Steels Ponge Marie-Curie Summer School
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Transcript of Steels Ponge Marie-Curie Summer School
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Max-Planck-Institut fr Eisenforschung GmbHMax-Planck-Institut fr Eisenforschung GmbH
Structural Materials - Steels
Structural Materials - Steels
D. Ponge
Marie Curie Summer School, Hrtgenwald
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ContentContent
Steels for Constructions:
High Strength LowAlloyed (HSLA) Steels
Steels for Automotive application
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success story: HSLA-steels up toReH=1100 MPa
fields of application:
offshore
pressure vessel
shipbuilding pipelines
cranes
automotive
bridges
success story: HSLA-steels up toReH=1100 MPa
fields of application: offshore
pressure vessel
shipbuilding pipelines
cranes
automotive
bridges
weight: 96 t
lifting capacity: 800 t
standard steels:lifting capacity: 140 t
until 1970s: St 37(S235), St 52 (S355)
oil-shocksin the 70s
motivation to save raw materials and energy
development of high strength low alloyed (HSLA) steels
High Strength Low Alloyed (HSLA) SteelsHigh Strength Low Alloyed (HSLA) Steels
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basic requirements:
high yield strength (Re)
high toughness even at low temperatures(ductile to brittle transition temperature (DBTT) should be low)
good weldabili ty(0.2%C (1) , limit for alloying elements)
High Strength Low Alloyed (HSLA) SteelsHigh Strength Low Alloyed (HSLA) Steels
(1): all compositions are given in mass%
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Strength and ToughnessStrength and Toughness
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Eng
ineering
stress[M
Pa]
Engineering strain [%]
ReH
ReL
Yield strengthYield strength
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S690QS690Q
S460NS460N
S355S355
S235S235
Engineering
stress[M
Pa]
Engineering strain [%]
Engineering stress-strain curvesEngineering stress-strain curves
minimum
ReHin MPa
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ToughnessToughness
Liberty shipsLiberty ships
Numberofb
rokenships
Totalnum
berofships
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m
H
h
sample
Av
0
300
Toughness: ducti le to britt le transit ion temperatureToughness: ducti le to britt le transition temperature
impact
notch
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Impact transition curveImpact transit ion curve
upper shelf
Lower shelf
transition
Test temperature in C
Impactenergyin
J
glossy
crystallinespot
mate
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Impact transition curveImpact transit ion curve
Test temperature in C
Impacte
nergyin
J
bcc
fcc
27J
DBTT
DBTT: ductile to brittletransition temperature
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Effect of carbon content on toughnessEffect of carbon content on toughness
0.11 %C
after F. B. Pickering in
Constitution and Properties
of Steels, p. 55, VCH 1992
0.31 %C
0.80 %C
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Test temperature in C
ImpactenergyinJ
standard steel
fine grained HSLA steels
DBTT
Grainrefinement
Effect of grain refinement on toughnessEffect of grain refinement on toughness
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Increase strengthIncrease strength
Increase the strength ofsteel is easy !Increase the strength ofIncrease the strength ofsteel is easy !steel is easy !
