JPH03188328A - Apparatus for measuring level of molten metal - Google Patents

Abstract

PURPOSE:To enhance response and detection accuracy by detecting the output change due to the contact of a plurality of Fe-Mo thermocouples vertically provided in a molten metal container at different depths with a molten metal and measuring the level of the molten metal from the vertically provided posi tion of the thermocouples. CONSTITUTION:The other end of the Fe strand 5a connected to a servo ampli fier 6 at one end thereof is vertically provided up to the dummy head 4 of the bottom part of a cast 1 and the other ends of Mo strands 5b, 5b... connected to the amplifiers 6 at one ends thereof are vertical provided in the molten metal in the cast 1 at different depths and the amplifiers 6 are connected to a display part 8 and a dummy bar driving apparatus 9 through a microcomputer 7. The difference between the distances of the leading end positions of two strands 5b, 5b is divided by the time difference of the generation of thermoelectromotive forces thereof to calculate the rising speed of the level of the molten metal and the rising speed and the level of the molten metal 3 calculated therefrom are displayed on the display part 8 and, when the level of the molten metal 3 reaches a predetermined position, the apparatus 9 is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring the level of molten metal in a tundish of continuous casting equipment, in a mold, or in a molten metal container such as a various melting furnace.

[Conventional technology]

Conventionally, devices that measure the molten metal level in the tundish of continuous casting equipment, in molds, or in molten metal containers such as various melting furnaces include devices that utilize radiation, devices that utilize electromagnetic induction phenomena, and devices that utilize thermoelectromotive force. There are several types, each of which is used depending on the target equipment, purpose, and desired measurement accuracy.

When measuring the level of molten metal in a mold of continuous casting equipment, the radiation level meter that uses radiation emits γ-rays from a γ-ray source installed on the side wall of the mold to the molten metal inside the mold. The level of molten metal is detected by measuring the amount of gamma rays transmitted, which changes depending on the amount of molten metal.

Therefore, as described above, since gamma rays are emitted to the molten metal through the mold and the amount of γ-rays transmitted is detected, the detection accuracy and response are poor, and this method is not suitable for detecting the molten metal level when the fluctuation range is large. If a large-capacity radiation source is provided in order to solve this problem, there is the disadvantage that not only the cost increases but also works such as mold maintenance are restricted in terms of safety management.

In addition, an electromagnetic induction level meter that utilizes electromagnetic induction phenomena places a coil energized with high-frequency current facing the surface of the molten metal, and measures the impedance or induced voltage of the coil that changes due to the eddy current generated on the surface of the molten metal. This is used to detect the molten metal level. As mentioned above, this level meter must be installed so that the coil faces the surface of the molten metal, and is protected against earthquakes that can damage the coil due to scattering of the molten metal from the surface of the molten metal, or burying the coil in the molten metal due to an abnormal rise in the molten metal level. Because of this, it is used only when the molten metal level is relatively stable, and is not suitable for detecting the molten metal level when the fluctuation range is large.

On the other hand, a thermocouple level needle that uses thermoelectromotive force detects the temperature of the molten metal through the mold using multiple thermocouples embedded in the depth direction of the inner wall of the mold, or detects the temperature of the molten metal through the mold from above the mold at different depths. The temperature of the molten metal is detected by directly contacting the molten metal with multiple vertically installed thermocouples, and if the detected temperature exceeds a predetermined value, it is determined that the molten metal level inside the mold has reached the position where the thermocouples were installed. It is something to do. However, the detection accuracy of the former thermocouple level meter depends on the number of thermocouples embedded in the inner wall of the mold, and therefore a large number of thermocouples are required to improve the detection accuracy. This installation work and maintenance are technically difficult, and therefore high detection accuracy cannot be obtained. Moreover, since the temperature of the molten metal is detected through the mold, there is a delay in response, and this method cannot be said to be suitable for detecting the level of the molten metal in a changing state. On the other hand, the latter type of thermocouple level meter does not require embedding the thermocouple in the mold and measures the temperature by directly contacting the molten metal, so it has good response and detection accuracy, and is easy to maintain. Therefore, it can be measured at low cost and is suitable for measuring the molten metal level when the fluctuation range is large.

[Problem to be solved by the invention]

By the way, in detecting the molten metal level using the latter thermocouple level meter, which is in practical use, the pt-PtRh13 thermocouple is mainly used because it has an appropriate operating temperature range and has good stability. However, Pt-PtRh
Thermocouple No. 13 is expensive, and when used for measurement, it must be inserted into an alumina protection tube to maintain its durability, resulting in a delayed response and poor detection accuracy. For this reason, it was not possible to obtain an accurate molten metal level, and furthermore, it was difficult to measure the rising rate of the molten metal level.

