GB2553378A

GB2553378A - Moulds for continuous casting

Info

Publication number: GB2553378A
Application number: GB1615157.3A
Authority: GB
Inventors: Nicolas Smart David
Original assignee: Materials Proc Institute
Current assignee: Materials Proc Institute
Priority date: 2016-09-06
Filing date: 2016-09-06
Publication date: 2018-03-07
Anticipated expiration: 2036-09-06
Also published as: GB201615157D0; GB2553378B

Abstract

A method of producing a mould panel (201, 202, 203, figure 2) for use in the continuous casting of metal comprises establishing a substrate panel of a first material 601, depositing a first layer of electrically insulating material 602 over an internal surface of the panel and a second layer of electrically conducting material 603 over the first layer to define a plurality of temperature responsive devices (701, 702, 703, 704, figure 7). A mould panel comprises a substrate panel comprising a deposited layer of electrically insulating material on an internal surface and a deposited layer of electrically conducting material defining temperature responsive devices. Also disclosed is an apparatus for the continuous casting of metal comprising a source of liquid metal (1501, figure 15), a mould defined by mould panels (1503, 1504) defining a strand of solidifying metal (1502), a water cooling device (1506) attached to outer surfaces of the panels and a plurality of thermocouple devices deposited on internal surfaces of the mould panels. The thermocouples may be established by patterned first and second layers of electrically conducting material deposited by a photolithographic process.

Description

(54) Title ofthe Invention: Moulds for continuous casting

Abstract Title: Mould panels and apparatus for continuous casting and methods of production of said panels (57) A method of producing a mould panel (201, 202, 203, figure 2) for use in the continuous casting of metal comprises establishing a substrate panel of a first material 601, depositing a first layer of electrically insulating material 602 over an internal surface of the panel and a second layer of electrically conducting material 603 over the first layer to define a plurality of temperature responsive devices (701, 702, 703, 704, figure 7). A mould panel comprises a substrate panel comprising a deposited layer of electrically insulating material on an internal surface and a deposited layer of electrically conducting material defining temperature responsive devices. Also disclosed is an apparatus for the continuous casting of metal comprising a source of liquid metal (1501, figure 15), a mould defined by mould panels (1503, 1504) defining a strand of solidifying metal (1502), a water cooling device (1506) attached to outer surfaces ofthe panels and a plurality of thermocouple devices deposited on internal surfaces ofthe mould panels. The thermocouples may be established by patterned first and second layers of electrically conducting material deposited by a photolithographic process.

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Moulds for Continuous Casting CROSS REFERENCE TO RELATED APPLICATIONS

This application represents the first application for a patent directed towards the invention and the subject matter.

BACKGROUND OF THE INVENTION

The present invention relates to a method of producing a mould panel for use in the continuous casting of metal. The present invention also relates to an apparatus for use as a mould panel in a continuous casting operation. The present invention also relates to an apparatus for the continuous casting of metal.

It is known to manufacture metal and in particular steel, by continuous casting processes. These processes convert liquid metal into solid products and have substantially taken over from additional batch process ingot casting when longer lengths of metal are required.

During continuous casting, molten metal is poured into an open-end of a cooled mould and the mould removes heat from the liquid, thereby forming a solid shell outer portion and a molten inner core, that is withdrawn from the opposite end of the mould in a continuous manner. The mould is configured primarily to contain the liquid metal and also to extract heat. Thus, the walls of the mould are suitably supported and the rate of withdrawal of a strand from the mould is matched with the inflow rate of the liquid steel, such that the product shell is maintained at a required thickness and uniformity to support the ferrosatic pressure of the liquid iron, for example. Furthermore, the mould is constructed from a high thermal conductively material, such as copper, and has an outer jacket into which cooling water is pumped, so as to carry away the heat. However, great care must be taken to ensure that cooling water does not make direct contact with the molten metal.

By measuring temperatures at various locations around a mould, it is possible to estimate the rate of heat transfer, from which it is possible to infer the quality of the shell in terms of thickness, uniformity and cracking potential; so as to minimise the risk of the shell sticking or tearing. If conditions of this type are detected, it is possible to reduce the withdrawal rate, so as to allow additional time for heat extraction to repair the damaged region of the shell before it reaches the mould exit. Thus, given these constraints, it is only possible to increase the productively and quality of continuous casting operations if it is possible to accurately measure and control the temperature of the strand.

