Casting Materials

Prof. Juhani Orkas

Overview

• Iron based – Grey iron – Nodular iron – White iron – Cast steel

• Nonferrous cast materials – Aluminium alloy – Magnesium alloy – Titanium alloy – Copper alloy – Nickel-base alloy

Iron-carbon diagram

• Cast iron – C > 2,06 %

• Grey cast iron – Stable system – Fe-C – Iron-graphite – Si, Ti, Al

• White cast iron – Metastable system – Fe-Fe3C – Iron-cementite – Mn, Cr, Mo

Classification of iron based materials

Iron based materials

Grey cast iron

Lamellar graphite

iron

GJL

Vermicular graphite

iron

GJV

Spheroidal graphite

iron

GJS ADI

Alloyed cast iron

White cast iron

Malleable iron

Whiteheart melleable

iron

GJMW

Blackheart malleable

iron

GJMB

Chilled iron

GJN

Cast steel

GS

http://www.hoffmann-group.com/download/de/zhb_2006_2007/teil/web_pdf/053-093.pdf

Cast iron

• Carbon cut out as Graphite – Grey color at the fracture surface

• Silicon – Graphite stabilizing

• Compressive strength higher than tensile strength (~2:1) – No bond between Iron and Carbon

• Good machinability – Carbon interrupts the metal micro-structure – Carbon lubricates the cutting tools

• Designation system: GJ(Symbol) - Rm

Cast iron - Overview

• Lamellar graphite iron (GJL) – Pressure and wear-resistant – Corrosion-resistant – Good damping characteristics – Low tensile strength and elongation at fracture – Low costs

• Vermicular graphite iron (GJV) – Between GJL and GJS – Low thermal expansion

• Spheroidal graphite iron (GJS) – Ductile – High tensile strength and elongation at fracture

Wikipedia: Datei:GGV-GGG.jpg

Cast iron - Overview http://mciron.mw.tu-dresden.de/lut/vorlesung/script_ft1/FT1%20VL%20%202%20Gu%C3%9Ftechnik.pdf

Un-etched photomicrograph

SEM image

Lamellar graphite iron GJL

• Ferritic-pearlitic structure – Rm ≤ 400 MPa – Poor toughness – Good compressive strength

• Cooling conditions affects microstructure – Tensile strength depends on wall-thickness – Higher strength in thin walls

• Very good damping capacity (Vibration) – GJL : GJS : Steel 1 : 1,8 : 4,3

• Notch-sensitive – High tension gradient at graphite flakes

• Good friction properties • Very good pouring properties

http:// http://www.htw-aalen.de/gta/de/eisenguss/eisenguss.htm

EN GJL-250

Surface hardening

• Thermophysical hardening – Martensitic hardening

• 55 – 60 HRC – Ledeburitic hardening

• Better wear resistance

• Thermochemical hardening

http://www.kug.bdguss.de/fileadmin/content/Publikationen-Normen-Richtlinien/buecher/GJL.pdf

• Gearbox for a printing machine – EN GJL-250

Lamellar graphite iron GJL

• Bed for machine tools – EN GJL-250 /-300 – Up to 12,8 m

www.claasguss.de/pdf/psst_ant_5_2007.pdf

Spheroidal graphite iron GJS

• Add magnesium or cerium – Spheriodal graphite

• Ferritic-pearlitic structure – Rm ≤ 800 MPa – Moderate toughness

• Less Notch-sensitive than GJL – Average tension gradient at

graphite spheres • Moderate damping capacity • For mechanical stresses parts

http:// http://www.htw-aalen.de/gta/de/eisenguss/eisenguss.htm

EN GJS-400

EN GJS-700

Spheroidal graphite iron GJS http://www.claasguss.de/html_e/pdf/THBl2_engl.pdf

• High C- and Si-level – Low strength and Brinell hardness – High elongation at fracture

Spheroidal graphite iron GJS

• Cylinder block for marine diesel engine – EN GJS-400-18U – 9 x 2.84 x 3.35 m – 81‘450 kg

• Rotor hub (1.5MW) – EN GJS-400-18U-LT – 3.128 x 2.7 x 2.1 m – 8’400 kg

http://www.fwh.de/produkte.html

Austempered ductile iron ADI

• Multi-step heat treatment of GJS • Bainitic-similar structure

– Acicular ferrite and carbon-enriched austenite (without carbide precipitation!)

