MXPA98003203A - System and method for minimizing the cutting content during the cover of a basic oxygen oven converter in the production of ac - Google Patents

Abstract

A system and method for detecting molten slag in the bleeding stream between a basic oxygen furnace for the manufacture of steel (BOF) and a corresponding pouring cauldron. BOFs are used in the manufacture of steel. An infrared detection or imaging device (IR) is used to represent / view the bleeding current from the BOF to the casting cauldron, the current transmits an energy that indicates whether the molten steel and / or the slag is in the current in a given time. The imaging device mainly uses long RI wavelengths (e.g. wavelengths from about 8 to 14æm) when plotting the fused bleed current, because these wavelengths are less susceptible to blockage or absorbents per The gases and particles in the air are often found in the BOF media. In certain embodiments, all different IR wavelengths greater than about 8æm are filtered out and not used to detect the slag in the blood stream.

Description

SYSTEM AND METHOD TO MINIMIZE SCRAP CONTENT DURING THE WASHING OF A BASTCO OXYGEN OVEN CONVERTER IN STEEL PRODUCTION This invention relates to a system and method for minimizing slag content while casting a basic oxygen furnace converter (BOF) during the production / manufacture of steel. More particularly, this invention relates to the use of an infrared imaging detector (Rl) in the far Rl range (i.e., using long wavelengths) to detect the presence of slag in a bleeding stream during pouring. of a BOF converter.

BACKGROUND OF THE INVENTION A problem of long years in the steelmaking industry has been the ability to control or minimize the slag content during casting of a BOF converter. The casting is the casting of molten metal from a BOF converter to a corresponding pouring cauldron, with the metal flowing from the converter through a pouring orifice defined herein. Ref. 27218 During the manufacture of steel, cast iron (known as hot metal) that has impurities (for example: C, Si, Mn, S, P, etc.) is typically introduced into a converter vessel known as an oxygen furnace. basic (BOF). In the BOF converter, gaseous oxygen (02) is injected or jetted onto the hot metal to remove the impurities to desirable levels. During this purification process, fluxes, such as lime (CaO) and MgO, are added in the furnace, and are combined with oxides such as S02, MnO and FeO formed during the oxidation process to form the molten "slag" in the converter. This slag floats on top of the molten steel in the BOF converter, because the density of the slag is less than that of the molten steel.

After the oxygen is introduced to the BOF converter for a long period of time (for example from about 16-25 minutes, depending on the volume of the BOF converter, the amount of molten steel, and the grade of the steel being manufactured) and it has formed the slag and the molten steel, it inclines and empties the converter vessel. During casting, the molten steel is poured through a pouring hole in the side of the converter BOF into a pouring cauld located below it. It is during this cast that the unwanted slag content may be present.

When the BOF converter vessel is properly emptied, a small amount of content may be present at the start of the casting, but the slag content of greatest interest occurs at the end of the casting when the largest amount of substantially purified molten steel has already been emptied. to the pouring cauldron below, and mainly the slag (instead of the steel mainly) remains in the BOF converter. When a typical BOF converter is tilted to a pouring position for casting, the molten steel is emptied through the pouring hole located on the side of the converter before the slag is discharged, due to the different densities of the two materials castings. If the operator (s) emptying the converter does not stop pouring (or emptying) at approximately the precise moment when the molten slag begins to flow through the pouring hole, unwanted molten slag is also emptied into the pouring cauldron below, above the molten steel already poured. When too much slag is poured into the pouring cauldron from the BOF converter, this affects cleaning and reintroducing impurities such as phosphorus (P) into the steel, adversely affecting the efficiency of the aluminum during bleeding, and prevents certain grades of steel since it is manufactured. Any attempt to eliminate or minimize the effect of excess slag cast in the pouring cauldron is costly, time consuming, and / or labor intensive. For example, if too much slag is accidentally emptied into the pouring cauldron, millions of dollars cost from alumina or other slag modifier (s) that has to be added to the slag in the molten melting pot to try to minimize the levels of FeO and other oxides not stable in the slag. In summary, the minimized slag content from the BOF converter to the pouring cauldron is essential for the efficient manufacture of high quality steel.

Many techniques have been used in an effort to control the slag content during casting of the BOF converters. For example, see Slag Carryover in Oxygen Converters: an International Review, by Da Silva Bergman, and Lindfors [pp. 91-95], the discovery of which is hereby incorporated by reference. In this magazine, numerous methods are discussed to control the slag content during casting of the BOF converter. For example, it is known to use refractory plugs, metal plugs, rigid plugs, fiber plugs, projected clay, dart-shaped floatation elements, and ball-shaped flotation elements, in an attempt to control or minimize the content of scum.

