ASTM Grade HK (25Cr-20Ni, J94224) Cast Stainless Steel
ASTM grade HK steel is an austenitic stainless steel formulated for casting. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. HK is the ASTM designation for this material. J94224 is the UNS number. And 25Cr-20Ni is the common industry name.
It has a moderately low ductility among the cast austenitic stainless steels in the database.
The graph bars on the material properties cards below compare ASTM grade HK 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
11 %
Fatigue Strength
150 MPa 22 x 103 psi
Poisson's Ratio
0.27
Shear Modulus
79 GPa 11 x 106 psi
Tensile Strength: Ultimate (UTS)
500 MPa 73 x 103 psi
Tensile Strength: Yield (Proof)
270 MPa 40 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 2540 °F
Melting Onset (Solidus)
1350 °C 2460 °F
Specific Heat Capacity
480 J/kg-K 0.12 BTU/lb-°F
Thermal Conductivity
15 W/m-K 8.5 BTU/h-ft-°F
Thermal Expansion
17 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
63 MJ/kg 27 x 103 BTU/lb
Embodied Water
200 L/kg 23 gal/lb
Common Calculations
PREN (Pitting Resistance)
27
Resilience: Ultimate (Unit Rupture Work)
48 MJ/m3
Resilience: Unit (Modulus of Resilience)
190 kJ/m3
Stiffness to Weight: Axial
14 points
Stiffness to Weight: Bending
25 points
Strength to Weight: Axial
18 points
Strength to Weight: Bending
18 points
Thermal Diffusivity
3.9 mm2/s
Thermal Shock Resistance
11 points
Alloy Composition
Among cast stainless steels, the composition of ASTM grade HK 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.
| Fe | 44.8 to 57.8 | |
| Cr | 24 to 28 | |
| Ni | 18 to 22 | |
| Mn | 0 to 2.0 | |
| Si | 0 to 2.0 | |
| C | 0.2 to 0.6 | |
| Mo | 0 to 0.5 | |
| 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 A297: Standard Specification for Steel Castings, Iron-Chromium and Iron-Chromium-Nickel, Heat Resistant, for General Application
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
CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015