BE1026975B1 - Continuous metal casting ingot mold, temperature measuring system and breakthrough detection system and method in a continuous metal casting plant - Google Patents

Abstract

This ingot mold (12) for continuous metal casting, of the type constituted by an assembly of metal plates (22) backed by cooling devices configured to allow the cooling of the metal plates by the circulation of a cooling fluid, comprises: - at least one optical fiber (28), comprising a plurality of Bragg filters, extending in a wall of at least one of said plates (22), - at least one groove (24) formed in a wall of at least one of said plates (22), in a direction not parallel to the casting axis of the mold in at least a portion of the length, the optical fiber (28) extending into the groove (24), and - a tongue (26) of substantially complementary shape to the groove (24) closing the groove over its entire length, the groove (24) and the tongue (26) having a shape adapted to the passage of the optical fiber (28).

Description

The invention relates to a continuous metal casting system and a system and method for detecting a breakthrough in a continuous metal casting plant. More particularly, the invention relates to an ingot mold for continuously casting metals. According to other of its aspects, the invention relates to a system for measuring the temperature in a continuous metal casting plant as well as a system and a method for detecting a breakthrough in a continuous metal casting plant.

A plant for the continuous casting of metals, for example a plant for the continuous casting of steel, generally comprises an ingot mold into which a liquid metal is poured with a view to its solidification in a suitable form. It may for example be a bottomless ingot mold, in which case the metal cools to form a slab. In order to cool the liquid metal, the walls of the ingot mold are contiguous or backed up by cooling devices, for example of the liquid type. The ingot mold and the cooling devices are sized according to the flow speed of the metal so that the slab, when it leaves the mold, has a solidified external surface of sufficient thickness to trap the still liquid metal. located at the heart of the slab.

When the liquid metal is flowing into the mold, it would be desirable to be able to have real-time temperature measurements at various points on the walls of the mold. For example, it may happen that the metal adheres to the walls of the mold, which is undesirable and can have considerable consequences on the production of the installation. This generates in particular the well-known breakthrough phenomenon. The adhesion of the metal to the wall creates a zone in the slab in which the solidification of the metal does not take place properly, so that the slab leaves the mold with an external surface of insufficient thickness in this zone. As a result, it tears apart and allows the still liquid metal in the core of the slab to flow out of it. Beyond the loss of efficiency, the liquid metal, therefore at very high temperature, can damage the installation or even constitute a danger for the operators of the installation. It is therefore necessary to detect these breakthroughs as soon as possible in order to be able to take preventive measures, for example slowing down the slab extraction speed, temporarily shutting down the installation or any other corrective measure.

-2- BE2019 / 5408 A method is known in the prior art for detecting whether the metal adheres to the walls of the ingot mold, a sign of an imminent breakthrough. It is based on measuring the temperature of the walls of the mold at various points. Indeed, it has been noticed that the walls have a particular temperature profile when the metal adheres to them. A known means of measuring this temperature consists in installing thermocouples regularly distributed on the walls of the mold so as to be able to detect any temperature anomaly as soon as possible.

This detection method is interesting but poses certain problems. In order to be able to measure the temperature of the walls in a maximum number of positions, it is necessary to install a large number of thermocouples. This not only increases the manufacturing cost of the mold but also makes the electrical connection of the thermocouples complex. Furthermore, thermocouples do not always make it possible to perform an accurate and reliable measurement of the temperature of the walls, so that they can generate an unsatisfactory number of false alarms, that is to say alarms indicating a breakthrough. imminent when it is not.

Another problem is linked to the configuration of the mold which is usually constituted by an assembly of metal plates backed by cooling devices configured to allow cooling of the metal plates by the circulation of a cooling fluid. To reach the areas of the mold where the temperature must be measured, it is necessary to pass through this cooling device and therefore through the circulating water. This leads to further sealing and wiring problems.

