JP2004136367A - JOINT STRUCTURE FOR CONTINUOUS CASTING NOZZLE HAVING CARBON CONTAINING CaO BASED REFRACTORY LAYER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent welding of a joining part to a nozzle body to be joined and abnormal erosion nearby, while the nozzle body is situated in the upper part of a continuous casting nozzle in which a clinker containing CaO as mineral phases and a carbon-containing CaO based refractory are arranged at least on the inner hole peripheral wall surface that comes in contact with molten steel, for the purpose of preventing precipitation from depositing on that surface. <P>SOLUTION: This is a joint structure between the upper end of a casting immersion nozzle 1 (nozzle 1) and the lower end of the nozzle body situated above the nozzle 1, in which the clinker containing CaO as mineral phases and the carbon-containing CaO based refractory are arranged at least on the wall surface of the inner hole 3 coming into contact with molten steel as a carbon-containing CaO based refractory layer. A recess 5 is provided on the upper end of the nozzle 1, a refractory ring 6 is fitted to the recess and fixed with a refractory adhesive. Upward from the upper end of the carbon-containing CaO based refractory layer of the nozzle 1, there are arrayed the refractory ring 6, a joint material 7 for the joining part, and the nozzle body 8 as an object to be jointed, in this order. In this array, each refractory to be joined is composed of materials having no reactivity with each other. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a joining structure of a continuous casting nozzle used for transferring molten steel from a ladle to a tundish or from a tundish to a mold in continuous casting of molten steel.

Conventionally, continuous casting nozzles have been required to have both corrosion resistance and spalling resistance, have long-term durability, and maintain the cleanliness of molten steel. Alumina-carbon materials, zirconia-carbon materials, and the like are often used as materials that are excellent in resistance to erosion and abrasion against steel and slag, and can withstand thermal shock and mechanical shock.

However, in the case of continuous casting of aluminum-killed steel or aluminum-silicon-killed steel, non-metallic inclusions such as alumina precipitated from molten steel adhere to the nozzle inner wall, gradually narrowing the nozzle hole and eventually closing. May occur.

For example, Al ₂ O ₃ + C-containing refractory immersion nozzles have a property that deposits easily adhere to the inner peripheral surface of the molten metal flowing portion of the nozzle hole through which the molten metal flows. Such deposits tend to adhere to a large temperature gradient on the inner wall surface of the non-immersed portion of the nozzle and to a portion where the flow rate of the molten metal decreases near the discharge port, and the deposits may make the casting operation difficult.

In addition, it is necessary to perform an operation of removing the deposits during casting, and the removed deposits are taken into the slab to become large inclusions, which deteriorates the quality of the slab. It is conceivable that the adhered precipitate contains αAl ₂ O ₃ as a main component, and Al ₂ O ₃ contained in the molten metal as a deoxidation product is deposited and deposited on the inner wall of the nozzle. The deposition of the precipitate on the inner wall of the immersion nozzle is particularly observed in continuous casting of aluminum-killed steel.

As a countermeasure to reduce the adhesion of precipitates in such a continuous casting nozzle, it is common practice to blow out an inert gas onto the inner peripheral surface of the nozzle or to arrange a material to which alumina is unlikely to adhere on the inner peripheral surface. Has been done.

As the latter means for reducing the deposits of precipitates in the continuous casting nozzle, a CaO-based refractory, which is effective for cleaning steel by adsorbing nonmetallic inclusions in molten steel into the inner hole of the casting nozzle. Some things are used. For example, Patent Literature 1 discloses an example in which dolomite and lime-like graphite is used as a lime-carbonaceous refractory in an inner hole, and Patent Literature 2 discloses a nozzle hole wall and a discharge port. It is disclosed that the material of the outlet is changed from conventional Al ₂ O ₃ —C (alumina graphite) to ZrO ₂ —CaO—C, to which molten steel precipitates hardly adhere.

Patent Literature 3 discloses a nozzle in which at least a part of the inside of a nozzle is made of a refractory made of droma and graphite. The doloma is a roasted dolomite and preferably contains at least 56.5% by weight of CaO and 41.5% by weight of MgO, so that the doloma removes soluble reactants that do not clog the nozzle. It is said that since it is produced, troubles due to clogging of deposits as seen in the refractory nozzle containing A1 ₂ O ₃ + C can be avoided.

When adopting the doloma / graphite refractory, the inner peripheral surface of the nozzle contacting the molten metal to be injected is made to be a doloma / graphite refractory, and the outer side where the injected molten metal does not come into contact, that is, a less expensive material for the so-called main body. Materials can be used. Even if a conventionally used refractory containing Al ₂ O ₃ + C is used as the main body material, the problem of nozzle clogging does not occur. Such a continuous casting nozzle using doloma / graphite is used for continuous casting of aluminum killed steel, and realizes casting with less nozzle clogging.
JP-A-61-531150 JP 2001-150109 A Japanese Unexamined Patent Publication No. Hei 11-506393

As described above, by employing the casting immersion nozzle in which the clinker containing CaO as a mineral phase and the carbon-containing CaO-based refractory containing carbon are arranged on at least the inner wall surface in contact with the molten steel, casting with less nozzle clogging is performed. be able to. However, CaO in this refractory reacts with Al ₂ O ₃ in the refractory constituting the nozzle body to be joined to generate a low-melting-point compound and is abnormally melted or fused to the joined intermediate nozzle. For this reason, the reuse rate of the nozzle is greatly reduced, and problems such as an increased risk of hot water leakage in operation are caused.

