JPH11188466A - Continuous casting device for molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous casting device which has a function for measuring a surface level position of a molten metal in a mold at the time of continuous casting of the molten metal. SOLUTION: In this continuous casting device for a molten metal, a given number of OFF time is provided while an alternating current is conducted to a magnetic coil being arranged in a manner to surround a mold. The current conducting condition of the alternating current in a given period is set as follows; frequency (f) is 60<=f<=400 (Hz), and current conducting ON/OFF pitch (To) is 30<=To<=300 (msec). At this setting value, casting is repeatedly carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting apparatus for a molten metal in which an electromagnetic coil is mounted and energization conditions are controlled.

[0002]

2. Description of the Related Art Generally, in continuous casting of molten metal,
Powder is supplied to the upper surface of the molten metal pool in the mold, and the powder melted by the heat from the molten metal flows between them due to the relative motion of the mold wall vibrating up and down and the solidified shell drawn at a constant speed, Due to the dynamic pressure generated during this inflow, the meniscus and the solidified shell tip are deformed, and since this deformation is repeated at the cycle of the mold oscillation, periodic wrinkles called oscillation marks are formed on the slab surface, Affects surface properties. However, if the depth of the wrinkles is large, it leads to defects in the surface of the slab, and depending on the type of steel, only specific elements are segregated in the oscillating mark valleys, and the capture of bubbles and inclusions increases. , Causing a reduction in yield.

As a method for controlling the oscillation mark, as described in Japanese Patent Application Laid-Open No. 52-32824, a molten metal is injected together with a lubricant into a water-cooled mold that vibrates at a constant period, and is continuously lowered. In the continuous casting method, an alternating current is continuously applied to the electromagnetic coil provided around the mold, and an electromagnetic force is applied to the meniscus of the molten metal in the mold using the electromagnetic force generated by the AC magnetic field, thereby forming a meniscus portion. There is disclosed a method of improving the surface properties of a slab by curving the surface of the slab. Japanese Patent Application Laid-Open No. 64-83348 discloses a powder supply method in which when an electromagnetic force is applied to a molten metal in a mold by an electromagnetic coil, an alternating magnetic field is applied in a pulsed manner to intermittently apply the electromagnetic force. Discloses a method for further improving the surface properties of a slab. Further, in Japanese Unexamined Patent Publication No. 8-805926, the amplitude of the alternating current is given the same strength as that of the mold vibration in order to apply an electromagnetic force, so that the mold vibration frequency (fm) and the alternating magnetic field frequency (f) are given.
p) is set within the range of 0.69 ≦ ln (fp / fm) ≦ 9.9 to form a stable meniscus, and a continuous casting technique for more stably obtaining the effect of improving the surface properties of the slab. It has been disclosed.

[0004]

However, when these conventional techniques are actually realized by a continuous casting apparatus equipped with an electromagnetic induction heating device, it is difficult to stably form a meniscus of a molten metal, and as a result, a good cast slab is obtained. It has become impossible to secure the surface properties, and a serious situation has occurred in which the yield decreases.
Furthermore, it also affects the detection of the level of the molten metal in the mold. In addition, as long as an electromagnetic coil is used, an AC magnetic field generated from the electromagnetic coil acts as noise. For example, when used in a magnetic field having a magnetic flux density of 1,000 (Gauss) and a frequency of 200 Hz, the output signal is saturated and cannot be measured, or even when a pulsed magnetic field is used, the output signal is saturated when the magnetic field is ON. As it is, the surface properties of the continuous cast slab are not stable, causing a problem that special electrical equipment is required separately for removing the noise.

[0005]

