JP7010160B2 - Liquid metal flow velocity measurement method and ultrasonic current meter - Google Patents

Description

The present application discloses a method for measuring a flow velocity of a liquid metal using an ultrasonic current meter.

Conventionally, a method widely used to improve the accuracy of measurement of liquid metal flow by an ultrasonic current meter is to change the measurement algorithm. This focuses on how to calculate velocity information with few errors from ultrasonic information acquired from the flow field. Non-Patent Document 1 is a known example showing that the measurement accuracy is improved by changing the measurement algorithm.

On the other hand, as a method focusing on the fact that there is no error in the acquired ultrasonic information, there is a method of immersing the probe in the working fluid for a long time. This is intended to improve the wettability of the working fluid to the probe surface and to remove gas phases and impurities that cause errors in ultrasonic information from the probe surface. Non-Patent Document 2 is a known example showing that the measurement accuracy is improved by immersing the probe in the working fluid for a long time.

In Patent Document 1, there is a proposal of a method and an apparatus for imparting good wettability to an ultrasonic transducer immersed in a liquid metal, and the fuel constituting the core of a high-speed neutron reactor cooled by liquid sodium. An example of an ultrasonic visual recognition device has been introduced for visual recognition of an aggregate, but there is a suggestion of applicability of flow velocity measurement, but there is no specific description. Further, in Patent Documents 2 and 3, in order to improve the wettability that affects the transfer of ultrasonic energy between the transducer device and the molten aluminum in the process of inspecting the quality of the molten aluminum using ultrasonic waves. There is a proposal for a probe made of a titanium material having corrosion resistance, stability, low thermal conductivity, and low thermal expansion in molten aluminum, but there is no description of a specific application method for flow velocity measurement.

Japanese Unexamined Patent Publication No. 62-299779 Special Fair 1-1141 Gazette Special Fair 1-52694 Gazette

Murakawa et al., Proceedings of the Japan Society of Mechanical Engineers (Vol. B) Vol. 79, No. 799 (2013-3), P356-367 M.Hirabayashi, et.al., 13th International Conference on Nuclear Engineering, Beijing, China, May16-20, 2005, ICONE13-50346

As disclosed in Non-Patent Document 2, when measuring the flow velocity of a liquid metal using an ultrasonic flow meter, it is necessary to immerse the ultrasonic probe in the liquid metal for several hundred hours, which is very troublesome. It takes. That is, in the prior art, when measuring the flow velocity of a liquid metal using an ultrasonic current meter, there is a problem that it is difficult to improve the measurement accuracy in a short time.

The present application is a method of measuring the flow velocity of a liquid metal using an ultrasonic flow meter equipped with an ultrasonic probe as one of means for solving the above-mentioned problems, in which the ultrasonic probe is immersed in the liquid metal. Previously, a method for measuring a flow velocity of a liquid metal is disclosed, in which a brazed metal layer capable of solute diffusion into the liquid metal is provided on the surface of the ultrasonic probe.

In the flow velocity measuring method of the present disclosure, it is preferable that the base metal of the ultrasonic probe is made of stainless steel.

In the flow velocity measuring method of the present disclosure, it is preferable that the thickness of the brazed metal layer is 10 μm or more and 5000 μm or less.

In the flow velocity measuring method of the present disclosure, it is preferable that Ag is contained in the metal element constituting the brazed metal layer.

The present application is an ultrasonic doppler current meter provided with an ultrasonic probe, which is used for measuring the flow velocity of a liquid metal as one of means for solving the above-mentioned problems, and the ultrasonic probe is attached to the surface thereof. Disclosed is an ultrasonic doppler current meter having a brazed metal layer capable of solute diffusion into a liquid metal.

In the flow velocity measuring method of the present disclosure, when the ultrasonic probe is immersed in the liquid metal, the brazed metal layer provided on the surface of the ultrasonic probe diffuses and mixes with the liquid metal, resulting in the ultrasonic probe. When the surface is easily wetted with the liquid metal in a short time, that is, when the flow velocity of the liquid metal is measured by using an acoustic doppler current meter, the measurement accuracy can be improved in a short time.

