JP3344929B2 - Nozzle for continuous casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting nozzle having excellent durability, particularly a long nozzle or an air seal pipe used for continuous casting.

[0002]

2. Description of the Related Art Conventionally, a long nozzle or an air seal pipe has been used for discharging molten metal from a ladle into a tundish in a continuous casting operation. As is well known, this long nozzle or air seal pipe is connected to the bottom of the ladle with a fixing jig or the like, and the lower end is immersed in the molten metal in the tundish without oxidizing the molten metal in the ladle. It is to be injected into. As a material for the long nozzle or the air seal pipe, generally, fused silica-containing alumina-graphite or non-silica alumina-graphite (Japanese Patent No. 1322795)
Or a zirconia-graphite material alone or in combination.

[0003] During casting, a heat insulating material is introduced into the tundish in order to keep the molten metal (molten steel) warm and prevent the molten metal surface in the tundish from being oxidized. In this insulation,
Materials composed of components such as rice husks, Al ₂ O ₃ , SiO ₂ , MgO, and CaO are used, and these are selectively used depending on steel types and use conditions. This heat insulating material floats on the surface of the molten metal (molten steel) in the tundish, and erodes the long nozzle violently due to the synergistic attack with the molten metal (molten steel) at the part in contact with the long nozzle and the air seal pipe. This greatly affected the life of the air seal pipe.

Further, when the same tundish is used and only a large number of ladles are exchanged for continuous casting, slag in the ladle is mixed into the tundish at the end of pouring molten steel in the ladle into the tundish. In some cases, the mixed slag accelerates erosion of the long nozzle in addition to the heat insulating material. Conventionally, the material of the long nozzle or the air seal pipe that hits the surface of the molten metal (molten steel) in the tundish is properly used depending on the heat insulating material, the component of the slag, the basicity, and the like so that the material is not worn as much as possible. Generally, as described above, Al ₂ O ₃ —SiO ₂ —C based material, Al ₂ O ₃ —C (non-silica) based material, ZrO ₂ —C
Although the system has been used, erosion is still severe even if complicated use is performed as described above, and conversely, if the countermeasures against only slag are taken, the overall strength of the long nozzle and the air seal pipe will be reduced. There was a drawback that the durability was poor overall, such as the occurrence of cracks and cracks. From a structural point of view, as shown in FIGS. 2 to 4, a nozzle structure in which the whole is made of a single material a (FIG. 2), a nozzle structure in which a slag line portion b is sandwiched by a main body a (FIG. 3), or In the case of a two-layer structure a, b, a nozzle structure (see FIG. 4, Patent No. 1322795) has been proposed. However, even if such structural measures are devised, the fundamental solution has not yet been achieved. is there.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a continuous casting nozzle having excellent durability used in continuous casting, and in particular, to discharge molten metal from a ladle to a tundish in a continuous casting operation. The long-nozzle used for the purpose of preventing the oxidation by air and the splash of the molten metal falling into the tundish or the slag line of the air seal pipe used for the purpose of preventing abrasion of the material and significantly improving the durability. The present invention relates to a continuous casting nozzle such as a long nozzle or an air seal pipe.

According to the present invention, a slag line portion of a continuous casting nozzle immersed in a molten metal has a multilayer structure, and the outermost layer of the multilayer structure is formed of Mg.
O: 50-80 wt%, C: 10-40 wt%, Si
_{C: 1~10wt%, B 4 C} : containing 110 wt.% Magnesia - the inner hole side of the superior continuous casting nozzle 2 slag line portion tolerability, characterized in that is constituted by graphite-based materials Material 3. The continuous casting nozzle according to the above-mentioned item 1, wherein the multi-layer structure of the slag line portion is three or more, and the outermost layer is made of alumina-graphite (containing fused silica or non-silica) or zirconia-graphite. 3. The nozzle for continuous casting according to any one of the above 1 or 2, wherein materials having different thermal expansions are sequentially arranged toward the inner hole side so as to reduce generated thermal stress. The continuous casting nozzle according to any one of the above items 1 to 3, wherein the nozzle is a long nozzle or an air seal pipe discharged from a pan into a tundish.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a slag line portion of a continuous casting nozzle immersed in a molten metal has a multilayer structure, and the outermost layer of the multilayer structure is made of a magnesia-graphite material. As shown in FIG. 2 or FIG. 3, it is conceivable that the entire nozzle body or the entire slag line portion is made of a magnesia-graphite material (see Japanese Patent Publication No. 6-65427 in a known example). Since the system material itself is low in strength and has a larger coefficient of thermal expansion than the alumina-graphite material, the spalling resistance is inferior and cracks and cracks are likely to occur when receiving steel. is not. For this reason, the outermost layer of the multilayer structure is made of a magnesia-graphite material, and the material on the inner hole side is made of an alumina-graphite (containing fused silica or non-silica) or zirconia-graphite material. By improving the spalling property, the durability of a continuous casting nozzle, such as a long nozzle or an air seal pipe, is generally improved.

