What is 303 Stainless Steel?

Stainless steel 303 is the most readily machineable austenitic stainless steel.

The addition of Sulphur in the steel composition improves machining but also causes a decrease in the corrosive resistance and a slight reduction of the toughness when compared to 304.

303 Stainless Steel Machinability

Cutting edges should be kept sharp as dull edges cause excess work hardening.

Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material.

You may also see 303 referred to as:

• 1.4305 Bar
• BS 303S31
• EN 58M
• AMS 5640
• AMS QQ-S-764B Cond A
• Australia – A S 2837-1986-303
• Germany - W.Nr 1.4305 X10CrNiS 18 9
• GB - BS970 Part3 1991 303S31, BS970 1955 EN58M
• Japan - JIS G4303 SuS 303
• USA - ASTM A582/582M-95b 303, SAE 30303 AISI 303, UNS S30300
• S31

Main attributes

• Excellent machinability
• Non-seizing and non-galling properties make it ideal for moving parts
• Good mechanical resistant properties
• Good corrosion resistance in mild environments (less corrosion resistance than 304)
• Not suitable for moist/marine environments
• Non-magnetic
• Good resistance to oxidisation when intermittently exposed to temperatures of up to 760°C and continuous exposure to 870°C although not recommended for continuous use at 425-860°C as sensitive to carbide precipitation
• Poor weldability

Finishing & treatments

303 stainless can’t be hardened by heat treatment. Solution treatment or annealing can be done by rapid cooling after heating to 1010-1120°C.

See our Finishing Processes page for further information on services that we can facilitate.

UK stock sizes

Here are the standard stock sizes/colours for 303 in the UK. Please note we do not supply stock material, the information provided is purely for design and research purposes.

Example Stainless 303 Stock Sizes

Stock sizes will vary depending on supplier. Please get in contact to discuss further.

303 Round Bar

• 3mm / 1/8" to 177mm / 7"

303 Hexagon Bar

• 0.3125" to 2.5"

Common Applications

• Shafts & axles
• Bearings & bushings
• Gears & driveshafts
• Food processing machinery & equipment
• Valves & pumps
• Fasteners & hardware
• Aircraft structures & fittings
• Springs

Technical properties

Physical properties

Mechanical properties

Thermal properties

Typical chemical composition (weight %)