EVOLUTION OF THE MICROSTRUCTURE OF STEEL IN FREIGHT CARRIER LOADING SYSTEMS DEPENDING ON CARBON CONTENT AFTER THERMAL LOADING

The creation of new structural materials (primarily metals and alloys) and the aim of obtaining products with high performance characteristics remains and will remain for a long time one of the most important problems of many areas of knowledge and industries.In technology, materials are usually classified according to the chemical classification method, which can be divided into metallic materials, inorganic non-metallic materials (ceramics), organic polymeric materials and composite materials.High speeds and increased loads dictate increased technical requirements not only for the strength of running gear, but also for the supporting systems of the car.Summarizing the available literature, it can be stated that today low-carbon high-strength steels represent a class of promising materials that are widely used.These include, first of all, 09G2S steel for the manufacture of upper trim of wagons, backbone beams, I-beams and other details of wagon construction, as well as for the construction of heavily loaded welded structures of responsible purpose, the operation of which is carried out in difficult climatic conditions.The need to obtain high strength in such steels along with high impact toughness and resistance to brittle fracture causes an ever-growing interest in the use of various thermomechanical options for their strengthening instead of heat treatment, which combines hot deformation and phase transformation.This article considers the results of dilatometric analysis, studies of changes in the hardness and structure of steel during heating, and constructs a thermokinetic diagram (TKD) of austenite decomposition, which ensures the obtaining of uniform mechanical properties due to controlled control of the processes of structure formation.The heating rate interval was established, at which the absence of such structural components as pearlite or high-temperature bainite in the steel structure after cooling, which adversely affect the resistance to brittle fracture of the steel, is ensured.Micro X-ray spectral analysis showed that the isothermal transformation of austenite when heated to 500C leads to the formation of a structure that is a uniform mixture of darker and lighter areas of small sizes and irregular shape, is ensured.