JPH02104610A - Instrument for detecting circulating condition of molten metal - Google Patents

Abstract

PURPOSE:To continuously and easily detect circulating condition of molten iron by arranging a sensor for measuring vibration of a vacuum vessel in a circulating type vacuum degassing apparatus and a computing element for grasping the circulating condition of the molten metal based on output from this sensor. CONSTITUTION:The molten metal 1 is introduced into the vacuum vessel 3 arranged above a molten metal vessel 2 from the uptake tube 3a to execute the degassing treatment and circulated into the vessel 2 through downtake tube 3b. The vacuum vessel 3 is vibrated in accordance with this circulating flow, and the vibrating quantity is increased as increasing the circulating quantity. The vibrating sensor 7 is set at the suitable position in the vacuum vessel 3 of this apparatus, and the vibration of the vacuum vessel 3 is detected with this and converted into voltage value corresponding to the vibration velocity with a converter 8, and the circulating quantity is calculated from the prepared relating equation between a vibrating velocity voltage value and circulating quantity with the computing element 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a device for detecting a reflux state of molten metal in a reflux type vacuum degassing facility.

[Conventional technology]

Generally, molten steel produced in steelmaking furnaces such as converters, electric furnaces, and open hearths that perform melting and refining in the atmosphere contains large amounts of gas components such as oxygen, hydrogen, and nitrogen. It precipitates during or after solidification of molten steel, which can cause various defects in products. Therefore, in order to reduce the gas components in the molten steel, eliminate these defects, reduce non-metallic inclusions, equalize the concentration and components, and improve the internal quality and mechanical properties,
Vacuum degassing equipment is used. One type of vacuum degassing equipment is to install two pipes at the bottom of the vacuum chamber, one for suction (rising pipe) and one for exhaust (downcoming pipe), and inert gas such as argon is blown into the rising pipe. There is a recirculation vacuum degassing facility (so-called RH vacuum degassing facility) that continuously sucks up and degasses molten steel using the principle of a gas lift pump.

In order to efficiently process molten steel in this RH vacuum degassing facility, it is necessary to feed the molten steel into the vacuum chamber in as short a time as possible, and it is important to process the molten steel at an optimal recirculation rate.

On the other hand, during degassing treatment, non-metallic inclusions accumulate in the rising pipe or downcomer pipe, reducing the inner diameter of the pipe, resulting in a reduction in the flow rate of the molten steel, and the processing may not be carried out efficiently. In such a case, if deterioration of the recirculation condition can be detected during processing, it is possible to maintain the optimum recirculation amount by increasing the amount of blown gas or introducing a deposit dissolving agent in the pipe.

Conventionally, various technologies have been proposed for estimating the recirculation flow rate of molten steel, such as ■ technology that adds tracers such as radioactive isotopes to molten steel and determines the recirculation flow rate from the amount of change, and ■ molten metal in a vacuum chamber. Technology for detecting the weight and determining the recirculation amount (Japanese Patent Application Laid-open No. 56-79915), ■ Downcomer cross section determined from the correlation between the annular coil attached to the downcomer and two pairs of electrode resistances placed opposite the downcomer. Technique for determining recirculation flow rate from area and downcomer flow velocity (Japanese Patent Application Laid-Open No. 60-98314)
etc. can be mentioned.

[Problem to be solved by the invention]

However, each of the above techniques (1) to (2) has the following drawbacks.

In the case of (2) above, continuous measurement is difficult, measurement accuracy is poor, and handling of the tracer is troublesome, so it is difficult to use in actual operation. In the case of (2) above, the weight of the molten metal in the vacuum chamber cannot be stably measured due to the vibration of the vacuum chamber during reflux. In the case of (2) above, the coil and electrode must be buried each time the downcomer pipe is replaced, which deteriorates maintainability and is extremely troublesome in practice.

Therefore, the main object of the present invention is to provide an apparatus that can continuously and easily detect the reflux state of molten metal.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a vacuum tank above the molten metal container, introduces the molten metal into the vacuum tank from the riser pipe, degasses it, and returns it to the molten metal container via the downcomer pipe. A recirculation type vacuum degassing apparatus characterized by having a vibration sensor that measures vibrations of the vacuum chamber, and a computing unit that grasps the recirculation state of the molten metal based on the output from the sensor. .

[For production]

The vacuum chamber vibrates as the molten metal circulates, and the amount of vibration increases in accordance with the amount of molten metal that circulates.

In the present invention, since the vibration of the vacuum chamber is measured by a vibration sensor, continuous measurement is possible, and the reflux state, such as the amount of reflux, can be detected stably, easily, and with high accuracy.

[Specific structure of the invention] ~ The present invention will be explained in more detail below.

FIG. 1 is a schematic explanatory diagram of an RH vacuum degassing apparatus to which the present invention is applied. A vacuum tank 3 is arranged above a molten steel ladle 2 filled with molten steel 1, and an ascending pipe 3a and a descending pipe 3b provided at the bottom of the vacuum tank 3 are immersed into the molten steel 1. After that, when the pressure in the vacuum chamber 3 is lowered using a vacuum pump (not shown) or the like,
The molten steel 1 is sucked up into the vacuum tank 3, and the suction of the molten steel 2 is stopped at a liquid level where the pressure exerted by the molten steel 1 thus sucked up becomes equal to the atmospheric pressure. Next, when an inert gas 6 such as argon gas is blown into the riser pipe 3a from the gas blowing pipe 4, the molten steel 1 is transferred to the riser pipe 3a by the principle of a gas lift pump.
After passing through the vacuum chamber 3 and undergoing degassing treatment, etc., it is returned to the molten steel ladle 2 through the downcomer pipe 3b.
Thereafter, the molten steel 1 is continuously circulated.

