H112
As extruded with guaranteed minimums. The normal choice for seatings, chocks and machined blocks.
Marine · Al-Mg extruded square bar
5083 & 5383 Marine Aluminium Square Bar
5083 square bar gives shipyards a weldable, seawater-resistant block section for chocks, foundations, rubbing strips and machined fittings that sit flat against 5083 hull plate. 5383 offers the same form with higher welded strength. Metline supplies both alloys as extruded square bar from about 10 to 220 mm in O, H111 and H112, cut to length and certified, to buyers worldwide.
- Alloys
- 5083 · 5383
- Tempers
- O, H111, H112
- Side length
- About 10 – 220 mm
- Standards
- EN 755 · ASTM B221 · IACS W25
What 5083 square bar is used for on a vessel
A square section has four flat faces and square corners, so it can be welded flush to plate on two sides, drilled and tapped on the others, and stacked or shimmed without packing pieces. In 5083 that geometry comes with the alloy's two marine advantages: excellent resistance to seawater and full weldability.
On aluminium vessels square bar turns up wherever a builder needs a solid, compact block: engine and generator seatings where holding-down bolts are tapped into the bar, chocks under deck machinery, keel and skeg doublers, gunwale and fender rubbing strips that take abrasion, and the anchor points of davits, cranes and lifting gear. Because the bar and the surrounding plate are the same alloy family, the welded joint has uniform strength and corrosion behaviour.
5383 square bar is specified when a designer wants to save weight or thickness at highly loaded joints. Its minimum proof strength in the as-extruded condition is about 70 % higher than standard 5083, and its welded strength and fatigue life are also better, while machining and welding practice are the same.
Composition of 5083 and 5383 (wt %)
Both alloys are aluminium-magnesium-manganese grades with very low copper. The 5083 values below are the registered limits used by ASTM, EN 573-3 and IACS UR W25; the 5383 column shows the tighter impurity and higher manganese limits that give it its extra strength.
| Element | 5083 | 5383 |
|---|---|---|
| Silicon (Si), max | 0.40 | 0.25 |
| Iron (Fe), max | 0.40 | 0.25 |
| Copper (Cu), max | 0.10 | 0.20 |
| Manganese (Mn) | 0.40 – 1.0 | 0.7 – 1.0 |
| Magnesium (Mg) | 4.0 – 4.9 | 4.0 – 5.2 |
| Chromium (Cr) | 0.05 – 0.25 | ≤ 0.25 |
| Zinc (Zn), max | 0.25 | 0.40 |
| Titanium (Ti), max | 0.15 | 0.15 |
| Zirconium (Zr), max | — | 0.20 |
| Others, each / total | 0.05 / 0.15 | 0.05 / 0.15 |
| Aluminium (Al) | Remainder | Remainder |
Mechanical properties of 5083 / 5383 square bar
Minimum values for extruded products in IACS UR W25. For 5083 these agree with ASTM B221 and EN 755-2. For square bar the size used to pick the elongation basis is the side length: A50 up to 12.5 mm, A5d above.
| Alloy and temper | Tensile strength Rm | Proof Rp0.2 (min) | Elongation A50 / A5d (min) |
|---|---|---|---|
| 5083-O | 270 – 350 MPa | 110 MPa | 14 % / 12 % |
| 5083-H111 | ≥ 275 MPa | 165 MPa | 12 % / 10 % |
| 5083-H112 | ≥ 270 MPa | 110 MPa | 12 % / 10 % |
| 5383-O / H111 | ≥ 290 MPa | 145 MPa | 17 % |
| 5383-H112 | ≥ 310 MPa | 190 MPa | 13 % |
Some supplier tables show different minimums for 5083-H112 bar over 12.5 mm. Design to the standard named on your order; the actual values for each lot are on the mill certificate.
Physical properties (5083)
- Density
- 2.66 g/cm³ (0.096 lb/in³)
- Modulus of elasticity
- About 70 GPa (10,200 ksi)
- Thermal conductivity
- About 117 – 120 W/m·K
- Electrical conductivity
- About 29 % IACS
- Coefficient of thermal expansion
- About 23.8 µm/m·°C (20 – 100 °C)
- Melting range
- About 591 – 638 °C
- Magnetic
- Non-magnetic
Tempers for square bar
O
Fully annealed with a maximum tensile limit. Pick O when square bar must be bent around a curved sheer line or fender profile.