It is a schematic diagram for demonstrating the structure of the experimental apparatus which measures the flow velocity of a liquid metal using an ultrasonic flow meter equipped with an ultrasonic probe. It is a figure comparing the echo intensities regarding the flow velocity of the liquid metal flowing in a certain direction between the case of using the ultrasonic probe provided with the brazed metal layer and the case of using the ultrasonic probe without the brazed metal layer. be. It is a diagram comparing the velocity distribution of the flow velocity in which the liquid metal flows in a certain direction between the case of using the ultrasonic probe provided with the brazed metal layer and the case of using the ultrasonic probe without the brazed metal layer. be. The thickness of the brazed metal layer provided on the surface of the ultrasonic probe and the time until the flow velocity of the liquid metal can be measured by the acoustic doppler current meter (the time until the ultrasonic probe is sufficiently wetted with the liquid metal). It is a figure which shows the relationship.

1. 1. Method for Measuring Flow Flow of Liquid Metal The method for measuring the flow velocity of liquid metal of the present disclosure is a method of measuring the flow velocity of liquid metal using an ultrasonic flow meter equipped with an ultrasonic probe, in which the ultrasonic probe is immersed in the liquid metal. Previously, one feature is to provide a brazing metal layer capable of solute diffusion into a liquid metal on the surface of the ultrasonic probe. Hereinafter, in the description of the present application, "solute diffusion into the liquid metal" means that the components of the brazed metal layer are diffused and mixed in the liquid metal. By providing a brazing metal layer on the surface of the ultrasonic probe before immersion in the liquid metal, the ultrasonic wave is generated in the ultrasonic flowmeter when immersed in the liquid metal as compared with the case where the brazing metal layer is not provided. The intensity of the reflected echo obtained by the above (hereinafter, simply referred to as "echo intensity obtained by the ultrasonic flowmeter") increases, and the time until the ultrasonic probe sufficiently gets wet with the liquid metal (by the ultrasonic flowmeter). The time until the obtained echo intensity becomes sufficiently large) is shortened.

1.1. An ultrasonic flow meter equipped with an ultrasonic probe The basic configuration and measurement principle of an ultrasonic flow meter provided with an ultrasonic probe are known as disclosed in Non-Patent Documents 1 and 2. Hereinafter, only the important part in the flow rate measuring method of the liquid metal of the present disclosure will be described, and the description of other configurations will be omitted because it is obvious. In the method for measuring the flow velocity of a liquid metal of the present disclosure, for example, the ultrasonic probe can be configured by a rod-shaped member using a predetermined metal as a base material (see FIG. 1). Needless to say, the base metal constituting the ultrasonic probe is a metal different from the liquid metal whose flow velocity is to be measured, and has a higher melting point than the liquid metal. For example, the base metal constituting the ultrasonic probe can form a passivation film in an active atmosphere (atmosphere, etc.). According to the findings of the present inventor, the presence of the passivation film further exacerbates the wettability of the ultrasonic probe to liquid metal. On the other hand, according to the liquid metal flow velocity measuring method of the present disclosure, by providing a predetermined brazed metal layer on the surface of the ultrasonic probe, the wettability of the ultrasonic probe to the liquid metal regardless of the type of the base metal. Can be improved. In particular, according to the new findings of the present invention, when the base metal of the ultrasonic probe is made of stainless steel, the effect of the liquid metal flow velocity measuring method of the present disclosure becomes more remarkable.

1.2. Liquid Metal In the method for measuring the flow velocity of the liquid metal disclosed in the present disclosure, the type of the liquid metal is not particularly limited. Conventionally, using molten low melting point metal, the flow state of molten steel in a converter in a steel mill, the flow state of molten steel poured into a mold from a dipping nozzle in casting, the flow state of molten steel in a ladle, etc. are simulated. Is being done. For example, in continuous slab casting, when hot water is normally supplied to the inside of a mold from a two-hole immersion nozzle, the molten steel is discharged diagonally downward, and the molten steel that hits the inner wall of the mold is divided into upper and lower parts, and ascending and descending. Form a stream. Under high-speed casting conditions, the molten steel discharge flow from the immersion nozzle melts the solidified shell on the short side of the mold and causes breakout, or the above-mentioned rising flow disturbs the molten metal surface in the mold and deteriorates the surface quality of the slab. The above-mentioned downward flow causes various adverse effects such as bringing non-metal inclusions deep into the slab and deteriorating the internal quality of the slab. Therefore, it is important to accurately grasp the flow state of the molten steel discharged from the nozzle and the flow state of the molten steel poured into the mold during continuous casting. However, since it is difficult to directly measure the flow state of the molten steel, it is effective to simulate the flow state of the molten steel using a low melting point metal. In such a case, there is a demand for measuring the flow velocity of the low melting point metal using an ultrasonic current meter. The low melting point metal in this case means a metal having a melting point of 300 ° C. or lower. That is, in the method for measuring the flow velocity of the liquid metal of the present disclosure, the melting point of the liquid metal is preferably 300 ° C. or lower. Specific examples of such a low melting point metal include at least one selected from Sn, Sn alloys, gallium alloys, and mercury.

