Continuous metal casting mold, temperature measurement system, and system and method for breakout detection in a continuous metal casting facility

Abstract

This metal continuous casting mold (12), of the type consisting of an assembly of metal plates (22) behind which is provided a cooling device configured to cool the metal plates by circulating a cooling fluid, also comprises: at least one optical fiber (28) extending into the wall of at least one of the metal plates (22), the optical fiber (28) comprising a plurality of Bragg filters; at least one groove (24) formed in the wall of at least one of the metal plates (22) over at least a part of its length in a direction not parallel to the casting axis of the mold, the groove (24) through which the optical fiber (28) extends; and a strip (26) having a shape substantially complementary to the groove (24) and closing the groove over its entire length, the groove (24) and the strip (26) having a shape suitable for the passage of the optical fiber (28).

Description

[Technical field]

[0001] The present invention relates to a continuous metal casting plant. More particularly, the present invention relates to a continuous metal casting mold. According to another aspect, the present invention relates to a temperature measurement system in a continuous metal casting plant and a system and method for breakout detection in a continuous metal casting plant. [Background technology]

[0002] Continuous metal casting plants, such as steel casting plants, typically have a mold into which the molten metal is poured to solidify into a desired shape, such as a bottomless mold, where the metal is cooled to form a slab. To cool the molten metal, the walls of the mold are flanked or backed by a cooling system, such as a liquid cooler. The mold and cooling system are designed to match the flow rate of the metal so that when the slab leaves the mold, its outer surface is solidified to a thickness sufficient to contain the metal still molten in the center of the slab.

[0003] When the molten metal is poured into the mold, it is desirable to know the temperature measurements at various points on the mold wall in real time. For example, metal can stick to the mold wall, which is undesirable and can significantly affect the production of the equipment. In particular, this can lead to the well-known phenomenon of breakouts. Metal sticking to the wall can lead to an insufficient zone on the outer surface of the slab when it leaves the mold, as the metal does not solidify properly. This can result in a break in the zone and the still molten metal in the center of the slab can flow out of the slab. This not only reduces the yield, but the molten metal can damage the equipment due to its extremely high temperature, and can also be dangerous for the equipment operators. It is therefore necessary to detect such breakouts as early as possible so that various preventive measures can be taken, including slowing down the extraction speed of the slab, temporarily stopping the equipment, and any other corrective measures.

[0004] Current technology knows how to detect metal build-up on the mold walls, which is a sign of an impending breakout. It is based on measuring the mold wall temperature at various points. In fact, it is known that the walls show a specific temperature profile when metal is built up on them. One of the known means of measuring that temperature is to place thermocouples regularly on the mold walls, allowing to detect temperature anomalies as early as possible.

[0005] Although this detection method is interesting, it has some problems. Indeed, if one wanted to measure the wall temperature at as many positions as possible, it would require the installation of a huge number of thermocouples, which would not only increase the cost of manufacturing the mold, but also complicate the electrical connections of the thermocouples. Also, thermocouples do not always measure the wall temperature accurately and reliably, and the number of false alarms from thermocouples, i.e. warning signals that a breakout is about to occur when in fact it is not, can be unacceptable.

[0006] Another problem is related to the construction of the mould, which usually consists of an assembly of metal plates behind which is placed a cooling device arranged so that the metal plates can be cooled by the circulation of a cooling fluid, through which it is necessary to pass in order to reach the zone of the mould where the temperature needs to be measured, thus crossing the circulating water, which gives rise to other problems of sealing and wiring.

