Performance Evaluation of High Speed Pearlite Railway Steel Joint by 3-Wire Electroslag Welding

In this study, novel 3-wire electroslag welding (ESW) technique is employed to join high speed pearlite railway steel, where performance of the welded joint is investigated by joint seamlessness, microstructure observation, and mechanical properties testing. Heat generation of 55.8 KJ/s has produced defect− free joint. Microstructure of the weld metal (WM) was ferrite and pearlite, where columnar shaped austenite grain size was 239 ± 68 × 69 ± 27 µm and pearlite interlamellar spacing was 834 ± 136 nm, which have produced hardness of 27.2 ± 0.5 HRC, tensile strength of 762 ± 9 MPa, and toughness of 13 ± 1 J. In the Heat Affected Zone (HAZ), the welding thermal cycles were associated with the long peak temperature holding time of 143 s and average \({{\text{T}}}_{8/5}\) ${\text{T}}_{8/5}$ cooling rates ranging from 1.07 to 0.92 °C/s. The microstructure of HAZ was complete pearlite with little pro-eutectoid ferrite. The austenite grain size was varying from 143 ± 35 to 22 ± 6 µm and pearlite interlamellar spacing was varying from 138 ± 26 to 454 ± 52 nm. Meanwhile, the fine pearlite formation has produced pearlite-perlite colonies impingement, cementite deformation, and cementite congregation; whereas, the coarse pearlite formation has produced cementite breaking and formed the cementite fragments. In HAZ, the hardness was varying from 33.9 ± 0.5 HRC to 29 ± 0.5 HRC, tensile strength was 1121 ± 15 MPa, and toughness was 16 ± 1 J, successively. Fracture force of the 3-wires ESW joint was 1369 KN that was further increased to 1496 KN after annealing. It is concluded that high heat generation of 3-wires ESW is advantageous that produces defect-free joint and fine pearlite microstructure of HAZ produces uniform mechanical properties.