The present invention has been made in view of such circumstances, and uses a Fe-Mo thermocouple as the thermocouple, and uses the Pe-M thermocouple.

It is an object of the present invention to provide a molten metal level measuring device that has good responsiveness and detection accuracy and can perform measurements at low cost by including a means that allows a thermocouple to be moved in the depth direction within a furnace.

[Means to solve the problem]

A first aspect of the molten metal level measuring device according to the present invention includes a plurality of Fe-Mo thermocouples vertically installed to different depths of a molten metal container, and an output caused by contact between each of the Fe-Mo thermocouples and the molten metal. and a means for detecting a change, and the molten metal level is measured by the vertically installed position of the Pe-Mo thermocouple whose output has changed. comprising means for enabling movement in the horizontal direction, distance detection means for detecting the moving distance of the Fe-Mo thermocouple, and means for detecting an output change due to contact between the Fe-Mo thermocouple and the molten metal, Fe-Mo with the output changed
It is characterized by measuring the molten metal level by the moving distance of the thermocouple.

[Effect]

In the first invention of the molten metal level measuring device according to the present invention, the thermocouple is made of Fe wire and Mo wire.
When multiple Mo thermocouples are placed vertically at different depths in a molten metal container, the tips of the Fe-Mo thermocouples that come into contact with the molten metal melt, creating a state of conduction through the molten metal.
This becomes a thermal contact point between the Fe-Mo thermocouple and the molten metal, and a thermoelectromotive force is generated. Therefore, Fe-
The tip position of the Mo thermocouple, that is, the Fe contacting the molten metal
-The tip position of Mo thermocouple and Fe where no electromotive force is generated-
The tip position of the Mo thermocouple, that is, F that is not in contact with the molten metal
It can be seen that there is a molten metal level between the position of the tip of the e-Mo thermocouple and the tip position of the e-Mo thermocouple.

Further, in the second invention, by providing means for making the Fe-Mo thermocouple movable in the depth direction within the molten metal container, the Fe-Mo thermocouple in contact with the molten metal generates heat. Electricity is generated. Therefore, by detecting the moving distance of the Fe-Mo thermocouple at the time when thermoelectromotive force is generated,
The level of molten metal is measured.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The molten metal level measurement according to the present invention will be specifically explained in detail below based on drawings showing embodiments thereof.

FIG. 1 is a schematic diagram showing a first invention of a molten metal level measuring device according to the present invention, and shows a case where the device is adapted to measure the level of molten metal inside a mold in continuous casting. 1st
In the figure, 1 is a cylindrical mold, into which molten metal 3 is injected from a tundish (not shown) through an immersion nozzle 2. Further, a dummy bar head 4 that serves as the bottom of the mold when pouring of the molten metal 3 is started is inserted into the mold 1 by a predetermined length from the bottom, thereby preventing leakage of the molten metal 3 when pouring is started. Between the immersion nozzle 2 and the mold 1 in the mold 1, one end of the Fe wire 5a, the other end of which is connected to the servo amplifier 6, is hung vertically from above the mold 1 to the insertion position of the dummy bar head 4. Further, the negative ends of a plurality of Mo wires 5b, 5b... whose other ends are respectively connected to the servo amplifiers 6゜6... It is set up. That is, a plurality of Fe--Mo thermocouples 5 whose other ends are connected to servo amplifiers 6, 6, . . . are vertically installed at different depths within the mold 1.

On the other hand, a servo amplifier 6 is connected to the input side of the microcomputer 7, and a display section 8 and a dummy bar drive device are connected to the output side, respectively.

Injection of the molten metal 3 into the mold 1 is started, and when the molten metal 3 is stored in the mold 1 and comes into contact with the Mo wire 5b, it contacts the Fe wire 5a via the molten metal 3. The strands 5b are brought into conduction, and a thermoelectromotive force is generated in the Fe--Mo thermocouple 5.

The generated thermoelectromotive force is applied to the microcomputer 7, which causes the microcomputer 7 to send a display signal indicating that the level of the molten metal 3 inside the mold 1 has reached the tip position of the vertical Mo wire 5b. Output to 8. Further, the microcomputer 7 includes two Mo wires 5b, 5b.
The distance difference between the tip positions of those two Mo wires 5b, 5b
The molten metal level rising speed is calculated by dividing by the time difference between thermoelectromotive force generation, and the values of the molten metal level rising speed and the level of the molten metal 3 calculated based on the molten metal level rising speed are outputted to the display section 8, respectively.

When the level of the molten metal 3 reaches a predetermined position, a drive signal is output from the microcomputer 7 to the dummy bar drive device 9, and based on the signal, the dummy bar is pulled out from the mold 1, and casting starts.

