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Defect

formation

in

cast

ironLennartElmquistSchoolofEngineeringJnkpingUniversitySweden

Tammerfors,Finland,November8,2012

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IntroductionCasting

Mouldcavity

Meltingprocess

Pouring

Solidification Mouldremoval

Cleaningandfinishing

Advantages Complexshapes

Holesandinnercavities

Widerange

of

alloys

Melttreatment

Economical

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Tammerfors 2012-11-082

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Introduction

Commondefects:

Blowholes

Pinholes

Shrinkage

Penetration

Inclusions

etc

Lennart Elmquist

Tammerfors 2012-11-08

DEFECTS!

Shrinkageporosity

Metalexpansionpenetration

Slaginclusiondefect

Carbonmonoxideblowhole3

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Outline Gasdefects

Gasabsorption

Gas

evolution Inclusions

Shrinkageporosity Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

Lennart Elmquist

Tammerfors 2012-11-084

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Outline Gasdefects

Gasabsorption

Gas

evolution Inclusions

Shrinkageporosity Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

Lennart Elmquist

Tammerfors 2012-11-085

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Outline Gasdefects

Gasabsorption

Gas

evolution Inclusions

Shrinkageporosity Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

Lennart Elmquist

Tammerfors 2012-11-086

(Source: Torsten Sjgren)

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Gasdefects

Introduction

Lennart Elmquist

Tammerfors 2012-11-08

Source: Diszegi, 2005 Source: UAB Casting Engineering Laboratory (CEL), 2005

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Gasdefects

Introduction

Degradationofbindermaterial

Gasprecipitate

during

solidification

due

to

decreasedsolubility

Gasmay

be

picked

up

by

the

melt

during

mouldfilling

Slagconstituentscanreactwithalloying

additionsin

the

metal

and

form

gaseous

reactionproducts

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Pinholes Hydrogen,nitrogen,CO

Revealedafter

machining

Usuallysmall

Roundshape

Graphitelining

Remedies

LowlevelsofAlandTi

Controlofsteelscrap

Coresandwaterbased

coatingsfully

cured

and

dried

Lennart Elmquist

Tammerfors 2012-11-08

Source: www.ikominerals.de

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PinholesHydrogenpinholes

Waterand

organic

materials

Airhumidity

Rustychargematerial

Damprefractory

material

Moistureinmoldandcore

Corebinder

Lennart Elmquist

Tammerfors 2012-11-08

Nitrogenpinholes

Resinbonded

cores

and

molds

Sandadditives

Coatingsand

glues

Chargematerials

Source: http://www.objet.sk/content/products/sand_casting_a4.pdf

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PinholesCarbonmonoxidepinholes

Reactionof

carbon

and

oxygen

Liquidslagrichinironoxide

CO2reactwithiron

Carbonreact

with

water

Nographitelining

MnSandslaginclusions

Lennart Elmquist

Tammerfors 2012-11-08

Source: www.ikominerals.de

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Blowholes Largecavities

Normallyirregular

in

shape

Smoothwalls

Graphitelining

Highturbulence

during

moldfilling

Highgaspressureinthe

mold

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Tammerfors 2012-11-08

Source: www.ikominerals.de

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Blowholes Castingdesign

Gating Sandpermeability

Coreprintarea

Typeof

resin

system

Extentofcureanddrying

Pouringtemperature

Rustychaplets

Cloggedvents

etc

Lennart Elmquist

Tammerfors 2012-11-08

Source: www.ikominerals.de

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Fissures Narrowcracklikecavities

