US 2008/0164004 A1Published application

Method and system of electromagnetic stirring for continuous casting of medium and high carbon steels

OwnerAnastasia Kolesnichenko, Anatoly F. Kolesnichenko +1inventors

InventorsAnastasia Kolesnichenko, Anatoly F. Kolesnichenko, Viktoria V. Buriak

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Abstract

A method and an apparatus are provided for electromagnetic stirring during a continuous casting process, especially for casting a billet and bloom of medium and high carbon steels. The method and apparatus provide a higher surface quality of the ingot, reduce the entrapping of nonmetallic inclusions into the ingot, and suppress issues regarding central segregation and central porosity. The method provides an improvement in the stirring process from the meniscus to the crater end—and relates to in-mold stirring and stirring in a zone of secondary cooling and up to the crater end. The in-mold stirring is geared towards the suppression of meniscus disturbance, for submerged casting, in particular, the reducing of helical and axial velocity components of the molten steel, the lowering of the initial solidification point to avoid the touching of a shell edge with the slag ring, and a decrease of oscillation marks.

Claims21

Dependent claims

A method of electromagnetic stirring of molten metal in an unsolidified portion of a continuously cast strand of an ingot, which comprises the steps of:

applying an alternating poly-harmonic current to at least four (six) coils of an in-mold stirrer;
supplying the alternating poly-harmonic current with two frequency components, including a low frequency component between f1=3.0-6.5 Hz and a high frequency component between f2=13-20 Hz;
setting a ratio of current amplitudes by equation:
(a high frequency current amplitude)/(a low frequency current amplitude)=0.5-0.75;
setting of ratio low frequency current component f3=0.5 fintr, fintr—intrinsic frequency of liquid part of billet 0.9-1.2 Hz, (about 1.0 Hz for 7×7 inch billet) with amplitude k times (0.2<k<2.0) higher than current amplitude of low frequency component f1=3-6.5 Hz—creates a pressure pulsation with frequency equal to intrinsic frequency of melt oscillation in the liquid portion of ingot, the oscillating pressure spreads along billet as acoustic waves that generate the pulse flow at the solidification front;
setting a ratio of current in dependence on a size of an ingot cross section for inducing a stirring torque below the mold for reducing a meniscus disturbance, for reducing particle entrapment into the ingot through a meniscus, for increasing mold powder flow into a gap formed between the mold and the ingot, and for decreasing oscillating marks on the ingot.

3 more elements

An electromagnetic stirrer system for stirring molten metal in an unsolidified portion of a continuously cast strand of an ingot, comprising:

a power source supplying an alternating poly-harmonic current;
and
an in-mold stirrer having a mold and at least four or six coils connected to said power source, said in-mold stirrer forming magnetic fields upon receiving the alternating poly-harmonic current to said at least four or six coils, the poly-harmonic current having two frequency components including a low pulse frequency component between 0.9-1.2 Hz, a middle rotate frequency component 3.0-6.5 Hz, and a high rotate frequency component between 13-20 Hz, a ratio of current amplitudes being defined by equation:
−a first low frequency current amplitude)/(a high frequency current amplitude)=1.5-1.7
in dependence on a size of an ingot cross section for inducing a pulse motion of molten metal along ingot axis up to final point of solidification;
−a second low frequency current amplitude)/(a high frequency current amplitude)=0.6-1.0 for creation of revolving torque in for rotate motion of melt inside mold;
and high 17-20 Hz frequency current amplitude for reducing a meniscus disturbance, for reducing particle entrapping into the ingot through a meniscus, for increasing mold powder flow into a gap defined between said mold and the ingot, and for decreasing oscillating marks on the ingot.

4 more elements

Dependencies are inferred from the claim text.