JPH09257820A - Apparatus and method for measuring flowing velocity of molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure flowing velocity of molten metal by vibrating a sensing bar at the part of a supporting bar set in cross sectional shape and thickness so that the moment of inertia of area becomes a specific range as a fulcrum. SOLUTION: A sensing bar 11 is fixed to the mounting part 21 of a supporting bar 20, positioned so as to cross the flow of molten metal in the metal, the bar 20 is moved down, and the end of the bar 11 is disposed in the discharging flow injected from a dipping nozzle from above the molten metal level of a casting mold. Thus, Karman vortex corresponding to the outer diameter of the bar 11 is slightly separated at the downstream of the bar 11, alternately radiated, the impact due to the radiation are repeated to vibrate the bar 11. The bar 11 is vibrated at the part set in cross sectional shape and thickness so that the moment of inertia of area becomes a range of 0.10×10<-4> to 430×10<-4> cm<4> between the fixing part 23 and the part 21 as a fulcrum, and the vibrating frequency is detected by a strain gage 25. The flowing velocity of the metal is accurately measured from the relationship between previously obtained vibrating frequency and the flowing velocity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a flow rate of molten metal and a method therefor, for example, in continuous casting of molten metal, a continuous flow rate of molten metal injected from a tundish into a mold through a dipping nozzle is continuously applied. TECHNICAL FIELD The present invention relates to an apparatus for measuring a flow rate of molten metal and a method therefor capable of directly measuring the same.

[0002]

2. Description of the Related Art In a continuous casting process of a molten metal, there is a step of distributing and injecting the molten metal from a tundish into a mold through a dipping nozzle. FIG. 7 shows a conceptual diagram of a cross-sectional structure around the immersion nozzle in this step, in which 1 in the drawing is a water-cooled mold, 2 in the drawing is an immersion nozzle led out from the bottom of a tundish (not shown). is there. Reference numeral 3 in the figure denotes a mold powder having a function of preventing oxidation of the surface of the molten metal, lubricating between the mold and the slab, catching floating inclusions, keeping the molten metal warm, and the like.

The immersion nozzle 2 is generally provided with a plurality of discharge ports in the vicinity of the lower portion. For example, as shown in the drawing, the lower side wall has two discharge ports 2a and 2b.
It is configured to discharge the same amount of molten metal from a and 2b. Usually, this discharge direction coincides with the longitudinal direction of the space 4 inside the mold as shown in the plan view of FIG.

The molten metal discharged from the immersion nozzle 2 is
The molten metal is supplied while being controlled so that the interface height in the mold is maintained at almost the same level, and the molten metal filled in the mold is removed by the mold and continuously drawn from the cooled and solidified lower side. This makes it possible to obtain pieces continuously.

By the way, it is known that when the immersion nozzle is used for a long time, the discharge amount of the molten metal from each discharge port becomes uneven. This is because the aluminum added in the molten steel for the purpose of deoxidation is oxidized into alumina, which adheres and deposits on the inner wall of the immersion nozzle and closes the immersion nozzle, obstructing the smooth flow of molten steel in the nozzle. is there. As a result, the discharge amount of the molten metal injected into the mold is deviated depending on the direction, causing non-uniform solidification in the mold and disturbance of the surface of the molten metal. Is known to cause a decrease in In order to avoid such a situation, it is important to detect the bias of the discharge flow ejected from the immersion nozzle at an early stage and to take measures to prevent this. For this,
Conventionally, various methods for detecting the bias of the discharge flow have been proposed. For example, a method of monitoring uneven temperature rise of mold cooling water and, when this is observed, estimating that there is an uneven discharge flow. A method of continuously measuring the fluctuation of the molten metal level at a plurality of positions in a mold, and presuming that there is an uneven discharge flow when the difference is observed. Etc. have been proposed and implemented. However, each of these methods has problems. First, the above-described methods for detecting the drift of molten metal are all indirect measurements, and their response is dull and cannot be quantitatively evaluated, and the measurement results are used for feedback control of peripheral devices. There is a problem that cannot be done. For example, when non-uniform discharge is detected, the electromagnetic brake in the mold is operated to individually control the discharge amount from each discharge port. Since quantitative measurement of drift is not possible, the data of drift detection cannot be used directly for electromagnetic brake control, and these controls have to rely on the experience and intuition of field workers as before. .

