Stainless Steel 303Se
UNS S30323 · ASTM A582 · JIS SUS303Se · GB Y1Cr18Ni9Se
303Se is the selenium-bearing free-machining version of 304, covered by UNS S30323 / ASTM A582 (X8CrNiS18-9, SUS303Se), with selenide inclusions replacing the sulphides used in 303.
Values for the Cold Drawn condition
303Se tempers and conditions
303Se is supplied in 3 conditions, soft to hard. Cold Drawn is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
solution annealed (softened) bar | Pick when maximum ductility, lowest hardness for secondary cold forming/heading, or fully non-magnetic behaviour is required. | 240 | 620 | 50 | 160 HB | — |
Cold DrawnDefault cold-drawn / turned-ground-polished bar (standard stock) | Standard commercial screw-machine stock: straight, close-tolerance bar with higher strength and better chip control than annealed. | 415 | 690 | 35 | 228 HB | — |
heavily cold-drawn bar (high-strength draw) | Choose when higher yield strength and wear resistance are needed in small diameters and forming/welding is not required. | 620 | 860 | 16 | 27 HRC | — |
What is 303Se?
303Se is the selenium-bearing free-machining version of 304, covered by UNS S30323 / ASTM A582 (X8CrNiS18-9, SUS303Se), with selenide inclusions replacing the sulphides used in 303. It is chosen for high-volume turned and cold-headed bar parts, rating 85 for machinability and producing smoother threads and knurls than 303; annealed bar gives 415 MPa yield, 690 MPa tensile, 35 % elongation and 228 HB (98 HRB). The inclusions cut corrosion resistance (score 55) and make the grade effectively unweldable, and formability is limited (score 40) — use 303 for lower cost or 304 where welding or better corrosion resistance is needed. 303Se has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,400°C (2,552 °F). 303Se has a yield strength of 415 MPa (60.2 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 62% of stainless steel grades. Elongation at break is 35% and the elastic modulus is 193 GPa (28 Msi).
What is 303Se used for?
- Machined fittings
- Threaded shafts
- Cold-headed screws and studs
- Valve stems
- Instrument spindles
- Electrical connector bodies
- Bushings and nozzles
Advantages
- Easy to machine — 85/100, better than 100% of stainless steel grades
Limitations
- Difficult to weld — 22/100, worse than 94% of stainless steel grades
303Se properties
Typical room-temperature values for 303Se-Cold Drawn; bars are the position among stainless steel grades.
Physical3
303Se has a density of 7.9 g/cm³ (0.285 lb/in³), heavier than 68% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
303Se has a yield strength of 415 MPa (60.2 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 62% of stainless steel grades. Elongation at break is 35% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
303Se is rated for continuous service to 760°C (1,400 °F). It conducts heat at 16.2 W/m·K (9.36 BTU/hr·ft·°F), better than 64% of stainless steel grades. Thermal expansion is 17.3 µm/m·K (9.61 µin/in·°F).
Electrical3
303Se conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 71% of stainless steel grades.
Sustainability4
Producing a kilogram of 303Se takes about 54 MJ of energy and emits 4.8 kg of CO₂ — less than 59% of stainless steel grades. Typical recycled content is 55%.
Manufacturability7
303Se's machinability is excellent (85/100, better than 100% of stainless steel grades); weldability poor (22/100); formability fair (40/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. 303Se is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 303Se
Is 303Se easy to machine?
Best-in-class austenitic machining — run 20–30% faster than 304, keep positive rake and sharp tools, coolant-rich; selenides give smoother finish and better threads/knurls than sulphide 303.
Can 303Se be welded?
Not recommended: selenium promotes severe hot cracking and porosity; if unavoidable, use 308L/309 filler, minimum heat input, no filler-free autogenous welds, and expect reduced joint corrosion resistance.
Can 303Se be formed, bent or molded?
Cold heading, thread rolling and knurling are acceptable (better than 303-S), but avoid severe bending or deep transverse forming because inclusions cause directional ductility loss; hot work 1150–1260 °C then anneal ~1040 °C and quench.
Manufacturability
The process limits FabDigit applies to 303Se. Every 303Se part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Excellent85 / 100 |
|---|---|
| ISO material group | M.1 |
| Cutting speed (rough / finish) | 150 / 180 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1.5 mm |
| Drill depth limit | 4× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
303Se chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | ≤ 0.15 | 0.08 |
| Cr | 17 – 19 | 18 |
| Ni | 8 – 10 | 9 |
| Mn | ≤ 2 | 1.5 |
| Si | ≤ 1 | 0.6 |
| Semin; free-machining addition | ≥ 0.15 | 0.2 |
| P | ≤ 0.2 | 0.04 |
| S | ≤ 0.06 | 0.02 |
| Fe | balance |
What surface finishes work on 303Se?
Passivate per ASTM A967 (nitric or citric) after machining to remove smeared inclusions; takes a good mechanical polish, but electroplating/electropolishing gives patchy results around selenide stringers; no anodizing.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
Organic Coating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 303Se in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S30323
- ASTM
- A582
- GB (China)
- Y1Cr18Ni9Se
- JIS
- SUS303Se
- Similar grades
- X8CrNiS18-9
How much does 303Se cost?
303Se is a standard-cost stainless steel ($$), cheaper than about 60% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
303Se — frequently asked
What is 303Se used for?
303Se is typically used for machined fittings, threaded shafts, cold-headed screws and studs, valve stems, instrument spindles and electrical connector bodies. In short: selenium machining stainless.
What is the yield strength of 303Se?
303Se has a typical yield strength of 415 MPa (60.2 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 62% of stainless steel grades. Strength varies by condition: see the 3 listed tempers.
Is 303Se easy to machine?
Yes — machinability is rated excellent (85/100, better than 100% of stainless steel grades). Best-in-class austenitic machining — run 20–30% faster than 304, keep positive rake and sharp tools, coolant-rich; selenides give smoother finish and better threads/knurls than sulphide 303.
Can 303Se be welded?
Not readily — weldability is rated poor (22/100). Not recommended: selenium promotes severe hot cracking and porosity; if unavoidable, use 308L/309 filler, minimum heat input, no filler-free autogenous welds, and expect reduced joint corrosion resistance.
What surface finishes work on 303Se?
Passivate per ASTM A967 (nitric or citric) after machining to remove smeared inclusions; takes a good mechanical polish, but electroplating/electropolishing gives patchy results around selenide stringers; no anodizing.
Can 303Se be formed, bent or molded?
Cold heading, thread rolling and knurling are acceptable (better than 303-S), but avoid severe bending or deep transverse forming because inclusions cause directional ductility loss; hot work 1150–1260 °C then anneal ~1040 °C and quench.
What is the maximum service temperature of 303Se?
303Se is rated for continuous use to about 760°C (1,400 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 303Se cost?
303Se is a standard-cost stainless steel ($$), cheaper than about 60% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in 303Se?
Yes — 303Se is available for CNC machining; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A582/A582M — Free-Machining Stainless Steel Bars — ASTM International (2021)
- SAE J405 / UNS S30323 chemical composition — SAE International (2013)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook — machinability ratings of stainless steels — Industrial Press (2020)
- GB/T 1220 (Y1Cr18Ni9Se) — SAC (2007)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.