JP2002066729A - Submerged nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a spouting hole structure in a submerged nozzle that reduces segregated flow of molten steel in mold in such a manner that molten steel flow in the submerged nozzle not to produce dead space in the vicinity of the spouting hole but to produce a condition nearly in full stream. SOLUTION: In a submerged nozzle 10, a vertically oriented straight inner bore 1 and spouting holes 3, that are opened horizontally at lower part of the nozzle inner bore and axis-symmetrically to the bore center axis, are provided. In each spouting hole 3, a step is prepared where the diameter of the hole 3 is enlarged toward the outside of the nozzle. The opening area of a spouting hole 3 to the inner bore 1 is provided in parallel to the counterparting spouting hole and a stepped portion 2 is formed at right angles to the inner surface of each spouting hole 3. And the relation between the inner bore cross sectional area Sn and the total spouting hole cross sectional area on the inner bore surface St is expressed as 1.0Sn<=St<1.3Sn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion nozzle used for continuous casting of steel, and more particularly to a shape of a discharge hole thereof.

[0002]

2. Description of the Related Art An immersion nozzle used in continuous casting of steel causes so-called nozzle blockage, in which inclusions in molten steel precipitate and deposit on the inner surface of an inner hole or a discharge hole and block a flow path of the molten steel. .

[0003] The deposits deposited on the inner surface of the inner hole or discharge hole not only block the flow path and make the casting operation difficult, but also cause unevenness and turbulence of the molten steel flow. Affects quality. Further, the adhered and deposited alumina or the like falls off during casting and mixes into the slab to form a defective portion of steel.

[0004] In particular, when inclusions adhere to and accumulate in the discharge holes, a drift state occurs in which the amount of molten steel discharged into the mold differs for each discharge hole due to the difference in the degree of deposition in the plurality of discharge holes. When drift occurs in the mold, slab cracks occur due to variations in the temperature of the molten steel in the mold, or the flow of molten steel on one side is severe, causing abnormal slabs due to entrainment of powder and powder erosion in the discharge holes. There is.

For this reason, much effort has conventionally been made to reduce the adhesion of non-metallic inclusions, such as alumina, to the discharge holes of immersion nozzles.

As one of the measures, a compound that reacts with alumina to form a low melt is disposed in the inner hole of the immersion nozzle, and the clogging is prevented by reducing the adhered alumina at the same time and removing it with the flow of molten steel. Is well known. For example, JP-A-62-288161 discloses that C
It is disclosed that a ZrO ₂ -CaO-graphite material using a calcium zirconate clinker containing aO-ZrO ₂ as a main component is applied to the inner hole of a immersion nozzle. However, the calcium zirconate clinker is expensive because it contains zirconia and is only partially used.

As another measure, Japanese Patent Publication No. 6-595
No. 33 discloses that a gas outlet is provided on an inner wall between nozzle discharge holes, and gas is bubbled from the outlet to prevent attachment and growth of inclusions on the nozzle inner wall. I have.

[0008] However, if the amount of gas bubbling increases, bubbles are generated in the steel, which tends to cause quality deterioration.
It is very difficult to control the flow rate, and since the gas is blown in the vicinity of the discharge hole, there is also a problem that a drift occurs if the blown gas is not uniformly dispersed in the plurality of discharge holes.

On the other hand, regarding the total discharge hole cross-sectional area represented by (discharge hole cross-sectional area × number of discharge hole holes) in a conventionally used immersion nozzle for continuous casting of steel,
If the total discharge hole cross-sectional area is too small, the flow rate will be limited at the time of blockage and it will be a bottleneck for casting.If it is too large, the side wall thickness of the immersion nozzle will be insufficient, and the risk of breakage will increase due to insufficient strength. It has a size of about 1.3 to 3.0 times the area.

