1.4305 steel (1.4305): properties, composition, equivalents
1.4305 (X8CrNiS18-9) is the EN free-machining 303: 18 % Cr, 8–10 % Ni, 0.15–0.35 % S. 190 MPa yield, 500–750 MPa tensile, machinability ~80 % of 1.4301. Data, limits and the 303/SUS303 equivalence.
What is 1.4305?
1.4305 (X8CrNiS18-9) is 18/8 stainless deliberately made dirty: 0.15–0.35 % sulphur forms manganese-sulphide inclusions that break chips and lubricate the tool, giving roughly 80 % of the machinability of free-cutting carbon steel and about double that of 1.4301. It is the grade of every automatic lathe shop that turns stainless fittings, nuts, shafts, valve stems and pins.
The sulphides cost something: pitting resistance drops (PREN nominally the same, but sulphide sites initiate attack), weldability is poor (hot-cracking and porosity), and transverse ductility is low, so 1.4305 is supplied only as bar, wire and hexagons — never as sheet. It is used for parts that see mild environments (indoor, fresh water, food-grade with cleaning) and no welding.
AISI 303, JIS SUS303 and GB Y12Cr18Ni9 are the same steel; the EN specification is slightly tighter on carbon (0.10 vs 0.15 %). For chloride service the free-machining 316 variant is 1.4570 (316F).
1.4305 chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | ≤ 0.1 | |
| Si | ≤ 1 | |
| Mn | ≤ 2 | |
| P | ≤ 0.045 | |
| S | 0.15 – 0.35 | manganese sulphide inclusions break the chip |
| N | ≤ 0.11 | |
| Cr | 17 – 19 | |
| Ni | 8 – 10 | |
| Cu | ≤ 1 |
EN 10088-3:2014 Table 3. Compared with 1.4301: higher C (0.10) and, above all, 0.15–0.35 % S — which is why corrosion resistance and weldability are lower.
1.4305 mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| Bar ≤ 160 mm, +AT solution annealed | ≥ 190 (≥ 27.6) | 500–750 (72.5–108.8) | 35 | ≤ 230 HB |
| Bright bar ≤ 16 mm, cold-drawn (+C) | ≥ 400 (typ.) (≥ 58.0 (typ.)) | 600–850 (typ.) (87.0–123.3 (typ.)) | 20 | ≈ 190–260 HB |
| Wire (EN 10088-3), +AT | ≥ 190 (≥ 27.6) | 500–750 (72.5–108.8) | 35 | — |
Solution annealed 1010–1110 °C. Cold-drawn values are typical supplier data, not standard minima. Elongation is lower than 1.4301 because of sulphide stringers; transverse ductility is markedly reduced.
1.4305 equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| 303 | AISI / SAE | Identical | UNS S30300 (ASTM A582): C ≤ 0.15, Cr 17–19, Ni 8–10, S ≥ 0.15, Mo ≤ 0.60. 1.4305 caps C at 0.10 and S at 0.35; dual-certified. |
| 303S31 | BS (superseded British) | Identical | BS 970 303S31: C ≤ 0.12, S 0.15–0.35. |
| Y12Cr18Ni9 | GB/T (China) | Identical | GB/T 1220 Y12Cr18Ni9 (formerly Y1Cr18Ni9): free-machining 18/8 with S 0.15–0.35. |
| SUS303 | JIS (Japan) | Identical | JIS G4303 SUS303: C ≤ 0.15, Cr 17–19, Ni 8–10, S ≥ 0.15. |
| 1.4570 | EN (European) | Near | X6CrMoNiS17-12-2 — the free-machining 316 (316F) for chloride service. |
| 1.4301 | EN (European) | Functional | Non-free-machining base grade: better corrosion resistance and weldability, poorer machinability. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for 1.4305 →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| X10CrNiS18 9 | DIN 17440 (withdrawn) | Same number 1.4305. |
| 303S31 / 303S21 | BS 970 | 303S31 is the closer match. |
| Z8CNF18-09 | NF A 35-574 |
Product forms and tolerance standards
Product forms: round, hexagon and square bar (bright drawn, peeled, ground), wire and profiles, forgings (limited), not produced as sheet or plate.
Dimensional tolerances: bright bar: EN 10278 (h9, h10, h11); hot-rolled bar: EN 10060.
Key property values
1.4305 yield strength
Rp0.2 ≥ 190 MPa (27.6 ksi) solution annealed; cold-drawn bright bar typically 400–500 MPa.
1.4305 tensile strength
500–750 MPa annealed; 600–850 MPa cold-drawn in small diameters.
1.4305 hardness
Max 230 HB annealed (≈ 95 HRB); cold-drawn bar 190–260 HB. Not hardenable by heat treatment.
Machinability
Index ≈ 75–80 % relative to 1.0715 (11SMn30) versus ≈ 45 % for 1.4301. Recommended: carbide, 100–160 m/min turning, generous coolant; chips break short.
Corrosion resistance
Reduced relative to 1.4301: suitable for indoor, dry and mildly humid atmospheres, fresh water and food contact with regular cleaning. Not for chlorides, marine air or acids. Passivation (nitric acid) after machining is recommended.
Physical properties
Density 7.9 g/cm³, E = 200 GPa, expansion 16 × 10⁻⁶/K, non-magnetic annealed (slightly magnetic after cold drawing).
Weldability
Not recommended. High sulphur causes hot cracking and porosity; if unavoidable, use 19 9 L / ER308L or 312 filler, low heat input, short welds, and accept reduced corrosion resistance. Design machined 1.4305 parts for mechanical joining (threads, press fits).
Machining, forming and heat treatment
This is what 1.4305 is for: automatic lathes, CNC turning, drilling, tapping and threading. Use sharp positive geometry, higher speeds than for 1.4301 (100–160 m/min carbide), and avoid dwelling. Threads and knurls come out clean; surface finish after turning is excellent. Cold forming is poor (sulphides); hot forging 1150–950 °C followed by solution anneal is possible but rarely economic.
Typical applications
- Turned fittings, adapters, nipples and unions
- Nuts, bolts and threaded studs (non-structural)
- Valve stems, spindles and shafts for pumps (mild media)
- Electrical and instrument components, pins, bushings
- Gears and worm shafts in food and packaging machinery (dry)
- Dental and laboratory hardware (non-implant)
Frequently asked questions
Is 1.4305 the same as 303?
Yes. 1.4305 (EN 10088-3) and AISI 303 (UNS S30300) are the sulphur-bearing free-machining versions of 18/8; the EN grade limits carbon to 0.10 % (303: 0.15 %) and sulphur to 0.35 %. Bar is routinely dual-certified.
Can 1.4305 be welded?
Only with difficulty. The 0.15–0.35 % sulphur causes hot cracks and porosity. For welded assemblies use 1.4301 or 1.4307 and accept slower machining.
Is 1.4305 food-safe?
It is used for food-machinery parts that are cleaned regularly and not exposed to chlorides or acidic media for long periods. For product-contact vessels and piping, 1.4301 or 1.4404 are the normal choices.
Why is 1.4305 slightly magnetic?
Cold drawing of bar produces a small amount of strain-induced martensite. Annealed 1.4305 is non-magnetic like other austenitic grades.
Related grades
Verified against EN 10088-3:2014; EN 10088-3:2014 Tables 3 and 13; ASTM A582/A582M (comparison). Last checked: September 2026.