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Tohoku Steel Co., Ltd.

Soft-magnetic Stainless Steel

Magnetic core material, which is essential in electromagnetic actuators, is required to have various different properties such as corrosion resistance, magnetic property, electrical resistance, and workability depending on the usage or performance.  We have broadened our lineup of soft-magnetic stainless steels to meet varying demands ever since we introduced the world’s first soft-magnetic stainless steel K-M31 over 40 years ago.


 Compared with pure iron magnetic materials:
  1. High corrosion-resistance
  2. High electrical resistance
 To meet processing methods:
  1. Free-cutting types
  2. Cold fogeabie types
 Compared to general ferrite stainless steel:
  1. Excellent magnetic properties


Fuel injectors, solenoid valve cores,
ABS sensor cores, magnetometric sensors, semiconductor valve stems,
massflow controller cores

Description of materials


  • K-M31 13Cr-2Si
  • K-M35FL 13Cr-0.7Si-0.2Al-0.2Pb
  • K-M38 18Cr-2Si-2Mo
  • K-M45 20Cr-2Si-2Mo
  • K-M60 13Cr-0.2Al-1Mo

[Standard heat treatment condition]

  • K-M31, K-M35FL, K-M60 950℃×3hr-furnace cooling
  • K-M38 850℃×3hr-furnace cooling
  • K-M45 1000℃×3hr-rapid cooling


[Soft-magnetic properties, pitting potential]

[Electromagnetic properties, pitting potential]

[Mechanical properties, hardness]


The characteristics above are those after standard heat treatment.


[Lead-free of free-cutting steel]

Lead-free is possible by dispersing TICS in steels.
Refer to Pb Free TICS Free-Cutting Soft-magnetic Stainless Steel.

[SEMI certified materials]

K-M45 is certified as the only alternative to ultrahigh pure grade material among ferrite stainless steels in F105-1107 "Guide to Metallic Material Compatibility in Gas Supply Systems".

※SEMI=Semiconductor Equipment and Material International

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