JP2000219907A - Pouring nozzle opening method and apparatus - Google Patents

Abstract

(57) [Problem] To supply molten steel by simply and quickly opening a pouring nozzle when the pouring nozzle is not opened. SOLUTION: A filler for closing a flow path is disposed in a flow path of a pouring nozzle disposed at a bottom of a steel receiving container or a region from the flow path to a bottom of the steel receiving container, and a tip of the pouring nozzle is provided. In starting the supply of the molten metal into the container arranged below by discharging the filler more, when the filler forms a sintered layer and the nozzle becomes a non-open hole where the supply of the molten metal becomes impossible. In, a gas blowing pipe is inserted through an opening and closing door of a seal member that holds a region from the pouring nozzle to a container arranged at the lower part of the steel receiving container in an inert gas atmosphere,
O ₂ gas is blown into the flow path of the pouring nozzle from this gas blowing pipe to melt the sintered layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for opening a pouring nozzle used in a casting technique of molten steel, and avoids a non-opening of the nozzle at the start of supplying molten steel by the pouring nozzle. In order to realize a stable operation, a ladle nozzle used for supplying molten steel contained in a ladle to a tundish will be described below as an example.

In the present invention, the opening of the nozzle means that a filler previously filled in the flow path of the nozzle is discharged from the tip of the nozzle and then the molten steel flows out.
The non-open hole of the nozzle means that even though the nozzle is opened to supply molten steel through the nozzle, the filler previously arranged in the flow path of the nozzle is not discharged and the supply of molten steel becomes impossible. State.

[0003]

2. Description of the Related Art A ladle used for continuous casting of molten steel by a converter steelmaking method is such that molten steel in the ladle is supplied to a tundish via a ladle nozzle provided at a bottom tuyere of the ladle. However, in order to contain molten steel in the ladle, in order to prevent the molten steel from flowing out from the ladle nozzle, once the ladle nozzle or the ladle tuyere including the flow path In general, the process is performed after filling a region up to the surface with a sand-like oxide (silica sand or the like). For a prior document relating to this point, see, for example, JP-A-62-63613. You.

[0004]

The filler disposed in the flow path of the ladle nozzle or in the region up to the tuyere including the flow path is not suitable for tapping work in which molten steel is stored in the ladle. At the beginning, the surface layer of the filler is blown by the flow of molten steel, but sintering is performed by the heat of the molten steel in the part that comes into stable contact with the molten steel, and the filler is filled from the lower side of the sintered part to the tip of the nozzle. Will remain sandy.

[0005] When the supply of molten steel by the ladle nozzle is started in such a state, the filler in the sand state flows out from the tip of the nozzle as it is, and the sintered portion remains in a bridge shape. However, since the static pressure of the molten steel in the ladle exceeds the strength of the remaining portion after sintering, the molten steel breaks the sintered layer and flows out of the nozzle.

Incidentally, in steel types in which so-called secondary refining is performed in a ladle to produce ultra-low carbon steel, steel having an extremely low nitrogen content, etc., such refining requires a long time, so that fillers are not used. The sintering reaction proceeds (sometimes even to the straight body of the nozzle body), and the sintering layer becomes excessively thick. As a result, the strength of the bridge of the sintering layer increases and the nozzle is opened. Even when the supply of molten steel from the pot was started, there was a case where the molten steel could not flow out.

When the ladle nozzle is in such a non-open state, a pipe is inserted into the tip of the nozzle and O ₂ gas is blown from the pipe to melt the lump of molten steel mixed in the sintered layer or to remove the molten steel. Either destroy the sintered layer with the force of O ₂ gas, or attach an aluminum wire to the end of the pipe and use thermite reaction heat to melt the mass of molten steel and discharge it from the nozzle to discharge the molten steel in the ladle. A hole opening operation of the nozzle for discharging the water was carried out. However, when supplying molten steel from the ladle to the tundish, from the ladle bottom including the ladle nozzle to the molten steel supply hole of the tundish, in order to prevent secondary oxidation of the molten steel and nitrification in the meantime. A long tubular refractory tube called a long nozzle that blocks the area from outside air is installed, and it is not possible to perform the hole opening work without removing it, and the long nozzle is removed. If the time is included, drilling takes a long time, so it is inevitable that the temperature of the molten steel in the ladle drops, which has the disadvantage of significantly impairing the casting operation and also makes it impossible to seal the molten steel flow after drilling. However, there is also a disadvantage that the quality is remarkably deteriorated, such as secondary oxidation of molten steel and nitrogen absorption.

