304L stainless steel – UNS S30403
Low-carbon Cr-Ni austenitic stainless steel
Low-carbon version (C ≤ 0.030%) of 304, with resistance to intergranular corrosion after welding without the need for post-weld solution annealing. It does not harden by heat treatment, only by cold work; non-magnetic in the solution-annealed condition.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | S30403 |
| W.Nr./EN | 1.4307 (X2CrNi18-9) / 1.4306 (X2CrNi19-11) |
| DIN | X2CrNi18-9 |
| JIS | SUS304L |
| Trade names | AISI 304L |
| Others | Frequently dual certified 304/304L |
Standards by product form
| Form | Standard |
|---|---|
| Bar | ASTM A276 / A479 (ASME SA-479) |
| Forging/flange | ASTM A182 F304L |
| Plate | ASTM A240 |
| Tube | ASTM A312 TP304L / A213 |
| Fittings | ASTM A403 WP304L |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7222.30.00 | 7222.30 | 7222.30.0024 | 7222 30 51 |
| Hot-rolled bar | 7222.11.00 | 7222.11 | 7222.11.0059 | 7222 11 11 |
| Plate (> 10 mm, width ≥ 600 mm) | 7219.21.00 | 7219.21 | 7219.21.0020 | 7219 21 10 |
| Seamless pipe | 7304.41.90 | 7304.41 | 7304.41.6045 | 7304 41 00 |
| Welded pipe | 7306.40.00 | 7306.40 | 7306.40.5085 | 7306 40 80 |
| Flange and fitting | 7307.21.00 | 7307.21 | 7307.21.5000 | 7307 21 00 |
Tariff class: stainless steel (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
ASTM A479 (A182 F304L: Ni 8.0–13.0%; A240: Si ≤ 0.75%, Cr 17.5–19.5%, Ni 8.0–12.0%)
| Element | Range (%) |
|---|---|
| C | ≤ 0.030 |
| Mn | ≤ 2.00 |
| P | ≤ 0.045 |
| S | ≤ 0.030 |
| Si | ≤ 1.00 |
| Cr | 18.0 – 20.0 |
| Ni | 8.0 – 12.0 |
| N | ≤ 0.10 |
| Fe | balance |
Mechanical properties
Solution annealed (ASTM A479 bar; A240 plate in parentheses)
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 170 MPa |
| Tensile strength | ≥ 485 MPa |
| Elongation | ≥ 30% (A240: ≥ 40%) |
| Reduction of area | ≥ 40% (A182: ≥ 50%) |
| Hardness | ≤ 201 HB (A240) |
Typical physical properties
| Property | Value |
|---|---|
| Density | 7.9 g/cm³ |
| Melting range | 1,400 – 1,450 °C |
| Modulus of elasticity | 193 – 200 GPa |
| Thermal conductivity (20 °C) | ≈ 15 W/m·K |
| Thermal expansion (20–100 °C) | ≈ 16.0 µm/m·K |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Usual use from cryogenic (–196 °C) up to ≈ 425 °C under load; above that prefer 304H/321/347. Oxidation: ≈ 870 °C intermittent, 925 °C continuous. |
| Heat treatment | Solution annealing 1,040 – 1,120 °C with rapid cooling (water/forced air). Not hardenable by quenching. Stress relief below 425 °C or by solution annealing. |
| Welding | Excellent weldability (TIG, MIG, covered electrode, submerged arc). Consumables AWS ER308L / E308L; for joining to carbon steel, ER309L. |
| Machining | Machinability lower than carbon steel: it work hardens quickly; use sharp tools, positive rake, constant feed without 'rubbing' and abundant coolant. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Welded tanks and vessels for the chemical and food industries
- Process piping and heat exchangers
- Dairy, brewery and pharmaceutical equipment
- Cryogenics (LNG, liquid oxygen)
- Welded structures and parts that cannot be solution annealed
Alternatives: 304 when there is no thick welding; 316L when chlorides are present (Mo improves pitting resistance); 321/347 or 304H for continuous service above ≈ 425 °C.
304L stainless steel: complete guide
What 304L stainless steel is
304L belongs to the family of 300-series austenitic stainless steels. The letter L stands for "low carbon": carbon is at most 0.030%, versus 0.08% in plain 304. That difference is what matters in welding: with low carbon, chromium carbides do not form at the grain boundaries of the heat-affected zone, and intergranular corrosion resistance is preserved without subsequent heat treatment.
304 or 304L
304 is slightly stronger (YS ≥ 205 MPa versus 170 MPa) and is the choice for parts that will not be welded or that can be solution annealed afterwards. 304L is the choice for welded structures, piping and process equipment. Much of the material on the market is "dual certified" 304/304L, meeting both standards at the same time.
Welding
Weldable by all processes with ER308L / E308L consumables, without preheating and without post-weld heat treatment. This is the main reason for choosing the L grade.
Corrosion and limits of use
It resists atmosphere, fresh water, food and nitric acid well, but suffers pitting and crevice corrosion in chlorides and stress corrosion cracking in hot chlorides. In those cases 316L, with molybdenum, is the choice. At temperature, the ASME code allows the L grade up to about 425 °C; above that 304H or the stabilized 321 and 347 are used.
Applications
Equipment and piping for the food, pharmaceutical and light chemical industries, tanks, exchangers, shafts, stems and fasteners, pump and valve components, architecture and hospital equipment.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, solution annealing in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of 304L stainless steel?
Per ASTM A479 (A182 F304L: Ni 8.0–13.0%; A240: Si ≤ 0.75%, Cr 17.5–19.5%, Ni 8.0–12.0%): C ≤ 0.030; Mn ≤ 2.00; P ≤ 0.045; S ≤ 0.030; Si ≤ 1.00; Cr 18.0 – 20.0.
Which standards cover 304L stainless steel?
Bar: ASTM A276 / A479 (ASME SA-479). Forging/flange: ASTM A182 F304L. Plate: ASTM A240. Tube: ASTM A312 TP304L / A213. Fittings: ASTM A403 WP304L.
Up to what temperature can 304L stainless steel be used?
Usual use from cryogenic (–196 °C) up to ≈ 425 °C under load; above that prefer 304H/321/347. Oxidation: ≈ 870 °C intermittent, 925 °C continuous.
Which materials can replace 304L stainless steel?
304 when there is no thick welding; 316L when chlorides are present (Mo improves pitting resistance); 321/347 or 304H for continuous service above ≈ 425 °C.
What is the difference between 304 and 304L stainless steel?
304L has a maximum carbon of 0.030%, versus 0.08% for 304. With less carbon, it does not precipitate chromium carbides during welding and does not suffer intergranular corrosion; in exchange, the minimum strength is slightly lower. Many mills certify the material as 304/304L, meeting both standards.
Is 304 stainless steel magnetic?
In the solution-annealed condition, no. After heavy cold work (bending, stamping) it may become slightly magnetic in the deformed regions, without that indicating a change of material.
Does 304 stainless steel rust?
It resists very well in atmosphere, fresh water and food, but can suffer pitting in chlorides and seawater. In those media, 316L or a duplex are the choices.
