Aluminum Temper Explained: O, H14, H24, T5 and T6

Aluminum Temper Explained: O, H14, H24, T5 and T6

Every aluminum order should end with a temper designation — O, H14, T5, T6 — and most buyers treat it as a footnote. The temper is what decides whether the sheet can be deep-drawn, whether the extruded profile will hold its straightness after installation, and whether the plate will spring back during machining. This guide decodes the most common tempers.

O Temper: Annealed, Softest

“O” means fully annealed. The alloy is as soft as it gets. O-temper is used when you need maximum formability: deep drawing, bending without cracking, and spinning. It is not strong and will deform under load. You will see O temper on 1xxx pure aluminum and some 3xxx coils used for cookware and packaging.

H Tempers: Cold-Worked

H tempers apply to non-heat-treatable alloys (1xxx, 3xxx, 5xxx). The second digit tells you the hardening state. H14 means strain-hardened to about half-hard; H24 means strain-hardened then partially annealed. Both give roughly the same strength range but H24 is slightly more ductile. Typical H tempers you will see:

• H14 / H24: half-hard — good balance of formability and strength (our 1060 H14 coil and 1060 H14 strip)
• H18: full-hard — strong but brittle, used for channel and rigid parts
• H32 / H34: stabilized, used on 5xxx marine alloys like our 5052 H32 plate

T5 and T6: Heat-Treated

T tempers apply to heat-treatable alloys (2xxx, 6xxx, 7xxx). T5 means cooled from extrusion and then artificially aged — this is the architectural temper used on 6063 T5 angle and 6063 T5 channel. T6 means solution heat-treated then artificially aged to full strength — the structural temper used on 6061 T6 flat and 6061 T6 plate. T6 is roughly twice as strong as T5 on the same alloy.

Common Specifying Mistakes

The most common mistake is ordering 6063 T6 thinking it is stronger than T5 — 6063 is not normally solution-heat-treated, and a “6063 T6” claim is often marketing rather than a real temper. The second mistake is ordering T6 parts for bending; T6 is springy and will crack on tight radii. If you need to bend after temper, choose O or H tempers and bend before heat treatment.

Confirm your temper requirement