SS321 AISI 321 Stainless Steel Properties, TP321 321H Composition

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AISI 321 Stainless Steel (SS321), 321H, TP321

AISI 321 stainless steel (SS321) is basically type 304 with the addition of titanium (Ti), which stabilizes carbides against sensitization to prevent intergranular precipitation of chromium carbide when the steel is heated to a temperature within the sensitization range (such as during welding). 321H is to obtain the best creep strength and creep rupture strength. TP321 stainless steel is for seamless, welded, and heavily cold worked pipes.

Grade 321 Stainless Steel Datasheet

The following tables and lists give grade 321 stainless steel datasheet and specification including chemical composition, physical properties and mechanical properties, machinability, heat treatment, welding, etc.

Chemical Composition

SS 321 stainless steel chemical composition is listed in the following table based on cast analysis.

Chemical Composition, %
ASTM Type AISI Type (UNS) C, ≤ Si, ≤ Mn, ≤ P, ≤ S, ≤ Cr Ni N, ≤ Other Elements Notes
ASTM A240/A240M 321 (UNS S32100) 0.08 0.75 2.00 0.045 0.03 17.0-19.0 9.0-12.0 0.10 ≥ Ti 5×(C+N), ≤ 0.70 Plate, Sheet, and Strip for Pressure Vessels
ASTM A276A/276M 1.00 Stainless Steel Bars and Shapes
ASTM A580/A580M ≥ Ti 5×C Stainless Steel Wire
ASTM A959 0.10 ≥ Ti 5×(C+N), ≤ 0.70 Wrought Stainless Steels
ASTM A473 ≥ Ti 5×C Stainless Steel Forgings
ASTM A314 ≥ Ti 5×(C+N), ≤ 0.70 Billets and bars for forging
ASTM A240/A240M 321H (UNS S32109) 0.04-0.10 0.75 2.00 0.045 0.03 17.0-19.0 9.0-12.0 0.10 ≥ Ti 4x(C+N), ≤ 0.70 Plate, Sheet, and Strip
ASTM A959 1.00 0.10 Wrought Stainless Steels
ASTM A312/A312M TP321 (UNS S32100) 0.08 1.00 2.00 0.045 0.03 17.0-19.0 9.0-12.0 0.10 ≥ Ti 5×(C+N), ≤ 0.70 Stainless Steel Pipes
TP321H (UNS S32109) 0.04-0.10 1.00 2.00 0.045 0.03 17.0-19.0 9.0-12.0 0.10 ≥ Ti 4x(C+N), ≤ 0.70

AISI 321 Stainless Steel Properties

The tables below list AISI 321 stainless steel properties, including physical and mechanical properties.

Physical Properties

AISI 321 steel physical properties are given in the following lists, including density, thermal expansion, elastic modulus, thermal conductivity, specific heat capacity and electrical resistance.

Notes:

  • 10-6·K-1 = 10-6/K
  • 1 Ω·mm²/m = 1 μΩ·m
  • 1 g/cm3 = 1 kg/dm3 = 1000 kg/m3
  • 1 GPa = 1 kN/mm2
  • 1 MPa = 1 N/mm2
SS321 Physical Properties
Density, g/cm3 (lb/in.3) 7.9 (0.29)
Melting point, °C (°F) 1400-1425 (2550-2600)
Specific heat capacity, J/kg·K (Btu/lb ·°F) 500 (0.12) at 20 °C
Electrical resistivity, μΩ·m 0.72 at 20 °C
Magnetic permeability 1.02 (Approximate)
Elastic modulus,  GPa (106 psi) 193 (28)
Thermal conductivity, W/m·K (Btu/ft · h ·°F) 16.1 (9.3) at 100 °C (212 °F)
22.2 (12.8) at 500 °C (932 °F)
Coefficient of thermal expansion, 10-6/K (μin./in. ·°F) 16.6 (9.2) at 0-100 °C (32-212 °F)
17.2 (9.6) at 0-315 °C (32-600 °F)
18.6 (10.3) at 0-538 °C (32-1000 °F)

Mechanical Properties

AISI 321 stainless steel mechanical properties are listed in the following tables.

