This standard material specification of ASTM A193 grade B7 covers fasteners of chromium-molybdenum alloy steel. These fasteners found their use in chemical and petroleum construction applications. They are made after tempering (heat
treatment) and quenching to acquire the ideal mechanical properties and hardness. B7 is one of the most grade used in ASTM A193 and is mainly implemented in zinc plating, zinc coating, hot-dip galvanizing, PTFE coating or coated,
and xylan coating to prevent corrosion. They are chiefly used in high-pressure and temperature services like valves, flanges, pressure valves, and fittings.
A193 Grade B7
| B7 |
Alloy steel, AISI 4140/4142 quenched and tempered |
Mechanical properties
| Size |
Tensile ksi, min |
Yield ksi, min |
Elong %, min |
RA % min |
HBW |
Rockwell |
| Up to 2-1/2 |
125 |
105 |
16 |
50 |
321 Max |
35 HRC max |
| 2-5/8 - 4 |
115 |
95 |
16 |
50 |
| 4-1/8 - 7 |
100 |
75 |
18 |
50 |
Chemical properties
| Element |
B7 (AISI 4140) |
| Carbon |
0.37 - 0.49% |
| Manganese |
0.65 - 1.00% |
| Phosphorus, max |
0.035% |
| Sulfur, max |
0.040% |
| Silicon |
0.15 - 0.35% |
| Chromium |
0.80 - 1.10% |
| Nickel |
- |
| Molybdenum |
0.15 - 0.25% |
Compatible hardware
| Bolt Grade |
Nut |
Washers |
| B7 |
A194 Grade 2H |
F436 |
