JPH09150242A - Continuous casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of the quality of a cast slab in a try top material caused by ladle slag and ladle plugged sand and the shortening the service life of a tundish refractory at the time of hot-reusing a tundish by surely preventing the flowing of the ladle slag and the ladle plugged sand into a tundish and fully eliminating the slag in the tundish at the time of pouring the molten steel into the tundish from the ladle for continuous casting. SOLUTION: At the initial stage of pouring the molten steel into the tundish 2 from the ladle 1, the ladle plugged sand B falling from a ladle steel tapping hole 3 is flown to the side part by blowing the gas G. At the end stage of pouring the molten steel, a shaking variation of the molten steel stream 12 is detected with a CCD camera and the flowing-out of the ladle slag C is prevented. By this method, the slag in the tundish is made almost zero, and at the time of completing the casting, the molten steel in the tundish is wholly cast or only the remaining steel in the tundish is discharged and the hot maintenance which is plactically not cooled, is executed to fully removed the adverse effect caused by the slag.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method in which molten steel from a ladle is poured into a tundish, and the tundish is cast into a mold to directly cast a slab or billet. .

[0002]

2. Description of the Related Art Generally, in a continuous casting method, molten steel melted in a steelmaking furnace such as a converter is put in a ladle and transported to a position above a continuous casting machine, where the ladle is placed on a ladle turret. It is supported by or a ladle car, and the molten steel in the ladle is cast into the mold through the tundish. The tundish is equipped with a tundish injection pipe (a large-diameter pipe for sealing the molten steel flow between the ladle and the tundish with Ar gas) in the upper part, a sliding nozzle device and a dipping nozzle in the lower part. It is an intermediate container that stores and rectifies the flow of molten steel at a constant rate, controls the injection flow rate, and sends it into the mold. At the same time, it also functions as a distribution container in a multi-strand that manufactures a plurality of cast pieces.

In such a continuous casting machine, in a small lot production in response to the high-grade and diversification of user needs for steel in recent years, when one trial of continuous casting is completed, the tundish used for casting is tanned by a crane or the like. Carry it to the dish maintenance yard and perform necessary maintenance (hereinafter referred to as cold maintenance) based on casting factors. During this maintenance, replace the new tundish that was in preheat standby with the next continuous casting. I am continuing. This cold maintenance includes the following.

In the tundish maintenance yard,
First, the residual steel is treated. As one method of residual steel treatment,
Performing so-called lapping that discards the residual steel and residue in the tundish by tilting the tundish after continuous casting, and then cleaning the inner surface by blowing oxygen before the temperature of the tundish falls completely, Further, there is a method of removing the metal / slag adhered to the inner surface of the tundish during the casting by using a breaker or the like. As another method of treating residual steel, the tundish after continuous casting is cooled by water cooling, etc., and then the metal / punch machine is used to push out the metal / slag that has adhered to the inner surface of the tundish during the previous casting. There is a method to remove it.

After such a residual steel treatment step, maintenance such as replacement of the sliding nozzle device provided at the lower part of the tundish and replacement of the immersion nozzle is performed, and further repair maintenance of the inner surface of the tundish is performed. After that, the tundish is reheated by a burner or the like and kept waiting until it is the time for molten steel injection.

That is, in the above-mentioned inner surface cleaning by blowing oxygen, the inner surface of the tundish cannot be completely cleaned, and further, the oxide is inevitably attached to the refractory surface on the inner surface of the tundish. Therefore, when casting is performed using this tundish, there is a problem that a large amount of slag / oxide is mixed in the molten steel and a huge inclusion is generated in the molten steel. For this reason, after using the tundish, remove the slag and metal attached to the inner surface, then cool the tundish completely and spray a new refractory to prepare the inner surface, or clean the inner surface by blowing oxygen. Without treading, the tundish is cooled after use, the metal is pushed out and removed, new refractory is sprayed to maintain the inner surface, and the tundish whose inner surface is completed is preheated by a burner or the like before casting. It is carried out.

