GB2061492A - Method and Apparatus for Detecting Level of Molten Metal in Steel Manufacturing - Google Patents
Method and Apparatus for Detecting Level of Molten Metal in Steel Manufacturing Download PDFInfo
- Publication number
- GB2061492A GB2061492A GB8032006A GB8032006A GB2061492A GB 2061492 A GB2061492 A GB 2061492A GB 8032006 A GB8032006 A GB 8032006A GB 8032006 A GB8032006 A GB 8032006A GB 2061492 A GB2061492 A GB 2061492A
- Authority
- GB
- United Kingdom
- Prior art keywords
- molten metal
- free surface
- mould
- signal
- level
- Prior art date
- Legal status (The legal status 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 status listed.)
- Granted
Links
- 239000002184 metal Substances 0.000 title claims description 72
- 238000000034 method Methods 0.000 title claims description 23
- 229910000831 Steel Inorganic materials 0.000 title abstract description 7
- 239000010959 steel Substances 0.000 title abstract description 7
- 238000004519 manufacturing process Methods 0.000 title description 4
- 230000008569 process Effects 0.000 claims description 5
- 230000003287 optical effect Effects 0.000 claims description 3
- 238000009749 continuous casting Methods 0.000 abstract description 5
- 238000005070 sampling Methods 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 239000000314 lubricant Substances 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 2
- 239000000941 radioactive substance Substances 0.000 description 2
- 239000000779 smoke Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 1
- 238000010291 electrical method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002285 radioactive effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D9/00—Level control, e.g. controlling quantity of material stored in vessel
- G05D9/12—Level control, e.g. controlling quantity of material stored in vessel characterised by the use of electric means
-
- 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
- B22D11/18—Controlling or regulating processes or operations for pouring
- B22D11/181—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level
- B22D11/185—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level by using optical means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/284—Electromagnetic waves
- G01F23/292—Light, e.g. infrared or ultraviolet
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/284—Electromagnetic waves
- G01F23/292—Light, e.g. infrared or ultraviolet
- G01F23/2921—Light, e.g. infrared or ultraviolet for discrete levels
- G01F23/2928—Light, e.g. infrared or ultraviolet for discrete levels using light reflected on the material surface
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- Automation & Control Theory (AREA)
- Mechanical Engineering (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
- Continuous Casting (AREA)
Abstract
In continuous casting, the level of molten steel 2 in mould 4 is detected by taking images of the free surface 5 with video camera 6, scanning lines substantially in parallel with the free surface. The video camera produces signals corresponding to images of the free surface and to those of background. The signals are converted into binary signals wherein the molten steel is represented by one level and the background by the other. The binary signals representing the molten steel are summed to obtain a total area of the molten steel. A predetermined area corresponding to the gravitational flow into the mould is subtracted from the total area to obtain the area of the free surface proportional to the level of the free surface. <IMAGE>
Description
SPECIFICATION
Method and Apparatus for Detecting Level of
Molten Metal in Steel Manufacturing
The present invention relates to a method and apparatus for detecting the level of molten metal in steel manufacturing.
In conventional mould level control system for continuous casting process, the level of molten metal in a mould has been detected by means of radioactive substance such as 60 Co or 137 Cs which radiates a y-ray. However, such a use of radioactive substance is very inconvenient because it requires careful handlings so the operators may not be exposed to radioactive rays.
As an alternative method, use may be made of temperature sensitive elements such as thermocouples or thermisters. However, the method is of a low or poor sensitivity because the temperature sensitive elements cannot be embedded in the mould with sufficiently small spacings. Further there is a problem of life of the elements.
It is therefore an object of the present invention to provide a method and apparatus for detecting the level of molten metal through an optoelectrical technique.
Another object of the present invention is to provide a method and apparatus which can detect the level of molten metal in a mould in a metal manufacturing process without accompanying any danger or any problem of accuracy of detection.
A further object of the present invention is to provide an opto-electrical method and apparatus which can accurately detect the level of molten metal in a mould without being disturbed by flames at the surface of the molten metal and reflections of such flames and molten metal at the mould walls.
