JPH09220651A - Long nozzle for continuous casting - Google Patents

Abstract

(57) [Summary] [Purpose] Continuous casting in which carbon does not elute during casting, and even if such elution occurs, the amount can be controlled within the allowable limits for quality and yield. There is a long nozzle for use. [Structure] In a long nozzle 1 for continuous casting, which is used when pouring a molten metal from a ladle into a tundish,
Al ₂ O ₃ and Mg containing no carbon in the side wall 4 of the inner hole
It is characterized in that a sleeve-shaped precast product having a conical outer side, which was cast-molded with an amorphous refractory material containing O as a main component, was inserted and taper-fitted to form an integral double structure. [Effect] By applying the product of the present invention, the required quality and yield of the steel were obtained with extremely high reliability. Also, the effect of arranging the precast product on the side wall of the inner hole was the effect of improving the durability of the long nozzle for continuous casting. By tapering the fitting, the structure became a more stable long nozzle for continuous casting, which was sufficiently effective for durability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long nozzle for continuous casting.

[0002]

2. Description of the Related Art The continuous casting of steel will be described below as an example.
The long nozzle for continuous casting is attached to the lower part of the sliding nozzle attached to the bottom hypodermic iron end of the ladle to control the flow rate of molten steel when supplying the molten steel from the ladle to the tundish. It is an important nozzle used for the purpose of non-oxidizing injection of molten steel into steel.

However, when the molten steel is injected, it is subjected to physical wear and chemical erosion due to the molten steel flowing down.
It is an unavoidable big problem to mix the composition components of the long nozzle for continuous casting into the cast steel. From this, in the composition of the steel to be cast, the selection of refractory materials for casting such as long nozzles for continuous casting when casting steel types that dislike the presence of carbon, which is the general main component of long nozzles for continuous casting. Is an extremely important issue in view of the above.

That is, suppressing the elution of carbon from the long nozzle for continuous casting in the continuous casting method is very delicate and important in order to obtain the quality and yield of steel at the required level. It is in the present situation.

[0005]

Conventionally, long casting nozzles for continuous casting have been made difficult to be wet with molten steel, and by imparting high heat resistance and high thermal conductivity, corrosion resistance and thermal shock resistance to a predetermined level. For the purpose of realizing, it consists of natural graphite as the main component. In the practical examples, alumina-graphite type, zirconia-graphite type, magnesia-graphite type and the like are used depending on the steel type and casting conditions. However, in any of the oxide-graphite refractory materials as described above, graphite is the main component in all cases, and the carbon eluted during casting as described above impairs quality and yield. It cannot be used when continuously casting steel grades.
The present invention has been made for such a reason, that is, the object of the present invention is that carbon does not elute during casting, and even if such elution occurs, the amount is acceptable in terms of quality and yield. The object is to provide a long nozzle for continuous casting that can be used within the limit value.

[0006]

The present invention has been made to solve the above problems, and the gist of the invention is to inject molten steel from a ladle into a tundish in continuous casting of steel. A long nozzle for continuous casting, which is sometimes used, inserts a precast product with a conical outer side made of sleeve-shaped carbon-shaped unshaped refractory precast in the side wall of the inner hole, and is fitted with a taper. It is a long nozzle for continuous casting characterized by having a one-body double structure.

The structure of the continuous casting long nozzle of the present invention and its excellent characteristics will be described in detail below.

The long nozzle for continuous casting according to the present invention is a material which does not contain carbon such as graphite in the side wall portion of the inner hole, that is, the flow path surface of molten steel, and is an amorphous refractory material containing Al ₂ O ₃ and MgO as main components. Insert a precast product that is cast into a sleeve shape, and set and stop it with refractory mortar etc. 1
The body has a double structure, and the thickness of the sleeve-shaped precast product is within the range of 3 to 35 mm or 5 to 50% of the thickness of the long nozzle for continuous casting, and the outside thereof. It is a conical sleeve.

Since the long nozzle for continuous casting of the present invention has a structure in which a precast product of a sleeve-shaped amorphous refractory containing no carbon such as graphite is arranged on the side wall of the inner hole where the passing molten steel comes into contact, Carbon elution phenomenon into molten steel during casting even when physical or chemical wear or erosion as described above occurs when used in continuous casting of steel types such as low carbon steel that require low carbon content. Will not happen at all. Therefore, by using the long nozzle for continuous casting of the present invention, the required quality and yield can be cleared.

The long nozzle for continuous casting according to the present invention comprises an amorphous refractory material containing, as main components, carbon-free Al ₂ O ₃ and MgO, which are sleeve-shaped and are fitted into the side wall of the inner hole forming the molten steel contact portion. The main body, excluding the thickness of the precast product that was cast-molded, is pressure-molded using a material composed of graphite-oxide-based components such as alumina-graphite-based materials that have been used conventionally as a raw material, and in an oxygen-free atmosphere. A precast product made of an amorphous refractory containing Al ₂ O ₃ and MgO as the main components, which does not contain carbon and has a sleeve-like shape with a conical outer side, which was manufactured by cast molding in advance in a tubular main body formed by firing below. It is a long nozzle for continuous casting characterized in that it has a one-body double structure by taper fitting, and it is desirable that both of them be securely fixed during use. In the long nozzle for continuous casting of the present invention, as a material for a conical sleeve-shaped precast product arranged on the side wall portion of the inner hole forming the molten steel contact portion, Al ₂ O ₃ and MgO are amorphous refractory materials containing no carbon. The main component is that Al ₂ O ₃ is excellent in molten steel resistance, and MgO brings good results in slag resistance. In order to prevent the elution of carbon into the molten steel while extending the service life of the long nozzle for continuous casting, the side wall of the inner hole forming the molten steel contact portion is made carbon-free. With this long nozzle for continuous casting, excellent resistance to molten steel and erosion resistance can be secured, carbon elution into molten steel can be eliminated, and the life of the long nozzle for continuous casting can be achieved as planned.

