JPH0135892B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of RH immersion tubes and aims to improve their durability.

Conventionally, RH immersion pipes have generally had the structure shown in Figures 1 and 2 of the drawings, and the problem with this conventional structure in use is that cracks have formed from the cut corner Pa of the lowermost brick 1a. This is caused by the intrusion of molten steel due to the opening of the joint between the lowest brick 1a and the middle brick 2a and the joint joint between the lowest brick 1a and the castable 3a. This intrusion of molten steel melts the steel shell 4a that maintains the refractories constituting the immersion pipe, and must be absolutely avoided. Note that 5a is a flange.

However, the lowermost brick 1a in the above conventional structure
The depth of cut is shallow, the engagement at the tip of the steel skin 4a is weak, the bottom brick 1a is not held down enough, and the joint between the middle brick 2a and the bottom brick 1a opens throughout the life of the immersion pipe. It was impossible to prevent this for a long time.

In addition, since the cutting height is long, the cutting corner Pa
The cracks were highly developed, allowing molten steel to penetrate. Therefore, as a means of preventing the intrusion of molten steel, it has been adopted to repair cracks and joints by spraying castable mixed with water from the outside when using a dipping pipe. However, this repair method causes an increase in RH treatment costs due to the expensive spraying material, which has a large impact on steel costs.

This invention was made in view of the above, and by limiting the shape of the cut portion of the lowermost brick,
An object of the present invention is to provide an RH immersion pipe that prevents molten steel from entering due to opening of joints or cracks in various parts.

Next, the present invention will be explained in detail with reference to FIGS. 3 to 5 below.

First, in the enlarged sectional view of the main part around the bottom brick 1 shown in Fig. 3, the cutting height a is set to 1/10 to 1/10 of the total height h.
It will be 1/5. In this case, if it is less than 1/10, the thickness of the iron skin 4 will be smaller than the normal thickness and the purpose of protecting the iron skin 4 with bricks will not be achieved, and conversely, the thickness will be 1/10 or less.
This is because if it is 5 or more, cracks will occur from the cut corner P. The cutting depth b is the total depth (1/5 to 1/2 of the working thickness d).
If it is less than 1/5, the engagement of the steel skin 4 will be shallow, weakening the brick holding, and causing gaps between joints, and if it is more than 1/2, the effective usable thickness will be less than half, This is because the durability from the aspect of melting and damage becomes a drag.

In addition, as in the embodiment shown in FIG. 4 of the drawings, if a protrusion 6 made of stainless steel or ceramics is embedded in advance during manufacturing of the lowermost brick 1, that is, during casting, the joining between the lowermost brick 1 and the castable 3 is prevented. Sexuality can be enhanced and improved. Furthermore, as the lowermost brick 1 is shortened, the thickness of the castable 3 portion increases, increasing the chance of flaking, but as shown in the embodiment shown in FIG. This can be prevented by doing so.

Next, the effects of this invention will be described with reference to Examples.

Example A dip tube having a structure based on the present invention was manufactured by N.
A field test was conducted at a steelworks. The results were very good and the following results were obtained.

Conventional structure Structure using this method Ascending pipe 60 times 110 times Descending pipe 60 times 140 times Total 120 times 250 times Conventionally, the reason why the structure can only last 60 times as a rising pipe is due to melting of the joint between the bottom brick and the top brick (Infiltration of molten steel) and erosion of the joint between the bottom brick and castable, which was actually obtained by spraying repairs every 5 to 6 times. After being used as an ascending pipe, it was further repaired with castables in the cold and was used as a descending pipe for 60 times. On the other hand, the immersion pipe according to the present invention shows no joint erosion as described above.
It exhibited approximately twice the durability as a riser pipe, and similarly demonstrated high durability as a downcomer pipe. This is due to a structural improvement in which the bricks at the bottom of the immersion pipe are now castable, which was a problem in the past, and the infiltration of molten steel can be avoided.

As described above, this invention defines the dimensions of the cut height a and the cut depth b of the cut portion of the lowermost brick, and limits the shape, so that the engagement between the lowermost brick and the steel shell is improved. This has the excellent effect of preventing molten steel from entering due to joint opening or cracking between the bottom brick and the castable.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a conventional RH immersion pipe, Fig. 2 is an enlarged longitudinal sectional view of the lowermost brick of the main part of the same, and Fig. 3 is an enlarged longitudinal sectional view of the lowermost brick of the main part of the same. Figures 4 and 5 are enlarged longitudinal cross-sectional views of other embodiments of the same as above. 1, 1a...lowest tier brick, 2, 2a...middle tier brick, 3, 3a...castable, 4, 4a...iron shell, 5a...flange, 6...protrusion, 7...wire mesh, a... ...Height of cut, b...Depth of cut, d...
...Thickness used, h...Overall height, P...Corner of cut.

Claims (1)

[Claims] 1. In the RH immersion pipe, in the vertical cross-sectional shape of the lowest brick, the cutting height a is 1/10 to 1/5 of the total height h,
Depth of cut b is 1/5 to 1/2 of the total depth (use thickness d)
An RH immersion tube characterized by satisfying the following conditions. 2. The RH immersion pipe according to claim 1, wherein a protrusion is provided on the lower end surface of the lowermost brick to improve bondability with the castable. 3. The RH immersion pipe according to claim 1, wherein a wire mesh is embedded in the lower castable of the lowermost brick.