However, in such cold maintenance, the process of maintaining a series of tundish takes about 8 hours, and in recent small-lot production, in order to prevent mixing of components of different steel types, one tundish is required. Since it is necessary to frequently replace and perform cold maintenance after each trial, it is necessary to prepare a large number of tundish.The life of the refractory in the tundish due to wear of the refractory due to maintenance and fatigue of the refractory due to temperature changes. However, there are some problems such as high cost of refractories, high refractory costs, increased heat loss due to repeated cooling and heating of the tundish, and the need for personnel dedicated to the maintenance of the tundish.

As a means for solving such a problem,
In Japanese Examined Patent Publication No. 26589/1993, after the completion of casting, residual steel and residue in the tundish are immediately discharged and hot maintenance is performed without substantially cooling, and the next casting is performed using this hot-prepared tundish. A continuous casting method has been proposed. In this continuous casting method, the tundish is moved to the side of the mold after the end of continuous casting, in a hot state immediately after the end of casting,
Discharge of slag and residual steel in the tundish, residual steel treatment such as inner surface cleaning and slag removal, replacement of sliding nozzles and immersion nozzles, and internal surface repair by spraying refractory locally on the inner surface of the tundish, if necessary. The hot tundish is set on the mold and the next casting is performed. Furthermore, at the start of casting, the tundish injected with molten steel is moved to the side of the mold, where the molten steel is non-oxidatively heated by a plasma torch, etc. and stirred by a stirrer, etc. to make the molten steel temperature distribution uniform and The slag and oxide inside are separated and floated.

[0009]

However, in the above-described conventional tundish hot maintenance method, although the above-mentioned problems associated with cold maintenance can be solved, the following problems occur. It was

(1) It is impossible to completely prevent the slag from being poured into the tundish at the end of the molten steel injection from the ladle to the tundish in the current equipment, which shortens the refractory life of the tundish. ing.

(2) Although the residue in the tundish is discharged in a hot state immediately after the end of casting and the slag is removed after that, the residual slag in the tundish cannot be completely removed. The quality of the try-top material for the next try (the tip of the slab in the initial stage of casting) deteriorates when used many times during hot working.

(3) Since slag remains in the tundish after casting, when the residual steel and residue are discharged in a hot state immediately after the casting, the residual steel is reused in a converter or the like. First, the residual steel and the slag must be separated.

To solve such problems, at the end of the molten steel injection from the ladle to the tundish, the residual steel in the tundish is reduced as much as possible to prevent a decrease in yield, and then it flows into the tundish. All you have to do is remove the slag. However, the slag outflow detection method used in the current continuous casting equipment is to embed the transmitter coil and the receiver coil around the tap hole at the bottom of the ladle, and obtain the conductivity distribution from the induced voltage of the receiver coil. Method of detecting slag ratio in molten steel, that is, slag outflow, based on difference in conductivity between molten steel and slag (see Japanese Patent Publication No. 7-41402: hereinafter, AMEPA
Since it is detected after the slag flows out, the slag inevitably mixes in the tundish,
The above-mentioned problems have occurred.

Further, there has been proposed a slag outflow timing prediction method capable of detecting the slag outflow immediately before the slag outflows at the final stage of molten steel injection (Japanese Patent Laid-Open No. 5-18520).
No. 1). This is a CCD camera that captures the liquid flow flowing out of the nozzle at the bottom of the ladle, and the image analysis / determination unit detects changes in the liquid flow fluctuations (striped pattern / contour) when the molten steel outflow changes to slag outflow. By this detection signal, the outflow of molten steel is stopped immediately before the outflow of slag to prevent the outflow of slag.

By adopting such a slag detection method, it is possible to prevent the slag from flowing into the tundish at the end of molten steel pouring. However, the above-mentioned slag detection method alone cannot prevent the inflow of ladle sand from the ladle to the tundish at the start of molten steel pouring, thus ensuring a stable quality of the tri-top material. Can not.

