A193 B7M Stud Bolts
B7 tempered to 22 HRC max for sour service — the NACE MR0175 bolting grade for wellheads, sour gas and H₂S process piping.
Threaded rod inserted through the holes of mating flanges, paired with heavy hex nuts. Available in every diameter and length, imperial and metric, for flanged connections in critical service. Supplied bare or coated, with full material traceability.
ASTM A193 Grade B7M is the controlled-hardness version of B7. It is the same chromium-molybdenum steel, tempered at a higher temperature to bring hardness under 235 HBW while holding a 100 ksi minimum tensile strength. That hardness ceiling is what qualifies it for sour service under NACE MR0175 / ISO 15156, where sulfide stress cracking rules out the harder B7.
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What A193 B7M must meet.
| Nominal diameter (in.) | Tensile strength, min (ksi) | Yield strength 0.2% offset, min (ksi) | Elongation in 4D, min (%) | Reduction of area, min (%) | Hardness, max |
|---|---|---|---|---|---|
| 4 and under | 100 | 80 | 18 | 50 | 235 HBW / 99 HRB (over 200 HBW / 93 HRB min) |
| Over 4 to 7 | 100 | 75 | 18 | 50 | 235 HBW / 99 HRB (over 200 HBW / 93 HRB min) |
Values per ASTM A193/A193M-24, Tables 1 and 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. B7M: 100 percent hardness testing (S3) is available on request; 235 HBW / 99 HRB max, over 200 HBW / 93 HRB min.
Quenched in a liquid medium and tempered at 1150 °F (621 °C) minimum. Per clause 6.1.6 a final stress relief (or a substitute temper) is performed after all machining, cutting and forming at not less than 50 °F below the original tempering temperature; where the original temper was by induction above 1300 °F and the stress relief is in a furnace, the minimum is 1200 °F. Every piece is then hardness tested to the 235 HBW / 99 HRB maximum.
Full A193 B7M data sheet: chemistry, physical properties and standards →
Made to standard or to your drawing.
- Sour gas wellhead and tree bolting
- H₂S process piping and vessel flanges
- Amine, sulfur recovery and hydrotreating units
- Subsea and offshore production equipment
- Gas plants and compressor stations
- Any A193 B7 application where NACE compliance is called out