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 TypeAISI Type (UNS)C, ≤Si, ≤Mn, ≤P, ≤S, ≤CrNiN, ≤Other ElementsNotes
ASTM A240/A240M321 (UNS S32100)0.080.752.000.0450.0317.0-19.09.0-12.00.10≥ Ti 5×(C+N), ≤ 0.70Plate, Sheet, and Strip for Pressure Vessels and for General Applications
ASTM A276A/276M1.00Stainless Steel Bars and Shapes
ASTM A580/A580M≥ Ti 5×CStainless Steel Wire
ASTM A9590.10≥ Ti 5×(C+N), ≤ 0.70Wrought Stainless Steels
ASTM A473≥ Ti 5×CStainless Steel Forgings
ASTM A314≥ Ti 5×(C+N), ≤ 0.70Billets and bars for forging
ASTM A240/A240M321H (UNS S32109)0.04-0.100.752.000.0450.0317.0-19.09.0-12.00.10≥ Ti 4x(C+N), ≤ 0.70Plate, Sheet, and Strip
ASTM A9591.000.10Wrought Stainless Steels
ASTM A312/A312MTP321 (UNS S32100)0.081.002.000.0450.0317.0-19.09.0-12.00.10≥ Ti 5×(C+N), ≤ 0.70Stainless Steel Pipes
TP321H (UNS S32109)0.04-0.101.002.000.0450.0317.0-19.09.0-12.00.10≥ 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·m0.72 at 20 °C
Magnetic permeability1.02 (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)17.2 (9.6) 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
ASTMAISI Type (UNS)ConditionsTensile 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/A276M321 (UNS S32100)Annealed, Hot finished515 (75)205 (30)4050Bars and Shapes
Annealed, Cold finished, Dia ≤ 12.7 mm (0.5 in.)620 (90)310 (45)3040
Annealed, Cold finished, Dia > 12.7 mm (0.5 in.)515 (75)205 (30)3040
ASTM A580/A580MAnnealed520 (75)210 (30)3550Wire
Cold finished620 (90)310 (45)3040
ASTM A473/A473MAnnealed,  Sections ≤ 5 in. (127 mm)515 (75)205 (30)4050Forgings
Annealed,  Sections > 5 in. (127 mm)70 (485)
ASTM A240/A240M321, 321H (UNS S32109)515 (75)205 (30)4020192Plate, Sheet, and Strip

