Related Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
ASTM A193 Grade B8 Class 1 Bolts
Carbide Solution Treated (Annealed) 304 Stainless Steel Bolting
ASTM A193 Grade B8 Class 1 is the base class for austenitic stainless steel bolting materials produced under the ASTM A193 specification. These fasteners are manufactured from AISI 304 stainless steel and are subjected to a carbide solution treatment, also known as annealing, to achieve maximum corrosion resistance and uniform hardness. Grade B8 Class 1 bolts are widely used in chemical processing, oil & gas, and high-pressure service environments where moderate strength and excellent corrosion resistance are required.
As 304 stainless bolts manufactured to the ASTM A193 / A193M-19 specification, B8 Class 1 stud bolts ship in the carbide-solution-treated condition (no post-anneal cold work) — guaranteed 75 ksi (515 MPa) minimum tensile, 30 ksi (205 MPa) minimum yield, 30% elongation in 4D, and 223 HBW maximum hardness across all diameters in the size range. The chemistry maps to UNS S30400 with the dual chromium-nickel balance (18–20% Cr, 8–11% Ni) that gives 304 its characteristic atmospheric and chloride-mild service resistance.
The Pitting Resistance Equivalent Number (PREN) of ASTM A193 Grade B8 is approximately 19, calculated from chromium content alone — Grade B8 contains no molybdenum, which limits service in aggressive chloride environments compared with the molybdenum-bearing B8M grade. For sour-gas service under NACE MR0175 / ISO 15156-3, solution-annealed B8 Class 1 satisfies the 22 HRC maximum hardness threshold for austenitic stainless steels in H₂S-containing environments (Table A.2). Specifying carbide-solution-treated material with mill-certified hardness verification is the procurement control for this compliance. B8 stud bolts in Class 1 condition are the qualified choice for offshore flange bolting, refinery process piping, and pressure-vessel internals where NACE certification is required.
Within the A193 B8 family, Class 1 sits at the solution-annealed baseline. Procurement specifications that demand higher tensile capacity without changing the underlying chemistry move to Class 2, where strain-hardening lifts strength into the 100-125 ksi band; see B8 Class 2 strain-hardened stud bolts for the full mechanical envelope. When the heat-treat sequence is critical to corrosion behaviour and the bar must enter service in its final annealed condition, B8 Class 1A solution-annealed-in-finished-condition bolts are specified instead of Class 1. For dimensional reference on hex-headed Class 1 bolts in inch-series, the ASME B18.2.1 hex bolt dimensions page governs head height, across-flats, and thread length tolerances.
ASTM A193 Grade B8 Bolts Properties
ASTM A193 Grade B8 Bolts Chemical Requirements
Austenitic Steels
| Grade | Description and UNS Designation | Classes | C | Mn | P | S | Si | Cr | Ni |
|---|---|---|---|---|---|---|---|---|---|
| ASTM A193 Grade B8 | 304, S30400 | 1 | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 18.0-20.0 | 8.0-11.0 |
| Product Analysis VariationB | 0.01 | 0.04 | 0.010 | 0.005 | 0.05 | 0.20 | 0.15 |
ASTM A193 Grade B8 Bolts Mechanical Requirements
Austenitic Steels (Inch)
| Grade | Diameter, in. |
Heat TreatmentB | Tensile Strength, min, ksi |
Yield Strength, min, 0.2 % offset, ks |
Elongation in 4 D,min | Reduction of Area, min | Hardness, max |
|---|---|---|---|---|---|---|---|
| ASTM A193 Grade B8 Classes 1 | All diameters | carbide solution treated | 75 | 30 | 30 | 50 | 223 HBW or 96 HRBC |
Austenitic Steels (Metric)
| Grade Class ,
mm |
Diameter | Heat TreatmentB | Tensile Strength,
min,MPa |
Yield Strength, min,
0.2 % offset, MPa |
Elongation in 4 D,min % | Reduction of Area, min % | Hardness,
max |
|---|---|---|---|---|---|---|---|
| ASTM A193M Grade B8 All diameters Classes 1 | All diameters | carbide solution treated | 515 | 205 | 30 | 50 | 223 HBW or 96 HRBC |
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