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WeldingWeldingMetallurgyMetallurgyNur Syahroni, ST., MT.
Welding Technology & Inspection (MO-091333)O
CEAN
ENGINE
ERING-
ITS
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PhasePhase
transor!ationtransor!ation
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PhasePhase
transor!ationtransor!ationTime-Temperature Transformation
(TTT) Diagram
Pearlite
Bainite Spheroidite
Martensite
Continuous Cooling
Transformation Diagram (CCT)Mechanical Properties of Carbon
Steels
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PearlitePearlite
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
Consider eutectoidrea"tion#
Te!$erature $lays an i!$ortant role in therate o the austenite-to-$earlitetransor!ation
Plot $er"entage o transor!ation %s.logarith!i" o ti!e and temperature is
maintained constant
Welding Technology & Inspection (MO-091333) 5Pearlite
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
Also &no'n asIsother!al
Transor!ation(iagra!
The diagra! assho'n )eside is%alid only or"ar)on steel 'ith
*.+'t C
Welding Technology & Inspection (MO-091333) 6Pearlite
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
Welding Technology & Inspection (MO-091333) Pearlite
c!"#on steel $ith 0%6$t '
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
Coarse pearlite (a)#
igh te!$erature /0ust)elo' eute"toidte!$erature
(i1usion rate o "ar)onato!s is high
Fine pearlite (b)
2o'er te!$erature
(i1usion rate o "ar)on
ato!s is lo'er igher strength 3
harder than "oarse$earlite
Welding Technology & Inspection (MO-091333) Pearlite
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
Welding Technology & Inspection (MO-091333) 9Pearlite
(i1erent"o!$osition osteels ha%e
di1erent sha$eo TTT-diagra!
4or steel 'iththe"o!$osition#1,13%wt CtheTTT diagra! assho'n )eside A: Austenite
C: Pro-eutectoid Cementite
P: Pearlite
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BainiteBainite
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
The !i"rostru"tureo bainite"onsistso ferriteandcementite$hases
(i1usional$ro"esses arein%ol%ed
5ainite )egin toor! at 67*oC/$oint N8 u$ to9:6oC.
Welding Technology & Inspection (MO-091333) 11Bainite
c!"#on steel $ith 0%6$t '
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
5ainite or!s asneedles or$lates,de$ending on
the te!$eratureo thetransor!ation
Welding Technology & Inspection (MO-091333) 12Bainite
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SpheroiditeSpheroidite
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
I a steel alloy ha%ing either$earliti" or )ainiti"!i"rostru"tures is heatedto, and let at, ate!$erature )elo' theeute"toid - or e;a!$le, at
a)out +**oC or asu
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MartensiteMartensite
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram Martensiteis or!ed 'hen
austeniti?ed iron@"ar)on alloys arera$idly "ooled /or uen"hed8 to arelati%ely lo' te!$erature /in the%i"inity o the a!)ient8
Martensite is a non-euili)riu!single-$hase stru"ture that results
ro! a di1usionless transor!ationo austenite
Martensiti" transor!ation o""urs'hen the uen"hing rate is ra$idenough to $re%ent "ar)on di1usion
The hori?ontal and linear "hara"tero these lines indi"ates that the
!artensiti" transor!ation isinde$endent o ti!e
Welding Technology & Inspection (MO-091333) 16Martensite
c!"#on steel $ith 0%6$t '
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
The 4CC austenitee;$erien"es a$oly!or$hi"transor!ation to a )ody-"entered tetragonal /5CT8!artensite
Martensite grains ta&e ona $late-li&e or needle-li&ea$$earan"e
The 'hite $hase in the!i"rogra$h is austenite
/retained austenite8 thatdid not transor! duringthe ra$id uen"h
Welding Technology & Inspection (MO-091333) 1Martensite
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Time-TemperatureTime-Temperature
Transformation (TTT) DiagramTransformation (TTT) Diagram
The $resen"e o alloyingele!ents other than"ar)on /e.g., Cr, Ni, Mo,and W8 !ay "ausesigniB"ant "hanges in
the $ositions andsha$es o the "ur%es inthe isother!al#
shiting to longer ti!es thenose o the austenite-to-$earlite transor!ation
the or!ation o a se$arate)ainite nose
Welding Technology & Inspection (MO-091333) 1Martensite
+lloy steel +I,I 4340
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E;a!$le $ro)le!E;a!$le $ro)le!
sing the isother!al transor!ation diagra! or aniron@"ar)on alloy o eute"toid "o!$osition s$e"iy thenature o the Bnal !i"rostru"ture /in ter!s o!i"ro"onstituents $resent and a$$ro;i!ate$er"entages8 o a s!all s$e"i!en that has )een
su)0e"ted to the ollo'ing ti!e@te!$eraturetreat!ents. In ea"h "ase assu!e that the s$e"i!en)egins at +*oC and that it has )een held at thiste!$erature long enough to ha%e a"hie%ed a"o!$lete and ho!ogeneous austeniti" stru"ture
D Ra$idly "ool to >6*oC, hold or :*7s, and uen"h to roo!
te!$erature
D Ra$idly "ool to 96*oC, hold or :** s, and uen"h to roo!te!$erature
D Ra$idly "ool to 6*oC, hold or 9* s, ra$id "ool to 7**oC, holdor :*>s, and uen"h to roo! te!$erature
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SolutionSolution
a. :** )ainiteand no urthertransor!ationis $ossi)le
). :**!artensite
". 6* $earliteand 6* )ainite
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