Machining
5A05 and 5A06 machine reasonably cleanly; 5A03 is softer and tends to build up on tools. Sharp, polished carbide and flood coolant work for all.
Marine · GB-standard Al-Mg round bar
5A01, 5A03, 5A05 & 5A06 Marine Aluminium Round Bar
Round bar in the Chinese 5A-series alloys is used for shafts, pins, bushes and machined fittings on vessels and equipment built to GB or GOST standards. The four grades step up from the easily welded 5A03 to the high-strength 5A06 and 5A01. Metline supplies 5A01, 5A03, 5A05 and 5A06 round bar from about 8 to 320 mm in O and H112 to GB/T 3191, cut and certified, worldwide.
- Alloys
- 5A01 · 5A03 · 5A05 · 5A06
- Tempers
- O, H112
- Diameter
- About 8 – 320 mm
- Standards
- GB/T 3190 · GB/T 3191
Choosing a 5A-series round bar
The 5A-series are the aluminium-magnesium grades of the Chinese GB/T 3190 standard. Three of them share their chemistry with the Soviet-era AMg alloys still specified across Russia and the CIS, which is why the same bar grades appear on Chinese and Russian-designed ships, pressure vessels and aerospace hardware.
5A03 (AMg3 type, about 3.5 % Mg) is the moderate-strength member with a deliberate silicon addition that reduces weld cracking; it suits general fittings and welded parts. 5A05 (AMg5 type, about 5 % Mg) is the classic rivet and welded-structure alloy, with roughly 50 % more strength than 5A03. 5A06 (AMg6 type, about 6 % Mg) is the strongest of the AMg family and the usual choice for high-load welded parts and pressure equipment. 5A01 (6 – 7 % Mg with chromium and zirconium) is a marine development aimed at higher strength with good resistance to stress and exfoliation corrosion.
All four are non-heat-treatable, so welding costs little strength, and all resist seawater well. The trade-off for the higher-magnesium grades is sensitivity to prolonged heat, covered below.
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.
Some published bar data sheets list 5A01 as a 3.5 – 4.5 % silicon alloy, or give 5A05 the composition of 5A03. Both are errors. Check magnesium on the certificate: 5A03 3.2 – 3.8 %, 5A05 4.8 – 5.5 %, 5A06 5.8 – 6.8 %, 5A01 6.0 – 7.0 %.
Mechanical properties of 5A-series round bar
Minimum values for extruded bar as commonly listed for GB/T 3191. The diameter 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.
In practice, H112 bar often tests above these minimums, especially in mid-range diameters, while O-temper bar gives more consistent ductility for bending and heading. Very large diameters (above about 150 mm) are usually supplied with agreed properties because the centre of a thick extrusion receives less working.
Equivalent grades and standards
| 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 |
Round bar in these grades is ordered to GB/T 3191 (extruded bars and rods), with composition to GB/T 3190. Russian equivalents are ordered to GOST 21488 for bars. None of the 5A grades is listed in IACS UR W25, which covers 5083, 5383, 5059 and 5086 for extruded Al-Mg products, so use on vessels classed outside Chinese or Russian rules requires the society's agreement.
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.
Round bar sizes and weights
Supply range
- Diameter
- About 8 – 320 mm extruded
- Length
- 1000 – 6000 mm; 3, 4 or 6 m standard; cut pieces on request
- Tempers
- O and H112 (5A01 normally H112)
- Finish
- Mill finish; peeled or turned for large diameters
Weight per metre = π/4 × d² × density ÷ 1000 kg. The table uses 2.64 g/cm³ (5A06 / 5A01); 5A03 is about 1 % heavier.
