Measurement lance for measuring the position and thickness of a slag layer on a molten metal

Abstract

The present invention relates to a measurement lance (1) for measuring, in a single measurement run, the position (has) of the atmosphere - slag interface (2as) between the atmosphere (4) and the slag layer (2) on the molten metal (3) and the position (hsm) of the slag - metal interface (2sm) between the slag layer (2) and the molten metal (3), the measurement lance (1) comprising: · a conveyance pipe (5) extending along an axis (X) between a proximal end (5p) and a distal end (5d) located downstream of the proximal end; · a measurement unit (6) coupled to the distal end (5d) of the conveyance pipe (5) and configured to pass through the slag layer (2), · an electric circuit (7) configured to detect the atmosphere - slag interface (2as), · a slag - metal interface detection unit (8) located downstream of the distal end (5d) and comprising at least first and second electrical measurement terminals (8ta, 8tb) and configured to measure a value of a first material property at the position (hsm) of the slag - metal interface (2sm) between the slag layer (2) and the molten metal (3), and · preferably, a sensor unit (9) comprising first and second electrical sensor terminals (9ta, 9tb) and configured to measure values of a second material property of the slag layer (2) and the molten metal (3), the measurement unit (6) including a cap (10) surrounding the slag - metal interface detection unit (8) and optionally the sensor unit (9) and configured to isolate the slag - metal interface detection unit (8) from the external environment.

Description

Technical Field

[0001] The present invention relates to a measuring lance for measuring the position and thickness of a slag layer on molten metal. The measuring lance is configured to measure, in one measurement run, the position of the atmosphere-slag interface between the atmosphere and the slag layer and the position of the slag-metal interface between the slag layer and the molten metal. The measuring lance requires reducing the number of electrical terminals for connection to external electrical parameter measurement hardware. This enables the measurement of the thickness of the slag layer in addition to existing measurements with a minimal change to the analysis device, which is the external electrical parameter measurement hardware connected to the measuring lance.

Background Art

[0002] Metal production lines generally include a plurality of containers for holding and transporting molten metal, such as ladles, tundishes or furnaces. As shown in FIG. 20, a ladle (21) can be used to transport molten metal from a furnace and inject it into a tundish (22), from where the molten metal can be cast through an injection nozzle into a mold (23) or tool for continuously forming slabs, billets, beams and thin slabs. A slag layer (2) formed from impurities in the metal or ore being processed, such as oxides or ash, is formed on the molten metal in the ladle (21), tundish (22) or even the mold (23).

[0003] Within the vessel, the slag layer floats on the molten metal, forming a continuous layer that separates the molten metal from the atmosphere, thereby protecting the molten metal from oxidation by the atmosphere and reducing heat loss. Measuring the position of the slag-metal interface and the thickness of the slag layer is very important because it makes it possible to determine the amount of molten metal contained within the vessel in order to prevent the slag from being entrained within the mold (23). The composition of the slag is known to have an adverse effect on the composition of the molten metal. For example, the slag can contribute to the deoxidation of molten steel. By adding a holding agent to the slag, deoxidation can be further promoted. The amount of holding agent introduced to reach the desired concentration depends on the volume of slag within the vessel, which can be determined by accurately measuring the positions of the atmosphere-slag interface and the slag-metal interface.

[0004] Controlling the amount of slag within the vessel is also important for evaluating the state of the molten metal within the vessel. For example, the amount of slag is important information for metallurgists to estimate the required amount of special deoxidizers (such as aluminum, silicon, titanium, etc.) added to the system because a portion is absorbed by the slag, which is often highly oxidized.

[0005] Currently, the positions of the atmosphere-slag interface and the slag-metal interface are typically determined using a dedicated measurement lance, which includes a measurement head configured to measure specific properties of the surrounding materials and detect changes in these specific properties when the lance is immersed within the vessel through the slag and molten metal, which have properties different from each other and from the surrounding atmosphere. By recording the position of the lance, the positions of the atmosphere-slag interface and the slag-metal interface are determined by identifying the positions where the specific properties change abruptly by an analysis device electrically connected to the measurement head via a plurality of terminals. The analysis device generally includes a voltmeter or an ohmmeter.

[0006] Measurement lances for measuring the positions of both the atmosphere-slag interface and the slag-metal interface, and thus the thickness of the slag layer on the molten metal, are known in the art.

[0007] U.S. Patent No. 7,876,095 B2 describes an apparatus for determining at least one interface of a slag layer on a molten metal. The apparatus includes a transfer pipe and a measurement head disposed at one end of the transfer pipe and configured to pass through the slag layer. The shank body of the measurement head is fixed to the transfer pipe and has an end face facing away from the transfer pipe. A circuit including an oscillator is disposed inside the shank body of the measurement head. The induction coil is connected to the oscillator and is disposed outside the shank body of the measurement head and in front of its end face. A signal line passing through the transfer pipe enables connection of the circuit having the oscillator to an external analysis device, such as a computer. The induction coil can be surrounded by a protective sheath fixed to the body of the measurement head, thereby being protected from the influence of the slag. The induction coil coupled to the oscillator enables detection of changes in the properties of the surrounding material during the transition from the slag to the conductive molten metal. Advantageously, the bus contact is disposed outside the body of the measurement head and in front of its end face. Since a short circuit occurs as soon as the bus contact touches the slag (normally, the slag itself is generally grounded), this bus contact enables additional determination of the interface between the slag layer above it and the atmosphere layer. The bus contact is connected to the analysis device via a signal line passing through the transfer pipe. Thereby, the upper and lower interfaces of the slag can be determined, and as a result, the thickness of the slag layer can be calculated. Additional sensors, such as thermoelectric elements, electrochemical sensors, or optical sensors, can be disposed on the measurement head so that additional measurements can be performed simultaneously. The additional sensors can be connected to the analysis device via other signal lines passing through the transfer pipe.

[0008] WO2012 / 171658 A1 describes a device aimed at measuring the thickness of slag on the surface of liquid metal contained within an ingot mold. The device is · a wire made of a conductive material that can be removed by the influence of heat at the temperature of the slag, the wire including a free end intended to be immersed in the slag, and · means for supplying a wire, capable of displacing the wire such that its free end is vertically immersed in the slag according to a predetermined trajectory; · measuring means capable of measuring the distance traveled by the free end of the wire during the time interval between two predetermined events when the latter of the two predetermined events is displaced by the action of the supply means; · means for controlling the supply means, the control means including detection means capable of detecting contact between the free end and the surface of the liquid metal.

[0009] The device automatically immerses the wire in the slag until it reaches the surface of the liquid metal contained in the ingot mold and holds it for a predetermined time sufficient for the portion of the wire immersed in the slag to be removed by the effect of heat. Then, it is possible to immerse the wire in the slag again until it reaches the surface of the liquid metal. The measuring means calculates the length of the wire not involved in the last immersion. This length corresponds to the portion of the wire immersed in the slag removed by the effect of heat and thus corresponds to the thickness of the slag.

[0010] EP330264 describes a method of measuring the level of the surface of the molten metal bath (i.e., the slag / metal interface) under the liquid layer of slag in a metallurgical vessel using a detector that moves through the slag layer into the metal bath and is then withdrawn. The detector used includes an oxygen concentration sensor that emits a signal enabling the position of the boundary between the molten metal and the slag to be identified. The signal from the detector is preferably monitored while the detector is being withdrawn from the metal. When the detector passes through the slag / metal interface from the molten metal into the slag, the measured increase in oxygen concentration is used as an indicator of the boundary.

[0011] The detector is immersed in a bath of molten metal where an oxygen concentration sensor is exposed to the molten metal to measure the oxygen concentration of the molten metal. Next, the detector is withdrawn from the bath of molten metal until the oxygen concentration sensor reaches the slag-metal interface and a sharp change in the oxygen concentration sensor is detected, thus identifying the location of the slag-metal interface. The detector continues to move outside the vessel until the oxygen concentration sensor reaches and crosses the atmosphere-slag interface. Even if this measuring lance can accurately detect the location of the slag-metal interface, the location of the atmosphere-slag interface is not for the following reasons. When the oxygen probe moves through the slag on its way out of the vessel, the oxygen probe is covered and contaminated with the slag material, and the slag material endangers the measurement of the location of the air-slag interface because the oxygen probe continues to measure the oxygen content of the slag adhering to its surface for at least some time after the oxygen probe is withdrawn from the slag and into the surrounding air.

[0012] To ensure the high quality of metal parts required by the industry, it is necessary to monitor some parameters of the molten metal flowing through the vessel. If the same sensor cannot be used to measure two different parameters of the facility, the number of terminals available on the analysis device increases accordingly. For example, if the same analysis device is connected to a first sensor (described above) that measures the thickness of the slag and a second sensor that measures the temperature of the slag and / or the molten metal, two sets of two terminals, i.e., four terminals, are required to measure the voltage or current from the two sensors. If a third sensor is used, the analysis device should be provided with three sets of two terminals, i.e., six terminals. This means that every time multiple sensor types are connected, a new analysis device with the corresponding number of terminals is required.

[0013] Therefore, there is still a need for a measurement lance that accurately measures the positions of both the atmosphere - slag interface and the slag - metal interface in a single run and requires minimal changes to the interfaced analysis device. In particular, the measurement lance should be suitable for performing measurements of the positions of the atmosphere - slag interface and the slag - metal interface, in addition to existing measurements such as temperature, without requiring additional electrical terminals for connection to an existing analysis device. The present invention proposes such a measurement lance. These and other advantages will be explained in detail in the following sections.

Summary of the Invention

[0014] The appended independent claims define the invention. The dependent claims define preferred embodiments.

