To meet the demands for large-scale application of the new generation martensitic heat-resistant steel G115 in ultra-supercritical units

a systematic formulation design and performance evaluation were carried out for its supporting submerged arc welding materials. The flux was designed based on a CaF

2

-CaO-MgO-Al

2

O

3

-SiO

2

ultra-low hydrogen high-alkalinity slag system (with a basicity BIIW=3.6)

achieving an ultra-low hydrogen level of H4. Through the Barton rigid fixed cold crack test

it was verified that cold crack occurrence can be effectively prevented under a preheating temperature of 200 ℃. The welding wire adopts a Cr-W-Co-V-Nb-C-N composite strengthening route to ensure the comprehensive performance stability of the deposited metal under different welding parameters and heat treatment conditions. High-temperature creep tests showed that the strength of the deposited metal at 650 ℃ for 100

000 hours is 86.5 MPa

meeting the design requirements of ultra-supercritical units. The XY-AF93 flux and XY-S93 welding wire formulations developed in this study balance strength and toughness with weldability

and are key to achieving excellent crack res

istance and high-temperature sustained strength of the weld. The research results provide a reliable welding material solution for the application of G115 steel in ultra-supercritical units.