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Stainless Steel 303, UNS S30300

Stainless Steel 303 UNSS S30300 Stainless Free-Machining

ASTM A276, ASTM A479, ASTM A312, ASTM A213, ASTM A269, ASTM A240, AMS 5639H, ASME SA276, QQ-S-763, Mil-S-862B/1

Level 4
Level 4
Resistance to Oxidation
Level 1
Not Magnetic
Level 1
Not Harden Able by Treatment

Farmers Copper LTD. stocks 303 stainless in Round Bar/Rod, Square Bar and Hex Bar; Flat Bar is available upon request. 303 is typically used because of its high machinability and good resistance to oxidation. This alloy is not magnetic and not harden able by treatment. To find a size, specification, or temper that is not listed, please request a quote to get in contact with a material expert today. We are ready to help meet your exact needs.

Since 1920, Farmer's has been serving the metal industry. Our knowledgeable sales staff will be happy to assist you with your request for stainless steel. 

303 stainless steel

303 UNSS S30300 Stainless Free-Machining Shapes

Wire Rod

Round, Square, Hex, and Flat Bar

303 UNSS S30300 Stainless Free-Machining Sizing

  • Round Bar/Rod - 1/8” to 8-1/2” dia
  • Square Bar - 3/16” to 3/4”
  • Hex Bar - 3/8” to 1-3/4”
  • Flat bar - Upon Request


Farmer’s Copper Ltd. extends its services throughout many industries. We provide the raw copper alloy materials in various standard shapes as well as custom cut copper alloys.

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Our 303 UNSS S30300 Stainless Free-Machining Inventory & Properties

Farmer’s diverse inventory of products and services offered provides our customers the largest and most extensive selection of alloys available, cut to precise specifications, and delivered with total quality control.

Standard Chemical Composition

Elements C MN P S SI CR NI
UNS 30300 AISI 303 Min%       0.15   17 8
Max% 0.15 2 0.2   1 19 10

Nominal Mechanical Properties (annealed condition)

Tensile Strength
ksi [MPa]
Yield Strength
ksi [MPa]
% Elongation 4d% Reduction in AreaHardness HB
90 [620]45 [310]3040170

Nominal Physical Properties

The values are at room temperature, unless otherwise specified.

Density 7.9 kg/m³  Mean Co-efficient of Thermal Expansion 0°C - 100°C 17.2 um/mK
Modulus of Elasticity 193
Specific Heat Capacity 500J/kgK Melting Range 1400°C - 1450°C
Thermal Conductivity @100° C 16.2W/mK Relative Permeability* 1.02

*Note: This grade is non-magnetic in annealed condition but becomes moderately magnetic after cold working.


Parts can be annealed at 1900°F–2000°F held for minimum 60 minutes per inch of thickness and water quenched. Prolonged exposure between 800°F–1500°F must be avoided to prevent embrittlement and loss of corrosion properties. This grade does not harden with heat treatment.


The chemistry of this grade is specially designed for high machinability. This can be machined at high speeds with conventional tools without the use of chip curlers/breakers.


Welding of 303 is generally not recommended. Fusion welding using 308, 310 or 312 electrodes is possible to a very limited extent. Type 312 weld metal contains a large amount of delta ferrite, which tends to overcome the tendency of hot cracking. Anneal after welding for maximum corrosion resistance.

Cold Workability

Cold working of this grade is possible to a limited extent, except under all compressive stresses, such as wire drawing. It still is not as good as 302/304 stainless steel. Heavy forming/reductions will require frequent intermediate annealing.

Hot Workability

This grade has limited forgeability. Heat uniformly to 2100°F–2300°F and should not go below 1800°F. This grade is susceptible to hot shortness. Parts should be water quenched after hot working for good corrosion resistance.

Corrosion Resistance

This grade has fair corrosion resistance in mildly corrosive atmosphere. It is much inferior to 304 SS. For maximum corrosion resistance, material should be used in annealed condition and parts should be passivated.

Our Commitment to Service

As a leading copper, brass, & bronze alloys supplier, Farmers Copper Ltd. attributes our success to serving our customers, through our service-minded employees and material readily available for prompt, accurate deliveries of copper, brass, bronze, stainless steel and other metal alloys.

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