Method and system for determining the temperature value of a molten metal bath - Patents.com

Abstract

The present invention relates to a method and a system for determining the temperature value of a molten metal bath. The method according to the invention has proven to be particularly suitable for repeatedly determining the temperature value, i.e., it allows multiple measurements with repeatedly newly generated front ends of the optical core wire.

Description

[Technical field]

[0001] The present invention relates to a method and system for determining a temperature value of a molten metal bath. [Background technology]

[0002] The temperature of the molten metal bath in a metallurgical vessel is a critical parameter during the metal manufacturing process and determines the quality of the resulting product. A possible means for measuring the temperature of a molten metal bath, especially iron or steel in the melting environment of an electric arc furnace (EAF), involves immersing an optical fiber surrounded by a metal tube into the molten metal. The optical fiber surrounded by a metal tube is often also referred to as an optical core wire.

[0003] To measure the temperature of the molten metal bath, the optical core wire can be sent into the metallurgical vessel. The front end of the optical core wire is immersed in the molten metal bath, and on the way there first encounters a high temperature atmosphere, then a slag layer, and then the molten metal bath. When a portion of the optical core wire is immersed below the surface of the molten metal bath, the optical fiber can transmit the thermal radiation received from the molten metal to a detector, for example a pyrometer. A suitable instrument can be associated with the detector to determine the temperature of the molten metal bath. During this measurement, the immersed portion of the optical core wire can be partially or completely consumed by the molten metal bath. Once the temperature measurement is finished, the tip of the optical core wire can be retracted from the molten metal bath. The retracted tip of the optical core wire becomes the new front end for the next temperature measurement.

[0004] Such devices are suitable for on-demand and semi-continuous temperature measurements in the form of a series of immersion cycles, allowing an operator to obtain temperature measurements without directly intervening in the hostile environment proximate to the metallurgical vessel.

[0005] To provide accurate measurements, blackbody conditions must be ensured near the immersed front end of the optical fiber while measurements are being taken. The fiber must be immersed to a sufficient depth below the metal bath surface and at a position within the vessel that is representative of the temperature of the liquid metal bath. On the other hand, deep immersion increases the buoyancy forces on the optical core wire, increasing wear during the measurement sequence.

[0006] For accurate temperature measurement, the use of an unvitrified optical fiber is essential, especially the condition of the front end. The devitrification rate depends on a variety of factors, among them the construction of the optical core wire, the thermal environment of the metallurgical vessel to which the optical core wire is exposed before, during and after each measurement cycle, the amount and type of slag layer covering the molten metal bath, and the actual conditions and temperature of the molten metal bath.

[0007] Many of the devices known in the prior art are generally constructed by using an optical fiber placed in a protective tube. The gap between the optical fiber and the metal tube may be filled with a filler material prior to immersion and data collection to further protect the optical fiber from the harsh environment and heat of the molten metal bath. The layered structure helps to keep the optical fiber cool for a relatively long time. Devitrification due to high temperatures that would destroy the optical fiber is delayed. For example, JP 10-176954 A describes a fiber surrounded by metal tubes at intervals. A tube made of a thermal barrier coating is arranged around this metal tube, and this thermal barrier coating is surrounded by an outer metal tube. This structure prevents the inner metal tube from melting too quickly.

[0008] When performing a series of measurements, exposure of the optical core wire to the environment inside the metallurgical vessel is of particular concern. In such cases, thermal exposure of the optical fiber occurs not only in the time frame immediately prior to the measurements being taken, but also in the intervals between measurements.

[0009] With regard to these multiple dips, JP 09-243459 A teaches the additional corrective measure of cutting the potentially damaged immersed optical fiber from the feed after each measurement cycle and providing a new front end before each measurement. This solution solves the problem of using the damaged portion of the optical fiber, but requires additional equipment and the size of the devitrified portion of the fiber is unknown.

[0010] Additionally, various methods have been proposed for delivering a consumable optical fiber to a bath of molten metal in order to deliver the optical fiber core to the molten metal before it devitrifies.

[0011] For example, JP 09-304185 A discloses an optical fiber feeding method in which the fiber wear rate must be greater than the devitrification rate. The method involves two feeding steps with an intervening wait period, where the first feeding is performed until a predetermined threshold temperature is recorded. Temperature measurements taken during each feeding step are then compared to determine whether additional measurement cycles are required.

[0012] US 2007-268477 discloses a feeding method in which the feed rate is adjusted during the measurement cycle. The thermal response is recorded during a first feeding step and compared to the change in the detected temperature in a second step. Although this method offers some advantages, it does not address the fact that during the initial step, the optical core wire is barely immersed in the molten metal bath, but encounters the melting furnace environment or the slag layer, resulting in inaccurate results.

[0013] Several prior art documents disclose methods for feeding a metal-coated optical fiber, which is further covered by a movable guide tube prior to immersion in the molten metal. For example, JP2010-071666 discloses a first stage in which the fiber and guide tube are fed from a retracted position to near the surface of the molten metal bath at a decreasing speed in three stages. The fiber is then fed into the bath and the temperature can be recorded. In JP10-185698, the feeding of the optical fiber is further controlled by several means, inter alia, based on feedback regarding the rate of increase of the measured temperature and a predetermined length of time.

