JPH02241665A - Method and apparatus for detecting flowing-out of slag - Google Patents

Abstract

PURPOSE:To quickly and accurately detect flowing-out of slag by detecting the fact that the slag slows out when molten metal stream flowing out from opening hole near bottom part of a vessel charging the molten metal and the floated slag increases with magnifying ratio of specific equation. CONSTITUTION:The molten steel 2 is supplied into a tundish 4 as the molten steel stream 5 from a ladle 1 through a nozzle 3 and further, the molten steel is supplied into a casting mold to cast a cast slag. Inert gas of Ar, etc., is sealed in the sealing material 7 to seal the molten steel stream. By opening an aperture 90, a speed meter 9 is set as facing to the molten steel stream 5. When the speed of the flowing-out material from the vessel increases to multiple of the value showing in the equation I, it is detected that the slag flows out. The detected signal with the speed meter 9 is given to a signal treating device 10 and the signal for controlling opening degree of a sliding nozzle 3 is given to prevent the flowing-out of slag. By this method, the flowing- out of slag is quickly and accurately detected and the great influence is developed to the improvement of quality and yield.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a slag outflow detection method for quickly and accurately detecting the presence of slag in a molten metal flow flowing out from a molten metal container. In particular, the present invention relates to a slag outflow detection method and device effective for preventing slag from flowing into the tundish and from the converter to the ladle in continuous casting.

[Conventional technology and its problems]

For example, during continuous steel casting, it is extremely important to prevent slag from flowing into the tundish from the ladle to ensure the quality of the slab.

Slag normally floats on top of the molten steel in the ladle, and flows out together with the molten steel at the end of tapping from the ladle to the tundish. Therefore, slag outflow can be detected quickly,
Thus, stopping the flow of molten steel with slag from the ladle to the tundish is an important control item in continuous casting.

The simplest conventional method and device for detecting slag outflow is visual inspection by an operator. This is done by raising the ladle relative to the tundish at the end of tapping from the ladle, creating a visual space between the tundish and the tundish, and from this space workers can visually observe the flow of molten steel and remove the slag. This is to monitor the outflow of water. However, in recent continuous casting, it is common to shield the molten metal flow between the ladle and the tundish with an inert gas to prevent oxidation. The shield is broken and the quality of the slab deteriorates due to oxidation of the molten steel.

Furthermore, a method is known in which the vibration of a nozzle of a tundish or slag is measured and the inflow of slag into the molten steel is detected from the amplitude change caused by the difference in viscosity and density between the molten steel and the slag. However, this method has problems with accuracy due to noise caused by vibrations from the crane or building.

A method is also known in which a detection coil is attached to the nozzle of a tundish or ladle and the outflow of slag is detected based on the difference in electrical conductivity between molten steel and slag. However, with this method, detection sensitivity decreases due to factors such as solidification of molten metal on the inside of the nozzle and adhesion of alumina used as flux, and it is difficult to distinguish it from slag when air passes through the nozzle. There's a problem.

In addition, a method has been proposed in which the surface of molten steel in the tundish is monitored using an imaging device, but at the end of casting, the slag from the previous charge has surfaced, so this is combined with the slag that has flowed from the tundish into the tundish. Not only does this cause the problem of making it difficult to distinguish between the
In practice, there is a problem that detection is delayed and automation is difficult.

From this point of view, in recent years, for example,
As seen in Japanese Patent No. 6383, a method has been proposed in which the i8 steel flowing out from the ladle is optically monitored and the outflow of slag is detected from the difference in brightness between the molten steel and the slag. However, as shown in FIG. 5, when the steel is tapped from the ladle, splashes 15 are generated extremely irregularly around the molten steel flow 5 below the sliding nozzle 3. For this reason, it is impossible to detect the radiant energy distribution with high precision as shown in FIG. 6 when the molten steel flow in the circle indicated by reference numeral 20 in FIG. 5 is optically imaged.

The present invention has been made in view of the problems of the conventional methods, and is capable of producing molten metal without being affected by disturbances such as molten metal splash and turbulence of the molten steel flow caused by sliding nozzle wear, etc. An object of the present invention is to provide a slag outflow detection method and device capable of accurately and quickly grasping the state of molten metal without destroying a seal against the flow, and capable of detecting slag outflow with high precision.

