FINITE-ELEMENT ANALYSIS OF COMPRESSION HOLDING STEP IN SEMISOLID FORGING AND EXPERIMENTAL CONFIRMATION

The technology of semi-solid forging (SSF) has been actively developed to fabricate near-net-shape products using light and difficult to for m materials. Generally, the SSF process is composed of slug heating, f orming, compression holding and an ejecting step. After the forming st ep in SSF, the slug is compressed during a certain holding time in ord er to completely fill the die cavity and to accelerate the solidificat ion rate. The compression holding time that can affect microstructural characteristics, mechanical properties and the shape of products is i mportant. This paper presents a procedure to predict the compression h olding time for obtaining the final shape of the product. Information is preheated temperature and the solid fraction for a cylindrical slug in the compression holding step of a closed-die compression process u sing heat transfer analysis and considering latent heat, by means of t he finite element method. The influence of the predicted compression h olding time on microstructural characteristics, mechanical properties and shape of the product is investigated by experiment. (C) 1998 Elsev ier Science S.A. All rights reserved.