Measuring probe for molten metal

Abstract

To provide an improved measuring probe for measuring at least one parameter of molten metal, and in particular, provide an improved measuring probe with a reduced response time.SOLUTION: The present invention relates to a measuring probe for molten metal, comprising a sensor unit adapted to determine at least one parameter of the molten metal, a signal line connected to the sensor unit, and a carrier element. The sensor unit comprises a sensing element and a metal body. The signal line comprises at least two wires, and an inner diameter of a carrier tube is 7 to 20 times an outer diameter of the wires.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a measurement probe for determining at least one parameter of a molten metal.In a further aspect, the present invention relates to a method for measuring at least one parameter of a metal melt.

[0002] During metal production processes, particularly those used in the steel industry, several parameters of the metal melt, such as the bath chemistry or the temperature of such melt, are important for controlling the metallurgical process. The ability to continuously and / or periodically monitor these variables is highly desirable for both economic and quality reasons. Accurate monitoring can significantly reduce energy consumption caused by overheating and material consumption caused by overprocessing. Other advantages of continuous monitoring include the ability to measure high-temperature phase changes, chemical reactions, and other related phenomena.

[0003] Methods and devices for determining these process-related parameters are known in the art and most involve the use of at least a disposable probe equipped with a sensor. Typically, the probe is placed below the surface of the melt in the form of a drop-in sensor or by a lance assembly. The lance assembly can be operated manually or fully or semi-automatically. The probe is typically connected by a wire or cable to a processing device for processing the recorded data, although wireless data transfer has also been described. The data is collected and processed in real time or near real time, providing metallurgical facility operators with important information regarding the progress or status of the metal production process occurring within the vessel.

[0004] In drop-in sensor measurements, a disposable probe is dropped into a vessel containing the molten metal. Suitable probes are disclosed, for example, in EP 0 758 445 A1 and EP 0 997 716 A1. Such probes include a metal measuring head attached to one end of a carrier tube. The measuring head is typically made of cast iron or steel to provide the mass necessary to penetrate the molten steel or slag layer deposited on top of the molten iron. A signal cable connected to the measurement system is wound inside the carrier tube and unwound from it as the carrier tube drops into the molten metal. A sensor unit, including at least one sensor, such as a temperature sensor and / or an electrochemical element for measuring the oxygen activity of the molten metal, is located within the measuring head. Typical response times for commonly used sensors range from 5 to 10 seconds. Because the response time determines the requirements for all other components of the probe, a short response time is desirable.

[0005] Probes applied to BOF vessels (basic oxygen furnaces) typically weigh several kilograms and carry up to 30 meters of cable. The cables used are selected and adapted to last the required transit time and to withstand the molten metal for at least the required sensor response time. Cables used in metallurgical applications can withstand this environment for more than 10 seconds and have an outer diameter of 9–10 mm. The cable contains two to three wires electrically insulated from each other and covered with an outer insulating layer made of a rubber material, the thickness of which is 2.5–3 mm. The space required for the cable determines the dimensions of the carrier tube and the mass of the measurement head. This mass must be sufficient to allow the cable to be pulled out of the tube and moved into the metal bath at a speed sufficient to move it without increasing transit time. Overall, such probes have a mass of 6–8 kg, of which the measurement head (the assembly immersed during the measurement sequence) accounts for approximately 50%. This material requirement results in high material costs associated with these probes, and it is desirable to reduce this cost factor.

[0006] Current practice involves introducing sensors from a relatively high height, typically 10–20 m above the molten metal level, above the vessel containing the molten metal. Several probes can be stored in a magazine, with one probe released from the magazine at a time for each measurement. The probe falls freely, accelerated by gravity, and sinks into the molten metal. The probe's final velocity upon reaching the molten metal surface is therefore determined by the distance between the drop station and the molten metal. To obtain reliable measurement data, the probe must have a certain mass to sink sufficiently deep below the melt surface. Additional components, such as a balance, are required to balance the probe and provide reliable data, or to enable measurements. These components are not involved in recording the measurement itself. Therefore, drop-in sensors introduce a relatively large amount of extraneous contaminants into the molten material being measured. Furthermore, the immersion point cannot be reliably controlled.

[0007] Molten metal is typically covered with a slag layer during production, which exposes any probe or sensor passing through it to more severe conditions, regardless of the particular method used, and therefore it is desirable to minimize the time of exposure as much as possible.

[0008] Particularly in the field of electric arc furnaces (EAFs), only limited methods are currently available for determining molten metal parameters while the vessel is in operation. EAFs produce steel by using an electric arc to melt one or more charges of scrap metal, hot metal, ferrous materials, or other meltable materials placed inside the furnace. In a typical EAF procedure, an operator manually inserts a lance equipped with an appropriate sensor into the furnace through a slag door, a relatively wide opening in the wall of the furnace shell. Such an intrusion process is highly undesirable because it disturbs the environment inside the vessel during the metallurgical process. Furthermore, when the slag door is opened, cold ambient air is drawn in through the slag door, wasting energy. Due to the design of the EAF, where the electrodes are positioned above the metal bath, standard drop-in probes cannot be applied in these installations.

[0009] Recent developments have made available sensors with faster response times, for example in the form of needle-shaped oxygen sensors. However, the state-of-the-art design of drop-in sensors does not allow the probe to take advantage of the improvements achieved. In view of the prior art, there is a need for an improved measurement probe with faster response times. Furthermore, the probe should have a simplified design so that it can be manufactured at low cost.

[0010] It is therefore an object of the present invention to provide an improved measurement probe for measuring at least one parameter of a molten metal which overcomes at least one of the problems mentioned above. In particular, one object is to provide an improved measurement probe which has a reduced response time.

[0011] A further aspect of the object of the present invention is to provide a measurement probe that allows for simplification of the hardware required to utilize the probe.

[0012] It is a further object of the present invention to provide a measurement probe that can be accelerated before taking a measurement.

[0013] It is a further object of the present invention to provide a measurement probe which can be introduced to the measurement point through available entry points of the metallurgical vessel, especially in an electric arc furnace (EAF).

