• ALLOY STEEL - 4140 / 42Crmo4 / 1.7225 / SCM440
  • 4140 / 42Crmo4 / 1.7225 / SCM440

4140 / 42Crmo4 / 1.7225 / SCM440

4140-steel-42crmo4-ai' target='_blank'>SAE 4140 Steel Mechanical Properties:

The alloy is readily machinable. Simple shapes might be machined following a normalizing treatment, whereas more complex shapes will require annealing. At the carbon level of this grade, a structure of coarse lamellar pearlite to coarse spheroidite is normally optimum for machinability.

4140-steel-42crmo4-ai' target='_blank'>AISI 4140 Chemical  Composition:

C(%) Mn(%)  Cr(%) Mo Si(%) P(%) S(%)
0.38–0.43 0.75–1.00 0.80–1.10 0.15–0.25 0.20-0.35 ≤0.035 ≤0.04
  • Introduction

  • Heat Treatment

  • Applications

  • Equivalent Grade

  • 4140 Steel Introduction:

    AISI/SAE 4140 grade is a versatile alloy with good atmospheric corrosion resistance and reasonable strength up to around 600º F (315º C.) It shows good overall combinations of strength, toughness, wear resistance and fatigue strength.

  • 4140-steel-42crmo4-ai' target='_blank'>AISI 4140 Steel Bar Heat Treatment:

    Heat treatment is carried out after hot working to render the steel suitable for machining, and to meet the mechanical property ranges specified for the steel’s particular applications. There are several ways to heat treat a given steel part and it is only through practice that the optimum treatments, temperatures and conditions may be defined. The following information should be taken as a guide only.



    Forgings of 4140 grade may be annealed by transferring the parts straight from the forging operation to a furnace held at a suitable temperature, between 1450 and 1550 º F (790 and 840 º C), holding for a suitable time then furnace cooling, forming a structure suitable for machining. This kind of treatment is best used for parts with simple shapes. If some areas of a forging will finish much colder than others then a uniform structure will not be obtained, in which case a spheroidizing anneal at around 1380 º F (750 º C) may be used. It is safe to say that experience alone will decide the best type of annealing treatment to be used prior to machining.


    Tempering is carried out to relieve stresses from the hardening process, but primarily to obtain the required mechanical properties. The actual tempering temperature will be chosen to meet the required properties, and in many cases will be a matter of trial and error. Tempering should not be carried out between 400 – 790 º F (200 – 420 ºC) to avoid the danger of embrittlement.



    This heat treatment results in the formation of martensite after quenching, hence a great increase in hardness and tensile strength together with some loss of ductility. The steel should be austenitized at 1500 to 1550 º F (815 to 845 º C), the actual temperature being a function of chemical composition within the allowed range, section size and cooling method. Austenitizing should ensure all micro-constituents in the steel are transformed to austenite. Smaller sections of 4140 might be quenched in oil, heavier sections in water.


  • AISI4140 Steel Applications:

    This alloy finds many applications as forgings for the aerospace and oil and gas industries, along with myriad uses in the automotive, agricultural and defense industries, Typical uses are forged gears and shafts, spindles, fixtures, jigs and collars.

  • 4140 Alloy Steel Equivalent Grade:

    4140 1.7225 42CrMo4


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