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8/12/2019 Uthaisangsuk2013-AHS Steels for Automotive Parts
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AHS Steels for Automotive Parts
Asst. Prof. Vitoon Uthaisangsuk, Dr.-Ing.
Department of Mechanical Engineering, Faculty of Engineering
King Mongkuts University of Technology Thonburi (KMUTT)
1
20-21June 2013BITEC Bangkok -Thailand
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Outline Automotive evolution
Car body structures
Automotive steels
Mild steels
High strength steels
Multiphase steels
Press hardened steels
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Materials used for car components - 1975
Source: Ducker Worldwide
Average 1975 vehicle weight
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5/102Source: Ducker Worldwide
Materials used for car components - 2007Average 2007 vehicle weight
5
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6/102Source: Ducker Worldwide
Trend of materials usage
6
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7/102Source: WorldAutoSteel
Aim of automotive industries (mass reduction)
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Aim of automotive industries (mass reduction)
Source: WorldAutoSteel
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Aim of automotive industries (mass reduction)
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Role of HSS and AHSS for vehicle mass reduction
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Growth of AHSS
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Increasing of safety regulations
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Evolution of North America crash tests
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13
Safety concept
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Safety concept
Source : http://www.autosteel.org
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Safety concept
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Safety concept
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17
Strength comparison AHSS vs conventional HSS
Component material strength
DP350/600
HSLA350/450
Yield strength (MPa)
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Conflict between mass reduction & safety regulations
Fuel economy / CO2emissions
Lower weight / lighter gauges
Safety Higher strength / heavier gauges
Conflict between safety & fuel economy / CO2 emissions
Seeking of new challenging materialsand manufacturing concept
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Outline Automotive evolution
Car body structures
Automotive steels
Mild steels
High strength steels
Multiphase steels Press hardened steels
19
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Steel sheet concept for automotive parts
Source : http://autospeed.com/cms/title_Steel-Identification-Using-Hardness-Testing/A_109717/article.html
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Source : http://mercedes-benz-blog.blogspot.com/2010/03/new-mercedes-benz-e-class-cabriolet_2785.html
2010 The new Mercedes-Benz E-Class
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Steel sheet concept for automotive parts
http://mercedes-benz/http://mercedes-benz/http://mercedes-benz/http://mercedes-benz/8/12/2019 Uthaisangsuk2013-AHS Steels for Automotive Parts
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Source : http://boronextrication.com/tag/list-of-vehicles-with-boron-and-uhss
2011 Volvo V70 Body Structure
22
Steel sheet concept for automotive parts
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23Source: http://carskeleton.blogspot.com/2012_04_01_archive.html
Steel sheet concept for automotive parts
2012 Audi A3 body Structure
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Source : http://www.autosteel.org24
Steel sheet concept for automotive parts
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25Source : http://www.autosteel.org
Steel sheet concept for automotive parts
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Cold rolled steels
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Overview of cold rolled steel sheets
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Strength evolutions of automotive steels
Source: http://www.metalformingfacts.com/industry-news/developments-gigapascal-strength-steels.html
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Outline Automotive evolution
Car body structures
Automotive steels
Mild steels
High strength steels
Multiphase steels Press hardened steels
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Mild steels
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Best formability
High and Ultra highstrength steels
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Mild steels
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Mild steels for cold forming
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max. C P S Mn Ti Al Si N
DC04 0,08 0,030 0,030 0,40 - 0,040 0,010 0,005
max. C P S Mn Ti Al Si N
DC04 0,08 0,030 0,030 0,40 - 0,040 0,010 0,005
>0,18
n90 value
>1,6
r90 valueYS MPa UTS MPa A 80% Ag %
140-210 270-350 >38% ~22>0,18
n90 value
>1,6
r90 valueYS MPa UTS MPa A 80% Ag %
140-210 270-350 >38% ~22
Microstructure: ferritic matrix
Carbides (few) and AlN
Mechanical properties:
Low yield strength and tensile strength
Low hardness
Very high total elongation
Great ductility and draw-ability
Specified value Typical valueSpecified value Typical value
