Toolox® is a highly fatigue-resistant tool steel

The importance of high fatigue resistance cannot be overstated. It’s estimated that 75-90% of engineering components fail due to fatigue after a certain number of load cycles, even if the steel is stressed well below its yield strength.

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Fatigue resistance


Toolox® is as clean as ESR steel

The fatigue resistance of a steel is directly related to its cleanliness. Thanks to SSAB’s world-class metallurgy processes, Toolox® has a cleanliness similar to the highest quality ESR (Electroslag Remelted) tool steels.

Ensuring long service life

The fatigue resistance of components made of Toolox® increases the reliability and service life of all kinds of machines. This makes Toolox® a natural choice for demanding customers.

High fatigue performance tested and confirmed

Toolox® 44 has been subjected to extensive fatigue testing by SWERIM, a Swedish metal research institute. The purpose of the tests was to compare different samples of Toolox® – in delivery condition, plasma nitrided and induction hardened – to a 42CrMo4 steel. The high core hardness of Toolox® 44 means that this steel doesn’t need as deep induction hardening as 42CrMo4. Surface hardening results in higher compressive stresses in the surface, which is always beneficial to the fatigue strength.

The fatigue tests were carried out with notched round bar samples in a rotary bending machine with a 2 million revolutions target. The tests showed that Toolox® 44 has a high fatigue strength in as-delivered condition. Through surface hardening with plasma nitriding and induction hardening the fatigue strength is increased even further, as shown in the table Fatigue limit. SWERIM concludes that Toolox® 44 is suitable for fatigue loaded components. Surface hardening is recommended for the most demanding applications.


Exceptional cleanliness ensures high fatigue resistance

Y = Relative area of inclusions X = Steel quality
A = Standard ingot cast steel 1 = Ordinary tool steel
B = Clean ingot cast steel 2 = Bearing steel
C = Very high cleanliness tool steel 3 = ESR remelted

Fatigue limit for Toolox® 44 as tested by SWERIM

Y = Fatigue limit in MPa (2x106 cycles) X = Kind of steel
1 = H13 tool steel
2 = Toolox® 44
3 = Toolox® 44 plus plasma nitriding
4 = Toolox® 44 plus induction

Learn more about Toolox® 44

Toolox® 44 is a pre-hardened tool and machine steel designed for demanding applications where strength, toughness and dimensional are crucial. Its unique composition and heat treatment process result in outstanding properties, including high hardness, excellent machinability, and superior resistance to wear and impact.

Multiple gears with meshing teeth

Toolox® properties that improve fatigue life

  • Exceptionally clean steel
  • High surface smoothness possible
  • High core strength withstands heavy loads
  • High toughness resists fracture
  • No need for heat treatment
  • Suitable for surface hardening

Read all about why Toolox® steel outperforms on every challenge

Get the full story of Toolox® engineering and tool steel from SSAB.


Read all about welding and cutting recommendations for Toolox® steel

Toolox® is easy to weld and easy to cut. In the brochure you’ll find the best practices.


Read all about machining of Toolox® steel

Toolox is a prehardened steel with high machinability for making finished parts without time-consuming and costly heat treatment.

Learn more about Toolox® tool and engineering steel