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Stainless steel 303
303 is an austenitic 18-8 stainless steel with added sulfur, 0.15% minimum, to break chips. It machines at about 78% of the 1212 rating, far better than 304 at 45%, which makes it the default for turned stainless parts on screw machines and CNC lathes. The tradeoff is lower corrosion resistance, poor weldability and poor cold formability.
- UNS
- S30300
- ASTM
- A582 Type 303
- EN 10088-3
- 1.4305 (X8CrNiS18-9)
- JIS
- SUS303
How does it compare?
Typical room-temperature values for 303 SS, against all 48 materials in the library.
- Tensile strength
- 620 MPa84th pct
- Yield strength
- 240 MPa30th pct
- Density
- 8 g/cm³89th pct
- Elongation
- 50 %70th pct
- Relative cost
- $$$$$
Bars are relative to the strongest, densest or hottest material in the SSG library. Percentile vs all 48 materials.
- Density
- 8 g/cm³ · 0.2890 lb/in³
- Tensile strength
- 620 MPa · 89.9 ksi
- Yield strength
- 240 MPa · 34.8 ksi
- Elongation
- 50%
- Elastic modulus
- 193 GPa · 28.0 Msi
- Hardness
- 160 HB
- Melting point
- 1400 °C · 2552 °F
- Thermal conductivity
- 16.2 W/m·K
- Machinability
- 78% of 1212 steel
When should you use 303 SS?
Strengths
- About 78% machinability versus 45% for 304
- Short chips suit screw machines and unattended Swiss turning
- Good corrosion resistance indoors and in fresh water
- Non-magnetic when annealed
Watch for
- Sulfide inclusions lower corrosion resistance, especially in chlorides and acids
- Poor weldability; welds hot-crack
- Not for cold heading, crimping or tight bending
- Needs a passivation process suited to free-machining grades to avoid flash attack
Typical parts
- Shafts, pins and bushings
- Valve stems and components
- Instrument and aircraft fittings
- Medical and lab equipment parts (non-implant)
- Food equipment hardware
- Electronic standoffs and nuts
How 303 SS is made into parts
Cost, finishes and design rules for each process in this material.
Screw machining in 303 SSTurned pins, fittings, shafts, and bushings made from bar stock on multi-spindle and Swiss screw machines at volume.
CNC machining in 303 SSCNC milling, turning, and production sawing from bar, plate, castings, and forgings, from prototype to production.
Offshore sourcing in 303 SSParts made by vetted overseas manufacturers, with landed-cost analysis, quality control, and logistics managed.
What does a part in 303 SS cost?
A representative part, screw machining. Raw material at about $6.50/kg is one line of it; process time and tooling usually matter more.
Turned shaft · Screw machining
Order total $22,503
- Tooling
- $1,800
- one-time, spread over the order
- Piece price
- $1.95
- before setup + tooling
- Lead time
- 4–6 weeks
- to first production
Size
Drag a row to adjust · click to type
Major diameter16.016.0 mm
Overall length60.060.0 mm
Step diameter10.010.0 mm
Quantity
Price per part falls as volume rises
Exact quantity1000010000 pcs
Material
Design checks pass
Open in builderBudgetary estimate for a representative part. Firm quotes come from principals after drawing review.
303 SS questions
303 vs 304 stainless?
303 machines about 70% faster (78% vs 45% machinability) thanks to added sulfur. 304 has better corrosion resistance, welds well and forms cold. Use 303 for turned parts in mild environments; use 304 when parts are welded, bent or exposed to chlorides.
Is 303 stainless magnetic?
No, not in the annealed condition. Heavy cold work can make it slightly magnetic.
Can 303 stainless be welded?
It is not recommended. The sulfur causes hot cracking in the weld. If a part must be welded, switch to 304 or 304L and accept slower machining.
Does 303 stainless need passivation?
It is recommended after machining to remove embedded iron. Use a nitric acid with sodium dichromate or a citric acid process validated for free-machining grades under ASTM A967 or AMS 2700, to avoid flash attack on the sulfide inclusions.
Similar materials
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