[0007] In Belgian patent application no. 2018 / 5193 it has already been proposed to solve the problem by providing at least one wall of the mould with a passage in which an optical fibre equipped with a number of Bragg filters is inserted. This solution is remarkable and gives a suitable answer to the problems mentioned above. However, the inventors have decided to develop an alternative method which could be carried out more quickly and cheaply and which may be adapted to the complex geometry of the mould. Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to remedy the above-mentioned drawbacks and improve the detection of breakouts. [Means for solving the problem]

[0009] The present invention provides a continuous metal casting mold of the type consisting of an assembly of metal plates behind which is provided a cooling device arranged to cool the metal plates by the circulation of a cooling fluid, - at least one optical fiber extending into a wall of at least one of said metal plates, said optical fiber comprising a plurality of Bragg filters; at least one groove formed in the wall of at least one of said metal plates, in a direction not parallel to the casting axis of the mold, over at least a portion of its length, in which an optical fiber extends; a strip having a shape substantially complementary to the groove and filling the groove over its entire length, the groove and the strip having a shape suitable for passing an optical fiber therethrough; A mold comprising:

[0010] To avoid confusion, the terms relating to the dimensions of the plates are defined as follows: the length and width of the plate are the dimensions in a cross section perpendicular to the casting axis of the mold, and the depth of the plate is the dimension along the axis of the mold.

[0011] Thus, the thermocouples of the prior art are replaced by optical fibers equipped with Bragg filters. The Bragg filters are able to measure the temperature in the walls at each filter level by emitting a light beam into the fiber and detecting at least one of the reflected and transmitted beams. It is understood that the grooves, optical fibers and strips are much more space-saving and much easier to install than thermocouples. Moreover, the temperature measurements by the Bragg filters are more accurate than those obtained by thermocouples, thereby reducing the number of false alarms.

[0012] Advantageously, the strip consists of several parts.

[0013] It is therefore possible to adapt the length of the strip by choosing the number of parts which it is made up of, and thus to match the dimensions of the mould.

[0014] Advantageously, the strip includes an insert which is entirely formed before filling the groove.

[0015] The strip is thus entirely formed before being placed in the mould, i.e. it is not formed in situ when filling the grooves, which facilitates its placement in the mould by simply placing the strip in the groove or by sliding it along the groove from one end of the groove. Advantageously, the grooves have a substantially uniform depth.

[0016] Therefore, the heat transfer between the plate and the optical fiber is also uniform.

[0017] Advantageously, the mould is made of copper or a copper alloy and the strip is also made of the same material.

[0018] These materials have high thermal conductivity, thereby contributing to uniform heat transfer.

[0019] The strip is preferably welded to the mold to fill the groove, such as by electron beam welding, although other welding techniques are possible, such as laser welding, x-ray welding, ion beam welding, any type of arc welding, including shielded arc welding, non-consumable electrode arc welding, consumable electrode arc welding, submerged arc welding, electrogas welding, diffusion welding, as well as brazing and soft brazing.

[0020] This allows the groove to be filled in a hermetically sealed manner.

[0021] Advantageously, the groove is located in at least one central portion of at least one of the plates.

[0022] Thereby, it is possible to measure the temperature in the central zone of the wall and thus obtain a measurement which is particularly representative of the wall temperature.

[0023] According to one embodiment, the groove extends over the entire length of at least one of the plates.

[0024] This allows the temperature of the poured metal to be measured at multiple locations, improving reliability of breakout detection.

[0025] Advantageously, the optical fiber is provided with a coating or tube.

[0026] They protect the optical fiber from mechanical stresses that could damage it, and the coating or tube also allows the diameter of the optical fiber to be adjusted.

[0027] Advantageously, the optical fiber has a diameter greater than 1.6 mm.

[0028] Advantageously, the mould comprises a plurality of optical fibres housed in a plurality of grooves which are generally parallel to one another.

[0029] Increasing the number of temperature measurement points on the wall will further improve the reliability of breakout detection.

[0030] Advantageously, if the mould is of the type for casting thin slabs and has a funnel-shaped section at the top, the groove is located at least over the entire funnel-shaped section. In fact, the solution proposed in Belgian patent application No. 2018 / 5193, in which the optical fibres are provided in passages drilled approximately parallel to the wall, is extremely difficult to implement in uneven sections of the wall.

[0031] It is easily understood that this embodiment is adaptable to any type of mold with complex shapes.

[0032] Advantageously, the wall comprises a groove in the funnel-shaped central portion and a passage perforated in the flat portion, the passage opening into the groove.

