JP2008180540A - Hydrogen concentration measuring method and device in molten metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method and a device capable of determining a hydrogen concentration in a molten metal quickly and simply. <P>SOLUTION: A lidded sealed container 2 for storing a sampling container 1 of the molten metal M is connected to a depressurized container 3 depressurized by a vacuum pump 5 through a communicating path 4, and the sampling container 1 is put into the sealed container 2, and then an on-off valve 8A in the communicating path 4 is opened, to thereby depressurize quickly the inside of the sealed container 2. Then, discharge of hydrogen gas is generated from the molten metal M in the sampling container 1, and molten metal splash M' is scattered upward from the surface of the molten metal M accompanied thereby. A pressure sensor 11 is arranged on the back of an opening/closing lid 2a of the sealed container 2, and the pressure sensor 11 outputs a signal in response to collision with the molten metal splash M', and a scattering amount of the molten metal splash M' can be known from the output signals. Consequently, it can be specified that the hydrogen concentration in the molten metal is within an acceptable level when a generation amount of the molten metal splash M' from the molten metal M which is a measuring object is lower than a threshold, by acquiring beforehand the generation amount of the molten metal splash relative to a high-quality molten metal and by setting the threshold properly. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrogen concentration measuring method and apparatus for grasping the hydrogen concentration in a molten metal.

  In recent years, the use of aluminum or aluminum alloy castings is expanding as automobile parts become aluminized. By the way, one of the casting defects is the generation of nests due to the release of hydrogen gas during solidification, and this generation of nests is a major cause of defective products, particularly in aluminum-based castings. Therefore, in general, a sample is generally taken from the molten metal in the melting furnace or holding furnace, solidified while reducing the pressure in a sealed container, and after solidification, the sample is cut and the nest in the cross section is compared with the limit sample. Thus, the hydrogen concentration in the molten metal was qualitatively evaluated. However, in such an evaluation method, since the result is not known until the sample is cut after being solidified in the sealed container, there is a problem that the production line waits and the productivity is lowered accordingly. In addition, for comparison with the limit sample, skill is required for the comparison, and in some cases, an error occurs in the evaluation and there is a possibility of causing great damage.

  In addition, conventionally, an apparatus for directly measuring a hydrogen concentration in a molten metal by dipping a measuring head (probe) in the molten metal is known (for example, refer to Patent Documents 1 and 2), and these measuring apparatuses are used. Thus, it is possible to eliminate the above-described problem occurrence. However, these measuring devices are troublesome to handle and expensive probes become consumables, and there are many problems in terms of operability and cost.

Japanese Patent Laid-Open No. 2-17441 JP 59-12348 A

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a measurement method and apparatus capable of quickly and easily grasping the hydrogen concentration in a molten metal.

In order to solve the above problems, the method and apparatus for measuring the hydrogen concentration in the molten metal according to the present invention releases hydrogen gas under reduced pressure from the molten metal collected in the collecting container, and the amount of molten droplets generated at this time It is characterized in that the hydrogen concentration of is specified. Since there is a correlation between the hydrogen concentration in the molten metal and the amount of molten metal droplets generated due to the release of hydrogen gas, the hydrogen concentration in the molten metal can be specified by measuring the amount of molten metal particles generated.
In the following, some aspects of the present invention will be illustrated and described.

(1) Put a sampling container in which the molten metal is collected into a sealed container and reduce the pressure to release hydrogen gas from the molten metal, and measure the amount of molten metal droplets generated with this hydrogen gas release over time. A method for measuring a hydrogen concentration in a molten metal, wherein the hydrogen concentration is specified based on a measurement result.

  In the hydrogen concentration measurement method described in this item (1), the collection container for collecting the molten metal is simply put in a sealed container and depressurized, so that the hydrogen concentration in the molten metal can be quickly grasped without any troublesome operations. Can do. In addition, since expensive parts are not consumed, the cost burden for measurement is small.

  In the method for measuring the hydrogen concentration described in the item (1), the method for specifying the hydrogen concentration is arbitrary. For example, a high-quality molten metal whose nest generation state is within a specified range is processed in advance. The amount of molten metal generated is grasped, an appropriate threshold value is set, and when the amount of molten metal generated for the molten metal to be measured is lower than the threshold value, the hydrogen concentration in the molten metal reaches the acceptable level. You may specify that there is. Alternatively, the same process as this method is performed for a molten metal with a known hydrogen concentration in advance, the amount of molten metal splash is determined, and the correlation between the amount of molten metal splash and the actual hydrogen concentration is obtained, and the measurement target The generation amount of molten metal splash for the molten metal may be collated with the correlation to specify the hydrogen concentration in the molten metal.

