부산대학교 도서관

Heat treatment is ordinarily conducted to reduce residual stress caused by plastic work. Also to improve physical properties of steel, such as tensile strength, heat treatment is conducted. For example, an appropriate way of quenching leads to compressive stress to improve of fatigue strength. To obtain an optical condition of the heat treatment, it is important to understand the phase transformation during the heat treatment. In the case of large forging, especially, the scale effect induces temperature difference inside the steel and it makes difficult to consider the phase transformation due to the heat treatment. Therefore a method to quantitatively evaluate the residual stress after hear treatment of large forging steal is required. In this paper, in the aim at reduction of heat treatment processes of a large size forged steel, finite element method (FEM) is conducted to find an optical condition of the heat treatment. The analysis considers the effects of both transformation plasticity and creep deformation. Furthermore, the transformation plastic deformation are also considered. Finite element analysis software ANSYS14.5 is used with user subroutine "Usermat".