303S42

Stainless Steel

303S42

British BS 970 stainless steel 303S42.

Chemical Composition (%)

C0.12
SI1
MN1.5
CR17
NI8
MO0.2
P0.06
S0.15

Applications

International high-end steel grade for aerospace, oil & gas, defense or engineering machinery.

Available Forms

Bar, plate, sheet, tube, forgings, strip, wire, powder

Uses

Austenitic stainless steel with excellent corrosion resistance, formability and weldability; non-magnetic in annealed condition. High nickel (≈9%) stabilises the austenite and improves toughness and pitting resistance. Molybdenum (≈0.4%) enhances resistance to chloride pitting and crevice corrosion — suited to marine and chemical service. Used in food processing, chemical plant, architecture, heat exchangers, kitchenware and medical devices.

Heat Treatment

Solution anneal 1010–1150 °C followed by rapid water quench to retain austenite; not hardenable by heat treatment. Sensitization avoided by low carbon or stabilizers (Ti/Nb).

Precautions

Weld with low-carbon or stabilized filler (e.g., 316L, 347) to avoid sensitization; passivate after fabrication. Not hardenable, but work-hardens rapidly — use sharp tools and rigid setups. Avoid chloride contact for 304 in warm service; specify 316/317 for marine or aggressive media.

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