– Rm ≤ 1400 MPa – Steely characteristics

• Very good wear resistance – Even greater with added hard carbides

(CADI) • Lower specific weigh than steel (~10%)

– Comparable mechanical properties

http://schonlau-werke.de/en/manufacturing-products/materials/austempered-ductile-iron http://www.claasguss.de/html_e/html/produkt_02_05.html

ADI 800/ EN GJS-800-8

Austempered ductile iron ADI

• Relative weight • Relative costs

http://www.ductile.org/didata/section4/4intro.htm

Multi-step heat treatment ADI

• Austenizing – Heating above AC1 temperature (840 - 950°C) – Completely austenitic microstructure

• Quenching – Avoid formation of perlite

• Austempering – Salt / oil bath or oven (250 – 450°C) – Isothermal transformation – Ferrite needles and austenite (Ausferrite) – Too short holding

• metastable residual austenite – Too long holding:

• real bainite (ferrite with carbide precipitation)

http://www.claasguss.de/html_e/pdf/THBl8_engl.pdf

Multi-step heat treatment ADI

• Austenitised at 950°C, austempered at 250°C for 50 min – high strength with high hardness

and high wear resistance but imited ductility

http://www.msm.cam.ac.uk/phase-trans/2001/adi/adimore.html http://www.claasguss.de/pdf/08_TH_ADI.pdf

• Austenitised at 950°C, austempered at 400°C for 53 min – low strength at higher elongation

at fracture

Austempered ductile iron ADI http://www.htw-aalen.de/gta/de/eisenguss/eis

http://www.ductile.org/didata/section4/4intro.htm enguss.htm

• ADI gears – Hymi Kymmene Engineering,

Finland

• ADI crankshaft – TVR sportscar

Vermicular graphite iron GJV

• Deliberately insufficent treatment to build Spheriodal graphite – Three-dimensional worms

• Properties between GJL and GJS

• Ferritic-pearlitic structure – Rm ≤ 600 MPa

• Especial suitable for thermal and mechanical stressed parts

http://www.claasguss.de/html_e/pdf/THBl12_engl.pdf

EN GJV-400

Vermicular graphite iron GJV

• Advantages to GJL – Better tensile strength and

elongation at fracture – Higher fracture toughness – Properties are less dependent

on wall thickness

• Advantages to GJS – Lower coefficient of thermal

expansion – Higher heat conductivity – Lower modulus of elasticity – Better thermoshock resistance

and lower tendency to distortion

– Better damping capacity – Better pouring properties

http://www.claasguss.de/html_e/pdf/THBl12_engl.pdf

Vermicular graphite iron GJV

• MAN TG-A cylinder block – EN GJV-450 – 430 PS

http://www.claasguss.de/html_e/pdf/THBl12_engl.pdf http://trucks.autoreview.ru/new_site/trucks/archives/2004/n03/4_man/1.htm

• Audi V12 TDI crankcase – EN GJV-450 – 500PS / 1‘000 Nm – More rigid and fatigue-resistant

• Thinner walls and less weigh

Austenitic cast iron materials GJSA

• > 20% nickel (Ni-Resist) • Austenitic structure • Extremely corrosion resistant

– Sea water & alkaline media • High heat resistance • Adjustable thermal coefficient of expansion

– Nickel contend • Max at ~20% • Min at ~35%

• Laminar and spheroidal graphite possible • Non-magnetizable • Good running properties

http://www.edelstahlwerke-schmees.de/content/picture/upload/image/werkstoffe/wk8_big.JPG

