Created by Jagadish...

EFFECT OF ALLOYING ELEMENTS
ALUMINUM -- Aluminum is probably the most active deoxidizer in
common use in producing steel. It is used in controlling inherent
grain size.
BORON -- Boron is added to steel in amounts of 0.0005 to 0.003% to
improve hardenability. In combination with other alloying elements,
boron acts as an “intensifier”, increasing the depth of hardening
during quenching.
CARBON -- When a small amount of carbon is added to iron, the
properties which give steel its great value begin to appear. As the
amount of carbon increases up to .80 or .90%, the metal becomes
harder, possesses greater tensile strength, and, what is most
important, becomes increasingly responsive to heat treatment with
corresponding development of very high strength and hardness.
If carbon were to be increased beyond certain limits in plain carbon
steel, the ability to be worked either hot or cold would disappear
almost entirely, and it would begin to assume the characteristics of
cast iron, which usually has 1.7 to 4.5% carbon.
CHROMIUM -- Chromium increases response to heat treatment. It
also increases depth of hardness penetration. Most chromium-bearing
alloys contain .50 to 1.50% chromium. Stainless steels contain
chromium in large quantities (12 to 25%), frequently in combination
with nickel, and possess increased resistance to oxidation and
corrosion.
COLUMBIUM -- Columbium in 18-8 stainless steel has a similar
effect to titanium in making the steel immune to harmful carbide
precipitation and resultant inter-granular corrosion. Columbium
bearing welding electrodes are used in welding both titanium and
columbium bearing stainless steels since titanium would be lost in
the weld arc whereas columbium is carried over into the weld
deposit.
COPPER -- Copper is normally added in amounts of .15 to .25% to
improve resistance to atmospheric corrosion and to increase tensile
and yield strengths with only a slight loss in ductility. Higher
strength properties can be obtained by precipitation hardening
copper-bearing steel.
IRON -- Iron is the chief element of steel. Normally commercial
iron contains other elements present in varying quantities which
produce the required mechanical properties. Iron lacks strength, is
very ductile and soft and does not respond to heat treatment to any
appreciable degree. It can be hardened somewhat by cold working,
but not nearly as much as even a plain low carbon steel.
LEAD -- Lead in steel greatly improves its machinability. When the
lead is finely divided and uniformly distributed it has no known
effect on the mechanical properties of the steel in the strength
levels most commonly specified. It is usually added in amounts from
.15% to .35%.
MANGANESE -- Next in importance to carbon is manganese. It is
normally present in all steel and functions both as a deoxidizer and
also to impart strength and responsiveness to heat treatment.
Manganese is usually present in quantities from 1/2% to 2%, but
certain special steels are made in the range of 10% to 15%.
MOLYBDENUM -- Molybdenum adds greatly to the penetration of
hardness and increases toughness. Molybdenum tends to help steel
resist softening at high temperatures and is an important means of
assuring high creep strength. It is generally use in comparatively
small quantities ranging from .10 to .40%.
NICKEL -- Nickel increases strength and toughness but is one of
the least effective elements for increasing hardenability. The most
general quantity addition is from 1 to 4%, although for certain
applications, percentages as high as 36% are used. Steels
containing nickel usually have more impact resistance, especially at
low temperatures. Certain stainless steels employ nickel up to
about 20%.
PHOSPHORUS -- Some phosphorus is present in all steel. In
addition to increasing yield strength and reducing ductility at low
temperatures, phosphorus is believed to increase resistance to
atmospheric corrosion.
SILICON -- Silicon is one of the common deoxidizers used during
the process of manufacture. It also may be present in varying
quantities up to 1% in the finished steel and has a beneficial
effect on certain properties such as tensile strength. It is also
used in special steels in the rage of 1.5% to 2.5% silicon to
improve the hardenability. In higher percentages, silicon is added
as an alloy to produce certain electrical characteristics in the socalled
silicon electrical steels and also finds certain applications
in some tool steels where it seems to have a hardening and
toughening effect.
SULPHUR -- Sulphur is an important element in steel because when
present in relatively large quantities, it increases machinability.
The amount generally used for this purpose is from .06 to .30%.
Sulphur is detrimental to the hot forming properties.
TELLURIUM -- The addition of approximately .05% tellurium to
leaded steel improves machinability over the leaded only steels.
TITANIUM -- Titanium is added to 18-8 stainless steels to make
them immune to harmful carbide precipitation. It is sometimes added
to low carbon sheets to make them more suitable for porcelain
enameling.
TUNGSTEN -- Tungsten is used as an alloying element in tool steel
and tends to produce a fine, dense grain and keen cutting edge when
used in relatively small quantities. When used in larger quantities
of 17 to 20% and in combination with other alloys, it produces a
high speed steel which retains its hardness at the high temperatures
developed in high speed cutting. Tungsten is also used in certain
heat resisting steel where the retention of strength at high
temperatures is important. It is usually used in combination with
chrome or other alloying elements.
VANADIUM -- Vanadium, usually in quantities from .15 to .20%
retards grain growth, even after hardening from high temperatures or
after periods of extended heating. Tool steel containing vanadium
seem to resist shock better than those which do not contain this
element do.