  (2) The method for measuring a hydrogen concentration in a molten metal according to (1) above, wherein the amount of molten metal splash is determined based on an output signal of a pressure sensor sensitive to the collision of the splash.

  In the method for measuring the hydrogen concentration described in the item (2), the type of the pressure sensor is arbitrary as long as it is sensitive to pressure, and even if it is composed of a piezoelectric element that generates electric charge under pressure, It may be composed of a plate capacitor whose capacitance changes under pressure, or may be composed of a conductor whose resistance value changes under pressure. Regardless of which pressure sensor is used, the pressure sensor is sensitive to the collision of the molten metal splash by disposing it in the splashed area of the molten metal droplet. Therefore, by analyzing the change in the output signal of the pressure sensor, the amount of molten metal splash can be determined quantitatively. In this case, in order to protect the pressure sensor from molten metal droplets, it is desirable to previously bond a heat-resistant film or sheet to the surface.

  (3) The method for measuring a hydrogen concentration in a molten metal according to (1) above, wherein the amount of molten metal splash is determined based on an output signal of an eddy current sensor sensitive to the approach of the splash.

  The eddy current sensor has a function of generating an eddy current in the object and measuring the position of the object from a change in the magnetic field, and by arranging the eddy current sensor above the area where the molten metal splashes, The output signal changes according to the scattering amount (generated amount). Therefore, by analyzing the change in the output signal of the eddy current sensor, the amount of molten metal splash can be quantitatively determined. in this case. Since the amount of generation can be obtained without contact with molten metal splash, no special protection is required.

  (4) The method for measuring a hydrogen concentration in a molten metal as described in (1) above, wherein the amount of molten metal splash is determined based on an image taken by an imaging means.

  The state of occurrence of the molten metal splash can be confirmed on the image by imaging the splash region of the molten metal with the imaging means. Therefore, for example, by analyzing the captured image and obtaining the number of molten metal splashes, the area ratio, etc., the amount of molten metal splashes can be quantitatively obtained. In this case, it is desirable to use a CCD camera that is advantageous for data analysis as the imaging means.

  (5) Any one of (1) to (4) above, wherein the weight of the molten metal collected in the collection container is measured, and the measurement result of the amount of molten metal splash is leveled with the weight to identify the hydrogen concentration. The method for measuring the hydrogen concentration in the molten metal according to claim 1.

  Since there is variation in the amount of molten metal pumped into the collection container, the weight of the molten metal collected in the collection container is measured as described in (5), and the measurement result of the amount of molten metal splash is expressed by the above weight. Measurement accuracy can be improved by leveling.

  (6) A sealed container with a lid for storing a sampling container for collecting molten metal, a decompression container connected to the sealed container by a communication path, a vacuuming means for evacuating the inside of the decompression container, and the communication path communicating with each other. An on-off valve for shutting off, a detecting means for detecting the amount of molten metal splashing from the surface of the molten metal in the sampling container stored in the closed container, and a signal for specifying the hydrogen concentration in the molten metal based on the output signal of the detecting means And a hydrogen concentration measuring device in the molten metal.

  In the hydrogen concentration measuring apparatus described in this item (6), since the sealed container and the decompression container are connected by the communication path, the sampling container in which the molten metal is sampled is put in the sealed container and the lid is closed. When the opening / closing valve of the passage is opened, the inside of the sealed container is rapidly depressurized. As a result, the release of hydrogen gas immediately before solidification is promoted, the generation of molten metal splash becomes active, and a significant difference is likely to occur in the measurement result. In addition, since the pressure in the sealed container depends on the volume of the sealed container and the volume of the decompression container, the decompression condition in the sealed container can always be kept constant by appropriately setting the pressure in the decompression container. This improves the reliability of hydrogen concentration measurement.

  (7) The apparatus for measuring a hydrogen concentration in a molten metal as described in (6) above, wherein a weighing scale for measuring the weight of the molten metal in the collection container is disposed in the sealed container.

  When a weighing scale that measures the weight of the molten metal collected in the collection container is provided as described in this section (7), the measurement result of the amount of molten metal generated is leveled with the weight to improve the measurement accuracy. Can be planned.

  According to the method for measuring the hydrogen concentration in the molten metal according to the present invention, it is possible to quickly grasp the hydrogen concentration in the molten metal without performing a troublesome operation, and the cost burden required for the measurement becomes small, and its utility value is reduced. There is a great thing.