EN GJSA-XNiCr20-2

Austenitic cast iron materials GJSA

• Cylinder block for LNG – 35% Nickel – Huge temperature difference

between suction and pressure valve

• Housing of turbocharger K16 BorgWarner – Temperatures around 1000°C

x

White cast iron Google Books: Gefüge Der Gusseisenlegierungen

White cast iron

Malleable iron

Whiteheart melleable

iron

GJMW

Blackheart malleable

iron

GJMB

Chilled iron

GJN

White cast iron

• Carbide stabilizing elements (Mn, S) – Graphite-free solidified

• Fe3C – Perlit and ledeburit (hypoeutectic) – White color at the fracture surface – Hard and brittle

• Less applications

• Intermediate product in steel production – Heat treatment for malleable iron

• Cementite decompose to temper carbon (equiaxed nodular graphite) • Temper carbon interrupts matrix less then carbon in grey iron

– Better mechanical properties

Google Books: Gefüge Der Gusseisenlegierungen

x

Whiteheart malleable cast iron GJMW http://www.hitzbleck.de/englisch/products.htm

• Malleablizing in oxygen containing atmosphere

• 60 to 120 h at 1000°C • Cementite decompose to Fe and C

– Fe3C → 3Fe + C • Carbon diffuses outwards • Converts in the surface to CO and CO2

– C + O2 → CO2

• Decarburization depends on wall-thickness – Max. 8mm for complete decarburization

• Residual carbon as Temper carbon

Functionally graded http://www.hitzbleck.de/gradienten.htm

• Surface – Graphite-free, ferritic structrue – High ductility – Excellent machinability – Suitability for welding – Suitability for surface treatment

• Transition – Ferritic-perlitic structrue with temper

carbon • Core

– Perlitic structure with temper carbon – High stiffness

Weldability http://www.hitzbleck.de/

• Residual carbon content < 0.3% at weld area

• No preparation and postprocessing • All welding methods • No hardness increaseing • Suitable for connecting complex

casted parts with semi-finished products

Cold forming http://www.hitzbleck.de/

Blackheart malleable cast iron GJMB

• Malleablizing in neutral atmosphere – Inert gas

• 1st level of graphitization – approx. 20 h at 940 - 960°C – Cementite decompose to Fe and C

• Fe3C → 3Fe + C – Temper carbon in a austenitic matrix

• 2nd level of graphitization – Cooling to 700 - 800°C – Eutectoid transformation γ → α + C

• Carbon from austenite diffused to existing temper carbon

– Cooling rate affects the final matrix

http://de.wikipedia.org/wiki/Temperguss http://www.msm.cam.ac.uk/phase-trans/2001/adi/cast.iron.html

Matrix of GJMB

• Ferritic structure – Slow cooling to 700 – 800°C – Stable eutectoid transformation – Temper carbon evenly distributed

• Perlitic structure – Fast cooling – Metastable solidification to perlite

• Martensitic structure – Very fast cooling – Suppressed diffusion – Martensite

• Mixed structure

http://de.wikipedia.org/wiki/Temperguss

Chilled iron GJN

• High S and Mn or rapid cooling • Surface

– White iron – Graphite-free cementite

• Ledeburiteutecticum – Up to 20 mm – Extreme hard and wear

resistant • Core

– Grey iron – Perlitic structure with laminar

graphite

x http://www.metallographie-ausbildung.de/wasist.html

Chilled iron GJN

• Extrealmy wear-resistant – Rolls – Milling disks – Ore crusher – Crawler elements – Armor plates

http://www.walzenirle.com/de/walzen/papierindustrie/produktspektrum/standard-kalanderwalzen/standard-kalanderwalzen.html

http://www.weartechnology.com.my/brochures/Castings.pdf

Cast steel GS

• Advantages – Mechanical properties of steel

together with the castability – Malleable – Wide range of materials – Adjusable strengt properties

• Heat treatment necessary

• Disadvantages – Higher melting point > 1400°C

• High demands on technology – Bad mould-filling capacity

• More viscouse than cast iron – hypoeutectic

– High shrinkage ~2% – Castings without heat

treatment unusable • Brittle • Coarse grain • Dendritic

http://www.maschinenbau-wissen.de/skript/werkstofftechnik/stahl-eisen/31-stahlguss

Cast steel GS http://www.voestalpine.com/giesserei_traisen/de/products/foundry_products.html

