303 stainless steel plate - UNS S30300 - ASTM-A-895

303 stainless steel is a free machining modification of the basic 18-8 stainless steel. This austenitic, nickel stainless steel was specially designed for improved machinability while maintaining good corrosion resistance. It is used primarily for parts requiring machining, grinding or polishing. The sulfur addition present in 303 SS assists in breaking up turnings which reduces drag on cutting tools. This alloy offers good corrosion resistance and oxidation resistance in mild environments and excellent forming properties. It is non-magnetic in the annealed condition and is not hardenable by heat treatment – it can only be work hardened through cold working. It is also difficult to weld, and may require filler rods and post-weld annealing to maintain corrosion resistance.

303 Inventory Size Ranges


0.1875" - 4.000"

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Characteristics of 303 stainless steel

The improved machinability of this 303 stainless steel alloy (UNS S30300) makes it ideal for screw machine applications, aircraft fittings, and fasteners. The additional sulfur that allows this material to be readily machined also lowers its corrosion resistance compared to a grade like 304 stainless steel. Overall toughness is lower but still good, despite the inclusion of sulfur, and is comparable to other austenitic grades of stainless steel. We offer grade 303 stainless steel plate in 0.1875” to 4.000” thicknesses.

Standard Inventory Specifications

  • UNS S30300
  • AMS 5640 Chem Only
  • ASTM A 895

Common Trade Names

  • AISI 303

Common Applications of 303

  • Aircraft applications including fittings, shafts and spindles
  • Automatic screw machine applications
  • Medical devices with screw threads, drilled or tapped holes
  • Pump and valve parts
  • Architectural applications
  • Nuts and bolts

Chemical Composition

Chemical Composition of 303 Stainless Steel
Element Percent by Weight
Cr Chromium 17.0 min - 19.0 max
Ni Nickel 8.0 min - 10.0 max
C Carbon 0.15 min
Mn Manganese 2.00 min
P Phosphorus 0.20 max
S Sulfur 0.15 min - 0.35 max
Si Silicon 1.00 max
Mo Molybendum 0.60 max
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Physical Properties of 303 Stainless Steel


Density lb/in3


Density g/cm3


Melting Point


Thermal Conductivity at 212°F (100°C)

112 BTU/hr/ft²/ft/°F

Thermal Conductivity at 212°F (100°C)

16.2 W/m-°K

Electrical Resistivity

28.3 Microhm-in at 68°C

Electrical Resistivity

72.0 Microhm-cm at 20°C

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Mechanical Properties of 303 Stainless Steel



(max) 202 (HBN)

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303 and 304 have similar chemistry and both are iron alloys, however Alloy 303 was purposefully developed for ease of machining. The additional sulfur present in 303 assists in breaking up turnings which reduces drag on the cutting tool and increases machining speeds. AISI 303 is not weldable and has limited formability due to its sulfur content. AISI 304 is weldable and machinable. It has very good drawability as well. Its low yield strength and high elongation allow it to be formed into complex shapes.

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The technical data provided is for information only and not for design purposes. It is not warranted or guaranteed.