JPH0399753A - Mold for electromagnetic casting - Google Patents

Abstract

PURPOSE:To obtain increase of electromagnetic force to molten metal in a mold and to miniaturize the equipment by constituting mold material at upper part, the boundary of which lies on almost the same surface line as meniscus and which does not come into contact with the molten metal in the mold, of non-magnetic metal having electric resistance larger than that of lower part. CONSTITUTION:The upper part of the mold 1, where almost the same surface line as the meniscus 5 is made as boundary and which does not come into contact with the molten metal 4, is constituted of the non-magnetic metal having high electric resistance, e.g., stainless steel or copper alloy having high electric resistance. The lower part in contact with the molten metal 4 is constituted of copper or copper alloy having electric resistance lower than that of the above copper alloy and a coil 3 is set in such manner that the upper face of coil 3 almost matches with the boundary 2. By this method, density of the magnetic flux flowing into the molten metal 4 in the mold after passing through the upper part 1a of mold from the coil 3 is increased and the electromagnetic force becomes about three times in comparison with the conventional copper- made mold and the exciting current is reduced.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention adjusts the meniscus shape by electromagnetic force in the mold of continuous casting equipment, stably supplies mold flux to the gear knob between the cast steel nonyl and the mold, This invention relates to the structure of a mold for manufacturing high-grade cast steel.

[Prior art] In in-mold electromagnetic casting, a coil is installed around the outer periphery of the mold, and when it is excited with an alternating current of 300 to 7,000 amperes and 50 to 10,000 cycles, the coil penetrates the mold and melts in the mold. The magnetic flux passing through the metal produces an electromagnetic force directed toward the center of the molten metal in the mold, and the shape of the mechanical can be adjusted by changing the excitation current or excitation frequency.

In addition, the penetration of the electromagnetic horn is improved by constructing the wall of the mold with a composite plate made of copper alloy on the inside and stainless steel on the outside. (Unexamined Japanese Patent Publication No. 58-
50157) [Problems to be Solved by the Present Invention] However, when magnetic flux passes through the nonmagnetic conductor constituting the mold, the magnetic flux density is attenuated as expressed by the following equation.

However, ΔB・Magnetic flux density attenuation rate t: Thickness of conductor [ml y: Electrical resistivity of conductor [Ω・ml μ. Vacuum permeability - 4π =0.o 1m, 5'=1.9XIO-
When a magnetic flux of 60I (z is passed through a copper plate of 8Ω・m, μs=I, an attenuation of =0 67 occurs. In other words, 2/3 of the generated magnetic flux is attenuated within the copper mold, and the remaining ■/ Therefore, only 3 will contribute to the electromagnetic force.

Therefore, in order to obtain the required electromagnetic force using the conventional copper mold, a large excitation power is required, which has the drawback of increasing the size of the equipment.

In addition, in order to reduce magnetic flux attenuation in the mold, metals with higher electrical resistivity than copper, such as stainless steel (P=7sx+
It is possible to use a mold made of o-8Ω・m, /ls''; 0.16, making it possible to significantly improve the attenuation of magnetic flux density. However, in the case of stainless steel molds, the thermal conductivity is about 1/20 compared to copper molds, and the cooling effect of mold cooling water is poor, resulting in only a few Charge and generate a crack due to enthusiastic horns,
Not only will it no longer function as a continuous casting mold, but if cooling water enters the molten metal in the mold through the cracks, a hydrogen explosion may occur.

In addition, when a composite plate of copper alloy and stainless steel is used for the mold wall, the cooling mechanism becomes complicated because heat dissipation is blocked by the outer stainless steel.

In view of these points, the present invention suppresses magnetic flux attenuation in the mold with a simple structure, increases electromagnetic force, and reduces excitation power without hindering cooling.

[Means for Solving the Problems] For this reason, the present invention provides a part of the mold that does not come into contact with the molten metal with a non-magnetic metal having high electrical resistance, such as stainless steel or It is made of a copper alloy with high electrical resistance, and the lower part in contact with the molten metal is made of copper or a copper alloy with a lower electrical resistance than the copper alloy in the upper part, and the top surface of the coil almost matches the boundary. Place the coils as shown.

[Function] Therefore, the magnetic flux density entering the molten metal in the mold from the coil through the upper part of the mold is increased, and the electromagnetic force is approximately three times that of a conventional copper mold, thereby significantly reducing the excitation current. In addition, since this part does not come into contact with molten metal within the mold, it is less affected by thermal stress (maintains the same lifespan as conventional copper molds).

[Example] Figure 1 is a schematic diagram showing an example of the present invention, where I is a mold;
The upper part 1a from the boundary 2 is made of stainless steel, and the lower part 1b is made of copper. 3 is a coil provided around the outer periphery of the mold, 4
is the molten metal in the casting chamber, 5iJ meniscus, 6 is the magnetic flux, 7
indicates the direction of electromagnetic force.

The inner diameter of the mold is 0.15m, and the thickness L is 0. The upper part 1a of the mold is made of stainless steel with an electrical resistivity T of 75 x 10-8 Ωm, and the lower part 1b is made of stainless steel with an electrical resistivity P of 1.9.
Made of copper with xlo-"Ω・m, the coil has 6oI-
Curve a in Figure 2 shows the results of measuring the magnetic flux density at the center of the mold axis when a current of 2000 A was applied.

In addition, as another example, a copper alloy with an electric resistivity P of 6.3XIO-8Ω·m is used for the upper part 1a of the mold, and the lower part 1b
is the electrical resistivity P month, 9×10-8Ω・m as above
When made of copper, the magnetic flux density was the same as the second drawing line.

On the other hand, in a conventional mold in which the entire mold l is made of copper with an electrical resistivity P of 1.9xlO-8 Ω·m, the measured value is as shown by curve C in FIG. 2.

As you can see from this characteristic distribution diagram, when the upper part of the mold is made of stainless steel, the magnetic flux density increases dramatically by about 1.8 times and the electromagnetic force by about 3.4 times compared to the conventional copper mold. death,
Even when a copper alloy is used, the magnetic flux density increases by about 1.3 times and the electromagnetic force increases by about 1.7 times.

Note that although the above embodiment shows the results of an experiment performed at a commercial frequency of 60I-12, as is clear from equation (1), a similar large improvement can be obtained in the high frequency region as well.

[Effects of the present invention] As described above, according to the present invention, the cooling effect can be improved by making the same surface as the mechanical part of the molten metal as the boundary, and changing the material of the upper part of the mold to a non-magnetic metal with high electrical resistance. The electromagnetic force applied to the molten metal in the mold can be dramatically increased while maintaining good retention, and effects such as miniaturization of equipment and energy saving can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a distribution curve of magnetic flux density. (2) is the mold, 1a is the upper part of the mold, Ib is the lower part of the mold, 2 is the border, 3 is the coil, 4 is the molten metal, 5 is the meniscus, 6 is the magnetic flux, and 7 is the direction of electromagnetic force.

Claims (1)

[Scope of Claims] 1. In a mold for an electromagnetic casting device that adjusts the shape of a meniscus by applying electromagnetic force to molten metal in the mold using a coil installed around the outer periphery of the mold, the mold An electromagnetic casting mold characterized in that the upper mold material that does not come into contact with the molten metal is made of a non-magnetic metal that has a higher electrical resistance than the lower mold material. 2. The electromagnetic casting mold according to claim 1, wherein the upper part is made of stainless steel or a copper alloy, and the lower part is made of copper or a copper alloy having a lower electrical resistance than the copper alloy of the upper part.