• Pelton wheel – High strengt

• Shunting switch – G-X120Mn12

Classification of nonferrous cast materials

Nonferrous cast materials

Light metal cast

Aluminum casting

G-Al

Magnesium casting

G-Mg

Titanium casting

G-Ti

Heavy metal cast

Copper casting

G-Cu

Pewter casting

G-Sn

Lead casting

G-Pb

Zinc casting

G-Zn

Precious metal cast

Gold casting

G-Au

Silver casting

G-Ag

Platinum casting

G-Pt

http://www.hoffmann-group.com/download/de/zhb_2006_2007/teil/web_pdf/053-093.pdf

Aluminum alloy

• Suitable for complex thin-walled parts • High dimensional accuracy • Low weight with high rigidity

– Good strength-weight ratio • Smooth surfaces and edges • Good machinability • High thermal conductivity • Good electrical conductivity • Corrosion and weathering resistance • Several surface treatments possible

http://www.openpr.de/news/278394/Aluminiumguss-verdraengt-herkoemmlichen-Grau-und-Stahlguss.html

Aluminum alloy – designation system http://www.eaa.net/eaa/education/TALAT/lectures/1501.pdf

Aluminum alloy http://www.eaa.net/eaa/education/TALAT/lectures/1501.pdf

Aluminum alloy

• Casting alloys – Most common

• 4xxx – For die casting

• 4xxx • 5xxx • 7xxx

– For gravity die casting • 2xxx • 4xxx • 5xxx • 7xxx

xxx

Aluminum alloy http://www.hoffmann-group.com/download/de/zhb_2006_2007/teil/web_pdf/053-093.pdf

http://www.msm.cam.ac.uk/phase-trans/abstracts/M7-8.html

• Al Si (4xxx) – Near eutectic (12% Si)

• Low melting point (576°C) • Good fluidity • Less shrinkage • High strength

– Hypereutectoid (up to 25% Si) • Used as piston alloy • Worse fluidity • Primary solidification of Si • Higher wear resistance due to

Si crystals • Lower coefficient of expansion

Aluminum alloy http://mciron.mw.tu-dresden.de/lut/vorlesung/script_ft1/FT1%20VL%20%202%20Gu%C3%9Ftechnik.pdf

Hypoeutectic Eutectic Hypereutectic

Aluminum alloy - Treatments

• “F” – Without treatment

• “O” – Solution annealed – Dead soft, low strength

• “T” – Heat treated

• “H” – Strain hardened – i.e. for non age

hardening alloys

http://aluminium.matter.org.uk/content/html/eng/default.asp?catid=214&pageid=2144417057

Precipitation hardening

• Before Treatment – Precipitates along grain

boundaries • Solution Heat Treatment

– Heat above solvus temperature

– Dissolve any precipitates – Alloying elements in solid

solution • Quench

– No time to diffuse – Supersaturated solid solution

http://www.hsc.csu.edu.au/engineering_studies/aero_eng/2580/aluminium_alloys.html http://www.azom.com/details.asp?ArticleID=2540

Precipitation hardening

• Hardening – Below solvus temperature – Alloying elements diffuses to

coherent precipitate clusters • Increases strength and

hardness – Natural ageing

• Room temperatur • Stops after several hours

– Artificial ageing • Precipitation heat treatment • Higher hardness then with

natural ageing

http://www.hsc.csu.edu.au/engineering_studies/aero_eng/2580/aluminium_alloys.html http://www.azom.com/details.asp?ArticleID=2540

Precipitation hardening

• Overageing – First partially coherent

precipitations – Later incoherent

precipitations – Reduced tensile strength

• Remember for designing

parts with a higher operation temperature!

http://www.hsc.csu.edu.au/engineering_studies/aero_eng/2580/aluminium_alloys.html

AlCu 2014-T6

Precipitation hardening

• Differential housing from KSM Castings GmbH – Cast-on rivets – Connect housing cover with

housing bell – Clinch rivets directly after

quench – Artificial ageing for final

strength and hardness

http://www.alumag.de/downloads/Innovation%20durch%20Aluminiumguss,%20KSM.pdf

• BMW integral cross member – EN AC - AlMg5Si2Mn – Weldable without pre-treatment

