# US 2010/0163207 A1 · Method and device for the electromagnetic stirring of electrically conductive fluids

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- Number: US 2010/0163207 A1
- Document ID: US20100163207A1
- Status: Published application
- Kind: A1
- Application number: 12/672,046
- Filed: 2008-08-01
- Published: 2010-07-01
- Earliest claimed: 2007-08-03
- Assignees: Forschungszentrum Dresden-Rossendorf E. V.; Technische UniversitäT Dresden
- Inventors: Petr A. Nikrityuk; Sven Eckert; Dirk Räbiger; Bernd Willers; Kerstin Eckert; Roger Grundmann; Gunter Gerbeth
- Web page: https://patentgrep.com/patent/US20100163207A1

## CPC

- B22D 27/02: Use of electric or magnetic effects {(for continuous casting B22D11/015, B22D11/11)}
- B01F 33/451: wherein the mixture is directly exposed to an electromagnetic field without use of a stirrer, e.g. for material comprising ferromagnetic particles or for molten metal
- B22D 11/115: by using magnetic fields
- B22D: CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES (shaping of plastics or substances in a plastic state B29C; metallurgical processing, selection of substances to be added to metal C21, C22)
- B01F: MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING (mixing paints B44D3/06)

## Abstract

The invention relates to a method and a device for the electromagnetic stirring of electrically conductive fluids by using a magnetic field RMF rotating in the horizontal plane, and a magnetic field WMF traveling in a vertical direction thereto. The object consists in avoiding asymmetric flow structures in containers filled with melts, in particular at the beginning and during the course of the solidification. Moreover, the aim is to achieve an effective mixing of the fluid and/or a controlled solidification of metallic alloys by avoiding the formation of separation zones in the solidification structure. The solution consists in the fact that both the rotating magnetic field RMF and the traveling magnetic field WMF are switched on discontinuously in the form of temporally restricted and adjustable periods and alternately in time one after another via associated induction coils.

## Claims

### Claim at position 1

1-19. (canceled)

### Claim 20

A method for the electromagnetic stirring of electrically conductive fluids by using a magnetic field RMF rotating in the horizontal plane, and a magnetic field WMF traveling in a vertical direction thereto, wherein both the rotating magnetic field RMF and the traveling magnetic field WMF are switched on discontinuously in the form of temporally restricted and adjustable periods and alternately in time one after another via associated induction coils.

### Claim 21 (depends on 20)

The method as claimed in claim 20, wherein the duration (TP,RMF) of the periods of a rotating magnetic field RMF, and the duration (TP,WMF) of the periods of a traveling magnetic field WMF lie in a time interval
0.2·ti.a.<TP,RMF=TP,WMF<2·ti.a. (I)
with the following definition for an initial adjustment time ti.a.
t
i
.
a
.
=
C
g
·
(
B
0

σω
ρ
)
-
1
,
(
III
)
the variables σ, ρ, ω and B0 representing the electrical conductivity and the density of the fluid, the frequency and the amplitude of the magnetic field RMF or WMF, and the constant Cg representing the influence of the size and shape of the volume of the fluid, and the initial adjustment time (ti.a.) representing the instant at which the volume-averaged kinetic energy of the meridional flow or the volume-averaged meridional speed Urz reaches a first maximum.

### Claim 22 (depends on 20)

The method as claimed in claim 20, wherein various periods TP,RMF, TP,WMF for the rotating magnetic field RMF and the traveling magnetic field WMF are adjusted in accordance with the following condition
0.5·TP,RMF<TP,WMF<5·TP,RMF (II).

### Claim 23 (depends on 20)

The method as claimed in claim 20, wherein the amplitude of the rotating magnetic field RMF (34) exceed the following two values
B
1
RMF
=
ρ
σω
·
100
·
V
sol
H
0


and
(
VI
)
B
2
RMF
=
ρ
σω
·
40
·
V
sol
3
/
2
H
0

v
,
(
VII
)
the parameters v, Vsol and H0 representing the kinematic viscosity of the melt, the rate of solidification and the height of the melt volume, and B1RMF and B2RMF are the lower limit values of the amplitudes of the rotating magnetic field RMF.

