Application of induction heating to control sheet flatness in cold rolling mills

Abstract

A system for rolling metal sheet having a substantially uniform flatness including a rolling mill including a pair of work rollers for reducing the thickness of a metal sheet, an induction heating apparatus in close proximity to at least one roller, bending jacks corresponding to each of the rollers, and a cooling spray system in proximity to rollers; a flatness measuring device positioned to measure a differential in flatness of the metal sheet; and an mill control interface connected between the flatness measuring device and the rolling mill's actuators, in which the mill control interface is configured to actuate the induction heating apparatus, the bending jacks and the cooling spray system to substantially eliminate flatness differentials is the metal sheet's flatness. The induction coil heating apparatus is configured to eliminate high tension on the strip edges caused by the temperature gradients in the work rolls at the edges of the metal strip.

1 . A method for manufacturing metal sheet comprising: 
 rolling a metal sheet between a pair of work rollers to form a rolled product;    measuring tension distribution of the rolled product from a center portion of the rolled product to at least one edge portion of the rolled product; and    adjusting a temperature in a singular roller of the pair of work rollers to provide an edge diameter of the singular roller that is greater than a center diameter of the singular work roller when the tension of the at least one edge portion of the rolled product is greater than the tension of the center portion of the rolled product.    
   
   
       2 . The method of  claim 1 , comprising measuring the tension distribution with a flatness bar.  
   
   
       3 . The method of  claim 1 , comprising measuring the tension distribution optically or acoustically.  
   
   
       4 . The method of  claim 2 , comprising a flatness bar to measure the tension distribution of the sheet downstream from the pair of work rollers.  
   
   
       5 . The method of  claim 2 , comprising placing at least one induction coil proximate to a portion of the singular work roller corresponding to the longitudinal edge of the metal sheet.  
   
   
       6 . The method of  claim 4 , wherein each induction coil may be displaced laterally along a width of the singular work roller.  
   
   
       7 . The method of  claim 1 , further comprising a cooling spray system configured to decrease a temperature in at least a center portion of the pair of work rollers.  
   
   
       8 . The method of  claim 1 , further comprising bending jacks configured to compensate for a force produced by the metal strip against the work roller during rolling.  
   
   
       9 . A method for manufacturing metal sheet comprising: 
 rolling a metal sheet between a pair of work rollers to form a rolled product;    measuring the flatness of the rolled product; and    adjusting the diameter of a portion of a single work roller of the pair of work rollers corresponding to the longitudinal edge of the metal sheet in response to the flatness of the rolled product.    
   
   
       10 . The method of  claim 9 , wherein the diameter of the portion of the single work roller is adjusted to provide a rolled product having a substantially uniform tension distribution across the width of the rolled product.  
   
   
       11 . The method of  claim 9 , comprising measuring the flatness with a flatness bar.  
   
   
       12 . The method of  claim 9 , comprising inducing a magnetic field that induces eddy currents in the singular work roller.  
   
   
       13 . The method of  claim 9 , comprising positioning at least one induction coil aligned to a longitudinal edge of the metal sheet.  
   
   
       14 . The method of  claim 9 , comprising actuating a cooling spray system in response to the flatness of the rolled product.  
   
   
       15 . The method of  claim 9 , further comprising actuating bending jacks in response to the flatness of the rolled product.  
   
   
       16 . A system for rolling metal sheet comprising: 
 a rolling mill with at least a pair of work rollers;    an induction heating apparatus positioned in close proximity to a singular work roller of the pair of work rollers;    a flatness measuring device positioned downstream of the pair of work rollers; and    a mill control interface connected between the flatness measuring device and the induction heating apparatus, wherein the mill control interface is configured to receive flatness measurements from the flatness measuring device and to send signals to actuate the induction heating apparatus.    
   
   
       17 . The system of  claim 16  further comprising at least one of bending jacks, a cooling spray system, and a roll side shifting mechanism to displace the pair of work rollers in opposite directions along their horizontal axis.  
   
   
       18 . The system of  claim 17 , wherein the mill control interface receives a signal from the flatness measuring device, analyzes the signal, and actuates at least one of the work roll side shifter, the bending jacks, the induction heating apparatus and the cooling spray system to provide a rolled product having a substantially uniform tension distribution across the width of the rolled product.  
   
   
       19 . The system of  claim 16  wherein the induction heating apparatus is an induction coil wound about a ferromagnetic core.  
   
   
       20 . The system of  claim 20 , wherein the rolling mill is a cold rolling mill.