Certain known techniques result in the interruption of the bleeding or metal discharge flow of the converter, almost at the end of the casting to minimize the slag content. The dart-shaped and ball-shaped flotation elements are frequently used for this purpose. In Figures 4 and 5 of the article referenced above, the unsatisfactory results frequently associated with these conventional methods are illustrated. For example, the dart and ball-shaped floatation elements are known to be unsuccessful when the slag is thick or viscous and it has been found that the positioning of these floatation elements within the converter is both difficult and critical. Also the structure of the pouring hole affects the efficiency of these types of flotation elements. As discussed in the article, some steel mills have reported that the balls sometimes close the pouring hole too soon, which results in the output of purified molten steel (affecting the performance) in the converter or by extending the Sangria (that is, both expensive and inefficient). Accordingly, it is known in the art that while the flotation elements can help to minimize the slag content, there is frequently inefficiency and the results are unpredictable. Still further, both the balls and darts are undesirably expensive.

Despite the fact that the techniques of prevention of both slag content are known, it is stated in the conclusion of the article referenced above that "none of the methods in use today can be considered universally applicable, since each has its limitations and can only achieve the expected results, if specific conditions exist. " In other words, there has been a need in long years in the art for a corresponding system and method to minimize the slag content during the casting of the BOF converters, which can be used in different media by operators of different levels of specialty. To date, no known technique has been found to be satisfactory with all commercial steel manufacturing means, because many techniques are not considered efficient enough and others are too expensive for use with ordinary steel grades.

In view of the inefficiency and non-effectiveness of the methods for the prevention of slag content in a known BOF, many steel plants simply rely on the operators to visually detect when the slag portion of the laundry is reached. Unfortunately, this method of preventing slag content is inefficient, even in the best of cases, because it is almost impossible for most humans to visually observe any visible difference between the purified molten steel that is emptied by the the pouring hole of the converter and the molten slag that is emptied through the pouring hole [both are fused and are yellow to hot white].

The U.S. Patent No. 4,222,506 discloses another method for controlling the slag content, mainly directed towards the detection of the slag in the laundry from a laundry cauldron to a tundish. In the '506 patent an infrared camera (Rl) estimates the molten metal that is emptied and attempts to detect the presence of slag. In an unfortunate way, it has been found that the system described in the '506 patent is inefficient and is unable in an easy, satisfactory and consistent way to detect the slag from the BOF to the pouring cauldron with the means of the steel mill. In column 2 of the '506 patent, an emissivity value of about 0.28 is mentioned. As can be seen below, this emissivity value may indicate that the short Rl wavelengths in the short Rl region (i.e., approximately 3-5 μm) are measured by the camera in the '506 patent to detect the human waste. However, it is important to that the '506 patent does recognize or appreciate any importance for any potential wavelength. It has been found that using Rl short wavelengths in this range is insufficient to efficiently detect the slag wash with the steel mill media from the BOF to the casting cauldron. Accordingly, the '506 patent suffers from at least the following problems.

First, the medium within which a BOF converter is emptied to let the molten steel flow into the pouring cauldron, often includes much more dust in the air, smoke, gases and particulate matter than the media from the pouring cauldron to the pouring trough. During the casting of the BOF converter, typically much smoke, gas, and particulate matter is emitted in the air surrounding the bleeding stream. This, at times, makes it very difficult for humans to see the bleeding current through smoke, gas, and other particulate matter in the air. Particulate matter in the air can block radiation with wavelengths smaller than the size of the particle (s). In the middle of the BOF, the particle size is such that the long wavelengths of radiation are probably better able to reach an Rl chamber. On the other hand, the smaller wavelengths will often be blocked. Because the wavelengths of Rl (near) short, including those in the range indicated by the '506 patent, are susceptible to blockage by dust and other particulate matter in the air, the' 506 patent system sometimes , is unable to accurately differentiate between slag and steel during casting.

Second, the gases emitted during casting from the BOF to the pouring cauldron also have an adverse effect on the Rl wavelengths indicated by the '506 system.

As will be discussed here, gases such as C02 and H20 emitted close to the bleeding current in the BOF media absorb certain wavelengths of Rl, notably those in the range of 3-5 μm (for example, approximately 4.2 μm). Therefore, in the BOF means, the wavelengths used in the '506 patent frequently can not be seen by the Rl camera. This is still another problem, because, without seeing these wavelengths, the image is unclear and the camera of the '506 can not be able to differentiate between slag and steel during casting.