Therefore, although this continuous casting nozzle can be used in continuous casting of small-quantity production such as continuous casting of stainless steel, it can be used for casting a large amount of molten metal such as continuous casting of ordinary steel. Since the carbon-containing CaO-based refractory part is eroded therein and the refractory part in contact with the carbon-containing CaO-based refractory proceeds to form a eroded part, the life of the immersion nozzle is short, Equal productivity and costs could not be maintained.

The problem to be solved by the present invention is to prevent clinker containing CaO as a mineral phase and a carbon-containing CaO-based refractory containing carbon at least in contact with molten steel in order to prevent deposition of precipitates on the inner wall surface. An object of the present invention is to prevent fusion of a joint portion with a nozzle object to be joined located above the continuous casting nozzle arranged on the hole wall surface and prevent abnormal melting damage in the vicinity thereof.

According to the present invention, the erosion during the casting of the casting immersion nozzle is concentrated in a region very close to the nozzle upper surface or the surface to be joined with the joint material, and the erosion progresses. Is based on the fact that the phenomenon progressing simultaneously with both the carbon-containing CaO-based refractory disposed on the inner wall surface of the nozzle and the joined intermediate nozzle was confirmed.

That is, the specific invention of the present invention is a molten steel injection port of a casting immersion nozzle in which a clinker containing CaO as a mineral phase and a carbon-containing CaO-based refractory layer containing carbon are formed at least on a wall surface of an inner hole portion in contact with molten steel. In a continuous casting nozzle, the upper end of the nozzle and the lower end of the nozzle body to be welded located above the upper end of the nozzle are provided with a concave portion at the upper end of the casting immersion nozzle that is to be joined to the nozzle body to be welded. A refractory ring is fitted in the recess, and if necessary, fixed with a refractory adhesive, and upward from the upper end of the carbon-containing CaO-based refractory layer, if necessary, a refractory ring. The joint material is arranged in the order of the joint material and the nozzle body to be joined. In this arrangement, the refractories constituting the joining portion react with each other, and are combined with materials that do not generate low-melting-point materials.

The present invention provides a refractory ring made of a material that does not generate a low-melting-point material by reacting with a CaO component on a portion of the inner-hole wall surface of a casting nozzle in contact with a refractory having a carbon-containing CaO-based composition. In addition to the provision of a material that does not lower the melting point, the portions where different types of refractories are joined together are provided so as to prevent the molten metal from leaking due to exfoliation and abnormal melting of the joined portions and to prevent mutual fusion. Thereby, the function of preventing the nozzle clogging by the CaO-based refractory, the refractory ring, and the durability of the material of the nozzle body to be joined are not affected by each other, and each of them has a sufficient function. Can be demonstrated.

The inner wall surface of the casting nozzle contains CaO as a mineral phase such as dolomite carbon, lime carbon, magnesia lime carbon, lime dolomite carbon, and magnesia dolomite carbon. By using the carbon-containing CaO-based refractory as the refractory for the inner hole, the effect of preventing inclusions from being adhered can be exhibited. For example, in the case of a dolomite-carbonaceous refractory (CaO-MgO-C), 0.03 ≦ MgO / CaO ≦ 0.05 ≦ C / (CaO + MgO + C) ≦ 0.4 and the sum of CaO + MgO + C Is preferably 90% by mass or more. Clinkers containing CaO as a mineral phase include calcia clinker, calcia-magnesia clinker including dolomite clinker, and the like.

(4) In the case of the CaO-MgO-C-containing refractory, the lower the MgO / CaO ratio, the higher the proportion of the CaO phase, so that the effect of preventing deposition of precipitates can be improved. When MgO / CaO is 32 or less, the CaO phase can be reliably present in the refractory, and the effect of preventing the deposition of deposits can be exhibited. It is more preferable that MgO / CaO ≦ 1. It is more preferable that MgO / CaO ≦ 0.72.

MgO phase of the other hand CaO-MgO-C refractories containing in the order to create a relatively high melting point reaction products with A1 ₂ O ₃ in the molten metal, to suppress the corrosion of the nozzle lumen wall refractories It has the function of Against _A1 2 _{O 3} in the molten metal, in order to perform this function, it is necessary to MgO / CaO ≧ 0.03. It is more preferable that MgO / CaO ≧ 0.2. More preferably, MgO / CaO ≧ 0.42.

