Steel Industry Glossary

2B, BA and No.4 Finishes: Standard cold rolled stainless sheet finishes: 2B is a smooth bright mill finish, BA is bright annealed and near-mirror, No.4 is a directional brushed finish.
Chloride Stress Corrosion Cracking (CSCC): Brittle cracking of austenitic stainless steel under tensile stress in a hot chloride environment, often with no measurable loss of metal.
Duplex Stainless Steel: A stainless steel with a roughly 50/50 ferrite-austenite microstructure, giving about twice the yield strength of austenitic grades together with strong chloride stress corrosion resistance.
Ferrite Content: The percentage of ferrite in a duplex microstructure or a weld, normally required to sit between 35% and 55% for the grade to behave as intended.
Low Carbon Grade (L): A stainless grade with carbon capped at 0.030% — 304L, 316L, 317L — so welded joints resist intergranular corrosion without post-weld heat treatment.
PREN (Pitting Resistance Equivalent Number): A single number that ranks a stainless steel's resistance to chloride pitting, calculated as %Cr + 3.3 x %Mo + 16 x %N.
Pickling & Passivation: Acid treatment that strips the heat tint and oxide scale from stainless, followed by a treatment that restores the passive chromium oxide film.
Precipitation Hardening (PH) Stainless: A stainless steel that gains its strength from a low-temperature ageing treatment which precipitates fine particles, rather than from quenching — 17-4 PH being the best known.
Sensitisation: The precipitation of chromium carbides at grain boundaries between roughly 425 and 815 °C, which strips chromium from the adjacent metal and leaves it open to intergranular corrosion.
Sigma Phase: A brittle chromium-molybdenum intermetallic that forms in duplex and high-alloy stainless between roughly 600 and 1000 °C, destroying toughness and corrosion resistance.
Solution Annealing: Heating stainless to roughly 1040-1120 °C and quenching rapidly, to dissolve carbides and intermetallics back into solution and restore full corrosion resistance.
Stabilised Grade: A stainless steel alloyed with titanium (321) or niobium (347) so that carbon is tied up as a stable carbide and cannot rob the grain boundaries of chromium.