The results of a study of the change in the microstructure of welded joints of rail steel are presented. Comparison of various methods of structural factor analysis is presented. Comparative studies of various methods of analyzing the structural factor in welded joints of K76F rail steels according to GOST R 51685-2013 are considered. It has been established that for this series of experiments, a decrease in hardness of the surface of the welded joint, as well as an increase in Barkhausen MP noise, is 65-75% of the mean value. That indicates the presence of tensile residual stresses in this zone. A coarse-grained structure of primary austenite grains with a grain score of 2 ... 3 is observed along the joint line and adjacent metal layers. A solid grid of ferrite precipitates is clearly observed along the grain boundaries of the primary austenite that indicates the low plastic properties of this section. As a result of conducted studies, it was found that the microstructure of the metal in the heat affected zone of the welded rail joint after the flash welding is represented by plate and globular perlite. The change in hardness in the heat affected zone is associated with a change in the interlamellar distance of perlite that in turn depends on the cooling conditions, i.e. thermal cycle of welding. Control of the thermal cycle during butt flash welding of rails will allow one to form the optimal structure in the welded joint.
The authors consider the possibilities of using welding in protective gasses with a melting electrode for the manufacture of parts of complex shape. The results of surfacing parts such as square and cylinder are presented. In the course of the research, the technological features associated with the parameters of the welding arc and melting of the surfacing wire were established. Arc current has the greatest effect on the appearance of the molding. The wire feed speed affects the height of the deposited roller. It is shown that the stability of the formation of deposited rollers depends on the transfer modes of the metal, which depend on the conditions of supply and input of wire into the melt pool. The additive technology of metal deposition allows one obtaining parts with a surface different from the base metal, high wear resistance at normal and elevated temperatures, and corrosion resistance. Surfacing can be performed both in the manufacture of new parts and in repair and restoration work, significantly extending the life of parts and assemblies, thereby ensuring a high economic effect.
A series of experiments for the melting of cast iron GI15, according to the sandwich-type scheme of the process with a modifier (composition 1, 2, 3) did not reveal any significant differences in the mechanical properties of the modified samples, depending on the mode of administration. Surface examination of the samples with the help of scanning electron microscopy showed significant differences in the structure of the metal surface. All the materials studied have the structure of gray iron on a ferrite-pearlitic basis with graphite of a laminar rectilinear form of the type PGf1, in unmodified samples. Modified samples have the form of inclusions of graphite of the type PGf4 nestshaped, vortical shape. The conducted studies of microstructures after mechanical tests of samples of cast iron GI30, modified with composition 2, showed the presence of inclusions of globular graphite. The introduction of small amounts of a modifier with nano-sized structures during the teeming leads to: an increase in the content of perlite in the metal base; change in the form of graphite inclusions of cast iron from lamellar to nest-shaped (rosette), spherical (globules); increase in strength up to 35-50%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.