AISI4140 Steel | 42CrMo4| SCM440|EN19

AISI 4140 steel is Chrome-Moly High Tensile Steel which has at least 0.8%Cr,0.15%Mo as strengthening alloy elements.The chromium content provides good hardness penetration, and the molybdenum content ensures uniform hardness and high strength. AISI 4140 steel can be oil hardened to a relatively high level of hardness with a tensile strength of 850 – 1000 MPa.AISI 4140 offers a very good balance of strength,toughness and wear-resistance.Compared with AISI 4130,it has a slightly higher carbon content which gives greater strength and heat treatment capabilities , however it is poor in weldability.Pre hardened and tempered 4140 can be further surface hardened by flame or induction hardening(can be surface hardened to a typical value 58HRC)and by nitriding( Surface hardness achievable is 600 to 650HV).

AISI 4140 Round bar

1.AISI 4140 steel Supply Form & Size

Form of SupplySize(mm)Length(mm)
Round barΦ6-Φ1,0003,000-10,000
Square bar100x100-600x6003,000-6,000
Plate/SheetThickness :20-400
Flat bar/BlcoksThickness :120-800

2.AISI 4140 steel Surface Finish&Tolerance

Surface FinishBlack-Forged Black-Rolled Turned   GrindingPolishedPeeledCold Drawn
Tolerance(0,+5mm)(0,+1mm)(0,+3mm)Best h9Best h11Best H11Best H11

3.AISI 4140 steel Chemical Composition&Related Specifications



4.AISI 4140 steel Mechanical Property

Ruling Section mm<254<127
Tensile Strength Mpa 690862
Yield Strength Mpa552758
Elongation %>20>13
Reduction of Area %>40>40
Charpy Impact -46°C, J>42>27
Hardness HB217-235285-341

5.AISI 4140 steel Forging

Forging temperature should be carried out between 1100℃-1200℃.Hold the temperature till uniform before forge,minimum forging temperature 850°C,cooling in sand after forged is recommended.

6.AISI 4140 steel Heat Treatment

  • Normalizing:870℃-900℃,Cool in air
  • Annealing:800℃-850℃,Cool in furnace
  • Hardening:840℃-875℃,oil or water quench
  • Tempering:450°C – 700°C, cool in still air
  • Nitriding:Heat to 500°C – 530°C and hold for sufficient time to develop the depth of case required
  • Flame and Induction Hardening:All materials consisting of de-carburized surfaces should be removed to ensure best results.Heat quickly to the required case depth at 860°C – 890°C and soak instantly in water or oil.Tempering at 150°C – 200°C helps reduce stresses in the case with marginal effect on its hardness


AISI 4140 alloy steel has good machinability,operations such as turning, hobbing, drilling, sawing, broaching, tapping and milling can be easily performed using the recommendations provided by the machine’s manufacturer for ideal tool type-feeds and speeds. AISI 4140 has the following properties:

  • Machinability rating at 66% of B1112
  • Average cutting speed of 110 ft/min.


AISI 4140 is commonly used for a variety of applications in the oil and gas ,aerospace,automotive, agricultural and defense industries.
Typical application:
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.