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AISI 431 (S43100) Stainless Steel

AISI 431 stainless steel is a martensitic stainless steel formulated for primary forming into wrought products. 431 is the AISI designation for this material. S43100 is the UNS number. Additionally, the British Standard (BS) designation is 431S29.

It can have a moderately high tensile strength among the wrought martensitic stainless steels in the database.

The properties of AISI 431 stainless steel include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare AISI 431 stainless steel to: wrought martensitic 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

250

Elastic (Young's, Tensile) Modulus

200 GPa 28 x 106 psi

Elongation at Break

15 to 17 %

Fatigue Strength

430 to 610 MPa 62 to 88 x 103 psi

Poisson's Ratio

0.28

Rockwell C Hardness

26

Shear Modulus

77 GPa 11 x 106 psi

Shear Strength

550 to 840 MPa 80 to 120 x 103 psi

Tensile Strength: Ultimate (UTS)

890 to 1380 MPa 130 to 200 x 103 psi

Tensile Strength: Yield (Proof)

710 to 1040 MPa 100 to 150 x 103 psi

Thermal Properties

Latent Heat of Fusion

280 J/g

Maximum Temperature: Corrosion

400 °C 760 °F

Maximum Temperature: Mechanical

850 °C 1550 °F

Melting Completion (Liquidus)

1510 °C 2750 °F

Melting Onset (Solidus)

1450 °C 2640 °F

Specific Heat Capacity

480 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

26 W/m-K 15 BTU/h-ft-°F

Thermal Expansion

12 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

2.6 % IACS

Electrical Conductivity: Equal Weight (Specific)

3.0 % IACS

Otherwise Unclassified Properties

Base Metal Price

9.0 % relative

Density

7.7 g/cm3 480 lb/ft3

Embodied Carbon

2.2 kg CO2/kg material

Embodied Energy

31 MJ/kg 13 x 103 BTU/lb

Embodied Water

120 L/kg 14 gal/lb

Common Calculations

PREN (Pitting Resistance)

16

Resilience: Ultimate (Unit Rupture Work)

140 to 180 MJ/m3

Resilience: Unit (Modulus of Resilience)

1270 to 2770 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

25 points

Strength to Weight: Axial

32 to 50 points

Strength to Weight: Bending

27 to 36 points

Thermal Diffusivity

7.0 mm2/s

Thermal Shock Resistance

28 to 43 points

Alloy Composition

Among wrought stainless steels, the composition of AISI 431 stainless steel is notable for containing comparatively high amounts of chromium (Cr) and nickel (Ni). Chromium is the defining alloying element of stainless steel. Higher chromium content imparts additional corrosion resistance. Nickel is primarily used to achieve a specific microstructure. In addition, it has a beneficial effect on mechanical properties and certain types of corrosion.

Iron (Fe) 78.2 to 83.8
Chromium (Cr) 15 to 17
Nickel (Ni) 1.3 to 2.5
Manganese (Mn) 0 to 1.0
Silicon (Si) 0 to 1.0
Carbon (C) 0 to 0.2
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 A176: Standard Specification for Stainless and Heat-Resisting Chromium Steel Plate, Sheet, and Strip

ASTM A473: Standard Specification for Stainless Steel Forgings

ASTM A479: Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels

ASTM A276: Standard Specification for Stainless Steel Bars and Shapes

Creep-Resistant Steels, Fujio Abe et al. (editors), 2008

Advanced Materials in Automotive Engineering, Jason Rowe (editor), 2012

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

Pressure Vessels: External Pressure Technology, 2nd ed., Carl T. F. Ross, 2011

Corrosion of Stainless Steels, A. John Sedriks, 1996

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