Increasing capacity of box annealing furnaces for coiled products - involves introducing scavenging gas during cooling phase to reduce cooling time and prevent oxidation of product surface

摘要

Means for increasing the unit capacity of box annealing furnaces involving heating and cooling the coiled products in a protective atmosphere, has the novelty that during the cooling stage a first scavenging phase is undertaken in which gas is introduced into the chamber such that the volume of gas entering equals that which leaves. A scavenging-free phase in which no protective gas leaves the chamber, then follows after which further gas can be introduced. During the scavenging-free phase, partial flow of protective gas is effected by circulating that which is already in the chamber. ADVANTAGE - The furnace capacity is increased by shortening the duration of the cooling phase in the protective gas atmosphere. Furthermore, oxidation reactions of the product surface leading to coloration of the coil's surface on its removal from the furnace, is avoided.