### Claim 24 (depends on 20)

The method as claimed in claim 20, wherein the amplitude (B0WMF) of the traveling magnetic field WMF is set to be exactly as large as or up to four times larger than the amplitude (B0RMF) of the rotating magnetic field RMF, that is to say
B0WMF=1 . . . 4·B0RMF (VIII).

### Claim 25 (depends on 20)

The method as claimed in claim 20, wherein other pulse shapes such as, for example, sine, triangle or sawtooth are implemented instead of the rectangular function when modulating the profile of the Lorentz force, the profile and the maximum value of the respective magnetic field RMF or WMF being defined such that an identical energy input results for the various pulse shapes.

### Claim 26 (depends on 20)

The method as claimed in claim 20, wherein the amplitudes of the magnetic fields RMF and WMF is set during the stirring in a fashion adapted continuously in accordance with the requirements derived from the process to be observed.

### Claim 27 (depends on 20)

The method as claimed in claim 20, wherein the individual periods in which one of the magnetic fields RMF or WMF is switched on are interrupted by a pause duration TPause, in which none of the two magnetic fields RMF or WMF act on the fluid, in which TPause≦0.5·TP,RMF or TPause≦0.5·TP,WMF.

### Claim 28 (depends on 20)

The method as claimed in claim 20, characterized in that the direction of the rotating magnetic field RMF and/or of the traveling magnetic field WMF is inverted between two pulses.

### Claim 29

A device for the electromagnetic stirring of electrically conductive fluids by using a magnetic field RMF rotating in the horizontal plane, and a magnetic field WMF traveling in a vertical direction, comprising at least
a cylindrical container,
a centrally symmetrical arrangement, surrounding the container, of at least three pairs of induction coils for forming a rotating magnetic field RMF producing a Lorentz force FL, and
an arrangement, surrounding the container, of at least two induction coils lined up one above another in a stack coaxially with the axis of symmetry in order to produce the vertically traveling magnetic field WMF, and
at least one temperature sensor for measuring the temperature of the fluid in the container and controlling the temperature by means of a control/regulation unit,
wherein that a power supply unit is connected to the induction coils by the control/regulation unit, the power supply to the induction coils being performed in a fashion set by the prescribed conditions
0.2·ti.a.<TP,RMF=TP,WMF<2·ti.a. (I) or
0.5·TP,RMF<TP,WMF<5·TP,RMF (II).

### Claim 30 (depends on 29)

The device as claimed in claim 29, wherein the container with the melt is arranged concentrically inside the induction coils.

### Claim 31 (depends on 30)

The device as claimed in claim 30, wherein the container is provided with a heating device and/or cooling device.

### Claim 32 (depends on 31)

The device as claimed in claim 31, wherein the baseplate of the container is in direct contact with a solid metal block through whose interior a coolant flows.

### Claim 33 (depends on 29)

The device as claimed in claim 29, wherein the side walls of the container are thermally insulated.

### Claim 34 (depends on 32)

The device as claimed in claim 32, wherein the metal block is connected to a thermostat.

### Claim 35 (depends on 32)

The device as claimed in claim 32, wherein a liquid metal film is located between the metal block and the container in order to attain a stable heat transfer in conjunction with a low transfer resistance.

### Claim 36 (depends on 35)

The device as claimed in claim 35, wherein the liquid metal film consists of a gallium alloy.

### Claim 37 (depends on 29)

The device as claimed in claim 29, wherein positioned in the baseplate and/or the side walls of the container in which the melt is located is at least one temperature sensor in the form of a thermocouple that supplies an information item relating to the instant of the beginning of the solidification, and is connected to the control/regulation unit for the purpose of controlling the temperature of the fluid.

### Claim 38 (depends on 20, 29)

The use of the device for the electromagnetic stirring of electrically conductive fluids as claimed in claim 29 in the form of metallic melts in metallurgical processes, or in the form of semiconductor melts in crystal growth, for the purpose of cleaning metal melts, during continuous casting or during the solidification of metallic materials by means of the method as claimed in claim 20.