[0015] The present invention relates to a measurement lance for measuring, in a single measurement run, the position of the atmosphere - slag interface between the atmosphere and a slag layer on molten metal (has) and the position of the slag - metal interface between the slag layer and the molten metal, the measurement lance comprising: · a transport tube extending along an axis (X) between a proximal end and a distal end located downstream of the proximal end; · a measurement unit coupled to the distal end of the transport tube and configured to pass through the slag layer, the measurement unit comprising: · an electric circuit configured to detect the atmosphere - slag interface; · a slag - metal interface detection unit located downstream of the distal end and provided with at least first and second electrical measurement terminals and configured to measure a value of a first material property at the position of the slag - metal interface between the slag layer and the molten metal; and · preferably, a sensor unit provided with first and second electrical sensor terminals and configured to measure a value of a second material property of the slag layer and the molten metal. · A cap configured to surround the slag-metal interface detection unit and optionally the sensor unit and separate the slag-metal interface detection unit from the external environment. The electrical circuit includes a first conductive element having a first end conductively coupled to the first electrical measurement terminal and / or the first electrical sensor terminal (9ta), and a second end disposed outside the cap, preferably downstream of the cap. The electrical circuit includes a temperature fuse located between the first end and the second end of the first conductive element and configured to melt and open the electrical circuit after the first conductive element contacts the air-slag interface. The term "downstream" is defined along the axis (X) in the direction from the proximal end to the distal end.

[0016] Preferably, the measurement lance includes the sensor unit which is a thermocouple, and the first and second electrical sensor terminals are configured to be electrically connected to an analysis device, which is preferably a voltage measurement device.

[0017] The slag-metal interface detection unit can have any one of the following detector configurations. · In the oxygen-configuration of the measurement lance according to the present invention, the slag-metal interface detection unit includes an oxygen probe for measuring the concentration of oxygen, the oxygen probe includes an oxygen cell connected to the first electrical measurement terminal and a reference electrode connected to the second electrical measurement terminal, the cap is configured to deteriorate and expose the oxygen probe to the ambient environment when exposed to a predetermined temperature for a predetermined exposure time, and the temperature fuse is preferably configured to melt at least when the cap deteriorates. · In the inductive configuration, the slag-metal interface detection unit includes an induction coil for detecting a change in the magnetic permeability of the ambient environment.

[0018] The electrical circuit can also have any one of the following electrical configurations that can be combined with any one of the aforementioned detector configurations in any manner.

[0019] In the sensor configuration of the electrical circuit of the measurement lance according to the present invention, · The first end of the first conductive element is conductively coupled to the first electrical measurement terminal, and the second end of the first conductive element is conductively coupled to the contact sensor. · The electrical circuit includes a second conductive element, and the second conductive element includes a first end that is conductively coupled to the second electrical measurement terminal and a second end of the second conductive element that is conductively coupled to the contact sensor.

[0020] The contact sensor is · A mechanical switch that is set to an open position and configured to move to a closed position when a mechanical force corresponding to the force generated upon contact between the mechanical switch and the air-slag interface is applied, thereby conductively connecting the first and second conductive elements, and the temperature fuse is configured to blow when the switch reaches the closed position, a switch configuration including a mechanical switch, or · A piezoelectric detector configured to generate an electric current when a mechanical force corresponding to the force generated upon contact between the piezoelectric detector and the air-slag interface is applied, and the temperature fuse is configured to blow after the piezoelectric detector generates an electric current, and it can be selected between a piezoelectric configuration.

[0021] In the ground configuration of the electrical circuit, the electrical circuit includes only the first conductive element. The slag and the second electrical measurement terminal are grounded to the earth.

[0022] In a preferred embodiment of the sensor configuration of the electrical circuit of a lance including a sensor unit (e.g., a thermocouple), · The first end of the first conductive element is conductively coupled to the first electrical sensor terminal, and the second end of the first conductive element is conductively coupled to the contact sensor. · The second conductive element includes a first end conductively coupled to the second electrical sensor terminal and a second end thereof conductively coupled to the contact sensor.

[0023] In a preferred embodiment, a part of the outer surface of the cap is conductive and is included in the first conductive element or optionally the second conductive element.

[0024] For example, a mechanical switch in a switch configuration of an electrical circuit is preferably · A second member belonging to the second conductive element and firmly attached to the cap, · A first member belonging to the first conductive element, non-conductively separated from the second member, and attached to the cap via an elastic member, wherein the elastic member is configured to separate the first member from the second member and to deform upon application of the mechanical force to conductively connect the first and second members.

[0025] In a preferred embodiment of a measurement lance including a sensor unit and having a sensor configuration in an electrical circuit, · The first end of the first conductive element is electrically coupled to both the oxygen cell of the oxygen probe and the first electrical sensor terminal, or · The second conductive element is connected to both the reference electrode of the oxygen probe and the second electrical sensor terminal.

[0026] The present invention also relates to a method for determining the position of an air-slag interface between the atmosphere and a slag layer on molten metal and the position of a slag-metal interface (2sm) between the slag layer and the molten metal in a metallurgical vessel, the method comprising - Positioning the measurement lance according to any one of the preceding claims on the air-slag interface with the second end of the first conductive element positioned closest to the air-slag interface, - Starting to measure the vertical position of the measurement lance along a vertical axis (Z) substantially perpendicular to the air-slag interface, - Starting to measure the value of the first material property using the slag-metal interface detection unit (8); - Starting to measure the electrical property of the first conductive element; - Translating the measurement lance downward along at least the vertical component parallel to the vertical axis (Z) and toward the air-slag interface; - Detecting the gradient of the electrical property of the first conductive element, and when it indicates that the second end of the first conductive element has contacted the air-slag interface, recording the vertical position of the measurement lance as the position (has) of the air-slag interface; - Continuing to translate the measurement lance sufficiently downward along the vertical component to ensure that the measurement unit is within the molten metal beyond the slag-metal interface; - Enabling the temperature fuse to blow and conductively separate the first end of the first conductive element from the second end; - Measuring the value of the first material property using the slag-metal interface detection unit, and maintaining the measurement unit within the molten metal (3) until the measured value of the first material property becomes substantially constant; - Translating the slag-metal interface detection unit upward along the vertical component and toward the slag-metal interface; - Detecting a steep gradient of the value of the first material property measured using the slag-metal interface detection unit, and recording the vertical position of the measurement lance as the position of the slag-metal interface; - Continuing to translate the measurement lance upward along the vertical component until the measurement lance is completely in the atmosphere, including.

[0027] In a preferred embodiment of the method according to the present invention, the slag-metal interface detection unit is an oxygen probe for measuring the concentration of oxygen, as defined above, and the measurement lance is · A sensor unit composed of a thermocouple for measuring the value of the temperature of the surrounding environment, · A mechanism for correcting the concentration of oxygen measured by the oxygen probe according to the temperature measured by the thermocouple.

[0028] To more fully understand the nature of the present invention, reference is made to the following detailed description in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14(a)

Figure 14(b)

Figure 15(a)

Figure 15(b)

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Mode for Carrying Out the Invention

[0030] As shown in FIG. 13, the present invention relates to a measuring lance (1) that measures, in one measurement run, on the one hand, the position (has) of the air - slag interface (2as) between the air (4) and the slag layer (2) on the molten metal (3), and on the other hand, the position (hsm) of the slag - metal interface (2sm) between the slag layer (2) and the molten metal (3). As shown in FIGS. 1 and 2, the measuring lance (1) includes a carrier pipe (5) that extends along an axis (X) between a proximal end (5p) and a distal end (5d) located downstream of the proximal end (5p). The term "downstream" is used herein with respect to the direction of movement of the measuring lance when the measuring lance passes through the slag and then enters the molten metal and is immersed in the container. For example, the carrier pipe (5) may be a pole or an elongated hollow pipe. As shown in FIGS. 1 and 2, the measuring lance (1) includes a measuring unit (6) that is coupled to the distal end (5d) of the carrier pipe (5) and is configured to pass through the slag layer (2). The measuring unit (6) · An electric circuit (7) configured to detect the air - slag interface (2as), and · A slag - metal interface detection unit (8) located downstream of the distal end (5d) of the carrier pipe (5) and having at least a first electrical measurement terminal (8ta) and a second electrical measurement terminal (8tb), wherein the slag - metal interface detection unit (8) is configured to measure the value of a first material property at the position (hsm) of the slag - metal interface (2sm) between the slag layer (2) and the molten metal (3), a metal interface detection unit (8), and · A cap (10) that surrounds the slag - metal interface detection unit (8) and is configured to separate the slag - metal interface detection unit (8) from the external environment of the cap (10).

[0031] As shown in FIG. 13, the metallurgical equipment is provided with means for driving the measuring lance in two directions along the vertical axis (Z) at a controlled speed so that the position of the measuring lance along the vertical axis (Z) is always known and recorded.

[0032] As shown in FIGS. 3 and 4, the measuring unit (6) preferably includes a sensor unit (9) having a first electrical sensor terminal (9ta) and a second electrical sensor terminal (9tb), and the sensor unit (9) is configured to measure values of second material properties of the slag layer (2) and the molten metal (3). The sensor unit (9) is preferably enclosed within a cap (10) to separate the sensor unit (9) from the external environment, but this is not necessary.

[0033] As shown in FIGS. 1 to 12, the measuring lance (1) includes a first conductive element (11) having a first end to which an electrical circuit (7) is conductively coupled to a first electrical measurement terminal (8ta) and / or a first electrical sensor terminal (9ta), and a second end disposed outside, preferably downstream, of the cap (10), where the term "downstream" in the present invention is defined along the axis (X) in the direction extending from the proximal end (5p) to the distal end (5d). The second end of the first conductive element (11) preferably defines the distal end of the measuring lance, that is, when the measuring lance enters the container through the slag layer along the vertical axis (Z) and enters the molten metal, it first contacts the air-slag interface.

[0034] The measuring lance (1) also includes a temperature fuse (13) located between the first end and the second end of the first conductive element (11) and configured to melt after the first conductive element (11) contacts the air-slag interface (2as) to open the electrical circuit (7).

[0035] Electrical circuit (7) The electrical circuit (7) is specifically configured to determine the position of the air - slag interface (2as). The principle of the electrical circuit (7) is that it is in a first electrical configuration while completely in the atmosphere (4), and when it contacts the air - slag interface (2as), it immediately shifts to a second electrical configuration. Some embodiments are proposed.

