http://fluxtrol.com

1. 4th Asian Conference on Heat Treatment
& Surface Engineering
ADVANCED INDUCTION HEAT
TREATMENT TECHNOLOGIES
AND DESIGN METHODS
Dr. Valentin NEMKOV
Fluxtrol Inc., Auburn Hills, Michigan, USA

2. Overview
• Advanced induction technologies – old and new
• Progress in power supplies and controls
• Computer Simulation and Virtual Prototyping
• Magnetic flux control
• Internal inductors
• Induction versus carburizing
• Induction hardfacing
• Induction treatment in Liquid Active Media
• Coating treatment
• Conclusions

3. Induction Technique
Ideas of induction heating appeared at the end
of XIX century. Many famous names must be
mentioned here, such as L. Foucault, N. Tesla
and others
Induction Surface Hardening is 75 years old and Dr. Edwin Northrup
two men may be considered as major pioneers: (1866-1940)
Dr. E. F. Northrup, USA and Prof. V.P. Vologdin,
Russia
Since crankshaft hardening (1934-1935) this
technology passed a long way with very big
achievements and continues to bring new
impressive results
Some technologies developed or proposed in 30-
50s maybe considered as advanced at present
time such as SDF hardening. Prof. Valentin Vologdin
(1881-1953)

4. Main Recent Achievements in
Induction Technique
Induction systems:
• Solid-state power supplies
• Control and monitoring
systems
Induction coils:
• Magnetic flux controllers
Minac 18/25 TWIN power supply, EFD
• CNC machining Induction
Design methods:
• Computer simulation
• Virtual prototyping
New technologies Scan hardening, Elta program

5. Modern Power Supplies
• Modern solid state power
supplies can provide any
required combination of
power and frequency
• Power – from 1 kW to
several MW
• Frequency – from line
frequency to 0.5 MHZ and
more (for small power)
• Intelligent systems
• Small dimensions
• High efficiency
Courtesy of EFD Induction, Inc

6. Simultaneous Dual Frequency
Hardening (SDF)
For contour hardening of gears and other parts of complex
geometry, special transistor power supplies were developed that can
generate two frequencies simultaneously. Power levels may be
programmed independently for each frequency, providing accurate
results and high process flexibility
Induction hardening installation: Gear hardened by SDF
Middle Frequency power 400 kW
High Frequency power 200 kW
Courtesy Eldec Induction U.S.A.

7. Virtual Prototyping (VP)
Virtual Prototyping is the use of
computer models to develop
and test the process and/or
component without having to
physically build or run it
VP includes detailed analysis
of the problem, development
and optimization of new
concept using modeling
At present time – EM, Thermal
FEA mesh for axle scan
and Structural tasks hardening with optimized
Emerging – Stresses and inductor
Distortions

8. Example of Virtual Prototyping:
Wheel Hub Hardening
Problem:
• Short coil life: 8,000 –
13,000 pieces
• Difficult setup with
big machine downtime,
personnel time and
scrap parts Typical process of wheel hub
heating with “stepped” coil

9. Modeling of Part
Temperature & Hardness
Temperature distribution in part with Predicted hardness pattern
new coil design
Flux 2D program + Metal 7

10. Modeling of Coil Temperature
Copper:
Copper temperature calculation
is available in Flux program
Heat transfer coefficient
calculated from water flow rate
Results: Max copper
temperature <100°C
Concentrator:
Special procedure had been
developed for the
concentrator temperature
calculation
It accounts for the magnetic
losses, radiation and glue
properties

11. Performance and Longevity Tests
• Test showed that precise
hardness pattern was
reached on the 3rd part
• Coil and process setup
became easy
• Lifetime was not anymore
a problem. Coil heated
170,000 parts and still
remained in good
conditions
>170,000 cycles

12. Hardness Pattern for Axle Scanned
with Original and Optimized Coils
Coil power 170 kW, Frequency 1 kHz

13. Magnetic Flux Control
Magnetic Flux control includes
concentration, shielding and
field modification
Advantages of magnetic controllers:
• Heat pattern control
• Coil current demand reduction
• Better use of induced power
• Elimination of unintended heating
of the part or machine components
• Coil parameter improvement
(efficiency, power factor)
Materials for magnetic control:
• Laminations
• Ferrites
• Soft Magnetic Composites (SMC) 13

14. Composite Materials for Magnetic
Flux Control
Soft Magnetic Composites
represented mainly by Fluxtrol and
Ferrotron materials, have a very
favorable combination of
mechanical, thermal and
electromagnetic properties:
• Can work in entire range of
induction heating frequencies (up
to 13 MHz)
• Have excellent machinability
• Can work in 3D magnetic fields
• Have good magnetic properties
• Have good thermal properties
• May be used as structural Composite materials
components in the coils manufactured by Fluxtrol Inc.