That is, the tapping mouth of the ladle to the tundish generally adopts a sliding nozzle system, which is composed of an upper nozzle arranged in the bottom of the ladle and a sliding nozzle device installed on the lower surface of the bottom of the ladle. Has been done. In the case of such a gate structure, molten steel is likely to solidify in the concave space formed by the upper nozzle, etc., so one of the means to prevent this is to collect silica sand etc. in the concave space before receiving steel. There is a method of filling potted sand, which prevents the molten steel from entering the recess space and causing nozzle clogging due to solidification of the molten steel. When such ladle stuffed sand flows into the tundish, the ladle stuffed sand itself becomes a non-metallic inclusion, and slag is generated by the oxygen supply from the ladle stuffed sand.

The present invention has been made to solve the above-mentioned problems, and its purpose is to insert molten steel from a ladle into a tundish of ladle slag or ladle sand. The slag in the tundish is completely eliminated by reliably blocking the inflow of the tundish, and the quality of the slab of the tri-top material deteriorates due to the ladle slag and ladle sand that occur during repeated hot use of the tundish and the tundish refractory life. It is an object of the present invention to provide a continuous casting method capable of reliably solving the problems such as the decrease of

[0018]

The present invention is a continuous casting method in which molten steel from a ladle is poured into a tundish and cast from the tundish into a mold to continuously cast a slab (1) At the beginning of the pouring of molten steel from the ladle to the tundish, the ladle sand falling from the ladle outlet is removed sideways by blowing gas, which allows the ladle sand to be opened when the ladle is opened. Of the ladle slag by detecting the change of the molten steel pouring flow by the visual sensor at the end of pouring, which stops the pouring of molten steel from the ladle into the tundish. As a result, the ladle slag that flows into the tundish at the end of the ladle is set to zero, and (3) when the ladle is continuously connected, an inert gas is introduced from the upper part of the tundish injection pipe provided on the upper part of the tundish with a closed structure. Blow in The slag in the tundish due to reoxidation of molten steel is prevented by contacting the molten steel with the atmosphere to prevent the generation of slag in the tundish. Hot maintenance of the tundish that does not substantially cool this tundish (remaining steel processing that discharges only the remaining steel if there is residual steel in the tundish, sliding nozzle device / immersion nozzle replacement, etc.) This tundish is hot-maintained, and the next casting is performed using the tundish. The tundish is hot-used many times.

By adopting the above means (1) and (2) or, if necessary, the means (3), the slag in the tundish can be made to be almost zero, whereby the tundish hot The total amount of molten steel in the tundish can be cast into the mold during repeated use, or a small amount can be left in the tundish, and only the residual steel in the tundish can be discharged during hot maintenance. Therefore, in the conventional hot maintenance, the influence of slag, which could not be completely removed at the time of discharge and remained in the tundish and deteriorated the quality of the try-top material for the next try, can be suppressed to a level that can be almost ignored. , It is possible to stably and surely secure the quality of the try-top material.

Further, since no slag or ladle sand is put in the tundish, the life of the tundish refractory is improved, the quality of the slab in the early stage of casting and the final stage of casting is not deteriorated, and It is possible to cast the entire amount into the casting mold at the final stage. Further, when the molten steel is left in the tundish, there is an advantage that no separation work from the slag is required when it is reused in a converter or the like because only the remaining steel is left in the tundish.

When comparing the present invention with conventional cold maintenance,
There is no need to peel off the tundish inner surface deposits during cold maintenance, damage to the tundish refractory can be prevented, and the temperature drop in the tundish is small, so the fatigue of the refractory is reduced and the tundish refractory is reduced. The life can be improved. In addition, since the tundish is repeatedly used hot, it is possible to theoretically reduce the number of tundish that has been conventionally required to two, and actually to three, which reduces refractory cost. It can be reduced. Furthermore, as a matter of course, it is possible to simplify the work of peeling off the deposits and to omit the transportation of the tundish to the maintenance yard by a crane or the like, so that the number of staff for tundish maintenance can be reduced. it can.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; FIG. 1 shows an example of equipment provided with each device for carrying out the continuous casting method according to the present invention. FIG.
FIG. 1A shows a state at the beginning of molten steel injection from the ladle to the tundish, and FIG. 1B shows a state at the end of molten steel injection. In FIG. 1, a ladle 1, a tundish 2 and a mold (not shown) are arranged in this order from the top on the upper part of the continuous casting machine.
Molten steel A in the ladle 1 is poured into the tundish 2 through a tap hole 3 at the bottom of the ladle, and the molten steel in the tundish 2 is cast into a mold through a dipping nozzle 4 or the like.

