JPH11124620A - Immersed tube for melting steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the fall-down of monolithic refractory at the lower end part of an immersed tube for melting steel. SOLUTION: In the immersed tube for melting steel provided with the refractory at the outer periphery, inner periphery and lower end part of a cylindrical core metal 1, at least a part of the refractory at the lower end part is made of the monolithic refractory 7a and a coiled metallic wire 8a is embedded along the peripheral direction of the immersed tube in the monolithic refractory 7a, and the coiled metallic wire is fixed to the cylindrical core metal. The coiled metallic wire is immanent in the monolithic refractory as the three dimensional state and then, the stress caused by thermal expansion and shrinkage is uniformly dispersed in the monolithic refractory structure and the crack in the horizontal direction is not induced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a dip tube mounted on a vacuum degassing device, a simple degassing device, or the like as molten steel processing equipment.

[0002]

2. Description of the Related Art A vacuum degassing device such as an RH type, a DH type, or a KTB type, or a simple degassing device called PI or CAS has a detachable dip tube for flowing molten steel at its lower end. It is attached to.

[0003] This immersion pipe for molten steel is basically constituted by providing a refractory on the inner circumference, outer circumference and lower end of a cylindrical cored bar. As a specific example of the conventional structure, for example,
In Japanese Patent No. 3236, a fixed refractory is provided on the inner periphery of the core metal, an irregular refractory on the outer periphery, and an irregular refractory on the lower end.
Japanese Patent Application Laid-Open No. 7-34119 discloses a structure in which a fixed refractory is provided on both the inner and outer circumferences.

[0004]

In the use of a dip tube, the heating applied during the flow of molten steel and the cooling accompanying a pause are alternately repeated. The refractory at the lower end of the immersion pipe has a problem that a crack is generated due to expansion and contraction of the core metal due to the heating and cooling, and the refractory easily falls off. Then, when the refractory at the lower end falls off and the core metal is exposed, the core metal is immediately melted, and the refractory falls off the entire immersion pipe.

As the refractory at the lower end of the immersion pipe, an irregular refractory which is easily supported by the stud is used. The shape of the stud is generally V-shaped or Y-shaped. In order to strengthen the support of the amorphous refractory, it is conceivable to increase the number of studs. However, the thermal expansion of the stud is large due to the metal, and as the number of the stud increases, cracking of the irregular refractory is promoted. In addition, the metal reduces the corrosion resistance of the refractory.

Japanese Patent Application Laid-Open No. 9-104616 discloses an example in which corrugated studs having a horizontal waveform are used. However, these studs, due to their horizontal corrugation, induce horizontal cracks and are by no means sufficient to prevent the refractory from falling off.

[0007]

SUMMARY OF THE INVENTION The present invention has solved the above-mentioned conventional problems in a immersion pipe for molten steel, and is characterized in that a refractory is provided on the outer periphery, inner periphery and lower end of a cylindrical cored bar. In the immersion pipe for molten steel provided, at least a part of the refractory at the lower end is made an irregular refractory, and a coil-shaped metal wire is embedded in the irregular refractory along the circumferential direction of the immersion pipe, And the coiled metal wire is fixed to the cylindrical cored bar.

Since the lower part of the immersion pipe is immersed in molten steel, there is a peculiar phenomenon that the lower part of the core metal is greatly expanded by thermal expansion. Then, V-shaped and Y-shaped studs provided at the lower end of the metal core largely move with expansion and contraction of the metal core, and cracks in the amorphous refractory structure causing the irregular refractory to fall off. Cause

[0009] Although corrugated studs reduce the propagation of thermal expansion of the core metal to the studs by the corrugated portions serving as cushioning margins, the corrugations in the horizontal direction tend to induce horizontal cracks.

In the present invention, the coiled metal wire has a role as a stud. Due to the coil shape, the propagation of thermal expansion of the core metal is reduced, and the crack generation rate of the amorphous refractory is greatly reduced. In addition, since the coil shape makes it three-dimensionally present in the indefinite refractory and the stress due to thermal expansion and contraction is evenly distributed in the indefinite refractory structure, the corrugate has a two-dimensional curved line in the horizontal direction. It does not induce horizontal cracks like studs.

[0011]

FIG. 1 is a longitudinal sectional view of an embodiment of a dip tube according to the present invention. FIG. 2 is an exploded view of a main part showing a connecting portion between a core metal and a coiled metal wire in the dip tube of the embodiment of FIG.

In FIGS. 1 and 2, the cylindrical cored bar (1) is provided with a flange (2) at the upper end so that it can be detachably attached to the lower end of a vacuum degasser or a simple degasser. I have. The inner peripheral refractory (3) is preferably a fixed refractory. In the same figure, as the inner peripheral refractory (3), fixed refractories are stacked in a plurality of stages vertically, but the invention is not limited to this.
An integral shaped refractory may be used. In addition, the support structure for the inner peripheral refractory (3) is not particularly limited, and the inner peripheral refractory (3) is formed by a receiving object (4) or the like.

