http://fluxtrol.com Virtual Prototyping of Induction Heat Treating

1. Virtual Prototyping of Induction
Heat Treating
Robert Goldstein
www.fluxtrol.com

2. Overview
• Advantages of Induction Heat Treating
• What is Virtual Prototyping?
• Steps in Virtual Prototyping of Induction
Heat Treatment
• Case Story – Wheel Hub Hardening
– Solve a Lifetime Issue on Production Machine
– Example of How Virtual Prototyping Could
Have Been Used to Avoid Problem
• Conclusions

3. Advantages of Induction Heat Treating
• Favorable for industrial environment (in-line
heating, no pollution, “push button” performance,
no toxic waste disposal)
• Energy savings due to selectivity and high
efficiency
• Good control and repeatability
• Better metallurgical results due to fast and clean
heating
• More predictable energy costs
• Safer work environment

4. Advantages Ctd.
• Less and more predictable dimensional
movement
• Short heating cycles and high production rates
• Minimal surface oxidation and decarburization
• Some processes may not be accomplished other
than by induction
• Smaller machine footprint
• Typically, much cleaner environment
• More Favorable for Computer Modeling

5. What is Virtual Prototyping?
Original Optimized
Position A
Design Design
• Virtual Case depth
10 mm 10 mm
at HRC 40
Prototyping is Total case
10.5 mm 10.7 mm
depth Both cases: 170 kW, 1 kHz
the use of Scan speed
9.5 10.7
mm/sec mm/sec
computer Original Optimized H
Position B R
Design Design
models to Case depth
C
13.5 mm 11 mm
at HRC 40
develop and test Total case A
15 mm 11.75 mm
depth
a process or Dwell time 10 sec 8 sec
component Position C
Original Optimized
Design Design
without having to Case depth
4.5 mm 6.5 mm
at HRC 40
physically build Total case
depth
5.25 mm 7.5 mm
B
or run it Dwell time 10 sec 8 sec
C

6. Advantages of Virtual Prototyping
• Parts are not required to run tests
– Models can be exchanged between heat treating
process and parts developers
– Simulation does not take machine time
• Fewer coil modifications
• Fewer trials required with a given coil
• Narrower development time window
• Reduced time to adapt to part changes
• Ability to predict the process and product
reliability and variability
• Leaves an excellent record for “out of control”
condition in conjunction with PPAP

7. Steps in Virtual Prototyping
• Preliminary analysis
of the specifications
and available
equipment.
• Preliminary process
design using
computer simulation
• Induction coil and
process design using
computer simulation

8. Steps ctd.
• Coil and/or machine
engineering using
CAD
• Coil and machine
manufacturing
• Experimental tests
• Final modification if
required
• Industrial
implementation

9. Case Story – Wheel Hub Hardening
Problem
• Short coil life – (8,000
– 13,000 pieces)
resulting in:
– Machine downtime
– Unacceptable
personnel time due to Typical process of induction heating of
wheel hubs
extended set-up
Note – Tooling Costs Not a Problem Due to
– Scrap parts Manufacturer Warranty

10. Virtual Prototyping Selected
• Traditional means were not able to find a
solution
• Due to unplanned downtime, production
was always behind and tests were difficult
to schedule
• Besides hardening, other stations were
working adequately
• Production line was already existing, so
not all steps are required

11. Analysis of Problem and Equipment
• Copper Cracking Under
Laminations due to
Overheating
• Lamination Degradation
• Already Had Very High
Water Pressure and Flow
Rate
• Existing machine – 150 kW,
15 kHz Hardening

12. Induction Coil and Process Design
• 2D EM + Thermal FEA to determine coil
required to produce required heat pattern
in specified time with current machine
• 2D EM + Thermal FEA to ensure all coil
components are kept cool enough to
survive for a sufficient period of time
(>50,000 pieces)
• Update of coil design as required to find
best combination of heat pattern and coil
copper temperatures

13. Model of Part
Temperature & Hardness
Temperature distribution in part with Predicted hardness pattern
new coil design
Flux 2D program

