|
Aluminium Alloys
Aluminium
is an important material in a large cross section of industries. It
is suitable for forming, welding and machining and provides the following
advantages;
- Non
- Magnetic
- Good
electrical conductivity; about 60% that of Copper but reduced by the
presence of alloying elements
- Highly
economic to recycle
- High
specific strength
- High
corrosion fatigue resistance
- Low
specific gravity approximately 1/3 of steel
Although
available in a number of grades, Aluminium can be divided into two major
categories of wrought alloys;
Work
Hardening Alloys
These
alloys ie., Non heat treatable, include commercially pure aluminium
and the alloys including manganese or magnesium. The degree of work
hardening is expressed
as a temper "H". these alloys can be fully or partly softened
by annealing at 350 - 400 deg Celcius.
| Old
Symbol |
New
Symbol |
Description |
| O |
O |
Annealed,
soft |
| F |
M |
As
fabricated |
| H12 |
H2 |
Strain-hardened,
quarter hard |
| H14 |
H4 |
Strain-hardened,
half hard |
| H16 |
H6 |
Strain-hardened,
three quarter hard |
| H18 |
H8 |
Strain-hardened,
fully hard |
| H22 |
H2 |
Strain-hardened,
partially annealed, quarter hard |
| H24 |
H4 |
Strain-hardened,
partially annealed, half hard |
| H26 |
H6 |
Strain-hardened,
partially annealed, three quarter hard |
Heat
Treatable Alloys
Heat
treatable alloys or precipitation hardening alloys include copper, magnesium,
zinc and silicon as important constituents. For these alloys, the designation
system uses the letter "T" following the grade;
| T3 |
Solution
heat-treated, cold worked and naturally aged to a substantially
stable condition. The designation applies to products which are
cold worked to improve strength after solution heat-treatment, or
in which the effect of cold work in flattening or straightening
is recognised in mechanical property limits. |
| T4 |
Solution
heat-treated and naturally aged to a substantially stable condition |
| T6 |
Solution
heat-treated and then artificially aged. The designation applies
to products which are not cold worked after solution heat-treatment,
or in which the effect of cold work in flattening or straightening
may not be recognised in mechanical property limits. |
| T7 |
Solution
heat-treatment and then artificially aged. This designation applies
to products which are artificially aged after solution heat-treament
to carry beyond the point of maximum strength to provide control
of some significant characteristic other than mechanical properties |
| T8 |
Solution
heat-treated, cold worked and then artificially aged. The designation
applies to products which are cold worked to improve strength, or
in which the effect of cold work in flattening or straightening
is recognised in mechanical property limits. |
| T9 |
Solution
heat-treated, artificially aged and then cold worked. This designation
applies to products which are cold worked to improve strength. |
| T651 |
Solution
heat-treated, stress relieved by stretching a controlled amount
(permanent set 0.5% to 3% for sheet; 1.5% to 3% for plate; 1% to
3% for rolled or cold-finished rod and bar) and then artificially
aged. The products receiev no further straightening after stretching. |
European
Specifications with British Standard Comparison
| EN
Number |
Content
|
BS1470:1987
|
BS1474:1987
|
| EN
485-1 |
Technical
conditions for inspection and delivery |
**
|
|
| EN
485-2 |
Mechanical
Properties |
**
|
|
| EN
485-3 |
Tolerances
on shape and dimensions for hot rolled products |
**
|
|
| EN
485-4 |
Tolerances
on shape and dimension for cold rolled products |
**
|
|
| EN
515 |
Temper
designations |
**
|
**
|
| EN
573-3 |
Chemical
composition |
**
|
**
|
| EN
573-4 |
Forms
of products |
**
|
**
|
| EN
755-1 |
Technical
conditions for inspection and delivery |
|
**
|
| EN
755-2 |
Mechanical
properties |
|
**
|
| EN
755-3 |
Round
bars, tolerances on dimension and form |
|
**
|
| EN
755-4 |
Square
bars, tolerances on dimension and form |
|
**
|
| EN
755-5 |
Rectangular
bars, tolerances on dimensions and form |
|
**
|
| EN
755-6 |
Hexagonal
bars, tolerances on dimension and form |
|
**
|
| EN
755-7 |
Seamless
tubes, tolerances on dimension and form |
|
**
|
| EN
755-8 |
Porthole
tubes, tolerances on dimension and form |
|
**
|
| EN
755-9 * |
Profile
tolerances on dimension and forms |
|
**
|
(*)
= Due for publication (**) = How European
relates to old British Standards
|
