What Are Stainless Steel 310S Fasteners?
Stainless Steel 310S Fasteners are bolts, nuts, studs, washers and screws forged from a low-carbon version of the 310 austenitic grade. Carbon content stays capped at 0.08%, which limits carbide formation at weld joints and keeps the material functional after repeated thermal cycling. This range falls within the broader stainless steel fasteners line, based on composition limits set under ASTM A276 and A479. Fabricators specify 310S over standard 310 grade when welded assemblies need to avoid sensitisation in the heat-affected zone.
Composition and Properties of SS 310S
SS 310S Fasteners benefit from a chromium content of 24-26% and a nickel content of 19-22%, close to double the nickel found in 304 grade material. This composition supports oxidation resistance up to 1150°C in continuous service and 1035°C under cyclic heating. Minimum tensile strength stands at 515 MPa, with yield strength starting from 205 MPa in the annealed condition.
Types of 310S Fasteners
Different Types of 310S Fasteners cover different joint and load conditions on a structure or vessel.
- Hex bolts and heavy hex bolts: Available from M6 to M64, used where clamping force has to hold steady through repeated heating and cooling cycles.
- Studs and threaded rods: Continuous or double-end thread designs secure flange assemblies exposed to thermal expansion; stainless steel studs maintain structural integrity under high heat.
- Nuts: Hex, heavy hex and lock nut variants, matched to bolt thread class to reduce galling during installation.
- Washers: Flat and spring forms that spread load and offset gasket creep at elevated temperature.
- Screws. Machine and self-tapping variants for lighter bracket and fixture work inside furnace housings.
These 310S Fastener Types are specified individually or as matched sets, depending on flange rating and the gasket used on the joint.
Applications in High-Temperature Environments
Furnace internals, heat treatment fixtures, kiln components and boiler baffles rely on 310S fasteners because the joints hold their clamp load after constant heating cycles. Refineries and petrochemical plants specify the grade for piping systems paired with stainless steel flanges operating above 800°C, where a carbon steel fastening would scale and lose tension. Ethylene cracking units, ceramic kiln cars and annealing furnace doors are three specific settings where 310S bolting holds up better than 304 or 316 alternatives on scaling resistance alone.
Specifications and Standards
Bolting material follows ASTM A193 Grade B8S, and nuts follow ASTM A194 Grade 8S, with comparable coverage under ASME SA193 and SA194 for pressure service. Mechanical testing follows tensile, hardness and impact protocols defined in these standards. Hardness stays under 95 HRB in the annealed condition, confirmed through Rockwell testing on sample lots. Material certification connects to the melt heat number for each production batch, so every fastener stays linked to its source material record.
Selecting the Right 310S Fastener Type
Match the fastener grade to the operating temperature first, then check the thread class against the mating component. Below 550°C, 316 or 321 grade fasteners often meet the technical requirements without the added nickel content that 310S carries. Above that threshold, or wherever scaling resistance has priority over other factors, 310S becomes the practical choice. Confirm the certification package, mill test report and dimensional tolerance before the order moves into production.
Sanghvi Overseas Forge manufactures and tests its 310S fasteners based on these standards at its facilities, using raw material and machinery suited to consistent batch quality.