It is known to provide thermal monitoring systems, in which holes are drilled into the mould to allow temperature sensors to be fitted. These holes can either be drilled directly into the mould material itself or drilled into the mould supporting bolts which themselves are already secured in the mould material using threaded holes. These holes need to be a safe distance from the mould’s hot internal surface to prevent water leaking into the mould itself. Thus, industrial thermocouples may be inserted into these holes and connected electrically to external temperature monitoring systems. Thermocouples of this type are constructed from two wires of dissimilar metals protected by a sheaving.

However, a problem exists, in that it is desirable to obtain more accurate information relating to the actual temperature of the metal at the mould surface. However, using known techniques, it is not possible to bring the thermocouples to the mould surface itself, given that this would introduce a hole into the water cooled mould.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a method of producing a mould panel for use in the continuous casting of metal, comprising the steps of: establishing a substrate panel of a first material, in which said substrate panel has an external surface and an internal surface; depositing a first layer of electrically insulating material over said internal surface; and depositing a second layer of electrically conducting material over said first layer to define a plurality of temperature responsive devices.

In an embodiment, the second material forms parts of thermocouples, such that said temperature responsiveness is established by a voltage that varies with respect to temperature, further comprising the steps of: depositing a third layer of an electrically insulating material; and depositing a fourth layer of an electrically conductive material, such that thermocouple devices are formed at junctions between components of said second layer and components of said fourth layer.

Preferably, a fifth layer of an electrically insulting material is deposited.

According to a second aspect of the present invention, there is provided an apparatus for use as a mould panel in a continuous casting operation, comprising: a substrate panel of a first material having an external surface and an internal surface; a deposited layer of electrically insulating material on said internal surface; and a deposited layer of electrically conducting material defining temperature responsive devices. Preferably, a third layer of an electrically insulating material is deposited and a fourth layer of an electrically conductive material is deposited, wherein thermocouple devices are formed at junctions between components of said second layer and components of said fourth layer.

According to a third aspect of the present invention, there is provided an apparatus for the continuous casting of metal, comprising; a source of liquid metal and a mould defined by mould panels, wherein; said mould panels define a strand of solidifying metal; a water cooling device is attached to an outer surface of said mould panels to maintain the temperature of the mould below the melting point of said mould panels; and a plurality of thermocouple devices are deposited on internal surfaces of said mould panels.

In an embodiment, the thermocouples are established by a patterned first layer of a first electrically conducting material deposited by a photolithographic process and a patterned second layer of a second electrically conducting material deposited by a photolithographic process.

The invention will now be described by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Figure 1 shows an apparatus for continuously casting! a metal;

Figure 2 details a mould of the type identified in Figure 1;

Figure 3 shows a schematic representation of layers defining temperature responsive devices;

Figure 4 illustrates the device of the type produced using process identified in Figure 3;

Figure 5 shows an alternative embodiment, in which the second layer of material forms parts of thermocouples;

Figure 6 shows an alternative embodiment with additional deposited material;

Figure 7 shows an arrangement of the third embodiment;

Figure 8 shows an inner surface of a substrate panel;

Figure 9 shows a first stage of a photolithography process;

Figure 10 shows the second stage of the photolithography process; Figure 11 shows a third stage of the photolithography process;

Figure 12 shows a fourth stage of the photolithography process;

Figure 13 shows a further stage of the photolithography process;

Figure 14 shows a final stage of the photolithography;

Figure 15 shows continuous casting operation in cross-section; and Figure 16 details a continuous casting operation with temperature measurement in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1

An apparatus for continuously casting a metal is illustrated in Figure 1, that includes a mould 101 and a tundish 102 for supplying molten metal 103 to the mould 101. A mould surface 104 is defined by the mould 101, such that an interfacial gap is established between the mould surface and a surface of solidifying slag surrounding a strand of molten metal.

In operation, molten metal is tapped into a ladle 105 and the ladle is transported to the top of the casting machine. Usually, more than one ladle is deployed in order to continuously supply molten material to the tundish 102, which in turn continuously supplies molten metal to the mould 101.