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Mild steels for cold forming
33
Microstructure:
Ferritic matrix
Precipitates (few) of micro-alloyedelements
Mechanical properties:
Low yield strength and tensile strength
High n-value
High r-value
High uniform elongation
Great ductility and draw-ability
max. C P S Mn Ti Al Si N
DC06 0,02 0,020 0,020 0,25 0,3 0,040 0,010 0,002
max. C P S Mn Ti Al Si N
DC06 0,02 0,020 0,020 0,25 0,3 0,040 0,010 0,002
>0,22
n90 value
>2,1
r90 valueYS MPa UTS MPa A 80% Ag %
140-170 270-330 >41% ~25>0,22
n90 value
>2,1
r90 valueYS MPa UTS MPa A 80% Ag %
140-170 270-330 >41% ~25
Specified value Typical valueSpecified value Typical value
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Outline Automotive evolution
Car body structures
Automotive steels Mild steels
High strength steels
Multiphase steels Press hardened steels
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High strength steels
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Increasing strength of steel sheets
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High strength steel by solid solution strengthening
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Solid solution strengthening (mixed crystal strengthening)
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Influence of alloying elements on the yield point
sub st i tut io nal ly diss olved: P, Si, Cu, Mn, Mo, Ni, Al, Cr and interst i t ial ly diss olved: C, N
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High strength steels by precipitation strengthening
Formation
40
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Increasing the yield point of -iron through different types of
precipitations
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HS steels by work hardening (dislocation strengthening)
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Dislocation density as a function of amount of deformation in pure iron
Degree of deformation
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Evolution of dislocation structure in deformed tensile samples
44
The area
next to the Lders band isnearly without dislocation
Dislocation in the area
of uniform elongation
Cell structure nearby
fracture
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Conventional high strength steels: Micro alloyed steels
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Micro alloyed steels: alloying concept
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Micro alloyed steels: properties, typical applications
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HSLA steels
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Microstructure:
Ferritic microstructure with a little pearlite
Precipitates of micro-alloyed elements
Mechanical properties:
High yield strength
High tensile strength
Limited draw-ability and stretch-ability
max. C P S Mn Ti Al (min) Si Nb
HX340LAD 0,11 0,030 0,025 1,00 0,15 0,015 0,50 0,09
max. C P S Mn Ti Al (min) Si Nb
HX340LAD 0,11 0,030 0,025 1,00 0,15 0,015 0,50 0,09
~0,14
n90 value
~1,0
r90 valueYS MPa UTS MPa A 80% Ag %
340-420 410-510 >21% ~14~0,14
n90 value
~1,0
r90 valueYS MPa UTS MPa A 80% Ag %
340-420 410-510 >21% ~14
Specified value Typical valueSpecified value Typical value
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Conventional high strength steel: High strength IF steels
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High strength IF steels: alloying concept
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High strength IF steels: properties, typical applications
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Conventional high strength steels: Bake hardening (BH) steels
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Schematic diagram of the bake hardening effect, by example of
the production of a car door
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Increasing strength by bake-hardening
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Bake-hardening behavior of different steel grades
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Bake-hardening steels: properties, typical application
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Outline Automotive evolution
Car body structures
Automotive steels Mild steels
High strength steels
Multiphase steels
Press hardened steels
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Metastable iron - carbon (Fe-C) phase diagram
10 20 30 40 50 60 70 80 90 100
1 2 3 4 5 6 7LQ
P S
O
G
K
F
D
CE
N
BA
I
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
M
L +Fe C
3
LH
Fe 3C
(Cementite)
L +
L +
+ Fe C3
+ Fe C3
aa
a
Cementite content in mass %
Carbon content in mass %
TemperatureinC
Source: Pitsch, W.; Sauthoff, G.; Hougardy, H.P. in:
Werkstoffkunde Stahl, Band 1: Grundlagen, Verein
Deutscher Eisenhttenleute, Springer-Verlag 1985
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Transformation-Temperature-Time (TTT) diagram
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Austenite
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Bainite Ferrite - Martensite
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Polymorphism of iron
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Mechanical properties of different phases in steels
Phase Re , MPa Rm, MPa A, % Hardening, HV
Interstitial free condition
(Ferrite)
100-150 280 50 -
Ferrite (unalloyed)
Ferrite (0,7% Ni, 0,6% Cr)Ferrite (13% Cr)
220
330300
300
550500
45
35 18
-
about 180-
Pearlite 900 1000 10 -