By vertically disposing a plurality of Fe-Mo thermocouples 5 at different depths within the mold 1 in this way, it becomes possible to automatically set the start of pouring in continuous casting.

FIG. 2 is a graph showing the thermoelectromotive force characteristics of a Fe-Mo thermocouple and a Pt-PtRh13 thermocouple, with the Fe-Mo thermocouple being shown by a solid line and the Pt-PtRh13 thermocouple being shown by a broken line. Also, in Figure 2, the horizontal axis is the temperature (“
C), the right vertical axis shows the thermoelectromotive force (mV) corresponding to the Fe-Mo thermocouple, and the left vertical axis shows the Pt-PtR
The thermoelectromotive force (mV) corresponding to the h13 thermocouple is respectively.

As is clear from FIG. 2, in the <Fe-Mo thermocouple, there is a linear relationship between temperature and thermoelectromotive force, and it can be seen that thermoelectromotive force corresponding to temperature can be measured. Furthermore, the slope of the straight line of the FeMo thermocouple is larger than that of the Pt-PtRh13 thermocouple, indicating that the Fe-Mo thermocouple is more sensitive to temperature changes than the Pt-PtRh13 thermocouple.

Therefore, the device of the present invention, which measures the molten metal level by bringing the Fe-Mo thermocouple 5 into direct contact with the molten metal without inserting a protective tube, can detect the molten metal level with better responsiveness and accuracy than before.

FIG. 3 is a schematic diagram showing a second invention of the molten metal level measuring device according to the present invention, and shows a case where the device is adapted to measure the level of molten metal 3 in a cylindrical melting furnace equipped with a tapping chamber.

In FIG. 3, reference numeral 11 denotes a tapping chamber 1 which communicates with the melting furnace 10, is provided at the lower part of the side wall thereof, and has an opening portion 11a at the top.
1, and at its bottom there is a tap hole 11 for extracting the molten metal 3 inside the melting furnace 10 from the tap chamber 1 to the outside of the melting furnace 10.
b is provided. Furthermore, an electrode rod 12 made of Fe and connected to a servo amplifier 20 is fixedly installed at the lower part of the side wall of the tapping chamber 11. The Mo wire 13, which forms a thermocouple by forming a pair with the electrode rod 12, is wound and held on a drum 14 provided above the opening 11a, and one end thereof is directed toward the opening 11a. The other end of the Mo wire 13 is connected to the servo amplifier 2.
Connected to 0. The hanging portion of the Mo wire 13 is connected to the pinch roller 1 provided below the drum 14.
5, and when the pinch roller 15 rotates, it moves in the depth direction within the tapping chamber ll. Furthermore, below the pinch roller 15, Mo
A lance 16 is provided to physically and chemically protect and insulate the hanging portion of the wire 13, and one end of the lance 16 is loosely fitted into the opening portion 11a, and is inserted into the tapping chamber 11 for a predetermined length. It is. A sensor 17 is attached to a predetermined position of the lance 16 to detect the tip of the Mo wire 13 when the Mo wire 13 passes through the lance 16.

The input side of the microcomputer 18 is connected to a motor 19 and a display unit 22 via a drive circuit (not shown), and the output side is connected to the motor 19, and includes a rotation detector 21 that generates a predetermined number of pulses per revolution. and servo amplifier 20
and sensor 17.

The motor 19 rotates the pinch roller 15 from the microcomputer 18, and moves the Mo wire 13 into the tapping chamber 11.
A signal for moving in the depth direction is given via a drive circuit, and a calculation result of the molten metal level, which will be described later, is given to the display section 22. On the other hand, pulses generated from the rotation detector 21 due to the rotation of the motor 19 that rotates the pinch roller 15 are given to the microcomputer 18.
By integrating the number of pulses, the microcomputer 18 can recognize the moving distance of the Mo wire 13. Furthermore, the microcomputer 18 includes a sensor 1
A detection signal for detecting the tip of the Mo wire 13 is sent from the servo amplifier 20 to the Mo wire 13 and the Fe electrode rod 1.
2 are electrically connected to each other through the molten metal 3, and a thermoelectromotive force is applied to each of them, and the detection signal causes the Mo wire 13 to
It can be recognized that the Mo wire has passed through the sensor 17 installation position, and it can be recognized that the tip of the Mo wire 13 has reached the molten metal level in the tapping chamber 11 due to the thermoelectromotive force.

FIG. 4 is a flow chart showing the operation of the microcomputer 18. First, the microcomputer 18
A signal for lowering the Mo wire 13 into the tapping chamber 11 and the molten metal 3 is given to the motor 19 via the drive circuit (step 1
), the pinch roller 15 is rotated.