15. Magnetic Permeability of Fluxtrol
Products
Materials are quasi-linear
Fluxtrol A material can support
permeability above 80 at high
magnetic loading (flux density up to Permeability vs Flux Density
9000 Gs) 125
Permeability
100 Ferrotron
SMC work well at very challenging 75 559
Fluxtrol 50
applications when properly selected 50
Fluxtrol A
and applied: 25
0
• Material must be selected with 0 3000 6000 9000 12000
account for orientation due to Flux Density, Gs
anisotropy
• Good thermal management by Information about Fluxtrol
means of application to the coil with and Ferrotron properties
thermally conductive glue or by means and application is available
of separate cooling on site www.fluxtrol.com
15

16. Examples of Coils with
Composite Flux Controllers
Coil for Al part brazing with Fluxtrol Internal coil with Fluxtrol controller
A controller

17. Selected Induction
Technologies

18. Induction Instead of Carburizing
Example:
Initial process with
furnace carburizing:
• Masking of the part
• Carburizing for about 80
hrs to a depth of 8 mm
• Demasking
• Furnace hardening
• Cryogenic treatment
• Tempering
• Grinding to correct
Scan hardening of an internal surface of
distortions
a big steel component (750 kg)
New process:
Magnetic concentrator strongly reduces the
• Induction scan hardening
coil current (2 times) and therefore size of
• Furnace/induction tempering the transformer and other equipment
• Final grinding

19. Induction Hardfacing/Cladding
The goals are to increase:
- Hardness
- Wear resistance
- Chemical resistance
Powders compositions:
•C 2.5 – 7.0 %
• Cr 20 – 40 %
• Mn < 15%
• Ni 0.5 – 5 %
• Si 1 – 2 %
• Others – Cu, B, W, Mo
Typical hard layer
thickness – 0.5 - 2 mm
Courtesy Freal & Co

20. Microstructures
Hard Layer
Substrate 155 mkm 30 mkm
Low porosity and Excellent transient zone
inclusions
Courtesy Freal & Co

21. Hardfacing of Harrow Discs
Life time is 2-3 times longer
than for traditionally treated
discs
Harrow disc with hardfaced teeth
Courtesy Freal & Co

22. Induction Hardfacing Process
Magnetic controllers
from Fluxtrol 50 for
temperature
distribution control
Courtesy Freal & Co

23. Induction Hardfacing Installation
4
3 1
5
2
Versatile automatic hardfacing installation 60 kW, 66 kHz
1 – Generator, 2 – Controls, 3 – Heat Station
4 – Cooling System, 5 - Machine
Courtesy Freal & Co

24. Thermo-Chemical Processing with
Induction Heating
Induction gas
carburizing is a well
known but not used
process
Combination of
induction processing in
liquid media, proposed
by Prof. Saveliy Gugel,
provides many new
opportunities
Courtesy Sanova LLC

25. Induction Treatment in LAM
Vapor blanket
Induction carburizing in liquid
active media (LAM) occurs at LAM
T
high temperature and very
high concentration (potential)
x
of carbon or other elements
(B, N, etc.)
Process is very flexible due
Insulation
to many variables: LAM
composition, temperature
variation on the part surface
and subsequent heat treating
Chamber
process parameters
Courtesy Sanova LLC

26. Variety of Structures on Steel
Surface
Ledeburite (a) Austenite (b) Martensite (c)
Courtesy Sanova LLC

27. Steel AISI 8620 after Treatment
Steel:
C 0.18/0.23; Cr 0.4/0.6; Mn
0.7/0.9; Mo 0.15/0.25; Ni
0.4/0.7; Si 0.15/0.35 50HRc
Example of processing:
- Carburizing 35 min - 1220 C
- Recrystallization Cooling
0.5 min
- Heating to 870 C and soaking, Fine M + F P+A
4 min
- Hardening in LAM, 0.5 min
45-25 HRc
- Self-tempering, 2.5 min 63-67 HRc
Case depth is around 2 mm
Courtesy Sanova LLC

28. Example of Ti Alloy Treatment
Treatment
increased
strength, wear
and fatigue
resistance
Erosion
resistance
increased more
than 3 times
Microstructure of Ti6Al4V (x100) and micro-hardness curve
after treatment in LAM for 20 min
Courtesy Sanova LLC

29. Installation for Processing
2
1
1 – Power supply
2 – Treatment block
3
3 – Control panel
Courtesy Sanova LLC

30. Electromagnetic Wiper
Induction heating is widely used for Preheating and Remelting
of strips and wires in galvanizing and galvannealing processes.
One new application – removal of excess of the molten coating
(zinc) from the parts. Electrodynamic forces are used here.
F
Courtesy Netshape Cast, USA

31. Conclusions
• There are many new applications of induction
heating in heat treating and surface engineering
• Some old technologies found new life due to
new environmental and technical requirements
and advanced techniques
• Advanced design methods based on computer
simulation may be called “Virtual Prototyping”
• Treatment in LAM, hardfacing, coating remelting
and “brushing” are the examples of new
induction technology in surface engineering

32. Acknowledgement
The author thanks
CHTS and Fluxtrol Inc.
for presentation support
Michigan, USA Beijing, China
www.fluxtrol.com www.chts.org.cn