Marine grade stainless

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Marine grade stainless, or SAE 316 stainless steel, is a molybdenum-alloyed steel and is the second most common austenite stainless steel (after grade 304). It is the preferred steel for use in marine environments because of its greater resistance to pitting corrosion than other grades of steel.[1][2] The fact that it is negligibly responsive to magnetic fields means that it can be used in applications where a non-magnetic metal is required. In addition to molybdenum, 316 also contains a number of other elements in varying concentrations (see table below). Like other grades of stainless steel, marine grade stainless steel-- though still a metal-- is a relatively poor conductor of both heat and of electricity.

While 316 is not completely rust-proof, the alloy is more corrosion-resistant than other common stainless steels. Surgical steel is made from subtypes of 316 stainless steel.

Stainless steel designations[3]
SAE  % Cr  % Ni  % C  % Mn  % Si  % P  % S  % N  % Mo Description and uses
316 16–18 10–14 0.08 2 0.75 0.045 0.03 0.10 2.0–3.0 General grade for food processing, chemical storage and transport, textile dying equipment, cladding of nuclear fuel, and oil refining equipment as well as some medical implants.
316L 16–18 10–14 0.03 2 0.75 0.045 0.03 0.10 2.0–3.0 Low-carbon grade for handling paper pulp as well as the production of rayon, rubber, textile bleaches, and high-temperature industrial equipment. This is the preferred grade for medical implants as it is immune from sensitization (grain boundary carbide precipitation).
316F 16–18 10–14 0.08 2 1 0.2 0.10 min - 1.75–2.5 Free-machining grade with reduced molybdenum and correspondingly increased phosphorus and sulfur for automatic machine screw parts as well as surgical implants and pharmaceutical processing equipment.
316N 16–18 10–14 0.08 2 0.75 0.045 0.03 0.10–0.16 2.0–3.0 High-nitrogen grade with increased resistance to pitting and to corrosion in crevices. Used for chemical handling accessories.

Non-standard grades include 316H which has a "high" carbon content of greater than 0.04% giving it a high creep rupture strength at high temperatures, 316L(Hi)N which is an extra-high nitrogen grade (0.16-0.30%), 316Ti which is stabilized by titanium, 316Cb which is stabilized by niobium, 316L-SCQ which is a high-purity version of 316L, and 316LS which specially adapted for surgical implants.[4]

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