ASTM A350

Covers — carbon and low-alloy steel forgings for piping components requiring notch toughness at low temperature: grades LF1, LF2, LF3 (3½Ni), LF5, LF6, LF9, with mandatory Charpy impact testing.

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

• Ambient/high-temperature forgings without impact testing → ASTM A105.
• Low-temperature seamless pipe → ASTM A333; low-temperature fittings → ASTM A420.
• Austenitic stainless (inherently tough at low temperature) → ASTM A182.

A350 = A105 chemistry plus mandatory impact testing for cold service.

A350 sets minimum requirements for low-temperature forgings:

• Chemistry — carbon/low-alloy (LF2) or nickel-alloy (LF3) composition for toughness.
• Mechanical Properties — tensile/yield plus mandatory Charpy V-notch impact energy at the specified test temperature.
• Heat Treatment — normalized, or quenched-and-tempered, to develop low-temperature toughness.
• Testing & Certification — impact and tension testing per heat/lot, with certification (EN 10204 3.1/3.2) and PMI where required.

ASTM A350 provides carbon and low-alloy steel forgings with the notch toughness needed for low-temperature piping components. Its defining feature over A105 is mandatory Charpy V-notch impact testing: LF2 is qualified for cold service (typically −50 °F), and LF3 (3½Ni) reaches cryogenic-approaching temperatures.

It pairs with A333 low-temperature pipe and A420 low-temperature fittings to form a complete cold-service material set. The substitution of A350 for A105 is one of the most important checks in cold-service material selection.

Engineering Note: Confirm the required impact test temperature matches the minimum design metal temperature — an LF2 forging impact-tested at the wrong temperature does not qualify the joint.