SAE 4340 Structural and constructional steels

Material group: Ferrous Alloys / Structural and constructional steels

Country / Standard: United States / SAE

Indicative price:

Data updates

Latest Update: 2023-11

Total number of updates: 18

Update History

2023-03 2021-04 2020-11 2020-08 2020-06 2020-04 2019-12 2019-09 2019-01 2018-10 2018-09 2018-01 2017-05 2017-02 2016-03 2016-01 2015-12

This material has 1330 properties — only a subset is shown here.

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SAE 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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SAE 4340 Physical Properties

Temperature

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

PROPERTY / VALUE

Compression Modulus

200 GPa

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Modulus of Elasticity

190 — 210 GPa

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Thermal Conductivity

val1 W/(m∙°C)

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Electrical Resistivity

val1 Ω∙mm²/m

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Density

val1 kg/dm³

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Electrical Conductivity

val1 S/m

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Poisson Coefficient

val1

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Shear Modulus

val1 GPa

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Coefficient of Thermal Expansion (CTE)

val1 10^-6/°C

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This material has 1330 properties — only a subset is shown here.

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SAE 4340 Heat Treatments

Preheating: Preheating until furnace stabilization in the 900 to 1200°F (482 to 649°C) range is recommended before heating parts above 1300°F (704°C) if the parts have previously been heat treated to a hardness greater than 35 HRC, have abrupt changes of section thickness, have sharp reentrant angles, have finished machined surfaces, have been welded, have been cold formed or straightened, have holes, or have sharp or only slightly-rounded notches or corners.

Annealing: Heated to 843°C (temperatures ≥ 704°C are to be cooled at a rate not to exceed 111°C per hour to below 427°C). Soaking time (for annealing, normalizing and austenitizing) is specified below. Air cooled to ambient temperature. Isothermal annealing treatments may be used provided equivalent hardness is obtained (heated to annealing temperature, soaked for the time specified above, cooled to a temperature below the critical, held for sufficient time to complete transformation, and air cooled to ambient temperature).

Subcritical annealing: When required, subcritical annealing shall be accomplished prior to hardening by heating to a set temperature between 1150 and 1250°F (621 and 677°C). Cooling to ambient temperature.

Pre-hardening stress relief: When required, pre-hardening stress relieving shall be done in accordance with AMS2759/11 prior to hardening by heating to a set temperature between 1000 and 1250°F (538 to 677°C). Cooling to ambient temperature.

Normalizing: Heated to 899°C. Circulated air or atmosphere is recommended for thicknesses greater than 76 mm. Normalizing may be followed by tempering or subcritical annealing.

Hardening (austenitizing and quenching): Heated to 816-843°C, any setpoint within this range is acceptable. The parts shall be cooled to or below the quenchant temperature or to a temperature low enough to achieve complete transformation, before tempering. Hardening quenchant should be oil or polymer. Prior to initial tempering parts may be snap tempered for 2 hours minimum at a temperature, usually 400°F (204°C), that is lower than the tempering temperature. Welded parts, and brazed parts with a brazing temperature above the normalizing temperature, shall be normalized before hardening. For welded or brazed alloys that are not normalized, the parts shall be annealed. Welded parts should be preheated. Parts identified as damage tolerant, maintenance critical, or fracture critical shall be in the normalized condition before hardening, unless the alloy is not normalized, in which case the part shall be annealed.

