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ACI-ASTM CN7MS (J94650) Cast Stainless Steel

ACI-ASTM CN7MS steel is an austenitic stainless steel formulated for casting. Cited properties are appropriate for the heat treated (HT) condition. CN7MS is the designation in both the ACI and ASTM systems for this material. J94650 is the UNS number.

It has a moderately low thermal conductivity and a moderately high ductility among cast austenitic stainless steels.

The graph bars on the material properties cards below compare ACI-ASTM CN7MS steel to: cast austenitic 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

160

Elastic (Young's, Tensile) Modulus

200 GPa 29 x 106 psi

Elongation at Break

39 %

Fatigue Strength

200 MPa 29 x 103 psi

Poisson's Ratio

0.28

Shear Modulus

77 GPa 11 x 106 psi

Tensile Strength: Ultimate (UTS)

540 MPa 79 x 103 psi

Tensile Strength: Yield (Proof)

230 MPa 34 x 103 psi

Thermal Properties

Latent Heat of Fusion

340 J/g

Maximum Temperature: Corrosion

420 °C 790 °F

Maximum Temperature: Mechanical

1040 °C 1910 °F

Melting Completion (Liquidus)

1400 °C 2540 °F

Melting Onset (Solidus)

1350 °C 2460 °F

Specific Heat Capacity

480 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

12 W/m-K 7.0 BTU/h-ft-°F

Thermal Expansion

16 µm/m-K

Otherwise Unclassified Properties

Base Metal Price

28 % relative

Density

7.9 g/cm3 490 lb/ft3

Embodied Carbon

5.1 kg CO2/kg material

Embodied Energy

71 MJ/kg 31 x 103 BTU/lb

Embodied Water

180 L/kg 22 gal/lb

Common Calculations

PREN (Pitting Resistance)

28

Resilience: Ultimate (Unit Rupture Work)

170 MJ/m3

Resilience: Unit (Modulus of Resilience)

140 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

25 points

Strength to Weight: Axial

19 points

Strength to Weight: Bending

19 points

Thermal Diffusivity

3.2 mm2/s

Thermal Shock Resistance

13 points

Alloy Composition

Among cast stainless steels, the composition of ACI-ASTM CN7MS steel is notable for containing comparatively high amounts of silicon (Si) and nickel (Ni). Silicon content is typically governed by metallurgical processing concerns, but it can also be added for the purpose of improving oxidation 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) 45.4 to 53.5
Nickel (Ni) 22 to 25
Chromium (Cr) 18 to 20
Silicon (Si) 2.5 to 3.5
Molybdenum (Mo) 2.5 to 3.0
Copper (Cu) 1.5 to 2.0
Manganese (Mn) 0 to 1.0
Carbon (C) 0 to 0.070
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 A743: Standard Specification for Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application

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

Corrosion of Austenitic Stainless Steels: Mechanism, Mitigation and Monitoring, H. S. Khatak and B. Raj (editors), 2002

Austenitic Stainless Steels: Microstructure and Mechanical Properties, P. Marshall, 1984

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

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

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