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Material data sheet

Steel grade

Last revised: Tue, 07 Feb 2023 13:38:00 GMT

General Information

18NiCrMo14-6 is a case hardening steel with high toughness used for bearing and transmission components. There are two different versions of the grade with high cleanliness requirements. The high hardenability ensures a through hardenability of large sections.

255G - Bearing quality (BQ) variant with low sulphur content and high cleanliness demands

255Q - Isotropic quality (IQ) with isotropic properties and improved fatigue strength due to higher cleanliness levels, and a finer size and distribution of non-metallic inclusions


IQ-Steel® is an isotropic quality ultra clean steel optimized for high fatigue strength under multi axial loading.

BQ-Steel® is a bearing quality clean steel optimized for fatigue strength and is also ideal for new design solutions outside the bearing industry.

Similar designations


Jominy hardenability according to ASTM A255.  255G data is average value with +/- standard deviation. En ISO 683-17 according to +H variant

Steel cleanliness

Micro inclusions -  Steel grade 255G   Macro inclusions - 255G
Applied standard ASTM  45   Applied standard

ISO 3763

(Blue fracture)

Sampling ASTM  A295   Sampling Statistical testing on billets
Maximum average limits 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  
Micro inclusions - Steel grade 255Q   Macro inclusions - 255Q
Applied standard DIN 50602  K1   Applied standard

10 M Hz UST

(Ovako internal standard)

Sampling Six random samples from final product dimension   Sampling Statistical testing on billets

The limit is dimension dependent. The average rating of six samples 

should not exceed the limits given in the graph


< 10 defects/dm3

> 0,2 mm FBH





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.