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

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).