uthaisangsuk2013-ahs steels for automotive parts

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)

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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

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6/102Source: Ducker Worldwide

Trend of materials usage

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7/102Source: WorldAutoSteel

Aim of automotive industries (mass reduction)

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Source: WorldAutoSteel

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9/102Source: WorldAutoSteel


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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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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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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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Car body structures

Automotive steels

Mild steels


Multiphase steels Press hardened steels

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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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http://mercedes-benz/http://mercedes-benz/http://mercedes-benz/http://mercedes-benz/


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Source : http://boronextrication.com/tag/list-of-vehicles-with-boron-and-uhss

2011 Volvo V70 Body Structure

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23Source: http://carskeleton.blogspot.com/2012_04_01_archive.html


2012 Audi A3 body Structure


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Source : http://www.autosteel.org24



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25Source : http://www.autosteel.org



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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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Car body structures

Automotive steels

Mild 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


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


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

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Microstructure:

Ferritic matrix

Precipitates (few) of micro-alloyedelements


Low yield strength and tensile strength

High n-value

High r-value

High uniform elongation

Great ductility and draw-ability


DC06 0,02 0,020 0,020 0,25 0,3 0,040 0,010 0,002


DC06 0,02 0,020 0,020 0,25 0,3 0,040 0,010 0,002

>0,22

n90 value

>2,1


140-170 270-330 >41% ~25>0,22

n90 value

>2,1


140-170 270-330 >41% ~25



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Car body structures

Automotive steels Mild 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

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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

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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


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


340-420 410-510 >21% ~14~0,14

n90 value

~1,0


340-420 410-510 >21% ~14



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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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Car body structures

Automotive steels Mild steels


Multiphase 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

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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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Car body structures

Automotive steels

Mild steels


Multiphase 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

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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

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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

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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

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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

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