A third problem with the scum detection system of the '506 patent is that it appears to be placed, rather closed to the stream of molten indentation that is emptied from the pouring cauldron into the tundish. It has been found by the instant inventors that the positioning of an Rl chamber in the vicinity of closed to a bleeding stream, sometimes results in less slag readings in the bleeding stream satisfactory due to the high temperature medium surrounding the Bleeding current in the BOF media. When the chamber is aimed at the opening of the pouring cauldron, the medium is undesirable living scum in the pouring cauldron, and this tends to affect the clarity of the image. Due to the appearance of a "hot" medium, it can be difficult to differentiate between slag and steel in the '506 patent.

In view of the foregoing, it is clear that the '506 patent system is less desirable than the BOF means for many reasons. It is believed that it is a result of the '506 patent to be primarily designed to detect the presence of slag in a medium from the pouring cauldron to the tundish, as compared to a medium from the BOF to the pouring cauldron where they are presented. many gases and other particulates in the air. It is noted, however, that the '506 patent discusses and illustrates that it is also possible to use this in the work of a converter to a pouring cauldron.

Yet another approach used by many in the industry to minimize the slag content in the BOF media is the positioning of electromagnetic reels over the pour holes in the BOF converter. Due to the monitoring of such spool (s), it is possible to determine when the slag begins to flow through the corresponding pouring orifice. With the spool that detects the slag, the pouring hole can be closed or the converter can be lifted up to stop the casting. Unluckily the electromagnetic reels are problematic, since they are placed inside the converter and frequently break down or fail frequently. Another problem with the reels is that they only produce an alarm, while the smelter (ie, the operator) is still the one who looks into the bleeding stream to ensure that the slag is discharged before stopping the bleeding. With slag splash, the converters operate for months and months at a time through many loads (for example, up to approximately 20,000 loads or up to 1 and 1.5 years). Therefore, if the spool in the pouring hole fails, there is no way to replace it or perform maintenance on it without stopping the operation of the BOF. In all practical ways, the reel can not be new until the next change of refractory parts in the BOF. This is highly undesirable, it reduces yields, there is less efficiency, and it quickly becomes rather expensive.

It is apparent from the foregoing that there is a need in the art for a system and method for minimizing the slag content during the casting of a BOF converter in steelmaking, where the system / method improves reliability relative to the techniques of the prior art has a higher success rate than the prior art techniques, results in improved slag detection, and reduces maintenance costs relative to known techniques.

It is a purpose of this invention to meet the needs described above in the art, as well as other needs which become apparent to the skilled artisan from the following detailed description of this invention.

BRIEF DESCRIPTION OF THE INVENTION In general terms, this invention meets the needs described above in the art by providing a method for the detection of slag during the casting of a BOF converter in steelmaking, the method comprising the steps of: providing a BOF converter for the storage of molten metal, and introduce oxygen into the converter to form the slag; provide a pouring kettle in which the molten metal flows from the BOF converter; bleed the BOF converter so that the bleed stream of molten metal flows from the BOF converter to the casting cauldron; Y represent by Rl the bleeding current during casting, using long Rl wavelengths greater than or equal to approximately 8 μm to detect the presence of molten slag in the bleeding stream.

A system (BOF) basic oxygen furnace for use in steel manufacturing, the BOF system comprises: a BOF converter for the storage of molten steel on which the slag floats during certain BOF processes, the BOF converter including a pour hole defined here, allows the molten steel to flow; a pouring cauld placed at a vertical lift downstream of the BOF converter to receive the molten steel, which flows from the BOF converter via the pouring orifice; an infrared imaging device (Rl) to represent a bleeding current of molten metal flowing from the pouring hole in the converter to the pouring cauldron to detect the presence of slag in the bleeding stream; Y wherein the Rl imaging device uses RI wavelengths of at least about 8 μm to detect the presence of slag in the bleeding stream.

In certain preferred embodiments, the system further includes a filter for filtering out substantially all Rl wavelengths less than about 8 μm, so that predominantly Rl wavelengths of at least about 8 μm are used to detect the slag in the stream of sangria.

This invention also meets the needs described above in the art by providing an apparatus for detecting slag in a stream of molten indentation flowing from a BOF to a pouring cauldron during steelmaking, the apparatus comprising: a BOF for converting iron cast in molten steel, and means for pouring molten steel from the BOF into the pouring cauldron via the molten drain stream; Y means of imaging by Rl to represent the melt bleed current, to determine whether the molten slag is present in the bleed stream, the imaging means by Rl measure only emissivity values of the molten steel in the bleed stream less than about 0.25.

