JPH08309485A - Mold for continuous casting wide thin slab, and continuous casting machine having the mold - Google Patents

Abstract

PURPOSE: To prevent generation of solidification of the molten metal surface, defective slag of the powder, and breakage of a nozzle by making the inner dimension in the vicinity of the shorter side on the longer side of a mold larger than the inner dimension at the center on the longer side of the mold to facilitate the use of a submerged nozzle having the width of a regular discharge port difficult to generate the nozzle clogging or eccentric flow. CONSTITUTION: A mold 1 for continuous casting of the wide thin slab is formed of a pair of longer sides 1a of the mold which are opposite to each other, and a pair of shorter sides 1b of the mold which are interposed between the longer sides 1a. The mold 1 is formed so that the inner dimension B in the vicinity of the shorter side 1b on the longer side 1a is larger than the inner dimension A at the center on the longer side 1a. Thus, a submerged nozzle 2 having the width of a regular discharge port 2a difficult to generate the nozzle clogging or the eccentric flow can be employed in the vicinity of the shorter side on the longer side with larger inner dimension B. By applying a continuous casting machine provided with such a mold, the molten metal can be appropriately fed in continuously casting the wide thin slab, and the inclusion of the powder, etc., can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for continuous casting of wide and thin slabs and a continuous casting apparatus equipped with this mold.

[0002]

2. Description of the Related Art In recent years, significant progress in refining technology and casting technology has facilitated the production of slabs with good quality properties, and the idea of labor saving and energy saving has been increasing. In addition to non-metals with relatively low melting points, iron-based metals as well have been attempted to directly and continuously manufacture thin sheet materials from molten steel without hot stripping or hot rolling. .

The following methods have been proposed so far as means for continuously casting the thin cast pieces. Continuous casting method using a belt type wall surface moving mold. Continuous casting method (SMS method) using a modified cross-section mold. Twin roll continuous casting method.

However, in the belt type continuous casting method, in addition to the problem that the maintenance cost and the running cost are increased due to the difficulty of cooling the belt, the degassing casting by the dipping nozzle which tends to be difficult to dispose is performed. There is a problem that it is very difficult to maintain the surface quality unless it is performed.

In the continuous casting method using the modified cross-section mold, a large frictional force is generated between the inner surface of the mold and the surface of the slab to reduce the cross-sectional area in the mold, but this frictional resistance is gradually increased. It has been pointed out that due to this, the inner surface of the mold is severely worn and the life of the mold is shortened. Further, in the twin roll type continuous casting method, there are problems that molten steel flows strongly during roll pressure in the unsolidified portion, it is difficult to float and separate inclusions, and segregation easily occurs.

As described above, the conventional thin cast continuous casting method is
Both methods have many unsolved problems from the viewpoint of stably producing thin slabs of sufficiently satisfactory quality under good workability, and especially hot rolling in industrial production of iron-based metal sheet materials. The reality is that it has not reached the level where it can be replaced by the conventional method.

In particular, in the continuous casting method for thin cast pieces, the method of supplying hot water into the mold is the greatest problem, and various proposals have been made regarding this. Sorting by purpose, hot water supply using multiple nozzles (see, for example, JP-A-55-126)
No. 355, JP-A-1-293942) Hot water supply by flat nozzle (for example, JP-A-58-742)
58, JP-A-60-12264, JP-A-60-13.
0456, JP-A-62-197252, JP-A-62.
-292255)

However, since the hot water supply by the flat nozzles is all performed by the straight nozzles, inclusions penetrate deeply during high speed casting and the cleanliness problem remains.
Therefore, it is attempted to reduce the penetration depth by devising a resistance in the immersion nozzle to reduce the discharge flow velocity. In addition, when the flat nozzle is used, the region where the space between the mold and the dipping nozzle is narrow is increased, the flow of molten steel is likely to be stagnant, and problems such as molten metal surface solidification and poor powder slagging occur.

As described above, in the continuous casting mold for producing wide and thin slabs, a mold having parallel long side wall surfaces facing each other (hereinafter, referred to as "parallel mold"), which has been generally adopted, is used. In such a case, not only the hot water supply method using the flat nozzle described above but also the hot water supply method using a plurality of nozzles must narrow the width of the discharge hole of the nozzle, resulting in nozzle clogging. There was a problem. Further, in the continuous casting method using the modified cross-section mold, in addition to the problem that a large frictional force is generated between the mold inner surface and the slab surface as described above, the level fluctuation of the molten metal at the center of the mold easily occurs, There is also a problem that entrainment of slag and poor slag formation occur.