Belgian patent application 2018/5193 already proposes a solution to this problem which consists in lining at least one of the walls of the mold with a channel in which is inserted an optical fiber comprising a plurality of Bragg filters. This solution is remarkable and provides an appropriate response to the problems mentioned above. However, the inventors sought to develop alternatives which could be implemented in a faster and less expensive manner and which could be adapted to complex mold configurations.

An object of the invention is to improve the detection of breakthroughs by overcoming the drawbacks stated above.

To this end, according to the invention there is provided an ingot mold for the continuous casting of metals, of the type consisting of an assembly of metal plates backed by cooling devices configured to allow the cooling of the metal plates by the circulation of a cooling fluid. , comprising: - at least one optical fiber, comprising a plurality of Bragg filters, extending in a wall of at least one of said plates,

-3- BE2019 / 5408 - at least one groove formed in a wall of at least one of said plates, in a direction not parallel to the casting axis of the mold in at least a portion of the length, the optical fiber s 'extending into the groove, and - a tongue of shape substantially complementary to the groove closing the groove over its entire length, the groove and the tongue having a shape adapted to the passage of the optical fiber.

To avoid any confusion, it is specified that the terminology of the dimensions of the plate is established as follows: the length and the width are the dimensions of the plate in a section perpendicular to the casting axis of the mold and the depth is the dimension of the plate in the axis of the mold.

Thus, the thermocouples of the prior art are replaced by an optical fiber comprising Bragg filters. These allow, by means of the emission of a light beam in the fiber and the detection of the reflected and / or transmitted beam, the measurement of the temperature in the wall at each of the filters. We understand that the groove, optical fiber and the tongue are much less bulky than thermocouples and that these elements are much simpler to put in place. In addition, the temperature measurement using Bragg filters is more precise than that obtained with thermocouples, so that the number of false alarms is reduced.

Advantageously, the tongue is made up of a plurality of parts.

It is thus possible to adapt the length of the tongue by choosing the number of parts of which it is made. This makes it possible to adapt to the dimensions of the mold.

Advantageously, the groove has a substantially uniform depth.

The heat transfers between the plates and the optical fiber are thus just as uniform.

Advantageously, the ingot mold is made of copper or of a copper alloy, the tongue being made of the same material.

These materials have high thermal conductivity and thus help to standardize heat transfers.

Preferably, the tongue is welded to the mold so as to close the groove, by electron beam welding but other welding techniques are also possible, such as for example laser welding, X-ray or beam welding. ion and all types of arc welding, including electric arc welding with coated electrodes, arc welding with non-fusible electrodes, arc welding with wire fusible electrodes, submerged arc welding flux, electrogas welding, diffusion welding, or brazing or soldering.

-4- BE2019 / 5408 This allows a tight closure of the throat.

Advantageously, the groove is located on at least a central part of at least one of the plates.

It is thus possible to measure the temperature in a central zone of the wall and thus obtain a measurement which is particularly representative of the temperature of the wall.

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

It is thus possible to measure the temperature of the cast metal at a large number of points, which contributes to making breakthrough detection more reliable.

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

This protects the optical fiber from mechanical stresses that could damage it. In addition, the coating or the tube make it possible to modulate the diameter of the optical fiber.

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

Advantageously, the mold comprises a plurality of optical fibers contained in a plurality of grooves substantially parallel to each other.

The number of wall temperature measurement points is thus further increased, which contributes to making breakthrough detection even more reliable.

Advantageously, when the mold is of the type for casting a thin slab and comprises a funnel-shaped portion in the upper part, the groove being at least in the entire funnel-shaped part. Indeed, the solution proposed in Belgian patent application 2018/5193 consisting in installing the optical fiber in a channel drilled substantially parallel to the wall is very difficult to practice in a non-planar portion of the wall.

It is easily understood that this embodiment is suitable for any type of mold of complex shape.

