17-4 Age-Hardening Martensitic Stainless Steel – Properties, Composition, Heat Treatments and Specifications

17-4 stainless steel is an age-hardening martensitic alloy combining high strength with the corrosion resistance of stainless steel. Hardening is achieved by a short-time, simple low-temperature treatment. Unlike conventional martensitic stainless steels, such as type 410, 17-4 stainless steel is quite weldable. The strength, corrosion resistance and simplified fabrication can make 17-4 stainless steel a cost-effective replacement for high strength carbon steels as well as other stainless grades.

Applications of 17-4 Stainless Steel

Typical Applications for the 17-4 stainless steel age-hardening martensitic alloy include:

  • Gate valves
  • Aircraft structures, accessories, engine parts
  • Chemical processing equipment
  • Food processing machinery
  • Pump shafts, gears, plungers
  • Valve stems, balls, bushings, seats
  • Pulp & paper mill equipment
  • Fasteners

Composition of 17-4 Stainless Steel

The composition range for 17-4 stainless steel is provided in table 1.

Table 1. Composition of 17-4 Age-Hardening Martensitic stainless steel.

Chemistry, %

Min

Max

Chromium

15.00

17.50

Nickel

3.00

5.00

Copper

3.00

4.00

Manganese

-

1.00

Silicon

-

1.00

Columbium + Tantalum

5 x C

0.45

Carbon

-

0.07

Phosphorus

-

0.04*

Sulfur

-

0.03*

Molybdenum

-

0.05

Iron

remainder

* 0.025 max, AMS 5622

Specifications

The various forms of 17-4 stainless steel are covered by the following standards:

  • UNS S17400 (Sheet, Plate, bar)
  • UNS S17480 (MIG, TIG & Coil Weld Wire)
  • UNS W37410 (Covered Electrodes)
  • DIN 1.4548

Table 3. Specifications relating to 17-4 stainless steel.

Product Form

AMS

ASME

ASTM

AWS

Sheet Plate

5604

SA-693

A 693

Bar

5643

SA-564

A 564

Forgings

SA-705 Type 630

A 705 Type 630

Weld Wire (S17480)

5803

A5.9 ER 630

Weld Wire (W37410)

5827

A5.4 E630

Heat Treatments for 17-4 Stainless Steel

17-4 stainless steel is a martensitic, precipitation-hardening stainless steel. At the solution treating temperature, 1900°F (1040°C), the metal is austenitic but undergoes transformation to a low-carbon martensitic structure on cooling to room temperature. This transformation is not complete until the temperature drops to 90°F (32°C). Subsequent heating to temperatures of 900 to 1150°F (480 to 620°C) for one to four hours precipitation strengthens the alloy. This hardening treatment also tempers the martensitic structure, increasing ductility and toughness.

Physical Properties of 17-4 Stainless Steel

Table 4. Physical properties of 17-4 stainless steel.

Property

Value

Melting Range

2560-2625°F (1404-1440°C)

For Condition H 900 Density lb/in3

0.282

Electrical resistivity Ohm · circular mil/ft

463

Specific Heat Btu/lb°F

0.11

Poisson’s Ratio 70°F

0.272

Modulus of Elasticity psi x 106

Tension 70°F

28.5

200°F

28.0

400°F

27.0

600°F

26.0

Torsion 70°F

11.2

Magnetic Permeability of 17-4 Stainless Steel

H=100 Oersted

H=200 Oersted

Max

90

56

135

Thermal Properties of 17-4 Stainless Steel

The thermal properties of 17-4 stainless steel are summarised in table 5.

Table 5. Mean Coefficient of Thermal Expansion inch/inch°F x 10-6.

Temperature Range

Mean Coefficient of Thermal Expansion

-100 to 70°F

5.8

70 to 200°F

6.0

70 to 400°F

6.1

70 to 600°F

6.3

70 to 800°F

6.5

Thermal Conductivity of 17-4 Stainless Steel

The thermal conductivity of 17-4 stainless steel are summarised in table 3.

Table 6. Thermal Conductivity of 17-4 stainless steel in Btuft/ft²·hr·°F.

At 300°F

10.3

500°F

11.3

860°F

13.0

900°F

13.1

Typical Mechanical Properties of 17-4 Stainless Steel

Table 7. Typical mechanical properties of 17-4 stainless steel.

Property

Ultimate Tensile Strength

0.2% Yield Strength

Elongation % in 2"

Reduction of Area

Hardness

Impact

Charpy V-notch

ksi

ksi

or 4XD

%

Brinell

Rockwell

ft.-lbs.

H 900**

200

185

14

50

420

C 44

15

H 925

190

175

14

54

409

C 42

25

H 1025

170

165

15

56

352

C 38

35

H 1075

165

150

16

58

341

C 36

40

H 1100

150

135

17

58

332

C 35

25

H 1150

145

125

19

60

311

C 33

30

H 1150-M

125

85

22

68

277

C 27

100

This information has been sourced, reviewed and adapted from materials provided by NeoNickel.

For more information on this source, please visit NeoNickel.

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