1.3. Braded metal layer In the liquid metal flow velocity measuring method of the present disclosure, before immersing the ultrasonic probe in the liquid metal (before measuring the flow velocity of the liquid metal), the surface of the ultrasonic probe is transferred to the liquid metal. A brazing metal layer capable of solute diffusion is provided. When the above-mentioned passivation film is present on the surface of the ultrasonic probe, it is preferable to remove the passivation film by, for example, flux, pickling, polishing, or the like, and then provide a brazed metal layer. Here, the "brazing metal layer" refers to a layer containing brazing metal. The "brazing metal" may be any metal that can be solute-diffused into the above liquid metal. Needless to say, the brazed metal has a lower melting point than the base metal of the probe. The type of brazed metal can be appropriately determined according to the base metal of the probe and the type of the liquid metal to be measured. For example, silver brazing, copper brazing, aluminum brazing, solder and the like can be mentioned. In particular, according to the new findings of the present inventor, when silver brazing metal is used as the brazing metal, the effect of the liquid metal flow velocity measuring method of the present disclosure becomes more remarkable. That is, in the method for measuring the flow velocity of the liquid metal of the present disclosure, it is preferable that the metal element constituting the brazing metal layer contains Ag, more preferably Ag, Cu and Zn, and Ag, Cu, Zn and It is more preferable that Sn is contained.

The brazed metal layer may be provided at least on the necessary portion (the portion where the wettability to the liquid metal should be improved) on the surface of the ultrasonic probe. Specifically, it is preferable that the brazed metal layer is provided at least at the tip of the ultrasonic probe. The method of providing the brazed metal layer on the surface of the ultrasonic probe is not strictly limited to "brazing". A brazed metal layer may be provided on the probe surface by a method other than brazing (for example, plating or sputtering). However, in consideration of cost and the like, it is preferable to provide the above-mentioned brazing metal layer on the probe surface by brazing that can be performed at low cost.

In the method for measuring the flow velocity of the liquid metal of the present disclosure, the thinner the thickness of the brazed metal layer, the longer the time until the ultrasonic probe gets wet with the liquid metal (the echo intensity obtained by the acoustic doppler current meter is sufficiently large). It is possible to shorten the time until it becomes. However, the lower limit of the practical thickness that can be brazed is about 10 μm. On the other hand, according to a new finding of the present inventor, by setting the thickness of the brazed metal layer to 5000 μm or less, the time required for the ultrasonic probe to get wet with the liquid metal is 1/100 or less (for example, 70 minutes or less). ) Can be shortened. In consideration of the above, in the method for measuring the flow velocity of the liquid metal of the present disclosure, the thickness of the brazed metal layer is preferably 10 μm or more and 5000 μm or less. The upper limit is more preferably 2500 μm or less, still more preferably 1500 μm or less.

2. 2. Acoustic Doppler Current Control The ultrasonic doppler current meter of the present disclosure is an ultrasonic flow meter provided with an ultrasonic probe used for measuring the flow velocity of a liquid metal, and the ultrasonic probe is applied to the liquid metal on its surface. One feature is that it has a brazed metal layer that can diffuse solutes. The preferred material of the ultrasonic probe, the preferred material of the brazed metal layer, the preferred thickness, and the like have already been described. A detailed description will be omitted here. According to such an ultrasonic flowmeter, when the ultrasonic probe is immersed in the liquid metal, the brazed metal layer provided on the surface of the ultrasonic probe is solutely diffused into the liquid metal, and as a result, the ultrasonic probe The surface is easily wetted with liquid metal in a short time. That is, when the flow velocity of a liquid metal is measured using an ultrasonic current meter, the measurement accuracy can be improved in a short time.

