4340 AISI 4340 SAE 4340 Alloy Steel - SAE AISI 1010 1015 1020 1025 1045 1018 1117 1035 1040 1050 1215 4140 4150

Alloy Steel 4340

4340 - Highly alloyed steel, nominally 1.8% Ni, .80% chromium and .25% molybdenum. High strength characteristics. Used for heavily stressed parts operating in fatigue and other duty conditions.

AISI 4340 has a favorable response to heat treatment usually oil quenching followed by tempering and exhibits a good combination of ductility and strength when treated thusly. Uses include piston pins, bearings, ordnance, gears, dies, and pressure vessels.

AISI 4340 is a Standard grade Alloy Steel. It is commonly called AISI 4340 Nickel-chromium-molybdenum steel. It is composed of (in weight percentage) 0.38-0.43% Carbon (C), 0.60-0.80% Manganese (Mn), 0.035%(max) Phosphorus (P), 0.04%(max) Sulfur (S), 0.15-0.30% Silicon (Si), 0.70-0.90% Chromium (Cr), 1.65-2.00% Nickel (Ni), 0.20-0.30% Molybdenum (Mo), and the base metal Iron (Fe). Other designations of AISI 4340 alloy steel include UNS G43400 and AISI 4340.

AISI 4340 is a heat treatable, low alloy steel containing nickel, chromium and molybdenum. It is known for its toughness and capability of developing high strength in the heat treating condition while retaining good fatigue strength.

Applications
Typical applications are for structural use, such as aircraft landing gear, power transmission gears and shafts and other structural parts.

Hardening
The alloy will harden by cold working or by heat treatment -- see "Heat Treatment" and "Tempering".

Machinability
Machining is best done with this alloy in the annealed or normalized and tempered condition. It can be machined by all conventional methods. However in the high strength conditions of 200 ksi or greater the machinability is only from 25% to 10% that of the alloy in the annealed condition.

Forming
4340 has good ductility in the annealed condition and most forming operations are carried out in that condition. It can be bent or formed by spinning or pressing in the annealed state. Bend radii should be 3t or greater.

Welding
The alloy can be fusion or resistance welded. Preheat and post heat weld procedures should be followed when welding this alloy by established methods.

Heat Treatment
Heat treatment for strengthening is done at 1525°F followed by an oil quench. For high strength (over 200 ksi) the alloy should first be normalized at 1650°F prior to heat treatment. See "Tempering" for strength levels.

Forging
Forging may be done in the range of 2250°F max. down to 1800°F.

Hot Working
4340 has very good cold forming capability so that hot working should not be needed. Hot working in any but the annealed condition can affect the strength level. Consult the alloy supplier in regard to hot working.

Cold Working
The 4340 alloy may be cold worked, in the annealed condition, by conventional methods and tooling. It has good ductility.

Annealing
A full anneal may be done at 1550°F followed by controlled (furnace) cooling at a rate not faster than 50°F per hour down to 600°F. From 600°F it may be air cooled.

Tempering
The temperature for tempering depends upon the strength level desired. Before tempering the alloy should be in the heat treated or normalized & heat treated condition - see "Heat Treatment". For strength levels in the 260 - 280 ksi range temper at 450°F. For strength in the 125 - 200 ksi range temper at 950°F. Do NOT temper the alloy if it is in the 220 - 260 ksi strength range as tempering can result in degradation of impact resistance for this level of strength.

Other Comments
AISI 4340 is considered to be a "through hardening" steel such that large section sizes can still be heat treated to high strength.

Chemical Composition

Carbon

0.38 - 0.43

Chromium

0.7 - 0.9

Iron

Balance

Manganese

0.6 - 0.8

Molybdenum

0.2 - 0.3

Nickel

1.65 - 2

Phosphorus

0.035 max

Silicon

0.15 - 0.3

Sulphur

0.04 max

Physical Properties

Density (lb / cu. in.)

0.28

Specific Gravity

7.8

Specific Heat (Btu/lb/Deg F - [32-212°F])

0.116

Melting Point (°F)

2600

Thermal Conductivity

Mean Coeff Thermal Expansion

6.6

Modulus of Elasticity Tension

Structural Steel Comparison Chart 1

Germany

China

England

France

Italy

Belgium

Swed

Spain

Japan

USA

Material No.