[0014] Another aspect of the present invention provides a method for measuring at least one parameter of molten metal or slag using the measurement probe of the present invention, which allows the parameter to be determined with reduced effort and expense in terms of equipment, control techniques and organization, while at the same time increasing the reliability and quality of the measurements obtained.

[0015] These objects are achieved by the subject matter defined in the independent claims.

[0016] The present invention provides a measurement probe for molten metal, comprising: a sensor unit adapted to determine at least one parameter of the molten metal, A sensing element; a metal body at least partially surrounding a sensing element; and - a signal line including at least two individual wires connected to the sensor unit; - a carrier element; The measurement probe is characterized in that the inner diameter of the carrier tube is 7 to 20 times the outer diameter of each wire.

[0017] Surprisingly, it has been found that measurement probes with individual wires and an optimized ratio between wire diameter and carrier dimensions improve the unwinding of the signal wire when measurements are taken. Furthermore, the probes are particularly well suited to acceleration and exhibit stable flight characteristics. Surprisingly, it has been observed that both factors result in a more reliable measurement probe. Furthermore, the individual wires allow for a minimalist design of the sensor unit, allowing it to be accelerated and / or immersed without applying excessive force to the signal wire.

[0018] It should be understood that the measuring probe of the present invention is not intended to be used in combination with a lance, i.e. the probe should not be immersed below the surface of the molten metal by an auxiliary article. The measuring probe of the present invention is particularly suitable for installation at the entry point of a metallurgical vessel, from which a part or parts, in particular a sensor unit, which need to be immersed in the molten metal to obtain measurements, are dropped or actively accelerated towards the molten metal.

[0019] Measurement probes can be used in almost any metallurgical vessel. Their small size, especially in EAFs, allows the use of available entry points, with the added benefit of eliminating the need to open the slag door to obtain measurements. Furthermore, interruptions to the metallurgical plant to obtain the required parameters can be minimized, particularly during continuous operation. This minimizes total operating costs, especially the required energy input, and increases the throughput of the plant and the quality of the products produced.

[0020] The present invention relates to a measurement probe for molten metal. The molten metal typically has a temperature above 600°C, in particular above 800°C, and preferably above 1000°C. The temperature of the molten metal may be, for example, in the range of 600 to 1800°C, more preferably in the range of 800 to 1700°C.

[0021] Preferably, the molten metal is molten steel. The terms "melt" or "molten metal" do not exclude the presence of any solid or gaseous parts, such as unmolten parts of the respective metal. The temperature of the metal melt varies and usually depends on the composition of the metal and the stage of the melting process.

[0022] The molten metal may be covered by a slag layer. The term "slag" refers to a non-steel by-product often produced in steelmaking furnaces, typically present as a molten material floating on top of the molten metal. Slag may contain metal oxides, metal sulfides, calcium oxide, magnesium oxide, magnesite, dolomite, iron oxide, aluminum oxide, manganese oxide, silica, sulfur, phosphorus, or combinations thereof. To obtain reliable measurements, a sensor introduced into the melt must pass through the slag layer as quickly as possible to minimize the effects of heat and corrosion and the solidification of slag material on the cold sensor unit before reaching the final measurement point in the molten metal. Such a solidified layer must melt when the sensor finally reaches the molten metal before a reliable measurement can be made, thus extending the time the sensor must withstand the decomposing environment of the molten metal.

[0023] The present invention relates to a measurement probe. The measurement probe is to be understood as a device equipped with a sensor unit that can be at least partially immersed in a liquid whose parameters are to be determined. The liquid of interest in this invention is molten metal, i.e., a high-temperature liquid. Prior to measurement, the sensor unit of the measurement probe must be placed below the surface of the molten metal. The method for immersing the sensor unit in the molten metal is not limited further; for example, the sensor unit can be dropped from a stationary point above the molten metal or accelerated by suitable means in addition to gravity. The compact design of the measurement probe of the present invention is compatible with various methods, enabling a variety of uses for the measurement probe. Preferably, the sensor unit is accelerated not only by gravity but also by, for example, a pneumatic accelerator.

[0024] A measurement sequence using the measurement probe of the present invention typically involves separating the sensor unit from the carrier element and subsequently immersing the sensor unit in the molten metal of interest.

[0025] The measuring probe includes a sensor unit adapted to determine at least one parameter of the molten metal. The sensor unit is typically configured as a disposable component that dissolves or decomposes in the molten metal after the parameter of interest has been determined. Parts of the sensor unit may already be dissolved before or during the parameter determination.

[0026] The parameter may be a physical, chemical, or metallurgical parameter, such as temperature, the presence, activity, and / or concentration of compounds, in particular oxygen activity, carbon content, aluminum content, or chemical composition.

[0027] "Determining a parameter" may be used herein as a synonym for measuring a parameter. The parameter may be determined from a single-point measurement or from a multi-point measurement. The determination may include determining a single parameter or a combination of parameters. For example, the determination may include measuring the oxygen activity or temperature of the molten metal. The determination may also include measuring the oxygen activity and temperature.

[0028] The sensor unit includes a sensing element. It should be understood that the sensing element is adapted to determine at least one parameter of the molten metal. The sensing element may be, for example, at least one selected from the group consisting of an electrochemical sensor, an electromagnetic sensor, an optical sensor, a thermoelectric sensor, a sensor for detecting voltage, a sensor for detecting current, or a sensor for detecting electrical resistance. The sensor unit may also include multiple sensing elements, preferably any combination of the specified sensing elements, which allows for a combination of several parameters to be measured. Therefore, "sensing element" should be understood within the present application as "at least one sensing element."

[0029] The thermoelectric sensor is preferably provided as a thermocouple. As known to those skilled in the art, a thermocouple comprises two wires (also called thermocouple legs) of different materials, which are typically joined at one end called the hot junction. Such a thermocouple may be provided in a protective element, such as a tube, preferably a quartz glass sheath. Depending on the type of thermocouple, such a quartz glass sheath may be, for example, at least one tubular or U-shaped quartz glass sheath.

