Technical Information 12
Effects of Minor and Trace Elements in Cast Iron
Small quantities of many elements can occur in cast irons and have a marked influence on the
structure and properties of the castings. Some are present as deliberate additions while others
arise from trace impurities in the raw materials. Several of these elements have beneficial effects,
particularly in grey irons, while others are very damaging and must be avoided as far as possible.
The following table lists the common sources of these elements, the levels at which they are likely
to occur and their principle effects. The use of some of these elements (e.g. chromium) as major
alloying elements is not included in the table.
Element
Aluminium
Al
Antimony
Sb
Arsenic
As
Barium
Ba
Bismuth
Bi
Boron
B
Calcium
Ca
Cerium
Ce
Chromium
Cr
Cobalt
Co
Copper
Cu
Hydrogen
H
Normal
Levels (%) Effects in Cast Irons
Promotes hydrogen pinholes in light sections
Al-killed steel scrap,
above about 0.005 %Al. Neutralizes nitrogen.
inoculants, ferro-alloys, light
Up to
Promotes dross formation. Detrimental to nodular
alloy components, additions
0.03
graphite above approx. 0.08%. May be neutralized
of aluminium.
by cerium. Strong graphite stabilizer.
Steel scrap, vitreous
Up to
Strong pearlite and carbide promoter.
enamel scrap, bearing
0.02
Inhibits nodularity in absence of rare earth’s.
shells, deliberate additions
Up to
Strong pearlite and carbide promoter.
Pig iron, steel scrap.
0.05
Improves nodular graphite shape.
Barium containing
Up to
Improves graphite nucleation and reduces fading.
0.003
Reduces chilling tendency and promotes graphite
inoculants.
Promotes chill and undesirable graphite forms.
Rarely
Deliberate additions, mould
Increases nodule number in ductile irons
above
coatings containing Bi.
containing rare earth’s (cerium). Excessive nodule
0.01
counts may cause shrinkage problems.
Above 5 ppm promotes ferrite. Above 10 ppm proVitreous enamel scrap,
Up to
motes carbides particularly in ductile irons. 20 ppm
0.01
deliberate additions as FeB.
improves annealing of malleable irons.
Improves spheroidization of graphite nodules.
Ferro-alloys, nodularizers,
Up to
Improves graphite nucleation.
0.01
inoculants.
Reduces chilling tendency and promotes graphite.
Normally not used in grey irons.
Most magnesium alloys or
Up to
Suppresses deleterious elements in ductile irons.
added as mishmetall or
0.02
Improves spheroidization of graphite. Carbide
other rare earth sources.
stabilizing due to segregation.
Alloy steel, chromium plate,
Promotes chill and pearlite. Increases strength.
Up to
Form carbide segregates in ductile irons above
some pig irons, ferro0.3
0.05%.
chromium.
Up to
Tool steel
No significant effects in cast irons.
0.02
Copper wire, copper-based
Promotes pearlite. Improves strength.
Up to
Impairs ferritization in ductile irons.
alloys, steel scrap,
0.5
No harmful effects.
deliberate additions of Cu.
Produces sub-surface pinholes. Has a mild chillDamp refractories, mould
promoting action. Promotes "inverse chill" when
materials and humid
there is insufficient manganese present to
additions.
neutralize sulphur. Promotes coarse graphite.
Common Sources
Elkem ASA, Foundry Products
Postal address
P.O.Box 5211 Majorstuen
NO-0302 Oslo
Norway
Office address
Hoffsveien 65B
Oslo
Norway
© Copyright Elkem ASA
Telephone
+47 22 45 01 00
Telefax
+47 22 45 01 52
Web
www.foundry.elkem.com
Org. no.
NO 911 382 008 MVA
Revision
No. 2.1
20.03.2004
Technical Information 12
Element
Common Sources
Lead
Pb
Old paints, some vitreous
enamel, free-cutting steel,
terne plate, solder, petrol
engine deposits.
Magnesium
Mg
Additions of magnesium
alloys (nodularizers).
Most pig irons, steel scrap,
additions of ferro
manganese lump or
briquettes.
Refined pig irons, alloy
Molybdenium
steels, ferro-molybdenum
Mo
additions.
Nickel
Nickel plate, steel scrap,
Ni
refined irons, NiMg alloy.
Coke, carburizers, core
Nitrogen
binders, steel scrap,
N
additions of nitrided ferromanganese.
Manganese
Mn
Phosphorous Phosphoric pig iron and
P
scrap, additions of FeP.
Silicon
Si
Ferro-silicon alloys, steel
scrap, pig iron.
Sulphur
S
Coke, carburizers, pig iron,
scrap iron, additions of iron
sulphide.
Strontium
Sr
Strontium containing
inoculants.
Tellurium
Te
Free-cutting copper, mould
coatings, cooling curve
carbon samples.
Tin
Sn
Titanium
Ti
Solder, tin plated steel
scrap, bronze components,
tin additions.
Some pig irons, some
paints and vitreous
enamels, CG-iron returns,
additions of titanium or
ferro-titanium
2
Normal
Levels (%) Effects in Cast Irons
Causes spiky and undesirable graphite structures
in grey irons and severely reduces strength at
levels above 0.004 %. Promotes pearlite and
Up to
carbides.
0.005
Cause degenerated nodular graphite forms.
Effects on graphite in ductile irons are neutralized
by rare earth’s (cerium).
Promotes nodular graphite in ductile irons.
0.03 - 0.08 Carbide stabilizing effect in ductile irons.
Not used in grey irons.
Neutralizes sulphur by forming MnS.
Promotes pearlite formation. Forms carbide
0.2 - 1.0 segregates in ductile irons. Promotes gas holes at
high levels in conjunction with high sulphur levels.
Mild pearlite promoter.
Up to
Increases strength.
0.1
Can promote shrinkage and carbides.
Up to
Small amounts have little effects.
0.5
Graphitizing effect in larger quantities.
Compacts flake graphite. Promotes pearlite.
Increases strength. High levels causes fissure
Up to
defects in heavier sections. Can be neutralized by
0.015
Al, Ti and Zr. Has little effect in ductile irons.
Increases CEV. Increases fluidity. Forms
Up to
phosphide eutectic. Damaging in ductile irons
0.1
above 0.05 %. At levels above 0.04%, can cause
metal penetration.
Promotes graphitization, reduces chill, stabilizes
0.8-4.0
ferrite, improves castability.
Very damaging to structure and properties unless
Up to 0.15 balanced by manganese. Improves grey irons
(grey
response to most inoculants. Increases Mg
irons)
requirements in ductile irons.
Should be below 0.03 % in ductile irons.
Up to
Improves graphite nucleation in grey and ductile.
0.003
Strongly reduces chilling tendency in grey irons.
Strongly promotes carbides. Causes many
undesirable forms of graphite. Effects observed as
Up to
low as 0.0003 %. Effects reduced by combination
0.003
with Mg and Ce in ductile irons.
Strongly promotes pearlite. Improves strength.
Up to
Embrittles ductile irons above 0.08 %.
0.15
No other harmful effects.
Up to
0.10
Neutralizes nitrogen in grey irons. Promotes
hydrogen pinholing due to aluminium. Promotes
undercooled graphite in grey iron. Suppresses
nodular graphite in CG-irons.
Tungsten
W
High speed tool steel
Up to
0.05
Rarely found in significant amounts.
Mild pearlite promoter.
Vanadium
V
Steel scrap, tool steel,
some pig irons, ferrovanadium additions.
Up to
0.10
Promotes chill formation. Refines flake graphite.
Markedly increases strength.