5052 Aluminum: O, H32 or H34, Bend Radius and Buying Mistakes

Many workshops order simply "5052 aluminum, 2 mm thick", then find the outer edge cracking on the press brake, or the sheet softer than the drawing requires. The cause is usually not the alloy but the temper code that follows it: O, H32 or H34. Within the same aluminum–magnesium alloy, these three tempers give clearly different strength, ductility and bend radius. This article compares the three most common tempers of 5052 aluminum sheet using standard data, then suggests how to choose for electrical enclosures, truck bodies and pressed parts.

Three common tempers of 5052 aluminum, 1.5–3 mm sheet (compiled by H&D Steel)

Why 5052 comes in several tempers

5052 belongs to the 5xxx series, containing 2.2–2.8% magnesium and 0.15–0.35% chromium per EN 573-3. Unlike the 6xxx series, 5052 cannot be strengthened by heat treatment. Its strength comes from cold rolling: the more it is rolled, the harder and less bendable the sheet becomes. The same alloy is therefore sold at several hardness levels, and the code after the letter H tells you how the sheet was processed.

• O (often written H111 under EN): fully annealed, the most ductile and the lowest strength.
• H32: cold rolled then stabilised at low temperature to quarter hard. This is the most common temper for 5052 sheet.
• H34: same process as H32 but to half hard, stronger and less ductile.

The first digit after H describes the process: 1 is cold rolled only, 2 is cold rolled then partially annealed, 3 is cold rolled then stabilised. The second digit describes the hardness level; the higher the number, the harder the sheet. Temper changes only the mechanical properties; density, elastic modulus and thermal conductivity stay almost the same, as explained in our article on physical properties of aluminum 1050, 3003, 5052.

O, H32 and H34 compared

The table combines data for 1.5–3 mm sheet from two standard systems. EN values follow EN 485-2 as published in datasheets by Dinco, Aalco and thyssenkrupp; ASTM values follow the ASTM B209 and AMS limits published by Aircraft Materials, converted from ksi to MPa. For H34, the EN source found lists only H24 at the same half-hard level, so H24 values are shown for reference.

Tensile strength is almost identical in both systems: under ASTM, H32 is 31–38 ksi (about 214–262 MPa) and H34 is 34–41 ksi (about 234–283 MPa). HB hardness in EN is for information only, not an acceptance criterion. The symbol t is the sheet thickness.

Yield strength: where EN and ASTM differ

The row to watch is yield strength. For H32, EN 485-2 requires a minimum of only 130 MPa, while ASTM B209 requires about 160 MPa (23 ksi). At half hard, EN lists 150 MPa for H24 while ASTM lists about 180 MPa (26 ksi) for H34. Two sheets both marked H32 on their mill test certificate (the mill's test report for each lot) can therefore both conform, yet differ by about 30 MPa in yield strength.

For enclosures or cladding the gap matters little. For parts designed on yield strength, such as gusset plates, brackets or load-bearing floors, state the standard and the minimum value on the order, then read the Rp0.2 line on the certificate rather than just the letters H32.

Bend radius: the number that decides whether the sheet cracks

Bend radius is given as a multiple of thickness. For example, 2 mm H32 sheet needs an inside radius of about 2–3 mm; H34 of the same thickness needs about 3–4 mm; O temper can be bent almost flat. The two sources differ slightly: Aircraft Materials gives 1t for H32 and 1.5t for H34, while the EN table gives 1.5t for H32 and 2t for H24 in the 1.5–3 mm range. For series production, use the larger figure.

The punch radius decides whether the aluminum sheet cracks at the bend — AI-generated illustration

• Small-radius punches commonly used for steel and stainless steel easily crack the outer edge of H34 sheet. Choose a punch radius no smaller than the table value.
• Bend lines should run across the rolling direction; bending parallel to the rolling direction cracks more easily.
• A 180° hem needs O temper, or H32 with a generous radius.
• Table values are recommendations; actual results also depend on the machine and tooling. Test-bend an offcut from the same lot before running production.

Choosing a temper by job

• Electrical enclosures, equipment boxes, cable trays with many bends: H32 is the balanced choice. The sheet is stiff enough for flat panels and bends 90° at 1–1.5t without cracking.
• Deep-drawn parts, large curves, 180° hems: choose O temper. For high-volume pressing from strip, consider 5052 aluminum coil and slit strip to reduce scrap.
• Flat panels with few bends that must resist dents and scratches: truck body walls, covers and cladding can use H34, or H32 one gauge thicker.
• Welded structures: welding heat anneals the zone next to the weld, so strength there drops close to O temper whether the sheet was bought as H32 or H34. Design welds on O-temper properties; paying extra for H34 does not make the weld zone stronger.

Also remember that H34 does not make a panel deflect less. The elastic modulus of every temper is about 70 GPa; to make a panel stiffer you must increase thickness or add formed ribs. Available thicknesses and sheet sizes are listed on our aluminum sheet 1050, 3003, 5052 page.

Five common mistakes when buying 5052 aluminum

1. Specifying the alloy but not the temper. "5052, 2 mm" could be soft O sheet or hard H34 sheet. An order should state alloy, temper, standard, thickness and size.
2. Not reading the standard and Rp0.2 lines on the certificate. The same H32 label carries minimum yield values about 30 MPa apart under EN and ASTM.
3. Treating H24 and H34 as the same. Tensile strength is similar but the processing differs. If the drawing specifies H34, ask before accepting a substitute.
4. Using a small steel punch radius on H34 sheet. The outer edge shows hairline cracks, especially when the bend line runs parallel to the rolling direction.
5. Choosing H34 for welded parts to make them "stronger". The zone next to the weld is still as soft as O temper, so the extra cost buys no strength where it is needed.

References

• Dinco – Aluminium Alloy 5052 H32 datasheet (EN 485-2)
• Aalco – Aluminium Alloy 5052 H32 Sheet and Treadplate datasheet
• thyssenkrupp Materials Processing – EN AW 5052 (H111, H22, H24 properties)
• Aircraft Materials – Aluminium 5052 in O, H32, H34 tempers
• Wikipedia – 5052 aluminium alloy (ASTM B209 limits)

If you need 5052 aluminum sheet or coil in the right temper and thickness for electrical enclosures, truck bodies or pressed parts, please send a request via our aluminum sheet and coil quotation page or call hotline/Zalo 0904 678 236 (Sales Department) for advice on the right temper for each job.