Suppression of bending after steel bar drawing by heavy-reduction pass

Abstract

Heavy-reduction drawing with a reduction in area of over 23 per cent was proposed in order to suppress bending after drawing of a steel bar. Firstly, as the result of experimental investigation, it was found that the drawing direction should be adjusted on the die axis to suppress bending, just as intuitively sensed. However, even if the drawing direction is appropriately adjusted, bending occurs when the bar is initially bent. This kind of initial bending is inevitable in industrial operation. After applying various kinds of reduction in the area of an initially bent bar, it was finally found that heavy-reduction drawing with a reduction in area of over 23 per cent is an effective method to suppress bending. Moreover, a series of numerical analyses was carried out on plate drawing in order to compare it with experimental bar drawing. The results of numerical plate drawing and experimental bar drawing were in good agreement qualitatively and quantitatively. By observing the axial stress of a drawn plate at the exit, the mechanism of high-reduction drawing to suppress bending was studied. A method to approximate a group of points into an arc with one radius was proposed. The approximation was used in the analysis to calculate curvature of the drawn plate.