If uneven flow is detected, it is possible to take measures such as increasing the output of the electromagnetic brake in the mold, increasing the amount of nozzle flushing gas, increasing the temperature of the molten metal in the tundish, or replacing the immersion nozzle as soon as possible. Although ideal, the conventional drift detection method has a slow response, so that the countermeasure tends to be delayed, and there is also a problem that the drift increases more and more.

In recent years, it has been required to increase the casting speed of continuous casting, and the demand for stable supply of product quality has become strict. Against this background, it is necessary to fully understand the flow of molten steel in the mold in order to find the optimum conditions for high speed casting. For example, if the casting speed is increased, the discharge amount from the discharge port of the immersion nozzle will naturally increase,
As shown in FIG. 9, the discharge flow collides with the solidification shell a, and in the worst case, there is a risk of breaking the solidification shell a and causing breakout. In addition, as shown in FIGS. 9 and 10, the mold powder 4 is entrained by the surface flow c (also referred to as reversal flow) generated when the mold is reversed near the meniscus b whose side surface is raised, or is discharged from the dipping nozzle and is upwardly moved. Since the non-metallic inclusions d being floated into the slab occur and these are the largest causes of surface defects in the cast slab, it is very important for quality control to grasp the flow velocity of these reversal flows.

As a method for solving such a problem, the present applicant has already filed Japanese Patent Application No. 5-165817.
In this method, as shown in FIG. 11, a detection rod 5 made of a heat-resistant material is immersed and inserted in the molten metal so as to cross the flow,
As shown in FIG. 12, the discharge cycle of the Karman vortex discharged to the downstream side of the detection rod 5 is not detected by the cycle of impact given to the detection rod 5. Specifically, this impact cycle is 13 is measured by a vibration detecting means such as a strain gauge attached to the detecting rod 5, as shown in FIG. 13, and the measurement result is applied to a relational expression between the frequency of the detecting rod and the flow velocity of the molten metal which is obtained in advance. Was to calculate the flow rate of the molten metal.

According to this method, the flow velocity of the discharge flow from the immersion nozzle or the flow velocity of the surface flow can be directly measured, and the peripheral device can be controlled by feeding back the obtained measurement data to the control system. In addition to the above, it has become possible to perform in-mold flow velocity analysis to find optimal conditions for high speed casting. After this application, improvement of flow velocity measurement accuracy by this method was recognized as an important theme. In response to this problem, the present invention intends to further improve the measurement accuracy in a molten metal flow velocity measuring apparatus and method for estimating the flow velocity from vibration detection of a detection rod caused by Karman vortex shedding.

[0010]

[MEANS FOR SOLVING THE PROBLEMS] In order to improve the measurement accuracy in this flow velocity measuring method, it is important to widen the measurable flow velocity range and to detect the noise component and the frequency component due to the discharge main flow which is the detection target frequency. It is to increase the output value of the peak of the frequency component to be detected so that it can be easily distinguished. The maximum width of the flow rate range of the molten metal predicted in the distribution injection of the molten metal using the immersion nozzle from the tundish to the mold in the continuous casting process of the molten metal covers a wide range of 10 to 300 cm / sec. In case of, 30-50 cm / sec
The practical flow within the mold can be analyzed if this range can be covered in practice. Therefore, it is a specific object of the present invention to establish a technique capable of detecting a target frequency component with a high output value such that a noise component can be ignored in the entire measurement target region.

The present inventor has conducted studies to solve this problem and has found that the natural frequency of the device is an important point in solving this problem. As described in Japanese Patent Application No. 5-165817, the frequency f of the Karman vortex due to the discharge main flow is K = (fD, where V is the flow velocity of the discharge main flow and D is the diameter of the detection rod. /
V). Here, K is a constant that does not depend on the type of molten metal. From this relational expression, when the diameter D of the detection rod is the same, the frequency f becomes higher as the flow velocity V becomes higher. In other words, the larger the flow velocity V is, the more the measuring device that can handle higher frequencies is required. And this frequency is the frequency when vibrating after holding the device in the state of a cantilever in the air,
That is, the present inventor has found that the natural frequency governs. It was also found that the maximum factor that defines this natural frequency is the second moment of area at the location that is the base point of vibration, that is, at the boundary between the non-vibrating portion and the vibrating portion. Then, it was concluded that in order to adjust the second moment of area, the longitudinal elastic modulus (Young's modulus) of the material forming the boundary and the cross-sectional shape of the pneumatic tube should be adjusted.

