Steel A209 T1-T1a
Grade
ASTM A209 T1 · UNS K11522
T1a = grade T1a
Pick when higher room-temperature strength and allowable stress are needed; slightly reduced weldability and higher hardness cap (85 HRB).
Values for the T1a condition
Other A209 T1 tempers and conditions
A209 T1 is listed in 5 conditions; see the grade overview at A209 T1.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Grade T1b | Lowest-carbon variant: best bending, expanding and welding behaviour where strength is not critical. | 225 | 410 | 37 | 125 HB | 45 W/m·K |
Cold drawn then heat treated ≥650 °C | Standard condition for precision cold-drawn tube: tight tolerances and bright bore with drawing stresses removed. | 255 | 445 | 36 | 138 HB | 9 % IACS |
T1Default Cooled from hot working and naturally aged | Default A209 grade: 0.10–0.20 % C with 0.5 % Mo — standard choice for boiler and superheater tubes to ~500 °C. | 260 | 450 | 35 | 140 HB | — |
T1aThis page Grade T1a | Pick when higher room-temperature strength and allowable stress are needed; slightly reduced weldability and higher hardness cap (85 HRB). | 265 | 460 | 33 | 150 HB | 44 W/m·K |
Hot finished | Economical condition for hot-finished tube where A209 does not mandate post-forming heat treatment; slightly coarser scale-bearing surface. | 270 | 460 | 33 | 145 HB | 9 % IACS |
What is A209 T1-T1a?
A209 T1-T1a is A209 T1 in the T1a grade — pick when higher room-temperature strength and allowable stress are needed; slightly reduced weldability and higher hardness cap (85 HRB). A209 T1-T1a has a yield strength of 265 MPa (38.4 ksi) and a tensile strength of 460 MPa (66.7 ksi) — weaker than 92% of steel grades. Elongation at break is 33% and the elastic modulus is 205 GPa (29.7 Msi). A209 T1-T1a has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). T1 is the default condition FabDigit quotes; T1a is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 33%, better than 96% of steel grades
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- Forms and bends easily — 70/100, better than 86% of steel grades
- Readily welded — 78/100, better than 78% of steel grades
Limitations
- Low strength — 265 MPa (38.4 ksi), worse than 92% of steel grades
A209 T1-T1a properties
Typical room-temperature values for A209 T1-T1a; 32 are specific to this condition. Other listed values are A209 T1 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A209 T1-T1a has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
A209 T1-T1a has a yield strength of 265 MPa (38.4 ksi) and a tensile strength of 460 MPa (66.7 ksi) — weaker than 92% of steel grades. Elongation at break is 33% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A209 T1-T1a is rated for continuous service to 500°C (932 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
A209 T1-T1a conducts electricity at 9 % IACS, better than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of A209 T1-T1a takes about 26 MJ of energy and emits 2.1 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 25%.
Manufacturability7
A209 T1-T1a's machinability is good (60/100, better than 83% of steel grades); weldability very good (78/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A209 T1-T1a
Is A209 T1 easy to machine?
Machines like annealed 4130-class low-alloy steel at ~60 % of 1212 speeds; carbide tooling, moderate feeds, good chip control with coolant.
Can A209 T1 be welded?
Readily welded with matched C-Mo consumables (E7018-A1 / ER80S-D2); 100–200 °C preheat on heavier walls and PWHT near 700 °C for code work.
Can A209 T1 be formed, bent or molded?
Good cold bending and tube expanding in the annealed condition (A209 requires flattening and flaring tests); hot bends should be re-heat-treated.
What surface finishes work on A209 T1?
No anodizing; use pickle/phosphate, aluminizing, or high-temperature silicone-aluminum paint for fireside and outdoor protection.
A209 T1 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 |
|---|---|---|
| CT1; T1a 0.15–0.25, T1b ≤0.14 | 0.1 – 0.2 | 0.15 |
| Mn | 0.3 – 0.8 | 0.55 |
| Si | 0.1 – 0.5 | 0.25 |
| Mocreep-strengthening addition, all grades | 0.44 – 0.65 | 0.52 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance | — |
A209 T1-T1a — frequently asked
What is A209 T1-T1a used for?
A209 T1-T1a is typically used for boiler superheater tubes, high-temperature piping and heat exchanger tubes. In short: low-cost C-Mo boiler tube; 510 °C service limit; good cold bending and expanding.
What is the yield strength of A209 T1-T1a?
A209 T1-T1a has a typical yield strength of 265 MPa (38.4 ksi) and a tensile strength of 460 MPa (66.7 ksi) — weaker than 92% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is A209 T1-T1a easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines like annealed 4130-class low-alloy steel at ~60 % of 1212 speeds; carbide tooling, moderate feeds, good chip control with coolant.
Can A209 T1-T1a be welded?
Yes — weldability is rated very good (78/100). Readily welded with matched C-Mo consumables (E7018-A1 / ER80S-D2); 100–200 °C preheat on heavier walls and PWHT near 700 °C for code work.
What surface finishes work on A209 T1-T1a?
No anodizing; use pickle/phosphate, aluminizing, or high-temperature silicone-aluminum paint for fireside and outdoor protection.
Can A209 T1-T1a be formed, bent or molded?
Good cold bending and tube expanding in the annealed condition (A209 requires flattening and flaring tests); hot bends should be re-heat-treated.
What is the maximum service temperature of A209 T1-T1a?
A209 T1-T1a is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A209 T1-T1 and A209 T1-T1b?
T1 is the default condition — default A209 grade: 0.10–0.20 % C with 0.5 % Mo — standard choice for boiler and superheater tubes to ~500 °C. T1b: lowest-carbon variant: best bending, expanding and welding behaviour where strength is not critical. Yield strength is 260 MPa in T1 versus 225 MPa in T1b.
Sources
- ASTM A209/A209M — Seamless Carbon-Molybdenum Alloy-Steel Boiler and Superheater Tubes — ASTM International (2018)
- ASME BPVC Section II Part D — Properties (Metric), C-Mo steel allowable stresses and physical properties — ASME (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13 — Corrosion — ASM International (2005)
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.