  Moreover, according to the hydrogen concentration measuring apparatus in the molten metal which concerns on this invention, since it can always measure on the same conditions, the reliability with respect to a measurement precision improves.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows an apparatus for measuring hydrogen concentration in a molten metal as a first embodiment of the present invention. In the figure, 1 is a collection container for collecting the molten metal M, 2 is a sealed container for housing the collection container 1, 3 is a decompression container connected to the sealed container by a communication path 4, and 5 is the communication path. 4 is a vacuum pump (evacuation means) connected in the middle of 4 by a pipe 6. A pipe 7 having one end opened to the atmosphere is connected to the middle of the communication path 5, and the pipe 7 and the pipe 6 connected to the vacuum pump 5 join at one place of the communication path 5. Yes. The communication passage 4 is provided with two on-off valves 8A and 8B across the junction of the pipes 6 and 7, and the on-off valves 8C and 8D are also provided on the pipes 6 and 7, respectively. Yes. In the following description, for convenience of explanation, the on-off valve 8A on the closed container 2 side is the first on-off valve, the on-off valve 8B on the decompression container 3 side is the second on-off valve, and the on-off valve 8C on the vacuum pump 5 side is. The vacuum valve and the open / close valve 8D on the atmosphere side will be referred to as the atmospheric valve.

  In the piping system described above, when the vacuum pump 5 is started with the first on-off valve 8A and the atmospheric valve 8D closed and the second on-off valve 8B and the vacuum valve 8C opened, the inside of the decompression vessel 3 is When the pressure is reduced and then the vacuum valve 8 </ b> C is closed, a predetermined vacuum pressure is contained in the pressure reducing container 3. On the other hand, when the first on-off valve 8A is opened from this state, the vacuum pressure in the decompression container 3 is introduced into the sealed container 2 through the communication path 4. The hermetic container 2 has an open / close lid 2a. When the first open / close valve 8A is opened with the open / close lid 2a closed, the inside of the hermetic container 2 is rapidly decompressed. At this time, since the pressure in the sealed container 2 depends on the volume of the sealed container 2 and the volume of the decompression container 3, by setting the pressure (vacuum pressure) in the decompression container 2 appropriately, the sealed container 2 The decompression condition is always constant.

  In the first embodiment, a weighing scale 10 is installed in the sealed container 2, and the collection container 1 for the molten metal M is placed on the weighing scale 10. The collection container 1 is the same as a sample container used in a conventional evaluation test by cutting, a so-called egg cup, and has an inner volume of about 40 mm in diameter and about 40 mm in height. However, the size of the collection container 1 is arbitrary, and a larger or smaller one than the egg cup may be used if desired. When measuring the hydrogen concentration, the inside of the sealed container 2 is depressurized while the collection container 1 from which the molten metal M has been collected is placed on the weighing scale 10, thereby releasing hydrogen gas from the molten metal M in the collection container 1. As a result, the molten metal splash M ′ scatters upward from the surface of the molten metal M.

  Thus, the pressure sensor 11 is joined to the back surface of the open / close lid 2a of the sealed container 2. Here, as the pressure sensor 11, a sheet-like piezoelectric element that generates an electric charge under pressure is used, and its surface is covered with a heat-resistant resin film (not shown). The size of the pressure sensor 11 is set slightly larger than the diameter of the collection container 1 and is horizontally disposed at a position facing the opening of the collection container 1 with the open / close lid 2a closed. On the other hand, the installation height of the open / close lid 2a of the sealed container 2 is set so as to be lower than the scattering height of the molten metal splash M ', whereby the molten metal droplet M' collides with the pressure sensor 11, and this The pressure sensor 11 is sensitive to the collision. Therefore, the pressure sensor 11 constitutes a detecting means for detecting the amount of molten metal splash M ′.

  As shown in FIG. 2, the present hydrogen concentration measuring device is provided with a separate signal processing device 12, to which the output signal of the pressure sensor 11 and the output signal of the weigh scale 10 are input. It has become so. Here, the signal processing device 12 has a mechanism for determining whether or not the hydrogen concentration is at an acceptable level from the generation amount of the molten metal splash M ′ for the molten metal M to be measured. It is displayed on the device 13.

