Each of the aluminum alloys has properties
publishes Unified Numbering System for Metals and
developed specifically for a certain type of
Alloys. It provides a clear and easily understood cross
reference from the designation of one numbering
application. The hard aluminum alloys are easier to
system to other systems where a similar metal is
machine than the soft alloys and often are equal to
involved. Some of the numbering systems that you
low-carbon steel in strength.
may need to identify are as following:
ZINC ALLOYS.--Zinc is a comparatively soft,
Aluminum Association (AA)
yet somewhat brittle, metal. Its tensile strength is
only slightly greater than that of aluminum. Because
American Iron and Steel Institute (AISI)
of its resistance to corrosion, zinc is used as a
Society of Automotive Engineers (SAE)
protective coating for less corrosion-resistant metals,
principally iron and steel.
Aerospace Materials Specifications (AMS)
Pure zinc has a strong anodic potential. It is used
American National Standards Institute (ANSI)
to protect the hulls of steel ships against electrolysis
between dissimilar metals caused by electric currents
American Society of Mechanical Engineers
(ASME)
set up by salt water. Zinc plates bolted on the hull,
especially near the propellers, decompose quite
American Society for Testing and Materials
rapidly, but greatly reduce localized pitting of the hull
(ASTM)
steel.
Copper Development Association (CDA)
TIN ALLOYS.--Pure tin is seldom used except
M i l i t a r y Specification (MIL-S-XXXX,
as a coating for food containers and sheet steel and in
MIL-N-XXXX)
some electroplating applications. Several different
grades of tin solder are made by adding either lead or
Federal Specification (QQ-N-XX, QQ-S-XXX)
antimony. One of the Navy's main uses of tin is to
make bearing babbitt. About 5 percent copper and 10
The Unified Numbering System lists all the
percent antimony are added to 85 percent tin to make
different designations for a metal and assigns one
number that identities the metal. This system covers
this alloy. Various grades of babbitt are used in
bearings. Each grade may have additional alloying
only the composition of the metal and not its
elements to give the babbitt the properties required.
condition, quality, or form. Use of the Unified
Numbering System by the various metal producers is
LEAD ALLOYS.--Lead is probably the heaviest
voluntary, and it could be some time before its use is
metal with which you will work. A cubic foot of it
widespread. Another useful publication is NAVSEA
weighs approximately 700 pounds. It has a grayish
0900-LP-038-8010, Ship Metallic Material
color and is amazingly pliable. It is obtainable in
Comparison and Use Guide.
sheets and pigs. The sheets normally are wound
around a rod, and pieces can be cut off quite easily.
The two major systems used for iron and steel are
One of the most common uses of lead is as an alloying
the Society of Automotive Engineers (SAE) and the
element in soft solder.
American Iron and Steel Institute (AISI). The
Aluminum Association method is used for aluminum
DESIGNATIONS AND MARKINGS OF
and is discussed later in this chapter. Other
METALS
nonferrous metals are designated by the percentage
and types of elements in their composition. The Navy
You must understand the standard designations of
uses these methods to mark metals so they can be
metals and the systems of marking metals used by the
identified readily.
Navy and industry so you can select the proper
material for a specific job. There are several different
Ferrous Metal Designations
numbering systems currently in use by different trade
You should be familiar with the SAE and AISI
associations, societies, and producers of metals and
alloys. You may find several different designations
systems of steel classifications. These systems,
which are in common use, have a four- or five-digit
that refer to a metal with the same chemical
number to indicate the composition of the steel. The
composition, or several identical designations that
major difference between them is that the AISI system
refer to metals with different chemical compositions.
normally uses a letter before the numbers to show the
The Society of Automotive Engineers, Inc. (SAE),
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