That is, in producing a CaO-MgO-C-containing refractory, dolomite is usually used as a CaO-MgO source. The MgO / CaO ratio in the refractory manufactured using dolomite will usually be in the range of 0.49 to 1, but within this range, a preferable MgO / CaO ratio can be realized.

ＣC in the CaO—MgO—C-containing refractory has a function of being excellent in heat spalling resistance due to the high thermal conductivity of C. In order to exhibit this function, C / (CaO + MgO + C) needs to be 0.05 or more. 0.15 is more preferable. However, if the C content is too high, the loss due to oxidation of C increases, so C / (CaO + MgO + C) ≦ 0.4. More preferably, C / (CaO + MgO + C) ≦ 0.35.

(4) In the CaO-MgO-C-containing refractory, the total of CaO + MgO + C is 90% by mass or more. If the content of the impurities exceeds 10%, the fire resistance is reduced, and a low melting point material with the main substance of the refractory is easily formed, so that the characteristics as the inner pore of the present invention cannot be obtained. .

The crystal structure of the CaO-MgO-C-containing refractory is a mixture of a CaO phase and a MgO phase, and C exists in the form of a plate-like filling between grains of crystal grains in which CaO and MgO coexist. are doing. Why deposition is less of Al ₂ O ₃ precipitates with the material of the lumen wall nozzle is CaO-MgO-C refractories containing, it A1 ₂ O ₃ deposited from molten metal deposited on the hole inner wall surface of the nozzle time, and CaO phase and adhered A1 ₂ O ₃ in the refractory reacting to form a low-melting material, precipitate adhering to their presumably because going floating on molten metal again.

The shape of the CaO-MgO-C-containing refractory is as follows: the nozzle body 2 of the continuous casting nozzle shown in Fig. 4 and the CaO-MgO-C-containing refractory constituting the inner hole refractory 3; If a method in which the CaO-MgO-C-containing refractory (also referred to as refractory for inner hole portion) 3 is separately manufactured and inserted into the inside of the refractory (nozzle body) 2 constituting the outside from above is adopted, Manufacturing is easy and preferable. In this case, at the discharge port 11 at the lower end of the continuous casting nozzle, as shown in FIG. 4, the refractory (nozzle body) 2 which constitutes the outside in the molten metal flow path is exposed. Is not a problem because it was not so many. Also, at the same discharge port 11, a contact portion between the refractory (nozzle body) 2 and the refractory 3 for the inner hole, which constitute the outside, is exposed to the molten metal flow passage. Although the erosion of the refractory at the contact portion does not directly cause the invasion of outside air, in order to minimize the erosion, the refractory (nozzle body) 2 constituting the outside of the nozzle contains SiO _2. It is preferable to use an Al ₂ O ₃ + C-containing refractory having an amount of 5% by mass or less.

Next, the refractory ring reacts with CaO in the refractory used for the nozzle body to be joined located above the molten steel injection port and the inner wall surface of the casting nozzle and does not generate a low melting point substance. The main materials include zirconia-based and magnesia-based materials, and combinations of these include zirconia-magnesia-based, zirconia-carbon-based, magnesia-carbon-based, and zirconia-magnesia-carbon-based carbons. For example, it is made of a refractory material containing one or more of ZrO ₂ , MgO, and C. When an adhesive is used, it reacts with the nozzle body, the inner wall surface, the joint joint material, and the like. Use similar refractories to avoid any adverse effects. For example, in the case of a magnesia-based refractory adhesive, a non-aqueous magnesia mortar containing no water is particularly preferable.

As described above, when a part or all of the nozzle inner wall surface excluding the upper end of the nozzle is formed of the carbon-containing CaO-based refractory, a refractory ring arranged at the nozzle upper end of the nozzle inner wall surface is formed. the refractory, preferably a material as described above, when in contact with carbon-containing CaO-based refractory constituting the hole wall or body portion in the nozzle, CaO · _A1 2 _{O 3} or CaO · SiO ₂ or the like of the low It must be a refractory that does not form melting points.

That is, the main material of the refractory ring is made of one or more of zirconia-based and magnesia-based materials or a refractory containing carbon, and contains SiO ₂ or Al ₂ O ₃ which is present in addition to the main component. It is desirable to keep the rate as low as possible. In particular, there is a problem with a large amount of SiO _2, and the content thereof may be 5% by mass or less, preferably 3% by mass or less. In the case of A1 ₂ O ₃ , it is more preferably 10% by mass or less and 5% by mass or less.

For zirconia-based refractories, ZrO ₂ is preferably 90% by mass or more from the viewpoint of corrosion resistance. For zirconia-carbonaceous, ZrO ₂ is 70 to 85 mass%, C content is in the range of 15 to 30 wt%. This makes it possible to fully utilize the properties of each material to prevent fusion and erosion due to the reactivity with CaO contained in at least the inner hole portion in contact with the molten steel, thereby improving the adhesion without reacting with the nozzle to be joined. A stable and stable bonding structure can be obtained.

