JPH10175059A - Nozzle for discharging molten metal of molten metal vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molten metal pouring nozzle naturally opening the hole at high hole opening ratio by forming the inner wall surface of the nozzle hole into a specific range of angle to the horizontal plane and using a mixed material composed of a specific range of wt.% of total content of Cr2 O3 and SiO2 and a specific wt.% or higher of Cr2 O3 content and the balance oxides of iron, Al and Mg as a plugging material for plugging into this nozzle hole. SOLUTION: The inner wall surface of the nozzle hole 5 for discharging the molten metal arranged in a square brick 3 fitted to the bottom opening hole part of a molten metal vessel and vertically penetrated, is made to 90 deg.±8 deg. of angle θ to the horizontal plane. As the plugging material for plugging into this nozzle hole, the mixed material composed of 50-70wt.% total content of Cr2 O3 and SiO2 and >=30wt.% Cr2 O3 content and as the balance the oxide of iron, Al and Mg, is used. The nozzle 5 has the contracting part 6 at the middle part and this contracting part 6 is made to the boundary and this upper part is formed as wider upper part which expands the diameter as going to the upper part, and this lower part is formed as wider lower part which expands the diameter as going to the lower part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle for tapping a molten metal container used for melting, refining, transporting, storing and the like in the course of metal refining.

[0002]

2. Description of the Related Art A molten metal container for melting or melting an ore or an alloy, refining, transporting, storing, etc., such as a general ladle and a ladle for refining, is provided at the bottom of the container (in some cases). Is provided with a nozzle for tapping molten metal from the side wall). For example, a ladle that stores molten metal and transports it to the next process, or a refining ladle that is used not only to transport but also to refine the stored molten metal, is a tapping device that can be opened and closed at the bottom. Alternatively, a tapping device capable of adjusting the flow rate is provided.

An example of such a tapping device provided at the bottom of the ladle will be described below. The nozzle hole provided at the bottom of the ladle is filled with a powdery filler to close the nozzle hole and to accommodate the molten metal. At the time of tapping, a sliding nozzle is connected below the nozzle hole, and by aligning the nozzle hole and the sliding nozzle, the powdery filling naturally falls and circulates, thereby opening the nozzle hole. What you do is normal. Regarding the improvement relating to such a tapping device, Japanese Patent Application Laid-Open No. 52-147523,
JP-A-53-26733, JP-A-55-9947
6, JP-A-55-10374, and JP-A-7-107.
Various proposals have been made in, for example, Japanese Patent No. 308763.

For example, Japanese Patent Application Laid-Open No. 52-147523 discloses that an upper layer in contact with a molten metal in a nozzle hole is filled with a refractory material powder that produces high-viscosity glass to prevent intrusion of molten metal, and a lower layer contains carbon. It describes that mixed refractory material powder is filled to prevent sintering. JP-A-53-26733 proposes that the inclination angle of the upper inner wall of the opening of the nozzle brick at the bottom of the container is 75 to 105 ^° . Japanese Patent Application Laid-Open No. 55-94776 discloses that the inside of a nozzle hole is filled with a coarse-grained filler to prevent sintering, and the surface thereof is covered with an irregular-shaped refractory which easily forms a sintered layer. A description is given of a device for preventing intrusion of molten metal. Japanese Patent Application Laid-Open No. 55-10374 discloses a structure in which a particulate filler containing an organic binder is filled in an upper portion in contact with a molten metal in a nozzle hole, and a normal particulate filler is filled in a lower portion. I have. Further, Japanese Patent Application Laid-Open No. Hei 7-308763 describes that a mixed powder of high-purity silica sand and chromium ore is used as a filling material for a nozzle hole.

[0005]

Although the one proposed in the above-mentioned publication has some features, if the relationship between the shape of the nozzle hole and the filler is not appropriate, the operating conditions may fluctuate. The natural porosity decreases, which may cause various troubles.

It is generally considered that the sintering property of the granular filler charged into the nozzle hole has a great effect on the natural opening and the non-opening. When the strength of the sintered layer becomes higher than the static pressure of the molten metal when the sliding nozzle is opened, holes are not opened. Conversely, if the sinterability of the filler is too low and sintering does not proceed, the molten metal penetrates between the filler particles to form a strong solidified layer, and the strength of this solidified layer becomes higher than the static pressure of the molten metal. The hole is not opened. Therefore, it is necessary to maintain an appropriate relationship with not only the properties of the granular filler but also the static pressure of the molten metal.

