Material 1.4404 or 1.4571: the difference is carbon, not marketing
Both are sold as V4A, so the word on your quotation is not a specification — it is a bet on a weld seam that corrodes from the inside, invisibly, until the day it does not. On shukchok you search by the number instead.
Side by side
The seven numbers you will actually meet
Material numbers follow EN 10027-2, the short names EN 10027-1. The AISI column is an approximation, not an equivalence — the compositions overlap, they are not identical.
| Number | Short name | ≈ AISI | Distinguishing feature |
|---|---|---|---|
| 1.4301 | X5CrNi18-10 | 304 | The standard austenitic grade, no molybdenum |
| 1.4307 | X2CrNi18-9 | 304L | Low-carbon version of 1.4301 |
| 1.4401 | X5CrNiMo17-12-2 | 316 | Molybdenum-alloyed, ordinary carbon content |
| 1.4404 | X2CrNiMo17-12-2 | 316L | Molybdenum-alloyed, carbon held to a maximum of 0.030 % |
| 1.4435 | X2CrNiMo18-14-3 | 316L (high Mo) | Like 1.4404 with a higher molybdenum and nickel content |
| 1.4571 | X6CrNiMoTi17-12-2 | 316Ti | Molybdenum-alloyed and titanium-stabilised instead of low-carbon |
| 1.4539 | X1NiCrMoCu25-20-5 | 904L | A different class — high nickel, copper-bearing, for aggressive media |
The same enemy
A weld runs straight through the temperature window that ruins both
Austenitic stainless steel owes its resistance to a thin chromium oxide layer. Anything that pulls chromium out of the metal beneath takes the resistance with it — exactly what happens between roughly 450 and 850 °C, where carbon and chromium combine into carbides along the grain boundaries.
The metal next to those boundaries is left depleted. The steel is then sensitised and corrodes along the boundaries rather than over the surface — and intergranular attack does its damage before it becomes visible.
Every fusion weld leaves a heat-affected zone that spent time in that window on the way down — on a pipe it is a continuous line around the joint. So the real question is not which steel is better but how each of them stops carbides from forming there.
- 1.4404 removes the cause: too little carbon to precipitate during normal welding
- 1.4571 redirects it: titanium binds the carbon before chromium can
- Both routes work — they differ in what they cost you elsewhere
On the actual part
The number is the precise handle. The word is the broad one.
A specification that says "stainless steel" gives you nothing to act on. A specification that says 1.4404 names the alloy family, the presence of molybdenum and the carbon ceiling — enough to decide whether a seal, a sensor body or a fitting belongs in a given medium.
shukchok is an open marketplace for industrial goods, and there the material is part of the specification table on the item page, with the search matching on it: 1.4404 returns five items, 316L two, and the general word for stainless steel twenty-three. That spread is itself the lesson.
Where a data sheet offers several housing variants, the material is often the only thing that changes between them — and it changes more than the price. Reading the variant table as a price list misses that.
- A polypropylene or PVDF body may survive an attack that 1.4404 does not
- The same choice can rule out an explosion-protected version of the same instrument
- Record the material number in your own spares list, not the trade name from the quotation
Where the choice shows up
Categories in which the number is the first filter
Two ways in
Search by the number, not by the word
The material is part of the specification on every item page and the search reads it, so a comparison takes a minute instead of a round of enquiries. And if you supply certified stock: buyers arrive here with the number already in hand, and a listing costs nothing until it sells.