[0033] The present invention also provides a temperature measurement system for a metal continuous casting system, comprising: a template as defined above, - a transmitter / receiver arranged to transmit light into an optical fiber and receive at least one of the reflected light and the transmitted light received at the transmitter / receiver; - a processor arranged to convert data relating to at least one of the reflected light and the transmitted light received by the transmitting / receiving device into information relating to the temperature at various points of the mould; - A terminal with a user interface connected to the processor; The present invention further provides a system comprising:

[0034] The present invention also provides a breakout detection system for a metal continuous casting system comprising a temperature measurement system as defined above, the system being arranged such that a processor converts data relating to at least one of the reflected light and the transmitted light received by the transmitting / receiving device into information relating to breakout detection.

[0035] Finally, the invention provides a method for detecting a breakout in a continuous metal casting plant, characterized in that it comprises measuring the temperature of the wall of the mould as defined above.

[0036] In the following, embodiments of the invention will be described, given as non-limiting examples, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0037] [Figure 1] 1 is a general view of a continuous metal casting installation including a mold according to the present invention; [Figure 2a] 2 is a diagram showing the operation of the facility 5 in FIG. 1. [Figure 2b] 2 is a diagram showing the operation of the facility 5 in FIG. 1. [Diagram 3] FIG. 2 is a cross-sectional view of the mold of the installation of FIG. 1. [Figure 4] FIG. 4 is a perspective view of the mold of FIG. [Diagram 5] FIG. 4 is a perspective view of a plate of the mold of FIG. 3. [Figure 5a] FIG. 1 shows various shapes of mould grooves and strips. [Figure 5b] FIG. 1 shows various shapes of mould grooves and strips. [Figure 5c] FIG. 1 shows various shapes of mould grooves and strips. [Figure 5d] FIG. 1 shows various shapes of mould grooves and strips. [Figure 6] 6 is a longitudinal cross-sectional view of an optical fiber included in the plate of FIG. 5. [Figure 7] 7A to 7C are diagrams illustrating the operation of the optical fiber in FIG. 6. [Figure 8a] FIG. 4 is a cross-sectional view of the mold of FIG. 3 illustrating the development of breakouts. [Figure 8b] FIG. 4 is a cross-sectional view of the mold of FIG. 3 illustrating the development of breakouts. [Figure 8c] FIG. 4 is a cross-sectional view of the mold of FIG. 3 illustrating the development of breakouts. [Figure 8d]FIG. 4 is a cross-sectional view of the mold of FIG. 3 illustrating the development of breakouts. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Figure 1 shows a continuous metal casting plant 2. The plant is of conventional design and most of its components will only be briefly introduced.

[0039] The plant 2 comprises ladles 4 containing the molten metal to be cooled. There are two ladles 4 here, both supported by a mechanical arm 6. This mechanical arm 6 is notably capable of transferring the ladles 4, which have been brought full to the pouring zone by a transfer system (such as an overhead crane, not shown) from a charging zone, such as a furnace or converter (not shown), in which the molten metal can be poured into the ladles 4 before they are brought to the position shown in Figure 1. The mechanical arm 6 is also capable of bringing the emptied ladles 4 to a position where they can be taken up again by the transfer system, from where they are transported to a preparation zone to be reconditioned and then returned to the charging zone.

[0040] The installation 2 comprises a tundish or distribution vessel 8 situated below a ladle 4. The ladle 4 has an openable bottom through which molten metal can be poured into the tundish 8.

[0041] The tundish 8 is provided with a sprue that can be closed with a stopper 10 that can control the flow of the molten metal. The sprue of the tundish leads to a submerged casting nozzle (SEN) 11 that can protect the molten metal being poured into the mold 12.

[0042] As can be seen best in Figure 2a and enlarged view in Figure 2b, the submerged casting nozzle 11 opens into the top opening of a mould 12. This is a bottomless mould with a vertical casting axis. The mould 12 will be described in more detail below.

[0043] The installation 2 comprises a cooling device 14 arranged on the outer surface of the mould 12. This is a liquid cooling device. To this end, the cooling device comprises pipes through which a cooling fluid, such as water, flows. The cooling fluid absorbs heat from the molten metal in the mould 12, thereby cooling it and solidifying it. In this case, the metal solidifies to form a slab with a solidified outer surface 18 encasing a liquid core 20.

