1.4301 Stainless Steel (304): Composition, Strength and Applications

What 1.4301 Stainless Steel Is

1.4301 stainless steel, written X5CrNi18-10 in the EN designation system, is an austenitic chromium-nickel stainless steel whose two main alloying elements are chromium and nickel. It is the grade that most of the world knows as 304, and the grade known in the Chinese system as 06Cr19Ni10 under GB/T 20878. Its chemistry places it in the 18-8 family, meaning roughly 18% chromium and 8% nickel.

The austenitic structure is the reason for its reputation. In the annealed condition the grade is essentially non-magnetic and has a face-centred cubic crystal structure, which gives it high ductility, low temperature toughness down to cryogenic service and very good formability, including deep drawing.

It is worth being precise about the designation, because a single grade carries several names. EN 10088-2 defines 1.4301 / X5CrNi18-10 as a flat product for general corrosion-resistant service, while ASTM A240 defines the same family of material as grade 304, with UNS number S30400. The nominal compositions are close but not identical, so a purchase specification should always state which standard applies.

Chemical Composition of 1.4301

The typical specification limits, taken from EN 10088-2 and from the ASTM A240 range for 304, are shown below. All values are mass percent.

Element	EN 10088-2 (X5CrNi18-10)	ASTM A240 / 304
Carbon, C	0.07 maximum	0.08 maximum
Silicon, Si	1.00 maximum	0.75 maximum
Manganese, Mn	2.00 maximum	2.00 maximum
Phosphorus, P	0.045 maximum	0.045 maximum
Sulfur, S	0.030 maximum	0.030 maximum
Chromium, Cr	17.50-19.50	18.00-20.00
Nickel, Ni	8.00-10.50	8.00-11.00
Nitrogen, N	0.11 maximum	0.10 maximum

Chromium is the element that provides the passive surface film responsible for atmospheric and mildly corrosive service; nickel stabilises the austenitic structure and contributes toughness and formability. Because the grade is molybdenum-free, its resistance to chloride pitting is limited and it should not be substituted for a molybdenum-bearing grade in aggressive chloride service.

Mechanical and Physical Properties

Mechanical properties for annealed flat product are specified in EN 10088-2 and are summarised below. Values are minimum requirements for the annealed condition, which is the condition in which the material is normally supplied and used.

Property	Value	Remark
0.2% proof strength, Rp0.2	205 MPa minimum	Note that Rp0.2 is the 0.2% proof stress, not an elongation value
Tensile strength, Rm	520-720 MPa	Annealed cold-rolled strip
Elongation, A	40% minimum	Measured on the standard gauge length
Hardness after solution treatment	about 187 HBW / 90 HRB typical	Value for annealed product; cold work raises it
Density	7.93 kg/dm³ (7,930 kg/m³)	Used for weight calculation per metre or per sheet
Modulus of elasticity	200 GPa	At room temperature
Thermal conductivity	about 16 W/(m·K)	Low compared with carbon steel, so heat builds up in welding

The combination of 205 MPa proof strength and 40% elongation explains the applications of the grade. It is strong enough for structural brackets and process equipment, yet ductile enough for heavy deep drawing, bending with tight radii and roll forming without cracking. Cold working increases both strength and hardness and makes the material slightly magnetic, which is relevant when a non-magnetic requirement applies.

Heat Treatment and Fabrication

1.4301 cannot be strengthened by heat treatment. Solution annealing, also called softening or quench annealing, is carried out in the range of 1010-1150 °C followed by rapid cooling, normally water quenching or forced-air cooling, so that carbides remain in solution and the material returns to its softest, most corrosion-resistant condition. Slow cooling through the sensitisation range should be avoided because it allows chromium carbides to precipitate at grain boundaries and reduces resistance to intergranular corrosion.

Forming. The grade deep draws, bends and roll forms well. Because it work hardens rapidly, severe forming sequences may need intermediate annealing.

Welding. All common arc and resistance welding processes are suitable, with matching filler metal and controlled heat input. Scale must be removed after welding to restore corrosion resistance.

Machining. The austenitic structure tends to work harden under the tool, so rigid setups, sharp tooling and constant feed are used. The free-machining variants of the family contain added sulfur and are a different material with lower corrosion resistance.

Cleaning. Carbon steel contamination from brushes, clamps or work benches must be avoided, as free iron particles become rust spots on the finished surface.

Where 1.4301 Is Used

Food and beverage equipment. Its corrosion resistance, cleanability and freedom from taint make it standard for conveying pipes, tanks, mixers and storage containers.

Chemical processing. It resists a wide range of mildly aggressive media and is used for reactors, storage tanks and pipework where molybdenum-bearing grades are not required.

Construction and architecture. Panels, handrails, cladding and structural parts use the grade for its appearance and its resistance to atmospheric attack, including in inland urban environments.

Medical and laboratory equipment. Cleanliness, corrosion resistance and the ability to be disinfected suit surgical instruments, benches and equipment housings.

Low temperature service. Because the austenitic structure retains toughness at low temperature, the grade is used for components in refrigerated and cryogenic equipment as well as in electrical and electronic hardware.

Questions Buyers Ask About 1.4301

Q: Is 1.4301 the same as 304 stainless steel?
They describe the same grade family under different standards. 1.4301 is the EN number for X5CrNi18-10, and 304 with UNS S30400 is the ASTM designation. Composition limits differ slightly between the standards, so the applicable standard should be stated on the order.

Q: Is 1.4301 magnetic?
In the fully annealed condition it is essentially non-magnetic. Cold working, such as bending, drawing or cutting, forms some martensite and increases magnetic response, so strongly formed parts may attract a magnet.

Q: Can 1.4301 be hardened by heat treatment?
No. The austenitic structure cannot be hardened by quenching. Strength is increased by cold working, and the only heat treatment used in practice is solution annealing to restore softness and corrosion resistance.

Q: Why is the source data sometimes listed as Rp0.2 of 205 MPa and 40% elongation?
Rp0.2 is the 0.2% proof strength, a stress value, while elongation is a separate ductility measure. Confusing the two leads to wrong design assumptions, so the two values should be read from separate rows of the material certificate.

Q: Which environments are unsuitable for 1.4301?
Chloride-rich conditions such as coastal atmospheres, salt water and chloride process streams can cause pitting and crevice corrosion, because the grade contains no molybdenum. A molybdenum-bearing austenitic grade or a duplex grade is selected for those duties.

Q: What heat treatment condition is supplied as standard?
Flat product is normally supplied in the solution annealed and pickled or bright annealed condition, with the treatment temperature in the 1010-1150 °C range followed by rapid cooling.