The flow rate of molten steel in the immersion nozzle is regulated by the cross-sectional area of the inner hole. Therefore, when the molten steel passes through the discharge hole and the molten steel passes through the discharge hole, the amount of molten steel in the discharge hole becomes unfilled, and along the inner wall surface of the discharge hole, in the ratio of the total discharge hole cross-sectional area and the inner hole cross-sectional area within this range. Creates a space (dead space). In this space, molten steel inclusions are liable to precipitate, and the accumulation of inclusions is repeated in the form of solidified metal. Due to the difference in the degree of deposition in the plurality of discharge holes, the molten steel is discharged into the mold for each discharge hole. There is a problem that the drifting states of different amounts are likely to occur.

[0011]

The problem to be solved by the present invention is to make the molten steel flow in the immersion nozzle flow in a state close to the filling flow without creating a dead space in the discharge hole, so that the molten steel flows into the mold. It is another object of the present invention to obtain a structure of a discharge hole that reduces the drift of the discharge hole.

[0012]

An immersion nozzle according to the present invention comprises:
The relationship between the inner-hole cross-sectional area Sn and the total inner-hole-side discharge-hole cross-sectional area St is set to 1.0Sn ≦ St <1.3Sn, and a step portion whose diameter increases outward is formed in the discharge hole. Features.

According to the present invention, the total discharge hole cross-sectional area (discharge hole cross-sectional area × number of discharge holes) of the immersion nozzle is set smaller, whereby the non-contact space of the inner wall of the discharge hole with the molten steel is reduced, and It is possible to reduce material accumulation and suppress occurrence of drift during casting due to adhesion of inclusions. In this case, the molten steel discharge flow rate increases due to the decrease in the total discharge hole cross-sectional area,
By causing the increase in the flow velocity to cause a pressure loss at the stepped portion provided on the inner wall surface of the discharge hole, it is possible to simultaneously reduce the flow rate to the current level or to the level lower than the current level.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 In FIG. 1 showing a first embodiment of the present invention by a vertical sectional view, an immersion nozzle 10 has a vertically straight inner hole 1 and a horizontal portion below the inner hole. The same shape is formed at the target position with respect to the vertical center axis of the inner hole,
The inside has two discharge holes 3 each having a stepped portion 2. The steps 2 are formed at right angles to the inner surfaces of the respective discharge holes 3. The cross-sectional area of the inner hole, indicated as Sn, represents the cross-sectional area at the upper end of the immersion nozzle.

As shown in FIG. 2 in which the discharge hole 3 of the immersion nozzle in FIG. 1 is enlarged, the inner hole side discharge hole 21 having the stepped portion 2 on the inner surface and having an outer diameter increased toward the outside is provided. And a hole 22. The cross-sectional area of the discharge hole means the cross-sectional area of the inner hole that appears on a plane perpendicular to the central axis A of the discharge hole.
t is the total cross-sectional area of the inner-hole side discharge holes, that is, the sum of the cross-sectional areas of the innermost discharge holes, and the relationship between the inner-hole cross-sectional area Sn and the total inner-hole-side discharge hole cross-sectional area St is 1.0Sn ≦ St. <
1.3 Sn.

As shown in FIG. 3 as viewed in the direction A in FIG. 2, the cross section of the discharge hole 3 is rectangular, the cross-sectional area of the discharge hole 3 is St1, the height of the discharge hole 3 is Is H1,
When the width of the inner side discharge hole is W1, the outer side discharge hole St2, the height of the outer side discharge hole H2, and the width W2 of the outer side discharge hole, the respective relations are almost as follows: St1 = H1 × W1, St2 = H2 × W2.

The length of the inner discharge hole 21 is L1 and the length of the outer discharge hole is L2. At this time, the inner hole diameter is 80
a mm, Uchianadan area Sn = 50.24cm ^2, Men槓is 30 cm ^2, the total hole-side discharge Anadan area St of one of the inner bore-side discharge hole 21 is 60cm ^2, St / Sn = 1.
19

As described above, the relationship between the inner-hole cross-sectional area Sn and the total inner-hole-side discharge-hole cross-sectional area St is 1.0Sn ≦ St <1.3S
It is preferably n. When St is less than 1.0 Sn, there is a problem that the flow rate is controlled by the discharge hole area,
When St is 1.3 Sn or more, the unfilled flow state becomes large and the volume of inclusions is generated, which is not preferable.

