H112
As extruded, with guaranteed minimums. The default for nuts, unions and fittings that are machined and not formed.
Marine · Al-Mg hexagonal bar
5454, 5456 & 5754 Marine Aluminium Hexagonal Bar
Hexagonal bar in 5454, 5456 or 5754 is used to make nuts, unions, couplings and spanner-flat fittings for boats and marine equipment, in an aluminium-magnesium alloy that matches the surrounding structure and resists seawater. 5454 is the choice for warm service, 5456 for the highest strength and 5754 for general fittings. Metline supplies all three in O, H111 and H112, cut and certified, worldwide.
- Alloys
- 5454 · 5456 · 5754
- Tempers
- O, H111, H112
- Across flats
- Up to about 200 mm
- Standards
- ASTM B221 · EN 755 · GB/T 3191
Three Al-Mg alloys for marine hex fittings
A hexagon is the natural starting shape for anything that will be turned with a spanner: nuts, plugs, unions, hose tails, adaptors and threaded bosses. Machining these from hex bar removes far less metal than starting from round, and the flats come ready-made.
In marine work the alloy matters as much as the shape. Brass and stainless fittings on an aluminium hull set up galvanic cells in seawater, so builders prefer fittings in the same aluminium-magnesium family as the hull. The three alloys on this page cover most needs:
5454 (about 2.7 % Mg) is the 5xxx alloy designed for elevated temperature. Because its magnesium stays below 3 %, it does not become sensitised in long service above 65 °C, which makes it the right hex bar for fittings on engine cooling, exhaust-adjacent and hot-fluid systems. 5456 (about 5.1 % Mg) is the strongest of the three, similar to 5083 but stronger, and suits highly loaded fasteners and fittings that stay cool. 5754 (about 3.1 % Mg) is the common European general-purpose grade, with very good corrosion resistance and formability.
Chemical composition of 5454, 5456 and 5754 (wt %)
| Element | 5456 | 5454 | 5754 |
|---|---|---|---|
| Silicon (Si), max | 0.25 | 0.25 | 0.40 |
| Iron (Fe), max | 0.40 | 0.40 | 0.40 |
| Copper (Cu), max | 0.10 | 0.10 | 0.10 |
| Manganese (Mn) | 0.50 – 1.0 | 0.50 – 1.0 | ≤ 0.50 * |
| Magnesium (Mg) | 4.7 – 5.5 | 2.4 – 3.0 | 2.6 – 3.6 |
| Chromium (Cr) | 0.05 – 0.20 | 0.05 – 0.20 | ≤ 0.30 * |
| Zinc (Zn), max | 0.25 | 0.25 | 0.20 |
| Titanium (Ti), max | 0.20 | 0.20 | 0.15 |
| Others, each / total | 0.05 / 0.15 | 0.05 / 0.15 | 0.05 / 0.15 |
| Aluminium (Al) | Remainder | Remainder | Remainder |
* For 5754, Mn + Cr must total 0.10 – 0.60 %. Limits are the registered Aluminum Association / EN 573-3 values, which IACS UR W25 also uses for 5456 and 5754.
The magnesium content drives both strength and heat sensitivity. 5456 has the most and is strongest; 5454 has the least and tolerates heat best. Some supplier tables in circulation give 5456 an iron limit of 0.25 % and add tin or zirconium limits to all three; these are not part of the registered compositions.
Mechanical properties of extruded hex bar
5454 and 5456 values are ASTM B221 minimums for extruded bar; 5754 values are EN 755-2 minimums. Chinese GB/T 3191 and European tables differ slightly (for example GB lists 5454-O from 200 MPa), so the standard on your order governs. For hex bar the "size" is the distance across flats.
| Alloy and temper | Tensile strength Rm | Proof Rp0.2 (min) | Elongation (min) |
|---|---|---|---|
| 5454-O | 215 – 285 MPa | 85 MPa | 14 % |
| 5454-H111 | ≥ 230 MPa | 130 MPa | 12 % |
| 5454-H112 | ≥ 215 MPa | 85 MPa | 12 % |
| 5456-O | 285 – 365 MPa | 130 MPa | 14 % |
| 5456-H111 | ≥ 290 MPa | 180 MPa | 12 % |
| 5456-H112 | ≥ 285 MPa | 130 MPa | 12 % |
| 5754-O / H111 | 180 – 250 MPa | 80 MPa | 14 – 17 % |
| 5754-H112 | ≥ 180 MPa | 80 MPa | 12 – 14 % |
| Physical property | 5454 | 5456 | 5754 |
|---|---|---|---|
| Density | 2.69 g/cm³ | 2.66 g/cm³ | 2.67 g/cm³ |
| Modulus of elasticity | About 70 GPa | About 71 GPa | About 70 GPa |
| Thermal conductivity | About 134 W/m·K | About 116 W/m·K | About 130 – 140 W/m·K |
| Melting range | About 602 – 646 °C | About 570 – 638 °C | About 600 – 640 °C |
| Long-term service above 65 °C | Suitable | Avoid (sensitisation) | Use with care |
Tempers for hex bar
O
Fully annealed and most ductile. Used where hex stock is upset or cold-headed into bolts and special fasteners.
