JPH0620626B2 - Leakage detector and potential detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molten metal leak detection device when an induction heating device is installed in a tundish in continuous casting of steel.

[Conventional technology]

In an induction heating apparatus for molten steel in a tundish for continuous casting as disclosed in Japanese Patent Laid-Open No. 61-38754, when molten metal leaks or a molten metal occurs in the tundish, the molten steel in the tundish is melted. When the iron comes into contact with the iron skin, a leaking dielectric current penetrates through the iron skin, causing an accident to spread and possibly leading to a serious accident.

In order to prevent this, it is necessary to equip a device for detecting molten metal leak or molten metal in the tundish in advance.

Conventional molten metal leak detection device, as shown in Japanese Utility Model Laid-Open No. 60-101792 and Japanese Patent Laid-Open No. 63-160760, due to the refractory structure and the difficulty of the furnace construction, compared to the tundish outer periphery, A method of embedding a molten metal leak sensor in a refractory around the induction coil mounting part, which has a high risk of molten metal leak and water leaking, and detects the conduction state generated when the molten steel in the tundish comes into contact.

[Problems to be Solved by the Invention]

With the conventional method, even if there is a leak or pouring of water in the part where the leak sensor is not embedded, it cannot be detected, and even if the leak sensor is embedded all around the tundish, the refractory is tundish iron. It is extremely difficult to lay it with a certain mesh without contacting with hundreds of iron protrusions called Y studs for fixing to the skin, and therefore it is impossible to completely prevent leakage of hot water. It was

FIG. 12 shows a tundish 2 equipped with an induction heating device 5.
The main part of the continuous casting apparatus using is shown. The tundish 2 is equipped with a dielectric heating device 5 to control the molten steel temperature. However, as shown in the leakage point 24, the molten steel 7 in the tundish is directly attached to the tundish iron shell 9 or attached to the tundish iron shell 9 in order to prevent the refractory 19 from peeling off due to the leakage or the pouring of water. When contact is made through a conductive substance such as the Y stud, the molten steel 1-the molten metal leak point 24-the tundish iron shell 9-the ground 3-the equipment (pinch roll etc.) 4-the molten steel 1 in contact with the iron piece 12 An abnormal external current path 23 is formed, an induction current (leakage induction current) flows due to a potential difference induced by the main magnetic flux of the induction heating device 5, and Joule heat causes the iron shell 9 and the like to melt red heat. There was an inevitable inconvenience.

An object of the present invention is to provide a hot water leak detection device that automatically detects the occurrence of a leak induction current due to a hot water leak or a water spout, and a potential detection device used therefor.

[Means for Solving the Problems]

The molten metal leak detecting device of the present invention is a device potential detecting device for detecting molten steel potential, a means for comparing its output with a reference value corresponding to operating conditions, and a tundish molten metal leak or hot water by the output of this comparing means. It is provided with a means for detecting the scale.

That is, the change in the phenomenon formed by the abnormal external current path other than the molten steel current path is detected by means for detecting the molten steel potential in each part in the tundish, and the casting conditions, such as the number of induction heating devices used and the heating power, etc. Is a hot water leak detecting device having means for detecting a hot water leak or a hot water bottle from the result of the comparison.

Further, the potential detecting device for detecting the molten steel potential is assumed to have a conductive electrode installed on the tundish in the height direction thereof and exposed so as to come into contact with the molten steel near the bottom of the tundish.

〔Example〕

FIG. 1 shows an embodiment of the molten metal leak detection device of the present invention. 1
Is molten steel, 2 is a tundish, 5 is an induction heating device provided in the tundish 2, and 9 is a tundish iron skin. An induction coil 6 is connected to a power source (not shown). Reference numeral 7 denotes a receiving chamber and 8 a pouring chamber. In the illustrated example, a potential detecting device including a conductive electrode 11 is provided on the side wall of the pouring chamber 8. Reference numeral 10 is a hot groove that connects the hot water receiving chamber 7 and the pouring chamber 8.

13 is an isolation amplifier, 14 is an analog-digital converter,
Reference numeral 15 is a process controller, 16 is an output device for outputting set values of casting conditions, and 17 is an alarm device.

2 and 3 show a vertical section and a front view of the electrode portion of the potential detecting device. Conductive electrode 11 is tundish 2
Along the refractory wall in a substantially vertical direction to the bottom of the tundish. The conductive electrode 11 is a heat-resistant conductor made of, for example, a refractory material in a graphite chamber, and is generally embedded in the refractory material 19 of the tundish 2, but the molten steel 1
A part of the molten steel 1 is exposed to the inner space of the tundish at the bottom of the tundish so that the molten steel 1 and the electrode 11 contact each other even if the level decreases.

Further, by disposing two identical electrodes 11, even if one fails in potential detection due to disconnection or sticking of glue, it is possible to continue detection with another. The electrode 11 has an appropriate length, is embedded along the height direction of the tundish 2, and is provided with a lead wire connecting end at the upper end to reduce the heat load on the lead wire, and as described above. It can be exposed to contact molten steel near the bottom. This increases durability.

