MATERIALS · August 9, 2026 · 6 MIN READ

Aluminium Alloy Designations: GB, AA and EN Compared for Forging

GB/T 3190 now lists the four-digit Aluminium Association designations directly, so 6061, 6082 and 7075 appear on Chinese mill certificates without translation. The legacy Chinese designations still matter because older drawings use them: 2A12 corresponds to 2024, 7A04 to 7075, 5A06 to the 5083 family and 6A02 to the 6061 family — with composition differences large enough that the substitution needs a property check, not a name match.

WHERE THIS APPLIES AT FORGEPRESS CHINA

ForgePress China forges 6061, 6082, 2A12 and 5A06 to GB/T 3190 or ASTM B221, 0.1–500 kg per part, with T6 heat treatment arranged off-line. Capacity: HKM3 hot-die forging line 1,000–5,000 t, part weight 0.1–500 kg, maximum envelope 1,200 × 800 mm, as-forged to ISO 8062 class C with critical dimensions machined to ±0.2 mm, process control to ISO 9001, first article 4–8 weeks from die design release.

KEY NUMBERS

Aluminium forging window is narrow: 6061 forges at 400–480 °C, with only about 80 °C of working range.
2A12 ≈ 2024, 7A04 ≈ 7075, 5A06 ≈ 5083-family, 6A02 ≈ 6061-family — closest equivalent, not identical.
6061-T6 typical: UTS 290–310 MPa, yield 240–260 MPa, elongation 8–12 %.
Aluminium needs 30–50 % more die clearance and 2–3× the draft of steel to avoid galling.

Legacy designations and what replaced them

Chinese aluminium designations were historically a letter-plus-number system: LF (aluminium-manganese), LY (aluminium-copper), LD (aluminium-magnesium-silicon), LC (aluminium-zinc). GB/T 3190 has since aligned with the four-digit AA system, but a drawing from 2005 will still say LD30 or LY12, and a supplier quoting from that drawing may interpret it loosely.

The table below is the mapping to use when converting an old drawing, with the honest caveat that "closest equivalent" is not "interchangeable".

Legacy GB	Current GB / AA	Family	Closest international	Forging suitability
LD30	6061	Al-Mg-Si	6061 / EN AW-6061	Excellent; the default forged aluminium
LD31	6063	Al-Mg-Si	6063 / EN AW-6063	Good, lower strength, architectural
LD2	6A02	Al-Mg-Si-Cu	6061 family (higher Cu)	Good, higher strength than 6063
LY12	2A12	Al-Cu-Mg	2024	Good but narrow window, corrosion-sensitive
LC4	7A04	Al-Zn-Mg-Cu	7075	Poor; high strength, low forgeability
LF6	5A06	Al-Mg	5083 family	Good; marine and cryogenic
L4	1050A	Pure Al	1050A	Excellent but very low strength

Composition limits differ between legacy GB grades and their international counterparts, especially copper and zinc. Verify mechanical properties on the first article rather than assuming equivalence.

Why 6061 dominates forged aluminium

6061 forges well, welds, machines cleanly, anodises to a consistent finish and is available in bar and billet from many mills. Its T6 condition — solution treated and artificially aged — reaches 290–310 MPa UTS with 8–12 % elongation, which is enough for structural brackets, flanges and housings.

6082 is the European answer to the same requirement, with slightly higher strength and slightly lower ductility. If a European drawing specifies EN AW-6082, a Chinese supplier can normally offer 6082 directly; substituting 6061 requires a strength check because 6082-T6 typically runs 10–15 % higher in yield.

Process differences that catch buyers out

Temperature window: 400–480 °C for 6061. Above 500 °C incipient melting causes surface blistering that only appears after heat treatment.
Draft angle: aluminium grips the die harder than steel, so use 5–7° minimum, not the 3° that works on carbon steel.
Die material: H13 is normal, but polished impressions and aluminium-specific coatings reduce galling substantially.
Lubrication: water-graphite works, but aluminium-specific lubricants avoid the staining that appears after anodising.
Heat treatment after forging: T6 requires a solution treatment at 530 ± 5 °C and a quench delay under about 10 s, which most forging shops cannot do in line — plan for a separate heat-treat supplier.

Frequently asked questions

Is 6061 available in China to the AA specification?

Yes. GB/T 3190 lists 6061 directly and most mills can certify to either GB/T 3190 or ASTM B221. Ask which certificate the mill will issue, because the mechanical property tables differ slightly between the two.

Can 2A12 replace 2024?

They are close but not identical: copper and magnesium limits differ, and 2A12 is generally supplied to a narrower strength range. For a fatigue-critical or aerospace part, the substitution needs a full property comparison and usually a customer approval.

Why did my aluminium forging blister after anodising?

Almost always overheating during forging or a slow quench after solution treatment. Incipient melting at the surface creates subsurface porosity that only shows up when the anodic layer is formed. Check the billet temperature log and the quench delay.