[0007] When secondary refining such as vacuum degassing, which has recently become very popular, is applied to molten steel in a ladle, the temperature of the molten steel is increased, the molten steel is fluidized, the refining time is extended, and continuous casting is performed. The upper part of the granular filler filled in the nozzle hole is washed away due to the fluctuation of the waiting time for matching with the nozzle, the sinterability of the granular filler changes, the molten metal between the particles of the granular filler Are penetrated to form a thick and solid core-infiltrated solidified layer, which is a factor that causes a decrease in the natural opening rate when the molten metal is to be discharged from the sliding nozzle. For example, a long time in a ladle
In the case of Ti, Nb-containing ferritic stainless steel that needs to be subjected to secondary refining, the spontaneous aperture may be about 40% to 50%.

If the hole is not spontaneously opened, an oxygen lance must be inserted from the lower nozzle, and oxygen gas must be blown to melt the sintered layer and the interstitial solidified layer over time, so-called oxygen opening. . Such oxygen opening is not only a very dangerous operation, but also lowers the yield due to the release (discarding) of the expensive molten metal, makes it impossible to secure the planned amount of molten metal, delays the molten metal discharge, and increases the temperature of the molten metal. The reduction in the temperature (outside of the control temperature) and the like have a great adverse effect on the processing operation of the next step, so that safety, quality and economic losses are very large.

An object of the present invention is to solve such a problem.

[0010]

According to the present invention, a mass brick mounted on a bottom opening of a molten metal container, a vertically penetrating nozzle hole provided in the mass brick, and the nozzle hole is filled. In the nozzle for tapping a molten metal container made of a granular filler, the angle θ between the inner wall surface of the nozzle hole and the horizontal is 90 ^° ± 8 ^°, and Cr ₂ O ₃ is used as a filler to be charged into the nozzle hole. The total amount of SiO ₂ is 50 to 70% by weight, the amount of Cr ₂ O ₃ is 30% by weight or more, and the balance is iron and A.
Disclosed is a tapping nozzle for a molten metal container, characterized by using a mixture of 1,1 and Mg oxides.

[0011]

1 shows an example in which a tapping nozzle according to the present invention is provided at the bottom of a ladle for molten steel. In FIG.
Reference numeral 1 denotes a ladle bottom substrate, and 2 denotes a ladle brick for the ladle floor. A mass brick 3 having a nozzle hole penetrating vertically is fitted into the opening of the bottom structure to form a nozzle hole in the ladle bottom. To form Filler 4 is loaded into this nozzle hole,
The nozzle hole is closed by the loading of the filler 4.

FIG. 2 schematically shows the shape of the mass brick 3. As shown in the figure, the mass brick 3 is a block having a cylindrical nozzle hole 5 in the center, and its outer shape has a shape matching the shape of the opening of the bottom structure of the ladle. In the example shown in the figure, the nozzle 5 has a constriction 6 in the middle, and at the boundary of the constriction 6, an upper portion forms an upper expanding portion 7 whose diameter increases as going upward, and a lower portion thereof forms a lower portion. A lower expanding portion 8 whose diameter increases as it goes down is formed.

After setting such a mass brick 3 in the opening at the bottom of the ladle, as shown in FIG. 1, an upper nozzle 9 is inserted from below, and the lower edge of the upper nozzle 9 is Support with. A hole having the same diameter as the lower end of the upper nozzle 9 is formed in the upper plate 10, and the upper nozzle 9 is fixedly supported by the outer edge of the hole of the upper plate 10 at a position where both holes communicate with each other. A lower plate 11 slidable left and right is attached to the lower surface of the upper plate 10. The lower plate 11 is also provided with a hole 12 having the same diameter as the upper plate 10, and when the hole 12 is slid to a position matching the hole of the upper plate 10, all the holes communicate.

The above is the part to be attached to the bottom of the ladle. At the time of tapping, the lower nozzle 13 is attached below the hole 12 of the lower plate 11. The lower nozzle 13 is detachable and is attached only during the tapping operation, and is removed at other times.

