©
COPYRIGHT 1999 THE ESAB GROUP, INC. LESSON
I, PART A 1.3
SPECIFICATIONS
Many steel producers have developed
steels that they market under a trade name such as Cor-Ten,
HY-80, T-1, NA-XTRA, or SS-100, but usually a type of steel is referred to by
its specification.
A variety of technical, governmental and industrial associations issue
specifications for the purpose of classifying
materials by their chemical composition, properties
or usage. The specification agencies most closely related to the steel industry
are the American Iron and Steel Institute
(AISI), Society of Automotive Engineers (SAE), American
Society for Testing and Materials (ASTM), and the American Society of
Mechanical Engineers (ASME).
1.3.0.1 The
American Iron and Steel Institute (AISI) and the Society of Automobile
Engineers (SAE) have collaborated in
providing identical numerical designations for their specifications.
The first two digits of a four digit index number refer to a series of steels
classified by their composition or
alloy combination. While the last two digits, which can
change within the same series, give
an approximate average of the carbon range. For example,
the first two digits of a type 1010 or 1020 steel indicate a “10”
series that has carbon
as its main alloy. The last two digits indicate an approximate average content
of .10% or .20%
carbon, respectively. Likewise, the “41”
of a 4130 type steel refers to a group that
has chromium and molybdenum as their main alloy combination with approximately
.30% carbon content.
1.3.0.2 The
AISI classifications for certain alloys, such as stainless steel, are somewhat
different. They follow a three
digit classification with the first digit designating the main
alloy composition or series. The
last two digits will change within a series, but are of an
arbitrary nature being agreed upon
by industry as a designation for certain compositions within
the series. For example, the “3” in a
300 series of stainless steel indicates chromium and
nickel as the main alloys, but a 308 stainless has a different overall composition
than a 347 type.
The “4” of a 400 series indicates the
main alloy as chromium, but there are different
types such as 410, 420, 430, and so forth within the series.
1.3.0.3 The
American Society for Testing and Materials (ASTM) is the largest
organization of its kind in the world.
It has compiled some 48 volumes of standards for materials,
specifications, testing methods and recommended practices for a variety of
materials ranging from textiles and
plastics to concrete and metals. 1.3.0.4
Two ASTM designated steels commonly
specified for construction are A36-77 and
A242-79. The prefix letter indicates the class of a material. In this
case, the letter “A” indicates
a ferrous metal, the class of widest interest in welding. The numbers 36
and 242