  In measuring the hydrogen concentration in the molten metal, the inside of the decompression vessel 3 is set to a predetermined degree of vacuum by the vacuum pump 5 in advance. Then, the collection container 1 from which the molten metal M has been collected is placed on the weighing scale 10 in the sealed container 2, and then the opening / closing lid 2a is closed to open the first opening / closing valve 8A. Then, the inside of the sealed container 2 is rapidly depressurized, and hydrogen gas is released from the molten metal M in the sampling container 1, and accordingly, the molten metal splash M ′ scatters upward from the surface of the molten metal M to the pressure sensor 11. collide.

  The pressure sensor 11 is sensitive to the collision of the molten metal splash M ′ and sends an output signal to the signal processing device 12. The signal processing device 12 amplifies the output signal of the pressure sensor 11, stores the signal waveform over time, and processes the signal waveform to specify the hydrogen concentration. The solid line in FIG. 3 shows an example of the signal waveform of the pressure sensor 11, and in the same figure, the signal waveform for a high-quality molten metal whose nest generation state is within the regulation is also shown by a one-dot chain line. For example, the signal processing device 12 determines the generation amount of the molten metal splash M ′ from the peak value, the number of peaks, the integrated amount, etc. of the signal waveform, and the relationship with the generated amount of the molten metal droplets obtained in advance for the high-quality molten metal. When the threshold value is lower than the preset threshold value, the hydrogen concentration in the molten metal is specified as being acceptable. In this case, since there is a variation in the amount of the molten metal M drawn into the collection container 1, the amount of molten metal M 'generated is equalized by the molten metal weight measured by the weigh scale 10, so that the hydrogen concentration in the molten metal passes. It is possible to accurately specify whether or not it is at the level.

  According to the apparatus and method for measuring the hydrogen concentration in the molten metal thus performed, the sampling container 1 from which the molten metal M has been collected is simply placed in the sealed container 2 and depressurized, so that the hydrogen concentration in the molten metal can be determined without performing a cumbersome operation. It is possible to grasp quickly. Particularly in the first embodiment, the vacuum pressure of the decompression container 3 is introduced into the sealed container 2 so that the inside of the sealed container 2 can be rapidly decompressed, so that the release of hydrogen gas immediately before solidification is promoted. Further, the generation of molten metal splash becomes active, and a significant difference is easily generated in the measurement result. In addition, the decompression condition in the sealed container 2 is uniquely determined by the volume of the sealed container 2, the volume of the decompression container 3, and the pressure in the decompression container 3, so that the constant decompression condition can always be reproduced, and the hydrogen concentration measurement Reliability is improved. Further, since the surface of the pressure sensor 11 is protected by a resin film, it can be reused by replacing the resin film, and as a result, expensive parts are not consumed, so that measurement is required. Cost burden is also small. After the measurement of the hydrogen concentration, the second on-off valve 8B on the decompression vessel 3 side is closed while the atmospheric valve 8D is opened, whereby the atmosphere is introduced into the sealed vessel 2 and the The sampling container 1 can be taken out.

  Here, in the first embodiment, the waveform of the output signal of the pressure sensor 11 is subjected to data processing and compared with a threshold value to determine whether or not the hydrogen concentration is at a desired level. The data processing method is arbitrary. For example, for a molten metal with a known hydrogen concentration in advance, the amount of molten metal splash is ascertained by the above method, and a correlation between the amount of molten metal splash generated and the actual hydrogen concentration is obtained in advance to obtain a molten metal for the molten metal M to be measured. The generation amount of the splash M ′ may be collated with the correlation, and the hydrogen concentration may be specified quantitatively.

  FIG. 4 shows an apparatus for measuring hydrogen concentration in molten metal as a second embodiment of the present invention. Since the overall structure of the hydrogen concentration measuring apparatus is the same as that of the first embodiment, the same components as those shown in FIG. . The feature of the second embodiment is that an eddy current sensor 20 is fixed on the back surface of the open / close lid 2a of the hermetic container 2 instead of the pressure sensor 11 described above. The eddy current sensor 20 has a function of generating an eddy current in an object and measuring the position of the object from a magnetic field change. Here, the eddy current sensor 20 is installed at a height that does not come into contact with the molten metal splash M ′. It is sensitive to the approach of M '. Therefore, the eddy current sensor 20 constitutes detection means for detecting the generation amount of the molten metal splash M ′ similarly to the pressure sensor 11.

  The output signal of the eddy current sensor 20 is sent to the signal processing device 12 as in the first embodiment, and the signal processing device 12 amplifies the output signal of the eddy current sensor 20. The signal waveform is memorized over time, and the signal waveform is processed to identify the hydrogen concentration. In this case, as a data processing method, a method of comparing with a threshold value as described above may be employed, or a method of collating with a correlation may be employed. In the second embodiment, by using the eddy current sensor 20, the amount of generation can be obtained in a non-contact manner with the molten metal splash M ′, so that no special protection is required.