14. Model of Inductor Temperature
Color Shade Results
Two cooling paths for Quantity : Temperature Deg. Celsius
better heat extraction Time (s.) : 2.5 Phase (Deg): 0
Scale / Color
from over-heated 33.00854 / 36.81434
36.81434 / 40.62014
copper regions 40.62014 / 44.42594
44.42594 / 48.23174
48.23174 / 52.03753
52.03753 / 55.84333
Heat transfer coefficient 55.84333 / 59.64913
59.64913 / 63.45493
applied, calculated from 63.45493 / 67.26073
67.26073 / 71.06651
water flow rate 71.06651 / 74.87231
74.87231 / 78.67812
78.67812 / 82.48392
82.48392 / 86.2897
Results: Max copper 86.2897 / 90.0955
temperature <100°C 90.0955 / 93.90131

15. CAD Design of Inductor
•Inductor needed to
reproduce predicted
heat treat results
•Contacts needed to
mount to machine
•Inductor had to fit
through primary quench
ring
•Inductor needed to be
compatible with material
handling system

16. Heating Tests of Inductor
•Hardness pattern
agreed well with
simulation results
•The hardness and
case depth were
verified to be within
specifications
•3rd Test Part
Shown

17. Longevity Testing of Inductor
Coil life and part
production
increased to
>170,000 hits
without coil
copper failure or
concentrator
degradation.
New induction coil after 170,000 heating cycles

18. Virtual Prototyping for Machine Design
• In this case, this problem could have been
avoided if Virtual Prototyping were used
before the machine was ever built
• Also, there was significant opportunity to
either increase productivity, or reduce the
number of stations on the machine to
reduce cost

19. Current Machine Layout
• 300 parts per hour production (12 s / station)
– 2 Shifts of Production to Meet Demand
• 4 Stations
– Harden & Pre-Quench
– Quench Completion
– Temper
– Final Cool
• Heat Treat Machine In-Line with Final
Machining

20. Where’s the Bottleneck
Induction Heat Treat Machining Operation
• Can we reduce cycle time • Can we reduce the
with 4 stations? number of stations to
– If yes, how much? reduce machine cost?
– If no
• What prevents us from it
• how many more do we
need

21. Induction Heat Treating
Hardening Tempering
• Time to Load (1 s) • Time to Load (1 s)
• Time to Lift & Rotate (1 s) • Time to Lift & Rotate (1 s)
• Time to Heat (2.5 s) • Time to Heat (?)
• Time to Drop (0.5 s) • Time to Drop (0.5 s)
• Time to Quench (?) • Final Cool (?)
We Need to Fill in the Question Marks

22. Time to Quench after Hardening
After 4 s, Sufficient Heat Has Been Removed to
Complete Martensite Transformation

23. Time to Temper
After 2.5 s, Entire Hardened Area Has Been
Tempered to Within Specification

24. Two Potential Machines
300 parts/min – 2 station 600 parts/min – 4 station
• Station 1 - Harden • Station 1 – Harden Heat
– Transfer (1 s) – Load (1 s)
– Lift & Rotate (4 s) – Lift & Rotate (2.5 s)
– Heat (2.5 s) – Heat (2.5 s)
– Drop (0.5 s) – Drop (0.5 s)
– Quench (4 s) • Station 2 - Quench
• Station 2 - Temper – Transfer(1 s)
– Transfer(1 s) – Quench (5 s)
– Lift & Rotate (1 s) • Station 1 – Temper Heat
– Load (1 s)
– Heat (2.5 s)
– Lift & Rotate (1.5 s)
– Drop (0.5 s)
– Heat (3 s)
– Final Cool (7 s) – Drop (0.5 s)
Eliminate 2 Stations or • Station 2 - Quench
1 Shift! – Transfer(1 s)
– Quench (5 s)

25. Conclusion
• Virtual Prototyping Has Several
Advantages Compared to Other
Development Methods
• Using Virtual Prototyping, Lifetime of a
Production Inductor Was Increased More
than 10 Times
• If Virtual Prototyping Were Used Up Front,
the Production Rate Could Have Been
Doubled or the Number of Heat Treating
Stations Cut in Half