At present the quality of steel is often improved by thermomechanical treatment (TMT). It is of interest to establish the effect of the state of austenite in strain caused by TMT on the properties of steels. This paper is devoted to the effect of various thermal-strain treatment regimes on the properties and structure of steels 25GSR and 20 with different stabilities of austenite.The technological process of thermomechanical strengthening of rolled steel permits substantial savings in power resources because the strengthening is conducted using the rolling heating after the strain treatment of the steel is finished. TMT also makes it possible to save alloying elements because it ensures a high level of properties (both strength and toughness) of the steel. Use of roiled stock with elevated strength properties creates conditions for the production of mechanisms, machines, and metal and ferroconcrete structures with a diminished consumption of metal [1].Another factor affecting the efficiency of such treatment of steel consists in that it can eliminate the negative effect of the processes of high-speed rolling in modem continuous mills characterized by an elevated temperature at the end of the process, which worsens the properties of the metal and especially the toughness characteristics.In the process of hot plastic strain of steel the elements are uniformly distributed over austenite grains and the harmful impurities positioned in near-boundary zones dissolve. As a result of dynamic and static recrystallization austenite grains are fractured. The high cooling rate of the rolled stock after it leaves the mill causes formation of highly dispersed products of decomposition of austenite and diminishes the size of austenite grains [2][3][4].The structural state that results after TMT increases the strength and fatigue resistance of the metal with a simultaneous substantial growth of the impact toughness even at negative temperatures (which is especially important). For example, low-alloy steels (09G2-14G2, 09G2S, and other grades) strengthened to o r = 520 and 600 N/mm 2 have an impact toughness a I > 35 J/cm 2 at -70~Institute of Ferrous Metallurgy of the National Academy of Sciences of Ukraine. 19It should be noted that the parameters of the thermalstrain treatment of steel in the process of the TMT can be varied in order to form a favorable structural state and obtain a high set of properties [5 -6].For this purpose we studied various temperature and strain regimes for treating steels 20 and 25GSR characterized by different stabilities of austenite. The specimens were rolled in a mill at the Institute of Ferrous Metallurgy of the National Academy of Sciences of Ukraine with a 30% reduction. The furnace heating for rolling was conducted by the following regime: the specimens were heated to 1100~ then placed in the furnace heated to various temperatures, and strained (see Table l). The rolled specimens were cooled in water in a special device at a mean flow rate of the water equal to 45-50 deg/sec. The accelerated co...

The purpose of the work is to study the microstructure and mechanical properties of 316L stainless steel samples made by the SLM method. 316L stainless steel has been extensively studied for the state after fabrication by selective laser melting (SLM). This is due to the wide use of this material in various industries, as it demonstrates sufficient corrosion resistance and excellent plasticity. Thus, its application can be found in the biomedical, aerospace, automotive and marine fields. Some of the studies conducted have shown the ability of SLM to improve the mechanical properties of parts compared to traditional methods. Metallographic analysis, determination of mechanical properties, and chemical analysis were used. The object of the study was austenitic grade 316L stainless steel. The material for making the samples was a 316L alloy powder with a particle size of 45 + 15 μm. Experimental samples for tensile tests were built on the equipment of "Additive Laser Technologies of Ukraine" LLC (Alfa-150) using SLM technology in identical modes: laser power - 290 W, scanning speed - 1100 mm/s, distance between tracks – 0.11 mm, scanning strategy - checkerboard fields, scanning order - Zig-Zag, field size - 5 mm, rotation of the layer relative to the previous one - 67°. From the results of the analysis of mechanical properties, it was established that the samples made on the 3-D printer of Additive Laser Technologies of Ukraine LLC are not inferior in terms of quality to leading global companies, and in some characteristics even exceed them. It should be noted that the results of determining the characteristics of the experimental samples were compared with the properties of the samples manufactured according to the optimal process parameters on the equipment of different manufacturers, but do not include the influence of the thickness of the applied layer. Comprehensive studies of the mechanical properties of the samples made of 316L steel showed full compliance with the samples produced on the equipment presented on the world market for the production of special-purpose products.