Means for Solving the Problems Accordingly, the present inventors have:
The company studied the production of continuous cast slabs of excellent quality by controlling the energizing conditions of the alternating current that generates the pulsed magnetic field to improve the surface properties of the slab, and reduced the cost of equipment for electrical equipment. Focusing on the fact that strong noise acts during the pulse application period (ON period), but almost no noise occurs during the pulse application suspension period (OFF period), the pulse ON period and the pulse OFF period are periodically repeated. In addition, it has been found that there is a certain relationship between the frequency and the ON / OFF pitch when AC current is supplied to the electromagnetic coil. Furthermore, by repeatedly outputting the set value derived from this relational expression and casting with this value, continuous casting was made possible under stable conditions without being affected by AC magnetic field noise generated from the electromagnetic coil. Things. A specific gist of the present invention is that an OFF time is set an arbitrary number of times during energization of an alternating current of an electromagnetic coil arranged so as to surround a mold, and an energizing condition of the alternating current at a constant cycle of the alternating current is set to a frequency (f), an energizing ON / OFF pitch (To) is 60 ≦ f
≦ 400 (Hz), and 30 ≦ To ≦ 300 (mse
This is a continuous casting apparatus for molten metal that is set to c) and is repeatedly cast at this set value.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a diagram illustrating a relationship between frequency and current, and FIG. 1B is a diagram illustrating a relationship between energization ON / OFF pitch and slab surface roughness. In the continuous casting apparatus for molten metal according to the present invention, the operation of energizing the current of the electromagnetic coil for 1 to 5 cycles, providing an OFF time during the energization any number of times, and then energizing for 1 to 5 cycles is repeated. , It is configured to start only when the energization is OFF. Based on this finding, according to the present invention, the OF of the present invention is turned on during energization of the electromagnetic coil arranged to surround the mold of the continuous casting apparatus.
An F time is provided an arbitrary number of times, and as a condition for energizing at a constant cycle of alternating current, the cycle of the repetition is represented by a frequency (f) and an energizing O.
The relationship with the N / OFF pitch is 60 ≦ f ≦ 400 (H
z) and casting was performed under the conditions of 30 ≦ To ≦ 300 (msec). This is, as shown in FIG.
In the present invention, the noise shows a minimum value near 200 Hz from the relationship between the frequency and the current, and the usable frequency is 60 to 400.
Hz range. At a frequency of 200 Hz, the slab surface roughness (Rmax) and the energization ON / OFF pitch (T
Looking at the relationship with o), as shown in FIG.
It can be seen that the slab surface roughness is significantly improved when the N / OFF pitch (To) is 200 msec. Therefore, from the viewpoint of slab roughness, the energization ON / OFF pitch (T
It is preferable to energize in the range of o) in the range of 30 to 300 msec. In addition, when To is 30 msec or less, or 300 msec or more, the slab roughness deteriorates, so that it is preferable to set the above range.

Further, in the present invention, as shown in FIG. 2, the power generation current has a periodically ON / OFF waveform as shown in FIG. 2A via an electromagnetic coil in the electromagnetic generator. Focusing on the fact that an AC magnetic field generated from the electromagnetic coil is generated in the ON state and no AC magnetic field is generated in the OFF state, the electromagnetic generator is operated in an ON / OFF pattern. On the other hand, when the electromagnetic generator is turned on /
As shown in (B), the continuous casting is performed by turning ON / OFF in parallel with the operation in the OFF pattern, that is, masking when the electromagnetic generator is in the ON pattern and performing signal processing only in the OFF pattern. went.
That is, the current of the electromagnetic coil in the electromagnetic generator is energized at a constant period, and during the energization, preferably, when the current of the electromagnetic coil is turned on, the direction of the rotating magnetic field is rotated forward / reversely.
The FF time is set an arbitrary number of times, and then the operation of energizing at a fixed cycle is repeated, and only the OFF time is measured and output by the eddy current level meter or the level meter with a built-in mold to perform continuous casting. It has become possible to stably obtain continuous cast slabs, billets and the like having excellent surface properties.

[0008]

As described above, according to the present invention, the ON / OFF pitch of the AC current can be reduced while the AC current is applied to the electromagnetic coil.
Preferably, the motor is rotated forward / reverse when turned on, and OF is turned on at a certain interval.
By providing an arbitrary number of F times and controlling the relationship between the frequency and the ON / OFF pitch of the alternating current at that time, it is possible to obtain a stable surface property, and furthermore, an inexpensive continuous casting equipment for electric equipment. Is now available.

[Brief description of the drawings]

FIG. 1A is a diagram showing a relationship between frequency and current,
(B) is a figure which shows the relationship between energization ON / OFF pitch and slab surface roughness.

FIG. 2 shows a current waveform (A) of an electromagnetic coil of the electromagnetic generator.
FIG. 7 is a diagram showing waveforms of a masking (B).

Claims (1)

[Claims] An OFF time is provided an arbitrary number of times during the AC current application of an electromagnetic coil arranged so as to surround a mold, and an energization condition in a constant AC cycle is set to a frequency (f) and energization ON / OF.
A continuous casting apparatus for molten metal, wherein the F pitch (To) is set to 60 ≦ f ≦ 400 (Hz) and 30 ≦ To ≦ 300 (msec), and the casting is repeatedly performed at the set values.