  FIG. 5 shows an apparatus for measuring the hydrogen concentration in a molten metal as a third embodiment of the present invention. Since the overall structure of the hydrogen concentration measuring apparatus is the same as that of the first embodiment, the same components as those shown in FIG. . A feature of the third embodiment is that a CCD camera (imaging means) 25 is installed on the upper surface of the open / close lid 2a of the hermetic container 2 instead of the pressure sensor 11 in the first embodiment, and this CCD camera 25, the occurrence state of the molten metal splash M ′ from the collection container 1 is photographed through the glass window 2b provided in the opening / closing lid 2a.

  The output signal of the CCD camera 25 is sent to the signal processing device 12 via the image analysis device 26. The image analysis device 26 has a function of analyzing an image picked up by the CCD camera 25, quantitatively obtaining the amount of molten metal splash M ', and outputting a signal corresponding to the amount. In this case, the method for specifying the generation amount of the molten metal splash M ′ is arbitrary. For example, the number of molten metal droplets M recognized on the image, the area ratio, and the like may be obtained. The signal processing device 12 captures and stores the output signal of the image analysis device 26 over time, and specifies the hydrogen concentration by data processing of the output signal. In this case, as a data processing method, a method of comparing with a threshold value as described above may be employed, or a method of collating with a correlation may be employed. In the third embodiment, since the CCD camera 25 provided outside the sealed container 2 is used as the detection means, there is no concern about contamination, and as a result, maintenance is simplified.

It is a schematic diagram which shows the principal part structure of the hydrogen concentration measuring apparatus which is the 1st Embodiment of this invention. It is a block diagram which shows the signal processing system in the hydrogen concentration measuring apparatus as the 1st embodiment. It is a graph which shows an example of the signal waveform of the pressure sensor in the hydrogen concentration measuring apparatus as the 1st embodiment. It is a schematic diagram which shows the principal part structure of the hydrogen concentration measuring apparatus which is the 2nd Embodiment of this invention. It is a schematic diagram which shows the principal part structure of the hydrogen concentration measuring apparatus which is the 3rd Embodiment of this invention. It is a block diagram which shows the signal processing system in the hydrogen concentration measuring apparatus as the 3rd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sampling container 2 Sealed container 3 Depressurization container 4 Communication path 5 Vacuum pump (evacuation means)
8A to D On-off valve 10 Weigh scale 11 Pressure sensor 12 Signal processing device 13 Display device 20 Eddy current sensor 25 CCD camera (imaging means)
M Molten metal M 'Molten metal splash

Claims (7)

  By collecting the molten metal sampled in a sealed container and reducing the pressure, hydrogen gas is released from the molten metal, and the amount of molten metal droplets generated as a result of this hydrogen gas release is measured over time. A method for measuring a hydrogen concentration in a molten metal, wherein the hydrogen concentration is specified based on the method.   2. The method for measuring a hydrogen concentration in a molten metal according to claim 1, wherein the amount of molten metal splash is determined based on an output signal of a pressure sensor sensitive to the collision of the splash.   The method for measuring a hydrogen concentration in a molten metal according to claim 1, wherein the amount of molten metal splash is determined based on an output signal of an eddy current sensor that is sensitive to the approach of the splash.   The method for measuring the hydrogen concentration in a molten metal according to claim 1, wherein the amount of molten metal splash is determined based on an image obtained by an imaging means.   The weight of the molten metal collected in the collection container is measured, and the hydrogen concentration is specified by leveling the measurement result of the amount of molten metal splash by the weight. Method for measuring hydrogen concentration in molten metal.   A sealed container with a lid for storing a sampling container for collecting molten metal, a decompression container connected to the sealed container by a communication path, a vacuum evacuation means for evacuating the inside of the decompression container, and an opening / closing for communicating and blocking the communication path A valve, a detecting means for detecting the amount of molten splash generated from the surface of the molten metal in the collection container stored in the closed container, and a signal processing means for specifying the hydrogen concentration in the molten metal based on an output signal of the detecting means; An apparatus for measuring the hydrogen concentration in a molten metal, comprising:   The apparatus for measuring a hydrogen concentration in a molten metal according to claim 6, wherein a weighing scale for measuring the weight of the molten metal in the collection container is disposed in the sealed container.

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