In the preferred embodiments, the imaging means by Rl measures emissivity values of the molten steel in the bleeding stream of less than about 0.20.

This invention will now be described with respect to certain modalities thereof, accompanied by certain illustrations, wherein: IN THE DRAWINGS Figure 1 is a schematic diagram illustrating a system for the detection of slag from the BOF to the ladle and a method for minimizing the slag content, according to one embodiment of this invention.

Figure 2 is a view, partial cross section, perspective illustrating another embodiment of this invention similar to the embodiment of Figure 1.

Figure 3 is a graph of emissivity versus wavelength (μm) illustrating a graph of emissivity versus wavelength of both molten slag and molten steel.

Figure 4 is a graph of the percentage of transmission versus wavelength (μm) for the region of total Rl, which illustrates how certain gases in the air present in the BOF media absorb the particular wavelengths of Rl, and reduce their utility.

Figure 5 is a block diagram of an Rl camera that can be used in certain embodiments of this invention.

DETAILED DESCRIPTION OF CERTAIN MODALITIES OF THIS INVENTION Now more particularly with reference to the accompanying drawings, in which similar reference numerals indicate similar parts in all the different views.

Figure 1 illustrates a system / method for controlling and / or minimizing the content of molten slag in a ladle 7 during the casting of a BOF 3 converter in steelmaking, according to one embodiment of this invention. As shown, the system / method includes a converter BOF 3, which is mounted on a pivot approximately on the axis 5, a pouring cauldron in which the molten metal is emptied via the pouring hole of the converter 11, a chamber of Rl 13 to monitor the melted indent stream, and a TV monitor 15. In certain embodiments of this invention the chamber is positioned from about 50-150 feet (preferably from about 50 to 100 feet) of the bleeding stream 9, to obtain a good low temperature medium relative to the melt bleed stream, and reduce the chances of damage to the chamber by the close to the BOF, and provide ease of service. This location is also more clear than the locations near the BOF.

The BOF 3 converter is first filled with cast iron. Then, the gaseous oxygen is introduced into the converter 3 to eliminate the impurities. An opening is provided on the top of the converter to let oxygen enter it. Due to the introduction of oxygen the unwanted elements are oxidized inside the converter 3 and form the slag, therefore the hot metal is purified and transformed into molten steel. Because the slag in the BOF has a lower density than that of the molten steel, the slag floats on top of the molten steel inside the converter 3.

After the oxygen gas is introduced, the converter 3 is rotated about its axis or inclined 4 approximately fixed to the axis 5, so that the indent stream 9 of molten metal is emptied from the converter 3 towards the pouring cauldron 7. When properly rotated about its axis, first the steel flows out of the pouring orifice 11 towards the pouring cauldron during casting, because the slag layer is placed on top of the steel and the pouring orifice.

Then, as the steel of the converter 3 is drained, the operator continues rotating on the axis 5 until the slag layer reaches the pouring hole 11. The infrared camera (Rl) 13 and the TV monitor 15 monitors or sees the current of bleeding 9 between the pouring orifice 11 and the pouring cauld 7, to detect when the slag begins to enter the bleeding stream 11 and flows into the pouring cauld 7 in substantial amounts.

Surprisingly, it has been found by the inventors that, in contrast to the wavelengths Rl indicated by the '506 patent, remarkably the improved slag stopping in the bleeding stream 11 results when (i) the Rl chamber 13 uses only wavelengths in the long Rl range (for example, Rl wavelengths greater than or equal to about 8 μm), and / or (ii) Long IR wavelengths (eg greater than or equal to about 8 μm) are monitored by camera 13 and filtered out other wavelengths of Rl. With the analysis, it has been found that these longer Rl wavelengths (different from the shorter wavelengths) are less susceptible to blockage by dust particles in the air and smoke, which are predominant in the media. BOF. Still further, as will be discussed below, it has been found that gases in the air (for example, C02 and H20) that are common in the BOF media absorb or block out the medium Rl and short Rl wavelengths ( for example, from about 3-8 μm), but not substantially absorb or block long Rl wavelengths (ie, those greater than about 3-8 μm).

In addition, these longer Rl wavelengths work better because at these wavelengths the difference in emissivity between the slag and the steel is greater, which results in a greater change in the color on the monitor. Also, because the Rl camera or imager is located at a distance from the BOF, it is not at risk of damage close to the BOF and its location allows ease of service / maintenance. The immediate inventors have found that when the lower wavelengths are tested in the BOF, the image on the monitor is unclear and it is difficult to tell the difference between the slag and the steel in the bleeding stream.

