JPH06240344A - Immersion pipe for molten steel treating device - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance in the slag line part of the immersion pipe to be mounted to a molten steel treating device, such as vacuum degassing device or CAS device. CONSTITUTION:The slag line part on the outer periphery of the immersion pipe formed by consisting the outer periphery and inner periphery of a metallic cylinder Y of refractories 2, 3 is composed of basic castable refractories 4 and the part lower than the slag line of the outer periphery is composed of aluminous castable refractories 5. The corrosion resistance is improved by using the basic castable refractories for the slag line on the outer periphery. The crack at the boundaries of bricks and castable refractories and the dislodgment of the bricks as admitted heretofore when the bricks are used for the slag line part do not arise any more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dip tube for a molten steel processing apparatus having excellent durability.

[0002]

2. Description of the Related Art An immersion pipe mounted in a vacuum degassing apparatus such as an RH type or a DH type or a molten steel processing apparatus such as a CAS apparatus is significantly worn due to the action of a molten steel flow. Therefore, the dip tube is removed from the flange when the amount of wear is reduced and replaced with a separately prepared dip tube.

Conventionally, an amorphous alumina refractory has been used as a material for the outer circumference of the dip tube. However, in recent years
Due to the need for high-purity steel and the operation of high basicity by adding CaF ₂ or CaO, in the conventional dip pipe, the outer slag line portion is severely worn, leading to an increase in the repair amount and a reduction in the service life.

As a measure against this, for example, the actual exploitation Sho 58-13
Japanese Patent No. 5457 and Japanese Utility Model Laid-Open No. 3-96344 propose a structure in which a brick with high corrosion resistance is embedded in an irregularly shaped refractory in the slag line portion on the outer periphery.

[0005]

However, while the brick has a dense structure and excellent corrosion resistance, it has a problem that cracks are likely to be formed at its boundary due to the difference in thermal expansion between the brick and the amorphous refractory. Boundary cracks lead to the falling of bricks and the entrainment of nitrogen due to air intrusion. Further, it is not easy to support the brick on the outer circumference of the dip tube, which makes the dip tube construction extremely complicated.

[0006]

Therefore, the present inventors have made various studies. As a result, the slag line portion on the outer periphery of the dip pipe and the lower portion of the slag line portion made of an amorphous refractory of a specific material have been found to be able to solve the above-mentioned conventional problems, and have completed the present invention. .

That is, according to the present invention, in a submerged pipe in which a metal cylinder is made of a refractory material on the outer circumference and the inner circumference, a slag line portion on the outer circumference is a refractory material with an irregular basic property, and a portion below the outer slag line portion is formed. It is a dip tube for molten steel processing equipment made of alumina type amorphous refractory.

The present invention will be described in more detail with reference to the drawings. In the longitudinal sectional view of the immersion pipe shown in FIG. 1, a metal cylinder 1 having a flange at the upper end has a role of supporting an outer peripheral refractory 2 and an inner peripheral refractory 3. The inner peripheral refractory 3 is not particularly limited. For example, bricks such as alumina-chromium and magnesia-chromium can be used as in the conventional case. Further, as long as it has high corrosion resistance, an amorphous refractory material such as alumina, alumina-magnesia, or alumina-spinel may be used.
When a brick is used, it is preferable that an irregular refractory is interposed between the brick and the metal cylinder 1 on the back surface thereof.

On the other hand, in the outer peripheral refractory 2, the slag line portion is the basic property amorphous refractory material 4, and the molten steel dipping portion thereunder is the alumina amorphous refractory material 5. Although not shown in the figure, in order to firmly support these outer peripheral refractory materials 2, it is preferable to implant studs on the outer peripheral surface of the metallic cylinder 1.

The back surface of the slag line portion not in contact with the slag may be made of a refractory material other than basic properties. The material above the slag line portion is not in contact with the molten steel or slag, so the material is not particularly limited, and may be an inexpensive material such as an alumina amorphous refractory or a chamotte amorphous refractory. .