Further, when a sintered layer having an excessive thickness is formed, even if the above-mentioned hole-opening operation is performed, the hole is opened only at the location where the O ₂ gas is applied, and the static pressure of the molten steel is increased. In this case, the bridge of the sintered layer is not broken, and the desired molten steel throughput (to
n / min), it was impossible to carry out the casting operation.

An object of the present invention is to eliminate the above-mentioned adverse effects due to sintering of the filler, to stably pouring the molten metal at a predetermined throughput, and to prevent deterioration of the quality of ultra-low carbon, low nitrogen steel and the like. It is an object of the present invention to propose a method and an apparatus for preventing nozzle opening.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a filler for closing a flow path in a flow path of a pouring nozzle disposed at the bottom of the steel receiving vessel or in a region from this flow path to the bottom of the steel receiving vessel. In order to start the supply of molten metal into the container disposed below by discharging the filler from the tip of the pouring nozzle and disposing the filler, the filler forms a sintered layer and it is impossible to supply the molten metal. When the nozzle becomes unopened, gas is blown through the opening / closing door of a seal member that keeps the area from the periphery of the pouring nozzle to the top lid of the container placed under the steel receiving container in an inert gas atmosphere. A method of opening a pouring nozzle, comprising inserting a pipe and blowing O ₂ gas into the flow path of the pouring nozzle from the gas blowing pipe to melt the sintered layer.

In the present invention, the filler is characterized in that at least a portion in contact with the molten steel is made of iron or iron alloy particles.

Further, in the present invention, a pouring nozzle arranged at the bottom of the steel receiving container is surrounded by a supply hole of a top cover of a molten steel container arranged at a lower end thereof to maintain the inside thereof in an inert gas atmosphere. A heat-resistant seal member with a door that can be opened and closed on the main body, and a nozzle opening that blows O ₂ gas into the passage of the pouring nozzle through this seal member door
An opening device for a pouring nozzle, comprising an O ₂ pipe.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the case where molten steel in a ladle is supplied to a tundish arranged below the ladle, quality problems due to secondary oxidation of the molten steel and the like are caused in a region from the ladle nozzle to the tundish. In general, the above-described long nozzle is mounted to avoid such a problem. In the present invention, instead of using such a long nozzle, a cylinder having an opening / closing door between the pouring nozzle at the bottom of the ladle and the molten steel supply hole of the tundish top lid and capable of supplying an inert gas inside. may be provided to Jo seal member, so by inserting the gas blowing pipe from the door when not opening of the nozzle blowing O ₂ gas from the tip of the ladle nozzle, as in the prior art long when non apertures of nozzles It is not necessary to remove the nozzle itself, the opening work is short, and casting can be performed without interrupting the inert gas seal of the molten steel flow.

When the filler is made of a sand-like oxide and at least a portion of the ladle in contact with the molten steel is made of iron or iron alloy granules, the portion in contact with the molten steel is molten, but so-called chiller. Because it is in a state where it is arranged, it will be in a solidified state after melting to some extent,
Once melted and solidified, the iron or iron alloy particles cover the sandy oxide underneath. In such a state, the sand-like oxide does not form a thick sintered layer. When the thickness of the melted and solidified particles of iron or iron alloy is particularly large, it cannot be said that the nozzle does not become an unopened hole. ₍₂₎ By blowing gas, almost the entire area can be melted in a relatively short time, the required throughput is secured without lowering the temperature of the molten steel in the ladle, and the opening time itself is shortened Therefore, there is no need to cause poor sealing.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to the drawings. FIG. 1 shows a nozzle opening device according to the present invention, wherein reference numeral 1 denotes a ladle as a steel receiving container, and 2 denotes a pouring nozzle arranged at the bottom of the ladle 1 (a ladle nozzle in the case of a ladle). The pouring nozzle 2 comprises a combination of an upper nozzle 2a embedded and fixed in the bottom tuyere 1a of the ladle 1, and a lower nozzle (sliding nozzle) 2b slidably connected to the upper nozzle 2a.