According to the present invention, the above and other objects can be accomplished, in a process wherein molten metal is poured into a mould as a gravitational flow of the molten metal to form a free surface of the molten metal in the mould, by a method for detecting level of the free surface of the molten metal in the mould, the method comprising steps of taking images of the free surface of the molten metal in the mould by video camera means which is located with scanning lines substantially in parallel with the free surface of the molten metal, said video camera means producing analogous signals corresponding to the images of the free surface of the molten metal and to those of background, converting the analogous signals into binary signals wherein the molten metal is represented by one of the two signal levels and the background by the other, summing the binary signals representing the molten metal to obtain total area of the molten metal, and subtracting from the total area of the molten metal a predetermined area which corresponds to the gravitational flow to thereby obtain area of the free surface of the molten metal which is proportional to the level of the free surface.
In an alternative method of the present invention, the free surface of the molten metal is discriminated from the gravitational flow from duration of the corresponding signal in each scan so that the area of the free surface of the molten metal can directly be calculated.
Thus, according to the present invention, there is provided a non-contact method for detecting the level of the molten metal without using any dangerous medium. The accuracy of detection can be determined as desired by the number of scans and it is possible to obtain a quick response. Since the method is based on an area calculating principle, the result of detection is not seriously affected by noises.
According to further feature of the present invention, there is provided an apparatus for carrying out the aforementioned method. If it is desirable, the apparatus may include filter means which passes light rays from the molten metal so that other noise-producing rays are blocked.
The above and other objects and features of the present invention will become apparent from the following descriptions of preferred embodiments taking reference to the accompanying drawings, in which:
Figure 1 is a diagrammatical sectional view of a continuous casting system having a level detecting apparatus in accordance with one embodiment of the present invention;
Figure 2(a) is a fragmentary sectional view particularly showing the arrangement of the video taking camera;
Figure 2(b) shows a horizontal section of the mould of the continuous casting system;
Figure 3 is an example of the pattern of the image taken by the camera;
Figure 4 is a block diagram of the electrical processing circuit employed in the level detecting apparatus;
Figure 5 is a diagram showing signals in various parts in the circuit shown in Figure 4;;
Figure 6 is a block diagram similar to Figure 4 but showing another embodiment;
Figure 7 is a diagram showing signals in various parts in the circuit shown in Figure 6;
Figures 8 through 10 show examples of images taken by apparatus without filtering means; and,
Figure 11 shows an example of image taken by an apparatus having filtering means.
Referring now to the drawings, particularly to
Figure 1 , there is shown a continuous casting system including a tundish 1 which is arranged beneath a ladle 8 so that it is supplied with molten metal 2 from the ladle 8. Beneath the tundish 1 , there is disposed a mould 4 and the tundish 1 has an outlet nozzle 1 c for continuously pouring the molten metal into the mould 4. The molten metal is cooled in the mould 4 and gradually solidified to form a continuous strand 9 having an outer shell which is continuously drawn from the mould 4 through a secondary cooling device (not shown) by means of paired pinch rolls 10. One of the pinch rolls 10 is connected through a gear mechanism with a motor M to be driven thereby. In Figure 1, the reference 3 designates gravitational flows of molten metal.
In the mould 4, the molten metal 2 forms a free surface 5 of which level is appropriately maintained by controlling the drawing speed of the strand 9 which is determined by the speed of the pinch rolls 10. In order to detect the level of the free surface 5 of the molten metal 2 in the mould 4, there is provided a video camera 6 which is arranged so as to take an image of the free surface 5 of the molten metal. The camera 6 produces an image signal S, corresponding to the image of the free surface 5 of the molten metal 2, the signal being applied to a signal processing circuit A which produces a level signal S2 and is connected with a level detecting circuit
B. The circuit B is connected with a control circuit
C which controls the motor M through a thyrister device D.A monitoring TV may be provided for visual observation of the free surface 5 of the molten metal 2.