SS 321 Mechanical Properties
ASTM AISI Type (UNS) Conditions Tensile Strength, MPa (ksi), ≥ 0.2% Yield Strength, MPa (ksi), ≥ Elongation in 50 mm (2 in.), %, ≥ Reduction of Area, %, ≥ Brinell Hardness (HBW), ≤ Rockwell Hardness (HRBW), ≤ Product forms
ASTM A276/A276M 321 (UNS S32100) Annealed, Hot finished 515 (75) 205 (30) 40 50 Bars and Shapes
Annealed, Cold finished, Dia ≤ 12.7 mm (0.5 in.) 620 (90) 310 (45) 30 40
Annealed, Cold finished, Dia > 12.7 mm (0.5 in.) 515 (75) 205 (30) 30 40
ASTM A580/A580M Annealed 520 (75) 210 (30) 35 50 Wire
Cold finished 620 (90) 310 (45) 30 40
ASTM A473/A473M Annealed,  Sections ≤ 5 in. (127 mm) 515 (75) 205 (30) 40 50 Forgings
Annealed,  Sections > 5 in. (127 mm) 70 (485)
ASTM A240/A240M 321, 321H (UNS S32109) 515 (75) 205 (30) 40 201 92 Plate, Sheet, and Strip

SS321 Young’s modulus: 180 GPa (26.0 x 106 psi), sheet, longitudinal orientation.

TP321 Mechanical Properties
ASTM AISI Type (UNS) Thickness (t), in. (mm) Tensile Strength, MPa (ksi), ≥ 0.2% Yield Strength, MPa (ksi), ≥
ASTM A312/A312M TP321, TP321H Welded 515 (75) 205 (30)
Seamless: t ≤ 0.375 (9.50)
Seamless: t > 0.375 in. (9.50) 485 (70) 170 (25)

Heat Treatment

  • Recommended annealing temperature for TP321 and 321 wrought stainless steel: 1040 °C (1900 °F); Minimum 1095 °C (2000 °F) for cold-worked 321H and 1050 °C (1095 °F) for hot-finished 321H
  • Stress-relieving treatments
    • For dimensional stability: Stress relieve at 205 to 480 °C (400 to 900 °F) and then slow cool (usual time, 4 h per inch of section).
    • Stress relief after severe forming: Anneal at 1065 to 1120 °C (1950 to 2050 °F) and then slow cool. Or Anneal at 1065 to 1120 °C (1950 to 2050 °F) and then quench or cool rapidly.
    • For removing peak stresses only: Stress relieve at below 480 °C (900 °F) and then slow cool.
  • Typical forging temperature: 925-1260 °C (1700-2300 °F).
Maximum service temperatures in air for for wrought stainless
AISI type Intermittent service Continuous service
SS321 870 (1600) 925 (1700)

Weldability

SS321 and TP321 has excellent weldability, no preheating is required. The filling material needs to have similar composition but higher alloy content. Liquation cracking in heat affected zone: low energy input. Fine grain size. Ferrite ≥ 5%.

Recommended filler metals are SS 321, 347, and 348. Electrode is E347 or E308L [service temperature < 370 °C (700 °F)].

Applications

Type 321, 321H and TP321 can be used in places where solution treatment after welding is not possible, such as steam lines and superheater pipes and exhaust systems in reciprocating engines and gas turbines with temperatures ranging from 425 to 870 °C (800 to 1600 °F). And fuel injection lines and hydraulic systems for aircraft and aerospace vehicles.

AISI 321 Stainless Steel Equivalent

AISI TP321, 321H and 321 stainless steel equivalent to European EN (German DIN EN, British BSI EN, France NF EN), ISO, Japanese JIS and Chinese GB standard (for reference).

AISI 321 stainless steel equivalent material
US European Union ISO Japan China Australia India Rusia Korea
Standard AISI Type (UNS) Standard Grade (Steel Number) Standard ISO Name (ISO Number) Standard Grade Standard Grade Standard Grade Standard Grade Standard Grade Standard Grade
AISI SAE;
ASTM A240/A240M; ASTM A276A/276M; ASTM A959
321 (UNS S32100) EN 10088-2; EN 10088-3 X6CrNiTi18-10 (1.4541) ISO 15510 X6CrNiTi18-10 (4541-321-00-I ) JIS G4321;
JIS G4304;
JIS G4305;
JIS G4309;
SUS321 GB/T 1220;
GB/T 3280
0Cr18Ni10Ti;
06Cr18Ni11Ti (new designation) (S32168)
321H (UNS S32109) X7CrNiTi18-10 (1.4940) X7CrNiTi18-10 (4940-321-09-I ) SUS321H 1Cr18Ni11Ti;
07Cr19Ni11Ti (new designation) (S32169)
ASTM  A312/A312M TP321 EN 10216-5; EN 10217-7; X6CrNiTi18-10 (1.4541) ISO 9329-4 X6CrNiTi18-10 JIS G3459;
JIS G3463
SUS321TP GB/T 14975;
GB/T 14976
0Cr18Ni10Ti;
06Cr18Ni11Ti (new designation) (S32168)

Related material: AISI 316, 316L stainless steel

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