DIN

AFNOR

UNI

NBN

UNE

JIS

AISI

1.0401

C15

080M15

CC12

C15C16

1350

F.111

1015

1.0402

C22

050A20

CC20

C20C21

C25-1

1450

F.112

1020

1.0501

C35

060A35

CC35

C35

C35-1

1550

F.113

1035

1.0503

C45

080M40

CC45

C45

C45-1

1650

F.114

1045

1.0535

C55

070M55

C55

C55-1

1655

1055

1.0601

C60

080A62

43D

CC55

C60

C60-1

1060

1.7015

9SMn28

Y15

230M07

S250

CF9SMn28

1912

11SMn28

SUM22

1213

1.0718

9SMnPb28

S250Pb

CF9MnPb28

1914

11SMnPb28

SUM22L

12L13

1.0722

10SPb20

10PbF2

CF10Pb20

10SPb20

1.0726

35S20

212M36

35MF4

1957

F210G

1140

1.0736

9SMn36

Y13

240M07

S300

CF9SMn36

12SMn35

1215

1.0737

9SMnPb36

S300Pb

CF9SMnPb36

1926

12SMnP35

12L14

1.0904

55Si9

55Si2Mn

250A53

55S7

55Si8

55Si7

2085

56Si7

9255

1.0961

60SiCr7

60SC7

60SiCr8

9262

1.1141

Ck15

080M15

32C

XC12

C16

C16-2

1370

C15K

S15C

1015

1.1157

40Mn4

40Mn

150M36

35M5

1039

1.1158

Ck25

C25-2

S25C

1025

1.1167

36Mn5

35Mn2

40Mn5

2120

36Mn5

SMn438

1335

1.1170

28Mn6

30Mn

150M28

14A

20M5

C28Mn

28Mn6

SCMn1

1330

1.1183

Cf35

35Mn

060A35

XS38TS

C36

1572

S35C

1035

1.1191

Ck45

080M46

XC42

C45

C45-2

1672

C45K

S45C

1045

1.1203

Ck55

070M55

XC45

C50

C55-2

C55K

S55C

1055

1.1213

Cf53

060A52

XC48TS

C53

1674

S50C

1050

1.1221

Ck60

60Mn

080A62

43D

XC60

C60

C60-2

1678

S58C

1060

1.1274

Ck101

060A96

1870

SUP4

1095

1.3401

X120Mn12

Z120M12

X120M12

XG120Mn12

X120Mn12

SCMn
H/1

1.3505

100Cr6

Gr15
45Gr

534A99

100C6

100Cr6

2258

F.131

SUJ2

52100

1.5415

15Mo3

1501-240

15D3

16Mo3KW

16Mo3

2912

16Mo3

ASTM A20Gr.A

Structural Steel Comparison Table 2

Germany

China

England

France

Italy

Belgium

Swe

Spain

Material No.

DIN

AFNOR

UNI

NBN

UNE

1.5426

16Mo5

1503-245-420

16Mo5

1.5622

14Ni6

16N6

14Ni6

18Ni6

15Ni6

1.5662

X8Ni9

1501-509;510

X10Ni9

10Ni36

XBNi09

1.5680

12Ni19

Z18N5

12Ni20

1.5710

36NiCr6

640A35

111A

35NC6

1.5732

14NiCr10

14NC11

16NiCr11

15NiCr11

1.5752

14NiCr14

655M13;655A12

36A

12NC15

13NiCr12

1.6511

36CrNiMo4

816M40

110

40NCD3

38CrNiMo4

35CrNiMo4

1.6523

21NiCrMo2

850M20

362

20NCD2

20NiCrMo2

2503

20NiCrMo2

1.6546

40NiCrMo2

311-Type7

40NiCrMo2

1.6582

34CrNiMo6

40CrNiMoA

817M40

35NCD6

35CrNiMo6

2541

1.6587

17CrNiMo6

820A16

18NCD6

17CrNiMo7

14CrNiMo13

1.7015

15Cr3

15Cr

523M15

12C3

15Cr2

1.7033

34Cr4

35Cr

530A32

18B

32C4

34Cr4(KB)

34Cr4

35Cr4

1.7035

41Cr4

40Cr

530M40

42C4

41Cr4

42Cr4

1.7045

42Cr4

40Cr

2245

42Cr4

1.7131

16MnCr15

18CrMn

(527M20)

16MC5

16MnCr15

2511

16MnCr15

1.7176

55Cr3

20CrMn

527A60

55C3

55Cr3

1.7218

25CrMo4

30CrMn

1717CDS110

25CD4

25CrMo4

2225

55Cr3

1.7220

34CrMo4

35CrMo

708A37

19B

35CD4

35CrMo4

34CrMo4

2234

34CrMo4

1.7223

41CrMo4

40CrMoA

708M40

19A

42CD4TS

41CrMo4

2244

41CrMo4

1.7225

42CrMo4

42CrMo;
42CrMnMo

708M40

19A

42CD4

42CrMo4

2244

42CrMo4

1.7262

15CrMo5

12CD4

2216

12CrMo4

1.7335

13CrMo44

1501-620Gr.27

15CD3.5;
15CD4.5

14CrMo44

14CrMo45

1.7361

32CrMo12

722M24

40B

30CD12

32CrMo12

2240

F.124.A

1.7380

10CrMo910

1501-622Gr.31;45

12CD9;10

12CrMo9,10

2218

TU.H

1.7715

14MoV63

1503-660-440

13MoCrV6

1.8159

50CrV4

50CrVA

735A50

50CV4

50CrV4

2230

51CrV4

1.8509

41CrAlMo7

905M39

41B

40CAD6,12

41CrAlMo7

2940

41CrAlMo7

1.8523

39CrMoV139

897M39

40C

36CrMoV12

36CrMoV13