Welding
High-Mg filler (5B06-type, ER5183 or ER5556) for 5A05, 5A06 and 5A01; ER5356 or ER5183 for 5A03. Clean oxide immediately before welding.
Marine · GB-standard Al-Mg square bar
5A01, 5A03, 5A05 & 5A06 Marine Aluminium Square Bar
Square bar in the 5A-series alloys gives builders working to GB or GOST drawings a solid, weldable aluminium-magnesium section for seatings, chocks, frames and machined blocks that matches 5A05 and 5A06 hull and tank plate. Metline supplies 5A01, 5A03, 5A05 and 5A06 square bar from about 10 to 200 mm in O and H112 to GB/T 3191, cut and certified, worldwide.
- Alloys
- 5A01 · 5A03 · 5A05 · 5A06
- Tempers
- O, H112
- Side length
- About 10 – 200 mm
- Standards
- GB/T 3190 · GB/T 3191
Square bar for GB-standard aluminium vessels
Square bar is the solid building block of welded aluminium structure: engine seatings, chocks under deck machinery, keel bars, hatch frames and lifting-point doublers. When the hull is in a 5A-series alloy, square bar in the same grade keeps strength, corrosion behaviour and welding procedure consistent.
Ships and craft designed to Chinese standards commonly use 5A05 and 5A06 plate for hulls, tanks and superstructures, with 5A01 for high-strength shell plating and 5A03 for lightly loaded parts. Square bar in each grade follows the same pattern: 5A06 or 5A01 for heavily loaded seatings and foundations, 5A05 for general welded structure and 5A03 where easy forming and welding matter more than strength.
Because none of these alloys is heat-treated, the bar keeps close to its supplied strength after welding. That gives it an advantage over 6xxx square bar such as 6061 or 6082, which loses up to half its proof strength next to a weld.
Chemical composition (wt %, GB/T 3190)
| Element | 5A01 | 5A03 | 5A05 | 5A06 |
|---|---|---|---|---|
| Silicon (Si) | Si + Fe ≤ 0.40 | 0.50 – 0.8 | ≤ 0.50 | ≤ 0.40 |
| Iron (Fe) | (see Si) | ≤ 0.50 | ≤ 0.50 | ≤ 0.40 |
| Copper (Cu) | ≤ 0.10 | ≤ 0.10 | ≤ 0.10 | ≤ 0.10 |
| Manganese (Mn) | 0.30 – 0.7 | 0.30 – 0.6 | 0.30 – 0.6 | 0.50 – 0.8 |
| Magnesium (Mg) | 6.0 – 7.0 | 3.2 – 3.8 | 4.8 – 5.5 | 5.8 – 6.8 |
| Chromium (Cr) | 0.10 – 0.20 | — | — | — |
| Zirconium (Zr) | 0.10 – 0.20 | — | — | — |
| Zinc (Zn) | ≤ 0.25 | ≤ 0.20 | ≤ 0.20 | ≤ 0.20 |
| Titanium (Ti) | ≤ 0.15 | ≤ 0.15 | — | 0.02 – 0.10 |
| Beryllium (Be) | — | — | — | 0.0001 – 0.005 |
| Aluminium (Al) | Remainder | Remainder | Remainder | Remainder |
Limits as listed in GB/T 3190 for each grade; "others" limits and minor elements vary slightly between editions, so confirm against the edition named on your drawing. Several supplier sheets in circulation show 5A01 with the manganese and magnesium columns swapped (6 – 7 % Mn); that is a transcription error. 5A01 is a 6 – 7 % magnesium alloy.
Mechanical properties of 5A-series square bar
Minimum values for extruded bar as commonly listed for GB/T 3191. The side-length (inscribed-circle) ranges shown are the bands to which these minimums apply; larger sizes are supplied with agreed values. The edition of GB/T 3191 on your order, and the mill certificate for the lot, govern acceptance.
| Alloy | Temper | Size band | Tensile Rm (min) | Proof Rp0.2 (min) | Elongation (min) |
|---|---|---|---|---|---|
| 5A01 | H112 | up to about 130 mm | 330 MPa | 170 MPa | 10 % |
| 5A03 | O, H112 | up to about 150 mm | 175 MPa | 80 MPa | 13 % |
| 5A05 | O, H112 | about 5 – 150 mm | 265 MPa | 120 MPa | 15 % |
| 5A06 | O, H112 | about 5 – 150 mm | 315 MPa | 155 MPa | 15 % |
| 5083 (for comparison) | H112 | ASTM B221 | 270 MPa | 110 MPa | 12 % |
5A01 values are less widely published than those of the other grades; treat them as indicative and confirm the guaranteed figures with the certificate before design.