Preferably, the camera 13 is set to predominantly use the Rl wavelengths of at least about 8 μm (i.e., long wavelengths), and more preferably wavelengths from about 8 μm to 12 μm. μm. The inventors have found that it is much easier to distinguish between slag and steel in a stream of BOF bleeding at these longer wavelengths, compared to shorter Rl wavelengths, probably because of the larger change in the emissivities of the molten steel and the slag at the longer wavelengths compared to the shorter Rl wavelengths. When these longer wavelengths are used, the chamber 13 can see the bleeding current from the BOF to the pouring cauldron through the smoke, gas, and dust in the air that usually surrounds the BOF bleeding stream, while it can not be done with the shorter wavelengths. The slag is detected as a color change in the monitor 15, since the visual detection by the operator is effective.

The instant invention reduces maintenance costs relative to conventional slag content minimization techniques, has improved reliability and efficiency relative to these techniques, and improves the manufacturer's control over the slag content in the BOF media. Due to the reduction of the slag content in the BOF, the following other advantages are obtained: it is reduced to the FeO content in the slag in the ladle, it is reduced to the consumption of expensive slag modifiers, the phosphorus the pouring cauldron, the desulfurization of steel in the casting cauldron is improved, the cleaning of steel is improved, the use of the retention system for expensive slag is reduced (for example, darts and balls), the iron production is improved , the reliability of the slag detection is improved, and there is no need to maintain leads and reels detectors in the BOF.

Figure 5 is a block diagram of an RL camera 13 that can be used to monitor the bleeding stream 9 in certain embodiments of this invention. A preferred camera 13 is an imaging radiometer by RL Model 760, available from Inframetrics, Inc. The camera 13 may be a system for autonomous thermal, archival and analytical imaging with integral color LCD, an optical imaging micro soft diskette and an integrated cooler, which can be used as an external monitor. The chamber may include a mercury / cadmium / tellurium detector that is cooled by an integrated cooler up to 77 ° K for maximum thermal sensitivity and high spatial resolution. With regard to the optical path of the camera, the thermal radiation of the bleeding current enters a scanning module evacuated through a collimating lens, is deflected by horizontal and vertical scanning mirrors, and exits through a second window to pass through the detector lens to the detector. As illustrated, camera 13 includes circuits for processing, translating to digital form and reformatting the Rl signal for color or black-and-white presentation on the integrated LCD, and / or external video / TV monitor 15. The microprocessor accesses individual image elements, then calculate the temperatures using the calibration tables corresponding to the optical filter / lens combination in use. The optical filters 30 in the scanning section 31 of the camera 13 can adapt the spectral response of the camera to optimize the measurement of the bleeding current of the BOF 9. In the preferred embodiments of this invention, a high-pass filter in the it is implemented within the chamber 13 to absorb or block the transmission of the Rl wavelengths from about 0-8 μm, thereby allowing the camera 13 to monitor the bleeding current only using long Rl wavelengths greater than or equal to at approximately 8 μm (ie, the long wave Rl region). In certain embodiments, the high pass filter allows the substantial transmission of only the Rl wavelengths from about 8-14 μm, or 8-12 μm, and substantially blocks transmission in and / or through the camera scanner of the camera. all other wavelengths of Rl. In the preferred camera referenced above, this high-pass filter is selected by its name in a SETUP menu, and inserted automatically. Using this filter (s), the camera 13 responds to the sum of the energies emitted, diverted, and transmitted coming from the drain current. This combination of energies is called radiosity of the current. To obtain the temperature of the current, the energy emitted is extracted by subtracting the deviated and transmitted energies from the incoming radiosity. The result is scaled by the emittance to obtain a black-body equivalent value that can be converted to the temperature by asking a table for calibration query. The resulting temperature of the bleeding current, which shows the differences in color (and emissivity) between the molten steel and the molten slag, is shown on the monitor 15. While the Rl imaging chamber identified above 13 is used in certain embodiments of this invention, it will be appreciated by those of skill in the art that other types of imaging devices / cameras per Rl, may be used in their place while being able to use long Rl wavelengths to detect the scoria in the bleed stream, and preferably be able to filter out other short wavelengths of Rl (ie microbolometers).

