VALIDATION AND NUMERICAL SIMULATION FOR SHRINKAGE POROSITY OF A X12 STEEL INGOT

摘要

The X12(12CrMoWVNbN) steel is used in ultra-supercritical steam turbine rotors, which play a crucial role in the large nuclear power plant. However, the quality of the heavy ingots has been commonly affected by their solidification structure. One of the most typical defects is the centerline shrinkage porosity. With this context, a 50×120mm X12 steel ingot was cut and polished. The distribution and size of the shrinkage porosity in the section surface was observed and analyzed. On basis of these experimental results, through the FEM simulation several thermal transfer coefficients between the casting and mould wall have been clarified and the suitable coefficient is λ=1000w/(m~2•k). With this result, the distribution and size of the simulated centerline shrinkage porosity agree well with the experimental results. Subsequently, by the simulation method and results, it is possible to improve the performance for simulate how to eliminate the shrinkage porosity by outfield method.