[0030] In a preferred embodiment, the thermocouple is a quartz glass sheathed thermocouple. The quartz glass sheathed thermocouple may include an outer closed-ended tube and an inner open-ended tube disposed within the outer closed-ended tube, preferably both tubes being quartz glass. A first leg of the thermocouple is disposed within the inner open-ended tube, and a second leg of the thermocouple is disposed in the hollow space between the inner open-ended tube and the outer closed-ended tube.

[0031] In an alternative embodiment, the thermocouple is provided without a sheath, in which case the thermocouple is preferably at least partially coated with a refractory material.

[0032] Electrochemical cells typically include a solid electrolyte material, a reference material, and an electrode. Electrochemical cells, particularly electrochemical cells for determining oxygen activity, may include a solid electrolyte tube closed at one end and including a reference material and an electrode at the closed end. Such sensors are disclosed, for example, in U.S. Patent Application Publication No. 2002100686 (A1). Electrochemical cells can also be provided as needle sensors including conductive wires functioning as electrodes having at least a solid electrolyte coating and a reference material coating. Such sensors are disclosed, for example, in U.S. Patent Application Publication No. 5,332,449 (A).

[0033] Preferably, the sensor unit comprises a thermocouple and / or an electrochemical cell for measuring the temperature of the molten metal, preferably an electrochemical cell for determining the oxygen activity of the molten metal.

[0034] The sensor unit may include a bath contact. The bath contact should be understood as a conductive means for providing an electrical contact between the sensor unit and the molten metal. The bath contact may be made of metal, for example, molybdenum (Mo) or steel. The bath contact may be ring-shaped or rod-shaped, and preferably the bath contact is ring-shaped.

[0035] A preferred sensor unit includes a needle sensor for determining oxygen activity, a thermocouple (preferably enclosed in a quartz glass sheath), and a ring-shaped bath junction surrounding the thermocouple. Such a sensor unit has a compact and robust design, which allows for miniaturization of the measurement probe on which the sensor unit is mounted.

[0036] Another preferred sensor unit includes a needle sensor for determining oxygen activity, a thermocouple with a refractory coating, and a ring-shaped bath junction surrounding the needle sensor and the thermocouple. Such a sensor unit has a compact and robust design, which allows for miniaturization of the measurement probe on which the sensor unit is mounted.

[0037] Preferably, the sensor unit is configured to provide at least one signal to a processing unit, such processing unit being configured to process the at least one signal to determine a parameter of the molten metal.

[0038] Preferably, the response time of the sensing element is less than 5 seconds, more preferably less than 3 seconds. If the sensor unit includes multiple sensing elements, it is particularly preferred that the response time of all sensing elements is less than 5 seconds, and even more preferably less than 3 seconds. The response time is the time required to obtain a constant and stable measurement signal after the sensing element is introduced into the molten metal whose parameter is to be determined. State-of-the-art sensing elements are, for example, thermocouples, which have a typical response time in molten steel of 6 to 8 seconds, or electrochemical cells for determining oxygen activity, which have a typical response time in molten steel of 8 to 10 seconds. Therefore, using sensing elements with faster response times makes it possible to use components with reduced mass and shielding.

[0039] The response time of a sensing element is primarily determined by the heat capacity of its active area. Sensing elements with smaller active areas have shorter response times due to the smaller heat capacity in this area. The active area of ​​a sensing element should be understood as the section of the sensing element where the required signal is generated. For example, in the case of a thermocouple, the active area is the hot junction, and in the case of a needle-shaped oxygen sensor, the active area is the tip of the needle. In a preferred embodiment, the diameter of the active area of ​​the sensing element is less than 2.5 mm, preferably less than 2 mm. For example, the diameter of the active area of ​​the sensing element can be in the range of 0.3 mm to 2.5 mm, preferably in the range of 0.5 mm to 2 mm.

[0040] The sensor unit includes a metal body that at least partially surrounds the sensing element. The metal body is provided by a sheath so that the sensing element remains operable during immersion of the immersion probe and throughout the measurement period. Furthermore, the metal body aligns the sensor unit when immersed so that the sensing element has a suitable orientation and measurement position for determining the parameter of interest. Furthermore, the metal body preferably surrounds the connection between the sensing element and the signal line, further protecting these sensitive and critical components of the sensor unit.

[0041] The metal body has two ends. The end of the metal body where the sensing element is located is called the immersion end, and the opposite end along the longitudinal axis of the metal body is called the rear end. The metal body at least partially surrounds the sensing element. In other words, the sensing element extends partially outward from the immersion end of the metal body.

[0042] Preferably, the metal body is made of a material with a high heat capacity. In a preferred embodiment, the metal body is made of steel, stainless steel, cast iron, or copper. Before a reliable measurement can be made, the active area of ​​the sensing element needs to reach thermal equilibrium with the molten metal, and the metal body needs to be protected for a sufficiently long time until this point can be reached. Most preferably, the metal body is at least partially made of copper. Copper has a high thermal conductivity, which allows it to reach thermal equilibrium faster, which allows for fast measurements. Copper is not usually considered a suitable material for such a metal body, as it will be mixed into the melt being processed. In the present invention, the metal body can be miniaturized in such a way that the introduced contaminants are negligible.

[0043] Preferably, the mass of the sensor unit is less than 500 g, more preferably less than 400 g, even more preferably less than 300 g, and most preferably less than 200 g. The mass of the sensor unit should be understood as the total mass of the sensing element and metal body, as well as any optional additional components of the sensor unit. In other words, the mass of the sensor unit refers to all components of the sensor unit enclosed by the outer contours of the sensing element and metal body. For example, the mass of the sensor unit is in the range of 80 to 500 g, more preferably in the range of 100 to 400 g, even more preferably in the range of 120 to 300 g, and most preferably in the range of 140 to 200 g. The mass of the measurement head of currently used drop-in sensors, including the metal body and sensor element, is in the range of 3 to 4 kg. A sensor unit with a significantly reduced mass minimizes the amount of material introduced into the molten metal during measurement, further reducing production costs due to the material savings. Furthermore, measurements are minimally affected by the cold mass introduced by the lightweight sensor unit, resulting in more reliable and accurate data.

