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 A320 / ASME SA-320 Grade B8M Stud Bolts (UNS S31600)
AISI 316 molybdenum-bearing austenitic stainless steel · Solution-treated (Class 1) or strain-hardened (Class 2)
ASTM A320 Grade B8M is an austenitic stainless steel bolting grade specified per ASTM A320/A320M-22 for low-temperature service. Assigned UNS number S31600. Manufactured from AISI 316 molybdenum-bearing austenitic stainless steel. The grade is supplied in Class 1 (solution-treated) or Class 2 (strain-hardened) condition, with Class 2 offering higher tensile strength through controlled cold work. Grade B8M offers improved chloride-pitting and crevice-corrosion resistance versus B8, and is NACE MR0175 compliant for sour service. Grade B8M is intended for stud bolts and hex bolts in pressure vessels, valves, flanges, and fittings exposed to corrosive or low-temperature environments. Grade B8M is equivalent to ASME SA-320 Grade B8M in the ASME Boiler and Pressure Vessel Code Section II Part A.
ASTM A320 Grade B8M properties
ASTM A320 Grade B8M chemical composition
| Grade Symbol | UNS Designation | C, max | Mn, max | P, max | S, max | Si, max | Ni | Cr | Mo | |
|---|---|---|---|---|---|---|---|---|---|---|
| ASTM A320 B8M | S31600(316) | Range,% | 0.08 | 2.00 | 0.045 | 0.030, max | 1.00 | 10.0 - 14.0 | 16.0 - 18.0 | 2.00 - 3.00 |
| Product Variation, % Over or Under | 0.01 over | 0.04 over | 0.010 over | 0.005 over | 0.05 over | 0.15 | 0.20 | 0.10 | ||
ASTM A320 Grade B8M mechanical properties
| Grade and Class | Diameter, in. [mm] | Heat Treatment | Tensile Strength, min, ksi [MPa] | Yield Strength, min, ksi [MPa] (0.2 % offset) | Elongation in 2 in. or 50 mm, min, % | Reduction of Area, min, % | Hardness, max |
|---|---|---|---|---|---|---|---|
| ASTM A320 B8M Class 1 | All diameters | carbide solution treated | 75 [515] | 30 [205] | 30 | 50 | 223 HBWDor 96 HRB |
| ASTM A320 B8M Class 2 | 3/4 [20] and under | carbide solution treated and strain hardened | 110 [760] | 95 [655] | 15 | 45 | 321 HBW or 35 HRC |
| over 3/4 to 1 [20 to 25], incl | 100 [690] | 80 [550] | 20 | 45 | 321 HBW or 35 HRC | ||
| over 1 to 11/4 [25 to 32], incl | 95 [655] | 65 [450] | 25 | 45 | 321 HBW or 35 HRC | ||
| over 11/4 to 11/2 [32 to 40], inclA | 90 [620] | 50 [345] | 30 | 45 | 321 HBW or 35 HRC |
What nuts and washers are specified for ASTM A320 Grade B8M?
For low-temperature service consistency, ASTM A320 Grade B8M stud bolts are paired with ASTM A194 Grade 8 series stainless heavy hex nuts and ASTM F436 hardened steel washers. TorqBolt supplies kit-matched A320 B8M + A194 + F436 sets with a single EN 10204 3.1 or 3.2 certificate covering all three components.
NORSOK M-650 qualification & EN 10204 3.1 / 3.2 certificates for A320 Grade B8M
TorqBolt’s ASTM A320 Grade B8M stud bolt production route is qualified to NORSOK M-650 for North Sea oil & gas offshore service. Each manufacturing record links heat number, melt analysis, heat-treatment batch, mechanical test, dimensional inspection, surface treatment, and dispatch. Standard certification is EN 10204 Type 3.1 (manufacturer’s test report); Type 3.2 third-party witnessed by Lloyd’s Register, DNV, BV, ABS, or TUV is available on request. The qualification packet covers ASME SA-320 B8M equivalence, NACE MR0175 / ISO 15156-2 sour-service compliance (where applicable), and PED 2014/68/EC for European pressure-equipment buyers.
Related ASTM A320 grades & companion specifications
- ASTM A320 Grade B8: AISI 304 austenitic stainless, the baseline B-series grade.
- ASTM A320 Grade B8M: AISI 316 molybdenum-bearing stainless for chloride exposure.
- ASTM A320 Grade B8C: AISI 347 niobium-stabilized stainless for intergranular corrosion resistance.
- ASTM A320 Grade B8T: AISI 321 titanium-stabilized stainless for sensitization resistance.
- ASTM A320 Grade L7: AISI 4140 / 4142 chromium-molybdenum alloy steel alternative.
- ASME B18.31.2 inch double-end stud bolts: dimensional reference for studs mating ASME B16.5 flanges.
- ASME B18.2.1 hex bolts: dimensional reference for A320 hex bolts.
ASTM A320 Grade B8M: related product searches
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