X5CrNi18-10 vs AISI 304: Equivalent Grade Comparison

Are X5CrNi18-10 and AISI 304 the Same Material?

Essentially yes. X5CrNi18-10 is the European designation and AISI 304 is the American designation for the same austenitic stainless steel. The grades are interchangeable in composition and properties, and the practical difference for a buyer lies in the standard system that governs the order, the test certificate that is issued and the designation that appears on the mill certificate.

Everything below sets out the designations, chemistry, mechanical data and selection rules that matter when a drawing quotes one name and the supplier quotes the other.

Designations and Standard Systems

Item	X5CrNi18-10	AISI 304
Standard system	EN 10088-2 (flat products) and EN 10088-3 (bar)	ASTM A240 / ASTM A480, with AISI and SAE designation practice
Numeric or UNS identity	EN 1.4301, formerly written X5CrNi18-10	UNS S30400
Equivalence	Equivalent to AISI 304 in composition and properties	Equivalent to EN 1.4301
Typical market	Europe and China, where GB/T 24511 style pressure-equipment plate follows the EN structure	North America, Japan and Korea, where JIS SUS304 is the equivalent designation

The naming logic is different in each system. The European name encodes composition: X for austenitic, 5 for a nominal carbon content of about 0.05%, and 18-10 for roughly 18% chromium and 10% nickel. The American name is a sequential AISI number with no compositional meaning.

Chemical Composition Comparison

Both listings describe the same alloy, and the small differences in the stated limits come from the standard tables rather than the steel.

Element	EN 1.4301 / X5CrNi18-10	ASTM A240 UNS S30400
Carbon	0.07% max	0.07% max
Chromium	17.5-19.5%	18.0-20.0%
Nickel	8.0-10.5%	8.0-10.5%
Manganese	2.00% max	2.00% max
Silicon	1.00% max	0.75% max
Phosphorus	0.045% max	0.045% max
Sulphur	0.030% max	0.030% max

Two points are worth noting for anyone reconciling certificates. First, older AISI listings and some national grades derived from them quote a carbon limit of 0.08% and a nickel range of 8.0 to 11.0%; those values should not be used to reject a heat that complies with the current EN or ASTM table. Second, silicon is the only element where the two standard tables differ in a way that can matter, so a heat rolled to 0.9% silicon satisfies EN 1.4301 but would not satisfy ASTM A240.

Mechanical Properties in the Solution-Annealed Condition

Property	EN 10088-2 / 1.4301	ASTM A240 / 304
0.2% proof strength	Not less than 210 MPa	Not less than 205 MPa
Tensile strength	500-700 MPa	Not less than 515 MPa
Elongation	40% min (typical)	40% min
Hardness	No limit stated for 1.4301	201 HBW / 92 HRB max
Density	8.0 g per cubic cm	8.0 g per cubic cm

The properties are effectively identical at room temperature, which is why the two designations are treated as one grade in purchasing and fabrication. Cold work raises both strength and magnetic response, so heavily formed parts may show slight magnetism with no change in material identity.

Corrosion, Welding and Fabrication Behaviour

Atmospheric corrosion resistance, resistance to water and neutral solutions and resistance to many organic chemicals are the same for both designations. The shared weakness is intergranular corrosion: without stabilisation, exposure in the sensitisation range of about 450 to 850 degrees C can precipitate chromium carbides at the grain boundaries and deplete chromium locally. Welded fabrications therefore use the low-carbon variant 304L, designated X2CrNi18-9 or EN 1.4307, or a stabilised grade such as 321 where elevated-temperature strength is also required.

Both designations are readily formed, bent and drawn, with a moderate work-hardening rate, and both weld with all common arc processes. Austenitic filler of the 308 series is the normal choice, and post-weld heat treatment is generally unnecessary on thin sections; it becomes advisable on heavy sections or where maximum corrosion resistance is specified after welding.

Frequently Asked Questions

Q: Can X5CrNi18-10 be used instead of AISI 304?
Yes. The two names describe the same alloy, so parts made from either designation are interchangeable where the applicable product standard and certificate requirements are satisfied.

Q: Why do the chemical ranges differ between EN and ASTM tables?
Because each standard writes its own limits for the same alloy. EN 1.4301 quotes chromium 17.5-19.5% and silicon 1.00% max, while ASTM A240 quotes chromium 18.0-20.0% and silicon 0.75% max.

Q: Which designation should be specified on a purchase order?
Specify the standard that the project or certificate must meet, then add both names for clarity, for example plate to ASTM A240 UNS S30400 with EN 1.4301 equivalence noted.

Q: Is X5CrNi18-10 the same as 1.4301?
Yes. EN 1.4301 is the material number, while X5CrNi18-10 is the shorter conventional designation used for the same composition in the EN system.

Q: Is 304 stainless steel magnetic?
In the annealed condition it is essentially non-magnetic. Cold working or welding can create some ferromagnetic martensite, so light magnetic attraction is not evidence of a different grade.

Q: When should 304L or 321 be used instead of 304?
When welded assemblies will see corrosive service or elevated temperature. The low-carbon 304L and the stabilised 321 both reduce the risk of chromium carbide precipitation and intergranular corrosion.

Q: Do both grades need passivation after fabrication?
Yes, ideally. Pickling and passivation remove heat tint and free iron after welding or forming and restore the chromium oxide film that provides corrosion resistance.