The Application of Hot Stamped Boron
Steel 15B22 on the Automotive Parts
Cheng-Kai ChiuHuang
Co-authors: S.W. Wang, P.K. Lee, T.R. Chen
Product Application Research Section
Iron & Steel Research & Development Department
China Steel Corporation
2016/11/15
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Outline
• Background
• Hot Stamping Manufacturing Process
• Characteristics of CSC Boron Steel 15B22
• Examples of Hot Stamping Die Tryout
• Conclusions
2
3
Background• Body Structure lightweight and safety are the main driving forces for the
development of hot stamping process.
• The strength of the parts made by hot stamping is higher than the
traditional forming technology.
The Application and Global Market for Hot Stamping Parts
Ref: www.schuler.com
• Due to the CO2 emission regulation and vehicle safety issue, the application
of hot stamping parts on the body structure shows a fast growth.
• Schuler forecasts that the hot stamping market will reach 5.7 billion Pcs by
2018.
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Ref: www.Gestamp.com
Ref: www.stampingjournal.com December 2006
Direct Process
Hot Stamping Manufacturing Process
• The blank is heated to 910 degree Celsius in the furnace.
• Then the blank is transferred to the die within 6 secs.
• Die closing for 15-20 secs to quench the blank.
• The part is trimmed by laser cutting.
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Mechanical Properties of Boron Steel 15B22
Ref: Garcia Aranda et al., 2002
• The blank is heated to austenite state followed by fast die quenching.
• The critical cooling rate to obtain the martensite microstructure is 27 K/sec.
15B22
Annealed
15B22
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Pros and Cons of Hot Stamping Process
Pros
• High Strength (TS > 1500 MPa)
• Good Formability (Forming at high Temperature)
• Lower Press Capacity Required (<1000 Ton)
• Good Part Dimension Control (No Springback)
Cons
• Higher Energy Consumption (Furnace for blank heating)
• Higher Die manufacturing cost (Cooling ducts required)
• Higher Investment for the Production line
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Example: U-Hat Hot Stamping Die
U-Hat Hot Stamping DieCSC 200 Ton Hydraulic Press
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CAE Model: Forming and Drawing
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Blank
Holder
Temperature Distribution and Phase Fraction
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Top
Top
Flange
Flange
Quench 2 Sec
Side wall
Side wall
Quench 2 Sec
Quench 10 Sec
Quench 10 Sec
CSC Hot Stamping R&D Capability
Die Design
Computer Simulation (Forming)
Inlet
Outlet
Cooling ducts design
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Computer
Computer Simulation (Water Flow)
Springback Comparions for Different Materials
Al 5182
270 Mild Steel
15B22
(No Springback)
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• Hot stamping parts have good size stability (No Springback).
Strength and Hardness Verification
Location
Str
ength
(M
Pa)
Location
Har
dnes
s (H
RC
)
• The strength meet the requirement of GM and Volkswagen standard.
GMW14400: TS 1000~1700MPa、YS 950~1250MPa、EL 5% min
TL4225: TS 1300~1650MPa、YS 1000~1250MPa、EL 5% min
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Mechanical Properties Before and After Hot StampingMechanical Properties Before and After Hot Stamping
0
200
400
600
800
1000
1200
1400
1600
0 5 10 15 20 25
Strain (%)
Ste
rss
(MP
a)
Before H.T.
After H.T.
CSC HC 15B22
Blank Status
Yielding
Strength(MPa)
Tensile
Strength (MPa)
Elongation(%)GL=50mm
Hardness(HRC)
Before H.S. 280 450 20 -
After H.S. 950 ~ 1250 1300 ~ 1650 6 40~49
Flat Area
Drawing
15B22
t=1.4 mm
Microstructure after Die Quenching
Forming
15B22
t=1.4 mm
• With appropriate die design, a uniform high-strength
martensite structure can be obtained after die quenching.
Corner Side Wall
Flat Area Corner Side Wall
Flat areaSide wall
Corner
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Before Hot Stamping
Ferrite + Pearlite
Hardness 80 ~ 90HRB
After Hot Stamping (Die quenching)
Martensite
Hardnbess 43 ~ 47HRC
(Heating to 930℃,Transfer to the die in 5 secs
followed by 15 secs die quenching)
CSC HC 15B22 Microstructure (Before and After Die
Quenching)
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Double-layeredFurnace
800 Ton Press
Blank TransferAutomatic blanking
Bumper(15B22)
A pillar(15B22)
Hot Stamping R&D Capacity-Cooperate with Local Research Institute
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Patchwork B-pillar
Patchwork B Pillar30% Lightweight compared to the cold-stamping design A-pillar and Door Beam
Automotive Parts Developed by Hot Stamping CSC 15B22
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Conclusions
• The demand for the hot stamping parts from the automotive industry
shows a strong growth. The annual demand is predicted to reach 5.7
billion pcs by 2018.
• China Steel Corporation has successfully developed non-coated and
coated high temperature oxidation resistant 15B22 boron steel for the
hot stamping process.
• After hot stamping (die quenching), the YS, TS and Elongation of
CSC 15B22 can reach 1090 MPa, 1510 MPa and 6.75% respectively.
• Through the test, it is sure that the developed 15B22 steel can meet
the requirement of GM standard (GM 14400) and VW standard
(TL4225) for hot stamping.
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