At a Glance
Gr. 3 Limit
−150°F (−101°C)
Scope
ASTM A333 covers seamless and welded carbon and alloy steel pipe intended for use at low temperatures. The defining requirement — and the entire reason to specify A333 over A106 — is mandatory Charpy V-notch impact testing at the minimum service temperature for each grade. Chemistry and mechanical properties are secondary to this.
While the specification technically permits electric resistance welding for some grades, A333 is seamless in practice across the industry. ERW A333 is not commercially stocked or produced in meaningful quantities. Specify seamless.
Grade Availability — Know Before You Specify
Min Temp-50°F (-46°C)
The workhorse of low-temperature pipe. C-Mn steel with mandatory Charpy impact testing at −50°F. Identical SMYS and SMTS to A106 Grade B — dual certification to A106 is common and commercially available when chemistry and mechanicals satisfy both specs. Grade 6 is the automatic choice when operating temperatures drop below −20°F in oil & gas, processing, and LNG applications.
Widely stocked. Standard lead times in most sizes and schedules.
Min Temp-150°F (-101°C)
The nickel grade. Grade 3 contains 3.3–3.7% nickel, which provides low-temperature toughness down to −150°F — well beyond what carbon manganese steel can achieve. This is not a carbon steel product in behavior or cost: expect pricing 3–5× Grade 6. Long lead times. Limited mill availability. Typically used in ethylene plants, deep cryogenic service, and LNG loading arm applications where Grade 6 is inadequate. When someone asks for Grade 3, confirm service temperature, alternatives (A312 TP304, A358), and lead time before committing.
Limited availability. Mill order in most cases. Extended lead times common. Verify with supplier before specifying.
Min Temp-50°F (-46°C)
Near obsolete. Grade 1 covers the same service temperature range as Grade 6 (−50°F minimum) but with lower strength (30 ksi SMYS vs 35 ksi) and slightly different chemistry. There is no practical advantage over Grade 6 in modern service. When encountered on older drawings or legacy project specs, Grade 6 is the modern equivalent. Do not stock or specify Grade 1 for new projects.
Rarely produced. Do not rely on availability for project work.
All Other Grades (1A, 4, 7, 8, 9, 10, 11)
Not commercially produced or stocked. Paper grades only. Grade 8 (9% Ni) exists in the spec but is produced in negligible quantities — if service requires 9% Ni pipe, specify ASTM A333 Grade 8 by name with the understanding that lead times will be extreme and alternatives (A312 TP304L) should be evaluated.
The Single Most Important Point
A333 is A106 with guaranteed impact toughness. Grade 6 and A106 Grade B share identical SMYS (35 ksi) and SMTS (60 ksi). The chemistry is similar. The one difference that matters: A333 Grade 6 has been Charpy tested at −50°F and passed. A106 has no impact requirement. When your design code requires impact-tested pipe or operating temperature drops below −20°F, A333 Grade 6 is the answer.