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Tohoku Steel Co., Ltd.

Free-cutting Invar (Patented in 2003)

Fe-Ni alloy is generally a soft, ductile material that is difficult to cut, and customer demand has called for free-cutting. However, since S-addition causes a great loss in hot workability, it used to be a difficult steel to make it free cutting.
Yet by adding TICS as a free-cutting element, free cutting has been realized.


  1. Using TICS to attain free-cutting has dramatically improved machinability.
  2. Features such as the coefficient of thermal expansion remain unchanged.

[Form of cutting chips]

Description of materials

Description of materials

[Basic composition]

  • Free-cutting invar (K-EL70CS) 36Ni-Fe-TICS
  • Free-cutting super invar (K-EL50CS) 32Ni-5Co-Fe-TICS
  • Free-cutting kovar (K-ET52CS) 29Ni-17Co-Fe-TIC


[Physical property]


Coefficient of thermal expansion: Upper α20-60℃, Lower α20-100℃

[Mechanical properties, hardness]




Please refer to Pb Free TICS Free-cutting Soft-magnetic Stainless Steel.

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