Abstract:Hot plate forming using a cell-typed die is a process for forming a large thick plate with a spherical shape for the manufacture of a large spherical LNG tank. Cell-typed upper and lower dies made of a framework of steel plates fitted to make a grid pattern are used in this process, and an air-cooling device is separately installed inside the lower die. A finite element analysis (FEA) technique was developed, which included hot forming, air flow, cooling and thermal deformation analysis for the hot plate forming process using the cell-typed die. Further, the convective and interface heat transfer coefficients were used to reproduce analytically the effects of the cooling device in the hot plate forming analysis. A small-scale model test of the process was conducted to verify the FEA technique. The analysis results show that the curvature of the final plate agrees well with that of the designed experiment within a maximum relative error of 0.03% at the corner of the plate.

Key words: cell-typed die; hot plate forming; spherical LNG tank; heat transfer coefficient