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

TP321 Mechanical Properties
ASTMAISI Type (UNS)Thickness (t), in. (mm)Tensile Strength, MPa (ksi), ≥0.2% Yield Strength, MPa (ksi), ≥
ASTM A312/A312MTP321, TP321HWelded515 (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 typeIntermittent serviceContinuous service
SS321870 (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
MaterialHardness, HBConditionDepth of cut, mm (in)High-speed steel toolTool material
SpeedFeed
m/minsfmmm/revin./revISOAISI
Wrought austenitic SS321135-185Annealed1 (0.04)341100.180.007S4, S5M2, M3
4 (0.15)27900.40.015
8 (0.30)21700.50.02
16 (0.625)17550.750.03
Nominal speeds and feeds for turning a variety of steels and cast irons with carbide-tipped single-point and box tools
MaterialHardness, HBConditionCarbide tool
UncoatedCoated
SpeedFeedTool material gradeSpeedFeedTool material grade
BrazedIndexable
m/minsfmm/minsfmmm/revin./revISOCm/minsfmmm/revin./revISOC
Wrought austenitic SS321135-185Annealed1053501204000.180.007K01, M10C-31605250.180.007CK01, CM10CC-3
1003251053500.40.0151354500.40.015
76250842750.50.02C-21053500.50.02CC-2
60200642100.750.03K20, M20
Nominal speeds and feeds for turning a variety of steels and cast irons with ceramic tools
MaterialHardness, HBConditionDepth of cut, mm (in)SpeedFeedType of ceramic
m/minsfmmm/revin./rev
Austenitic SS321135-185Annealed1 (0.040)42514000.130.005Cold-pressed alumina
4 (0.150)2759000.250.010
8 (0.300)1856000.400.015
Nominal speeds and feeds for turning a variety of steels and cast irons with high-speed steel and carbide cutoff and form tools
MaterialHardness, HBConditionSpeedFeed, mm/rev (in./rev)Tool material grade
Cutoff tool widthForm tool width
m/minsfm1.5 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.)ISOAISI or C
Austenitic SS321135-185Annealed26850.033 (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, M40M2, M3, C-2
84275
Speeds and feeds for the deep-hole trepanning of various steels with high-speed tool steels and carbide tools
MaterialHardness, HBConditionSpeedFeedTool material grade
m/minsfmmm/revin./revISOAISI or C
Austenitic: SS321135-185Annealed20650.0750.003S4, S5M2, M3
842750.150.006K20C-2
225-275Cold drawn18600.0750.003S4, S5M2, M3
692250.100.004K20C-2
Nominal speeds for the thread grinding of ferrous alloys and carbides
MaterialHardness, HBConditionThread designationWheel identification ANSIWheel speedWork speed
Pitch, mmThreads per 25 mm (1 in.)m/ssfmm/minsfm
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, 385135-275Annealed or cold drawn6-2.54-12A90RB438,5001.24.0
2-113-27A120SB469000
0.8-0.4528-63A180TB489500
0.4-0.3564-80A220UB5110000
Recommended speeds and feeds for the face milling of ferrous and nonferrous alloys with both high-speed steel and carbide cutters
MaterialHardness, HBConditionDepth of cut, mm (in.)High-speed steel toolCarbide tool
UncoatedCoated
SpeedFeed 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 321135-185 HBAnnealed1 (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
MaterialHardness, HBConditionDepth of cut, mm (in.)SpeedFeed per toothHigh-speed steel tool material
m/minsfmmm (in.)ISOAISI
Wrought austenitic stainless steel 321135-185 HBAnnealed1 (0.040)551800.15 (0.006)S4, S2M2, M7
4 (0.150)431400.20 (0.008)
8 (0.300)341100.25 (0.010)
Recommended speeds and feeds for the end milling (peripheral) of ferrous and nonferrous alloys with both high-speed steel and carbide
cutters
MaterialHardness, HBConditionRadial depth of cut, mm (in.)High-speed steel toolCarbide 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.)
SS321135-185 HB)Annealed0.5 (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
USEuropean UnionISOJapanChinaAustraliaIndiaRusiaKorea
StandardAISI Type (UNS)StandardGrade (Steel Number)StandardISO Name (ISO Number)StandardGradeStandardGradeStandardGradeStandardGradeStandardGradeStandardGrade
AISI SAE;
ASTM A240/A240M; ASTM A276A/276M; ASTM A959
321 (UNS S32100)EN 10088-2; EN 10088-3X6CrNiTi18-10 (1.4541)ISO 15510X6CrNiTi18-10 (4541-321-00-I )JIS G4321;
JIS G4304;
JIS G4305;
JIS G4309;
SUS321GB/T 1220;
GB/T 3280
0Cr18Ni10Ti;
06Cr18Ni11Ti (new designation) (S32168)
321H (UNS S32109)X7CrNiTi18-10 (1.4940)X7CrNiTi18-10 (4940-321-09-I )SUS321H1Cr18Ni11Ti;
07Cr19Ni11Ti (new designation) (S32169)
ASTM  A312/A312MTP321EN 10216-5; EN 10217-7;X6CrNiTi18-10 (1.4541)ISO 9329-4X6CrNiTi18-10JIS G3459;
JIS G3463
SUS321TPGB/T 14975;
GB/T 14976
0Cr18Ni10Ti;
06Cr18Ni11Ti (new designation) (S32168)

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