On numerical modelling of multi-rifled tube drawing

Abstract

Abstract Production of precision seamless steel tubes in Zeleziarne Podbrezova is divided into several technological steps, with final cold drawing determining final tube dimensions. The drawing itself usually takes several drawing passes with intermediate heat treatment. For multi-rifled tubes, the last drawing pass utilizes a special, free-to-rotate plug with multiple helical grooving so to produce a helical rifling pattern on the inner surface of the tube. A crucial factor to meet stringent dimensional tolerances on rifling geometry is to determine proper input dimensions of the tube just before the final rifling pass. Also, drawing velocity is another key factor that not only determines the overall productivity but the quality of the rifling as well. Due to the high costs of plant trials in early stage of technology development, computer simulation approach can easily serve the purpose very well, thus saving us from laborious and costly pilot experiments. Numerical modelling software DEFORM-3D has been utilized in Zeleziarne Podbrezova for drawing technology development and optimization for T12 steel tubes with 28.6 × 6.3 mm (O.D. × W.T.) In particular, both input dimensions and drawing velocity were optimized while meeting rather strict dimensional requirements on tube rifling. Resulting tube & rifling dimensions were in good accordance with dimensions from experimental proofing trials, where the actual dimensions were obtained via 3D optical scanning of multi-rifled tubular samples.