Tempering: Parts should be tempered within two hours of quenching. Suggested tempering temperatures:
for TS 862-1034 MPa, HRC 26-34 and oil or polymer quenchant is 649°C
for TS 1034-1172 MPa, HRC 33-38 and oil or polymer quenchant is 593°C
for TS 1103-1241 MPa, HRC 36-40 and oil or polymer quenchant is 552°C
for TS 1241-1379 MPa, HRC 40-43 and oil or polymer quenchant is 496°C
for TS 1379-1517 MPa, HRC 43-46 and oil or polymer quenchant is 441°C (at least two tempering operations required).
Steel is not recommended for other TS ranges.
Suggested approximate tempering temperatures based on as-quenched hardness:
for TS 965-1103 MPa: HRC 47-49 is 538°C, HRC 50-52 is 566°C, HRC 53-55 is 593°C, HRC 56-58 is 635°C, for HRC ≥ 59 is 663°C
for TS 1034-1172 MPa: HRC 47-49 is 496°C, HRC 50-52 524°C, HRC 53-55 is 552°C, HRC 56-58 is 593°C, HRC ≥ 59 is 621°C
for TS 1103-1241MPa: HRC 50-52 482°C, HRC 53-55 is 524°C, HRC 56-58 is 566°C, for HRC ≥ 59 is 593°C
for TS 1172-1310 MPa: HRC 50-52 is 454°C, HRC 53-55 is 496°C, HRC 56-58 is 538°C, for HRC ≥ 59 is 566°C
for TS 1241-1379 MPa: HRC 50-52 is 427°C, HRC 53-55 is 468°C, HRC 56-58 is 510°C, for HRC ≥ 59 is 538°C
for TS 1310-1448 MPa: HRC 50-52 is 385°C, HRC 53-55 is 427°C, HRC 56-58 is 482°C, for HRC ≥ 59 is 524°C
for TS 1379-1517 MPa: HRC 53-55 is 399°C, HRC 56-58 is 454°C, for HRC ≥ 59 is 510°C (at least two tempering operations required).
Steel is not recommended for other hardness ranges.
Soaking time shall be not less than 2 hours plus 1 hour additional for each inch (25 mm) of thickness or fraction thereof greater than 1 inch (25 mm). Thickness is defined in AMS2759. When load thermocouples are used, the soak time shall be 2 to 3 hours. Multiple tempering cycles are permitted. When multiple tempering cycles are required, parts shall be cooled to ambient temperature between tempering treatments. When tempering cannot be started within 4 hours from the end of quenching, parts shall be snap tempered for 2 hours minimum at a temperature that is lower than the final tempering set temperature, usually 400°F (204°C). For parts having minimum tensile strength below 180 ksi (1241 MPa), straightening may be accomplished cold without stress relieving. For parts hardened and tempered to minimum tensile strength of 180 ksi (1241 MPa) and higher, straightening shall be accomplished during tempering, or by heating to not higher than 50°F (28°C) below the tempering temperature. Hot or warm straightening after tempering shall be followed by stress relieving. It is permissible to retemper at a temperature not higher than the last tempering temperature after straightening during tempering.

Soak time for annealing, normalizing, and austenitizing:

t ≤ 6.35 mm, minimum soak time (air or atmosphere) is 25 minutes or 18 minutes (salt)
6.35 < t ≤ 12.70 mm, minimum soak time (air or atmosphere) is 45 minutes or 35 minutes (salt)
12.70 < t ≤ 25.40 mm, minimum soak time (air or atmosphere) is 1 hour or 40 minutes (salt)
25.40 < t ≤ 38.10 mm, minimum soak time (air or atmosphere) is 1 hour and 15 minutes or 45 minutes (salt)
38.10 < t ≤ 50.80 mm, minimum soak time (air or atmosphere) is 1 hour and 30 minutes or 50 minutes (salt)
50.80 < t ≤ 63.50 mm, minimum soak time (air or atmosphere) is 1 hour and 45 minutes or 55 minutes (salt)
63.50 < t ≤ 76.20 mm, minimum soak time (air or atmosphere) is 2 hours or 1 hour (salt)
76.20 < t ≤ 88.90 mm, minimum soak time (air or atmosphere) is 2 hours and 15 minutes or 1 hour and 5 minutes (salt)
88.90 < t ≤ 101.60 mm, minimum soak time (air or atmosphere) is 2 hours and 30 minutes or 1 hour and 10 minutes (salt)
101.60 < t ≤ 114.30 mm, minimum soak time (air or atmosphere) is 2 hours and 45 minutes or 1 hour and 15 minutes (salt)
114.30 < t ≤ 127.00 mm, minimum soak time (air or atmosphere) is 3 hours or 1 hour and 20 minutes (salt)
127.00 < t ≤ 203.20 mm, minimum soak time (air or atmosphere) is 3 hours and 30 minutes or 1 hour and 40 minutes (salt)
> 203.20 mm, minimum soak time is 4 hours and 30 minutes for every 76 mm or increment of 76 mm greater than 203 mm (air or atmosphere) or 2 hours plus 20 minutes for every 76 mm or increment of 76 mm greater than 203 mm (salt)