[0014] These solutions provide a long-lasting protective environment for the fiber and have low fiber wear demands, but require additional equipment.

[0015] US Patent Application Publication No. 2018-180484 discloses a method for measuring the temperature of a molten metal bath, suitable for multiple measurement cycles and without the need for additional equipment. The proposed feed scheme includes two feed rates followed by a rest period, after which a temperature measurement is performed. On the one hand, the method solves some of the problems previously known for certain conditions in metallurgical processes. On the other hand, it does not address the exact level of the metal bath. Since the first feed requires a reliable immersion of the front end of the optical core wire below the molten metal bath surface, the amount of optical core wire consumed during a measurement cycle may be higher than necessary.

[0016] In view of the prior art, there is a need for a measurement method and system that provides high accuracy over the full range of possible conditions typical in the processing of molten metals, particularly the various parameters of the molten metal bath and the various construction details of metallurgical vessels. Summary of the Invention

[0017] It is therefore an object of the present invention to provide an improved method for determining the temperature value of a molten metal bath by means of an optical core wire, which solves at least one of the above mentioned problems. In particular, one of the objects is to provide an improved method for determining the temperature value more reliably over a wide range of application conditions. In particular, the object is to improve the melting and decomposition behavior of the optical core wire during and after the determination of the temperature value. Another object is to provide a device which makes it possible to minimize the wear of the optical core wire during the determination. It is further an object to provide a method for obtaining temperature values ​​at a specific immersion depth of the optical core wire.

[0018] It is a further object of the present invention to provide an improved system for carrying out the method of the present invention.

[0019] These objects are achieved by the subject matter defined in the independent claims.

[0020] The present invention relates to a method for determining a temperature value of a molten metal bath using an apparatus comprising an optical core wire and a detector, comprising: (a) providing an optical core wire having a front end at a position p1 above the surface of a molten metal bath; (b) moving the front end directed toward the molten metal bath from position p to position p at an immersion depth i below the surface of the molten metal bath at a speed v over a first time period from t to t; (c) feeding the front end at a speed v to a position p at an immersion depth i below the surface of the molten metal bath for a second time period from t to t; (d) advancing the front end at a speed v3 to a position p4 at an immersion depth i3 below the surface of the molten metal bath for a third time period from t3 to t4; (e) pausing the feeding of the leading end or feeding the leading end at a speed v4 for a fourth time period from t4 to t5, respectively; (f) after t5, retracting the front end at a speed v5 to a position above the surface of the molten metal bath; (g) acquiring temperature information of the molten metal bath within a measurement time period from t2 to t5; including the immersion depth and speed have the following relationships: (i) i2 > i1 (ii) i3 > i2 (iii) v1 > v2 (iv) v2 < v3 and (v) v4 < v1 or v2 or v3 having provides a method.

[0021] To avoid misunderstanding, the positions p1, p2, p3, and p4 described in steps (a) to (d), and the position above the surface of the molten metal bath described in step (f) are the positions of the front end of the optical core wire. A person skilled in the art will understand that "feeding the front end" and "sending the front end" necessarily include feeding and sending the optical core wire, that is, feeding the optical core wire having the front end, and moving the optical core wire having the front end to the above-described positions.

[0022] The time points t1, t2, t3, t4, and t5 follow immediately after each other, that is, they follow without a gap.

[0023] Furthermore, the present invention provides a system for carrying out the method according to the present invention.

[0024] More preferred embodiments are defined in the dependent claims. The preferred embodiments may be realized individually or in any possible combination.

[0025] The method according to the invention has proven to be particularly suitable for repeatedly determining temperature values, i.e. the method allows multiple measurements with a front end of an "endless" optical core wire, which is repeatedly newly generated. The method according to the invention allows a reliable positioning of the front end of the optical core wire, and therefore further allows determining an accurate temperature value with a minimum of wear and tear of the optical core wire. The term "wear and tear" as used herein refers to the destruction of the optical core wire, such as, for example, melting and dissolving the optical core wire by and into the molten metal bath, decomposition or burning of the entire optical core wire or different parts thereof. In particular, the method according to the invention ensures that the front end of the optical core wire is in an optimal state for determining a temperature value at a specific immersion depth.

[0026] The present invention provides a method for determining the temperature value of a molten metal bath.

[0027] "Determining a temperature value" may be used herein as a synonym for measuring a temperature, which will be understood to refer to obtaining a single point measurement, or a method that includes multiple single point measurements and optional associated data processing.

[0028] As used herein, the term "molten metal bath" is used to describe the melt in a vessel. An alternative term to "molten metal bath" known to those skilled in the art is "metal melt". The molten metal of the molten metal bath is not particularly limited. According to a preferred embodiment, the molten metal is molten steel. The term molten metal bath does not exclude the presence of any solid or gaseous parts, including, for example, non-molten parts of the respective metal. The molten metal bath may be covered with a slag layer.