[0036] In the first configuration (= "grounding configuration") shown in FIGS. 1, 3, 6, 9, and 10, only the first conductive element (11) is coupled to the measuring unit (6). As described above, the first conductive element (11) has a first end conductively coupled to the first electrical measurement terminal (8ta) and / or the first electrical sensor terminal (9ta), and a second end disposed at a defined position along the outside of the cap (10) and the axis (X) of the measuring unit. The second end is preferably disposed downstream of the cap (10) so as to be the first component of the measuring lance that contacts the air - slag interface when the measuring lance is immersed in the container. This is advantageous because when contact occurs between the second end and the air - slag interface, the air - slag interface is not disturbed as the measuring lance penetrates the slag layer. The slag is electrically grounded. As shown in FIGS. 6 and 10, when the second end of the first conductive element (11) contacts the electrically grounded slag layer (2), the entire electrical circuit (7) is electrically grounded and short - circuited. When this occurs, the analysis device (16) measures a zero - voltage difference or current indicating the position of the air - slag interface (2as). This embodiment can be implemented in metallurgical equipment, and the slag is conductive, but not always.

[0037] In the second configuration (= "sensor - configuration") shown in FIGS. 2, 4, 5, 7, 8, 11, and 12, the first end of the first conductive element (11) is conductively coupled to the first electrical measurement terminal (8ta) and / or the first electrical sensor terminal (9ta), and the second end of the first conductive element (11) is conductively coupled to the contact sensor (14). The electrical circuit (7) includes a second conductive element (12) having a first end conductively coupled to the second electrical measurement terminal (8tb) and / or the second electrical sensor terminal (9tb) and a second end thereof conductively coupled to the contact sensor (14). This embodiment can be implemented regardless of whether the slag is conductive or not.

[0038] As shown in FIGS. 2, 4, 7, 8, 11, and 12, the contact sensor (14) is preferably a mechanical switch (14s) (= "switch - configuration"), and the mechanical switch (14s) is set to an open position and is configured to move immediately to a closed position when it contacts the air - slag interface (2as) when a mechanical force is applied to the air - slag interface (2as). Thus, the electrical circuit (7) is closed, so the electrical circuit (7) is short - circuited when the first conductive element (11) is conductively connected to the second conductive element (12). When this occurs, a zero - voltage or current is measured by the analysis device (16), which indicates the position of the air - slag interface (2as).

[0039] Alternatively, as shown in FIG. 5, the contact sensor (14) may be a piezoelectric detector (14p) (= "piezoelectric configuration"), and the piezoelectric detector (14p) is configured to generate a current when a mechanical force corresponding to the force generated when the piezoelectric detector (14p) is brought into contact with the air - slag interface (2as) is applied. When this occurs, a different voltage or current is measured by the analysis device (16), which indicates the position of the air - slag interface (2as).

[0040] As shown in Fig. 21 (prior art), the first and optionally the second conductive elements (11, 12) were able to form an electrical circuit (7) independent of the electrical measurement terminals and the sensor terminals. However, this increased the number of electrical terminals connected to the analysis device (16). And this seemingly simple modification of adding the electrical circuit (7) to the measurement lance requires providing a new analysis device (16) with more connection terminals. According to the present invention, the first and optionally the second conductive elements (11, 12) do not require new connection terminals for coupling the electrical circuit (7) to the analysis device, so that they are coupled to either one, optionally any two of the first and second electrical measurement terminals (8ta, 8tb) of the slag-metal interface detection unit (8) or the first and second electrical sensor terminals (9ta, 9tb) of the sensor unit (9). Thus, the same analysis device (16) can be used with a measurement lance without the electrical circuit (7) according to the prior art and with a measurement lance provided with the electrical circuit (7) according to the present invention.

[0041] When the second end of the first conductive element (11) or the contact sensor (14) contacts the air-slag interface (2as), the electrical circuit (7) immediately transitions to a second electrical configuration that is a short circuit in the case of the ground-and-switch configuration and a stress-voltage in the case of the piezoelectric configuration. This is not important when the electrical circuit (7) is independent of the slag-metal interface detection unit (8) or the sensor unit (9). However, as discussed above, in order to reduce the number of electrical terminals connected to the analysis device, the first and optionally the second conductive elements (11, 12) are coupled to either one or two of the first and second electrical measurement terminals (8ta, 8tb) of the slag-metal interface detection unit (8) and the first and second electrical sensor terminals (9ta, 9tb) of the sensor unit (9). This has the effect that the analysis device (16) measures an electrical signal that is strongly affected by the second electrical configuration of the electrical circuit (7). This varies depending on the immersion depth of the piezoelectric detector (14p) and the density of the medium it passes through (i.e., the slag layer and the molten metal), and in particular, · When the second electrical configuration is a short circuit and zero-voltage or current can be measured by the analysis device (16), and · Applies when the contact sensor (14) is a piezoelectric detector (14p).

[0042] In such a situation, the slag-metal interface detection unit (8) and / or the sensor unit (9) cannot measure any parameters at all, or at least cannot measure them with sufficient accuracy. Therefore, it is necessary to "neutralize" the electrical circuit that has completed the function of identifying the position of the atmosphere-slag interface (2as). As a result, from that moment on, both the slag-metal interface detection unit (8) and the sensor unit (9) are configured to be able to measure the corresponding parameters again. "Neutralizing" the electrical circuit means, in this specification, modifying the electrical circuit (7) so as not to affect the voltage difference between the first and second electrical measurement terminals (8ta, 8tb) measured by the analysis device (16), or between the first and second electrical sensor terminals (9ta, 9tb).

[0043] To "neutralize" the influence of the electrical circuit (7) in the case of the second electrical configuration, the present invention proposes opening the electrical circuit. In all embodiments except for the piezoelectric detector (14p), this corresponds to the first electrical configuration. When the electrical circuit is opened, the slag-metal interface detection unit (8) and the sensor unit (9) can measure the parameters they were designed for again. To open the electrical circuit (7), the thermal fuse (13) is arranged between the first end and the second end of the first conductive element (11). The thermal fuse is configured to melt and open the electrical circuit (7) when the first conductive element (11) is exposed to high temperature after contacting the atmosphere-slag interface (2as).

[0044] Thermal fuse (13) The thermal fuse (13) is configured to blow and open the electrical circuit (7) after the first conductive element (11) contacts the atmosphere - slag interface (2as). Preferably, the measuring unit (6) is configured to permanently maintain the opening of the electrical circuit (7) when the thermal fuse (13) blows and the measuring unit (6) comes into contact with the molten metal (3).

[0045] Various parameters must be controlled to establish the time when the thermal fuse blows after the first conductive element (11) contacts the slag layer (2) and the position along the vertical axis (Z). It is essential that the thermal fuse does not blow before the position of the atmosphere - slag interface (2as) is determined by the electrical circuit (7) as described above. The thermal fuse must blow before the slag - metal interface detection unit (8) reaches the slag - metal interface (2sm) when the lance is withdrawn from the vessel. These two events define the time window during which the thermal fuse blows. The time window can be easily converted into a corresponding position window. The position window is defined within the position of the measuring lance when: · when the contact sensor (14) or the second end of the first conductive element (11) contacts the atmosphere - slag interface (2as), and · when the slag - metal interface detection unit (8) is downstream and at the level of the slag - metal interface (2sm), i.e., within the molten metal (3), when the measuring lance is withdrawn from the vessel.

[0046] The thermal fuse blows when it reaches a predetermined blow - off temperature. Thus, the instant and position at which the thermal fuse blows depend on the type of thermal fuse used. It also depends on the temperature of the surrounding external environment, including the temperature of the slag layer and the molten metal. Finally, it depends on the heat transfer rate from the external environment to the thermal fuse. This can vary significantly when the thermal fuse is enclosed within a housing, reducing the heat transfer rate that depends on the insulating properties of the housing.

[0047] The thermal fuse (13) may be arranged in the recess or on the outer surface of the measuring unit (6). Preferably, the thermal fuse (13) is attached to the measuring unit (6) or fully embodied or incorporated in a housing forming an integral part of the measuring unit (6), and the walls of the housing are made of a material that forms thermal insulation between the inside and the outside of the housing. The wall material can be, for example, cardboard or a refractory material. The wall material is configured to thermally shield the thermal fuse (13) from the high temperatures of the slag layer and the molten metal. When the measuring unit (6) pierces the slag layer (2) or the molten metal (3), the increase in the temperature of the fuse (13) caused by the heat transmitted from the slag layer (2) or the molten metal (3) to the fuse (13) can thus be retarded by the heat-insulating effect of the housing wall. For a specific type of thermal fuse that melts at a predetermined temperature, the type and thickness of the wall material shielding the fuse (13) can be adjusted by the designer to ensure that the thermal fuse reaches the predetermined temperature and melts within the time window or position window described above, that is, between the moment the air-slag interface is detected and the moment the slag-metal interface detection unit (8) reaches the slag-metal interface (2sm) when the measuring lance is withdrawn from the vessel.

[0048] The displacement speed of the measuring lance must be adjusted to the heat exchange rate between the external environment and the thermal fuse to ensure that the thermal fuse melts reliably within the time window and the position window. Thus, if the housing is damaged when the thermal fuse is in the slag layer or the molten metal, the temperature of the thermal fuse will rise almost instantaneously and melt. Therefore, the position window can also be determined by the degradation temperature of the housing. A person skilled in the art can easily optimize these parameters, namely, the heat exchange rate, the displacement speed and the housing degradation temperature, to ensure that the thermal fuse reaches the predetermined melting temperature within the time window and the position window.

[0049] Preferably, the thermal fuse (13) is configured to blow when it reaches a temperature between 100 °C and a temperature 5 °C lower than the maximum value of the temperature of the slag layer (2) or the molten metal (3), preferably a temperature exceeding 150 °C. The thermal fuse is preferably enclosed within a housing that insulates it from the external environment and reduces the heat exchange rate between the external environment and the thermal fuse.

[0050] Electrical terminals (8ta, 8tb, 9ta, 9tb) As shown in FIGS. 1 to 4, the first and second electrical measurement terminals (8ta, 8tb) are configured to electrically connect the slag-metal interface detection unit (8) to the analysis device (16). This connection is preferably carried out through the transport pipe (5), preferably via a slag-metal interface detection unit conductive wire that extends along the entire lumen between the proximal end and the distal end (5p, 5d) of the hollow transport pipe (5). There are two slag-metal interface detection unit conductive wires. The analysis device (16) is configured to measure or detect one or more electrical parameters between the first and second electrical measurement terminals (8ta, 8tb), and the one or more electrical parameters are preferably selected from voltage amplitude, current amplitude, electrical resistance, and short circuit. The electrical parameters between the first and second electrical measurement terminals (8ta, 8tb) measured by the analysis device (16) are useful in the present invention for determining the position of the slag-metal interface (2sm).

