Standardization of process flow in arc striking and hot-topping stages of electroslag fusion welding: experimental and numerical analysis

Electroslag fusion welding (ESFW) carries a serious risk of metallurgical defects in fusion welding zone (FWZ), especially during the arc striking and hot-topping stages. This study integrates experimental and numerical approaches to standardize these processes. Key parameters investigated include arc initiation height, fusion welded component preheating temperature, electrode melting rate, and hot-topping electrical parameters. When the preheating temperature of fusion welded component is 700 K and the height of arc initiation section does not exceed the initial slag height by 15 mm, the lack of fusion defects at the bottom of FWZ can be eliminated and complete melting can be guaranteed. The hot-topping process effectively minimizes shrinkage cavities but prolongs local solidification time (LST), increasing grain size at the top of FWZ. Chromium macrosegregation analysis reveals that hot-topping exacerbates positive segregation in the FWZ center while reducing negative segregation (index > −0.04) at lower melting rates (<2.6 kg min −1 ). A power-law relationship between the average equivalent circular diameter of grains and LST of ZG04Cr13Ni5Mo supermartensitic stainless steel has been established, providing a basis for homogenization control during its smelting process. Through multi-physics coupling modeling (experimentally validated), records of electrical parameter variations based on constant electrode melting rate control were obtained and can be extended to other geometric dimensions. This study provides theoretical and practical basis for the optimization of process parameters and defect control of ESFW, and provides feasible guidance for the rapid manufacturing of large-scale high-end equipment.