H111
Annealed then lightly strain-hardened in straightening. Higher proof stress than O for the same ductility class.
Cold-finished
Drawn hex bar (ASTM B211 or EN 754) gives tighter flats and a brighter surface for screw-machine work.
Standards and class acceptance
Hex bar is usually ordered to ASTM B221 (extruded) or ASTM B211 (cold-finished), EN 755 or EN 754, or GB/T 3191. Fastener-grade material may also call for ASTM B316, which covers rivet and cold-heading wire and rod. Note that the IACS UR W25 extrusion table names 5083, 5383, 5059 and 5086 (plus 6005A, 6061 and 6082); it does not list 5454, 5456 or 5754 for extruded products. These alloys are therefore used for fittings and machinery parts rather than primary hull structure, or accepted by a society case by case. Check with your surveyor if a hex fitting forms part of a classed structure.
| Alloy | UNS | EN designation | Werkstoff | JIS |
|---|---|---|---|---|
| 5454 | A95454 | EN AW-5454 (AlMg3Mn) | 3.3537 | A5454 |
| 5456 | A95456 | EN AW-5456 | — | — |
| 5754 | A95754 | EN AW-5754 (AlMg3) | 3.3535 | — |
Hex bar sizes and weights
Supply range
- Across flats
- From about 6 mm up to about 200 mm (largest inscribed circle)
- Length
- Usually 3000 – 6000 mm; up to about 12 m or cut pieces by arrangement
- Tempers
- O, H111, H112; cold-finished in smaller sizes
- Processing
- Saw cutting, chamfered ends, packing to protect the flats
A hexagon of across-flats size s has an area of 0.866 s². Weight per metre is 0.866 × s² × density ÷ 1000. The table uses 5454 (2.69 g/cm³); 5456 and 5754 are about 1 % lighter.
| Across flats (mm) | kg per metre | kg per 3 m bar | kg per 6 m bar |
|---|---|---|---|
| 10 | 0.233 | 0.70 | 1.4 |
| 13 | 0.394 | 1.18 | 2.4 |
| 17 | 0.673 | 2.02 | 4.0 |
| 19 | 0.841 | 2.52 | 5.0 |
| 22 | 1.13 | 3.38 | 6.8 |
| 24 | 1.34 | 4.03 | 8.1 |
| 27 | 1.70 | 5.09 | 10.2 |
| 30 | 2.10 | 6.29 | 12.6 |
| 36 | 3.02 | 9.06 | 18.1 |
| 41 | 3.92 | 11.75 | 23.5 |
| 46 | 4.93 | 14.79 | 29.6 |
| 50 | 5.82 | 17.47 | 34.9 |
| 60 | 8.39 | 25.16 | 50.3 |
| 70 | 11.42 | 34.25 | 68.5 |
| 80 | 14.91 | 44.73 | 89.5 |
| 100 | 23.30 | 69.89 | 139.8 |
| 120 | 33.55 | 100.64 | 201.3 |
| 150 | 52.42 | 157.25 | 314.5 |
Hex bar tolerances
Typical tolerances for extruded hex bar. 5454 falls in the lower-magnesium column; 5456 and 5754 use the wider column.
| Across flats (mm) | 5454 tolerance | 5456 / 5754 tolerance | Corner radius, max |
|---|---|---|---|
| 10 – 18 | ±0.22 | ±0.30 | 1.5 mm |
| over 18 – 25 | ±0.25 | ±0.35 | 1.5 mm |
| over 25 – 40 | ±0.30 | ±0.40 | 2.0 mm |
| over 40 – 50 | ±0.35 | ±0.45 | 2.0 mm |
| over 50 – 65 | ±0.40 | ±0.50 | 2.0 mm |
| over 65 – 80 | ±0.50 | ±0.70 | 2.5 mm |
| over 80 – 100 | ±0.55 | ±0.90 | 3.0 mm |
| over 100 – 120 | ±0.65 | ±1.0 | 3.0 mm |
| over 120 – 150 | ±0.80 | ±1.2 | 4.0 mm |
| over 150 – 180 | ±1.00 | ±1.4 | 4.0 mm |
| over 180 – 220 | ±1.15 | ±1.7 | 5.0 mm |
Form tolerances
- Straightness
- About 0.8 mm in any 300 mm up to 80 mm across flats, 1.0 – 1.5 mm above; roughly 2 – 3 mm per metre overall
- Twist
- About 1° per metre for small bars up to 2.5° for the largest; 1.5 – 4° over the full length
- Length
- Fixed lengths plus-only, around +5 to +14 mm
Machining, threading and joining
Machining
All three alloys are soft and can smear. Sharp, polished carbide inserts with high positive rake, chip breakers and flood coolant give clean threads. H112 and H111 machine better than O.
Threads
Roll threads where possible: rolled threads in Al-Mg alloys are stronger and more fatigue-resistant than cut ones. Use anti-seize on aluminium-to-aluminium threads to prevent galling.