Referring now to Figure 2, it will be noted that the camera 6 hasan optical axis 7 which makes an angle 6 with the inner wall surface 4a of the mould 4. The camera 6 is so arranged that its scanning lines are substantially in parallel with an edge 5a of the free surface 5. Since the molten metal 2 is of a high contrast with respect to backgrounds such as the inner wall 4a of the mould 4, it is possible to determine an appropriate threshold value so as to convert the image signal S1 into a binary signal. For the purpose, a signal converting circuit E is provided between the camera 6 and the processing circuit
A. Figure 3 shows an image on the monitoring TV 11 as produced by the binary signal.
The processing circuit A functions to calculate the area S from which the level lx of the molten metal is obtained. More specifically, referring to
Figure 3, the area S can be represented by the formula S=LA'lx+(Nik) L, (1) where: L8 is the width of the gravatational flow 3,
LA the width of the free surface 5 lx the level of the free surface, and N the height of the display frame.Thus, the level lx can be represented by the formula lx=(S=La N)/(LALa) (2)
The values LA and L1 may be determined in advance in accordance with the image taking conditions from the value lx, the actual level lx' may be calculated as desired.
Referring now to Figure 4, there is shown details of the processing circuit A and the signal converting circuit E. It will be noted in Figure 4 that the circuit E includes a comparator 11 which is connected with the signal output of the camera 6 to receive an analogous signal S, therefrom. The comparator 11 is further connected with a threshold device 12 for receiving a threshold level signal t, therefrom. The comparator 11 produces a level "ONE" signal when the signal S, is greater than the signal t, and a level "ZERO" signal when the signal Ss is smaller than the signal t,. The binary signal thus produced is designated as the reference t2 and applied to the circuit A.
The circuit A includes a control signal generator 1 8 which is connected with the camera 6 for receiving a horizontal sweep signal S,2 and a vertical sweep signal S,3 to produce control signals C1, C2, C3 and C4. The circuit A further includes a sampling circuit 1 3 which is connected with the comparator 11 to receive the signal t2 and with the control signal generator 1 8 to receive the control signal C1 which represents the duration of a single scan. The sampling circuit 13 functions to convert the binary signal t2 into a series of pulse signals t3 when the control signal
C, is applied thereto.It will therefore be understood that the number of the pulse signals t3 is proportional to the duration of the signal t2 which represents the width of the image of the molten metal.
The sampling circuit 1 3 is connected with a counter 14 to apply the pulse signals t3 thereto.
The counter 14 is also connected with the control signal generator 1 8 to receive the control signals
C2 and C3. The control signal C2 serves to clear the count in the counter 14 so that a new counting is started. The control signal C3 represents the time of scanning the whole video frame. The counter 14 functions to count the number of the pulse signals t3 when the control signal Ca is applied thereto. It will be understood that the counted number of the pulse signal t3 corresponds to the area of the molten metal. The counter 14 is connected with a register circuit 15 to apply its output t4 thereto. The register circuit 1 5 is also connected with the control signal generator 18 to receive the control signal C4 which represent the end of the scan of the whole video frame.When the control signal C4 is applied to the register circuit 15, it receives the output t4 from the counter 14 and the count is maintained until a new count is received.
The register circuit 1 5 produces an output signal t5 which is an area signal and applied to an operating circuit 1 6. The circuit 16 performs a calculation in accordance with the equation (2) and produces a free surface level signal t6 which is applied to a second operating circuit 1 7. The circuit 1 7 performs a calculation in accordance with the following equation, lx'=.lx X/sinS where X is the ratio of the actual dimension to the dimension of the image taken by the camera.
The circuit 1 7 thus produces the signal S2. Of course, the second operating circuit 17 may be omitted and the output of the operating circuit 1 6 may be used as the signal S2.
In the foregoing descriptions, the area of the free surface 5 has been digitally calculated, however, it should be noted that the calculation may be performed analogously.