Further, in Japanese Patent Application No. 165817/1993, the main purpose is to establish the basic theory, so that the detection rod is an integral one from the base end support to the tip, but such a form is not practical. . Therefore, in the present invention, the base end side of the detection rod to which the vibration detection means is attached is formed separately from the detection rod, and this portion is newly named as a support rod. Then, a mounting portion is provided at the tip of the support rod, and by mounting the detection rod by this mounting portion, only the detection rod can be replaced when the detection rod is consumed.

The molten metal flow velocity measuring device of the present invention made based on such an idea has the following constitution. The second moment of area of the cross section is 0. from the detection rod in which the detection unit is positioned in the molten metal so as to cross the flow of the molten metal, and the mounting unit where the base end of the detection rod is mounted is the vibration-sealing fixed unit.
A supporting rod extending through a portion whose cross-sectional shape and wall thickness are set so as to be in the range of 10 × 10 ^{−4 to} 430 × 10 ⁻⁴ cm ⁴ , a measuring rod composed of the supporting rod, and the detection rod. And the vibration detection means for detecting the vibration of the detection rod, and the vibration frequency of the detection rod measured directly or indirectly by the vibration detection means is applied to the relational expression between the vibration frequency of the detection rod and the flow velocity of the molten metal, which is obtained in advance. And a means for calculating the molten metal flow rate.

[0014] This way the detection rod is practical be replaceable on the support rod by the mounting section, the second moment of the detection rod from the fixing portion without providing the mounting portion 0.10 × 10 ^{- In} some cases, it may be integrally extended through a portion whose cross-sectional shape and wall thickness are set so as to be in the range of ^{4 to} 430 × 10 ⁻⁴ cm ⁴ .

The second moment of area is 0.10 × 10 ^-4 ~
The portion set within the range of 430 × 10 ⁻⁴ cm ⁴ is a portion that serves as a fulcrum of deflection when receiving a shock due to Karman vortex shedding, and the detection rod vibrates with this portion as a fulcrum.
The deflection fulcrum may have the same diameter and the same thickness as the portions located on both sides thereof, but it is preferable that the deflection fulcrum has a smaller wall thickness than the portions located on both sides thereof. The thin portion may be a section having a constant length instead of one point, and in this case, the bending fulcrum is set within this section.

In order to efficiently and selectively detect the vibration due to the discharge of the Karman vortex, the thin-walled portion has a rectangular cross-section and is positioned so that its long side surface is parallel to the flow of the molten metal. .

The flow velocity V of the molten metal should be theoretically determined by an estimation formula of V = f · D / K (K is a constant) or V = af · D + b (a and b are constants). Actually, since the rigidity of the portion where the strain gauge is attached, which is the portion where the frequency signal is taken out, is related, it deviates from the linear relationship in the high speed region. Therefore, the present invention also proposes, as a means for correcting this, to create a calibration curve for each type of measurement rod and to determine the flow velocity of the molten metal in the actual measurement based on this calibration curve. When creating this calibration curve, it is assumed that a low melting point alloy that can easily simulate the measurement environment is used, and the measurement rod is immersed in this low melting point alloy and the relationship between the frequency of the detection rod and the flow velocity of the molten metal. Based on the above, a calibration curve for estimating the flow velocity of the molten metal is obtained from the frequency of the detection rod.

Further, the detection rod becomes thin due to melting loss with the passage of immersion time, or becomes thick due to the adhesion of molten metal depending on the material, but the influence on the measurement result due to the change of the outer diameter should be corrected. Is also preferable.

[0019]