[0029] The temperature of the metal melt varies and typically depends on the composition of the metal and the stage of the melting process. Preferably, the temperature of the molten metal bath is in the range of 1500-1800°C, more preferably in the range of 1500-1700°C.

[0030] The molten metal bath may be contained within a vessel that includes an inlet suitable for feeding the optical core wire, which may be located in a sidewall panel or roof covering the vessel.

[0031] The present invention provides a method for determining a temperature value using a device comprising an optical core wire, preferably an optical fiber surrounded laterally by a metal tube.

[0032] Preferably, the optical fiber is a flexible, transparent fiber. Optical fibers are most often used as a means of transmitting light, especially in the IR wavelength range, between two ends of the fiber. Preferably, the optical fiber is made of glass or plastic, more preferably quartz glass. Preferably, the optical fiber is selected from the group consisting of graded index fiber and single mode step index fiber.

[0033] The metal tube surrounding the optical fiber may completely surround the optical fiber, or may be at least partially open so that the casing does not completely surround the optical fiber.

[0034] Preferably, the metal of the metal tube surrounding the optical fiber is iron or steel, preferably stainless steel.

[0035] In a preferred embodiment, the linear density of the optical core wire is in the range of 25-80 g / m, even more preferably in the range of 35-70 g / m. Linear density is defined by the mass per unit length.

[0036] Preferably, the optical core wire is laterally surrounded by at least one additional metal tube, i.e. at least two metal tubes laterally surround the optical fiber, more preferably, the optical core wire is disposed in the center of the at least one additional metal tube.

[0037] Preferably, the at least one additional metal tube is not in contact with the optical core wire. More preferably, the gap between these at least two metal tubes is at least partially filled with a material selected from the group consisting of a gaseous material or a solid material or a combination thereof. The solid material is preferably selected from the group consisting of an inorganic material, a natural polymer, a synthetic polymer and a combination thereof. The gaseous material is preferably a gas or a mixture of gases. More preferably, the gas is air or an inert gas.

[0038] According to a preferred embodiment, the optical core wire comprises a plurality of separating elements arranged in at least one metal tube, said separating elements forming at least one compartment between said separating elements. Here, the term "compartment" relates to the volume between different separating elements in the tube. The term "separating element" relates to a portion arranged in the tube that subdivides the volume in the tube. Preferably, the separating element is a disc-shaped element arranged inside the tube, said disc-shaped element comprising an opening through which the optical core wire extends and which is capable of at least partially supporting the optical core wire. The material of the separating element is preferably selected from the group consisting of silicone, preferably two-component silicone, rubber, leather, cork, metal and combinations thereof.

[0039] The optical core wire is optionally surrounded by at least one additional layer, which may or may not replace the at least one additional metal tube described above. In a preferred embodiment, the at least one additional layer includes a plurality of portions, and more preferably, the layer includes a fiber.

[0040] In a further preferred embodiment, the material of the at least one additional layer has the form of a woven, net, woven or knitted structure.

[0041] Preferably, the at least one additional layer is made of a variety of materials, more preferably the material is a non-metallic material, most preferably an organic material.

[0042] It should be appreciated that the optical core wire may include any combination of the above configurations. For example, it may be advantageous for the optical core wire to be surrounded laterally by an additional layer and a second metal tube.

[0043] The device used to apply the method according to the invention further comprises a detector, which may be coupled to one end of the optical core wire and which may receive the optical signal, particularly in the IR wavelength range, transmitted by the optical fiber. The detector in the context of the present invention may be a pyrometer.

[0044] The optical core wire has a immersed end and an opposite end. The front end of the optical core wire is the tip of the immersed end of the optical core wire. Preferably, when the method according to the invention is applied, the optical core wire is consumed in a direction from the immersed end to the opposite end, such that after each measurement sequence, another part of the optical core wire becomes the immersed end. That is, after each measurement sequence, the front end is newly generated. The opposite end is connected to a detector and is not consumed during the measurement.

[0045] In step (a) of the method according to the invention, an optical core wire is provided with its front end at a position p1 above the surface of the molten metal bath.

[0046] The surface of the molten metal may be the surface that faces the gas atmosphere above it in the vessel or it may be the surface that faces the slag layer, if one is present.

[0047] Position p1 may be above the vessel, or preferably within the vessel. The front end of position p1 may or may not contact any slag present.

[0048] In step (b) of the method according to the invention, the front end directed towards the molten metal bath is sent with a speed v1 from position p1 to position p2 at an immersion depth i1 below the surface of the molten metal bath over a first time period from t1 to t2.

[0049] Movement toward the molten metal bath may include passing the leading end through a layer of slag as described above, which may or may not be present.

[0050] The immersion depth in relation to the present invention is to be understood as the distance of the front end from the surface of the molten metal bath, measured along an axis perpendicular to the surface.

[0051] It may be advantageous for the immersion angle to be in the range of 45°-90°, preferably in the range of 60°-90°, most preferably the immersion angle is 90°. This angle is defined as the angle between the surface of the molten metal bath and the axis along the optical core wire in a best straight line. 90° may be understood as the immersion of the optical core wire perpendicular to the surface of the molten metal bath.

