When purchasing carbon steel flanges and fittings, many buyers come across two common material grades: ASTM A105 and ASTM A350 LF2. Although both are widely used in piping systems, they are not the same material. Understanding the difference between them is important for selecting the right grade for your project.

1. Standard and Application

• ASTM A105: Standard specification for carbon steel forgings for piping applications. It is mainly used for ambient- and high-temperature service in pressure systems.

• ASTM A350 LF2: Standard specification for carbon and low-alloy steel forgings requiring notch toughness testing. It is primarily used for low-temperature service applications, such as cryogenic piping and storage tanks.

2. Chemical Composition

• ASTM A105: Carbon ≤ 0.35%, Manganese 0.60–1.05%, Silicon 0.15–0.35%, with limits on phosphorus and sulfur.

• ASTM A350 LF2: Contains similar elements but with tighter control to ensure toughness at low temperatures.

3. Mechanical Properties

• ASTM A105:

  • Tensile strength ≥ 485 MPa

  • Yield strength ≥ 250 MPa

  • Elongation ≥ 22%

• ASTM A350 LF2:

  • Tensile strength ≥ 485 MPa

  • Yield strength ≥ 250 MPa

  • Impact test required at –46°C to ensure toughness

4. Temperature Suitability

• A105: Suitable for general piping, valves, and flanges at normal or high temperature.

• LF2: Designed for low-temperature applications where toughness is critical.

5. Common Uses

• ASTM A105: Oil & gas pipelines, boiler fittings, valves, and flanges in ambient or high-temperature environments.

• ASTM A350 LF2: LNG projects, cryogenic piping, refrigeration systems, and low-temperature storage tanks.

The main difference between ASTM A105 and ASTM A350 LF2 lies in their service temperature range. A105 is used for ambient and high-temperature service, while LF2 is specifically for low-temperature service requiring notch toughness. Buyers should always confirm the project’s temperature conditions before choosing between the two materials.