JPH08155608A - Method for continuously casting molten metal - Google Patents

Abstract

PURPOSE: To restrain the disturbance of molten metal surface at the same time of pinching the molten metal in a mold and to obtain the uniform surface characteristic by providing two sets of electromagnetic coils in parallel at the outside of a fixed mold pouring and solidying the molten metal and conducting the electric current from two sets of small capacity electric sources in a low cost to these two sets of electromagnetic coils, respectively. CONSTITUTION: A current control device 7 commands a conducting current condition to the electric sources 5a, 5b according to the current conducting condition set to a setter 8. In the setter 8, the combination of current waveform of conducting current, conducting current, conducting time, these changing over conditions, etc., to the electromagnetic coils 3a, 3b from two electric sources 5a, 5b are set, and the electric current conduction is continuously executed to the electromagnetic coils 3a, 3b from the electric sources 5a, 5b. In this way, the molten metal in the mold is pinched by combining the current waveform of the conducting current from two small capacity electric source and conducting the electric current and also, the disturbance of the meniscus is restrained and the cast slab having good surface characteristic can be cast.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly a continuous casting method for molten metal using a fixed mold for casting steel, stainless steel, alloys, aluminum, etc., in which an electromagnetic coil is arranged outside the mold. The present invention relates to a continuous casting method for molten metal in which a pinch force is applied to the molten metal in the mold to accelerate the feeding of the lubricant and to suppress the disturbance of the molten metal surface in the mold.

[0002]

2. Description of the Related Art Conventionally, for example, in a continuous casting process of steel, a lubricant added to the molten steel surface and melted is
It flows in and is consumed by these interactions or a natural drop between the mold that vibrates under a predetermined condition and the solidified shell that is pulled out at a constant speed, and it is consumed. It is known that the quality of the slab, especially the surface quality, is greatly affected.

The consumption of this lubricant is considered to be an important factor controlling the lubrication between the mold and the solidified shell, and various measures have been proposed to increase the consumption. For example, in Japanese Patent Laid-Open No. 52-32834, for example,
As shown in FIG. 7, an electromagnetic coil 3 is arranged outside the fixed mold 1 made of a copper plate 1a so as to surround it via a back plate 2, and a dipping nozzle 4 is arranged in this mold. The molten metal s is injected from the dipping nozzle into the mold, and the electromagnetic coil 3 is energized from the power supply 5 to pinch the molten metal s in the mold in the vicinity of the mold with an electromagnetic force to melt the molten metal surface. It is disclosed that by forming the recessed portion 6 by curving the mold in the vicinity of the mold 1, the feeding of the lubricant (powder) p is promoted to improve the lubricity and the surface quality of the cast slab sc after solidification is improved. ing.

In the continuous casting method as disclosed herein, when the electromagnetic coil arranged outside the fixed mold is energized to apply an electromagnetic force to the molten metal in the mold to raise the meniscus of the molten metal in the mold. In addition, due to electromagnetic force, abnormal flow occurs, the molten metal surface sf is disturbed (abnormal flow) as shown by the dotted line, the meniscus undergoes undesirable deformation, and a slab having a uniform surface texture is obtained. There is a problem that you can not.

As a means for suppressing the occurrence of such a phenomenon, for example, Japanese Patent Laid-Open No. 5-293613 proposes to apply an AC magnetic field and a DC magnetic field to the molten metal in the mold, and also to an electromagnetic coil. Attempts have also been made to control the current waveform of the applied current. However, in order to combine the energizing currents of various current waveforms in this way, a considerably large and complicated power supply facility is required, so that there is a problem in terms of facility cost.

[0006]

SUMMARY OF THE INVENTION In the present invention, an electromagnetic coil is arranged outside a fixed mold for injecting and solidifying molten metal, and the molten metal in the mold is pinched by electromagnetic force to perform casting. In the continuous casting method, a simple and inexpensive means is used to combine the current waveforms of the electromagnetic coils to apply a pinch force to the molten metal in the mold and to suppress the disturbance (abnormal flow) of the molten metal surface, resulting in a uniform surface. It is intended to provide a continuous casting method of molten metal capable of casting a slab having a property.

[0007]

The first invention of the present invention is as follows:
In a continuous casting method for molten metal, in which an electromagnetic coil is arranged outside a fixed mold for injecting and solidifying the molten metal, and the molten metal in the mold is pinched by electromagnetic force for casting,
The electromagnetic coils are arranged in parallel in the thickness direction of the mold or in the casting direction so that the two electromagnetic coils are driven by different power sources, and the energizing currents for the two electromagnetic coils are combined to pinch the molten metal. A continuous casting method for molten metal, characterized by controlling force. A second aspect of the invention is characterized in that, in the first aspect of the invention, different current waveforms from respective power sources are energized when energizing the two electromagnetic coils arranged in parallel. In the first invention, when energizing two electromagnetic coils arranged in parallel, one electromagnetic coil is energized with an alternating current, and the other electromagnetic coil is energized with a DC on-off current. It is what

[0008]

In the present invention, two electromagnetic coils are arranged side by side on the outside of the fixed mold for injecting and solidifying the molten metal, and the two electromagnetic coils are energized by two inexpensive small capacity power sources, respectively. Since it has such a configuration, the equipment cost can be greatly improved, and one electromagnetic coil and a large
As in the case of the above-mentioned conventional method in which individual power sources are arranged, the molten metal in the mold is pinched, and at the same time, the disturbance (abnormal flow) of the molten metal in the mold is suppressed to cast a slab with a uniform surface texture. it can.

