Method and apparatus for stretch-bend leveling metal strip

Abstract

The invention relates to a method and to a device for the stretch-bend leveling of a metal strip (B), wherein the metal strip (B) is alternately bent around stretching rollers (1-5) under a tensile stress and the degree of stretching is thus increased, wherein one or more stretching rollers (1-5) are provided with a non-metal coating. The method and the device are characterized in that one or more stretching rollers are provided with a coating (8) of plastic.

1 . A method of stretch-bend leveling metal strip, the method comprising the steps of:
 bending the metal strip alternately around a plurality of stretching rollers under a tensile stress, and increasing the stretching rate in a downstream strip-travel direction,   providing one or more stretching rollers with a plastic jacket.   
     
     
         2 . The method according to  claim 1 , further comprising the steps of:
 passing the metal strip through an inlet tension roller set for establishing tension and through an outlet tension roller set for dissipating the tension, the strip is bent alternately around the stretching rollers between the inlet tension roller set and the outset roller set, and the stretching rate of the strip being increased in the strip-travel direction.   
     
     
         3 . The method according to  claim 1  wherein each of the stretching rollers is provided with a respective jacket of plastic. 
     
     
         4 . The method according to  claim 1 , wherein the jacket consists of polyurethane. 
     
     
         5 . The method according to  claim 1 , wherein the jacket has a Shore A hardness of at least 90. 
     
     
         6 . The method according to  claim 1 , wherein the metal strip passes through the stretching rollers in dry operation without any spray medium or the like being sprayed onto the stretching rollers. 
     
     
         7 . The method according to  claim 1 , wherein an angle of wrap around the stretching rollers is adjusted as a function of strip tension so that a maximum linear load applied to the jacket is not exceeded. 
     
     
         8 . The method according to  claim 1 , wherein a stretching rate of at least 0.2% is produced by the stretching rollers. 
     
     
         9 . The method according to  claim 1 , wherein the strip is under a tensile stress of at least 15% of the yield point of the metal strip. 
     
     
         10 . The method according to  claim 1 , wherein the jacket is at least 1 mm thick. 
     
     
         11 . The method according to  claim 1 , wherein the stretching rollers each have a diameter of 25 mm to 100 mm. 
     
     
         12 . The method according to  claim 1 , further comprising the step of:
 supporting each of the stretch rollers individually.   
     
     
         13 . The method according to  claim 1 , further comprising the step of:
 adjusting one or more or all of the stretching rollers individually.   
     
     
         14 . The method according to  claim 1 , wherein three to five stretching rollers are provided between the inlet tension roller set and the outlet tension roller set. 
     
     
         15 . The method according to  claim 1 , further comprising the step of:
 supporting the stretching rollers are each supported individually on at least two backing or intermediate rollers.   
     
     
         16 . The method according to  claim 15 , further comprising the step of:
 providing the backing rollers or the intermediate rollers also provided with a jacket of plastic.   
     
     
         17 . An apparatus for stretch-bend leveling metal strip the apparatus comprising:
 an inlet tension roller set for establishing strip tension,   an outlet tension roller set for releasing the strip tension,   a plurality of stretching rollers between the inlet tension roller set and the outlet tension roller set, the to strip being bent in alternation around the stretching rollers with an increase in the stretching rate,   a plastic jacket on one or more stretching rollers.   
     
     
         18 . The apparatus according to  claim 17 , wherein the jacket is of polyurethane 
     
     
         19 . The method according to  claim 1 , wherein the jacket is 3 mm to 7 mm thick.