Although it is not conceivable that the material on the inner hole side is made of a magnesia-graphite material, such a structure is not preferable. This is because, when the magnesia-graphite material is used as the material on the inner hole side, for example, the magnesia-graphite material layer having a large thermal expansion expands by receiving heat during casting and is provided thereon. This is because an outer layer made of an alumina-graphite or zirconia-graphite material having low thermal expansion is cracked. Therefore, the outermost layer of the multilayer structure can absorb or reduce the thermal stress generated by the magnesia-graphite material, and the alumina-graphite material having different thermal expansion toward the inner hole side, that is, the thermal expansion gradually decreases toward the inner hole side. It is desirable that the system or the zirconia-graphite material be, for example, two or more layers (three or more layers in total including the outermost layer), and these are selected or combined and arranged. As a result, the generation and cracking of the continuous casting nozzle during steel receiving or casting can be effectively prevented.

The material of the outermost layer is MgO: 50-80 wt.
%, C: 10 to 40 wt%, SiC: 1 to 10 wt%,
Magnesia containing B ₄ C1~10wt% as a main component - it is desirable to configure in graphite-based material. As described above, MgO is 50 to 80 wt%, but if it is less than 50 wt%, the corrosion resistance to molten steel is insufficient, and the alumina-graphite or zirconia-
This is because there is no significant difference in corrosion resistance as compared with graphite-based materials. Conversely, if MgO exceeds 80 wt%,
The coefficient of thermal expansion becomes too high, and there is a limit even if the structure is devised so that the thermal stress generated in the magnesia-graphite material can be absorbed or reduced as described above, and the spalling resistance is reduced, This is because it is not preferable.

[0010] C is 10 to 40 wt%, C is 10 wt%
If it is less than wt%, the spalling resistance is significantly reduced, and if it exceeds 40 wt%, the corrosion resistance to molten steel is reduced. Also, SiC: 1 to 10 wt.
% Is for improving the oxidation resistance. 1w
If it is less than t% or more than 10 wt%, the effect is not obtained.
Further, the addition of 1 to 10 wt% of B ₄ C is for the purpose of preventing the oxidation of the material and improving the strength. However, if the content is less than 1 wt% or more than 10 wt%, the effect is lost.
This range was set.

FIG. 1 shows an example of the nozzle structure of the present invention. FIG. 1 shows a three-layer structure, in which a indicates the nozzle body and the inner hole side, b indicates an intermediate layer located in the slag line portion, and c indicates a magnesia-graphite material located in the slag line portion. Shows the outermost layer. Needless to say, such a nozzle structure of the present invention can be widely applied not only to a long nozzle or an air seal pipe but also to a continuous casting nozzle having an attack by slag floating on a molten metal.

[0012]

Next, an embodiment will be described. Material a shown in Table 1,
In addition to selecting b and c, a long nozzle shape as shown in FIG. 1 was formed using CIP. This was further fired at 900 ° C. to 1100 ° C. in a reducing atmosphere to obtain a long nozzle. The apparent porosity, bulk specific gravity, bending strength, and coefficient of thermal expansion (10
(At 00 ° C.) is as shown in Table 1. Thus, the outermost layer c in the embodiment is a magnesia-graphite material. This magnesia-graphite material has high resistance to slag as described later,
It can be seen that the bending strength is lower and the coefficient of thermal expansion is considerably higher than that of the material No. Next, using this long nozzle, low carbon steel was cast using a tundish (using an actual machine) into which ladle (ladle) slag having a basicity (CaO / SiO ₂ ) of 1.7 was mixed. Table 2 shows the results.

