SUS430 vs SUS304: Ferritic vs Austenitic Stainless Steel

Two Families, Two Structures

SUS304 and SUS430 represent the two most common families of stainless steel: austenitic and ferritic. SUS304 is an austenitic grade with a face-centered cubic crystal structure, containing 18 to 20 percent chromium and 8 to 10.5 percent nickel, and is non-magnetic in the annealed condition. SUS430 is a ferritic grade with a body-centered cubic structure, containing 16 to 18 percent chromium and no nickel, and is magnetic.

Corrosion Resistance

The nickel in SUS304 stabilizes the austenitic structure and significantly improves corrosion resistance in atmospheric, food, and mildly chemical environments. SUS430 offers good corrosion resistance for dry and mildly corrosive service but is inferior to 304 in wet, acidic, or chloride-bearing conditions, where it is prone to pitting and rusting.

Mechanical and Processing Differences

SUS304 is more ductile and formable, making deep drawing and complex forming straightforward, and it welds readily without special precautions. SUS430 has lower ductility and can thicken grain in the weld heat-affected zone, but it often offers better machinability for bar products and is markedly cheaper because it contains no expensive nickel.

Magnetic Behavior

SUS304 is essentially non-magnetic, although cold working can induce slight magnetism from strain-induced martensite. SUS430 is ferromagnetic and attracts a magnet in all conditions. This difference matters for applications such as kitchen appliances, electronics enclosures, and magnetic chucks.

Typical Applications

SUS304 is used for kitchen sinks, food processing equipment, medical instruments, chemical containers, and architectural trim. SUS430 is used for appliance trim, cutlery, cookware, automotive exhaust components, and decorative panels where economy and moderate corrosion resistance are sufficient.

Selection Guidance

Choose SUS304 when corrosion resistance, formability, or non-magnetic behavior is required. Choose SUS430 when cost is the priority and the service environment is mild, dry, or indoor, and when magnetic response is acceptable or desired.

Frequently Asked Questions

Q: Is SUS430 magnetic?

A: Yes, as a ferritic grade it is magnetic in all conditions.

Q: Is SUS304 magnetic?

A: No, it is non-magnetic unless heavily cold worked.

Q: Which grade is more corrosion resistant?

A: SUS304, thanks to its nickel content.

Q: Why is SUS430 cheaper?

A: It contains no nickel.

Q: Which grade forms better?

A: SUS304 has better ductility and deep drawing behavior.

Q: What are typical applications?

A: SUS304 for food and medical equipment; SUS430 for appliances and cutlery.

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