JPS6360055A - Continuous casting nozzle - Google Patents

Abstract

PURPOSE:To restrain the stick of alumina to an inner wall of nozzle and to prevent the clogging of nozzle by making a molten metal flowing passage at lower end part, which is submerged into molten metal in a continuously casting nozzle, to a shape broadening toward the lower end. CONSTITUTION:The continuously casting nozzle 12 is composed of a discharging hole nozzle part 20, sliding nozzle 22, connecting nozzle 24 and submerged nozzle 26. The submerged nozzle 26 has an oval-shape broadening toward the lower end at the lower end part of molten metal flowing passage 34, which is submerged into the molten metal 16 in a mold 18, and a right circular cylinder-shape at the upper part of molten metal flowing passage 34, which is not submerged into the molten steel 16. In this way, by reducing the resistance at the lower part side of nozzle, lowering the molten surface height in the inside face of nozzle and reducing the volume of boundary layer for molten steel flow in the nozzle and the molten metal quantity passing through this boundary layer, the stick of alumina is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a continuous casting nozzle for injecting molten metal in a tundish into a mold.

[Conventional technology]

Continuous casting nozzles for injecting molten metal in a tundish into a mold are conventionally known to include sliding nozzles and immersion nozzles. The sliding nozzle is used to adjust the amount of molten steel injected from the tundish into the mold, and the immersion nozzle is disposed such that its lower end is immersed in the molten steel in the mold in a steady state.

By the way, as shown in FIGS. 5(a) and 5(b), the immersion nozzle 2 normally has a molten steel flow path (molten metal flow path) 4 extending along the axial direction to the vicinity of the lower end of the nozzle, and It has a molten steel discharge port (molten metal flow path) 6 that communicates with the lower end and opens on the side surface of the nozzle. However, since the molten steel flow path 4 of the conventional immersion nozzle is shaped like a right cylinder, the height 11 of the molten steel surface 8 becomes high, and this results in a boundary layer of the molten steel flow flowing through the molten steel flow path 4, which has a low flow velocity. The proportion of the portion becomes larger. Therefore, the amount of molten steel 10 passing through this slow-flowing boundary layer increases, which causes molten steel 1
The alumina (AI!203) in the immersion nozzle 2 tends to adhere to the inner wall of the immersion nozzle 2. A in this melt w410, ffz
The adhesion of 03 is due to A and f' in the refractory material constituting the nozzle 2.
This is due to sintering with Al 203, but it can cause blockage of the nozzle 2, and also cause Al adhering to the inner wall of the nozzle 2.
103 peels off from the inner wall of the nozzle 2 and becomes interposed in the steel, causing a deterioration in product quality.

Therefore, in the past, inert gas such as argon gas (Ar gas) was blown into the nozzle 2 to clean the A and j7203 attached to the inner wall of the nozzle 2.

[Problem that the invention seeks to solve]

However, if a large amount of this inert gas is blown into the melt, the level of the hot water will fluctuate, causing quality defects such as powder entrainment. For this reason, it is necessary to restrict the gas inlet to a limited range, and this cannot be said to be a sufficient measure to prevent the adhesion of A and f'203.

The present invention has been made based on the above circumstances.
The object of the present invention is to provide a continuous casting nozzle that suppresses the adhesion of alumina to the inner wall of the nozzle and prevents the nozzle from clogging.

[Failure to solve the problem]

In order to solve the above problem, the present invention provides a continuous casting nozzle for injecting the molten metal in the tundish into the mold, in which the molten metal flow path at least in the lower end portion immersed in the molten metal is shaped to widen toward the lower end. be.

[Effect]

By forming the molten metal flow path at least in the lower end portion of the nozzle, which is immersed in the elution, into a shape that widens toward the lower end, the resistance on the lower end side of the nozzle is reduced, and the height of the molten metal level within the nozzle is reduced. This reduces the volume of the boundary layer of the molten steel flow in the nozzle and reduces the amount of molten metal passing through this boundary layer, thereby reducing alumina deposition.

〔Example〕

1 Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a continuous casting machine, and 12 in this figure is a continuous casting nozzle for injecting the molten steel 16 in the tundish 14 into the mold 18. This continuous casting nozzle 12 is
It is composed of an outflow hole nozzle section 20, a sliding nozzle 22, a connecting nozzle 24, and an immersion nozzle 26.

The outlet nozzle part 20 is made of porous brick and is attached to an outlet hole 28 formed in the bottom of the tundish 14. An inert gas such as Ar gas is supplied into the casting nozzle 12 through this outlet nozzle section 20.

The sliding nozzle 22 has an outflow hole nozzle portion 20
It consists of a fixed platen 30 that is attached to the fixed platen 30 and a sliding plate 32 that is slidably attached to the fixed platen 30. The injection of molten steel 16 from 14 to mold 18 is controlled.

The connecting nozzle 24 is for connecting the immersion nozzle 26 to the sliding plate 32.

The immersion nozzle 26 has a molten steel flow path (molten metal flow path) 34 that extends along the axial direction to near the lower end of the nozzle, and a molten steel discharge port (molten metal flow path) that communicates with the lower end of the molten steel flow path 34 and opens on the side surface of the nozzle. ) 36, and is disposed such that its lower end is immersed in the molten steel 16 in the mold 18 in a steady state.