FIG. 4 shows the molten steel internal current path 20 and the external current path 21 when the induction heating device is used only on the second strand side.

FIG. 5 shows an equivalent circuit of the induction heating current loop shown in FIG. As shown in this figure, the electric potential between each pouring chamber 8 and the earth 3 is V ₁ , V ₂ , the electric potential induced in the steel by the main magnetic flux of the dielectric heating device is Vn, and the molten steel earth on the one strand side the resistance between the R _1, the resistance between the two strands side of molten steel grounded and R _2, when the resistance of the water groove molten steel is heated and Ru, with respect to an external current path 21 in a normal, V 1 _{= {(} Vn / 2) / (R ₁ + R ₂ )} × R ₁ ≈Vn / 4V ₂ = {(Vn
/ 2) / (R ₁ + R ₂ )} × R ₂ ≈Vn / 4 where R ₁ ≈R ₂ ,
R ₁ , R ₂ >> Ru, and the potentials between the molten steel and the ground in the pouring chamber 8 show almost the same value.

From this state, when the molten steel is poured into the refractory wall in the pouring chamber 8 on the side of the two strands and the molten steel comes into contact with the iron shell at the position 24,
The external current path 21 in FIG. 5 changes as shown in FIG.
It becomes the abnormal external current path 23.

Therefore, the potentials V ₁ and V ₂ between the pouring chamber and the ground are V ₁ ≈Vn / 2 and V ₂ ≈0.

In the present invention, the state of molten metal leakage is detected by detecting such a change in potential. FIG. 7 shows an example of the change in potential. A large difference in potential, which exceeds the detection level, appears due to the leakage of water with respect to the difference in potential under normal conditions | V ₁ −V ₂ |.

That is, the potential difference between each of the pouring chamber and the ground and the mutual potential difference are detected, and the abnormality determination is performed by the change in the potential difference at the time of abnormality with respect to the potential difference at the time of normality.

FIG. 8 shows the current path in the molten steel at the normal time when the 1-strand side and 2-strand side co-induction heating devices are used. In this case, by reversing the polarities of the induction coils on the 1st strand side and the 2nd strand side, the external current path by the 1st strand side induction heating device and the external current path by the 2nd strand side induction heating device cancel each other. Therefore, the potentials V ₁ and V ₂ between the pouring chamber and the ground are V ₁ ≈0 and V ₂ ≈0 as shown in FIG.

In this state, when the molten steel is poured into the hot water receiving chamber 7 and the molten steel comes into contact with the iron shell, an external current path is generated as shown in FIG. 10, and the potentials V ₁ and V ₂ between the pouring chamber and the ground are V _{1 1} ≈ Vn / 2, V ₂ ≈ Vn / 2 and the potential rises.

FIG. 11 shows an example of change in potential. With respect to V ₁ and V _{2 under} normal conditions, a large electric potential exceeding the detection level appears due to the occurrence of molten metal leak.

Although two examples have been described above, the present invention, by incorporating operating conditions and operating conditions of the induction heating device, changes the potential between the pouring chamber and the ground in normal and abnormal states, which changes depending on the conditions in all forms. The molten metal leakage is detected by comparing and calculating the potential level actually detected by the patterned determination logic, and determining the abnormality in time series.

Referring back to FIG. The potentials of the first-strand and second-strand electrodes 11 are amplified and level-calibrated by the isolation amplifiers 13, converted into digital data by the A / D converters 14, and given to the process controller (computer) 15. . The process controller 15 includes (1) a detection reference potential (the seventh reference value) from the input heating power at the time of induction heating in which only the induction heating coil 6 of one strand is energized.
Calculates a one-dot chain line) Vs in FIG., The absolute value of the difference between the output data of the two A / D converter 14 Vd | v ₁ -v ₂ | is calculated and when Vd> Vs is informed leakage water, And Vd
> Vs continues for a set time or more, or Vd> Vs
When it becomes + Va, a process control program for stopping the energization of the induction heating coil 6 and (2) a detection reference potential (from the input heating power at the time of induction heating energizing both the one-strand and the two-strand induction heating coils 6 ( 11 (dashed-dotted line in FIG. 11) is calculated, and the average value Vm = (V ₁ of the output data of the two A / D converters 14 is calculated.
-V ₂ ) / 2 is calculated, and when Vm / Vs, the leak of water is notified, and when Vm / Vs continues for a set time or more, or when Vm> Vs + Va, the induction heating coil 6 is energized. Contains the process control program, which stops the process.

Casting condition information is given to the process controller 15 from the input device 16. That is, when the number of used strands (selection information of (1) and (2) above) and induction heating power are given, and the number of used strands is 1, the controller 1
5 executes the above (1), and when the number of used strands is 2, the above (2) is executed.