The length L1 of the inner side discharge hole is 0.1T ≦ L1 ≦ L with respect to the thickness T of the discharge hole portion of the immersion nozzle.
0.9T is more preferable from the viewpoint of resistance to breakage of the step protrusion caused by the molten steel flow, and furthermore, 0.2T ≦ L1 ≦
It was found that the drift prevention effect was higher in the case of 0.7T.

The height B of the step is 1 mm or more and 30 mm
If it is less than or equal to, it is sufficient, and more preferably 3 mm or more and 20 mm or less. If it is less than 1 mm, sufficient loss to reduce the flow velocity cannot be obtained, and if it exceeds 30 mm, the pressure loss is excessive and the ability to expand the molten steel in the mold decreases, and insufficient melting of the powder and uneven slabs hinder casting. .

Embodiment 2 FIG. 4 shows a second embodiment of the present invention in which the discharge hole of the immersion nozzle has two steps, and the discharge hole has a rectangular cross section. , The cross-sectional areas of the discharge holes from the inside toward the outside are St1, St2, S
t3 has a relationship of St1 <St2 <St3.

Embodiment 3 FIG. 5 shows a third embodiment of the present invention. The sectional shape of the discharge hole is circular, and the central axis of the discharge hole is directed upward toward the inner hole of the immersion nozzle. The inner surface of the hole has one step. The cross-sectional area across the step of the discharge hole is
St1 <St2 that spreads outward.

The above embodiment shows an example in which the step is formed over the entire inner surface of the discharge hole. However, if the above-mentioned relation of the sectional area is satisfied, the step is partially formed on the inner surface. It may be done. The installation position of the step in the thickness direction can be set to any position as long as it is inside the thickness.

Further, regardless of the cross-sectional shape of the discharge hole, any shape may be satisfied as long as the cross-sectional area increases outward through the step.

[0026]

As a result of using the immersion nozzle having a step on the inner wall surface of the discharge hole obtained by the present invention in an actual furnace, it is possible to reduce the adhesion of inclusions and reduce the drift due to the reduction of the accumulation space of the inclusions.
Further, an increase in the discharge flow rate can be suppressed. As a result,
Steel quality improved.

[Brief description of the drawings]

FIG. 1 shows a vertical sectional view of an immersion nozzle according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a discharge hole of the immersion nozzle of FIG.

FIG. 3 shows a view of the ejection hole shown in FIG. 2 as viewed from a direction A.

FIG. 4 is an enlarged sectional view of a discharge hole of an immersion nozzle according to a second embodiment of the present invention.

FIG. 5 is an enlarged sectional view of a discharge hole of an immersion nozzle according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 inner hole 2 stepped portion 3 discharge hole 10 immersion nozzle of the present invention 21 inner hole side discharge hole 22 outer surface side discharge hole

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Yuzo Kawazu 1-1-1, Higashihama-cho, Yawatanishi-ku, Kitakyushu-city, Fukuoka Prefecture (72) Inventor Toshihide Masuda 1-1-1, Higashihama-machi, Yawatanishi-ku, Kitakyushu-shi, Fukuoka F term in Kurosaki Harima Co., Ltd. (reference) 4E004 FB02 FB04 4E014 DB03

Claims (1)

[Claims] 1. The relationship between the inner-hole cross-sectional area Sn and the total inner-hole-side discharge-hole cross-sectional area St is 1.0Sn ≦ St <1.3Sn, and the stepped portion whose diameter increases outward in the discharge hole. An immersion nozzle, characterized in that an immersion nozzle is formed.