Machining
Higher-Mg grades (5A05, 5A06, 5A01) machine more cleanly than 5A03, which is soft and gummy. Use sharp polished carbide, positive rake and coolant.
Marine · GB-standard Al-Mg hex bar
5A01, 5A03, 5A05 & 5A06 Marine Aluminium Hexagon Bar
The 5A-series alloys are the Chinese-standard aluminium-magnesium grades used on ships and equipment designed to GB, CCS or GOST practice. As hexagon bar they are machined into nuts, unions, couplings and threaded fittings that match the 5A-series plate around them. Metline supplies 5A01, 5A03, 5A05 and 5A06 hex bar in O and H112 to GB/T 3191, cut and certified, worldwide.
- Alloys
- 5A01 · 5A03 · 5A05 · 5A06
- Tempers
- O, H112
- Across flats
- Up to about 200 mm
- Standards
- GB/T 3190 · GB/T 3191
What the 5A-series alloys are
In the Chinese designation system an "A" in the second position marks a national alloy that is not an Aluminum Association registration. The 5A-series are aluminium-magnesium alloys with a long history in Chinese and Soviet-designed shipbuilding, aerospace and pressure equipment, and three of them closely match the Russian AMg grades.
They step up in magnesium and strength: 5A03 (about 3.5 % Mg) is a moderate-strength, easily welded alloy; 5A05 (about 5 %) and 5A06 (about 6 %) are progressively stronger; and 5A01 (6 – 7 % Mg with chromium and zirconium) is a high-strength marine development. All are non-heat-treatable, resist seawater well and weld with Al-Mg fillers.
Hexagon bar in these grades matters to buyers maintaining or building vessels to GB drawings, where substituting an AA alloy would need design approval. It is used for spanner-flat fittings: nuts and lock nuts for aluminium structures, pipe unions, hose connectors, bulkhead glands and threaded bosses.
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 hex bar
Minimum values for extruded bar as commonly listed for GB/T 3191. The across-flats 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.
Approximate physical properties
- Density
- 5A03 about 2.67; 5A05 about 2.65; 5A06 and 5A01 about 2.64 g/cm³
- Modulus of elasticity
- About 70 GPa
- Thermal expansion
- About 23 – 24 µm/m·°C
- Magnetic
- Non-magnetic
Equivalent and comparable grades
Where a project allows substitution, these are the usual comparisons. None of the 5A grades is an exact match for an AA alloy, so substitution needs the designer's approval.
| 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 |
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.
Hex bar sizes and weights
Supply range
- Across flats
- From about 10 mm to about 200 mm (maximum inscribed circle)
- Length
- 3000, 4000 or 6000 mm; cut pieces on request
- Tempers
- O, H112 (5A01 normally H112)
- Standards
- GB/T 3191; dimensions and tolerances per the GB/T or EN 755 tables agreed
Weight per metre = 0.866 × s² × density ÷ 1000 kg, with s across flats in mm. The table uses 2.64 g/cm³ (5A06 / 5A01); add about 1 % for 5A03.
| Across flats (mm) | kg per metre | kg per 3 m bar | kg per 6 m bar |
|---|---|---|---|
| 10 | 0.229 | 0.69 | 1.4 |
| 14 | 0.448 | 1.34 | 2.7 |
| 17 | 0.661 | 1.98 | 4.0 |
| 19 | 0.825 | 2.48 | 5.0 |
| 22 | 1.11 | 3.32 | 6.6 |
| 24 | 1.32 | 3.95 | 7.9 |
| 27 | 1.67 | 5.00 | 10.0 |
| 32 | 2.34 | 7.02 | 14.0 |
| 36 | 2.96 | 8.89 | 17.8 |
| 41 | 3.84 | 11.53 | 23.1 |
| 46 | 4.84 | 14.51 | 29.0 |
| 55 | 6.92 | 20.75 | 41.5 |
| 65 | 9.66 | 28.98 | 58.0 |
| 75 | 12.86 | 38.58 | 77.2 |
| 90 | 18.52 | 55.56 | 111.1 |
| 110 | 27.66 | 82.99 | 166.0 |
| 130 | 38.64 | 115.92 | 231.8 |
| 150 | 51.44 | 154.33 | 308.7 |
Hex bar tolerances
| Across flats (mm) | Width tolerance | Corner radius, max | Twist per 1 m / full length |
|---|---|---|---|
| 10 – 18 | ±0.30 | 1.5 mm | 1° / 1.5° |
| over 18 – 25 | ±0.35 | 1.5 mm | 1° / 1.5° |
| over 25 – 40 | ±0.40 | 2.0 mm | 1.5° / 2.5° (above 30 mm) |
| over 40 – 50 | ±0.45 | 2.0 mm | 1.5° / 2.5° |
| over 50 – 65 | ±0.50 | 2.0 – 2.5 mm | 1.5° / 2.5° |
| over 65 – 80 | ±0.70 | 2.5 mm | 1.5° / 2.5° |
| over 80 – 100 | ±0.90 | 3.0 mm | 2° / 3° |
| over 100 – 120 | ±1.0 | 3.0 mm | 2° / 3° |
| over 120 – 150 | ±1.2 | 4.0 mm | 2.5° / 4° |
| over 150 – 180 | ±1.4 | 4.0 mm | 2.5° / 4° |
| over 180 – 220 | ±1.7 | 5.0 mm | 2.5° / 4° |
Other tolerances
- Straightness
- 0.8 mm in any 300 mm up to 80 mm; 1.0 – 1.5 mm for larger sizes; 2 – 3 mm per metre overall
- Fixed lengths
- Plus-only: +5 / +7 / +10 mm up to 100 mm across flats for lengths ≤ 2, 2 – 5 and over 5 m
Machining, threading and welding
Threads
Roll threads where possible and use anti-seize; aluminium-on-aluminium threads gall if dry.