[0010]

That is, in the production of wide and thin slabs, in the casting method in which the short side length of the mold is directly targeted as the thickness of the slab, a dipping nozzle for injecting molten steel into the mold is used. Cannot take the same shape as a normal immersion nozzle, and the width of the discharge hole is narrowed to 20 to 30 mm.
There is a problem that stable hot water cannot be supplied. In other words, since it is necessary to make the wall thickness thinner and wider than the normal immersion nozzle, the heat radiation area becomes large and the width of the discharge hole inevitably passes molten steel, that is, the width of the discharge hole becomes narrower, so nozzle clogging easily occurs and one-way flow easily Become. When the one-sided flow occurs, fluctuations in the molten metal surface and powder entrainment are likely to occur, resulting in deterioration of the quality of the cast piece.

Further, particularly when a low flow rate hot water is supplied to a wide slab, the discharge flow from the dipping nozzle does not reach the vicinity of the short side, solidification of the molten metal surface occurs, and powder slag failure or cutting damage of the dipping nozzle occurs. Problems are more likely to occur.

The present invention has been made in view of the above-mentioned conventional problems, and when continuously casting wide and thin slabs, an immersion nozzle having a width of an ordinary discharge hole in which nozzle clogging and one-sided flow hardly occur. A mold that can be used and that does not cause problems such as solidification of the molten metal surface, poor powder slag, and nozzle breakage due to the discharge flow not flowing near the short side, and a wide and thin mold equipped with this mold. An object of the present invention is to provide a continuous casting device for cast slabs.

[0013]

In order to achieve the above-mentioned object, the mold for continuous casting of wide and thin slabs of the present invention is designed such that the inner side of the central portion of the long side of the mold is closer to the shorter side of the long side of the mold. The inner dimension is increased, and the continuous casting apparatus of the present invention has a large inner diameter of the wide casting mold for continuous casting of the present invention. A 2-hole immersion nozzle with holes, a downward discharge hole on the center side of the long side of the mold, and a 2-hole immersion nozzle with upward discharge holes on the short side of the long side of the mold, or the center of the long side of the mold One of the one-hole dipping nozzles having a downward discharge hole is disposed on the side of the section.

[0014]

The wide-width thin slab continuous casting mold of the present invention has a larger inner dimension in the vicinity of the short side of the long side of the mold than in the center of the longer side of the mold. It is possible to use a submerged nozzle having a width of a normal discharge hole in which the nozzle clogging and the one-sided flow hardly occur near the short side in the long side.

The inventors of the present invention estimated the flow of hot water in the mold using a water model when hot water was supplied to the mold of the present invention using the two immersion nozzles having the width of this normal discharge hole. As shown in FIG. 3, it was confirmed that a sufficient hot water flow condition can be secured as in the case of hot water supply using one flat nozzle.

Further, the continuous casting apparatus of the present invention may be a two-hole immersion nozzle having downward discharge holes in the vicinity of both short sides of the long side of the mold having a large inner dimension of the present invention, or in the center of the long side of the mold. Part of the long side of the mold with a downward discharge hole on the short side of the long side of the mold, or a single-hole immersion nozzle with a downward discharge hole of the central side of the long side of the mold. Since either is arranged,
As shown in, the molten steel can be sufficiently supplied to the vicinity of the short side of the meniscus, heat can be secured, and hot water supply can be optimized. That is, when a conventional parallel mold is used, the gap between the mold and the dipping nozzle is narrow, so that molten steel stagnates and solidification of the molten metal surface and poor slag formation of powder occur. When used, such a problem does not occur because the casting nozzle installation portion has a large mold thickness.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The casting mold for wide and thin cast pieces of the present invention and the continuous casting apparatus equipped with this casting mold will be described below with reference to the embodiments shown in FIGS. FIG. 1 is a view showing an example of a continuous casting apparatus equipped with a wide-width thin cast piece continuous casting mold according to the present invention, and FIG. 1 (a) is a view seen from the mold plane direction of the first embodiment,
(B) is the figure seen from the mold plane direction of 2nd Example, (c)
Is a schematic front view seen from the short side direction of the mold, FIG.
(C) is a figure which shows the example of arrangement | positioning of the immersion nozzle installed in the casting mold for wide-width thin cast pieces of this invention.

In FIG. 1, reference numeral 1 denotes a wide and thin slab of the present invention which is formed by a pair of long mold sides 1a opposed to each other and a pair of short mold sides 1b interposed between the long mold sides 1a. It is a mold for continuous casting. The mold 1 is formed so that the inner size A of the central portion of the mold long side 1a is larger than the inner size B of the mold long side 1a near the mold short side 1b.