Frequentlyhave

dendritic

structures

Excessivenitrogenmain

cause

Hydrogenmayintensifythe

defect

Sources

Nitrogencontent

high

Highnitrogencontentin

corebinder

Poor

core

venting

Lennart Elmquist

Tammerfors 2012-11-0815

Source: www.ikominerals.de

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Solubilityof

gases

1. Diffusionofgastothesurface

2. Chemicalreaction

on

the

surface

3. Diffusionofoneormore

reactionproductsawayfrom

thesurface

Lennart Elmquist

Tammerfors 2012-11-08

HgH 22

2

HPKH H

Source: Svensson et al, 1980

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Solubilityof

gases

Hydrogen Nitrogen

Lennart Elmquist

Tammerfors 2012-11-08

Influenceofalloyingelementsonsolubility

Source: Weinstein et al, 1963 Source: Dawson et al, 1965

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Solubilityof

gases

Thesolubilityofhydrogen

andnitrogenaffecteach

other

Cumulativeeffectthat

increasethe

risk

for

porosity

Lennart Elmquist

Tammerfors 2012-11-08

2

NPKN N

22 NHTOT PPP

Source: Svensson et al, 198018

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Gas

levels

in

production

Meltingmethods

Differentfoundries

Differentfurnaces

Longperiodoftime

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Gas

levels

in

productionOxygen

Dissolvedoxygen

Oxygenfound inoxides

Totalamount of oxygen

Difference betweenprocesses

Lennart Elmquist

Tammerfors 2012-11-0821

1250 1300 1350 1400 1450 1500 15500

0.5

1

1.5

2

2.5

3

3.5

4

Temperature [C]

Dissolvedoxygen[ppm

]

Source: Elmquist, Orlenius, Diszegi, 2007

1280 1320 1360 1400 1440 1480Temperature [C]

0

4

8

12

Totaloxygen[ppm]

Cupola furnace

Induction furnace

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Aftermoldfilling

Gas

levels

in

production

Lennart Elmquist

Tammerfors 2012-11-08

1 2Sample No

0

20

40

60

80

100

120

140

Nitrogenconcentration[ppm]

