Stainless steels fall into five families defined by their microstructure: austenitic, ferritic, martensitic, duplex (including super duplex) and precipitation-hardening. Each balances corrosion resistance, strength and formability differently, from everyday 304 and 316L to high-performance duplex and super duplex grades. The family is set by composition - mainly the balance of chromium, nickel and nitrogen.
What are the five families of stainless steel?
Stainless steels are grouped by microstructure into five families:
| Family | Structure | Key traits | Example grades |
|---|---|---|---|
| Austenitic | Austenitic (300-series) | High Cr and Ni, non-magnetic, very ductile | 304, 316L |
| Ferritic | Ferritic (400-series) | Cr with little Ni, magnetic | 430 |
| Martensitic | Martensitic | Heat-treatable for high strength and hardness | 410 |
| Duplex & super duplex | Mixed austenitic-ferritic | ~22-25% Cr, ~2x strength, strong corrosion resistance | 2205, Ferralium® 255, Alloy 32750, Alloy 32760 |
| Precipitation-hardening | Age-hardenable | Very high strength via heat treatment | 17-4 PH |
How do you choose a stainless steel type?
The right family depends on the balance of corrosion resistance, strength, formability and cost your application needs. Austenitic grades suit general corrosion service and fabrication; ferritic and martensitic grades suit lower-cost or hardenable uses; duplex and super duplex grades are chosen where high strength and chloride resistance matter together. For a direct comparison, see duplex vs super duplex stainless steels.
Which types does Langley Alloys specialise in?
Langley Alloys focuses on the higher-alloy end - duplex, super duplex and nickel alloys - alongside selected stainless grades such as Alloy 316L and 17-4 PH. For a primer on the top family, see what is super duplex material?