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

Abstract

A series of experiments on the mechanical reduction of 263 mm diameter round billets of 13%Cr steel by forging with a liquid core was carried out, with variation in the amount of reduction. The decrease in the centre cavity with the amount of reduction was investigated. Then the conditions preventing centre cavity formation and the influence of the presshead shape were assessed 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 demonstrated by FEM analysis to give a reduction in area almost equal to the percentage shrinkage. The use of a round presshead with a radius similar to the original billet is recommended for efficient centre cavity reduction.