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GRADE PROFILE

1.4435 — high-molybdenum 316L / X2CrNiMo18-14-3

1.4435 carries the same AISI 316L and the same UNS S31603 as 1.4404 without being the same grade. Molybdenum 2.5 to 3% instead of 2 to 2.5%, nickel 12.5 to 15% instead of 10 to 13%. It is the grade pharmaceutical specifications name when they refuse an ordinary 316L.

When to choose it

When the specification names it. That is the dominant case: bioprocessing, aseptic piping, pharmaceutical equipment where delta ferrite content is capped for cleanability and polishing behaviour. 1.4435 wins there not because it resists corrosion better, but because its structure is more homogeneous.

It also earns its place in moderately chlorinated media where 1.4404 sits right at the limit. Two PREN points are not decisive on paper, but they shift the useful threshold by a few tens of ppm of chlorides — enough to settle the question on process water that varies with the season.

When not to choose it

As an automatic substitute for 1.4404. The premium is real and the gain stays marginal outside the cases above: on ordinary process piping, 1.4404 gives the same service.

In seawater, like every molybdenum-bearing austenitic: a PREN of 27 remains far below the 40 required for that service.

In concentrated chlorides, where PREN logic gives way to stress corrosion cracking. An austenitic cracks with no loss of metal; duplex, with its two-phase structure, is substantially more robust there.

Composition

Chemical composition (% by mass)
Element %
C ≤ 0.03
Cr 17–19
Ni 12.5–15
Mo 2.5–3
Mn ≤ 2
Si ≤ 1
N ≤ 0.11

Mechanical properties

We only publish mechanical properties tied to a specific standard and product form — welded tube, seamless tube and bar do not share the same values, and the gap routinely exceeds 30%. The figures that apply to your specification appear on the material certificate; ask us at enquiry stage.

Designations and standards

Equivalent normative designations
Reference Designation
EN (numeric) 1.4435
EN (symbolic) X2CrNiMo18-14-3
ASTM / AISI 316L
UNS S31603
JIS SUS316L
AFNOR —

Tube product standards :

  • EN 10216-5
  • EN 10217-7
  • ASTM A312

Availability

Welded, seamless and heat exchanger tube, Ø 6 to 273 mm. Partner stock or mill depending on the size and quantity: no restriction in principle. EN 10204 3.1 material certificates supplied with the goods. In polished finish, the target internal roughness is specified at order stage.

Related grades

  • 316L (1.4404) — the reference grade, less alloyed and cheaper, the default unless the specification says otherwise.
  • 317L (S31703) — the step up in molybdenum, 3 to 4%, PREN 28 to 33.
  • Duplex 2205 (1.4462) — the change of family when chlorides or mechanical loading move beyond austenitic territory.

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Frequently asked questions

Can 1.4404 be supplied against an order for 316L?
It depends on what was specified. If the order says "316L" or "S31603" with nothing further, 1.4404 is compliant. If it says "1.4435", it is not — even though the AISI and UNS coincide. This is why a pharmaceutical specification should quote the EN number, never the AISI alone.
What is delta ferrite and why cap it?
A residual phase from solidification, magnetic and of different composition from the austenitic matrix. On a polished surface serving a sterile process, it creates heterogeneities that complicate cleaning and can initiate localised corrosion. The higher nickel of 1.4435 reduces its proportion.
Is 1.4435 harder to weld?
No, its weldability is that of a 316L. However, a poorly chosen filler metal reintroduces ferrite into the weld and cancels the advantage sought: where ferrite is the issue, the filler is specified alongside the tube.