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UNS S17700 (17-7 PH, Alloy 631) Stainless Steel

S17700 stainless steel is a precipitation-hardening stainless steel formulated for primary forming into wrought products. S17700 is the UNS number for this material. 17-7 PH is the common industry name.

It can have the lowest ductility among the wrought precipitation-hardening stainless steels in the database.

The properties of S17700 stainless steel include four common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare S17700 stainless steel to: wrought precipitation-hardening stainless steels (top), all iron alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Brinell Hardness

180 to 430

Elastic (Young's, Tensile) Modulus

200 GPa 28 x 106 psi

Elongation at Break

1.0 to 23 %

Fatigue Strength

290 to 560 MPa 42 to 81 x 103 psi

Poisson's Ratio

0.28

Rockwell C Hardness

41 to 46

Shear Modulus

76 GPa 11 x 106 psi

Shear Strength

740 to 940 MPa 110 to 140 x 103 psi

Tensile Strength: Ultimate (UTS)

1180 to 1650 MPa 170 to 240 x 103 psi

Tensile Strength: Yield (Proof)

430 to 1210 MPa 62 to 180 x 103 psi

Thermal Properties

Latent Heat of Fusion

290 J/g

Maximum Temperature: Corrosion

410 °C 770 °F

Maximum Temperature: Mechanical

890 °C 1640 °F

Melting Completion (Liquidus)

1440 °C 2620 °F

Melting Onset (Solidus)

1400 °C 2550 °F

Specific Heat Capacity

480 J/kg-K 0.12 BTU/lb-°F

Thermal Conductivity

15 W/m-K 8.9 BTU/h-ft-°F

Thermal Expansion

11 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

2.3 % IACS

Electrical Conductivity: Equal Weight (Specific)

2.7 % IACS

Otherwise Unclassified Properties

Base Metal Price

13 % relative

Density

7.7 g/cm3 480 lb/ft3

Embodied Carbon

2.8 kg CO2/kg material

Embodied Energy

40 MJ/kg 17 x 103 BTU/lb

Embodied Water

150 L/kg 17 gal/lb

Common Calculations

PREN (Pitting Resistance)

17

Resilience: Ultimate (Unit Rupture Work)

15 to 210 MJ/m3

Resilience: Unit (Modulus of Resilience)

460 to 3750 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

25 points

Strength to Weight: Axial

42 to 59 points

Strength to Weight: Bending

32 to 40 points

Thermal Diffusivity

4.1 mm2/s

Thermal Shock Resistance

39 to 54 points

Alloy Composition

Among wrought stainless steels, the composition of S17700 stainless steel is notable for including aluminum (Al). Aluminum is used to improve oxidation resistance. It can also enhance the effects of heat treatment.

Iron (Fe) 70.5 to 76.8
Chromium (Cr) 16 to 18
Nickel (Ni) 6.5 to 7.8
Aluminum (Al) 0.75 to 1.5
Manganese (Mn) 0 to 1.0
Silicon (Si) 0 to 1.0
Carbon (C) 0 to 0.090
Phosphorus (P) 0 to 0.040
Sulfur (S) 0 to 0.030

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM A693: Standard Specification for Precipitation-Hardening Stainless and Heat-Resisting Steel Plate, Sheet, and Strip

ASTM A564: Standard Specification for Hot-Rolled and Cold-Finished Age-Hardening Stainless Steel Bars and Shapes

ASTM A276: Standard Specification for Stainless Steel Bars and Shapes

Welding Metallurgy and Weldability of Stainless Steels, John C. Lippold and Damian J. Kotecki, 2005

ASTM A959: Standard Guide for Specifying Harmonized Standard Grade Compositions for Wrought Stainless Steels

Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993

Corrosion of Stainless Steels, A. John Sedriks, 1996

ASM Specialty Handbook: Stainless Steels, J. R. Davis (editor), 1994

Advances in Stainless Steels, Baldev Raj et al. (editors), 2010

CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015