Abstract
Today, in the manufacture of long-length rail strings, the obligatory heat treatment is provided after the flash butt welding operation. The basis for this operation is the unsatisfactory mechanical properties of the rail joints immediately after welding. Welding heat cycles at pulsed reflow do not always allow a welded joint with a sufficient level of ductility to be obtained. In this case, the induction heat treatment used at rail welding enterprises in Russia increases the length of the heat-affected zone, which adversely affects the wear resistance of the rails during operation. This paper presents studies in industrial conditions that were previously conducted in laboratory conditions. Studies show the possibility of obtaining the necessary mechanical properties by controlling welding heat cycles without the use of induction heat treatment.
Highlights
Welded joints of rail strings after electric contact welding are necessarily subjected to heat treatment at induction plants
In the manufacture of long-length rail strings, the obligatory heat treatment is provided after the flash butt welding operation
The induction heat treatment used at rail welding enterprises in Russia increases the length of the heat-affected zone, which adversely affects the wear resistance of the rails during operation
Summary
Welded joints of rail strings after electric contact welding are necessarily subjected to heat treatment at induction plants. The use of compressed air provided better heat treatment of welded joints, which is especially relevant in connection with the expansion of the use of alloyed steels on domestic railways, including alloyed with chromium For these steels, quenching cooling with an air-water mixture contributes to the formation of structures with the presence of martensite, which sharply reduces the resistance of rails to fatigue and brittle fracture of rail steel [1]. During the last third stage after welding, heat treatment is applied similar to preheating to reduce the cooling rate after welding – an electric current is transmitted through the welded joint in several pulses. The exposure time is determined by the incubation period of the required structure formation and is regulated by the number of current pulses [3]
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