Thickness is the minimum dimension of the heaviest section of the part.
Parts coated with copper plate or similar reflective coatings that tend to reflect radiant heat shall have their soak time increased by at least 50%, unless load thermocouples are used. This increase does not apply to salt bath heat treating, tempering, or sub-zero processing.
The parts shall be held for sufficient time to ensure that the center of the most massive area has reached temperature and the necessary transformation and diffusion have taken place.
Maximum soak time at temperature shall not exceed three times the minimum soak time including time additions for copper plating or similar reflective coating.
Longer times may be necessary for parts with complex shapes or parts that do not heat uniformly.
Annealing temperature: 843°C (1550°F), cool at a rate not to exceed 111°C (200°F) per hour to below 427°C (800°F). Normalizing temperature: 899°C (1650°F); Austenitizing temperature: 816 - 843°C (1500 - 1550°F). Hardening quenchant: oil, polymer, inert gas. (Marquenching in a nitrate/nitrite salt bath, oil bath, or alternate quenchant operated at a set temperature applicable to the alloys processed is permitted. The parts shall be in the marquenching bath only for sufficient time to stabilize the parts at the bath temperature, but not less than 2 minutes, followed by cooling to approximately ambient temperature. Salt residues shall be removed by a hot water rinse before air tempering).
Tempering: 218 - 254°C (425 - 490°F), at least two tempering operations are required.
All parts, shall be in one of the following conditions prior to austenitizing: normalized, normalized or tempered or hardened. If those parts have been normalized only without tempering or overaging, they shall be preheated before exposure to the austenitizing temperature.

SAE 4340 Mechanical Properties

Temperature

≤ 0°C 0 - 30°C

PROPERTY / VALUE

Tensile Strength

≥ 677.5 MPa

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Brinell Hardness (HB)

187 — 322

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Elongation, A

val1 %

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Compression Yield Strength

val1 MPa

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Grain Size

val1

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Impact Energy

val1 J

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Reduction of Area

val1 %

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Rockwell Hardness (HR)

val1

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Yield Strength, Rp0.2

val1 MPa

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SAE 4340 International Equivalent Materials

Showing 15 of 408 results.

MATERIAL

STANDARD

COUNTRY / PRODUCER

EQUIVALENCE CATEGORY

MATERIAL

SNB 24-1

STANDARD

JIS

COUNTRY / PRODUCER

Japan

EQUIVALENCE CATEGORY

Official

MATERIAL

SNCM439

STANDARD

JIS

COUNTRY / PRODUCER

Japan

EQUIVALENCE CATEGORY

Official

MATERIAL

G43400

STANDARD

UNS

COUNTRY / PRODUCER

United States

EQUIVALENCE CATEGORY

Official

MATERIAL

40Ni6Cr4Mo3

STANDARD

COUNTRY / PRODUCER

India

EQUIVALENCE CATEGORY

Official

MATERIAL

40Ni2Cr1Mo28

STANDARD

COUNTRY / PRODUCER

India

EQUIVALENCE CATEGORY

Official

MATERIAL

G43406

STANDARD

UNS

COUNTRY / PRODUCER

United States

EQUIVALENCE CATEGORY

Official

MATERIAL

J24060

STANDARD

UNS

COUNTRY / PRODUCER

United States

EQUIVALENCE CATEGORY

Official

MATERIAL

A 646 Grade 4340

STANDARD

ASTM

COUNTRY / PRODUCER

United States

EQUIVALENCE CATEGORY

Official

MATERIAL

EN 24

STANDARD

B.S.

COUNTRY / PRODUCER

United Kingdom

EQUIVALENCE CATEGORY

Official

MATERIAL

SNB 24-1

STANDARD

COUNTRY / PRODUCER

Korea

EQUIVALENCE CATEGORY

Official

MATERIAL

SNB 24-2

STANDARD

COUNTRY / PRODUCER

Korea

EQUIVALENCE CATEGORY

Official

MATERIAL

SNB 24-3

STANDARD

COUNTRY / PRODUCER

Korea

EQUIVALENCE CATEGORY

Official

MATERIAL

SNB 24-4

STANDARD

COUNTRY / PRODUCER

Korea

EQUIVALENCE CATEGORY

Official

MATERIAL

SNB 24-5

STANDARD

COUNTRY / PRODUCER

Korea

EQUIVALENCE CATEGORY

Official

MATERIAL

4340

STANDARD

NBR

COUNTRY / PRODUCER

Brazil

EQUIVALENCE CATEGORY

Official

Equivalence categories reflect chemical-composition and mechanical-property comparison — always verify suitability against the governing specification for your application.

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408Cross References

76Composition
219Mechanical Properties
68Physical Properties
27Heat Treatment
18Metallography
3Machinability

34Stress-Strain
2Formability
32Fatigue
3Fracture
-Creep

1Joints
-Coatings
97Dimensions
-Tribology

2Corrosion
1Ageing
-Weatherability
-Irradiation

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