Stainless Steel Grade 303Se (UNS S30323)

Stainless Steel Grade 303Se (UNSS30323)

Grade 303 represents the optimum in machinability among the austenitic stainless steels. It is primarily used when production involves extensive machining in automatic screw machines. Machinability Rating (compared to B1212) is approximately 78%.

Stainless steel Motor Control Systems and Generator

303 is also available as a "Ugima" Improved Machinability grade, with machinability even higher than that of the standard 303.

The sulphur addition which is responsible for theimprovedmachiningandgalling characteristics of Grade 303 lowers its corrosion resistance to below that of Grade 304. As for other austenitic grades the structure gives 303 excellent toughness, although the sulphur in 303 reduces its toughness slightly.

Grade 303Se (UNS S30323) has a selenium rather than sulphur addition, improving the hot and cold forming characteristics over those of 303 and providing a smoother machined surface finish. The machinability rate is also slightly reduced compared to 303. Grade 303Se is not readily available in Australia.

Stainless Steel Grade 303Se Corrosion Resistance 

Good resistance to mildly corrosive atmospheres, but significantly less than Grade 304 due to the sulphur addition; the sulphide inclusions act as pit initiation sites. Grade 303 should not be exposed to marine or other similar environments, as these will result in rapid pitting corrosion. Because the sulphide inclusions in 303 are primarily aligned along the rolling direction the corrosion resistance is particularly reduced in cross-sections.

Grade 303, like other common austenitic stainless steels, is subject to stress corrosion racking in chloride containing environments above about 50°C.

Consult Atlas Technical Assistance for specific environmental recommendations.

Stainless Steel Grade 303Se Heat Resistance 

Good oxidation resistance in intermittent service to 760°C and in continuous service to 70°C. Continuous use in the 425-860°C range is not usually recommended due to carbide precipitation - 303 usually does not have a low carbon content so is susceptible to sensitisation, which can lead to intergranular corrosion.

Stainless Steel Grade 303Se Fabrication 

As well as reducing the corrosion resistance, the sulphur additions in 303 also result in poor weldability and reduced formability compared to Grade 304. Sharp bends should not be attempted in 303. A practical compromise alternative may be a 304 Ugima Improved Machinability grade - this does not machine as readily as 303, but does offer better formability (as well as excellent weldability and
significantly better corrosion resistance).

Stainless Steel Grade 303Se Heat Treatment 

 Solution Treatment (Annealing) Heat to 1010-1120°C and grade cannot be hardened treatment.

Stainless Steel Grade 303Se Welding 

Not generally recommended but, if unavoidable use Grade 308L or 309 electrodes. AS 1554.6 does not pre-qualify welding of must be annealed for maximum resistance, but even then poor mechanical and corrosion properties will result.

Stainless Steel Grade 303Se Machining 

A "Ugima" improved machinability version of grade 303 is available in many bar products. This machines significantly standard 303, giving very high machining rates and lower tool wear in many operations.

For ultra-high machining rates there available special grade variants such as Ugima 303UX. This includes copper to work hardening rate, in addition high sulphur and Improved Machinability steel making practices.

Stainless Steel Grade 303Se Typical Applications 

Nuts and bolts. Bushings. Shafts. Electrical switchgear components. Gears. In general any component that is heavily machined and where the corrosion resistance properties of 303 are viable.

Stainless Steel Grade 303Se Specified Properties

These properties are specified for long product (bar) in ASTM A582M. Similar but not necessarily identical properties are specified for other products such as wire and forgings in their respective specifications. Grade 303 is not produced in flat rolled products.