Aluminum 2198-O (Annealed)
Temper
AA 2198 · UNS A92198
Softest condition for severe forming or intermediate processing; must be re-solution treated and aged for service strength.
Values for the O condition
Other 2198 tempers and conditions
2198 is listed in 8 conditions; see the grade overview at 2198.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
OThis page Annealed | Softest condition for severe forming or intermediate processing; must be re-solution treated and aged for service strength. | 130 | 250 | 22 | 70 HB | 35 % IACS |
Solution heat treated and naturally aged | Unstretched naturally aged condition used for formed details before final artificial ageing. | 230 | 360 | 22 | 100 HB | 23 % IACS |
Solution heat treated, cold worked and naturally aged | Formable sheet condition for skins that will be stretch-formed or bent, then optionally aged to T8. | 270 | 395 | 20 | 110 HB | 23 % IACS |
T3, stress relieved by stretching | Low-residual-stress plate for machined parts that will be aged after rough machining, or used as-is for high-toughness applications. | 280 | 405 | 18 | 115 HB | 23 % IACS |
Solution treated, ~1 % cold worked and artificially aged | Thin-gauge variant of the aged temper where only light stretching is applied; slightly lower strength, better flatness. | 415 | 470 | 10 | 142 HB | 28 % IACS |
T8Default Solution heat treated, cold worked and artificially aged | Standard supply condition for 2198 fuselage/skin sheet: peak-strength, damage-tolerant, corrosion-stable. | 430 | 480 | 11 | 145 HB | 28 % IACS |
T8, stress relieved by stretching | Peak-aged, low-residual-stress plate for machined ribs, floor beams and integrally machined panels. | 450 | 500 | 8 | 152 HB | 29 % IACS |
Extruded, stretched and artificially aged | Extruded stringers and stiffeners in peak-aged condition where straightness and low residual stress matter. | 470 | 510 | 8 | 155 HB | 29 % IACS |
What is 2198-O?
2198-O is 2198 in the O temper — softest condition for severe forming or intermediate processing; must be re-solution treated and aged for service strength. 2198-O has a yield strength of 130 MPa (18.9 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 73% of aluminum grades. Elongation at break is 22% and the elastic modulus is 76 GPa (11 Msi). 2198-O has a density of 2.7 g/cm³ (0.0975 lb/in³), lighter than 59% of aluminum grades. It melts at 560°C (1,040 °F). T8 is the default condition FabDigit quotes; O is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 38 MPa·√m (34.6 ksi·√in), better than 96% of aluminum grades
- Ductile — tolerates forming and impact — 22%, better than 91% of aluminum grades
- Forms and bends easily — 80/100, better than 89% of aluminum grades
Limitations
- Difficult to machine — 40/100, worse than 81% of aluminum grades
- Limited service temperature — 120°C (248 °F), worse than 79% of aluminum grades
2198-O properties
Typical room-temperature values for 2198-O; 10 are specific to this condition. Other listed values are 2198 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
2198-O has a density of 2.7 g/cm³ (0.0975 lb/in³), lighter than 59% of aluminum grades. It melts at 560°C (1,040 °F).
Mechanical14
2198-O has a yield strength of 130 MPa (18.9 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 73% of aluminum grades. Elongation at break is 22% and the elastic modulus is 76 GPa (11 Msi).
Thermal6
2198-O is rated for continuous service to 120°C (248 °F). It conducts heat at 125 W/m·K (72.2 BTU/hr·ft·°F), worse than 72% of aluminum grades. Thermal expansion is 23 µm/m·K (12.8 µin/in·°F).
Electrical3
2198-O conducts electricity at 35 % IACS, better than 52% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 69% of aluminum grades.
Sustainability4
Producing a kilogram of 2198-O takes about 215 MJ of energy and emits 13.5 kg of CO₂ — more than 93% of aluminum grades. Typical recycled content is 5%.