Reference numeral 3 denotes a container such as a tundish disposed below the ladle 1, and reference numeral 4 denotes a sealing member (injection cylinder) for maintaining a region from the pouring nozzle 2 to the container 3 in an inert gas atmosphere. As shown in FIG. 2, the sealing member 4 has a cylindrical sealing member main body 4b made of, for example, ceramic wool and incorporating a framework 4a of an iron bar or an iron plate.
The sealing member main body 4b is provided with an opening / closing door 4c made of the same material as the main body 4b. Reference numeral 5 denotes an opening / closing door 4c, which is carried in through the opening portion thereof, and
This is a gas blowing pipe for opening a nozzle for blowing O ₂ gas.

To accommodate molten steel in the ladle 1, the lower nozzle 2b of the pouring nozzle 2 is slid so that the flow paths of the upper nozzle 2a and the lower nozzle 2b are shifted as shown in FIG.
The filling material P is filled in the flow path a or the region including the flow path a up to the bottom tuyere 1a of the ladle 1, and thereafter the molten steel is supplied into the ladle 1. I do.

In the case of a sand-like oxide in which the filler P is conventionally used, a sintered layer is easily formed, and when the contact with the molten steel lasts for a long time, it is broken even by the static pressure of the molten steel. Since a sintered layer that is difficult to be formed is formed, even if the lower nozzle 2b is slid to match the flow path of the upper nozzle 2a with the flow path of the lower nozzle 2b and the supply of molten steel is started, the nozzle becomes an unopened hole. Molten steel cannot be supplied. In this case, it is necessary to remove the long nozzle provided to prevent secondary oxidation and nitriding of the molten steel to perform the hole opening operation. When the nozzle is not opened, the opening / closing door 4c of the seal member 4 is opened, a gas blowing pipe 5 is inserted from here, and O ₂ gas is blown from the tip of the lower nozzle 2b to melt the lump of molten metal in the sintered layer. I tried to make it
There is no need to remove the seal member 4 itself, and the opening operation of the nozzle can be completed in a short time. Further, even when the opening and closing door 4c is opened, the pressure inside the seal member 4 is maintained higher than the atmospheric pressure so that the inert gas atmosphere can be maintained. Secondary oxidation and nitrogen absorption which cause deterioration are avoided.

When the secondary smelting in a ladle is intended for steel, especially for a long time, the sintering layer of the filler becomes thick, and even when the hole is opened by gas injection, the passage is formed in the channel. It may not be easy to remove the formed sintered layer,
In such a case, there may be a case where the predetermined throughput cannot be obtained and the casting operation cannot be performed.

For this reason, in the present invention, at least a portion of the filler made of oxide, which is in contact with molten steel, is made of iron or iron alloy particles. For example, in FIG. 3 described above, a sand-like oxide as conventionally used as a filler is disposed in the upper nozzle 2a, and the above-mentioned granular material is placed in the upper part thereof, that is, in the concave part of the bottom tuyere 1a of the ladle 1. When it is placed, the part in contact with the molten steel melts, but as it were, the so-called chill is placed, so after it has melted to some extent, it solidifies and the granular material once melted and solidified is Cover the filler (oxide). In such a state, the sand-like oxide no longer forms a thick sintered layer, and even if the nozzle becomes non-open, the cause is due to the portion where the particulate matter has melted and solidified. Since this can be easily melted by blowing O ₂ gas, the opening operation of the nozzle becomes extremely easy.

As the granular material of iron or iron alloy used in the present invention, a nail head which is a by-product of a nail manufacturing process, grinding powder generated at the time of cutting, or the like can be used. Is particularly preferred.

Examples of the steel type suitable for carrying out the present invention include ultra-low carbon steel, which requires a long processing time in the secondary smelting in a ladle, steel that requires a very low nitrogen content, and stainless steel. Steel or the like is advantageously suitable.

