9--Is sometimes used to express extra hard
H--Strained hardened (wrought only)
As with temper, it is important that you are aware
H1--Strain hardened only
of hardness conditions as a metal worker, especially in
H2--Strain hardened, then partially
welding applications. When you weld, heat, roll, or
annealed
bend aluminum, you will change the hardness of
H3--Strain hardened, then stabilized
aluminum. In certain applications, you may have to use
special precautions or post treatments to prevent
changing the characteristics of the aluminum. In some
W--Solution heat treated--unstable temper
applications, you may not be able to use a repaired
aluminum structure for a specific amount of time while
T--Treated to produce stable tempers
the aluminum age hardens.
T2--Annealed (cast only)
The following are two examples of a complete
T3--Solution heat treated, then cold
aluminum classification broken down into its
worked
component parts:
T4--Solution heat treated and naturally
2218-T72---Aluminum/copper alloy with
aged at room temperature to a substantially
special control over impurities, alloy #18 in the
stable temper
aluminum/copper group, solution heat treated
T5--Artificially aged
(T7), then stabilized to 1/4 hard (2).
T6--Solution heat treated, then artificially
1060-H18---99.60% pure aluminum with no
aged
special control over impurities, strain hardened
T7--Solution heat treated then stabilized
(Hl) to full hard (8).
to control growth and distortion
Material Cross-Referencing
T8--Solution heat treated, cold worked,
then artificially aged
Due to the numerous specification and classification
T9--Solution heat treated, artificially
systems used and the availability of specified material
aged, then cold worked
from blueprints, you will be required to cross-reference
metal from one specification to another.
It is important that you be aware of these conditions
as a metal worker. When you weld, heat, roll, or bend
Continuous Identification Marking System
aluminum, you will change the temper of aluminum. In
The continuous identification marking system is
certain applications, you may have to use special
used to identify different metal shapes and forms. The
precautions or post treatments to prevent changing the
marking is printed on the metal with heavy ink or paint
characteristics of the aluminum.
in constantly recurring symbols at intervals of no more
Hardness Designations.--In many cases, a second
than 3 feet throughout the length of the material. The
digit may appear to the right of the temper designation.
manufacturer is required to make these markings on the
This digit indicates the degree of hardening. The
material before delivery. The marking system consists
numbers 2 through 9 are used to express this hardness.
of the following information (refer to fig. 13-20):
Hardness is obtained by heat treatment, aging, or the
cold working of aluminum. The following is a list of
The name or trademark of the producer who
the numbers and their meaning:
performs the final processing before marking.
2--1/4 hard
The commercial designation or the material,
such as the ASTM, AISI, ASE, or FED/MIL
4--1/2 hard
specification.
6--3/4 hard
Physical condition and quality designation that
shows temper or other physical condition
approved by a nationally recognized technical
8--Full hard
13-18