But it has a price But it has a priceBut it has a price
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-10
-5
0
5
10
0 2.5 5.0 7.5 10.0Increase of yield strength in MPa
Change
oftransitiontemperatureinC
Solids
olution
hardeningb
ycarbo
n
Solids
olution
hardening
bycarb
on
Strengthenin
gbydisloca
tions
Strengthenin
gbydisloca
tions
Precipitationhard
ening
Precipitationhard
ening
Grainrefinem
ent
Grainrefinement
Effect on strengthening mechanisms on toughnessEffect on strengthening mechanisms on toughness
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WeldabilityWeldability
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Iron-Cementite DiagramIron-Cementite Diagram
LiquidLiquid
as cast iron
Fe3C
(austenite)face centered cubic (fcc)
Max. C solubility: 2.06%
(ferrite)body centered cubic (bcc)
Max. C solubility: 0.02%
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Cooling time t8/5 [s ]
HardnessHV10
M
icrostructure[%]
Continuous-cooling-transformation (CCT) diagram of S355NContinuous-cooling-transformation (CCT) diagram of S355N
Time [s]
Temperat
ure[C]
Austenitization: 900C for 5 min
Chemical composition in mass%:
phase transformation phase transformation
170435
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Heating by weldprocess
Welding rod
Heat Affected Zone (HAZ):
Zone, in which the parent
material is affected (usually adegradation) by the weldtemperature cycle
Affection of base material by weld temperature cycleAffection of base material by weld temperature cycle
Temperature in C
TimeHAZ
HAZ
Temperature cycle
in the weld region
Temperature cycle
in the weld regionfusion zone
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S235 (St37-2) C=0.15 E360 (St70-2) C=0.45
not welded
welded
Brit tle fracture due to
excessive hardening (martensite)
C 0.2%
max.hardness:
350 HV
Effect of carbon contentEffect of carbon content
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cold cracks
Cause:
Cooling rate to high
Avoiding cold cracks by preheatingAvoiding cold cracks by preheating
Steels with a high hardenability have to bepreheated before fixing and welding
Effect: cooling rate is reduced => avoiding
untempered martensite (no excessive hardening)Preheating temperature: 100C to 400C
Eff t f iti ld k tibil it
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%massin
15
NiCu
5
VMoCr
6
MnC)IIW(CE
++
++++=
Besides C also other elements can increase the hardenability:
if CE(IIW) 0,40 %: low cold crack susceptibility
Effect of composition on cold crack susceptibil ityEffect of composition on cold crack susceptibil ity
Carbon equivalent CE:
International Institute for Welding
C fC l i f t l d i
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Conclusions for steel designConclusions for steel design
improves weldability
improves toughness decreases strength
Increasing strength mainly by: grain refinement (improves also toughness)
precipitation hardening (microalloying)
Decreasing carbon content:
(Carbon content 0.2%)
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Normalized structural steelsNormalized structural steels
example: S460N
N li iNormali ing
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+ Ac3
Temp
erature
Conventional hot rolling
Ar3
Ar1
+ Pearlite
normalizing
Time
approx. 50C
Pearlite
NormalizingNormalizing
Austenite Austenite
PearliteFerrite
R t d ti f t it i th b AlNRetardation of austenite grain growth by AlN
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900 1000 1100 1200 1300 1400
12
10
8
6
4
2
0
-2
-4
Austenitizing temperature in C
ASTM
grainsize
number Coarse grain
Coarse grain
Fine grainFine grain
0.047% Al
0.017% N
0.004% Al
0.010% N
Austenitization time: 30 minAustenitization time: 30 min
Retardation of austenite grain growth by AlNRetardation of austenite grain growth by AlN
Austenite grain size as function
of austenitization temperature
Austenite grain size as function
of austenitization temperature
AlN: retards grain growth
Effect of microalloying additions on austenite grain coarseningEffect of microalloying additions on austenite grain coarsening
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after G. R. Speich, L..J.
Cuddy, G. R. Gordon, A.J.DeArdo, in: Phase
Transformations in Ferrous
Allys: A. R. Marder et al.
