Study On Improving The Quality Of Mid-Large Diameter Rolled Pieces During Cross Wedge Rolling By Optimization Of Temperature Field

The shaft parts which produced by the cross wedge rolling had been widely usded in the railway and motor vehicles industry. With the rapid development of the transport industry, the diameter of drive shaft parts was increased observably, it is necessary to study a efficient new technology and product large shaft parts for the social and market development. However, because of the Mannesmann effect, the quality of the cross wedge rolling pieces internal part was significantly decreased. For this problem, by investigation, the method of non-uniform temperature field can weaken the transverse tensile stress and enhance the plastic deformation of the heart to achieve the purpose of improving the quality of the heart department. In this paper, variables were the diameter of rolling piece and reduction of area, to obtained the cooling coefficient of reasonable non-uniform temperature field, using the finite element analysis tool to sudy the theoretical analysis, it has important significance to the pratical applications of reasonable non-uniform temperature field method.The curve between press rates and the tensile stress curve of the rolling pieces internal part can be got by using the slip line theory. Obtained the ratio between diameter and width when transverse tensile stress of heart department was zero in different press rates. Under the guidance of this curve, using different diameters and press rate as variables, through two-dimensional numerical simulation, got the ideal thickness and temperature of outside layer under non-uniform temperature field.According to the above conclusion, in the corresponding rolling pieces diameter and reduction of area conditions, analyse the stress and strain in the rolling pieces internal part under the ideal non-uniform temperature field using three-dimensional numerical simulation. Find that the deformation of the two-roll cross wedge rolling process and the two boards stretch round billet is not exactly the same. With the section shrinkage rate increases, the transverse tensile stress decreases, but the relative increase of the axial tensile stress, resulting in the mean stress is unchanged. Using the mean stress as the standard of heart department quality, obtained the relation curve between the diameter of rolling piece and thickness of outside layer under ideal non-uniform temperature field.Based on the conclusions of the ideal non-uniform temperature field, using diameter and water-cooled heat transfer coefficient and water-cooled time as variables, get the method of reasonable non-uniform temperature field, provide a theoretical basis for non-uniform temperature field applied to the mid-large diameter shaft part of cross wedge rolling process.