SS321 AISI 321 Stainless Steel Properties, TP321 321H Composition, Machinability

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SS321, AISI 321 Stainless Steel 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
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)).

Machinability and Machining

Grade 321 stainless steel machinability is 36% in annealed conditoin based on a machinability rating of 100% for 1212 steel.

Nominal speeds and feeds for turning a variety of steels and cast irons with high-speed steel (HSS) single-point and box tools
Material Hardness, HB Condition Depth of cut, mm (in) High-speed steel tool Tool material
Speed Feed
m/min sfm mm/rev in./rev ISO AISI
Wrought austenitic SS321 135-185 Annealed 1 (0.04) 34 110 0.18 0.007 S4, S5 M2, M3
4 (0.15) 27 90 0.4 0.015
8 (0.30) 21 70 0.5 0.02
16 (0.625) 17 55 0.75 0.03
Nominal speeds and feeds for turning a variety of steels and cast irons with carbide-tipped single-point and box tools
Material Hardness, HB Condition Carbide tool
Uncoated Coated
Speed Feed Tool material grade Speed Feed Tool material grade
Brazed Indexable
m/min sfm m/min sfm mm/rev in./rev ISO C m/min sfm mm/rev in./rev ISO C
Wrought austenitic SS321 135-185 Annealed 105 350 120 400 0.18 0.007 K01, M10 C-3 160 525 0.18 0.007 CK01, CM10 CC-3
100 325 105 350 0.4 0.015 135 450 0.4 0.015
76 250 84 275 0.5 0.02 C-2 105 350 0.5 0.02 CC-2
60 200 64 210 0.75 0.03 K20, M20
Nominal speeds and feeds for turning a variety of steels and cast irons with ceramic tools
Material Hardness, HB Condition Depth of cut, mm (in) Speed Feed Type of ceramic
m/min sfm mm/rev in./rev
Austenitic SS321 135-185 Annealed 1 (0.040) 425 1400 0.13 0.005 Cold-pressed alumina
4 (0.150) 275 900 0.25 0.010
8 (0.300) 185 600 0.40 0.015
Nominal speeds and feeds for turning a variety of steels and cast irons with high-speed steel and carbide cutoff and form tools
Material Hardness, HB Condition Speed Feed, mm/rev (in./rev) Tool material grade
Cutoff tool width Form tool width
m/min sfm 1.5 mm (0.062 in.) 3 mm (0.125 in.) 6 mm (0.250 in.) 12 mm (0.500 in.) 18 mm (0.750 in.) 25 mm (1.00 in.) 35 mm (1.50 in.) 50 mm (2.00 in.) ISO AISI or C
Austenitic SS321 135-185 Annealed 26 85 0.033 (0.0013) 0.041 (0.0016) 0.050 (0.002) 0.050 (0.002) 0.041 (0.0016) 0.036 (0.0014) 0.030 (0.0012) 0.025 (0.001) S4, S5, K40, M40 M2, M3, C-2
84 275
Speeds and feeds for the deep-hole trepanning of various steels with high-speed tool steels and carbide tools
Material Hardness, HB Condition Speed Feed Tool material grade
m/min sfm mm/rev in./rev ISO AISI or C
Austenitic: SS321 135-185 Annealed 20 65 0.075 0.003 S4, S5 M2, M3
84 275 0.15 0.006 K20 C-2
225-275 Cold drawn 18 60 0.075 0.003 S4, S5 M2, M3
69 225 0.10 0.004 K20 C-2
Nominal speeds for the thread grinding of ferrous alloys and carbides
Material Hardness, HB Condition Thread designation Wheel identification ANSI Wheel speed Work speed
Pitch, mm Threads per 25 mm (1 in.) m/s sfm m/min sfm
