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EN 1.6311 (20MnMoNi4-5) Molybdenum Steel

EN 1.6311 steel is an alloy steel formulated for primary forming into wrought products. Cited properties are appropriate for the quenched and tempered condition. 1.6311 is the EN numeric designation for this material. 20MnMoNi4-5 is the EN chemical designation.

It has a moderately high density among EN wrought alloy steels. In addition, it has a fairly low thermal conductivity and a moderately high base cost.

The graph bars on the material properties cards below compare EN 1.6311 steel to: EN wrought alloy 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

200

Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

19 %

Fatigue Strength

340 MPa 49 x 103 psi

Impact Strength: V-Notched Charpy

51 J 38 ft-lb

Poisson's Ratio

0.29

Shear Modulus

73 GPa 11 x 106 psi

Shear Strength

400 MPa 59 x 103 psi

Tensile Strength: Ultimate (UTS)

650 MPa 94 x 103 psi

Tensile Strength: Yield (Proof)

490 MPa 72 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

410 °C 780 °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

39 W/m-K 22 BTU/h-ft-°F

Thermal Expansion

13 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.4 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.5 % IACS

Otherwise Unclassified Properties

Base Metal Price

2.9 % relative

Density

7.9 g/cm3 490 lb/ft3

Embodied Carbon

1.6 kg CO2/kg material

Embodied Energy

22 MJ/kg 9.3 x 103 BTU/lb

Embodied Water

51 L/kg 6.1 gal/lb

Common Calculations

PREN (Pitting Resistance)

2.1

Resilience: Ultimate (Unit Rupture Work)

120 MJ/m3

Resilience: Unit (Modulus of Resilience)

650 kJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

23 points

Strength to Weight: Bending

21 points

Thermal Diffusivity

10 mm2/s

Thermal Shock Resistance

19 points

Alloy Composition

Among alloy steels, the composition of EN 1.6311 steel is notable for containing a comparatively high amount of manganese (Mn) and including nitrogen (N). Manganese is used to improve hardenability, hot workability, and surface quality. There is some loss of ductility and weldability, however. Nitrogen has a substantial strengthening effect, but may contribute to strain aging unless the steel is deoxidized with aluminum.

Iron (Fe) 95.9 to 98
Manganese (Mn) 1.0 to 1.5
Nickel (Ni) 0.4 to 0.8
Molybdenum (Mo) 0.45 to 0.6
Chromium (Cr) 0 to 0.5
Silicon (Si) 0 to 0.4
Carbon (C) 0.15 to 0.23
Copper (Cu) 0 to 0.2
Phosphorus (P) 0 to 0.035
Sulfur (S) 0 to 0.035
Vanadium (V) 0 to 0.020
Nitrogen (N) 0 to 0.012

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

Followup Questions

Similar Alloys

Further Reading

EN 10028-2: Flat products made of steels for pressure purposes - Part 2: Non-alloy and alloy steels with specified elevated temperature properties

EN 10250-3: Open die steel forgings for general engineering purposes - Part 3: Alloy special steels

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

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

Ferrous Materials: Steel and Cast Iron, Hans Berns and Werner Theisen, 2008

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