The refractory 4 having an irregular base property provided in the slag line portion has an excellent effect on slag erosion resistance. In order to fully exert this effect, a basic refractory raw material of magnesia or spinel is used as a main material. Specific examples include magnesia-spinel, magnesia-alumina, magnesia-chromium, magnesia-zircon,
Examples thereof include magnesia-spinel-alumina.

The width of the slag line portion in the height direction is, for example, 100 to 250 mm in consideration of the vertical transition of the slag surface.
The degree.

The alumina amorphous refractory 5 provided below the slag line is mainly composed of alumina refractory raw materials such as alumina and high alumina, and if necessary, may be supplemented with auxiliary raw materials such as magnesia, spinel and chrome ore. It is a thing.

The amorphous refractories 4 and 5 are
Fibers, refractory ultrafine powders, dispersants, etc., which are known as additives for amorphous refractories, are added as necessary. FIG. 2 shows an example in which not only the slag line portion but also the upper portion thereof is made of the refractory material 4 having an irregular basic property. Here, the refractory material on the outer periphery has two layers, one above the other. Construction is easier than construction of the outer periphery in three layers as shown in FIG.

[0015]

It is already known that basic slag is provided in the slag line portion to improve the corrosion resistance of the slag line portion. Brick has a difference in thermal expansion due to the difference in material from the amorphous refractory, or due to its unfamiliarity, cracks may occur at the boundaries with the irregular refractory located above and below, bricks may fall off, and nitrogen entrapment due to air intrusion may occur. Invite.

On the other hand, in the present invention, a refractory having an irregular basic property is used in the slag line portion. Since it is an amorphous refractory, there is little difference in thermal expansion from the amorphous refractories above and below it, and it is familiar, so there is almost no cracking at the boundary, and the corrosion resistance of the slag line part with basic properties is improved. The effect is demonstrated without any limitation.

Further, with the conventional structure in which bricks are provided in the slag line portion, it is difficult to construct a dip pipe by providing bricks in a predetermined portion, but in the present invention, the entire outer periphery is an irregular refractory material, Construction is easy.

When the dipping pipe is used, slag is attached and deposited on the outer peripheral surface thereof. The slag is removed when it becomes extremely large, but with the conventional structure in which the slag line part is made of brick, the brick may fall off due to the external force when removing the slag. On the other hand, the structure of the outer periphery in the present invention is an entirely refractory material including the slag line portion, and there is no problem as described above when a brick is used.

The refractory having an irregular basic property has excellent corrosion resistance to slag, but is inferior in spalling resistance and hot strength. For this reason, when a refractory having an irregular basic property is used below the slag line, the lower end will fall off. Therefore, in the present invention, below the slag line portion, an alumina amorphous refractory having high spalling resistance and hot strength is used. As described above, the present invention is completed by using an amorphous refractory having a basic property for the slag line portion and an alumina amorphous refractory material below the slag line portion.

[0020]

EXAMPLES Examples of the present invention and comparative examples will be described below. Table 1 shows the materials of the refractory materials used in the examples and comparative examples of the present invention, and Table 2 shows the examples and comparative examples of the present invention and the test results thereof.

[0021]

[Table 1]

[0022]

[Table 2]

In Example 1, Example 2, Example 3 and Comparative Example 1, as shown in FIG. 1, the outer peripheral refractory of the dip pipe is arranged in the height direction in the slag line portion / above the slag line portion / slag line portion. It was divided into three lower layers. In Example 4 and Example 5, as shown in FIG. 2, the refractory around the outer periphery of the dip pipe was divided into two layers in the height direction, the upper part including the slag line part and the lower part than the slag line part. In Comparative Example 2, the entire outer peripheral refractory of the dip tube was made of the same material.

