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Using nonlinear finite element method, a thermo-mechanical coupled simulation model for the formation mechanism of the laminated crack defect has been established in the upsetting of heavy disk-shaped forgings. Through numerical simulation, the distributions of stress, equivalent strain and strain rate were analysed. Meanwhile the distribution diagram of stress state evolution was obtained, and the uncoordinated deformation, under tri-lateral compression, is determined as the main reason leading to laminated crack defect. To reveal the characteristics of the uncoordinated deformation, the variations of each variable and its gradient in numerical simulation were presented, and a combined prediction model of laminated crack defect were proposed based on degree of deformation and gradient of deformation speed. Subsequently, the morphology and distribution of laminated crack were obtained in the centre of forging using the prediction model. Comparison of calculation results and experimental data indicates that both of them match well. In addition, the effect of friction coefficient on the deformation is also presented. The results show that the decreasing of friction coefficient is an effective measure to restrain the laminated crack defect. Abstract: Using nonlinear finite element method, a coupling thermo-mechanical simulation model for the formation mechanism of the laminated crack defect has been established in the upsetting of heavy disk-shaped forgings. Through numerical simulation, the distributions of stress, equivalent strain and strain rate were analyzed. Meanwhile the distribution diagram of stress state evolution was obtained, and the uncoordinated deformation, under tri-lateral compression, is determined as the main reason leading to laminated crack defect. To reveal the characteristics of the uncoordinated deformation, the variations of each variable and its gradient in numerical simulation were presented, and a combined prediction model of laminated crack defect were proposed based on degree of deformation and gradient of deformation speed. Subsequently, the morphology and distribution of laminated crack were obtained in the centre of forging using the prediction model. Comparison of calculation results and experimental data indicates that both of them match well. In addition, the effect of friction coefficient on the deformation is also presented. The results show that the decreasing of friction coefficient is an effective measure to restrain the laminated crack defect.

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The influence and signification of casting parameters on the solidification process of steel ingot were discussed based on the finite element method (FEM) results by orthogonal experiment method. The range analysis, analysis of variance (ANOVA) and optimization project were used to investigate the FEM results. In order to decrease the ingot riser head and improve the utilization ratio of ingot, the casting parameters involved casting temperature, pouring velocity and interface heat transfer were optimized to decrease shrinkage pore and microporosity. The results show that the heat transfer coefficient between melt and heated board is a more sensitive factor. It is favor to decrease the shrinkage pore and microporosity under the conditions of low temperature, high pouring velocity and high heat transfer between melt and mold. If heat transfer in the ingot body is quicker than that in the riser, the position of shrinkage pore and microporosity will be closer to riser top. The results of optimization project show that few of shrinkage pore and microporosity reach into ingot body with the rational parameters, so the riser size can be reduced.