According to the molten metal measuring method of the present invention, the detection rod attached to the support rod which is the base end side of the vibration detecting means is positioned in the flow in the molten metal so as to cross the flow. Positioning of the detection rod is performed by fixing a gripping portion, which is a base end side portion of the detection rod, to a support rod. The detection rod is fixed to the support rod by a mounting portion provided at the tip of the support rod. This support is installed on the lifting device,
The elevating device is operated to position the vicinity of the tip of the detection rod from above the molten metal surface of the mold, for example, in the discharge flow ejected from the immersion nozzle. When positioned in the discharge flow, Karman vortices corresponding to the outer diameter of the detection rod are discharged to the downstream side of the detection rod alternately at a slight distance in the direction orthogonal to the flow direction of the discharge flow. The accompanying shock is applied to the sensing rod. Repeated shocks cause the detection rod to vibrate. At this time, as for the vibration of the detection rod, the second moment of area provided between the fixed portion and the mounting portion that seal the vibration of the support rod is 0.
The fulcrum is performed with a portion whose cross-sectional shape and wall thickness are set to be in the range of 10 × 10 ^{−4 to} 430 × 10 ⁻⁴ cm ⁴ . Then, the vibration frequency of the detection rod is detected by the vibration detection means. The frequency of vibration caused by the discharge of Karman vortices is defined by the outer diameter of the detection rod immersed in the molten metal and the flow velocity of the molten metal, so if the relationship between the frequency and the flow velocity is obtained in advance, the flow velocity You can ask. Further, according to the present invention, the moment of inertia of area of a portion which is a fulcrum of vibration, that is, a fulcrum of deflection is 0.10 × 10 ^{−4 to} 430 × 10.
^-Since the cross-sectional shape and wall thickness are set so as to fall within the range of ^-4 cm ⁴ , practical use of the molten metal flow velocity range predicted in the molten metal distribution injection using the immersion nozzle from the tundish to the mold It is possible to deal with the entire required range, and it is possible to detect the target frequency component as a high output value in which the noise component can be ignored in the entire measurement target region.

When the detection rod is immersed in the molten metal, the surface flow channel may not be known. In this case, in order to position the detection rod so as to obtain a high output, it may be desired to know the flow direction of the surface flow. In such a case, the place where the vibration detecting means is provided is formed into a circular cross section or a polygonal cross section, and three or more parts are attached adjacent to each other in the circumferential direction or the adjacent surface direction of the place. The magnitude of the output value is compared to identify the flow direction of the surface flow, and the flow velocity is measured in consideration of the flow direction of the surface flow.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will now be described with reference to the illustrated embodiments. FIG. 1 is an explanatory view of a main part of a flow velocity measuring device according to the present invention. This flow velocity measuring device is composed of a measuring rod 30, a strain gauge 25 as a vibration detecting means, and a calculator (not shown). The measuring rod 30 is further composed of a detecting rod 11 and a supporting rod 20 supporting the same. .

As the detecting rod 11, a hollow rod having a circular cross section and a bottom is mainly used. The detection rod 11 may be solid, but is preferably hollow from the viewpoint of mechanical strength. Further, if it is hollow, a thermocouple can be installed near the tip of the detection rod 11, and while controlling the temperature of the molten metal to be discharged, early detection of an abnormal situation such as melting and breakage of the detection rod 11 can be performed at the same time. Will be able to. The material of the detection rod 11 can be appropriately selected as long as it is a material having sufficient heat resistance and corrosion resistance at the operating temperature. For example, when the molten metal is molten steel, alumina, zirconia or the like is preferably selected. These materials are suitable because they have hot strength, erosion resistance and abrasion resistance. In particular, when a mold powder layer is present on the surface of the molten metal, it is necessary to coat that portion with a material having excellent slag erosion resistance. In addition, the tip of the detection rod 11 does not need to be particularly hemispherical, and generally, planar processing is sufficient. Also, inexpensive stainless steel or brass can be used if they are to be used for a short period of time.

2 to 4 show the support bar 20, and FIG.
2A is a front view, FIG. 4B is a side view, FIG. 3 is a longitudinal sectional view, and FIGS. 4A, 4B, and 4C are A- in FIG.
It is an A'sectional view, a BB 'sectional view, and a CC' sectional view.
As shown in the drawing, the support bar 20 includes a mounting portion 21, a thin portion 2
2 and a fixed part 23. The mounting portion 21 is a tubular member for mounting the detection rod 11 in a replaceable manner. The mounting structure is such that the detection rod 11 is fitted inside, and a ring 15 is screwed as shown in FIG. The screw 16 is fixed to the screw hole 24 from the outside.

The fixed portion 23 is a portion gripped by an elevating mechanism (not shown) and is firmly held by the elevating mechanism so as not to vibrate.

The thin portion 22 is located between the fixed portion 23 and the mounting portion 21 and when the detection rod 11 is impacted by the emission of Karman vortices, the thin portion 22 bends preferentially to other portions, thereby vibrating the detection rod 11. Is a fulcrum of deflection, that is, a fulcrum of vibration. How the sensing rod 11 responds well to a wide range of vibration frequencies,
Moreover, how the detected target frequency component can be surely detected by distinguishing it from the noise component depends on the second moment of area of the thin portion.

