4140 High Tensile Steel

4140 is a 1% chromium – molybdenum medium hardenability general purpose high tensile steel – generally  supplied hardened and tempered in the tensile range of 850 – 1000 Mpa (condition T).
4140 is now available with improved machinability, which greatly increases feeds and/or speeds, while also extending tool life without adversley affecting mechanical properties.
Pre hardened and tempered 4140 can be further surface hardened by flame or induction hardening and by nitriding.
4140 is used extensively in most industry sectors for a wide range of applications such as:
Adapters, Arbors, Axle Shafts, Bolts, Crankshafts, Connection Rods, Chuck Bodies, Collets, Conveyor Pins & Rolls, Ejector Pins, Forks, Gears, Guide Rods, Hydraulic Shafts & Parts,Lathe Spindles, Logging Parts, Milling Spindles, Motor Shafts, Nuts, Pinch Bars, Pins Various, Pinions, Pump Shafts, Rams, Sockets, Spindles, Sprockets, Studs, Tool Holders, Torsion Bars, Worms etc..

Colour Code

Stocked Sizes

Rounds

10mm to 690 mm Diameter

Hexagons

19 mm to 55 mm A/F

HollowBar

63 mm to 250 mm OD

 Bar Finish

Peeled, Cold Drawn
Turned and Polished,
Centreless Ground.
or Hot Rolled.

Related Specifications

Australia

AS 1444-1996-4140

Germany

DIN 17212 W.Nr 1.7223 Type 41CrMo4
DIN 17200-1654 W.Nr 1.7225 Type 42CrMo4
DIN 17200 W.Nr 1.7227 Type 42CrMoS4

Great Britain

BS970-1955 EN19A
BS970 Part 3:1991 709M40

International

ISO 683/II Type 3
ISO 683/IV Type 3a
ISO 683/IV Type 3b

Japan

JIS G 4103 SNCM4
JIS G 4105 SCM4
JIS G 4105 SCM440

USA

AISI 4140
ASTM A29/A29M-91 4140
ASTM A322 4140
ASTM A331 4140 (Cold Finish)
SAE 4140

Chemical Composition

Min.%

Max.%

 Carbon

 0.36

0.44

 Silicon

 0.10

0.40

 Manganese

 0.65

1.10

 Chromium

 0.75

1.20

 Molybdenum

 0.15

0.35

 Phosphorous

 0

0.04

 Sulphur

 0

0.04

Mechanical Property Requirements for Steels in the Heat-Treated Condition for Turned,
Peeled or Ground Finish to AS1444-1996 4140 and BS970 Part 3-1991 709M40

Mechanical
Property
Designation

Limited
Ruling
Section
mm

Tensile
Strength
Mpa

0.2%
Proof Stress
Mpa

Elongation
on 5.65
%

Izod
Impact
J

Charpy
Impact
J

Brinell
Hardness
HB

(Min)

(Max)

Min

Min.

Min.

Min.

Min

Max

R

250

700

850

480

15

34

28

201

255

S

250

770

930

540

13

27

22

223

277

S

150

770

930

570

15

54

50

223

277

*T

100

850

1000

665

13

54

50

248

302

U

63

930

1080

740

12

47

42

269

331

V

30

1000

1150

835

12

47

42

293

352

W

20

1080

1230

925

12

40

35

311

375

*Material stocked generally in condition T
Check test certificate if critical for end use.

Mechanical Property Requirements for Steels Heat-Treated, and then Cold Finished to
AS 1444 – 1996, and BS 970 Part 3 – 1991 709 M40

Mechanical
Property
Designation

Limited
Ruling
Section

Tensile
Strength
Mpa

0.20%
Proof Stress
Mpa

Elongation
on 5.65 
%

Brinell
Hardness
HB

Min

Max

Min

Min

Min

Max

R

63

700

850

525

12

201

255

S

63

770

930

585

11

223

277

T

63

850

1000

680

9

248

302

U

63

930

1080

755

9

269

331

V

63

1000

1150

850

9

293

352

*Material stocked generally in condition T
Check test certificate if critical for end use.

Forging

Heat to 1150 oC – 1200 oC maximum, hold until temperature is uniform throughout the section.
Do not forge below 850 oC.
Following forging operation the work piece should be cooled as slowly as possible.

Heat Treatment

Annealing

Heat to 800 oC – 850 oC, hold until temperature is uniform throughout the section and cool in furnace.

Flame or Induction Hardening

4140 hardened and tempered bar can be further surface hardened by either the flame or induction hardening methods resulting in a case hardness in excess of Rc 50.
Parts should be heated as quickly as possible to the austenitic temperature range (840 C – 870 C) and “required case depth followed by an immediate oil or water quench, depending upon hardness required, workpiece” size/shape and quenching arrangements.
“Following quenching to hand warm, most components should be tempered between 150 C – 200 C to remove” quenching stresses in the case. This will have little effect on case hardness and will reduce the risk of grinding cracks.

Hardening

Heat to 840 oC – 875 oC, hold until temperature is uniform throughout the section, soak for 10 – 15 minutes per 25 mm section, and quench in oil, water, or polymer as required.
*Temper immediately while still hand warm.

