ASTM A333

Covers — steel pipe for low-temperature service:

• Seamless and welded manufacturing.
• Grades 1, 3, 4, 6, 7, 8, 9, 10, 11 (Grade 6 is the ubiquitous carbon steel low-temp standard, rated down to -50°F / -45°C).
• Flare gas, LPG, ammonia, and cryogenic services.

Does NOT cover (exclusions) — the following are governed elsewhere:

• General or high-temperature carbon steel → ASTM A106 or A53.
• Pipe dimensions → ASME B36.10M.

A333 guarantees mechanical properties at sub-zero temperatures:

• Chemical Composition — strict control of Carbon and Manganese to promote fine grain structure and low-temperature toughness.
• Heat Treatment — requires normalizing (or normalizing + tempering) to refine the grain structure, which is critical for cold toughness.
• Impact Testing — mandates Charpy V-Notch impact testing at the specified low temperature for the grade (e.g., -50°F for Grade 6) to guarantee a minimum absorbed energy (toughness).

Carbon steel ordinarily becomes brittle at low temperatures, making standard A106 pipe dangerous for cold fluids. A333 Grade 6 solves this through fine-grain practice and heat treatment, retaining ductility.

Temperature Limits by Grade

• Grade 6: Carbon steel, tested to -50°F (-45°C).
• Grade 3: Nickel alloy (3.5% Ni), tested to -150°F (-100°C).
• Grade 8: Nickel alloy (9% Ni), tested to -320°F (-195°C, suitable for LNG).

Where to find it in the code: Impact temperature by grade → Table 4 · Impact energy requirements → Table 5.