Welding
Weld 5454 with ER5554 for service above 65 °C, or ER5356; weld 5456 with ER5556 to keep strength; weld 5754 with ER5356 or ER5183.
Galvanic isolation
When an aluminium fitting meets a stainless or bronze part, add an insulating washer or sleeve and keep the joint sealed from seawater.
Anodising
All three anodise well; hard anodising improves thread wear resistance on fittings that are assembled often.
Cold heading
O-temper 5454 and 5754 head and upset well for special bolts and rivets; 5456 needs more force and larger radii.
Marine uses of Al-Mg hex bar
- Fuel and cooling systems: unions, adaptors and hose tails in 5454 for warm lines and tanks
- Fasteners: nuts, special bolts and studs for aluminium structures where stainless would cause galvanic attack
- Deck hardware: stanchion bases, threaded sockets and awning fittings in 5754
- Structural fittings: highly loaded threaded bosses and tie-rod ends in 5456
- Pipe supports: threaded spacers and standoffs for pipe and cable trays
- Shore and offshore: pontoon connectors, ladder fittings and aquaculture hardware
A typical example is a fuel-system fitting kit on an aluminium fast ferry: tank sender bosses and fill-line unions are turned from 5454-H112 hex bar because the fuel return can run warm, while the matching tank plate is 5454 or 5083 depending on location.
5454 vs 5456 vs 5754 vs 5083 hex bar
| Property | 5454-H112 | 5456-H112 | 5754-H112 | 5083-H112 |
|---|---|---|---|---|
| Min tensile | 215 MPa | 285 MPa | 180 MPa | 270 MPa |
| Min proof | 85 MPa | 130 MPa | 80 MPa | 110 MPa |
| Magnesium | 2.4 – 3.0 % | 4.7 – 5.5 % | 2.6 – 3.6 % | 4.0 – 4.9 % |
| Service above 65 °C | Yes | No | Limited | No |
| Listed in UR W25 (extruded) | No | No | No | Yes |
| Typical role | Warm-service fittings | High-strength fittings | General fittings | Structural bar |
If a hex part must be certified as hull structure, 5083 hex bar is usually the simplest route. See the 5083 marine hex bar page.
How to order marine hex bar
- SpecifyAlloy and temper, across-flats size and length or cut pieces, quantity and the governing standard with its edition (ASTM B221 / B211, EN 755 / 754 or GB/T 3191). If the vessel is classed, name the society and whether a class certificate is required.
- ConfirmWe confirm the standard and tolerance class can be met, which tests are included (tensile, chemistry, corrosion tests where the standard calls for them) and the delivery terms: EXW, FOB, CIF or DAP.
- InspectMaterial is checked for dimensions, straightness, twist and surface condition before packing; third-party or class surveyor inspection can be arranged on request.
- DocumentEach lot ships with a mill test certificate to EN 10204 3.1 showing the cast analysis and mechanical results, traceable by cast or lot number.
- Pack and shipBars or plates are bundled or cased with moisture protection, marked with alloy, temper, size and lot, and shipped by sea or air to your port or yard.
References and standards
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles and Tubes
- ASTM B211 – Aluminum and Aluminum-Alloy Rolled or Cold-Finished Bar, Rod and Wire
- EN 755-2 – Aluminium and aluminium alloys: extruded rod/bar, tube and profiles, mechanical properties
- EN 573-3 – Aluminium and aluminium alloys: chemical composition and form of wrought products
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- IACS UR W25 – Aluminium alloys for hull construction and marine structure
Marine aluminium (aluminum) hex bar: FAQs
Which alloy should I choose for hex fittings near an engine?
5454. Its magnesium content stays below 3 %, so it does not become sensitised to intergranular corrosion in long service above 65 °C, unlike 5456 or 5083.
Is 5456 hex bar stronger than 5083?
Yes. In H112, ASTM B221 minimums are 285 MPa tensile and 130 MPa proof for 5456 against 270 and 110 MPa for 5083. Like 5083, it should be kept away from long exposure above 65 °C.
Are 5454, 5456 and 5754 hex bars class-approved for hull structure?
IACS UR W25 does not list these three alloys for extruded products, so they are normally used for fittings and equipment. A society can accept them case by case; for certified structural hex parts, 5083 or 5383 is the usual choice.
How much does an aluminium hex bar weigh?
Weight per metre is 0.866 × s² × density ÷ 1000, with s the across-flats size in millimetres. A 30 mm 5454 hex bar weighs about 2.10 kg per metre.
Can aluminium hex nuts be used on a boat instead of stainless?
Yes, on aluminium structures where galvanic corrosion is the main risk. They have lower strength than stainless, so size them accordingly and use anti-seize to prevent galling.
Can Metline cut hex bar to length?
Yes. We supply full bars or cut pieces with chamfered or deburred ends, packed to protect the flats, with an EN 10204 3.1 certificate, worldwide.
Need marine hex bar in 5454, 5456 or 5754?
Send the alloy, across-flats sizes, temper and quantities. We will reply with availability, certification and a delivered price.
