JP3179326B2 - Immersion nozzle for continuous casting of wide thin cast slab and continuous casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slit-shaped discharge on both side surfaces of a lower end portion used in a continuous casting method of a wide thin cast piece using a cooling mold such as a twin drum type continuous casting method or a twin belt type continuous casting method. The present invention relates to an immersion nozzle having holes and a continuous casting method of a wide and thin cast piece using the immersion nozzle.

[0002]

2. Description of the Related Art In recent years, a method of directly manufacturing a thin slab having a thickness of about several mm to several tens mm close to the final shape from molten metal such as molten steel has attracted attention. This continuous casting method does not require the conventional hot rolling process in multiple stages, and the rolling to the final shape may be light, so that the processes and equipment can be simplified.

One of such continuous casting methods is a twin-drum continuous casting method.

In this twin-drum system, as shown in FIG. 3, a pair of cooling drums 1a and 1b rotating in opposite directions and side dams 2 abutting on both ends of the drum.
a, 2b, through a nozzle (not shown) mounted on a tundish from the top, slit-shaped discharge ports 5 (5a, 5b,
The molten metal is supplied through the immersion nozzle 6 having 5c), and the molten metal is discharged into the moving mold 3 to form the pool 8 at a predetermined level as the molten steel discharge flows 7a, 7b, 7c. Is pressed and integrated at the gap formed at the closest part of the cooling drums 1a and 1b of
Is to be cast.

In this twin-drum continuous casting, in order to form a solidified shell having a uniform thickness and to stably cast a thin slab having no surface defects such as entanglement, hot water provided between cooling drums is required. It is required to supply the molten metal to the reservoir as a smooth flow and to stabilize the cooling conditions in the meniscus near the cooling drum. For example, JP
Japanese Patent Application Laid-Open No. 2-282753 discloses that a porous filter is built in an immersion nozzle to obtain a turbulent discharge flow over the entire width of the nozzle.

However, in this case, the filter is liable to be clogged, the filter function is easily lost, and it is difficult to maintain the discharge flow in a preferable state for a long period of time. Is not sufficient for stable casting.

In Japanese Patent Application Laid-Open No. 3-297542, an intermediate container floating in a molten metal and having a nozzle hole at a position below the liquid surface is floated in a molten metal pool in a mold, and the molten metal is placed in the floating intermediate container. A twin-roll continuous casting method in which the molten metal in the container is continuously injected and discharged from the nozzle hole is shown.

In this case, it is difficult to secure a sufficient capacity as a buffer since the size of the floating intermediate container is limited by the pool of hot water in the mold. For this reason, the discharge flow discharged from the intermediate container does not have a rectifying portion, and is not easily discharged uniformly due to the influence of the flow of the molten metal in the intermediate container. As a result, the non-uniform flow of the molten metal pool in the mold is caused. Further, the discharge hole in the wall surface of the intermediate container has a short flow path length, and it is difficult to stabilize the discharge angle.

Further, Japanese Patent Application Laid-Open No. 7-68357 discloses a flow distribution of molten metal flowing out of a slit-shaped nozzle hole by disposing a rectifying refractory (filter) having a large number of through holes at the bottom of the nozzle. The flat outer nozzle for twin drums for equalizing is shown.

However, since the rectifying refractory in this case is a porous body, not only the symmetry in the thickness direction is not guaranteed, but also the problem of clogging cannot be solved. Further, in this shape, uniformity of the discharge flow in the width direction tends to be hindered, so that it is difficult to stabilize the discharge flow.

[0011]

In FIG. 3, all the molten metal supplied to the pool 8 passes through the immersion nozzle 6, and discharge holes 5a to 5c (three holes on one side in FIG. The number and the discharge angle are not limited.) At this time, the discharge flow is affected by the flow inside the nozzle 6, and the discharge flow tends to be uneven in the thickness direction of the slab. The non-uniformity of the discharge flow causes a change in the level of the molten metal in the pool 8 and local undulations, leading to defects in the quality of the cast slab and instability of the operation.
Therefore, an object of the present invention is to improve the pouring immersion nozzle so as to maintain the symmetry of the discharge flow in the thickness direction of the slab for a long period of time while maintaining the fluctuation and waving of the molten metal surface and the floating on the molten metal surface. An object of the present invention is to provide an injection nozzle for continuous casting of a wide and thin slab that can suppress the material entrapment and can cast a wide and thin slab of uniform thickness without surface defects at low cost.

[0012]

Means for Solving the Problems The first invention of the present invention is:
An injection nozzle for continuous casting of a wide thin cast slab having an inner nozzle insertion hole in the upper part and slit-shaped discharge holes on both side surfaces of the lower end part, in which molten metal supplied from a tundish is cast. 5 mm to 12 mm arranged to dispense and discharge from the slit-shaped discharge holes symmetrically in one thickness direction.
It is characterized by having an interior part with a through hole equivalent to a diameter of mm. Accordingly, the symmetry of the discharge flow in the thickness direction of the slab can be secured for a long time without using an expensive filter interior, and a stable operation can be performed.

