AISI 4340 Structural and constructional steels

Material group: Ferrous Alloys / Structural and constructional steels

Country/Standard: United States / AISI

Data updates

Latest Update: 2024-07

Total number of updates: 16

Update History

2023-11 2023-05 2023-03 2020-11 2020-08 2020-06 2020-03 2019-09 2019-03 2018-01 2017-05 2017-02 2016-03 2015-12 2015-04

This material has 1334 properties — only a subset is shown here.

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AISI 4340 Chemical Composition

CRITERIA

VALUE

UNIT

CAS NUMBER

CRITERIA

VALUE

0.38 – 0.43

UNIT

CAS NUMBER

7440-44-0

CRITERIA

VALUE

0.70 – 0.90

UNIT

CAS NUMBER

7440-47-3

CRITERIA

VALUE

≤ 0.35

UNIT

CAS NUMBER

7440-50-8

CRITERIA

VALUE

val1

UNIT

CAS NUMBER

7439-96-5

CRITERIA

VALUE

val1

UNIT

CAS NUMBER

7439-98-7

CRITERIA

VALUE

val1

UNIT

CAS NUMBER

7440-02-0

CRITERIA

VALUE

val1

UNIT

CAS NUMBER

7723-14-0

CRITERIA

VALUE

val1

UNIT

CAS NUMBER

7439-92-1

CRITERIA

VALUE

val1

UNIT

CAS NUMBER

7704-34-9

CRITERIA

VALUE

val1

UNIT

CAS NUMBER

7440-21-3

SAE J 404: 2009 / Chemical compositions of SAE alloy steels

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AISI 4340 Physical Properties

Temperature

≤ 0°C 0 - 30°C 30 - 100°C 100 - 300°C ≥ 300°C

PROPERTY / VALUE

Modulus of Elasticity

190 — 210 GPa

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Compression Modulus

200 GPa

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Shear Modulus

val1 GPa

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Density

val1 kg/dm³

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Poisson Coefficient

val1

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Coefficient of Thermal Expansion (CTE)

val1 10^-6/°C

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Thermal Conductivity

val1 W/(m∙°C)

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Electrical Resistivity

val1 Ω∙mm²/m

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Electrical Conductivity

val1 S/m

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This material has 1334 properties — only a subset is shown here.

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AISI 4340 Heat Treatments

Normalizing: 871-927°C (1600-1700°F), air quenched. Annealing: 829-857°C (1525-1575°F). Furnace cool to 538°C (1000°F) or below (rate of furnace cool should be 28°C (50°F) per hour or slower). Recommended subcritical anneal temperature is 677°C (1250°F).
Austenitizing: 816-843°C (1500-1550°F). Medium for quenching: oil.
Normalized by heating to 870-925°C in an atmosphere neutral to the specified carbon range, holding at heat for not less than 1 hour per 25 mm of maximum cross-section and cooling in air to room temperature and tempered by heating to not lower than 595°C, holding at heat for not less than1 hour and cooling in air. Harden by heating to 815°C +/-15°C holding at heat for not less than 30 minutes and quenching in oil. Double temper by heating to 425°C +/-8°C holding at heat for 2 hours +/-15 minutes and cooling in air after each tempering operation.

AISI 4340 Mechanical Properties

Temperature

≤ 0°C 0 - 30°C

PROPERTY / VALUE

Yield Strength, Rp0.2

val1 MPa

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Compression Yield Strength

val1 MPa

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Tensile Strength

val1 MPa

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Elongation, A

val1 %

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Reduction of Area

val1 %

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Impact Energy

val1 J

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Brinell Hardness (HB)

187 — 322

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Rockwell Hardness (HR)

val1

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Grain Size

val1

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426 Cross References

75 Composition
214 Mechanical Properties
68 Physical Properties
24 Heat Treatment
18 Metallography
4 Machinability

5 Stress-Strain
2 Formability
32 Fatigue
3 Fracture
- Creep

1 Joints
- Coatings
114 Dimensions
- Tribology

2 Corrosion
1 Ageing
- Weatherability
- Irradiation

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