A105 vs A350 LF2 vs A694
ASTM A105, A350 LF2, and A694 F65 are all carbon steel forging specifications used for flanges and fittings. They share similar chemical compositions but differ in impact test requirements, which determine the minimum design temperature for each material.
Comparison Table
| Property | ASTM A105 | ASTM A350 LF2 | ASTM A694 F65 |
|---|---|---|---|
| Material type | Carbon steel forging | Low-temperature carbon steel forging | High-yield carbon steel forging |
| Carbon content (max) | 0.35% | 0.30% | 0.26% |
| Manganese (max) | 1.05% | 1.35% | 1.65% |
| Min yield strength | 250 MPa (36 ksi) | 250 MPa (36 ksi) | 450 MPa (65 ksi) |
| Min tensile strength | 485 MPa (70 ksi) | 485 MPa (70 ksi) | 535 MPa (77 ksi) |
| Impact test required | No (unless specified) | Yes (Charpy V-notch at -46°C) | No (unless specified) |
| Min design temperature | -29°C (-20°F) per ASME B31.3 | -46°C (-50°F) | -29°C (-20°F) typical |
| Max design temperature | 425°C (800°F) | 345°C (650°F) | 232°C (450°F) |
| Typical application | Standard process piping | Low-temperature / cryogenic services | High-pressure pipeline (API 6D) |
| Flange standard | ASME B16.5, B16.47 | ASME B16.5, B16.47 | ASME B16.47, MSS SP-44 |
| NACE MR0175 compliant | With additional requirements | With additional requirements | Typically compliant (low CE) |
| Weldability | Good (PWHT may apply) | Good (controlled chemistry) | Good (fine-grain, low carbon) |
| Relative cost | 1.0x (baseline) | 1.2-1.4x | 1.5-2.0x |
Key Differences
Impact testing. This is the primary differentiator between A105 and A350 LF2. A105 does not require Charpy impact testing unless the purchaser adds it as a supplementary requirement. A350 LF2 mandates Charpy testing at -46°C, guaranteeing that the material retains toughness at low temperatures. For services below -29°C, A350 LF2 (or LF3 for even lower temperatures) must be specified instead of A105.
Yield strength. A694 F65 has a minimum yield strength of 450 MPa (65 ksi), nearly double that of A105 and A350 LF2. This high-strength grade is designed for large-diameter, high-pressure pipeline flanges where wall thickness and weight reduction are critical. It is commonly used for API 6D pipeline valves and ASME B16.47 large flanges.
Temperature range. A105 covers the broadest temperature range (-29°C to 425°C). A350 LF2 extends the lower limit to -46°C but has a lower upper limit (345°C). A694 F65 is primarily a pipeline grade with moderate temperature limits.
Chemistry and weldability. A350 LF2 has lower carbon and controlled chemistry to ensure toughness at low temperatures. A694 F65 achieves its higher strength through higher manganese and fine-grain practice, while maintaining good weldability with a low carbon equivalent.
For more on forged fitting materials, see the ASME B16.11 forged fittings guide.
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