Next, it is checked whether the tip of the Mo wire 13 that is descending thereby has passed the sensor 17 (step 2),
If it has not passed, the operation of step 2 is performed again, and if it has passed, the integration of the number of pulses generated by the rotation detector 21 is started from that point (step 3). Then, it is determined whether an electromotive force is generated in the thermocouple between the Mo wire 13 and the Fe electrode rod 12, that is, whether the tip of the Mo wire 13 has contacted the molten metal 3 (step 4). If no pulses have occurred, repeat step 4, and if they have occurred, stop integrating the number of pulses at that point (step 5).The relationship between the number of pulses and the distance that has been input into the microcomputer 18 in advance. , the moving distance l of the Mo wire 13 is calculated based on the integrated pulse number.Step 6)
The molten metal level h is determined by calculating the difference between the distance H from the position 7, that is, the inner bottom of the tapping chamber 11 to the sensor 17 (see FIG. 3), and the moving distance l of the Mo wire 13. (Step 7). Then, output this result to the display section 22 (Step 9), M.

A signal for raising the strand 13 is applied to the motor 19 via the drive circuit (step 9) to rotate the pinch roller 15 and raise the Mo strand 13. Furthermore, it is determined whether or not to continue measuring the molten metal level (step 10). If the measurement is to be continued, the process returns to step 1 and the same operation as described above is repeated; if the measurement is not to be continued, the measurement is ended here.

Note that by repeatedly measuring the molten metal level at predetermined time intervals, the rate of increase in the molten metal level can be determined.

In this way, since the Fe-Mo thermocouple is brought into direct contact with the molten metal 3 using a means that allows the Fe-Mo thermocouple to be moved in the depth direction within the tapping chamber 11, the response is not affected by slag. The molten metal level can be measured with good performance and measurement accuracy.

In this example, a case has been described in which a plurality of Mo wires are hung vertically from above a molten metal container and the molten metal level is measured, but instead of this, Fe wires and M wires are used.

A plurality of pairs of strands may be hung vertically from above the molten metal container. Similarly, the molten metal level may be measured by moving a pair of Fe wire and Mo wire from above the molten metal container. In these cases, it goes without saying that a thermoelectromotive force is generated due to the contact between the junction of the Fe wire and the Mo wire and the molten metal.

〔effect〕

As detailed above, in the first invention of the molten metal level measuring device according to the present invention, it is sensitive to temperature changes,
In the second invention, an inexpensive Fe-Mo thermocouple is installed vertically in the depth direction of the molten metal container, and a means for making the Fe-Mo thermocouple movable in the depth direction of the molten metal container;
o Since it is equipped with a detection means for detecting the moving distance of the thermocouple, the position of the tip of the Fe-Mo thermocouple that has come into contact with the molten metal inside the molten metal container and generated a thermoelectromotive force, that is, the position of the tip of the Fe-Mo thermocouple that has come into contact with the molten metal inside the molten metal container. The level of the molten metal can be measured from the tip position of the Mo thermocouple, and measurement with good responsiveness and detection accuracy can be performed at low cost. Moreover, from this, the molten metal level can be repeatedly measured at predetermined time intervals with high accuracy, and the rising rate of the molten metal level can be determined.

Therefore, when used to measure the molten metal level in continuous casting, it is possible to automatically set the start of pouring.
Further, when used for measuring the level of molten metal in a steel melting furnace, the present invention has excellent effects such as improving the fuel source unit, optimizing the tapping timing, and stabilizing the operation.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the first invention of the molten metal level measuring device according to the present invention, and FIG. 2 shows a Fe-Mo thermocouple and a Pt-
Graph showing thermoelectromotive force characteristics of PtRh13 thermocouple, 3rd
The figure is a schematic diagram showing the second invention of the molten metal level measuring device according to the present invention, and FIG. 4 is a flowchart showing the operation of the microcomputer 18. 3... Molten metal 5a... Fe wire 5b, 13
...Mo wire 5...Fe-Mo thermocouple 6.2
0... Servo amplifier 12... Fe1iJ electrode rod
14...Drum 15...Pinch roller 19
···motor

Claims (1)

[Claims] 1. A plurality of Fe vertically installed to different depths of the molten metal container
-Mo thermocouples, and means for detecting output changes due to contact between each of the Fe-Mo thermocouples and the molten metal, and depending on the vertical position of the Fe-Mo thermocouples where the output changes,
A molten metal level measuring device characterized by measuring a molten metal level. 2. means for making the Fe-Mo thermocouple movable in the depth direction of the molten metal container; distance detection means for detecting the moving distance of the Fe-Mo thermocouple; and contact between the Fe-Mo thermocouple and the molten metal. A molten metal level measuring device, comprising: means for detecting a change in output due to the change in output, and measures a molten metal level based on a moving distance of the Fe-Mo thermocouple whose output has changed.