Transcript CPF Project - Hot Stamping

R&D at Center for Precision Forming- CPF
Engineering Research Center for Net Shape Manufacturing (ERC/NSM)
www.ercnsm.org
Center for Precision Forming (CPF)
www.cpforming.org
Taylan Altan, PhD, Professor Emeritus
The Ohio State University
Columbus, OH
July 2013
Center for Precision Forming - CPF
CPF is supported by NSF and 16 member
companies, interested in metal forming.
Interlaken
Technology Corporation
IMRA
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CPF – Current Projects
• Material Characterization
• Friction / Lubrication
• Process Simulation / Forming Al & AHSS-Software:
•DEFORM-forging, PAMSTAMP/LS-DYNA-stamping
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Die Wear in Forming AHSS
Edge Quality in Blanking / Shearing
Hot Stamping of UHSS
Servo Drive Presses and Hydraulic Cushions
•Project experiments are conducted in cooperation with CPF
members
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Material Characterization
Viscous Pressure Bulge (VPB) Test
Laser Sensor
Downward
motion
clamps the
sheet
Continued
downward
motion forms
the bulged
sheet
Test Sample
Viscous Medium
Pressure
Transducer
Stationary Punch
Before Forming
After Forming
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Material Characterization – Flow Stress
Viscous Pressure Bulge (VPB) Test
True Stress (MPa)
1000
Uniform Strain
from Tensile
Test = 0.16
800
True Stress (ksi)
145
Tensile data with Power Law
(σ=Kεn)
116
600
Useful strain 87
from Bulge
Test = 0.49
400
58
200
Material, DP600, 1 mm
0
0
0.1
0.2
0.3
True Strain
VP Bulge Test
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Tensile Test
0.4
0.5
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Material Characterization – VPB Test
Test sample
Before bursting
After bursting
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Material Characterization – VPB Test
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Determination of Sheet Formability
Using VPB Test
Graph shows dome height comparison for SS 304 sheet material from eight
different batches/coils [10 samples per batch].
Dome height before burst (in)
(mm)
1.6
40
(in)
1.6
Maximum bulge height before fracture
1.4
1.2
30
1.2
1
20
0.8
0.8
0.6
10
0.4
0.4
0.2
0
A
B
C
D
E
F
G
H
Coil/Heat/Supplier
Batch / Coil
/ Heat / Supplier ID
Highest formability  G , Most consistent  F
Lower formability and inconsistent  H
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Materials Tested with VPB Test at CPF
(data available to CPF members)
St 14
St 1403
AISI 1018
AKDQ
1050
DR 120
DDS
BH 210
HSS
DP500
DP 590
DP 600
Steels
DP 780-CR
DP 780-HY
Bare DP 980 Y-type X
Bare DP 780 T-Si type
GA DP 780 T- AI Type
GA DP 780 Y-type U
GA DP 780 Y-type V
DQS-270F GA-Phosphate coated
DQS-270D GA-Phosphate coated
DP 780
TRIP 780
DP 980
Aluminum and Magnesium Alloys
AA 6111
AA 5754-O
X626 -T4P
AZ31B
AZ31B-O
Stainless Steels
SS 201
SS 301
SS 304
SS 409
SS 410 (AMS 5504)
SS 444
LDX 2101
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Material Characterization – Dome Test
Dome Test (Frictionless)
When the
blank is well
lubricated, it
fails at the
center of the
dome.
Necking /
fracture moves
with increased
friction.
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Friction/Lubrication – Cup Draw Test
Evaluation of Lubricants
Performance
evaluation
criteria
(cups drawn to same depth):
i. Higher the Blank Holder Force (BHF)
that can be applied without fracture in the
drawn cup, better the lubrication condition
ii. Smaller the flange perimeter, better
the lubrication condition (lower coefficient
of friction)
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Friction – Cup Draw Test
Cup Draw Test
Lubrication performance:
Shorter Perimeter
Higher BHF before fracture
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Friction / Tribology
Temperatures in Cup Draw Test – DP 600
Contact area
with die
Challenges:
1) Higher contact pressure and higher temperature are detrimental for lubricants,
2) Temperature and pressure additives are needed
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Ref: Kim et al 2009
Friction / Lubrication
Evaluation of Lubricants for Forming
Al 5182-0 (1.5 mm)
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Forming of Al Alloys in a Servo Drive Press
Material draw-in
Thinning (%)
28.4
20.5
12.7
4.9
-2.9
-10.7
-18.5
-26.3
Min =
Max =
-26.3
28.4
Maximum thinning ~28%
Draw depth = 155 mm
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Warm Forming of Al, Mg, Ti & SS
in an Aida Servo Drive Press
Insulation plate
Die ring
Heaters
Sheet
Punch
Blank holder
Water inlet
Cushion pins
AZ31B-O
AA5754-O
T(°C)
RT
250
300
LDR
2.1 Velocity : 2.5-50mm/sec
2.5
2.9 Cup diameter: 40 mm
T(°C)
RT
275
275
LDR
2.6
3.2
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Forming of AHSS in a Servopress
Forming of AHSS in Servo Press
980 MPa
(145 ksi)
590 MPa
(85 ksi)
440 MPa
(65 ksi)
270 MPa
(40 ksi)
Can we use servo drive properties to improve
formability and reduce springback in forming
AHSS?
