ASTM A691 pipes belong to chromium-molybdenum alloy steel welded pipes. The material properties vary in composition and performance according to the specific grade (such as CM70, 5Cr, 9Cr, etc.). The core features are as follows:
Basic material properties
- Alloy system
Main elements: Chromium (Cr) and Molybdenum (Mo) are the core alloying elements, supplemented by basic components such as carbon (C), manganese (Mn), and silicon (Si).
High temperature resistance: Chromium forms a dense oxide film to improve oxidation resistance, and molybdenum enhances high temperature creep strength (working temperature can reach 600℃).
- Mechanical properties
General indicators: Tensile strength ≥415 MPa, yield strength ≥205–415 MPa (depending on grade), elongation ≥18–30%.
Low temperature toughness: CL22 grade requires -40℃ impact energy ≥60J, suitable for high-cold environments.
Process and performance guarantee
- Manufacturing process
Adopt Electric fusion welding (EFW) or Submerged arc welding (SAW) to force double-sided penetration of the weld;
After welding, normalizing + tempering heat treatment (such as 920℃ normalizing + 680–720℃ tempering) eliminates stress and optimizes the structure.
- Quality control
100% weld non-destructive testing (UT/RT);
Sulfur-containing environment requires NACE MR0175 sulfur corrosion resistance certification.
Core application scenarios
Energy field: steam pipelines of supercritical thermal power units (9Cr grade), oil and gas gathering and transportation high-pressure pipelines (CM70 grade);
Petrochemical engineering: hydrogenation reactor pipelines (1.25Cr–2.25Cr grade);
Extreme environment: high-cold areas (CL22 grade), sulfur-containing corrosion environment (requires NACE certification).