Magnesia-based refractory, MgO is preferred as the material of the refractory metallic ring in that it does not form _{A1 2 O 3, A1 2 O} 3 reacts with CaO compared to -SiO ₂ based low-melting compound. And MgO of 90 mass% or more with magnesia, other (including MgO · _Al 2 _{O 3)} in the range of 10 wt% _A1 2 _O 3, at least the inner bore thereof in contact with the molten steel a material containing _Cr 2 _{O 3,} etc. It can be used as long as it reacts with CaO in the refractory used for the part and does not reduce the melting. In magnesia carbon, MgO is preferably 70 to 80% by mass, and C is preferably 15 to 30% by mass. This makes it possible to fully utilize the properties of each material to prevent fusion and erosion due to the reactivity with CaO contained in the inner bore, and to maintain the adhesion without reacting with the nozzle body to be welded, thus ensuring stability. It becomes a joined structure.

In the refractory a composite of zirconia and _magnesia, if the ZrO ₂ + MgO ZrO 2 is 40 to 10% by weight, preferably 60 to 90 wt% _MgO, if the ZrO 2 + MgO + C, ZrO 2 is 10 to 20 wt%, MgO Is preferably 60 to 85% by mass, and C is preferably 5 to 15% by mass. As a result, the properties of each material can be fully utilized to prevent fusion and erosion due to reactivity with CaO contained in the refractory for the inner hole portion, and maintain adhesion without reacting with the nozzle body to be joined. A stable bonding structure is obtained.

The material of the refractory ring 6 in the above invention does not contain Al ₂ O ₃ as a main component, and contains as little impurities as possible of Al ₂ O ₃ and SiO ₂ . As described above, it is most preferable to select a material that does not cause erosion even when it comes into contact with the inner-hole-portion refractory 3 as the refractory ring 6. On the other hand, in the tundish in which the immersion nozzle 1 is installed, in order to prevent outside air from entering the molten metal passage 12, the upper end 24 of the immersion nozzle 1 prevents erosion of the joint surface 13 with the nozzle body 8 to be joined. It is most important to do it. Therefore, in the case where the refractory ring 6 is arranged in the same manner as in the above invention, the state shown in FIGS. 5A and 5B can be considered, and even if the refractory ring 6 and the refractory 3 for the inner hole are joined. Even if the erosion 25 as shown in FIG. 5A occurs on the surface 14, the invasion of outside air does not necessarily occur immediately due to the erosion. However, FIG. 5A is preferable in terms of the pressure-bonding holding structure at the joint surface 14 when erosion occurs in FIG. 5B.

The fifth invention of the present invention has been made based on the above findings, and as shown in FIGS. 1 and 2, a part or all of the inner peripheral surface of the nozzle except for the upper end of the nozzle is made of a carbon-containing CaO-based refractory. The refractory ring 6 is disposed at the upper end of the nozzle on the inner peripheral surface of the nozzle. As a result of disposing the refractory ring 6, the refractory 3 for the inner hole of the immersion nozzle 1 does not contact the lower end of the nozzle body 8 to be joined. No erosion of the refractory occurs at the joint surface 13.

In the fifth invention, since the material of the refractory ring 6 is relaxed, a low-melting substance is formed between the refractory ring 6 and the adjacent refractory 3 for the inner hole depending on the selection of the refractory ring material. Erosion of the refractory may progress on the surface. However, as shown in FIG. 5A, even if the erosion progresses to form the erosion 25 as long as the erosion is not extreme, the surface that communicates with the outside air, that is, the upper surface of the refractory ring 6 and the nozzle to be joined are formed. If the contact surface with the body 8 is sound, the molten metal flow passage 12 does not come into contact with the outside air.

The material of the refractory ring 6 in the fifth invention includes MgO, MgO + Al ₂ O ₃ , MgO + Al ₂ O ₃ MgO spinel, MgO + Cr ₂ O ₃ , MgO + Al ₂ O ₃ + Al ₂ O ₃ MgO subinel, Al ₂ O ₃ + Al It contains ₂ O ₃ MgO _{spinel, Al 2 O 3 + Cr 2} O 3, MgO + C, MgO + Al 2 O 3 + C, Al 2 O 3 + C, ZrO 2 + C, one of Al ₂ O 3 MgO spinel + C 90 wt% or more It is preferable to select one. The above materials include those containing Al ₂ O ₃ as a main component. Al ₂ O ₃ forms a low-melting substance in contact with the CaO—MgO—C-containing refractory 3, but the melting point of the refractory is not so large. 1 does not lead to melting damage that would shorten the life of the battery. Therefore, any of the above refractories does not cause erosion enough to reduce the life of the immersion nozzle 1 due to the reaction with the CaO-MgO-C-containing refractory 3 at the temperature at the time of continuous casting of steel. This is effective as a refractory material of the product ring 6. The concentration of impurities other than the main components is 10% by mass or less. If the content of impurities exceeds 10%, fire resistance is reduced, and it becomes easy to form a low-melting substance with a main substance of the refractory, so that characteristics as the refractory ring 6 of the present invention cannot be obtained. It is.

