Is there a way to visually distinguish the difference between a Class 1 and Class 2 stainless steel bolt?
Yes there is. A193 and A320 grades B8 and B8M are assumed to be Class 1 unless otherwise specified. Class 1 fasteners are carbon solution treated, while class 2 fasteners are carbide solution treated and strain hardened. The work hardening that occurs in the manufacturing of Class 2 fasteners increases their strength. Class 2 fasteners are differentiated by a line under the grade symbol which appears on the heads of bolts or the ends of threaded rods.
|A193 Grade B8||Type 304||High temperature / High pressure||B8||B8SH|
|A320 Grade B8||Type 304||Low temperature||B8||B8|
|A193 Grade B8M||Type 316||High temperature / High pressure||B8M||B8MSH|
|A320 Grade B8M||Type 316||Low temperature||B8M||B8M|