GDIS2017 Welding Solutions for Advanced High-Strength Steels Menachem Kimchi 1 A. Peer 1 , Y. Lu 1 , W. Zhang 1 , C. Ji 2 , Y. Park 2 , T. Abke 3 , S. Malcom 3 1 The Ohio State University, 2 Dong-Eui University, 3 Honda R&D Americas, Inc. Sponsored Work by: Honda R&D Americas, Inc. & WorldAutoSteel
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Welding Solutions for Advanced High-Strength Steels/media/Files/Autosteel/Great Designs in Steel... · in Sheet Metal Welding Conference XVII. Livonia, (10 2016). 23 #GDIS | #SteelMatters
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GDIS2017
Welding Solutions for
Advanced High-Strength Steels
Menachem Kimchi1
A. Peer1, Y. Lu1, W. Zhang1, C. Ji2, Y. Park2, T. Abke3, S. Malcom3 1The Ohio State University, 2Dong-Eui University, 3Honda R&D Americas, Inc.
Sponsored Work by: Honda R&D Americas, Inc. & WorldAutoSteel
#GDIS | #SteelMatters 3
Global Formability Diagram for Today’s AHSS Grades
#GDIS | #SteelMatters 4
Outline
• Issues in RSW of AHSS
− Hot Stamped Boron Steel
• Case Study 1:
− Coating Effects
− Parameter Optimization Technique
• Case Study 2:
− Failure Behavior
− Initial Development of Criterion for Crash Simulation
#GDIS | #SteelMatters 5
Failure Modes on Resistance Spot Welds in AHSS
• Destructive inspection
− Chisel test
− Peel test
• Modes of failure
• Implied cooling rates (1000s of oC/s)
• Martensite formation
FB PIF FIF
#GDIS | #SteelMatters 6
Fracture Behaviors of RSW Button pulled without
evidence of interfacial
fracture
Partial thickness
fracture with button
pull
Partial thickness
fracture with no
button pull
Interfacial fracture with
button pull and partial
thickness fracture
Full interfacial
Fracture No fusion Interfacial fracture
with button pull
Interfacial fracture
with partial thickness
fracture
• In AHSS
applications,
the acceptable
strength can be
achieved with
PP or IF failure
#GDIS | #SteelMatters 7
Liquid Metal Embrittlement (LME) in AHSS
• Presence of tensile stress
• Presence of liquid metals(low
melting alloy from coating)
• Susceptible
Microstructure(Austenite in
TRIP,TWIP Steels)
#GDIS | #SteelMatters 8
Possible Solutions to Improve Failure Mode in AHSS
− Long weld time
− Pre/post pulsing
− Down sloping
− Short hold time
− Weld and temper
− Pulsation
− Dilution (AHSS to Mild Steel, HSLA)
− Increased minimum weld size
(0.87 mm, 980 MPa)
#GDIS | #SteelMatters 9
Case Study 1
• Hot Stamped Boron Steel
−Coating Effects
−Parameter Optimization Technique
• C. Ji, M. Kimchi, Y. Kim and Y. Park, "The application of pulsed current
in resistance spot welding of zn-coated hot-stamped boron steels," in
Advances in Resistance Welding, Miami, FL, 2016.