The vacuum chamber 3 vibrates as a result of the reflux, and the amount of vibration increases as the reflux flow increases. Therefore, if the amount of vibration is preferably continuously measured, the reflux state can be grasped.

In order to investigate the relationship between the amount of vibration and the amount of recirculation mentioned above, processing capacity 1
Figure 2 shows the results of refluxing using a 60 ton RH vacuum degassing facility. Here, the recirculation amount is the following formula (experimental formula) (1)
This is the value obtained from .

-・4 X10-'D'・4G11・3I・110.
+! , −−−−−−−−−−−・・ (1) Ga:
Circulation flow rate (7on/+m1n) D: Immersion pipe diameter (cm) G: Blowing gas I (Il/m1n) ■Second blowing height (C11) As is clear from Figure 2, the amount of vibration, such as the vibration speed, is measured. By doing this, the reflux amount can be determined.

Next, the specific configuration of the present invention will be explained again with reference to FIG.
The RH vacuum degassing apparatus according to the present invention includes a vibration sensor 7 installed at an appropriate position in a vacuum chamber 3, a converter 8 that converts the charge output of the vibration sensor 7 into voltage, and an output of the converter 8. The system is equipped with a recirculation state detection device comprising a calculator 9 that calculates the recirculation amount based on the following. When reflux starts in the RH vacuum degasser, the vibration of the vacuum chamber 3 that occurs at that time is detected by the vibration sensor 7, which is converted into a voltage value corresponding to the vibration speed by the converter 8, and the vibration is detected by the calculator 9. Then, the recirculation amount can be determined from the relational expression between the vibration velocity voltage value and the recirculation amount (see FIG. 2) created in advance.

Next, the mounting location of the vibration sensor in the present invention will be explained with reference to FIG.
The upper exhaust gas pipe 1 is fixed to a support frame 11 installed in the
It vibrates using the expansion 13 of No. 2 as a spring.

Therefore, it is preferable to install the vibration sensor 7 at a position away from the supporting part at the center of the tank because a large amount of vibration can be obtained. On the other hand, if it is located too low in the vacuum chamber, it will approach the molten steel surface (not shown), and the radiant heat of the molten steel will cause trouble to the vibration sensor and cable. Therefore, for example, in the case of a vacuum chamber of the size specifically shown numerically in FIG. 3, the position is preferably about 1 m or more below the support frame, usually 2 m below.

The amount of vibration in the present invention can be detected in the form of vibration velocity, vibration acceleration, displacement, etc. However, high-frequency vibrations are generally detected by vibration acceleration, and low-frequency vibrations are detected by vibration velocity or displacement. Therefore, it is preferable to detect the vibration speed. Note that an example of measurement conditions in this case will be added.

Vibration sensor type: Piezoelectric acceleration sensor Vibration sensor Charge sensitivity: 15.1 pc/g Charge amplifier (converter) Voltage sensitivity: 316 mvs/cm The vibration sensor in the present invention includes a piezoelectric vibration sensor,
Any known vibration sensor such as an electrodynamic vibration sensor or a servo acceleration sensor can be used.

In fact, when the vibrations were measured as described above, the results shown in FIG. 2 were obtained, and the deviation was ±0.5 mV, indicating that there was an extremely strong correlation and that the reflux state could be sufficiently determined.

In FIG. 4, 3H and 5H2 also have peaks, but according to the findings of the present inventors, these are based on the natural vibration of the vacuum chamber and are not directly related to the reflux amount. By the way, as shown in Figure 5, even in a non-reflux state, 3H2
and 5H2 peak. Therefore, 10H2
It was found that only the peak of was related to the reflux amount. In this way, vibrations are unique to the type and size of the vacuum chamber, so after measuring the vibration state in a non-reflux state in advance, it is possible to pink up the frequency and peak that indicate the reflux amount. desired.

On the other hand, in the present invention, although it is desirable that the amount of vibration be detected continuously, it may be detected intermittently. Further, the detection result of the amount of vibration may be used not only to obtain the reflux amount but also to determine the quality of the reflux state.

〔Effect of the invention〕

As described above, according to the present invention, the reflux state of molten metal can be detected continuously and easily.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the outline of the present invention, Fig. 2 is a graph showing the relationship between the amount of circulation and the amount of vibration, Fig. 3 is an explanatory diagram of the mounting position of the vibration sensor, and Fig. 4 is the vibration when the vacuum chamber vibrates. FIG. 5 is a frequency band diagram during non-vibration. 1... Molten steel (molten metal), 2... Molten steel pot (molten metal container), 3... Vacuum tank, 3a... Rising pipe, 3b...
- Descending pipe, 4... Circulation gas pipe, 6... Inert gas, 7... Vibration sensor, 8... Converter, 9... Arithmetic unit. Figure 1 Figure 2 fist (Ton/min + Figure 3

Claims (1)

[Claims] (1) In a recirculation type vacuum degassing device in which a vacuum chamber is provided above the molten metal container, the molten metal is introduced into the vacuum chamber from the riser pipe, degassed, and then refluxed to the molten metal container via the downcomer pipe. A molten metal circulation state detection device comprising: a vibration sensor that measures vibrations of the vacuum chamber; and a computing unit that grasps the molten metal circulation state based on the output from the sensor.