SUS430 Stainless Steel

Overview of SUS430

SUS430 is the most widely used ferritic stainless steel in the JIS system, with 16-18% chromium and no intentional nickel addition. The ferritic crystal structure gives it three practical advantages over austenitic SUS304: lower material cost, higher thermal conductivity and permanent magnetism. Its balanced corrosion resistance and excellent formability make it a standard choice for household appliances and architectural trim where austenitic grades would be overspecified.

Chemical Composition

Element (wt%)	SUS430 per JIS G4303	S43000 per ASTM A240
C	0.12 max	0.12 max
Si	1.00 max	1.00 max
Mn	1.00 max	1.00 max
P	0.040 max	0.040 max
S	0.030 max	0.030 max
Cr	16.00-18.00	16.00-18.00
Ni	-	0.75 max

The composition is essentially identical between the JIS and ASTM systems; the EN counterpart is 1.4016 (X6Cr17). The chromium level of 16-18% provides the passive film that gives the grade its corrosion resistance in mild service.

Mechanical Properties

In the annealed condition, plate per ASTM A240 shows minimum tensile strength 450 MPa (65 ksi), minimum yield strength 205 MPa (30 ksi) and elongation 20% minimum, with typical annealed hardness near 183 HB maximum per JIS G4304 data. Tensile strength is lower than austenitic grades, but yield strength is comparable, and the grade is notably easy to form, deep draw and polish. High-temperature strength is limited: the ferritic structure softens well before austenitic grades, so SUS430 is not a heat-resisting material.

Corrosion Resistance and Magnetism

SUS430 resists rusting in dry indoor environments, resists food acids and detergents, and survives mild outdoor exposure in inland climates with normal cleaning. It is not suitable for coastal salt spray or chloride-rich service, where pitting occurs; for those conditions SUS316 is the appropriate grade. Because the ferritic structure is magnetic, SUS430 is used for magnetic knife strips, magnetic catches, sensors and separators, an advantage that austenitic SUS304 cannot offer.

Forming and Welding

The grade draws and bends readily, which is why kitchen sinks, oven panels and refrigerator liners are made from it. Welding is possible with TIG or MIG using matching 430-type filler, but the heat-affected zone is prone to grain growth that reduces ductility, so heat input must be kept low and multi-pass welding avoided. Annealing at 700-800 C after heavy forming or welding can restore ductility in thick sections. Preheating may be needed for thick sections to prevent cracking.

Typical Applications

Kitchen appliances: sinks, oven bodies, microwave and dishwasher panels. Architecture: elevator panels, wall cladding, decorative trim, roofing components in dry climates. Industry: heat exchanger shells, automotive trim, food processing equipment that does not see strong acids or chlorides. Cost-sensitive projects: any non-corrosive indoor application where SUS304 would be overspecified.

FAQ

Why is SUS430 so popular in kitchen appliances?

Because it balances cost and performance. It is nickel-free and typically 30-40% cheaper than SUS304, resists food spills and detergents with its 16-18% chromium, polishes to a bright stainless finish, and forms easily into sinks, oven doors and refrigerator panels.

Can SUS430 be welded?

Yes, with care. Use TIG or MIG with matching 430 filler, keep heat input low and cool quickly to limit grain growth. Avoid multi-pass welding without cooling. Welded thick sections may need preheating, and annealing at 700-800 C restores ductility where needed.

Is SUS430 suitable for outdoor use?

In dry inland climates it can serve for years as building trim with occasional cleaning. In humid or coastal environments salt and moisture cause pitting; use SUS316 there, or apply a protective coating and choose a smooth polished finish to slow attack.

What are the main limitations of SUS430 versus SUS304?

SUS430 has lower pitting resistance in chlorides, lower tensile strength, worse impact toughness and little high-temperature strength. Its advantages are lower cost, better thermal conductivity and magnetism. Choose it for mild, indoor, non-corrosive service and SUS304 or SUS316 for demanding conditions.

Is SUS430 magnetic?

Yes. Its ferritic body-centered cubic structure makes it magnetic, which suits applications like magnetic knife strips, magnetic fixtures, sensors and separators. Welding may slightly reduce magnetism locally, but the material remains magnetic overall.

Which standards cover SUS430?

JIS G4303 covers bars, G4304 hot-rolled plate, and G4305 cold-rolled sheet and strip. The ASTM designation is UNS S43000 per A240 (plate) and A276 (bar); the EN designation is 1.4016.