According to a second aspect of the present invention, in the first aspect, the molten metal having passed through the through-hole is provided at the inner bottom of the nozzle by arranging the interior material having a through-hole for rectification and distribution above the position of the discharge hole. In this case, the discharge flow uniformity in the width direction is ensured by spreading in the nozzle width direction. As a result, a uniform discharge flow can be obtained regardless of the arrangement interval of the through holes, and a uniform steel plate can be cast in the width direction.

According to a third aspect of the present invention, in the first or second aspect, the length of the through hole of the rectification interior mounted inside the immersion nozzle is at least six times the inner diameter of the through hole. Thus, the flow path resistance in the through hole is ensured, and rectification is promoted. If (length L) / (inner diameter D) is secured to 6 or more, a stable discharge flow can be secured without disturbing the flow of the molten metal on the upstream side of the rectification interior to the downstream, and stable operation can be performed. it can. Here, the shape of the through hole does not need to be circular, and may be elliptical, rectangular, or the like. In this case, the inner diameter is calculated as a converted diameter D '= 4 (flow path cross-sectional area) / (flow path cross-sectional circumferential length). By setting the area of the upper hole of the through hole larger than the area of the lower hole, it is possible to obtain a discharge flow with less pulsation.

[0015] The fourth invention of the present invention is the first or second invention .
In the present invention, the bottom surface of the nozzle of the hot water drop portion is formed into a mountain shape or a trapezoid shape having an inclined surface connected to the discharge hole, so that a run-up (rectification) distance of the discharge flow is secured, and a stable discharge flow angle set in advance is obtained. A jet can be obtained. This makes it possible to secure a stable meniscus shape with little swelling of the molten metal surface, and to cast a wide and thin slab of uniform thickness without surface defects at low cost. The fifth of the present invention
The invention is directed to the continuous casting according to any one of the first to fourth inventions.
For continuous casting of wide thin cast slabs using immersion nozzles
It is.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional explanatory view showing an outline of a pouring nozzle according to a first embodiment of the present invention. FIG. 1 (a) is a front view, and FIG. 1 (b) is a cross-sectional view taken along line XX in FIG. It is an outline explanatory view, and FIG. (C) is an outline explanatory view taken along the arrow YY in FIG. (B), and FIG. (D) is an outline explanatory explanatory view taken along the arrow ZZ in FIG. (B). This pouring nozzle is used in the mold in the same manner as the conventional example of FIG.
Corresponding members and the like are designated by the same reference numerals, and in the following description, reference numerals in FIG. 3 are appropriately used.

The pouring nozzle 6 in FIG. 1 has a slit-shaped discharge hole at the lower part of the side surface facing the cooling drums 1a and 1b, as in FIG. The area and number of the discharge holes can be appropriately selected depending on the casting speed and the nozzle width. Inside the nozzle 6,
As shown in FIG. 2B, a fireproof interior having through holes 11 (11a, 11b) formed symmetrically in the thickness direction is installed. The molten metal is supplied from the upper part through the inner nozzle 4 to the nozzle 6
To form an intermediate pool in the upper part of the interior 12. It is necessary that this intermediate pool is in communication with the injection flow from the inner nozzle, and the through-hole 11 (11a, 1
The area of 1b) must be set so that the total is smaller than the ejection area of the inner nozzle 4. The diameter of each through hole is 5 mm to 1 from the viewpoint of clogging and securing the rectification effect.
About 2 mm is desirable. Also, the height h of the interior object is desirably three times or more the height d of the discharge hole from the viewpoint of ensuring the rectification effect. Although FIG. (C) illustrates a circular through hole, the present invention is not limited to this, and the shape of the through hole is not particularly limited as long as the strength is secured. The molten metal filled in the nozzle 6 is almost evenly distributed to the through holes 11a and 11b, and the discharge holes 5a and 5a ', 5b and 5b', 5c and 5c '
From the nozzles. As a result, fluctuations in the molten metal level and undulations caused by the loss of the discharge balance can be prevented, and stable casting and high quality slabs can be ensured.

FIGS. 2A and 2B are a front view and a sectional view showing an outline of a pouring nozzle according to a second embodiment of the present invention. FIG. 2A is a front view, and FIG. 2B is X in FIG. FIG. 8C is a schematic cross-sectional view as viewed in the direction of the arrow X, FIG. 10C is a schematic cross-sectional explanatory view as viewed in the direction of the arrow YY in FIG. It is. In this example, the through hole 11 (1) of the rectifying interior 12 having the partition 13 in the nozzle 6 is provided.
1a, 11b) The outlet is located above the discharge hole, and the nozzle bottom surface 10 has a chevron-shaped prism shape. The molten metal flow discharged from the through hole is discharged while maintaining the symmetry in the thickness direction. Pouring from The partitioning part 13 partitions the lower end inside the immersion nozzle 6 at the center of the thickness, and is installed so that mixing of the molten metal on both sides does not occur. At this time, the discharge flow is discharged obliquely downward along the inclined surface of the nozzle bottom surface 10. The discharge flow angle at this time is selected according to the casting amount and the type of casting steel. Also in this case, as in the first invention, stable casting without fluctuations in the molten metal surface and waving can be realized, and a cast piece having a uniform thickness without surface defects can be obtained.

