Compiled by Ed Caffrey

The primary ingredient in steel is iron, one of the most common elements found in the earth.
It is usually found  in the form of iron oxide (iron ore) and then smelted down into cast iron (pig iron).
The cast iron is then further refined and other elements are added to bring about the desired
qualities in the finished alloy.   The most common element that has an effect on hardness in an alloy is carbon,
which not only increases the hardness but can also make the steel quite brittle. 
Thus, using a steel with a high carbon content will result in a very hard (and sometimes brittle) blade,
while using a steel with a low carbon content will
result in a tough  blade that will not hold an edge. 
(Of course there are ways around most problems, but that's another story)


The element content of an alloy is expressed as a POINT , with each point
signifying 0.01 percent of the alloy.  As an example, a 60-point carbon alloy
will contain approximately 0.60% carbon.

CARBON (C):  Has by far the greatest influence of any of the elements.
  Steel could not exist without carbon.  Martensite, along with banite give steel
a microstructure of hard, tough carbide. 
None of the other elements so dramatically alter the strength and hardness as do small changes in carbon content. 
Carbon iron crystalline structures have the widest number and variety known to exist in
metallurgy.  They also combine with other elements to furnish steel with an
assortment of iron alloy carbide systems.
MANGANESE (Mn):  Is normally present in all steel and functions as a
deoxidizer.  It also imparts strength and  responsiveness to heat treatment.  It is
usually present in quantities less than 1.00 %......
NICKEL (Ni):   Increases strength and toughness but is ineffective in
increasing hardness.  It is generally added in amounts ranging from 1 percent to 4
percent.  In some stainless steels it is sometimes as high as 20 %.......
SILICON (Si):  Has a beneficial effect upon tensile strength and improves
hardenability of an alloy.  It has a toughening effect when used in combination
with certain other elements. 
conductivity of an alloy.  Amounts are usually 0.30 % ,spring steels may contain up to 2%
CHROMIUM (Cr):  Increases the depth penetration of hardening and also the
responsiveness to heat treatment.  It is usually added with nickel (Ni) for use in
stainless steels.  Most of the chromium (Cr) bearing alloys contain 0.50 to 1.50
percent chromium;  some stainless steels contain as much as 20 percent or
more.  It can affect forging, causing a tendency in the steel to crack.
VANADIUM (V):  Retards grain growth within steel even after long exposures
at high temperatures, and helps to control grain structures while heat treating.  It
is usually present in small quantities of 0.15 to 0.20 for grain refining which increases toughness .
Additional amounts up to about 4-5 % for carbides.  Most tool steels
which contain this element seem to absorb shock better that those that do not
contain vanadium (V).

MOLYBDENUM (Mo):  Adds greatly to the penetration of hardness and
increases toughness of an alloy.  It causes steel to resist softening at high
temperatures, which defeats the purpose of forging.  If the alloy has below 0.020
percent molybdenum (Mo), you should be able to forge this alloy with little difficulty.
TUNGSTEN (W):  Also known as wolfram, is used as an alloying element in
tool steels, as it tends to impart a tight, small, and dense grain pattern and keen
cutting edges when used in relatively small amounts.  It will also cause steel to
retain its hardness at higher temperatures and hence will have a detrimental
effect upon the steel's forgeability (otherwise known as "red hard")
SULFUR (S):  Is usually regarded as an impurity in most alloys and its addition
to steel is held to a minimum as it is damaging to the hot forming characteristics
of steel.  It is, however added to increase machinability.  A word of caution, some
alloys are offered in different forms, an example is E52100.  This particular steel
can be had in either a "Bearing Quality" or " free machining grade "  the latter having
sulfur (S) added to increase machinability.
LEAD (Pb):  Increase the machinability of steel and has no effect upon the
other properties of the metal.  It is usually added to an alloy only upon request
and then in quantities of 0.15 to 0.30 percent.
PHOSPHORUS (P):  Is present in all steel.  It increases yield strength and
reduces ductility at low temperatures.  It is also believed to increase resistance to
atmospheric corrosion.  Phosphorus (P) is usually treated as an impurity in most alloys.
Some common blade steels....and their element content.
52100:  Carbon  1.00%    Manganese  0.35%    Silicon  0.25%    Chromium  1.50%
5160: Carbon .60%  Manganese .85%  Phosphorus .035% max  .80% chromium Sulphur .040% max .
1084: Carbon .80%/.94%  Manganese .60%/.90%
1095: Carbon .90%/1.04%  Manganese .60%/.90%
15N20: Carbon .75%  Manganese .75%  Silicon .25%  Nickel 1.5%
O-1: Carbon 1.00%  Manganese .60%  Silicon .30%  Chromium .50% Vanadium .30%  Molybdenum 1.10 v L-6: Carbon .75%  Manganese .70%  Silicon .25%  Chromium .80%  Nickel 1.5%  Molybdenum .30%
A-2: Carbon  1.00%    Manganese  0.85%    Silicon  0.35%    Chromium  5.25%    Molybdenum   1.10%    Vanadium  0.25%
D-2: Carbon  1.55%    Manganese  0.35%    Silicon  0.45%    Chromium  11.50%    Molybdenum  0.90%   Vanadium  0.80%

some of the text above has been Changed
and some of the changed information came from Robert Cella metallurgist
with permition of Ed Caffrey

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