Advantageously, the wall will include a groove in the central funnel-shaped part and a channel pierced in the flat part, the channel opening into the groove.

There is also provided according to the invention a system for measuring the temperature in a continuous metal casting system, comprising: - an ingot mold as defined in the above, - a transceiver arranged to send light into the fiber optical and receive reflected and / or transmitted light received by the transceiver, - a processor arranged to transform data on the reflected and / or transmitted light received by the transceiver into information on the temperature at different points of the ingot mold, and

° BE2019 / 5408 - a terminal including a user interface, connected to the processor.

Also provided according to the invention is a breakthrough detection system in a continuous metal casting system, comprising a temperature measurement system as defined in the above in which the processor is arranged to transform data on light reflected and / or transmitted received by the transceiver into information on the detection of a breakthrough.

Finally, according to the invention, a method is provided for detecting a breakthrough in a continuous metal casting installation, characterized in that the temperature of a mold wall as defined in the above is measured.

We will now present an embodiment of the invention given by way of nonlimiting example and in support of the appended figures in which: FIG. 1 is an overall view of an installation for the continuous casting of metals comprising an ingot mold according to the invention, - Figures 2a and 2b are diagrams illustrating the operation of the installation 5 of Figure 1, - Figure 3 is a sectional view of the installation mold of Figure 1, - Figure 4 is a perspective view of the mold of Figure 3, - Figure 5 is a perspective view of a plate of the mold of Figure 3, - Figures 5a, 5b, 5c and 5d are diagrams illustrating different shapes for a groove and a tongue of the mold, - Figure 6 is a longitudinal sectional view of an optical fiber contained in the plate of Figure 5, - Figure 7 is a diagram explaining the operation of the optical fiber of Figure 6, and - Figures 8a, 8b, 8c and 8d are sectional views of the mold of FIG. 3 illustrating the genesis of a breakthrough.

FIG. 1 shows an installation for the continuous casting of metals 2. It has a conventional configuration, so that most of its constituent elements will be presented only briefly.

The installation 2 includes pockets 4 containing liquid metal that you want to cool. The pockets 4 are here two in number and are carried by a motorized arm 6. This motorized arm 6 is in particular able to move the pockets 4 which are brought full into the casting zone by a transport system (for example an overhead crane. , not shown) from a filling zone where molten metal can be poured therein, for example an oven or a converter (not shown) before bringing them to the position shown in figure 1. After emptying the ladle 4 , the motorized arm 6 also makes it possible to position the empty bag in a position where the transport system can pick it up and bring it to the preparation zone where it will be reconditioned before returning to the filling zone.

The installation 2 comprises a distributor or distributor basin 8 located below the pockets 4. The latter have an openable bottom allowing the liquid metal to flow into the distributor 8.

The distributor 8 comprises a flow orifice which can be closed by a stopper rod 10 which makes it possible to control the flow of liquid metal. The dispenser outlet is extended by a submerged inlet pouring tube 11 (SEN) making it possible to protect the liquid metal poured into the mold 12.

As is more visible in FIG. 2a and on a larger scale in FIG. 2b, the submerged inlet pouring tube 11 opens into an upper opening of an ingot mold 12. This is a bottomless ingot mold. having a casting axis which is vertical. The mold 12 will be described in more detail below.

The installation 2 comprises cooling devices 14 positioned on an external surface of the mold 12. These are liquid type cooling devices. For this purpose, they include conduits in which a refrigerant fluid, for example water, flows. The refrigerant fluid absorbs the heat from the liquid metal in the mold 12 in order to cool and solidify it. Here, the metal solidifies in the form of a slab having a solidified outer surface 18 enclosing a liquid core 20.

Installation 2 comprises a roller guide 16 located downstream of the mold

12. The guide 16 makes it possible to guide the slab, an outer surface 18 of which is solidified, out of the mold 12. As can be seen in FIG. 2a, the slab gradually solidifies as it moves in the guide 16. In other words, the further one moves away from the mold 12, the more the solidified external surface 18 of the slab increases in volume and the more the liquid core 20 of the slab decreases in volume.

