Stainless Steel 303

OVERVIEW

303 stainless steel is a free-machining austenitic stainless steel developed for improved machinability through added sulfur content. Classified by the American Iron and Steel Institute (AISI) as Type 303, it offers good corrosion resistance, strength, and excellent performance in precision machining applications such as fasteners, shafts, and fittings.

CHEMICAL COMPOSTION OF 303 STAINLESS STEEL 

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

MECHANICAL PROPERTIES OF 303 STAINLESS STEEL 

Property Value
Tensile Strength ≥ 620 MPa
Yield Strength (0.2% Offset) ≥ 240 MPa
Elongation ≥ 50 %
Hardness ≤ 262 HB
Modulus of Elasticity 193 GPa

PHYSICAL PROPERTIES OF 303 STAINLESS STEEL

Property Value
Density 8.03 g/cm³
Melting Range 1400 – 1455°C
Thermal Conductivity 16.3 W/m·K
Electrical Resistivity 0.72 µΩ·m
Specific Heat 500 J/kg·K
Magnetic Properties Non-magnetic (annealed condition)

APPLICATION

Due to its superior machinability, 303 stainless steel is widely used in precision-machined components.

Common Applications Include:

  • Shafts and precision machined parts
  • Nuts, bolts, and threaded fasteners
  • Aircraft fittings
  • Electrical connectors
  • Valve components
  • Pump shafts
  • Gears and bushings

Industries using 303 stainless steel include:

  • Automotive manufacturing
  • Aerospace engineering
  • Food processing equipment (non-aggressive environments)
  • Chemical equipment

EQUIVALENT GRADES OF 303 STAINLESS STEEL 

Standard Equivalent Grade
AISI 303
UNS S30300
EN / DIN 1.4305 (X8CrNiS18-9)
JIS SUS303
BS 303S31

ADVANTAGES OF 303 STAINLESS STEEL 

  • Outstanding machinability compared with other austenitic grades.
  • Good corrosion resistance in atmospheric environments.
  • Excellent surface finish after machining.
  • Non-magnetic in annealed condition.