Aluminum 3A21-H12
Temper
GB 3A21 · UNS A93003
H12 = strain hardened, quarter hard
Light cold work when moderate stiffness is needed but the part still has to be roll-formed or bent.
Values for the H12 condition
Other 3A21 tempers and conditions
3A21 is listed in 10 conditions; see the grade overview at 3A21.
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 |
H12This page 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-H12?
3A21-H12 is 3A21 in the H12 temper — light cold work when moderate stiffness is needed but the part still has to be roll-formed or bent. 3A21-H12 has a yield strength of 125 MPa (18.1 ksi) and a tensile strength of 130 MPa (18.9 ksi) — weaker than 75% of aluminum grades. Elongation at break is 10% and the elastic modulus is 69 GPa (10 Msi). 3A21-H12 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). H14 is the default condition FabDigit quotes; H12 is available on request or by drawing note.
Advantages
- Readily welded — 92/100, better than 95% of aluminum grades
- Forms and bends easily — 82/100, better than 91% of aluminum grades
- Good corrosion resistance — 72/100, better than 83% of aluminum grades
- High electrical conductivity — 42 % IACS, better than 81% of aluminum grades
- Conducts heat well — 163 W/m·K (94.2 BTU/hr·ft·°F), better than 77% of aluminum grades
Limitations
- Difficult to machine — 36/100, worse than 84% of aluminum grades
- Hard to polish — 45/100, worse than 76% of aluminum grades
- Low strength — 125 MPa (18.1 ksi), worse than 75% of aluminum grades
3A21-H12 properties
Typical room-temperature values for 3A21-H12; 12 are specific to this condition. Other listed values are 3A21 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
3A21-H12 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-H12 has a yield strength of 125 MPa (18.1 ksi) and a tensile strength of 130 MPa (18.9 ksi) — weaker than 75% of aluminum grades. Elongation at break is 10% and the elastic modulus is 69 GPa (10 Msi).
Thermal6
3A21-H12 is rated for continuous service to 150°C (302 °F). It conducts heat at 163 W/m·K (94.2 BTU/hr·ft·°F), better than 77% of aluminum grades. Thermal expansion is 23.2 µm/m·K (12.9 µin/in·°F).
Electrical3
3A21-H12 conducts electricity at 42 % IACS, better than 81% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), better than 83% of aluminum grades.
Sustainability4
Producing a kilogram of 3A21-H12 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-H12's machinability is fair (36/100, worse than 84% of aluminum grades); weldability excellent (92/100); formability very good (82/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 3A21-H12
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.
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.
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 | — |
3A21-H12 — frequently asked
What is 3A21-H12 used for?
3A21-H12 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-H12?
3A21-H12 has a typical yield strength of 125 MPa (18.1 ksi) and a tensile strength of 130 MPa (18.9 ksi) — weaker than 75% of aluminum grades. Strength varies by condition: see the 10 listed tempers.
Is 3A21-H12 easy to machine?
Not especially — machinability is rated fair (36/100, worse than 84% 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-H12 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-H12?
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-H12 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-H12?
3A21-H12 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.