Type 304 Stainless Steel

Type 304 stainless steel is basically the same as Type 302 except for a higher chromium and lower carbon content. Its lower carbon minimizes chromium carbide precipitation due to welding and its susceptibility to intergranular corrosion. In many instances, Type 304 can be used in the “as welded” condition while Type 302 must be annealed in order to retain adequate corrosion resistance.

Type 304 has the same excellent combination of strength, corrosion resistance and workability as Type 302, and it costs the same. Consequently this type is widely used and is more popular than type 302.

Type 304L

Type 304L is an extra low carbon variation of Type 302. The .03% maximum carbon content eliminates carbide precipitation due to welding.  Consequently, the alloy can be used in the “as welded” condition even in severe corrosive conditions. In many cases it eliminates the necessity of annealing weldments except for applications where stress relief is specified. Type 304L has slightly lower mechanical properties than Type 304.

Available Forms

Types 304 and 304L stainless steel are available in:

  • Bar
  • Wire
  • Sheet
  • Strip
  • Billets

Specifications

The following specifications are generally applicable:

Sheets and Plates Bars, Wire, and Billets
  • MIL-S-5059
  • AMS 5513
  • ASTM A 167
  • ASTM A 240
  • MIL-S-7720
  • QQ-S-763
  • AMS A 276
  • ASTM A 276
  • ASTM A 479

Standard Heat Treatments

  • Anneal: Heat to 1900 – 2050 F and water quench
  • Harden: Type 303 cannot be hardened by heat treatment

Corrosion Resistance

  • 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

Forgeability

  • 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

Machinability

  • Excellent machinability

Formability

  • Type 303 has limited formability because of its sulfur content

Weldability

  • 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

Type 304 Stainless Steel Composition & Properties

Property Type 304% Type 304L%
Carbon .08 max .03 max
Manganese 2.00 max 2.00 max
Phosphorus .045 max .045 max
Sulfur .030 max .030 max
Silicon 1.00 max 1.00 max
Chromium 18.0 – 20.0 18.0 – 20.0
Nickel 8.0 – 12.0 8.0 – 12.0
Type 304 Type 304L
Property Sheet & Strip Bar & Wire Sheet & Strip Bar & Wire
Ultimate Tensile Strength, psi 85,000 85,000 80,000 80,000
.2% Yield strength, psi 35,000 35,000 30,000 30,000
Elongation, % om 2″ 55 60 55 60
Rockwell Hardness B80 B80 N75 B75
Reduction of area % NA 70 NA 70
Impact Strength, Izod V Notch, ft-lbs NA 100-120 NA 100-120
Endurance Limit, psi NA 34,000 NA 34,000

Typical Applications

  • Low carbon Content of 304 and 304L is more conducive to welding than type 302
  • Applications include architectural mouldings and trim and kitchen equipment
  • Alloys are widely used for welded components of processing equipment for textile

Machinability

When machined, Types 304 and 304L will work-harden.  Therefore tools must not ride or glaze the surface without cutting. Heavy feeds and slow speeds are recommended

Weldability

Both these stainless steels are readily welded by most welding processes such as TIG, MIG and resistance welding.  However, all arc welding not using a shielded gas should have the filler rods coated.  Type 308 and 308L welding rods are suggested for best results.

Formability

Types 304 and 304L have very good drawability. Their combination of low yield strength and high elongation permits successful forming complex shapes.  However,these grades work harden rapidly.  To relieve stresses produced in severe forming spinning, parts should be full annealled or stress-relief annelaed as soon as possible after forming

Corrosion Resistance

Like Type 302, Types 304 and 304L stainless steel have excellent resistance to a wide range of corrosive media and to atmospheric exposures.  The low carbon content of Type 304 and especially 304L, by reducing or eliminating carbide precipitation due to welding, makes these types of stainless suitable for a much wider range of corrosive service than Type 302.