An upper nozzle 5 made of brick is embedded in the bottom of the ladle 1, and a sliding nozzle device 6 for sliding and opening a nozzle hole is attached to the lower part of the upper nozzle 5, and the upper nozzle 5 and the sliding nozzle device are installed. The tap hole 3 is composed of 6 and the like. The ladle sand B is filled in the concave space formed by the nozzle hole 5a of the upper nozzle 5 and the upper part of the sliding nozzle hole 6a of the sliding nozzle device 6.

A lower nozzle 7 is provided in the lower part of the sliding nozzle device 6, a tundish injection pipe 9 is provided in a tundish lid 8 of the tundish 2, and it is attached to the lower nozzle 6 during steady casting. The lid (so-called Jinkasa) 10 abuts on the upper surface of the tundish injection pipe 9 to cover it, and the molten steel injection flow passage 11 from the lower nozzle 7 to the tundish 2 is blocked from the outside, and the inert gas introduced into the inside. The molten steel flow 12 is sealed by the above.

In such a structure, the present invention employs a plurality of means as described below in order to ensure the quality of the try-top material in a stable manner by completely eliminating the slag in the tundish 2.

(1) Initial stage of molten steel injection: Removal of clogging sand by blowing gas when ladle is opened Like between Japanese Patent Application No. 7-69407 and Japanese Patent Application No. 7-256038, between ladle 1 and tundish 2. A gas spraying device 20 for horizontally spraying a gas G such as air or an inert gas is installed on one side of the molten steel injection flow path 11 in, and only the ladle sand B flowing out when the ladle is opened is directed to the side. Blow away,
Only molten steel A is injected into the tundish 2 (see FIG. 1 (a)).

This gas spraying device 20 has a plurality of nozzles 21 arranged horizontally at intervals and a plurality of nozzle headers 22 in the vertical direction (the molten steel injection flow passage direction) in which the nozzles 21 are arranged. And a supply pipe 23 for supplying gas to each header 22, a flow rate adjusting valve 24, and a compressor or a tank / pressure booster. Each of the nozzle headers 22 is a pipe extending in a horizontal direction in an arc shape or a linear shape in a plan view, and a plurality of nozzles 21 are attached in the horizontal direction at an arrangement pitch. Further, the distance from the center line of the molten steel injection channel 11 to the nozzle header 22 is set to an appropriate distance, and each nozzle 21 in the same plane in each nozzle header 22 is set.
The jet directions of the jet gas G are such that the jet gas G is jetted in parallel to each other in the horizontal plane.

On the opposite side of the gas blowing device 20 with the molten steel injecting passage 11 interposed therebetween, a ladle-filled sand collecting container 25 having a dust collecting function, or a suction duct / collecting container / suction device is provided. Arrange a ladle sand suction device that positively suctions and collects ladle sand. With the above structure, ladle sand is removed as follows.

A) In the steel-making process, the sliding nozzle device 6 is closed, the ladle sand B is filled in the concave space of the ladle 1, and the steel is received from the converter into the ladle 1. Then, after performing secondary refining such as vacuum degassing, the ladle 1 is transported to the continuous casting machine.

When the ladle 1 is placed on the tundish 2, the sliding nozzle device 6 is opened to start the injection into the tundish 2, but immediately before the sliding nozzle device 6 is opened, the gas blowing device is opened. 20 is activated to start spraying the gas G. The flow rate of gas G is
The flow rate (flow velocity) should be set within a proper range obtained by experiments. Here,
At the time of steady casting, the Jinkasa 10 and the tundish injection pipe 9 are in contact with each other, and the molten steel injection channel 11 is completely covered by these, so that the ladle 1 is raised and the Jinkasa 10 and the tundish injection pipe 9 are raised. A space is provided between and, and the gas G can be blown to the molten steel injection flow passage 11 from this space.

