Inoculation of Cast Irons ΠAn Overview - Foundry

1 55th Indian Foundry Congress 2007 Inoculation of cast Irons An Harvey and HarveyTennant MetallurgicalGroup Ltd,Chesterfield,United NobleTennant MetallurgicalGroup Ltd,Chesterfield,United KingdomInoculation of cast Irons - an overview34355th Indian Foundry Congress 2007344J. N. Harvey and G. A. NobleInoculation of cast Irons An Harvey and NobleINTRODUCTIONoWhy inoculate?oHow to inoculate?oWhat inoculant?oCase OF DUCTILE & GREY IRONThe main purpose of Inoculation is to achieve best mechanical properties and optimummachinability characteristics of graphite or reduction of of casting section Indian Foundry Congress 2007 Inoculation of cast Irons - an overview345 Fig.

2 1 : iron Carbon equilibrium diagramFig. 2 : Carbon equivalent diagramFig. 3 : Eutectic transformation55th Indian Foundry Congress 2007346J. N. Harvey and G. A. NobleFig. 4 : Cooling CurveFig. 5 : Cooling Curve - Chill FormationDUCTILE INOCULATIONoOptimum nodule shapeoDegree of nodularityoImproves nodule countoPrevention of formation of carbidesoIncreases ferrite NODULE SHAPEU ninoculated Ductile IronNodular GraphiteStereoscan 950 Nodular Graphite55th Indian Foundry Congress 2007 Inoculation of cast Irons - an overview34780%60%Degree of Nodularity95%55th Indian Foundry Congress 2007348J.

3 N. Harvey and G. A. NobleImprovement in Nodule CountPrevention of Formation of CarbidesCarbide in Ductile IronInverse Chill55th Indian Foundry Congress 2007 Inoculation of cast Irons - an overview349 GREY iron INOCULATIONP romote formation of type A graphitePrevent formation of undercooled graphitePrevent formation of Rosette graphiteNil Pearlite - Completely Ferritic 100x-EtchedIncreases Ferrite Content4% Picral 100 Stereoscan 60055th Indian Foundry Congress 2007350J. N. Harvey and G. A. NobleEffect of low % Sulphur on ductileiron microstructureMaterial ferritic ductile 420N/mm2 minimum tensilestrength, 12% low nodule count <100mm2 5% carbide, < S in base metaltreated with 6% Mg, 1%TRE FeSiMg, additionat 1500 addition FeSi 4% Allin pouring increased % S to in increased nodule count>100mm2, no carbide, at Low TemperaturesCasting continuously cast ductile iron ferritic depth of chill on surfaceof the bar FeSi.

4 Al at1300 C into change inoculant to FeSi+ 5% Ba + 9% Mn reduced chill depth onsurface, greaterconsistency of nodulecount and to arrive at exact quantity ofinoculant?Ductile Irons add minimum quantity toachieve:onodule countonodule shapeocarbide freeofully iron wedge test to give minimumchill in casting, microstructure type Agraphite, cooling curve analysis computer software Inoculation eutectic cell count,shrinkage defects (sinks/draws).Factors Affecting Fade TimesType of melting furnace cupola orinduction melting?

5 Charge composition % steel, % pig of recarburiser graphite temperature from time before Inoculation . Traceelement of Austenitic Ni-ResistFor Chromium containing Ni-Resist (D2,D2-B, D3, D3-A, D4, D5B and D5-S) Inoculation is more aims to minimise thequantity of Cr carbide, distribute evenlycarbides in a fine form and improvenodule recommends Si addition, aFeSi 75 in ladle, FeSi 75 in the baseof the Foundry making thin sectionedD5S add of FeSi 4% Al or FeSi 2% Ca plus in the mould Indian Foundry Congress 2007 Inoculation of cast Irons - an overview351 Rosette Flake GraphiteStereoscan 100 Undercooled GraphiteStereoscan 1004% Picral 1004% Picral 10055th Indian Foundry Congress 2007352J.

6 N. Harvey and G. A. NobleMagnesium Based InoculantThere are no commercially available ladleor metal stream inoculants containingMg. However, it is a necessary addition inthe production of in the mould inoculantblocks utilising powder metallurgicaltechniques. Typically of Size and Shape onInoculationIn the mould and sintered metallurgical , shape, weight - tailor to iron iron uniforms structure in disvantage-increases tendency DO WE INOCULATE Irons ?ADDITION RATES FOR GREY &DUCTILE IRONL adle Inoculation up to , stream Inoculation to ,typically the mould Inoculation to melted Irons require up to 50%higher addition than cupola melted OF INOCULANTS FOR GREYAND DUCTILE IRONI ntroductionMajority of inoculants are FeSi based.

7 Silevel 75% or 45% content. FeSi as a purematerial has no Inoculation effect. Acombination of active elements Al,Ca, Ba, Mn, Zr, Sr, Bi when added to FeSiwill inoculate. Ba, Zr, Sr, Bi are moreFormation of ChillFig. 6 : Cross section of Indian Foundry Congress 2007 Inoculation of cast Irons - an overview353 Fig. 7 :Schematic of Inoculation 8 :Ladle Indian Foundry Congress 2007354J. N. Harvey and G. A. NobleFig. 9 :In stream inoculation55th Indian Foundry Congress 2007 Inoculation of cast Irons - an overview355 Fig. 10 :In the mould SprueRunner BarFig.

8 11 : In the mould Basin55th Indian Foundry Congress 2007356J. N. Harvey and G. A. Noblepowerful active elements than Al and Cain FeSi based inoculants. This results inlower addition ElementsAluminiumTypical of pinholing in green sand greyiron production if Al> + AI total of as inoculating grade commercially used FeSi inoculant,ManganeseTypical 3-10%.Used in combination with other elements,typically Ba, lower melting point fade resistance in combination withother up N2 from melting chill formation in combinationwith other fade EarthsTypical up to 10%.

9 Combinations of in low S content grey up to and Sintered Inoculant Indian Foundry Congress 2007 Inoculation of cast Irons - an overview357 Combination with in thin section ductile with Ca and chill reductionLower shrinkage S grey Irons and ductile Irons treatedwith high RE FSM reduce OF INOCULANTS - OURADVICEGrey iron ladle -1 % Sr or 2% iron ladle -1 % Sr or 4% Zr/4% iron ladle -1% RE forthin iron ladle - 2% Ba or 2% Zr forthicker iron late - 4% Al or 4% Zr/4% times 8 to 10 STUDIES In the Mould InoculationCasting steering knuckle - ductile iron grade 400/15impact properties ofminimum 60J at minus30 C unnotched failure to meet 5% pearlite in test piecemicrostructures.

10 Micro-shrinkage in test addition of Al, 1%Ca FeSi in pouring addition of ladle inoculant FeSi+ Al + 1% in the mould block - 70% Si, 4%Al, 1% Ca Result - typically 80-100 Jat minus 30 C impact of High Mg Treatment onInoculationCasting Automotive grade 450N/mm2 minimumtensile strength, 10%minimum changed from a cored wirecontaining 70% Mg, 30%FeSi to 98% Mg wireresulting in in the mouldinoculant FeSi FeSi Al into FeSi into metal in the mould - elimination of carbide.