Complete Guide to SS304 Stainless Steel Fasteners

SS304 is an austenitic stainless steel containing 18% chromium and 8% nickel (hence its alternative name, 18/8 stainless steel). The chromium forms a passive oxide layer on the steel surface that prevents rust — and uniquely, this layer self-repairs if damaged. SS304 stainless steel fasteners are non-magnetic in the annealed state (though they can become slightly magnetic after cold working), which matters for electronics and scientific instrument applications. The grade meets ASTM A193, ISO 3506 (A2-70 designation), and IS standards — you'll see these markings on certified fasteners.

SS304 stainless steel fasteners deliver solid mechanical performance: tensile strength of 515–700 MPa depending on the product form, 0.2% proof stress (yield) of 205 MPa minimum, and elongation at break of 40% minimum — meaning they deform visibly before fracture rather than snapping suddenly. Hardness runs around 201 HB Brinell maximum. For higher-strength requirements in stainless, look at cold-worked or strain-hardened SS304 variants, or specify A4-80 SS316 fasteners. ScrewBazar stocks SS304 screws, bolts, nuts, and washers to ISO 3506 Class A2-70.

SS304 stainless steel resists oxidation, most organic acids, many inorganic chemicals, and atmospheric corrosion including rain, humidity, and mild industrial environments. It performs well outdoors across most of India's climate zones — from Bangalore's mild climate to Mumbai's coastal humidity. However, SS304 is susceptible to pitting in high-chloride environments (salt spray, swimming pools, sea air within 500m). For marine or coastal applications, upgrade to SS316. For most inland outdoor applications, SS304 stainless steel fasteners provide a long service life without protective coatings.

The applications for SS304 stainless steel fasteners are broad: food processing equipment (dairy, beverage, bakery — where hygiene and regular washing-down occur), commercial kitchens and canteen equipment, pharmaceutical manufacturing (non-sterile areas), architectural cladding and curtain walls, hospital and laboratory furniture, HVAC systems and ductwork, automotive trim and exhaust heat shields, outdoor signage and street furniture, and electronic enclosures. In most of these contexts, the combination of corrosion resistance, appearance, and food-safe status makes SS304 the standard specification.

ScrewBazar supplies a comprehensive range of SS304 stainless steel fasteners: Machine screws (Allen SHCS, Phillips Pan, CSK, Torx — M2 to M12), Hex bolts and Allen bolts (M4 to M24), Hex nuts, nyloc nuts, flange nuts, Plain washers and spring washers, Self-tapping screws (Pan Phillips, CSK), and Threaded rods. All supplied with material certification on request. Contact us for items not listed — we regularly source specialty SS304 items for OEM buyers.

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SS304 stainless steel fasteners are more prone to galling (thread seizure) than carbon steel fasteners, especially bolt-to-nut assemblies. Prevent galling by: applying anti-galling lubricant (never-seize compound) before assembly, not using power tools at full speed for stainless fasteners, and slowing down the installation speed. Torque values for SS304 are lower than for equivalent Grade 8.8 carbon steel — do not apply carbon steel torque specs to stainless fasteners. For M6 SS304 bolts, recommended installation torque is approximately 8–9 Nm (vs 11 Nm for Grade 8.8).

For most applications SS304 stainless steel fasteners are the cost-effective correct choice. Upgrade to SS316 only when the environment includes chloride exposure (coastal locations, swimming pools, marine use), strong acids, or bleach-based cleaning chemicals used regularly. The price premium for SS316 is 20–40% — unnecessary in most inland and non-aggressive environments. If you're unsure which grade to specify, ScrewBazar's team will assess your environment and recommend the right material.