In the process of producing stainless steel, Cr:
In order to melt special ferritic stainless steel of 30 wt% and C: 30 ppm, after applying the equipment (ladle capacity: 120 ton) with the configuration shown in FIG. Secondary scouring is performed under the conditions of decarburization and denitrification in the VOD process, and then the ladle nozzle (upper nozzle size: 6
When supplying molten steel to a tundish through 5 mmφ and the size of the lower nozzle: 65 mmφ, the time required for hole opening work in the event of non-opening of the nozzle has a conventional structure in which a simple long nozzle is arranged (opening and closing) (The type without the door and the long nozzle itself is removed: conventional method). As a result, in the conventional method, the opening of the nozzle took about 7 minutes, whereas in the case of the present invention (the sealing member is made of ceramic wool), it can be performed in about 2 minutes. It was confirmed that the opening operation could be performed extremely easily.

In the structure shown in FIG. 1, 5 kg of SiO ₂ sand (particle size: 1 to 3 mm) is supplied to the flow path of the upper nozzle 2a.
After filling, a nail head (grain of about 5 mm) is formed as iron granules from the upper part to the concave part of the bottom tuyere of the ladle.
When 20kg is inserted (arranged in a mountain shape) (applicable example) and all are SiO ₂
(Comparative example), the complete opening ratio (opening ratio of 100 when the ladle nozzle is not opened)
% To obtain a predetermined throughput).

As a result, in the comparative example, the complete opening ratio at the time of non-opening was 25% (one complete opening at which a predetermined throughput was obtained for four non-openings). In the adaptation according to the invention, the full porosity was 100%.

FIG. 4 shows the results of investigation of the transition of nitrogen in molten steel when molten steel is supplied to a tundish. In the figure, “when a long nozzle is used and opened” indicates a case where the long nozzle is normally used and the hole is opened. In this case, since the molten steel is isolated from the outside air by the long nozzle from the start of the injection to all the time during the injection, the absorption of nitrogen into the molten steel is small. On the other hand, "when the long nozzle unusable opening" shall be deemed to be replaced in order was not open hole, remove the long nozzle, which was subjected to opening operation by O _2, because there is no cutoff with the outside air by the long nozzle, High nitrogen absorption. When the molten steel is supplied by opening the nozzle according to the present invention,
It can be seen that the nitrogen content in the molten steel changes in a very low region, indicating that there is no quality deterioration.

According to the present invention, even if the pouring nozzle is not opened, the hole can be easily opened, so that the load required for the opening operation is extremely reduced. Further, since the molten steel can be injected at a predetermined throughput, a stable casting operation can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a nozzle opening device conforming to the present invention.

FIG. 2 is a view showing a structure of a seal member constituting the hole opening device.

FIG. 3 is a diagram showing a configuration of a main part of a ladle nozzle.

FIG. 4 is a graph showing a transition of a nitrogen content with a change in an injection ton number at the time of supplying molten steel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ladle 2 Pouring nozzle 3 Container 4 Seal member 5 Gas blowing pipe

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shigeho Tateno 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in the Chiba Works of Kawasaki Steel Corporation (reference) 4E014 FA00 4K002 BD01

Claims (3)

[Claims] A filler for closing a flow channel is disposed in a flow path of a pouring nozzle disposed at the bottom of the steel receiving container or in a region from the flow path to the bottom of the steel receiving container. When the supply of the molten metal was started by discharging the filler from the leading end into the container arranged at the lower portion, the filler formed a sintered layer and became a nozzle non-opening that could not supply the molten metal. In this case, a gas injection pipe is inserted through an opening / closing door of a seal member for maintaining an area from the injection nozzle to the container disposed at the lower part of the steel receiving container in an inert gas atmosphere. A method for opening a pouring nozzle, comprising blowing an O ₂ gas into a flow path of the nozzle to melt the sintered layer. 2. The method according to claim 1, wherein the filler at least in contact with the molten steel is made of iron or iron alloy particles. 3. A door which can be opened and closed by surrounding a pouring nozzle arranged at the bottom of a steel receiving container together with a supply hole of a molten steel container arranged at a lower end thereof to maintain the inside thereof in an inert gas atmosphere and to open and close the main body thereof. and heat resistance of the seal member having, O ₂ in the path of the pouring nozzle through the doors of the sealing member
An opening device for a pouring nozzle, comprising: a nozzle opening O ₂ pipe for blowing gas.