Stainless Steel (Ferritic) (Fe+Cr)
Ferritic stainless steels are chromium-containing (10.5–30% Cr) grades with a body-centered cubic crystal structure and no or minimal nickel content. They offer good corrosion resistance at lower cost than austenitic grades, are magnetic, and resist stress corrosion cracking — making them ideal for automotive exhaust, appliances, and architectural applications.
Properties
- Density
- 7,700–7,800 kg/m³
- Melting Point
- 1,425–1,510 °C
- Boiling Point
- 2,750 °C
- Thermal Conductivity
- 24–27 W/(m·K)
- Electrical Resistivity
- 5.8–6.7 × 10⁻⁷ Ω·m
- Tensile Strength
- 380–550 MPa
- Yield Strength
- 210–380 MPa
- Hardness
- 150–220 HB
- Elongation
- 18–30%
- Crystal Structure
- BCC (Ferrite)
Common Grades
- 430 (1.4016): Standard ferritic grade — 16% Cr. Kitchen sinks, automotive trim, appliance panels.
- 439 (1.4510): Titanium-stabilized, 17% Cr. Automotive exhaust systems, heat exchangers.
- 441 (1.4509): Dual-stabilized (Ti+Nb), 18% Cr. Exhaust manifolds, catalytic converters, boiler casings.
- 444 (1.4521): Mo-bearing ferritic (18Cr-2Mo). Superior pitting resistance. Hot water tanks, solar collectors.
Applications
- Automotive: Exhaust systems, catalytic converter housings, fuel tanks, trim pieces
- Appliances: Washing machine drums, dishwasher interiors, microwave liners, oven panels
- Architecture: Elevator interiors, cladding panels, roofing, indoor decorative surfaces
- Water Heating: Hot water cylinders, solar thermal collectors, condensing boiler heat exchangers
FAQ
Why are ferritic stainless steels cheaper than austenitic?
Ferritic grades contain little to no nickel (the most expensive alloying element in stainless steel at €14,000–18,000/tonne). Grade 430 has 16% Cr and 0% Ni, versus 304 with 18% Cr and 8% Ni. This makes ferritic grades 30–50% cheaper, with more stable pricing since they avoid nickel market volatility.
Are ferritic stainless steels magnetic?
Yes, ferritic stainless steels are magnetic because their BCC crystal structure is ferromagnetic, similar to carbon steel. This is in contrast to austenitic grades (304, 316) which are generally non-magnetic. Magnetism is a quick way to identify ferritic vs. austenitic stainless steel.
Why is ferritic stainless steel used for car exhaust systems?
Ferritic grades 439 and 441 combine good high-temperature oxidation resistance (up to 950°C), immunity to chloride stress corrosion cracking, thermal fatigue resistance, and significantly lower cost than austenitic alternatives. The stabilized grades resist sensitization during welding, critical for exhaust manufacturing.