[0044] Preferably, the length of the metal body is 70 mm or less, more preferably 60 mm or less, and even more preferably 50 mm or less. The length of the metal body may be, for example, in the range of 20 to 70 mm, more preferably in the range of 30 to 60 mm. The length of the metal body should be understood as the length along the central longitudinal axis from the immersed end to the rear end.

[0045] Preferably, the diameter of the metal body is 40 mm or less, more preferably 35 mm or less, and even more preferably 30 mm or less. The diameter of the metal body may be, for example, in the range of 10 to 40 mm, more preferably 15 to 35 mm. The diameter of the metal body should be understood as the diameter perpendicular to the central longitudinal axis from the immersed end to the rear end.

[0046] Preferably, the density of the metal body is greater than the density of the molten metal. Typically, the density of molten steel is about 7.0 g / cm 3 Preferably, the density of the metal body is 7.2 g / cm 3higher than 7.6 g / cm 3 The density of the metal body is, for example, 7.2 to 8.8 g / cm 3 more preferably in the range of 7.6 to 8.6 g / cm 3 may be in the range of

[0047] Preferably, the ratio of the mass of the sensor unit to the net density of the sensing element and the metal body is 100 cm 3 Less than 70cm, preferably 3 It is preferably 50 cm or less. 3 For example, this ratio is 15 to 100 cm 3 range, more preferably 20 to 70 cm 3 Or 20~50cm 3 For state-of-the-art drop-in probes with an average mass of 3500 g, this ratio is typically in the range of 400 cm 3 It has been found that minimizing the ratio allows for a compact design of the sensor unit and improves the overall response time of the sensor unit provided by the sensing element.

[0048] In a preferred embodiment, the density of the immersed end of the metal body is higher than the density of the trailing end. Advantageously, the sensing element is vertically oriented when immersed in the molten metal. The density gradient of the metal body, with the density decreasing towards the trailing end, supports such orientation.

[0049] The metal body may be a monolithic component or may include multiple components. The modular design of the metal body may allow for control of the density distribution within the metal body and facilitate its manufacture.

[0050] The metal body may be hollow having a tubular structure, but preferably the metal body has a cylindrical structure symmetrical along a central longitudinal axis extending from the immersed end to the rear end, and it should be understood that the metal body includes a central void.

[0051] Preferably, the maximum cross-sectional area of ​​the central void of the metal body is less than 25%, more preferably less than 20%, of the maximum total cross-sectional area of ​​the metal body. Cross-sectional area should be understood as the area of ​​a cross section perpendicular to the central longitudinal axis from the immersed end to the rear end. The small area percentage of the void ensures sufficient density of the metal body.

[0052] The metal body may include multiple cross-sectional areas along its length, for example the metal body may include shoulders at the immersed end and / or the rear end, in other words the metal body may include recessed sections at the periphery of its ends, thus reducing the cross-sectional area of ​​this or these sections.

[0053] The central void may include a constant cross-sectional area along the length of the metal body, or may include sections with different cross-sectional areas. For example, the central void may include an annular step. Such a modular or stepped design of the void may be advantageous for assembly of the sensor unit, and the sensing element may be secured within the central void. For example, the metal body may include multiple cylinders arranged axially in line with one another and having internal bores with a diameter that decreases toward the rear of the metal body.

[0054] The sensor unit may include a housing that surrounds the sensing element or elements. Preferably, the housing surrounds the connection between the sensing element and the signal wire. Such a housing can strengthen the connection and further facilitate assembly of the sensor unit. The housing may include, for example, a body of refractory material, such as refractory cement, adhesive filler, and / or a metal support.

[0055] In a preferred embodiment, the sensing element, preferably at least one sensing element enclosed in a housing, fills the void of the metal body; in other words, the sensing element or the housing surrounding the at least one sensing element is at least partially molded to fit into the central void of the metal body. This further enhances the compact design of the sensor unit and avoids low-density voids. Furthermore, no additional filler elements are required as a solution to increase the overall density of the drop-in probe, as disclosed, for example, in EP 0 758 445 A1.

[0056] Preferably, the combined net density of all components enclosed by the outer contour of the sensing element and the metal body is higher than the density of the molten metal. The combined net density of all components enclosed by the outer contour of the sensing element and the metal body should be understood as the combined density of these components, i.e., the density of the entire building block, which may also include voids or further elements enclosed by the metal body (e.g., electrical contact elements or the housing of the sensing element). In the following, for brevity, this parameter will be referred to as the combined net density of the sensing element and the metal body. In a preferred embodiment, the combined net density of the sensing element and the metal body is at least 5% higher, more preferably at least 8% higher, and even more preferably more than 10% higher than the density of the molten metal. The combined net density of the sensor unit and the metal body is 7.2 g / cm 3 Higher, preferably 7.5 g / cm 3 Higher, more preferably 7.8 g / cm 3 The combined net density of the metal body may be, for example, 7.2 to 8.6 g / cm 3 more preferably in the range of 7.6 to 8.4 g / cm 3 In a preferred embodiment, the combined net density of the sensing element and metal body is at least 80%, more preferably at least 90% of the density of the metal body.

[0057] In a preferred embodiment, the proportion of the void enclosed by the sensing element and metal body is less than 20%, more preferably less than 15%, and most preferably less than 10% of the net external volume of the sensing element and metal body. The void enclosed by the sensor unit is a cavity having a density less than 20% of the combined net density of the sensing element and metal body. The net external volume of the sensing element and metal body should be understood as the volume enclosed by the outer contours of the sensing element and metal body.

[0058] Preferably, the sensor unit does not include any additional mass or buoyancy components. The low mass of the sensor unit makes it particularly suitable for acceleration, and therefore high speed, before being immersed in the molten metal bath, eliminating the need for such additional balancing. Therefore, the design of the sensor unit can be simplified and miniaturized. This miniaturization further enables the sensor unit to be introduced into a metallurgical vessel through available entry points (for which conventional drop-in sensors or lance systems are too large).

