INVESTIGATION OF THE DISTRIBUTION OF RESIDUAL STRESSES IN THE ZONE OF THE WELDED SEAM OF RAILS OF THE R65 TYPE OF THE DT350 CATEGORY

Abstract

Rails are the most important element of the superstructure of the railway track. To increase the smoothness of the ride, reduce dynamic loads at the junctions of the rails, contact welding of rails in a whip in stationary conditions and aluminothermic welding directly on the way are becoming more common. Despite the improvement in the quality of the joints, the zone of welded joints, due to a change in the structure due to the physical processes of welding and heat treatment, is still a place with lower mechanical characteristics compared to the metal of solid- rolled rails. The development of defects in welded butt joints is one of the main reasons for removing rails from service. An important component of ensuring the quality of rails and welded joints is the formation of a favorable diagram of residual stresses. In order to assess the effect of induction heating and hardening, a study was made of the distribution of residual stresses before and after heat treatment of the welded joint, full-profile samples of R65 type rails of the DT350 category of steel grade E76HF, the current production of EVRAZ ZSMK JSC. It has been established that compressive residual stresses predominate in the rail head both before and after heat treatment,heating reduces the overall stress level to the level of 210–264MPa, the maximum compressive stress level equal to 586 MPa is fixed at joint No. 224, after hardening heat treatment. Tensile stresses predominate in the neck of the rail, a sharp increase in stresses after hardening heat treatment was noted, the stress level increased more than three times, from 68 MPa to 254 MPa. After heating the welded joint, a slight decrease in residual stresses in this area is observed. Compressive stresses are recorded in the rail sole, with identical diagram, regardless of heat treatment. A minimum of stress is fixed in the center of the sole, with a subsequent increase towards the edge of the feather. The greatest difference was recorded after hardening heat treatment, from 57MPa to 537MPa, respectively.