Next, a long nozzle for continuous casting according to the present invention will be described with reference to the drawings.

First, FIG. 2 is a longitudinal sectional view of a conventional continuous casting long nozzle, and FIG. 1 is an example of the same longitudinal sectional view of a continuous casting long nozzle of the present invention.

In FIG. 1, a sleeve-shaped insulative refractory having an inner side wall portion 4 which is in contact with the inside of the main body portion 3, that is, which is physically and chemically worn and which is preformed by casting, has a conical outer portion. A precast product is inserted, and it has a double structure with joints depending on open joints or refractory mortar.
The thickness of the sleeve-shaped precast product whose conical side is 3 to 35 mm, or 5 to 50% of the wall thickness of the long nozzle for continuous casting, is due to melting loss at 3 mm or 5% or less of the wall thickness. This is because the structure is easily destroyed by peeling or peeling and the purpose for a long time can not be fulfilled, and if it is 35 mm or 50% or more of the wall thickness, the wall thickness of the main body part 3 becomes thin and mechanical strength is reduced. Becomes smaller, causing breakage or breakage of the continuous casting long nozzle itself, and the function cannot be exhibited.

In the long nozzle for continuous casting of the present invention, it is inserted as a side wall portion of the inner hole which forms the molten steel contact portion, and is fitted with an amorphous refractory material containing carbon-free Al ₂ O ₃ and MgO as main components. The material of the sleeve-shaped precast product whose outer side is conical is Al ₂ O ₃ 40-
90 wt%, MgO 3 to 65 wt% Al ₂ O and M
It is desirable that the content of the gO component is 95% by weight or more. This is because when Al ₂ O _{3 is} 40% by weight or less, molten steel resistance and corrosion resistance due to slag are low, and when 90% by weight or more, spall resistance is poor and cracking occurs. If the MgO content is 3% by weight or less, the performance required for slag resistance is not satisfied, and 60% by weight
This is because the spall resistance is impaired by the above.
Table 1 shows typical values of the quality characteristics of the sleeve-shaped precast product of the present invention, which is made of an amorphous refractory material containing Al ₂ O ₃ and MgO containing no carbon as main components and having a conical outer side. In FIG. 1, the outer side of the sleeve-shaped precast product 4 is conical and the fitting with the main body is tapered.
This is for the purpose of speedily fitting the sleeve-shaped precast product 4 and the main body 3 into a one-body double structure and further increasing the reliability of the connection, thereby further stabilizing the continuous casting. Especially. The conical taper has a lower outer diameter D ₁ and an upper outer diameter D ₂ of the sleeve-shaped precast product, and is D ₂ −D ₁ ,> 5 mm. 5 mm
Below, the effect of taper cannot be exhibited. The taper range is preferably 5 to 15 mm. The following results were obtained when the long nozzle for continuous casting of the present invention was used for casting ultra-low carbon steel by a continuous casting machine having a ladle capacity of 300 t. Number of charges 2 Casting time 136 minutes Casting carbon elution amount 12 PPm (conventional 20 to
30PPm) A long nozzle residual thickness for continuous casting of 65% (conventional 30%) (side wall of inner hole) was obtained.

[0015]

[Table 1]

[0016]

According to the long nozzle for continuous casting of the present invention,
Examples of the main body 3 are shown in Table 1. A that does not contain carbon
By inserting a sleeve-shaped precast product 4 with a conical outer side, which is obtained by casting an amorphous refractory material containing l ₂ O ₃ and MgO as main components, and taper-fitting it into a double-body structure, this part is formed. However, the carbon-less material eliminates the elution of carbon into the molten steel during casting, and for continuous casting of steel types that need to restrict the carbon content, the product of the present invention can be applied to improve the quality and The residue was very reliable and the desired result was obtained. Furthermore, it has the effect of improving the durability of the long nozzle for continuous casting. The conical outer surface of the main body portion 3 and the tapered outer surface of the sleeve-shaped precast product 4 provide a more stable long nozzle for continuous casting as a structure, and the durability effect is obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a long nozzle for continuous casting according to the present invention.

FIG. 2 is a vertical cross-sectional view of a conventional continuous casting long nozzle.

[Explanation of symbols]

1 Long nozzle for continuous casting 2 Inner hole 3 Body part 4 Inner hole Side wall part D ₁ Sleeve-shaped precast product lower outer diameter D ₂ Sleeve-shaped precast product upper outer diameter

Claims (1)

[Claims] 1. A long nozzle for continuous casting, which is used when pouring a molten metal from a ladle into a tundish, wherein Al ₂ O ₃ having a thickness of ₃ to 35 mm and not containing carbon is contained in a side wall portion of an inner hole forming a molten steel contact portion. And a continuous one-piece double structure by inserting a sleeve-shaped precast product with a conical outer side, which is cast-molded with an amorphous refractory containing MgO as a main component, and has a one-piece double structure. Long nozzle for casting.