Transformation behavior and weldability of alloy rail steels

Effects of electric flash butt (EFB) welding on standard carbon and alloy rail steels were investigated. Time-temperature data acquired during the EFB welding of rails were used in a finite element method (FEM) based heat transfer model to estimate heating and cooling rates, and peak temperatures in the heat affected zone (HAZ) of the weld. Transformation behavior of the rail steels was studied by dilatometry when they were subjected to the simulated welding cycles derived from the FEM heat transfer model.;The standard carbon and head hardening type rail steels were found to form pearlite in the HAZ and thus possess good weldability. The medium hardness type rail steel showed some tendency to form bainite near the weld bond line (WBL) whereas the alloy rail steels of the type Cr-Si-V and Cr-Mo were found to form the undesirable martensite and bainite phases in the HAZ. Estimation of residual stresses in the welded rails showed that whereas postheating or extended preheating reduced the level of the residual stresses, the decrease was not substantial. The tensile residual stresses were still as high as 50 ksi at the WBL.