The mold 12 has been shown in more detail in FIG. 3. It has here four plates 22 (the fourth not being visible due to the position of the cutting plane). The plates 22 are made of copper or a copper alloy, which are materials exhibiting high thermal conductivity and therefore facilitate heat exchange between the cooling devices 14 and the mold 12. The plates 22 are arranged so that the mold 12 has a generally rectangular or square cross section. However, provision could be made to arrange the plates so that the mold has a completely different shape of cross section.

The mold 12 has been shown from a different angle in Figure 4. At least the upper part of the mold 12 has a funnel shape 23 partially receiving the pouring tube 11, the lower end of which is flattened. This shape is particularly suitable when the mold is intended for thin slab casting.

FIG. 5 shows one of the plates 22 of the mold 12. It has a groove 24 extending in a direction not parallel to the casting axis. It extends here in a substantially horizontal direction, over the entire length of the plate. However, it is possible that the groove 24 extends only over a part of the length of the plate 22, for example the central part in the case of an ingot mold for casting a thin slab. The groove 24 has a substantially uniform depth over its entire length.

There is shown in Figure 5a to 5d different shapes that the groove 24 can take. The groove 24 is closed over its entire length by a tongue 26 of a shape substantially complementary to the groove. The tongue 26 is preferably made of the same material as the plates 22, that is to say of copper or a copper alloy.

The groove 24 and the tongue 26 have a shape adapted to the passage of an optical fiber, the function of which will be described below. In this case, as can be seen in Figures 5a to 5c, the groove 24 or the tongue 26 (or both) has (have) a groove 27 intended to house the optical fiber. Once the optical fiber is housed in the groove, the tab 26 is welded so as to close the groove 24 over its entire length, for example by electron beam welding.

In an alternative embodiment, the tongue 26 consists of a plurality of parts welded together. It is thus possible to modulate the length of the tongue 26, in particular as a function of the length of the groove 24, by choosing the number of parts of which it is constituted.

In the embodiment of FIG. 5a, the groove 24 and the tongue 26 have a curved profile, and it is the tongue 26 which carries the groove 27.

In the embodiment of Figure 5b, the groove 24 and the tongue 26 have a curved profile, and it is the groove 24 which carries the groove 27.

In the embodiment of FIG. 5c, the groove 24 and the tongue 26 have a straight profile, and it is the groove 24 which carries the groove 27.

In the embodiment of FIG. 5d, the groove 24 and the tongue 26 have a frustoconical cross section, and it is the groove 24 which carries the groove 27. In particular, the section of the groove 24 is such that the groove widens towards its depth. In this way, the shape of the groove 24 makes it possible to retain the tongue 26 in position once placed in the groove 24, for example by sliding it along the groove 24 from one of its ends. || It is thus not necessary to weld the tab 26 to the mold 12, which presents an economic advantage. In order to allow easier insertion of the tongue 26 in the groove 24, it is possible to put the plate very slightly in flexion around an axis parallel to the groove 24 located on the other side of the plate 22, for example. at the level of the throat. Thus, the groove 24 is open and the tongue 26 can be slipped there without difficulty. Preferably, this bending is carried out while remaining within the elastic deformation limit of the copper plate.

Referring to Figures 6 and 7, an optical fiber 28 is housed in the groove 24. The optical fiber 28 comprises an optical cladding 30 as well as a core 32 surrounded by the optical cladding 30. The optical fiber 28 comprises in its core 32 several Bragg filters 34. Optical fiber 28 comprises at least ten Bragg filters per meter, preferably at least twenty Bragg filters per meter, preferably at least thirty Bragg filters per meter, and even more preferably in minus forty Bragg filters per meter.

