What Is ASTM A333? Low Temperature Pipe

ASTM A333 is the standard specification for seamless and welded steel pipe designed for low-temperature service. It covers grades suited for operating temperatures down to -196°C (-320°F), making it the go-to specification for cryogenic piping in LNG plants, air separation units, and cold-climate pipelines.

The specification requires mandatory Charpy V-notch impact testing at the designated minimum temperature for each grade. This separates ASTM A333 from standard carbon steel specs like ASTM A106, which do not guarantee impact toughness at low temperatures.

Grade	Min. Temperature	Material Type	Yield (min)	Tensile (min)
1	-46°C (-50°F)	C-Mn steel	240 MPa (35 ksi)	415 MPa (60 ksi)
3	-101°C (-150°F)	3.5% Nickel steel	240 MPa (35 ksi)	450 MPa (65 ksi)
6	-46°C (-50°F)	C-Mn steel (killed, fine grain)	240 MPa (35 ksi)	415 MPa (60 ksi)
7	-62°C (-80°F)	2.5% Nickel steel	240 MPa (35 ksi)	450 MPa (65 ksi)
8	-196°C (-320°F)	9% Nickel steel	517 MPa (75 ksi)	690 MPa (100 ksi)
9	-73°C (-100°F)	Ni-Cu-Cr-Mo alloy	310 MPa (45 ksi)	483 MPa (70 ksi)
10	-46°C (-50°F)	C-Mn-Si steel	240 MPa (35 ksi)	415 MPa (60 ksi)
11	-46°C (-50°F)	C-Mn-Si-Cb steel	275 MPa (40 ksi)	450 MPa (65 ksi)

Grade 6: The Most Common

ASTM A333 Grade 6 is the workhorse for low-temperature carbon steel piping. Its chemistry and mechanical properties are similar to ASTM A106 Grade B, but it is produced as killed, fine-grain steel and must pass Charpy impact tests at -46°C with a minimum absorbed energy of 18 J (average of three specimens).

Grade 6 is specified for:

• Cold-climate pipeline stations and process plants
• Refrigeration systems
• LPG storage and handling facilities
• Depressurization systems where Joule-Thomson cooling occurs

Grade 8: Cryogenic Service

For true cryogenic applications (-101°C to -196°C), Grade 8 (9% nickel steel) is the standard choice. The high nickel content provides excellent fracture toughness at liquid nitrogen temperatures. Grade 8 pipe is used in:

• LNG liquefaction and regasification plants
• Air separation units (oxygen, nitrogen, argon lines)
• Ethylene plants (cryogenic sections)

Pro Tip

ASTM A333 Grade 6 can be used down to -46°C, but many EPC specifications allow it down to -29°C only when extra corrosion allowance or thicker schedules are specified. For temperatures between -46°C and -101°C, Grade 3 (3.5% Ni) or Grade 7 (2.5% Ni) is required. Below -101°C, Grade 8 (9% Ni) is the only carbon/low-alloy option; otherwise, switch to austenitic stainless steel (ASTM A312 TP304/TP316).

Impact Testing

All ASTM A333 grades require Charpy V-notch impact testing at or below the specified minimum service temperature. The acceptance criteria are:

• Minimum average absorbed energy: 18 J (13 ft-lbs) for full-size specimens
• No single specimen below 14 J (10 ft-lbs)
• Sub-size specimen values are proportionally reduced

This mandatory impact testing is what justifies the specification for low-temperature use and what differentiates it from ASTM A106 and ASTM A53.

Read the full guide to pipe types