(Eds.), Warrendale:TMS-
AIME, pp. 341-389
Effect of microalloying additions on austenite grain coarseningEffect of microalloying additions on austenite grain coarsening
V Al NbTi
Austenite
Austenite C-Mn
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Thermomechanically rolled steels (TM)Thermomechanically rolled steels (TM)
example: S460M
Effect of finishing rolling temperature on transformationEffect of finishing rolling temperature on transformation
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high finishing roll ing temperature low
conventional rolling controlled rolling
partiallytrans-formedmicro-structure
partiallytrans-formedmicro-
structure
micro-structurebefore
trans-formation
micro-structurebefore
trans-formation
-recrystallization
Effect of finishing rolling temperature on transformationEffect of finishing rolling temperature on transformation
acceleratedcooling
grain
matrix
deformation band nuclei in matrix
: additional nuclei due to controlledrolling or accelerated cooling
: additional nuclei due to controlledrolling or accelerated cooling
magnified
after I. Kozasu in
Constitution and Properties
of Steels, p. 189, VCH 1992
Retardation of austenite recrystall ization by NbRetardation of austenite recrystall ization by Nb
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1000
900
800
10 10 10 10
-1 0 1 2
Rollingtem
peratur
einC
Time to start of recrystallization in s
0 mass% Nb
0.04 mass% Nb
Maximumstrain induced
NbC precipitation
Maximumstrain induced
NbC precipitation
Retardation of austenite recrystall ization by NbRetardation of austenite recrystall ization by Nb
Change of Yield strength and DBTTChange of Yield strength and DBTT
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Change of Yield strength and DBTTChange of Yield strength and DBTT
Increaseo
fyieldstrengthinMPa
Changeoftransitiontemperaturein
C
Grain size in mm-1/2 Grain size in mm-1/2
Grain
refin
ementP
recipitation
h
ardening
Precipitatio
n
hardening
S355 with 0.05% Nb or 0.1%V or 0.1% TiS355 with 0.05% Nb or 0.1%V or 0.1% Ti
TM steelsTM steels
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Goal: decrease pearl ite content and carbon equivalent at the
same or even higher strength
10 m
Ferrite: very soft (approx. 60 HV)
Cementite: very hard (approx. 800HV)
Pearlite
TM steelsTM steels
[1]
[2]
from [3]
[1]: J.J. Irani, D. Burton, J.D. Jones , A. B.
Rothwell: Strong tough structural steels, London
1967 (Spec. Rep. Iron Steel Inst. No. 104) pp.
110
[2]: W. E. Duckworth, R. Phillips, J. A.
Chapman, J. Iron Steel Inst. 203 (1965) p. 1108
[3]: B. Msgen, H. de Boer, H. Frber, J.Petersen, Normal and High Strength Structural
Steels, in Steel Vol. 2, Springer Verlag
Stahleisen 1993, p. 40
Comparison microstructure normalized and TM- steelComparison microstructure normalized and TM- steel
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S355 J2G3S355 J2G3 S355 MCS355 MC
NormalizedNormalized Thermomechanically rolled (TM)Thermomechanically rolled (TM)
Comparison microstructure normalized and TM steelComparison microstructure normalized and TM steel
pearlite
ferrite
Typical compositions of normalized steel and TM steelsTypical compositions of normalized steel and TM steels
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Typical compositions:
Typical compositions of normalized steel and TM steelsyp p
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Quenched and tempered HSLA-steelsQuenched and tempered HSLA-steels
example S690Q, S1100Q
Quenched and tempered HSLA-steelsQuenched and tempered HSLA-steels
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Water quenching:
martensite (0,2%C)
HSLA:at relative high temperingtemperatures
(typically 600-680C)for sufficient ductility
hardeninghardening temperingtempering+
pp
Time [s]
Temperatu
re[C]
Development of HSLA-steelsDevelopment of HSLA-steels
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1850 1900 1950 2000
0
200
400
600
800
1000
1200
Minim
umy
ield
strengt
hinMPa
Year
Hot rolled: S235
normalized
S355J2G3; S355N
thermo-
mechanically(TM) rolled
S700MC
S420MC
quenched and
tempered:
S960Q
S890Q
S690Q
S1100QLS960M
TM+accelerated
cooling (ACC)
and tempering
p
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New Developments
Mechanical PropertiesMechanical Properties
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Normalised Ultra Fine
Grain
Ultra Fine
Grain
TMCP
Ferrite Grain Size, dF (m)40 10 5 3 1
2 6 10 14 18 22 26 30 34
dF-1/2 (mm-1/2)
900
800
700
600
500
400
300
200
YieldStreng
thR
eH
(M
Pa)
p
Yield Strength Yield Strength
Transition
Temperature (0C)(50% FATT)
0
- 80
- 40
-120
-160-200
-240
Transition
Temperature
bergangstemp
Hall-
Petch
Cottrell-Petch
Mechanical PropertiesMechanical Properties
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ReH or Rp0,2, MPa after Nagai200 300 400 500 600 700
CMnSi
%N0m
Steel:
0.1%C
0.7%Mn0.2%Si
0.005%NdF=10m
Steel:0.1%C
0.7%Mn0.2%Si
0.005%NdF=10m
dF: 2 1m
dF: 5 2m
dF: 10 5m
Mn: 0.7
3.0%
N: 0.0050.02%
Si: 0.21.0%
Streckgren
ze
p
MicrostructureMicrostructure
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0.2% C; 1.5%Mn; 0.2%Si0.2% C; 1.5%Mn; 0.2%Si
Further reading: Microstructure and crystallographic texture of an ultrafine grained CMn steeland their evolution during warm deformation and annealing, R. Song, D. Ponge, D. Raabe, R.Kaspar, Acta Materialia 53 (2005) 845858
ContentContent
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Steels for Constructions:
High Strength LowAlloyed (HSLA) Steels
Steels for Automotive application
Fraction of conventional and high strength steel for carsFraction of conventional and high strength steel for cars
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0
20
40
60
80
fractio
nin%
conventional high strength
1990 1995 2000 2005
Steel grades for car bodySteel grades for car body
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Mehrphasen-Sthle
Dualphasen-Sthle
DP 280/600
DP 300/500DP 350/600
DP 400/700
DP 500/800
DP 700/1000
CP 700/800
Misc.
BH 210/340BH 260/370
IF 300/420
HSLA 350/450
MS 950/1200
MS 1250/1520
1%4%
30%22%
4%
3%
8%
7% 1%4% 6% 4%2%1%
3%
TRIP 450/800
CP 700/800
Martensit-Sthle
Fraction of different steel grades in a car body (Porsche Cayenne)
Car body
Porsche Cayenne
Application ofhigh strength steelswith UTS up to 1000 MPa
High strength Dual Phase steel
TRIP-steel
Martensitic
steels
Dual Phase
steels
Multiphasesteels
Ductil ity/Strength combinations of steels for automotive applicationsDucti lity/Strength combinations of steels for automotive applications
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TRIP(Mn+Al) (Mn+Si) Mn+Si+Nb
TRIP(Mn+Al) (Mn+Si) Mn+Si+Nb
austeniticstainless
Fe-Mn-Al-C
Fe-Mn-Al-SiTWIPFe-Mn-Al-SiTWIP
Fe-Mn-Al-SiTRIPFe-Mn-Al-SiTRIP
Al-alloys
Fe P06
Fe P01-P05HSLA
HSLABH(P)
DualPhase(DP)
CPCP
MartensiticMartensitic
BH t l
Bake-hardening effectBake-hardening effect
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Stress
Strain
C
After
press
forming
Bake
hardening
Work
hardening
Conventional
steel
Baking
BH steel
after M. Kurosawa, S. Sato,
T. Obara, K. Tsunoyama,
Age-hardening behaviour
and dent resistance ofbake-hardenable and extra
deep-drawable high strengh
steel, Kawasaki Steel Tech.