The present inventors have described a continuous casting method for molten metal, in which an electromagnetic coil is arranged outside a fixed mold for injecting and solidifying molten metal, and casting is performed while pinching the molten metal in the mold by electromagnetic force. Through various experiments, when electromagnetic force is generated in the electromagnetic coil to raise the molten metal level in the mold, the electromagnetic force causes disturbance (abnormal flow) on the molten metal surface, and a good slab with uniform surface properties is obtained. I found that I could not.

As described above, with respect to the disturbance of the molten metal surface in the mold, the current waveform of the energizing current to the electromagnetic coil is combined to temporarily reduce the electromagnetic force to the molten metal in the mold to zero or to zero. Based on the recognition that it is effective to perform such control, an inexpensive means for that purpose was studied and the present invention was completed.

According to the present invention, two electromagnetic coils driven by two independent small-capacity power sources are arranged side by side in the thickness direction of the mold or in the casting direction outside the mold, and the two electromagnetic coils are energized from their respective power sources. It is something that is done.

More specifically, two inexpensive low-capacity power supplies are used to combine the current waveforms of the respective electromagnetic coils by changing the current waveforms, or one of the electromagnetic coils is supplied with an alternating current. , By passing a DC on-off current to the other electromagnetic coil, the electromagnetic force to the molten metal in the mold is temporarily weakened, but a sufficient pinch force is secured and the disturbance of the molten metal surface is suppressed. To do.

Regarding the combination of the current waveforms of the energizing current to the electromagnetic coil, the casting conditions such as the casting object, the mold shape, the mold size, the immersion nozzle condition, the casting speed, etc. can be preliminarily or learned through experiments, results, calculations, etc. Can be selected according to.

The present invention provides a continuous casting method using not only steel but also stainless steel, alloys, aluminum, etc. as a casting object, using a fixed mold in which an electromagnetic coil is arranged outside and a molten metal in the mold can be pinched. Is also applicable.

[0015]

【Example】

(Embodiment 1) Hereinafter, an embodiment in which the present invention is applied to a continuous casting method for molten steel will be described together with an embodiment apparatus example. In this embodiment, as shown in FIG. 1, in a continuous casting apparatus using a square fixed mold, two electromagnetic coils 3a, 3b driven by two independent small-capacity power supplies 5a, 5b outside the mold 1 are used. Are arranged side by side in the thickness direction of the mold, and the two electromagnetic coils 3a and 3b are provided with respective power supplies 5a and 5b.
It is designed to be energized from.

Reference numeral 7 denotes a current control device, which commands the power supply current conditions to the power supplies 5a and 5b in accordance with the current power supply conditions set in the setter 8. The setting device 8 is set with a combination of current waveforms of the energization currents from the two power supplies 5a and 5b to the electromagnetic coils 3a and 3b, the energization current, the energization time, and switching conditions between these power supplies 5a and 5b.
To the electromagnetic coils 3a and 3b are interlocked with each other.

In this way, by combining the current waveforms of the energizing currents from the two inexpensive low-capacity power sources to energize, various energizing patterns can be selected,
It is possible to pinch the molten metal in the mold, suppress the disturbance of the meniscus, and cast a slab having good surface properties.

FIG. 2 shows another embodiment of the present invention. In this example, two electromagnetic coils 3a, 3 are energized from independent power sources 5a, 5b outside the mold 1.
b are juxtaposed in the casting direction. In this way, two electromagnetic coils are arranged side by side in the casting direction and the energization pattern for the electromagnetic coils is selected in the same manner as in the embodiment of FIG. 1 to arrange the two electromagnetic coils side by side in the thickness direction of the mold. 1
It is possible to obtain substantially the same effect as in the case of the above embodiment.

(Embodiment 1-1) A mold 1 having a construction as shown in FIG. 1 is used, and a small capacity power source 5a (capacity: capacity: internal dimension: 1700 mm × 450 mm) is used for an electromagnetic coil 3a (size: internal dimension: 1700 mm × 450 mm). From 400 kvA), a sinusoidal alternating current with a peak value of 250 A and a frequency of 50 Hz as shown in FIG. 3 is applied, and the electromagnetic coil 3b (size: internal dimensions: 1950 mm × 7)
(00 mm) from the power source 5b (capacity: 600 kvA), a direct current of a rectangular waveform with a peak value of 1000 A-0 A as shown in FIG. 4 is applied to generate a magnetic flux density as shown in FIG. Continuous casting of steel was carried out.