Welding
Use high-Mg fillers: 5B06-type or ER5183/ER5556 for 5A05, 5A06 and 5A01; ER5356 or ER5183 for 5A03.
Isolation
Separate from stainless and copper alloys with insulating washers and sealant.
Heat
Keep long-term temperature below about 65 °C for 5A05, 5A06 and 5A01.
Finishing
Sulphuric anodising for corrosion protection and wear; hard anodise for frequently assembled threads.
Uses of 5A-series hex bar
- Fasteners: nuts, lock nuts and special bolts for 5A05 / 5A06 structures
- Pipework: unions, adaptors, bulkhead fittings and hose tails
- Deck equipment: threaded sockets, stanchion bases and fitting bodies
- Cable and pipe supports: threaded spacers and standoffs
- Equipment and machinery: fittings on pumps, valves and pressure equipment to GB drawings
A typical case is repair stock for a vessel built to GB standards: the hull is 5A05 or 5A06 plate, and replacement pipe unions and bulkhead glands are turned from 5A06-H112 hex bar so that they match the original alloy and certificates.
Choosing among the 5A grades
| Factor | 5A03 | 5A05 | 5A06 | 5A01 |
|---|---|---|---|---|
| Min tensile (bar) | 175 MPa | 265 MPa | 315 MPa | About 330 MPa |
| Weldability | Very good | Good | Good | Good |
| Machinability | Fair | Good | Good | Good |
| Long-term above 65 °C | Use with care | Avoid | Avoid | Avoid |
| Typical use | General fittings | Fasteners, welded parts | High-strength fittings | High-strength marine fittings |
How to order 5A-series hex bar
- SpecifyAlloy and temper, across-flats size 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)
- IACS UR W25 – Aluminium alloys for hull construction and marine structure
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
5A-series marine aluminium (aluminum) hex bar: FAQs
What does the "A" in 5A06 mean?
It marks a Chinese national alloy registered in GB/T 3190 rather than an international Aluminum Association alloy. 5A06 was formerly called LF6 and matches the Russian AMg6.
What is the international equivalent of 5A05 and 5A06?
5A05 corresponds closely to Russian AMg5 and 5A06 to AMg6. There is no exact AA equivalent; 5456 and 5083 are the nearest in behaviour but differ in composition.
How strong is 5A06 hex bar?
GB/T 3191 lists minimums of 315 MPa tensile, 155 MPa proof and 15 % elongation for O and H112 bar in the standard size range.
Is 5A01 the same as 5A06?
No. 5A01 has slightly more magnesium (6.0 – 7.0 %) plus chromium and zirconium additions, and is a higher-strength marine alloy. Some published tables wrongly show 5A01 with 6 – 7 % manganese; it is magnesium.
Can 5A-series hex bar replace 5083 fittings?
Only with design approval. 5A05 or 5A06 often has equal or greater strength, but the composition and standards differ, and class approval follows the society's rules.
Do you supply 5A-series bar with certificates?
Yes. Metline supplies 5A01, 5A03, 5A05 and 5A06 hex bar with EN 10204 3.1 certificates stating GB/T 3191 results, cut to length and export-packed.
Need 5A-series hex bar for a GB-standard vessel?
Send grade, across-flats sizes, temper and quantities. We will reply with availability, certification and a delivered price.