From the ladle 105, the molten metal is transferred via a refractory shroud 107, with a similar refractory nozzle 108 supplying molten metal from the tundish to the top of the mould 101.

in a typical configuration for the continuous casting steel, the mould may have a depth of between half a metre and two metres, with primary cooling been provided by the passage of cooling water through the mould itself; thereby ensuring that molten metal will start to solidify when placed in contact with the mould. Furthermore, the mould may oscillate in a substantially vertical direction to prevent the metal sticking to the walls of the mould.

The nozzle 108 may be positioned such that the hot molten metal exits below the surface of a slag layer formed on the top of the molten material within the mould and as such is referred to as a submerged entry nozzle.

In the mould 101, a thin shell of metal next to the mould wall solidifies before a middle strand section leaves the base of the mould for entry into a spray chamber. The bulk of the metal within these solidifying walls of the strand remains molten. Thus, the strand is supported by closely spaced water-cooled rollers 109 which support the walls of the strand against the ferrosatic pressure of the solidifying liquid within the strand 110. After solidifying, the strand is cut, possibly by an acetylene torch 111, to produce slabs, blooms or billets 112 of a predetermined length.

Figure 2

Mould 101 is detailed in Figure 2. The mould includes apparatus for use as mould panels, including a first mould panel 201, a second mould panel 202 and a third mould panel 203. To complete the mould, a fourth mould panel is present, although not shown in Figure 2. Panels 201 to 203 are defined by a substrate of a first material, typically copper defining an external surface and an internal surface. Thus, panel 203 defines an external surface 204 and an internal surface 205.

In the embodiment of Figure 2, a layer of electrically insulating material has been deposited on each internal surface, including internal surface 205. Furthermore, a layer of an electrically conducting material has been deposited that defines temperature responsive devices. Thus, in the embodiment of Figure 2, temperature measurement is achieved by monitoring temperature responsive devices physically attached to the internal surfaces of the mould panels. In operation, as illustrated in Figure 16, the devices are much closer to the region where temperature measurement is required in order to achieve enhanced performance.

Figure 3

A schematic representation of layers defining temperature responsive devices is illustrated in Figure 3. An example of a substrate panel of a first material is shown at 301. Thus, the method of producing a mould panel for use in the continuous casting of metal is initiated by the establishment of a substrate panel 301 of a first material (typically copper) defining an external surface (such as surface 204) and an internal surface, such as surface 205.

A first layer of electrically insulting material 302 is deposited over the internal surface of the substrate panel 301. A second layer of electrically conducting material 303 is deposited over the first layer; so as to define a plurality of temperature responsive devices; examples of which are illustrated in Figure 4 and in Figure 5.

In an embodiment, a third layer of an electrically insulating material

304 is deposited over the second layer 303. In an embodiment, this third layer may provide a robust mechanically protective layer, with examples of such materials known to those skilled in the art.

In an alternative embodiment, the third layer may be an electrically insulating material such as aluminium oxide. To this, a fourth layer 305 of a robust mechanically protective material, such as nickel, may be deposited.

Figure 4

In an embodiment, the second material, formed as the second layer of conductive material 303, provides temperature responsiveness by presenting variable resistances with respect to temperature. As described with respect to Figures 8 to 12, an etching process is performed, possibly as part of a photolithographic process, so as to define electrical conductors in the second layer having a configuration substantially as shown in Figure 4.

A first resistive element 401 is shown, along with a second resistive element 402. In an embodiment, the horizontal displacement 403 between adjacent resistive elements such as resistive elements 401 and 402, typically has a dimension of several millimetres, possibly ranging from four millimetres to twelve millimetres for example. Furthermore, a similar displacement is provided between adjacent devices in a vertical direction 403.

As illustrated in Figure 4, in order to provide distributed coverage over a two dimensional region of an inner surface of a mould panel, the position of the temperature responsive devices is effectively staggered in a step like fashion such that, as they progress in a horizontal direction, the length of the vertical displacement increases. This occurs for a plurality of iterations, until sufficient depth has been achieved, whereafter the pattern may be repeated. However, it should be appreciated that alternative configurations of these devices are possible and that the approach defined herein allows substantially more devices to be included per unit area of mould panel.

