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Quantitative Assessment of the Effectiveness of Hardening Mechanisms for Carbon and Low-Alloy Steels with Different Structural States

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Document pages: 9 pages

Abstract: The aim of the work is a quantitative approximate assessment of the contribution of various hardening mechanisms for carbon and low alloy steels according to their chemical composition and parameters of a thin metallographic structure. It is generally accepted that the work is of scientific and practical interest, since, as is known, there is currently no theory that satisfactorily describes hardening mechanisms, especially for new promising hardening methods (combined hardening methods, combined heat treatment methods, plasma, laser processing, etc.). There are only approximations that describe the existing hardening mechanisms, which do not provide a rigorous quantitative assessment of the yield strength of steels with different structural states. In this paper, by analyzing the literature data and our own experimental studies (on chemical composition and structure parameters), the approximate contribution of various hardening mechanisms to the yield strength of carbon, wheel and low-alloy steels was quantified. The assessment is not strict, based on a number of assumptions. It was established that for hot-rolled steel (St5ps) [1] the greatest contribution to the yield strength is made by solid-solution and grain-boundary hardening (37.3 and 33.3 ), in low-alloy steel 16G2AF [2], along with these components of hardening, dispersion hardening plays a noticeable role (21.5 ). It is shown that the combined heat-strain treatment of St.5ps steel leads to an increase in dislocation hardening up to 32 due to an increase in the density of dislocations and the preservation of most of the dislocations in rolled metal during accelerated cooling of hot-deformed austenite. In wheeled steel, thermally treated by traditional technology (intermittent hardening and tempering), the main contribution to strength is the grain-boundary and dislocation hardening (~ 33 ). In the same steel, subjected to surface plasma hardening, due to the strong grinding of the structure and formation of the nano-structured phase components, strength indices increase significantly (42 ).

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