Differences Between 303 and 303se Stainless Steel

When selecting stainless steel for high-speed machining or precision components, AISI 303 and AISI 303Se are two popular choices. Both grades belong to the Austenitic 18-8 stainless steel family (Cr-Ni steels), offering good strength, non-magnetic behavior, and corrosion resistance.
However, subtle differences in their chemical composition - particularly the use of sulfur (S) in 303 and selenium (Se) in 303Se - lead to distinct variations in machinability, surface finish, and corrosion resistance.

 

What is 303 stainless steel?
303 stainless steel is an austenitic stainless steel known for its excellent machinability, a quality it gains from the addition of sulfur. While this makes it easier to cut and form, it comes at the cost of slightly lower corrosion resistance and toughness compared to grades like 304. It is non-magnetic and cannot be hardened by heat treatment, making it ideal for parts with complex machining needs.

 

What is 303se stainless steel?
303Se stainless steel is an austenitic stainless steel that is a modified version of grade 303. It is a "free-machining" alloy designed for improved machinability due to the addition of selenium, which substitutes for sulfur. This modification also provides better cold-forming properties than 303, and it retains good strength and corrosion resistance.

 

1. Chemical Composition 

303 improves machinability with sulfur (S).303Se achieves similar machinability using selenium (Se), resulting in a cleaner surface and better corrosion resistance.

Element	AISI 303 (%)	AISI 303Se (%)
Carbon (C)	≤ 0.15	≤ 0.15
Manganese (Mn)	≤ 2.00	≤ 2.00
Silicon (Si)	≤ 1.00	≤ 1.00
Phosphorus (P)	≤ 0.20	≤ 0.20
Sulfur (S)	0.15–0.35	≤ 0.03
Selenium (Se)	-	0.15–0.35
Chromium (Cr)	17.0–19.0	17.0–19.0
Nickel (Ni)	8.0–10.0	8.0–10.0
Iron (Fe)	Balance	Balance

Mechanical Properties

Property	AISI 303	AISI 303Se
Tensile Strength (MPa)	620 min	620 min
Yield Strength (MPa)	240 min	240 min
Elongation (%)	40	40
Hardness (HB)	≤ 190	≤ 190
Density (g/cm³)	8.03	8.03
Modulus of Elasticity (GPa)	193	193

 

Corrosion Resistance

Although both grades belong to the 300-series stainless steels, the sulfur in 303 slightly lowers its corrosion resistance compared to 303Se. Selenium does not form the same type of sulfide inclusions, allowing a cleaner passive film to form on the steel surface.

 

Heat Treatment

Solution Treatment (Annealing)
Heat to 1010-1120°C and cool rapidly. This grade cannot be hardened by thermal treatment.

Welding

Not generally recommended but, if unavoidable use Grade 308L or 309 electrodes. AS 1554.6 does not pre-qualify welding of 303. Welds must be annealed for maximum corrosion resistance,but even then, poor mechanical and corrosion properties will result.

 

303 Stainless Steel Round Bar Price per kg (October 2025)

Product	Material Grade	Size Range	Surface Finish	Approx. Price (USD/kg)
Stainless Steel Round Bar	303	Ø 6–200 mm	Bright, Peeled	$2.80–$3.10/kg
Stainless Steel Round Bar	303Se	Ø 6–150 mm	Bright, Polished	$2.90–$3.20/kg
Stainless Steel Rod (Free-Cutting Type)	303 / 303Se	Customized	Turned, Ground	$2.85–$3.25/kg

💡 Note:Prices vary by surface treatment, diameter, and order quantity. Gnee offers factory-direct pricing, fast global delivery, and custom machining options to support industrial and OEM clients.

 

Packaging, MOQ & Delivery

Minimum Order Quantity (MOQ): 500 kg

Lead Time: 7–15 working days

Packaging: Export wooden pallets, moisture-proof wrapping

Delivery Terms: EXW, FOB, CIF, DDP available

Payment Terms: T/T, L/C, Western Union accepted

Gnee ensures all stainless steel bars are ISO, SGS, BV certified and delivered with mill test certificates (EN 10204 3.1) for full traceability.