[0052] The immersion angle is kept constant during the steps involving feeding, i.e., steps (b), (c), (d) and (e).

[0053] In a preferred embodiment, v1 is in the range of 2 to 4 m / s, more preferably in the range of 2.5 to 3.5 m / s.

[0054] According to a preferred embodiment, i1 is in the range of 0.01 to 0.35 m below the surface of the molten metal bath, more preferably in the range of 0.05 to 0.35 m.

[0055] Preferably, the length of the first period from t1 to t2 is in the range of 0.1 to 1 seconds, preferably in the range of 0.25 to 0.75 seconds.

[0056] In step (c) of the method according to the invention, the front end is brought to a position p3 at an immersion depth i2 below the surface of the molten metal bath with a speed v2 over a second time period from t2 to t3.

[0057] According to the present invention, i2>i1, i.e., i2 is deeper below the surface of the molten metal bath than i1.

[0058] According to the invention, the speed v2 is lower than the speed v1.

[0059] In a preferred embodiment, v2 is in the range of 0.05 to 0.5 m / s, more preferably in the range of 0.1 to 0.3 m / s.

[0060] According to a preferred embodiment, i2 is in the range of 0.05 to 0.4 m, more preferably in the range of 0.1 to 0.3 m.

[0061] In a preferred embodiment, the length of the second period from t2 to t3 is in the range of 0.2 to 2.0 seconds, preferably in the range of 0.3 to 1.5 seconds.

[0062] In step (d) of the method according to the invention, the front end is fed at a speed v3 to a position p4 at an immersion depth i3 below the surface of the molten metal bath over a third time period from t3 to t4.

[0063] According to the present invention, i3>i2, i.e., i3 is deeper below the surface of the molten metal bath than i2, and velocity v2 is lower than velocity v3.

[0064] Advantageously, v3 is in the range of 0.5 to 4.5 m / s, preferably in the range of 1.5 to 3.5 m / s.

[0065] According to a preferred embodiment, i3 is in the range of 0.1 to 1.0 m, more preferably in the range of 0.2 to 0.8 m.

[0066] In a preferred embodiment, the length of the third period from t3 to t4 is in the range of 0.05 to 0.45 seconds, preferably in the range of 0.05 to 0.25 seconds.

[0067] According to a preferred embodiment, v1 and v3 are both higher than v2.

[0068] In step (e) of the method according to the invention, the feeding of the leading edge is paused or the leading edge is fed at a speed v4 for a fourth time period from t4 to t5, respectively.

[0069] As used herein, "pausing the feeding of the leading edge" means not actively moving the leading edge.

[0070] In an alternative embodiment, the leading end is fed at a speed v4, preferably less than the speed at which the leading end of the optical core wire moves back towards the surface of the molten metal bath due to some consumption of the optical core wire during melting.

[0071] In either alternative, there is a shift in the position of the leading end towards the surface of the molten metal bath due to wear, nevertheless the leading end is still immersed below the surface of the molten metal bath.

[0072] Preferably, the entire optical core wire that was routed below the surface of the molten metal bath between t1 and t5 is completely consumed by t5.

[0073] According to a preferred embodiment, v4 is less than 0.2 m / s, more preferably less than 0.1 m / s.

[0074] In a preferred embodiment, the length of the third period from t4 to t5 is in the range of 0.05 to 0.5 seconds, preferably in the range of 0.1 to 0.4 seconds.

[0075] In a preferred embodiment, the fourth period of time from t4 to t5 is (i) providing a data set relating measurement data of a molten metal bath to an amount of time; (ii) obtaining measurements during a time prior to t4; (iii) selecting a fourth length of time from the provided data set that corresponds to measurement data obtained during a time prior to t4; The method includes:

[0076] The term "dataset" is used herein as a database containing corresponding data, i.e., such a set includes data pairs in which one particular value of one type of data is assigned to a particular value of another type of data, it may also include data pairs in which one particular value of one type of data is assigned to a model, a sequence of some steps, etc.

[0077] Preferably, the measurement data comprises a temperature value. More preferably, the measurement data is a series of temperature values. Most preferably, the measurement data is the slope of a function describing the series of temperature values.

[0078] Advantageously, the length of the fourth period of time is shorter the higher the temperature values ​​obtained during the period before t4.

[0079] In step (f) of the method according to the invention, the front end is retracted at a speed v5 to a position above the surface of the molten metal bath after t5, i.e. the front end is moved backwards towards a position p1.

[0080] The retraction in step (f) may or may not result in positioning of the front end to position p1.

[0081] Preferably, v5 is in the range of 2 to 4 m / s, more preferably in the range of 2.5 to 3.5 m / s.

[0082] In step (g) of the method according to the invention, temperature information of the molten metal bath is obtained within a measurement time period from t2 to t5.

[0083] "Obtaining temperature information" is used herein to describe the process that results in the determination of a temperature value. This may involve measuring a single data point or measuring more than one data point, i.e., measuring a series of data points.

[0084] Preferably, obtaining the temperature information involves measuring a series of data points.

[0085] The measured temperature may be an average value of a series of data points. In a further embodiment, the obtained temperature may be derived based on application of an algorithm processing the series of data points.

