Continous hot-rolling facility

Abstract

A continuous hot-rolling mill includes an upper rolling unit including a plurality of rolling stands, and a lower rolling unit including a plurality of rolling stands and disposed downstream with respect to the upper rolling unit in a workpiece passing direction in which a workpiece to be rolled is passed. The two or more rolling stands of the lower rolling unit are differential or very-small-diameter rolling stands. Each of the two or more differential or very-small-diameter rolling stands of the lower rolling unit is provided with a drive motor having a capacity greater than that of any one of drive motors included in the rolling stands disposed upstream the differential or very-small-diameter rolling stands. The continuous hot-rolling mill is suitable for producing hot-rolled, fine-grained steel sheets and is excellent in sheet passing abilities for preventing the steel sheet from meandering and for rolling the steel sheet in a desired shape.

1 . A continuous hot-rolling mill comprising: 
 an upper rolling unit including a plurality of rolling stands; and a lower rolling unit including a plurality of rolling stands and disposed downstream with respect to the upper rolling unit in a workpiece passing direction in which a workpiece to be rolled is passed;    wherein two or more rolling stands of the lower rolling unit are differential or very-small-diameter rolling stands,    each of the two or more differential or very-small-diameter rolling stands of the lower rolling unit is provided with a drive motor having a capacity greater than a capacity of any one of drive motors included in the rolling stands disposed upstream with respect to the differential or very-small-diameter rolling stands.    
   
   
       2 . The continuous hot-rolling mill according to  claim 1 , wherein successive two or more rolling stands of the lower rolling unit including a last rolling stand are the differential or very-small-diameter rolling stands.  
   
   
       3 . The continuous hot-rolling mill according to  claim 1 , wherein the lower rolling unit includes three or more rolling stands, and two or three rolling stands among the three or more rolling stands of the lower rolling unit are the differential or very-small-diameter rolling stands.  
   
   
       4 . The continuous hot-rolling mill according to  claim 1 , wherein at least one of the rolling stands of either the upper or the lower rolling unit has a CVC function.  
   
   
       5 . The continuous hot-rolling mill according to  claim 1 , wherein the drive motors of the two or more differential or very-small-diameter rolling stands of the lower rolling unit have different capacities, respectively, and drive motors of lower rolling stands have capacities not lower than capacities of drive motors of upper rolling stands.  
   
   
       6 . The continuous hot-rolling mill according to  claim 5 , wherein three rolling stands including a last rolling stand of the lower rolling unit are differential or very-small-diameter rolling stands, 
 respective capacities of the drive motors of the differential or very-small-diameter rolling stands meet a condition expressed by:       P   n   >P   n−1   ≧P   n−2  or  P   n   ≧P   n−1   >P   n−2     where P n , P n−1  and P n−2  are capacities of the drive motors of the last rolling stand, a second last rolling stand precedent to the last rolling stand, and a third last rolling stand precedent to the second last rolling stand, respectively.    
   
   
       7 . The continuous hot-rolling mill according to  claim 5 , wherein respective capacities of the drive motors of the two or more differential or very-small-diameter rolling stands of the lower rolling unit are greater by 15% or above than any one of capacities of the drive motors of the rolling stands disposed upstream with respect to the differential or very-small-diameter rolling stands.  
   
   
       8 . The continuous hot-rolling mill according to  claim 1 , wherein a maximum capacity among respective capacities of the drive motors of the two or more differential or very-small-diameter rolling stands of the lower rolling unit is greater by 30% or above than any one of capacities of the drive motors of the rolling stands disposed upstream with respect to the differential or very-small-diameter rolling stands.  
   
   
       9 . The continuous hot-rolling mill according to  claim 1 , wherein water-curtain cooling means are disposed at respective exits of the two or more differential or very-small-diameter rolling stands of the lower rolling unit in order to cool a rolled workpiece.