For each device (401, 402) shown in Figure 4, a relatively high resistive wire portion 103 is provided, having a resistance that varies in proportion to temperature over a substantially linear operational range. Each device, such as device 401, receives electrical current via a positive terminal 404 and a negative terminal 403. Thus, by applying a known voltage across these terminals and measuring the resulting current, it is possible to determine (by Ohms law) the resistance of the resistive region 403.

As is known in the art, for devices of this type, it is necessary to connect wires between terminals 404 and 405, which in turn connect to a control system; such as that shown in Figure 16. Thus, these wires should be of a relatively low resistance, such that variations in resistance are made predominantly by the devices themselves and not by the connecting wiring. It is also appreciated that devices of this type may be problematic, due to the environment inducing electrical noise.

Figure 5

An alternative embodiment is illustrated in Figure 5, in which the second layer of material forms parts of thermocouples, such that the temperature responsiveness is established by a voltage that varies with respect to temperature. In this embodiment, a thermocouple is created between components 501, 502, 503 and 504 defined in the second layer of conductive material 303. A thermocouple device is established at the location of each temperature responsive device by forming a junction with the actual substrate panel of the first material.

Given that the substrate is constructed from copper, it is possible to define a type T thermocouple, with elements 501 to 504 being deposited material of constantan. As is known in the art, thermocouples of this type, have a sensitively of about forty-three microvolts per degree centigrade. However, such a configuration does include inherent stability issues, particularly given that the device will be operating at the top end of its temperature range.

A deposited track 505 connects component 501 to an electrical terminal 506. A second terminal 507 is connected to the copper substrate, allowing measuring devices to determine voltages across the terminals. Thus, similar terminals 508 and 509 are provided for component 502, with terminals 510 and 511 for component 503, and terminals 512 and 513 for component 504.

Figure 6

An alternative embodiment is illustrated in Figure 6. In this embodiment, the second material, deposited as a second layer, also forms parts of thermocouples, such that the temperature responsiveness is established by a voltage that varies with respect to temperature. Again, a panel, such as panel 204, provides a substrate 601 of a first material. A first layer of insulating material 602 is deposited and this is followed by a second layer 603 of conducting material. The second layer of conducting material is etched to define parts of the thermocouple devices, whereafter a third layer of insulating material 603 is deposited and appropriately etched.

A fourth layer of conductive material 605 is applied and etched in accordance with a different pattern such that, as shown in Figure 7, thermocouple devices are defined at locations where components with the fourth layer of conductive material connect with portions of the second layer of conductive material.

Thereafter, it is possible to deploy a fifth layer of insulating material 606, which may also provide robust mechanical protective properties.

In an embodiment, a fifth layer of an electrically insulting material 606 may be applied, such as aluminium oxide, followed by a sixth layer 607 of a protective material, such as nickel. However, it should be appreciated that all of the layers are relatively thin and when deposited, continue to present a smooth surface internally. Typically, the combined assembly of Figure 6 creates a layer of only several micrometres.

Figure 7

Following the procedure identified in Figure d, temperature responsive devices 701 to 704 are established. For each of these, a first component 705, derived from the second layer of conductive material, forms a junction with a second component 706, derived from the fourth layer of conductive material 605. In this way, it is possible for the two components of a thermocouple to be defined without being constrained by the presence of the copper in the panel substrate. Thus, it should be appreciated, that elements 705 are insulated from the substrate by the first layer of insulating material 602 and the second elements 706 are insulated by both the third layer of insulating material and the first layer of insulating material, with a junction being present at the position of overlap 707.

In an embodiment, the first component 705 may be defined using platinum, with a second component 706 being a platinum/rhodium alloy. In this way, stability is improved, particularly at higher temperatures.

In the embodiment of Figure 7, terminals 707 and 708 provide connections to the first device 701. Similar terminals are provided for devices 702 to 704 thereby, in this example, giving a total of eight terminals.

