Optimization of the Mode of Contact Butt Welding of Railway Rails

Optimization of the technological process for manufacturing of long-length rail lashes is a difficult problem since in addition to a large number of operations, the equipment used today for contact butt welding of railway rails by pulsation reflow has many technological parameters (input factors) that affect the quality of the resulting welded joint (output factors). So many parameters do not allow one to select the full the optimal welding modes and leads to the impossibility to use a complete or fractional factorial experiment. In the work, the data of 79 experimental welding was processed by the regression analysis. The main stages of a welding process are identified: the first stage of melting; the second stage of melting; forcing; and precipitation. Based on the obtained oscillograms of the welding process using a K1100 rail welding machine when welding rails of the R65 type of the DT350 category, we have determined the average values of current, voltage, movement speed of the movable frame at various stages of melting, as well as precipitation force, precipitation time under current, and precipitation paths at the last stage. The obtained regression equations that determine the results of tests for static three-point bending were analyzed, and unsatisfactory parameters with respect to Student’s t -criterion were eliminated from them. The finally obtained regression equations consider the influence of each technological stage of the contact butt welding of railway rails on the output properties and the model is adequate according to Fisher’s F-criterion. Using these regression models, the recommended modes of contact butt welding by pulsation reflow were obtained and tested at a rail welding company.