A temper designation follows the alloy number, for example 6063-T6 or 3003-H14, and tells you the processing condition of the metal. The main letters are:
- F: as fabricated, no guaranteed properties.
- O: annealed, softest and most formable.
- H: strain hardened (non-heat-treatable alloys). H1x is cold worked only, H2x is cold worked and partly annealed, H3x is cold worked and stabilised. The second digit shows hardness: 2 is quarter hard, 4 half hard, 6 three-quarter hard, 8 full hard.
- W: solution heat treated, unstable.
- T: heat treated. T4 is solution treated and naturally aged, T5 is cooled from the hot working temperature and artificially aged, T6 is solution treated and artificially aged.
Why it matters when buying
- The same alloy can differ widely in tensile strength and bendability between O and H18 or between T4 and T6.
- Specify temper on every RFQ and check it on the mill test certificate.
- Forming after delivery may need a softer temper; welding reduces strength locally in heat-treated tempers.
Notes
Extrusions in 6063 are commonly supplied in T5 or T6; sheet in 5052 is often H32. See also the alloy designation system.