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Introduction to Ferrous Materials (I) WS 2017/18Lecture 6Cast IronsDr. Javad MolaInstitute of Iron and Steel Technology (IEST)Tel: 03731 39 2407E-mail: mola@iest.tu-freiberg.de1
Fe-C Phase DiagramDashed lines:Fe-Gr. diagramStable systemIntroduction to Ferrous Materials (I) WS 2017/18Solid lines:Fe-Fe3C diagramMetastable system LPeritectic reactionSteels๐น ๐ณ๐๐.Steelsandcastirons๐๐๐๐ ๐ช , ๐.๐๐ ๐๐%๐ชAustenite Fe3C / Gr.๐ธEutectoid reaction๐ญ๐ ๐ช๐ธี๐ถ แ ๐๐ฎ๐.Ferrite Fe3C / Gr.Eutectic reactionCastirons๐ณ๐๐. ี ๐ธ แ๐ญ๐๐ ๐ช๐ฎ๐.SteelCast IronASM Handbook: Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys, ASM International, Materials Park, Ohio, 1992.2
Carbon Equivalent Concept๐ช๐ฌ %๐ช Introduction to Ferrous Materials (I) WS 2017/18Si displaces theeutectic point to lowercarbon concentrations.The Carbon Equivalent(CE) equation belowtakes into account theeffect of Si and P onthe displacement of theeutectic point. Eutecticcomposition is wherethe CE is equal to 4.3.(%๐บ๐ %๐ท)๐Pseudo-binary Fe-2.5 wt.%Si-C Phase DiagramASM Handbook: Volume 15: Casting, ASM International, Materials Park, Ohio, 1992.3
Hypo-eutectic(primary formation aboveeutectic temp.)4.3%CEutecticHyper-eutectic(primary Fe3C or Gr. formationabove eutectic temp.)Liq. Gr. (kish Gr.)Liq.Liq. Liq. Fe3C1150 C๐ณ๐๐.๐๐๐๐ ๐ช , ๐.๐ ๐๐.%๐ช๐ญ๐ ๐ช๐ธ แ ๐๐ฎ๐.White iron (ledeburite)Gray ironGraphitizationpotential low๐ธ๐๐๐๐๐๐๐ (๐ญ๐๐ ๐ช ๐ธ)๐ญ๐๐ ๐ช๐๐๐๐๐๐๐ (๐ญ๐๐ ๐ช ๐ธ)Graphitizationpotential high๐ธ๐๐๐๐๐๐๐ (๐ฎ๐. ๐ธ)๐ฎ๐.๐๐๐๐๐๐๐ (๐ฎ๐. ๐ธ)723 C34wt.%C564Introduction to Ferrous Materials (I) WS 2017/18Constitution of Cast Irons
Cast Irons: OverviewPearlite Gr. Gr.(cooling througheutectoid interval)Gray castironSlowFerrite Gr.Graphite shapeHighFlakeLiquidcast alMottledcast iron Fe3C Gr.Low Fe3CSolid-statetransformation(cooling througheutectoid interval) Fe3C Gr.Cool througheutectoidintervalFastPearlite Temper Gr.Hold aboveeutectoidintervalPearlite Fe3CWhite ironReheat aboveeutectoidinterval Fe3CSlowFerrite Temper Gr.Malleable ironASM Handbook: Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys, ASM International, Materials Park, Ohio, 1992.5Introduction to Ferrous Materials (I) WS 2017/18FastSolid-statetransformation
Introduction to Ferrous Materials (I) WS 2017/18Cast Iron: Applications6
Decreasing graphitization potentialIntroduction to Ferrous Materials (I) WS 2017/18Graphitization; Role of Alloying ickelHigh graphitization adiumHigh negative graphitization potentialASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996.7
Chemical CompositionIntroduction to Ferrous Materials (I) WS 2017/18Carbon and silicon composition ranges ofdifferent classes of cast irons and steels.4.32.0ASM Handbook: Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys, ASM International, Materials Park, Ohio, 1992.8
The tendency of an iron to solidify as white or gray iron may be evaluated bycasting a wedge-shaped specimen. The fracture surface is then examined andthe distance from the wedge tip to the end of the white zone is measured. Thelarger the white zone, the higher the tendency of the steel to solidify as white iron.Gray๐ณ๐๐. ี ๐ธ ๐ญ๐๐ ๐ช ๐ฎ๐. Mottled๐ณ๐๐. ี ๐ธ ๐ญ๐๐ ๐ชThinner section,higher cooling rate๐ณ๐๐. ี ๐ธ ๐ฎ๐.WhiteG.F. Vander Voort, Metallography, Principles and Practice, ASM International, 1984.9Introduction to Ferrous Materials (I) WS 2017/18Wedge Test
