ASTM A193 Grade B7, a chromium-molybdenum steel quenched and tempered to 125 ksi minimum tensile in sizes up to 2-1/2 in, used for flanges, valves and pressure vessels at moderate temperatures. It is normally supplied as full-thread stud bolts with A194 Grade 2H heavy hex nuts. B7M is a lower-hardness version for sour service, where hydrogen sulfide makes harder steel prone to cracking.
Flange takes eight seven-eighths B7 studs with 2H nuts, and lube the threads and nut faces before bolt-up.
Blue or green coated B7 has a fluoropolymer finish that changes the nut factor, so it gets its own torque table.
Also heard as
- A193 B7
- B7 stud
Related terms
Stud
A headless rod threaded at both ends or along its full length, used with nuts or screwed into a tapped hole.
Bolt-up
The assembly and tightening of a gasketed flange or bolted joint as a job, done in a pattern over several passes.
All-thread
Shop name for threaded rod: steel bar threaded end to end, cut to length for hangers, anchors and long studs.
Heavy hex
A hex head or nut wider across the flats than the regular series, used for structural and pressure bolting.