[0086] Preferably, the temperature information is obtained within a measurement time period from t3 to t5.

[0087] The measurement time starts It may be advantageous to be at or after t3+(t4-t3) / 2.

[0088] The measurement time ends It may be advantageous to be before t4+(t5-t4) / 2.

[0089] In a preferred embodiment, at least one of the velocities v1, v2, or v3 is selected based on the properties of the optical core wire, in particular the wall thickness of the tube, the compound material, the specific design, or a combination thereof.

[0090] A "particular design" refers, for example, to a selected combination of the optical core wire embodiments described above, i.e., layer and material selections, among others.

[0091] In another preferred embodiment, at least one of the velocities v1, v2, or v3 is (i) providing a data set relating an expected temperature of the molten metal bath to a velocity v1, v2 or v3; (ii) providing an expected temperature value of the molten metal bath; (iii) selecting, from the provided data set, at least one of the velocities v1, v2, or v3 that corresponds to a predicted temperature; The method includes:

[0092] An expected temperature may be understood as a temperature that is neither measured nor determined, i.e., a temperature obtained based on empirical data, for example. Such empirical data may be properties of the molten metal bath or operational parameters of the metal manufacturing process, such as the energy provided for the melting process or the duration of the process. Properties of the molten metal bath include physical properties of the molten metal bath, for example, the input mass of the molten metal or the composition of the metal.

[0093] In a preferred embodiment, at least one of the first, second, third, or fourth time lengths is selected based on the properties of the optical core wire, in particular the wall thickness of the tube, the compound material, the particular design, or a combination thereof.

[0094] In another preferred embodiment, at least one of the first, second, third or fourth periods of time is: (i) providing a data set relating an expected temperature of the molten metal bath to first, second, third and fourth lengths of time; (ii) providing an expected temperature value of the molten metal bath; (iii) selecting, from the provided data set, at least one of the first, second, third, and fourth time lengths corresponding to an expected temperature; The method includes:

[0095] In a preferred embodiment, at least one of the immersion depths i1, i2, or i3 is selected based on the properties of the optical core wire, in particular the wall thickness of the tube, the compound material, the specific design, or a combination thereof.

[0096] In another preferred embodiment, at least one of the immersion depths i1, i2 or i3 is (i) providing a data set relating an expected temperature of the molten metal bath to an immersion depth i1, i2 or i3; (ii) providing an expected temperature value of the molten metal bath; (iii) selecting from the provided data set at least one of the immersion depths i1, i2 or i3 corresponding to a predicted temperature; The method includes:

[0097] Preferably, the method may further comprise the step (a1) of measuring the level of the surface of the molten metal bath.

[0098] A wide variety of methods for measuring the level of a molten metal bath are known to those skilled in the art, including, for example, determining the payload mass of the material in conjunction with the known density of the molten material and the design of the vessel, contact-based measurements such as utilizing a submerged lance or contact sensor, non-contact-based determinations that may be based on radar or microwaves, and indirect methods such as measuring the pressure within the vessel.

[0099] Preferably, step (a1) is carried out before step (a).

[0100] The invention further relates to a system for carrying out the method according to the invention.

[0101] For preferred embodiments of the method of the present invention, please refer to the above preferred embodiments.

[0102] Preferably, the system comprises the aforementioned device comprising an optical core wire and a detector.

[0103] In one embodiment, the system may comprise a feeding means, which in the context of the present invention may be understood as a means allowing the feeding of the optical core wire into the molten metal bath, such a means may be selected from the group consisting of a feeder, a feed control device, a straightener and a guide tube.

[0104] In a variant of this embodiment, the system also comprises a control means, which is configured to control the operation of the device to carry out the above-mentioned method. The control means may comprise hardware, a memory unit and a processing unit.

[0105] According to a preferred embodiment, the system may further comprise a coil corresponding to the length of the optical core wire. [Brief description of the drawings]

[0106] The concepts underlying the invention are explained in more detail below with reference to the embodiments shown in the drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

[0107] [Figure 1] 1A-1D are schematic cross-sectional views of various designs of optical core wires. [Diagram 2] 1 is a schematic diagram of an exemplary system for measuring the temperature of a molten metal bath. [Diagram 3] 1 is a graph of position versus time of the front end of an optical core wire in accordance with the present invention. [Figure 4] 1 shows the position of the front end within a representative vessel at different steps of the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0108]

[0011] Figure 1 is a schematic cross-sectional view of various designs of optical core wires according to exemplary embodiments of the present invention. Figure 1A shows an optical core wire 1' that includes an optical fiber 2' surrounded by a metal tube 3'.

[0109] FIG. 1B shows an optical core wire 1'' comprising an optical fiber 2'' surrounded by a metal tube 3''. A second metal tube 4'' further surrounds the metal tube 3''. The gap between the two metal tubes 5'' is not filled with a solid material, i.e., the gap may contain a gas or a gas mixture.

[0110] FIG. 1C shows an optical core wire 1''' comprising an optical fiber 2''' surrounded by a metal tube 3''' and a second metal tube 4'''. The gap between the two metal tubes 5''' is filled with a filling material, e.g. an organic material or a fiber from E-glass.