Cementite 3000 - - -
Bainite ( 0,1% C) 400-800 550-1200 25 about 320
Martensite ( 0,1% C)Martensite ( 0,4% C)
8002400
1200-
5-
about 380-
Austenite (18% Cr, 8% Ni) 300 600 40 -
Phase Re , MPa Rm, MPa A, % Hardening, HV
Interstitial free condition
(Ferrite)
100-150 280 50 -
Ferrite (unalloyed)
Ferrite (0,7% Ni, 0,6% Cr)Ferrite (13% Cr)
220
330300
300
550500
45
35 18
-
about 180-
Pearlite 900 1000 10 -
Cementite 3000 - - -
Bainite ( 0,1% C) 400-800 550-1200 25 about 320
Martensite ( 0,1% C)Martensite ( 0,4% C)
8002400
1200-
5-
about 380-
Austenite (18% Cr, 8% Ni) 300 600 40 -
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Homogeneity of grain structure - properties
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Characteristics of AHSS
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Microstructures of modern multiphase steelsHigher strength
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Microstructures vs mechanical properties of modern multi-phase steels
Tensile strength in MPa
200 400 600 800 1200 1400 16000
10
20
30
40
50
strainin%
perlite retained austenite
bainite martensite
TRIPTRIP
MSMS
1000
CPCP
DPDP
F+P
ferrite
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Adjustment of multiphase structures of hot-rolled strip
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Multiphase steels
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Characteristics of Dual Phase (DP) steels
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Dual Phase steels: materials concept
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Multiphase steels
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Characteristics of TRIP steels
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TRIP steels: TRansformationInducedPlasticity
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TRIP steels: The TRIP-effect
Strain
Stress
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Multiphase steels
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Characteristics of complex phase steels
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Complex phase steels: materials concept
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Stress-strain behavior of automotive steels
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Outline Automotive evolution
Car body structures
Automotive steels
Mild steels
High strength steels
Multiphase steels
Press hardened steels
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Direct - indirect press hardening
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Properties of press-hardened steel sheet
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Temperature gradient during press hardening
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f f
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Protection of blank surface
85
D d th f ti
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Demands on the surface coating
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Ch i f f d i t t
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Changing of surface and microstructure
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T d f h t f i f t l
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Trend of hot forming of steel
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Hot stamping
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Hot stamping
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H t t d f t il d bl k
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Hot stamped of tailored blanks
90
Innovation Tailored Tempering
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Innovation Tailored Tempering
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Press hardened B pillar
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Press-hardened B-pillar
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Body of Audi A4
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Body of Audi A4
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Press hardened parts in VW Passat
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Press-hardened parts in VW Passat
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Heating of the blank
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Heating of the blank
96
Blank B-Pillar after heating just before hot stamping
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Blank B Pillar after heating just before hot stamping
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Application of advanced high strength steels
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Application of advanced high strength steels
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Trend of advanced high strength steels
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Trend of advanced high strength steels
JapanWorld100
References
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References
- Jody N. Hall, Evolution of advanced high strength steels in automotive
applications, General Motors Company, Chair, Joint Policy Council,
Auto/Steel Partnership, 2011.
- Wagner S., Schmid P., Forming of high strength steel sheet, IFU,
Stuttgart, 2012.
- Smith, W.F. and Hashemi, J., Foundation of metarials science and
engineering, 5th edition, McGraw-Hill, ISBN 978-007-131114-4.
- Bleck, W., Material Science of Steel, RWTH Aachen University, 2007,
ISBN: 3-86130-923-8.
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Thank You
Thank You102