Reduction of centre cavity by forging with liquid core in round billet

A series of experiments on the mechanical reduction of 263 mm diameter roun d billets of 13%Cr steel by forging with a liquid core was carried out, wit h variation in the amount of reduction. The decrease in the centre cavity w ith the amount of reduction was investigated. Then the conditions preventin g centre cavity formation and the influence of the presshead shape were ass essed by a deformation model using finite element modelling (FEM) analysis. In the experiments it was found that the centre cavity was nearly removed by a 2 mm reduction with a round presshead. A 3 mm reduction was demonstrat ed by FEM analysis to give a reduction in area almost equal to the percenta ge shrinkage. The use of a round presshead with a radius similar to the ori ginal billet is recommended for efficient centre cavity reduction.