| Design note | Detail |
|---|---|
| Size basis | For square bar the property bands use the inscribed-circle diameter, which equals the side length |
| Weld zone | Falls to about O-temper strength; for O and H112 bar this is close to the purchased minimum |
| Stiffness | Modulus about 70 GPa, one third of steel; size seatings for deflection as well as strength |
| Density | About 2.64 – 2.67 g/cm³ depending on grade |
Equivalent grades and class acceptance
| GB grade | Nominal Mg | Closest international counterpart | Comment |
|---|---|---|---|
| 5A01 | 6.0 – 7.0 % | No direct equivalent; similar concept to 5059 and Russian 1561 | Zr- and Cr-bearing high-strength marine alloy |
| 5A03 | 3.2 – 3.8 % | AMg3 (GOST, 1530); between 5754 and 5086 | Si addition to reduce weld cracking |
| 5A05 | 4.8 – 5.5 % | AMg5 (GOST, 1550); near 5056 / 5456 in Mg | Common rivet and welded-structure alloy |
| 5A06 | 5.8 – 6.8 % | AMg6 (GOST, 1560) | Highest-strength of the classic AMg series |
Square bar is ordered to GB/T 3191; tolerances follow the GB/T tables or, by agreement, EN 755-4. IACS UR W25 does not list 5A-series alloys, so vessels classed outside Chinese or Russian rules need prior agreement with the society. For those, 5083 or 5383 square bar is often the simpler choice.
All four grades except 5A03 carry more than about 4.5 % magnesium. Like 5083 and 5456, they should be kept out of long-term service above about 65 °C, where β-phase can form on grain boundaries and cause intergranular or stress-corrosion cracking. 5A01's chromium and zirconium additions are intended to improve its resistance, but the temperature limit should still be respected.
Square bar sizes and weights
Supply range
- Side length
- About 10 – 200 mm (maximum inscribed circle about 200 mm)
- Length
- 3000, 4000, 6000 mm or cut pieces
- Tempers
- O, H112 (5A01 normally H112)
- Processing
- Saw cutting, end deburring, bundling with spacers
Weight per metre = side² × density ÷ 1000 kg. The table uses 2.64 g/cm³ (5A06 / 5A01).
| Side (mm) | kg per metre | kg per 3 m bar | kg per 6 m bar |
|---|---|---|---|
| 10 | 0.264 | 0.79 | 1.6 |
| 12 | 0.380 | 1.14 | 2.3 |
| 16 | 0.676 | 2.03 | 4.1 |
| 20 | 1.06 | 3.17 | 6.3 |
| 25 | 1.65 | 4.95 | 9.9 |
| 30 | 2.38 | 7.13 | 14.3 |
| 40 | 4.22 | 12.67 | 25.3 |
| 50 | 6.60 | 19.80 | 39.6 |
| 60 | 9.50 | 28.51 | 57.0 |
| 70 | 12.94 | 38.81 | 77.6 |
| 80 | 16.90 | 50.69 | 101.4 |
| 100 | 26.40 | 79.20 | 158.4 |
| 120 | 38.02 | 114.05 | 228.1 |
| 150 | 59.40 | 178.20 | 356.4 |
| 180 | 85.54 | 256.61 | 513.2 |
| 200 | 105.60 | 316.80 | 633.6 |
Square bar tolerances
| Side (mm) | Side tolerance | Corner radius, max | Twist per 1 m / full length |
|---|---|---|---|
| 10 – 18 | ±0.30 | 1.5 mm | 1° / 3° |
| over 18 – 25 | ±0.35 | 1.5 mm | 1° / 3° |
| over 25 – 40 | ±0.40 | 2.0 mm | 1.5° / 4° (above 30 mm) |
| over 40 – 50 | ±0.45 | 2.0 mm | 1.5° / 4° |
| over 50 – 65 | ±0.50 | 3.0 mm | 2° / 5° |
| over 65 – 80 | ±0.70 | 3.0 mm | 2° / 5° |
| over 80 – 100 | ±0.90 | 3.0 mm | 2° / 5° |
| over 100 – 120 | ±1.0 | 3.0 mm | 2° / 5° |
| over 120 – 150 | ±1.2 | 4.0 mm | 3° / 6° |
| over 150 – 180 | ±1.4 | 4.0 mm | 3° / 6° |
| over 180 – 200 | ±1.7 | 5.0 mm | 3° / 6° |
Other tolerances
- Angle
- Within 1 % of side up to 100 mm; about 1.0 – 1.5° above
- Straightness
- 0.8 – 1.5 mm in any 300 mm; 2 – 3 mm per metre overall
- Fixed lengths
- Plus-only, about +5 to +14 mm by size and length
Fabrication and installation
Seatings
Machine the top face flat after welding if engine alignment demands it; allow machining stock in the bar size.