[0051] As shown in FIGS. 3 to 4, the first and second electrical sensor terminals (9ta, 9tb) are configured to electrically connect the sensor unit (9) to the second analysis device (16). In FIGS. 3 and 4, the first and second analysis devices (16) are represented as a single device. This is a preferred embodiment. In other figures, the first and second analysis devices are represented separately for the purpose of distinguishing the description between the connection from the electrical sensor terminals (9ta, 9tb) to the electrical measurement terminals (8ta, 8tb).

[0052] This connection is preferably carried out via a sensor unit conductive wire that passes through the transfer tube (5) and preferably extends along the entire lumen between the proximal and distal ends (5p, 5d) of the hollow transfer tube (5). There are two sensor unit conductive wires. The second analysis device (16) is configured to measure or detect one or more electrical parameters between the first and second electrical sensor terminals (9ta, 9tb) representing the properties of the slag and molten metal, such as temperature. The one or more electrical parameters are preferably selected from voltage amplitude, current amplitude, electrical resistance, and short circuit. As shown in FIGS. 3 and 4, the first and second analysis devices can be separate or belong to the same analysis device.

[0053] As shown in FIGS. 5 to 6, when the measuring lance includes a sensor unit (9), preferably, the slag-metal interface detection unit (8) and the sensor unit (9) share at least one conductive wire connected to the first and second analysis devices, and are connected to the analysis device (16) to reduce the number of conductive wires connecting all the units. For example, one of the first or second electrical measurement terminals (8ta, 8tb) can be electrically connected to one of the first or second electrical sensor terminals (9ta, 9tb) and share the same potential.

[0054] Sensor unit (9) As shown in FIG. 7, the sensor unit (9) of the measuring lance (1) is preferably a thermocouple (15), and the second material property measured by the sensor unit (9) is temperature. The first and second electrical sensor terminals (9ta, 9tb) are configured to be electrically connected to a second analysis device (16) configured to measure an electrical parameter including at least a voltage or current between the first and second electrical sensor terminals (9ta, 9tb). Preferably, the analysis device (16) is configured to calculate a numerical value of temperature in degrees Celsius or Kelvin, for example, based on the electrical signal (e.g., voltage) measured between the first and second electrical sensor terminals (9ta, 9tb). Preferably, the analysis device (16) is configured to display the numerical value of temperature to the user.

[0055] Preferably, the cap (10) surrounds the thermocouple (15), and the cap (10) is configured to deteriorate when exposed to a predetermined temperature for a predetermined exposure time so that the thermocouple (15) contacts the surrounding environment, which is, for example, the atmosphere (4), molten metal (3) or slag (2), and its temperature can be measured, thereby exposing the thermocouple (15) to the surrounding environment of the measurement head (6).

[0056] The thermocouple (15) can be a metal thermocouple or a ceramic thermocouple. The sensor unit (9) can also include a thermistor or be a thermistor. The second material property measured by the sensor unit (9) is temperature, and the second analysis device (16) is preferably configured to measure electrical parameters including at least electrical resistance.

[0057] Oxygen probe (8o) In addition to measuring the oxygen concentration (an important characteristic for ensuring the quality of the casting) in the slag layer (2) and the molten metal (3), the only function of the slag-metal interface detection unit (8) according to the present invention is to detect the position of the slag-metal interface (2sm) because the position of the air-slag interface is detected by the electric circuit (7) as described above. In a preferred embodiment of the measurement lance (1) according to the present invention, the slag-metal interface detection unit (8) includes an oxygen probe (8o) for measuring the concentration of oxygen. As shown in FIGS. 7 to 8, the oxygen probe (8o) includes an oxygen cell (8c), preferably a zirconia cell, connected to a first electrical measurement terminal (8ta), and a reference electrode (8r) connected to a second electrical measurement terminal (8tb). The cap (10) surrounding the oxygen probe (8o) is configured to deteriorate and expose the oxygen probe (8o) to the ambient environment of the measurement head (6) when exposed to a predetermined temperature for a predetermined exposure time. The predetermined temperature at which the cap (10) deteriorates is preferably between 1350°C and 1500°C, more preferably between 1400°C and 1450°C, and the predetermined exposure time at which the cap (10) deteriorates is preferably between 1.0 second and 3.0 seconds, between 1.5 seconds and 2.0 seconds. As will be described below, the cap (10) is designed and dimensioned so that when the measurement lance is withdrawn from the vessel, it deteriorates before reaching the molten metal (3) downstream of the slag layer (2) in order to expose the oxygen probe (8o) to the molten metal first before the oxygen probe contacts the slag layer (2). When the oxygen probe (8o) is exposed to the molten metal (3), the measurement of the oxygen concentration in the molten metal can be started. The measurement lance can be withdrawn from the vessel, and when the oxygen probe (8o) reaches the slag-metal interface (2sm), the sudden change in the measured oxygen concentration is measured. As the measurement lance continues to move outside the vessel, similar to a prior art measurement lance provided with an oxygen probe (8o), the oxygen probe (8o) passes through the slag layer with impurities adhering to its surface until it reaches the air-slag interface (2as), and the oxygen probe (8o) should theoretically measure the second sudden change in the measured oxygen concentration at the air-slag interface (2as). However, the oxygen probe (8o) is contaminated by the impurities adhering to its surface and does not immediately measure the change in the oxygen concentration.The advantage of the present invention over the prior art measuring lance is that the position of the air - slag interface (2as) does not depend on the oxygen probe (8o), which, for the reasons mentioned above, is of low reliability but is already very accurately determined by the electrical circuit (7).

[0058] As shown in FIGS. 14 and 15, in the measuring lance (1) including the oxygen probe (8o), the temperature fuse (13) is · configured to melt either before the cap (10) deteriorates and exposes the oxygen probe (8o) and optionally the sensor unit (9) to the ambient environment (see FIGS. 14(a) and 14(b)), or · only after the cap (10) has deteriorated. Since this must occur when the cap is immersed in the molten metal, it is important that the temperature fuse rapidly melts and opens the electrical circuit (7) afterwards so that the analysis unit can start measuring the oxygen concentration.

[0059] Induction coil (8i) As an alternative to the oxygen probe (8o), the slag - metal interface detection unit (8) of the measuring lance (1) can include an induction coil (8i) that detects changes in the magnetic permeability of the ambient environment, as shown in FIGS. 9 - 10. The cap (10) surrounding the induction coil (8i) is configured to separate the induction coil (8i) from the external environment outside the cap (10) and not to deteriorate when exposed to the temperatures of the molten metal (3) and the slag (2) during the measurement operation, and is also configured not to deteriorate when passing through the slag layer (2).

[0060] Electrical circuit (7) including contact sensor (14) In one embodiment, the electrical circuit (7) includes first and second conductive elements (11, 12) together with the contact sensor (14). As shown in FIGS. 2, 4, 5, 7, 8, 11 and 12, the sensor (14) is coupled to the second ends of both the first and second conductive elements (11, 12). To maintain the same total number of electrical terminals connected to the analysis device (16) as in the prior art measuring lance without the electrical circuit (7), the first and second conductive elements (11, 12) are · The first end of the first conductive element (11) is · Conductively coupled to the first electrical measurement terminal (8ta) (see FIG. 1), or · An embodiment that is conductively coupled to the first electrical sensor terminal (9ta) (see FIG. 4), and · The first end of the second conductive element (12) is · Conductively coupled to the second electrical measurement terminal (8tb) (see FIG. 1), or · An embodiment that is conductively coupled to the second electrical sensor terminal (9tb) (see FIG. 4), can be conductively coupled to any one combination.

[0061] Connecting the first end of either the first and second conductive elements (11, 12) to the first or second electrical sensor terminals (9ta, 9tb) is, of course, only possible if the measurement lance includes the sensor unit (9). If there is no sensor unit (9), the first ends of both the first and second conductive elements (11, 12) must be connected to the first and second electrical measurement terminals (8ta, 8tb), respectively.

[0062] The contact sensor (14) is preferably disposed downstream of the cap (10). Preferably, the contact sensor (14) is the most downstream part of the measurement lance (1). In this way, the sensor contacts and breaks the air - slag interface when the lance is immersed in the container, enabling a more accurate measurement than when the sensor reaches the air - slag interface after another part of the measurement lance has already contacted and broken the interface. It is the first component of the measurement lance.

[0063] In one embodiment, the contact sensor (14) is a mechanical switch (14s) set to an open position, and the first and second conductive elements (11, 12) are non-conductively separated, i.e., separated and not in electrical contact. The mechanical switch (14s) is configured to move to a closed position upon application of a mechanical force corresponding to the force generated upon contact of the mechanical switch (14s) with the atmosphere-slug interface (2as), thereby electrically connecting the first and second conductive elements (11, 12). The thermal fuse (13) is configured to blow when the mechanical switch (14s) moves from the open position to the closed position or thereafter.

[0064] The first and second conductive elements (11, 12) can each be formed independently of one another by a conductive cable or wire or a conductive portion of any component of the measuring unit. For example, as shown in FIGS. 11 and 12, the second conductive element (12) can be part of a cap (10), such as a conductive strip made of a conductive material, or the entire cap (10) can be conductive and form the second conductive element (12). The cap or its conductive strip must be electrically coupled to the second electrical measurement or sensor terminal (8tb, 9tb). In these configurations, the mechanical switch (14s) is · Conductively connected to the second end of the first conductive element (11) or forming an integral part of the second end, a first member (14a), and · Can include a second member (14b) firmly attached to or forming an integral part of the cap (10) or its conductive strip.

[0065] The first member (14a) is elastically separated from the second member (14b). The elasticity can be achieved by the elastic properties of the first conductive element (11) or by an elastic member (17) such as a spring that can be (non-conductively) attached to the cap (10) as shown in FIGS. 11 and 12. As shown in FIGS. 11 and 12, the elastic member (17) is set to naturally separate the first member (14a) from the second member (14b) and deforms upon application of a mechanical force corresponding to the force generated when the mechanical switch (14s) contacts the air-slag interface (2as), configured to conductively connect the first and second members (14a, 14b). In other words, the elastic member (17) is naturally set to position the first and second members (14a, 14b) so that there is no electrical contact between them, and deforms upon application of a mechanical force to cause electrical contact between the first and second members (14a, 14b), resulting in a short circuit that is immediately identified by the analysis device (16).