Wedge TestASM Handbook: Volume 15: Casting, ASM International, Materials Park, Ohio, 1992.Introduction to Ferrous Materials (I) WS 2017/18Gray IronFe-3.52 C-2.55 Si-1.01 Mn-0.215 P-0.086 S10
ationrangeCast nVolume change upon solidification (%)SteelExpansionupon freezinggray ironsallows toproduceriserlesscastingsCarbon, mass-%(Eutectic)TemperatureSchematic illustration of three shrinkageregimes in most alloys: in the liquid;during freezing; and in the solid stateJ. Campbell, Castings, Butterworth Heinemann, 2nd Edition, 2003.The volume change on freezingof Fe-C alloys.11Introduction to Ferrous Materials (I) WS 2017/18Expansion during Graphite Formation
Primary above eutectoidtemperature, pearlite ( Fe3C) below eutectoidtemperatureLedeburite( Fe3C right after eutecticsolidification, pearlite Fe3C below eutectoidtemperature)12Introduction to Ferrous Materials (I) WS 2017/18White Cast Iron
High hardness and abrasion resistance Low Carbon Equivalents (CEs) Usually used after alloying with Cr (high-Cr white iron) or Ni Cr (Ni-hard whiteiron) for higher hardnesses The high hardness originates from a hard martensitic matrix and the presenceof a large fraction of hard alloy carbides such as M3C and M7C3 (M denotesCr, Fe, )Example compositions of high-alloy white 3.61.3 max0.8 max3.3-3.51.4-41.0 maxNi-Hi Cr2.5-3.61.3 max1.0-2.25.0-7.07.0-11.01.0 max12%Cr2.4-2.80.5-1.51.0 max0.5 max11.014.00.5-1.020%Cr-Mo-LC2.0-2.60.5-1.51.0 max1.5 max18.023.01.5 max25%Cr2.3-3.00.5-1.51.0 max1.5 max23.028.01.5 maxASM Handbook: Volume 15: Casting, ASM International, Materials Park, Ohio, 1992.13Introduction to Ferrous Materials (I) WS 2017/18White Cast Iron
Typical graphiteshapes according toASTM A247 standard.SpheroidalCompactedImperfect spheroidalCrabIntroduction to Ferrous Materials (I) WS 2017/18Gray Iron: Graphite ShapesTemperExplodedFlakeASM Handbook: Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys, ASM International, Materials Park, Ohio, 1992.14
Introduction to Ferrous Materials (I) WS 2017/18Gray Iron (Iron with Flake Graphite)Graphite flakes in a ferritic matrix Graphite flakes in FG iron can take various shapes, sizes, and orientations depending oncomposition and casting conditions Excellent damping capacity Brittle Good machinability because of easy chip formation and cutting tool lubrication by graphite Good heat conduction due to interconnected graphite flakes The matrix microstructure depends on the cooling conditions through the eutectoid interval(usually pearlite or ferrite rather than martensite) Graphitization is aided by the inoculation process. Inoculation agent (usually ferrosilicon orgraphite) which is added to the melt just before casting promotes the nucleation of graphiterather than cementite during solidification.ASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996.15
Introduction to Ferrous Materials (I) WS 2017/18Ductile Iron (Iron with Spheroidal Graphite)Graphite nodules in a ferritic matrix Also known as spheroidal graphite (SG) iron or nodular ironGraphite is more or less spherical in shapeThe size and the number of graphite nodules per unit area influences mechanical propertiesHigher ductility than gray ironThe matrix microstructure depends on the cooling conditions through the eutectoid interval(usually pearlite, ferrite or a mixture of both although martensite formation is also possible athigh cooling rates) Spherical graphite is achieved by the addition of elements such as Mg. The process of Mgaddition to the melt is challenging because of its ready evaporation.ASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996.16
