Larger beams are frequently straightened discontinuously in gag presses but also in continuously operating roller straightening machines. During gag pressing the bending forces are directly introduced into the flanges, whereas the straightening effect results from the acting of the straightening discs on the web root areas when roller straightening is applied. Press straightened sections show a surface almost free from faults; on roller straightened sections, however, flow figures become visible - a clear indication for the influence upon the material properties by the straightening process. In particular the residual stress condition is affected disadvantageously using the conventional roller straightening method.
The new flange supported straightening-technique combines the advantage of the roller straightening - straightening operation in the processing flow - with such of gag pressing, a straightening method, gentle and appropriate for the material involved. For the roller straightening using the technique of flange supported straightening especially designed straightening discs are employed (see figure showing straightening disc). These discs are characterised by a conically shaped backing ring with a flanged guiding device of larger diameter (EP Patent).
The introduction of the straightening forces immediately into the flange without coming into contact with the web is specific for the flange supporting straightening. The decisive advan-tage of the FS - technique is the production of beams low on residual stress: The critical peaks of the residual stresses in the web root areas are avoided (red curve, figure “residual stress distribution”). In contrast to conventional straightened beams neither straightening defects like cracks and holes are generated in the transition zone between the web and the flange nor an increase of the section height occurs.
Besides a fundamental improvement of the product properties the employment of the FS - straightening technique leads to an effective increase of the economic manufacture of H-sections: The FS-straightening of large and even of difficult to straighten sections on roller straightening plants reduces the straightening time to 1/10 compared to press straightening and saves the costs for the construction and operation of presses.
The new flange supported straightening technology can be applied to every straightening plant provided that the screwdown path an the pitch of the straightening axis are large enough to run the straightening process using FS-straightening discs with the highest possible diameter.