Rep. 18 (1988), pp. 61-65
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AdvancedAdvanced HighHigh--StrengthStrength
and Supraand Supra--Ductile LightDuctile Light--WeightWeight
SteelsSteelsG.G. FrommeyerFrommeyer and U.and U. BrBrxx
MaxMax--PlanckPlanck--InstitutInstitut for Iron Researchfor Iron Research
DuesseldorfDuesseldorf, Germany, Germany
Further reading: Supra-Ductile and High-Strength Manganese-TRIP/TWIPSteels for High Energy Absorption Purposes, G. FROMMEYER, U. BRX andP. NEUMANN, ISIJ International, Vol. 43 (2003), No. 3, pp. 438446
Engineering stress-strain curvesEngineering stress-strain curves
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0 20 40 60 80 1000
200
400
600
800
1000
1200
TRIPLEX-steel
X110 MnAl 26 11
TRIP-steel
X5 MnAlSi 15 3 3
TWIP-steel
X5 MnAlSi 25 3 3
stress[
MPa]
plastic strain pl
[%]
characteristic stress-strain-curves of TRIP-, TWIP-
and TRIPLEX-steels (strain rate = 10-4s-1)&
Twinning Induced Plasticity
Transformation Induced Plasticity
Dominant deformation mechanismsDominant deformation mechanisms
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TWIPdeformation twinning
TRIP Martensitetransformation
Austenitic FeMn [Al, Si]Steels
Austenitic / Ferritic FeMn [Al, Si] Steels
Temperature-dependence of mechanical propertiesTemperature-dependence of mechanical properties
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TWIP steel (X5 Mn Al Si 25 3 3)
-200 -100 0 100 200 300 4000,0
200
400
600
800
1000
1200
1400
III II I
un
f
Rp0,2
Rm
Strength[
MPa]
Temperature T [C]
0
20
40
60
80
100
St
rain
[%]
= 10-4 s-1.
M:1000x
T = 400 C, = 50 %T = 50 C, = 78 %
DuctilityDuctility
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TWIP steel (X5 Mn Al Si 25 3 3)TWIP steel (X5 Mn Al Si 25 3 3)
Undeformed sampleUndeformed sample
Sample after tw isting by 1080 (T = 20 C)Sample after twisting by 1080 (T = 20 C)
Undeformed sampleUndeformed sample
Deformed sample (uniform elongation of 70%)Deformed sample (uniform elongation of 70%)
High Strength TRIPLEX Light-Weight SteelHigh Strength TRIPLEX Light-Weight Steel
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TEM images of a high carbon Fe-Mn-Al-C steel
revealing a fine shear band structure (BF) (a),SADP of the twinning region (b),
E21-structured -carbides (DF) (c),theoretical SADP of-matrix and E21-carbides (d)
fcc(111)
fcc(111)
fcc(111)
fcc(002)
fcc(111)
E2 (001)1
E2 (110)1E2 (001)1
E2 (110)1
7 874 /3
Density vs. Al-concentration of quaternary Fe-Mn-Al-C alloysDensity vs. Al-concentration of quaternary Fe-Mn-Al-C alloys
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12 14 16 18 20 226,4
6,5
6,6
6,7
6,8
6,9
7,0
7,1
7,2
7,3
7,4
7,5
18
16
14
12
10
8
6
Mn content [At.-]
,
, ,
, ,
, ,
, ,
, ,
, , resulting density
aluminium content [At.-%]
density
[g/cm
3]
Eisen
= 7.874 g/cm3
percentagereductioninden
sity
(0-)/0*100
: 8
: 9 : 17
: 10 : 19
: 11 : 21
: 12 : 22
: 13 : 23
: 16 : 24
density reduction resulting
from the lattice dilatation
ApplicationsApplications
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TRIPTWIP
TRIPLEX
Lightweight constructionand
crashresistent
High strengthand safety against brittle failure
High toughness
at low temperatures
since
Development of steels with high strength and formabilityDevelopment of steels with high strength and formabili ty
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0 10000 20000 30000 40000 50000
2002
1996
1996
1990
1990
1990
1985
1985
1981
1978
1975
FeMnAlC TRIPLEX steels
high manganese TWIP steels
high manganes TRIP steels
Conventional TRIP steels
SULC steels
Isotropic streels
highstrength IF steels
Bake-Hardening steels
Dualphase steels
Phosphorus alloyed steels
Microalloyed steels
ultimate tensile strength * total elongation [MPa %]