Thus, the molten steel 16 in the tundish 14 passes through the outflow hole nozzle section 20, the sliding nozzle 22, the connecting nozzle 24, and the immersion nozzle 26 in order, and then enters the mold 18.
is injected into the solidified shell 3 and cooled by the mold 18 to form a solidified shell 3.
8 is formed.

Next, to further explain the immersion nozzle 26, as shown in FIGS. 1(a) and 1(b), the immersion nozzle 26
The molten metal flow passage 34 at the lower end portion (immersed portion 34a) that is immersed in the molten steel m16 in the mold 18 has an elliptical shape that widens toward the lower end, and the upper portion (non-immersed portion 34b) that is not immersed in the molten steel 16. The molten metal flow passage 34 is shaped like a right cylinder.

Next, the flow of the melt m16 inside the immersion nozzle 26 will be explained.

As shown in FIGS. 1 and 2, a gap is created within the immersion nozzle 26 due to the effect of blowing Ar gas, and the molten steel 16 freely falls onto the molten metal surface 40 within the nozzle 26. Therefore, the molten steel flow in the nozzle 26 is divided into a free-falling portion and a portion filled with the molten steel 16 and flowing in a circular pipe.

Note that the molten metal surface 40 in the nozzle 26 is located above the meniscus 42 in the mold 18, considering the resistance of the discharge port 36 and the pressure of Ar gas.

Such a flow within the pipe creates a boundary layer in a portion close to the wall surface of the nozzle 26 where the flow velocity is reduced due to the influence of the viscosity of the fluid.

The equation of motion and continuity equation in this boundary layer are as follows.

The boundary conditions are u-v-Q at y-o and u-U at y-flash.
It is.

Here, ν is the kinematic viscosity coefficient (-μ/ρ, μ: viscosity coefficient, ρ
: density), U is the velocity of the main stream, X is the distance below the melt surface in the nozzle, and y is the thickness of the boundary layer at X.

f(η)−f. When converted into an ordinary differential equation by setting (u) dl f-(η)-1, it becomes as follows.

f　f　　'+　2t　II/　l-.

The boundary conditions are η-0 and f-f--Q η-(1) and f
″−1.

Here, f is a Blasius function.

Dimensionless velocity u/U is 99% at the position y-δ from the wall surface
If it reaches u/U −f −−0,99, then η−5,0, so the thickness δ of the boundary layer is δ−5,0 Here, in general, the thickness of the boundary layer is As shown in Figures 4(a) and (b), if the average thickness of the boundary layer reduced due to the influence of viscosity is δ, then δ*U-J"" (
U-u)dy The upper limit of this component is just the distance at which the speed is steady, so if η-7,8, then f(η)-f3.079, so the short diameter of the nozzle 26 shown in Fig. 1 is dl and the major axis is d2, then d2-ax+d+ (a>1). Further, the diameter of the nozzle 2 shown in FIG. 5 is assumed to be dl. Molten steel Q passing through the nozzle 26.2 per unit time
Assuming that Q is the same, A1ρ δ2/δ1-r, f Since the nozzle 26 has a shape that widens toward the end, the resistance at the discharge port 36 decreases, so the molten metal level 40 in the nozzle 26 decreases (
)2kuno1).

Therefore, the volume of the boundary layer v1. v2 is Ll.

If L2 is the length of the inner circumference of each nozzle 2, 26, then V2/Vl.

Therefore, in the nozzle 26, the volume of the boundary layer is smaller than that in the nozzle 2, and the amount of melt m16 passing through the boundary layer is reduced.
'I is reduced, and clogging of the nozzle 26 can be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, in the continuous casting nozzle for injecting the molten metal in the tundish into the mold, the molten metal flow path at least at the lower end portion immersed in the molten metal is shaped to widen toward the lower end, so that the nozzle It has excellent effects such as suppressing the adhesion of alumina to the inner wall and preventing nozzle clogging.

[Brief explanation of the drawing]

Figures 1 to 4 show one embodiment of the present invention.
Figure (a) is a cross-sectional view of the immersion nozzle, Figure 1 (b) is a cross-sectional view of the molten steel flow path, Figure 2 is a cross-sectional view of the continuous casting machine, and Figure 3 is a cross-sectional view of the boundary layer along the wall surface. A diagram showing the relationship between thickness and distance, Figure 4 (a) is a diagram showing the actual flow of the boundary layer, and Figure 4 (b) is a diagram showing the virtual flow replaced by the excluded thickness of the boundary layer. , Fig. 5 shows a conventional example, and Fig. 5 (
FIG. 5(a) is a sectional view of the immersed nozzle, and FIG. 5(b) is a diagram showing the sectional shape of the molten steel flow path of the immersed nozzle. 12... Continuous casting nozzle, 14... Tandish, 16... Molten metal (molten ji4), 18... Mold,
34... Molten metal flow path. Applicant's agent Patent attorney Takehiko Suzue (a) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A continuous casting nozzle for injecting molten metal in a tundish into a mold, characterized in that a molten metal flow path at least at a lower end portion immersed in the molten metal has a shape that widens toward the lower end.