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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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.
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.
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.
| 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 |
| 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 |
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.
Get the full story of Toolox® engineering and tool steel from SSAB.
Toolox® is easy to weld and easy to cut. In the brochure you’ll find the best practices.
Toolox is a prehardened steel with high machinability for making finished parts without time-consuming and costly heat treatment.