[0044] The installation 2 comprises a roller guide 16 downstream of the mould 12. The guide 16 is capable of guiding the slab, whose outer surface 18 has solidified, out of the mould 12. As can be seen in Figure 2a, the slab solidifies gradually as it moves through the guide 16. That is, as it moves away from the mould 12, the volume of the solidified outer surface 18 of the slab increases and the volume of the liquid core 20 of the slab decreases.

[0045] The mold 12 is shown in more detail in Figure 3, which shows four plates 22 (the fourth is not visible due to the orientation of the cross-sectional view). The plates 22 are made of copper or a copper alloy, a material that has a high thermal conductivity and therefore facilitates heat exchange between the cooling device 14 and the mold 12. The plates 22 are arranged so that the mold 12 has an overall rectangular or square cross-section. However, the plates can be arranged so that the mold has other cross-sectional shapes.

[0046] Another angle of the mold 12 is shown in Figure 4. At least the upper part of the mold 12 is shaped as a funnel 23 that partially receives the flattened lower end of the submerged casting nozzle 11. This shape is particularly suitable when the mold is intended for casting thin slabs.

[0047] One of the plates 22 of the mold 12 is shown in Figure 5. The plate has grooves 24 that extend in a direction not parallel to the casting axis. In this figure, the grooves extend in a substantially horizontal direction over the entire length of the plate. However, the grooves 24 may extend only over a portion of the length of the plate 22, for example only over a central portion in the case of a mold for thin slab casting. The grooves 24 have a substantially uniform depth over their entire length.

[0048] The various shapes that the groove 24 can take are shown in Figures 5a to 5d. The groove 24 is filled over its entire length by a strip 26 of approximately complementary shape to the groove. The strip 26 is preferably made of the same material as the plate 22, i.e. copper or a copper alloy. The strip 26 comprises an insert which is entirely formed before filling the groove 24. The strip 26 is therefore entirely formed before being placed in the mould 12. In other words, the strip 26 is not formed in situ when filling the groove 24.

[0049] The groove 24 and the strip 26 have a shape suitable for passing an optical fiber having the function described below. In this particular case, as can be seen in Figures 5a to 5d, the groove 24 or the strip 26 (or both) have a small groove 27 for accommodating the optical fiber. After the optical fiber is placed in the groove, the strip 26 is welded, for example by electron beam welding, so as to fill the groove 24 over its entire length.

[0050] In an alternative embodiment, the strip 26 is made up of several parts welded together before filling the groove 24 with the strip 26. In this way, it is possible to adjust the length of the strip 26 and, in particular, the length of the groove 24 by choosing the number of parts that make up the strip 26.

[0051] In the embodiment of FIG. 5 a , the groove 24 and the strip 26 have a rounded contour, and it is the strip 26 that has the small groove 27 .

[0052] In the embodiment of FIG. 5 b , the groove 24 and the strips 26 have rounded contours and it is the groove 24 that has the grooves 27 .

[0053] In the embodiment of FIG. 5 c , the grooves 24 and the strips 26 have a straight contour and it is the grooves 24 that have the small grooves 27 .

[0054] In the embodiment of FIG. 5d, the groove 24 and the strip 26 have a tapered or frustoconical cross section, and it is the groove 24 that has the small grooves 27. In particular, the cross section of the groove 24 is such that the groove widens as it deepens. The shape of the groove 24 therefore makes it possible to hold the strip 26 in place once it has been placed in the groove 24, for example by sliding it along the groove 24 from either end. This avoids the need to weld the strip 26 to the mould 12, which is economically advantageous. To make it easier to insert the strip 26 into the groove 24, the plate can be very slightly curved, for example at the groove level, around an axis parallel to the groove 24, which is located on the opposite side of the plate 22. The groove 24 then takes on an open shape, and the strip 26 can be slid into it without difficulty. Preferably, this curvature is performed without exceeding the elastic deformation limits of the copper plate.