B) When the sliding nozzle device 6 is opened and the injection is started, first the ladle sand B filled in the ladle tapping steel mouth 3 falls, and then the molten steel A flows down.
The ladle sand B is blown off by the gas G blown to the molten steel injection channel 11 and is directly collected in the collection container 20 or is sucked and collected via the suction duct. Since the ladle sand B is a particle that can move independently and has a density smaller than that of molten steel, it is easily moved by a gas jet, and most of the ladle sand B is blown off to the side. On the other hand, the molten steel A has a high density and a high interfacial tension, and since the flow rate of the gas jet flow is set to an appropriate flow rate in advance, the molten steel flow partially disengages and scatters even if its surface shape is slightly disturbed. There is no such thing, and all is poured into the tundish 2.

(2) Molten steel pouring end: Prevention of ladle slag mixture by visual sensor at the end of ladle As in Japanese Patent Laid-Open No. 5-185201, at the end of pouring molten steel in the ladle, slag from molten steel A currently flowing out Immediately before changing to the outflow of C, it is detected by a camera and image processing that there is a change in the liquid flow surface of the molten steel A that is currently outflowing, and it is assumed that the slag outflow will start immediately after this change in the fluctuation. To prevent the outflow of slag C (see FIG. 1 (b)).

For example, a CCD camera 30 is used as the camera, and the CCD camera 30 is used for the ladle 1 and the tundish 2.
The molten steel flow 12 is installed in a position to face the molten steel flow 12 between them, the change in the molten steel flow is imaged, the acquired image is processed by the image analysis / determination unit 31, the occurrence of the fluctuation of the molten steel flow 12 is determined, and the fluctuation occurs. The gate opening / closing device 32 closes the sliding nozzle device 6 to stop the outflow of the molten steel flow. If the molten steel A is sufficiently stored in the ladle 1, as shown in FIG.
As shown in (a), the molten steel flow 12 stably flows out and the surface flow is linear, but when the residual amount of the molten steel A decreases and immediately before the slag C flows out, FIG. As shown in (b), fluctuations (blurring) occur in the molten steel flow 12.

In the image analysis / determination unit 31, the acquired image is subjected to image processing such as binarization processing, for example, the area change and position change of the molten steel flow are obtained, and this is compared with that in the steady flow. When the difference becomes larger than the set value, it is determined that the fluctuation has occurred and the slag is about to flow out. By using such a method, immediately before the slag C flows out (0.5
Slag C
It is possible to reduce the amount of molten steel A in the tundish and to improve the yield while completely preventing the outflow of iron.

The CCD camera 30 is arranged at a position where the ladle sand B blown off by the gas blowing device 20 does not hit the initial stage of the molten steel injection, and the ladle 2 is used.
Are imaged from between the Jinkasa 10 and the tundish injection tube 9 and the shape of the Jinkasa 10 is changed in order to protect it from the molten steel splash and heat. That is,
As shown in FIG. 4, the cap 10 is made wider than the current one, and the CCD camera 30 is installed on the lower surface of this outer peripheral portion.
If an intermediate seal tube (not shown) is provided between the tundish injection tube 9 and the cap 10, the image may be taken from an opening window provided in the intermediate seal tube.

As to the durability of the CCD camera 30, as shown in FIG. 5, the camera sensor portion is covered with a protective tube 33 having a window 33a at its tip, and a cooling gas 35 is introduced into the protective tube 33. To deal with. As a result, it was confirmed that the surface of the protective tube became 77 ° C. or lower and there was no problem. It was also confirmed that there is no problem by using a heat resistant tube (for example, an empire tube) for the cable 34.

