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Type 321 Stainless Steel
Description
 Type 321 (UNS S 32100) is an austenitic chromium-nickel steel containing titanium. This grade is recommended where it is preferred to omit the annealing operation after welding. It is also recommended for use at temperatures between 800-1650°F. This alloy also is not recommended for use in decorative applications.

Product Forms
Ingots, Slabs, Hot bands, Sheet, Strip

Typical Applications

  • Aircraft exhaust manifolds and flanges
  • Chemical equipment
  • Collector rings
  • Heat exchangers
  • Jet engine parts
  • Welded parts
  • Fire walls
  • Pressure tanks

Chemical Composition
Carbon Manganese Silicon Chromium Nickel Titanium
0.08 max. 2.00 max. 1.00 max. 17.00/19.00 9.00/12.00 5xC min.

Typical Material Properties
Finish/
Condition		 Yield
Strength
psi		 Tensile
Strength
psi		 Elongation
in 2 in.,
%		 Hardness
Rockwell
B
No. 1/2D Finish,
annealed		 31,000 79,000 58 72
No. 2/2B Finish,
annealed		 37,000 81,000 57 80

Processing

  • Annealing
    Cool rapidly from 1750-1950°F. Air cooling may be employed for light sections; otherwise, water quenching from the annealing temperature is required.
  • Hardening
    This grade can be hardened only by cold working. See table of Typical Mechanical Properties.
  • Stress Relieving
    The recommended temperature range for stress relieving is 400-750°F, although temperature up to 1500°F may be employed when time at temperature is kept to a short period of one to two hours.

Hot Working

  • Preheating temperature--Large sizes should be heated slowly to 1500-1600°F and equalized at this temperature before heating rapidly to hot working temperature.
  • Forging and pressing temperature--2100-2300°F.
  • Finishing temperature-1700°F (the reductions below 1800°F should be light).

Forming
This grade can be formed into most shapes. However, as it will work harden, an annealing treatment should precede and follow each severe cold forming operation.

Physical Properties
Density
lb./cu. in.		 Modulus of
Elasticity
in Tension
x 10^6, psi		 Specific
Heat
Btu/°F/lb		 Thermal
Conductivity
Btu/hr/ft^2/ft/		 Mean Coefficient
of Thermal Expansion
per °F(x 10^-6)		 Melting
Point
Range		 Electrical
Resistivity
microohn-cm
32-212 °F °F °F °F @ 70 °F
0.29 28.0 0.12 212 932 32-212 32-600 32-1000 32-1200 2550/2600 72
9.3 12.8 9.3 9.5 10.3 10.7

Elevated Temperature Strength
Creep Strength,
load for 1% elong
10,000 hr,psi		 Temperature
1000 °F 1100 °F 1200 °F 1300 °F
18,000 13,000 8000 4500

Welding
This grade can be welded by electronic arc, gas fusion or electric resistance processes.
Type 321 is one of the stabilized grades designed to eliminate intergranular corrosion by preventing carbide precipitation. Post-weld heat treatment is not normally required to maintain corrosion resistance in the heat effected zone. However, low temperature stress relieving is sometimes necessary. As titanium is lost in gas or electronic welding, a Type 347 (columbium-stabilized) filler metal or electrode is required.

Corrosion
The corrosion resistance of Type 321 in fully annealed condition is about the same as Type 302. Type 321 has superior resistance to Type 302 and Type 304 when service covers 800-1600°F, or follows exposure to welding temperatures without reannealing. When service is both severely corrosive and at elevated temperatures between 800-1600°F, Type 347 should be used.
In various chemical media, Type 321 has corrosion resistance equivalent to Types 302 and 304.

Oxidation
Oxidation or scaling resistance of this grade depends on atmospheric and operating conditions. For continuous service, the maximum recommended temperature is 1650°F; and for intermittent service, 1500°F.
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