Study of metal quality and structure of the weld-affected zone during wide-layer surfacing of defective rails

The surfacing of railway rails with defects of the rolling surface with one wide-layer bead is proposed. This is reasoned by the fact that the steel from which the rails are made belongs to the group of poorly weldable metals and the use of single-pass surfacing not only increases the productivity of the restoration process, but also allows to obtain high quality metal in the weldaffected zone (WAZ). To perform single-pass surfacing, a multi-electrode method was selected, allowing surfacing at high thermal power with dissipated heat input into the base metal. The structure of the base metal was studied and characteristic defects of the rolling surface were identified. For rails with deep defects, a two-layer surfacing is proposed. Low-alloy wire grade Sv-08KhNM and flux AN-60 are used as welding materials. The results on structure formation in the WAZ and the quality of metal obtained with both single-layer and two-layer single-pass surfacing are presented. It is established that the adopted thermal power of the surfacing process and an increase in the number of deposited layers to two contribute to the formation of a finegrained structure in the heat-affected zone, which serves as a reserve for increasing the fatigue strength of the base metal. The deposited metal has a ferrite-pearlite structure with a hardness of 27–30 HRC. Metal with such hardness is characterized by high resistance to thermomechanical damage, and the required wear resistance will be achieved during operation due to cold working of the rail running surface. As surfacing equipment, it is proposed to use a conventional welding tractor, converted for simultaneous feeding of four wires to the surfacing zone.