Composite Materials for Magnetic Field Control in EM Processing of Materials

V. Nemkov, R. Ruffini (Fluxtrol Inc., USA) A. Kolesnichenko (Net Shape Cast, USA)

Effects of Magnetic Flux Controllers

• Field Pattern Control

• Better Power Utilization in the Part (mainly in heating processes)

• Coil Efficiency Improvement

• Coil Power Factor Improvement

• Reduced Coil Current Demand

• Loss Reduction in Power Supplying Circuitry

• Shielding

Effect of magnetic flux concentrator

made of Fluxtrol A

Materials for Magnetic Flux Control

Available materials belong to three major groups:

• Soft Magnetic Composites (SMC) or Magnetodielectrics (MD)

• Laminations

• Ferrites

Fluxtrol Inc. produces 3 primary MD materials:

• Fluxtrol A

• Fluxtrol 50

• Ferrotron 559 H

Primary Fluxtrol Products

Note: frequency ranges and resistivity values are only for reference

Magnetic Properties of Fluxtrol Products

Compared to laminations and

ferrites, Fluxtrol materials are

almost linear.

Fluxtrol A material can support

permeability above 50 at high

magnetic loading (flux density

up to 14000 Gs), which is

important for high power and

low frequency applications.

Relatively low permeability of

MDM compared to laminations

does not influence their

performance in non-closed

magnetic circuits.

Flux Density vs Magnetic Field Strength

0

2000

4000

6000

8000

10000

12000

14000

0 50 100 150 200

Field Strength, A/cm

Flu

x D

en

sit

y, G

s

Fluxtrol A

Fluxtrol 50

Ferrotron 559 H

Permeability vs Flux Density

0

25

50

75

100

125

0 3000 6000 9000 12000

Flux Density, Gs

Perm

eab

ilit

y

Ferrotron 559

Fluxtrol 50

Fluxtrol A

Comparison of Laminations

and MDM Properties Characteristics Laminations Ferrotron/Fluxtrol

Frequency, kHz up to 20 kHz Any

Effective saturation, T 1.5 – 1.6 1.2 – 1.5

Initial permeability Above 1000 18 - 63

Max permeability Around 5000 20 - 120

Permeability grades No 4 grades

Anisotropy Very strong Low to Middle

Temperature resistance, C Probably 300 – 400 C Long – 250 C

Performance in 3D field Very bad Good

Complex geometry Difficult Easy

Installation Laborious Easy

Cooling Difficult Easy – many methods

In-field adjustment Difficult Easy

Use as construction part Problematic Good

Fluxtrol Material Blocks for Large Installations

Fluxtrol MDM for magnetic flux concentration and shielding. Self-gluing film

insulation may be applied to the blocks if required. Largest plates at present

time are 6” x 8.5” x 2”

Copper Tubes with Matching Netshape

LRM Concentrators

Advantages:

1. More effective copper

and Fluxtrol cooling

2. Higher mechanical

strength

3. Minimized

manufacturing costs

4. Possibility to work

effectively in 3D

magnetic fields

Selected Material Processing Technologies

Technology Frequency

range,

Power

range, kW

Magnetic core material

Existing Proposed

Induction melting 50 -10000 Hz 50 -10000 Air or Lams Lams + MDM in

3D area

Cold-crucible melting of

metals 500 – 5000 Hz 50 - 2000 Air MDM shunts

EM pouring control 50 – 150 kHz 25 – 100 Ferrite MDM

Vacuum or controlled

atmosphere furnaces 50-3000 100 -10000 No or lams

MDM or MDM +

Lams

Liquid coating wiping 100-200 kHz 25-50 Lams or air MDM

Semi-levitation and

levitation 50 – 10000 Hz 50 - 500 Air MDM

Pulse treatment in

casting 1-2 Hz 100 - 200 Lams Lams + MDM

EFG Crystal growth 10-30 kHz 10 - 30 Ferrite or

MDM MDM

Monocrystal growth 10-500 kHz 10 - 30 Air MDM

Magnetic Control in

Cold Crucible Melting Furnace

With No controller With Fluxtrol controller

Advantages:

• Improvement of coil efficiency and power factor

• Reduction of losses in the furnace chamber and other

components

• Possibility to use smaller chamber

Melting Inductor for Glove Box Environment

Example of shielding effect and

efficiency improvement

Fluxtrol A shields on the side and

bottom coil surfaces allowed to:

•Strongly reduce losses in the

chamber walls and bottom plate

•Increase the furnace volume in

the same chamber

•Increase coil efficiency from 23 to

63% due to reduced losses in

chamber walls, bottom plate and

in the coil

Fluxtrol

plates

Induction coil for melting of radioactive

materials in protective atmosphere

Magnetic field lines and color map of

power density in a shielded coil

Glove Box walls

Fluxtrol plates

Molten metal

Shielding in Furnaces with Special Atmosphere

Due to the magnetic field

shielding it is possible:

• reduce the furnace size

or

increase the furnace

loading

• improve efficiency and

power factor of the

inductors, especially for

the bottom ones

• Fluxtrol Inc. has very good

experience in such designs

Possible Combinations of Lams and MDM

3D area

Use of MDM in combination with

laminations in 3D areas of shunts MDM inserts in magnetic core for gradient

field formation in pulse magnetic device for

steel stirring in continuous slab casting

Due to machinability, ability to work in 3D areas and serve as structural

components, MDM may be effectively used in combination with laminations

Magnetic “Wiper” Concept

Electrodynamic forces created by magnetic field help to “blow out” excess of

coating material (Zn or other) from the surface of wire (left) or strip (right).

Required frequency is usually high (up to 200 kHz) and MDM material is the

only choice for magnetic material