[0066] As an alternative to the mechanical switch (14s), the contact sensor (14) may be a piezoelectric detector (14p), which is configured to generate an electric current upon application of a mechanical force corresponding to the force generated when the piezoelectric detector (14p) contacts the air-slag interface (2as). The thermal fuse (13) is configured to blow when or after the piezoelectric detector (14p) generates an electric current.

[0067] In an embodiment of the measuring lance (1) including the contact sensor (14) and the sensor unit (9), preferably, as shown in FIGS. 8, 11, and 12, the first end (11) of the first conductive element is electrically connected to both the first electrical measurement terminal (8ta) and the first electrical sensor terminal (9ta). Alternatively, the second conductive element (12) is electrically connected to both the second electrical measurement terminal (8tb) and the second electrical sensor terminal (9tb) (not shown).

[0068] An electrical circuit (7) having a single first conductive element (11) Alternatively, as shown in FIGS. 1, 3, 6, 9, and 10, the electrical circuit (7) does not include the second conductive element (12) and the contact sensor (14). The second end of the first conductive element (11), which is disposed outside the cap (10), preferably downstream, includes a downstream-facing electrical contact tip. Preferably, the electrical contact tip is the most downstream part of the measurement unit (6). As shown in FIG. 1, when the first end of the first conductive element (11) is electrically connected to the first electrical measurement terminal (8ta), the second electrical measurement terminal (8tb) is connected to the ground potential. In this embodiment, the slag layer, which must be conductive, is electrically grounded to the same ground as the second electrical measurement terminal (8tb). As shown in FIG. 3, when the first end of the first conductive element (11) is electrically connected to the first electrical sensor terminal (9ta), the second electrical sensor terminal (9tb) is connected to the ground potential.

[0069] Since both the slag layer (2) and the second electrical measurement or sensor terminal (8tb, 9tb) are grounded to the same ground, as soon as the electrical contact tip at the second end of the first conductive element (11) contacts the air-slag interface (2as), the first conductive element (11) is also grounded to the ground and short-circuited. The analysis device can detect that there is no potential difference between the first electrical measurement terminal and the second electrical measurement terminal (8ta, 8tb) indicating the position of the air-slag interface (2as).

[0070] Cap (10) The cap (10) protects the slag-metal interface detection unit (8) and optionally the sensor unit (9) from contact with the slag layer (2) and the molten metal (3) when the measurement lance is immersed in the vessel. When the slag-metal interface detection unit (8) includes an induction coil (8i), the cap (10) must resist and protect the slag-metal interface detection unit (8) from contact with the slag and the metal throughout the entire measurement operation. When the slag-metal interface detection unit (8) includes an oxygen probe (8o) that must come into contact with a medium in which the O2 concentration is measured by the oxygen probe (8o), the cap does not deteriorate before being immersed in the molten metal (3) downstream of the slag-metal interface (2sm). When entering the molten metal, the cap (10) preferably deteriorates rapidly to shorten the measurement operation. It is important that the cap (10) does not deteriorate while still in the slag layer (2) because the oxygen probe (8o) is exposed to the slag and impurities adhere to its surface, contaminating the measurement value. The cap (10) can be configured to deteriorate chemically upon contact with the slag. However, the cap (10) preferably deteriorates thermally when entering the molten metal (3) through the slag layer (2) to expose the oxygen probe (8o) to the molten metal (3).

[0071] Depending on the requirement (oxygen probe (8o) or induction coil (8i)), and the temperature of the slag layer and the molten metal, the cap (10) can be manufactured from metal, cardboard, or a combination thereof. In one embodiment, a part of the outer surface (10s) of the cap (10) is conductive and is included in one of the first or second conductive elements (11, 12), preferably the second conductive element (12). Preferably, the cap (10) is configured to be used with molten steel and can be manufactured from steel having a melting point between 1520 °C and 1540 °C.

[0072] Method The present invention also relates to a method for determining the position (has) of the air - slag interface (2as) between the air (4) and the slag layer (2) on the molten metal (3) and the position (hsm) of the slag - metal interface (2sm) between the slag layer (2) and the molten metal (3) in a metallurgical vessel. The method comprises · positioning the measurement lance (1) according to the present invention completely in the air (4) on the air - slag interface (2as) with the second end of the first conductive element (11) positioned closest to the air - slag interface (2as); · starting to measure, preferably record, the vertical position of the measurement lance (1) along a vertical axis (Z) substantially perpendicular to the air - slag interface (2as); · starting to measure, preferably record, the value of a first material property using the slag - metal interface detection unit (8); · starting to measure the electrical property of the first conductive element (11), preferably detecting a short - circuit between the first conductive element (11) and the ground potential; · moving the measurement lance (1) downward, i.e., towards the air - slag interface (2as), along at least a vertical component parallel to the vertical axis (Z); · detecting the gradient of the electrical property of the first conductive element (11), and when it indicates that the second end of the first conductive element (11) has contacted the air - slag interface (2as), recording the vertical position of the measurement lance (1) as the position (has) of the air - slag interface (2as); · continuing to move the measurement lance (1) downward along at least the vertical component until it reaches the slag - metal interface (2sm) and contacts the molten metal (3) with the measurement unit (6); · when the temperature fuse (13) melts, thus enabling the first end of the first conductive element (11) to be conductively separated from the second end and electrically insulated; · Using the slag-metal interface detection unit (8), measure the value of the first material property, and maintain the measurement unit (6) in the molten metal (3) until the measured value of the first material property becomes substantially constant, representing the value of the first material property of the molten metal (for example, until the value changes by 10% or less, preferably 5% or less). · Move the slag-metal interface detection unit (8), preferably the oxygen probe (8o), upward along the vertical component, that is, translate it parallel to the slag-metal interface (2sm). · When detecting a sudden change in the value of the first material property measured using the slag-metal interface detection unit (8), record the vertical position of the measurement lance (1) as the position (hsm) of the slag-metal interface (2sm) from the value representing the first material property of the molten metal to the value representing the first material property of the slag. · Continue to move the measurement lance (1) upward along the vertical component until the entire measurement lance (1) enters the atmosphere (4).

[0073] Preferably, in the method according to the present invention, the slag-metal interface detection unit (8) of the measurement lance (1) is an oxygen probe (8o) for measuring the oxygen concentration. Preferably, the measurement lance (1) · Includes a sensor unit (9) consisting of a thermocouple (15) for measuring the value of the ambient temperature, · Preferably, a mechanism for correcting the oxygen concentration measured by the oxygen probe (8o) according to the temperature measured by the thermocouple (15).

[0074] Operating principle - Figures 14 and 15 Figures 13 to 15 show various stages of a method for measuring the position and thickness of the slag layer (2) using the measurement lance (1) according to the present invention. The measurement lance (1) according to the present invention · Move the measurement lance downward along the vertical axis (Z) with the measurement unit moving from the atmosphere (4), through the slag layer (2), and reaching the molten metal (3) and entering the container (refer to stages (A), (B) to (E) in Figures 13, 14(a) and 15(a)), and then · In one measurement execution consisting of a cycle in which the measurement lance moves upward along the vertical axis (Z) and the measurement unit exits the container in a state of reaching the atmosphere (4) from the molten metal (3) through the slag layer (2) (see steps (E) and (F) in FIGS. 13, 14(a) and 15(a)), the position (has) of the atmosphere-slag interface (2as) and the position (hsm) of the slag-metal interface (2sm) are measured.

[0075] In other words, passing the measuring unit (6) once downward from the atmosphere (4) above the slag layer (2) to the molten metal (3) and then once upward from the molten metal (3) to the atmosphere (4) is sufficient to measure the thickness and position of the slag layer (2). Figure 13 shows a measuring lance (1) oriented vertically, and the transport axis (X) extending between the proximal end (5p) and the distal end (5d) of the transport tube (5) is kept parallel to the vertical axis Z of the tundish (22) throughout the measuring cycle. However, in other embodiments of the method according to the invention, the measuring lance (1) can be tilted at an angle such that the transport axis (X) extends along an oblique axis and thus is not parallel to the vertical axis Z of the metallurgical vessel. Such a configuration is particularly interesting for some types of metallurgical vessels, and in order to access the surface of the liquid metal, the measuring lance (1) can be inserted into the metallurgical vessel through a passage extending along a non-vertical axis or needs to be inserted. This is typically the case for an EAF (electric arc furnace), where the measuring lance usually needs to be inserted into the liquid metal through a slag door opening located on the side wall of the EAF and extending along a non-vertical slag door opening axis. Therefore, the insertion of the measuring lance (1) through the slag door opening is advantageously carried out with the measuring lance (1) tilted at an oblique angle such that the carrier axis (X) is substantially parallel to the slag door opening axis. Next, during the measuring cycle, the measuring lance (1) is advantageously driven to enter and exit the metallurgical vessel along the slag door opening axis. When such an oblique translation of the measuring lance (1) is carried out, the method according to the invention can still be carried out by simply recording the vertical position of the measuring lance (1) at the atmosphere-slag interface (2as) and the slag-metal interface (2am). Alternatively, the oblique positioning of the measuring lance (1) along the slag door opening axis can be recorded at the atmosphere-slag interface (2as) and the slag-metal interface (2am). In that case, the respective vertical positions of those interfaces (2as, 2am) can be determined based on their oblique positions by using appropriate trigonometric identities that relate the position along the slag door opening axis to its projection along its vertical axis.

[0076] Figures 14(a) and 14(b) and Figures 15(a) and 15(b) show various stages of using a measurement unit characterized by a slag-metal interface detection unit (8) including an oxygen probe (8o) and an electric circuit (7) including first and second conductive elements (11, 12) coupled to a mechanical switch (14s). Unless otherwise specified, the discussions made with respect to the embodiments shown in Figures 14(a) and 14(b) and Figures 15(a) and 15(b) generally apply to any embodiment included within the scope of the present invention, i.e., the invention according to the claims.

