Study On The Forging Process Of Large-Size Head With Flange

With the rapid economy development of our country, the demand for energy sources is rising rapidly; the building of one million kilowatt-level nuclear-power plant is especially imminent. However, there are still many technical problems which can not be solved, properly in nuclear power technology development of our country.The nuclear power units'pressure vessel is the core part of the nuclear reactor, and the heads are key parts of the pressure vessels. Because the flange thickness of ball crown head with flange is much greater than its thickness, the process method of conventional head is not applicable to the head with flange, and it is necessary to study new process method.This paper introduced the forging process of large-size head with flange, took finite element analysis software DEFORM-3D as the analysis platform and made optimal selection on the blank and dies with the associative measures of the forward simulation. The paper has carried on the analysis to the head forming. The forming process phase divides into three stages based the results: formed initial period, the formed intermediate stage and the formed later period. The paper has calculated the thickness reduction of head in each stage, and introduced the head forming stress and strain condition. It has carried on 3D rigid-viscoplastic coupled thermo-mechanical FEM simulation in the forging process of head, has obtained the influence rule of the shape coefficient and the internal the temperature field, stress field, strain field and deformation load and flow velocity field in with different depress.Based on the coupled thermo-mechanical FEM simulation, the paper has calculated the expand ratio in the internal blank of the forging process of large-size thick-wall head with flange with the theory of expand ratio, forecasted the easy crack position, meanwhile, considered the influence of the distortion speed, the friction factor and the forging temperature to the expand ratio. Through to these analogue result analysis, it have promulgated the forging forming rule of large-size thick-wall head with flange. These results have the important theory guiding sense and the practical value to the constituting of large-size thick-wall head forging process.