EN 1.4401 Stainless Steel: Equivalent Grades, Composition and Properties
What EN 1.4401 Stainless Steel Is
EN 1.4401, also written as X5CrNiMo17-12-2, is a molybdenum-bearing austenitic stainless steel. The molybdenum addition gives it markedly better resistance than 1.4301 (X5CrNi18-10) to pitting and crevice corrosion in chloride-bearing environments and to attack by non-oxidizing acids, which is why it is one of the most widely used materials in chemical plant and food processing equipment.
The material number system is the quickest way to keep the family straight. EN 1.4401 is the standard-carbon austenitic grade, while EN 1.4404 (X2CrNiMo17-12-2) is its low-carbon variant. The lower carbon of 1.4404 reduces chromium carbide precipitation during welding, so it is preferred for heavy welded structures where post-weld heat treatment is impractical.
International Equivalents of EN 1.4401
The grade is standardized across the major specification systems. The equivalents below are the ones a purchaser should expect to see on a mill certificate or a cross-reference table.
| Standard system | Equivalent designation |
|---|---|
| USA (ASTM / UNS) | AISI 316, UNS S31600 |
| ISO | X5CrNiMo17-12-2 (4401-316-00-I) |
| China (GB) | 0Cr17Ni12Mo2, 06Cr17Ni12Mo2 |
| Japan (JIS) | SUS316 |
| EN / DIN material number | 1.4401, low-carbon variant 1.4404 |
Note that the Chinese designations correspond to an older and a newer national standard respectively; both describe the same 17% chromium, 12% nickel, 2% molybdenum austenitic composition.
Chemical Composition and Physical Properties
Composition limits for 1.4401 come from EN 10088-2 for flat products and EN 10088-3 for semi-finished, bar and rod products.
| Element | Limit (%) |
|---|---|
| Carbon (C) | 0.07 max |
| Silicon (Si) | 1.00 max |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulfur (S) | 0.030 max |
| Chromium (Cr) | 16.5–18.5 |
| Nickel (Ni) | 10.0–13.0 |
| Molybdenum (Mo) | 2.00–2.50 |
| Nitrogen (N) | 0.10 max |
| Physical property | Value |
|---|---|
| Density | 8.0 g/cm³ |
| Magnetism | Non-magnetic |
| Electrical resistivity at 20 °C | 0.75 μΩ·m |
| Specific heat capacity at 20 °C | 500 J/(kg·K) |
| Thermal conductivity at 20 °C | 15.0 W/m·K |
| Thermal expansion, 20–100 °C | 16.0 × 10⁻⁶/K |
| Thermal expansion, 20–500 °C | 18.0 × 10⁻⁶/K |
Mechanical Properties at Room and Elevated Temperature
Properties below apply to the solution-annealed condition, which is the normal delivery state for this grade.
| Property | Value |
|---|---|
| Tensile strength | 500–700 MPa |
| 0.2% proof strength | 200 MPa min |
| 1.0% proof strength | 235 MPa min |
| Elongation | 40% min |
| Impact toughness, longitudinal | 100 J min |
| Modulus of elasticity at 20 °C | 200 GPa |
Proof strength falls steadily as temperature rises, which matters for hot-wall design and for bolting. Representative 0.2% proof values are 175 MPa at 100 °C, 145 MPa at 200 °C, 127 MPa at 300 °C, 115 MPa at 400 °C and 110 MPa at 500 °C. Modulus of elasticity over the same range falls from 200 GPa at 20 °C to 165 GPa at 500 °C.
Heat Treatment, Forging, Welding and Applications
Solution annealing: 1030–1110 °C followed by rapid air or water cooling to dissolve carbides and restore a fully austenitic structure.
Hot working: 1150–850 °C with air cooling afterwards.
Forging: preheat at 1150–1180 °C, forge within 1180–950 °C, then cool rapidly in air or water to avoid detrimental phase formation.
Descaling: remove scale and surface contamination by pickling or another suitable method, or corrosion resistance at the surface will be lost.
Welding: excellent weldability with or without filler metal; a matching molybdenum-bearing filler such as 1.4430 is recommended and interpass temperature should be held at or below 150 °C.
Because 1.4401 carries more carbon than 1.4404, chromium carbides can form in the heat-affected zone of thick welds. Where a welded structure is exposed to aggressive media, either a post-weld solution anneal or the low-carbon variant should be selected.
Corrosion performance is usually expressed through the pitting resistance equivalent number, which falls in the range 23.1–28.5 for this composition thanks to the 2.0–2.5% molybdenum. Typical applications include chemical and pulp processing equipment, paint and coating production, oil, soap and textile plant, dairy equipment, brewery components and instrumentation.
Frequently Asked Questions
Q: What is EN 1.4401 equivalent to in the American system?
It is equivalent to AISI 316 and UNS S31600. The low-carbon variant 1.4404 corresponds to 316L and UNS S31603.
Q: What is the difference between 1.4401 and 1.4404?
The alloys are otherwise the same, but 1.4401 has up to 0.07% carbon while 1.4404 is limited to 0.03%, which gives 1.4404 better resistance to intergranular corrosion after welding.
Q: Is 1.4401 suitable for marine environments?
It performs well in many chloride-bearing duties but is not a seawater alloy. For permanent immersion or high chloride exposure, higher-molybdenum grades should be considered.
Q: Can 1.4401 be hardened by heat treatment?
No. Austenitic stainless steels cannot be hardened by heat treatment. Strength is increased only by cold working, which reduces ductility.
Q: What filler metal is used for welding 1.4401?
A matching molybdenum-bearing austenitic filler such as 1.4430 is recommended, with interpass temperature controlled and the finished weld cleaned of heat tint.
Q: Which product standards cover 1.4401?
EN 10088-2 covers flat products and EN 10088-3 covers semi-finished products, bars and rods; equivalent ASTM and other national standards are widely cross-referenced in supply specifications.
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