In an embodiment, the terminals are taken to the edge of the panel where it is possible for them to be attached to a connector 709 that includes terminals, including terminals 710 and 711, that electrically connect with terminals 707 and 708 respectively. A wire extends from each of these and the wires may be collected together to define a cable 712 that is conveyed to a control system, as illustrated in Figure 16.

Figure 8

Panel 203 is shown in Figure 8, with inner surface 205 forming the exposed surface of a substrate panel of the first material.

In an embodiment, the thermocouple components, illustrated in Figure 7, may be produced by a process of photolithography. Similarly, the thermocouple components in Figure 5 may be produced in this way, and the resistive elements in Figure 4 may be created by this process.

Referring to the example of Figure 7, the thermocouple components for the second material 603 may be produced by the process of photolithography. Similarly, the thermocouple components formed by the fourth layer 605 may be produced a process of photolithography. In the example shown in Figure 6, a third layer of insulating material 604 is introduced between the second layer of conducting material 603 in the fourth layer of conducting material 605. In some embodiments, it may not be necessary to include this third layer, given that all the required insulation may be provided by the provision of the first layer of insulating material 602 and the fifth layer of insulating material 603.

In the example of Figure 7, the elements of the second layer only overlap with the elements at the fourth layer at positions where overlap is required, in order to define the junction and insulation may be provided elsewhere due to their relative displacement. A photolithographic process for defining the second layer of conductive material of the first embodiment (layer 303) or of the second embodiment (layer 603) will be described with reference to Figures 9 to 14.

Figure 9

At a first stage for producing a mould panel in accordance with the disclosed embodiments, a first layer of electrically insulating material 602 is deposited upon the substrate panel of the first material 601. In the embodiments of Figures 6 and 7, this represents a fully insulting layer, given that the copper substrate 203 will not play any part in the temperature measuring operations.

Figure 10

In the embodiment of Figure 6, a second layer of conductive material

603 is deposited upon the first layer of insulating material 602. This material will define elements 705 of the devices shown in Figure 7. Upon a second similarly iteration, similar components 706 will be defined.

A photoresist 1001 is deployed over the second layer 603 so as to completely cover it. The photoresist 1001, applied over coating 603; is then baked; so as to form a solid coating.

Figure 11

After the baking operation has been performed, the photoresist is exposed to a pattern of intense light which causes a chemical change that allows some of the photoresist to be removed by the application of a developer.

Thus, a pattern is defined by a mask 1101 and the combination is then illuminated by source 1102.

Figure 12

The deployment of developer 1201 is illustrated in Figure 12. With a positive photoresist, the material that has been exposed to light source 1102 is removed by the application of the developer 1201, so as to reveal the required components of the layer under consideration.

Figure 13

Exposed components, after the application of the developer 1201 are illustrated in Figure 13. These show the position of the required components but at this stage they are obscured by the resist that has not been removed. Thus, as indicated by arrow 1301, resist stripper 1302 is deployed to remove the remaining resist, while retaining the required components of the second layer.

Figure 14

Thus, a resulting second layer is shown in Figure 14. This is now in a condition for the operation previously described to be repeated, allowing a third insulating layer to be deployed (if required) followed by the depositing of the fourth layer of conductive material 605.

Figure 15

A continuous casting operation is shown in cross-section in Figure 15. A supply device, in the form of a nozzle 1501 supplies molten metal 1502 into the mould. The internal surface of the mould panels, such as surface 1503 and surface 1504, restrain the molten metal 1502 and a meniscus 1505 is established; with molten slag maintained above this meniscus position and solidifying slag forming below this meniscus position thereby defining an outer solidifying wall.

A water cooling device 1506 is provided that supplies a continuous flow of cooling water, in the direction of arrow 1507 and arrow 1508, through a first cooling assembly 1509, attached to an outer surface 1510 of a first panel and a second cooling assembly 1511 attached to an outer surface 1512 of a second panel. Each panel in turn includes channels for receiving cooling water such that, when performing a cooling operation, the cooling water is brought closer to the inner surfaces 1503 and 1504.

Thus, it can be seen that temperature measurement at any position away from the actual inner surface will produce results that are influenced significantly by the cooling water and these results in turn may only provide a vague indication as to the actual temperature at the inner surfaces. Furthermore, given the fluctuations in water flow and water temperature, non-equilibrium situations may exist which in turn produce inaccuracies and limit the dynamic ability of the system to respond appropriately.