The optical fiber 28 can be housed bare in the groove 24 as well as provided with a protective coating or be inserted into a tube before being installed. This coating or tube may have the function of increasing the radius of the optical fiber 28 in order to fill all or almost the entire diameter of the groove 24. It is preferable that the optical fiber has a diameter greater than 1.6 mm, in taking into account the possible presence of a coating or of a tube as mentioned above.

The operation of optical fiber 28 is illustrated in FIG. 7. Bragg filters 34 are filters which make it possible to reflect light over a range of wavelength centered on a predetermined value, called the reflected wavelength, adjustable by the constructor of the filter. This predetermined value is moreover a function in particular of the temperature at which the filter is located, so that we can write for each filter: Aréfléchie = f (Ao, T) WHERE Aréfléchie is the wavelength effectively reflected by the filter, f is a known function, T is the temperature of the filter and Ao the wavelength reflected by the filter at a predetermined temperature, for example at room temperature.

These two properties make it possible to use the optical fiber 28 as a temperature sensor. Firstly, Bragg filters 34 are installed in optical fiber 28 having values of reflected wavelength λ, distinct and chosen, for example shifted one by one by 5 nanometers. A light beam having a polychromatic spectrum 35a, for example white light, is then sent into the optical fiber 28 and then the wavelength peaks represented in the spectrum of the reflected beam 35b are determined. At each peak, the measured value Areflected and the theoretical value of the reflected wavelength at room temperature Ao are compared, and the temperature T of the filter in question is calculated using the function f. So

The alternative BE2019 / 5408, it is also possible to perform these steps on the basis of the pits in the spectrum of the transmitted beam 35c if the configuration of the channel 24 in which the optical fiber 28 is housed allows it.

Thus, the installation of the optical fiber 28 in one of the plates 22 of the mold 12 makes it possible to measure the temperature of this plate in predetermined positions to follow its evolution over time. In order to obtain a sufficient number of measurement points, it is preferred to place at least one optical fiber 28 in two facing plates 22, or even in each of the four plates 22 of the mold 12.

Furthermore, it is also preferred to place two optical fibers 28 per plate 22 so as to be able to measure the temperature of the mold 12 at two different altitudes. For example, one can place the two optical fibers 28 in each plate so that they are parallel and spaced 15 to 25 centimeters from each other.

The breakthrough detection is done as follows.

There is shown in Figures 8a to 8d the propagation of a zone 36 in which the metal contained in the mold 12 adheres to one of the plates 22 thereof. The graphs located in the lower right-hand zone of each of these figures represent the evolution of the temperature measured by a Bragg filter 34 of an upper optical fiber 28a (top curve) and by a Bragg filter 34 of an optical fiber lower (28b) as a function of time.

As can be seen in the graphs of Figures 8a and 8b, the upper optical fiber 28a detects an abnormal temperature rise which corresponds to the adhesion of the metal to the mold 12 in the area 36. || this is the first sign that a breakthrough is imminent.

Then, as can be seen in the graphs of Figures 8c and 8d, the lower optical fiber 28b detects the abnormal temperature rise previously detected by the upper optical fiber 28a. This is a second sign that a breakthrough is imminent, providing confirmation that the breakthrough does not appear preventable.

In order for the information recorded by the optical fibers 28a and 28b to be communicated to the users of the installation 2, the latter comprises: a transceiver designed to send light into the optical fiber and receive reflected light and / or the light transmitted by the optical fiber, - a processor arranged to transform data on the reflected and / or transmitted light received by the transceiver into information on the temperature at various points of the mold, and - a terminal comprising a user interface, connected to the processor.

- 10 - BE2019 / 5408 The processor is further arranged to transform the data on the reflected and / or transmitted light received by the transceiver into information on the detection of a breakthrough.

Thanks to these elements (which have not been shown in the figures for reasons of clarity), it is possible to transform the temperature measurement carried out by the optical fibers 28 into information, understandable by the users of the installation 2. , whether or not a breakthrough is detected.

