Class 1A Low Temperature Fasteners - AISI 304 Solution Treated Grade
ASTM A320/A320M Grade B8A Class 1A is the Class 1A form of Grade B8 (AISI 304, UNS S30400): the bolting is carbide solution treated in the finished condition, after forming and threading, for corrosion resistance (Table 1 footnote C, 11.1). Class 1A has the same 75 ksi [515 MPa] tensile and 30 ksi [205 MPa] yield minimums as Class 1, with a lower maximum hardness of 192 HBW or 90 HRB against 223 HBW or 96 HRB for Class 1. The marking B8A identifies the solution-treated condition in the finished state (13.1), and Class 1A Grade B8A is exempt from impact testing above -425°F [-255°C] (6.2.1.1), making ASTM A320/A320M Grade B8A Class 1A suitable for low temperature service.
| Grade Symbol | UNS Designation | C, max | Mn, max | P, max | S, max | Si, max | Ni | Cr | |
|---|---|---|---|---|---|---|---|---|---|
| ASTM A320 B8A Class 1A | S30400(304) | Range,% | 0.08 | 2.00 | 0.045 | 0.030 |
1.00 | 8.0-11.0 | 18.0 - 20.0 |
| Product Variation, % Over or Under | 0.01 over | 0.04 over | 0.010 over | 0.005 over | 0.05 over | 0.15 | 0.20 | ||
| 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 B8A: Class 1A | All diameters | carbide solution treated in the finished condition | 75 [515] | 30 [205] | 30 | 50 | 192 HBW or 90 HRB |