[0055] 6 and 7, an optical fiber 28 is placed within the groove 24. The optical fiber 28 includes a cladding 30 and a core 32 surrounded by the cladding 30. The optical fiber 28 includes a plurality of Bragg filters 34 within the core 32. The optical fiber 28 includes at least 10 Bragg filters per meter, preferably at least 20 Bragg filters per meter, more preferably at least 30 Bragg filters per meter, and even more preferably at least 40 Bragg filters per meter.

[0056] When placed within groove 24, optical fiber 28 may be bare, may have a protective coating, or may be inserted into a tube prior to installation. The coating or tube may serve to increase the radius of optical fiber 28, thereby making up all or nearly all of the diameter of groove 24. Preferably, the optical fiber has a diameter greater than 1.6 mm, taking into account that sometimes coatings or tubes as mentioned above may be present.

[0057] The operation of the optical fiber 28 is shown in Figure 7. The Bragg filter 34 is a filter capable of reflecting light in a wavelength band centered on a given value, called the reflection wavelength, which can be adjusted by the filter manufacturer. This given value is also a function, among other things, of the temperature at which the filter is placed, and the relationship can be written for each filter as follows: λ 反射 =f(λ0,T) Here, λ 反射 is the wavelength effectively reflected by the filter, f is a known function, T is the temperature of the filter, and λ 0 is the wavelength reflected by the filter at a given temperature, e.g., ambient temperature.

[0058] These two properties make it possible to use the optical fiber 28 as a temperature sensor. First, a Bragg filter 34 is arranged in the optical fiber 28, each having a different reflected wavelength value λ0, chosen, for example, 5 nanometers apart. Then, a light beam of polychromatic spectrum 35a, for example white light, is sent into the optical fiber 28 and the wavelength peaks appearing in the spectrum 35b of the reflected beam are determined. For each peak, the measured value λ 反射 and the theoretical reflected wavelength λ0 at ambient temperature, and the temperature T of the filter is calculated by the function f. Alternatively, if the configuration of the groove 24 (passage 24) in which the optical fiber 28 is placed allows, these steps can be performed based on the spectral valley of the transmitted beam 35c.

[0059] Thus, by placing an optical fiber 28 on one of the plates 22 of the mold 12, it is possible to measure the temperature at a given location on that plate and follow its changes over time. To obtain a sufficient number of measurement locations, it is preferable to place at least one optical fiber 28 in two opposing plates 22, and preferably in each of the four plates 22 of the mold 12.

[0060] It is also preferable to provide two optical fibers 28 for each plate 22 so that the temperature of the mold 12 can be measured at two different heights. For example, two optical fibers 28 can be provided on each plate so that they are parallel to each other and spaced 15 to 25 centimeters apart.

[0061] Breakout detection is performed as follows.

[0062] The propagation of the zone 36 where the metal in the mould 12 adheres to the mould plate 22 is shown in figures 8a to 8d. The graphs in the lower right corner of the figures respectively show the time course of the temperature measured by the Bragg filter 34 of the upper optical fibre 28a (upper curve) and the time course of the temperature measured by the Bragg filter 34 of the lower optical fibre (28b).

[0063] As can be seen from the graphs of Figures 8a and 8b, the upper optical fiber 28a detects an anomalous increase in temperature in zone 36 corresponding to metal deposits on the mold 12. This is the first indication that a breakout is imminent.

[0064] Subsequently, as can be seen from the graphs of Figures 8c and 8d, the lower optical fiber 28b detects the abnormal increase in temperature that was previously detected by the upper optical fiber 28a, which is a second sign that a breakout is imminent and confirms that a breakout is likely unavoidable.

[0065] In order to allow information detected by the optical fibers 28a and 28b to be notified to users of the facility 2, the facility - a transmitter / receiver arranged to transmit light into an optical fiber and receive at least one of reflected light and transmitted light by the optical fiber; - a processor arranged to convert data relating to at least one of the reflected light and the transmitted light received by the transmitting / receiving device into information relating to the temperature at various points of the mould; - a terminal having a user interface connected to a processor; Equipped with.

[0066] The processor is also arranged to convert data relating to at least one of the reflected light and the transmitted light received at the transceiver device into information relating to breakout detection.

