904L Stainless Steel Seamless Pipe & Tube
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1.4539 – a steel for tough media
1.4539 (AISI 904L), designated X1NiCrMoCu25-20-5, is a super austenitic stainless steel: approx. 25% nickel, 20% chromium, 4–5% molybdenum and added copper, with very low carbon. This chemistry delivers corrosion resistance that standard acid-resistant grades can’t match – above all in dilute and medium-strength sulfuric acid, in phosphoric acid and in chloride-bearing solutions. The high nickel content also protects against stress corrosion cracking, which attacks 304 and 316L in warm chlorides. How it develops and how to spot it is covered in the article Stress corrosion cracking in stainless steel.
Chemical composition and PREN
| Grade | C | Cr | Ni | Mo | Cu | PREN |
|---|---|---|---|---|---|---|
| 1.4539 / 904L | ≤ 0.020 | 19.0–21.0 | 24.0–26.0 | 4.0–5.0 | 1.2–2.0 | approx. 34–36 |
| 1.4404 / 316L (for comparison) | ≤ 0.030 | 16.5–18.5 | 10.0–13.0 | 2.0–2.5 | – | approx. 24–26 |
Values in wt. % per EN 10088-1. Equivalents: 1.4539 = X1NiCrMoCu25-20-5 = AISI 904L = UNS N08904. How the pitting resistance equivalent number is calculated is explained in PREN – calculating the pitting resistance of steel.
904L pipe and tube sizes
We carry seamless 1.4539 tube in the following sizes: 25 × 2.6 mm, 38 × 2.6 and 3.2 mm, 76.1 × 4 mm, 88.9 × 5 mm, 114.3 × 8.8 mm and 159 × 6.3 and 8 mm OD, in lengths from 10 cm up to full random lengths, and cut to length. The grade is expensive, so buying exactly the length you need makes a real difference to the cost of the installation. An EN 10204 3.1 mill test certificate showing the actual heat chemistry can be ordered with every shipment.
Where is 904L pipe and tube used?
1.4539 pipe and tube is used in systems that produce and carry sulfuric and phosphoric acid, in heat exchangers and coolers running on seawater or brackish water, in flue gas desulfurization, in pulp bleach plants, in the fertilizer and pharmaceutical industries and in electroplating shops. It is also the material of choice for lines in environments where 316L suffers pitting or stress corrosion cracking and moving up to nickel alloys would not be cost-justified. The steel welds and cold-forms well, although – like any high-nickel steel – it calls for careful heat input control when welding.
904L, 316L or duplex?
For potable water and most industrial installations, 316L / 1.4404 seamless tube or titanium-stabilized 316Ti / 1.4571 tube will do the job. When the problem is chlorides and mechanical load rather than acids, duplex 1.4462 and super duplex 1.4410 tube is often a good and usually less expensive alternative. 904L comes out ahead where reducing acids are present, sulfuric acid in particular, and where the high ductility and weldability of austenite count.
See also: other grades in the category seamless tube and hollow bar.