In each of the examples, a dip pipe of a 100 tRH type vacuum degassing device was constructed. Many studs are planted on the outer circumference of the metal cylinder. A magnesia-chromic fired brick layer was provided on the inner circumference. With the dip tube turned upside down, a castable refractory was cast on the outer circumference.

In the casting of the outer periphery, a flat vibration fixing vibrator was attached to the outer frame and a rod-shaped vibrator was inserted directly into the irregular refractory. If the outer peripheral refractory had different materials in the height direction, different materials were cast in order in the height direction. In the case where the slag line part was made of brick, the brick was fixed to the part corresponding to the slag line part in the outer frame, and the irregular refractory was cast.

Although not shown in the drawing, an ascending pipe of the immersion pipe is embedded with an inert gas introducing pipe for raising the molten steel by a gas lift. The material of each part of the peripheral refractory material is as shown in Table 2.

The immersion tube constructed as described above was cured and dried for several hours, then actually attached to a vacuum degassing apparatus for use and tested. The test items are as follows. Corrosion resistance of the slag line portion: The melt loss dimension of the slag line portion after 50 times of use was measured, and the melt loss dimension was shown by the melt loss index with the test result of Comparative Example 2 as 100. The smaller the number, the less melting loss.

In Examples 1 to 5 and Comparative Example 1, since the amorphous refractory having basic properties or the brick was used, the melt loss index was small. Comparative Example 2 using an alumina amorphous refractory
Has a large melt loss index.

Occurrence of cracks in the slag line section: Observing the occurrence of cracks in the slag line section and below
The evaluation was made in three levels, large, small and none. In each of Examples 1 to 5, there is no crack. In Comparative Example 1 in which brick is used in the slag line portion, a large crack is generated. Comparative Example 2
Since the whole is made of the same material, there are no cracks in the slag line and below it.

Workability: The time required for the construction of the refractory around the dip pipe was measured. In Comparative Example 1, it was difficult to install the brick in the slag line portion, and it took a considerable time.

Service life: The service life of the entire immersion tube.
Comparative Example 1 was excellent in corrosion resistance of the slag line portion,
Molten steel and slag infiltrate into the cracks generated at the boundary between the slag line portion and the lower portion thereof, and local melting loss is remarkable, and the life of the entire immersion pipe is inferior to that of the embodiment of the present invention. Comparative Example 2
Since the entire peripheral refractory is made of alumina amorphous refractory,
Smelting of the slag line is remarkable.

Although not shown in the test items of Table 2, in Comparative Example 1 in which the slag line portion was provided with bricks, several bricks fell off due to the external force of the removal metal fittings during slag removal. The part was repaired with a patching refractory and used.

Although the immersion pipe of the RH type vacuum degassing apparatus was mentioned in the examples, the present invention can also obtain the same effect with the immersion tube of the DH type vacuum degassing apparatus or the CAS apparatus.

[0034]

As described above, the dip tube of the present invention is easy to construct and has excellent durability, and therefore is effective in reducing the repair man-hours and refractory unit consumption. Further, the durability and reduction of repair man-hours greatly contribute to the improvement of the operation rate of the molten steel processing apparatus.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 1 Metal cylinder 2 Outer peripheral refractory 3 Inner peripheral refractory 4 Basic property irregular refractory 5 Alumina irregular refractory

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michio Fukuoka 1-3-1 Niihama, Arai-cho, Takasago, Hyogo Prefecture Harima Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A submerged pipe having a refractory material on the outer and inner circumferences of a metal cylinder, wherein the outer peripheral slag line is made of a refractory having an irregular basic property, and the lower portion of the outer peripheral slag line is made of alumina-based material. Immersion pipe for molten steel processing equipment that is a standard refractory. 2. A submerged pipe having a refractory material on the outer and inner circumferences of a metal cylinder, wherein the outer peripheral slag line portion and the upper portion of the slag line portion are refractory materials having an irregular basic property, and the outer peripheral slag line portion. Immersion pipe for molten steel processing equipment with lower part made of alumina amorphous refractory.