ASTM A209/A209M — Carbon-molybdenum alloy steel tubes for boilers and superheaters
Grades
T1, T1a, T1b
Chemical composition and mechanical properties
| Grade | Chemical composition | Mechanical properties |
|---|---|---|
| T1 | C≤0.10-0.20, Mn 0.30-0.80, P≤0.025, S≤0.025, Si 0.10-0.50, Mo 0.44-0.65 | Rm ≥380 MPa, Rp0.2 ≥205 MPa, A≥30%, HB≤146 |
| T1a | C≤0.15-0.25, Mn 0.30-0.80, P≤0.025, S≤0.025, Si 0.10-0.50, Mo 0.44-0.65 | Rm ≥415 MPa, Rp0.2 ≥220 MPa, A≥30%, HB≤153 |
| T1b | C≤0.14, Mn 0.30-0.80, P≤0.025, S≤0.025, Si 0.10-0.50, Mo 0.44-0.65 | Rm ≥365 MPa, Rp0.2 ≥195 MPa, A≥30%, HB≤137 |
Application scope
ASTM A209/A209M specifies seamless carbon-molybdenum alloy steel tubes for boilers and superheaters, with the addition of molybdenum to enhance high-temperature strength and creep resistance. Grades include T1, T1a, and T1b, with slight differences in composition to meet varying strength requirements, suitable for boiler heating surface tube systems subjected to long-term pressure at medium to high temperatures.
Typical applications
Primarily used in high-temperature pressure-bearing components such as superheater tubes, reheater tubes, and high-temperature steam pipelines in power plant boilers. Carbon-molybdenum alloying provides good high-temperature strength and creep resistance, making it suitable for heated surface tube banks, serpentine tubes, and steam transmission pipelines that operate continuously under high-temperature conditions. It is a commonly used carbon-molybdenum alloy pipe material in the superheater and reheat sections of boilers.
