In order to save the cooling time of billets on cooling bed, a fog-jet cooling process has been investigated. The main results obtained are as follows :
(1) To realize homogeneous and regulating cooling of billets, the most favorable cooling process consists of on-corner arrangement of billets and air-atomized fog-jet cooling
(2) From the standpoints of depressing the cracking and deforming of billets by forced-cooling and to save required time for cooling, the following two step cooling process is suitable: the natural cooling for high temperature zone (the initial to about 500°C) and the fog-jet cooling for low temperature zone (under about 500°C).
(3) In the cases of 123mm square billets containing from 0.2 to 0.8wt% carbon they are naturally cooled from about 1 000°C down to about 550°C (billet core temperature), and then fog-cooled under impinged water flux equal or lower than 20 and 40
l/m
2·min at top and bottom, respectively, and are scarecely unfavorably affected in their structures and mechanical properties.
In addition, the following items have been studied: influence of billets arrangement on cooling time, fog-cooling conditions of decreasing bending of billets, influence of carbon content on cooling curves during natural cooling, influence of scale on billet surfaces on cooling curves during fog-cooling, deflection of asrolled hot billets, selection of fog nozzle free from clogging, and an example of basic design of a billet cooling bed with fog-cooling facilities.
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