A high content of SiO _{2 in} the material of the refractory ring 6 is not preferable because CaO.SiO ₂ having a low melting point is formed on the joint surface 14 with the refractory 3 for the inner hole. Therefore, it is preferable that the content of SiO ₂ in the refractory ring 6 is 5% by mass or less. More preferably, the SiO ₂ content is 3% by mass or less.

The refractory ring 6 has, as its form, an outer diameter a and an inner diameter b at the joint surface with the upper part, an outer diameter c at the lower part of the upper connection target nozzle body 8 at the joint part, and an inner diameter d. Let d <a <c, b> d. This is because the difference in the width and thickness of the refractory ring 6 (a / 2 / b / 2) is smaller than the difference in the joining surface width and the thickness of the joining target nozzle body 8 (c / 2 and d / 2). Since the thickness of the product ring 6 is located within the range of the thickness of the nozzle body 8 to be welded, even when the nozzle body 8 to be welded is eccentric with respect to the refractory ring 6, the ring made of the refractory material is cast during molten steel casting. Air suction from the set joint can be suppressed, and deterioration of steel quality can be suppressed.

The refractory ring 6 has an outer diameter a, an inner diameter b, an outer diameter a ', and an inner diameter b'. Assuming that the outer diameter of the upper end face of the carbon-containing CaO-based refractory layer which is 3 is e and the inner diameter is f, the outer diameter can be a ≧ a ′> e and the inner diameter can be b> b ′ = f. . This is because the outer diameters a and a 'of the refractory ring 6 are larger than the outer diameter e of the inner hole refractory 3, so that even if the inner hole refractory 3 is lost due to melting, the refractory The falling off of the ring 6 can be prevented.

When the refractory ring 6 has an outer diameter of the joint surface with the upper side of a, an inner diameter of b, and an outer diameter of the fitted lower end surface of a ′ and an inner diameter of b ′, a> a ′, b ≧ b If the outer peripheral wall surface is provided with a taper of ', the filling property of the refractory adhesive at the time of setting the refractory ring 6 is improved, and joint erosion and air suction from the joint portion can be further suppressed.

(4) The thickness of the refractory ring 6 itself is not particularly limited, and a ring having sufficient strength and durability capable of suppressing wear of the inner wall surface may be fitted.

Further, when a joint joint material 7 located above the molten steel injection port of the casting nozzle 1 is used, carbon is used as an alumina-based material, an alumina-silica-based material, a magnesia-based material, or the like that forms the nozzle body 8 to be joined. Alumina, alumina-silica, zirconia, magnesia-based, non-reactive to the lower end made of refractory material, containing refractories containing carbon in these materials Can be used as That is, the joint joint material 7 serves to prevent air from entering from the joint surface with each refractory to be joined and leakage due to molten steel entry. The joint material 7 is interposed between the nozzle body 8 to be welded and the immersion nozzle 1, is interposed in a compressed state while being sandwiched by high pressure, and is made of a combination of materials that do not react with the nozzle body 8 to be welded positioned above. Think and apply.

As an example of the joint material, in the case of magnesia, magnesia is applied in an amount of 60 to 90% by mass, and the remaining material such as clay, frit and carbon black is applied in an amount of 10 to 30% by mass. It is not suitable as a joint joint material 7 because the amount of auxiliary materials is too large and the fire resistance is poor. On the other hand, when the content of magnesia exceeds 90% by mass, the amount of the auxiliary material becomes too small, and the plasticity and sealing property during hot work are deteriorated.

In the case of an alumina-based material, 60 to 90% by mass of alumina and the remaining material such as clay, frit, and carbon black are applied in a range of 10 to 30% by mass. It is unsuitable as a joint joint material 7 because it becomes too much and has poor fire resistance. On the other hand, if the amount of alumina exceeds 90% by mass, the amount of the auxiliary material is reduced, and the plasticity and sealing property during hot work are deteriorated.

This prevents the materials of the nozzle body 8 to be joined and the refractory ring 6 from reacting with each other, thereby preventing fusion and preventing exfoliation and wear which cause abnormal melting. Needless to say, the same effect can be obtained with other listed main components.

The nozzle body 2 and the slag line portion 4 are mainly made of alumina carbonaceous material, zirconia carbonaceous material, zirconia lime carbonaceous material, and alumina A system such as zirconia-carbon is used. The composition is not particularly limited, and those generally used conventionally can be applied. For example, in a zirconia-carbonaceous system, 10 to 30% by mass of carbon and 90 to 70% by mass of zirconia are used. Things can be used.