[0077] The embodiment shown in Figure 14(a) ·differs from the embodiment shown in Figure 15(a) in that in Figure 14(a), the temperature fuse (13) is configured to blow before the cap (10) is sufficiently deteriorated to expose the slag-metal interface detection unit (8) to the molten metal (3). This embodiment is referred to as the first embodiment - 14 (see Figure 14). ·In Figure 15(a), the temperature fuse (13) is configured to blow after the cap (10) is sufficiently deteriorated to expose the slag-metal interface detection unit (8) to the molten metal (3). This embodiment is referred to as the second embodiment - 15 (see Figure 15). Since the cap (10) should not deteriorate before the slag-metal interface detection unit (8) reaches the level of the molten metal, in order to shorten the measurement operation time, preferably, the temperature fuse (13) blows as soon as possible after the cap deteriorates.

[0078] Subsequently, the following nomenclature for the electric circuit configuration is used. ·Sensor-configuration = a measurement head including an electric circuit (7) including first and second conductive elements (11, 12) coupled to a contact sensor (14). The sensor-configuration can be one of the following. ·Switch configuration = a measurement head including an electric circuit (7) including first and second conductive elements (11, 12) coupled to a mechanical switch (14s). ·Piezoelectric configuration = A measuring head including an electric circuit (7) containing first and second conductive elements (11, 12) coupled to a piezoelectric detector (14p). ·Grounding configuration = A measuring head including an electric circuit (7) containing only the first conductive element (11) with the slag and the second electrical measurement terminal (8tb) grounded to earth.

[0079] Use the following nomenclature for the slag - metal interface detector unit configuration. ·Oxygen configuration = The slag - metal interface detector unit (8) includes an oxygen probe (8o). ·Inductive configuration = The slag - metal interface detector unit (8) includes an induction coil (8i).

[0080] Furthermore, as described above, use the following nomenclature as well. ·First embodiment - 14 = As shown in FIG. 14, the temperature fuse blows before the cap deteriorates. ·Second embodiment - 15 = As shown in FIG. 15, the temperature fuse blows after the cap deteriorates.

[0081] For clarity, the following conditions are established in the following description. A person skilled in the art can easily generalize to any alternative configuration. ·The first conductive element (11) is conductively coupled to the first electrical measurement terminal (8ta), and for the sensor - configuration, the second conductive element (12) is conductively coupled to the second electrical measurement terminal (8tb). A person skilled in the art can generalize if either the first and second conductive elements (11, 12) are coupled to any one of the first and second electrical sensor terminals (9ta, 9tb). ·The analysis device (16) measures the voltage difference between the first and second electrical measurement terminals (8ta, 8tb). The same conclusion regarding the operating principle also applies when the analysis device (16) measures another electrical parameter such as intensity.

[0082] Operating principle (A) At the initial time (A) of the measurement process shown in FIGS. 13, 14(a) and 15(a), the measurement lance (1) according to the present invention including the measurement unit (6) is positioned entirely in the atmosphere (4) on the atmosphere - slag interface (2as). The cap (10) is intact and the electric circuit (7) is in the first electrical configuration with the temperature fuse (13) not blown. At the initial time (A), both the first embodiment - 14 and the second embodiment - 15 are identical.

[0083] The second end of the sensor (14) of the sensor - configuration and the first conductive element (11) of the grounding configuration are preferably positioned closest to the atmosphere - slag interface (2as) because when the electric circuit (7) reaches the atmosphere - slag interface, the latter is disrupted and agitated if any other component of the measurement lance reaches the atmosphere - slag interface first, thus reducing the accuracy of the measurement.

[0084] The initial vertical position of the measurement lance (1) along the vertical axis (Z) is measured and recorded. Since the electric circuit (7) is conductively coupled to the first and second electrical measurement terminals (8ta, 8tb), the electrical signal measured by the analysis device (16) depends on the value measured by the slag - metal interface detection unit (8) and the electric circuit (7). At the initial time (A), the analysis device (16) measures the voltage difference Vmes(A), and the value of the voltage difference Vmes(A) depends on the slag - metal interface detection unit (8) and the first electrical configuration of the electric circuit (7) as follows.

[0085] The slag - metal interface detection unit (8) measures the following characteristics. · Oxygen - configuration: The oxygen probe (8o) measures the voltage difference V8(A) between the oxygen cell (8c) representing the oxygen concentration in the cap (10) surrounding the oxygen probe (8o) and the reference cell (8r). · Inductive - configuration: The inductive coil (8i) measures the magnetic permeability of the atmosphere (4) surrounding the cap (10).

[0086] The electrical circuit (7) is in a first electrical configuration. The voltage difference Vmes(A) measured by the analysis device (16) depends on the configuration of the electrical circuit (7). · Switch - configuration: Open the electrical circuit as shown in FIG. 16 so that the analysis device measures a voltage difference Vmes(A)=V8(A)≠0 (V), where V8(A) is the voltage difference measured by the slag - metal interface detection unit 8 (at the initial time (A), it represents the oxygen concentration in the cap (10) (see FIGS. 14(b) and 15(b) at time (A)). When the electrical circuit is instead connected to the first and second electrical sensor terminals (9ta, 9tb), the measured voltage Vmes(A) is, of course, a parameter measured by the sensor unit (9), for example, if the sensor unit is a thermocouple, it represents temperature. · Piezoelectric configuration: The piezoelectric detector (14p) is at a static voltage (V14p0). The analysis device measures a voltage difference that is a function of the characteristics measured by the slag - metal interface detection unit (8) and the static voltage, that is, Vmes(A)=f(V8(A),V14p0)≠0 (V). · Grounding configuration: Open the electrical circuit so that the analysis device measures the characteristics measured by the slag - metal interface detection unit (8). Similar to the switch - configuration case, the analysis device measures a voltage difference Vmes(A)≠0 (V) that represents the oxygen concentration in the cap (10).

[0087] Operating principle (B) Subsequently, as shown in FIGS. 13, 14(a) and 14(b), move the measuring lance (1) downward parallel along the vertical component parallel to the vertical axis (Z) towards the atmosphere - slag interface (2as) until the second end of the contact sensor (14) or the first conductive element (11) of the electrical circuit (7) contacts the atmosphere - slag interface (2as) at time (B). At time (B), the first embodiment - 14 and the second embodiment - 15 are the same.

[0088] The slag - metal interface detection unit (8) measures the following characteristics. · Oxygen - configuration: As shown in Fig. 17, since the cap remains undamaged at time (B), the slag - metal interface detection unit (8) measures the same voltage difference as the initial time (A), that is, the voltage difference V8(B)=V8(A), which represents the oxygen concentration inside the cap (10) surrounding the slag - metal interface detection unit (8). · Induction - configuration: The induction coil (8i) measures the magnetic permeability of the medium around the cap (10). When the second end of the first conductive element (11) of the contact sensor (14) or the electrical circuit (7) first contacts the air - slag interface (2as), the induction coil (8i) is still surrounded by the air (4), and the magnetic permeability is measured in the same way as the initial time (A). On the other hand, when the electrical circuit (7) reaches the air - slag interface (2as) and the slag - metal interface detection unit (8) is already inside the slag layer (2), the induction coil (8i) measures the magnetic permeability of the slag layer (2).

[0089] The electrical circuit (7) changes from the first electrical configuration at the initial time (A) to the second electrical configuration at time (B). The change from the first electrical configuration to the second electrical configuration triggers a jump in the voltage difference ΔVmes = Vmes(B)-Vmes(A) measured by the analysis device (16) that instantaneously identifies the position along the vertical axis (Z) of the air - slag interface (2as). The voltage difference Vmes(B) measured by the analysis device (16) depends on the configuration of the electrical circuit (7). · Switch - configuration: The mechanical switch (14s) is closed by the force applied to it when the measuring lance presses the air - slag interface (2as). Thus, the electrical circuit is closed and short - circuited so that the analysis device measures zero - voltage, that is, Vmes(B)=0(V), between the first and second electrical measurement terminals regardless of the value of the voltage difference V8(B) measured by the slag - metal interface detection unit (8) at time (B). (See Figs. 14(b) and 15(b) at time (B)). The same applies when the electrical circuit is connected to the first and second electrical sensor terminals (9ta, 9tb) instead. · Piezoelectric configuration: The piezoelectric detector (14p) is under the stress voltage (V14p1). The analysis device measures the voltage difference, which is a function of the slag-metal interface detection unit (8) and the characteristics measured by the stress voltage, i.e., Vmes(B)=f(V8(B),V14p1)≠Vmes(A). · Grounding configuration: When the second end of the first conductive element (11) contacts the air-slag interface (2as) grounded to the ground, it is also grounded to the ground. Since the second electrical measurement terminal (8tb) is also grounded to the ground, the electrical circuit is closed and short-circuited so that the analysis device can measure the zero-voltage between the first and second electrical measurement terminals, i.e., Vmes(B)=0(V), regardless of the value of the voltage difference V8(B) measured by the slag-metal interface detection unit (8) at time (B).

[0090] At time (B), the measurement lance (1) successfully measured the position of the air-slag interface with high accuracy.

[0091] Operating principle (C, D) After contacting the air-slag interface (2as) with the electrical circuit (7) of the measurement unit (6), the measurement lance (1) continues to move downward along the vertical component parallel to the vertical axis (Z), and the measurement unit (6) including the cap (10) enters the molten metal (3) through the slag layer (2) as shown in the position (E) of Figure 13 and the positions (C), (D), (E) of Figures 14(a) and 15(a). For example, the time taken for the slag-metal interface detection unit (8) to move through the slag layer (2), i.e., from position (A) or (B) to position (C), (D) or (E), is between 0.5 seconds and 1 second.

[0092] The second electrical configuration that migrates when the electrical circuit (7) comes into contact with the atmosphere - slag interface (2as) enables the accurate identification of the position of the atmosphere - slag interface (2as), but also masks any reasonable readings of the measured values of the slag - metal interface detection unit (8). In fact, as described above with respect to time (B), the first and second electrical measurement terminals (8ta, 8tb) are short - circuited in both the switch - configuration and the ground - configuration, and the stress voltage V14p1 measured by the piezoelectric detector in the piezoelectric - configuration varies according to the penetration depth and density of the medium through which the piezoelectric detector passes.

[0093] In order for the analysis device (16) to reasonably read the measured values obtained by the slag - metal interface detection unit (8), the electrical circuit (7) must be neutralized. This is achieved by melting the thermal fuse (13) to open the electrical circuit.

