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ACI-ASTM CA6NM (J91540) Cast Stainless Steel

ACI-ASTM CA6NM steel is a martensitic stainless steel formulated for casting. Cited properties are appropriate for the heat treated (HT) condition. CA6NM is the designation in both the ACI and ASTM systems for this material. J91540 is the UNS number.

The graph bars on the material properties cards below compare ACI-ASTM CA6NM steel to: cast 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

17 %

Fatigue Strength

380 MPa 55 x 103 psi

Poisson's Ratio

0.28

Reduction in Area

40 %

Shear Modulus

76 GPa 11 x 106 psi

Tensile Strength: Ultimate (UTS)

850 MPa 120 x 103 psi

Tensile Strength: Yield (Proof)

620 MPa 90 x 103 psi

Thermal Properties

Latent Heat of Fusion

280 J/g

Maximum Temperature: Corrosion

390 °C 740 °F

Maximum Temperature: Mechanical

770 °C 1420 °F

Melting Completion (Liquidus)

1450 °C 2630 °F

Melting Onset (Solidus)

1400 °C 2560 °F

Specific Heat Capacity

480 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

25 W/m-K 14 BTU/h-ft-°F

Thermal Expansion

10 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

2.8 % IACS

Electrical Conductivity: Equal Weight (Specific)

3.2 % IACS

Otherwise Unclassified Properties

Base Metal Price

10 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

2.5 kg CO2/kg material

Embodied Energy

34 MJ/kg 15 x 103 BTU/lb

Embodied Water

110 L/kg 13 gal/lb

Common Calculations

PREN (Pitting Resistance)

15

Resilience: Ultimate (Unit Rupture Work)

130 MJ/m3

Resilience: Unit (Modulus of Resilience)

1000 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

25 points

Strength to Weight: Axial

30 points

Strength to Weight: Bending

26 points

Thermal Diffusivity

6.7 mm2/s

Thermal Shock Resistance

31 points

Alloy Composition

Among cast stainless steels, the composition of ACI-ASTM CA6NM steel is notable for containing comparatively high amounts of nickel (Ni) and chromium (Cr). Nickel is primarily used to achieve a specific microstructure. In addition, it has a beneficial effect on mechanical properties and certain types of corrosion. Chromium is the defining alloying element of stainless steel. Higher chromium content imparts additional corrosion resistance.

Iron (Fe) 78.4 to 84.6
Chromium (Cr) 11.5 to 14
Nickel (Ni) 3.5 to 4.5
Molybdenum (Mo) 0.4 to 1.0
Manganese (Mn) 0 to 1.0
Silicon (Si) 0 to 1.0
Carbon (C) 0 to 0.060
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 A356: Standard Specification for Steel Castings, Carbon, Low Alloy, and Stainless Steel, Heavy-Walled for Steam Turbines

ASTM A352: Standard Specification for Steel Castings, Ferritic and Martensitic, for Pressure-Containing Parts, Suitable for Low-Temperature Service

ASTM A743: Standard Specification for Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application

Welding Metallurgy of Stainless Steels, Erich Folkhard et al., 2012

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

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