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Forming of AHSS
Forming of AHSS in Servo Press
Punch
Blank holder
Materials of interest:
DP 600
DP 980
Maybe others?
Die
Bottom die set
Die design (in progress) for testing AHSS.
Top die set
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Forming of AHSS in a Servopress
Forming of AHSS in Servo Press
1) Straight bending,
BLANK
2) Shrink flanging,
BLANK
BLANK
BLANK
BLANK
BLANK
3) Stretch flanging,
4) U-Bending,
5) Curved U-Bending,
DIE
6) Deep Drawing.
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Forming of AHSS in a Servopress
Forming of AHSS in Servo Press
Thinning (%)
9.0
5.8
2.7
-0.4
-3.5
-6.6
-9.7
-12.8
Min =
Max =
Max. Thinning ~ 9%
-12.8
9.0
Deep drawn sample
DP 600, t0 = 0.83 mm
Draw depth = 50 mm
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Forming of AHSS
Die Wear in Forming of AHSS
Die Insert
Press
Motion
Die Insert
r = 5 mm
t0 = 0.77 mm
Punch
(Stationary)
Press
Motion
r = 5 mm
r = 20 mm
Dp = 152.4 mm
Ironing
t ≈ 0.70 mm
Currently with DP590
In future, Stainless Steel
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Blanking/Piercing of AHSS
Blanking / Piercing
Schematic of piercing
Blanked edge
(obtained from FE simulations)
Roll over zone (Zr)
Shear zone (Zr)
Fracture zone (Zf)
Burr zone (Zb)
vp = punch velocity
fb = blank holder force
dp = punch diameter
dd = die diameter
rp = punch corner radius
rd = die corner radius
db = blank holder diameter
t = sheet thickness
Punch-die clearance (% of sheet thickness) = (dd-dp)/2t*100
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Blanking/Piercing of AHSS
Hole Expansion Test
Schematic of hole expansion test
Before and After Hole Expansion
(conical punch)
dd
DIE
rd
dh
θ
dp
Blank Holder
fb
Punch
db
vp
vp=punch velocity
fb=blankholder force
θ=punch angle (conical)
dd=diameter of the die
db=diameter of blankholder rd=die radius
dh=diameter of pierced hole in the blank
dp=punch diameter (hemispherical)
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Blanking/Piercing of AHSS
Reduction of strains at blanked surface
3
2.5
Single shear
Conical with flat tip
Effective strain
2
1.5
Flat
Humped
Conical
1
0.5
Conical with
spherical tip
Humped
0
0.6
1
1.5
2
2.5
3
3.5
3.6
Distance from the top surface of the sheet (mm)
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Hot Stamping
Easier to Form
22MnB5
At ~950°C
(1750ºF)
Austenite
3-5 min.s
in Furnace
Less force and
springback
Mn-B alloyed steel
(As delivered)
Ferrite-Pearlite
Quenched in the die
>27°C/s (~49°F/s)
Quenched
Martensite
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Ref: Grote 2009, Gutermuth 2011.
Hot Stamping
FE Simulation of parts with uniform properties
Colors other than gray:
Thinning >20%.
Part stamped at the participating
company
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Hot Stamping
FE Simulation of cooling channel analysis
Nodal temperature - Membrane
230
200
171
142
112
83
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1.3 mm roof rail die,
After 10 stampings.
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Hot Stamping
FE Simulation of cooling channel analysis
After 10 stampings.
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Hot Stamping
FE Simulation of parts with tailored properties
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)
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Formability
Stretch Bending
DP780
Underbody structural part
Challenge:
This type of fracture cannot be predicted using
conventional Forming Limit Curve (FLC).
DP980
B-pillar inner
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Ref: Shi and Chen 2007
Prediction of fracture/necking from strain or
thickness variations (tensile data from Jim
Dykeman-Honda HRA)
1400
0.6
1200
0.5
Major Strain (mm/mm)
Stress (MPa)
New Project: Prediction of Fracture
1000
800
600
400
0.3
0.2
0.1
200
0
0.4
0
0
0.02
0.04
0.06
0.08
Strain (mm/mm)
0.1
0.12
0.14
0
50
100
Time (s)
150
31
200
Multiple Point Control – Hydraulic Cushion
Deep Drawing
One solution to this problem is:
Optimizing blankholder pressure, including multi-point cushion systems.
Al 6111-T4, t=1 mm
BH210, t=0.8mm
DP500, t=0.8mm
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Ref: Palaniswamy and Altan 2006
Multi-Point Control – Hydraulic Cushion
Application of MPC die cushion technology in stamping
Sample cushion pin configuration (hydraulic MPC unit) for drawing stainless steel double sink.
(Source: Dieffenbacher, Germany)
MPC is routinely used in deep drawing of stainless steel sinks
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Case studies in process simulation
Multi-Point Control Systems (MPC)
 Use of Multi-Point Control (MPC) die-cushion systems helps to control metal flow.
 Each cushion pin is individually controlled by a cylinder (hydraulic/ nitrogen gas /servo control).
Location of cushion
pins/ cylinders in the
die
 MPC can be used to accommodate variations in sheet properties & assist in forming AHSS.
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Questions / Comments?
For more information , please contact:
Dr. Taylan Altan ([email protected]), 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
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