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ACI-ASTM CK20 (J94202) Cast Stainless Steel

ACI-ASTM CK20 steel is an austenitic stainless steel formulated for casting. Cited properties are appropriate for the heat treated (HT) condition. CK20 is the designation in both the ACI and ASTM systems for this material. J94202 is the UNS number.

It has a moderately high ductility among the cast austenitic stainless steels in the database.

The graph bars on the material properties cards below compare ACI-ASTM CK20 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

150

Elastic (Young's, Tensile) Modulus

200 GPa 29 x 106 psi

Elongation at Break

37 %

Fatigue Strength

220 MPa 31 x 103 psi

Poisson's Ratio

0.28

Shear Modulus

78 GPa 11 x 106 psi

Tensile Strength: Ultimate (UTS)

530 MPa 77 x 103 psi

Tensile Strength: Yield (Proof)

260 MPa 38 x 103 psi

Thermal Properties

Latent Heat of Fusion

310 J/g

Maximum Temperature: Corrosion

440 °C 830 °F

Maximum Temperature: Mechanical

1100 °C 2010 °F

Melting Completion (Liquidus)

1400 °C 2550 °F

Melting Onset (Solidus)

1430 °C 2610 °F

Specific Heat Capacity

480 J/kg-K 0.12 BTU/lb-°F

Thermal Conductivity

14 W/m-K 8.1 BTU/h-ft-°F

Thermal Expansion

15 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

2.0 % IACS

Electrical Conductivity: Equal Weight (Specific)

2.3 % IACS

Otherwise Unclassified Properties

Base Metal Price

25 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

4.4 kg CO2/kg material

Embodied Energy

62 MJ/kg 27 x 103 BTU/lb

Embodied Water

190 L/kg 23 gal/lb

Common Calculations

PREN (Pitting Resistance)

26

Resilience: Ultimate (Unit Rupture Work)

160 MJ/m3

Resilience: Unit (Modulus of Resilience)

170 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

3.7 m2/s

Thermal Shock Resistance

13 points

Alloy Composition

Among cast stainless steels, the composition of ACI-ASTM CK20 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) 46.7 to 58
Chromium (Cr) 23 to 27
Nickel (Ni) 19 to 22
Manganese (Mn) 0 to 2.0
Silicon (Si) 0 to 2.0
Molybdenum (Mo) 0 to 0.5
Carbon (C) 0 to 0.2
Phosphorus (P) 0 to 0.040
Sulfur (S) 0 to 0.040

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 of Stainless Steels, Erich Folkhard et al., 2012

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