[0111] FIG. 2 is a schematic diagram of an exemplary system 6 for determining a temperature value of a molten metal bath 7 .

[0112] The system 6 comprises an optical core wire 1, which is at least partially placed on a coil 8 and at least partially unwound from the coil 8 for performing measurements. One end of the optical core wire 9 is connected to a detector 10, which can be connected to a computer system (not shown) for processing data acquired by the device 6. The molten metal bath 7 is contained in a vessel 11, which can be an electric arc furnace, a ladle, a tundish or any vessel known to a person skilled in the art of molten metal processing. The optical core wire 1 is fed by a feeder 12 through a guide tube 13 into the vessel 11, which has an inlet 14. The illustrated configuration is used as an example, a roof with a respective inlet is not a prerequisite for realizing the invention.

[0113] The illustrated configuration has a front end 15 which is connected to a molten metal bath MB S 1 shows an exemplary measurement position of the optical core wire 1 immersed below the surface of the molten metal bath MB S The immersion angle of the optical core wire 1 with respect to the surface of the metallurgical equipment is 90°. However, this angle can be varied depending on the construction details of the metallurgical equipment.

[0114] The temperature of the portion of the optical core wire 1 that extends from the coil to the inlet of the vessel 14 may be considered low, for example, at a temperature ranging from room temperature to 100° C. As it passes through the inlet 14 towards the molten metal bath 7, it first encounters a high temperature atmosphere of up to 1700° C. or more, then a slag layer 17, and then the molten metal bath 7. The slag layer 17 may be liquid, primarily liquid or foamy. The inlet 14 to the vessel may be provided with a blowing lance 18 to prevent the ingress of metal and slag into the guide tube 13.

[0115] In order to carry out the method of the invention under various circumstances, it may be advantageous to have at least a basic knowledge of the design of the vessel and the molten metal contained therein. S The optimum level of the surface of the molten metal bath MB can be known approximately for each metallurgical vessel depending on its design and mode of operation. In practice, the actual surface level is not a fixed value due to vessel erosion or excess skull or refractory deposits and / or changes in the vessel wall profile due to tilting operations. S Many methods are known for measuring the level of the surface of the molten metal. For example, a measuring bar may be immersed from a position above the bath surface with a known reference point and burned down to the surface of the molten metal. The distance between the remaining bar and the reference point determines the level of the molten metal M S It is possible to calculate the surface level of the surface MB by conductivity measurements with a suitable probe. S The position of the electrical conductivity may be measured. This may be done in situ, meaning that the conductive portion of the optical core wire acts as a conductivity probe. Such measurements are known in the art and are not a limitation of the practice of the present invention.

[0116] To determine the temperature value, the optical core wire 1 is fed with its front end at the immersion end 15 towards the molten metal bath 7 to the required immersion depth. A suitable feeding system 12 precisely controls the feeding speed of the optical core wire 1.

[0117] After the measurement sequence, the portion 19 of the optical core wire immersed in the molten metal bath is melted and therefore consumed. The length of this portion is L C As shown in the figure.

[0118] After the temperature has been measured, the portion of the optical core wire 20 that is located in the high temperature atmosphere and extends through the slag layer may be sent back towards the coil 8 and reused for the next measurement.

[0119] Figures 3 and 4 show the method of the invention in more detail. In particular, Figure 3 shows the movement of the front end during an exemplary feed scheme. The x-axis shows time and the y-axis shows the position of the front end. Molten metal bath MB S The location of the surface of the wire and the feed rate for different lengths of time are also shown for illustration purposes. For clarity, acceleration and deceleration are ignored. The melting and devitrification behavior of the optical core wire depends on the amount of heat transfer from the environment, which is directly related to the speed at which the front end is fed.

[0120] In a first step, the front end of the optical core wire is positioned at position p1. The optical core wire is then fed at high speed (v1) towards and according to a preferred embodiment into the molten metal bath, immersing the front end at a certain immersion depth i1 (position p2). Tests have shown that i1 is preferably within the centimeter range.

[0121] In the next step, the feed rate is reduced to v2. The length of time of this second feed can be selected so as not to melt the outer metal tube of the optical core wire that is immersed in the molten metal bath.

[0122] Then, the feed rate is increased to a rate v3, and the front end of the optical core wire is fed to an immersion depth i3, which is the deepest position of the molten metal bath p4. Since v3 is higher than v2, the front end can reach a sufficient immersion depth to ensure a homogeneous state of the molten metal bath.

[0123] After reaching the deepest position p4, the feed is preferably paused, i.e., a resting phase, as shown in the schematic diagram. Alternatively, under certain circumstances, a slower feed may be advantageous. For the sake of clarity, the melting and decomposition processes and the resulting movement of the emerging front edge are not shown in FIG. 3.

[0124] Temperature measurements are taken during the measurement time, which is also shown in the figure. In the preferred embodiment shown, this time overlaps in time with the third time and quiescent phase during which the optical core wire is fed at v3. Temperature values ​​taken during earlier feeding phases often do not represent the bulk temperature of the molten metal bath. Furthermore, data taken due to a damaged front end can be prevented.

