An experimental study on direct current dieless drawing of 4130 steel tubes

Forming of tubes in various shapes has been a major interest in vehicle, instrumentation, decoration and precision industries. Due to a variety of shapes that can be achieved by tube forming, this manufacturing process has taken a major part in research and application. In this manufacturing process, a tube with a certain diameter and thickness can be considered to shape the part. The shaping or forming can be achieved by end forming, expanding the section, bending the section, buckling the tube, and/or reducing the section. Traditionally, to form these sections the rigid tool, flexible tool or fluid pressure would be needed to shape the tube. However, tools like mandrel or plug and their sizes limit the size of the tube to be formed. In this paper, tubes are formed by stretching them while simultaneously passing the direct current through. This process has been explored earlier by heating the tube using induction heating or rotary laser heating method. However, as no dies or tools are used to form these tubes, the process is considered dieless tube drawing which involves heating the tubes and drawing them into a reduced section. This study considers two different thicknesses but the same outer diameter tubes. The drawing force, shape, and microstructure are investigated. Based on the stress-strain curve, the yield to fracture and tensile to fracture strains are determined and discussed.