ASTM A350 LF2 Class 1 / Class 2 Forging Specification | Flanges Fittings

ASTM A350 LF2 Class 1 / Class 2 Forging Specification for Flange / Fittings

The ASTM A350 LF2 Class 1 / Class 2 Forging Specification PDF provides a comprehensive technical reference for low-temperature carbon steel forgings used for pipe flanges, forged fittings, valves, and pressure components. This specification covers chemical composition, mechanical properties, impact testing requirements, heat treatment, manufacturing process, dimensions and tolerances, testing and inspection, and typical applications in low-temperature and cryogenic service environments.

ASTM A350 Standard

ASTM A350 is the standard specification for carbon and low-alloy steel forgings requiring notch toughness testing for piping components intended for low-temperature service. Materials produced under ASTM A350 are designed to maintain adequate toughness and impact resistance at subzero operating temperatures.

Grade LF2 is the most widely used grade under ASTM A350 and is commonly specified for low-temperature pressure piping systems.

Material Grade: ASTM A350 LF2 Class 1 & Class 2

  • Standard: ASTM A350 / ASME SA350

  • Grade: LF2

  • Classes: Class 1, Class 2

  • Material Type: Carbon Steel for Low-Temperature Service

  • Product Form: Forgings for Flanges, Fittings, Valves, and Components

Class 2 LF2 forgings are supplied with higher strength requirements compared to Class 1 and are commonly specified where higher pressure resistance is required.

Chemical compostion,Mechanical Properties,Impact Test,Carbon Equivalent

Category Item LF2 Class 1 LF2 Class 2
Chemical Composition (wt%) Carbon, max 0.30 0.30
Manganese 0.60–1.35 0.60–1.35
Phosphorus, max 0.035 0.035
Sulfur, max 0.040 0.040
Silicon 0.15–0.30 0.15–0.30
Nickel, max 0.40 0.40
Chromium, max 0.30 0.30
Molybdenum, max 0.12 0.12
Copper, max 0.40 0.40
Niobium, max 0.02 0.02
Vanadium, max 0.08 0.08
Mechanical Properties Tensile Strength (MPa) 485–655 485–655
Yield Strength, min (MPa) 250 260
Elongation (%) 22 22
Reduction of Area (%) 30 35
Impact Test Test Temperature (°C) -46 -18
Average Impact Energy (J) 20 27
Minimum Single Specimen (J) 16 20
Carbon Equivalent CE max (≤2 in) 0.47 0.47
CE max (>2 in) 0.48 0.48

Heat Treatment

ASTM A350 LF2 Class 1 / Class 2 forgings are typically supplied in one of the following conditions:

  • Normalized

  • Normalized and tempered

Proper heat treatment is essential to achieve the required mechanical properties and impact toughness.

Manufacturing Process

ASTM A350 LF2 carbon steel forgings are manufactured by:

  • Hot forging or rolling

  • Heat treatment in accordance with ASTM A350

  • Machining of flanges and fittings (if required)

  • Final inspection and testing

The forging process ensures refined grain structure and reliable mechanical performance.

ASTM A350 LF2 prodct standard

Dimensions of ASTM A350 LF2 forgings are governed by applicable dimensional standards, including:

  • ASME B16.5 / ASME B16.47 for pipe flanges

  • ASME B16.11 for forged fittings

  • Project-specific drawings for custom components

Dimensional controls include outside diameter, thickness, bore size, facing finish, and machining tolerances.

Testing & Inspection

Each ASTM A350 LF2 forging may be subjected to:

  • Chemical analysis

  • Tensile testing

  • Charpy V-notch impact testing

  • Non-destructive testing (UT / MT, if specified)

  • Dimensional and visual inspection

Mill Test Certificates (EN 10204 3.1) are typically supplied.

Applications

  • Low-Temperature Piping Systems

  • Oil & Gas Pipelines

  • LNG & Cryogenic Facilities

  • Refineries

  • Petrochemical Plants

  • Pressure Vessels and Valves

ASTM A350 LF2 Class 1 / Class 2 forgings are widely used where low-temperature toughness and pressure resistance are critical.

Download ASTM A350 LF2 Class 1 / Class 2 Forging Specification PDF

Download the complete ASTM A350 LF2 Class 1 / Class 2 Forging Specification PDF, including chemical composition limits, mechanical requirements, impact testing criteria, heat treatment conditions, and testing procedures.

👉 Download ASTM A350 LF2 Class 1 / Class 2 Forging Specification PDF

👉 Download ASTM A350 Standard Specification PDF

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