Stainless steel for machined parts is usually one of four austenitic grades from EN 10088-3: 1.4301 (AISI 304), 1.4404 (AISI 316L), 1.4571 (AISI 316Ti) and the free-machining 1.4305 (AISI 303). They trade corrosion resistance, weldability and machinability against each other, and each EN grade is a close equivalent of its AISI counterpart, not an identical one.
Which stainless steels are used for machined parts?
Bar stock for turned and milled parts is delivered to EN 10088-3, the European standard for stainless steel bars, rods and sections for general purposes. The grade list itself is EN 10088-1. The current editions are EN 10088-3:2023 and EN 10088-1:2023, which replaced the 2014 editions. DIN Media lists a draft revision of part 3, planned for publication in December 2026; its summary names a composition change only for the ferritic grade 1.4106. Status as of 2026-10-30.
Table 1. Austenitic stainless steels common in machined parts, limits in mass %
| EN number | EN name | AISI / UNS | Cr | Ni | Other | Where it fits |
|---|---|---|---|---|---|---|
| 1.4301 | X5CrNi18-10 | 304 / S30400 | 17.5–19.5 | 8.0–10.5 | C max 0.07 | General purpose, no heavy chloride load |
| 1.4305 | X8CrNiS18-9 | 303 / S30300 | 17.0–19.0 | 8.0–10.0 | S 0.15–0.35 | Turned parts in volume, no welding |
| 1.4404 | X2CrNiMo17-12-2 | 316L / S31603 | 16.5–18.5 | 10.0–13.0 | Mo 2.00–3.00, C max 0.030 | Chlorides, food, pharma, welded parts |
| 1.4571 | X6CrNiMoTi17-12-2 | 316Ti / S31635 | 16.5–18.5 | 10.5–13.5 | Mo 2.00–2.50, Ti 5 × C to 0.70 | Welded parts, higher temperature |
Source: EN 10088-3:2023 composition as tabulated by BSSA; AISI and UNS designations from the Deutsche Edelstahlwerke (DEW) data sheets; fit column summarises the same data sheets.
The 2023 edition changed the composition of 1.4404. Data sheets written before 2024 still show the earlier molybdenum range of 2.0 to 2.5 %. 1.4307 (AISI 304L, carbon max 0.030 %) is the low-carbon version of 1.4301.
Is 1.4301 the same as 304, and 1.4404 the same as 316L?
No. The grades belong to the same families, but EN 10088-3 and ASTM A276 set different limits, so a bar can meet one and miss the other.
Table 2. EN 10088-3:2023 against ASTM A276, solution-annealed bar
| Property | 1.4301 | AISI 304 | 1.4404 | AISI 316L |
|---|---|---|---|---|
| Carbon, max % | 0.07 | 0.08 | 0.030 | 0.030 |
| Chromium, % | 17.5–19.5 | 18.0–20.0 | 16.5–18.5 | 16.0–18.0 |
| Molybdenum, % | – | – | 2.00–3.00 | 2.0–3.0 |
| Yield strength Rp0.2, min MPa | 190 | 205 | 200 | 170 |
| Tensile strength Rm, MPa | 500–700 | min 515 | 500–700 | min 485 |
Source: EN 10088-3:2023 as tabulated by BSSA (bars up to 160 mm); ASTM A276 values as quoted in the DEW data sheets 1.4301 and 1.4404.
A bar with 17.7 % chromium and 195 MPa yield strength conforms to 1.4301 but not to 304. A 316L bar at 175 MPa conforms to A276 but not to 1.4404. A drawing that says "304" or "316L" without a standard leaves the receiving inspector to decide which table applies.
How do the grades compare on corrosion, welding and machining?
DEW rates the four grades in its data sheets. The ratings are the producer's, not part of the standard, but they agree with the composition differences.
Table 3. Producer ratings of the four grades
| Grade | Corrosion resistance | Machinability | Weldability | Polishable |
|---|---|---|---|---|
| 1.4305 | medium | very good | poor | no |
| 1.4301 | good | medium | excellent | yes |
| 1.4404 | very good | medium | excellent | yes |
| 1.4571 | very good | medium to poor | excellent | no |
Source: DEW (Deutsche Edelstahlwerke) data sheets Acidur 4301, 4305, 4404, 4571, "Allgemeine Eigenschaften".
Two points matter for design. 1.4301 resists intergranular corrosion only in the delivered condition, not after welding, so DEW recommends the low-carbon 1.4307 where a part is welded without later annealing. 1.4404 and 1.4571 stay resistant after welding. None of 1.4301, 1.4404 or 1.4571 is suitable for seawater: DEW lists a pitting risk in seawater at 20 °C for all three.
How machinable are 1.4301, 1.4404 and 1.4571?
A single machinability figure depends on tooling, coolant and bar condition, so this article gives none. The useful comparison is relative. Outokumpu's machining guideline takes 1.4307 as 100 % (a typical recommendation of 160 m/min with cemented carbide, 25 m/min with high-speed steel). In its chart 1.4301, 1.4307 and 1.4306 sit at the top. The titanium-stabilised 1.4571 and 1.4541 and the molybdenum grades 1.4404 and 1.4401 sit lower, and the richer molybdenum grades 1.4434 and 1.4439 lowest.
