304
1.4301 · EN 10088 / AISI · 1.4301
304 is a stainless steel (Austenitic family) to EN 10088 / AISI (1.4301). It has a specified 0.2 % proof stress of 210 MPa and a typical tensile strength of about 520 MPa, with a uniform elongation of 45 %. For nonlinear FEA, a bilinear model uses E = 193 GPa up to yield and a tangent modulus of 694 MPa above it. Its austenitic structure gives excellent corrosion resistance, formability and cryogenic toughness, but it cannot be hardened by heat treatment.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 45.0% · conservative analysis limit ½εu = 22.5%
Bilinear (BISO) approximation. Elastic modulus E up to the 0.2% proof stress R_p0.2, then a single tangent slope Eₜ to the ultimate tensile strength: Eₜ = (Rₘ − R_p0.2) / (εu − R_p0.2/E − 0.002), where εu is the uniform elongation and Rₘ is a typical (nominal) UTS within the specified band. The half-εu figure is a conservative strain limit for the analysis. Treat these as guidance for first-pass models; for critical work use a measured true stress–strain curve for the actual product and condition.
Ratings — engineering judgement
Weldabilitygood
Readily weldable by all common processes. Use 304L filler (or 308L) to avoid HAZ sensitisation; no preheat, keep interpass below ~150 °C.
Formabilityexcellent
Outstanding — deep drawing, spinning and bending all easy. Work hardens strongly, so allow for higher forces and spring-back.
Machinabilitypoor
Work-hardens rapidly; sharp carbide tooling, positive rake, firm feeds and flood coolant. Never let the tool rub or dwell.
Corrosion resistancegood
Excellent general and atmospheric resistance, but no molybdenum — noticeably less pitting/crevice resistance than 316 in chlorides. The workhorse where chlorides aren’t the issue.
Hardenabilitynone
Cannot be hardened by heat treatment; strengthen only by cold work.
Toughnessexcellent
Superb toughness at all temperatures including cryogenic; no ductile-to-brittle transition. Used to −196 °C and below.
Expert notes
304 is the default stainless — if someone says “stainless” without qualification, they almost always mean 304. It’s the yardstick the others are measured against, and the right choice for the large majority of corrosion applications that don’t involve chlorides.
The one decision that matters is 304 vs 316. 316’s molybdenum buys chloride pitting resistance for marine, coastal, pool and de-icing-salt environments; everywhere else 304 does the same job for less money and machines and welds a little more easily. Don’t pay the 316 premium out of habit.
For anything welded, specify 304L (≤ 0.03 % C). It sidesteps carbide sensitisation in the HAZ entirely, and the small strength drop is irrelevant in practice — most fabricated 304 is really 304L.
It arrives non-magnetic but cold work (bending, machining, deep drawing) can raise a faint magnetic response — that’s normal for austenitic steel and not a sign of contamination.
Fasteners: 304 is property class A2. Like all austenitics it galls viciously thread-on-thread — use anti-seize or nitronic/silver-plated fasteners for anything you’ll undo.
Mechanical properties
| Condition | Section | Yield (MPa) |
|---|---|---|
| 304 · solution annealed | t ≤ 75 mm | 210 |
UTS 520–720 MPa · Impact ≥ 60 J @ 20 °C (often >150 J) · Hardness ≤ 215 HB
Physical properties
| Density | 7900 | kg/m³ |
| Elastic modulus | 193 | GPa |
| Shear modulus | 74 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 17.3 | ×10⁻⁶/°C |
| Thermal conductivity | 16 | W/(m·K) |
| Specific heat | 500 | J/(kg·K) |
| Magnetic | No (annealed) |
Chemical composition (wt %)
Available forms
Equivalent grades
| Standard | Grade | Note |
|---|---|---|
| EN 10088 | X5CrNi18-10 / 1.4301 | |
| AISI | 304 | |
| BS 970 Pt 4 | 304S31 | |
| JIS | SUS304 | |
| UNS | S30400 | |
| GB | 06Cr19Ni10 |
Historical designations
| Standard | Grade | Note |
|---|---|---|
| BS 970:1970 Pt 4 | 304S31 | British designation on older UK drawings. |
| Trade | 18/8 | The classic shorthand — ~18 % Cr, 8 % Ni. |
| Werkstoff Nr. | 1.4301 | German material number. |
Common applications
- Food, dairy and beverage equipment
- Architectural cladding, handrails and trim
- Kitchen and catering equipment
- Chemical and general process vessels (non-chloride)
- Fasteners and fittings (A2 class)
- Sinks, splashbacks and sanitaryware
History
304 is the direct commercial descendant of the first austenitic stainless steel — the “18/8” patented at Krupp in 1912 — and remains the most-produced stainless grade in the world.
- 1912Strauss & Maurer patent the 18/8 austenitic stainless at Krupp (Nirosta)
- 192918/8 in volume production for cutlery, dairy and architectural use
- 1950AISI 304 established as the standard austenitic grade
- 1970Low-carbon 304L introduced to solve weld sensitisation