For example, the thickness is 50 mm and the width is 2000 m.
When casting a thin slab with a size of m at a speed of 5.0 m / min, the inner dimension A is set to a target slab thickness of 50 mm within the range of the central part width 1000 mm on the long side 1a of the mold. 500m near the short side 1b of the mold on the long side 1a
In the case of m, the inner dimension B is 90 mm.

By the way, the connecting portion between the inner dimensions A and B has the same shape in the longitudinal direction of the mold 1 (drawing direction of the slab), that is, if there is no narrowing, it is not linear as shown in FIG. 1 (a). Alternatively, as shown in FIG. 1 (b), for example, the radius of curvature R may be curved with a range of 9000 to 10000 mm. In addition, the length of the central portion on the long side 1a of the mold and the length of the short side 1b of the long side 1a of the mold are not particularly specified, but the length of the central portion must be at least the minimum slab width or more. is there.

FIG. 2 is a view showing an arrangement state of the immersion nozzles 2 installed in the vicinity of both the mold short sides 1b in the mold long side 1a having a large inner size of the above-mentioned mold 1, (a) showing from 20 to 20 from the horizontal. The arrangement state of the two-hole immersion nozzle 2 in which the discharge holes 2a are provided downward at an angle of 45 ° is shown in FIG.
The arrangement state of the two-hole immersion nozzle 2 provided with the downward discharge hole 2a and the 0-10 ° upward discharge hole 2a is shown in (c).
Shows the arrangement state of the one-hole immersion nozzle 2 in which the discharge hole 2a is provided downward from the horizontal by an angle of 20 to 45 °.

In the case of the two-hole immersion nozzle 2 shown in FIG. 2 (b), the downward discharge hole 2a is located on the central side of the mold long side 1a and the downward discharge side 2a is located on the short side of the mold long side 1a. The discharge holes 2a are arranged so as to face. Also, FIG.
In the case of the 1-hole immersion nozzle 2 shown in (c), the long side of the mold 1
It is arranged so that the downward discharge hole 2a faces the central portion side of a.

By the way, in the case of the mold 1 having the above-mentioned dimensions, for example, the outer diameter is 60 mm × 150 mm, and the outer diameter is 45 mm.
The two-hole immersion nozzle 2 of FIG. 2 (a) having the discharge hole 2a facing downward at an angle of ° is arranged at a position 450 mm from the mold short side 2b. By arranging the dipping nozzle 2 at this position, it is possible to change the width of 400 mm on both sides during casting.

As described above, hot water is supplied to the mold 1 in which the immersion nozzle 2 is arranged to produce a wide and thin slab, and the slab 3 drawn from the mold 1 is arranged, for example, immediately below the mold 1. The unrolled pressure is reduced by 20 mm on each side by three pairs of rolls 4 so that the widthwise central portion has the same thickness on both sides. The roll down of these three pairs of rolls 4 is the first roll 4
10 mm, and then the following second and third rolls 4 carry out a top strong reduction of 5 mm each. This is because it was found from the strain integration model that the occurrence of internal cracks can be suppressed because the strain is less accumulated under the top strong compression.

When a slab having a target thickness is manufactured by using the continuous casting apparatus equipped with the mold of the present invention, the short side has a convex shape due to buckling deformation. There is no problem in the case of hot rolling in the subsequent process.

Next, the results of the tests carried out to confirm the effects of the present invention will be described. [Example 1] In a 2-strand curved continuous casting machine, low carbon aluminum killed steel having the chemical composition shown in Table 1 below was cast at a speed of 5.0 m / min to obtain a thickness of 50 mm and a width of 200.
A wide thin strip of 0 mm was produced.

In this embodiment, on the one strand side of a two-strand curved continuous casting machine, the two-hole immersion nozzle shown in FIG. 2 (a) (nozzle outer diameter: 5) is provided in the mold of the present invention shown in FIG. 1 (a).
Two pieces of 0 mm thickness, discharge angle: 45 ° downward were arranged at a distance of 400 mm from the short side of the mold to supply hot water. In this example on the one-strand side, the roll was rolled down from 90 mm to 50 mm just below the mold, and the rolling down pattern was a top strong rolling down pattern of 15-10-10-5 mm. As a comparison, on the two-strand side, hot water was supplied using a single immersion nozzle in a conventional parallel mold having an inner size of 50 mm.