Aluminum alloy

• Daimler valve body – AlSi9Cu3 – Wall-thickness: 2-6mm – Drafts: 1° (valve core 5°)

http://www.alumag.de/downloads/Innovation%20durch%20Aluminiumguss,%20KSM.pdf

Magnesium alloy

• Lightest of all structural metals – ~ 1800 kg/m3

– Excellent strength-weight ratio

• Hexagonal lattice – High strength – High electrical and thermal conductivity – Without Al and Zn

• Brittle • Notch-sensitive

• Excellent machinability • Good damping coefficient

– Better vibration reduction than Al or GJx

http://www.dynacast.com/casting/magnesium/

Magnesium alloy

• Al and Zn – Avoid problems with brittleness

and notch-sensitivity • Mg

– Increases corrosion resistance • Ce and Th

– Increases high temperature strength

• Zr – Grain refinement – Increases strength and

formability

Roos, Maile: Werkstoffkunde für Ingenieure

Magnesium alloy – designation system

• Two letters for the major alloying elements • Two digits for the approximate percentage of the elements • May an additional letter for the different alloy modifications • Example: AZ91C

– Approx. 9% Al; approx. 1% Zn; the 3th modification

http://www.arcraftplasma.com/welding/weldingdata/metalstd.htm

Titanium alloy

• Very high tensile strength and toughness – even at extreme temperatures

• Light weight • Properties depending on phase

– α phase – α+β phase – β phase

• Extreme corrosion resistance – Very dense TiO2 layer – Biocompatibility

• Expensive

xx

Titanium alloy

• α phase – Good fracture toughness – Good creep resistance – Not heat-treatable

• α+β phase – High mechanical strength

• Up to 1000 MPa – Heat-treatable

– Ti6Al4V (50% of world usage)

• β phase – Heat-treatable – Very high strength

• up to 1400 MPa

http://www.substech.com/dokuwiki/doku.php?id=classification_of_titanium_alloys

Copper alloy xx

• Properties – Corrosion resistance – Good bearing qualities – Attractive appearance

• Bronze – CuSn

• Brass – CuZn

• Red brass (gunmetal) – CuZnSn

• Aluminium bronze – CuAl

CuSn11 (50:1)

CuAl20 (500:1)

Bronze (CuSn) http://www.kupfer-institut.de/front_frame/frameset.php3?client=1&lang=1&idcat=33&parent=14

• Up to 20% Sn – 9 – 12% for casting alloys

• Nonmagnetic • High thermal and electrical

conductivity • High corrosion resistance

– Seawater resistance • Good wear resistance • Good damping coefficient • Red brass (CuZnSn)

– Cheaper due to cheap Zn – Similar properties

Brass (CuZn)

• 5 to 45 % Zn • Tensile strength up to 750 MPa • No cryogenic embrittlement • Good corrosion resistance

– Depends on alloying element • Antimicrobial

– Used at public places • Specialbrass

– CuZn + other element

• Impeller for a pump – CuZn37Mn3Al2PbSi

http://www.kupfer-institut.de/front_frame/pdf/i05_0307.pdf http://www.otto-fuchs.com

• Multi Cone Synchro System – Depends on the application

Aluminium bronze (CuAl)

• 9 – 14% Al • High corrosion resistance

– Seawater resistance • Good wear resistance • Good cavitation resistance • Applications

– Ship propeller – Sliding elements – Bearings – Chemical industries – Gear wheels

• World largest ship propeller (MMG) – CuAl9Ni6Fe5Ma – Container ship with 120,000 PS – 9,6 m; 131 t

http://www.kupfer-institut.de/front_frame/frameset.php3?client=1&lang=1&idcat=33&parent=14

Nickel-base alloy

• Pure nickel – Ductile and tough

• face-centered cube crystal structure up to its melting point

• High resistance against – Corrosion environments – High temperatures (≤1100°C) – High stresses

• Base for developing specialized alloys

• Intermetallic phases – very high strength alloys – low- and high-temperature

http://www.kupfer-institut.de/front_frame/frameset.php3?client=1&lang=1&idcat=33&parent=14