Aluminum 3A21
GB 3A21 · UNS A93003
Chinese national-standard Al-Mn wrought alloy essentially equivalent to international 3003, widely produced and stocked in China as sheet, tube and rod for corrosion-resistant, formable, low-strength structural and food/chemical equipment applications.
Reference datasheet — 3A21 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the H14 condition
3A21 tempers and conditions
3A21 is supplied in 10 conditions, soft to hard. H14 is the default FabDigit quotes; the values on this page are for it.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for maximum ductility: deep drawing, spinning, tube bending, complex-formed vessels. | 42 | 110 | 33 | 28 HB | 50 % IACS |
As fabricated | As-extruded/as-forged stock bought for subsequent forming or annealing; mechanical properties not guaranteed. | 45 | 110 | 25 | 29 HB | 48 % IACS |
Strain hardened from hot working only | Standard condition for hot-rolled thick plate, extruded tube/bar and forged blanks of 3A21. | 50 | 115 | 22 | 30 HB | 49 % IACS |
Strain hardened and partially annealed, quarter hard | Same strength class as H12 but with extra residual ductility — choose for formed parts made from light-gauge coil. | 110 | 130 | 14 | 35 HB | 42 % IACS |
Strain hardened, quarter hard | Light cold work when moderate stiffness is needed but the part still has to be roll-formed or bent. | 125 | 130 | 10 | 35 HB | 42 % IACS |
Strain hardened and partially annealed, half hard | Very common Chinese stock condition for 3A21 coil/sheet needing H14-level strength plus bendability. | 135 | 150 | 11 | 40 HB | 41 % IACS |
H14Default Strain hardened, half hard | The default stocked sheet/coil condition: balanced strength, flatness and workability for panels, tanks and ducting. | 145 | 150 | 8 | 40 HB | 41 % IACS |
Strain hardened and partially annealed, three-quarter hard | H16 strength level with improved bend behaviour; used for roll-formed profiles and shutter/fin stock. | 160 | 180 | 8 | 46 HB | 40 % IACS |
Strain hardened, three-quarter hard | Use where higher strength and dent resistance matter and only mild bending is required. | 170 | 180 | 5 | 47 HB | 40 % IACS |
Strain hardened, full hard | Maximum strength/springiness of the alloy; for flat parts, fin stock and shells that need no further forming. | 185 | 200 | 4 | 55 HB | 40 % IACS |
What is 3A21?
Chinese national-standard Al-Mn wrought alloy essentially equivalent to international 3003, widely produced and stocked in China as sheet, tube and rod for corrosion-resistant, formable, low-strength structural and food/chemical equipment applications. 3A21 has a density of 2.73 g/cm³ (0.0986 lb/in³), heavier than 61% of aluminum grades. It melts at 643°C (1,189 °F). 3A21 has a yield strength of 145 MPa (21 ksi) and a tensile strength of 150 MPa (21.8 ksi) — weaker than 68% of aluminum grades. Elongation at break is 8% and the elastic modulus is 69 GPa (10 Msi).
What is 3A21 used for?
- chemical equipment tanks
- food processing vessels
- heat exchanger tubing
- sheet metal enclosures
- kitchenware
Advantages
- Readily welded — 92/100, better than 95% of aluminum grades
- Good corrosion resistance — 72/100, better than 83% of aluminum grades
- Forms and bends easily — 70/100, better than 83% of aluminum grades
- High electrical conductivity — 41 % IACS, better than 78% of aluminum grades
Limitations
- Difficult to machine — 40/100, worse than 81% of aluminum grades
- Hard to polish — 45/100, worse than 76% of aluminum grades
3A21 properties
Typical room-temperature values for 3A21-H14; bars are the position among aluminum grades.
Physical3
3A21 has a density of 2.73 g/cm³ (0.0986 lb/in³), heavier than 61% of aluminum grades. It melts at 643°C (1,189 °F).
Mechanical10
3A21 has a yield strength of 145 MPa (21 ksi) and a tensile strength of 150 MPa (21.8 ksi) — weaker than 68% of aluminum grades. Elongation at break is 8% and the elastic modulus is 69 GPa (10 Msi).
Thermal6
3A21 is rated for continuous service to 150°C (302 °F). It conducts heat at 159 W/m·K (91.9 BTU/hr·ft·°F), better than 74% of aluminum grades. Thermal expansion is 23.2 µm/m·K (12.9 µin/in·°F).
