Determination of Hardness of High-Strength Steels by Brinell Method. Part 2. Improvement of the Method and Measurement Results

• Published in: Strength of materials 2022-09, Vol.54 (5), p.802-808
• Main Authors: Katok, O. A., Muzyka, M. R., Shvets, V. P., Sereda, A. V., Kharchenko, V. V., Bisyk, S. P.
• Format: Article
• Language: English
• Subjects: Analysis; Base metal; Brinell hardness; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Cleanliness; Degassing of metals; Diameters; Hardness; High strength steels; Indentation; Machining; Material properties; Materials Science; Measurement; Metals; Methods; Solid Mechanics; Thickness
• ISSN: 0039-2316; 1573-9325
• DOI: 10.1007/s11223-022-00456-6

The methodology for determining more reliable values of hardness of high-strength steels has been improved, which contains, in addition to the requirements of DSTU ISO 6506 standards, requirements for the preparation of the outer (front) and back sides of the sheet in the plane of rolling by removing the decarburized metal layer, requirements for surface cleanliness and the choice of indenter load. The influence on the measured hardness values of the surface decarburized metal layer that occurs on the front surfaces of the sheet as a result of “burnout” of oxygen on the surfaces of the sheets during the manufacturing process is determined. This decarburized metal layer distorts the hardness values obtained during indentation. By layer-by-layer metal removal, the size of the decarburized layer was determined. The obtained results made it possible to determine the nature of the hardness distribution over the thickness of the sample, to establish the thickness of the decarburized layer and to determine the level of surface cleanliness of the base metal sufficient to obtain reliable hardness values. The results of experimental studies on determining the Brinell hardness values of high-strength steels are presented. The experimental data show that the existing regulatory documents do not fully provide reliable information about the properties of materials. The requirements for instruments for testing high-strength steels for hardness by the Brinell method are considered. The analysis on the choice of load on the indenter is made. The load is selected such that the ratio of the diameter of the imprint to the diameter of the ball is in the range from 0.3 to 0.4.