JPH0243551Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention aims to extend the life of the nozzle by preventing erosion and clogging, especially around the discharge port, and enables continuous casting for long periods of time. Regarding immersion nozzles for use.

[Conventional technology]

Conventionally used immersion nozzles for continuous casting suffer from erosion of the powder line of the nozzle, defects around the discharge port due to expansion of the discharge port, and precipitation of non-metallic inclusions such as deoxidation products on the inner surface of the nozzle. Nozzle clogging due to adhesion occurs within a relatively short operating time, resulting in a short nozzle life. Therefore,
As a countermeasure, the thickness of the powder line may be increased, or a slit may be provided to blow out inert gas from the inner surface of the nozzle, as disclosed in JP-A-58-151948 and JP-A-55-114449. For example, there are those shown in FIGS. 6 and 7.

Reference numeral 1 denotes a nozzle body of an immersion nozzle, which is attached to the bottom of the tundish 2 in order to supply molten steel in the tundish 2 to the mold 3. The molten steel passes through the passage 1a of the nozzle 1, flows down through the discharge port 4 into the mold 3, and is drawn from there after the extremely thin layer on the surface begins to cool and solidify. When the amount of molten steel in the tundish 2 falls below a certain amount due to continued drawing,
Molten steel is replenished from a melting furnace (not shown), etc.
It is now possible to perform continuous extraction for several hours.

Reference numerals 5, 6, 7, etc. are outlets for inert gas, such as Ar gas. Reference numeral 5 denotes a bolus portion formed of a porous member, to which Ar gas is supplied through a gas conduit 8, and 6 and 7 denote slits provided on the inner surface of the nozzle 1 to which Ar gas is supplied through a gas conduit 9. Ru.
Ar gas is simultaneously blown out from these gas outlets 5, 6, and 7 to the inner surface of the nozzle to prevent the nonmetallic pressure substances from depositing and adhering to the inner surface of the nozzle 1, etc.

[Problem that the invention attempts to solve]

However, in the case of such conventional immersion nozzles, a lot of melting damage occurs at the position of the outlet 7 (section A in Fig. 6), which shortens the nozzle life, and also prevents Ar gas from being blown into the nozzle. However, as shown in FIG. 7, there was a problem in that it was not possible to prevent the nonmetallic inclusions 11 deposited on the nozzle bottom 10 from narrowing the discharge port 4 or clogging it. . This invention was made in view of such conventional problems, and by providing an air outlet at the bottom of the nozzle in addition to the air outlet provided on the inner surface of the nozzle,
The purpose is to solve the above problems.

[Means for solving problems]

This invention is an immersion nozzle for continuous casting that has an inert gas outlet on its inner surface, in which the outlet of the immersion nozzle is directed diagonally downward, and the outlet is provided at the bottom of the immersion nozzle. , an immersion nozzle for continuous casting, characterized in that an outlet is provided for blowing inert gas upward from the bottom against the flow of molten steel flowing down within the immersion nozzle. be.

[Effect]

Molten steel flowing down from the tundish passes through a passage within the nozzle and collides with the nozzle bottom, and at this time, nonmetallic inclusions in the molten steel tend to precipitate and adhere to the nozzle bottom. However, since the inert gas is blown upward from the outlet at the bottom of the nozzle against the flow of molten steel flowing down inside the immersion nozzle, non-metallic inclusions are prevented from adhering to the bottom, blocking the outlet. The state is controlled.

Furthermore, if inert gas is blown upward from the bottom of the immersion nozzle against the flow of molten steel flowing down inside the nozzle, this inert gas can eliminate the negative pressure generated at the top of the nozzle discharge port. .
Therefore, there is no flow from the molten steel surface to the negative pressure above the nozzle discharge port, which suppresses the progress of erosion of the discharge port, etc. due to mold powder entrainment, and extends the life of the immersion nozzle. can be achieved.

〔Example〕

This invention will be explained below based on the drawings. 1 to 5 are diagrams showing an embodiment of this invention.
Note that the same parts as in the conventional example are given the same reference numerals, and redundant explanation will be omitted.

