Carbide Solution Treated 347 Columbium Stabilized Continuous & Double-End Studs
ASTM A320 Grade B8C Class 1 are carbide solution treated AISI 347 (UNS S34700) stainless steel, stabilized with columbium (niobium) plus tantalum of 10 times the carbon content minimum, 1.10 % maximum (Table 3). Manufactured as fully threaded continuous studs or double end studs, these Class 1 fasteners offer 75 ksi [515 MPa] minimum tensile strength with maximum hardness of 223 HBW or 96 HRB (241 HBW or 100 HRB permitted for sizes 3/4 in. [20 mm] and smaller). Class 1 Grade B8C is exempt from impact testing above -425°F [-255°C] (6.2.1.1), making B8C Class 1 suitable for low temperature pressure vessel, valve, flange, and fitting bolting.
| Grade Symbol | UNS Designation | C, max | Mn, max | P, max | S, max | Si, max | Ni | Cr | Nb E + Ta | |
|---|---|---|---|---|---|---|---|---|---|---|
| ASTM A320 B8C | S34700(347) | Range,% | 0.08 | 2.00 | 0.045 | 0.030 |
1.00 | 9.0- 12.0 | 17.0- 19.0 | 10 × C content, min -1.10 max |
| Product Variation, % Over or Under | 0.01 over | 0.04 over | 0.010 over | 0.005 over | 0.05 over | 0.15 | 0.20 | 0.05 under | ||
| Grade and Class | Diameter, in. [mm] | Heat Treatment | Tensile Strength, min, ksi [MPa] | Yield Strength, min, ksi [MPa] (0.2 % offset) | Elongation in 2 in. or 50 mm, min, % | Reduction of Area, min, % | Hardness, max |
|---|---|---|---|---|---|---|---|
| ASTM A320 B8C Class 1 | All diameters | carbide solution treated | 75 [515] | 30 [205] | 30 | 50 | 223 HBWDor 96 HRB |