The holes 12 in the lower plate 11 are
When the filler 4 is loaded into the nozzle hole 5 in a state where it is not aligned with that of FIG. 0 (the state of FIG. 1), preparation for receiving the molten metal into the ladle is made, and the molten metal is injected in this state. Then, a sintered layer is formed on the upper layer of the filler 4.

In such a tapping device at the bottom of the ladle,
The type of the filler 4 and the shape of the nozzle hole 5 provided in the mass brick 3 were changed as described below and used for a ladle for refining stainless steel (a ladle set in a vacuum degassing apparatus).

Table 1 shows the typical composition of the filler 4 used. Each of A to F has an average particle size of 0.5 to 2.5 m.
m, and the amount of Cr ₂ O ₃ is increased in the order of A to E. The reason why the average particle size is set to 0.5 to 2.5 mm is that when the average particle size exceeds 2.5 mm, the molten metal easily penetrates between the particles when the molten metal is received, and when the average particle size is less than 0.5 mm, the molten metal is formed by the heat of the molten metal. This is because the sintered layer to be formed tends to be thick.

[0018]

[Table 1]

With respect to the shape of the nozzle hole 5, the angle θ formed by the inner wall of the nozzle hole 5 and the horizontal direction was changed as shown in FIG. Is the angle formed by the inner wall of the nozzle hole 5 above the constricted portion 6 with the horizontal direction. An upper nozzle 9 is inserted below the constricted portion 6, and the angle formed by the inner wall surface of the upper nozzle 9 and the horizontal direction is equal to or larger than θ. That is, the mass brick 3
The upper nozzle 9 having an angle equal to or larger than the angle θ (the angle formed with the horizontal direction) was used in accordance with the angle θ of the nozzle hole 5 formed in the nozzle hole 5 for practical use.

For the fillers A to F in Table 1, θ is 8
The molten stainless steel was subjected to vacuum degassing using a ladle equipped with a mass brick having nozzle holes of 0, 82, 90, and 98 ^° . When the molten steel was received in each ladle, the temperature of the molten steel was 1700 ° C. to 1850 ° C., and the time for storing the molten steel was 60 to 200 minutes. As the stainless steel to be treated, a Ti, Nb-added stainless steel molten steel, which is difficult to spontaneously open, was particularly selected. Hot water from each ladle was supplied to a tundish of a continuous casting apparatus with the lower nozzle 13 of FIG. 1 attached. FIG. 4 shows the natural aperture ratio at that time. The plots in FIG. 4 are all the average values of N = 100 in the ferritic steels containing Ti and Nb.

As can be seen from the results in FIG. 4, the natural opening ratio of 100% was achieved because the three types of fillers C, D and E in Table 1 were used for mass bricks of θ = 82, 90 and 98 ^° . Is used only when the same C, D, and E fillers are used.
^{In the case of o} , the natural aperture ratio was reduced to about 80%. Also θ
= 82, 90, 98 ^° , the natural opening ratio is at most 80% for the fillers A and B having a low Cr ₂ O ₃ content, and θ for the filler F not containing Cr ₂ O _3. = 82,
Even at 90 and 98 ^° , about half did not spontaneously open. Also,
Although the aperture ratio tends to increase as θ increases, when the filler is low in Cr ₂ O ₃ , when θ is large (θ = 9
In ^8o ), the aperture ratio tends to decrease. Note that the nozzle hole angle θ: 82 to 98 ^° can also be expressed as 90 ^° ± 8 ^° . If exceeding 90 ^o is that facing down spread.

As described above, by setting the θ to 82 to 98 ^° and using a filler containing Cr ₂ O _{3 in an amount} of 30% by weight or more, even after a long processing and storage of 200 minutes, , It is clear that there is a natural opening with a probability of almost 100%.

