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 B8MLN Stud Bolts (UNS S31653)
AISI 316LN low-carbon nitrogen-strengthened molybdenum-bearing austenitic stainless steel · Solution-treated (Class 1)
ASTM A320 Grade B8MLN is an austenitic stainless steel bolting grade specified per ASTM A320/A320M-22 for low-temperature service. Assigned UNS number S31653. Manufactured from AISI 316LN low-carbon nitrogen-strengthened 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 B8MLN combines 316 chloride resistance with low-carbon weldability and nitrogen strengthening. Grade B8MLN is intended for stud bolts and hex bolts in pressure vessels, valves, flanges, and fittings exposed to corrosive or low-temperature environments. Grade B8MLN is equivalent to ASME SA-320 Grade B8MLN in the ASME Boiler and Pressure Vessel Code Section II Part A.
ASTM A320 Grade B8MLN properties
ASTM A320 Grade B8MLN chemical composition
| Grade Symbol | UNS Designation | C, max | Mn, max | P, max | S, max | Si, max | Ni | Cr | Mo | N | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| ASTM A320 B8MLN Class 1 | S31653 | Range,% | 0.030 | 2.00 | 0.045 | 0.030 | 1.00 | 10.0-13.0 | 16.0-18.0 | 2.00-3.00 | 0.10-0.16 |
| Product Variation, % Over or Under | 0.005 over | 0.04 over | 0.010 over | 0.005 over | 0.05 over | 0.15 | 0.20 | 0.10 | 0.01 | ||
ASTM A320 Grade B8MLN 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 B8MLN Class 1 | All diameters | carbide solution treated | 75 [515] | 30 [205] | 30 | 50 | 223 HBWDor 96 HRB |
|---|
What nuts and washers are specified for ASTM A320 Grade B8MLN?
For low-temperature service consistency, ASTM A320 Grade B8MLN 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 B8MLN + 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 B8MLN
TorqBolt’s ASTM A320 Grade B8MLN 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 B8MLN 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 B8MLN: related product searches
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