Air-atomized Mist-jet Cooling of Hot Billets

Abstract

In order to sane the cooling time of billets on cooling bed, mist-jet cooling process has been investigated. The main results obtained are as follows:
(1) The most favorable process for a homogeneous and regulated cooling of billets consists of on-corner arrangement of billets and air-atomized mist-jet cooling.
(2) To avoid cracking and deformation o f billets by forced-cooling and to shorten the cooling time, the following two-step cooling process is suitable: a natural cooling at high temperatures down to about 500°C and the mist-jet cooling at lower temperatures under about 500°C.
(3) When 123mm square billets containing 0.2 to 0.8wt% carbon are naturally cooled from about 1000°C down to about 550°C (billet core temperature), and then mist-cooled under impinged water with a flux equal or lower than 20 and 40l/m2•min at the top and the bottom, respectively, their structures and mechanical properties are scarcely affected unfavorably.
The following studies have also been made: influence of billets arrangement on cooling time, mist-cooling conditions to decrease bending of billets, influence of carbon content on cooling curves during natural cooling, influence of scale on billet surfaces on cooling curves during mist-cooling, deflection of as-rolled hot billets, selection of mist nozzles free from clogging, and an example o f basic design of a billet cooling bed with mist-cooling equipment.