Drawing force and forming load in reshaping cylindrical steel pipes into square by draw bench method

摘要

Characteristics of the drawing force acting on a hydraulic cylinder ram and the forming load acting on each pair of idler rolls are experimentally investigated in a draw bench process for reshaping cylindrical steel pipes (t{sub}0/D{sub}0 = 2.2～4.5%, t{sub}0 = initial wall thickness, D{sub}0 = initial outer diameter) into square shapes (69×69, 72 × 72, 75 × 75 mm). The results are compared with the results obtained by extroll-forming. The drawing force is found to increase with the increase in the reduction and the increase in the cross-sectional size ratio t{sub}0/D{sub}0 of a mother pipe. The forming load acting on each pair of idler rolls is also found to increase with the increase in the drawing force acting on the rolls concerned. From these experimental results, equations for estimating the drawing force and the forming load are formulated.