Consolidated Tech Man - Holo-Krome

EFFECTS OF ALLOYING ELEMENTS IN STEEL
Steel, by definition, is a combination of iron and carbon. Various
other elements are added to steel to improve physical properties
and to produce special properties, such as resistance to corrosion
or heat. The specific effects of the addition of such elements
are outlined below:
ALUMINUM (AI). Aluminum is a deoxidizer and degasifier. It
retards grain growth and is used to control austenitic grain size.
In nitriding steels, aluminum aids in producing a uniformly hard
and strong nitrided case when used in amounts of 1.00% - 1.25%.
BORON (B). A potent and economical addition to a fully deoxidized
steel; normally used in alloy steels. Added to the melt in
extraordinarily small amounts (on the order of 0.001%), it has a
powerful effect on hardenability. During times of shortages of
nickel, chromium and molybdenum, boron is used to replace a
portion of these elements which are used to increase hardenability.
Boron cannot be added in large amounts as it caused hot-shortness
(brittleness in steel in the hot forming range).
BISMUTH (Bi). Used in the same manner as lead as an additive
in small amounts to improve machinability in the faster machining
grades of certain proprietary screw machine steels.
Carbon (C). While carbon is not usually considered an alloying
element, it is the most important constituent of steel. It increases
the tensile strength, hardness and resistance to wear and abrasion.
However, carbon lowers the ductility, machinability and
toughness.
CHROMIUM (Cr). Chromium increases tensile strength, toughness,
hardness and hardenability, as well as resistance to wear
and abrasion. It also increases resistance to corrosion and scaling
at elevated temperatures.
COBALT (Co). Cobalt increases strength and hardness in addition
to permitting higher quenching temperatures. Also, it intensifies
the effects of the other major elements in more complex steels.
COLUMBIUM (Cb). Columbium in stainless steel has an effect
similar to titanium and tantalum in making the steel more resistant
to carbide precipitation and the resulting inter-granular corrosion.
COPPER (Cu). Copper improves resistance to atmospheric corrosion
and increases the tensile and yield strength with very little
loss in ductility.
IRON (Fe). Iron is the chief element from which the various steels
are made. Pure iron lacks strength, is very soft and ductile and
does not respond satisfactorily to heat treatment. Commercial
iron normally contains other elements which produce the required
physical properties.
LEAD (Pb). Lead, while not strictly an alloying element, is added
to improve machinability. It is almost completely insoluble in steel,
and minute lead particles, dispersed throughout the steel, reduce
friction where the cutting edge contacts the work. Also, the addition
of lead improves chip-breaking formations.
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MANGANESE (Mn). Manganese is a deoxidizer and degasifier.
It also reacts with sulphur to improve forgeability. Manganese
increase tensile strength, hardness, hardenability, resistance to
wear and the rate of carbon penetration in carburizing. It also
decreases the tendency toward scaling and distortion.
MOLYBDENUM (Mo). Molybdenum increase strength, toughness,
hardness, and hardenability as well as creep resistance
and strength at elevated temperatures. It improves machinability,
corrosion resistance and intensifies the effects of the other
alloying elements. In hot-work steels, molybdenum increases
red-hardness properties.
NICKEL (Ni). Nickel increases strength and hardness with no
loss of ductility and toughness. It also increases resistance to
corrosion and scaling at elevated temperatures when introduced
suitable quantities in high chromium stainless steels.
NITROGEN (N). Important in several respects; 1) as a strong
austenitizer which can substitute for a portion of the nickel in stainless
steels; 2) as an element in nitriding and carbonitriding certain
alloy steels containing aluminum or chromium to produce an
extremely hard case; 3) added to the melt of some of the freemachining
steels to enhance machinability by producing a vary
fine chip.
PHOSPHORUS (P). Phosphorus increases strength and hardness
and improves machinability. However, it adds brittleness or
cold-shortness to steel.
SELENIUM (Se). Related to sulphur and tellurium in the chemical
classification of elements, it has the similar effect of improving
machinability when added in small amounts to some freemachining
steels.
SILICON (Si). Silicon is a deoxidizer and degasifier. Also, it increases
the tensile and yield strength, forgeability, hardness and
magnetic permeability.
SULPHUR (S). Sulphur improves machinability in free-cutting
steels. It decreases weldability, ductility and impact strength. Also,
the addition of sulphur without sufficient manganese produces
brittleness at red heat.
TANTALUM (Ta). Tantalum is used as a stabilizing element in
stainless steels. It has a high affinity for carbon and forms carbides
which are uniformly dispersed throughout the steel, thus
preventing localized depletion of carbon at grain boundaries.
TITANIUM (Ti). Titanium, like tantalum and columbium, is added
to stainless steels to make them resistant to harmful carbide precipitation.
TUNGSTEN (W). Tungsten increases strength, toughness and
hardness. At elevated temperatures tungsten steels have superior
hotworking characteristics and greater cutting efficiency.
VANADIUM (V). Vanadium increases strength, hardness, and
impact resistance. By retarding grain growth vanadium permits
higher quenching temperatures. It also improves the red-harness
properties of high-speed mental cutting tools and intensifies
the individual effects of other major elements.