[0125] Finally, the optical core wire is retracted from the molten metal bath at a speed v5 back to a position above the surface.

[0126] FIG. 4 shows the molten metal bath 7, its surface MB2 of the optical core wire 1 and its front end 15 in a representative vessel 11 at different steps of an exemplary embodiment of the method according to the invention. S , and its position relative to the slag layer 17.

[0127] Before the start of the measurement sequence, the front end of the optical core wire may be placed outside the high-temperature environment in a metallurgical vessel, i.e. a vessel containing a molten metal bath. In particular, if previous measurements have been made, a part of the immersed end, including the front end 15, may already be damaged. In such a case, it has been observed that this part of the optical core wire cannot be used for reliable measurements. The longer the residence time during the previous measurement sequence in the thermal demand zone, the more damage can be observed. By applying the method according to the invention, this damage is minimized.

[0128] 4A shows the front end 15 of the optical core wire 1 at position p1. This may be inside the metallurgical vessel or may be close to the entrance, i.e., near the point where the optical core wire enters the vessel.

[0129] According to a preferred embodiment, the optical core wire is subsequently fed into the molten metal bath 7 to immerse its front end at a certain immersion depth i1, which corresponds to the position p2 shown in FIG. 4B. As a result, the front end of the optical core wire 15 can contact the molten metal bath 7 from this point on. Depending on the conditions of the metallurgical installation, the first immersion depth i1 may be reduced if the bath level is considered stable. This depth may be increased if the bath level is unstable. The stability of the bath level depends on various circumstances and may be influenced by the operator's choice or by external influences such as scrap quality.

[0130] After the next feed step, the front end reaches position p2 shown in Fig. 4C. During this step, the possibly damaged part can be preheated in the molten metal environment. The undamaged part of the optical core wire 1 can remain in a zone of low thermal demand above the surface of the molten metal bath, and the optical fiber can be thermally protected by its jacket.

[0131] The front end of the optical core wire is then fed to the deepest position p4 in the molten metal bath with an immersion depth i3, which corresponds to the configuration shown in FIG. 4D. Due to preheating during the second feeding stage, the outer metal tube starts to melt during this third feeding, so that a new front end 15* may be built up from the undamaged part of the optical core wire. During this stage, the feed rate v3 is greater than the previous feed rate v2, so that the front end 15 can reach a sufficient immersion depth to ensure a homogeneous state of the molten metal bath. The deepest immersion depth i3 at position p4 in the liquid metal bath should be selected to be greater than the temperature gradient length in the bath and is preferably also greater than the typical slag layer thickness. If this is followed, the newly formed front end of the optical core wire 15* is exposed to the heat of the slag layer 17 only for a limited time.

[0132] FIG. 4E shows the position of the newly formed front end 15* after a fourth time length of stationary or nearly stationary phase, i.e. a phase in which the front end is not actively moved or fed at a slow speed. Preferably, the optical core wire is consumed to the surface of the molten metal bath. The time required for the immersed portion of the optical core wire to be completely consumed to the surface of the molten metal bath depends on the temperature of the molten metal and the properties of the optical core wire. Since the higher the temperature of the molten metal bath, the faster the optical core wire is expected to be consumed, the shorter the time length of this stationary or nearly stationary phase may be the higher the expected temperature of the molten metal bath, i.e. the temperature assumed before the measurement sequence or measured in the early stages of the measurement sequence. The properties of the optical core wire that affect the melting or consumption behavior mentioned above include its design and the material from which it is composed. For example, a metal tube with a thicker wall thickness melts slower than a metal tube of the same material with a thinner wall thickness. The selected material also determines the exact melting behavior, and in particular the melting point is a defining parameter. Furthermore, the linear density, which is a result of the combination of the design and the selected material, may affect the consumption behavior. For given reasons, it may be advantageous for the parameters of the feeding strategy to be adjusted to the properties of the optical core wire used.

[0133] Finally, the optical core wire is retracted from the molten metal bath back to a position where the front end 15* is above the surface (FIG. 4F).

[0134] As is evident from the above description, the portion of the optical core wire immersed in the molten metal bath is consumed during the measurement sequence according to the invention, the portion of the optical core wire exposed to the environment in the vessel containing the molten metal may be damaged and become unsuitable for further measurements.

[0135] In the following, exemplary conditions according to the invention are given. EXAMPLES

[0136] An optical core wire with a linear density of 46 g / m, comprising a graded-index fiber with a core diameter of 50 μm and a stainless steel tube with an outer diameter of 1.3 mm embedded in a stainless steel tube with an outer diameter of 6 mm and a wall thickness of 0.3 mm, is used in a feeding system installed in an electric arc furnace with a configuration according to FIG.