[0059] The sensor unit may include electrical contact elements adapted to connect the sensor unit to suitable means for transferring measured data, typically signal lines. Such contact elements facilitate mounting of the sensor unit, provide stable contact to the signal lines, and reduce forces on the sensing element. Preferably, the bath contact and the sensing element are electrically connected to the electrical contact elements.

[0060] Advantageously, the electrical contact element is arranged completely within the metal body, in particular within a central cavity of the metal body.

[0061] The measurement probe comprises a signal line connected to the sensor unit, the signal line being adapted to transfer signals acquired by the sensor unit, in particular the sensing element, to a suitable processing unit or transfer means adapted to transfer the signals to such a processing unit. In other words, the signal line preferably provides a connection between the sensor unit and the processing unit.

[0062] Preferably, the signal line is connected to the rear end of the sensor unit, preferably by an electrical contact element, which should be understood as the end where the rear end of the metal body is located, and extends from the connection section, which is the part connected to the signal unit, to the rear section, which is the opposite part.

[0063] The signal line includes at least two individual wires, i.e., at least two single wires that are not enclosed in a common cable sheath. In the context of the present invention, a wire is to be understood as a conductive core, typically made of a metallic material, e.g., rubber or silicone material, embedded in an insulating sheath. The conductive core may also include multiple single fibers or filaments. A cable is to be understood as multiple wires enclosed in a common cable sheath. Surprisingly, it has been found that the use of individual wires improves the unwinding behavior of the signal wire from the carrier element and further improves the free-flight phase of the sensor unit when the sensor unit is directed toward molten metal. Furthermore, a single wire has a smaller mass, thus reducing the mass of the sensor unit that needs to pull the signal wire during free flight.

[0064] The signal wires must meet several requirements. They must withstand the measurement environment long enough for the sensor unit to reach the measurement point and obtain the required data. Furthermore, they must be compatible with methods for immersing the sensor unit, for example to allow acceleration of the sensor unit. In particular, for methods that include a free-flight phase of the probe, the signal wires must support the control of this phase without interference. Therefore, the flexibility and material of the signal wires must be selected accordingly.

[0065] The metallic material may be selected from the group including copper (Cu), copper-nickel (CuNi), chromel (nickel (Ni) based alloy containing chromium (Cr)), and alumel (nickel (Ni) based alloy containing aluminum (Al), manganese (Mn), and silicon (Si)). In a preferred embodiment, the wire comprises a copper (Cu) or copper-nickel (CuNi) conductive core. The cross-sectional area of ​​the conductive core is between 0.05 and 3 mm. 2 , preferably 0.1 to 2.5 mm 2 may be in the range of

[0066] Suitable materials are, for example, rubber, preferably silicone rubber or EPDM (ethylene propylene diene monomer) rubber. Preferably, the material of the insulating sheath does not melt completely when in contact with the molten material, but preferably decomposes at least partially into inorganic materials. Such decomposition behavior allows the conductive core of the wire to be protected for a longer period of time, thus increasing the signal line's life before failure. Preferably, the insulating material is silicone rubber.

[0067] Preferably, the outer diameter of each individual wire is less than 3 mm, more preferably less than 2 mm, and even more preferably less than 1 mm. For example, the outer diameter of each individual wire ranges from 0.2 to 3 mm, more preferably from 0.4 to 2 mm, and even more preferably from 0.3 to 1 mm. The outer diameter of the wire refers to the cross-sectional area perpendicular to the longitudinal length of the wire through the conductive core and insulating sheath. Wires commonly used in state-of-the-art sensor units typically have diameters greater than 4 mm, which results in relatively high stiffness. Wires that can be used in the sensor unit according to the present invention can have smaller diameters, resulting in greater flexibility. Such flexibility has been shown to be advantageous for the stability of the connection between the signal line and the sensor unit. Furthermore, a more compact design of the entire measurement probe, particularly the carrier element, is possible.

[0068] In a preferred embodiment, the ratio of the diameter of the active area of ​​the sensing element to the diameter of the individual wires is in the range of 1-1 to 1-4, preferably 1-2 to 1-3. This area ratio ensures that the individual wires are matched to the response time of the sensing element.

[0069] Preferably, the density of the signal wire is lower than the density of the molten metal. In such a configuration, the signal wire generates a buoyancy force when the sensor unit is immersed in the molten metal and supports vertical alignment of the sensor unit during measurements. Preferably, the density of the signal wire is within the range of the density of the slag layer that typically covers the molten metal, averaging about 1.8 g / cm. 3 Such a configuration creates a buoyant force on the portion of the signal wire immersed in the molten metal, and an opposing gravitational force on the portion located in the slag layer. Preferably, the density of the signal wire is 5 g / cm 3 less than 4 g / cm 3 The density of the signal line is, for example, 1 to 5 g / cm 3 range, more preferably 2 to 4 g / cm 3 may be in the range of

[0070] In a preferred embodiment, the density of the signal wire is less than the combined net density of the sensing element and the metal body. It has been found that the density of the signal wire advantageously corresponds to the combined net density of the sensing element and the metal body. The balance between the densities of these components improves the sinking and rising behavior when the sensor unit is immersed in molten metal for measurement, and also supports vertical alignment of the sensor unit during measurement. Preferably, the density of the signal wire is 50% or less, more preferably 40% or less, and even more preferably 30% or less of the combined net density of the sensing element and the metal body.

[0071] A signal line may include a single portion or multiple portions connected to each other, where a portion should be understood as a section comprising the same material.

[0072] It should be understood that the length of the signal line is selected to be long enough to bridge the distance from the measurement point of the sensor unit to the processing unit, or at least to the connection means for transferring the sensor unit's signal.

[0073] The sensor unit may include a steering element that adjusts the balance of the sensor unit during the free flight phase of immersion, thereby improving the behavior of these components during this movement phase. Additionally, the steering element may provide additional support to the signal line, ensuring that the signal line unwinds in an orderly manner during the movement phase of the sensor unit during the measurement sequence.

