carbon equivalent

Colorado School of Mines Colorado School of Mines -- CSMCSMCenter for Welding, Joining and Coatings Research Center for Welding, Joining and Coatings Research -- CWJCRCWJCR

Basicity Index Type Equations Basicity Index Type Equations -- II

2

%' ,1869%

O from Metal OxideMrajek s Index MrazekO from SiO

= −

2

% ,1901%

CaOVee Ratio BlumSiO

= −

BCaO MgOSiO P O

=++

% .% .

14%0 84%2 2 5 B I

Sum of Basic OxidesSum of Acidic Oxides

. .=

( ) ( )B CaO MgO MnO SiO P O TiO= + + − + +% % % % % %2 2 5 2

BCaO

SiO Al OLF =+

%% %2 2 3

BCaO MgOSiO Al OLF =

++

% .% .

14%0 6%2 2 3

( )( )B

CaF CaO MgO BaO SrO Na O K O Li O MnO FeOSiO Al O TiO ZrO

=+ + + + + + + + +

+ + +2 2 2 2

12

21

2 2 3 2 2

( )( )B

CaO MgO BaO SrO Na O K O Li O MnO FeOSiO Al O TiO ZrO

=+ + + + + + + +

+ + +2 2 2

12

21

2 2 3 2 2 Tuliani’s Formula, 1978Tuliani’s Formula, 1978


Basicity Index Type Equations Basicity Index Type Equations -- IIII

Optical BasicityElectron Donor Power of Oxygen in Oxide Systems

Electron Donor Power of Free Oxide Anions=

O BZ R

GZ Coordination Numberof Cation A

RMolesof Cation A

Molesof Oxygen AtomsG Basicity Moderating Parameterdependingon Pauling sElectronegativity

A A

AAllCations

A

A

A

. .

##

'

=

=

=

=

∑ 21971 - Duffy and Ingram1971 - Duffy and Ingram

BIonicFractionof Free AnionsO intheDissociated Slag

Sumof All AnionsandCationsof theSystemZ =−2

( )( ) ( )B

m m m m m

m m m m m m m nZ

Me O MeO Al O SiO TiO

Me O MeO CaF BaF SiO TiO Al O O

=+ − + +

+ + + + + + +

∑ ∑∑ ∑ −

2 2 3 2 2

2 2 2 2 2 2 3 2

2 2

2 3 2Zeke, 1980Zeke, 1980


High and Medium Strength Steels High and Medium Strength Steels Subjected to Welding Heat CycleSubjected to Welding Heat Cycle

Comparison between High and Low Heat Inputs Comparison between High and Low Heat Inputs

(Svensson, 95)


Heat Heat Affected Affected Zone Zone Properties Properties

((DürenDüren, Korkhaus, and Niederhoff, 3R International, 87), Korkhaus, and Niederhoff, 3R International, 87)


Typical Problems observed in High Typical Problems observed in High Strength Steel WeldingStrength Steel Welding

Metallurgical Origin:HAZ CrackingWM MicrofissuringHAC Cracking

(Rowe and Liu, 99)

(Rowe and Liu, 99)(Rowe and Liu, 99)

Processing Origin:Processing Origin:Porosity at Long Arc or Improper StartPorosity at Long Arc or Improper StartSlag Inclusions at Low CurrentSlag Inclusions at Low CurrentVariable Current at Different PositionsVariable Current at Different Positions


Steel Weldability Map: Cracking Steel Weldability Map: Cracking ConcernsConcerns

(Graville, 76)

(ASM, Welding Handbook V. 6, 93)

HSLA-80/100

HY-80/100

HSLA-65

EH-36


Steel Weldability Indices Steel Weldability Indices -- Carbon Carbon Equivalent Type ExpressionsEquivalent Type Expressions

