Stress analysis and deformation prediction of a heavy hydraulic turbine blade casting during casting and heat treatment

Abstract

Owing to their large and curved shape, blade castings, a key component for heavy hydro turbines, are susceptible to deformation during casting and heat treatment. In the present paper, the stress analysis of a blade casting during both casting and heat treatment is performed. The coupled thermo-stress and thermo-phase transformation stress models are used for casting and heat treatment respectively. Machining allowance distribution is used as the deformation criterion and an algorithm of inverse deformation determination is presented. The mechanical properties of the martensitic stainless steel ZG₀Cr₁₃Ni₄Mo (13Cr–5Ni–1Mo) at different temperatures are measured under as cast and heat treated status. Finally, the inverse deformation of the blade during both casting and heat treatment processes is obtained, and a series of sections of the blade casting with inverse deformation design are given for pattern making. The calculated deformation results are compared to the measured one, and they are basically in agreement.

Keywords:

• Turbine blade
• Casting
• Heat treatment
• Phase transformation
• Stress
• Deformation

The project is funded by the National Science and Technology Program (project nos. 2007BAF02B07 and 2007BAF02B02) and the Major National Sci-Tech Project (project no. 2009ZX04014-082), China.