Select family
Strength comparison — fy min / fu min
Representative grades, minimum values (annealed condition)
Family overview
Austenitic (300 series)
- FCC crystal structure, non-magnetic
- Best corrosion resistance & formability
- Cannot be hardened by heat treatment
- Work hardens significantly
- Typical: 304, 316, 321, 310
Ferritic (400 series)
- BCC structure, magnetic
- Lower Ni content → more economical
- Good resistance to stress-corrosion cracking
- Limited toughness at low temperature
- Typical: 430, 409, 441, 444
Martensitic (400 series)
- Hardenable by quench & temper
- Magnetic, highest strength of SS families
- Lower corrosion resistance than austenitic
- Typical: 410, 420, 440C
Duplex
- Mixed austenitic + ferritic microstructure
- Higher strength than austenitic at lower cost
- Excellent SCC and pitting resistance
- PREN > 34 (standard), > 40 (super duplex)
- Typical: 2205, 2507, LDX 2101
PREN — Pitting Resistance Equivalent Number
PREN = %Cr + 3.3×%Mo + 16×%N | Higher = better pitting corrosion resistance
PREN values for selected grades