The second moment is determined by the cross-sectional shape, width cross-sectional shape b, a thickness h, or vibrating in the thickness direction, moment of inertia of area I is represented by I = bh ^3/12 It As described above, the wall thickness h becomes the third power and greatly contributes to the second moment of area. Therefore, it is effective to increase the wall thickness h of the thin portion which is the thin portion in order to increase the second moment of area. In continuous casting of molten metal, the maximum width of the molten metal flow rate range predicted for distribution injection from the tundish into the mold through the dipping nozzle is 10 to 3
Although it is in the range of 00 cm / sec, the fluctuation range of the surface flow velocity is, for example, 30 to 50 cm / sec, and practically, it is sufficient to measure the flow velocity of the molten steel in the mold if this range can be covered. Therefore, it can be said that the object of the present invention is to make it possible to detect the peak of the frequency component due to the discharge flow, which is the detection target, with an output value large enough to be discriminated from the noise component in the entire flow velocity range. For that purpose, first of all, it is necessary that the measuring rod 30 can cope with a high frequency particularly in the vicinity of the upper limit of the flow velocity range. This can be realized by adjusting the natural frequency of the measuring rod 30. The inventor has found it. Since the natural frequency of the measuring rod 30 is governed by the moment of inertia of area of the thin portion 22, the problem of enabling measurement over the entire range of flow velocity is ultimately the moment of inertia of area of the thin portion 22 of the measuring rod 30. It is all about finding the proper range. As a result of repeated theoretical analysis and various experiments, the present inventor has determined that the second moment of area of the thin portion 22 is 0.1.
It was confirmed that the frequency components in the flow velocity range can be detected by setting the range of 0 × 10 ^{−4 to} 430 × 10 ⁻⁴ cm ⁴ .

However, as a problem when the second moment of area is increased, the natural frequency is increased, but the amount of vibration deflection of the thin portion 22 is suppressed, the output value of the frequency peak is reduced, and the noise component is sharply separated. The problem that it will be difficult will emerge. This problem can be avoided by increasing the length of the thin portion 22 of the support rod 20 and increasing the vibration width of the detection rod 11.

As a method for discriminating frequency peak noise from noise, increasing the diameter of the detection rod 11 is also an extremely effective means. Velocity V and emission frequency f of Karman vortex
As can be seen from the relational expression K = fD / V, the frequency f becomes lower as the diameter D of the detection rod 11 becomes larger, and the frequency f becomes higher as the diameter D becomes smaller, under the same flow velocity. In other words, if the frequency of the ambient noise that greatly affects the measurement is known in advance, the diameter of the detection rod 11 that does not cause a frequency peak in the vicinity of the frequency of the ambient noise is appropriately selected, so A distinction is possible. The present inventor has also found that the weight per unit length of the detection rod 11 greatly contributes to the increase of the adaptive flow velocity range of the device. When the material and specifications of the support rod 20 are the same, and further, the length and the diameter of the detection rod 11 are the same, the smaller the weight per unit length of the detection rod 11 is, that is, the same thickness, the material with the smaller density. The present inventor has also confirmed that, in the case of the same material, the range of measurable flow velocity becomes larger when the wall thickness is smaller. When the material is the same, the second moment of area of the thin portion 22 is defined by the cross-sectional shape of the thin portion 22 and its thickness. Various shapes can be adopted as the thin portion 22, but in order to efficiently receive the impact caused by the Karman vortex due to the discharge main stream, a rectangular cross section as shown in FIG. 4B is used. It is preferable to use and set such that the long side surface is parallel to the flow of the molten metal.

The measuring rod described above is a case where the detecting rod can be replaceably mounted on the mounting portion 21 provided on the support rod 20. In the case of this example, if the detection rod 11 is melted or broken, it can be replaced with a new detection rod 11. Although it is not practical, the mounting part 2
There is also a case where the detection rod 11 is not replaceably attached by 1 but the detection rod 11 is integrally extended from the fixed portion 23 via the thin portion 22.