[0013]

[Table 1]

[0014]

Comparative Example Next, a comparative example will be described. As in the example, materials a and b shown in Table 1 were selected, and a long nozzle shape as shown in FIG. 3 was formed using CIP. This was further fired at 900 ° C. to 1100 ° C. in a reducing atmosphere to obtain a long nozzle. As is clear from Table 1, the outermost layer of the comparative example is an alumina-graphite system.
Next, using this long nozzle, the basicity (CaO / S
Low carbon steel was cast using a tundish mixed with iodine (ladder) slag of iO ₂ ) 1.7. The results are shown in Table 2 as in the example.

[0015]

[Table 2]

As is clear from Table 2, in the comparative example in which the outermost layer is made of alumina-graphite, the service life is 600-600.
In contrast to the case of 650 minutes, in the embodiment of the present invention in which the outermost layer c is a magnesia-graphite material, the service life is 800 to 8 minutes.
It was 50 minutes, and it was confirmed that the life was improved by about 30% in the present invention.

As described above, the slag line portion of the continuous casting nozzle immersed in the molten metal has a multilayer structure, and the outermost layer of the multilayer structure is made of a magnesia-graphite material. 50-80 wt%, C: 10
40wt%, SiC: 1~10wt%, B 4 C1~10
By using a magnesia-graphite-based material containing wt.%, it is possible to prevent wear due to slag, and at the same time, to use a high-strength material as the material on the inner hole side, and to arrange alumina so as to absorb or reduce thermal stress. -The service life of the long nozzle or the air seal pipe is remarkably increased by using graphite (containing fused silica or non-silica) or zirconia-graphite material. In the above, the present invention has been described based on the example of the long nozzle, but this is merely an example, and various changes can be made without departing from the gist of the present invention. The present invention includes all of them.

[0018]

According to the present invention, a continuous casting nozzle used for continuous casting, particularly a long nozzle or a slag of an air seal pipe used for discharging molten metal from a ladle to a tundish in a continuous casting operation. The slag of the material hitting the line was prevented from being worn and the durability of the long nozzle or the air seal pipe was significantly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a long nozzle showing an example of the present invention.

FIG. 2 is an explanatory sectional view of a conventional long nozzle having an integral structure in which a main body and a slag line portion are made of the same material.

FIG. 3 is an explanatory cross-sectional view of a conventional long nozzle as a comparative example.

FIG. 4 is an explanatory cross-sectional view of a conventional long nozzle in which a refractory material of another material is provided in a portion corresponding to a slag line at a lower portion of a main body.

[Explanation of symbols]

a: Refractory material on the nozzle body or inner hole side b: Intermediate layer located on slag line part c: Outermost layer of magnesia-graphite material located on slag line part

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoyuki Sugiyama 1st Minamifuji, Ogakie-cho, Kariya-shi, Aichi Pref. Toshiba Ceramics Co., Ltd. Kariya Works (56) References JP-A-57-1550 (JP, A) JP-A-9-277031 (JP, A) JP-A-7-51821 (JP, A) JP-A-61-245951 (JP, A A) JP-A-56-169177 (JP, A) JP-A-57-196764 (JP, A) JP-A-60-6256 (JP, A) JP-A-60-166259 (JP, A) JP-A Sho 57 −52553 (JP, A) Fully open 60-186953 (JP, U) Fully open 60-186952 (JP, U) Really open 7-3850 (JP, U) (58) Field surveyed (Int.Cl) . ^7, DB name) B22D 11/10 320 B22D 11/10 330 B22D 41/54

Claims (4)

(57) [Claims] 1. A slag line portion of a continuous casting nozzle immersed in a molten metal has a multilayer structure, and the outermost layer of the multilayer structure has MgO: 50 to 80 wt%, C: 10 to 40 wt.
_{%, SiC: 1~10wt%, B} 4 C: 1~10wt%
A continuous casting nozzle excellent in durability, comprising a magnesia-graphite material containing 2. The continuous casting nozzle according to claim 1, wherein the material of the inner hole side of the slag line portion is made of an alumina-graphite (containing fused silica or non-silica) or zirconia-graphite material. 3. The multi-layer structure of the slag line portion has three or more layers, and materials having different thermal expansions are sequentially arranged toward the inner hole side so as to reduce thermal stress generated in the outermost layer. Item 3. The continuous casting nozzle according to any one of Items 1 or 2. 4. The continuous casting nozzle according to claim 1, wherein the nozzle is a long nozzle or an air seal pipe for discharging the molten metal from a ladle into a tundish.