(3) Continuous Sealing Method Normally, at the time of continuous connection, as shown in FIG. 2, the upper part of the tundish injection pipe 9 is released. By blowing 40 horizontally, deterioration of the sealing property is prevented. As a result, contact between molten steel A and the atmosphere is prevented, and generation of tundish slag due to reoxidation of molten steel is prevented.

When the molten steel injection from the ladle 1 into the tundish 2 is completed by adopting the above means, since the slag C does not exist in the tundish 2, the molten steel A in the tundish 2 is cast. The casting is completed by pouring the entire amount inside or leaving a small amount of steel, and then the tundish is moved to the side of the mold for hot maintenance that does not substantially cool the tundish. The tundish is repeatedly used hot, that is, the next casting is performed by using.

As for hot maintenance, since there is no slag C in the tundish 2, for example, when there is residual steel, the tundish is tilted and the residual steel is treated, the sliding nozzle device and the immersion nozzle are replaced. If necessary, the inner surface may be repaired by spraying a refractory material.
After such hot maintenance, it is set on the mold without preheating, and if necessary, preheating to compensate for the temperature decrease is performed.

Next, specific numerical examples will be described. Under the following conditions, (1) ladle sand removal by gas blowing was performed, (2) slag outflow prediction by fluctuation detection, and (3) continuous sealing.

A) Gas spraying device Gas used: compressed air Gas pressure: 2 × 10 ^-1 MPa Nozzle diameter: 10 mm, number of nozzles: 5, nozzle pitch P: 20 mm Nozzle header: 2 steps (vertical direction), pipe inner diameter : 15mm Distance from center line of molten steel injection channel to nozzle header L: 150mm b) Fluctuation detection Tundish capacity: 85T Tundish nozzle diameter: 75mm Camera: CCD camera Ladle sand removal by gas blowing is carried out (gas blowing) The timing was 10 to 15 seconds immediately before opening the slide gate of the ladle tapping opening at the start of pouring).
It was confirmed that there was no mixing of ladle sand in the tundish. As a result, the ladle sand as non-metallic inclusions is eliminated, and the reoxidation of molten steel due to the ladle sand is suppressed to prevent the generation of slag in the tundish. Has improved.

Next, FIG. 6 shows the results of the slag thickness in the tundish after the completion of the molten steel injection. AM commonly used
In the EPA, slag in the tundish having an average thickness of 4 mm was confirmed, but in the fluctuation detection by the CCD camera of the present invention, the slag in the tundish was not confirmed.
FIG. 7 shows the slag signal of the conventional AMEPA when the fluctuation is detected, but the fluctuation detection of the present invention is a normal AMEP.
It was confirmed that the detection was performed 3 seconds earlier than the end of A. At this time, the rising of the slag signal was not seen, and it is clear that the ladle slag did not flow out.

As described above, by adopting the means (1), (2), (3), it becomes possible to make the slag in the tundish 2 almost zero, and the tundish 2 is hot-heated. Even if it is used repeatedly, the tundish refractory life, which has been a problem in conventional hot maintenance, the quality of the try-top material (the tip of the slab) of the next try deteriorates, and it is reused in the converter. It was possible to eliminate the separation of residual steel and residue.

Further, when compared with the conventional cold maintenance, the present invention can reduce the number of tundish, and there is no wear of the refractory due to maintenance or fatigue of the refractory due to temperature change. It is possible to improve the life of the object, reduce the cost of refractory materials, eliminate heat loss because the tundish is not repeatedly cooled and heated as in the past, and it is possible to reduce the number of personnel dedicated to tundish maintenance. There are advantages such as being possible.

[0045]

As described above, according to the present invention, at the initial stage of injecting molten steel from the ladle to the tundish, the ladle sand is removed laterally by blowing gas to the molten steel in the tundish. Inflow is blocked, at the end of molten steel pouring, molten steel flow fluctuations are detected by a visual sensor to prevent outflow of ladle slag, the opening of the tundish is sealed at successive times, and it is cooled substantially after pouring into the tundish. Not doing hot maintenance, so that the tundish is repeatedly used hot, the following effects are achieved.

