Limits of management strengthening of structural steel

Purpose. For structural steels to increase their strength is only advisable provided concomitant increase structural strength of products and structural elements, due to the lack of metal embrittlement features in products. The objective of this work was to determine the limits of the rational increase strength steels 40 and 30ХГСА based on the criterion of maximum load capacity models with regulated notch. Methodology. Tensile testing of standard samples of smooth 6 mm diameter circular specimens with notch. Findings. The relationship σ0,2 conditional yield strength with an average nominal voltage failure σNF specimens with the stress by increasing the strength of steel in the range from 374 MPa to 1533 MPa. It has been shown that increasing the bearing capacity notched specimen is only possible if the indicator Br break resistance steel exceeds a certain critical value of 1,6...1,8 for this type of stress concentrator. Originality. It was shown that a decrease in break resistance Br below the critical value with an increase in strength σ0,2 become an indicator of reaching the limit of its sound reinforcement, not threatening manifestation of signs of embrittlement in the presence of stress concentrators. Practical value. Establishing the limits of rational hardening steels help in technological practice in the selection of optimal technology of hardening steel, and engineering and design practice - to link the choice of steel products to increase its structural reliability.