[0074] The steering element is preferably provided on or at the rear end of the metal body of the sensor unit.

[0075] The steering element may be an elongated component, e.g., a wire-shaped element. The steering element may be made of metal, e.g., copper, steel, or stainless steel. In a preferred embodiment, the steering element is a steel wire. The diameter of the steel wire may be in the range of 0.3 to 3 mm, preferably in the range of 0.8 to 2.5 mm.

[0076] The length of the steering element may be in the range of 5 to 25 cm, preferably in the range of 10 to 20 cm.

[0077] In a preferred embodiment, the first section of the signal line is laid in at least one loop along the steering element. This looped guide of the signal line provides a certain amount of slack that moves with the signal unit as soon as it moves, ensuring a stable connection between the signal line and the sensor unit. Preferably, the length of the first section of the signal line is no more than five times, preferably no more than three times, the length of the steering element.

[0078] The loop of signal wire may be secured to the steering element by suitable securing means, such as a clip or paper tape. Preferably, only one leg of the loop of the first section of signal wire is secured to the steering element. Such single-leg securing allows for more balanced movement of the sensor unit with the steering element during use.

[0079] Another aspect of the invention is a sensor assembly that includes a sensor unit having a steering element and a signal line connected to a sensing element of the sensor unit.

[0080] The aspects of the present invention directed to the sensor unit, steering element and signal line of the measurement probe of the present invention described above are also preferred aspects of the sensor assembly of the present invention.

[0081] The measurement probe comprises a carrier element, which is preferably a hollow body, for example a tube, preferably a cardboard tube, configured to hold and / or accommodate other components of the measurement probe, such carrier element protecting and holding the other components of the measurement probe prior to use.

[0082] The signal wire may be wound within a carrier element. For example, the signal wire may pass through the interior of a carrier tube and be wound in at least one layer around its longitudinal axis within the carrier tube. Preferably, the signal wire is wound in a loop having a diameter in the range of 7 to 20 times, preferably 8 to 15 times, the outer diameter of the individual wires. The loop diameter refers to the outer diameter of the loop. If the signal wire is wound in multiple layers, the diameter refers to the outer diameter of the inner layer. The inner layer should be understood as the layer having the greatest distance to the inner surface of the carrier element.

[0083] The inner diameter of the carrier element is 7 to 20 times the outer diameter of the individual wires of the signal line, preferably 8 to 15 times the outer diameter of the individual wires. Surprisingly, it has been shown to be advantageous if the outer diameter of the individual wires of the signal line corresponds to the inner diameter of the carrier element, particularly when the carrier element is a tube. Such a ratio ensures sufficient fixation of the signal line within the carrier element while still allowing for unwinding control without the need for additional pulling forces.

[0084] Preferably, the outer diameter of the individual wires of the signal line is less than 3 mm, and the inner diameter of the carrier element is 7 to 20 times the outer diameter of the individual wires. Such a correlation has been found to be advantageous for a compact design of the measurement probe, while still ensuring sufficient stability of the signal line configuration within the carrier element.

[0085] Preferably, the inner diameter of the hollow body of the carrier element is in the range of 20 to 60 mm, more preferably in the range of 25 to 50 mm.

[0086] The sensor unit is preferably separable from the carrier element. In other words, the sensor unit may be releasably mounted in or on the carrier element. In use, the signal line can be pulled out from the rear of the carrier element while the sensor unit is released from the carrier element and immersed in the molten metal. It should be understood that the signal line is not released from the sensor unit but remains connected at least until the measurement sequence is finished.

[0087] For example, the measurement probe may include a first coupling component configured to releasably engage a second coupling component disposed on or in the sensor unit, and the measurement probe may also include a catch element that releases the sensor unit when a certain force is applied.

[0088] The sensor unit may be arranged at least partially within the carrier element, the end of the carrier element at which the sensor unit is arranged being referred to as the front end of the carrier element and the opposite end being referred to as the rear end of the carrier element.

[0089] The measurement probe may include a retaining element that enables a mechanism for releasing the sensor unit from the carrier element. The retaining element may be fixed to the carrier element and may be configured to releasably engage one end of the sensor unit. The retaining element may include at least one opening for a signal line.

[0090] The measurement probe may include a fixation element disposed within the carrier element. The fixation element is configured to appropriately fix and organize the signal wire within the carrier element. Depending on the length of the signal wire, it may be necessary to adjust the deceleration of the signal wire. This can be achieved by increasing the pulling force required to remove the last of the rear section of the signal wire from its one or more windings. The fixation element further relieves pulling forces from the signal wire on the sensor unit and the connection element during probe immersion.

[0091] Preferably, the fixing element is disposed at the rear end of the carrier element. In a preferred embodiment, the fixing element is disposed on the signal line, i.e., the signal line extends at least partially between the interior of the carrier element and the fixing element. The fixing element may include an opening configured to allow the signal line to pass freely. Such an opening allows the signal line to slide freely when the winding is unwound in a free fall.

[0092] The fixation element may, for example, be provided as a ring having an opening through which the signal line can pass.

[0093] The measurement probe may include a probe contact element adapted to be connected to the rear section of the signal line. Such an electrical connection element may preferably be adapted to be disposed within a carrier element, which may for example be a plug-type element.

[0094] Preferably, the probe contact elements are adapted to transfer the signals of the signal lines to a processing unit, for example by wired or wireless transmission.

[0095] The measuring probe may include a protective element. Such a protective element protects the sensor unit from damage caused by impact with the molten metal surface during handling. Preferably, the measuring probe may include a protective cap surrounding at least the sensor unit and made of a material that dissolves or melts in the molten metal. The protective element may be made of, for example, aluminum or copper, preferably copper.

[0096] The protective element is preferably provided on or at the immersion side of the sensor unit, preferably on the immersion end of the metal body of the sensor unit, and is therefore the first part of the sensor unit to come into contact with the molten metal when the sensor unit is immersed.

