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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.

Iron (Fe) 44.8 to 57.8
Chromium (Cr) 24 to 28
Nickel (Ni) 18 to 22
Manganese (Mn) 0 to 2.0
Silicon (Si) 0 to 2.0
Carbon (C) 0.2 to 0.6
Molybdenum (Mo) 0 to 0.5
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 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