Before casting

In the mold

22Source: Orlenius, Elmquist, Diszegi, 2007

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Outline Gasdefects

Gasabsorption

Gasevolution

Inclusions

Shrinkageporosity Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

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Tammerfors 2012-11-0823

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Gas

absorption

Lennart Elmquist

Tammerfors 2012-11-08

Source: Orlenius et al, 2008

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Gas

absorption Investigaterelationshipgasabsorption moldfilling

Compare

simulation

realityTurbulenceduringfilling

Permeability

Binders

Lennart Elmquist

Tammerfors 2012-11-08

Source: Orlenius et al, 2008

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Gas

absorption

Lennart Elmquist

Tammerfors 2012-11-08

Source: Orlenius et al, 2008

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Gas

absorptionFillingvelocity

Lennart Elmquist

Tammerfors 2012-11-08

Source: Orlenius et al, 2008

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Gas

absorption Turbulentmouldfilling

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Tammerfors 2012-11-0828

Source: UAB Casting Engineering Laboratory (CEL), 2005

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Outline Gasdefects

Gasabsorption

Gasevolution

Inclusions

Shrinkageporosity Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

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Mould

and

core

gas

evolutionVolumeandrateofgasevolution

Lennart Elmquist

Tammerfors 2012-11-08

Source: Orlenius et al, 2008

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Gas

evolutionCoregeometry

Volumeequal

Amountofbinderequal

Highestrateforparallelepiped

Lennart Elmquist

Tammerfors 2012-11-08

Source: Orlenius et al, 2008

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Gas

evolutionBindertype

Inorganicbinder

Organicbinder

Amountofbinder

Storagetime

Temperature

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Tammerfors 2012-11-08

Source: Orlenius et al, 2008

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Gas

evolutionCoatings

Improvesurface

Aluminiumsilicate

Zircon

Dryingprocess

Lennart Elmquist

Tammerfors 2012-11-08

Source: Orlenius et al, 2008

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Outline Gasdefects

Gasabsorption

Gasevolution

Inclusions

Shrinkageporosity Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

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Tammerfors 2012-11-0834

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Inclusions

sand

Occuratwidelyvarying

positions

Sandtornawaybymetal

stream

InassociationwithCO

blowholesand

slag

Carefullyblowoutmold

cavities

Avoidhigh

pouring

rates

Ensureuniformmold

compaction

Edgedisintegration

Sand

crust

formation Erosion

Lennart ElmquistTammerfors 2012-11-08

Source: www.ikominerals.de

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Inclusions

slag

Irregularshape

Non

metallic

inclusions Uppercastingsurfaces

FormationofCO

Possiblecauses

Oxidecontentofthechargetoohigh

Poordissolutionofinoculants

Poorslagpractice

Lennart ElmquistTammerfors 2012-11-08

Source: www.ikominerals.de

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Inclusions

slag Filter

Designof

the

gating

system slagtraps

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Outline Gasdefects

Gasabsorption

Gasevolution

Inclusions

Shrinkageporosity Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

Lennart ElmquistTammerfors 2012-11-08

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Introduction

Lennart ElmquistTammerfors 2012-11-08

39

Source: Elmquist et al, 2008

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Shrinkage

Introduction

Shrinkagedefects

Openshrinkagedefects

(macroshrinkage)

Closedshrinkagedefects

(shrinkageporosity)

Generally

Liquidcontraction

Liquidtosolidcontraction

Solidcontraction

Lennart ElmquistTammerfors 2012-11-08

Castiron graphiteexpansion

Source: Stefanescu, 2005

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Shrinkage

Introduction

Factorspromotingshrinkageporosity

Natureandpropertiesofthesandmould

Metalcomposition

Pouringtemperature

Degreeofeutecticnucleationofthemetal

Solidificationmode

Compensatesfortheshrinkage

Feedingof

metal

Graphiteexpansion

Lennart ElmquistTammerfors 2012-11-08

Atmosphericgas Dissolvedgas(hydrogen,

nitrogen)

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Shrinkage

Introduction Differenttypesof

shrinkage

Relatedtocoolingcurve

Lennart ElmquistTammerfors 2012-11-08

42

Source: Soivio, Elmquist, 2012

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Shrinkage

Introduction

Lennart ElmquistTammerfors 2012-11-08

43

Source: Elmquist, Adolfsson, Diszegi, 2008

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Defect

characterization

Twofoundries

Twodesigns

Productionline

Withand

without

porosity

Lennart ElmquistTammerfors 2012-11-08

Case:CylinderHeads Economy

Environment

Shrinkageporosity Characteristicfeatures Knowledgeaboutmechanisms

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Defect

characterizationSimilarities

Positiononcasting

Surfacedefect

Connectionsurface

porosity

Lennart ElmquistTammerfors 2012-11-08

10mm

Penetratingthroughthe

casting

Enclosingcertainunits

Primarycrystals?

46

Source: Elmquist, Adolfsson, Diszegi, 2008

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Defect

characterization Borderbetweensurfaceandporosity

Oxidelayer connectionto

atmosphere

Nographitelayer

Lennart ElmquistTammerfors 2012-11-08

ShrinkagePorosityvs.Penetration

47

Source: Elmquist, Adolfsson, Diszegi, 2008

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Outline

Gasdefects Gasabsorption

Gasevolution

Inclusions Shrinkageporosity

Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

Lennart ElmquistTammerfors 2012-11-08

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Heatisremovedduringsolidification

Differentcoolingconditionsindifferentparts

Initialtemperaturesincasting/mold

Partofthecastingthatsolidifieslast

Migratesduringsolidification

Dependsongeometry

Heatremoval

Global/Localhotspots

Migratinghotspot

Lennart ElmquistTammerfors 2012-11-08

Y

T

L

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Migratinghotspot

Thermalcentre

at

mold/metal

interface

Migratinghotspot

Lennart ElmquistTammerfors 2012-11-08

CH1 CH2

50

Source: Elmquist, Adolfsson, Diszegi, 2008

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Migratinghotspot

Hotspotmigrates

Casting/moldinterface

Shrinkageporosity

Metalexpansionpenetration

Geometrydevelopedby

simulations

Finalpositionofhotspot

Lennart ElmquistTammerfors 2012-11-08

1200

1100

500

800

9001000

700

600

SOLTIME [s]

51

Source: Elmquist, Adolfsson, Diszegi, 2008

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Outline

Gasdefects Gasabsorption

Gasevolution

Inclusions Shrinkageporosity

Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

Lennart ElmquistTammerfors 2012-11-08

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ShrinkagePorosity

Developacastingthatgeneratesshrinkageporosity

Lennart ElmquistTammerfors 2012-11-08

53

Source: Elmquist, Diszegi, 2008

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Geometry generating porosity

