“Stainless steel” on a drawing is not enough — the grades differ considerably in corrosion resistance, machinability and price. Here are the grades most often used for turned and milled parts, each with its European material number to EN 10088 and its American AISI designation.
The common grades at a glance
| Material | AISI | Strengths | Limits |
|---|---|---|---|
| 1.4301 (X5CrNi18-10) | 304 | the standard, easy to weld, good resistance | not for chloride environments |
| 1.4307 (X2CrNi18-9) | 304L | like 304, low carbon: better for thicker welded parts | not for chloride environments, slightly lower strength |
| 1.4305 (X8CrNiS18-9) | 303 | much better machinability | less resistant, only partly weldable |
| 1.4404 (X2CrNiMo17-12-2) | 316L | with molybdenum: resistant to chlorides | more expensive, harder to machine than 304 |
| 1.4571 (X6CrNiMoTi17-12-2) | 316Ti | like 316L, titanium-stabilised | harder to machine |
| 1.4462 (X2CrNiMoN22-5-3) | duplex | high strength, very good resistance | tough, demanding to machine |
1.4301 (AISI 304): the standard stainless steel
1.4301 (steel name X5CrNi18-10) is the most widely used stainless steel. It is an austenitic chromium-nickel steel with around 18 % chromium and 8 to 10.5 % nickel, but no molybdenum. In the US and UK it is known as AISI 304; German workshops often call it “V2A”.It is easy to weld, easy to form and reliably resistant in dry or normal environments — the right choice for most parts in mechanical engineering, indoor applications and housings. Its weak point is chlorides (salt, seawater, chlorinated cleaning agents): there, pitting and crevice corrosion are a risk.
In machining, 1.4301 is tough and work-hardens under the tool — perfectly feasible, but slower than free-cutting steel or 1.4305 (303).
1.4307 (AISI 304L): 1.4301 with low carbon
1.4307 (X2CrNi18-9) is the low-carbon variant of 1.4301. EN 10088 limits carbon to a maximum of 0.030 %, while 1.4301 may contain up to 0.07 %. Chromium (around 18 %) and nickel are in the same range as in 1.4301, and 1.4307 contains no molybdenum either. As with 316L, the “L” in 304L stands for “low carbon”.The advantage shows in welding: if the steel next to the weld stays hot for longer, carbon can combine with chromium to form carbides at the grain boundaries. The adjacent microstructure then lacks chromium, and intergranular corrosion becomes a risk. With low carbon this tendency is considerably smaller — which matters above all for thicker cross-sections that cool more slowly after welding. In return, 1.4307 has slightly lower strength than 1.4301.
Corrosion resistance and machinability are similar to 1.4301: without molybdenum it is not suitable for chloride environments, and without added sulphur it is much harder to machine than 1.4305 (303). In practice, material is often supplied dual-certified as 1.4301/1.4307 (304/304L) and then meets the requirements of both grades. If the drawing explicitly calls for 1.4307, the material certificate should state this grade.
1.4305 (AISI 303): the free-machining stainless steel
1.4305 (X8CrNiS18-9) has almost the same basic composition as 1.4301, but additionally contains 0.15 to 0.35 % sulphur. The sulphur forms manganese sulphides that break the chip: short chips, fewer built-up edges, higher cutting data. For turned parts in series, this is the main advantage of the grade.The price: the sulphides are weak points for corrosion, so 1.4305 is less resistant than 1.4301. Welding is only possible to a limited extent because of the risk of hot cracking. 1.4305 is well suited to turned parts that are neither welded nor exposed to strong corrosion — axles, pins, bushings and fittings for indoor use.
1.4404 (AISI 316L): resistant to chlorides
1.4404 (X2CrNiMo17-12-2) is alloyed with 2 to 2.5 % molybdenum. The molybdenum makes it considerably more resistant to pitting caused by chlorides. Carbon is limited to a maximum of 0.03 % (the “L” in 316L stands for “low carbon”) — so it remains resistant to intergranular corrosion even after welding.1.4404 belongs wherever salt, chlorides or aggressive cleaning agents are involved: food and pharmaceutical engineering, swimming pools, coastal areas and shipbuilding. It is more expensive than 1.4301 and somewhat tougher to machine.
1.4571 (AISI 316Ti): the titanium-stabilised alternative
1.4571 (X6CrNiMoTi17-12-2) is chemically closely related to 1.4404 but protects itself against intergranular corrosion in a different way: titanium binds the carbon. In Germany, 1.4571 has traditionally been very common; in many applications 1.4404 and 1.4571 are equivalent.For machining the difference matters: the hard titanium carbides cause more tool wear. If the drawing allows both grades, that makes production easier — but whether one grade may replace the other is always decided by your specification.
1.4462 (duplex 2205): strong and highly resistant
1.4462 (X2CrNiMoN22-5-3) is a duplex steel: its microstructure consists of roughly equal parts ferrite and austenite. With around 22 % chromium, 3 % molybdenum and added nitrogen, it is more resistant to pitting and stress corrosion cracking than 1.4404 (316L), and its yield strength is roughly twice that of the austenitic grades.Duplex is the choice when strength is required in addition to corrosion resistance, for example for pump, valve and offshore parts. It is tough and demanding to machine — and, unlike the austenitic grades, magnetic.