The nozzle body 8 to be joined refers to a lower nozzle, an intermediate nozzle, a sliding nozzle lower plate, a ladle tapping nozzle, and the like, and the above-mentioned alumina, alumina-silica, magnesia or a carbon component as a refractory. What is included is used. Furthermore, calcia or those containing a carbon component can also be used for the inner wall portion of the inner hole portion in contact with the molten steel in consideration of compatibility with the material of the nozzle body 8 to be joined.

The nozzle for continuous casting of the present invention exhibits the best effect when used as a dipping nozzle 1 connected to a dandysh, but is not limited to this application. The same effect can be obtained even when used as a continuous casting nozzle when metal is poured into a dandysh.

By using a combination of joints using the refractory ring 6 of the present invention, even when a carbon-containing CaO-based refractory is used, it is possible to prevent hot water leakage due to peeling of the joint and abnormal melting, and to make a connection with other refractories to be joined. It exhibits the effect of preventing fusion, and can also make full use of the characteristics of the refractory at each point in the durability of the joint.

Also, even in the use in multiple casting, the quality can be improved and maintained in the steel material production and stable operation can be continued without causing nozzle clogging.

Hereinafter, the best mode for carrying out the present invention will be described with reference to examples.

As shown in FIG. 1, the immersion nozzle 1 of the present invention includes a tundish 20 in which an upper nozzle 30 and a fixed plate, a moving plate, and a sliding nozzle body 40 including a fixed plate, and an intermediate nozzle 8 as a nozzle body to be joined. It is mounted via a joint structure having a refractory ring 6 above the immersion nozzle 1 and a joint joint 7 to be joined thereto.

FIG. 2 is an exploded sectional view showing the immersion nozzle 1 of the present invention including the upper portion of the nozzle body 8 to be joined. (A) shows the immersion nozzle 1 of the present invention, 2 is a nozzle body, 3 is a refractory for an inner hole portion, 4 is a slag line portion, 5 is a concave portion provided in a molten steel injection portion, and 6 is a concave portion 5. And a refractory ring fitted to the intermediate nozzle 8 as a nozzle object to be joined by a joint joint material 7. (B) shows a cross section of the intermediate nozzle 8, (c) shows a cross section of the joint joint material 7, and (d) shows a refractory ring 6.

The refractory ring 6 has an outer diameter a 'at the lower end fitted into the recess 5 equal to the outer diameter a at the upper end on the upper joint joint material 7 side, or the refractory ring 6 is fitted. In order to improve the filling of the adhesive 9 at the time, the difference g is slightly small. The outer diameter a 'at the lower end of the refractory ring 6 is larger than the outer diameter e at the upper end face of the refractory layer of the inner hole refractory 3. The inner diameter b is larger than the inner diameter b 'at the lower end, and the inner diameter f and the inner diameter b' of the upper end face of the refractory layer of the inner hole refractory 3 are the same, and the whole is a wall surface inclined in the axial direction. The joint portion joint material 7 may have an outer diameter larger than the outer diameter c of the joint surface of the intermediate nozzle 8, and the inner diameter may be equal to the inner diameter d of the joint surface of the intermediate nozzle 8. The refractory ring 6 fitted in the recess 5 of the nozzle body 2 is joined to the intermediate nozzle 8 via a joint joint 7 and has a difference in width and thickness of the refractory ring 6 (two-half). b) is within a range smaller than the thickness difference of the joint surface width of the intermediate nozzle 8 (d of c / 2 / d).

The shape of the refractory 3 for the inner hole portion includes a refractory material forming the nozzle body 2 of the continuous casting nozzle 1 and a refractory material containing CaO-MgO-C forming the wall surface of the refractory material 3 for the inner hole portion. Are manufactured separately, and the method of inserting the refractory 3 for the inner hole portion from the upper side into the inside of the nozzle body 2 is preferable because the manufacturing is easy. In this case, at the discharge port 11 at the lower end of the nozzle for continuous casting, the refractory constituting the nozzle body 2 is exposed. However, there is no problem since deposits originally adhered not so much to this portion.

Further, at the same discharge port 11, a contact portion between the refractory constituting the nozzle body 2 and the CaO-MgO-C-containing refractory constituting the inner-hole refractory 3 is exposed to the molten metal flow passage. Although the erosion of the refractory at the contact portion does not directly cause the adverse effect of the invasion of the outside air, in order to minimize the erosion, the refractory constituting the nozzle body 2 has a SiO ₂ content of 5% by mass. It is preferable to use the following refractories containing A1 ₂ O ₃ + C.

Then, as in the joint structure shown in FIG. 3, the refractory ring 6 is inserted into the recess 5 while the upper end surface of the refractory layer of the inner hole refractory 3 is pressed against the molten steel inlet of the nozzle body 2. It is fitted and fixed with an adhesive 9, and joined to the intermediate nozzle 8 via a joint 7.

In the following, as the refractory 3 for the inner hole portion of the nozzle, the refractory containing CaO-MgO-C is partially or entirely excluding the upper end of the nozzle, and the refractory (nozzle body) 2 constituting the outside contains Al ₂ O ₃ + C. A continuous casting of aluminum-killed steel was performed on the refractory and further on the slag line portion 4 by using a continuous casting nozzle 1 shown in each of the above figures using zirconia-carbon.