Tapped holes
Use helical-coil inserts for bolts that are removed in service.
Isolation
Insulate steel engine feet and stainless fasteners with pads, sleeves and washers.
Forming
Bend O-temper bar cold over a former; avoid warm forming of the high-Mg grades.
Heat
Keep 5A05, 5A06 and 5A01 seatings away from long-term heat above about 65 °C.
Applications on vessels and equipment
- Machinery seatings: main and auxiliary engine, generator and pump foundations
- Deck machinery bases: winch, capstan, crane and davit chocks
- Keel and stem bars: solid bars along keel lines and stems of small craft
- Frames and coamings: hatch, door and window frames
- Tank structure: stiffeners and flange blocks on 5A05 / 5A06 tanks
- Offshore and coastal: pontoon, gangway and aquaculture structures
In a typical GB-standard patrol craft, the shell is 5A01 or 5A06 plate, longitudinal frames are extruded profiles, and each engine bed is a pair of 5A06-H112 square bars welded to the floors and machined flat after welding.
5A-series square bar versus 5083 and 6082
| Factor | 5A06-H112 | 5A05-H112 | 5083-H112 | 6082-T6 |
|---|---|---|---|---|
| Min tensile | 315 MPa | 265 MPa | 270 MPa | 310 MPa |
| Min proof | 155 MPa | 120 MPa | 110 MPa | 260 MPa |
| Strength across welds | Retained | Retained | Retained | Roughly halved |
| Listed in UR W25 (extruded) | No | No | Yes | Yes |
| Best fit | GB / GOST vessels | GB / GOST vessels | IACS-classed vessels | Bolted, unwelded parts |
How to order 5A-series square bar
- SpecifyAlloy and temper, side length and length or cut pieces, quantity and the governing standard with its edition (GB/T 3191 and GB/T 3190, with edition year). 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
- GB/T 3190 – Chemical composition of wrought aluminium and aluminium alloys
- GB/T 3191 – Aluminium and aluminium alloy extruded bars and rods
- GOST 4784 – Aluminium and wrought aluminium alloys: grades (AMg3, AMg5, AMg6)
- EN 755-4 – Extruded square bar: tolerances on dimensions and form
- IACS UR W25 – Aluminium alloys for hull construction and marine structure
5A-series marine aluminium (aluminum) square bar: FAQs
Which 5A grade should I use for an engine seating?
5A06, or 5A01 where it matches the hull plate. Both have the highest strength in the family and keep it after welding. Keep seatings away from long-term heat above about 65 °C.
What is the strength of 5A05 square bar?
GB/T 3191 lists minimums of 265 MPa tensile, 120 MPa proof and 15 % elongation for O and H112 bar in the standard size range.
Can 5A-series square bar be used on an IACS-classed vessel?
Only with prior agreement from the society, because UR W25 does not list these alloys. 5083 or 5383 square bar is the usual alternative.
How much does 5A06 square bar weigh?
Side² × 2.64 ÷ 1000 kg per metre. A 50 mm bar weighs about 6.6 kg per metre.
Why not use 6082 square bar instead?
6082-T6 is stronger before welding but loses roughly half its proof strength in the heat-affected zone and needs coating in seawater. 5A-series bar keeps its strength across welds.
Do you cut square bar to a list?
Yes. Metline supplies cut pieces with EN 10204 3.1 certificates against GB/T 3191, export-packed for delivery worldwide.
Need 5A-series square bar?
Send grade, side lengths, temper and quantities. We will reply with availability, certification and a delivered price.