IIWIIW

WintertonWinterton

CottrellCottrell

*

6 5 15+ + + +

= + + +Mn Si Cr Mo V Ni CuCE C

6 40 10 20 50 10= + + + + − −

Mn Cu Cr Ni Mo VCE C

0.00016 5 3 4

+= + + + + +

Mn Cr Mo V NbCE CC S

* Omitted in the original Dearden & O’Neill formula


DnVDnV

DD

PPCMCM

CENCEN


24 10 40 5 4 14+

= + + + + + +Si Mn Ni Cu Cr Mo VCE C

25 16 20 20 15+ +

= + + + + +Si Mn Cu Cr Ni Mo VCE C

530 20 15 10 60

+ += + + + + + +CM

Si Mn Cu Cr Mo V NiP C B

( ) 524 6 15 20 5

+ + +⎡ ⎤= + ⋅ + + + + +⎢ ⎥⎣ ⎦Si Mn Cu Ni Cr Mo Nb VCEN C A C B


Steel Weldability Indices Steel Weldability Indices –– Fundamental Fundamental ApproachesApproaches

Thermodynamic ApproachThermodynamic Approach'

' 'Mn Si C

oMn Si

C K Mn K Si K CLnCCE K

K MnLnMn K SiLnSi

⎡ ⎤+ + + += ⎢ ⎥

+ + +⎢ ⎥⎣ ⎦

…

…

Kinetics Approach

[ ]1o C Mn SiCE K C K C K Mn K Si′ ′ ′ ′= + + + +…

Partitioning Approach

1 C Mn Si LCo

LC LMn LSi

K C K Mn K Si K LnCCE K C

K CLnC K MnLnMn K SiLnSi′′ ′′ ′′ ′′+ + + + +⎡ ⎤

′′= ⎢ ⎥′′ ′′ ′′+ + + +⎣ ⎦

……

(Liu et al., 1986)



YuriokaYurioka

( ) ( )

( )

80

8 / 5

442 99 206 402 90 arctanlog 2.3 1.35 0.882

1.15 0.673 0.601

24 6 15 12 8 4

24 5 10 18 2.5 3

3.6 20 9

+= + + + − ⋅

− − +=

− −

= + + + + + + + ∆

+ += + + + + + +

= + + + +

Max II II

I III

I III

I

II

III

H C CE C CE xt CE CEx rad

CE CESi Mn Cu Ni Cr MoCE C H

Si Mn Cr V Cu Ni Mo NbCE C

Mn Cu NiCE C5 4

+Cr Mo

( ),∆ =H f B N ( )2884 1 0.3 294= − +MHV C CFor fully martensite microstructure:


Steel Weldability Indices Steel Weldability Indices --∆∆tt8/58/5 CalculationCalculation

Rosenthal Solution (1946)

∆t8/5 is directly related to the heat input (H)

48 5 8.149 10

2Ht x ηπκ

− ⎛ ⎞∆ = ⎜ ⎟⎝ ⎠

26

8 5 22.767 104 p

Ht xh C

ηπκρ

−⎛ ⎞

∆ = ⎜ ⎟⎜ ⎟⎝ ⎠

η = Efficiency

H = Heat input

κ = Thermal conductivity

ρ = Specific gravity

Cp = Specific Heat



Lorenz & DürenLorenz & Düren

DürenDüren –– For 100% Microstructure (M or B) in HAZ

( ) ( ) ( )8/ 5 8 / 5

*

2019 1 0.5log 0.3 66 1 0.8log

8 11 5 6 3 17 9

16 25 10 15 40

= − ⋅ + − + −⎡ ⎤⎣ ⎦

= + + + + + + +

+ += + + + + +

H t C CE C t

Mn Si Cr Mo V Ni CuCE C

Mn Cu Si Cr V Mo NiCE C * For pipeline grade steels

For 100% Microstructure (M or B) in HAZ802 305

350 1018 11 5 6 3 17 9

= +

⎛ ⎞= + + + + + + + +⎜ ⎟⎝ ⎠

M

B

HV CMn Si Cr Mo V Ni CuHV C


WELD STRENGTH MODEL WELD STRENGTH MODEL

( ) ( )( )