Ductile IronElement categoryElementSpheroidizer:Magnesium, calcium, rareearth elements (cerium,lanthanum, etc.), yttriumNeutral:Iron, carbon, alloyingelementsAnti-spheroidizer:Aluminum, arsenic,bismuth, tellurium, titanium,lead, sulfur, antimonyIntroduction to Ferrous Materials (I) WS 2017/18Influence of minor elements on graphite shapeThe amount of Mg required to produce spheroidal graphite is 0.03-0.05 wt.%. In practice,however, more Mg is required to account for the recovery rate of the technique used for the Mgaddition and to compensate for the Mg loss due to the MgS formation;Mg added 0.75 S net Mg level needed for spheroidizationRecovery of Mg in the Mg addition technique utilized(fraction of Mg which actually enters the melt)ASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996.17
Ductile IronIntroduction to Ferrous Materials (I) WS 2017/18Bullโs-eye microstructures in SG ironFe3C-free ferriticlayer next tographite nodulesPearlitic matrixAs cast iron cools throughthe eutectoid interval, Cdiffusion to the alreadyexisting graphite nodulescauses an Fe3C-free layernext to the graphite nodules18
Matrix TypesIntroduction to Ferrous Materials (I) WS edductile iron (ADI)19
Austempered Ductile Iron (ADI)Introduction to Ferrous Materials (I) WS rmation(austempering)TemperatureTemperatureFerrite GraphitePearliteMsBainiteMartensiteTime1 ksi 7 MPaTimehttp://www.totalmateria.com/page.aspx?ID CheckArticle&site kts&NM 24320
Introduction to Ferrous Materials (I) WS 2017/18Compacted Graphite IronCompacted graphite in a ferritic matrix Also known as CG iron or vermicular graphite iron Graphite shape intermediate between spheroidal and flake Microstructure of CG iron is free of flake graphite and the amount of spheroidal graphite is lessthan 20% Properties intermediate between FG and SG Produced by the addition of Mg in amounts lower than needed to obtain SG or by combinedaddition of spheroidizing and anti-spheroidizing elements (for example Mg Ti addition)ASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996.21
Introduction to Ferrous Materials (I) WS 2017/18Malleable IronTemper graphite in a ferritic matrix Also known as temper graphite (TG) iron Production method: Solidification as white iron (therefore not applicable to heavy sections) Subsequent reheating and holding at temperatures between eutectoid and eutectictemperatures (typically 950 C) for cementite decomposition to temper graphite (1st stage) Controlled cooling to obtain the desirable matrix microstructure (2nd stage) Graphite morphology and mechanical properties similar to SG Applicable to thin sections where solidification as ductile iron is not possible Small amounts of elements such as Bi and Te are used to suppress graphite formation duringsolidification (0.01 wt.% Bi, 0.0005-0.001 wt.% Te) Elements such as B and Al are used to speed up the cementite decomposition during the 1 st heattreatment stage (0.001 wt.% B, 0.005 wt.% Al)ASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996.22
Introduction to Ferrous Materials (I) WS 2017/18Malleable Ironundissolved cementiteTemper carbon graphite surroundedby ferrite in a matrix of pearliteExample of incomplete malleablizationheat treatment.23
Driveline yokesConnectingrodsSteering gearhousingDiesel pistonsASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996.24Introduction to Ferrous Materials (I) WS 2017/18Mealleable Iron: Automotive Applications