[0094] Since the oxygen probe (8o) must be in contact with the medium whose oxygen concentration is measured by the oxygen probe (8o), the cap must also be removed or deteriorated in order for the analysis device (16) to reasonably read the measured values obtained by the slag - metal interface detection unit (8). This is as shown in Figure 18, where the fuse melts and the cap deteriorates. This is not necessary for the induction - configuration since the induction coil (8i) does not need to be in direct contact with the medium to measure the magnetic permeability of the medium.

[0095] These two operations, namely, the operation of melting the thermal fuse to neutralize the electrical circuit (7) and the operation of deteriorating the cap to expose the oxygen probe (8o), are executed at times (C) and (D) respectively, as shown in Figures 14(a) and 15(a). It can be seen that the sequence of these two operations is reversed between the first embodiment - 14 and the second embodiment - 15, which will be described separately.

[0096] Operating principle (C, D) - First embodiment - 14, sequence (C)-(D) As shown in Fig. 14(a), in the first embodiment - 14, the thermal fuse melts at time (C) before the cap (10) deteriorates over time (D).

[0097] Time (C) The high temperature of the molten metal (3) in contact with the slag layer (2) and the measuring unit (6) causes the thermal fuse (13) to melt at time (C) and open the electrical circuit (7). As a result, the first and second ends of the first conductive element (11) are electrically insulated from each other, and there is no longer a current that can flow through the electrical circuit. It is said that the electrical circuit (7) is neutralized at that point because it does not affect the voltage difference Vmes(C) between the first and second electrical measurement terminals (8ta, 8tb) measured by the analysis device (16).

[0098] The thermal fuse (13) may melt at any time after the position of the air - slag interface is determined at time (B). The thermal fuse (13) must melt before the slag - metal interface detection unit (8) reaches the slag - metal interface (2sm) when the measuring lance is pulled upward outside the container at time (F) in Fig. 14(a).

[0099] The thermal fuse (13) melts because the temperature rises to the melting temperature when the measuring unit comes into contact with the slag layer (2) and / or the molten metal (3). As described above, when the measuring head is driven downward into the molten metal (3) through the slag layer (2), the time and position at which the thermal fuse (13) melts after contacting the air - slag interface (2as) can be controlled by selecting the type of fuse, the downward translational speed of the measuring lance, and the heat exchange rate through the housing surrounding the thermal fuse (13).

[0100] When the thermal fuse melts, the electrical circuit is neutralized, and the analysis device (16) can measure V8(C), which is the voltage difference measured by the slag - metal interface detection unit (8). This applies to all configurations of the electrical circuit (7). · Oxygen - configuration: Since the cap remains undamaged at time (C), the slag - metal interface detection unit (8) measures the same voltage difference as the voltage difference at time (A), which represents the oxygen concentration in the cap (10) surrounding the slag - metal interface detection unit (8) therein, that is, the voltage difference V8(C)=V8(A). As a result, in a state where the electric circuit is neutralized, the analysis device measures, at time (C), as shown in Fig. 14(b), the voltage difference Vmes(C)=V8(C)=Vmes(A). · Induction - configuration: The induction coil (8i) measures the magnetic permeability of the medium around the cap (10). When the electric circuit is neutralized, the analysis device (16) measures the voltage difference Vmes(C) representing the medium around the induction coil (8i) when moving into the molten metal (3) through the slag layer (2).

[0101] Time (D) In the oxygen - configuration of the first embodiment - 14, the cap deteriorates at time (D) after the thermal fuse melts at time (C). Since the function of the cap (10) is to protect the oxygen probe (8o) from any contact with the slag that can contaminate the oxygen probe (8o) and endanger the measurement accuracy, the cap (10) of the measurement head (6) is configured not to deteriorate before the cap (10) reaches the molten metal (3). The cap (10) can be configured to deteriorate chemically due to contact with the slag. However, the cap (10) preferably deteriorates thermally when entering the molten metal (3) through the slag layer (2) and exposes the oxygen probe (8o) to the molten metal (3).

[0102] After time (D), the analysis device (16) measures the voltage difference V8(D) which is the voltage difference representing the oxygen concentration in the molten metal (3). Since the analysis device (16) measures the voltage difference Vmes(D)=V8(D), the oxygen concentration of the molten metal can be determined from time (D), as shown in Fig. 14(b) at time (D).

[0103] In the induction-configuration case, since the induction coil (8i) does not need to be in direct contact with the medium to measure its magnetic permeability, the cap (10) does not need to deteriorate and preferably does not deteriorate during the entire measurement operation. When the temperature fuse (13) blows when the induction coil (8i) is in the slag layer (2), the voltage difference measured by the analysis device (16) at time (C) represents the magnetic permeability of the slag. When the measurement lance is driven downward and the induction coil (8i) reaches the slag-metal interface (2sm), the analysis device detects a sharp change in the voltage difference representing the magnetic permeability gradient between the slag and the molten metal. This sharp change in the voltage difference identifies the position of the slag-metal interface (2sm), and thus the characterization of the position and thickness of the slag layer (2) is completed.

[0104] On the other hand, if the temperature fuse (13) blows only after the induction coil (8i) reaches the molten metal (3), the position of the slag-metal interface (2sm) remains unknown.

[0105] Operating principle (C, D) - Second embodiment - 15, sequence (D) - (C) As shown in FIG. 15(a), in the second embodiment - 15, the cap (10) deteriorates at time (D) before the temperature fuse blows at time (C).

[0106] Time (D) As described above, since direct contact between the medium and the induction coil (8i) is not required in the induction-configuration, the cap must deteriorate only for the oxygen-configuration. In the oxygen-configuration, the cap (10) must not deteriorate before the cap (10) reaches the molten metal (3) and protects the oxygen probe (8o) from contact with the slag. Since the electrical circuit (7) is in the second electrical configuration, the analysis device (16) measures the following voltage difference Vmes(D) at time (D). · Slag-configuration and ground configuration: The electrical circuit (7) is short-circuited, and the analysis device (16) measures no voltage difference, i.e., Vmes(D) = 0 V (see FIG. 15(b) at time (D)). · Piezoelectric - Configuration: The piezoelectric detector (14p) is at V14p1, which is a stress voltage that changes as it reaches deeper into the molten metal (3) through the slag layer (2). The analysis device (16) measures a voltage difference, which changes but is hardly usable because its change depends on variable parameters.

[0107] Time (C) As described above, the thermal fuse (13) melts when exposed to heat, thereby opening and neutralizing the electrical circuit (7) in such a way that the electrical circuit (7) no longer adversely affects the voltage difference measured by the analysis device (16). In the second embodiment 15-, since the thermal fuse melts after the cap (10) has deteriorated, and the cap (10) must deteriorate only after reaching the molten metal (3), the thermal fuse (13) must melt when the slag - metal interface detection unit (8) is immersed in the molten metal (3).

[0108] Thus, with the electrical circuit neutralized, the analysis device (16) measures the voltage difference (i.e., Vmes(C)=V8(C)) at the slag - metal interface detection unit (8) that represents the position of the measurement lance in the molten metal without being interfered with by the electrical circuit. At this stage, the position of the slag - metal interface (2sm) is unknown for all configurations.

[0109] Operating Principle (E) With the electrical circuit (7) neutralized and the slag-metal interface detection unit (8) measuring the properties of the surrounding medium, as soon as the slag-metal interface detection unit (8) is kept in the molten metal (3), for all configurations and embodiments, the analysis device measures that Vmes(E) = constant, which is a substantially constant voltage difference (see Figures 14(b) and 15(b) against time (E)). The residence time ((E)-(C)) or ((E)-(D)) of the slag-metal interface detection unit (8) in the molten metal must be long enough to ensure that the temperature fuse (13) blows and the cap (10) deteriorates for the oxygen-configuration, and as short as safely possible the total time required to detect both the air-slag interface (2as) and the slag-metal interface (2sm). For example, the residence time ((E)-(C)) or ((E)-(D)) of the slag-metal interface detection unit (8) in the molten metal can be between 5 seconds and 8 seconds.

[0110] Operating principles (F, G) After the residence time in the molten metal, the measuring lance (1) is driven externally upward from the molten metal along the vertical component parallel to the vertical axis (Z), and the slag-metal interface detection unit (8) is driven outside the molten metal (3), through the slag-metal interface (2sm) and the slag layer (2) into the atmosphere (4). The slag-metal interface detection unit (8) crosses the slag-metal interface (2sm) at time (F) as shown in Figures 13, 14(a), and 15(a). From the last times (C) and (D), the analysis device (16) measures the voltage difference representing the properties of the medium surrounding the slag-metal interface detection unit (8).

[0111] When the slag-metal interface detection unit (8) crosses the slag-metal interface (2sm), the voltage difference Vmes(F) measured by the analysis device (16) changes abruptly. · Oxygen-configuration: This is because the oxygen concentration in the slag is different from the oxygen concentration in the molten metal, and · Inductive-configuration: This is because the magnetic permeability of the slag is different from the magnetic permeability of the molten metal.

[0112] The position of the slag-metal interface (2sm) is identified by a sudden change in the voltage difference measured by the analysis device. At this point, the measurement of the position and thickness of the slag layer (2) is completed for the following reasons. · The position (has) of the air-slag interface (2as) is measured over time (B) using an electrical circuit (7), and · The position (hsm) of the slag-metal interface (2sm) is measured over time (F) by the slag-metal interface detection unit (8).

[0113] The measurement lance can be fully withdrawn outside the vessel. The slag-metal interface detection unit (8) continues to measure the properties of the medium passing therethrough. However, in the case of the oxygen configuration shown in FIG. 19, the oxygen probe (8o) is contaminated by impurities when crossing the slag layer (2), which can impair the reliability of the measurement as shown in FIGS. 14(b) and 15(b) by the wavy curves of the voltage difference over time (F) and time (G).

[0114] The oxygen configuration has additional constraints compared to the induction configuration. The additional constraint is that the cap (10) must not deteriorate during the period separating the two crossings of the slag-metal interface (2sm) by the detection unit (8) as it descends into the vessel and then exits the vessel upward. The advantage of the oxygen configuration is that in addition to the position and thickness of the slag layer (2), the oxygen probe (8o) can also obtain the oxygen concentration in the molten metal and the slag layer, which is important information.