Although the outer peripheral refractory (5a) is made of only an irregular refractory here, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-34119, the entire outer periphery or a part of the slag line or the like is made a fixed refractory. Is also good. In addition, the outer peripheral refractory (5a)
Is supported by studs (6) for irregular-shaped refractories and metal fittings for regular-shaped refractories.

As the refractory at the lower end of the cored bar (1), an irregular refractory (7a) which can be easily supported by studs is used.
In the present invention, a coil-shaped metal wire (8a) serving as a stud is buried in the irregular-shaped refractory (7a) located at the lower end of the metal core. At the lower end of the cored bar, the coiled metal wire (8a) is provided along the circumferential direction of the dip tube.
The fixation of the coiled metal wire (8a) to the metal core (1) is as follows.
It may be directly or via a hanging rod (9) as shown in the figure.

FIG. 3 is an enlarged sectional view of a main part below a dip tube showing another embodiment. In FIG. 1, this corresponds to an enlarged view of a portion surrounded by a dotted line. FIG. 4 is a developed view showing a connection portion between the core metal and the coiled metal wire in the embodiment of FIG.

In the embodiment shown in FIGS. 3 and 4, an irregular refractory (7b) is provided on the entire lower end surface of the dip tube. When the irregular refractory (7b) occupies a large proportion at the lower end of the immersion pipe as described above, in order to support in a wider range,
It is preferable to make the cross section of the spiral shape of the coiled metal wire (8b) laterally long.

FIG. 4 is an enlarged sectional view of a main part showing another embodiment. In FIG. 1, this corresponds to an enlarged view of a portion surrounded by a dotted line. FIG. 5 is a developed view showing a connection portion between the core metal and the coiled metal wire in the embodiment of FIG. In this embodiment, a fixed refractory is provided on the inner and outer circumferences of the immersion tube, and the fixed refractory reaches the lower end surface of the immersion tube. For example, when the irregular refractory (7c) at the lower end of the immersion pipe is present only in the portion where the regular refractory is sandwiched, the coil-shaped metal wire (8c) can be included in the limited place. In addition, it is preferable that the cross section of the helical form is vertically long.

In each of the above embodiments, the spiral cross section of the coiled metal wires (8a), (8b) and (8c) is circular or elliptical. no change.

In the immersion tube of the RH type vacuum degassing device,
Using Y-shaped studs, corrugated studs, and coiled metal wires for the support structure of the refractory at the lower end,
The other conditions were the same and the durability of the dip tubes was compared. As a result, although the corrugated stud is superior to the Y-shaped stud in preventing the falling of the irregular refractory at the lower end of the immersion pipe, the irregular refractory at the lower end falls off due to the horizontal cracking. did. On the other hand, in the example of the present invention using the coil-shaped metal wire, the irregular-shaped refractory at the lower end did not fall off at all, and the durability was remarkably improved.

[0020]

The present invention has the effect of preventing the falling of the irregular refractory at the lower end of the immersion tube, which is the biggest bottleneck in the life of the immersion tube.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a dip tube of the present invention.

FIG. 2 is an essential part developed view showing a connection part between a core metal and a coiled metal wire in the dip tube of the embodiment of FIG. 1;

FIG. 3 is a longitudinal sectional view of another embodiment of the dip tube of the present invention.

FIG. 4 is a development view of a main part showing a connection part between a core metal and a coiled metal wire in the dip tube of the embodiment in FIG. 3;

FIG. 5 is a longitudinal sectional view of another embodiment of the dip tube of the present invention.

FIG. 6 is an essential part developed view showing a connection part between the core metal and the coiled metal wire in the dip tube of the embodiment of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core metal 2 Flange 3 Inner peripheral refractory 4 Receptacle 5 Outer peripheral refractory 6 Stud 7a, 7b, 7c Irregular refractory at the lower end of immersion pipe 8a, 8b, 8c Coiled metal wire 9 Hanging rod

Claims (2)

[Claims] 1. A molten steel immersion pipe having a refractory provided on an outer periphery, an inner periphery, and a lower end of a cylindrical core metal, wherein at least a part of the refractory at the lower end is made into an irregular refractory, and A immersion pipe for molten steel, wherein a coil-shaped metal wire is buried in a fixed refractory along a circumferential direction of the immersion pipe, and the coil-shaped metal wire is fixed to the cylindrical core metal. 2. The immersion pipe for molten steel according to claim 1, wherein the spiral shaped cross section of the coiled metal wire is vertically long or horizontally long.