H22
Quarter-hard, partially annealed. The most common temper: good for folding, panel work and boat building.
Medium-strength Al-Mg sheet
5251 Aluminium Sheet & Plate
5251 is a 2 % magnesium aluminium alloy with medium strength, very good formability and high corrosion resistance, including in marine environments. It is a long-established British and European sheet grade for boats, vehicle panels, pressings and containers. Metline supplies 5251 sheet and plate in O, H22, H24 and H26 to EN 485, worldwide.
- Alloy
- 5251 (Al-Mg 2-Mn)
- Tempers
- O, H22, H24, H26
- Thickness
- 0.5 – 50 mm
- Standards
- EN 485 · EN 573-3
What is 5251 aluminium?
5251 contains 1.7 – 2.4 % magnesium and 0.1 – 0.5 % manganese. It is non-heat-treatable, work hardens quickly and welds readily. In the UK it replaced the old BS 1470 grade NS4, and it remains a common stock grade there and in Commonwealth markets.
The alloy sits between 5005 and 5754: stronger than 5005 or 3003, slightly weaker than 5052 or 5754, and very easy to form. In the H22 temper it folds and presses cleanly while keeping enough stiffness for vehicle panels, boat superstructures and enclosures. It also anodises well, which makes it useful where a protective or decorative finish is needed on a formed part.
Because its magnesium content is low, 5251 does not suffer the sensitisation that limits 5083 and 5086 above 65 °C, so it can be used for heat-transfer equipment and boiler casings as well as marine work.
5251 chemical composition (wt %)
| Element | Minimum | Maximum |
|---|---|---|
| Silicon (Si) | — | 0.40 |
| Iron (Fe) | — | 0.50 |
| Copper (Cu) | — | 0.15 |
| Manganese (Mn) | 0.10 | 0.50 |
| Magnesium (Mg) | 1.7 | 2.4 |
| Chromium (Cr) | — | 0.15 |
| Zinc (Zn) | — | 0.15 |
| Titanium (Ti) | — | 0.15 |
| Others, each / total | — | 0.05 / 0.15 |
| Aluminium (Al) | Remainder |
Limits per EN 573-3 for EN AW-5251 (AlMg2).
5251 mechanical properties by temper
The ranges below are EN 485-2 specified values for thin sheet; thicker plate has slightly different bands. Use the band for your thickness when designing.
| Temper | Tensile strength Rm | 0.2 % proof Rp0.2 (min.) | Typical hardness |
|---|---|---|---|
| O / H111 | 160 – 200 MPa | 60 MPa | ≈ 45 HB |
| H22 / H32 | 190 – 230 MPa | 120 MPa | ≈ 56 HB |
| H24 / H34 | 210 – 250 MPa | 140 MPa | ≈ 63 HB |
| H26 / H36 | 230 – 270 MPa | 170 MPa | ≈ 69 HB |
Physical properties (typical)
- Density
- 2.69 g/cm³
- Modulus of elasticity
- about 70 GPa
- Coefficient of thermal expansion
- about 24 µm/m·°C
- Melting point
- about 625 °C
Choosing a 5251 temper
H24
Half-hard, partially annealed. More strength for flat panels and covers with moderate bends.
H26
Three-quarter-hard. For stiff panels, chequer and flat parts with little forming.
O
Annealed for deep drawing, spinning and heavy pressings.
The H2x tempers are rolled harder than needed and then partially annealed back. Compared with H1x tempers of the same strength, they bend more easily, which is why H22 rather than H12 is the normal fabrication temper.
5251 supply range and weights
Supply range
- Thickness
- Sheet 0.5 – 6 mm; plate up to about 50 mm
- Sizes
- 1000 × 2000, 1250 × 2500, 1500 × 3000 mm; 2500 × 1250 mm (8 × 4 ft); cut-to-size
- Surface
- Mill finish, PVC film, tread plate
- Processing
- Shearing, guillotining, laser and waterjet blanks
| Thickness (mm) | kg per m² | 1000 × 2000 mm (kg) | 1250 × 2500 mm (kg) | 1500 × 3000 mm (kg) |
|---|---|---|---|---|
| 0.7 | 1.88 | 3.8 | 5.9 | 8.5 |
| 1 | 2.69 | 5.4 | 8.4 | 12.1 |
| 1.2 | 3.23 | 6.5 | 10.1 | 14.5 |
| 1.5 | 4.04 | 8.1 | 12.6 | 18.2 |
| 2 | 5.38 | 10.8 | 16.8 | 24.2 |
| 2.5 | 6.72 | 13.4 | 21.0 | 30.3 |
| 3 | 8.07 | 16.1 | 25.2 | 36.3 |
| 4 | 10.76 | 21.5 | 33.6 | 48.4 |
| 5 | 13.45 | 26.9 | 42.0 | 60.5 |
| 6 | 16.14 | 32.3 | 50.4 | 72.6 |
| 8 | 21.52 | 43.0 | 67.2 | 96.8 |
| 10 | 26.90 | 53.8 | 84.1 | 121.0 |
Fabrication and finishing
Bending
H22 sheet typically bends to an inside radius of about 0.5 – 1 × thickness; H24 needs a little more.
