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ALLOY 321 / 321H


Stainless Steel 321 / AMS 5510 / AMS 5645 / SAE 30321 /Alloy 321 Steel, Corrosion and Heat Resistant


Applications of Alloy Steel AISI 321 / AISI 321H / UNS S32100 / UNS S32109 :

Alloy 321 (UNS S32100) is titanium stabilized austenitic stainless steel with good general corrosion resistance. It has excellent resistance to intergranular corrosion after exposure to temperatures in the chromium carbide precipitation range of 800 - 1500°F (427 - 816°C). The alloy resists oxidation to 1500°F (816°C) and has higher creep and stress rupture properties than alloys 304 and 304L. It also possesses good low temperature toughness.

Alloy 321H (UNS S 32109) stainless steel is the higher carbon (0.04 - 0.10) version of the alloy. It was developed for enhanced creep resistance and for higher strength at temperatures above 1000oF (537°C). In most instances, the carbon content of the plate enables dual certification.

Alloy 321 Stainless Steel cannot be hardened by heat treatment, only by cold working. It can be easily welded and processed by standard shop fabrication practices.

Stainless Steel Alloys 321 and 321H Pipe, Flanges and Fittings are common to the petroleum refining industries. Alloy 321 and 321H is often used to make radiant super heaters, boiler tubes, high pressure steam pipes, and general refinery piping. They are also used for heavy-duty exhaust systems and manifolds.


Properties of Alloy Steel AISI 321 / AISI 321H / UNS S32100 / UNS S32109 :

Alloy 321 is austenitic stainless steel that contains stabilizing elements. It is easily welded. Annealing is often not required after welding unless stress relief is desired. It has excellent resistance to oxidation and corrosion.  The addition of titanium in 321 Stainless Steel give some desired characteristics:

  • Prevents harmful carbide precipitation in the heat affected zone (HAZ) of the weld area
  • Imparts partial immunity to inter granular corrosion
  • Reduced embrittlement in the HAZ of the weld area

321H stainless steel is a widely used stainless steel, where parts are heated within carbide-precipitation temperature range (800°F-1500°F) and exposed to corrosive atmosphere.  321 Stainless Steel is similar to 304 Stainless Steel, but with higher nickel content and stabilized with titanium. Titanium preferentially reacts with carbon in the steel and prevents precipitation of chromium carbides at the grain boundaries, thus preserving corrosion-resistant properties by preventing depletion of chromium near the grain boundaries during exposure within critical temperature range. This grade responds well to hardening by cold working. It has good welding characteristics; and post-weld annealing is not normally required to restore its excellent performance in a wide range of corrosive conditions.

  • Responds well to hardening by cold working
  • Good welding characteristics
  • Excellent corrosion resistance in a wide variety of corrosive media
  • High creep & stress rupture properties


Technical Data Sheet of Alloy Steel AISI 321 / AISI 321H / UNS S32100 / UNS S32109 :

Chemical Composition Limits / Chemistry of SS 321 / 321H
 Weight% C Si Mn P+S Cr Ni Ti N Fe Mo
AMS 5510 0.08 max 0.25-1.00 2.0 max 0.040P0.030S 17-19 43443 0.7 max 0.1 max Bal 0.75
Alloy 321


Typical Mechanical Properties of Alloy Steel AISI 321 / AISI 321H / UNS S32100 / UNS S32109 :

Material Condition Tensile Strength (ksi) Yield Strength (ksi) % Elongation Hardness HB
Alloy 321 AMS 5510 Sheet (Sol Trtd) 70-100 25 40 -
AMS 5510
Alloy 321 AMS 5645 Bar (Sol Trtd) - - - 255 max
AMS 5645


Applications of Alloy Steel AISI 321 / AISI 321H / UNS S32100 / UNS S32109 :

  • Aerospace – piston engine manifolds
  • Chemical Processing
  • Expansion Joints
  • Food Processing – equipment and storage
  • Petroleum Refining – polyphonic acid service
  • Waste Treatment – thermal oxidizers
  • Pharmaceutical Production


Availability of Alloy Steel AISI 321 / AISI 321H / UNS S32100 / UNS S32109 :
Type 321 is available in Sheet, Plate, Coil, Strip, Bar (Round, Hex, Flat, Square), Pipe, Tube, Seamless, Welded and Forging Stock. 321 Foil (Shim) is available in various thicknesses. 

Type Sizes Schedules ASTM Standards
Bar 1/2" to 12"   A276, A479
Butt Weld Fittings 1/2" to 12" Sch 10, 40, 80, 160 & XXH A403
Forgings 1/2" to 12"   A182
Pipe Welded & Seamless 1/2" to 12" Sch 10, 40, 80, 160 & XXH A312
Tube, Welded 1/2" to 12" Sch 10, 40, 80, 160 & XXH A249
Tube, Seamless 1/2" to 12" Sch 10, 40, 80, 160 & XXH A213
Plate, Sheet, Coil 4 mm to 100 mm   A240
Flange & Pressure Fittings All Descriptions    



Specifications of Alloy Steel AISI 321 / AISI 321H / UNS S32100 / UNS S32109 :

The following specifications cover Stainless Steel 321 / SAE 30321 / AMS 5510 / AMS 5645

SS 321 / SS 321H Sheet SS 321 / SS 321H Seamless Pipe
SS 321 / SS 321H Plate SS 321 / SS 321H Welded Pipe
SS 321 / SS 321H Coil SS 321 / SS 321H ERW Pipe
SS 321 / SS 321H Round Bar SS 321 / SS 321H Seamless Tube
SS 321 / SS 321H Bar SS 321 / SS 321H Welded Tube
SS 321 / SS 321H Fittings SS 321 / SS 321H ERW Tube
AMS 5510 Sheet / strip / plate ASTM A276 / ASME SA276
AMS 5557 Welded/seamless tube ASTM A314 / ASME SA314
AMS 5559 Welded / thin wall tube ASTM A320 Grade B8T
AMS 5570 Seamless tube ASTM A479 / ASME A479
AMS 5576 Welded tube ASTM A484 / ASME SA484
AMS 5645 Bars / wire / forging AISI 321
MIL-S-6721 BS 2S129
MIL-T-8606 Seamless tube BS T67 Tube
MIL-T-8606 Welded tube  BS S524 Sheet
MIL-T-8808 Seamless tube BS S526 Sheet
MIL-T-8808 Welded tube BS 970; 321S31
QQ-S-766 EN58B
ASTM A240 / ASME SA240 WS 1.4541
ASTM A167 / ASME SA167 Z10CnNb18-11 
ASTM A193 Grade B8T CL1 UNS S32100 

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