Corrosion resistance in numbers: the PREN
A rough guide to pitting resistance is the pitting resistance equivalent number PREN = % Cr + 3.3 × % Mo + 16 × % N. Depending on the actual composition it is around 18 to 20 for 1.4301 (304) and 1.4307 (304L), around 24 to 26 for 1.4404 (316L) and 1.4571 (316Ti), and around 34 to 36 for duplex 1.4462. 1.4305 (303) is close to 1.4301 on paper, but less resistant in practice because of the sulphides.
The number is no substitute for choosing a material for a specific application — it only shows the ranking.
What this means for machining
Austenitic stainless steels work-harden during machining, are tough and conduct heat poorly. They need sharp tools, a steady cut and adapted cutting data — machining takes longer than with structural steel. In our costing we therefore apply a cycle-time surcharge for stainless steel compared with aluminium.
Our tip: always state the material number and check whether a free-machining grade meets the requirements. More about our stainless steel turned parts.
Frequently asked questions
1.4305 vs 1.4404: what is the difference?
Both are austenitic chromium-nickel steels, but made for opposite goals. 1.4305 (AISI 303) contains sulphur, which makes it much easier to machine, but less corrosion-resistant and only partly weldable. 1.4404 (AISI 316L) contains 2 to 2.5 % molybdenum and little carbon: it resists chlorides and is easy to weld, but is harder to machine and more expensive. Rule of thumb: 1.4305 for turned parts in dry environments, 1.4404 as soon as salt, chlorides, food contact or welding are involved.
1.4301 vs 1.4305: which is better?
That depends on the part. Both have the same basic composition with around 18 % chromium and 8 to 10 % nickel. 1.4305 (303) additionally contains sulphur: it breaks the chip and makes machining faster and therefore cheaper. 1.4301 (304), on the other hand, is more corrosion-resistant and easy to weld. For a turned part that is not welded and does not operate in a corrosive environment, 1.4305 is usually the more economical choice.
1.4301 vs 1.4404: when do I need 316L?
As soon as chlorides are involved: salt, seawater, road salt, chlorinated cleaning agents and disinfectants. 1.4404 (316L) contains 2 to 2.5 % molybdenum and is therefore considerably more resistant to pitting than 1.4301 (304). In dry or normal environments 1.4301 is sufficient — and cheaper.
What is the difference between 304 and 304L (1.4301 vs 1.4307)?
The carbon content. 1.4307 (AISI 304L) is the low-carbon variant of 1.4301 (AISI 304): EN 10088 allows a maximum of 0.030 % carbon, compared with up to 0.07 % for 1.4301. Chromium and nickel are in the same range, and neither contains molybdenum. The low carbon reduces the tendency to intergranular corrosion after welding — which matters above all for thicker cross-sections. Corrosion resistance and machinability are otherwise similar; 1.4307 has slightly lower strength. Material is often supplied dual-certified as 1.4301/1.4307 and then meets both grades.
304L vs 316L (1.4307 vs 1.4404): which stainless steel?
The environment decides. Both are low-carbon (maximum 0.030 % carbon) and therefore well suited to welded parts. 1.4404 (AISI 316L) additionally contains 2 to 2.5 % molybdenum, which makes it considerably more resistant to pitting caused by chlorides: salt, seawater, chlorinated cleaning agents. 1.4307 (AISI 304L) contains no molybdenum and is sufficient in dry or normal environments; it is cheaper and somewhat easier to machine. Rule of thumb: 1.4307 for welded parts without chlorides, 1.4404 as soon as salt, chlorides or aggressive cleaning agents are involved.
Is 1.4404 the same as 316L?
Largely, yes. 1.4404 is the European material number to EN 10088; AISI 316L is the American designation for a molybdenum-alloyed chromium-nickel steel with low carbon. Likewise, 1.4301 corresponds to 304 and 1.4305 to 303. However, the limits in the standards are not identical for every element — where it matters, the drawing should name the standard to which the material is supplied.
What is the difference between 1.4404 and 1.4571?
Both are molybdenum-alloyed grades (316 family). 1.4404 (316L) protects itself against intergranular corrosion after welding through very low carbon, 1.4571 (316Ti) through added titanium. In many applications they are interchangeable; 1.4571 is somewhat harder to machine because of the titanium carbides. Whether one grade may replace the other is decided by your specification.
Is 1.4301 (304) stainless steel magnetic?
In the solution-annealed condition, the austenitic grades 1.4301, 1.4307, 1.4305, 1.4404 and 1.4571 are practically non-magnetic. Cold working, for example in cold-drawn bar, can make them slightly magnetic — this is not a sign of a wrong grade. Duplex 1.4462, by contrast, is magnetic because of its ferrite content.
What do V2A and V4A mean?
They are old German trade names that are still common in workshops. V2A stands for chromium-nickel steels without molybdenum such as 1.4301 (304) and 1.4307 (304L), V4A for the molybdenum-alloyed grades such as 1.4401, 1.4404 and 1.4571 (316, 316L, 316Ti). A drawing should state the material number instead — only that defines the grade unambiguously.