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Tests were carried out on two high-Mn steels: 27Mn-4Si-2Al-Nb with Nb microaddition and 24Mn-3Si-1.5Al-Nb-Ti with Nb and Ti microadditions. High-manganese austenitic steels, due to their good strength and plastic properties belong to the AHSS (Advanced High-Strength Steel) group and are used in the automotive industry. The main difficulties faced during the casting of the steel and hot working are hot cracks, which can appear in the surface of the ingot. Cracks on the edges of the sheet after hot rolling are the reason for cutting the edges of the sheet and increasing production costs and material losses. The main reason for the formation of hot cracks is the decrease in metal ductility in the high-temperature brittleness range (HTBR). The width of the HTBR depends on mechanical properties and microstructural factors, i.e., non-metallic inclusions or intermetallic phases at austenite grain boundaries. In this paper, a hot tensile test was performed. The research was performed on the GLEEBLE 3800 thermomechanical simulator. This test allows us to determine the width of the high-temperature brittleness range (HTBR), the Nil Strength Temperature (NST), the Nil Ductility Temperature (NDT), and the Ductility Recovery Temperature (DRT). Hot ductility was determined from the value of the reduction in area R(A). The obtained results make it possible to determine the temperature of the beginning of hot working from the tested high-Mn steels. Fractographic research enabled us to define mechanisms of hot cracking. It was found that hot cracks form as a result of disruptions in the liquid film on crystals’ boundaries.

The solidification microstructure of an Fe–Mn–C–Al high-Mn steel with added Nb was studied by optical microscopy and scanning electron microscopy. The results showed that the size of the columnar and equiaxed grains in the solidified structure of the high-Mn steel without added Nb was large. When Nb was added, the size of the equiaxed and columnar grains in the solidification structure of the high-Mn steel decreased. The twin-induced plasticity in the high-Mn steel with added Nb clearly refined the grain size of the solidified structure and simultaneously increased the equiaxed crystallization rate. The high-melting-point second-phase particles increased the heterogeneous nucleation rate, which was beneficial for grain refinement. A large amount of Nb precipitates from the solidification process increased the equiaxed crystallization rate of the solidified microstructure. The increased crystallization rate affected the growth direction of the columnar and equiaxed grains during solidification and indirectly decreased the probability of crack formation, which improved the quality of the twin-induced plastic steel.

The paper presents results of dynamic tensile investigations of high-manganese Fe – 20 wt.% Mn – 3 wt.% Al – 3 wt.% Si – 0.2 wt.% steel. The research was carried out on a flywheel machine, which enables to perform dynamic tensile tests and impact bending with a linear velocity of the enforcing element in the range of 5÷40 m/s. It was found that the studied steel was characterized by very good mechanical properties. Strength of the tested materials was determined in the static tensile test and dynamic deformation test, while its hardness was measured with the Vickers hardness test method. The surface of fractures that were created in the areas where the sample was torn were analyzed. These fractures indicate the presence of transcrystalline ductile fractures. Fractographic tests were performed with the use of a scanning electron microscope. The structure was analyzed by light optical microscopy. Substructure studies revealed occurrence of mechanical twinning induced by high strain rates. A detailed analysis of the structure was performed with the use of a transmission scanning electron microscope STEM.

Рассмотрены особенности образования пористости в ходе затвердевания литой плиты из высокомарганцовистой стали. Предложена модель оценки влияния данного вида дефекта на напряженно-деформационное состояние плиты, возникающее в результате ударных нагрузок рудоподготовительных дробилок. Методом конечных элементов в программном пакете DEFORM рассчитаны эквивалентные напряжения в характерных сечениях плиты для различных параметров макропор круглого сечения. The paper considers the features of porosity formation during solidification of a cast plate of high-manganese steel. The model is suggested for estimation of influence of this type of defect on the plate’s strained state resulting from ore-preparation crusher impact load. Equivalent stresses in characteristic cross-sections of the plate are calculated using finite element method in programming tool set DEFORM for different parameters of macropores having circular cross-section. Ердаков Иван Николаевич, кандидат технических наук, доцент кафедры металлургии и литейного производства, Южно-Уральский государственный университет. 454080, г. Челябинск, пр. Ленина, 76. Тел.: (351)2679096. E-mail: techproect74@mail.ru. I.N. Erdakov, South Ural State University, Chelyabinsk, Russian Federation, techproect74@mail.ru. I.N. Erdakov, South Ural State University, Chelyabinsk, Russian Federation, techproect74@mail.ru

There is article discusses the process of modification of high-manganese steel, Hadfield, which will significantly increase the yield of the casting at the stage of melting and casting the steel. The steel modification performed integrated alloy FASC (ferroalumisilicocalcium) in an amount of 03 - 0,5% by weight of the metal. The integrated alloy unlike traditional methods of modification leads to globalizatsii and purification of steel from nonmetallic inclusions and for grinding grains of austenite, thereby greatly increases its mechanical properties.