Nitriding

4140 hardened and tempered bar can also be successfully nitrided, giving a surface hardness of up to Rc 60. Nitriding is carried out at 490 oC – 530 oC, followed by slow cooling (no quench) reducing the problem of distortion. Parts can therefore be machined to near final size, leaving a grinding allowance only. The tensile strength of the core is usually not affected since the nitriding temperature range is generally below the original tempering temperature employed.

Normalizing

Heat to 870 oC – 900 oC, hold until temperature is uniform throughout the section, soak for 10 – 15 minutes and cool in still air.

Stress Relieving

Heat to 680 oC – 700 oC, hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm section, and cool in still air.

Tempering

Re-heat to 550 oC – 700 oC as required, hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm of section, and cool in still air.

Notes on Heat Treatment

Heating temperatures, rate of heating and soaking times will vary due to factors such as work piece size/shape also furnace type employed, quenching medium and work piece transfer facilities etc..
Please consult your heat treater for best results.

Machining

4140 in the hardened and tempered as supplied condition has good to very good machinability and operations such as sawing, turning, drilling, broaching, hobbing, milling and tapping can be carried out satisfactoraly using machine manufacturers recommendations for suitable tool type – feeds and speeds.

Welding

Welding of 4140 in the hardened and tempered condition (as normally supplied), is not recommended and should be avoided if at all possible, as the mechanical properties will be altered within the weld heat affected zone. It is preferred that welding be carried out on 4140 while in the annealed condition, and that the work piece, immediately on cooling to hand warm, is then stress relieved at 595 oC – 620 oC prior to hardening and tempering.
If welding in the hardened and tempered condition is really necessary, then the work piece, immediately on cooling to hand warm, should be if possible stress relieved at 15 oC below the original tempering temperature (if known).

Welding Procedure

Welding of 4140 in whatever condition should always be carried out using low hydrogen electrodes – please consult your welding consumables supplier.

Suggested pre-heat temperature

C

Si

Mn

P

S

Ni

Cr

Mo

Al

Ti

Min

0.38

0.15

0.75

–

–

–

0.80

0.15

–

–

Max

0.43

0.35

1.00

0.035

0.040

–

1.10

0.25

–

–

Nb(Cb)

Cu

Co

B

Fe

W

V

N

O

H

Min

–

–

–

–

Rest

–

–

–

–

–

Max

–

–

–

–

–

–

–

–

–

–

-40ºC

20ºC

200ºC

Tensile strength, yield (min.)

–

551 MPa (80 ksi)

–

Tensile strength, yield (typical)

–

–

–

Tensile strength, ultimate (min.)

–

689 MPa (100 ksi)

–

Tensile strength, ultimate (typical)

–

–

–

Tensile modulus (typical)

–

205 GPa

–

Torsion modulus (typical)

–

80 GPa

–

Elongation (min.)

–

20%

–

Red. of area (min.)

–

40%

–

Charpy V-notch impact (typical)

–

–

–

Fracture toughness KIC (typical)

–

–

–

Hardness (ISO 15156-3 limit)

–

22 HRC

–

Hardness (typical)

–

–

–

Fatigue strength (% of T.S.U)

–

–

–

-40ºC

20ºC

200ºC

Tensile strength, yield (min.)

–

758 MPa (110 ksi)

–

Tensile strength, ultimate (min.)

–

896 MPa (130 ksi)

–

Elongation (min.)

–

13%

–

Red. of area (min.)

–

30%

–

-40ºC

20ºC

200ºC

Density

–

7.85 kg/l

–

Thermal expansion coefficient

–

12.2 10-6/ºC

–

Thermal conductivity

–

42.7 W/mK 1)

–

Specific heat

–

0.477 J/gK

–

Electrical resistivity

–

0.22 mWm

–

Poisson’s ratio

–

0.29

–

Magnetic permeability

–

–

–

Good

Excellent

General corrosion

Abrasive wear

–

Sulphide Stress Cracking

Adhesive wear

–

Mechanical Properties

Properties

 Conditions 

T (°C)

Treatment

Density (×1000 kg/m3)

7.7-8.03

25

Poisson’s Ratio

0.27-0.30

25

Elastic Modulus (GPa)

190-210

25

Tensile Strength (Mpa)

655.0 

25 

annealed at 815°C  more

Yield Strength (Mpa)

417.1 

Elongation (%)

25.7 

Reduction in Area (%)

56.9 

Hardness (HB)

197 

25 

annealed at 815°C more

Impact Strength (J)
(Izod)

54.5 

25 

annealed at 815°C  more

Thermal Properties

Properties

 Conditions 

T (°C)

Treatment

Thermal Expansion (10-6/ºC)

12.3 

20-100 more

oil hardened, tempered 600°C 

Thermal Conductivity (W/m-K)

42.7 

100 more

Specific Heat (J/kg-K)

473 

150-200 more

Electric Properties

Properties

 Conditions 

T (°C)

Treatment

Electric Resistivity (10-9-m)

222 

20 more