Referring now to Figures 6 and 7, there is shown another embodiment of the processing circuit A. As in the previous embodiment, a binary signal t2 is produced in the signal converting circuit E. The processing circuit A includes a control signal generator 30 which is connected to the camera 6 to receive a horizontal sweep signal S,2 and a vertical sweep signal S13 for producing control signals C1, C2, C3, C4 and C5. The processing circuit A further includes a sampling circuit 23 which is connected with the circuit E to receive the signal t2 and with the control signal generator 30 to receive the control signal C, corresponding to the duration of each horizontal scan.The sampling circuit 23 functions as the sampling circuit 13 in the previous embodiment to produce a series of output pulses t3 which are applied to a counter 24. The counter 24 functions to count the number of pulses in each series to calculate the width of the molten metal and produces an output t4. The control signal C2 is applied to the counter 24 to clear a previous count before a new counting is started. The output t4 of the counter 24 is applied to a comparator 25 which is connected with a reference circuit 26 to receive a reference signal t5 therefrom and with a control signal generator 30 to receive the control signal C3 which represents the end of each horizontal scan.The comparator 25 functions to compare the signal t4 with the reference signal t5 and produce "ONE" signal when the signal t4 is not smaller than the signal t5 and "ZERO" signal when the signal t4 is smaller than the signal t5.
The output of the comparator 25 is designated as the reference to and applied to a summing circuit 27 which is also applied with the control signal C4 to clear a previous count before a new count is started. The circuit 27 functions to sum the "ONE" signal to until the whole scanning of the video frame is completed and produces an area signal,.
The summing circuit 27 is connected with a register circuit 28 to apply the signal t, thereto.
The circuit 28 is also applied with the control signal C5 which represents the end of the scan of the whole video frame so that the area signal t, is taken into the circuit 28 when the scan is completed. The area signal stored in the register circuit 28 is applied in the form of a signal ta to an operating circuit 29 which performs a calculation to obtain a surface level signal S2 from the area signal. This embodiment is advantageous over the previous embodiment because it is possible to eliminate any possibility of error due to possible fluctuations of the gravitational flow portions of the molten metal.
In the aforementioned methods, it may be possible that light rays from combustion flames and smoke of lubricant as well as the reflections at the mould walls may be taken by the camera to cause a measuring error. It has however been found that these noise producing light rays have wave lengths which are substantially different from those light rays from the surface of molten metal. In fact, the noise producing light rays are mostly in infrared region and long wave length region of spectrum, whereas the light rays from the molten metal surface are generally in the infraviolet region and have wave lengths between 3000 and 70000 A.It will therefore be understood that by passing the signal S, from the camera 6 through a filter circuit F which passes only those signals corresponding to the light rays of short wave length as shown in Figure 1, it is possible to eliminate the aforementioned noise.
Figures 8 through 10 show examples of image patterns taken by the system having no filtering circuit F. It will be noted in Figure 8 that, due to the combustion flames of lubricant, the image of the molten metal surface is significantly disturbed. In Figure 9, the image of the molten metal surface is broken off due to the combustion smoke of lubricant. In Figure 10, a ghost image is produced due to the reflection at the mould wall.
By the contrary, it will be noted in Figure 11 that a clear image is produced without any noise. The filter circuit F may be substituted by a diffraction grating, an optical filter or any other suitable means.
The invention has thus been shown and described with reference to specific embodiments, however, it will be noted that the invention is in no way limited to the details of the illustrated arrangements but changes and modifications may be made without departing from the scope of the appended claims.
Claims (7)
1. In a process wherein molten metal is poured into a mould as a gravitational flow of the molten metal to form a free surface of the molten metal in the mould, a method for detecting level of the free surface of the molten metal in the mould, the mould comprising steps of taking images of the free surface of the molten metal in the mould by video camera means which is located with scanning lines substantially in parallel with the free surface of the molten metal, said video camera means producing analogous signal corresponding to the images of the moltem metal and to those of backgroud, converting the analogous signals into binary signals wherein the molten metal is represented by one of two signal levels and the background by the other, summing the binary signals representing the molten metal to obtain total area of the moltem metal, and subtracting from the total area of the molten metal a predetermined area which corresponds to the gravitional flow to thereby obtain area of the free surface of the molten metal which is proportional to the level of the free surface.