　本発明例においては、図１に示す構成のノズルを用いた。浸漬ノズル１の外側を構成する耐火物（ノズル本体）２はＡｌ_２Ｏ_３−Ｃ含有耐火物であり、内孔部の上端を除く部分には内孔部用耐火物３を配置し、内孔部用耐火物３の上端には耐火物製リング６を配置している。比較例Ｎ０．１においては図６に示す構成のノズルを用いた。内孔部用耐火物３の上端に耐火物製リング６を有していない以外は本発明例と同様である。比較例Ｎｏ．２においては、浸漬ノズル１の内孔部用耐火物３にＣａＯ−Ｍｇ〇−Ｃ含有耐火物を配置しておらず、その他の点は比較例Ｎｏ．１と同様である。いずれの実施例においても、各耐火物の組成は表２に示すとおりである。

　浸漬ノズル１と中間ノズル８の接合面１３における耐火物溶損状況ついては、４００分鋳造後の湯漏れの発生率によって評価を行った。接合面１３において耐火物が溶損すると、その結果として当該箇所で湯漏れが発生するからである。鋳造においてはノズル内へのＡｒ吹き込みは行わず、浸漬ノズル１の内周面へのノズル絞り（ノズル詰り）の発生状況について、ノズル絞りが発生するまでの鋳造可能時間を比較した。ノズル絞り発生鋳造可能時間指数は、比較例２の鋳造可能時間を１として相対的に評価した。 In continuous casting of aluminum killed steel, in the continuous casting apparatus to which the present invention is applied, the number of strands is 2 strands, ladle capacity is 310 tons, tundish capacity is 50 tons, casting size is 1500 mm wide × 242 mm thick, casting speed. Is approximately 1.3 m / min. Two sets of continuous casting nozzles are arranged at the bottom of the tundish, and the injection amount is adjusted by a sliding nozzle. Table 1 shows the components of the cast aluminum killed steel.

In the example of the present invention, the nozzle having the configuration shown in FIG. 1 was used. The refractory (nozzle body) 2 constituting the outside of the immersion nozzle 1 is an Al ₂ O ₃ -C-containing refractory, and a refractory 3 for an inner hole is disposed at a portion other than the upper end of the inner hole. A refractory ring 6 is arranged at the upper end of the hole refractory 3. In Comparative Example N0.1, the nozzle having the configuration shown in FIG. 6 was used. This is the same as the example of the present invention except that the refractory ring 6 is not provided at the upper end of the inner hole refractory 3. Comparative Example No. In Comparative Example No. 2, the CaO—Mg〇—C-containing refractory was not arranged in the refractory 3 for the inner hole portion of the immersion nozzle 1, and the other points were the same as those of Comparative Example No. Same as 1. In each example, the composition of each refractory is as shown in Table 2.

The state of refractory erosion at the joint surface 13 between the immersion nozzle 1 and the intermediate nozzle 8 was evaluated based on the incidence of molten metal leakage after 400 minutes of casting. This is because if the refractory material is melted and damaged at the joint surface 13, as a result, hot water leaks at the location. In the casting, Ar was not blown into the nozzle, and the time during which the nozzle was narrowed (nozzle clogging) on the inner peripheral surface of the immersion nozzle 1 was compared with the casting available time until the nozzle was narrowed. The castable time index for nozzle throttle generation was relatively evaluated with the castable time of Comparative Example 2 as 1.

Table 3 shows the results. Comparative Example No. In the case of Comparative Example No. 1, while the rate of molten metal leakage after casting for 400 minutes occurred at a level of 20%. In No. 2, the rate of hot water leakage was 0%. Further, the casting available time until the nozzle throttling occurred was determined in Comparative Example No. 2 is Comparative Example No. The present invention example is four times as large as Comparative Example No. 1. Casting for as long as 6 times as long as 1 was possible. Factors for stopping the casting are described in Comparative Example No. No. 2 is a nozzle throttle, and Comparative Example No. In contrast to No. 1 in which the molten metal leaked and the slag line was damaged, the present invention example was able to continue the casting until the slag line was damaged.

The continuous casting nozzle of the present invention exhibits the most excellent effect when used as a dipping nozzle connected to a tundish, but is not limited to this application.For example, it is connected to a ladle to melt molten metal. Even when used as a continuous casting nozzle when pouring into a tundish, the same effect can be exhibited.

1 shows a state in which the immersion nozzle of the present invention is incorporated in a tundish. It is sectional drawing which shows the component part of the immersion nozzle of this invention. It is a figure showing the joined state of the immersion nozzle of the present invention, and the upper middle nozzle. It is a figure which shows the immersion nozzle of this invention, (a) is sectional drawing, (b) is a side view, (c) is CC arrow view, (d) is DD arrow sectional view, (e). ) Is a sectional view taken along the line EE. It is a fragmentary sectional view of the immersion nozzle of the present invention. It is a fragmentary sectional view showing the situation where a conventional nozzle for continuous casting was attached to a tundish as an immersion nozzle.

