Material number S31600: 316
S31600 is the Unified Numbering System designation for 316, austenitic chromium-nickel-molybdenum stainless steel specified in ASTM A240.
What S31600 means
UNS numbers (ASTM E527 / SAE J1086) use a letter for the alloy family and five digits: G = AISI/SAE carbon and alloy steels (G41400 = 4140), S = stainless and heat-resisting steels (S30400 = 304), K = miscellaneous steels (K02600 = A36), T = tool steels, N = nickel alloys. The UNS number identifies a composition, not a product form or property level, so S31600 appears in several ASTM specifications (plate, bar, pipe) with different mechanical requirements.
316 at a glance
Type 316 is the second most common stainless steel and the first choice where 304 pits: an 18-8 austenitic base with 2–3 % molybdenum and 10–14 % nickel, UNS S31600 (316) or S31603 (316L, carbon ≤ 0.03 %). Molybdenum raises the pitting resistance equivalent from about 18 to 24, which is the difference between tea-staining and staying bright in coastal air, de-icing salt, brackish water and most acidic process streams. That is why 316 is called 'marine grade' and why A4 stainless fasteners, boat fittings, pharmaceutical equipment and chemical piping are made from it.
Mechanically 316 is a twin of 304: 205 MPa (30 ksi) yield and 515 MPa (75 ksi) tensile minimum, 40 % elongation, non-magnetic, no low-temperature transition, hardenable only by cold work. It is slightly stronger than 304 at elevated temperature and has better creep resistance; 316H is the creep-rated version above 525 °C.
Most coil, plate and pipe today is dual-certified 316/316L — carbon ≤ 0.03 % with the higher 316 strength minimums — so a specification for either is normally satisfied by the same stock. EN 1.4401/1.4404, JIS SUS316/316L and GB 06Cr17Ni12Mo2 are identical for procurement; the table also grades the high-Mo (1.4436) and Ti-stabilized (1.4571) European variants.
Full data sheet for 316 → · Equivalent grades →