aluminum foil temper

The right choice of aluminum foil temper often determines whether your product performs flawlessly or fails in production. Between O temper and H18 temper, the performance gap is enormous—the same alloy can either form perfectly or crack repeatedly, depending solely on this single designation.

O and H18 sit at opposite ends of the temper spectrum: one is extremely soft, the other extremely hard. Choose correctly, and everything runs smoothly; choose wrong, and you will face cracking, deformation, or spring-back issues in subsequent processing.

So what exactly sets O temper apart from H18? And how do you decide?

From the Mill: Annealed vs. Unannealed

The fundamental difference between these two tempers comes down to heat treatment.

O temper (soft / fully annealed) : After cold rolling to the target thickness, the foil undergoes full annealing—heating to a controlled temperature and cooling slowly. Annealing eliminates internal stresses from cold working, allowing the grain structure to relax. The result: maximum softness and highest elongation.

H18 temper (full hard) : The foil is cold-rolled to final thickness without annealing, preserving the work-hardened state. The grains remain compressed and dense. The result: maximum strength and stiffness, but almost no plasticity.

In short: O temper is “let the foil relax completely”; H18 is “keep the foil tight and rigid.”

Performance Comparison: Hard Numbers

Using 8011 alloy as a reference, the mechanical differences are striking:

H18 offers more than 1.5 times the tensile strength of O temper, but the price is a drastic drop in elongation—from 15–25% down to just a few percent. Simply put: O temper bends and stretches; H18 stands firm but breaks when bent.

> Note that these values vary with foil thickness. Mingtai Aluminum supplies foil from 20 microns (0.02 mm) upward, available in both O and H18 tempers.

Where Each Temper Excels

Each temper has its own territory. Using the wrong one—even with the best material—will lead to disappointment.

O temper – the forming specialist

Thanks to its high elongation and excellent plasticity, O temper is the first choice for any application requiring complex shaping:

– Food packaging: yogurt lids, chocolate wrappers, container forming (deep drawing, stretching, contour fitting)

– Pharmaceutical packaging: cold-formed blister foils

– Battery soft packs: aluminum laminate layers that must flex with cell contours

– Household foil: everyday cooking and wrapping

– Laminated composites: combining with plastic or paper

H18 temper – the rigid backbone

With its high strength and stiffness, H18 is ideal for applications that demand shape retention and resistance to deformation:

– Pharmaceutical hard foil: PTP blister cover stock, surviving high-speed packaging pressures

– Electronic shielding: circuit‑board shields requiring some structural strength

– Battery foil / capacitor foil: high strength with low elongation

Mismatching the temper has direct consequences: using H18 for a deep‑drawn food container will cause cracking during forming; using O temper for a rigid structural part will result in sagging and collapse.

How to Choose: A Three‑Step Decision

Step 1 – Look at your process

– Does your subsequent processing involve deep drawing, stretching, or complex forming? → Choose O temper

– Is your process mainly slitting, laminating, or high‑speed packaging where stiffness matters? → Choose H18 temper

Step 2 – Define the performance you need

– Do you need high elongation (bend and stretch without cracking)? → O temper

– Do you need high strength (stiff, compression‑resistant, dimensionally stable)? → H18 temper

Step 3 – Consider overall cost

H18 generally costs slightly more to produce due to higher cold‑rolling reduction. However, the final price depends on alloy, thickness, and order volume—it is best to consult your supplier for a specific quote.

FAQ

Q: Can O temper be converted to H18, and vice versa?  

A: Yes—O can be cold‑rolled to H18, and H18 can be annealed back to O, but choosing the right temper at the time of purchase is far more economical than post‑processing.

Q: Does thickness affect the performance difference?  

A: Both tempers are available from 20 microns upward, but as thickness increases, the work‑hardening effect diminishes—always refer to the supplier’s mill certificate for actual values.

Q: Is there a surface quality difference?  

A: O temper (fully annealed) typically has a cleaner surface with little residual rolling oil; H18 may have trace oil residue—if printing or laminating follows, this should be considered.

Making the Right Temper Decision

Selecting the correct aluminum foil temper is ultimately a trade‑off between formability and strength. Understanding your own forming process and end‑use requirements will point you to the right answer.

For high‑quality O‑temper and H18‑temper foil—20 microns and above, in a range of alloys—Mingtai Aluminum offers consistent quality and reliable supply. Reach out to discuss your specific temper and specification needs.