PRIMARY COOLING METHOD ON CONTINUOUS ANNEALING OF STEEL STRIP

PROBLEM TO BE SOLVED: To provide an efficient and inexpensive primary cooling method in a continuous annealing of steel strip capable of reducing the consumption of expansive H2 gas to improve the economization and improving the safety. SOLUTION: This primary cooling method in the continuous annealing of the steel strip is provided with a heating process A, a soaking process B, a primary cooling process C having rapidly cooling treatment process at least ion the latter half, an overaging treatment process D and a finish cooling process E. In such a case, as the cooling gas used for the cooling treatment process, and inert gas containing the H2 has is used, and further, in the rapidly cooling treatment process, the H gas concn. is changed over between two ranges of a low concn. range and a high concn. range. Therefore, the consumption of the expensive H2 has is reduced and the economization is improved, and also, the safety is improved and the primary cooling can be executed most efficiently.