ASTM A193 Grades B8LN and B8MLN (304LN / 316LN)
304LN and 316LN bolting — low carbon for weld-zone corrosion resistance, nitrogen to recover the strength that low carbon gives away.
What A193 B8LN / B8MLN is.
ASTM A193 Grades B8LN and B8MLN cover bolting in Types 304LN and 316LN. The L grades hold carbon to 0.030 percent so that welding or hot service does not sensitise the steel, and the N addition puts back the strength that low carbon removes, so both meet the standard Class 1 requirement of 75 ksi tensile and 30 ksi yield.
These grades are common in LNG, cryogenic and nuclear specifications. We supply both from certified bar in Class 1 and Class 1A.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.030 |
| Manganese | Mn | — | 2.00 |
| Phosphorus | P | — | 0.045 |
| Sulfur | S | — | 0.030 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 18.0 | 20.0 |
| Nickel | Ni | 8.0 | 11.0 |
| Nitrogen | N | 0.10 | 0.16 |
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.
Mechanical properties.
| Nominal diameter (in.) | Tensile strength, min (ksi) | Yield strength 0.2% offset, min (ksi) | Elongation in 4D, min (%) | Reduction of area, min (%) | Hardness, max |
|---|---|---|---|---|---|
| Class 1 / 1D — all diameters | 75 | 30 | 30 | 50 | 223 HBW / 96 HRB |
| Class 1A (B8LNA / B8MLNA) — all diameters | 75 | 30 | 30 | 50 | 192 HBW / 90 HRB |
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. No Class 2 (strain-hardened) condition is listed for these grades.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.030 |
| Manganese | Mn | — | 2.00 |
| Phosphorus | P | — | 0.045 |
| Sulfur | S | — | 0.030 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 16.0 | 18.0 |
| Nickel | Ni | 10.0 | 13.0 |
| Molybdenum | Mo | 2.00 | 3.00 |
| Nitrogen | N | 0.10 | 0.16 |
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.
Specifications that apply.
How A193 B8LN / B8MLN ships from Houston.
- Full-thread studs and stud bolts
- Hex and heavy hex bolts
- Socket head cap screws
- Hex nuts in the same alloy
- Threaded rod
- Machined components from certified bar
A193 B8LN / B8MLN fasteners we make.
Every item is manufactured to your drawing or standard in A193 B8LN / B8MLN, imperial or metric, with an EN 10204 3.1 certificate.
What are B8LN and B8MLN?
The LN stainless grades solve a trade-off. Reducing carbon to 0.03 percent prevents chromium-carbide precipitation and keeps the steel corrosion resistant after welding, but plain 304L and 316L are noticeably weaker than 304 and 316. Adding 0.10 to 0.16 percent nitrogen restores the strength, so 304LN and 316LN match the standard grades at 75 ksi tensile while keeping the low-carbon benefit. A193 lists them in Class 1, 1A and 1D only; the nut grades are 8LN and 8MLN.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade or alloy marking B8LN or B8MLN and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
ASTM A193 Grade B8 Class 1 (304 Stainless)
304 stainless bolting — Class 1 for corrosion resistance and cryogenic-to-1500 °F service, Class 2 strain hardened to 125 ksi for strength.
ASTM A193 / ASME SA-193ASTM A193 Grade B8M Class 1 (316 Stainless)
316 stainless bolting with molybdenum for chloride and pitting resistance — offshore, marine, chemical and coastal plant fasteners.
ASTM A193 / ASME SA-193ASTM A193 Grade B8N Class 1B (304N Stainless)
304N stainless bolting — nitrogen lifts the solution-treated yield to 35 ksi and tensile to 80 ksi without cold work, for larger diameters and higher design stresses.