[0023] Incidentally, although filler Table 1 reduces the amount of SiO ₂ in accordance with the greater the amount of Cr ₂ O _3, Cr ₂
Based on the fact that good results were obtained for C, D and E in which the amount of O ₃ + SiO ₂ was 50 to 70%, it was found that Cr ₂ O ₃ + Si
It is desirable that the amount of O ₂ be 50 to 70% by weight and the amount of Cr ₂ O ₃ be 30% by weight or more. The balance is Fe ₂ O ₃ , Mg
O, Al ₂ O _{3 and the} like. This filler is in a state where a material having a melting point higher and a material having a lower melting point than the temperature of the molten steel to be contained are mixed. It is conceivable that this filler does not cause the bridging phenomenon of the particulate matter in the nozzle hole due to the thermal expansion seen in silica sand or the like.

In the above embodiment, the ladle used for stainless steel refining is a molten metal container, but it is considered that the same results can be obtained for other molten metal containers.

At the time of tapping, when the holes 12 of the lower plate 11 to which the lower nozzles 13 are attached are aligned with the holes of the upper plate 10, even when the holes are naturally opened, the tapping is slightly delayed from the time of the alignment. Begin. That is,
First, the molten metal is discharged after a few seconds after the particulate filler has naturally fallen well. This means that no bridging or solidification layer was formed in the lower granular material, and a sintering layer of an appropriate thickness was formed only in the upper layer of the filler, and the filler below this sintered layer was dropped. After this, the bridge of the sintered layer is formed for a while, but it may be considered that the tapping starts when the sintered layer bridge is broken by the static pressure of the molten metal. On the other hand, if the sintered layer becomes too thick, or if the molten metal penetrates the filler to form a solidified layer, it is presumed that the molten metal is not broken by static pressure and the clogging occurs.

As can be seen from the above-described embodiment, according to the present invention, the spontaneous porosity is greatly increased even after tapping for a long time of secondary refining of 200 minutes or for tapping for a short time of about 60 minutes. There is almost no need to change the packing material due to changes in refining and storage time, since a significant improvement can be obtained. Further, according to the present invention, the natural porosity can be greatly improved with respect to the ferrite stainless steel containing Ti and Nb having a low porosity. This means that carbon steel, S
In US304 and SUS430, it means that a high spontaneous opening ratio can be obtained. Therefore, there is almost no need to change the filler corresponding to the type of steel.

[0027]

As described above, according to the present invention,
It is possible to provide a pouring nozzle that naturally opens at a high opening ratio even when operating conditions fluctuate. Therefore, it is possible to reduce the number of dangerous and poorly operable oxygen drilling operations and to improve the quality.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an embodiment in which a pouring nozzle according to the present invention is applied to a molten steel ladle.

FIG. 2 is a perspective view showing an example of a mass brick to be attached to an opening at the bottom of the container.

FIG. 3 is a view for explaining an angle of an inner wall surface of a nozzle hole formed to penetrate vertically in a central portion of a mass brick mounted on an opening of a container bottom.

FIG. 4 is a diagram showing the relationship between the angle θ of the inner wall surface of the nozzle hole, the type of filler, and the natural aperture ratio.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container bottom plate 2 Container brick 3 Mass brick attached to opening of container bottom 4 Filler loaded in nozzle hole 5 Vertically penetrating nozzle hole provided in mass brick 6 Constriction of nozzle hole 9 Downward of nozzle hole Nozzle inserted from above 10 Upper plate supporting upper nozzle 11 Lower plate sliding to upper nozzle

Claims (3)

[Claims] 1. A molten metal container comprising a mass brick attached to a bottom opening of a molten metal container, a vertically penetrating nozzle hole provided in the mass brick, and a granular filler filled in the nozzle hole. The angle θ between the inner wall surface of the nozzle hole and the horizontal surface is 90 ^° ± 8 ^°, and the total amount of Cr ₂ O ₃ and SiO ₂ is 50 to 70 wt. A molten metal tapping nozzle for a molten metal container, comprising a mixture containing 30% by weight or more of Cr ₂ O ₃ and the balance consisting of oxides of iron, Al and Mg. 2. The tapping nozzle according to claim 1, wherein the molten metal container is a ladle of molten steel. 3. A vertically penetrating nozzle hole provided in a mass brick has a constriction in the middle thereof, and an upper nozzle is mounted below the constriction, and an angle formed by an inner wall surface of the upper nozzle and the horizontal is horizontal. 3. The tapping nozzle according to claim 1, wherein the angle of the nozzle hole in the upper part of the nozzle is equal to or greater than the angle θ.