Aluminum Coil Temper – Simple Selection Guide

When selecting aluminum coils, many buyers focus only on the alloy grade (such as 3003, 5052, 6061 coils) while overlooking an equally critical parameter: aluminum coil temper. Coils with the same alloy but different tempers can vary by several times in strength, formability, and weldability. Choosing the wrong temper leads to cracking during processing or even total product failure. This guide explains the core differences between O, H, and T tempers and provides a practical selection method.

Three Basic Tempers: What Do O, H, and T Mean?

The temper designation of aluminum coils follows international standards (ASTM/EN). The three most common categories are:

– O Temper (Full Soft)

Fully annealed, with the lowest strength (tensile strength typically 80–110 MPa) but the highest elongation (20%–30%). Suitable for deep drawing and complex curved shapes – for example, radiator fins, deep-drawn cans, and automotive fuel tanks.

– H Temper (Strain Hardened)

Used for non-heat-treatable alloys (1xxx, 3xxx, 5xxx series). Strength is increased by cold working. The first digit after H has a fixed meaning: H1x (strain hardened only), H2x (strain hardened and partially annealed), H3x (strain hardened and stabilized). The second digit (2/4/6/8) indicates the hardness level – 2 = quarter hard, 4 = half hard, 6 = three‑quarters hard, 8 = full hard.

– T Temper (Heat Treated)

Used for heat-treatable alloys (2xxx, 6xxx, 7xxx series). High strength is achieved by solution treatment and aging. T4 is naturally aged (medium strength, good formability), while T6 is artificially aged (highest strength, poorest formability).

Performance Comparison and Typical Applications of Common Tempers

The table below covers over 90% of the most common aluminum coil temper requirements in the market.

> Note: H22 offers better long‑term stability than H12 (less susceptible to natural aging softening), making it suitable for products with long storage periods or those that will be welded later.

Direct Selection Based on Your Actual Fabrication Process

You don’t need to understand all parameters. Just answer one question: What processing steps will my aluminum coil go through?

1. Requires repeated bending (over 90°) or flanging

→ Choose O, H12, H22, or H32. O temper is the safest but has the lowest strength.

2. Requires stamping or shallow drawing (depth < diameter)

→ H14, H24, or T4 are balanced choices. For example, 3003 H14 is widely used for cookware bottoms.

3. Requires deep drawing (depth > diameter, e.g., cans, motor housings)

→ Must choose O temper. H temper almost always cracks under deep drawing.

4. Little or no forming, only hardness or wear resistance required

→ H16, H18, or T6. Be aware that H18 cannot be bent meaningfully – it works only for flat parts.

5. Requires welding and the welded part will bear load

→ Prefer O or H1x (the heat‑affected zone of H2x softens noticeably). Avoid welding H18 or T6 directly, as post‑weld strength drops sharply to near O temper.

Three Most Common Pitfalls

– Mistake 1: Full hard (H18) is better because it is stronger

In reality, if H18 coils are used for sheet metal parts that need bending, the rejection rate can exceed 50%. Higher hardness means higher brittleness.

– Mistake 2: H22 and H12 are similar and interchangeable

Not true. H22 is partially annealed, so its natural aging softening effect after cold working is much weaker. After three years, its hardness changes less than that of H12. For long‑term use or export to humid environments, choose H22.

– Mistake 3: As long as the temper is correct, any alloy works

Wrong. For the same H14 temper, 1100 H14 has a hardness of about 32 HB, while 3003 H14 reaches 45 HB. You must specify both the alloy and the temper together.

Quick Decision Flow (Three Steps)

Confirm the alloy family – Does it require heat treatment? Welding? Corrosion resistance? → First decide the alloy (e.g., 5052, 3003).

List the most demanding forming operation – Deep drawing → only O; 90° bending → H12/22 or softer; no forming → H18/T6.

Select the lowest temper that meets your strength requirement from the table above, then try one or two grades higher to evaluate cost. Typically H14 saves 20% in material thickness compared to O temper, but tooling wear increases.

FAQ

Q1: What is the main difference between O and H tempers?

A: O temper is the softest with excellent deep‑drawing performance, while H tempers increase strength through cold working at the cost of reduced ductility.

Q2: Which is better for bending, H22 or H24?

A: H22 (quarter hard) bends more easily than H24 (half hard), with a lower risk of cracking.

Q3: Can aluminum coil temper be converted by annealing?

A: Yes, any H or T temper coil can be fully annealed back to O temper.

Q4: Can I skip specifying the second digit (e.g., the “4” in H14) when purchasing?

A: Not recommended. Roughly specifying “H1x” may result in receiving H12 or H16, which have very different performance.

Q5: What is the most common temper for 5052 aluminum coil?

A: H32 – offering medium strength, good bendability, and excellent seawater corrosion resistance.

Q6: For bending applications, what is the hardest recommended temper?

A: No harder than H14 (half hard). H16 and above crack easily when bent.

Q7: How can I quickly verify if the delivered aluminum coil meets the specified temper?

A: Use a portable Webster hardness tester and compare the reading with standard values, or request a tensile test report from your supplier.

Q8: Can T6 aluminum coil be stamped?

A: Almost never. T6 will crack under stamping. Instead, form it in T4 temper, then artificially age it to T6.

If you are selecting an aluminum coil temper for a specific project, Mingtai Aluminum provides full‑temper samples (from O to H38, T4 to T6) with actual measured performance data. Request a comparison sample – it is more reliable than looking up tables alone.