SUS304 Stainless Steel: Ultimate Durability for Industrial Use

Introduction: The Workhorse Austenitic Grade

SUS304 is the Japanese Industrial Standard designation for the 18 percent chromium, 8 percent nickel austenitic stainless steel known internationally as AISI 304, UNS S30400 and EN 1.4301 (X5CrNi18-10). It combines good corrosion resistance, strength, formability, weldability and hygiene, which is why it accounts for the largest share of stainless steel consumption worldwide. The properties below follow JIS G4304 for hot-rolled plate and JIS G4303 for bar, with ASTM A240 values applying to equivalent American plate product.

Chemical Composition (JIS G4304, SUS304)

Element	Requirement (wt %)
Carbon (C)	0.08 max
Silicon (Si)	0.75 max
Manganese (Mn)	2.00 max
Phosphorus (P)	0.045 max
Sulfur (S)	0.030 max
Chromium (Cr)	18.00 - 20.00
Nickel (Ni)	8.00 - 10.50
Iron (Fe)	Balance

Mechanical Properties (JIS G4304, Plate)

Property	Value
Tensile strength	520 MPa min
Yield strength (0.2% offset)	205 MPa min
Elongation	40% min
Hardness	200 HB max

Corrosion Resistance

The chromium-rich passive film gives SUS304 good resistance to atmospheric corrosion, fresh water, food acids, most organic chemicals and mild inorganic acids. It is not resistant to strong reducing acids or to concentrated chlorides. In coastal or de-icing salt environments, pitting and stress corrosion cracking can occur, and a molybdenum grade such as SUS316L should be considered. The low sulfur limit and good weldability mean welded structures retain corrosion resistance without post-weld heat treatment.

Heat Resistance

SUS304 resists oxidation in continuous service up to about 870 C (1600 F) and intermittent service up to about 925 C (1700 F). However, exposure in the sensitization range of roughly 425 to 850 C can precipitate chromium carbides unless the carbon is reduced or the steel is stabilized, so design codes limit allowable stresses accordingly.

Fabrication and Hygiene

The grade forms, bends and deep draws well, welds by all conventional processes and polishes to the bright finishes required in sanitary applications. Its non-magnetic austenitic structure, smooth weldability and easy cleaning make it the default material for equipment that contacts food, beverages and pharmaceuticals.

Applications

Food and beverage processing tanks, piping and conveyors

Medical instruments and hospital equipment

Architectural cladding, railings and kitchen equipment

Automotive trim and exhaust components

Chemical storage and process vessels in mild media

Water treatment and domestic appliances

FAQ

1. What does SUS stand for?

SUS is the JIS prefix for stainless steel, from the combination of Steel Use Stainless. SUS304 is the JIS name for grade 304, with chemistry controlled by JIS G4303 and G4304.

2. Is SUS304 the same as AISI 304?

Yes, they are the same grade family with very similar chemistry limits. Small differences exist in element ranges between JIS and ASTM tables, but the two designations are interchangeable for most applications.

3. Is SUS304 magnetic?

In the annealed condition it is essentially non-magnetic. Cold working can transform some austenite to martensite, producing slight magnetism.

4. Can SUS304 be used in seawater?

Not recommended. Chlorides attack the passive film and cause pitting and stress corrosion cracking. SUS316L or a duplex grade is required for seawater.

5. What is the difference between SUS304 and SUS304L?

SUS304L limits carbon to 0.030 percent maximum, which prevents sensitization during welding. For heavy welded sections, SUS304L is preferred.

6. How is SUS304 supplied?

It is available as plate, sheet, strip, bar, wire, pipe and tube under JIS G4304, G4305, G4303 and G3459, with corresponding ASTM products under A240, A666 and A312.