JPH0921679A - Apparatus for detecting surface level of molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improved the accuracy of molten method injection stopping control by detecting the surface level in a mold in real time with an ultrasonic sensor immediately before the stop of the molten metal injection, and to achieve the surface property improvement of case products, the floating of enclosure and the improvement of quality by controlling the casting speed. SOLUTION: Ultrasonic wave transmitted from an ultrasonic sensor 1 enters a mold 7 through a reflecting plate 3. The wave is reflected from a reflecting plate 2, which is set on powder 10 of a molten metal surface 9, and receiving by the sensor 1. The received signal is amplified 4, and the noises are removed with a majority filters 5. The signal corresponding to the level of the molten metal surface 9 is indicated 6. Since the received and amplified level signal is the hunting noise, the detected indication value is not stable. The noises are removed until the digital indication by the filter 5. In the filter 5, the hunting signal is regarded as the noise when the hunting signal is less than a reference number for a specified time, the noises is disregarded and the previous signal value is held. When the reference number is exceeded, the signal value at the time of exceeding is made to be the detected value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the surface level of molten metal in a casting mold in real time.

[0002]

2. Description of the Related Art When casting a molten metal, the injection of the molten metal must be stopped when the level of the molten metal in the mold reaches a predetermined level. If the pouring stop time is incorrect, the molten metal will overflow, leading to an accident, or defective casting due to insufficient pouring. Therefore, conventionally, the weight of the ladle is measured and the level of the molten metal in the mold is estimated from the change, or the floating level floating on the molten metal is observed to detect the molten metal level and stop pouring. Was being done. The detection of the molten metal level by floating is performed by observing the positional change of the floating above the ladle.

However, with respect to the level detection of the molten metal, the means by changing the weight of the ladle is indirect and has a problem in accuracy, and the means by floating observation measures until the end of casting when the space above the mold is narrow. Therefore, the conventional pouring stop control was not satisfactory.

[0004] In addition, in order to control the casting speed optimally, the surface quality of the cast product and the quality requirements such as inclusions and gas levitation have been attempted. It became necessary to measure the rising speed of the. In this case, the means for changing the weight of the ladle cannot be adopted because of the problem of accuracy, and the means using the float has a measurement range when the space above the mold is narrow in relation to the ladle and the injection nozzle. There was a problem that it could not be adopted because it was limited.

[0005]

SUMMARY OF THE INVENTION The present invention improves the precision of pouring stop control by detecting the level of the molten metal surface in the mold in real time immediately before pouring stop when casting a molten metal. The purpose is to control the casting speed and improve the surface quality of the cast product and improve the quality such as floating of inclusions.

[0006]

The present invention for achieving the above object includes an ultrasonic sensor for transmitting and receiving ultrasonic waves, a first reflecting plate floating on the surface of a molten metal to be detected, the sensor and the first reflection. A molten metal level detecting device comprising a second reflector provided between the plates and a majority filter for processing a received ultrasonic signal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The device of the present invention will be described with reference to the example of FIG. FIG. 1 is an example of under-casting of an ingot. The molten metal in the ladle 11 is poured into the mold 7 via the injection pipe 13 by adjusting the opening of the sliding nozzle 12. In the molten metal 8 in the mold 7, powder 10 is placed on the molten metal surface 9 for heat retention and lubrication. The space above the mold 7 is narrow because of the ladle 11. The device of the present invention detects the level of the molten metal surface 9 rising by pouring in such a mold 7 in real time with high precision, and the ultrasonic sensor 1, the first reflector 2,
It is characterized by having a second reflector 3 and a majority filter 5.

In the apparatus of the present invention, the ultrasonic wave transmitted from the ultrasonic sensor 1 is bent by the second reflecting plate 3 into the mold 7 and is placed on the powder 10 on the molten metal surface 9 of the first reflecting plate. It is reflected at 2, and is received by the ultrasonic sensor 1 through the same path. The received signal is amplified by the amplifier unit 4, noise is removed by the majority decision filter 5, and a signal corresponding to the height level of the molten metal surface 9 is displayed on the display 6 as the molten metal level.

In the present invention, the received and amplified level signal has a detection indication value that is not stable due to hunting noise, but the majority filter 5 removes the noise until it can be digitally displayed. In the majority decision filter 5, if the hunting signal is equal to or less than the reference number N at a fixed time t, these are regarded as noises and ignored, and the previous signal value is held, and when the reference number N is exceeded, the time when the reference number N is exceeded. The signal value of is the detected value. By adopting proper values for the fixed time t and the reference number N, it is possible to obtain a stable and accurate detection value.

Since the apparatus of the present invention adopts the ultrasonic reflection method as described above, even when the space above the mold 7 is narrow as shown in FIG. 1, the level of the molten metal is kept from the start of pouring to the end of pouring. It can be detected continuously. Further, the ultrasonic sensor 1 can be arranged at a position where the radiant heat of the molten metal 8 does not directly hit. Therefore, the ultrasonic sensor 1 has a mold 7
It suffices to provide a heat-resistant protective cylinder for protecting from radiant heat from the ladle 11 and the ladle 11, and it is not necessary to flow a purge gas for cooling. Therefore, there is no noise due to the purge gas, and the accuracy of detecting the molten metal level is improved.

