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 mm2/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.
| Fe | 46.7 to 58 | |
| Cr | 23 to 27 | |
| Ni | 19 to 22 | |
| Mn | 0 to 2.0 | |
| Si | 0 to 2.0 | |
| Mo | 0 to 0.5 | |
| C | 0 to 0.2 | |
| P | 0 to 0.040 | |
| 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