Steel strip continuous annealing apparatus

A steel strip continuous annealing apparatus comprising:

• a heating-soaking zone for heating a steel strip to a predetermined temperature and for soaking the steel strip at said temperature;
• a first cooling zone subsequent to said heating-soaking zone for rapidly cooling the steel strip at a predetermined cooling rate;
• first forcible cooling means incorporated in said first cooling zone for operation of the rapidly cooling;
• a second cooling zone subsequent to said first cooling zone for slowly cooling the steel strip or holding the steel strip at a predetermined temperature;
• hot-cold change-over means in said second cooling zone for selectively either slowly cooling the steel strip or holding the steel strip at the predetermined temperature;
• third forcible cooling means comprising:
• a third cooling zone subsequent to said second cooling zone for cooling the steel strip to substantially room temperature;
• and
• second forcible cooling means incorporated in said third cooling zone for operation of the cooling to substantially room temperature;
• a steel strip feeder for feeding the steel strip into said heating-soaking zone;
• a steel strip carry-out device for carrying the steel strip out of said third cooling zone;
• means for directly bypassing the steel strip from the heating-soaking zone through a first bypass passageway to said second cooling zone;
• means for directly bypassing the steel strip from the first cooling zone through a second bypass passageway to said steel strip carry-out device;
• and
• heat insulating means at the boundary portion between the first cooling zone and the first bypass passageway, for insulating the first bypass passageway from the first cooling zone thermically, whereby different grades of steel may be processed.

A steel strip continuous annealing apparatus comprising:

• a heating-soaking zone for heating a steel strip to a predetermined temperature and for soaking the steel strip at said temperature;
• a first cooling zone subsequent to said heating-soaking zone for rapidly cooling the steel strip at a predetermined cooling rate;
• first forcible cooling means incorporated in said first cooling zone for operation of the rapidly cooling;
• a second cooling zone subsequent to said first cooling zone for slowly cooling the steel strip or holding the steel strip at a predetermined temperature;
• hot-cold change-over means in said second cooling zone for selectively either slowly cooling the steel strip or holding the steel strip at a predetermined temperature;
• a third cooling zone subsequent to said second cooling zone for cooling the steel strip to substantially room temperature;
• second forcible cooling means incorporated in said third cooling zone for operation of the cooling to substantially room temperature;
• a steel strip feeder for feeding the steel strip into said heating-soaking zone;
• a steel strip carry-out device for carrying the steel strip out of said third cooling zone;
• means for directly bypassing the steel strip from the heating-soaking zone through a first bypass passageway to said second cooling zone;
• means for directly bypassing the steel strip from the first cooling zone through a second bypass passageway to said steel strip carry-out device;
• heat insulating means at the boundary portion between the first cooling zone and the first bypass passageway, for insulating the first bypass passageway from the first cooling zone thermically;
• and
• tension control means for controlling the tension of the steel strip.