Development of the Billet Cooling Devise Using Mist-jet and Its Performance

Abstract

New mist cooling equipment for billets has been developed at kamaishi Works, Nippon Steel Corporation. The equipment has a walking beam type cooling bed, and as-rolled hot billets are arranged on their corners and rotated on the bed in walking.
The billets are natural-cooled from the initial temperature to about 550°C (core temperature) at the front part of bed and then mist-jet-cooled to about 100°C at the later part.
This report concerns the new techniques developed, the basic design and main specifications of the equipment, the passages of constructions and operating performances, improved points and unsettled problems, and others.
Main techniques developed are the billet straightening mechanism using a billet pusher, the system of on-corner arrangement and rotation of billets on the cooling bed, and the mist-jet cooling device of billets having the crossflow type mist nozzles.
This installation has been smoothly operated since June 1975 with a sufficient cooling capacity using the mist-cooling method for all billets containing carbon lower than 0.75wt%. This has given no cracking and less deformation, very small reject level of billets (about 0.05%), and no nozzle clogging for about ten years.