Burn on

Explosion Penetration

Micro Shrinkage

Penetration

Sand inclusions

Swells

Broken Mould

Metal Penetration

Lustrous Carbon Inclusions

Scarred Surface

Pin Holes Roughness

ScabsSlag inclusions

Fissure Defect

Blow Holes

Blow Holes at Angles

Erosion

Nature of DefectFirmly adhering agglomeratesof sand/metal at hot spots andin softly rammed areas.

RemediesReduce compactability of thesand. Improve ramming of themoulds. Increase amount ofcarbonaceous additive and cokein the moulding sand.

Nature of DefectThin sand crusts firmlyadhering to the casting.Defect occursmore frequentlywith thickwalled castings athigh castingtemperature.

RemediesIncrease amount of lustrouscarbon producers and coke pro-ducers in the moulding sand.Increase amount of new sandif sintering point of the sand islow and oolitization is high.

Nature of DefectFlash-like metal penetration inthe mould, sometimes parts ofthe mould are included in thecasting.

RemediesAdd more bentonite to increasegreen tensile strength.Raise compactability of themoulding sand.

Nature of DefectThe sand is washed away,mostly near to the sprue, oftenaccompanied by sand inclu-sions. Bulges arise on thecasting near to the gate.

RemediesAvoid drying out of the moul-ding sand. Increase amount ofbentonite in the sand. Increasemilling time of the mouldingsand. Increase mould com-paction. Use carbonaceousadditive with a high lustrouscarbon producing ability.

Nature of DefectExtensive penetration, whenthe mould is filled too quickly.

RemediesReduce amount of free water.Increase milling time of themoulding sand. Increase ooliti-zation rate of the mouldingsand.

Nature of DefectFormation of surface irregula-rities, inclusions and laps dueto non-wetting characteristic oflustrous carbon, often associ-ated with the use of Cold-Boxcores.

RemediesUse dried Cold-Box cores.Reduce amount of lustrouscarbon producer in themoulding sand. Use carbon-aceous additive with a highercoking residue.

Nature of DefectNarrow, crack-like cavitiesvertical to the surface. Dendriteformation in the cavities.

RemediesThe defect is of a metallurgicalnature due to too much nitro-gen contained in the iron.Reduce the amount of nitrogenin the moulding sand. Use lownitrogen containing carbon-aceous additive. Reduceaddition of carbonaceousadditive in the moulding sand.

Nature of defectPorous structure found in thearea of the casting which is lastto solidify.

RemediesDefect occurs with alloys havinga wide solidification range.Little influencing by the moul-ding sand. Reduction of organicmaterial and an increase in themoisture level will improvethermal conductivity of themoulding sand.

Nature of DefectScarred casting surface aroundhot spots, particularly with SGcast iron.

RemediesReduce amount of impuritiespresent in the sand that aredestroying the oxide skin.

Nature of DefectCavities with smooth walls,singularly or in groups.

RemediesLow casting temperatures areoften the cause. Benefits maybe obtained by increasingmould permeability.Reduce fines or add coarsernew sand. Reduce organicadditions to the sand.

Nature of DefectRoughness caused by themolten metal penetrating theimmediate sand grains of themould surface, particularly insoftly rammed areas.

RemediesUse finer sand. Improve ram-ming of the moulds. Reducecompactability of the mouldingsand. Increase amount ofcarbonaceous additive. Increaseamount of coke in the moul-ding sand.

Nature of DefectAccumulation of small sub-surface rounded holes.Defects appear after annealingand light machining.

RemediesNormally the defect is of ametallurgical nature.The mould material may havea certain effect. In case of pinholes the moisture, the organicadditions and the amount ofnitrogen in the moulding sandshould be reduced.

Nature of DefectRough casting surface finishdue to coarse sand.

RemediesUse finer sand. Increase amountof lustrous carbon producingmaterial in the moulding sand.Increase the amount of finese.g. coke in the sand.

Nature of DefectIrregularly formed sandinclusions just underneath thecasting surface, associated withproducts from the metal slagreaction in other areas.

RemediesKeep the moulding sand suffi-ciently plastic by good sandpreparation and sand cooling.Adjust to optimum compac-tability. Reduce the tendencyof the mould to stick to thepattern by the use of partingagents.

Nature of DefectNon-metallic irregular shapedinclusions, when occurring,tend to be on upper castingsurfaces.

RemediesThe defects are caused byslag being present with themolten metal in the pouringladle. If the formation is dueto eroded sand, reduce theamount of inert fines and usea more active lustrous carbonproducer. Increase milling timeof the moulding sand.

Nature of DefectMushroom type defect withsharp edges parallel to thecasting surface.

RemediesIncrease bentonite level.Use carbonaceous additive witha wide softening range.Increase the amount ofcarbonaceous additive in themoulding sand.

Nature of DefectIrregular bulges, in most caseswidely spread, sometimes withrough surface and/or pene-tration.

RemediesReduce compactability of themoulding sand. Ram mouldsbetter and more evenly.Make sand less sensitive toover- and underramming byincreasing the amount ofbentonite.

Nature of DefectSmooth wall cavities at theangles of the casting.

RemediesThe cause is insufficient feedingand rate of solidification.Influencing by moulding sandis possible. Reduce the moisturecontent and the organicadditions of the sand.Improve the venting of themould.

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dS&B Industrial Minerals GmbH