PURPOSE: To prevent the development of abnormality, such as meandering, buckling, of a steel plate in a continuous annealing furnace by heating or cooling a hearth roll with crown in the continuous annealing furnace for the steel plate as the occasion demands and suitably controlling the crown shape.
CONSTITUTION: The steel plate is carried with the hearth rolls 1 with crown in the continuous annealing furnace 11 and annealed by heating and cooling. The temps. of the steel plate 9 and the hearth rolls 1 are different in a heating zone and a cooling zone in the annealing furnace and such troubles as to occur the meandering of the steel plate in the heating zone and occur the buckling or the breakage of the steel plate in the cooling zone are occasionally caused by variation on the crown shape due to temp. difference between both zones. In this case, fluid is spouted from nozzles 4 of headers 3 for spouting the fluid, arranged in the hearth roll. The temp. distribution on the hearth roll is estimated from the temp. in the furnace, the temp. and the width of steel plate, the material property values of the steel plate, the hearth roll and the fluid spouted, and the temps. at the outer parts of hearth roll passing parts. By this method, the crown of the hearth roll is suitably controlled by adjusting the flow rate and the temp. of the fluid for heating or for cooling, and the occurence of the abnormality in carrying the steel plate on the hearth roll is prevented.
IMANAKA NARIKAZU
IKEDA MOTOKI
