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Material data sheet

Steel grade

Last revised: Thu, 01 Oct 2020 13:00:20 GMT

General Information

Ovako 355B is a quench and tempering steel with high toughness and cleanliness. Oil hardening steel for quench and tempering. Used for large axles, machine componenets etc. that require high tensile strength and high toughness. The grade is inside the SAE 4340 specification but is slightly enhanced with Vanadium for improved tempering resistance. The grade has a low controlled sulphur content to ensure machinability yet with a high sulphidic cleanliness. Oxygen content is kept low for high oxidic cleanliness. The steel is of Bearing Quality cleanliness (BQ).

Can be flame or induction hardened

Through hardenability corresponding to a bar with approx. Ø100mm (oil quenching)

Available as hot rolled bars, tubes and rings

Delivered in as-rolled, soft annealed, normalized or quench and tempered condition


(Bearing Quality) is a bearing quality clean steel optimized for fatigue strength by a strict control of steel cleanliness. BQ-steel is also ideal for new design solutions in a wide array of demanding applications outside the bearing industry that require longer performance and higher loads. The BQ-steel offer is the result of the Ovako clean steel program. Purity of production means that the material has significantly smaller inclusions compared to conventional steel and, as a result, the fatigue strength of the steel is increased dramatically. Use of the material allows components to be manufactured in smaller sizes. The BQ-steel  has for decades been the problem-solver.

* Designation followed by "*" is not an official EN standard grade but named according to the rules in EN 10027.

Similar designations

SAE 4340

Steel cleanliness

Micro inclusions - Steel grade 355B   Macro inclusions - 355B
Applied standard ASTM E45 Applied standard

ISO 3763

(Blue fracture)

Sampling ASTM A295 Sampling Statistical testing on billets

Maximum average


A B C D Limits < 2,5 mm/dm2
Th He Th He Th He Th He
2.0 1.5 0.8 0.1 0 0 0.5 0.4

Other properties (typical values)

Youngs module (GPa)Poisson´s ratio (-)Shear module (GPa)Density (kg/m3)
210 0.3 80 7800
 Average CTE 20-300°C (µm/m°K) Specific heat capacity 50/100°C (J/kg°K) Thermal conductivity Ambient temperature (W/m°K) Electrical resistivityAmbient temperature (µΩm)
 12  460 - 480  40 - 45  0.20 - 0.25

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The information in this document is for illustrative purposes only. The data and examples are only general recommendations and not a warranty or a guarantee. The suitability of a product for a specific application can be confirmed only by Ovako once given the actual conditions.The purchaser of an Ovako product has the responsibility to ascertain and control the applicability of the products before using them. Continuous development may necessitate changes in technical data without notice. This document is only valid for Ovako material. Other material, covering the same international specifications, does not necessarily comply with the properties presented in this document.