| Diameter (mm) | kg per metre | kg per 3 m bar | kg per 6 m bar |
|---|---|---|---|
| 8 | 0.133 | 0.40 | 0.8 |
| 12 | 0.299 | 0.90 | 1.8 |
| 16 | 0.531 | 1.59 | 3.2 |
| 20 | 0.829 | 2.49 | 5.0 |
| 25 | 1.30 | 3.89 | 7.8 |
| 30 | 1.87 | 5.60 | 11.2 |
| 40 | 3.32 | 9.95 | 19.9 |
| 50 | 5.18 | 15.55 | 31.1 |
| 60 | 7.46 | 22.39 | 44.8 |
| 80 | 13.27 | 39.81 | 79.6 |
| 100 | 20.73 | 62.20 | 124.4 |
| 120 | 29.86 | 89.57 | 179.1 |
| 150 | 46.65 | 139.96 | 279.9 |
| 180 | 67.18 | 201.54 | 403.1 |
| 200 | 82.94 | 248.81 | 497.6 |
| 250 | 129.59 | 388.77 | 777.5 |
| 300 | 186.61 | 559.83 | 1119.7 |
| 320 | 212.32 | 636.96 | 1273.9 |
Diameter tolerance and straightness
| Diameter (mm) | Typical tolerance (mm) |
|---|---|
| 8 – 18 | ±0.22 |
| over 18 – 25 | ±0.25 |
| over 25 – 40 | ±0.30 |
| over 40 – 50 | ±0.35 |
| over 50 – 65 | ±0.40 |
| over 65 – 80 | ±0.45 |
| over 80 – 100 | ±0.55 |
| over 100 – 120 | ±0.65 |
| over 120 – 150 | ±0.80 |
| over 150 – 180 | ±1.00 |
| over 180 – 220 | ±1.15 |
| over 220 – 270 | ±1.3 |
| over 270 – 320 | ±1.6 |
High-precision grade per GB/T 3191 tables. Normal-grade tolerances are wider; state which grade you need.
Form tolerances
- Straightness, high precision
- 0.8 mm in any 300 mm up to 80 mm, rising to 3 mm for 220 – 320 mm; 2 – 6 mm per metre overall
- Straightness, normal
- About 3 – 12 mm per metre overall depending on diameter
- Fixed lengths
- Plus-only: about +7 / +9 / +12 mm for 100 – 200 mm bars at ≤ 2, 2 – 5 and over 5 m
Machining and welding notes
Welding
Use high-Mg filler (5B06-type, ER5183 or ER5556) for 5A05, 5A06 and 5A01; ER5356 or ER5183 for 5A03.
Cold heading
O-temper 5A05 bar and rod heads well for rivets and special fasteners.
Bearings and bushes
Al-Mg alloys gall against themselves; use a dissimilar bearing material or hard anodise one surface.
Galvanic isolation
Insulate from stainless, bronze and steel in seawater service.
Heat
Avoid long-term service above about 65 °C for the high-Mg grades.
Applications
- Ship fittings: hinge pins, davit pins, bollard bodies and pad eyes welded to 5A05 or 5A06 structure
- Fasteners and rivets: 5A05 and 5A06 rod for rivets, bolts and studs
- Pressure and tank parts: nozzles, flanges and bosses for 5A06 tanks and vessels
- Shafts and bushes: lightly loaded shafts, rollers and spacers
- Electrical: earthing studs and cable-tray fittings on aluminium vessels
A typical example is a fuel tank built to GB drawings in 5A06 plate: the filler, vent and drain bosses are machined from 5A06-H112 round bar and welded with matching high-Mg filler, so the tank has uniform strength and corrosion behaviour.
How to order 5A-series round bar
- SpecifyAlloy and temper, diameter, tolerance grade 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)
- GOST 21488 – Pressed bars of aluminium and aluminium alloys
- IACS UR W25 – Aluminium alloys for hull construction and marine structure
5A-series marine aluminium (aluminum) round bar: FAQs
Which 5A grade is strongest?
5A01 and 5A06 are the strongest. GB/T 3191 lists 5A06 bar at 315 MPa minimum tensile; 5A01 is quoted at about 330 MPa. 5A05 follows at 265 MPa and 5A03 at 175 MPa.
Is 5A06 the same as AMg6?
Their compositions are practically identical (5.8 – 6.8 % Mg, 0.5 – 0.8 % Mn, Ti and trace Be), so 5A06 is widely treated as the Chinese counterpart of Russian AMg6 (1560).
Can I substitute 5083 for 5A05 bar?
Mechanically 5A05 is similar to or slightly stronger than 5083, but the compositions differ. Substitution needs approval from the designer and, on classed vessels, the society.
Are 5A-series bars suitable for seawater?
Yes. All four resist seawater well. The high-magnesium grades must be kept out of long-term heat above about 65 °C to avoid sensitisation.
What diameters are available?
Extruded 5A-series round bar is typically available from about 8 mm to 320 mm, in 3 – 6 m lengths or cut pieces.
Do you supply certificates to GB standards?
Yes. Each lot is supplied with an EN 10204 3.1 certificate showing composition and mechanical results against GB/T 3190 and GB/T 3191.
Need 5A-series round bar?
Send grade, diameters, temper and quantities. We will reply with availability, certification and a delivered price.