As shown in FIGS. 5A and 5B, strain gauges 25, 25 as vibration detecting means are attached to the long side surface of the thin portion 22 having a rectangular cross section to prevent the thin portion 22 from bending. The vibration frequency of the thin portion 22 can be detected from the cycle of this bending. As the vibration detecting means, an optical displacement meter using an LED, an infrared ray, a laser, or the like can be used instead of the strain gauges 25, 25. However, when light in the infrared wavelength range is emitted from molten steel, use of infrared light is not preferable. If there is a light-shielding substance such as smoke, the strain gauge 2
It is preferable to use 5,25.

In such a molten metal flow velocity measuring device, the detection rod 11 is attached to the support rod, and the base end of the support rod 20 is held by an elevating device (not shown) to move up and down to move the detection rod 11 into the molten metal. Of the discharge flow of the Karman vortex is repeatedly measured and recorded in the form of a vibration frequency, and the flow velocity V of the discharge flow from the vibration frequency is measured or measured in real time. To calculate. The flow velocity of the discharge flow is derived from the vibration frequency by calculating a relational expression between the vibration frequency f and the flow velocity V in advance using the same measuring rod, and applying the measured vibration frequency f to this relational expression. In the calculation, the flow velocity V is expressed by V = a · f · D + b, and the flow velocity V and the frequency f should have a linear relationship, but in reality, since the rigidity of the portion where the strain gauge is attached also has a relationship, Come off. For this reason, when higher accuracy is required, the flow velocity V
And a vibration frequency f, a calibration curve is obtained, and this calibration curve is used to calculate the flow velocity from the vibration frequency in the actual measurement thereafter. This calibration curve shall be performed using a low melting point alloy that is easy to simulate the measurement environment.The measurement rod is immersed in this low melting point alloy and the regression line is calculated from the relationship between the frequency of the molten metal and the frequency of the detection rod. Obtained by analysis. The present inventor has confirmed that the calibration curve obtained for the low melting point alloy is consistent with the result in molten steel, and in many cases, this calibration curve can also be approximated by a linear regression equation. The inventor has confirmed.

Further, there is a phenomenon that the detection rod becomes thin due to melting loss with the passage of immersion time or becomes thick due to adhesion of molten metal depending on the material. Generally, it is said that it does not easily react with molten metal and has good corrosion resistance. For example, ceramics and the like also tend to be corroded and thin when exposed to the heat and flow of molten metal. On the other hand, for example, iron, stainless steel, brass, etc., which are said to have good thermal conductivity, when immersed in molten metal, they take heat from the molten metal and transfer it upward to radiate heat, so the molten metal adhered to the surface tends to harden and thicken. . Since such a phenomenon causes an error, it is preferable to include a correction term for correcting this error in the estimation formula. The correction term is expressed as a function of the immersion time and the temperature of the molten metal, and specifically, it can be considered to be obtained in advance by a test. According to the research conducted by the present inventor, it has been confirmed that the relationship between the immersion time and the change in outer diameter can be treated as a substantially linear relationship when the flow velocity V and the temperature of the molten metal are constant. However, the change in the outer diameter of the detection rod 11 does not occur uniformly over the entire immersion portion, and generally the deeper the immersion position is, the faster the flow velocity is, and therefore the change in the outer diameter is large. Therefore, it should be noted that the concept of the outer diameter used here does not mean the outer diameter at a specific position.

Further, in the above-mentioned one, the strain gauge is provided in the thin portion 2
The second long side surface is attached to the two long side surfaces and the long side surface is positioned parallel to the flow direction, but this is based on the premise that the flow direction is known. When the flow direction of the flow velocity to be detected is not known, the identification of the flow direction is the first problem. In such a case, the influence of the reversal flow (surface flow) generated when the main flow of the discharge flow discharged from the immersion nozzle is reflected on the mold wall surface cannot be ignored, and the flow velocity of the reversal flow needs to be measured. There is. In such a case, the cross-sectional shape of the thin-walled part shall be circular or square or regular polygonal such that there is no directionality or little directionality, and the thin-walled part may be circumferentially or circumferentially oriented in the circumferential direction. Or, by adhering three or more strain gauges adjacent to each other in the direction of the adjacent surface and comparing the magnitude of the output value from each strain gauge, the flow direction of the surface flow to be detected is specified and the measured flow is measured. Measure the flow velocity considering the direction.

In the above description, the support rod is formed with a portion thinner than both sides thereof, and this portion is used as the fulcrum of vibration, that is, the fulcrum of deflection, but it is supported without forming a thin portion. The case where the rods have the same diameter over the entire length is also an object of the present invention. In this case, it is preferable to lengthen the detection rod in order to make it easy to bend.