Manufacturability8
2198-O's machinability is fair (40/100, worse than 81% of aluminum grades); weldability poor (30/100); formability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 2198-O
Is 2198 easy to machine?
Machines like a hard 2000 series: sharp polished-flute carbide, high speed, generous coolant; T8/T851 gives good chip control, but keep Li-bearing fines wet and segregated from other Al swarf.
Can 2198 be welded?
Not recommended for conventional MIG/TIG (hot cracking, Li oxidation); friction stir welding and laser beam welding with 4047/4000-series-type filler are the qualified joining routes, otherwise rivet/bolt.
Can 2198 be formed, bent or molded?
Form in T3/T4/O; T8 has limited bend ductility and pronounced planar anisotropy, so orient blanks to rolling direction and allow generous bend radii.
What surface finishes work on 2198?
Standard aerospace chain: alkaline clean, deoxidize, tartaric-sulfuric or chromic anodize, chromate-free conversion coat plus epoxy primer; avoid bare contact with steel or CFRP without sealant.
2198 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 |
|---|---|---|
| Cu | 2.9 – 3.5 | 3.2 |
| Liprincipal density-reducing / modulus-raising addition | 0.8 – 1.1 | 0.95 |
| Mg | 0.25 – 0.8 | 0.5 |
| Agpromotes fine T1 precipitation | 0.1 – 0.5 | 0.3 |
| Zrgrain-structure control | 0.04 – 0.18 | 0.11 |
| Mn | ≤ 0.5 | — |
| Zn | ≤ 0.35 | — |
| Ti | ≤ 0.1 | — |
| Feimpurity limit | ≤ 0.1 | — |
| Siimpurity limit | ≤ 0.08 | — |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Al | balance | — |
2198-O — frequently asked
What is 2198-O used for?
2198-O is typically used for fuselage skin, aerospace sheet structure, laser-welded stiffened skin panels, lower wing skin panels, formed frames and clips and extruded stringers for welded panels. In short: most formable Al-Li sheet here; weight saving over 2024; laser and FSW weldable.
What is the yield strength of 2198-O?
2198-O has a typical yield strength of 130 MPa (18.9 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 73% of aluminum grades. Strength varies by condition: see the 8 listed tempers.
Is 2198-O easy to machine?
Not especially — machinability is rated fair (40/100, worse than 81% of aluminum grades). Machines like a hard 2000 series: sharp polished-flute carbide, high speed, generous coolant; T8/T851 gives good chip control, but keep Li-bearing fines wet and segregated from other Al swarf.
Can 2198-O be welded?
Not readily — weldability is rated poor (30/100). Not recommended for conventional MIG/TIG (hot cracking, Li oxidation); friction stir welding and laser beam welding with 4047/4000-series-type filler are the qualified joining routes, otherwise rivet/bolt.
What surface finishes work on 2198-O?
Standard aerospace chain: alkaline clean, deoxidize, tartaric-sulfuric or chromic anodize, chromate-free conversion coat plus epoxy primer; avoid bare contact with steel or CFRP without sealant.
Can 2198-O be formed, bent or molded?
Form in T3/T4/O; T8 has limited bend ductility and pronounced planar anisotropy, so orient blanks to rolling direction and allow generous bend radii.
What is the maximum service temperature of 2198-O?
2198-O is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 2198-T8 and 2198-O?
T8 is the default condition — standard supply condition for 2198 fuselage/skin sheet: peak-strength, damage-tolerant, corrosion-stable. O: softest condition for severe forming or intermediate processing; must be re-solution treated and aged for service strength. Yield strength is 430 MPa in T8 versus 130 MPa in O.
Sources
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- AIRWARE 2198 sheet/plate technical data — Constellium (2021)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- MMPDS — Metallic Materials Properties Development and Standardization (Al-Li chapters) — Battelle/FAA (2023)
- AMS 4472 / AMS 4473 — Aluminum-Lithium alloy sheet and plate — SAE International (2019)
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.