[0028]

[Table 1]

Continuous casting can be continuously carried out on the one strand side to which the present invention is applied, and continuous casting can be continuously carried out at a maximum of 7 times in a 100-ton ladle. On the other hand, on the conventional 2 strand side, the outer diameter of the dipping nozzle is only allowed up to 30 mm.
At the end of casting in a 00-ton ladle, the immersion nozzle was clogged and it became impossible to continue casting.

The opening of the sliding nozzle was clogged with an increase in the casting amount on the side of the two strands, and as shown in FIG. 4, the opening gradually increased to 80 to 90%, and finally the controllability was increased. Became very bad. On the other hand, on the one strand side to which the present invention is applied, the opening of the sliding nozzle is stable at about 20 to 30%, which is about half, and casting can be completed without impairing controllability even at the end of casting. .

Example 2 A low carbon steel was cast at 5.0 m / min under the same casting conditions as in Example 1. Two types of immersion nozzles shown in FIGS. 2B and 2C were applied to the one-strand side, and comparison was made with the conventional two-strand side.

When the single-hole immersion nozzle shown in FIG. 2 (c) was applied, the fluctuation of the molten metal surface level near the short side was suppressed, but the surface became slightly skinned, and surface defects such as pinholes tended to increase. It was Further, when the two-hole immersion nozzle shown in FIG. 2 (b) was applied, the tendency of skinning near the short side was reduced, and casting for a long time was possible. FIGS. 5 and 6 show a comparison of the level variation of the molten metal level and the occurrence of surface defects in Example 2 with the conventional one. As a result, the superiority of the present invention was confirmed.

Example 3 Low carbon steel was cast at 5.0 m / min under the same casting conditions as in Example 1. On the one-strand side to which the present invention was applied, when the pressure was reduced from 90 mm to 50 mm on both sides in the vicinity of the short side of the mold, casting was performed by changing the pressing pattern directly below the mold. In case 1, the reduction pattern is 15
The top strong reduction pattern of -10-10-5 mm was adopted, and in Case 2, the uniform reduction pattern of 10-10-10-10 mm was applied to compare and investigate the occurrence of internal cracks.
As shown in FIG. 7, it can be seen that the occurrence of internal cracking is suppressed when the top strong reduction pattern of Case 1 is adopted. The short side of the slab after rolling had a convex shape, but could be rolled without problems.

[0034]

As described above, when the casting mold for wide and thin cast pieces of the present invention and the continuous casting apparatus provided with this casting mold are applied, hot water is appropriately supplied when continuously casting wide and thin cast pieces. Since this can be done, it is possible to prevent the entrainment of powder and the like, and stable operation is possible. That is, according to the present invention, a thin slab of good quality can be stably manufactured.

[Brief description of drawings]

FIG. 1 is a view showing an example of a continuous casting apparatus equipped with a wide-width thin cast piece casting mold according to the present invention, in which (a) is a view seen from the mold plane direction of the first embodiment, and (b) is The figure seen from the mold plane direction of 2nd Example, (c) is the schematic front view seen from the mold short side direction.

2 (a) to 2 (c) are views showing an example of arrangement of immersion nozzles installed in a mold for continuous casting of wide and thin slabs of the present invention.

FIG. 3 is a diagram in which a hot water flow state in the mold when hot water is supplied to the mold of the present invention is estimated using a water model.

FIG. 4 is a diagram showing the effect of the present invention of the first embodiment on the opening of the sliding nozzle.

FIG. 5 is a diagram showing the effect of the present invention of the second embodiment on the variation of the molten metal level.

FIG. 6 is a diagram showing the effect of Example 2 on the occurrence of surface defects.

FIG. 7 is a diagram showing the results of Example 3 showing the difference in the internal crack occurrence state due to the rolling pattern.

[Explanation of symbols]

 1 Mold 1a Mold long side 1b Mold short side 2 Immersion nozzle 2a Discharge hole A Inner dimension at the center of the longer side of the mold B Inner dimension near the shorter side of the longer side of the mold

Claims (2)

[Claims] 1. A continuous casting mold for producing wide and thin slabs, characterized in that the inner dimension in the vicinity of the short side of the long side of the mold is larger than the inner dimension of the central part in the longer side of the mold. Thin casting mold for continuous casting. 2. A two-hole immersion nozzle in which downward discharge holes are provided in the vicinity of both short sides of a long side of a mold having a large inner dimension of the mold for continuous casting of wide thin thin pieces according to claim 1, or a long side of the mold. 2 dipping nozzle with a downward discharge hole on the central side of the mold and an upward discharge hole on the short side of the long side of the mold, or 1 hole dipping with a downward discharge hole on the central side of the long side of the mold A continuous casting device characterized in that any one of the nozzles is arranged.