Advanced High Strength Steels/media/Files/Autosteel/Great...state on TRIP steels formability is different than for other steels w w w . a u t o s t e e l . o r g Bendability Bendability
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Advanced High Strength Steels
Formability
Alex A. KoniecznyU. S. Steel Automotive Center
February 19, 2003Great Designs in Steel Seminar
Livonia, MI
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Formability Introduction
σσ22
σσ11
DDS r >> 1DDS r >> 1 DP r = 1DP r = 1
AA
BB
•• FormabilityFormability•• Experimental Forming Limit DiagramsExperimental Forming Limit Diagrams•• BendabilityBendability TestTest•• Other Forming Tests Other Forming Tests
AA
BBComparison of Yield Strength, Tested As Delivered, L-dir.
0
200
400
600
800
1000
1200
0 0.05 0.1 0.15 0.2 0.25True Strain
True
Stre
ss
DP800 HSLA340 DDS HSLA550 DP1000 DP600 T600
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Typical Mechanical Properties
Example of Typical Mechanical PropertiesExample of Typical Mechanical Properties
UTS (UTS (MPaMPa)) El (%)El (%)GRADEGRADE YS YS ((MPaMPa)) YPE (%)YPE (%) nn--value value
(10%(10%--UE)UE) nn--value (4value (4--6%)6%)
IFIF 163163 282282 49.049.0 -- 0.2400.240 --
DDSDDS 183183 314314 42.942.9 -- 0.2300.230 --
CMn440CMn440 354354 455455 39.039.0 3.63.6 0.1560.156
HSLA340HSLA340 377377 443443 28.428.4 2.82.8 0.1700.170 --
SF600SF600 490490 615615 28.628.6 3.23.2 0.1480.148 --
HSLA480HSLA480 487487 604604 28.028.0 2.22.2 0.1280.128 --
HSLA550HSLA550 641641 672672 13.513.5 3.33.3 0.040*0.040* --
DP600DP600 340340 602602 29.029.0 -- 0.1700.170 0.2080.208
T600T600 393393 631631 34.034.0 -- 0.2300.230 --
DP800DP800 459459 838838 17.217.2 -- 0.115*0.115* 0.1680.168
T800T800 475475 822822 28.028.0 0.60.6 0.2400.240 --
DP1000DP1000 726726 10031003 10.810.8 -- 0.060*0.060* 0.080.08
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True Stress – Strain Curves
Workhardening of selected materials
0
100
200
300
400
500
600
700
800
0.00 0.05 0.10 0.15 0.20 0.25True Strain
True
Stre
ss [M
Pa]
T600 HSLA340 DP600
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Work Hardening Index
Instantaneous n - value
00.050.1
0.15
0.20.250.3
0 5 10 15 20 25 30
Engineering Strain [%]
n - v
alue
T600 DP600 HSLA340
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Strain Distribution Ability
Instantaneous n - value
00.050.1
0.150.2
0.250.3
0 5 10 15 20 25 30Engineering Strain [%]
n - v
alue
T600 DP600 HSLA340
Comparison of Thinning
-20-15-10
-505
1015202530
0 10 20 30 40
Location #
Thin
ning
(%)
HSLA DP
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Experimental FLDs for Dual Phase Steel
Forming Limit Diagram for DP800 1.2 mm
10
20
30
40
50
60
70
80
90
-30 -20 -10 0 10 20 30
Minor Strain [%]
Maj
or S
train
[%]
TheorExperFailedMarginalSafe
Forming Limit Diagram for DP600 1.2 mm
10
20
30
40
50
60
70
80
90
-30 -20 -10 0 10 20 30Minor Strain [%]
Maj
or S
train
[%]
TheorExperFailedMarginalSafe
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Experimental FLD for T600
Forming Limit Diagram for TRIP T600 1.2 mm
0102030405060708090
100
-30 -20 -10 0 10 20 30 40 50 60 70
Minor Strain [%]
Maj
or S
train
[%]
ExperimentCalculatedFailedMarginalSafe
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FLD Comparison
Forming Limit Curves for T600, DP600, HSLA340, DDS, 1.2mm
10
20
30
40
50
60
70
80
90
100
-30 -20 -10 0 10 20 30 40 50 60Minor Strain [%]
Maj
or S
train
[%]
T600DP600HSLA340DDS
••The FLCThe FLC of T600 is of T600 is comparable to DDS steel comparable to DDS steel in draw forming area, and in draw forming area, and exceeds DDS steel exceeds DDS steel formability up to 10% in formability up to 10% in balanced biaxial formingbalanced biaxial forming
••Influence of strain rate, Influence of strain rate, temperature and stress temperature and stress state on TRIP steels state on TRIP steels formability is different formability is different than for other steelsthan for other steels
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Bendability
BendabilityBendability is needed for dimensional accuracy control is needed for dimensional accuracy control in stampingin stamping
T600-0tT600-0.5t
DP600 HSLA 550
DP800-0.5t
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Cup Drawing Test
Rp0
0.51
1.52
2.5
IFCMn4
40 H
SLA 34
0/440
SF600
HSLA
440/6
00
DP600
DP800
T800
DP1000
Material
Lim
it D
raw
ing
Rat
io
Rp=2mm Rp=6mm Rp=25mm
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Stretch Forming Test