[0097] The protective element may have a conical or frustoconical shape, which on the one hand improves the flight behavior of the immersion probe and on the other hand reduces the frictional forces when the probe is immersed in the molten metal.

[0098] The protective element may comprise openings, for example circular, oval or slit-shaped openings, which enhance the melting behavior of the protective element, especially in the case of protective elements provided as metal caps.

[0099] In another aspect, the present invention relates to a method for measuring at least one parameter of molten metal or slag using a measurement probe of the present invention, the method comprising: i) providing a measurement probe; ii) separating the sensor unit from the carrier element; iii) immersing the sensor unit in the molten metal; and iv) measuring at least one parameter of the molten metal.

[0100] The steps of the method are performed in a given sequential order.

[0101] The above-described aspects of the invention directed to the measurement probe of the invention are also preferred aspects of the method of the invention.

[0102] It has been found that the measurement probe of the present invention is particularly suitable for further acceleration. Surprisingly, accelerating the sensor unit rather than solely by gravity has several advantages: the mass, dimensions and number of components of the probe housing the sensor unit can be reduced; the reduced material demands reduce costs and also reduce contaminants introduced into the molten metal; this miniaturization of the sensor and measurement probe allows the sensor unit to be introduced through openings of reduced size, which previously could not be used for introducing probes using state-of-the-art methods.

[0103] The method according to the invention comprises separating the sensor unit from the carrier element, i.e. the sensor unit is released from the carrier element of the measuring probe before immersion of the sensor unit, which can be achieved for example by a release mechanism provided on the measuring probe and / or by a corresponding release means provided by an external device.

[0104] The method according to the present invention includes immersing the sensor unit in the molten metal, i.e., the sensor unit enters the molten metal from the surface of the molten metal, and if a slag layer is present in the molten metal, the sensor unit passes through this slag layer before entering the molten metal.

[0105] The method includes measuring at least one parameter of the molten metal. It should be understood that the measurement is performed when the sensor unit is immersed below the surface of the molten metal. "Measuring" is used herein to describe the step of obtaining a determination of the at least one parameter. This step may include measuring a single data point or may include measuring multiple data points, i.e., measuring a series of data points. Measuring may include additional steps, such as transmitting the data to a processing unit and / or processing the data.

[0106] The method may include further steps, for example the method may include accelerating the sensor unit towards the molten metal by suitable acceleration means, for example a pneumatic accelerator.

[0107] After measuring the parameter, further steps may follow, such as releasing or ejecting parts of the measurement probe, cutting remaining cables, etc.

[0108] The following schematic drawings illustrate aspects of the present invention in relation to several exemplary views to enhance understanding of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals indicate corresponding like parts. [Brief explanation of the drawings]

[0109] [Figure 1] FIG. 2 is a schematic cross-sectional view of a measurement probe. [Figure 2] 1 shows the sensor unit in more detail. [Figure 3] 1 shows an exemplary setup for measurements using a measurement probe. [Figure 4] 1 shows a sensor assembly having a sensor unit including a steering element.

[0110] FIG. 1 shows a cross-sectional view of a measurement probe 1. The probe 1 includes a cardboard tube as a carrier element 2 around which a signal wire 3 is wound. A sensor unit 4 is at least partially mounted at one end within the carrier tube 2 and held by a release mechanism 5. Within the sensor unit 4, a sensing element 6 is embedded in a copper body 7. To protect the sensing element 6 during handling of the measurement probe 1, a protective cap 8 made of a material that dissolves or melts in molten metal surrounds the sensing element 6. The protective cap 8 may be made of copper, for example. Along the inside of the carrier tube 2, the signal wire 3 is wound into a winding 9. One end of the signal wire 3 is connected to the sensor unit 4, and the other end of the signal wire 3 is connected to a probe contact element 10 at the rear end of the carrier tube 2. The probe contact element 10 can provide a suitable connection point to an extension cable or to a means for wirelessly transferring signals acquired by the sensor unit 4 to a processing device.

[0111] Figure 2 shows a cross-sectional view of the sensor unit 4 in more detail. The sensor unit 4 includes a needle-shaped oxygen measuring cell 21 and a thermocouple 22 as sensing elements. Therefore, when the sensor unit 4 comes into contact with a molten metal, it can measure the oxygen activity and temperature of the molten metal. The needle cell 21 is, for example, a molybdenum (Mo) pin, which is coated with a layer of a chromium-chromium dioxide mixture (Cr-Cr2O3) as a reference material under a layer of stabilized zirconium oxide (stabilized zirconia) as a solid electrolyte. The diameter of the oxygen sensor tip ranges from 0.5 to 2 mm. Suitable thermocouples include, for example, Type B, Type D, Type G, or Type C thermocouples. Among these, Type C thermocouples with tungsten-rhenium legs (W / Re) alloys (95 wt% W / 5 wt% Re vs. 74 wt% W / 26 wt% Re) are preferred. The thermocouple's hot junctions have a diameter of 2 mm or less to ensure a fast response time. Both sensing elements (21, 22) are encapsulated in a ring-shaped bath contact 23. The sensing elements (21, 22) are connected to an electrical connector 24, to which the signal line 3 is also connected. The connection between the sensing elements (21, 22) and the electrical connector 24 can be secured by a housing 25 of refractory cement, any other suitable refractory material, or partially by a suitable adhesive. The housing 25 of the sensing elements (21, 22) has a generally cylindrical outer shape and is sized to fit snugly within a bore 26 in the metal body 7. The central longitudinal bore 26 extends through the body 7 from the immersion end 27 to the rear end 28 and can be drilled, for example, in a cast solid metal body. The mass of the complete assembly is 8 g / cm 3 The density is about 180g, of which 150g is related to the metal body.

[0112] During the measurement sequence, the measurement probe is positioned above the molten metal bath. Once in position, release and separation of the sensor unit from the carrier can be initiated by suitable means. The sensor unit is then accelerated either by gravity alone or by an additional external acceleration mechanism to move towards the molten metal.

