ASTM A193 Grade B8P Class 2 (305 Strain Hardened)
High-nickel 305 bolting cold worked to 125 ksi tensile in ¾ in. and under — strength with the lowest magnetic permeability of the strain-hardened 18-8 grades.
What A193 B8P Class 2 is.
ASTM A193 B8P Class 2 is the strain-hardened version of the 305 grade. The bar is carbide solution treated and then cold reduced, which raises the tensile strength from the annealed minimum to 125 ksi in ¾ in. and smaller sizes. Because cold work cannot penetrate a large section evenly, the specification steps the required strength down by diameter and stops at 1½ in.
We supply B8P Class 2 studs, bolts and cap screws from strain-hardened certified bar, marked B8PSH, and match them with ASTM A194 8P nuts. The chemistry, corrosion resistance and companion nut are identical to B8P Class 1; only the condition and strength differ.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.12 |
| Manganese | Mn | — | 2.00 |
| Phosphorus | P | — | 0.045 |
| Sulfur | S | — | 0.030 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 17.0 | 19.0 |
| Nickel | Ni | 11.0 | 13.0 |
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 2 — ¾ and under | 125 | 100 | 12 | 35 | 321 HBW / 35 HRC |
| Class 2 — over ¾ to 1 | 115 | 80 | 15 | 35 | 321 HBW / 35 HRC |
| Class 2 — over 1 to 1¼ | 105 | 65 | 20 | 35 | 321 HBW / 35 HRC |
| Class 2 — over 1¼ to 1½ | 100 | 50 | 28 | 45 | 321 HBW / 35 HRC |
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 2 is limited to 1½ in. Strain-hardened austenitic steel may not show uniform properties through the section, particularly over ¾ in. diameter.
Specifications that apply.
How A193 B8P Class 2 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 B8P Class 2 fasteners we make.
Every item is manufactured to your drawing or standard in A193 B8P Class 2, imperial or metric, with an EN 10204 3.1 certificate.
What is ASTM A193 B8P Class 2?
B8P Class 2 is 305 stainless steel, solution treated and then strain hardened to the B8 Class 2 strength table. 305 carries 11 to 13 percent nickel, which keeps the austenite stable under cold work; where cold-worked 304 becomes noticeably magnetic, cold-worked 305 stays close to non-magnetic. That makes B8P Class 2 the choice when a strong stainless bolt must not disturb a magnetic field, and for cold-headed fasteners that need the strength of a strain-hardened bar.
Why the strength drops with size
- ¾ in. and under: 125 ksi tensile, 100 ksi yield. Cold work reaches the core of a small bar.
- Over ¾ to 1 in.: 115 ksi tensile, 80 ksi yield.
- Over 1 to 1¼ in.: 105 ksi tensile, 65 ksi yield.
- Over 1¼ to 1½ in.: 100 ksi tensile, 50 ksi yield. The largest size certified as Class 2 for this grade.
Class 2 or Class 1?
Specify Class 2 when the joint needs bolt strength close to alloy steel and runs below about 800 °F. Specify Class 1 for hot service, for large diameters, for sour service to NACE MR0175 / ISO 15156 where cold-worked austenitic bolting is restricted, and wherever the design only needs the annealed strength. Both classes share one chemistry, so the corrosion performance is the same.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade symbol B8PSH and manufacturer's identification on every piece
- Hardness checked on the finished product; 321 HBW / 35 HRC maximum
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
ASTM A193 Grade B8P Class 1 (305 Stainless)
305 stainless bolting — the low-work-hardening 18-8 for cold-headed and deep-formed fasteners that must stay non-magnetic.
ASTM A193 / ASME SA-193ASTM A193 Grade B8 Class 2 (304 Strain Hardened)
304 stainless bolting cold worked after solution treatment — 125 ksi tensile in ¾ in. and under, with strength stepping down by diameter to 1½ in.
ASTM A194 / ASME SA-194ASTM A194 Grade 8 (304 Stainless)
304 stainless heavy hex nut for A193 and A320 B8 studs — solution treated, 80 ksi proof load, corrosion resistant from cryogenic to 1500 °F.