AISI 430 Ferritic Stainless Steel

What Is AISI 430 Stainless Steel?

AISI 430 is the most widely used ferritic stainless steel, with a body-centred cubic ferritic microstructure and a chromium content of 16.00-18.00 percent. It is designated UNS S43000 in ASTM A240/A240M, EN 1.4016 (steel name X6Cr17) in EN 10088-2, and SUS430 in JIS G4304/G4305. Because it contains only trace nickel (0.75 percent maximum), it is considerably less expensive than austenitic grades such as 304 while still offering useful corrosion resistance in mild environments. The grade is magnetic, has good thermal conductivity and a low thermal expansion coefficient, and cannot be hardened by heat treatment. It is the standard choice for kitchenware, automotive trim, washing machine drums and architectural cladding where deep drawing and moderate corrosion resistance are required.

Chemical Composition

Limiting values from ASTM A240/A240M (UNS S43000) and EN 10088-2 (1.4016).

Element	C	Mn	Si	P	S	Cr	Ni
% by mass	≤0.12	≤1.00	≤1.00	≤0.040	≤0.030	16.00-18.00	≤0.75

Mechanical and Physical Properties

Property	Value
Tensile strength	450-620 MPa
Yield strength (0.2% offset)	≥205 MPa
Elongation	≥22%
Hardness	≤88 HRB / ≤183 HB
Density	7.70 g/cm3
Melting range	1425-1510 C
Mean thermal expansion (20-100 C)	10.4 x 10-6 /K
Thermal conductivity	26.1 W/(m.K)
Magnetic response	Ferromagnetic

Corrosion and Oxidation Resistance

430 performs well in rural and urban atmospheres, fresh water, food products and dilute organic acids, and it resists nitric acid well. Its weak points are chlorides: without nickel and molybdenum it is prone to pitting, crevice attack and stress corrosion cracking in wet chloride environments, so it is not suitable for marine exposure or swimming-pool atmospheres. Its oxidation resistance is adequate for continuous service around 815-870 C in dry air, which covers domestic heating appliances and automotive exhaust components that are not severely loaded.

Fabrication and Heat Treatment

430 has excellent ductility for deep drawing, spinning and roll forming, and it machines better than austenitic grades because of its ferritic structure. Welding is possible but requires care: preheating at 150-200 C is often used, and the weld should avoid prolonged exposure to the 400-600 C range where 475 C embrittlement occurs; grain growth in the heat-affected zone can reduce toughness. The grade cannot be hardened by heat treatment; a soft anneal at 760-815 C followed by air cooling restores ductility after heavy cold working. For corrosion resistance in welded or formed parts, a post-weld anneal and pickling or passivation treatment is recommended.

Typical Applications

Typical uses include kitchen sink bowls, cookware and cutlery, dishwasher and washing machine inner drums, refrigerator liners, automotive trim and exhaust systems, building interior cladding and roofline products, fasteners and nuts, and domestic appliance components where the lower cost of a magnetic ferritic grade is an advantage over 304.

Frequently Asked Questions

Q1. Is AISI 430 stainless steel magnetic?
Yes. 430 is a ferritic grade with a body-centred cubic structure, so it is strongly magnetic, unlike annealed austenitic grades such as 304 or 316.

Q2. Can 430 be hardened by heat treatment?
No. Ferritic stainless steels do not respond to hardening by quenching and tempering; only cold working increases their strength.

Q3. What is the difference between 430 and 304?
304 is an austenitic 18/8 grade with roughly 8% nickel, better corrosion resistance, better weldability and non-magnetic behaviour, but it costs more. 430 substitutes chromium for nickel, giving lower cost at the expense of chloride resistance and toughness.

Q4. Is AISI 430 suitable for marine environments?
Generally not. Without molybdenum it pits and can suffer stress corrosion cracking in chloride-rich coastal atmospheres and seawater; for marine duty, 316 or higher-alloyed grades are preferred.

Q5. What is the maximum service temperature of 430?
For oxidation resistance in dry air it can be used up to roughly 815-870 C, but its mechanical strength at those temperatures is low, so it is limited to lightly loaded components.