1. What is the significance of "Class 22" in ASTM A671 CJH115?
Class 22 indicates a hydrostatic test pressure of 22,000 psi (152 MPa), making it suitable for ultra-high-pressure cryogenic systems.
CJH115 certifies Charpy V-notch impact toughness at -115°F (-81°C) with longitudinal (J) and high-strength (H) requirements.
2. Where is this grade typically used?
LNG export terminals: For high-pressure transfer lines.
Deep-sea oil/gas pipelines: Where low-temperature and high-pressure resistance are critical.
Cryogenic processing plants: Ethylene, nitrogen, or oxygen transport.
3. Key mechanical properties?
Tensile strength: ≥80 ksi (552 MPa)
Yield strength: ≥50 ksi (345 MPa)
Impact energy: ≥30 ft-lb (41 J) at -115°F
Elongation: ≥16% (2" gauge length).
4. Chemical composition requirements?
Low carbon: ≤0.22% (ensures weldability and toughness).
Manganese: 1.00–1.60% (optimizes strength and low-T performance).
Microalloying: Nb/V/Ti additions for grain refinement and precipitation hardening.
5. Fabrication and quality control?
100% radiographic testing (RT) and ultrasonic testing (UT) for weld integrity.
Strict PWHT protocols to prevent brittle fracture.
Third-party certification for material traceability (e.g., NACE MR0175 for sour service).