When these selected wavelengths are used by the RL camera 13 to see the drain current 9, the difference in emissivity between the molten slag and the molten steel in the TV monitor 15 becomes readily apparent. With reference to Figure 1, the molten steel in the bleeding stream 9 looks rather dark compared to the molten slag, and when the slag begins to enter the bleeding stream 9, said slag appears on the monitor 15 as a color (for example, light white) which is very different from that of steel. As shown in the embodiment of Figure 1, the slag is presented by a white color, while the steel by a dark color. This allows the casting operators to easily determine when the slag has entered the bleeding stream 9, so that an operator (s) can stop the casting or emptying when a white coloration appears substantially in the stream 9 on the monitor 15 Therefore, when the operator looks at the monitor 15 and sees that the slag begins to dominate the indent stream 9, he stops the casting, either ascending by tilting the converter 3 approximately to the 5 axis or by closing the orifice. 11. In any case, the excessive slag content is prevented from the converter 3 towards the pouring cauld 7.

According to certain embodiments of this invention, the casting of the BOF 3 converter can be automatically stopped or stopped when the camera detects a predetermined amount of slag in the drain stream 11. For example, using comparison proportions in gray scale, the system The casting can be programmed to stop (ie tilt the converter up or upright) when by contrast the monitored drain current reaches a predetermined level that indicates the presence of a predetermined amount of slag in the drain stream.

According to still further embodiments of this invention, the inclination of the BOF converter during casting can be controlled by the amount of slag detected by the chamber 13 in the bleeding stream. For example, at the beginning of the casting, the system can be programmed to tilt the converter 3 to a degree where less than a predetermined amount of slag is poured through the drain hole 11 into the pouring cauld 7, and the angle of inclination of the converter 3 can be adjusted according to the program to minimize the slag in the drain current. Then, as shown above, when a predetermined amount of slag (a predetermined emissivity difference) is detected in the bleeding stream after casting for a predetermined amount of time (i.e., near the end of the casting), the system can automatically stop the laundry. Due to the correction of the angle of inclination of the BOF converter during casting, the presence of slag in the stream can be substantially eliminated until the end of casting.

Figure 2 illustrates an embodiment of this invention that is similar to the embodiment of Figure 1, except that the converter 3 and the pouring cauldron have different structural characteristics. The converter 3 still rotates about its axis about axis 5 to empty the stream of molten metal 9 out of the pouring hole 11. When the chamber 13 detects the slag in stream 9, an operator can stop the casting as discussed above. . Another significant feature with respect to the embodiment of Figure 2 is the presence of a circular or rectangular window 21 located inside the box of the camera 23. The camera is mounted on the structure 25 inside the box 23, so that the The camera sees the indent stream 9 through the window 21. If the preferred embodiments of this invention, the window 21 is transmissible at long IR wavelengths (e.g., Rl wavelengths greater than about 8 μm). In certain embodiments, the window 21 is made of glass that is substantially transmissible or transparent to all or only a few wavelengths of Rl. However, window 21 does not need to be transparent, at non-Rl wavelengths in certain modalities.

In certain embodiments, the window 21 is made of a substantially transparent microcrystalline material that includes calcium fluoride, this is a non-hygroscopic window. Said window is available from Heise's Online Thermographic Services (H.O.T.S.), located in Knoxville, Tennessee, as its Cometa 21 H.VIR window.

This window is approximately 95% transmissible of wavelengths of Rl and almost 100% transmissible of visual wavelengths.

Also HOTS long-wave inspection windows 21 are also available, such as model number H.VIR 75, which is transmissible at least about 95% (eg 98%) at Rl wavelengths of 8-12. μm, said window having no sensitivity to UV rays and a thermal conductivity of approximately 11.72 W / mK at 13 ° C. This type of window may or may not be transmissible at other wavelengths outside the range of 8-12 μm. Preferably, the window 21 has a transmission of at least about 95% for wavelengths of Rl greater than about 8 μm.

In other modalities, window 21 may include ZnSe, GaAs, Germanium, CdTe, or ZnS, and have characteristics similar to those described above. However, coatings may be required in some of these alternative windows, including such as the ZnSe in the windows.

The window 21 is in addition to possible filters located within the camera 13, which allow an operator to selectively determine which wavelengths of the camera 13 to use. The different materials can be used as the window 21, and the use of this window instead of a filter is for the protection of the camera. An important characteristic of the window is that it has a high transmittance in the range of 8-12 μm, and therefore we will be able to use the Rl camera or the imager with its own 8-12 μm filters.

Figure 3 is a graph of emissivity versus wavelength that illustrates how the emissivity of both slag and steel varies as a function of wavelength of Rl. As can be seen, when only long IR wavelengths are used (for example, at least about 8 μm) to determine if there is slag within a melt stream of molten steel, it is more readily detectable than in other lengths of wave due to the greater difference between the emissivity of steel and the slag in these longer wavelengths.

