JPH11277196A - Lower nozzle for vessel for molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to prevent the suction of air in spite of the occurrence of crack in a lower nozzle at the time of use by providing the lower nozzle with a metal case which integrally covers the projecting part of the fitting part of a concave mold, the stepped part of the fitting part of a convex mold and the outer peripheral part thereof. SOLUTION: The surfaces the projecting part 6 of the fitting part 3 of the concave mold and the stepped part 7 of the fitting part 4 of the convex mold are previously provided with a difference 12 in level in the portion covered by the metal case 9 and is made flush with the portion not covered by the metal case 9. The upper part of the lower nozzle is press fitted to a plate brick and the lower part to an immersion nozzle, etc., in the fitting part of the lower nozzle 1. Then, the top end and bottom end of the integrated metal case 9 are completely closed and, therefore, there is no room for the infiltration of the air at all and consequently, even if the crack occurs in the lower nozzle body 2, the possibility of sucking the air is very little. Accordingly, the quality of the steel is stabilized and the life of the nozzle is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lower nozzle for a molten metal container, and more particularly to a lower nozzle used in a sliding nozzle device for controlling a flow rate of molten steel.

[0002]

2. Description of the Related Art As shown in FIG. 2, a refractory used in a sliding nozzle device has an upper nozzle 31 attached to a discharge port at the bottom of a molten metal container, a plate brick 32 for controlling a flow rate, and a plate brick. There is a lower nozzle 33 mounted below the brick. Usually, an immersion nozzle or a long nozzle is mounted on the lower nozzle. Depending on the use conditions, a second nozzle (sometimes called an intermediate nozzle) may be provided between the lower nozzle and the plate brick.
It is included in the lower nozzle. These refractories are based on alumina raw materials, carbon,
An alumina-based material using zirconia, metal powder, or the like is generally used. This refractory material passes through high-temperature molten steel of about 1600 ° C. without being preheated at the time of use, and is used repeatedly many times. Therefore, heat resistance, heat shock resistance, corrosion resistance, wear resistance, and the like are required. .

The lower nozzle is used to connect the plate brick to the immersion nozzle or the long nozzle. When the lower nozzle is used, the temperature of the inner hole and the outer peripheral surface is increased due to the outside being in contact with air. Since the difference is extremely large, a crack is easily generated from the outer peripheral surface toward the inner hole. When a crack occurs, the quality of the steel is reduced due to the inhalation of air from the crack, and the refractory may be locally melted and damaged. This erosion is presumed to be due to the oxygen in the air sucked in through the cracks, which oxidizes the molten steel in contact with the inner hole surface, and turns into iron oxide that is easy to dissolve the refractory, so that the area around the cracks is locally eroded. Is done. As a method for preventing the inhalation of air from the crack, Japanese Utility Model Laid-Open Publication No. 50564/1981 discloses that only the side surface of the lower nozzle body 41 is covered with a metal case 42 as shown in FIG.

[0004]

Problems to be Solved by the Invention
With the metal case disclosed in 564, the adverse effects of cracks have been improved for the time being, but the air suction is not completely eliminated because the coating is only on the sides.
It still occurred occasionally and was one of the causes of nozzle damage.
This is presumed to be due to the fact that the metal case becomes hot and expands during use, so that a gap is generated between the lower nozzle body and the metal case, and air is sucked through the gap. Accordingly, an object of the present invention is to provide a lower nozzle for a molten metal container that can prevent air from being sucked in even when a crack occurs in the lower nozzle during use.

[0005]

The gist of the present invention is as follows. (1) In a lower nozzle for a molten metal container in which one fitting portion is concave and the other fitting portion forms a convex shape, the protrusion of the concave fitting portion, the step portion of the convex fitting portion, and A lower nozzle for a molten metal container, comprising a metal case for integrally covering an outer peripheral portion. (2) The lower nozzle for a molten metal container according to claim 1, wherein a mortar filling portion having a thickness of 0.5 to 5 mm is provided between the metal case and the lower nozzle body.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention is as described above. However, as shown in FIG.
On the other hand, in the present invention, it is presumed that air is sucked from between the metal case and the lower nozzle body during use, and the fitting portion between the concave portion and the convex portion is covered with the metal case. The present invention is illustrated in FIG. FIG. 1 is a sectional view of a lower nozzle 1 showing an embodiment of the present invention. This lower nozzle is of the type also referred to as an intermediate nozzle of the type that is connected to another lower nozzle below, and usually a submerged nozzle is connected below the other lower nozzle. The lower nozzle body 2 has a concave fitting part 3 on the upper side for fitting with the plate brick, and a convex fitting part 4 on the lower side for fitting with another lower nozzle. Has an inner hole 5 through which molten steel passes.