Migrating hotspot

Lennart ElmquistTammerfors 2012-11-08

ShrinkagePorosity

54

Source: Elmquist, Diszegi, 2008

l d f

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Solidification

Solidificationofgreycastiron

Nucleation

Growth

Primaryaustenite

Eutecticcells

Lennart ElmquistTammerfors 2012-11-08

55

Source: Elmquist et al, 2008

S lidifi i

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Solidification

Lennart ElmquistTammerfors 2012-11-08

Equiaxed zoneColumnar

zoneMacrostructure

Microstructure

DendriteArmSpacing(SDAS)

FractionAustenite

Eutecticcellsize

Columnardendrites

Equiaxed dendrites

CET

56

Source: Elmquist et al, 2008

Sh i k d h

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Shrinkageandthemacrostructure

Similarities Shrinkageporosity

Surface

defects Penetratingnetwork

Contactwithatmosphere

Lennart ElmquistTammerfors 2012-11-08

57

Source: Elmquist, Diszegi, 2008

Sh i k d th t t

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Shrinkageandthemacrostructure

DAAS(DirectAustempering

AfterSolidification

Macrostructure

Equiaxeddendrites

Columnardendrites

CET

Lennart ElmquistTammerfors 2012-11-08

Columnarzone

Abnormalcolumnarzone

SimilarCET

58

Source: Elmquist, Diszegi, 2008

Sh i k d th t t

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Shrinkageandthemacrostructure

Porositybetweenprimarycrystals

Lennart ElmquistTammerfors 2012-11-08

59

Source: Elmquist, Diszegi, 2008

Sh i k d th t t

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Shrinkageandthemacrostructure

Formationofshrinkage

porosity

Hotspot

Migration

Lastareaofsolidification

Weakcolumnarzone

Atmosphericgas

Shrinkageporosity

Surfacedefect

Lennart ElmquistTammerfors 2012-11-08

60

Source: Elmquist, Diszegi, 2008

Outline

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Outline

Gasdefects Gasabsorption

Gasevolution

Inclusions Shrinkageporosity

Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

Lennart ElmquistTammerfors 2012-11-08

61

Penetration Introduction

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Penetration Introduction

Metalpenetrationisacastingconditionresulting

fromreactionsatthemouldmetalinterface

Physical

Mechanical

Thermochemical

Lennart ElmquistTammerfors 2012-11-08

Metalpenetrationisdefinedastheconditioninwhichcast

metalhasenteredintotheporespacesofthemoldandcore

beyondthe

mid

point

of

the

surface

layer

of

sand

grains.

(Draper and Gaindhar, 1977)

62

Penetration Introduction

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Penetration Introduction

Fourbasicmechanisms:

Mechanical(liquidstate)

Chemical

Vaporstate

Explosionpenetration

Theliquidmetalexerts:

Staticpressure

Dynamicpressure

Pressurebecauseofexpansion

Lennart ElmquistTammerfors 2012-11-08

Source: Stefanescu, 2008

Source: Draper and Gaindhar, 1977

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Penetration Introduction

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Penetration Introduction

Generallyoccursatlocationswherethesandisthehottest

(cores,concavesections)andisoflowestdensity

Lowsurface

tension

HighP,Si,orMncontent

Elevatedstaticordynamicmetalpressure

Highmetal

and

sand

temperature

Sandtoocoarse,orinsufficientlyrammed

Thermalconductivityofsandtoolow

Poorquality

mold

wash

or

blacking

Lennart ElmquistTammerfors 2012-11-08

(AFS International atlas of casting defects)

64

Penetration Introduction

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Penetration Introduction

Onlyremovedbyextensivechippingandgrinding

Oftensoseverethatcastingsarebeyondthepointof

economicalrework

and

must

be

scrapped

Toolwear

Lennart ElmquistTammerfors 2012-11-08

(Source: Levelink and Julien, 1973) 65

Penetration Introduction

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Penetration Introduction

Lennart ElmquistTammerfors 2012-11-08

Source: Diszegi and Dugic, 2007

66

Metal Expansion Penetration

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MetalExpansionPenetration

CASEStudy Cylinderheads

Shrinkage noPenetration

Noshrinkage Penetration

Lennart ElmquistTammerfors 2012-11-08

ShrinkagePorosityvs.Penetration

Migrating hotspot isrelated also topenetrationproblems

67

Source: Elmquist et al, 2008

Outline

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Outline

Gasdefects Gasabsorption

Gasevolution

Inclusions Shrinkageporosity

Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

Whatabout

the

future?