In other words, the mold 12 equipped with the optical fibers 28, the transceiver, the processor and the terminal form a breakthrough detection system.

If a breakthrough is detected positively, users can take actions to reduce the damage caused by the breakthrough or even prevent it.

The invention is not limited to the embodiments presented and other embodiments will be apparent to those skilled in the art.

Provision can in particular be made for the mold to be more conventional with a straight shape without a funnel.

Provision can be made to provide the mold with several optical fibers contained in a plurality of grooves which are substantially parallel to one another.

Nomenclature 2: installation (continuous metal casting) 4: ladle 6: motorized arm 8: distributor 10: stopper rod 11: pouring tube 12: ingot mold 14: cooling devices 16: guide 18: solidified external surface 20: liquid core 22 : plate 23: funnel 24: groove 26: tongue 27: groove 28: optical fiber 30: optical sheath

LS BE2019 / 5408 32: core 34: Bragg filter 35a: polychromatic spectrum 35b: spectrum of the reflected beam 36: zone

Claims (13)

-12- BE2019 / 5408 Claims 1. Ingot mold for continuous casting of metals (12), of the type constituted by an assembly of metal plates (22) backed by cooling devices (14) configured to allow cooling of the metal plates (22) by the circulation of a cooling fluid, comprising: - at least one optical fiber (28), comprising a plurality of Bragg filters (34), extending in a wall of at least one of said plates (22), - at least one groove ( 24) formed in a wall of at least one of said plates (22), in a direction not parallel to the casting axis of the mold (12) in at least a portion of the length, the optical fiber (28) s 'extending into the groove (24), and - a tongue (26) of substantially complementary shape to the groove (24) closing the groove over its entire length, the groove (24) and the tongue (26) having a shape adapted to the passage of the optical fiber, the ingot mold (12) being made of copper or copper alloy and the tongue (26) being made of the same material. 2. Ingot mold according to the preceding claim, wherein the tab (26) consists of a plurality of parts. 3. Ingot mold according to any preceding claim, wherein the groove (24) has a substantially uniform depth. 4. Mold according to any one of the preceding claims, in which the tab (26) is welded, for example by electron beam welding, to the mold so as to close the groove (24). 5. Ingot mold according to any one of the preceding claims, in which the groove (24) is located on at least a central part of at least one of the plates (22). 6. A mold according to any preceding claim, wherein the groove (24) extends over the entire length of at least one of the plates (22). 7. Mold according to any one of the preceding claims, in which the optical fiber (28) is provided with a coating or a tube. 8. Ingot mold according to any one of the preceding claims, wherein the optical fiber (28) has a diameter greater than 1.6 mm. 9. A mold according to any one of the preceding claims, comprising a plurality of optical fibers (28) contained in a plurality of grooves (24) substantially parallel to each other. -13- BE2019 / 5408 10. Ingot mold (12) according to any one of the preceding claims, of the type for thin slab casting, comprising a funnel-shaped portion (23) in the upper part, the groove (24) being at least in the whole part. funnel-shaped (23). 11. System for measuring the temperature in a continuous metal casting system, comprising: - an ingot mold (12) according to any one of the preceding claims, - a transceiver arranged to send light into the optical fiber ( 28) and receive the reflected and / or transmitted light received by the transceiver into information on the temperature at different points of the mold (12), - A processor arranged to transform data on the reflected light and / or transmitted received by the transceiver in information on the temperature at different points of the mold, and - a terminal comprising a user interface, connected to the processor. 12. A breakthrough detection system in a continuous metal casting system, comprising a temperature measurement system according to the preceding claim in which the processor is arranged to transform data on the reflected and / or transmitted light received by the. transceiver into breakthrough detection information. 13. A method of detecting a breakthrough in a continuous metal casting installation, characterized in that the temperature of an ingot mold wall according to any one of claims 1 to 10 is measured.