The protrusion 6 of the concave fitting portion 3 of the lower nozzle body, the step 7 of the convex fitting portion, and the outer peripheral portion 8
Are covered by an integrated metal case 9. When the lower nozzle 1 is repeatedly used, the inner hole 5 gradually wears out, so that the inner hole diameter increases. Therefore, when the metal case is covered to the vicinity of the inner hole in the fitting portion and the inner hole expands, the metal case comes into contact with and melts the molten steel, so that there is a possibility that the molten steel may become a path through which the molten steel leaks. Therefore, in the fitting portion, since it is preferable to be sufficiently away from the inner hole surface,
The metal case 9 covers up to the protruding portion 6 in the concave fitting portion and up to the step portion 7 in the convex fitting portion. A mortar 10 is filled between the metal case 9 and the lower nozzle body 2. The mortar is a general mortar and can be used without any problem. For example, refractory fine powder obtained by adding a binder such as clay and water glass or aluminum phosphate can be used. The filling thickness of the mortar is suitably 0.5 to 5 mm. That is, 0.5m
If it is less than m, the filling amount is insufficient, and if it exceeds 5 mm, a gap is easily generated due to the effect of shrinkage of the mortar, which is not preferable.

In FIG. 1, the front end portion 11 of the metal case on the side surface of the lower nozzle is welded to the other metal case of the upper and lower fitting portions along the entire circumference. In the mounting operation of the metal case, mortar is applied to the outer peripheral portion and the fitting portion of the lower nozzle main body in advance. The metal case is divided into two parts in advance, and the metal case is separately mounted from the upper side and the lower side. One of the two divided metal cases shares a side surface with one of the fitting portions, and the other one has only the remaining donut-shaped fitting portion. When the metal case having the fitting portion is mounted on the lower nozzle body first, excess mortar protrudes. Therefore, after completely removing the mortar, the metal case of the lower fitting portion is mounted. Thereafter, the upper and lower metal cases are welded to integrate the metal case. Although the metal case shown in FIG. 1 has a thickness of 2 mm, the metal case of the present invention is 0.5 to 5 mm.
Is appropriate.

On the surface of the projection of the concave fitting portion and the surface of the convex fitting portion, a step 12 is provided in advance in a portion covered by the metal case, and is formed on the same surface as the portion not covered by the metal case 9. I am trying to become. At the fitting portion of the lower nozzle, the upper portion of the lower nozzle is press-bonded to a plate brick and the lower portion is press-bonded to a submerged nozzle or the like via mortar or a joint material. Therefore, since the upper and lower ends of the integrated metal case are completely closed, there is no room for air to enter, and even if a crack occurs in the lower nozzle body, the possibility of sucking air is very low.

[0010]

According to the present invention, there is provided a lower nozzle for a molten metal container in which one fitting portion is concave and the other fitting portion forms a convex shape. Since the metal case covers the joint and outer periphery integrally, even if the metal case expands during use, air is not sucked through the gap between the lower nozzles, and the quality of steel is stable. In addition, the effect of improving the life of the nozzle can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lower nozzle for a molten metal container according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a lower nozzle having a sliding nozzle device.

FIG. 3 is a sectional view showing a conventional lower nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower nozzle 2 Lower nozzle main body 3 Concave fitting part 4 Convex fitting part 5 Inner hole 6 Projection part 7 Step part 8 Outer part 9 Metal case 10 Mortar 11 Tip part 12 Step part

Claims (2)

[Claims] In a lower nozzle for a molten metal container in which one fitting portion is concave and the other fitting portion is convex, a projection of the concave fitting portion and a step of the convex fitting portion are provided. A lower nozzle for a molten metal container, comprising a metal case that integrally covers a portion and an outer peripheral portion. 2. The lower nozzle for a molten metal container according to claim 1, wherein a mortar filling portion having a thickness of 0.5 to 5 mm is provided between the metal case and the lower nozzle body.