H111
Annealed and lightly stretched for straightness, giving a higher proof stress than O.
Weld zone
Heat from welding anneals the bar locally towards O-temper strength. Because O and H112 minimums are similar, the loss is small, unlike 6xxx alloys.
Standards and classification requirements
Square bar for structural use on classed ships falls under the extruded-products section of each society's material rules, which follow IACS UR W25. That document covers 5083, 5383, 5059 and 5086 in O, H111 and H112, and requires manufacture at works approved for the grade, a tensile test per batch weight and, for closed profiles, checks on press welds (not relevant to solid bar). For non-structural fittings, a mill certificate to ASTM B221 or EN 755-2 is often sufficient; agree this with the designer and surveyor first.
| Standard | Scope for square bar |
|---|---|
| EN 755-1 / -2 | Technical delivery conditions and mechanical properties of extruded bar |
| EN 755-4 | Tolerances on dimensions and form for extruded square bar |
| ASTM B221 (ASME SB-221) | Extruded bar, rod, wire, profiles and tube, including 5083 |
| GB/T 3191 | Extruded bars and rods to Chinese standards |
| IACS UR W25 | Unified requirement for aluminium in hull construction |
| EN AW-5083 / UNS A95083 / 3.3547 | Equivalent designations for 5083 |
Square bar sizes and weights
Supply range
- Side length
- About 10 – 220 mm extruded
- Length
- 3000, 4000 and 6000 mm standard; cut lengths on request
- Corners
- Sharp or with small radius, within the standard corner tolerance
- Surface
- Mill finish; protective film or interleaving for visible trim parts
Square bar weighs side² × 2.66 ÷ 1000 kg per metre, with the side in millimetres.
| Side (mm) | kg per metre | kg per 3 m bar | kg per 6 m bar |
|---|---|---|---|
| 10 | 0.266 | 0.80 | 1.6 |
| 12 | 0.383 | 1.15 | 2.3 |
| 15 | 0.599 | 1.80 | 3.6 |
| 20 | 1.06 | 3.19 | 6.4 |
| 25 | 1.66 | 4.99 | 10.0 |
| 30 | 2.39 | 7.18 | 14.4 |
| 35 | 3.26 | 9.78 | 19.6 |
| 40 | 4.26 | 12.77 | 25.5 |
| 50 | 6.65 | 19.95 | 39.9 |
| 60 | 9.58 | 28.73 | 57.5 |
| 70 | 13.03 | 39.10 | 78.2 |
| 80 | 17.02 | 51.07 | 102.1 |
| 100 | 26.60 | 79.80 | 159.6 |
| 120 | 38.30 | 114.91 | 229.8 |
| 150 | 59.85 | 179.55 | 359.1 |
| 180 | 86.18 | 258.55 | 517.1 |
| 200 | 106.40 | 319.20 | 638.4 |
| 220 | 128.74 | 386.23 | 772.5 |
Tolerances on side, corners, twist and straightness
Typical tolerances for extruded square bar in the higher-magnesium alloy group, consistent with EN 755-4 and GB/T 3191. Closer tolerances can be agreed for machined or cold-drawn bar.
| Side length (mm) | Side tolerance (mm) | Corner radius, max (mm) | Twist per 1 m / full length (°) |
|---|---|---|---|
| 10 – 18 | ±0.30 | 1.5 | 1 / 3 |
| over 18 – 25 | ±0.35 | 1.5 | 1 / 3 |
| over 25 – 40 | ±0.40 | 2.0 | 1.5 / 4 (above 30 mm) |
| over 40 – 50 | ±0.45 | 2.0 | 1.5 / 4 |
| over 50 – 65 | ±0.50 | 3.0 | 2 / 5 |
| over 65 – 80 | ±0.70 | 3.0 | 2 / 5 |
| over 80 – 100 | ±0.90 | 3.0 | 2 / 5 |
| over 100 – 120 | ±1.0 | 3.0 | 2 / 5 |
| over 120 – 150 | ±1.2 | 4.0 | 3 / 6 |
| over 150 – 180 | ±1.4 | 4.0 | 3 / 6 |
| over 180 – 220 | ±1.7 | 5.0 | 3 / 6 |
Form tolerances
- Straightness
- About 0.8 mm in any 300 mm up to 80 mm side, rising to 1.5 mm for the largest sizes; 2 – 3 mm per metre overall
- Squareness of corners
- About 1 % of the side up to 100 mm; 1.0 – 1.5° for larger bars
- Fixed lengths
- Plus-only, roughly +5 to +14 mm depending on size and length
Welding, machining and fitting square bar
Welding to plate
Fillet-weld with ER5183 for full strength. Clean the oxide film by stainless brushing just before welding and keep the joint dry; hydrogen from moisture causes porosity.