Wrought austenitic stainless steels: 321, 201, 202, 301, 302, 302B, 304, 304L, 305, 308, 309, 309S, 310, 310S, 314, 316, 316L, 317, 330, 347, 348, 384, 385 135-275 Annealed or cold drawn 6-2.5 4-12 A90RB 43 8,500 1.2 4.0
2-1 13-27 A120SB 46 9000
0.8-0.45 28-63 A180TB 48 9500
0.4-0.35 64-80 A220UB 51 10000
Recommended speeds and feeds for the face milling of ferrous and nonferrous alloys with both high-speed steel and carbide cutters
Material Hardness, HB Condition Depth of cut, mm (in.) High-speed steel tool Carbide tool
Uncoated Coated
Speed Feed per tooth, mm (in.) Tool material grade, ISO (C) Speed, m/min (sfm) Feed per tooth, mm (in.) Tool material grade, ISO (C)
Speed, m/min (sfm) Feed per tooth, mm (in.) Tool material, ISO (AISI) Brazed, m/min (sfm) Indexable, m/min (sfm)
Wrought austenitic stainless steel 321 135-185 HB Annealed 1 (0.040) 40 (130) 0.20 (0.008) S4, S2 (M2, M7) 130 (430) 145 (475) 0.20 (0.008) K10, M20 (C-2) 215 (700) 0.20 (0.008) CK10, CM20 (CC-2)
4 (0.150) 30 (100) 0.30 (0.012) S4, S2 (M2, M7) 100 (325) 110 (360) 0.30 (0.012) K20, M30 (C-2) 145 (475) 0.30 (0.012) CK20, CM30 (CC-2)
8 (0.300) 24 (80) 0.40 (0.016) S4, S2 (M2, M7) 70 (230) 85 (280) 0.40 (0.016) K30, M40 (C-2) 105 (350) 0.40 (0.016) CK30, CM40 (CC-2)
Recommended speeds and feeds for the slab (or plain) milling of ferrous and nonferrous alloys with high-speed steel cutters
Material Hardness, HB Condition Depth of cut, mm (in.) Speed Feed per tooth High-speed steel tool material
m/min sfm mm (in.) ISO AISI
Wrought austenitic stainless steel 321 135-185 HB Annealed 1 (0.040) 55 180 0.15 (0.006) S4, S2 M2, M7
4 (0.150) 43 140 0.20 (0.008)
8 (0.300) 34 110 0.25 (0.010)
Recommended speeds and feeds for the end milling (peripheral) of ferrous and nonferrous alloys with both high-speed steel and carbide
cutters
Material Hardness, HB Condition Radial depth of cut, mm (in.) High-speed steel tool Carbide tool
Speed, m/min (sfm) Feed, mm/tooth (in./tooth), at cutter diameter of: Tool material, ISO (AISI) Speed, m/min (sfm) Feed, mm/tooth (in./tooth), at cutter diameter of: Tool material, ISO (C)
10 mm (.375in) 12 mm (.5 in) 18 mm (.75 in) 25-50 mm (1-2 in.) 10 mm (.375in) 12 mm (.5 in) 18 mm (.75 in) 25-50 mm (1-2 in.)
SS321 135-185 HB) Annealed 0.5 (0.020) 34 (110) 0.025 (0.001) 0.050 (0.002) 0.102 (0.004) 0.13 (0.005) S4, S5, S2 (M2, M3, M7) 110 (360) 0.013 (0.0005) 0.025 (0.001) 0.050 (0.002) 0.102 (0.004) K20, M20 (C-2)
1.5 (0.060) 24 (80) 0.050 (0.002) 0.075 (0.003) 0.13 (0.005) 0.15 (0.006) 82 (270) 0.025 (0.001) 0.050 (0.002) 0.075 (0.003) 0.13 (0.005)
diam/4
diam/4
21 (70) 0.025 (0.001) 0.050 (0.002) 0.102 (0.004) 0.13 (0.005) 72 (235) 0.025 (0.001) 0.038 (0.0015) 0.063 (0.0025) 0.102 (0.004)
diam/2
diam/2
18 (60) 0.025 (0.001) 0.038 (0.0015) 0.075 (0.003) 0.102 (0.004) 67 (220) 0.013 (0.0005) 0.025 (0.001) 0.050 (0.002) 0.075 (0.003)

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)

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