[0035]

EXAMPLES Specific examples 1 to 7 of the present invention are shown in Table 1.
Examples 1 to 7 are based on the shapes shown in FIGS. 1 to 5,
The elements related to the detection rod and the support rod are changed. The theoretical value of the natural frequency of each of these probes and the corresponding flow velocity range confirmed by the experiment are shown. As can be seen from these results, all of Examples 1 to 7 of the present invention are 30 to
It can be seen that the flow velocity range of 50 cm / sec can be completely dealt with. In addition, all of them were able to obtain sufficiently large output values that can be distinguished from noise.

[0036]

[Table 1]

[0037]

According to the invention described in claim 1, it is possible to measure the flow velocity of the molten metal in the mold with high accuracy over the entire expected flow velocity range while eliminating the influence of noise. Become.

Further, as described in claim 4, the portion for setting the second moment of area in the range of 0.10 × 10 ^{−4 to} 430 × 10 ⁻⁴ cm ⁴ is made thinner than the portions located on both sides thereof. In addition, when the thin-walled part has a rectangular cross-sectional shape and its long side faces are positioned so as to be parallel to the flow of molten metal, vibrations due to the discharge of Karman vortices acting in the direction perpendicular to the discharge flow are generated. It becomes possible to measure efficiently and selectively.

Further, when the influence on the measured value due to the change in the outer diameter of the detection rod with the passage of the immersion time is corrected as in the eighth aspect, it is possible to further improve the measurement accuracy.

According to a ninth aspect of the present invention, the location where the vibration detecting means is provided has a circular cross section or a polygonal cross section, and three or more vibration detecting means are provided adjacent to each other in the circumferential direction or the adjacent surface direction of the location surface. When installing and comparing the magnitude of the output value from each vibration detection means to identify the flow direction of the discharge flow and measure the flow velocity, measure the flow direction such as reverse flow that is unknown. The scope of application of the present invention is broadened.

[Brief description of drawings]

FIG. 1 is a front view showing the overall appearance of a probe used in a flow velocity measuring device of the present invention.

FIG. 2 shows a support rod portion of the probe, (a) is a front view and (b) is a side view.

FIG. 3 is a vertical sectional view of a support rod portion of the probe.

FIG. 4 shows a cross-sectional view of the support rod portion of the probe,
2A is a sectional view taken along the line AA ′ in FIG. 2A, FIG. 2B is a sectional view taken along the line BB ′ in FIG. 2A, and FIG.
CC 'sectional view in (a)

FIG. 5 shows a state in which a strain gauge is attached to the probe, (a) is a front view and (b) is a side view.

FIG. 6 is an explanatory view showing a state in which the thin portion of the support rod is positioned such that its long side surface is parallel to the flow direction of the discharge flow.

FIG. 7 is a schematic sectional view showing how molten metal is injected into a mold through an immersion nozzle.

FIG. 8 is an explanatory plan view showing the relationship between the mold and the direction of the discharge flow from the immersion nozzle immersed in the mold.

FIG. 9 is a schematic diagram showing various flows of molten steel in a mold.

FIG. 10 is a conceptual diagram showing the flow of molten steel near the inner surface of the mold.

FIG. 11 is an explanatory diagram of a basic principle of measuring a flow velocity by detecting a vibration caused by a Karman vortex.

FIG. 12 is a schematic diagram showing how Karman vortices are emitted on the downstream side of the detection rod.

FIG. 13 is a graph showing an output example of the vibration detection means.

[Explanation of symbols]

c Karman vortex 1 Mold 2 Immersion nozzle 2a, 2b Discharge port 3 Mold powder 4 Mold space 5 Detecting rod 5a Long side surface 11 Detecting rod 15 Ring 16 Screw 20 Supporting rod 21 Mounting part 22 Thin part 23 Fixing part 24 Screw hole 30 Measuring rod

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Atsushi Hayashi 1-7-40 Mishimae, Takatsuki City, Osaka Prefecture Inside Hereus Electronight Co., Ltd. (72) Yukio Terauchi 1-7-Mishimae, Takatsuki City, Osaka Prefecture 40 Hereus Electronight Co., Ltd.