The present inventor pays attention to the solute diffusion of the solid metal A into the liquid metal B, and if the surface of the ultrasonic probe can be wetted with the solid metal A, the solid metal A is solute-diffused in the liquid metal B. As a result, it was expected that the ultrasonic probe would get wet with the liquid metal B. As a result, it was considered that the ultrasonic probe and the liquid metal B would be wetted, and the measurement accuracy of the ultrasonic current meter would be improved. Then, as a result of considering a method of wetting the solid metal A with the ultrasonic probe, it was found that brazing is suitable. When the solid metal A was actually brazed to the ultrasonic probe using the solid metal A and the liquid metal B as described above, it was confirmed that the solid metal A was sufficiently wetted with the ultrasonic probe. Further, in the liquid metal B, the solid metal A on the ultrasonic probe was solute-diffused into the liquid metal B, and it was confirmed that the ultrasonic probe and the liquid metal B were wet. Hereinafter, the method for measuring the flow velocity of the liquid metal of the present disclosure will be described in more detail with reference to Examples and Comparative Examples.

1. 1. Evaluation procedure A flow measurement experiment was conducted using an ultrasonic probe (base metal: stainless steel (SUS316L)) with silver brazing at the tip and an ultrasonic probe without any treatment. The configuration of the experimental device is schematically shown in FIG. As shown in FIG. 1, a small bath was filled with molten Sn as a liquid metal. I put a screw here to drive the flow. An ultrasonic probe of an ultrasonic current meter was installed in a direction diagonally crossing the flow from the upstream side to the downstream side.

2. 2. Evaluation Results Figure 2 shows the results of the echo intensity of ultrasonic waves when measuring the flow velocity. It can be seen that the ultrasonic probe with silver brazing obtains an echo of sufficient intensity regardless of the measurement distance, while the ultrasonic probe without silver brazing obtains a low level of echo.

FIG. 3 shows the measured velocity distribution. It can be seen that the ultrasonic probe with silver brazing can obtain the flow velocity distribution of Sn, while the ultrasonic probe without silver brazing cannot obtain the flow velocity distribution of Sn at all.
In this measurement, the direction of the flow toward the ultrasonic probe is negative.

Next, silver brazing with different thicknesses was applied to the ultrasonic probe, and the time until the ultrasonic probe was sufficiently wetted with Sn, that is, the time until the flow velocity of Sn could be measured was investigated. The results are shown in FIG. It can be seen that the thicker the silver brazing, the longer it takes for the ultrasonic probe to get sufficiently wet with Sn. As is clear from the results shown in FIG. 4, by setting the thickness of the brazed metal layer to 5000 μm or less, the time required for the ultrasonic probe to get wet with the liquid metal is conventionally (see, for example, Fig. 17 of Non-Patent Document 2 :. The time required for the vertical axis of the ultrasonic wave amplitude to rise to 0.8 or more can be shortened to 1/100 or less (for example, 70 minutes or less) of about 120 hours or less.

The technique of the present disclosure is useful as a means for grasping the flow state of the liquid metal, for example, when simulating and reproducing the flow of the molten steel using the liquid metal. For example, it is used to accurately grasp the flow state of molten steel in the furnace during converter blowing, the flow state of molten steel discharged from the immersion nozzle during continuous casting, and the flow state of molten steel poured into the mold. It is possible.

Claims (5)

It is a method of measuring the flow velocity of liquid metal using an ultrasonic current meter equipped with an ultrasonic probe.
Before immersing the ultrasonic probe in the liquid metal, a brazed metal layer capable of solute-diffusing into the liquid metal is provided on the surface of the ultrasonic probe.
A method for measuring the flow velocity of liquid metal. The base metal of the ultrasonic probe is made of stainless steel.
The method for measuring a flow velocity of a liquid metal according to claim 1. The thickness of the brazed metal layer is 10 μm or more and 5000 μm or less.
The method for measuring a flow velocity of a liquid metal according to claim 1 or 2. Ag is contained in the metal element constituting the brazed metal layer.
The method for measuring a flow velocity of a liquid metal according to any one of claims 1 to 3. An ultrasonic current meter equipped with an ultrasonic probe used to measure the flow velocity of liquid metal.
The ultrasonic probe has a brazed metal layer on its surface capable of solute-diffusing into the liquid metal.
Ultrasonic current meter.

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