[0115] Prior art measurement lance FIG. 21 is a schematic diagram of an example of a prior art measurement lance described in U.S. Patent No. 7,876,095 that shares the function of measuring at least the positions (has, hsm) of the air-slag interface (2as) and the slag-metal interface (2sm) in the state shown in FIGS. 9 and 10 of the measurement lance according to the present invention. The slag-metal interface detection unit of the measurement lance of U.S. Patent No. 7,876,095 includes · An electrical circuit for detecting the position (has) of the air-slag interface, and ·An induction coil (8i) configured to detect the position (hsm) of the slag-metal interface.

[0116] The vibration generated by the oscillator coupled to the induction coil (8i) indicates the magnetic permeability of the medium surrounding the induction coil (8i). When the induction coil approaches the conductive molten metal, the vibration decays until it stops when immersed in the molten metal. The decay of the vibration indicates the position (hsm) of the slag-metal interface.

[0117] In the measuring lance described in U.S. Patent No. 7,876,095 without a temperature fuse (13), an additional analysis device (16e) connected to the ground potential and the electrical circuit (7) is therefore necessary to detect a short circuit between the first conductive element (11) and the ground potential when the electrical contact touches the air-slag interface (2as) at time (B).

[0118] In the measuring lance according to the embodiment of the present invention shown in FIGS. 9 and 10 provided with a temperature fuse (13), the first conductive element (11) of the electrical circuit (7) can be coupled to any one of the first and second electrical measurement and sensor terminals (8ta, 8tb, 9ta, 9tb). Since the number of electrical terminals is the same as in the case without an electrical circuit, an additional analysis device is not required and the same analysis device can be used alone.

[0119] FIG. 22 shows a combination of U.S. Patent No. 7,876,095 and the measurement lance of the present invention. The first conductive element (11) is connected to the first electrical measurement terminal (8ta), which is different from the embodiment shown in FIG. 9 in that the electrical circuit (7) does not include a thermal fuse (13). In the absence of the thermal fuse (13), from the moment when the electrical circuit (7) is short-circuited when transitioning to the second electrical configuration upon contact of the first conductive element (11) with the air-slag interface, the measurement lance (1) cannot measure any value of the magnetic permeability of the medium through which it subsequently passes. In the absence of a mechanism to neutralize the short-circuited electrical circuit (7), the analysis device (16) continues to measure that there is no voltage difference at any time after time (B), that is, Vmes = 0 V for all times > (B). Therefore, the analysis device (16) measures that there is no voltage difference at time (F) and cannot determine the vertical position of the slag-metal interface (2sm).

Table 1-1

Table 1-2

Claims

Claim 1 A measuring lance (1) for measuring, in a single measurement run, the position (has) of the atmosphere-slag interface (2as) between the atmosphere (4) and the slag layer (2) on the molten metal (3) and the position (hsm) of the slag-metal interface (2sm) between the slag layer (2) and the molten metal (3), comprising: - a conveying pipe (5) extending along an axis (X) between a proximal end (5p) and a distal end (5d) located downstream of the proximal end (5p); - a measuring unit (6) coupled to the distal end (5d) of the conveying pipe (5) and configured to pass through the slag layer (2); The measuring unit (6) comprises: - an electric circuit (7) configured to detect the atmosphere-slag interface (2as); - a slag-metal interface detection unit (8) located downstream of the distal end (5d) and provided with at least first and second electrical measurement terminals (8ta, 8tb), configured to measure the value of a first material property at the position (hsm) of the slag-metal interface (2sm) between the slag layer (2) and the molten metal (3); and - preferably, a sensor unit (9) provided with first and second electrical sensor terminals (9ta, 9tb), configured to measure the value of a second material property of the slag layer (2) and the molten metal (3); The measuring lance (1) includes a cap (10) surrounding the slag-metal interface detection unit (8) and optionally the sensor unit (9) and configured to separate the slag-metal interface detection unit (8) from the external environment; The electric circuit (7) includes a first conductive element (11) having a first end conductively coupled to the first electrical measurement terminal (8ta) and / or the first electrical sensor terminal (9ta), and a second end disposed outside the cap (10), preferably downstream of the cap (10); The electric circuit (7) includes a temperature fuse (13) located between the first end and the second end of the first conductive element (11) and configured to blow and open the electric circuit (7) after the first conductive element (11) contacts the atmosphere-slag interface (2as); The term "downstream" is defined along the axis (X) in the direction from the proximal end (5p) towards the distal end (5d). Measuring lance (1), characterized in that. Claim 2 The measurement lance (1) according to claim 1, comprising the sensor unit (9) which is a thermocouple (15), wherein the first and second electrical sensor terminals (9ta, 9tb) are configured to be electrically connected to an analysis device (16), and the analysis device is preferably a voltage measuring device.

3. The slag-metal interface detection unit (8) includes an oxygen probe (8o) for measuring the concentration of oxygen. The oxygen probe (8o) includes an oxygen cell (8c) connected to the first electrical measurement terminal (8ta) and a reference electrode (8r) connected to the second electrical measurement terminal (8tb). The cap (10) is configured to deteriorate and expose the oxygen probe (8o) to the ambient environment when exposed to a predetermined temperature for a predetermined exposure time. The temperature fuse (13) is preferably configured to blow at least when the cap (10) deteriorates. The measurement lance (1) according to claim 1 or 2.

4. The slag-metal interface detection unit (8) according to claim 1 or 2, includes an induction coil (8i) for detecting a change in the magnetic permeability of the ambient environment.

5. - The first end of the first conductive element (11) is conductively coupled to the first electrical measurement terminal (8ta), and the second end of the first conductive element (11) is conductively coupled to the contact sensor (14). - The electrical circuit (7) includes a second conductive element (12). The second conductive element (12) includes a first end conductively coupled to the second electrical measurement terminal (8tb) and a second end of the second conductive element (12) conductively coupled to the contact sensor (14). The measurement lance (1) according to any one of claims 1 to 5.

6. - The first end of the first conductive element (11) is conductively coupled to the first electrical sensor terminal (9ta), and its second end is conductively coupled to the contact sensor (14). - The electrical circuit (7) includes a second conductive element (12) including a first end conductively coupled to the second electrical sensor terminal (9tb) and a second end thereof conductively coupled to the contact sensor (14). The measurement lance (1) according to any one of claims 1 to 4.

7. The contact sensor (14) - A mechanical switch (14s) configured to be set to an open position and move to a closed position upon application of a mechanical force corresponding to a force generated when the mechanical switch (14s) contacts the air - slag interface (2as), and configured to conductively connect the first and second conductive elements (11, 12), wherein the thermal fuse (13) is configured to blow when the switch (14s) reaches the closed position, or - A piezoelectric detector (14p) configured to generate an electric current upon application of a mechanical force corresponding to a force generated when the piezoelectric detector (14p) contacts the air - slag interface (2as), wherein the thermal fuse (13) is configured to blow after the piezoelectric detector (14p) generates an electric current, the measurement lance (1) according to any one of claims 5 or 6, which is selected between the mechanical switch (14s) and the piezoelectric detector (14p).

8. A part of the outer surface (10s) of the cap (10) is conductive and is included in one of the first or second conductive elements (11, 12), the measurement lance (1) according to any one of claims 5 to 7.

9. The mechanical switch (14s) is - A second member (14b) belonging to the second conductive element (12) and firmly attached to the cap (10), and - A first member (14a) belonging to the first conductive element (11), non - conductively separated from the second member (14b), and attached to the cap (10) via an elastic member (17), wherein the elastic member (17) is set to separate the first member (14a) from the second member (14b) and to deform upon application of the mechanical force to conductively connect the first and second members (14a, 14b), the measurement lance (1) according to claim 7, which includes the first member (14a).

10. Including the sensor unit (9), - The first end of the first conductive element (11) is electrically coupled to both the oxygen cell (8c) of the oxygen probe (8o) and the first electrical sensor terminal (9ta), or - The second conductive element (12) is connected to both the reference electrode (8r) of the oxygen probe (8o) and the second electrical sensor terminal (9tb), the measurement lance (1) according to claim 6.

11. A method for determining the position (has) of the air - slag interface (2as) between the atmosphere (4) and the slag layer (2) on the molten metal (3) and the position (hsm) of the slag - metal interface (2sm) between the slag layer (2) and the molten metal (3) in a metallurgical vessel, - Positioning the measurement lance (1) according to any one of claims 1 to 10 on the air - slag interface (2as) with the second end of the first conductive element (11) positioned closest to the air - slag interface (2as), - Starting to measure the vertical position of the measurement lance (1) along a vertical axis (Z) substantially perpendicular to the air - slag interface (2as), - Starting to measure the value of the first material property using the slag - metal interface detection unit (8), - Starting to measure the electrical properties of the first conductive element (11), - Translating the measurement lance downward along at least the vertical component parallel to the vertical axis (Z) towards the air - slag interface (2as), - Detecting the gradient of the electrical properties of the first conductive element (11), and when it indicates that the second end of the first conductive element (11) has contacted the air - slag interface (2as), recording the vertical position of the measurement lance (1) as the position (has) of the air - slag interface (2as), - Continuing to translate the measurement lance sufficiently downward along the vertical component to ensure that the measurement unit (6) is within the molten metal (3) beyond the slag - metal interface (2sm), - Allowing the temperature fuse (13) to blow to enable electrically separating the first end of the first conductive element (11) from the second end, - Measuring the value of the first material property using the slag - metal interface detection unit (8) and maintaining the measurement unit (6) within the molten metal (3) until the measured value of the first material property becomes substantially constant, - Translating the slag - metal interface detection unit (8) upward along the vertical component towards the slag - metal interface (2sm), - When detecting a steep gradient in the value of the first material property measured using the slag-metal interface detection unit (8), recording the vertical position of the measurement lance (1) as the position (hsm) of the slag-metal interface (2sm); - Continuing to translate the measurement lance (1) upward in parallel along the vertical component until the measurement lance (1) is completely in the atmosphere (4). A method comprising the steps of:

12. The slag-metal interface detection unit (8) is an oxygen probe (8o) that measures the concentration of oxygen, as defined in claim 3, and the measurement lance (1) - A sensor unit (9) consisting of a thermocouple (15) that measures the value of the temperature of the ambient environment; - A mechanism for correcting the concentration of oxygen measured by the oxygen probe (8o) according to the temperature measured by the thermocouple (15). The method according to claim 11, comprising:

Images