ASTM 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.
What A193 B8N Class 1B is.
ASTM A193 Grade B8N is bolting in Type 304N, a 304 with 0.10 to 0.16 percent nitrogen. Nitrogen strengthens the austenite in solution, so Class 1B B8N reaches 80 ksi tensile and 35 ksi yield in any diameter, against 75 and 30 for plain B8, and its allowable stresses in the ASME codes are correspondingly higher.
We supply B8N studs and bolts from certified 304N bar in Class 1B and, for small sizes, Class 2 strain hardened.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.08 |
| 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 1B / 1D — all diameters | 80 | 35 | 30 | 40 | 223 HBW / 96 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. Class 1 sizes ¾ in. and smaller may be 241 HBW / 100 HRB. Strain-hardened Class 2 properties are on the B8N Class 2 page.
Specifications that apply.
How A193 B8N Class 1B 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 B8N Class 1B fasteners we make.
Every item is manufactured to your drawing or standard in A193 B8N Class 1B, imperial or metric, with an EN 10204 3.1 certificate.
What is ASTM A193 B8N?
Nitrogen is a powerful interstitial strengthener of austenite. At 0.10 to 0.16 percent it raises the annealed strength of 304 by roughly a third while leaving corrosion resistance, weldability and toughness unchanged. A193 recognises this with Class 1B, a solution-treated condition rated at 80 ksi tensile and 35 ksi yield with no size limit, which is the practical advantage of B8N: the higher strength is available in 2 inch and 3 inch studs where strain-hardened Class 2 stops at 1½ inch.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade or alloy marking B8N 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 B8N Class 2 (304N Strain Hardened)
Nitrogen-strengthened 304N bolting cold worked to 125 ksi tensile in ¾ in. and under — Class 2 strength on a grade that already starts at 80 ksi annealed.
ASTM A193 / ASME SA-193ASTM 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 B8MN Class 1B (316N Stainless)
316N stainless bolting — the chloride resistance of 316 with 80 ksi tensile and 35 ksi yield in the solution-treated condition.