JPH08155602A - Method for continuously casting molten metal - Google Patents

Abstract

PURPOSE: To prevent a continuous casting method of molten metal capable of preventing the entrapment of lubricator into molten metal, improving the quality on the surface layer part of a cast slab and also improving the casting productivity. CONSTITUTION: The molten metal 6 is poured into a water-cooling mold 4 giving a fixed cycle of oscillation inn the vertical direction, and also, the lubricant 3 is given on the molten metal surface and further, electromagnetic force A is given in the perpendicular plane with an electromagnetic coil 1 arranged so as to surround the mold 4 to execute the continuous casting of the molten metal 6. In this method, frequency of three phase AC current to be applied to a linear electromagnetic coil 1 is adjusted to 1/2n ((n) is the integer of >=1) of the frequency of the mold oscillation. Further, the direction of the electromagnetic force is directed to the oblique upward to the vertical.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method for molten metal, and more particularly to a continuous casting method capable of improving the surface layer of a slab by applying an electromagnetic force to the molten metal from the circumferential direction.

[0002]

2. Description of the Related Art For example, when performing continuous casting of steel, molten steel is injected through a nozzle into a mold having a water-cooled structure, and a lubricant (powder) is added to the surface of the molten steel to cause the mold to have a constant vertical cycle. The molten steel was solidified from its periphery while being vibrated, and was drawn downward to obtain a cast piece. In order to obtain a slab with good surface properties during this casting,
By placing an electromagnetic coil around the position corresponding to the molten steel meniscus part of the mold, a pinch force is applied to the molten steel by the electromagnetic force directed to the center of the mold, and by raising the molten steel surface in a convex shape, between the slab and the mold. A technique for making lubricant enter smoothly is widely known (Japanese Patent Publication No. 57-2140).
No. 8).

However, in the conventional continuous casting method in which the pinch force is applied by the electromagnetic coil surrounding the mold, as shown in FIG. 2, the electromagnetic force generated in the molten steel by the electromagnetic coil 11 of the single-phase alternating current is the mold 14 Although it induces a horizontal flow toward the center, the electromagnetic force indicated by the arrow a is strong on the coil center side and weaker on the end side, so that independent vertical stirring flows b ₁ and b ₂ are generated as shown in the figure. . These agitated flows become a flow that hits the solidified shell 15, and as a result, the agitated flow b ₁ causes the lubricant 13 to be entrained in the molten steel, and the entrained lubricant is trapped in the solidified shell 15 to cause defects in the slab. It was a cause of occurrence.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and prevents the lubricant from being entrained in the molten metal to improve the quality of the surface layer of the cast slab and at the same time, to perform the casting production. It is an object of the present invention to provide a continuous casting method for molten metal which can also improve the property.

[0005]

SUMMARY OF THE INVENTION The gist of the present invention is to inject molten metal into a water-cooled mold that imparts vibrations of a certain period in the vertical direction and at the same time add a lubricant to the surface of the molten metal to further surround the mold. In the method for continuously casting molten metal by applying an electromagnetic force in the vertical plane by the linear electromagnetic coils arranged in parallel, the frequency of the three-phase alternating current applied to the linear electromagnetic coil is 2n (n is the frequency of the mold vibration). A continuous casting method for molten metal is characterized in that the direction of the electromagnetic force is directed obliquely upward in the vertical direction while being adjusted so as to be 1 / integral.

[0006]

The function of the present invention will be described in detail below. In the normal continuous casting, the water-cooled mold is oscillated in the vertical direction at a constant cycle as described above, but this mold vibration causes a concave defect called an oscillation mark on the surface of the slab. This defect has a one-to-one correspondence with vertical mold vibration. This is because the force exerted by the mold vibration on the solidified shell via the lubricant varies with the mold vibration period.

Therefore, in the present invention, first, a linear electromagnetic coil for enclosing the mold and applying an electromagnetic force in the vertical plane is supplied with a three-phase AC current instead of a single phase, and its frequency is set to the mold. The frequency is controlled to be 1 / n of 2n (n is an integer of 1 or more). By doing so, the mold vibration is synchronized with the frequency of the fluctuation of the electromagnetic force due to the moving magnetic field, the generation of oscillation marks is prevented, and the deformation of the solidified shell is suppressed.