FIG. 1 is a sectional view of a main part of the embodiment, and FIG. 2 is a partially enlarged view thereof. In the figure, 22 is the bottom of the immersion nozzle 21, and 23 is an Ar gas outlet provided at the bottom. A indicates the lower end of the discharge port 4, and B indicates the upper end. The discharge port 4 is formed diagonally downward.

Now, when the molten steel flows down from the tundish 2 into the immersion nozzle 21, collides with the bottom part 22, and is supplied from the discharge port 4 into the mold 3, the porous part 5, which is a blowout port, the slit 6, and the bottom blowout port 2.
At the same time, Ar gas is blown out from the nozzle 21 and the non-metallic inclusions 11 deposited on the inner surface of the nozzle 21 and the upper surface of the bottom 22 are deposited at a significantly slow rate.

Next, a description will be given of suppressing the progress of erosion of the nozzle discharge port due to mold powder entrainment.

The molten steel flowing out of the tundish 2 collides with the nozzle bottom 22, but since the discharge port 4 is formed to face diagonally downward, the molten steel flows down into the mold without reducing its flowing speed much. . At this time, in the vicinity of the nozzle discharge port 4, that is, in the area RO in Fig. 2, negative pressure is generated due to the high dynamic pressure of the molten steel, resulting in a pressure state similar to that of the conventional nozzle shown in Fig. 3, which will be described later. . In this case, the upper end portion (b) of the nozzle discharge port 4 is melted and damaged due to the entrainment of mold powder.

On the other hand, air is blown upward from the air outlet 23.
Since the Ar gas is blown out against the flow of molten steel, it eliminates the negative pressure that tends to occur near the upper end of the nozzle outlet 4, so the flow of mold powder from the molten metal surface to the upper end is reduced. Erosion damage around the upper end of the discharge port 4 due to mold powder is also reduced.

Figure 3 shows the measurement results of the pressure distribution near the discharge port 4 using a water model. In the conventional nozzle, the negative pressure generated near the top end of the discharge port 4 is shown by a solid line. As is clear from the examples, it has been improved to provide positive pressure.

Figure 4 shows the relationship between the nozzle usage time (casting time) and the height of non-metallic inclusions.
It can be seen that for the same usage time (280 minutes), the performance of the example is significantly lower than that of the conventional example. Figure 5 shows
This figure shows the relationship between the casting time and the speed of expansion due to melting or chipping of the discharge port, and it can be seen that the speed of expansion is extremely low in the examples.

As a result, the conventional 1 nozzle with 6 units (heat size
230 tons), but it has now become possible to perform eight continuous castings with one nozzle.

[Effect of idea]

As explained above, according to this invention, there is a blowout port at the bottom of the immersion nozzle that blows out inert gas upward from the bottom against the flow of molten steel flowing down inside the immersion nozzle. Because of this, it is possible to provide an immersion nozzle for continuous casting that can significantly reduce the blockage depth of the nozzle and also suppress expansion of melting damage at the discharge port.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main part of the embodiment according to the present invention, Figure 2a is a partially enlarged view of Figure 1, Figure b is a sectional view taken along line B-B in Figure a, and Figure 3 is a water model test. Fig. 4 is a comparison diagram between the embodiment and the conventional example showing the relationship between casting time and the accumulation height of nonmetallic inclusions, and Fig. 5 shows the casting time and enlargement of the discharge port. A comparison diagram between the embodiment and the conventional example showing the relationship with speed, FIG. 6 is a sectional view of a main part of the conventional example, and FIG. 7 is a partially enlarged sectional view of the conventional example. 1, 21...Immersion nozzle, air outlet -5
... Porous part, 6 ... Slit, 23 ... Bottom outlet; 10, 22 ... Bottom.

Claims (1)

[Scope of utility model registration request] An immersion nozzle for continuous casting having an inert gas outlet on the inner surface, the immersion nozzle having the outlet facing diagonally downward,
Further, the immersion nozzle is characterized in that the bottom thereof is provided with an outlet for blowing inert gas upward from the bottom against the flow of molten steel flowing down within the immersion nozzle. Immersion nozzle for continuous casting.