By performing casting while applying such a magnetic flux density in the mold, a period in which the strong pinch force acts on the molten steel in the mold and a period in which the pinch force hardly acts alternately appear, so that the molten steel melt The surface repeats a state in which it rises largely and a state in which it hardly rises. As a result, the feeding of the lubricant between the molten steel and the mold is promoted, and at the same time, the disturbance of the meniscus is suppressed and stable casting can be performed. The obtained slab has an average oscillation mark depth of 70μ.
m showed good surface quality.

(Comparative Example) One conventional electromagnetic coil (size: internal dimension 17) as shown in FIG. 7 to which the present invention is not applied.
00mm × 450mm) and one power supply (capacity: 1000kv
Continuous casting was carried out using the mold in which A) was placed while applying a current waveform as shown in FIG. 6 to the electromagnetic coil. As a result, the obtained slab had an oscillation mark with an average depth of 75 μm and exhibited surface properties equivalent to those of the present example. However, this comparative example requires one large power supply facility and an expensive device for obtaining a complicated current waveform, and the facility cost is increased by about 20% as compared with the case of the present embodiment.

Casting Conditions (Common to Examples and Comparative Examples) Cast Steel Type: Carbon Steel Size: Width 1500 mm, Cavity Thickness 250 mm Mold Height: 800 mm Center Mold Plate Thickness: 25 mm Back Plate (SUS304) Thickness: 40 mm Casting Speed: Oscillation applied to 2m / min mold: frequency 120cpm, stroke ± 5mm

[0023]

According to the present invention, two electromagnetic coils are arranged side by side on the outside of a fixed mold for injecting and solidifying a molten metal, and these two electromagnetic coils are provided with two inexpensive small-capacity power sources, respectively. Since it has a configuration to energize, the equipment cost can be greatly improved, and the molten metal in the mold can be removed in the same manner as in the conventional case where one electromagnetic coil and one large power source are arranged. At the same time as pinching, the disturbance (abnormal flow) of the molten metal surface in the mold is suppressed, and a cast piece having a uniform surface texture can be cast.

[Brief description of drawings]

FIG. 1 (a) is a vertical cross-sectional schematic explanatory view showing an example of a mold structure of a continuous casting apparatus for carrying out the present invention, and FIG. 1 (b) is a schematic plan explanatory view of FIG. 1 (a).

FIG. 2 is a vertical cross-sectional schematic explanatory view showing another mold structure example (electromagnetic coil arrangement example) in the present invention.

FIG. 3 is a schematic explanatory view showing a waveform of a current passed through one of the electromagnetic coils in the embodiment of the present invention.

FIG. 4 is a schematic explanatory diagram showing a waveform of current passed through the other electromagnetic coil in the embodiment of the present invention.

FIG. 5 is a schematic explanatory view showing a magnetic flux density generation state with respect to molten steel in a mold in an example of the present invention.

FIG. 6 is a schematic explanatory diagram showing a waveform of a current passed through an electromagnetic coil in a comparative example.

FIG. 7 (a) is a vertical cross-sectional schematic explanatory diagram showing an example of a molten steel continuous casting apparatus to which the present invention is applied, and FIG. 7 (b) is a plan schematic explanatory diagram of FIG. 7 (a).

[Explanation of symbols]

 1 Mold 1a Copper Plate 2 Back Plate 3, 3a, 3b Electromagnetic Coil 4 Immersion Nozzle 5, 5a, 5b Power Supply (for Electromagnetic Coil) 6 Depression of molten metal 7 Current Controller 8 Setting Device s Molten Steel (Molten Metal) sf Molten Steel sc Slab p Lubricant (powder)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takehiko Fuji, 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corp. Technology Development Division

Claims (3)

[Claims] 1. A continuous casting method for molten metal, wherein an electromagnetic coil is arranged outside a fixed mold for injecting and solidifying the molten metal, and the molten metal in the mold is cast while being pinched by electromagnetic force. The coils are arranged side by side in the thickness direction of the mold or in the casting direction so that these two electromagnetic coils are driven by different power sources, and the energizing currents for these two electromagnetic coils are combined to create a pinch force against the molten metal. A continuous casting method for molten metal, characterized by controlling. 2. The continuous casting method for molten metal according to claim 1, wherein different current waveforms are supplied from respective power sources when the two electromagnetic coils arranged in parallel are energized. 3. When energizing two electromagnetic coils arranged in parallel, one electromagnetic coil is energized with an alternating current, and the other electromagnetic coil is energized with a dc on-off current. The continuous casting method for molten metal according to claim 1.