Figure 16

An embodiment provides for an apparatus for the continuous casting of metal, as illustrated in Figure 16. Nozzle 1601 supplies molten metal into the mould 1602. Heat is extracted from the molten metal by the copper mould, which is water cooled. The mould is defined by mould panels 1603 that in turn define a strand of solidifying metal. A water cooling device is attached to an outer surface of the mould panels to maintain the temperature of the mould below the melting point of the mould panels. Thermocouple devices are deposited on the internal surfaces of the mould panels and allow temperature data to be determined at a control unit 1604 electrically connected to the thermocouples via cables 713.

As previously describe, the thermocouples are established by a 5 patterned first layer of a first electrically conducting material deposited by a photolithographic process and a patterned second layer of a second electrically conducting material deposited by a similar lithographic process.

Claims

CLAIMS The invention claimed is:

1. A method of producing a mould panel for use in the continuous casting of metal, comprising the steps of:

establishing a substrate panel of a first material, in which said substrate panel has an external surface and an internal surface;

depositing a first layer of electrically insulating material over said internal surface; and depositing a second layer of electrically conducting material over said first layer to define a plurality of temperature responsive devices.

2. The method of claim 1, wherein a third layer of electrically insulating material Is deposited over said second layer.

3. The method of claim 2, wherein said third layer also provides a robust mechanically protective layer.

4. The method of claim 2, wherein a fourth layer of a robust mechanically protective material is deposited over said third layer.

5. The method of any of claims 1 to 4, wherein said second material provides temperature responsiveness by presenting variable resistances with respect to temperature.

6. The method of any of claims 1 to 4, wherein said second material forms parts of thermocouples, such that said temperature responsiveness is established by a voltage that varies with respect to temperature.

7.

The method of claim 1, wherein said second material forms parts of thermocouples, such that said temperature responsiveness is established by a voltage that varies with respect to temperature, further comprising the steps of:

depositing a third layer of an electrically insulating material; and depositing a fourth layer of an electrically conductive material, such that thermocouple devices are formed at junctions between components of said second layer and components of said fourth layer.

8. The method of claim 7, further comprising the step of depositing a fifth layer of an electrically insulating material.

9. The method of claim 8, wherein said fifth layer also provides a robust mechanically protective layer.

10. The method of claim 8, further comprising the step of depositing a sixth layer of a robust mechanically protective material.

11. The method of any of claims 7 to 10, wherein thermocouple components are formed in said second material by a process of photolithography.

12. The method of any of claims 7 to 11, wherein thermocouple components are formed in said fourth layer by a process of photolithography.

13. The method of any of claims 1 to 12, further comprising the step of creating electrical conductors in said second layer that extend to connectable terminals.

14. The method of claim 13, further comprising the step of attaching an electrical connector to said terminals.

15. The method of claim 14, further comprising the step of connecting temperature analysing equipment to said electrical connector.

16. An apparatus for use as a mould panel in a continuous casting operation, comprising:

a substrate panel of a first material having an external surface and an internal surface;

a deposited layer of electrically insulating material on said internal surface; and a deposited layer of electrically conducting material defining temperature responsive devices.

17. The apparatus of claim 16, further comprising:

a deposited third layer of an electrically insulating material; and a deposited fourth layer of an electrically conductive material, wherein thermocouple devices are formed at junctions between components of said second layer and components of said fourth layer.

18. The apparatus of claim 17, further comprising a fifth electrically insulating layer.

19. An apparatus for the continuous casting of metal, comprising: a source of liquid metal;

a mould defined by mould panels, wherein:

said mould panels define a strand of solidifying metal; a water cooling device is attached to an outer surfaces of said mould panels to maintain the temperature of the mould below the melting point of said mould panels; and a plurality of thermocouple devices deposited on internal surfaces of said mould panels.

20. The apparatus of claim 19, wherein said thermocouples are established by a patterned first layer of a first electrically conducting material deposited by a photolithographic process and a patterned second layer of a second electrically conducting material deposited by a photolithographic process.

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Application No: GB1615157.3 Examiner: Dr Karen Payne