Claims (9)

[Claims] 1. A moment of inertia of area from a detection rod in which a detection portion is positioned in the molten metal so as to cross the flow of the molten metal, and a mounting portion to which a base end of the detection rod is attached, from a fixing portion which shuts off vibration. Is 0.10 × 10 ^{−4 to} 430 × 10 ⁻⁴ c
a support rod extending through a portion whose cross-sectional shape and wall thickness are set so as to be in the range of m ⁴ , a measurement rod configured by: a vibration detection means for detecting the vibration of the detection rod; The vibration frequency of the detection rod measured by the vibration detection means is applied in advance to the relational expression between the vibration frequency of the detection rod and the flow velocity of the molten metal to calculate the flow velocity of the molten metal. Flow velocity measuring device. 2. The second moment of area is from 0.10 × 10 ^{−4 to} 430 × from the fixed portion that seals the vibration of the detection rod in which the detection portion is positioned in the molten metal so as to traverse the flow of the molten metal.
A measuring rod integrally extending through a portion whose cross-sectional shape and wall thickness are set so as to be in the range of 10 ⁻⁴ cm ⁴ , and a vibration detecting means for detecting the vibration of the detecting rod, The vibration frequency of the detection rod measured by the vibration detection means is applied in advance to the relational expression between the vibration frequency of the detection rod and the flow velocity of the molten metal to calculate the flow velocity of the molten metal. Flow velocity measuring device. 3. The second moment of area is 0.10 × 10 ^−4.
The molten metal flow velocity measuring device according to claim 1 or 2, wherein the portion set in the range of 430 x 10 ^-4 cm ⁴ is thinner than the portions located on both sides thereof. 4. The molten metal flow velocity measuring device according to claim 3, wherein the thin-walled portion has a rectangular cross-sectional shape and is positioned so that its long side surface is parallel to the flow of the molten metal. 5. The thickness h of the thin portion of the support rod is 1.0 to 3.
5 mm, thin portion width b is 5.0 to 15.0 mm, thin portion length L is 30 to 130 mm, and detection rod length is 50 to 5
00 mm, weight per unit length 0.2-2.5 g /
The molten metal flow velocity measuring device according to claim 1 or 2, wherein the flow velocity measuring device has a diameter of cm. 6. The detection rod positioned so as to cross the flow of the molten metal to be measured has a second moment of area of 0.10 × 10 ^{−4 to} 430 × 10 ⁻⁴ from the fixed portion that seals the vibration.
a measuring rod extending through a portion whose cross-sectional shape and wall thickness are set so as to fall within the range of cm ⁴ , vibration detecting means for detecting the vibration of the detecting rod, and the vibration detecting means measures the vibration. The frequency of the detection rod is calculated in advance by applying the relational expression between the frequency of the detection rod and the flow velocity of the molten metal to the flow velocity of the molten metal. A method for measuring the flow velocity of a metal, wherein a second moment of area of a Karman vortex generated on the downstream side of a detection rod is 0.10.
× regarded as the vibration of 10 ^-4 to 430 × 10 ^-4 in the range of cm ⁴ as its cross-sectional shape and the detection rod to the thickness was without a fulcrum deflection portion set continuously by the vibration detecting means the vibration A method for measuring the flow rate of molten metal, which is obtained by applying the measured frequency to the relational expression between the frequency of the detection rod and the flow rate of the molten metal, which is obtained in advance, and calculating the flow rate of the molten metal. 7. The molten metal flow velocity is estimated from the frequency of the detection rod based on the correlation between the frequency of the detection rod and the flow velocity of the molten metal for each type of measurement rod measured experimentally in a low melting point alloy. 7. The method for measuring the flow velocity of molten metal according to claim 6, wherein a calibration curve to be obtained is derived for each type of measurement rod, and in the case of actual measurement using a measurement rod of the same type, this calibration curve is used thereafter. 8. A correction term using the immersion time and the temperature of the molten metal as parameters is previously obtained by a test in order to correct the influence of the change in the outer diameter of the detection rod on the measured value with the passage of the immersion time. The molten metal flow velocity measuring method according to claim 6, wherein the measurement result is corrected using a correction term. 9. The flow velocity measuring method according to claim 6,
The location where the vibration detecting means is provided has a circular cross section or a polygonal cross section, and three or more vibration detecting means are attached adjacent to each other in the circumferential direction or the adjacent surface direction of the surface of this location, and the output from each vibration detecting means A method for measuring the flow velocity of molten metal by comparing the magnitudes of values and specifying the flow direction.