Stainless Steel Alloy 303

Stainless Steel Alloy 303 is mainly used when the application will require extensive machining. There is also a 303 grade called “Ugima” which provides a machinability considerably higher than the standard 303.

It is the addition of sulphur to the alloy which increases the machinability of the Ugima 303 alloy. However, the addition of sulphur also lowers the toughness of the steel and makes it more susceptible to corrosion.

There is a steel alloy 303 which has selenium. Designated as 303Se, the addition of selenium creates an alloy with hot and cold forming ability this is an improvement over regular stainless steel alloy 303. While 303Se will provide a smoother finished surface, its machinability is lowered.

Alternative stainless steel alloys that are possible substitutions for stainless steel alloy 303 are 304, 316 and 416. Better formability or corrosion resistance, with lower or higher machinability can be obtained by using one of these alternative alloys.

While 303 has a good resistance to corrosion, there are some limits to the types of corrosive atmospheres that it should be exposed to. Extensive pitting can occur with marine or saltwater exposure. Environments containing chloride are likely to result in cracking at stress points.

The addition of sulphur to the SST-303 makes it a poor choice for welding or forming. It is not recommended to attempt sharp bends in 303, which is one reason why 304 Ugima is often used instead; it’s not easily machines, but forms and welds better, and has better corrosion resistance.

Hardening by heat treatment is fairly impossible with this grade of stainless steel alloy. Neither does it respond well to welding unless specific electrode grades are used.

Uses for stainless steel alloy 303 include some of the following applications: gears, electrical switchgear components, nuts and bolts, bushings and shafts. For applications requiring heavy machining and fabrication with good corrosion resistance you will find the 303 alloy an acceptable solution.

For more information about the actual chemical composition of Stainless Steel Alloy 303.

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