0.2

0.178 / 5

3.1 0.1 80

0.065

= −

=

nP MaxR MPa H

n tAkelsen, Rørvik, Onsøien, and Grong

50232 1.9 0.26 0.09= + − −YS t T GS

50313 8.3ln 1.8 3.8 0.36 0.08⎛ ⎞= − + − −⎜ ⎟⎝ ⎠

dTUTS t T GSdt

Blackburn et al. (1997)

YS = 0.2 % offset yield strength, ksit = thickness, cmT50 = 50 % transformation temperature, oCGS = austenite grain sizeUTS = ultimate tensile strength, ksi

= calculated cooling rate, oC/sdTdt


Application: Steel Weldability IndexApplication: Steel Weldability Index

WeldMetal

BaseMetal


Heat Affected Heat Affected Zone PropertiesZone Properties

Empirical Relationships

(Svensson, 95)


Weld Metal Weld Metal Properties

(Svensson, 95)

Properties

Empirical Empirical RelationshipsRelationships


0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.500

50

100

150

200

250

Risk of Cracking

No Cracking

TM Steels up to X-100

Pre

heat

ing

Tem

pera

ture

(o C)

Carbon Equivalent (%)

Possibilities of CrackPossibilities of Crack--Free Free XX--100 Steel Welds 100 Steel Welds

6 mm Cylindrical Specimens 6 mm Cylindrical Specimens with spiral notchwith spiral notchHeat Input: 8Heat Input: 8--9 kJ/cm9 kJ/cmThickness of Backing Plate: Thickness of Backing Plate: 20 mm20 mmCritical implant Critical implant Stress/Yield Strength: Stress/Yield Strength: 100%100%[H][H]DifDif ≥ ≥ 40 cm40 cm33/100g/100g

(According to Implant Test Resultsusing Cellulosic Electrodes)

(Hillenbrand, Niederhoff, Hauck,Pertender, Wellnitz, 1997)


Hydrogen Embrittlement Susceptibility:Hydrogen Embrittlement Susceptibility:Martensite Start Temperature Martensite Start Temperature -- MsMs

∆ ∆ Martensite Start Temperature Martensite Start Temperature -- ∆∆MsMsAndrew – Linear (1965)Ms = 539 – 423C – 30.4Mn – 17.7 Ni – 12.1Cr – 7.5Mo

Self et al. (1986) – Wrought Metal:Ms = 521 – 350C – 14.3Cr – 17.5Ni –28.9Mn – 37.6Si – 29.5Mo

– 1.19Cr.Ni + 23.1(Cr+Mo)CSelf et al. (1986) – Weld Metal:Ms = 521 – 350C – 13.6 Cr – 16.6Ni – 25.1Mn – 30.1Si – 40.4Mo

– 40 Al – 1.07Cr.Ni + 21.9(Cr+0.73Mo)C

∆Ms = MsWM - MsHAZ

Other Ms Equations include Payson & Savage (1944), Carapella (1944), Rowland & Lyle (1946), Grange & Stewart (1946), Nehrenberg (1946), Steven & Haynes (1956), and Others.


CrackingCracking--No Cracking MapNo Cracking Mapfor High Strength Steel Weldsfor High Strength Steel Welds

(Wang and Liu, 97)

(Rowe and Liu, 99)

(Olson, Wang, Liu et al, 96)


Weld Undermatching and Overmatching:Weld Undermatching and Overmatching:NonNon--Uniform Hydrogen DistributionUniform Hydrogen Distribution

MicrofissuringTransverse Cracking

-60 -40 -20 0 20 40 60-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

∆H (H

WM -

HH

AZ) (

ml/1

00g

met

al.a

tm1/

2 )

∆Ms (MsWM - MsHAZ) (oC)

OvermatchedWeld Metal

OvermatchedWeld Metal

EvenmatchedWeld Metal

EvenmatchedWeld Metal

UndermatchedWeld Metal

UndermatchedWeld Metal

HAZCracking

(Wang and Liu, 97)

carbon equivalent

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