Introduction to Hot Stamping and Trends
By
Dr. Eren Billur, Post-doctoral Researcher
and
Dr. Taylan Altan, Director and Professor
Presented at ESI Hot Forming Die Engineering Seminar
October 15th, 2013
Center for Precision Forming (CPF)
www.cpforming.org / www.ercnsm.org
© Copyright Center for Precision Forming (CPF). All Rights Reserved.
Center for Precision Forming - CPF
CPF is supported by NSF and 16 member
companies, interested in metal forming.
Interlaken
Technology Corporation
IMRA
2
CPF – Current Projects
• Material Characterization
• Friction / Lubrication
• Process Simulation / Forming Al & AHSS
• Die Wear in Forming AHSS
• Edge Quality in Blanking / Shearing
• Hot Stamping of UHSS
• Servo Drive Presses and Hydraulic Cushions
3
Sponsors & Partners of Hot Stamping Research
Interlaken
Technology Corporation
TSG
IMRA
Tooling Systems
Group
4
Crashworthiness
Crumple Zone
Passenger Zone
Crumple Zone
5
Images from: media.Daimler.com
Crashworthiness
Passenger Zone
Roof rail
Crumple Zone
A-pillars
B-pillars
Door beams
Intrusion Resistance
Ultra High Strength
Absorbing Energy
High Strength + Elongation
6
Ref: Hilfrich 2008.
Summary of Hot Stamping
Mild Steels
70
L-IP
Conventional High
Strength Steels
Better Formability
Total Elongation (%)
60
50
40
30
20
Aust.
SS
IF
TWIP
Advanced High
Strength Steels
Mild
BH
Al
CMn
2nd Generation
AHSS
Higher Press Forces
TRIP
Al
Aluminum Alloys
(hs)
10
0
MART
0
200
400
600
800
1000 1200 1400
Ultimate Tensile Strength (MPa)
1600
1800
2000
7
Summary of Hot Stamping
Mild Steels
70
L-IP
Conventional High
Strength Steels
Total Elongation (%)
60
50
Aust.
SS
IF
40
BH
CMn
2nd Generation
AHSS
Al
Al
20
(hs)
10
0
Advanced High
Strength Steels
Lightweight Potential for
Intrusion Resistance
Mild
30
TWIP
Higher Springback
Aluminum Alloys
MART
0
25
50
75
100
125
150
175
3
Specific Strength (MPa/(k g/m ))
200
225
250
8
Summary of Hot Stamping
Heated >950 C
Austenite
70
Indirect Process:
2
Total Elongation (%)
60
50
IF
3-5 min.s
Mild in Furnace
40
TWIP
Quenched in the die
>27 C/s
Direct Process:
BH
30
CMn
20
Mn-B Alloyed steel
(as delivered)
Ferrite & Pearlite
10
0
Aust.
SS
0
200
400
1
TRIP
Quenched
Martensite
MART
600
800
1000 1200 1400
Ultimate Tensile Strength (MPa)
1600
1800
2000
9
Hot Stamping - Trends
Mass % of hot stamped
steel in BIW
Audi
A3
Volvo
XC90
SAAB
9000
VW
Passat
19%
1984
≈
7%
2003
Volvo
XC90
44%
Volvo
26%
V40
VW
Golf VII
28%
20%
2006
2012
2014
10
Ref: Lund 2009, Holzkamp 2011, Lindh 2011, Bielz 2012, Mattsson 2012, VW Media Services.
Hot Stamping - Trends
Parts per year (in millions)
550
500
450
400
350
300
250
200
150
100
50
0
>20
Parts/
Vehicle
8-10
Parts/
Vehicle
6 Parts/
Vehicle
450 million
per year
(2013)
4 Parts/
Vehicle
3 million
per year
(1987)
1987
Ref: Oldenburg 2010, Hund 2011.
95 million
per year
(2007)
8 million
per year
(1997)
1997
Year
210+ lines
around the world
+55 planned
2007 ’08 ’09 ’10 ’11 ’12 ’13 11
Hot Stamping - Trends
Passenger
Zone
Deformation
Zone
(a) Front view
before crash
(b) Side view
after crash
12
Ref: Macek 2006, Image from: IIHS.
Hot Stamping - Trends
22MnB5
1500 MPa
(215 ksi)
HSLA 340
(50 ksi)
Tailor Rolled Blanks Tailor Welded Blanks
Ref: Rehse 2006, Hilfrich 2008, Lee 2012, Images from: IIHS, VW Media Services.
Tailored Hot
Stamping
13
Hot Stamping - Trends
550 C
Tailored Heating
(Austenitizing)
20 C
Tailored Quenching
Ref: Breidenbach 2009, Hedegärd 2011, Süß 2011, Steinhoff 2013. Image from: IIHS.
Post Tempering
14
Hot Stamping - Trends
900
800
Temperature ( C)
700
A+F
600
A+P
500
400
A+B
Ms
A+M
300
Mf
200
100
Time to cool (s)
Cooling Rate ( C/s)
Hardness (HV)
8
100
475
27 40 80 133 266
3
30 20 10 6
474 417 278 232 182
1143
0.7
163
4000
0.2
150
15
Finite Element Simulation of Hot Stamping
Our simulations aim to predict the final properties of hot
stamped components:
1) Presence of defects: cracks, wrinkles or local necking,
2) Hardness distribution (both in uniform and in tailored parts),
3) Cooling channel analysis,
4) Distortion of the final part.
16
Finite Element Simulation of Hot Stamping
Fluid Mechanics
Heat generation due to
plastic deformation.
