Phase and structural transformations when forming a welded joint from rail steel. Report 3. The use of thermokinetic and isothermal diagrams of austenite decomposition for selection of optimal modes of electric contact welding

During contact flash welding of rails, the metal is heated and continuously cooled in zone thermal influence. Accelerated heating subsequent intensive cooling, implemented by pulsed flashing-off method, lead to formation quenching structures. Subsequently, during operation rails welded joint, this leads cracks brittle destruction. We have investigated possibilities using after avoid structures joint made R350LHT rail steel. The cycles were recorded. regularity weld structure was established including influence for It shown that pulse slows down cooling prevents However, when suboptimal modes can also opposite effect. determined with a significant investment heat heating, rate exceeds critical one, transformation process passes through diffusion-free mechanism martensite coarse-grained structure. use thermokinetic isothermal diagrams austenite decomposition at known allows us significantly narrow search limits optimal butt railway heating. makes it possible obtain minimum length heat-affected zones reduced hardness without rails.