Three mechanisms matter:
- Work hardening: all austenitic grades harden under the tool. DEW's data sheet for 1.4301 says the depth of cut must be large enough to cut under the hardened zone.
- Titanium: in 1.4571 titanium forms titanium carbonitrides, which DEW names as the reason for higher tool wear.
- Sulphur: in 1.4305 the 0.15 to 0.35 % sulphur makes chips break short, which is why DEW calls it the classic austenitic grade for automatic machines. The sulphur also limits resistance in acid and chloride media, the grade is not resistant to intergranular corrosion, and it tends to hot cracking when welded.
Machinability-optimised variants exist. Outokumpu's Prodec versions of 1.4307 and 1.4404 plot clearly above 100 % in the guideline chart, and Outokumpu states that corrosion resistance is similar to conventional grades. DEW offers narrowed analyses of its standard grades on request. Whether a variant is acceptable is a design decision, so it belongs in the order, not in the supplier's discretion.
Which grade should you choose?
- 1.4301: parts in natural environments without larger chloride and salt loads. DEW excludes seawater and swimming pools. Use 1.4307 if the part is welded.
- 1.4404: moderate chloride and salt exposure, food and pharmaceutical processing, and welded parts. DEW notes that its molybdenum gives clearly better chloride resistance than 1.4301 and 1.4307.
- 1.4571: corrosion resistance comparable to 1.4404, with higher strength when hot: the minimum Rp0.2 at 300 °C is 145 MPa against 119 MPa for 1.4404 (EN 10088-3, as quoted by DEW). DEW lists it as not polishable, and it wears tools faster.
- 1.4305: turned fittings and pins in mild environments, where nothing is welded and the part is not polished.
Welded stainless assemblies add weld-filler and heat-treatment questions of their own, see welded assemblies.
What should a drawing and an order specify?
Name the grade by EN number with standard and year, for example "1.4404, EN 10088-3:2023", not "V4A" or "316". Then add four items:
- Delivery condition: the EN tables above are for solution-annealed bar (+AT).
- Certificate: an EN 10204 3.1 certificate shows the heat analysis and mechanical values against the named standard, see EN 10204 inspection certificates.
- Machinability variant: state whether a narrowed or machinability-optimised analysis is allowed.
- Surface after machining: passivation and pickling change the surface, not the grade, see surface treatments for machined parts.
Put grade, condition and certificate requirement into the RFQ for CNC turning and CNC milling so the quote covers the same material the drawing calls for.
Frequently asked questions
- Is 1.4301 the same as AISI 304?
- They are equivalent grades, not identical ones. EN 10088-3:2023 allows 17.5 to 19.5 % chromium and at least 190 MPa yield strength for 1.4301 bars. ASTM A276 requires 18.0 to 20.0 % chromium and at least 205 MPa for 304. A certificate has to state which standard the bar was tested to.
- Which stainless steel is easiest to machine?
- 1.4305 (AISI 303). Its sulphur content of 0.15 to 0.35 % makes chips break short, and the producer Deutsche Edelstahlwerke rates its machinability very good, against medium for 1.4301 and 1.4404. The price is lower corrosion resistance, poor weldability and no polishability.
- What is the difference between 1.4404 and 1.4571?
- Both contain about 17 % chromium, 2 to 3 % molybdenum and resist intergranular corrosion after welding. 1.4571 is stabilised with titanium (5 × C up to 0.70 %), which gives higher strength at elevated temperature but increases tool wear. 1.4404 is the low-carbon alternative and the easier one to machine and polish.
- Can 1.4305 be welded?
- Not as a rule. Deutsche Edelstahlwerke advises against welding it because of hot cracking, with friction welding as the exception. Where a part is welded, use 1.4301, 1.4307 or 1.4404 instead.
- Is a machined stainless steel part allowed to be magnetic?
- Slightly, yes. Austenitic grades such as 1.4301 and 1.4404 can be weakly magnetic, and cold deformation during forming or machining raises the effect. A magnet is not a grade test. Check the material certificate or run a positive material identification.
Sources
- BS EN 10088-3:2023, stainless steel bars, rods and sections, supersedes the 2014 edition (BSI)
- EN 10088-3:2023, status and revision in development (Genorma)
- DIN EN 10088-3:2026-12, draft, planned publication 2026-12 (DIN Media)
- DIN EN 10088-3:2014-12, withdrawn, replaced by DIN EN 10088-3:2024-04 (DIN Media)
- EN 10088-1:2023, list of stainless steels, replaces the 2014 edition (Genorma)
- Chemical composition of stainless steel long products to BS EN 10088-3 (2023 tables, BSSA)
- Mechanical properties of austenitic long products to BS EN 10088-3:2023 (BSSA)
- Acidur 4301, 1.4301 data sheet, 27.11.2015 (Deutsche Edelstahlwerke)
- Acidur 4305, 1.4305 data sheet, 28.11.2016 (Deutsche Edelstahlwerke)
- Acidur 4404, 1.4404 data sheet, 08.06.2016 (Deutsche Edelstahlwerke)
- Acidur 4571, 1.4571 data sheet, 02.12.2015 (Deutsche Edelstahlwerke)
- Standard austenitic stainless steel grades, machining guideline, March 2014 (Outokumpu)
- Prodec, stainless steels for superior machinability (Outokumpu)
- Steel grades, properties and global standards, EN and ASTM designations (Outokumpu)
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