MakeItFrom.com
Menu (ESC)

ASTM A372 Grade K Alloy Steel

ASTM A372 grade K steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the quenched and tempered condition. ASTM A372 Grade K is the ASTM designation for this material. Older literature may refer to this material as Type VI, but this is now discouraged.

It has a moderately high ductility among wrought alloy steels in the same category. In addition, it has a very high tensile strength and a moderately high base cost.

The graph bars on the material properties cards below compare ASTM A372 grade K steel to: wrought alloy steels in the same category (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

230

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

23 %

Fatigue Strength

440 MPa 64 x 103 psi

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

490 MPa 71 x 103 psi

Tensile Strength: Ultimate (UTS)

780 MPa 110 x 103 psi

Tensile Strength: Yield (Proof)

620 MPa 89 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

440 °C 830 °F

Melting Completion (Liquidus)

1460 °C 2670 °F

Melting Onset (Solidus)

1420 °C 2590 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

48 W/m-K 28 BTU/h-ft-°F

Thermal Expansion

13 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.8 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.9 % IACS

Otherwise Unclassified Properties

Base Metal Price

4.4 % relative

Density

7.9 g/cm3 490 lb/ft3

Embodied Carbon

1.8 kg CO2/kg material

Embodied Energy

24 MJ/kg 10 x 103 BTU/lb

Embodied Water

57 L/kg 6.8 gal/lb

Common Calculations

PREN (Pitting Resistance)

2.7

Resilience: Ultimate (Unit Rupture Work)

160 MJ/m3

Resilience: Unit (Modulus of Resilience)

1010 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

27 points

Strength to Weight: Bending

24 points

Thermal Diffusivity

13 mm2/s

Thermal Shock Resistance

23 points

Alloy Composition

Among alloy steels, the composition of ASTM A372 grade K steel is notable for including nickel (Ni) and containing a comparatively high amount of chromium (Cr). Nickel is used to improve mechanical properties, and to make the alloy easier to heat treat. Chromium is used to improve corrosion resistance and most mechanical properties (particularly at higher temperatures).

Iron (Fe) 93.4 to 96.6
Nickel (Ni) 2.0 to 3.3
Chromium (Cr) 1.0 to 1.8
Molybdenum (Mo) 0.2 to 0.6
Manganese (Mn) 0.1 to 0.4
Silicon (Si) 0.15 to 0.35
Carbon (C) 0 to 0.18
Phosphorus (P) 0 to 0.015
Sulfur (S) 0 to 0.010

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM A372: Standard Specification for Carbon and Alloy Steel Forgings for Thin-Walled Pressure Vessels

Pressure Vessels: External Pressure Technology, 2nd ed., Carl T. F. Ross, 2011

ASM Specialty Handbook: Carbon and Alloy Steels, J. R. Davis (editor), 1996

Manufacture and Uses of Alloy Steels, Henry D. Hibbard, 2005

Steels: Processing, Structure, and Performance, 2nd ed., George Krauss, 2015