JP2979278B2 - Continuous casting method of molten metal with different components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously casting molten metal having different components without inserting an iron plate or the like into a mold in continuous casting of molten metal.

[0002]

2. Description of the Related Art In a continuous casting method, when continuously casting molten metal having different components, a method of inserting a partition plate at a portion where the component changes to block the molten metal and thereby minimize a component mixing zone. Has been done. In such a method, the casting is temporarily interrupted, and the casting is restarted after the iron plate is inserted into the mold manually or by a machine.

[0003]

This operation requires the removal of molten slag in the mold, the handling of inserting heavy iron plates is extremely dangerous, the workability is very poor, the partition plate There is a problem that costs are high. In addition, since the casting is temporarily interrupted, not only is there a high possibility that the productivity will decrease or the slab surface properties and internal quality will deteriorate, but also the stopper or sliding nozzle will be fully closed to temporarily stop the injection flow. When the temperature of the molten metal is low, there is a problem that the molten steel near the stopper or the sliding nozzle at the time of pouring is solidified and it becomes difficult to continue casting again.

Accordingly, an object of the present invention is to provide a method for continuously casting molten metals having different components without inserting a partition plate or the like into a mold and minimizing the interruption time of casting. I have.

[0005]

SUMMARY OF THE INVENTION The gist of the present invention is that when continuous casting of a molten metal of a certain component is completed and continuous casting of a molten metal having a different component is performed, the molten metal meniscus in the mold is removed. A DC magnetic field having a substantially uniform magnetic flux density distribution whose magnetic flux density distribution in the width direction is within ± 15% of its average value is applied to the slab thickness direction over the entire width direction of the mold. To form a direct current magnetic field zone, and at the same time, while flowing the molten metal discharge flow from the nozzle in a direction parallel to the magnetic field lines, the components having different components without interrupting the continuous casting.
A continuous casting method for molten metals having different components, characterized by continuously casting molten metals of various types. Thereby, the widthwise distribution of the downflow of the molten metal in the horizontal section of the lower pool of the DC magnetic field band is made uniform, and the length of the component mixing zone is minimized.

[0006]

According to the present invention, the flow in the mold is controlled by applying a DC magnetic field having a substantially uniform magnetic flux density within ± 15% of the average value in the width direction over the entire width direction of the mold in the thickness direction. I do.

In order to clarify the influence of the nozzle discharge direction which is important in this method, a model experiment using mercury equivalent to about 1/2 scale of an actual machine was conducted. DC magnetic field
For example, as shown in FIG. 1, it is obtained by passing a direct current through a pair of coils 2 at opposite positions of a U-shaped iron core 1. Further, by setting the width of the magnetic pole 3 to be equal to or larger than the width of the mold 4, a DC magnetic field having a uniform magnetic flux density in the width direction can be obtained. As shown in FIG. 2, the distribution of the magnetic flux density in the height direction is a parabolic distribution having a maximum value at the center of the magnetic pole in the height direction. In the magnetic pole, a magnetic flux density of 80% or more of the magnetic flux density at the center of the magnetic field in the height direction is applied.

FIG. 3 shows the relationship between the direction of the nozzle discharge flow and the direction of the line of magnetic force, and FIG. 4 shows the positional relationship between the immersion nozzle and the magnetic pole. Here, the magnetic field position was below the position where the nozzle discharge flow collides with the long side or short side of the mold under any conditions. As a result, the uniformity of the downward flow distribution in the horizontal section of the pool below the region where the magnetic flux density at the center of the magnetic pole in the height direction is 80% or more (hereinafter referred to as the magnetic field zone) is determined by the nozzle discharge direction. It turned out to be very different. Table 1 shows the results. Here, the term “uniform” means that the circulating flow is not formed below the magnetic field zone, and the descending flow rate in the horizontal section of the pool is three times the value obtained by dividing the nozzle discharge flow rate by the pool horizontal sectional area (corresponding to the casting speed). It means that you are within.