[0067] These elements (not shown for clarity) allow the temperature measurement by the optical fiber 28 to be converted into a breakout detection or non-detection information that is understandable to the user of the equipment 2. In other words, the mold 12 equipped with the optical fiber 28, the transmitter / receiver, the processor and the terminal form a breakout detection system. In the event of a breakout detection, the user can take measures to limit or even prevent damage caused by the breakout.

[0068] The invention is not limited to the described embodiment, and other embodiments will be apparent to those skilled in the art.

[0069] In particular, the mould could be designed to have a more conventional, straight, funnel-free shape.

[0070] The mold could be designed to accommodate a number of optical fibers housed in a number of grooves that are generally parallel to one another. [Explanation of symbols]

[0071] 2. Equipment (metal continuous casting equipment) 4 Ladle 6 Mechanical Arm 8 Tundish 10 Stopper 11 Casting nozzle 12 Mold 14 Cooling device 16 Guide 18 Solidified outer surface 20 Liquid core 22 Plate 23 Funnel 24 groove 26 Strip 27 Small ditch 28 Optical Fiber 30 Clad 32 cores 34 Bragg Filter 35a Multicolor Spectrum 35b Spectrum of reflected beam 36 Zone

Claims

1. 1. A metal continuous casting mould (12) of the type consisting of an assembly of a metal plate (22) behind which is provided a cooling device (14) adapted to allow cooling of said metal plate (22) by the circulation of a cooling fluid, Each metal plate (22) has a wall adapted to contact the molten metal in the metal continuous casting mold (12); at least one optical fiber (28) extending into said wall of at least one of said metal plates (22), said optical fiber (28) comprising a number of Bragg filters (34); at least one groove (24) made in said wall of at least one of said metal plates (22) in a substantially horizontal direction over the entire length of said at least one plate, said groove (24) in which said optical fiber (28) extends; a strip (26) having a shape substantially complementary to said groove (24) and filling said groove over its entire length, said groove (24) and said strip (26) having a shape suitable for passing said optical fiber.

2. The mold of claim 1, wherein the strip (26) is made of multiple pieces.

3. 3. The mold of claim 1 or 2, wherein the strip (26) includes an insert that is entirely formed prior to filling the groove (24).

4. The mold of any one of claims 1 to 3, wherein the grooves (24) have a substantially uniform depth.

5. The mold according to any one of the preceding claims, wherein the mold is made of copper or a copper alloy, and the strip (26) is also made of the same material.

6. The mold of any one of claims 1 to 5, wherein the strip (26) is welded to the mold to fill the groove (24).

7. The mold of any one of claims 1 to 6, wherein the optical fiber (28) is provided with a coating or tube.

8. The mold of any one of claims 1 to 7, wherein the optical fiber (28) has a diameter greater than 1.6 mm.

9. The mold of any one of claims 1 to 8, comprising a plurality of optical fibers (28) housed in a plurality of generally parallel grooves (24).

10. 10. The mold (12) according to any one of claims 1 to 9, which is of the type for casting thin slabs and has a funnel-shaped portion (23) at its upper part, said grooves (24) being located at least over the entirety of said funnel-shaped portion (23).

11. 1. A temperature measurement system in a metal continuous casting system, comprising: - a mould (12) according to any one of claims 1 to 10, a transmitter / receiver arranged to transmit light into said optical fibre (28) and to receive at least one of the reflected and transmitted light received by said transmitter / receiver as information relating to the temperature of the various points of said mould (12); a processor arranged to convert data received by said device relating to at least one of said reflected and transmitted light into information relating to the temperatures at various points of said mould; a terminal with a user interface connected to said processor; A system comprising:

12. 12. A breakout detection system for a metal continuous casting system comprising the temperature measurement system of claim 11, wherein the processor is arranged to convert data relating to at least one of the reflected light and the transmitted light received by the transceiver into information relating to breakout detection.

13. A method for detecting a breakout in a continuous metal casting plant, characterized in that it comprises measuring the temperature of the wall of the mould according to any one of the preceding claims.

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