[Means to solve the problem]

In the present invention, the flow velocity of the molten metal flowing out from the opening near the bottom of the container at the final stage of the molten metal outflow when almost only slag remains in the container is different from that when the flow has changed to a slag outflow. The timing of slag outflow is detected by measuring the outflow speed of molten metal.

[Operation] In the present invention, the difference between the velocity of molten metal when it flows out from a container in which most of the molten metal has flowed out and only slag remains, and the slag flow velocity when slag flows out is detected, and based on this, the difference is detected. The inflow of slag into the molten metal stream is detected.

[Principle of the invention]

Hereinafter, the principle of the present invention will be briefly explained with reference to the drawings.

First, the basic principle of the present invention is Torricelli (Torricelli).
(Ricelli)'s theorem will be explained.

As shown in FIG. 1, when a water tank 51 is filled with a liquid 52 and the liquid 52 is caused to flow out from a small hole 53 opened near the bottom of the water tank 51, the streamline of the liquid 52 in the water tank 51 approximately resembles an arrow mark. The streamline of the liquid 52 in this case cannot be strictly called a steady flow, but if the size of the small hole 53 is sufficiently small, the rate at which the liquid level falls is 0. Here, in FIG. 1, the water tank 51
Liquid 52 flowing out from point B of small hole 53 near the bottom of
Let V be the speed of

Further, assuming that the position of the liquid level is point A, the pressure at both points A and B is atmospheric pressure Po.

If the depth of point B from point A is h, Bernoulli (Be
According to the theorem of Rnoull i), the following equation (1) is established.

Po+Pgh-Po+'Apv2-(11 where ρ: density of liquid g: gravitational acceleration Therefore, the following equation (2) holds true.

v-V2gh ・+2+ This is called Torricelli's theorem.

By the way, at the end of the flow of molten metal from a ladle to a tundish used in continuous casting, almost only slag exists in the ladle, and therefore (1
) in the formula ``ρghJ'' is the density of the slag, and ``〃ρ
ρ of “v2” is the density of the molten metal.

Figure 2 (al shows the state in which most of the molten metal, here the molten metal 82, has flowed out from the ladle 1 through the nozzle 3. Usually, the ladle used for continuous casting has a diameter of about 3 m; Since the diameter of the nozzle is approximately 100 fi, the above-mentioned assumption in Bernoulli's theorem that the falling speed of the liquid level can be ignored holds true.

The density of molten steel 2 and slag 8 is such that the density of molten steel 2 is approximately 7.2.
On the other hand, that of slag 8 is about 2.5, so the molten steel is about three times as large. Therefore, in the state shown in Figure 2 fat, 2m is the density of the molten metal.

If ρS is the density of slag, then from the +1+ formula, ρS gh+
1lllApIII v2, and if ρm=3ρS as mentioned above, ρsgh=%3ρS v2 Also, there is no molten steel 2 in the cider 1, and the slag 8
With regard to the discharge speed (■) of the slag 8 in the state shown in FIG.

Therefore, when changing from molten steel flow to slag flow, the flow velocity is 73
Therefore, by measuring the flow rate of the molten steel 2 from the ladle 1, it is possible to detect the flow of slag.

[Embodiments of the invention]

Hereinafter, the slag outflow detection device of the present invention will be explained in detail.

FIG. 3 is a schematic diagram showing the configuration of the apparatus of the present invention based on the above-mentioned principle, that is, the method of the present invention.

In FIG. 3, 1, 2, and 3.8 represent one dollar, molten steel, nozzle (sliding nozzle), and slag, respectively, as described above.

Also, 4 is a tandem pipe, in which the steel 2 is passed from the ladle 1 through the sliding nozzle 3. It is supplied as steel flow 5. In actual continuous casting, molten steel is continuously supplied from the tundish 4 to the casting mold, so that slabs are continuously cast.

