ASTM A691 — High-temperature and high-pressure electrofusion welded alloy steel pipes
Grades
Gr.CM-65, Gr.CM-70, Gr.1-1/4Cr-1/2Mo, Gr.2-1/4Cr-1Mo, Gr.5Cr-1/2Mo, Gr.9Cr-1Mo-V
Chemical composition and mechanical properties
| Grade | Chemical composition | Mechanical properties |
|---|---|---|
| Gr.CM-65 | C≤0.20, Mn 1.05-1.50, P≤0.030, S≤0.030, Si 0.13-0.32, Mo 0.25-0.45 | Rm ≥450 MPa, Rp0.2 ≥260 MPa, A≥17%, Killed steel |
| Gr.CM-70 | C≤0.20, Mn 1.05-1.50, P≤0.030, S≤0.030, Si 0.13-0.32, Mo 0.25-0.45 | Rm ≥485 MPa, Rp0.2 ≥280 MPa, A≥15%, Killed steel |
| Gr.1-1/4Cr-1/2Mo | C≤0.15, Mn 0.40-0.70, P≤0.030, S≤0.030, Si 0.50-1.00, Cr 1.00-1.50, Mo 0.45-0.65 | Rm ≥415 MPa, Rp0.2 ≥205 MPa, A≥18%, Normalizing + Tempering |
Application scope
ASTM A691 specifies electrofusion welded alloy steel pipes for high-temperature and high-pressure applications, including multiple grades of carbon manganese steel and chromium-molybdenum series. The standard uses electrofusion welding to produce large-diameter steel pipes, emphasizing high-temperature strength and creep resistance. It is suitable for welded pressure piping systems, serving the manufacture of high-temperature and high-pressure pipelines in power plants and petrochemical plants, and is an important reference for the design and material selection of pressure equipment.
Typical applications
Widely used in the manufacture of high-temperature and high-pressure pipelines for power plants, oil refining and hydrogenation units, and petrochemical high-temperature and high-pressure process pipes. Chromium-molybdenum alloying combined with electrofusion welding for large-diameter forming provides excellent high-temperature strength, creep resistance, and hydrogen resistance, making it suitable for pipelines, headers, and piping systems operating under harsh high-temperature and high-pressure conditions. Appropriate grades can be selected according to the medium, temperature, and pressure requirements.