[0009]

[Table 1]

When the nozzle discharge direction is perpendicular to the direction of the line of magnetic force and in the case of vertical + horizontal (four-way discharge), the distribution of the descending flow below the magnetic field zone in the horizontal section is not uniform, but the nozzle discharge flow is not uniform. It was found that the distribution of the downflow can be made uniform by making the direction parallel to the direction of the magnetic field lines.

[0011]

EXAMPLE The size is 570 mm in width × 360 mm in thickness, the component (%) is C: 0.13, Mn: 1.40, Si: 0.
2, P: 0.018, S: 0.005, Sol-Al:
At the end of the process, that is, when the amount of molten steel in the tundish is about 4 t, the casting is not stopped and the component (%) is continuously changed to C: 0.025, with the balance being Fe and unavoidable impurities. 0.45, Mn: 0.75, S
i: 0.30, P: 0.020, S: 0.005, So
1-Al: 0.025, molten steel consisting of the balance Fe and inevitable impurities was injected into the tundish, and casting was continued. Table 2 shows the casting conditions and results. The length of the component mixing area was smallest when the direction of the nozzle discharge flow was parallel to the direction of the line of magnetic force, as compared with the case where the partition plate was not inserted. On the other hand, when the direction of the nozzle discharge flow is perpendicular to the direction of the line of magnetic force and in the case of vertical + horizontal (four-direction discharge),
The length of the component mixing zone was almost the same as when the partition plate was not inserted, and the effect of applying a magnetic field was not so much observed.

[0012]

[Table 2]

[0013]

According to the method of the present invention, it is possible to make the horizontal cross-sectional distribution of the downward flow below the magnetic field zone uniform without inserting a partition plate or the like into the mold, and to minimize the component mixing zone. . In addition, since a partition plate or the like is not inserted into the mold, the operation becomes extremely simple. In addition, since the casting is not stopped once, the productivity is improved, and not only is there no fear of nozzle blockage or the like, but also the deterioration of the surface properties and internal quality of the slab is eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a magnetic field coil used to carry out the present invention, which generates a DC magnetic field having a uniform magnetic flux density distribution in a width direction.

FIG. 2 is a diagram illustrating a magnetic flux density distribution in a height direction of a magnetic field having a uniform magnetic flux density distribution in a width direction.

FIG. 3 is a diagram illustrating a relationship between a direction of a line of magnetic force and a direction of a nozzle discharge flow.

FIG. 4 is a diagram showing a positional relationship between an immersion nozzle and a magnetic field zone.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Iron core 2 Coil 3 Magnetic pole 4 Mold 5 Immersion nozzle 6 Long side 7 Short side 8 Magnetic field band

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ken Sugawara 12 Nakamachi, Muroran-shi, Hokkaido Inside Nippon Steel Corporation Muroran Works (56) References JP-A-3-94959 (JP, A) JP-A-4 JP-A-52057 (JP, A) JP-A-61-1459 (JP, A) JP-A-60-121052 (JP, A) JP-A-5-96346 (JP, A) JP-A-4-104251 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B22D 11/10 B22D 11/10 350 B22D 11/04 311 B22D 27/02

Claims (1)

(57) [Claims] When a continuous casting of a molten metal of a certain component is completed and a continuous casting of a molten metal having a different component is performed, a magnetic flux in a width direction is positioned below a molten metal meniscus in a mold. The density distribution is ± 15 with respect to the average value.
% DC magnetic field having a substantially uniform magnetic flux density distribution within
A direct current magnetic field zone is formed by applying in the slab thickness direction over the entire width direction of the mold, and at the same time, the molten metal discharge flow from the nozzle flows in a direction parallel to the line of magnetic force, and the components are different without interrupting continuous casting A continuous casting method for molten metals having different components, wherein two types of molten metals are continuously cast.