In the above-mentioned embodiment, the leakage or the pouring of the pouring chamber 8 or the receiving chamber 9 is detected in the induction heating mode set for the original purpose of continuous casting. In one embodiment, the induction heating coil set for the original purpose of continuous casting is interrupted with a predetermined cycle or a predetermined time-series pattern to energize the induction heating coil for detecting the leakage of molten metal. The hot water leak detection of the hot water chamber 8, the hot water leak detection of the hot water receiving chamber 8 of the second strand, and the hot water leak detection of the hot water receiving chamber 7 are performed.

That is, at the molten metal leak detection timing of the predetermined cycle or the predetermined time series pattern, the process controller 15
First, only the induction heating coil 6 of the first strand is energized with the input power set for inspection, V ₁ (see FIGS. 5 and 6) is read, and it is the lower limit criterion assigned to the input power. If it is below the value, if it is below the value, it is notified that there is a leak in the pouring chamber 8 of the first strand. Next, only the induction heating coil 6 of the second strand is energized with the input power set for inspection,
V ₂ (see FIGS. 5 and 6) is read, and it is checked whether it is below the lower limit reference value assigned to the input power.
I will notify you that there is a leak of water. Finally, the induction heating coils 6 of the first strand and the second strand are both energized, and the leakage of the hot water in the hot water receiving chamber 7 is checked in the same manner as (2) above. When the above is completed, the induction heating mode set for the original purpose of continuous casting is restored.

〔The invention's effect〕

According to the present invention, conventionally, only the leak of water can be detected at the portion where the leak sensor is embedded, but the leak of the entire circumference of the tundish can be achieved by installing a plurality of conductive electrodes. It is possible to prevent serious accidents due to suspension or leakage of hot water.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, in which the tundish shows a cross section. FIG. 2 is an enlarged cross-sectional view showing a part of FIG. 1 enlarged. FIG. 3 is an enlarged vertical sectional view of the tundish shown in FIG. FIG. 4 is a perspective view showing a loop of an induction current flowing through molten steel or the like in the tundish when one of the induction heating coils 6 shown in FIG. 1 is energized. Fig. 5 shows the number 4 when the tundish does not leak.
It is a circuit diagram which shows the electric equivalent circuit of the induction current loop shown in the figure. Fig. 6 shows the number 4 in the case of hot water leak in the tundish.
It is a circuit diagram which shows the electric equivalent circuit of the induction current loop shown in the figure. FIG. 7 is a graph showing the relationship between the coil input power and the molten steel potential in the tundish when one of the induction heating coils 6 shown in FIG. 1 is energized. FIG. 8 is a perspective view showing a loop of the induction current flowing through the molten steel or the like in the tundish when the two induction heating coils 6 shown in FIG. 1 are energized. Fig. 9 shows the 8th time when there is no water leak in the tundish.
It is a circuit diagram which shows the electric equivalent circuit of the induction current loop shown in the figure. FIG. 10 is a circuit diagram showing an electric equivalent circuit of the induced current loop shown in FIG. 8 when there is a leak in the tundish. FIG. 11 is a graph showing the relationship between the coil input power and the molten steel potential in the tundish when the two induction heating coils 6 shown in FIG. 1 are energized. FIG. 12 is a cross-sectional view showing an abnormal current path when a molten metal leak occurs in the tundish. 1: Molten Steel, 2: Tundish, 3: Earth 4: Pinch Roll, 5: Induction Heating Device, 6: Induction Coil, 7: Hot Water Chamber, 8: Pouring Room, 9: Tundish Iron Skin, 10: Yukata 11 : Conductive electrode, 12: Cast piece, 13: Isolation amplifier 14: Analog-digital converter (11, 13, 14: Potential detection device) 15: Process controller (Comparison means, Detection means) 16: Input device, 17 : Alarm device, 18: Lead wire 19: Refractory, 20: Current path in molten steel, 21: External current path 22: Trench resistance, 23: Abnormal external current path, 24: Hot water leak location

Front page continuation (72) Inventor Yuji Sato 12 Nakamachi, Muroran City, Hokkaido Inside Nippon Steel Co., Ltd.Keisha Muroran Works (72) Inventor Etsuru Kamogiya, 12th Nakamachi, Muroran City Hokkaido Shinro Nippon Steel Co., Ltd. Inside the ironworks

Claims (2)

[Claims] 1. A device for detecting leakage of molten steel from a tundish having an induction heating device for continuously pouring molten metal into a conductive mold through a nozzle, and a potential detection device for detecting molten steel potential in the tundish, Means for comparing the output of the potential detecting device with a reference value corresponding to operating conditions, and means for detecting the leakage of the tundish or the saucer by the output of the comparing means Detection device. 2. A tundish having an induction heating device for continuously pouring molten metal into a conductive mold through a nozzle is provided with a conductive electrode in the height direction of the tundish, and the tundish is provided near the bottom of the tundish. An electric potential detection device characterized in that it is exposed so as to come into contact with molten steel.