Aluminum 5251 · temper
Aluminum 5251-O
Properties of the O condition, compared with the other 5251 tempers.
Pick for deep drawing, tight-radius bending, stretch forming or spinning where maximum ductility matters.
What is 5251-O?
5251-O is 5251 in the O temper — pick for deep drawing, tight-radius bending, stretch forming or spinning where maximum ductility matters. 5251-O has a yield strength of 75 MPa (10.9 ksi) and a tensile strength of 180 MPa (26.1 ksi) — weaker than 91% of aluminum grades. Elongation at break is 23% and the elastic modulus is 70 GPa (10.2 Msi). 5251-O has a density of 2.69 g/cm³ (0.0972 lb/in³), lighter than 67% of aluminum grades. It melts at 607°C (1,125 °F).
Advantages
- Forms and bends easily — 92/100, better than 94% of aluminum grades
- Ductile — tolerates forming and impact — 23%, better than 92% of aluminum grades
- Readily welded — 88/100, better than 85% of aluminum grades
- Good corrosion resistance — 72/100, better than 83% of aluminum grades
- Conducts heat well — 160 W/m·K (92.4 BTU/hr·ft·°F), better than 75% of aluminum grades
Limitations
- Low strength — 75 MPa (10.9 ksi), worse than 91% of aluminum grades
- Difficult to machine — 35/100, worse than 86% of aluminum grades
5251-O properties
Typical room-temperature values for 5251-O — 11 properties are specific to this condition; the rest are grade-level values shared by every 5251 temper. Each bar shows where the value sits among the aluminum grades in FabDigit's library — further right is higher.
Physical3
5251-O has a density of 2.69 g/cm³ (0.0972 lb/in³), lighter than 67% of aluminum grades. It melts at 607°C (1,125 °F).
Mechanical10
5251-O has a yield strength of 75 MPa (10.9 ksi) and a tensile strength of 180 MPa (26.1 ksi) — weaker than 91% of aluminum grades. Elongation at break is 23% and the elastic modulus is 70 GPa (10.2 Msi).
Thermal6
5251-O is rated for continuous service to 150°C (302 °F). It conducts heat at 160 W/m·K (92.4 BTU/hr·ft·°F), better than 75% of aluminum grades. Thermal expansion is 23.8 µm/m·K (13.2 µin/in·°F).
Electrical3
5251-O conducts electricity at 35 % IACS, better than 52% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), better than 83% of aluminum grades.
Sustainability4
Producing a kilogram of 5251-O takes about 200 MJ of energy and emits 12.5 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 30%.
Manufacturability7
5251-O's machinability is fair (35/100, worse than 86% of aluminum grades); weldability excellent (88/100); formability excellent (92/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 5251 tempers and conditions
5251 is also supplied in 14 other conditions. The full side-by-side table is on the 5251 overview.
- H34Stabilised half-hard sheet/plate for load-bearing panels, tread plate and welded fabrications needing stable properties in service.180 MPa yield · 65 HB
- H24Choose when H22 strength is insufficient but moderate forming (brake bending to generous radii) is still required.180 MPa yield · 65 HB
- H22The standard stocked 5251 sheet/coil temper: good balance of strength, bending and weldability for panels, tanks, vehicle bodywork and marine fittings.150 MPa yield · 57 HB
- H1125251-H112 is hot-worked plate or extruded product that acquires slight strain hardening during fabrication and is supplied to guaranteed minimum strength limits.85 MPa yield · 48 HB
- OPick for deep drawing, tight-radius bending, stretch forming or spinning where maximum ductility matters.75 MPa yield · 45 HB
- F5251 in the as-fabricated condition — properties result from the forming process only and are not guaranteed, giving soft, highly formable Al-Mg2Mn sheet, plate or extrusion.75 MPa yield · 45 HB
Working with 5251-O
Is 5251 easy to machine?
Machinable but gummy in O/H22 — use sharp polished-flute carbide, high rake, high speed and flood lubrication to avoid built-up edge; harder H2x/H3x tempers chip better.
Can 5251 be welded?
Excellent for GTAW/GMAW and resistance welding with 5356 or 5183 filler; weld metal returns to about O-temper strength, so design joints on annealed properties.
Can 5251 be formed, bent or molded?
Very good cold formability — deep draw and spin in O, brake-bend H22/H24 with generous radii and allow for springback; avoid warm working above ~150 °C which softens H tempers.
What surface finishes work on 5251?
Anodises brightly (clear, hard or colour) and takes chromate/pretreated paint and powder coat well; mechanical polishing is fair, so brushed or embossed finishes are common.
5251 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| SiEN 573-3 | ≤ 0.4 | 0.15 |
| Fe | ≤ 0.5 | 0.25 |
| Cu | ≤ 0.15 | 0.03 |
| Mn | 0.1 – 0.5 | 0.3 |
| Mgprincipal strengthening element | 1.7 – 2.4 | 2 |
| Cr | ≤ 0.15 | 0.05 |
| Zn | ≤ 0.15 | 0.05 |
| Ti | ≤ 0.15 | 0.03 |
| Others (each)total 0.15 max | ≤ 0.05 | — |
| Al | balance | — |
5251-O — frequently asked
What is 5251-O used for?
5251-O is typically used for vehicle body sheet, architectural panels and cladding, tread plate flooring and walkways, welded tanks and containers, road tanker and trailer panels and marine and industrial enclosures. In short: european 5251 sheet alloy.
What is the yield strength of 5251-O?
5251-O has a typical yield strength of 75 MPa (10.9 ksi) and a tensile strength of 180 MPa (26.1 ksi) — weaker than 91% of aluminum grades. Strength varies by condition: see the 15 listed tempers.
Is 5251-O easy to machine?
Not especially — machinability is rated fair (35/100, worse than 86% of aluminum grades). Machinable but gummy in O/H22 — use sharp polished-flute carbide, high rake, high speed and flood lubrication to avoid built-up edge; harder H2x/H3x tempers chip better.
Can 5251-O be welded?
Yes — weldability is rated excellent (88/100). Excellent for GTAW/GMAW and resistance welding with 5356 or 5183 filler; weld metal returns to about O-temper strength, so design joints on annealed properties.
What surface finishes work on 5251-O?
Anodises brightly (clear, hard or colour) and takes chromate/pretreated paint and powder coat well; mechanical polishing is fair, so brushed or embossed finishes are common.
Can 5251-O be formed, bent or molded?
Very good cold formability — deep draw and spin in O, brake-bend H22/H24 with generous radii and allow for springback; avoid warm working above ~150 °C which softens H tempers.
What is the maximum service temperature of 5251-O?
5251-O is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 5251-O?
Yes — 5251-O is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- EN 573-3 Aluminium and aluminium alloys — chemical composition of wrought products — CEN (2019)
- EN 485-2 Aluminium and aluminium alloys — sheet, strip and plate: mechanical properties — CEN (2016)
- 5251 Aluminium alloy sheet data — Aalco Metals (2023)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol.13 — Corrosion — ASM International (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.