(Heat Treatment of Metals)

Processing

Structure

Properties

Application

-- ,, --Heat treatmentHeat treatment--

------

--HardnessHardness--Tensile StrengthTensile Strength--DuctilityDuctility

heat treatment - Process Annealing- Stress Relief

heat treatment - Normalizing- Full Annealing- Spheroidizing- Quenching and Tempering

Process AnnealingT :

T : 300 [ 600 C

() T

[ oxidizing

[ annealing [ (grain growth)

Stress Relief

T : [ , , extrusion[ (thermal stress)

, [

stressT residual stress

T :

Critical Temperature

A1 = lower critical temperatureA3 = upper critical temperature hypoeutectoid

carbon steelAcm = upper critical temperature hypereutectoid

carbon steel

A3 Acm austenite

Normalizing

T , extrusion

T normalizing

T : A3 Acm 50 K austenite

Full AnnealingFull Annealing

T : plastic deformation

T : A3 A1 (A3 hypoeutectoid carbon steel A1 hypereutectoid carbon steel) 50 K austenite

T normalizing

Normalizing Full Annealing pearlite

Spheroidizing

T (0.25-1.1%C) pearlite pearlite (, , , , )

T : Fe3C pearlite

T : eutectoid temperature ( 700 C) 15 [ 25

Spheroidized 1.1%C steel 1000x

Quenching and Tempering

T (>0.3 %C)

T : upper critical temperature austenite ( mAustenitizingn) ( mQuenchingn) 100 [ 500 C ( mTemperingn)

tt

TT

austenitizingaustenitizing

temperingtempering

quenchingquenching

T FCC BCC eutectoid mixture , mMartensiten ()

T quench Tempering

FCC with C atom BCC w/o C atom BCC with C atom

CC

MartensiteMartensite

Precipitation Hardening

T

T : second phase solid solution mSolution treatmentn (Quenching) quench mAgingn

tT

Solution TreatmentSolution Treatment

AgingAging

quenchingquenching

TT00 B B A A TT2 2 lever arm rulelever arm rule

Precipitation HardeningPrecipitation HardeningT B A

B A (Supersaturated solid solution)

T

T Supersaturated solid solution (Aging) aging (over aging)

supersaturated supersaturated solid solutionsolid solution

mmNatural agingNatural agingnn mmArtificial agingArtificial agingnn

aging aging