[0137] After a certain integrated power consumption of the electric arc furnace system or by manual input, the front end of the optical core wire is positioned 120 cm above the surface of the molten metal bath. The first feed is started at a speed of 3 m / s for 0,45 seconds. The feed is then slowed down to a speed of 0,2 m / s. If the expected temperature of the molten metal bath is 1600 °C, this feed is performed for 0,4 seconds. At the end of this slow feed, the damaged part of the optical core wire is close to the molten state, while the length of the core wire placed in the slag layer is in a preheated state. In a third stage, the feed speed is increased again to 2,3 m / s and the front end is positioned 0,5 m below the surface of the molten metal bath. After reaching this deepest immersion depth, the feed is temporarily stopped for 0,15 seconds. Measurements of the data required to measure the temperature are taken during the third fast feed and rest stage. A number of data points representing the temperature are taken by the detector. Other measurement intervals and time lengths are possible, but sufficient and most accurate temperature detection values ​​can be obtained within this interval.

[0138] Finally, the optical core wire is retracted at a speed of 3 m / s to position the newly constructed front end above the surface of the molten metal bath. For the entire length of the optical core wire, the position of the front end has been moved in the direction of the end connected to the detector by the length consumed during the measurement method, 0.5 m in the described example. If necessary, this measurement sequence can be repeated. [Explanation of symbols]

[0139] 1, 1', 1'', 1''' Optical Core Wire 2, 2', 2'', 2''' optical fiber 3', 3'', 3''' metal tube 4'', 4''' 2nd metal tube 5'', 5'''' Air gap between metal tubes 6. System 7 Molten metal bath 8 Coils 9 Opposite end (the end of the core wire connected to the detector) 10. Detector 11 Container; metallurgical container 12 Feeder 13 Guide tube 14 Entrance 15, 15 * Front end of optical core wire MB S Surface of a molten metal bath 17 Slag layer 18 Blowing Lance 19 The portion of the core wire immersed in the molten metal bath 20 Part of the core wire exposed to high temperature atmosphere and slag p1-p5 Position of the leading edge during the measurement sequence v1-v5 Front end velocity during the measurement sequence i1-i4 Immersion depth of the front end during the measurement sequence

Claims

1. 1. A method for determining a temperature value of a molten metal bath using an apparatus comprising an optical core wire and a detector, comprising: (a) providing the optical core wire with a front end at a position p1 above a surface of the molten metal bath; (b) moving the front end directed toward the molten metal bath from a position p1 to a position p2 at an immersion depth i1 below the surface of the molten metal bath at a speed v1 over a first time period from t1 to t2; (c) feeding the front end at a speed v to a position p at an immersion depth i below the surface of the bath of molten metal for a second time period from t to t; (d) advancing the front end at a speed v3 to a position p4 at an immersion depth i3 below the surface of the molten metal bath for a third time period from t3 to t4; (e) pausing the feeding of the leading end or feeding the leading end at a speed v4 for a fourth time period from t4 to t5, respectively; (f) after t5, retracting the front end at a speed v5 to a position above the surface of the molten metal bath; (g) acquiring temperature information of the molten metal bath within a measurement time period from t2 to t5; Including, The immersion depth and the velocity have the following relationship: (i) i2>i1 (ii) i3>i2 (iii) v1>v2 (iv) v2<v3, and (v) v4<v1 or v2 or v3 having The method, wherein the optical core wire is preheated in an unmelted state in steps (b) and (c) and begins to melt in step (d).

2. The method of claim 1 , wherein the molten metal bath is a molten steel bath.

3. The method of claim 1 or 2, wherein the optical core wire is laterally surrounded by at least one additional metal tube.

4. 4. The method according to any one of claims 1 to 3, wherein the linear density of the optical core wire is in the range of 25 to 80 g / m.

5. The fourth time length from t4 to t5 is (i) providing a data set relating measurement data of a molten metal bath to an amount of time; (ii) obtaining measurements during a time prior to t; (iii) selecting, from the provided data set, the fourth length of time that corresponds to the measurement data acquired during the time prior to t4; The method according to any one of claims 1 to 4, wherein the compound is selected by a method comprising:

6. The method of claim 5 , wherein the measurement data is a temperature value.

7. 7. The method of claim 1, wherein the portion of the optical core wire that is fed below the molten metal bath surface is consumed by t5.

8. The method of claim 1 , wherein the temperature information is obtained within a measurement time period from t3 to t5.

9. The method according to any one of claims 1 to 8, wherein the start of the measurement time is on or after t3+(t4-t3) / 2.

10. The method according to any one of claims 1 to 9, wherein the end of the measurement time is before t4+(t5-t4) / 2.

11. 11. The method of claim 1, wherein at least one of the first length of time, the second length of time, the third length of time, or the fourth length of time is selected based on a characteristic of the optical core wire.

12. At least one of the velocities v1, v2, or v3 is (i) providing a data set relating an expected temperature of the molten metal bath to a velocity v1, v2 or v3; (ii) providing an expected temperature value of the molten metal bath; (iii) selecting, from the provided data set, at least one of the rates that corresponds to the predicted temperature; The method according to any one of claims 1 to 11, wherein the compound is selected by a method comprising:

13. The method comprises: (a1) measuring the level of the surface of the molten metal bath; The method of claim 1 , further comprising:

14. A system for carrying out the method of any one of claims 1 to 13.

15. The system of claim 14 , wherein the system comprises a feeding means.

Images