from the strand 20 and is detected by a photodetector in the interferometer 24. The photodetector, such as a photodiode, produces an electric signal which has a frequency proportional to the modulation frequency fs. The electric signal is amplified and unwanted low frequency components resulting from accidental vibration, noise and mechanical instability are filtered out be the interferometer. The electric signal is then sent to the tomographic processing apparatus 26.
It is noted that an additional light source, such as a laser, is used in conjunction with the interferometer 24 to illuminate the surface of the strand 20 and thereby enhance the performance of the interferometer 24.
It is noted that an integral part of the on-line monitoring and control systems of the invention is a collection of signal processing methods enabling the determination of the physical state of the strand 20. The preferred embodiment of the present invention described above in relation to Fig. 1 includes the use of tomographic imaging and this is one of the signal processing methods. The signal processing methods also include:
(a) spectral matching; and
(b) surface defect detection.
Tomographic imaging is a mathematical process which can be used to form a two-dimensional representation of the internal physical state of the strand 20 having a degree of resolution in both dimensions of the order of the sample spacing. If the measurand is the time taken for the ultrasonic wave to travel through the strand 20, then a tomograph of velocity can be generated. On the other hand, if the relative amplitude of the received ultrasonic wave with respect to that generated on the strand 20 is determined, then a tomograph of attenuation can be generated. Knowing the relation between attenuation and temperature and/or velocity and temperature a two dimensional temperature profile may be displayed. Spectral analysis of received waveforms also provides information for tomographically determining solidified strand structural information such as columnar/equiaxed ratio.
Spectral matching can be used to determine columnar/equiaxed ratio, segregation and porosity in the strand 20 not requiring tomographic imaging. By comparing the spectral content of received waveforms with known characteristics, strand structure can be determined.
Surface defect detection is conducted by analysing surface waves propagating on the surface of the strand 20. By measuring amplitude, spectral content and velocity of surface waves, surface defects can be characterized and located.
The invention provides an integrated system for on-line monitoring and control of continuous casting and enables improved process optimization and continuous caster design. In addition, the invention enables less reliance on post-mortem and accumulated impircal data and a better understanding of the solidification process in the continuously cast strand.
It will be obvious to persons skilled in the art that numerous alterations and modifications can be made to the preferred embodiments of the invention described above without departing from the basic concepts of the invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:
1. A system for on-line monitoring of a continuous casting process comprising:
(a) a laser source for providing a pulsed beam incident on the surface of a strand drawn from a continuous caster, said pulsed beam causing generation of an acoustic wave in or on the surface of the strand;
(b) means for detecting the acoustic wave on the surface of the strand following interaction with the strand and for generating signals representative of the detected acoustic wave; and
(c) a processing means for analysing the signals generated by the detector means and for producing therefrom information which is representative of the physical state of the strand.
2. The system defined in claim 1, wherein the laser source comprises a scanning means to provide a number of acoustic wave source positions around the periphery of the strand.
3. The system defined in claim 1, wherein the laser source comprises a plurality of individual laser beam sources spaced around the periphery of the strand.
4. The system defined in any one of the preceding claims, wherein the detector means comprises an interferometer.
5. The system defined in claim 4, wherein the interferometer comprises:
(a) means for generating a reference laser beam;
(b) means to direct the reference beam at the surface of the strand such that the reference beam is modulated by the acoustic wave;
(c) means to detect the modulated reference beam;
(d) means to determine a measurand from said detected modulated reference beam.
6. The system defined in claim 5, wherein the interferometer comprises a scanning detector means to detect the acoustic wave around the periphery of the strand.
7. The system defined in claim 5, wherein the interferometer comprises a plurality of individual detectors spaced around the periphery of the strand.
8. The system defined in any one of the preceding claims, wherein the acoustic wave generated by the laser source is of an ultrasonic frequency.
9. The system defined in any one of the preceding claims, wherein the processing means comprises one or more of a tomographic imaging means, a spectral matching means, and a surface defect detection means.
10. A method of on-line monitoring of a continuous casting process comprising:
(a) directing a pulsed laser beam onto the surface of a steel strand drawn from a continuous caster to generate an acoustic wave which interacts with the strand;
(b) detecting the acoustic wave on the surface of the strand after the acoustic wave has interacted with the strand;
(c) generating signals representative of the detected acoustic wave; and
(d) analysing the signals and producing therefrom information representative of the physical state of the strand.
11. A control system for a continuous casting process comprising, the on-line monitoring system defined in any one of claims 1 to 9, and a control means for modifying the continuous casting process in response to the on-line monitoring system.
PCT/AU1991/000180 1990-05-01 1991-05-01 The inspection of continuously cast metals WO1991017009A1 (en)

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Cited By (6)

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WO1993024830A1 (en) * 1992-06-03 1993-12-09 Lucas Industries Public Limited Company Ultrasonic evaluation of a sample
US5884685A (en) * 1995-03-29 1999-03-23 Nippon Steel Corporation Quality prediction and quality control of continuous-cast steel
WO2002099412A1 (en) * 2001-06-04 2002-12-12 Aea Technology Plc Optical ultrasonic measurement
WO2011054903A1 (en) * 2009-11-06 2011-05-12 Sms Siemag Ag Method for regulating the temperature profile and the speed of a cast strand in a continuous casting system, and continuous casting system for carrying out the method
DE102013223083A1 (en) 2013-11-13 2015-05-13 Sms Siemag Ag Method and device for contactless checking of the condition of a metallurgical cast product
WO2022172260A1 (en) * 2021-02-15 2022-08-18 SteeLEMAT S.à r.l Agile undt device comprising a dual emat/laser-pulse matrix array for scanning metallurgical objects

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FR2292539A1 (en) * 1974-11-27 1976-06-25 Poncet Pierre Continuous casting bath level control - dependent on the thermal radiation emitted from the nozzle and slag layer
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DE102009052172A1 (en) 2009-11-06 2011-05-19 Sms Siemag Ag Method for controlling the temperature profile and the speed of a casting strand in a continuous casting plant and continuous casting plant for carrying out the process
DE102009052172B4 (en) 2009-11-06 2024-08-01 Sms Group Gmbh Method for controlling the temperature profile and the speed of a cast strand in a continuous casting plant and continuous casting plant for carrying out the method
DE102013223083A1 (en) 2013-11-13 2015-05-13 Sms Siemag Ag Method and device for contactless checking of the condition of a metallurgical cast product
WO2015071018A1 (en) 2013-11-13 2015-05-21 Sms Siemag Ag Method and device for contactless testing of the quality of a metallurgical casting product
RU2665342C1 (en) * 2013-11-13 2018-08-29 Смс Груп Гмбх Metallurgical cast product condition non-contact inspection method and device
WO2022172260A1 (en) * 2021-02-15 2022-08-18 SteeLEMAT S.à r.l Agile undt device comprising a dual emat/laser-pulse matrix array for scanning metallurgical objects
FR3119892A1 (en) * 2021-02-15 2022-08-19 SteeLEMAT S.à r.l Agile UNDT dual-array EMATs/Laser-Pulse device for scanning metallurgical objects

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