303 Stainless Steel

303 is a non-magnetic, austenitic stainless steel that is not hardenable by heat treatment. It is the free machining modification of the basic 18% chromium / 8% nickel stainless steel.

303 stainless steel

303 Stainless Steel is the most readily machineable of all the austenitic grades of stainless steel.

Type 303 is a type of steel used in applications that require parts to be heavily machined while maintaining good mechanical and corrosion resistant properties, demonstrating excellent toughness. Applications include; nuts and bolts, gears, shafts, aircraft fittings etc.

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303 Stainless Steel Properties and Specifications

303 stainless steel owes its machineable nature to the presence of Sulphur in the composition. However, it should be noted that the Sulphur also decreases the corrosion resistance of the steel and slightly lowers its toughness. The toughness is still excellent as with other austenitic grades. AISI 304 stainless steel offers higher corrosion resistance than 303.

  • Austenitic Stainless Steel
  • Excellent machining characteristics
  • Free machining version of Types 302 and 304 is used for parts requiring extensive machining
  • Annealed condition is non-magnetic
  • Type 303 is slightly magnetic when cold worked
  • Good corrosion resistance
  • Good oxidation resistance up to 1700 degrees F

303 stainless steel is covered by the following specifications:

  • AMS 564OG
  • ASTM A314-63
  • ASTM A320-65
  • ASTM 581-67
  • ASTM 582-67
  • QQ-S-764A
  • MIL-S-862B
  • Anneal: Heat to 1900 – 2050 F and water quench.
  • Harden: Type 303 cannot be hardened by heat treatment.
  • Type 303 should be heated slowly to 2000-2150 F.
  • Soaked for a sufficient time, then raised to 2200 – 3250 F.
  • Should not be forged below 1700 F.
  • Excellent corrosion resistance.
  • Effectively resist attack in atmospheric exposures, sterilizing solutions, most organic and many inorganic chemicals, most dyes nitric acid and foods.
  • For best corrosion resistance finished parts should be free from scale and foreign particles.
  • Only fair weldability.
  • Can be welded using proper procedures.
  • Weldability can be improved by using methods that minimize dilution of the weld metal with the melted base metal.
  • Reducing the time that welds are in the hot-short temperature range and use of Type 312 (29-9) filler metal helps obtain satisfactory results.

Composition & Properties


Type 303%


.15 max


2.00 max


.20 max


.15 min




1.00 max


17.00 – 19.00


8.00 – 10.00


.60 max

Typical Mechanical Properties Annealed

Ultimate Tensile Strength, psi


.20% Yield strength psi


Elongation, % in 2″


Reduction of area, %