Generally, in the casting of molten metal, a powder 10 is placed on the molten metal surface 9 to keep the molten metal 8 warm and to lubricate the mold 7 with the molten metal 8 or the solidified slab. Therefore, even if an ultrasonic range finder is simply used to detect the molten metal level, the ultrasonic waves are irregularly reflected due to the irregularities on the surface of the powder 10 and cannot be detected. Since the first reflecting plate 2 is placed on the powder 10 in the device of the present invention, the reflected wave from the reflecting plate 2 can be reliably received by the ultrasonic sensor 1, and the level of the molten metal can be detected.

The first reflector 2 may be an iron plate or the like when the molten metal 8 is a ferrous metal, and may be a non-ferrous metal such as a metallic plate of the same system as the molten metal that floats on the molten metal surface 9 and melts. A metal plate or the like that does not can be adopted. The second reflection plate 3 may be a similar metal plate, or may be made of another material because it is unlikely to be melted by the molten metal. The surface of the first reflection plate 2 or the second reflection plate 3 may be made as smooth as possible and may be a flat surface, but by making the reflected ultrasonic waves converge by forming a concave surface with an appropriate curvature, the reception of the ultrasonic sensor 1 may be improved. The wave intensity can also be increased.

Since the signal received by the ultrasonic sensor 1 and amplified by the amplifier unit 4 contains noise, it cannot be displayed as it is as the molten metal level. This noise is
It is difficult to remove with a normal noise removal filter, and even if the sample averaging process or peak-peak process is performed, the problem is not solved, and the adoption of the majority filter makes it possible to remove noise before the surface level can be displayed digitally. . In addition, 14 is a power supply. Therefore, with the device of the present invention, the level of the molten metal in the mold 7 can be detected in real time with high accuracy, and by controlling the closing of the nozzle 12 of the ladle 11 by the result of the display 6, it is possible to perform highly accurate pouring. Hot water stop control can be performed.

Further, by using the apparatus of the present invention, it is possible to display the level of the molten metal on the display 6 and also to display the rising speed of the molten metal 9 on the display 16 by differentiating it by the calculator 15. Then, the optimum casting speed and casting speed distribution for the surface properties and internal quality of the slab are obtained in advance, and based on the molten metal level detection speed obtained by the device of the present invention, based on the molten metal rising rate obtained by the calculator 15. It is also possible to control the casting speed by adjusting the opening of the sliding nozzle 12 of the ladle 11. The device of the present invention can be applied not only to the above-mentioned bottom pouring casting but also to the top pouring casting. It can also be applied to the detection of the molten metal level in the vibration mold during continuous casting.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of the present invention having the structure shown in FIG.
In the downward pouring casting of molten steel subjected to VIM (vacuum induction melting) processing, the level of the molten metal in the mold 7 was detected and the casting speed was controlled. The depth of the mold 7 is 2400 mm, the distance from the upper surface of the mold 7 to the center of the second reflector 3 is 200 mm, the distance from the center of the second reflector 3 to the tip of the ultrasonic sensor 1 is 6000 mm, Ultrasound with a frequency of 20 kHz was used. The ultrasonic beam diameter on the second reflector 3 was about 100 mm. Iron plates were used for the first reflector 2 and the second reflector 3, and the ultrasonic reflection surfaces of the iron plates were smooth flat surfaces.

FIG. 2 shows the result of detecting the molten metal level in the example of the present invention. FIG. 2 is an analog display of the ultrasonic reflected wave signal after being processed by the majority filter 5, and the result was digitally displayed on the display 6 and could be sufficiently put to practical use.
Further, the casting speed control can be performed by utilizing the pouring stop control and further obtaining the molten metal level rising speed by the calculator 15.

As a comparative example, the first reflector 2 was not used,
Further, FIG. 3 shows a result of detection of the molten metal level when the majority filter 5 is not passed. This result cannot be used for pouring stop control because it contains a lot of noise and its fluctuation is large.
In addition, it could not be used for controlling the casting speed.

[0018]

The apparatus of the present invention detects the level of the molten metal in the mold by the ultrasonic reflection method when casting a molten metal such as molten steel, and starts pouring even if the space above the mold is narrow. It is possible to detect with high accuracy in real time from to just before stopping. Therefore, it is possible to prevent the overflow accident of the molten metal and the occurrence of defective casting due to incomplete casting. Further, by controlling the casting speed, it is possible to improve the surface properties of the cast product and improve the quality such as floating of inclusions.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of the device of the present invention.

FIG. 2 is a graph showing a change over time of a molten metal level in the example of the present invention.

FIG. 3 is a graph showing a change over time of a molten metal level in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ultrasonic sensor 2 ... 1st reflecting plate 3 ... 2nd reflecting plate 4 ... Amplifier unit 5 ... Majority filter 6 ... Indicator 7 ... Mold 8 ... Molten metal 9 ... Molten surface 10 ... Powder 11 ... Ladle 12 ... Sliding nozzle 13 ... Injection tube 14 ... Power supply 15 ... Calculator 16 ... Display

Claims (1)

[Claims] 1. An ultrasonic sensor for transmitting and receiving ultrasonic waves, a first reflecting plate floating on a molten metal surface to be detected, a second reflecting plate provided between the sensor and the first reflecting plate, and a received ultrasonic signal. An apparatus for detecting the level of molten metal, comprising a majority filter for processing.