Figure 4 is a plot of transmission versus wavelength of Rl illustrating the amplitude at which particular gases absorb (ie, prevent transmission) certain wavelengths of Rl. For example, it is noted that the H20 gas substantially absorbs a long portion of wavelengths between 5 and 8 μm. Similarly, it is noted that H20 and / or C02 absorbs many wavelengths between 1 and 5 μm. This graph illustrates that the greatest transmission through these gases (for example, C02, 03, H20) occurs when wavelengths are used from approximately 8-14 μm. Since C02 and H20 are gases, which often exist close to the BOF drain streams, it can be seen that the slag and steel in the BOF indent stream can be more easily seen / detected using high bit lengths. R1 wave (e.g., wavelengths of at least about 8 μm).

According to the alternative embodiments of this invention, the camera or monitor of any mode discussed herein can be used with an electric furnace in the production of steel, instead of a BOF.

Electric furnaces are typically exposed to media similar to those surrounding BOFs, electric steel making furnaces have selectively open / closed base exit ports, from which the molten steel flows into the pouring cauld located below it (it is say, there is no side pouring hole). In these embodiments, the chamber 13 sees / represents the molten hot metal stream flowing from the base outlet port of the furnace to the pouring cauldron, and detects the presence of slag in any way shown above.

Once the discovery is made, many other characteristics, modifications, and refinements become apparent to the skilled artisan. Such features, modifications, and refinements are therefore considered to be part of this invention, the scope of which is determined by the following claims.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

Claims (25)

1. A method of detecting slag during the casting of a BOF converter in steelmaking, characterized in that the method comprises the steps of: provide a BOF converter for the storage of molten metal, with oxygen being introduced into the converter to form the slag inside the converter; provide a pouring kettle in which the molten metal flows from the BOF converter; bleed the BOF converter, so that a bleed stream of molten metal flows from the BOF converter to the casting cauldron; Y represent by Rl the bleeding current during casting using long Rl wavelengths greater than or equal to approximately 8 μm to detect the presence of molten slag in the bleeding stream.

2. The method according to claim 1, characterized in that it further comprises the step of stopping the casting of the converter BOF when a predetermined amount of slag is detected in the bleeding stream.

3. The method according to claim 1, characterized in that during imaging, the emissivity values of the slag in the molten metal drain stream between about 0.7 and 0.9 are plotted and output on a monitor, and the emissivity values of molten steel in the stream of molten metal bleeding less than about 0.25 are represented and come out on the monitor.

4. The method according to claim 3, characterized in that during the values of emissivity in the formation of images by Rl of molten steel in the bleeding stream less than about 0.20 are represented and come out on the monitor to indicate when the slag appears in the bleeding stream.

5. The method according to claim 1, characterized in that the formation of images by Rl of the bleeding current, only the wavelengths of Rl greater than or equal to approximately 8 μm are represented and output on a corresponding monitor, so that An operator can identify when the slag appears in the bleeding stream by looking at the image on the monitor.

6. The method according to claim 5, characterized in that it further comprises the step of substantially filtering out the wavelengths less than about 8 μm during the imaging by Rl, so that the long wavelengths of Rl are used to detect the presence of slag in the stream of sangria.

7. The method according to claim 6, characterized in that it further comprises the step of filtering out all the wavelengths of Rl less than about 8 μm during the imaging by R1, so that the image data of these wavelengths Filtered outside are not used to detect the presence of slag in the bleeding stream.

8. A basic oxygen furnace (BOF) system for use in steel manufacturing, characterized in that the system comprises: a BOF converter for the storage of molten steel and molten slag, the molten slag floats on top of the molten steel, the BOF converter includes a pouring orifice defined herein to allow molten steel to flow therefrom; a pouring cauld placed at a vertical elevation below the BOF converter to receive the molten steel, which flows from the BOF converter via the pouring orifice into the bleeding stream; an infrared imaging device (Rl) to represent the bleeding current of molten steel and the molten slag flowing from the pouring hole in the converter to the pouring cauldron to detect the presence of slag in the bleeding stream; Y wherein the Rl imaging device uses RI wavelengths of at least about 8 μm to detect the presence of slag in the bleeding stream.

9. The system according to claim 8, characterized in that it includes a filter for filtering out all Rl wavelengths less than about 8 μm, so that predominantly Rl wavelengths of at least about 8 μm are used to detect the scum in the stream of sangria.

10. The system according to claim 8, characterized in that it further comprises a box within which the imaging device is mounted by RI, the box and the imaging device is located from about 50 to 150 feet from the current of sangria.

