EN 1.4404 Stainless Steel: Standard, Composition and Properties

EN 1.4404 at a Glance

EN 1.4404 is the material number for the molybdenum-bearing austenitic stainless steel designated X2CrNiMo17-12-2, the low-carbon counterpart of EN 1.4401 and the grade most engineers know as 316L. The 0.030% maximum carbon content keeps carbon in solution during welding, so welded assemblies normally keep their intergranular corrosion resistance without a post-weld solution anneal.

The grade is catalogued in the EN 10088 series for general-purpose flat and long products, and it is called up by EN 10028-7 for pressure vessel plate, by EN 10216-5 and EN 10217-7 for seamless and welded tube, and by EN 10222-5 for forgings. Typical service covers chemical process vessels, pharmaceutical and food piping, heat exchanger tubing, desalination plant and architectural components exposed to chlorides and mild acids.

Chemical Composition of EN 1.4404 (X2CrNiMo17-12-2)

The table below lists the heat analysis limits for the grade. Values are percentage by mass; a single figure is a maximum unless a range is shown.

Element	C	Si	Mn	P	S	N	Cr	Mo	Ni
% max / range	0.030	1.00	2.00	0.045	0.015	0.10	16.50-18.50	2.00-2.50	10.00-13.00

For improved machinability a controlled sulfur range of 0.015-0.030% is permitted when the order specifies it; the standard limit stays at 0.015% maximum. The 2.00-2.50% molybdenum addition is what separates 1.4404 from the molybdenum-free 1.4301 and lifts pitting resistance in chloride-bearing media. Chromium and nickel together stabilise the fully austenitic structure, while nitrogen is held low to preserve ductility and impact toughness at sub-zero temperature.

Mechanical Properties at Room Temperature

The values below apply to the solution-annealed condition. Product form codes follow the EN 10088 flat and long product tables: C is cold-rolled strip and sheet, H is hot-rolled strip and sheet, P is hot-rolled plate, L is bar and section, and Tw/s is drawn wire and bar.

Form	Max. thickness (mm)	Rp0.2 (MPa)	Rp1.0 (MPa)	Rm (MPa)	A (%)	ISO-V impact, long. / trans. (J)
C	≤ 8	240	270	530-680	40	- / -
H	≤ 13.5	220	260	530-680	40	100 / 60
P	≤ 75	220	260	520-670	45	100 / 60
L	≤ 160	200	235	500-700	40	100 / -
L	≤ 250	200	235	500-700	- / 30	- / 60
Tw/s	≤ 60	190	240	490-690	40 / 30	100 / 60

Two practical points follow from the table. Proof strength falls as section thickness rises, so heavy plate and bar are designed to a lower allowable stress than thin cold-rolled strip. Longitudinal elongation and impact values are also consistently higher than transverse values, which matters whenever a component is formed across the rolling direction or loaded in the short-transverse orientation.

Physical Properties and Thermal Expansion

The physical data used for thermal and structural design are listed below as typical values for the annealed grade.

Property	Value
Density at 20 °C	8.0 kg/dm³
Modulus of elasticity at 20 °C	200 kN/mm²
Thermal conductivity at 20 °C	15 W/m·K
Specific heat capacity at 20 °C	500 J/kg·K
Electrical resistivity at 20 °C	0.75 Ω·mm²/m

Temperature range	Mean linear expansion (10−&sup6; K−¹)
20 to 100 °C	16.0
20 to 200 °C	16.5
20 to 300 °C	17.0
20 to 400 °C	17.5
20 to 500 °C	18.0

Heat Treatment, Hot Forming and Fabrication

Operation	Temperature	Cooling / note
Hot forming	1150 to 850 °C	Air cooling; finish the operation above 850 °C to limit sigma-phase precipitation
Solution annealing	1030 to 1110 °C	Water quenching, or air cooling for thin sections
Resulting microstructure	Austenite with a low ferrite content	Fully austenitic and essentially non-magnetic in the annealed state

Because 1.4404 is kept corrosion-resistant by its low carbon content rather than by stabilising additions, it is normally delivered annealed and pickled and is welded with matching low-carbon filler metal. Cold forming hardens the surface and slightly raises magnetic permeability, so heavy cold work should be followed by annealing where permeability or corrosion resistance is critical. A thermal conductivity of about 15 W/m·K is low compared with carbon steel, which concentrates heat input during welding and increases the risk of distortion in thin-wall tube assemblies.

Frequently Asked Questions

Q: Is EN 1.4404 the same as 316L?
Yes. 1.4404 is the EN material number for X2CrNiMo17-12-2, the low-carbon version of the 316 composition that the AISI system calls 316L. The composition limits are effectively identical.

Q: What is the difference between 1.4404 and 1.4401?
Only the carbon limit changes. 1.4404 caps carbon at 0.030% while 1.4401 allows up to 0.070%, so 1.4404 keeps welds free of chromium carbide precipitation without a post-weld anneal.

Q: What is the maximum service temperature of 1.4404?
The grade is normally used up to about 550 °C in continuous service and remains suitable for low-temperature work down to −196 °C, where it keeps good impact toughness in the annealed condition.

Q: How is 1.4404 heat treated?
Solution anneal between 1030 °C and 1110 °C and cool rapidly in water; air cooling is acceptable for thin sections. Hot forming is carried out between 1150 °C and 850 °C.

Q: Why does proof strength differ between plate and bar?
Proof strength is specified per product form and thickness: thin cold-rolled strip reaches 240 MPa Rp0.2, while heavy bar and plate are specified from 190 to 200 MPa Rp0.2.

Q: Is 1.4404 magnetic?
In the annealed condition it is essentially non-magnetic. Cold working or welding can generate small amounts of martensite or ferrite, so lightly magnetic areas may appear after severe forming.