SS 304 / 304L / 304H Screws Manufacturer & Exporter in India

The three grades share the same 18Cr-8Ni base composition but differ in carbon content and intended application. SS 304 (0.08% max carbon) is the general-purpose grade for the majority of structural and process applications. SS 304L (0.03% max carbon) is the low-carbon variant specified wherever screws are used in welded assemblies – the reduced carbon prevents sensitisation and intergranular corrosion in the heat-affected zone without post-weld heat treatment. SS 304H (0.04-0.10% carbon) is the high-carbon variant that delivers superior creep and stress-rupture strength above 425°C, making it the correct choice for high-temperature pressure equipment per ASME Section VIII and ASME B31.3. When in doubt for ambient-temperature welded applications, specify 304L. For elevated-temperature service above 425°C, specify 304H.

SS 304 / 304L / 304H screws are available in a comprehensive range of head styles to suit structural, hygienic, and aesthetic requirements. Common types include socket head cap screws (DIN 912 / ISO 4762), hex head screws (DIN 933 / ISO 4017), countersunk socket screws (DIN 7991 / ISO 10642), button head socket screws (ISO 7380), pan head machine screws (DIN 7985), cheese head screws (DIN 84), and self-tapping screws (DIN 7981 / DIN 7982). Drive types include hexagon socket (Allen), Phillips, Torx, slotted, and combination drives. Custom head profiles for hygienic or tamper-resistant applications are available on request with 15 working day lead time.

SS 304 screws perform well in standard atmospheric and mildly corrosive outdoor environments including urban, industrial, and inland rural locations. However, in coastal environments with direct salt spray exposure or in applications involving prolonged contact with chloride-containing solutions, SS 316 or 316L screws are strongly recommended. The absence of molybdenum in 304 means it has a PREN of approximately 18-20, which is insufficient to resist pitting corrosion in chloride concentrations above 200 ppm at elevated temperatures. For splash-zone marine structures, offshore platforms, or swimming pool environments, always upgrade to 316L or duplex 2205.

SS 304 and 304L screws are classified as ISO 3506-1 Property Class A2-70 when cold worked, delivering a minimum tensile strength of 700 MPa and yield strength of 450 MPa – significantly higher than the annealed ASTM A276 minimums of 515 MPa tensile and 205 MPa yield. A2-50 (500 MPa tensile) applies to larger diameters above M39 where cold working is impractical. SS 304H screws are typically supplied to ASTM A193 Grade B8 Class 1 (annealed) or Class 2 (strain hardened) for high-temperature pressure equipment. Always confirm the required property class at the time of order, as the same material grade can be supplied to different strength levels depending on the manufacturing route.