Welding
MIG and TIG with ER5356 or ER5183 filler; weld zone softens towards O temper.
Anodising
Very good response for both decorative and protective anodic films.
Machining
Fair; use sharp tools and lubricant to avoid built-up edge.
Corrosion
High resistance in marine and industrial atmospheres; isolate from copper and steel.
Temperature
Suitable for elevated-temperature service, unlike higher-magnesium alloys.
Where 5251 is used
- Marine: small boats, superstructures, marine fittings and panelling
- Vehicles: body panels, van linings and trailer sides
- Pressings: panels, covers and formed housings
- Process equipment: silos, containers, heat-transfer devices and boiler casings
- Furniture: tubing and formed components
- Aircraft: secondary non-structural parts, ducting and fairings
5251 compared with 5005, 5052 and 5754
| Property | 5005 | 5251 | 5052 | 5754 |
|---|---|---|---|---|
| Magnesium | 0.5 – 1.1 % | 1.7 – 2.4 % | 2.2 – 2.8 % | 2.6 – 3.6 % |
| O-temper tensile range | 100 – 145 MPa | 160 – 200 MPa | 170 – 215 MPa | 190 – 240 MPa |
| Formability | Excellent | Excellent | Very good | Very good |
| Marine resistance | Good | Very good | Very good | Very good |
| Main use | Anodised panels | Boats, vehicle panels | Tanks, enclosures | Car structures, tanks |
Where 5251 is not stocked, 5052 or 5754 is the usual alternative, giving slightly higher strength.
How to order 5251
- SpecifyAlloy and temper (e.g. 5251-H22), thickness, size, quantity, standard (EN 485) and surface or film needs.
- QuoteWe confirm alloy, temper, tolerances, certification, packing and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- ProcessSheets are cut, filmed if required and inspected for dimensions and surface.
- DocumentEach delivery carries a mill test certificate to EN 10204 3.1 with the cast analysis and mechanical test results; third-party inspection can be arranged on request.
- ShipSheets and plates are interleaved or film-protected, packed in seaworthy wooden cases or on pallets, and shipped by sea or air on EXW, FOB, CIF or DAP terms.
References and standards
- EN 485-1 to -4 – Aluminium and aluminium alloys: sheet, strip and plate (technical conditions, mechanical properties, tolerances)
- EN 573-3 – Aluminium and aluminium alloys: chemical composition and form of wrought products
- BS 1470 (withdrawn) – Wrought aluminium and aluminium alloys for general engineering purposes: plate, sheet and strip (grade NS4)
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets)
5251 aluminium (aluminum) sheet: frequently asked questions
What is 5251 aluminium used for?
Boat building, marine panelling, vehicle body panels, pressings, containers, silos and heat-transfer equipment: anywhere a formable, weldable sheet with good corrosion resistance is needed.
Is 5251 marine grade?
It has high resistance to seawater and marine atmospheres and is widely used on small boats. For large welded hulls, higher-strength 5083 or 5086 is normally specified.
What is the old British name for 5251?
NS4 under the withdrawn BS 1470; H22 material was formerly described as NS4 H3.
What is the difference between 5251-H22 and H24?
H22 is quarter-hard (190 – 230 MPa), H24 half-hard (210 – 250 MPa). H22 bends more easily; H24 is stiffer.
Is there an ASTM equivalent of 5251?
5251 is mainly a European grade. In ASTM-based markets, 5052 is the closest commonly stocked alternative.
Need 5251 sheet or plate?
Send the temper, thickness, sizes, quantity and destination. We will confirm availability and a delivered price.
