Method and device for continuously stretch-bend-leveling metal strips

Abstract

The invention relates to a method and a device for continuously stretch-bend-leveling metal strips, wherein a strip under a tensile stress below the elastic limit is alternatingly bent about at least four straightening rollers in the plastic or elastic-plastic region and thereby undergoes plastic stretching. The bending radii of all four straightening rollers are thereby set dually and independently of each other, as the straightening rollers are set up having individually controlled positions.

1 . A method for continuously stretch-bend-leveling metal strips, where a strip under tension below the elastic limit is bidirectionally bent in the plastic or elastic range about at least four straightening rollers and thereby undergoes plastic stretching, wherein
 the bending radii at all four straightening rollers are set individually and independently of each other.   
     
     
         2 . The method according to  claim 1 , wherein for setting the bending radii, all four straightening rollers are adjusted in a position-controlled manner. 
     
     
         3 . The method according to  claim 1 , wherein the strip is bent about more than four straightening rollers, wherein the bending radii, at least at the last four straightening rollers, are set individually and independently of each other by individually adjusting preferably at least the last four straightening rollers in a position-controlled manner. 
     
     
         4 . The method according to  claim 1 , wherein the positions of the straightening rollers are set with an accuracy, for example control accuracy, which corresponds to an accuracy with regard to the wrap angles of the strip about the straightening rollers of ±0.05° or less, preferably ±0.02° or less. 
     
     
         5 . The method according to  claim 1 , wherein the wrap angles of the strip about one or a plurality of straightening rollers, preferably about all four straightening rollers are 0.5° to 60°. 
     
     
         6 . The method according to  claim 1 , wherein the stretch ratio is 0.1% to 1.5%. 
     
     
         7 . The method according to  claim 1 , wherein the tension in the strip is 10% to 90% of the elastic limit of the strip or the strip material. 
     
     
         8 . The method according to  claim 1 , wherein the spacing between at least two straightening rollers provided one behind the other with regard to the travel direction of the strip is at least 15% of the maximum strip width. 
     
     
         9 . The method according to  claim 1 , wherein the spacing between two straightening rollers provided one behind the other is at least 150 mm. 
     
     
         10 . The method according to  claim 8 , wherein the spacing between two straightening rollers provided one behind the other is provided at all four straightening rollers. 
     
     
         11 . The method for continuously stretch-bend-leveling metal strips, wherein a strip under tension below the elastic limit is bidirectionally bent in the plastic or elastic range about at least four straightening rollers and thereby undergoes plastic stretching according to  claim 1 , wherein the spacing in the travel direction of the strip between at least two straightening rollers is set in a variable manner. 
     
     
         12 . The method according to  claim 1 , wherein the target values for the positions of the straightening rollers or the target values for the wrap angles of the strip about the straightening rollers are determined with a calculation model that takes into account at least stress in longitudinal and transverse directions and, as calculation parameters, processes the strip thickness, the modulus of elasticity, the Poisson's ratio, the cyclic strength behavior of the strip, the tension in the strip, the roller radii or the geometry of the strip track about the rollers, or the target values of the strip thickness or the yield strength. 
     
     
         13 . The method according to  claim 12 , wherein the target values are determined with the calculation model with the proviso that the residual longitudinal curvature and the residual transverse curvature becomes zero. 
     
     
         14 . The method according to  claim 12 , wherein the target values are determined with the calculation model with the proviso that the residual curvature becomes zero and the residual longitudinal curvature takes a defined value. 
     
     
         15 . The method according to  claim 1 , wherein downstream of one or a plurality of straightening rollers the cross bow of the strip over the strip width is measured. 
     
     
         16 . The method according to  claim 15 , wherein the feedback control of the position or wrap angle is carried out taking into account the obtained measured values for the cross bow. 
     
     
         17 . The method according to  claim 16 , wherein the feedback control is based on a calculation model that considers at least stress in the longitudinal and transverse directions and, as calculation parameters, processes the strip thickness, the modulus of elasticity, the Poisson's ratio, the cyclic strength behavior of the strip, the tension in the strip, the roller radii and the geometry of the strip track about the rollers, and a certain cross bow is associated with a residual longitudinal or transverse curvature. 
     
     
         18 . The method according to  claim 1 , wherein the calculation model or the calculation models is/are based on the finite element method by the expected maximum nonplanarity of the strip or the nonplanarity of the strip measured prior to straightening, the optimal stretch ratio or the elastically/plastically acting straightening rollers' optimal horizontal spacings, which result in the minimal residual nonplanarity, are calculated using the finite element methods. 
     
     
         19 . An apparatus for continuously stretch-bend-leveling metal strips according to a method according to  claim 1 , comprising at least four straightening rollers about which a strip under tension below the elastic limit is bidirectionally bent in the plastic or elastic/plastic range, and further comprising at least one controller working with or without feedback, wherein
 the bending radii at all four straightening rollers can be set individually and independently of each other.   
     
     
         20 . The apparatus according to  claim 19 , wherein all four straightening rollers are connected to a controller and can be adjusted in a position-controlled manner. 
     
     
         21 . The apparatus according to  claim 19 , wherein the diameters of one or a plurality of straightening rollers and preferably all four straightening rollers are 15 mm to 150 mm. 
     
     
         22 . The apparatus according to  claim 19 , wherein of the four straightening rollers at least the last two straightening rollers are provided directly one behind the other without interposing further rollers. 
     
     
         23 . The apparatus according to  claim 22 , wherein the four straightening rollers are provided directly one behind the other without interposition of further rollers. 
     
     
         24 . The apparatus for continuously stretch-bend-leveling metal strips according to a method according to  claim 1 , comprising a plurality of straightening rollers about which a strip under tension below an elastic limit is bidirectionally bent in the plastic or elastic/plastic range wherein the spacing between at least two straightening rollers can be variably set in the travel direction of the strip. 
     
     
         25 . The apparatus according to  claim 24 , wherein the position of at least one straightening roller, preferably of all straightening rollers along the strip travel direction can be set. 
     
     
         26 . The apparatus according to  claim 19 , wherein upstream or downstream of at least one straightening roller, an adjacent deflection roller is provided, the deflection roller or the deflection rollers preferably having three times the diameter of the straightening roller. 
     
     
         27 . The apparatus according to  claim 26 , wherein the upstream deflection roller or the downstream deflection roller has a concave or convex roller shape. 
     
     
         28 . The apparatus according to  claim 26 , wherein the upstream deflection roller or the downstream deflection roller is equipped with a roller bending mechanism in the horizontal or vertical direction. 
     
     
         29 . The apparatus according to  claim 19 , wherein upstream of the first straightening roller a shape-variable tensioning roller or deflection roller is provided that is wrapped by the metal strip for example by at least 120°. 
     
     
         30 . The apparatus according to  claim 19 , wherein the straightening rollers can be adjusted by actuators. 
     
     
         31 . The apparatus according to  claim 19 , wherein individual position-adjustable straightening rollers or each of a plurality of position-adjustable straightening rollers are commonly and additionally provided with a quick adjusting mechanism.