#GDIS | #SteelMatters 10
Previous Research of Hot-Stamped Boron Steel
High speed Camera
Al-Si coated Hot stamped boron steel
#GDIS | #SteelMatters 11
Analysis of Hot-Stamped Boron Steel Coating Layer (Zn)
#GDIS | #SteelMatters 12
Pulsed Current Approach
Coating layer behavior & Contact area
during Initial welding time
Heat Generation Pattern & Nugget
formation
Nugget growth and Expulsion behavior
Based on
#GDIS | #SteelMatters 13
1st Pulse
• Heat generation pattern of 1st Pulse
W
eld
ing
Cu
rren
t (k
A)
Welding Time(Cy)
Wel
din
g
Cu
rren
t (k
A)
Welding Time(Cy)
#GDIS | #SteelMatters 14
1st Pulse
• Coating melting behavior & nugget formation of 1st pulse
#GDIS | #SteelMatters 15
1st Pulse - Results
Molten
B.M
Molten Coating layer
8 kA, 1 cycle 4 kA, 3 cycle
#GDIS | #SteelMatters 16
2nd Pulse
• Comparison of heat generation pattern by 2nd pulse
2mm
4kA 25cy
2mm
5.5kA 10cy
Wel
din
g
Cu
rren
t (k
A)
Welding Time(Cy)
Wel
din
g
Cu
rren
t (k
A)
Welding Time(Cy)
#GDIS | #SteelMatters 17
2nd Pulse
• Comparison of nugget diameter and contact diameter by 2nd pulse
a b
#GDIS | #SteelMatters 18
2nd Pulse - Results
• Comparison of nugget diameter and contact diameter by
2nd pulse
4 6 8 10 12 14 16 18 20 220
2
4
6
8
Dia
me
ter
(mm
)
Welding time (cycle)
a b
a
b
#GDIS | #SteelMatters 19
3rd Pulse
#GDIS | #SteelMatters 20
3rd Pulse
• Optimized welding conditions using three pulsed current
steps
4.5 5.0 5.5 6.0 6.5 7.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
1.5 kA
Bu
tto
n D
iam
ete
r (m
m)
Weld Current (kA)2Cy
8kA-1Cy
2Cy Wel
din
g C
urr
ent
(kA
)
Welding Time(Cy)
5.5kA- 12Cy
15Cy
5.0 -6.5 kA
#GDIS | #SteelMatters 21
Optimized Conditions
Wel
din
g C
urr
ent
(kA
)
Welding Time(Cy)
8kA-1Cy
5.5kA- 12Cy
5.0 -6.5 kA
15Cy
#GDIS | #SteelMatters 22
Case Study 2
• Hot Stamped Boron Steel
−Failure Behavior
− Initial Development of Criterion for Crash
Simulation
• Andrea Peer, Ying Lu, Tim Abke, Menachem Kimchi, and Wei Zhang "Deformation Behaviors of Subcritical Heat
Affected Zone of Ultra-high Strength Steel Resistance Spot Welds." in 9th International Seminar & Conference on
Advances in Resistance Spot Welding. Miami, (3 2016). Paper No. 12
• Ying Lu, Andrea Peer, Tim Abke, Menachem Kimchi, and Wei Zhang "Heat-Affected Zone Microstructure and Local
Constitutive Behaviors of Resistance Spot Welded Hot-Stamped Steel." in Sheet Metal Welding Conference XVII.
Livonia, (10 2016).
#GDIS | #SteelMatters 23
UHSS Performance Testing Approach • Objective: Develop an understanding of the deformation and failure
behavior of resistance spot welds of ultra-high strength steels
#GDIS | #SteelMatters 24
Metallographic Characterization
• The spot weld microstructure is highly inhomogeneous
#GDIS | #SteelMatters 25
Temperature Profile
Martensitic Microstructure
Base Metal
Weld Nugget
Coarse Grain HAZ
Fine Grain HAZ
Unique Microstructure
Subcritical HAZ
#GDIS | #SteelMatters 26
Hardness Profile
• A ring of “softened” material surrounds the
weld nugget
Subcritical Heat Affected Zone (SCHAZ)
• Usibor® BM & WM: > 500 HV
• SCHAZ: ~300 HV
0.7 mm
#GDIS | #SteelMatters 27
Constitutive Behavior Development
YS (MPa) UTS (MPa)
Base Metal 1179 1464
CGHAZ 1342 1811
SCHAZ 618 866
• Ncorr Post-Processing
Extended Stress Strain Curve Example of SCHAZ
tensile test. Virtual
extensometer of 2 mm
used to extract data.
#GDIS | #SteelMatters 28
Single-Sided Wedge Testing
• Observe the localized deformation with the aid of DIC