0
5
10
15
20
25
30
IFCMn4
40 HSLA
340/4
40 SF60
0 HSLA
440/6
00DP60
0
DP800
T800
DP1000
Material
Dom
e H
eght
[mm
]
Rp=2mm Rp=6mm Rp=25mm
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Hole Expansion Test
020406080
100120140160180200
IFCMn4
40 HSLA
340/4
40 SF60
0 HSLA
440/6
00
DP600
DP800
T800
DP1000
Material
Hol
e E
xpan
sion
Rat
io [%
]
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T-Channel Drawing Test
T-Chanel Drawing
0
10
20
30
40
50
60
70
80
90
100
IFCMn4
40 HSLA
340/4
40
SF600
HSLA44
0/600
DP600
DP800
T800
DP1000
Material
Hei
ght [
mm
]
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Plane Strain Drawing Test
WWWoWo=48mm=48mm
Delta W = WDelta W = W--WoWo
Rd
010
2030
4050
60
200 400 600 800 1000UTS [MPa]
Del
ta W
[mm
]
R=3mm R =7mm R=10mm
Springback
0
10
20
30
40
50
60
IFCMn4
40 HSLA
340/4
40
SF600
HSLA44
0/600
DP600
DP800
T800
DP1000
Material
Del
ta W
[mm
]
Rd=3mm Rd=7mm Rd=10mm
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Conclusions
•• DP and TRIP steels display excellent formability as DP and TRIP steels display excellent formability as compared to conventional HSS and better capacity to compared to conventional HSS and better capacity to distribute strain over the part surfacedistribute strain over the part surface
•• AHSS display very good AHSS display very good bendabilitybendability•• ASM FLC approximation (KeelerASM FLC approximation (Keeler--Brazier) is applicable for Brazier) is applicable for
DP and TRIP steelsDP and TRIP steels•• Due to excellent combination of strength with formability, Due to excellent combination of strength with formability,
TRIP steel has potential for economic application (possibility TRIP steel has potential for economic application (possibility for reduction of the number of parts in the car)for reduction of the number of parts in the car)
•• A need to understand AHSS unique characteristics to A need to understand AHSS unique characteristics to successfully make partssuccessfully make parts
-- OneOne--forfor--one direct substitution with other HSS may cause issuesone direct substitution with other HSS may cause issues
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References
1.1. KoniecznyKonieczny, A. A., On the Formability of Automotive TRIP Steels, SAE, , A. A., On the Formability of Automotive TRIP Steels, SAE, 20032003--0101--521521
2. 2. KamuraKamura M., M., OmijaOmija Y., Shaw J., Chen M., Formability and Y., Shaw J., Chen M., Formability and SpringbackSpringbackCharacterization of Advanced High Strength Steel, SAE, 2003Characterization of Advanced High Strength Steel, SAE, 2003--0101--522522
3.3. KoniecznyKonieczny, A. A., An Overview of Formability, Technological and , A. A., An Overview of Formability, Technological and MicrostructuralMicrostructural Aspects of the Automotive TRIP Steels, Processing and Aspects of the Automotive TRIP Steels, Processing and Fabrication of Advanced Materials, 11th Int. Symposium 2002, ASMFabrication of Advanced Materials, 11th Int. Symposium 2002, ASM Materials Materials Solution Conference and Exposition, 7Solution Conference and Exposition, 7--10 October, 2002, Columbus, Ohio10 October, 2002, Columbus, Ohio
4.4. KoniecznyKonieczny A. A., On Formability Assessment of the Automotive Dual Phase A. A., On Formability Assessment of the Automotive Dual Phase Steels, IBEC, 2001Steels, IBEC, 2001--0101--30753075
5.5. KoniecznyKonieczny A. A., A. A., HoydickHoydick D. P., An Overview of Formability, Technological and D. P., An Overview of Formability, Technological and MicrostructuralMicrostructural Aspects of the Automotive DualAspects of the Automotive Dual--Phase Steels, Processing Phase Steels, Processing and Fabrication of Advanced Materials, Ninth Int. Symposium 2000and Fabrication of Advanced Materials, Ninth Int. Symposium 2000, ASM , ASM Materials Solution Conference and Exposition, 9Materials Solution Conference and Exposition, 9--12 October, 2000, St. Louis, 12 October, 2000, St. Louis, MissouriMissouri
6.6. Shi M. F., Thomas G. H., Chen X. M., Shi M. F., Thomas G. H., Chen X. M., FeketeFekete J. R., Formability Performance J. R., Formability Performance Comparison between Dual Phase and HSLA SteelsComparison between Dual Phase and HSLA Steels,, Process Symposium 43rd Process Symposium 43rd Mechanical Working and Steel Processing Conference, Iron & SteelMechanical Working and Steel Processing Conference, Iron & Steel Society, Society, 20012001
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