(1) The slag in the tundish can be made to be almost zero, whereby the molten steel in the tundish can be entirely cast into the mold in many hot use of the tundish, or in the tundish. It is possible to leave only a small amount and discharge only the residual steel in the tundish during hot maintenance, and the quality of the slab in the state where the casting amount is small (tri-top), which is a problem when repeatedly used in the conventional hot, Since there is almost no slag in the tundish, it can be suppressed to a level that is almost the same as when cold maintenance was performed, and the quality of the try-top material can be stably and reliably ensured.

(2) Since no slag or ladle-filled sand enters the tundish, the service life of the tundish refractory is improved compared to conventional hot maintenance, and casting at the beginning and end of casting The quality of the piece does not deteriorate. Further, it becomes possible to cast the entire amount into the casting mold at the final stage of casting, thereby improving the yield.

(3) When leaving molten steel in the tundish,
Since there is only residual steel in the tundish, it is not necessary to separate it from the slag when it is reused in a converter or the like, and labor can be saved and working time can be shortened.

(4) Compared with the conventional cold maintenance, the number of tundish can be reduced by repeatedly using the tundish hot, and the life of the refractory can be improved. The material cost can be suppressed to 1/10 or less. Also, the time required for preheating can be reduced, and heat loss can be reduced. In addition, the number of tundish maintenance personnel can be reduced.

[Brief description of the drawings]

FIG. 1 is an example of equipment for carrying out a continuous casting method according to the present invention, where (a) is a sectional view showing a state at the beginning of molten steel injection, and (b) is a sectional view at the end of molten steel injection.

FIG. 2 is a cross-sectional view showing a sealed state during continuous casting in the continuous casting method according to the present invention.

FIG. 3 shows a detection method for preventing outflow of ladle slag in the final stage of molten steel injection according to the present invention. (A) shows a state of molten steel flow at the time of normal casting, and (b) shows molten steel flow at the end of ladle. It is explanatory drawing of a state.

FIG. 4 is a cross-sectional view showing an installation state of a camera for detecting a ladle slag according to the present invention in comparison with a conventional state.

FIG. 5 is a cross-sectional view showing the structure of a camera for detecting ladle slag according to the present invention.

FIG. 6 is a graph comparing the slag thickness in the tundish between the slag detection method of the present invention and the conventional slag detection method.

FIG. 7 is a graph showing a difference in detection timing between slag detection of the present invention and conventional slag detection.

[Explanation of symbols]

 A ... Molten steel B ... Ladle stuffed sand C ... Ladle slag 1 ... Ladle 2 ... Tundish 3 ... Ladle tapping mouth 4 ... Immersion nozzle 5 ... Upper nozzle 6 ... Sliding nozzle device 7 ... Lower nozzle 8 ... Tundish Lid 9 ... Tundish injection pipe 10 ... Lid part (Jinkasa) 11 ... Molten steel injection flow path 12 ... Molten steel flow 20 ... Gas spraying device 21 ... Nozzle 22 ... Nozzle header 23 ... Supply pipe 24 ... Flow rate adjusting valve 25 ... Ladle packing Sand collection container 30 ... CCD camera 31 ... Image analysis / determination unit 32 ... Gate opening / closing device 33 ... Protective tube 34 ... Cable 35 ... Cooling gas 40 ... Inert gas

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Claims (1)

[Claims] 1. A continuous casting method in which molten steel from a ladle is poured into a tundish, and the tundish is cast into a mold to continuously cast slabs, in which molten steel is started to be poured from the ladle into the tundish. At the beginning of pouring, ladle lapping sand that falls from the ladle tap hole is removed to the side by blowing gas, and the pouring of molten steel from the ladle to the tundish is completed. It detects the change of the flow and prevents the outflow of ladle slag, and when the casting is completed, the molten steel in the tundish is entirely cast in the mold, or the molten steel remains in the tundish and the tundish is not cooled substantially. A continuous casting method characterized in that hot maintenance of a dish is performed and the following casting is performed using this hot-prepared tundish.