11. The system according to claim 10, characterized in that the box includes a window of the box, which is substantially opaque for certain wavelengths of Rl between 0 and 8 μm and is substantially transparent for certain wavelengths of Rl greater than approximately 8 μm, the imaging device by Rl is placed inside the box to see the bleeding flow through the box window.

12. The system according to claim 8, characterized in that it includes a filter in the imaging device by Rl to filter out certain Rl wavelengths between approximately 0 and 8 μm and a window in a box enclosing the training device of images by Rl, also to block out certain Rl wavelengths between about 0 and 8 μm, and wherein the imaging device optically sees the bleeding current through each filter and window.

13. The system according to claim 12, characterized in that the filter filters out, or is opaque to, all the wavelengths of Rl between about 0 and 8 μm.

14. An apparatus for detecting slag in the molten drain stream flowing from a basic oxygen furnace (BOF) to a casting cauldron during steelmaking, characterized in that the apparatus comprises: a basic oxygen furnace (BOF) for converting molten iron to molten steel, and for pouring molten steel from the BOF into the pouring cauldron in the form of the molten drain stream; Y the imaging means by R1 to represent the melt bleed current, to determine if the slag is present in the drain stream, the imaging means by R1 measuring only the emissivity values of molten steel in the stream of bleeding less than about 0.25.

15. The apparatus according to claim 14, characterized in that the imaging means by Rl measure emissivity values of the molten steel in the bleeding stream of less than about 0.20.

16. The apparatus according to claim 14, characterized in that it further comprises means for filtering out the emissivity values of the molten steel in the bleeding stream which are greater than about 0.25.

17. The apparatus according to claim 16, characterized in that all emissivity values of the molten steel greater than about 0.25 are filtered out and are not used to determine if the slag is present in the bleeding stream.

18. A method of casting molten metal from a steelmaking vessel into a ladle during steelmaking, characterized in that the method comprises the steps of: provide a vessel for the manufacture of steel that stores a volume of molten metal, the molten metal includes the molten steel and the molten slag; providing an imaging chamber for monitoring a stream of molten metal flowing from the container to the pouring cauldron; causing the molten metal to flow in the stream out of the container through a hole defined here, and flowing down into the pouring cauldron; monitor the current with the imaging chamber by Rl using Rl wavelengths between approximately 8 and 14 μm, so that the differences in emissivity in the current between the molten steel and the molten slag are represented on a corresponding monitor; see the monitor to determine when a substantial amount of slag enters the stream; and observe a color change in the current on the monitor, which indicates a substantial amount of slag in the stream flowing from the vessel to the casting cauldron, and the operator in response to this stops the casting of molten metal and minimizes the slag content in the pouring cauldron.

19. The method according to claim 18, characterized in that the container is one of a converter BOF and a furnace for the manufacture of electric steel.

20. A system for determining when the molten slag is present in substantial quantities in the bleeding stream from the BOF to the pouring cauldron, characterized in that the system comprises: a BOF having at least one pour hole defined here; a pouring cauld located at an elevation below the BOF; a box into which an imaging device is placed, the imaging device for representing the bleeding stream from the BOF to the casting cauldron to determine when the molten slag is presented in substantial amounts; Y a window defined in the box, the window is at least about 95% transparent at long infrared wavelengths (Rl), and wherein the imaging device gives an image of the bleeding stream through the window.

21. An apparatus for the manufacture of steel, characterized in that it comprises: a container for the manufacture of steel for the storage of molten hot metal including slag and steel; an opening in the container to allow the molten hot metal to flow from the container down into the pouring kettle via a stream of hot metal; an infrared imaging device (Rl) to represent the stream of molten metal flowing between the opening and the ladle to detect the presence of slag in the stream; and wherein the Rl imaging device uses RI wavelengths of at least about 8 μm to detect the presence of slag in the bleeding stream.

22. The apparatus according to claim 21, characterized in that the container is a BOF and the opening is a pouring orifice defined in the side portion of the BOF.

23. The apparatus according to claim 21, characterized in that the container is a furnace for the manufacture of electric steel and wherein the opening is defined at the bottom of the furnace.

24. A system for detecting slag in the stream, characterized in that the system comprises; a vessel for emptying a stream of molten metal, the current includes both molten steel and molten slag; an imaging device for representing the current for detecting the presence of slag, wherein the imaging device uses RI wavelengths of at least about 8 μm to detect the presence of slag in the stream.

25. The system according to claim 20, characterized in that the window is at least about 98% transmissible for certain wavelengths of Rl greater than about 8 μm, and includes some coating of calcium fluoride, ZnSe, ZnS, CdTe, GaAs, and germanium.