Summary

Lennart ElmquistTammerfors 2012-11-08 68

Metal Expansion Penetration

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MetalExpansionPenetration

Lennart ElmquistTammerfors 2012-11-08

Geometry generating metalpenetration

69

Source: Elmquist, Diszegi, 2008

Metal Expansion Penetration

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MetalExpansionPenetration

Lennart ElmquistTammerfors 2012-11-08

Columnar zone

Equiaxed zone

TestCasting

Source: Diszegi and Dugic, 2007

70

Metal Expansion Penetration

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MetalExpansionPenetration

Lennart ElmquistTammerfors 2012-11-08

Thevolumetric changes causeeither asurplusora

deficitofmelt

Hotspot atcasting/mold interface theweakest part

Source: Diszegi and Dugic, 2007

71

Metal Expansion Penetration

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MetalExpansionPenetration

Lennart ElmquistTammerfors 2012-11-08

Sand grains.

Equiaxed

austenite grains.

Columnar

austenite grains.

Liquid metal.

Eutectic cells.

Eutectic strip.

Penetrated

eutectic phase.

Source: Diszegi and Dugic, 2007

72

Metal Expansion Penetration

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MetalExpansionPenetration

Lennart ElmquistTammerfors 2012-11-08

Sand grains

Equiaxed

austenite grains.

Columnar

austenite grains.

Columnar to

equiaxed

transition.

Eutectic cells.

Penetrated

anomalous

phase containing

late nucleated

austenite

dendrites.

Source: Diszegi and Dugic, 2007

73

Outline

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Outline

Gasdefects Gasabsorption

Gasevolution

Inclusions Shrinkageporosity

Defectcharacterization

Migratinghotspot

Primaryaustenite

Metalexpansionpenetration Primaryaustenite

Otherqualityproblems

What

about

the

future? Summary

Lennart ElmquistTammerfors 2012-11-08 74

OtherProblems

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Residualstresses

Priorhistory

of

the

material

Segregation

Degeneratedgraphite

Lennart ElmquistTammerfors 2012-11-08 75

Source: Soivio, Elmquist, 2011

Source: Elmquist

WhatAboutFuture?

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Inspection/detection

Mostoftheproblemsneverreachthecustomer

Research

Processcontrol/thermalanalysis

Castingsimulation

Optimization

Manyoftheproblemscanbesolvedorminimizedwitha

combinationof

process

control

and

optimal

design

of

componentaswellasgatingsystem

Lennart Elmquist

Tammerfors 2012-11-08 76

Future

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Sustainability

Life

cycle

analysisTheinfluenceofdefects

Nearnetshape

Minimizethe

need

for

machining

Highperformingcastironmaterials

Increasedstrength

Lessvariationsinproperties

Lennart Elmquist

Tammerfors 2012-11-08 77

Outline

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Gasdefects Gasabsorption

Gasevolution

Inclusions Shrinkageporosity

Defectcharacterization

Migratinghotspot

Primary

austenite Metalexpansionpenetration

Primaryaustenite

Otherqualityproblems

What

about

the

future? Summary

Lennart Elmquist

Tammerfors 2012-11-08 78

Summary

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y

Casting

Mouldcavity

Meltingprocess

Pouring

Solidification

Mouldremoval

Cleaningandfinishing

Advantages

Complexshapes

Holesandinnercavities

Widerangeofalloys

Melttreatment

Economical

Lennart Elmquist

Tammerfors 2012-11-08 79

Summary

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Why?

Who

cares?

Lennart Elmquist

Tammerfors 2012-11-08 80

8/12/2019 Defect Formation in Cast Iron

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Thankyouforyourattention!

Lennart Elmquist

Tammerfors 2012-11-08 81