Further, an electromagnetic coil 1 for passing a three-phase alternating current
As shown in FIG. 1, if the R phase, the S phase, and the T phase are connected in this order, each wire is covered with the groove of the iron core 2 and installed around the mold 4, the coil current is shown in FIG. As described above, since the same waveform is obtained by changing the phase every 120 °, an upward moving magnetic field is sequentially generated in the molten metal within the installation range of this coil. Therefore, due to this upward moving magnetic field and the electromagnetic force toward the center side due to the original pinch force of the coil, the direction of the electromagnetic force-induced flow of the molten metal 6 is different from the conventional one, and the direction is toward the mold center and the vertical direction. It becomes a direction (arrow A in the figure) directed obliquely upward, and the stirring flow also becomes an upward flow as shown by arrow B, so that the lubricant (powder) is not entrained in the molten metal, and the lubricant mold 4 As a result of promoting the inflow into the solidified shells 5, good slab properties can be obtained and casting productivity can be improved.

[0009]

【Example】

Casting conditions ・ Casting material: Normal steel aluminum killed material ・ Mold size: 150mmφ × 800mmh ・ Mold vibration: Stroke 6mm, cycle 180cpm
(3 Hz) lubricant, the main component _{C-CaO-SiO 2 -Al 2} O 3 -NaF
System ・ Viscosity 2 poise Electromagnetic force condition ・ Coil: When the molten metal level is 100 mm below the upper end of the mold, it is placed at a position 200 mm below the molten metal level Comparison conditions No electromagnetic force applied Conventional single-phase AC method 60 Hz 1200 Gauss ( Maximum effective value) Three-phase alternating current of the present invention, 1.5 Hz (1/2 of mold vibration),
1200 gauss (maximum effective value)

The results of casting under the above respective conditions are shown on the basis of the lubricant entrainment defect index of FIG. 4 and the slab surface roughness index of FIG. 5, and the defect index of the method of the present invention is the most excellent. The surface properties are slightly inferior to those of the conventional methods, but the properties are almost comparable.

[0011]

As described above, according to the casting method of the present invention, an electromagnetic force corresponding to the vibration of the mold is applied to the molten metal, so that the force applied to the solidified shell is synchronized and defects such as oscillation marks occur. do not do. In addition, a three-phase alternating current is used as an electric current that produces an electromagnetic force that imparts a pinch force to the molten metal, and an electromagnetic force that is vertically obliquely upward is generated in this current, which prevents the lubricant from being entrained in the molten metal. It is possible to improve the quality of the surface layer on one side, and by applying an electromagnetic force that has optimum directivity in synchronization with mold vibration,
Since the casting work is performed efficiently, it is possible to improve the productivity.

[Brief description of drawings]

FIG. 1 is an explanatory sectional view showing an example of a casting facility in which a three-phase electromagnetic coil is arranged to carry out the method of the present invention.

FIG. 2 is an explanatory sectional view showing an apparatus in which a single-phase electromagnetic coil is arranged to carry out a conventional casting method.

FIG. 3 is an explanatory diagram showing waveforms of three-phase coil currents used in the present invention.

FIG. 4 is a graph showing the effect of a lubricant entrapment defect index in the example of the present invention in comparison with the conventional example and the comparative example.

FIG. 5 is a graph showing the effect of the surface roughness of the cast slab in the example of the present invention in comparison with the conventional example and the comparative example.

[Explanation of symbols]

 1 Three-phase electromagnetic coil 2 Iron core 3 Lubricant 4 Mold 5 Solidification shell 6 Molten metal

Claims (1)

[Claims] 1. A linear electromagnetic coil is provided, in which molten metal is injected into a water-cooled mold that vertically vibrates at a constant cycle, a lubricant is injected into the surface of the molten metal in the mold, and the mold is surrounded by a linear electromagnetic coil. In the method for continuously casting molten metal by applying electromagnetic force in the vertical plane, the frequency of the three-phase alternating current applied to the linear electromagnetic coil is 2n (n is an integer of 1 or more) of the frequency of mold vibration. The continuous casting method for molten metal is characterized in that the direction of the electromagnetic force is directed obliquely upward in the vertical direction while being adjusted so as to be 1.