Graphite flakes act as internal defects and cause stress concentration. Stressconcentration is especially pronounced in the case of flake graphite.GraphiteflakeJ. Peterseim, Lecture notes for Materials Engineering II (Werkstofftechnik II), FH Mรผnster.Graphitenodule25Introduction to Ferrous Materials (I) WS 2017/18Stress Concentration at Graphite Flakes
Vibration oads/2011/03/Reducing-Gear-Noise.pdfIntroduction to Ferrous Materials (I) WS 2017/18Relative damping behaviors of steel, ductile &malleable irons and gray iron26
Rough comparison of the properties of steels and gray cast ironsSteelGray Cast IronCarbon contentless than about 2 wt.%more than about 2 astabilitylowhighConsumptionhighlowGraphite hWeldabilityhighlow27Introduction to Ferrous Materials (I) WS 2017/18Steel vs. Cast Iron
28Introduction to Ferrous Materials (I) WS 2017/18
ASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996. WS 2017/18 23 Malleable Iron . heat treatment. undissolved cementite. WS 2017/18 24 Mealleable Iron: Automotive Applications ASM Specialty Handbook: Cast Irons, ASM International, Materials Park, Ohio, 1996. Driveline yokes Connecting rods Diesel pistons .
200 series, 302, 303, 304, 316 stainless steel (austenitic) 304l, 316l stainless steel (martensitic) 403, 410, 416, 440 high strength tool steels 4140, 4340, 6150, 5210, a2, d2, p20, h11, h13, s2, 01 carbon steels 1000โs, 1100โs, 1300โs ductile ductile cast irons cast irons gray cast irons material /
Resistance to heat, oxidation and corrosion are appreciably enhanced with alloyed irons. However, since cast irons contain more than 2% carbon, 1 to 3% silicon and up to 1% . This high value results from many factors, one of which is the control of microstructure and properties that can be achieved in the as-cast condition, enabling a high .
resistance provides relatively long service lives. Resistance to heat, oxidation and corrosion are appreciably enhanced with alloyed irons. However, since cast irons contain more than 2% carbon, 1 to 3% silicon and up to 1% manganese, . The microstructure provides properties that make malleable irons ideal for applications where toughness and .
Iron, Fe Remainder 2.2. As-Cast Gray Cast Iron The original microstructure of the as-cast GI is shown in Figure1. The main components in the matrix were graphite ๏ฌakes, ferrite, and pearlite. Metals 2019, 9, x FOR PEER REVIEW 3 of 14 Figure 2. Table 1. Alloy content for gray cast iron. Elements Percentage Carbon, C 3.53% Silicon, Si 2.71%
heat treatment by holding at 7500 C for 6 h, cooling at , 300 C/h to 6500 C, and holding at 6500 C for 36 h. The 1095 steel was spheroidized by holding at 7150 C for 6 h, followed by a 36-h hold at 6800 C. Cast irons were prepared il1 60- and 120-lb heats by induction melting in magnesium oxide crucibles.
Selection of bolting for equipment subject to the Pressure Equipment Directive 97/23/EC 12.8.2016 CEN EN 1562:2012 Founding โ Malleable cast irons 12.8.2016 CEN EN 1563:2011 Founding โ Spheroidal graphite cast irons 12.8.2016 CEN EN 1564:2011 Founding โ Ausfer r itic sp
equipment subject to the Pressure Equipment Directive 97/23/EC CEN EN 1562:2012 Founding - Malleable cast irons EN 1562:1997 Note 2.1 Date expired (30.9.2012) CEN EN 1563:2011 Founding - Spheroidal graphite cast irons EN 1563:1997 Note 2.1 Date expired (3.8.2012) C 128/2 Official Journal of the European Union 4.5.2013EN
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