[0113] FIG. 3 shows an exemplary measurement setup in which the measurement probe 1 of the present invention can be advantageously used. A metallurgical vessel 30, such as an electric arc furnace (EAF), has an acceleration means (accelerator 31) integrated into its sidewall. EAFs used in steelmaking typically include a vessel 32 holding a molten metal bath 33 and a removable lid 35 through which one or more electrodes 36 can enter the furnace. A slag layer 34 covers the molten metal 33. The electrodes 36 used to heat the metal are positioned on top of the vessel 32. Typically, the interior of the metallurgical vessel 30 is heated to temperatures of about 600-2000°C or even higher during processing.

[0114] 3, the first step is to mount the measurement probe 1 on the accelerator 31 (as shown). An extension cable 39 connects the sensor unit of the measurement probe 1 to a processing device 40 that may be located remotely from the vessel 30.

[0115] Inside the accelerator 31, the sensor unit is separated from the carrier part of the probe 1. This separation can be achieved by a suitable device, for example a shoulder or a barrel-shaped cone inside the accelerator 31, against which the holding means of the probe 1 are pressed and the sensor unit is released. It should be emphasized that none of the connections between the sensor unit and the signal lines or suitable connectors are released, but are all arranged to remain in place at least until the measurement sequence is completed.

[0116] The sensor unit is then accelerated, for example by compressed air, and released with high initial velocity and momentum from the accelerator 31 into the interior of the vessel 30, towards the molten metal bath 33. The sensor unit flies in a straight line path towards the molten metal 33, penetrating the surface 38. A signal line connected to the sensor unit is led out of the carrier element behind the sensor unit, and is selected to survive the harsh environment inside the vessel for a sufficiently long time to ensure that measurements can be taken.

[0117] Due to the individual wires, the associated minimized size and mass, and the optimized dimension ratios, the measurement probe according to the invention is particularly suitable for measurement sequences involving active acceleration.

[0118] Once the sensor unit is immersed below the surface of the molten metal bath, the desired parameters can be measured and the respective signals transferred to a suitable processing device 40. After recording the required data, the accelerator 31 can be removed from the elements of the probe 1 that have not been injected into the molten metal, for example by ejecting them into the molten metal bath 33.

[0119] FIG. 4 illustrates a sensor assembly 50 having a sensor unit 4 including a steering element 51. The steering element 51 supports a first section of a signal line 3 connected to a sensing element within a metal body 6 (connections not shown). The steering element 51 is wire-shaped, e.g., a steel wire, and its first end is attached to the metal body 7 of the sensor unit 4. In the illustrated embodiment, the signal line 3 includes three individual wires. The wires are routed along the steering element 51 in a single, elongated loop and partially secured to the steering element 51. The securing means may be, for example, paper tape 52, which easily burns away as soon as the sensor unit 4 enters the molten metal. The sensor assembly 50 includes a cup-shaped protective element 8 having an elongated lateral slit 53. Such an opening accelerates the melting of the protective element 8 in the molten metal. The cap may include multiple lateral openings.

[0120] Those skilled in the art will appreciate that changes and modifications can be made to the above-described embodiments without departing from the broad inventive concept of the present invention. It is therefore understood that the invention is not limited to the particular embodiments disclosed, but that it is intended to cover all embodiments falling within the scope of the appended claims. [Explanation of symbols]

[0121] 1 measuring probe 2. Career Elements 3 Signal Line 4 Sensor Unit 5 Release mechanism 6 Sensing Elements 7 Metal body 8 Protective cap 9 Signal line winding 10 Probe Contact Elements 21 Oxygen measuring cell 22 Thermocouple 23 Bath contact 24 Electrical Connectors 25 Sensing element housing 26 Metal body bore 27 Immersed end of metal body 28 Rear end of metal body 30 Metallurgical vessels 31 Accelerator 32 Container 33 Molten metal bath 34 Slag layer 35 Removable Lid 36 EAF electrodes 37 Entry Point 38 Surface of a molten metal bath 39 Extension Cable 40 Processing equipment 50 Sensor assembly 51 Steering element 52 Paper Tape 53 Openings in protective elements

Claims

1. 1. A measurement probe for molten metal, comprising: a sensor unit adapted to determine at least one parameter of the molten metal, A sensing element; a metal body at least partially surrounding the sensing element; and a signal line including at least two individual wires connected to the sensor unit; a carrier element; A measuring probe, characterized in that the inner diameter of the carrier tube is 7 to 20 times the outer diameter of said individual wires.

2. The measurement probe of claim 1 , wherein the individual wires have an outer diameter in the range of 0.2 to 3 mm.

3. The measurement probe of claim 1 , wherein the signal wire is wound within the carrier element.

4. The measurement probe according to claim 1 , wherein the mass of the sensor unit is in the range of 80 to 500 g.

5. The measurement probe of claim 1 , wherein the sensor unit includes a plurality of sensing elements.

6. The measurement probe of claim 1 , wherein the sensor unit includes a thermocouple and / or an electrochemical cell.

7. The measurement probe of claim 1 , wherein the active area of ​​the sensing element has a diameter of less than 2.5 mm.

8. 2. The measurement probe of claim 1, wherein the ratio of the diameter of the active area of ​​the sensing element to the diameter of the individual wires is in the range of 1-1 to 1-4.

9. The measurement probe of claim 1 , wherein the at least one sensing element has a response time of less than 5 seconds.

10. The measurement probe of claim 1 , wherein the combined net density of the sensing element and the metal body is at least 80% of the density of the metal body.

11. The measurement probe of claim 1 , wherein the maximum cross-sectional area of ​​the central void of the metal body is less than 25% of the maximum total cross-sectional area of ​​the metal body.

12. The measurement probe of claim 1 , wherein the density of the signal wires is no more than 50% of the combined net density of the sensing element and the metal body.

13. The measurement probe of claim 1 , wherein the sensor unit includes a steering element.

14. 10. A method for measuring at least one parameter of molten metal or slag using a measurement probe according to claim 1.

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