[0019]

EXAMPLE A 1500 ° C. austenitic stainless steel was used as a molten metal, and this was poured into a pool 8 as shown in FIG. 3 at a flow rate of 1.5 t / min using a pouring nozzle shown in FIG. Hot water. The diameter of the through-hole at this time was 10 mmφ, and the discharge angle was 30 ° downward. According to the visual observation of the molten metal surface, there was no local swelling, the surface flow near the meniscus was secured, and no solidification of the molten metal surface or entrapment of suspended matter was observed.

The finally obtained thin slab was also of good quality with a standard deviation of the plate thickness in the width direction of 0.04 or less.

[0021]

As described above, by using the pouring nozzle of the present invention, it is possible to obtain a uniform discharge flow in both the thickness and width directions for a long time when pouring into a moving mold. It has become possible to realize stable casting without fluctuations and ripples in the molten metal. As a result, it has become possible to produce a wide thin cast piece having a uniform thickness without any surface defects.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional explanatory view showing an outline of a pouring nozzle according to a first embodiment of the present invention, in which FIG. 1 (a) is a front view, and FIG. It is an outline explanatory view, FIG. (C) is an outline explanatory view taken along the line YY in FIG. (B),
FIG. (D) is a schematic cross-sectional explanatory view taken along the arrow ZZ in FIG. (B).

FIGS. 2A and 2B are a front view and a cross-sectional view schematically showing a pouring nozzle according to a second embodiment of the present invention, wherein FIG. 2A is a front view, and FIG. 2B is an XX arrow in FIG. FIG. 4C is a schematic cross-sectional explanatory view taken along the line YY in FIG.
FIG. (D) is a schematic cross-sectional explanatory view taken along the arrow ZZ in FIG. (B).

FIG. 3 is a perspective view schematically showing a twin-drum continuous casting method in which an immersion nozzle having slit-shaped discharge holes on both side surfaces of a lower end portion is applied.

[Description of Signs] 1a, 1b Cooling drums 2a, 2b Side dam 3 Moving mold 4 Inner nozzle for pouring 5 Discharge hole 6 Immersion nozzle (outer nozzle) 7a, 7b, 7c Discharge flow of molten steel 8 Hot water pool 9 Wide thin casting Piece 10 Submerged nozzle bottom 11 Through hole 12 Rectifying interior 13 Partition

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-183759 (JP, A) JP-A-4-262837 (JP, A) JP-A-5-1777312 (JP, A) JP-A-3-3 294051 (JP, A) JP-A-61-289953 (JP, A) JP-A-58-361 (JP, A) JP-A-62-2822753 (JP, A) JP-A-3-297542 (JP, A) JP-A-7-290203 (JP, A) JP-A-7-60414 (JP, A) JP-A-6-126395 (JP, A) JP-A-6-71392 (JP, A) JP-A-7-68357 (JP, A) JP-A-8-39207 (JP, A) JP-A-2-148756 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/10 330 B22D 11 / 06 330 B22D 11/06 340 B22D 11/103 B22D 41/50 520

Claims (5)

(57) [Claims] 1. An immersion nozzle 6 for continuous casting of a wide thin cast slab having an inner nozzle 4 insertion hole at an upper portion and slit-shaped discharge holes 5 on both side surfaces at a lower end portion. In order to distribute and discharge the metal from the slit-shaped discharge holes 5 symmetrically in the slab thickness direction, the immersion nozzle 6
Inside, a lower end portion of the nozzle is partitioned at the center of the thickness, and a partition portion 1 is installed so that mixing of molten metal on both sides thereof does not occur.
3. An immersion nozzle for continuous casting of a wide and thin cast piece, comprising: a rectifying interior 12 having a through hole 11 symmetrically in the thickness direction of the cast piece. 2. A rectifying interior 1 mounted inside an immersion nozzle.
2. An immersion nozzle for continuous casting of a wide thin slab according to claim 1, wherein the lower end of the two through-holes 11 is positioned higher than the nozzle discharge holes 5 so that the discharge flow is made uniform in the width direction. . 3. A rectifying interior 1 mounted inside an immersion nozzle.
2 has a ratio L / D between the inner diameter D and the length L of the through hole 11.
3. The immersion nozzle for continuous casting of a wide thin cast slab according to claim 1 or 2, characterized in that: = 6 or more. 4. A discharge jet at a desired stable discharge angle by setting the cross-sectional shape of the discharge hole contact portion 10 to a mountain shape or a trapezoidal shape and setting an inclination angle thereof. An immersion nozzle for continuous casting of a wide thin slab according to claim 2. 5. A continuous casting method for a wide thin cast slab, wherein the continuous casting is carried out using the continuous casting immersion nozzle according to any one of claims 1 to 4. A continuous casting method for slabs.