Electrical3
3A21 conducts electricity at 41 % IACS, better than 78% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), better than 83% of aluminum grades.
Sustainability4
Producing a kilogram of 3A21 takes about 200 MJ of energy and emits 13 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 35%.
Manufacturability7
3A21's machinability is fair (40/100, worse than 81% of aluminum grades); weldability excellent (92/100); formability very good (70/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the aluminum family
Yield strength against density for every aluminum grade FabDigit runs. 3A21 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 3A21
Is 3A21 easy to machine?
Soft and gummy — use polished high-rake carbide, high speed, generous feed and lubricant to avoid built-up edge; H18 machines noticeably cleaner than O.
Can 3A21 be welded?
Excellent by TIG/MIG with ER1100 or ER4043 filler and by resistance/torch brazing; the HAZ softens to near-O strength, so design joints for annealed properties.
Can 3A21 be formed, bent or molded?
Outstanding deep drawing, spinning and roll forming in O/H2x tempers; anneal at 415 °C (air cool) between heavy draws; no heat-treat strengthening is possible.
3A21 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| SiGB/T 3190; some editions specify Si+Fe ≤ 0.7 | ≤ 0.6 | 0.25 |
| Fe | ≤ 0.7 | 0.4 |
| Cu | ≤ 0.2 | 0.05 |
| Mnmain strengthening/corrosion element | 1 – 1.6 | 1.3 |
| Mg | ≤ 0.05 | 0.02 |
| Zn | ≤ 0.1 | 0.03 |
| Tigrain refiner | ≤ 0.15 | 0.03 |
| Others (each) | ≤ 0.05 | |
| Others (total) | ≤ 0.15 | |
| Al | balance |
What surface finishes work on 3A21?
Takes chemical conversion coating, paint and clear/protective anodize well, but the anodic film is grey-toned and non-uniform on bright-decorative work; polishes only to a satin lustre.
Surface treatments FabDigit runs on aluminum parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Equivalent designations
Standards and trade names that resolve to Aluminum 3A21 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- A93003
- GB (China)
- LF21
- Other
- 3003
How much does 3A21 cost?
3A21 is a standard-cost aluminum ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
3A21 — frequently asked
What is 3A21 used for?
3A21 is typically used for chemical equipment tanks, food processing vessels, heat exchanger tubing, sheet metal enclosures and kitchenware. In short: 3003-equivalent Al-Mn sheet; excellent weldability and formability; low strength, no heat treatment.
What is the yield strength of 3A21?
3A21 has a typical yield strength of 145 MPa (21 ksi) and a tensile strength of 150 MPa (21.8 ksi) — weaker than 68% of aluminum grades. Strength varies by condition: see the 10 listed tempers.
Is 3A21 easy to machine?
Not especially — machinability is rated fair (40/100, worse than 81% of aluminum grades). Soft and gummy — use polished high-rake carbide, high speed, generous feed and lubricant to avoid built-up edge; H18 machines noticeably cleaner than O.
Can 3A21 be welded?
Yes — weldability is rated excellent (92/100). Excellent by TIG/MIG with ER1100 or ER4043 filler and by resistance/torch brazing; the HAZ softens to near-O strength, so design joints for annealed properties.
What surface finishes work on 3A21?
Takes chemical conversion coating, paint and clear/protective anodize well, but the anodic film is grey-toned and non-uniform on bright-decorative work; polishes only to a satin lustre.
Can 3A21 be formed, bent or molded?
Outstanding deep drawing, spinning and roll forming in O/H2x tempers; anneal at 415 °C (air cool) between heavy draws; no heat-treat strengthening is possible.
What is the maximum service temperature of 3A21?
3A21 is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 3A21-H14 and 3A21-O?
H14 is the default condition — the default stocked sheet/coil condition: balanced strength, flatness and workability for panels, tanks and ducting. O: pick for maximum ductility: deep drawing, spinning, tube bending, complex-formed vessels. Yield strength is 145 MPa in H14 versus 42 MPa in O.
How much does 3A21 cost?
3A21 is a standard-cost aluminum ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B209 / B221 (3003 equivalent) — ASTM (2021)
- Aluminum Standards and Data (Teal Sheets) — The Aluminum Association (2015)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.