Explanation of reference numerals

1 Immersion nozzle (nozzle for casting)
2 Nozzle body 3 Refractory for inner hole (CaO-MgO-C containing refractory)
4 Slag-in part 5 Recess 6 Refractory ring 7 Joint joint material 8 Nozzle body to be joined (intermediate nozzle)
REFERENCE SIGNS LIST 9 adhesive material 10 joint material for joint at inner hole portion 11 discharge hole 12 molten metal passage 13 joint surface with nozzle body to be joined 14 joint surface with refractory for inner hole 20 tundish 24 upper end 25 of immersion nozzle meltdown 30 Upper nozzle 40 Sliding nozzle body a Refractory ring outer diameter a 'Outer diameter of refractory ring lower end b Refractory ring inner diameter
b 'Inner diameter of the lower end of the refractory ring c Outer diameter of the joining surface of the intermediate nozzle d Inner diameter of the joining surface of the intermediate nozzle e Outer diameter of the upper end face of the refractory layer inside the submerged nozzle f Upper end face of the refractory layer inside the submerged nozzle G Difference between upper outer diameter and lower end outer diameter of refractory ring

Claims (10)

Nozzle upper end of casting dipping nozzle in which clinker containing CaO as a mineral phase and carbon-containing CaO-based refractory containing carbon are arranged as a carbon-containing CaO-based refractory layer on at least the inner wall surface in contact with molten steel, and above it The joining structure with the lower end of the nozzle body to be joined located at
A recess is provided at the upper end of the nozzle of the casting immersion nozzle, and a refractory ring is fitted into the recess, and the refractory is formed upward from the upper end of the carbon-containing CaO-based refractory layer of the casting immersion nozzle. A joining structure of continuous casting nozzles arranged in the order of a ring and a nozzle body to be joined. The carbon-containing CaO-based refractory is a dolomite-carbon-based dolomite-graphite refractory having a composition of 0.03 ≦ MgO / CaO ≦ 32 and 0.05 ≦ C / (CaO + MgO + C) ≦ 0.4. The joint structure for a continuous casting nozzle according to claim 1, wherein the total of CaO + MgO + C is 90% by mass or more. 3. The continuous casting nozzle according to claim 1, wherein the main material of the refractory ring is one or more of zirconia-based and magnesia-based materials, or a refractory containing carbon therein. 4. Joint structure. The continuation according to claim 1 or 2, wherein the composition of the ring of the refractory ring comprises a refractory containing 90% by mass or more of ZrO ₂ + C, MgO + C, ZrO ₂ + MgO + C, MgO, MgO + Cr ₂ O _3. Bonding structure of casting nozzle. The composition of the ring of the refractory steel _{rings, MgO, MgO + A1 2 O} 3, MgO + A1 2 O 3 MgO _{spinel, MgO + Cr 2 O 3,} MgO + A1 2 O 3 + A1 2 O 3 MgO _{spinel, A1 2 O 3 + A1 2} O 3 MgO _{spinel, A1 2 O 3 + Cr 2} O 3, MgO + C, MgO + A1 2 O 3 + C, A1 2 O 3 + C, ZrO 2 + C, A1 2 O 3 MgO spinel + refractories containing more than 90% by mass or C The joining structure for a continuous casting nozzle according to claim 1, comprising: Junction structure of the continuous casting nozzle as claimed in any crab 5, wherein the SiO ₂ content in the refractory metallic ring is not more than 5 wt%. The joint structure for a continuous casting nozzle according to any one of claims 1 to 6, wherein a joint joint material is provided between the refractory ring and the nozzle body to be joined. The joint joint material reacts with a lower end portion made of a refractory material containing carbon such as an alumina-based material, an alumina-silica-based material, and the like to form a nozzle body to be joined, and does not generate a low-melting substance. The joint structure for a continuous casting nozzle according to claim 7, wherein the nozzle is selected from a combination of siliceous, zirconia, and magnesia materials, and refractories containing carbon. When the refractory ring has an outer diameter of a joining surface with the upper side of a and an inner diameter of b, and an outer diameter of a joining portion at a lower portion of the upper nozzle body to be joined as c and an inner diameter of d, these are: 9. The joining structure of a casting immersion nozzle according to claim 1, wherein d <a <c and b> d. The outer diameter of the joining surface with the upper part of the refractory ring is a, the inner diameter is b, the outer diameter of the lower end face to be fitted is a ', the inner diameter is b', and the carbon-containing CaO-based refractory layer on the inner wall surface. 9. When the outer diameter of the upper end face is e and the inner diameter is f, the outer diameter is in a relationship of a ≧ a ′> e, and the inner diameter is b> b ′ = f. Structure of the immersion nozzle for casting.

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