JPS6345906B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a steelmaking nozzle that reduces nozzle clogging due to solidification of molten steel or adhesion of nonmetallic inclusions.

Conventionally, materials such as high alumina, zircon, and zirconia have been used for steelmaking nozzles, and they generally have a single-piece structure.

These materials have excellent corrosion resistance, but when aluminum-killed steel is cast, inclusions containing Al ₂ O ₃ tend to precipitate on the nozzle operating surface (inner diameter surface) and cause blockage of the nozzle hole. Yes, this is especially true for high alumina nozzles.

For this reason, even though the damage to the nozzle is slight and the remaining wall thickness is sufficient for safety reasons, the blockage often makes it impossible to control the flow rate, forcing the nozzle to be discarded. Ta.

It was found that the main causes of nozzle hole clogging were the cooling solidification of molten steel and the adhesion of nonmetallic inclusions on the nozzle operating surface.

In addition to this, the nozzle material naturally has corrosion resistance,
It is necessary to satisfy basic conditions such as mechanical strength and heat spalling resistance, but it can be said that there is no material that has all of these characteristics.

The present invention has been made in view of these circumstances, and provides a steelmaking nozzle having a three-layer structure that skillfully combines the characteristics of different materials to produce a synergistic effect.

The gist of this invention is to have a three-layer structure consisting of a first layer on the working surface side in contact with molten steel, a second layer outside the first layer, and a third layer outside the second layer, Moreover, the present invention provides a steelmaking nozzle in which the first layer is made of a refractory that has poor wettability with molten steel, the third layer is made of a heat insulating material, and the second layer is made of a corrosion-resistant refractory.

In this invention, since the first layer on the side where the nozzle is operated is provided with a refractory material having poor wettability with molten steel, adhesion of inclusions can be prevented. The second layer is made of a material with excellent corrosion resistance and mechanical strength, which is commonly used for steel manufacturing nozzles, so that it functions as a safety nozzle base. The third layer is a heat insulating layer, and the outer periphery of the second layer is coated with a heat insulating material to prevent cooling. By forming the three-layer structure in this way, it is highly safe in use, and has a synergistic effect, especially in preventing nozzle clogging.

Embodiments of the present invention will be described below with reference to the drawings.

First, referring to FIG. 1, an embodiment in which the present invention is applied to a sliding nozzle will be described. The upper nozzle 10 consists of a first layer 11, a second layer 12, and a third layer 13, each of which is made of the following materials.

(A) Regarding the first layer 11, natural graphite is used as a material that is difficult to wet with molten steel.
% of Al ₂ O ₃ --C refractory, which is generally used for immersion nozzles, was selected.

Sessile is a well-known method for measuring wettability.
When the contact angle was measured by the drop method, the following data were obtained. In other words, although it varies somewhat depending on the steel type, it is 140 to 145° for Al ₂ O ₃ -C steel, and 140 to 145° for Si ₃ N ₄
130-135° for BN, 135-140° for BN, while 60-90° for high alumina, 110-115° for zircon, ZrO ₂
is 120 to 125°, and it has been found that a preferable wettability for molten steel is 130° or more for the interior of the three-layer structure steelmaking nozzle of the present invention.

The appropriate thickness of the first layer 11 is 5 to 20 mm.
If the thickness is less than 5 mm, it is difficult to manufacture. In addition, the inside of the nozzle hole may need to be cleaned with enzymes due to unexpected troubles, and with Al ₂ O ₃ -C material, there is a possibility of abnormal erosion due to carbon oxidation. There is a risk of a steel leakage accident.

(B) Regarding the second layer 12, it has a proven track record in terms of corrosion resistance and mechanical strength.
A high alumina refractory containing 80% Al ₂ O ₃ was used.
Other materials such as ZrO ₂ material, zircon material, MgO material, and spinel material are also possible, but syamoto material is not preferable because it has inferior corrosion resistance than the Al ₂ O ₃ --C material of the first layer.

(C) Regarding the third layer 13, a molded body of Al ₂ O ₃ --SiO ₂ fibers was used. Its thermal conductivity is 0.1 Kcal/m・h・℃ at 350°C, 2.1 Kcal/m・h・℃ for high alumina material and 42 Kcal/m・m・cm for the Al ₂ O ₃ -C material of the first layer 11. h・℃
much smaller. In addition, the thermal conductivity is 0.1~
0.5Kcal/m・h・℃ fireproof insulation bricks can also be used.

The first layer 11, second layer 12, and third layer 13 are separately molded, and then molded using high alumina mortar or the like.
The upper nozzle was assembled as shown in Figure 1.

When the above-mentioned upper nozzle 10 was incorporated into a sliding nozzle for tundishing, the following effects were observed.

Conventionally, a high alumina nozzle (hole diameter 70 mm) was used that was entirely made of the same material as the base material of the second layer 12 of the nozzle of the present invention, but such a conventional nozzle had an Al content of 0.03. When continuously casting ~0.05% aluminum-killed steel, it became necessary to clean the inside of the nozzle hole from the end of the third continuous cast of the 160-ton ladle, which was a major factor in the deterioration of the quality of the slab. Nozzle blockages are also observed in plate refractory holes and submerged nozzle holes, but not to the extent that they affect casting speed. After continuous casting, in the conventional upper nozzle, metal and inclusions adhered to the hole, and the remaining effective hole diameter was reduced to about 15 to 18 mm.

On the other hand, when the nozzle according to the present invention is used, it becomes possible to stably perform up to 8 continuous castings without oxygen cleaning, and it has become possible to perform up to 11 continuous castings at maximum.

2 and 3 respectively show plate refractories 1 of a three-layer sliding nozzle according to the present invention.
5 and an open nozzle 16 are shown.

In the case of the plate refractory 15 shown in Fig. 2, the sliding surface 1
Since the hole edge 15b on the 5a side is the most important part for controlling the flow rate, the base material is left at a predetermined height H from the sliding surface 15a, for example, 10 to 20 mm, and the other hole diameter inner surface is used as the first layer 11. Al ₂ O ₃ -C quality and BN
It is made of a material that does not easily get wet. Further, the materials of the second layer 12 and the third layer 13 are the same as in the example shown in FIG.

In the example of the open nozzle 16 shown in FIG. 3, the first layer 11 is provided over the entire hole diameter, and the third layer 13 is provided over the entire circumference except for the upper part of the second layer 12. First layer 11, second layer 12 and third layer 1
The material of 3 is the same as that in FIG.

[Brief explanation of the drawing]

1, 2, and 3 are schematic sectional views showing a first embodiment, a second embodiment, and a third embodiment of the present invention, respectively. 11...first layer, 12...second layer, 13...third layer.

Claims (1)

[Claims] 1. The first layer on the working surface side that comes into contact with molten steel;
It has a three-layer structure with a second layer outside the first layer and a third layer outside the second layer, and the first layer is made of a refractory that has poor wettability with molten steel, and the third layer is made of a heat insulating material. 1. A steelmaking nozzle characterized in that the second layer is made of a corrosion-resistant refractory material.