Machining with F-125 Steel

Machining with F-125 Steel

F-125 steel, is a chromium-molybdenum steel within the group of F-120 steels and F-130, high-strength alloy steels. The steels are metals formed by iron-carbon alloys (Fe3C) which can also contain certain alloy elements to improve some physical, chemical or mechanical properties. The F-125 steel belongs depending on the percentage of carbon to the medium steels in carbon content, since its content is 0.38 to 0.45% by weight of carbon. Medium steels in carbon content can be heat treated by austenizing, quenching and hardening in order to improve their mechanical properties. The microstructure is usually tempered martensite. These steels are stronger than low carbon steels but less ductile and malleable.

F-125 steel applied to pieces without broad thicknesses, subjected to great efforts of fatigue, admits tempering by induction and welding being widely used in the automotive and aeronautics sectors. It allows to reach resistance of 80/120 Kg/mm² maintaining a good tenacity in pieces of small sections.

The addition of elements such as Chrome and Molybdenum in steel, facilitates the heat treatment of these steels and facilitates the tempering of the pieces of considerable thickness and prevents deformations and cracks in the treated parts.

Table of equivalences of steel F-125:

UNE: F125/F1252


  • DIN: 42CrMo4

  • AFNOR: 42CD4

Average chemical composition in %:

  • C 0.38/0,45
  • Si 0,40 maximum
  • Mn 0,60/0,90
  • P 0,025 maximum        
  • S 0,035 maximum        
  • Cr 0,90/ 1,20
  • Mo 0,15/ 0,30


F-125 steel is usually used for parts of not very large sections that must have great strength and good toughness: gears, crankshafts, connecting rods, pinions, sleeves, transmissions, shafts, half shafts and in general parts and components for machinery and engines.

If you need to machine a part with F-125 steel or any precision machining of parts, you can call: +0034 96 652 22 48 or if you prefer, email: mecasinc@mecanizadossinc.com. In Mecanizados Sinc we will provide you with different solutions for all types of machining, processing and/or finishing of parts.

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