Note that 7 is a sealing material, which is provided between the nozzle 3 and the tundish 4 to prevent the molten steel flow 5 from coming into contact with air and being oxidized. Specifically, an inert gas such as argon is sealed in the sealing material 7 and the nozzle 3 is sealed.
The molten steel flow 5 is sealed from air between the tundish 4 and the tundish 4.

A window 90 is opened in a part of the sealing material 7, and the speed meter 9 is installed so as to face the molten steel flow 5 through the window 90. Specifically, the speedometer 9 is suitably a non-contact speedometer using a laser Doppler system, for example.

10 is a signal processing device. This signal processing device 10 is given a detection signal from the above-mentioned speedometer 9, and based on this detects the outflow of slag according to the above-mentioned principle, it is also given a signal indicating the opening degree of the above-mentioned sliding nozzle 3. Furthermore, a control signal for controlling the opening degree of the sliding nozzle 3 is provided from the signal processing device 10.

FIG. 3 is a graph showing actual measurement results of the outflow velocity of the steel flow 5 or slag 8 from the ladle 1 to the tundish 4 based on the method of the present invention.

The results shown in this graph show that when the slag flows out, the flow velocity V' is approximately 1.7 times higher than the flow velocity (2) of the molten steel flow 5. Therefore, just before the flow velocity V of the normal molten steel flow 5 is measured by the speed meter 9 and a measurement value approximately 1.7 times that value is detected, the nozzle opening degree is changed from the signal processing device 10 to the sliding nozzle 3. If a control signal is given so as to do this, slag outflow from the ladle 1 to the tundish dish 4 can be avoided.

In the above embodiment, a non-contact speed meter is used as the speed meter 9, but in addition, for example, an electromagnetic flow meter may be attached to a position near the upper end of the sliding nozzle 3 to measure the average flow rate of the molten steel 2. However, it is of course possible to adopt a configuration in which outflow of slag is detected by detecting a change in the velocity component.

Further, in the above embodiments, the present invention was mainly applied to continuous casting of steel, but it goes without saying that it is also applicable to other treatments of other molten metals.

〔Effect of the invention〕

As described above, the slag outflow detection method and device according to the present invention have a simple configuration with only one speedometer, and the signal processing device monitors changes in the signal of the speed measurement value given from the speedometer. It is not affected by splash, and is not affected by various external vibrations, solidification of molten metal or adhesion of alumina to the inner surface of the nozzle, and is also free from detection delays or seal breakage. It becomes possible to quickly and accurately detect slag outflow without causing any trouble. Therefore, it has a great effect on improving the quality or yield of metal products.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of Torricelli's theorem for explaining the present invention in detail, and FIG. 2 fa1. (bl is a schematic diagram showing the flow of molten steel from the ladle to the tundish, Fig. 3 is a schematic diagram showing the configuration of the device of the present invention, and Fig. 4 is a schematic diagram showing the timing of slag outflow according to the present invention. The graph, FIGS. 5 and 6 are explanatory diagrams of the prior art. 1... Ladle 2... Molten steel 3... Sliding nozzle 4... Tandishu 5...
- Molten steel flow 8...Slag 9...Speed meter 1
0...Signal processing device patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono p. po Funeral Diagram Funeral Diagram Approximately 100φ Funeral Diagram (a) Funeral Diagram (b) Funeral Diagram Diagram 4 Funeral Diagram

Claims (1)

[Claims] 1. A method for detecting that slag is contained in a molten metal flow flowing out from an opening near the bottom of a container containing molten metal and slag floating thereon, comprising: A slag outflow detection method is characterized in that slag outflow is detected when the flow velocity of the outflow increases by a factor of √(ρm/ρs), where ρm: molten metal density ρs: slag density. 2. In a device for detecting that slag is contained in a molten metal flow flowing out from an opening near the bottom of a container containing molten metal and slag floating thereon, the flow rate of the effluent from the container is A speed detection means to measure, a value detected by the speed detection means is √(ρm/ρs), where ρm: molten metal density ρs: slag density, a comparison means for detecting that the slag density has doubled, and a comparison result by the comparison means. A slag outflow detection device comprising means for detecting outflow of slag from the container based on.