ASTM A694

Applies to: Carbon and alloy steel forgings (flanges, fittings, valves, parts) for high-pressure gas and liquid transmission service; grades F42–F80 with yield strength matched to connected API 5L pipe grade; ASME Class 300 and above or working pressures above standard A105 capability.

Does NOT cover: Standard boiler/pressure vessel forgings (use ASTM A105/A182); low-temperature service without separate impact testing specification.

• Grade selection matched to pipe yield strength (F65 flange for X65 pipe)
• Charpy V-notch impact testing per grade requirement
• Heat treatment: normalized, or Q&T per grade
• Chemical composition limits including carbon equivalent for weldability
• Marking includes grade, heat number, and manufacturer's ID

ASTM A694 forgings are specified when standard carbon steel flanges (ASTM A105, 36 ksi yield) would be undermatched against high-strength pipeline pipe. The grade suffix directly indicates minimum yield strength in ksi — F52, F60, F65, F70, F80 — mirroring API 5L grade naming and simplifying pipeline specification writing.

Engineering note: Using an undermatched flange (e.g., A105 on X65 pipe) creates a weak-link at the flange that can govern the system pressure rating. Pipeline engineers routinely specify A694 F65 or F70 weld-neck flanges to maintain grade continuity across the system.