Mechanical Field
- Mechanical material
properties,
- Volume change due
to phase
transformation.
Thermal expansion.
Phase
Microstructure
transformation
depends on
depends on
temperature.
stress and strain.
Heat transfer to the
coolant medium.
Thermal Field
- Thermal material
properties,
- Latent heat due to
phase
transformation.
Microstructure Evolution
17
Ref: Åkerström 2006, Porzner 2012.
Finite Element Simulation of Hot Stamping
Only needed in tailored parts
Gravity
Holding
Forming
Die Quenching
Springback
Air
Quenching
Mechanical
Thermal +
Mechanical
Thermal +
Mechanical
Thermal + Metallurgical
Mechanical
Thermal +
Metallurgical
18
Predicting Defects
Crack prediction in a Side Member Reinforcement
Colors other than gray:
Thinning >20%.
Part stamped at the participating
company
19
Predicting Defects
Die Segment 1
Die Segment 2
Die Segment 3
Blank (Ti = 850 C)
Heated Dies (Ti = 450 C)
Cooled Dies (Ti = 20 C)
20
Predicting Defects
Crack / wrinkle prediction in a tailored part
With one-piece blankholder
With two-piece blankholder
15 kN
20 kN
5 kN
Crack
Wrinkles in
the soft area
Non-symmetric
draw-in
No wrinkles or
cracks
21
Hardness Distribution
Die Quenching Optimization
Martensite phase fraction
1.00
0.85
0.71
0.57
0.42
0.28
0.14
0.00
Min =
Max =
0.00
1.00
4 seconds die quenching
10 seconds die quenching
22
Hardness Distribution
Heat Transfer Coefficient (W/m 2C)
100
140
Air Quenching Stage
Maximum Austenite (%)
Convection
120
80
100
60
80
60
40
40
20
20
0
Ref: Shapiro 2009.
Radiation
0
10 20020
400 40 600
30
50
Temperature
Time (s) (C)
60800 70
1000
80 23
Hardness Distribution
Results
Soft zone:
310 – 330 HV
920 – 1020 MPa
(~135 – 150 ksi)
Literature:
[George 2011] , 400°C dies = 790-840 MPa
[Feuser 2011], 450°C dies = ~850 MPa
Hardened zone:
485 – 515 HV
1500 – 1590 MPa
(~220 – 230 ksi)
24
Cooling Channel Analysis
Cooling channel performance
1.3 mm 22MnB5 “roof rail”
Mass produced for a European car.
25
Cooling Channel Analysis
Cooling channel performance – tailored part
1.2 mm 22MnB5 “B-pillar”
1605
300
925
920
1595
915
1589.4 MPa
1590
910
1590.3 MPa
1585
905
250
Temperature ( C)
1600
Minimum UTS (MPa)
Maximum UTS (MPa)
921.4 MPa
Max
219 C
200
150
100
50
Min
20 C
903.8 MPa
1580
900
1
2
3
4
5
6
Part # (Cycle)
7
8
9
10
0
0
20
40
60
80
Time (s)
100
120
140
160
26
Distortion Analysis
Ongoing work: Distortion in Tailored Parts
stra in
au steni tisati on
0.0 15
0.0 1
ma rten sitic
tra nsformati on
+Initial,
undistorted grid
0.0 05
+Interstitial dissolved
carbon
0
+ carbon, tetragonal distorted
grid
200
-0.0 05
Ref: Porzner 2012.
Material 1
400
600
800
100 0
120 0
Material 2
temperatu re
27
Summary and Conclusions
Several case studies were used to develop, calibrate and
validate material models, conversion factors and methods to
predict:
1)
2)
3)
4)
Defects (cracks, wrinkles, local necks),
Vickers hardness, yield and ultimate tensile strengths,
Cooling channel / heating cartridge performance,
Distortion in a non-uniform part.
28
What is next?
1) New materials with
High Strength (USIBOR 2000, even higher strength:
MBW1900, HPF 2000)
More lightweight potential
and increased
productivity.
22MnB5 (USIBOR 1500,
MBW1500, HPF1470)
2) New coatings: better
corrosion properties and
friction conditions.
Engineering Stress (MPa)
2000
1500
1000
500
High Elongation (DUCTIBOR 500,
MBW500)
0
0
5
10
Engineering Strain (%)
Ref: Lanzerath 2011, Vietoris 2011, Ferkel 2012, Lee 2012.
15
3) New heating, forming
and quenching methods
to improve productivity.
20
Competition: DP, TRIP, TWIP, and
29
3gAHS Steels with high YS and UTS.
Deliverables / Hot Stamping
As of September 2013:
- 15 CPF Reports (Literature review and FE simulations),
(5 in the last 6 months) [confidential to members],
- 6 Stamping Journal R&D Updates
(+1 more in progress),
- 6 Conference Proceedings (+1 more submitted),
- 1 Book Chapter in “Sheet Metal Forming: Vol 2:
Processes and Applications”, (see next slide),
30
- And a new “Hot Stamping” book in progress!
Questions / Comments?
For more information , please contact:
Dr. Eren Billur (billur.1@osu.edu), Ph 614-292-1785
Dr. Taylan Altan (altan.1@osu.edu), Ph-614-292-5063
Center for Precision Forming –CPF (www.cpforming.org)
339 Baker Systems,1971 Neil Ave,
Columbus, OH-43210
Non-proprietary information can be found at web sites:
www.cpforming.org
www.ercnsm.org
References can be sent upon request.
31