2. In a process wherein molten metal is poured into a mould as a gravitational flow of the molten metal to form a free surface of the molten metal in the mould a method for detecting level of the free surface of the molten metal in the mould, the method comprising steps of taking images of the free surface of the molten metal in the mould by video camera means which is located with scanning lines substantially in parallel with the free surface of the molten metal, said video camera means producing analogous signal corresponding to the images of the free surface of the molten metal and to those of background, converting the analogous signals into binary signals wherein the molten metal is represented by one of two signal levels and the background by the other comparing durations of the binary signals representing the molten metal with a reference value, summing the binary signals of which durations are larger than the reference to thereby obtain area of the free surface of the molten metal which is proportional to the level of the free surface.
3. Apparatus for detecting level of free surface of molten metal in a mould, said apparatus comprising video camera means arranged with scanning lines substantially in parallel with the free surface of the molten metal for taking images of the free surface, means for converting analogous signals from the camera means into binary signals wherein the molten metal is represented by one of two signal levels and background by the other, processing means for obtaining area of the free surface of the molten metal from the binary signal, wave length selecting means for passing to the processing means only those signals corresponding to light rays of wave lengths which are substantially the same as those of light rays radiated from the molten metal.
4. Apparatus in accordance with claim 3 in which said wavelength selecting means is a diffraction grating disposed between the camera means and the processing means.
5. Apparatus in accordance with claim 3 in which said wave length selecting means is optical filter means provided in the camera means.
6. A process as claimed in claim 1 or claim 2 substantially as hereinbefore described.
7. An apparatus as claimed in claim 3 substantially as hereinbefore described with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1979139932U JPS5658522U (en) | 1979-10-09 | 1979-10-09 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2061492A true GB2061492A (en) | 1981-05-13 |
| GB2061492B GB2061492B (en) | 1983-11-02 |
Family
ID=15257019
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8032006A Expired GB2061492B (en) | 1979-10-09 | 1980-10-03 | Method and apparatus for detecting level of molten metal in steel manufacturing |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5658522U (en) |
| DE (1) | DE3038183C2 (en) |
| ES (1) | ES495737A0 (en) |
| GB (1) | GB2061492B (en) |
| IT (1) | IT1150967B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2015035A1 (en) * | 2006-05-01 | 2009-01-14 | Olympus Corporation | Liquid level detecting apparatus |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3145301A1 (en) * | 1981-11-14 | 1983-05-19 | ESB Schweißbetrieb Burbach & Bender oHG, 5900 Siegen | Method and apparatus for determining the quantity of molten metal in a treatment or transfer vessel |
| US4597048A (en) * | 1983-09-07 | 1986-06-24 | United States Steel Corporation | Digital flow regulation of liquid-level control for a continuous casting mold |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1458181B2 (en) * | 1964-12-11 | 1974-01-17 | Pierre Lyon Poncet (Frankreich) | Arrangement for the automatic adjustment of the bath level of a metal melt in a continuous casting mold |
| JPS51126302A (en) * | 1975-04-26 | 1976-11-04 | Sanyu Gijutsu Kenkyusho:Kk | A method of controlling melt levels of iron etc. and an apparatus for it |
-
1979
- 1979-10-09 JP JP1979139932U patent/JPS5658522U/ja active Pending
-
1980
- 1980-10-03 GB GB8032006A patent/GB2061492B/en not_active Expired
- 1980-10-08 ES ES80495737A patent/ES495737A0/en active Granted
- 1980-10-09 DE DE3038183A patent/DE3038183C2/en not_active Expired
- 1980-10-09 IT IT8025245A patent/IT1150967B/en active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2015035A1 (en) * | 2006-05-01 | 2009-01-14 | Olympus Corporation | Liquid level detecting apparatus |
| EP2015035A4 (en) * | 2006-05-01 | 2010-04-07 | Olympus Corp | Liquid level detecting apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| ES8107401A1 (en) | 1981-10-01 |
| DE3038183A1 (en) | 1981-04-30 |
| GB2061492B (en) | 1983-11-02 |
| ES495737A0 (en) | 1981-10-01 |
| JPS5658522U (en) | 1981-05-20 |
| DE3038183C2 (en) | 1984-04-26 |
| IT1150967B (en) | 1986-12-17 |
| IT8025245A0 (en) | 1980-10-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |