Wrought Aluminum Alloy Designations. The mechanical and other properties of the wrought aluminum used for roll forming are influenced by the alloying elements, heat treatment, and cold work.
The numbering system used by the Aluminum Association standards classifies the commonly used aluminum alloys by their major alloying elements (see Figure 6). The 3000 series alloys, such as 3003, 3004, and 3105, are used most frequently by roll formers. Aluminum alloys called "building sheets" and other trade names usually belong to this group of alloy.
Basic Temper Designation. In aluminum alloys, temper designations are as follows:
F As fabricated, no mechanical limits specified
O Annealed to achieve the lowest strength temper
H Work hardened by rolling, with or without additional heat treatment
W Can be formed right after heat treatment, age hardened at room temperature
T Heat treated, aged at high temperature, with or without strain hardening
H1 Strain hardened only
H2 Strain hardened and partially annealed
H3 Strain hardened and stabilized by low-temperature heat treatment
A second digit after the H designations indicates a variation of the temper:
H12 1/4 hard H32 1/4 hard (and stabilized)
H14 1/2 hard H34 1/2 hard (and stabilized)
H16 3/4 hard H36 3/4 hard (and stabilized)
H18 Full hard H38 Full hard (and stabilized)
For three-digit designations such as H112, H364, and others, fabricators should consult the appropriate standards.
Numbers T1 to T10 refer to the combinations of hot and cold working, heat treatment, cooling, and aging. The basic treatment depends on the type of alloy and on the properties to be achieved.
Two-digit tempers such as T51 and others may refer to stress relieving by a stretching (or compressing) process.
Note that 1000, 2000, 4000, and 5000 series alloys cannot be heat-treated.
Cladding. The good corrosion resistance of the 1000 or other series of alloys can be combined with the high strength of other alloys. A thin layer of the low-strength, corrosion-resistant alloy is metallurgically bonded (hot-rolled) on both sides of the higher-strength, less-corrosion-resistant alloy. During roll forming, additional care has to be taken not to scratch or damage the protective surface of the clad alloys.
Bimetals. Aluminum also can be bonded to other metals such as stainless steel. The combination provides a relatively lightweight product with the stainless steel's (or other metal's) properties.
It is not too difficult to roll form these types of bimetals, but more attention must be paid to the forces applied by the rolls. The larger force required to form stainless steel reduces the thickness of aluminum. Uneven thickness reduction can create an unacceptable camber, twist, or other imperfections.
Influence of Primary Metal Processes on Roll Forming
Several processes are applied to metal during production, and these processes have an effect on roll forming results:
1. Hot and cold rolling
2. Coating
3. Slitting