Tapped holes
Threads in 5083 are softer than in steel. Use thread inserts (helical coil) for bolts that will be removed often, such as engine holding-down bolts.
Machining
Use sharp, polished tools and generous coolant; 5083 is gummy in O temper. Climb milling and high spindle speeds improve finish.
Isolation
Separate steel engine feet and stainless fasteners from the bar with insulating pads, sleeves and washers, and seal the faying surfaces.
Bending
Order O temper for bars that follow a curve; bend cold over a former with a radius of several times the side length.
Heat exposure
Keep long-term metal temperature below about 65 °C; position seatings away from uninsulated exhaust runs.
Typical uses of 5083 square bar
- Machinery seatings: engine, gearbox, generator and pump foundations with tapped holding-down holes
- Deck hardware bases: chocks and doublers under winches, capstans, davits and crane pedestals
- Rubbing and fender strips: sacrificial square bar along gunwales and chines of workboats and pilot boats
- Keel and skeg reinforcement: solid bar welded along the keel line to take grounding loads
- Hatch and door frames: machined frames and coamings that carry gaskets and dogs
- Offshore structures: gangway, ladder and boat-landing fittings exposed to splash
In a typical patrol-boat engine room, each engine bed is a pair of 5083 square bars welded to the floors, with steel-backed rubber mounts bolted through helical-coil inserts. The bars spread the engine loads into the hull while staying compatible with the surrounding 5083 structure.
5083 square bar versus 6082 square bar and plate strip
| Factor | 5083-H112 square bar | 5383-H112 square bar | 6082-T6 square bar | Strip cut from 5083 plate |
|---|---|---|---|---|
| Min proof strength | 110 MPa | 190 MPa | 260 MPa | Depends on plate temper |
| Strength across weld | Near parent metal | Highest welded value | Drops to about half | Near parent metal |
| Seawater immersion | Excellent | Excellent | Needs coating | Excellent |
| Straightness and corners | Controlled | Controlled | Controlled | Cut edges need dressing |
| Best use | Welded, wet fittings | Highly loaded welded joints | Bolted, dry, unwelded parts | One-off large blocks |
How to order 5083 square bar
- SpecifyAlloy and temper, side length and length or cut pieces, quantity and the governing standard with its edition (EN 755-2, ASTM B221, GB/T 3191 or class rule). 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
- IACS UR W25 – Aluminium alloys for hull construction and marine structure
- EN 755-2 – Aluminium and aluminium alloys: extruded rod/bar, tube and profiles, mechanical properties
- EN 755-4 – Extruded square bar: tolerances on dimensions and form
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles and Tubes
- 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)
5083 marine aluminium (aluminum) square bar: FAQs
What sizes of 5083 square bar can be supplied?
Extruded 5083 and 5383 square bar is commonly available from about 10 mm to 220 mm side length, in 3, 4 or 6 metre lengths or cut to your sizes.
Is 5383 square bar worth the extra cost?
It is when the bar carries high loads across welds or cyclic loads. 5383-H112 has a minimum proof strength of 190 MPa against 110 MPa for 5083-H112, with better welded and fatigue strength, which can allow smaller sections.
Can I tap threads directly into 5083 square bar?
Yes, but threads in a soft Al-Mg alloy wear if bolts are removed often. For machinery holding-down bolts or covers, fit helical-coil thread inserts.
Why not use 6082 square bar on a boat?
6082-T6 is stronger before welding, but its heat-affected zone loses roughly half its proof strength and it needs coating for permanent immersion. It suits bolted, above-water parts better than welded underwater fittings.
What tolerance applies to extruded square bar?
Typically ±0.30 mm on the side for small sizes rising to ±1.7 mm at 220 mm, with limits on corner radius, twist and straightness, per EN 755-4 or the equivalent standard on your order.
Does Metline supply class-certified 5083 square bar?
Tell us the classification society when you enquire. Class certification requires material from a works approved by that society, and we confirm whether it can be provided for your sizes before you order.
Need 5083 square bar for seatings or fittings?
Send side lengths, temper, cut lengths, quantities and the class society. We will confirm availability, certification and a delivered price.
