JPH09220650A - Long nozzle for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the elution of carbon into molten steel during casting by inserting and fitting a precast formed sleeve-like spinel material refractory to a position of contact with the molten steel in the inner hole side wall part of a long nozzle for continuous casting. SOLUTION: The precast refractory composed of precast formed sleeve-like monolithic refractory having 3-35mm is inserted to the inner hole side wall surface position in contact with the molten steel at the inner hole 3 side of a body part 2 of the long nozzle 1 for continuously casting the steel and physically and chemically worn. Then, the precast material and the body part are integrally formed into double-structure by no joint or joining with refractory mortar. The material of the precast refractory is the spinel material consisting essentially of Al2 O3 and MgO and no carbon. It is desirable to contain 40-90wt.% Al2 O3 and 3-65% MgO and >=95% the total of both. By this constitution, the contact part with the molten steel in the inner hole 3 of the nozzle is made of the carbon-less material and thus, the elution of the carbon into the molten steel at the time of casting is eliminated.

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 fact, in the composition of the steel to be cast, the refractory for casting such as the long nozzle for continuous casting when casting the steel type that dislikes the existence of carbon, which is a general main component of the long nozzle for continuous casting, is selected as described above. Considering this, it is a very important issue. That is, suppressing the elution of carbon from the long nozzle for continuous casting in the continuous casting method is extremely delicate and important in order to obtain the quality and yield of steel at the required level.

[0004]

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 to prevent carbon elution during casting, and even if such elution occurs, the amount of carbon is acceptable in terms of quality and yield. It is to provide a long nozzle for continuous casting that can be used while being controlled within a limit value.

[0005]

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 and fits a precast product consisting of a sleeve-shaped carbon-free amorphous refractory precast into the sidewall of the inner hole that forms the molten steel contact part. It is a long nozzle for continuous casting characterized by having a structure of one body and two kinds.

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

The long nozzle for continuous casting according to the present invention is a material containing no carbon such as graphite in the side wall portion of the inner hole, that is, the flow path surface of molten steel, and has a spinel amorphous shape containing Al ₂ O ₃ and MgO as main components. A precast product in which a refractory material has been cast into a sleeve shape is inserted, and is set and joined together through refractory mortar to form an integral double structure. The thickness of the sleeve precast product is 3 to 5 mm or more. The range is 5 to 50% of the thickness of the long nozzle for continuous casting.

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

In the long nozzle for continuous casting of the present invention, the main body portion excluding the thickness of the precast product made of the sleeve-shaped amorphous refractory fitted to the side wall portion of the inner hole is conventionally used alumina-graphite. A material that is composed of graphite-oxide type components such as a system material is pressure-molded and fired in a non-oxidizing atmosphere. It is desirable that a spinel precast product made of a standard refractory material is fitted to form a one-body double structure so that both are securely fixed during use.

In the long nozzle for continuous casting according to the present invention, as the material of the sleeve-shaped precast product arranged on the side wall of the inner hole of the molten steel contact portion, an amorphous refractory containing no carbon is used, and spinel of Al ₂ O ₃ and MgO is used. The main component is based on the following reasons. That is, Al ₂ O ₃ has excellent resistance to molten steel, and MgO provides good results to slag resistance, which is useful for extending the life of the long nozzle for continuous casting and preventing elution of carbon into molten steel. Therefore, the side wall of the inner hole that comes into contact with the molten steel is carbonless.

With this long nozzle for continuous casting, excellent molten steel resistance 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 realized 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, the inner hole side wall portion 4 which contacts the inside of the main body 3, that is, the molten steel, is physically and chemically worn away.
A precast product consisting of a sleeve-shaped insulative refractory that has been cast-molded in advance is inserted into this to have a double structure with joints depending on the joints or refractory mortar. The thickness of the sleeve-shaped precast product is set to 3 to 35 mm or 5 to 50% of the wall thickness of the long nozzle for continuous casting because 3 mm or 5% or less of the wall thickness is due to melting loss or peeling. This is because the structure is easily destroyed and the purpose for a long time can not be achieved, 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 the mechanical strength becomes small, This is because the long nozzle for continuous casting itself will be broken or broken and its function cannot be exhibited.

In the long nozzle for continuous casting according to the present invention, the spinel material is an amorphous refractory material mainly composed of carbon-free Al ₂ O ₃ and MgO which are inserted and fitted as the inner wall side wall portion forming the molten steel contact portion. As a material for the sleeve-shaped precast product, Al ₂ O _{3 is} preferably 40 to 90% by weight, MgO _{3 to} 65% by weight, and the content of Al ₂ O and MgO components is preferably 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 slag resistance does not satisfy the required performance, and 6
This is because if it is 0% by weight or more, the spall resistance is impaired. Table 1 shows typical values of the quality characteristics of the sleeve-shaped precast product obtained by cast molding of the carbon-free amorphous refractory material. 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 142 minutes Casting carbon elution amount 12PPm (conventional 20 to 30PP
m) A long nozzle residual thickness of 59% (conventional 30%) (side wall of inner hole) was obtained.

[0017]

[Table 1]

[0018]

INDUSTRIAL APPLICABILITY The long nozzle for continuous casting according to the present invention is a sleeve-shaped precast obtained by casting with an amorphous refractory material of spinel containing Al ₂ O ₃ and MgO containing no carbon as shown in Table 1. Insert and fit the product into one body 2
By adopting a heavy structure, the molten steel contact part is made carbonless so that the elution of carbon into the molten steel at the time of casting is eliminated, and it is suitable for continuous casting of steel types that need to limit the carbon content. By applying the invention, the required results were obtained with extremely high reliability of steel quality and yield.
Furthermore, it has the effect of improving the durability of the long nozzle for continuous casting.

[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

Claims (1)

[Claims] In the long nozzle for continuous casting which is used when the method according to claim 1] to inject molten metal from the ladle into the tundish, the thickness of 3~35mm the bore side wall portion forming the molten steel contact portion, Al ₂ which does not include the carbon A long nozzle for continuous casting, characterized in that a sleeve-shaped precast product cast from a spinel-shaped amorphous refractory containing O ₃ and MgO as main components is inserted and fitted to form a one-piece double structure. .