AISI 304LN low-carbon nitrogen-strengthened austenitic stainless steel · Solution-treated (Class 1)
ASTM A320 Grade B8LN is an austenitic stainless steel bolting grade specified per ASTM A320/A320M-21 for low-temperature service. Assigned UNS number S30453. Manufactured from AISI 304LN low-carbon nitrogen-strengthened austenitic stainless steel. The grade is supplied in Class 1 (carbide solution treated) or, as Grade B8LNA, Class 1A (solution treated in the finished condition); Table 1 provides no Class 2 for B8LN. Grade B8LN combines low-carbon corrosion resistance with nitrogen strengthening. Grade B8LN is intended for stud bolts and hex bolts in pressure vessels, valves, flanges, and fittings for low-temperature service. Grade B8LN is equivalent to ASME SA-320 Grade B8LN in Section II of the ASME Boiler and Pressure Vessel Code.
| Grade Symbol | UNS Designation | C, max | Mn, max | P, max | S, max | Si, max | Ni | Cr | N | |
|---|---|---|---|---|---|---|---|---|---|---|
| ASTM A320 B8LN Class 1 | S30453 | Range,% | 0.030 | 2.00 | 0.045 | 0.030 | 1.00 | 8.0-11 | 18.0-20.0 | 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 | 0.01 | ||
| 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 B8LN : Class 1 | All diameters | carbide solution treated | 75 [515] | 30 [205] | 30 | 50 | 223 HBWDor 96 HRB |
Section 10.2 of ASTM A320 requires Grade B8LN bolts, studs, and stud bolts to be equipped with austenitic alloy nuts to ASTM A194/A194M Grade 8LN; impact tests are not required for Grade 8LN nuts above -425°F [-255°C]. Washers for austenitic bolting are made of austenitic steel as agreed between manufacturer and purchaser (10.5); ASTM F436 hardened steel washers are specified for ferritic bolting only (10.4). TorqBolt supplies kit-matched A320 B8LN + A194 Grade 8LN + austenitic washer sets with a single EN 10204 3.1 or 3.2 certificate covering all three components.
TorqBolt’s ASTM A320 Grade B8LN 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 B8LN equivalence, NACE MR0175 / ISO 15156-3 sour-service compliance (where applicable), and PED 2014/68/EU for European pressure-equipment buyers.
