The low-pressure final-stage long blades constitute one of the critical components of a steam turbine, significantly impacting the safe operation of the unit. Within ultra-supercritical units, these blades shoulder approximately 10% of the turbine's output, exerting a substantial influence on the overall efficiency of the turbine. Exhaust losses account for the largest proportion of the turbine's total losses; increasing the length of the final-stage blades can effectively reduce exhaust losses and enhance the operational efficiency of the unit. However, longer blades necessitate higher rotational speeds, thereby subjecting them to more severe operating conditions. This imposes stringent requirements on the material properties of long blades, which must not only exhibit high strength and toughness but also withstand the combined effects of substantial steam forces, excitation forces, vibration, and the erosion caused by water droplets carried by wet steam.

To develop a novel high-strength stainless steel material for long blades, Shanghai Turbine Works has optimised the content and composition of alloying elements in the traditional 17-4PH long blade material, thereby achieving a new high-strength stainless steel 15Cr long blade material. Concurrently, the technical team conducted multiple material and thermal process trials to develop the optimal hot working process for the 15Cr long blade material. This enabled the material to achieve a yield strength of 1160 MPa, representing a significant improvement over the 17-4PH material. Building upon this foundation, Shanghai Turbine Works further investigated the corrosion fatigue and water erosion resistance of the 15Cr material. The material demonstrated outstanding corrosion fatigue and water erosion resistance properties, fully meeting the operational requirements for low-pressure final-stage blades in ultra-supercritical units.